ALDH2 Deficiency Research Articles

Abstract 2211: ALDH2 deficiency and alcohol intake: Opportunity for precision cancer prevention

Abstract Alcoholic beverages and the main metabolite of alcohol, acetaldehyde, are known carcinogens, according to the International Agency for Research on Cancer. Many studies have shown that alcohol consumption is a modifiable risk factor for breast, esophageal, colorectal, and other cancers, and that individuals deficient in metabolizing acetaldehyde are at higher risk for alcohol-associated cancers. A genetic variant in aldehyde dehydrogenase 2 (ALDH2, G>A, rs671), the main enzyme responsible for breaking down acetaldehyde, results in decreased efficiency of ALDH2, or ALDH2 deficiency. This is the most common single genetic variation in humans worldwide, mostly found in some East Asian populations. While having one or both deficient alleles can lead to adverse physical effects when drinking, including facial flushing, nausea, and palpitations, studies done in Asian countries have shown that many affected individuals still consume alcohol, increasing their risk for some cancers. We sought to explore the scope and design of potential intervention in the U.S. by examining alcohol consumption behavior in individuals with and without ALDH2 deficiency within the All of Us Research Program, a current large, diverse, national U.S. cohort. Relationships between self-reported alcohol consumption and sociodemographic factors were examined among 380,845 participants. Genomic data was available for 296,254 of them. Overall, 72.7% of the cohort reported drinking alcohol in the past year, with the majority drinking moderately (≤1 drink/day for women and ≤2 drinks/day for men). Among those who drank, 42.7% reported at least one binge drinking episode (≥6 drinks on one occasion). Among our genomic cohort who identified as Asian individuals, 23.6% had at least one deficient ALDH2 allele compared to <4% in all other groups. 63.7% of individuals with one deficient ALDH2 allele and 25.4% with two deficient ALDH2 alleles reported drinking in the past year. 29.9% of individuals with ALDH2 deficiency reported binge drinking in the past year. Multivariate analysis showed that male sex, younger age, higher education level, higher household income, and being born in the U.S. were associated with alcohol consumption among both individuals with and without ALDH2 deficiency. Our study shows that ALDH2 deficiency is fairly common among Asian Americans and that many affected individuals still drink alcohol. With the growing population of Asian Americans in the U.S. (currently >7% of the total U.S. population, projected to be ~38 million individuals by 2050), our findings suggest a significant opportunity for precision cancer prevention for a substantial portion of the population. Citation Format: Danielle Forman, Manxi Yang, Ryan Chien, Hester Nguyen, Caressa Wong, Jacqueline H. Kim, Argyrios Ziogas, Hannah Lui Park. ALDH2 deficiency and alcohol intake: Opportunity for precision cancer prevention [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2211.

Host ALDH2 deficiency aggravates nonalcoholic steatohepatitis through gut-liver axis

Nonalcoholic steatohepatitis (NASH) is the major cause of liver dysfunction. Animal and population studies have shown that mitochondrial aldehyde dehydrogenase (ALDH2) is implicated in fatty liver disease. However, the role of ALDH2 in NASH and the underlying mechanisms remains unclear. To address this issue, ALDH2 knockout (ALDH2−/−) mice and wild-type littermate mice were fed a methionine-and choline-deficient (MCD) diet to induce a NASH model. Fecal, serum, and liver samples were collected and analyzed to investigate the impact of the gut microbiota and bile acids on this process. We found that MCD-fed ALDH2−/− mice exhibited increased serum pro-inflammation cytokines, hepatic inflammation and fat accumulation than their wild-type littermates. MCD-fed ALDH2−/− mice exhibited worsened MCD-induced intestinal inflammation and barrier damage, and gut microbiota disorder. Furthermore, mice receiving microbiota from MCD-fed ALDH2−/− mice had increased severity of NASH compared to those receiving microbiota from MCD-fed wild-type mice. Notably, the intestinal Lactobacillus was significantly reduced in MCD-fed ALDH2−/− mice, and gavage with Lactobacillus cocktail significantly improved MCD-induced NASH. Finally, we found that ALDH2-/- mice had reduced levels of bile salt hydrolase and specific bile acids, especially lithocholic acid (LCA), accompanied by downregulated expression of the intestinal FXR-FGF15 pathway. Supplementation of LCA in ALDH2−/− mice upregulated intestinal FXR-FGF15 pathway and alleviated NASH. In summary, ALDH2 plays a critical role in the development of NASH through modulation of gut microbiota and bile acid. The findings suggest that supplementing with Lactobacillus or LCA could be a promising therapeutic approach for treating NASH exacerbated by ALDH2 deficiency.

