
==== Front
Animal Model Exp Med
Animal Model Exp Med
10.1002/(ISSN)2576-2095
AME2
Animal Models and Experimental Medicine
2096-5451
2576-2095
John Wiley and Sons Inc. Hoboken

38853347
10.1002/ame2.12436
AME212436
AMEM-2023-0168.R1
Review
Regular Article
Review
Uncovering the impact of alcohol on internal organs and reproductive health: Exploring TLR4/NF‐kB and CYP2E1/ROS/Nrf2 pathways
Zheng et al.
Kong Eason Qi Zheng https://orcid.org/0009-0004-8128-1955
1 ekon0010@student.monash.edu

Subramaniyan Vetriselvan 1 2
Lubau Natasha Sura Anak 1
1 Pharmacology Unit, Jeffrey Cheah School of Medicine and Health Sciences Monash University Malaysia Subang Jaya Selangor Malaysia
2 Center for Global Health Research, Saveetha Medical College Saveetha Institute of Medical and Technical Sciences Chennai Tamil Nadu India
* Correspondence
Eason Kong Qi Zheng, Pharmacology Unit, Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway, Subang Jaya 47500, Selangor, Malaysia.
Email: ekon0010@student.monash.edu

09 6 2024
8 2024
7 4 10.1002/ame2.v7.4 Themed Issue: Study on Cardiovascular and Cerebrovascular Diseases 444459
25 12 2023
10 5 2024
© 2024 The Author(s). Animal Models and Experimental Medicine published by John Wiley & Sons Australia, Ltd on behalf of The Chinese Association for Laboratory Animal Sciences.
https://creativecommons.org/licenses/by/4.0/ This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Abstract

This review delves into the detrimental impact of alcohol consumption on internal organs and reproductive health, elucidating the underlying mechanisms involving the Toll‐like receptor 4 (TLR4)/Nuclear factor kappa light chain enhancer of activated B cells (NF‐kB) pathway and the Cytochrome P450 2E1 (CYP2E1)/reactive oxygen species (ROS)/nuclear factor erythroid 2‐related factor 2 (Nrf2) pathways. The TLR4/NF‐kB pathway, crucial for inflammatory and immune responses, triggers the production of pro‐inflammatory agents and type‐1 interferon, disrupting the balance between inflammatory and antioxidant responses when tissues are chronically exposed to alcohol. Alcohol‐induced dysbiosis in gut microbes heightens gut wall permeability to pathogen‐associated molecular patterns (PAMPs), leading to liver cell infection and subsequent inflammation. Concurrently, CYP2E1‐mediated alcohol metabolism generates ROS, causing oxidative stress and damaging cells, lipids, proteins, and deoxyribonucleic acid (DNA). To counteract this inflammatory imbalance, Nrf2 regulates gene expression, inhibiting inflammatory progression and promoting antioxidant responses. Excessive alcohol intake results in elevated liver enzymes (ADH, CYP2E1, and catalase), ROS, NADH, acetaldehyde, and acetate, leading to damage in vital organs such as the heart, brain, and lungs. Moreover, alcohol negatively affects reproductive health by inhibiting the hypothalamic–pituitary‐gonadal axis, causing infertility in both men and women. These findings underscore the profound health concerns associated with alcohol‐induced damage, emphasizing the need for public awareness regarding the intricate interplay between immune responses and the multi‐organ impacts of alcohol consumption.

Chronic alcohol exposure disrupts toll‐like receptor 4/nuclear factor kappa light chain enhancer of activated B cells and Cytochrome P450 2E1/reactive oxygen species/nuclear factor erythroid 2‐related factor 2 pathways, causing inflammation, gut dysbiosis, liver issues, and oxidative stress in vital organs. Excessive alcohol intake inhibits the hypothalamic–pituitary‐gonadal axis, negatively impacting fertility. This highlights the urgent need for public awareness of the intricate interplay between immune responses and the widespread health effects of alcohol consumption.

alcohol
health impact
inflammation
metabolism
molecular pathways
the Jeffrey Cheah School of Medicine and Health Sciences and the Library Resources, Monash University Malaysia source-schema-version-number2.0
cover-dateAugust 2024
details-of-publishers-convertorConverter:WILEY_ML3GV2_TO_JATSPMC version:6.4.8 mode:remove_FC converted:03.09.2024
Kong EQZ , Subramaniyan V , Lubau NSA . Uncovering the impact of alcohol on internal organs and reproductive health: Exploring TLR4/NF‐kB and CYP2E1/ROS/Nrf2 pathways. Anim Models Exp Med. 2024;7 :444‐459. doi:10.1002/ame2.12436

Funding information

There is no funding support for this review study. The entire study was supported by the Jeffrey Cheah School of Medicine and Health Sciences and the Library Resources, Monash University Malaysia
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pmc1 INTRODUCTION

Alcohol, a globally prevalent habit, exerts profound health consequences that extend beyond its well‐documented impact on the liver. This review focuses on the intricate interplay between the toll‐like receptor 4 (TLR4)/nuclear factor kappa light chain enhancer of activated B cells (NF‐kB) pathway and the cytochrome P450 2E1 (CYP2E1)/reactive oxygen species (ROS)/nuclear factor erythroid 2‐related factor 2 (Nrf2) pathway. These molecular events underlie the detrimental effects of chronic alcohol intake on internal organs and reproductive health, disrupting the delicate balance between inflammatory and antioxidant responses. 1 , 2 , 3

The TLR4/NF‐kB pathway, crucial for inflammatory and immune responses, recognizes pathogen‐associated molecular patterns (PAMPs) in microorganisms. 4 , 5 Chronic alcohol consumption disrupts gut microbial equilibrium, increasing permeability to PAMPs and causing inflammation in internal organs like the heart, brain, and lungs. 2 , 6 The CYP2E1/ROS/Nrf2 pathway, initiated by alcohol metabolism, leads to oxidative stress and cellular damage. Nrf2 acts as a countermeasure, regulating gene expression to restore the disrupted balance. 7 This review also explores alcohol's negative impact on reproductive health, inhibiting the hypothalamic–pituitary‐gonadal (HPG) axis and causing infertility. 8 , 9 Exploring the TLR4 signal pathway, we examine its structure, activation mechanisms, and downstream pathways, emphasizing their roles in alcohol‐induced damage. In summary, this exploration highlights the complex nature of immune responses and the urgent need for public awareness regarding the widespread health consequences of excessive alcohol consumption.

2 TLR4 SIGNAL PATHWAY: UNVEILING THE INTRICACIES OF HOST DEFENSE

Excessive alcohol consumption increases the intestinal level of miR‐212 that binds to the tight junction of epithelial cells, namely zona occludens‐1 (ZO‐1), inhibiting the synthesis of its mRNA. This increases the gut permeability to PAMPs such as fungi, bacteria, parasites and viruses, enabling the translocation of bacteria from intraintestinal lumen into extraintestinal space, transporting alcohol molecule to the blood stream, and activating the TLR4 signal pathway. 10 , 11 TLR4 is a transmembrane protein that recognizes lipopolysaccharide (LPS), one of the components found in the outer membrane of Gram‐negative bacteria, and it stimulates the immune response against these bacteria. 12 , 13 , 14 , 15 In the membrane, TLR4 monomers are associated with adaptor protein myeloid differentiation factor 2 (MD‐2), and cluster of differentiation 14 (CD‐14). 16 , 17 , 18 In the extracellular fluid, LPS is bound by LPS‐binding protein (LBP), then transferred to CD‐14, which allows interaction with the MD‐2/TLR4 complex. 13 , 14 The dimerization of TLR4 occurs after formation of the final activated heterodimer (LPS/MD/TLR4)2 on the extracellular side, and interaction between two toll‐interleukin receptor (TIR) domains and the two TLR4 monomers on the intracellular side. 19 , 20 This process activates the intracellular signals, which are the myeloid differentiation primary response 88 (My‐D88) dependent pathway and the TIR‐domain‐containing adapter‐inducing interferon‐β (TRIF) dependent pathway. 21 , 22 The MyD88, TIR domain, toll interleukin 1 receptor adaptor protein (TIRAP), TRIF‐related adaptor molecule (TRAM) and TRIF are necessary for both pathways to occur 23 (Figure 1).

FIGURE 1 Toll‐like receptor 4 (TLR4) signal pathway, highlighting key molecular interactions and signaling events involved in the recognition of lipopolysaccharide (LPS) and subsequent activation of downstream pathways.

Chronic alcohol consumption activates the TLR4/NF‐κB pathway, inducing a cascade of pro‐inflammatory responses that contribute to tissue damage in internal organs such as the liver. Activation of NF‐κB triggers the release of inflammatory mediators and cytokines, promoting inflammation and tissue injury over time. This mechanism highlights the intricate interplay between alcohol‐induced inflammation and the development of organ damage.

3 MY‐D88 DEPENDENT PATHWAY: UNRAVELING THE ROLE OF PRO‐INFLAMMATORY CYTOKINES

As shown in Figure 2, In the MyD88‐dependent pathway, the TIR‐TIR dimer recruits TIRAP, which contains a phosphatidylinositol 4,5‐biphosphate‐binding domain, serving as a site to join with MyD88. 19 , 24 MyD88 binds to interlukin‐1 receptor‐associated kinases 2 (IRAK 2) and interlukin‐1 receptor‐associated kinases 4 (IRAK4), forming myddosome. 20 , 25 This process leads to autophosphorylation of IRAK4 and phosphorylation of IRAK1 by IRAK4. 23 , 26 TNF receptor associated factor 6 (TRAF6) forms a trimer with phosphorylated IRAK1, and attaches itself to the amino acid lysine at position 63 (Lys63) by polyubiquitin chains, which combine with adaptor protein TAK‐1 binding protein 2/TAK‐1 binding protein 3 (TAB2/TAB3). 27 This complex activates TGF‐beta activated kinase (TAK‐1) protein, which phosphorylates the inhibitor of the nuclear factor kB (IkB) kinase (IKK) complex, thereby activating it to unmask the nuclear localization of NF‐kB by NF‐kB inhibitor alpha (IkBα). 22 , 26 , 27 NF‐kB enters the nucleus and drives the transcription of genes that produce pro‐inflammatory cytokines and chemokines. 16 , 23 Furthermore, there is another signaling branch coming from TAK‐1 protein which activates the mitogen‐activated protein kinases (MAPKs). The MAPKs recruit c‐Jun NH2‐terminal kinase (JNK) protein, which phosphorylates the activating protein‐1 (AP‐1) transcription factor to transcribe pro‐inflammatory cytokines and chemokines, resulting in recruitment of inflammatory cells. 28

FIGURE 2 The figure depicts the MyD88‐dependent pathway, elucidating the molecular events from TLR4 activation to the transcription of pro‐inflammatory cytokines. Key interactions involving TIRAP, MyD88, IRAKs, TRAF6, TAK‐1, and downstream signaling components. IRAK, interlukin‐1 receptor‐associated kinases; TIRAP, toll interleukin 1 receptor adaptor protein; TLR4, toll‐like receptor 4; TRAF6, TNF receptor associated factor 6.

4 TRIF‐DEPENDENT PATHWAY: UNVEILING THE INFLUENCE ON TYPE‐1 INTERFERONS

In the TRIF‐dependent pathway, TRIF‐related adaptor molecule (TRAM) protein, which is a membrane‐bound bridging adaptor, is recruited to TIR domain. 20 , 22 , 25 It recruits and activates TRIF, followed by activation of receptor‐interacting serine/threonine‐protein kinase 1 (RIP‐1), TNF receptor associated factor 3 (TRAF‐3), TANK‐binding kinase 1 (TBK‐1), and interferon regulatory factor 3 (IRF‐3) proteins, which will be phosphorylated and transferred into the nucleus to initiate transcription of type‐1 interferon gene. 29

Type‐1 IFN binds to a heterodimeric transmembrane receptor that contains subunits of interferon alpha and beta receptor subunit 1 (IFNAR1) and interferon alpha and beta receptor subunit 2 (IFNAR2). Ligation of IFNAR activates the receptor‐associated protein tyrosine kinases Janus kinase 1 (JAK1), tyrosine kinase 2 (TYK2), signal transducer and activator of transcription 1 (STAT1) and signal transducer and activator of transcription 2 (STAT2) molecules. STAT 1 and STAT 2 dimerize, translocate into the nucleus and bind to interferon regulatory factor 9 (IRF9) to produce ISG factor 3 (ISGF3) complex associated with IFN‐stimulated response elements. Transcription of ISG is activated, which gives the immune cells antiviral, antibacterial and anti‐apoptotic properties. 30 , 31

Type‐1 interferon limits the spread of infectious agents, promotes antigen presentation, regulates the function of natural killer cell, stimulates T and B cells responses and induces immunological memory, 23 as expressed in the Figure 3.

FIGURE 3 The figure depicts the TRIF‐dependent pathway, outlining molecular events from TLR4 activation to type‐1 interferon gene transcription. It also illustrates downstream signaling initiated by type‐1 interferon binding to its receptor, featuring key interactions with TRAM, TRIF, RIP‐1, TRAF‐3, TBK‐1, IRF‐3, IFNAR1, IFNAR2, JAK1, TYK2, STAT1, STAT2, and IRF9. IFNAR1, interferon alpha and beta receptor subunit 1; IRF‐3, interferon regulatory factor 3; JAK1, Janus kinase 1; RIP‐1, receptor‐interacting serine/threonine‐protein kinase 1; STAT1, signal transducer and activator of transcription 1; TBK‐1, TANK‐binding kinase 1; TLR 4, toll‐like receptor 4; TRAF‐3, TNF receptor associated factor 3; TRAM, TRIF‐related adaptor molecule; TRIF, TIR‐domain‐containing adapter‐inducing interferon‐β; TYK2, tyrosine kinase 2.

5 NF‐KB SIGNAL PATHWAY: ORCHESTRATING THE SYMPHONY OF IMMUNE RESPONSES

NF‐kB is a transcription factor, which regulates a wide range of genes to produce proteins that are involved in immune and inflammatory responses. 32 , 33 , 34 Its nuclear localization is often masked by a family of inhibitory proteins, which includes family members of IkB and precursor proteins. It is unmasked by degradation of these inhibitory proteins through phosphorylation. After nuclear translocation, it binds with the specific DNA component, kB enhancer to form heterodimers or homodimers, initiating the transcription process of the gene. 35

There are two different signaling pathways, which are the canonical and noncanonical pathways. 36 The canonical pathway involves in all aspects of immune responses, and responds to large number of stimuli, including pattern‐recognition receptors (PRRs), TNF receptor (TNFR), cytokine receptors, T‐cell receptor and B‐cell receptor. 37 The activation of NF‐kB is induced by degradation of IkBα through phosphorylation by the IKK complex at two N‐terminal serines, leading to nuclear translocation of canonical NF‐kB. 32 , 38 , 39 , 40 In contrast to the canonical NF‐kB pathway, the noncanonical pathway cooperates with the canonical pathway in stimulation of adaptive immune responses, and selectively responds to a specific group of stimuli, including members of TNFR such as lymphotoxin beta receptor (LTBR), cluster of differentiation 40 (CD40), B‐cell activating factor receptor (BAFFR) and receptor activator of nuclear factor kB (RANK) 41 , 42 (Figure 4). This pathway involves degradation of C‐terminal IkB‐like structure in NF‐kB2 precursor protein, p100, through phosphorylation by NF‐kB‐inducing kinase (NIK), leading to nuclear translocation of noncanonical NF‐kB. 43 , 44

FIGURE 4 The figure details the nuclear factor kappa light chain enhancer of activated B cells (NF‐kB) signaling pathway, highlighting canonical and noncanonical pathways, their mechanisms, and collaborative role in immune responses. It depicts key interactions, including NF‐kB, inhibitory proteins (IkB, p105, and p100), phosphorylation events, and specific receptors.

6 CYP2E1 SIGNAL PATHWAY: DECODING THE INTRICATE INTERPLAY WITHIN THE CNS

CYP2E1 is a major alcohol‐metabolizing enzyme in the brain that leads to production of ROS and acetaldehyde, which damage the liver and the other internal organs. 45 , 46 Results from certain studies suggested the involvement of CYP2E1 in alcohol metabolism in neuron is greater than alcohol dehydrogenase (ADH), as ADH is known to have low level in these cells. 47 In the brain, CYP2E1 is the only enzyme involved in ethanol oxidation and ROS production, leading to lipid peroxidation, oxidative stress, and apoptosis. 47 , 48 , 49 , 50 If chronic alcohol consumption is continued, the permeability of the blood–brain barrier increases, and mitochondrial dysfunction causes neurodegeneration through entry of neurotoxic substances such as toxins, pathogens, inflammatory molecules, and harmful proteins. 51 , 52 , 53

Some studies have also suggested that CYP2E1 has a major role in microsomal ethanol oxidizing system (MEOS), as it catalyzes the oxidation of ethanol. 49 , 52 Chronic alcohol consumption leads to a decrease in the level of antioxidants such as catalase, superoxide dismutase, and glutathione S‐transferase, resulting in cellular damage due to oxidative stress. For instance, an increase in MEOS activity leads to proliferation of smooth endoplasmic reticulum (SER), causing ER stress because there is imbalance between the need for protein folding and the capacity of ER. 52 To respond to ER stress, a signaling pathway known as the unfolded protein response (UPR) is activated which can trigger cell death if the stress is severe and prolonged. 54 In addition to that, an increase in CYP2E1 due to high MEOS activity inhibits the function of ADH, resulting in accumulation of acetaldehyde. The combination of high ROS and acetaldehyde damages DNA and protein, reduces oxygen uptake by liver cells and increases glutathione depletion, thereby inhibiting tissue building and repair 52 (Figure 5).

FIGURE 5 The figure illustrates the Cytochrome P450 2E1 (CYP2E1) signaling pathway in the central nervous system (CNS), emphasizing its role in ethanol metabolism and associated tissue damage risks. It depicts key interactions, including CYP2E1, ethanol metabolism, reactive oxygen species (ROS) production, oxidative stress, and downstream effects on CNS cells.

7 ROS PATHWAY: EXPLORING THE IMPACT ON INFLAMMATION AND CELL FATE

As shown in Figure 6, ROS are small molecules that are temporarily present inside the body and are highly reactive. 55 They can be oxygen‐derived free radical molecules such as hydroxyl radicals (OH•) and superoxide anions (O2 •−) or non‐radical molecules such as hydrogen peroxide (H2O2). 56 , 57 Production of ROS is caused by environmental stress attributed to xenobiotics, which are toxic compounds such as heavy metals, microparticles, nanoparticles, quinone compounds, inflammatory cytokines, environmental toxins, various pharmaceutical agents, UV radiation, ionizing radiation, aldehydes and pesticides that can be catalyzed by NADPH oxidases, xanthine oxidases and cytochrome P450 reductase to produce free radicals. 57 , 58 , 59 , 60 When these radicals react with oxygen, they will generate superoxide anions (O2 •−) which either react with nitric oxide (NO•), a reactive nitrogen species (RNS), to produce peroxynitrite (ONOO−), or are catalyzed by superoxide dismutase (SOD) to produce H2O2. 61 H2O2 will either be detoxified by antioxidants such as catalase and glutathione peroxidase to produce water or will undergo the Fenton reaction to produce OH• through reduction. The production of free radical molecules leads to damage to macromolecules such as proteins, lipids, and nucleic acids when there is an imbalance between production of ROS and the antioxidant defenses against ROS, causing oxidative stress and cell apoptosis. 56 , 60

FIGURE 6 The figure depicts the influence of reactive oxygen species (ROS) pathways on cell fate and inflammation, emphasizing its multifaceted impact on survival, death, differentiation, and anti‐inflammatory factor production. Key interactions involving ROS, free radicals, environmental stressors, production pathways, and downstream effects on macromolecules are shown.

8 NRF2 PATHWAY: UNVEILING CELLULAR DEFENSE MECHANISMS AGAINST OXIDATIVE STRESS AND INFLAMMATION

Nrf2 is a transcription factor that contributes to anti‐inflammatory and detoxification processes by regulating gene expression to inhibit inflammatory progression due to oxidative damage. 62 Once the inflammatory response is activated, the immune cells such as lymphocytes, mast cells and monocytes are recruited to the site of injury and generate the production of ROS that damage the macromolecules. 63 , 64 , 65 This process can be inhibited by an anti‐inflammation response by Nrf2.

Nrf2 consists of seven domains, one of which is Nrf2‐ECH homology (Neh)2. 66 It contains DLG and ETGE, which serve as attachments that interact with Nrf2 and Kelch‐like ECH‐associated protein 1 (Keap1), which inhibits the transcription of Nrf2 to activate antioxidant mechanisms through proteasomal degradation and ubiquitination. 67 , 68 Under oxidative stress, Nrf2 dissociates from Keap1 binding due to modification of Keap1. 62 , 69 Activated Nrf2 translocates into the nucleus and binds with small musculoaponeurotic fibrosarcoma (Maf) protein, activating the antioxidant response element (ARE) genes. 68 , 69 , 70 , 71 Nrf2 binds with ARE genes such as heme oxygenase 1 (HO‐1) to deactivate the inflammatory response. 72 HO‐1 breaks down heme into carbon monoxide (CO) and free ions and breaks down biliverdin into bilirubin. 65 , 73 Degradation of pro‐inflammatory free heme leads to reduced production of proinflammatory cytokines. CO acts as an anti‐inflammatory compound that inhibits the NF‐kB signaling pathway, while bilirubin acts as a strong antioxidant that protects the cells from oxidative stress, and suppresses hepatitis and autoimmune encephalomyelitis, a condition where the body's immune system attacks the brain. 73

There are three ways for Keap1/Nrf2/ARE signaling pathway to inhibit generation of NF‐kB, thereby inhibiting the production of proinflammatory cytokines. First, Keap1 degrades IKKβ through ubiquitination and proteosome degradation, inhibiting the phosphorylation of inhibitory proteins and preventing NF‐kB from translocating into the nucleus for gene transcription. 74 Second, oxidative stress activates the transcription of NF‐kB to produce proinflammatory cytokines such as cyclooxygenase‐2 (COX‐2). The terminal product of COX‐2, 15‐deoxy‐Δ 12 , 14 ‐prostaglandin J2 (15d‐PGJ2), induces the Nrf2 pathway. 75 Third, Nrf2 binds with CREB‐binding protein (CBP), small Maf and other transcriptional cofactors to drive the transcription of ARE genes. 76 Both activation and inhibition occur between NF‐kB pathway and Nrf2 pathway. Increased expression of Nrf2 inhibits NF‐kB transcriptional activity while decreased expression of Nrf2 increases NF‐kB transcriptional activity, showing that there is balance between inflammatory and anti‐inflammatory responses 72 , 77 , 78 (Figure 7).

FIGURE 7 The figure depicts the role of the nuclear factor erythroid 2‐related factor 2 (Nrf2) pathway in anti‐inflammation and defense against oxidative stress. It shows key interactions, including Nrf2, Keap1, and ARE gene activation, and downstream effects on inflammatory mediators and cell adhesion molecules.

9 ALCOHOL'S MULTI‐ORGAN IMPACT: UNDERSTANDING THE COMPLEXITIES OF INTERNAL ORGAN DAMAGE

After alcohol is ingested, it is absorbed from the small intestine into the veins that collect blood from the stomach and bowels and is then carried to the liver via the portal vein. Alcohol readily diffuses across membranes and distributes through all cells and tissues and affects cell function by producing harmful byproducts and interacting with certain protein and cell membranes, stimulating the immune signaling pathway. 79 , 80 At high concentrations or during chronic alcohol consumption, alcohol is eliminated at a high rate and metabolizing enzymes are overproduced because of high enzymatic activity. 81

Alcohol is metabolized by two different pathways, namely oxidative and non‐oxidative pathways. In the oxidative pathway, ADH metabolizes alcohol and generates acetaldehyde, which forms ROS after it reacts directly with oxygen. 82 This reaction involves the reduction of +nicotinamide adenine dinucleotide (NAD+) by two electrons, forming nicotinamide adenine dinucleotide + hydrogen (NADH). This process mainly occurs in the liver as ADH is located in the cytosol of liver cells. 83 Acetaldehyde, ADH, ROS, and NADH produced from this reaction are harmful to body tissues and organs. Acetaldehyde interacts with certain proteins such as lipoproteins, tubulin, hemoglobin, albumin, collagen, and cytochrome enzymes to form adducts, which will be recognized as foreign substance and attacked by immune cells, causing liver inflammation. ADH forms adducts with dopamine in the brain to form salsolinol, which may cause alcohol dependence, and with DNA to form carcinogenic DNA adducts, producing cancerous cells, and developing alcohol‐associated tumors. 84 ADH also binds to proteins such as microtubules, microsomal proteins, and enzymes to form protein adducts, which impair protein secretion, causing enlargement of liver, known as hepatomegaly. 85 , 86 ROS activate the body defense mechanism and stimulate the release of inflammatory cytokines, such as tumor necrosis factor alpha (TNF‐α), that can contribute to scar tissue formation in the liver due to inflammation, known as fibrosis. 87 Furthermore, ROS combine with DNA, lipids and proteins, and alter the membrane permeability of mitochondria through peroxidation, causing molecules contained in the mitochondria, such as cytochrome c, to be released into the cytosol, inducing a cascade of biochemical reactions that cause cell death. 88 , 89 ROS also alter the distribution of electrical charges across the mitochondrial membrane, reducing the level of adenosine triphosphate (ATP), and disrupting the cellular respiration process that stores energy for cell survival. The production of NADH from this reaction increases the NADH: NAD+ ratio, resulting in more electrons passing through the electron transport chain, and attaching to free oxygen to form superoxide radicals, causing tissue damage. 90 , 91 , 92 , 93

Two pathways of alcohol metabolism occur in non‐liver tissues such as brain, heart, and lungs that do not contain ADH or contain only low levels ADH. This type of metabolism is catalyzed by CYP2E1 and catalase. 94 CYP2E1 is an enzyme present in the microsomes that metabolizes alcohol into acetaldehyde when there is high rate of consumption of alcohol. 95 CYP2E1 disrupts the CYP2E1‐mediated metabolism of medication such as pain killers, blood thinners, propranolol, and the sedative diazepam, as during chronic alcohol consumption more of this enzyme is used to metabolize alcohol, causing a reduction in the efficacy of the medication. Moreover, CYP2E1 activates the pro‐carcinogens found in tobacco smoke, increasing the risk of getting cancer in the esophagus, oral cavity, and larynx. 96 , 97

After oxidation of alcohol into acetaldehyde has occurred, acetaldehyde is further oxidized into acetate by aldehyde dehydrogenase 2 (ALDH2), and NAD+ is simultaneously reduced to NADH. This process primarily occurs in liver, so any damage caused associated with alcohol metabolism by these enzymes would affect that organ. 98 , 99 The production of acetate and NADH by this reaction leads to adverse effects in different organs. Acetate escapes from the liver into the blood and is further oxidized into carbon dioxide (CO2) in heart, skeletal muscle, and brain, damaging the CNS and other metabolic processes occuring in the affected organs. 85 Acetate is also metabolized to acetyl coenzyme A (acetylCoA) which is involved in the biosynthesis of lipid and cholesterol in mitochondria of peripheral and brain tissues. 100 The production of NADH has the potential to cause liver cell damage due to oxygen deficit in these cells, known as hypoxia. This is because NADH is oxidized by a series of chemical reactions in mitochondria that transfer electrons to oxygen (O2), forming oxide ions (O2−). This reaction increases the demand for oxygen because more oxygen is needed to accept the electrons, causing a lack of oxygen to carry out cellular respiration, and eventually leading to cell death, 101 , 102 as shown in Figure 8.

FIGURE 8 The figure shows alcohol's impact on organs, focusing on absorption, metabolism, and effects on various systems. Key interactions include alcohol metabolism, liver damage, oxidative stress, and downstream effects on tissues.

10 NONOXIDATIVE PATHWAY: UNRAVELING THE VARIED MANIFESTATIONS OF ALCOHOL‐INDUCED DAMAGE

Besides the oxidative pathway, a smaller fraction of alcohol is metabolized through a non‐oxidative pathway to produce metabolites such as ethyl glucuronide (EtG), ethyl sulphate (EtS), phosphatidylethanol (PEth) and fatty acid ethyl ester (FAEE) that will cause tissue damage. These are the biomarkers of alcohol consumption, and they will be detected in the blood, urine or hair of heavy drinkers over a longer period than in light drinkers. 103 , 104 Although a relatively small portion of alcohol is metabolized through this pathway, the damaging effects of will be prolonged due to the slower elimination of the metabolites through excretion; the metabolites will remain in the body fluids longer than alcohol. 105

EtG is formed when the enzyme glucuronyl moiety from uridine 5′‐diphospho (UDP)‐ glucuronic acid is transferred to ethanol, catalyzed by UDP‐ glucuronosyltransferases (UGTs), while Ets is formed by sulphonation of ethanol, which is catalyzed by sulphotransferases (SULT). 106 EtG has been shown to activate TLR4 signaling, causing allodynia, which is the condition where a stimulus that normally does not cause pain causes a feeling of pain. 107

PEth is formed by transphosphotidylation of phospholipids with ethanol, catalyzed by phospholipase D (PLD). 82 , 105 If there is a high concentration of alcohol, PEth synthesis disrupts other PLD‐mediated cellular processes such as synthesis of phosphatidic acid (PA), as PLD is needed in those processes. 108 Studies have shown that formation of PEth promotes intestinal hyperplasia, which is the change in the mucous membrane of stomach and intestinal epithelium associated with cancer development, and influences other phospholipid signaling pathways that affect structural properties, and the function and fluidity of biomembranes. 105 , 109

FAEEs are formed through the enzymatic esterification of ethanol with fatty acids, catalyzed by FAEE synthase (FAEES). FAEEs cause ethanol‐induced toxicity, which leads to inhibition of cell proliferation, destabilization of lysosomes, mitochondrial depolarization, and induction of apoptosis. 110 , 111 The combination of ethanol and fatty acids also causes inflammation, necrosis, alcoholic pancreatitis, mitochondrial depolarization, depletion of cellular ATP and sustained elevations of intracellular Ca2+ 112 (Figure 9).

FIGURE 9 Nonoxidative pathway‐mediated alcohol damage. The figure illustrates the diverse effects of alcohol‐induced tissue damage, highlighting the biomarker metabolites (EtG, EtS, PEth, FAEE) and their impact on cellular signaling and organelle functions.

11 IMPACTS OF ALCOHOL ON REPRODUCTIVE HEALTH: UNVEILING GENDER‐SPECIFIC RAMIFICATIONS

11.1 Effects of alcohol on female reproductive health

Acute alcohol consumption in females significantly increases oestradiol, causing alterations in oestrous cycling. 113 The increase in testosterone caused by chronic alcohol consumption suppresses the HPG unit. 114 Some studies have shown that the effect includes a reduction in the level of estrogen, which alters maturation of follicles. Low estrogen levels decrease the secretion of luteinizing hormone‐releasing hormone (LHRH) from the hypothalamus, causing a decrease in luteinizing hormone (LH) production, and inhibiting ovulation. 115 Besides its effect on HPG activity, chronic alcohol consumption can also affect female reproduction via the opioid pathway. Research has shown that alcohol increases opioid activity in the brain, inhibiting the secretion of hypothalamic LHRH and inhibiting the HPG axis. 116 , 117 Alcohol also lowers the level of insulin‐like growth factor (IGF‐1) in the bloodstream, which has the function of activating LHRH release and increasing the production of LH. 118 , 119 All these disruptions in hormone levels in the reproductive system cause irregular menstrual cycles, inhibition of ovulation, infertility, and early menopause. Besides suppressing ovulation, heavy alcohol consumption can affect ovarian reserves, which are a measure of a woman's reproductive potential, based on the number of oocytes available in the ovary during the woman's lifetime. This can be determined by measuring the levels of follicle stimulating hormone (FSH) and anti‐Mullerian hormone (AMH), with low levels indicating a lower reproductive potential due to binge drinking alcohol. 120 , 121 , 122

11.2 Effects of alcohol on male reproductive health

Chronic alcohol consumption in males disrupts the hypothalamic–pituitary‐testicular (HPT) axis, affecting the male reproductive glands by significantly reducing the level of gonadotropin releasing hormone (GnRH) due to the disruption of the nitric oxide (NO) pathway. Excessive alcohol consumption prevents NO from binding to the heme group of cyclooxygenase‐1, which helps in the synthesis of GnRH, because alcohol inhibits cyclooxygenase activity. 9 As a result, the levels of LH and FSH will be reduced as GnRH triggers their production in the pituitary gland, causing a reduction in testosterone levels and numbers of Leydig cells. 123 Low levels of FSH and LH will also cause loss of secondary sexual characteristics such as erectile dysfunction, issues with arousal and desire, infertility, hypogonadism, reduced sperm production, and impotence. 9 Besides inhibition of the HPT axis, high alcohol consumption also reduces testosterone levels by stimulating the activity of aromatase which converts testosterone to oestradiol. When the estrogen level is elevated, the synthesis of FSH and GnRH is inhibited, which results in low sperm production. 124 , 125 In addition, production of ROS from alcohol metabolism causes protein and DNA damage in the sperm cells, increased risk of cell apoptosis, abnormalities in meiotic division, reduced gamete viability, poorly condensed chromatin, and disruption in sperm maturation due to changes in gene regulation, changes in mitochondrial ribonucleic acid (RNA), and accelerated loss of the acrosome due to oxidative damage of membrane lipids and proteins that alters the membrane's permeability and lipid fluidity. This makes it difficult for the sperms to penetrate the egg's coat, reducing fertilizing rates. Furthermore, the production of ROS causes oxidative damage of the epididymis due to loss of antimicrobial properties as a result of altered mRNA expression of β‐defensin, and disruption in expression of proliferating cell nuclear antigen (PCNA) in germ cells, resulting in cell apoptosis, and reduced production of sperm cells, 125 , 126 , 127 as shown in Figure 10.

FIGURE 10 Alcohol's impact on reproductive health. This figure explores the gender‐specific effects of alcohol on reproductive health, highlighting disruptions in hormone levels. In females, alcohol alters oestradiol and testosterone, affecting the HPG unit and opioid pathway, leading to menstrual irregularities and infertility. In males, chronic alcohol consumption disrupts the hypothalamic‐pituitary‐gonadal (HPT) axis, reducing GnRH and gonadotropin levels, resulting in decreased testosterone production and reproductive dysfunctions.

Alcohol metabolism via Cytochrome P450 2E1 (CYP2E1) generates ROS, leading to oxidative stress in reproductive organs. This oxidative stress can disrupt cellular function, damage DNA, and impair reproductive hormone regulation, ultimately affecting fertility and reproductive health. Activation of the Nrf2 pathway serves as a protective mechanism against oxidative damage, but chronic alcohol consumption may overwhelm this defense mechanism, exacerbating reproductive dysfunction. Understanding these pathways provides insight into how alcohol impacts reproductive health at the molecular level, facilitating the development of targeted interventions to mitigate alcohol‐related reproductive issues.

11.3 Gender differences in alcohol‐induced damage

Previous studies have shown that negative psychological effects due to problematic drinking are more significant in women than men, as there is gender difference in alcohol pharmacokinetics and neurotransmitter systems and the influence on these of gonadal steroid hormones. In terms of pharmacokinetics, women have a higher blood alcohol concentration than men despite consuming the same amount of alcohol because women have a lower proportion of body water than men, and ADH activity in stomach and liver in women is lower than in men due to a difference in gastric mucosa ADH activity. Thus, an alcohol molecule in women takes longer to be metabolized, resulting in a more persistent high alcohol blood level in women compared to men after consumption of alcohol. Regarding neurotransmitters, there is a difference in neurotransmitter release and neurotransmitter receptor subunit expression between men and women in response to alcohol consumption. In addition, the effect of alcohol consumption on gonadal hormones in women is greater, and many neurobiological responses are affected by changes in estrogen levels, and the concentration of serotonin and serotonin‐receptor subtypes, increasing the risk of depression or mental health issues in women after chronic alcohol consumption. 128 Therefore, it is important for healthcare practitioners and policymakers to work together to mitigate alcohol‐induced damage and alcohol abuse through various clinical interventions such as screening, brief interventions, and referral for treatment (SBIRT). In terms of screening, the U.S. Preventive Task Force recommends the Alcohol Use Disorders Identification Test (AUDIT) to assess the frequency of alcohol consumption. Brief interventions can range from brief written or verbal advice to motivational interviews with trained advisers offering suggestions on the patient's behavior in relation to alcohol consumption. Referral for treatment will be more effective among populations with severe alcohol‐related problems as it involves more intensive interventions. 129

12 CONCLUSION

In conclusion, TLR/NF‐kB plays a pivotal role in inflammatory and immune responses to excessive alcohol consumption, increasing the likelihood of bacterial endotoxins invading liver cells due to chronic alcohol consumption. On the other hand, CYP2E1/ROS/Nrf2 is a key pathway in oxidative stress and antioxidant responses. The excessive production of liver enzymes and the generation of ROS, NADH, acetaldehyde, and acetate can lead to damage in internal organs such as the heart, brain, and lungs. Furthermore, excessive alcohol intake adversely affects reproductive health by inhibiting the HPG unit, resulting in infertility.

AUTHOR CONTRIBUTIONS

E.K.Q.Z and V.S. conceived and designed the structure of the review. E.K.Q.Z conducted literature research and drafted the entire manuscript. V.S. and N.S.A.L edited the manuscript. E.K.Q.Z and V.S. contributed to the key parts of the text associated with it. All authors have read and agreed to the published version of the manuscript.

FUNDING INFORMATION

There is no funding support for this review study. The entire study was supported by the Jeffrey Cheah School of Medicine and Health Sciences and the Library Resources, Monash University Malaysia.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflict of interest.

ETHICS STATEMENT

Ethical approval was not required for this review study as it did not involve primary data collection or human or animal subjects. The entire study was supported by the Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia.

ACKNOWLEDGMENTS

We express our sincere gratitude to Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia for providing the necessary support that enabled the completion of this study. Open access publishing facilitated by Monash University, as part of the Wiley ‐ Monash University agreement via the Council of Australian University Librarians.
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REFERENCES

1 Walke G , Gaurkar SS , Prasad R , Lohakare T , Wanjari M . The impact of oxidative stress on male reproductive function: exploring the role of antioxidant supplementation. Cureus. 2023;15 (7 ): e42583.37641770
2 Simon L , Souza‐Smith FM , Molina PE . Alcohol‐associated tissue injury: current views on pathophysiological mechanisms. Annu Rev Physiol. 2022;84 :87‐112.35143331
3 Subramaniyan V , Lubau NSA , Mukerjee N , Kumarasamy V . Alcohol‐induced liver injury in signalling pathways and curcumin's therapeutic potential. Toxicol Rep. 2023;11 :355‐367.37868808
4 Dejban P , Nikravangolsefid N , Chamanara M , Dehpour A , Rashidian A . The role of medicinal products in the treatment of inflammatory bowel diseases (IBD) through inhibition of TLR4/NF‐kappaB pathway. Phytother Res. 2021;35 (2 ):835‐845.32929778
5 Wu Z , Mehrabi Nasab E , Arora P , Athari SS . Study effect of probiotics and prebiotics on treatment of OVA‐LPS‐induced of allergic asthma inflammation and pneumonia by regulating the TLR4/NF‐kB signaling pathway. J Transl Med. 2022;20 (1 ):130.35296330
6 Liu X , Vigorito M , Huang W , Khan MA , Chang SL . The impact of alcohol‐induced dysbiosis on diseases and disorders of the central nervous system. J Neuroimmune Pharmacol. 2022;17 (1–2 ):131‐151.34843074
7 Saha S , Buttari B , Panieri E , Profumo E , Saso L . An overview of Nrf2 signaling pathway and its role in inflammation. Molecules. 2020;25 (22 ):5474.33238435
8 Heidarzadeh S , Azarbayjani MA , Matin Homaei H , Hedayati M . Evaluation of the effect of aerobic exercise and curcumin consumption on HPG Axis (hypothalamus‐pituitary‐gonadotropic) in alcohol binge drinking rats. Nutr Food Sci Res. 2020;7 (2 ):13‐19.
9 Finelli R , Mottola F , Agarwal A . Impact of alcohol consumption on male fertility potential: a narrative review. Int J Environ Res Public Health. 2021;19 (1 ):328.35010587
10 Kany S , Janicova A , Relja B . Innate immunity and alcohol. J Clin Med. 2019;8 (11 ):1‐31. doi:10.3390/jcm8111981
11 Subramaniyan V , Chakravarthi S , Jegasothy R , et al. Alcohol‐associated liver disease: a review on its pathophysiology, diagnosis and drug therapy. Toxicol Rep. 2021;8 :376‐385. doi:10.1016/j.toxrep.2021.02.010 33680863
12 Naoto K . Chapter 11—The role of stem cells in the hepatobiliary system and in cancer development: a Surgeon's perspective. In: Yun‐Wen Z , ed. Stem Cells and Cancer in Hepatology. Academic Press; 2018:211‐253.
13 Kuzmich NN , Sivak KV , Chubarev VN , Porozov YB , Savateeva‐Lyubimova TN , Peri F . TLR4 signaling pathway modulators as potential therapeutics in inflammation and sepsis. Vaccines (Basel). 2017;5 (4 ):1‐25. doi:10.3390/vaccines5040034
14 Adams JL , Duffy KJ , Moore ML , Yang J . 5.11—Cancer immunotherapy—an emerging field that bridges oncology and immunology research. In: Samuel C , David R , Simon EW , eds. Comprehensive Medicinal Chemistry III. Elsevier; 2017:357‐394.
15 Fox CB , Carter D , Kramer RM , Beckmann AM , Reed SG . Chapter 6—Current status of toll‐like receptor 4 ligand vaccine adjuvants. In: Virgil EJCS , Derek TOH , eds. Immunopotentiators in Modern Vaccines. 2nd ed. Academic Press; 2017:105‐127.
16 Terry KM . Chapter 17—Toll‐like receptors in SLE. In: Robert GL , ed. Systemic Lupus Erythematosus. 5th ed. Academic Press; 2011:293‐306.
17 Yoshinori N , Kiyoshi T . Chapter 26—Role of the immune system in obesity‐associated inflammation and insulin resistance. In: Ronald Ross W , ed. Nutrition in the Prevention and Treatment of Abdominal Obesity. Academic Press; 2014:281‐293.
18 Allen TH , Brian MC , Henry K , Sean AP , Roland GWS . Chapter four—Recent developments in targeting Neuroinflammation in disease. In: Manoj CD , ed. Annual Reports in Medicinal Chemistry. Academic Press; 2012:37‐53.
19 Valkov E , Stamp A , DiMaio F , et al. Crystal structure of toll‐like receptor adaptor MAL/TIRAP reveals the molecular basis for signal transduction and disease protection. Proc Natl Acad Sci. 2011;108 (36 ):14879‐14884. doi:10.1073/pnas.1104780108 21873236
20 Enokizono Y , Kumeta H , Funami K , et al. Structures and interface mapping of the TIR domain‐containing adaptor molecules involved in interferon signaling. Proc Natl Acad Sci. 2013;110 (49 ):19908‐19913. doi:10.1073/pnas.1222811110 24255114
21 Mahsa K‐F , Nima R . Chapter 3—Vaccines, adjuvants, and delivery systems. In: Nima R , Mahsa K‐F , eds. Vaccines for Cancer Immunotherapy. Academic Press; 2019:45‐59.
22 Guven‐Maiorov E , Keskin O , Gursoy A , et al. The architecture of the TIR domain signalosome in the toll‐like Receptor‐4 signaling pathway. Sci Rep. 2015;5 (1 ):13128. doi:10.1038/srep13128 26293885
23 Lin S‐C , Lo Y‐C , Wu H . Helical assembly in the MyD88–IRAK4–IRAK2 complex in TLR/IL‐1R signalling. Nature. 2010;465 (7300 ):885‐890. doi:10.1038/nature09121 20485341
24 Lin Z , Lu J , Zhou W , Shen Y . Structural insights into TIR domain specificity of the bridging adaptor mal in TLR4 signaling. PLoS One. 2012;7 (4 ):e34202. doi:10.1371/journal.pone.0034202 22485159
25 Gay NJ , Symmons MF , Gangloff M , Bryant CE . Assembly and localization of toll‐like receptor signalling complexes. Nat Rev Immunol. 2014;14 (8 ):546‐558. doi:10.1038/nri3713 25060580
26 Ferrao R , Zhou H , Shan Y , et al. IRAK4 dimerization and <em>trans</em>‐autophosphorylation are induced by Myddosome assembly. Mol Cell. 2014;55 (6 ):891‐903. doi:10.1016/j.molcel.2014.08.006 25201411
27 Marene L . The TAK1–TRAF6 signalling pathway. Int J Biochem Cell Biol. 2010;42 (5 ):585‐589. doi:10.1016/j.biocel.2009.12.023 20060931
28 Ines A , Nataliya L , Gabriela G , Catharina S . Chapter 106—Urinary tract infections and the mucosal immune system. In: Jiri M , Warren S , Michael WR , Brian LK , Hilde C , Bart NL , eds. Mucosal Immunology. 4th ed. Academic Press; 2015:2039‐2058.
29 Liu S , Cai X , Wu J , et al. Phosphorylation of innate immune adaptor proteins MAVS, STING, and TRIF induces IRF3 activation. Science. 2015;347 (6227 ):aaa2630. doi:10.1126/science.aaa2630 25636800
30 Ivashkiv LB , Donlin LT . Regulation of type I interferon responses. Nat Rev Immunol. 2014;14 (1 ):36‐49. doi:10.1038/nri3581 24362405
31 McNab F , Mayer‐Barber K , Sher A , Wack A , O'Garra A . Type I interferons in infectious disease. Nat Rev Immunol. 2015;15 (2 ):87‐103. doi:10.1038/nri3787 25614319
32 Singh S , Singh TG . Role of nuclear factor kappa B (NF‐κB) signalling in neurodegenerative diseases: an mechanistic approach. Curr Neuropharmacol. 2020;18 (10 ):918‐935.32031074
33 Szatkowski P , Krzysciak W , Mach T , Owczarek D , Brzozowski B , Szczeklik K . Nuclear factor‐κB‐importance, induction of inflammation, and effects of pharmacological modulators in Crohn's disease. J Physiol Pharmacol. 2020;71 (4 ):453‐465.
34 Carrà G , Lingua MF , Maffeo B , Taulli R , Morotti A . P53 vs NF‐κB: the role of nuclear factor‐kappa B in the regulation of p53 activity and vice versa. Cell Mol Life Sci. 2020;77 :4449‐4458.32322927
35 Sun SC , Chang JH , Jin J . Regulation of nuclear factor‐κB in autoimmunity. Trends Immunol. 2013;34 (6 ):282‐289. doi:10.1016/j.it.2013.01.004 23434408
36 Sun SC . Non‐canonical NF‐κB signaling pathway. Cell Res. 2011;21 (1 ):71‐85. doi:10.1038/cr.2010.177 21173796
37 Zhang H , Sun SC . NF‐κB in inflammation and renal diseases. Cell Biosci. 2015;5 (1 ):63. doi:10.1186/s13578-015-0056-4 26579219
38 Iacobazzi D , Convertini P , Todisco S , Santarsiero A , Iacobazzi V , Infantino V . New insights into NF‐kB signaling in innate immunity: focus on Immunometabolic Crosstalks. Biology. 2023;12 (6 ):776.37372061
39 Gaptulbarova K , Tsyganov M , Pevzner A , Ibragimova M , Litviakov N . NF‐kB as a potential prognostic marker and a candidate for targeted therapy of cancer. Exp Oncol. 2020;42 (4 ):263‐269.33355866
40 Khongthong P , Roseweir AK , Edwards J . The NF‐KB pathway and endocrine therapy resistance in breast cancer. Endocr Relat Cancer. 2019;26 (6 ):R369‐R380.32013374
41 Sun SC . The noncanonical NF‐κB pathway. Immunol Rev. 2012;246 (1 ):125‐140. doi:10.1111/j.1600-065X.2011.01088.x 22435551
42 Sun SC , Liu ZG . A special issue on NF‐κB signaling and function. Cell Res. 2011;21 (1 ):1‐2. doi:10.1038/cr.2011.1 21196938
43 Moghadam YJ , Asadi MR , Abbaszadeh V , et al. Analysis of NFKB1 and NFKB2 gene expression in the blood of patients with sudden sensorineural hearing loss. Int J Pediatr Otorhinolaryngol. 2023;166 :111470.36773447
44 Laurindo LF , Santos AR , Carvalho ACA , et al. Phytochemicals and regulation of NF‐kB in inflammatory bowel diseases: an overview of in vitro and in vivo effects. Meta. 2023;13 (1 ):96.
45 Jin M , Ande A , Kumar A , Kumar S . Regulation of cytochrome P450 2e1 expression by ethanol: role of oxidative stress‐mediated pkc/jnk/sp1 pathway. Cell Death Dis. 2013;4 (3 ):e554. doi:10.1038/cddis.2013.78 23519123
46 Zhu L , Yang X , Feng J , et al. CYP2E1 plays a suppressive role in hepatocellular carcinoma by regulating Wnt/Dvl2/β‐catenin signaling. J Transl Med. 2022;20 (1 ):194. doi:10.1186/s12967-022-03396-6 35509083
47 García‐Suástegui WA , Ramos‐Chávez LA , Rubio‐Osornio M , et al. The role of CYP2E1 in the drug metabolism or bioactivation in the brain. Oxidative Med Cell Longev. 2017;2017 :4680732. doi:10.1155/2017/4680732
48 Lin Q , Kang X , Li X , et al. NF‐κB‐mediated regulation of rat CYP2E1 by two independent signaling pathways. PLoS One. 2019;14 (12 ):e0225531. doi:10.1371/journal.pone.0225531 31881060
49 Arnaud Fondjo K , Brice Ayissi O , Rodrigue F , Frédéric Nico N , Paul Fewou M . Inhibition of CYP2E1 and activation of Nrf2 signaling pathways by a fraction from Entada africana alleviate carbon tetrachloride‐induced hepatotoxicity. Heliyon. 2020;6 (8 ):e04602. doi:10.1016/j.heliyon.2020.e04602 32904230
50 Kim S‐M , Grenert JP , Patterson C , Correia MA . CHIP−/−‐mouse liver: adiponectin‐AMPK‐FOXO‐activation overrides CYP2E1‐elicited JNK1‐activation, delaying onset of NASH: therapeutic implications. Sci Rep. 2016;6 (1 ):29423. doi:10.1038/srep29423 27406999
51 Wang RY , Chen XW , Zhang WW , Jiang F , Liu MQ , Shen XB . CYP2E1 changes the biological function of gastric cancer cells via the PI3K/Akt/mTOR signaling pathway. Mol Med Rep. 2020;21 (2 ):842‐850. doi:10.3892/mmr.2019.10890 31974627
52 Jörn MS , Mark JC . Regulation of the effects of CYP2E1‐induced oxidative stress by JNK signaling. Redox Biol. 2014;3 :7‐15. doi:10.1016/j.redox.2014.09.004 25462060
53 Cao XL , Du J , Zhang Y , Yan JT , Hu XM . Hyperlipidemia exacerbates cerebral injury through oxidative stress, inflammation and neuronal apoptosis in MCAO/reperfusion rats. Exp Brain Res. 2015;233 (10 ):2753‐2765. doi:10.1007/s00221-015-4269-x 26238404
54 Read A , Schröder M . The unfolded protein response: an overview. Biology (Basel). 2021;10 (5 ):1‐10. doi:10.3390/biology10050384
55 Maureen R‐D , Diana AA‐B . Activation of apoptosis signalling pathways by reactive oxygen species. Biochim Biophys Acta. 2016;1863 (12 ):2977‐2992. doi:10.1016/j.bbamcr.2016.09.012 27646922
56 Nogueira V , Hay N . Molecular pathways: reactive oxygen species homeostasis in cancer cells and implications for cancer therapy. Clin Cancer Res. 2013;19 (16 ):4309‐4314. doi:10.1158/1078-0432.Ccr-12-1424 23719265
57 Perillo B , Di Donato M , Pezone A , et al. ROS in cancer therapy: the bright side of the moon. Exp Mol Med. 2020;52 (2 ):192‐203. doi:10.1038/s12276-020-0384-2 32060354
58 Finkel T . Signal transduction by reactive oxygen species. J Cell Biol. 2011;194 (1 ):7‐15. doi:10.1083/jcb.201102095 21746850
59 Zhang J , Wang X , Vikash V , et al. ROS and ROS‐mediated cellular signaling. Oxidative Med Cell Longev. 2016;2016 :4350965. doi:10.1155/2016/4350965
60 Villalpando‐Rodriguez GE , Gibson SB . Reactive oxygen species (ROS) regulates different types of cell death by acting as a rheostat. Oxidative Med Cell Longev. 2021;2021 :9912436. doi:10.1155/2021/9912436
61 Nakamura H , Takada K . Reactive oxygen species in cancer: current findings and future directions. Cancer Sci. 2021;112 (10 ):3945‐3952. doi:10.1111/cas.15068 34286881
62 Syed Minhaj Uddin A , Lin L , Akhileshwar N , Xiu Jun W , Xiuwen T . Nrf2 signaling pathway: pivotal roles in inflammation. Biochim Biophys Acta. 2017;1863 (2 ):585‐597. doi:10.1016/j.bbadis.2016.11.005
63 Mittal M , Siddiqui MR , Tran K , Reddy SP , Malik AB . Reactive oxygen species in inflammation and tissue injury. Antioxid Redox Signal. 2014;20 (7 ):1126‐1167. doi:10.1089/ars.2012.5149 23991888
64 Haftcheshmeh SM , Abedi M , Mashayekhi K , et al. Berberine as a natural modulator of inflammatory signaling pathways in the immune system: focus on NF‐κB, JAK/STAT, and MAPK signaling pathways. Phytother Res. 2022;36 (3 ):1216‐1230. doi:10.1002/ptr.7407 35142403
65 Hussain MS , Altamimi ASA , Afzal M , et al. Kaempferol: paving the path for advanced treatments in aging‐related diseases. Exp Gerontol. 2024;188 :112389. doi:10.1016/j.exger.2024.112389 38432575
66 He F , Ru X , Wen T . NRF2, a transcription factor for stress response and beyond. Int J Mol Sci. 2020;21 (13 ):1‐23. doi:10.3390/ijms21134777
67 Canning P , Sorrell FJ , Bullock AN . Structural basis of Keap1 interactions with Nrf2. Free Radic Biol Med. 2015;88 :101‐107. doi:10.1016/j.freeradbiomed.2015.05.034 26057936
68 Ian MC . The Keap1–Nrf2 cell defense pathway – a promising therapeutic target? In: Gabrielle MH , ed. Current Concepts in Drug Metabolism and Toxicology. Academic Press; 2012:43‐79.
69 Kim KM , Ki SH . Chapter 28—Nrf2: a key regulator of redox signaling in liver diseases. In: Pablo M , ed. Liver Pathophysiology. Academic Press; 2017:355‐374.
70 Hirotsu Y , Katsuoka F , Funayama R , et al. Nrf2–MafG heterodimers contribute globally to antioxidant and metabolic networks. Nucleic Acids Res. 2012;40 (20 ):10228‐10239. doi:10.1093/nar/gks827 22965115
71 Niture SK , Jaiswal AK . 2.26—Antioxidant induction of gene expression. In: Charlene AM , ed. Comprehensive Toxicology. 2nd ed. Elsevier; 2010:523‐528.
72 Veera GN , Shyam SS , Ashutosh K . Potential therapeutic effects of the simultaneous targeting of the Nrf2 and NF‐κB pathways in diabetic neuropathy. Redox Biol. 2013;1 (1 ):394‐397. doi:10.1016/j.redox.2013.07.005 24024177
73 Haines DD , Tosaki A . Heme degradation in pathophysiology of and countermeasures to inflammation‐associated disease. Int J Mol Sci. 2020;21 (24 ):1‐25. doi:10.3390/ijms21249698
74 Lee DF , Kuo HP , Liu M , et al. KEAP1 E3 ligase‐mediated downregulation of NF‐kappaB signaling by targeting IKKbeta. Mol Cell. 2009;36 (1 ):131‐140. doi:10.1016/j.molcel.2009.07.025 19818716
75 Cheng L , Egon U , Tõnu V , Andres M . The role of COX‐2 and Nrf2/ARE in anti‐inflammation and antioxidative stress: aging and anti‐aging. Med Hypotheses. 2011;77 (2 ):174‐178. doi:10.1016/j.mehy.2011.04.002 21530094
76 Alam MM , Okazaki K , Nguyen LTT , et al. Glucocorticoid receptor signaling represses the antioxidant response by inhibiting histone acetylation mediated by the transcriptional activator NRF2. J Biol Chem. 2017;292 (18 ):7519‐7530. doi:10.1074/jbc.M116.773960 28314773
77 Wardyn JD , Ponsford AH , Sanderson CM . Dissecting molecular cross‐talk between Nrf2 and NF‐κB response pathways. Biochem Soc Trans. 2015;43 (4 ):621‐626. doi:10.1042/bst20150014 26551702
78 Wang L , He C . Nrf2‐mediated anti‐inflammatory polarization of macrophages as therapeutic targets for osteoarthritis. Front Immunol. 2022;13 :967193. doi:10.3389/fimmu.2022.967193 36032081
79 Nowak AJ , Relja B . The impact of acute or chronic alcohol intake on the NF‐κB signaling pathway in alcohol‐related liver disease. Int J Mol Sci. 2020;21 (24 ):1‐35. doi:10.3390/ijms21249407
80 Czerwińska‐Błaszczyk A , Pawlak E , Pawłowski T . The significance of toll‐like receptors in the Neuroimmunologic background of alcohol dependence. Front Psych. 2021;12 :797123. doi:10.3389/fpsyt.2021.797123
81 Haseba T , Ohno Y . A new view of alcohol metabolism and alcoholism—role of the high‐km class III alcohol dehydrogenase (ADH3). Int J Environ Res Public Health. 2010;7 (3 ):1076‐1092. doi:10.3390/ijerph7031076 20617019
82 Hyun J , Han J , Lee C , Yoon M , Jung Y . Pathophysiological aspects of alcohol metabolism in the liver. Int J Mol Sci. 2021;22 (11 ):1‐16. doi:10.3390/ijms22115717
83 Claudio DA , Mauro M . Chapter 21—Alcohol and epigenetic modulations. In: Vinood BP , ed. Molecular Aspects of Alcohol and Nutrition. Academic Press; 2016:261‐273.
84 Setshedi M , Wands JR , Monte SM . Acetaldehyde adducts in alcoholic liver disease. Oxid Med Cell Longev. 2010;3 (3 ):178‐185. doi:10.4161/oxim.3.3.12288 20716942
85 Zakhari S . Overview: how is alcohol metabolized by the body? Alcohol Res Health. 2006;29 (4 ):245‐254.17718403
86 Grzegorz WT . 17—Hepatomegaly. In: Robert MK , Heather T , Brett JB , Donald B , eds. Nelson Pediatric Symptom‐Based Diagnosis: Common Diseases and their Mimics. 2nd ed. Elsevier; 2023:306‐319.e1.
87 Luangmonkong T , Suriguga S , Mutsaers HAM , Groothuis GMM , Olinga P , Boersema M . Targeting oxidative stress for the treatment of liver fibrosis. In: Nilius B , de Tombe P , Gudermann T , Jahn R , Lill R , eds. Reviews of Physiology, Biochemistry and Pharmacology. Vol 175 . Springer International Publishing; 2018:71‐102.
88 Guo C , Sun L , Chen X , Zhang D . Oxidative stress, mitochondrial damage and neurodegenerative diseases. Neural Regen Res. 2013;8 (21 ):2003‐2014. doi:10.3969/j.issn.1673-5374.2013.21.009 25206509
89 Zorov DB , Juhaszova M , Sollott SJ . Mitochondrial reactive oxygen species (ROS) and ROS‐induced ROS release. Physiol Rev. 2014;94 (3 ):909‐950. doi:10.1152/physrev.00026.2013 24987008
90 Wu D , Cederbaum AI . Alcohol, oxidative stress, and free radical damage. Alcohol Res Health. 2003;27 (4 ):277‐284.15540798
91 Chianese R , Pierantoni R . Mitochondrial reactive oxygen species (ROS) production alters sperm quality. Antioxidants. 2021;10 (1 ):92.33440836
92 Korge P , Calmettes G , Weiss JN . Reactive oxygen species production in cardiac mitochondria after complex I inhibition: modulation by substrate‐dependent regulation of the NADH/NAD(+) ratio. Free Radic Biol Med. 2016;96 :22‐33. doi:10.1016/j.freeradbiomed.2016.04.002 27068062
93 Juan CA , Pérez de la Lastra JM , Plou FJ , Pérez‐Lebeña E . The chemistry of reactive oxygen species (ROS) revisited: outlining their role in biological macromolecules (DNA, lipids and proteins) and induced pathologies. Int J Mol Sci. 2021;22 (9 ):2‐21. doi:10.3390/ijms22094642
94 Edenberg HJ , Bosron WF . 4.06 ‐ Alcohol Dehydrogenases. In: Charlene AM , ed. Comprehensive Toxicology. 2nd ed. Elsevier; 2010:111‐130.
95 Heit C , Dong H , Chen Y , Thompson DC , Deitrich RA , Vasiliou VK . The role of CYP2E1 in alcohol metabolism and sensitivity in the central nervous system. Subcell Biochem. 2013;67 :235‐247. doi:10.1007/978-94-007-5881-0_8 23400924
96 Zhang P , Li Y , Wang K , et al. Altered DNA methylation of CYP2E1 gene in schizophrenia patients with tardive dyskinesia. BMC Med Genet. 2022;15 (1 ):253. doi:10.1186/s12920-022-01404-8
97 Peng Q , Chen H , Huo JR . Alcohol consumption and corresponding factors: a novel perspective on the risk factors of esophageal cancer. Oncol Lett. 2016;11 (5 ):3231‐3239. doi:10.3892/ol.2016.4401 27123096
98 David FW , Franz MM . Ethanol metabolism: the good, the bad, and the ugly. Med Hypotheses. 2020;140 :109638. doi:10.1016/j.mehy.2020.109638 32113062
99 Joana GM , Claudia DB , Patricia AC , Ariane Z , Patricia SB . Chapter 51—Ethanol exposure during development, and brain oxidative stress. In: Victor RP , ed. Neuroscience of Alcohol. Academic Press; 2019:493‐503.
100 Moffett JR , Puthillathu N , Vengilote R , Jaworski DM , Namboodiri AM . Acetate revisited: a key biomolecule at the nexus of metabolism, epigenetics and Oncogenesis‐part 1: acetyl‐CoA, Acetogenesis and acyl‐CoA short‐chain Synthetases. Front Physiol. 2020;11 :580167. doi:10.3389/fphys.2020.580167 33281616
101 Pirjo HM , Zoe MU . Chapter 21—Hypoxia. In: Hemanshu P , ed. Complications in Neuroanesthesia. Academic Press; 2016:169‐180.
102 Xiao W , Wang RS , Handy DE , Loscalzo J . NAD(H) and NADP(H) Redox couples and cellular energy metabolism. Antioxid Redox Signal. 2018;28 (3 ):251‐272. doi:10.1089/ars.2017.7216 28648096
103 Trius‐Soler M , Praticò G , Gürdeniz G , et al. Biomarkers of moderate alcohol intake and alcoholic beverages: a systematic literature review. Genes Nutr. 2023;18 (1 ):7. doi:10.1186/s12263-023-00726-1 37076809
104 Hugbart C , Verres Y , Le Daré B , et al. Non‐oxidative ethanol metabolism in human hepatic cells in vitro: involvement of uridine diphospho‐glucuronosyltransferase 1A9 in ethylglucuronide production. Toxicol In Vitro. 2020;66 :104842. doi:10.1016/j.tiv.2020.104842 32283135
105 Heier C , Xie H , Zimmermann R . Nonoxidative ethanol metabolism in humans‐from biomarkers to bioactive lipids. IUBMB Life. 2016;68 (12 ):916‐923. doi:10.1002/iub.1569 27714979
106 Stachel N , Skopp G . Identification and characterization of sulfonyltransferases catalyzing ethyl sulfate formation and their inhibition by polyphenols. Int J Legal Med. 2016;130 (1 ):139‐146. doi:10.1007/s00414-015-1159-5 25680553
107 Susannah SL , Mark RH , Yingning Z , et al. Glucuronic acid and the ethanol metabolite ethyl‐glucuronide cause toll‐like receptor 4 activation and enhanced pain. Brain Behav Immun. 2013;30 :24‐32. doi:10.1016/j.bbi.2013.01.005 23348028
108 Park KE , Kim JD , Nagashima Y , et al. Detection of choline and phosphatidic acid (PA) catalyzed by phospholipase D (PLD) using MALDI‐QIT‐TOF/MS with 9‐aminoacridine matrix. Biosci Biotechnol Biochem. 2014;78 (6 ):981‐988. doi:10.1080/09168451.2014.910102 25036123
109 Jencks DS , Adam JD , Borum ML , Koh JM , Stephen S , Doman DB . Overview of current concepts in gastric intestinal metaplasia and gastric cancer. Gastroenterol Hepatol (N Y). 2018;14 (2 ):92‐101.29606921
110 Anton P , Rutt LN , Twardy SM , McCullough RL . Fatty acid ethyl ethers: new modulators of acute ethanol‐mediated hepatotoxicity? Cell Mol Gastroenterol Hepatol. 2023;15 (2 ):505‐506.36435276
111 Huang W , Booth DM , Cane MC , et al. Fatty acid ethyl ester synthase inhibition ameliorates ethanol‐induced Ca2+−dependent mitochondrial dysfunction and acute pancreatitis. Gut. 2013:1313‐1324.24162590
112 Clemens DL , Schneider KJ , Arkfeld CK , Grode JR , Wells MA , Singh S . Alcoholic pancreatitis: new insights into the pathogenesis and treatment. World J Gastrointest Pathophysiol. 2016;7 (1 ):48‐58. doi:10.4291/wjgp.v7.i1.48 26909228
113 Erol A , Ho AM , Winham SJ , Karpyak VM . Sex hormones in alcohol consumption: a systematic review of evidence. Addict Biol. 2019;24 (2 ):157‐169. doi:10.1111/adb.12589 29280252
114 Hauger RL , Saelzler UG , Pagadala MS , Panizzon MS . The role of testosterone, the androgen receptor, and hypothalamic‐pituitary‐gonadal axis in depression in ageing men. Rev Endocr Metab Disord. 2022;23 (6 ):1259‐1273. doi:10.1007/s11154-022-09767-0 36418656
115 Frydenberg H , Flote VG , Larsson IM , et al. Alcohol consumption, endogenous estrogen and mammographic density among premenopausal women. Breast Cancer Res. 2015;17 (1 ):103. doi:10.1186/s13058-015-0620-1 26246001
116 Mitchell JM , O'Neil JP , Janabi M , Marks SM , Jagust WJ , Fields HL . Alcohol consumption induces endogenous opioid release in the human orbitofrontal cortex and nucleus accumbens. Sci Transl Med. 2012;4 (116 ):116ra6.
117 Wehbeh L , Dobs AS . Opioids and the hypothalamic‐pituitary‐gonadal (HPG) Axis. J Clin Endocrinol Metab. 2020;105 (9 ):e3105‐e3113.
118 Nguyen VA , Le T , Tong M , Silbermann E , Gundogan F , De la Monte SM . Impaired insulin/IGF signaling in experimental alcohol‐related myopathy. Nutrients. 2012;4 (8 ):1058‐1075.23016132
119 Hiney JK , Srivastava VK , Les Dees W . Insulin‐like growth factor‐1 stimulation of hypothalamic KiSS‐1 gene expression is mediated by Akt: effect of alcohol. Neuroscience. 2010;166 (2 ):625‐632.20034543
120 Van Heertum K , Rossi B . Alcohol and fertility: how much is too much? Fertil Res Pract. 2017;3 :10. doi:10.1186/s40738-017-0037-x 28702207
121 Stella L , Maria J , Marcos Sean T , Marta T . Chapter 7—Endocrinological causes of female infertility. In: Antonio Simone L , Antonino G , eds. Management of Infertility. Academic Press; 2023:65‐70.
122 Jirge PR . Ovarian reserve tests. J Hum Reprod Sci. 2011;4 (3 ):108‐113. doi:10.4103/0974-1208.92283 22346076
123 Sepideh K , Pegah V . Gonadotropin releasing hormone. Reference Module in Biomedical Sciences. Elsevier; 2018.
124 Aguirre LE , Colleluori G , Fowler KE , et al. High aromatase activity in hypogonadal men is associated with higher spine bone mineral density, increased truncal fat and reduced lean mass. Eur J Endocrinol. 2015;173 (2 ):167‐174. doi:10.1530/eje-14-1103 26142101
125 Omu AE . Sperm parameters: paradigmatic index of good health and longevity. Med Princ Pract. 2013;22 :30‐42. doi:10.1159/000354208 24051979
126 Sabeti P , Pourmasumi S , Rahiminia T , Akyash F , Talebi AR . Etiologies of sperm oxidative stress. Int J Reprod Biomed. 2016;14 (4 ):231‐240.27351024
127 Sadeghzadeh M , Shirpoor A , Naderi R , et al. Long‐term ethanol consumption promotes changes in β‐defensin isoform gene expression and induces structural changes and oxidative DNA damage to the epididymis of rats. Mol Reprod Dev. 2019;86 (6 ):624‐631. doi:10.1002/mrd.23138 30825392
128 Jeong JE , Joo SH , Hahn C , Kim DJ , Kim TS . Gender‐specific association between alcohol consumption and stress perception, depressed mood, and suicidal ideation: the 2010‐2015 KNHANES. Psychiatry Investig. 2019;16 (5 ):386‐396. doi:10.30773/pi.2019.02.28
129 Knox J , Hasin DS , Larson FRR , Kranzler HR . Prevention, screening, and treatment for heavy drinking and alcohol use disorder. Lancet Psychiatry. 2019;6 (12 ):1054‐1067. doi:10.1016/s2215-0366(19)30213-5 31630982