To determine the frequency of aldehyde dehydrogenase type 2 (aldh2) deficiency in aplastic anaemia: A single center experience from pakistan.

Aplastic anaemia is a rare bone marrow failure syndrome and is defined by pancytopenia associated with a hypo-cellular bone marrow with no increase in reticulin and the absence of any abnormal infiltrate. The objective of the study was to determine the frequency of Aldehyde Dehydrogenase type 2 (ALDH2) deficiency in patients with Aplastic Anaemia and investigate its correlation with patient and disease characteristics. It was a descriptive cross-sectional study conducted at Armed Forces Bone Marrow Transplant Centre Rawalpindi from 01-08-2022-01-02-2023, over 6 months. A total of 56 patients who were diagnosed with aplastic anaemia during this period, fulfilling inclusion criteria were enrolled. Patients were genotyped as GG (homozygous) and GA (heterozygous). GG had normal ALDH2, while GA were patients with ALDH2 deficiency. Data was collected on the patient's demographics, type and severity of anaemia, type of hematopoietic stem cell transplant (HSCT) and frequency of ALDH2 deficiency. Results were analyzed for ALDH2 deficiency and its correlation with patient and disease characteristics was investigated. A total of 56 patients were included in the study. The median age of the patients was 28 years (20-39). According to the type of aplastic anaemia, 2 (3.6%) had Fanconi anaemia and 54 (96.4%) had acquired aplastic anaemia. In our study, 18 (32.1%) patients had undergone HSCT while the remaining 38 (67.9%) could not undergo HSCT. The frequency of the presence of ALDH2 deficiency was 2 (3.6%). There was no statistically significant correlation between the frequency of ALDH2 deficiency with variables like gender, age distribution, type of aplastic anaemia, the severity of aplastic anaemia and hematopoietic stem cell transplant. We concluded from our study the frequency of ALDH2 was rare in patients with aplastic anaemia. There was no statistically significant correlation between the frequency of ALDH2 deficiency with variables like gender, age distribution, type of aplastic anaemia, the severity of aplastic anaemia and hematopoietic stem cell transplant.

Aldh2 deficiency plays a dual role in lung tumorigenesis and tumor progression

Aldh2 deficiency plays a dual role in lung tumorigenesis and tumor progression

Abstract 2: A Model of Public Health Campaign on the Awareness of Alcohol Flushing and Prevention of Upper Aerodigestive Tract Cancers in East Asia

Abstract Purpose: The purpose of this study is to share a model of public health campaign on the awareness of alcohol flushing and prevention of upper aerodigestive tract cancers in East Asia. East Asians suffers the highest cancer burden attributable to alcohol use with a particularly high incidences of esophageal cancer and other upper aerodigestive trac (UADT) cancers. Alcohol use and carrying the common East Asian-specific dysfunctional mutation in the aldehyde dehydrogenase (ALDH2) gene are two major and synergistic risk factors. Alcohol flushing or alcohol intolerance is the better-known manifestation of ALDH2 deficiency following alcohol consumption. Although UADT cancers are highly preventable, there is a lack of awareness and education on alcohol flushing and its associated health risks in East Asian countries and Asian communities in the U.S. Methods: Several small-scale university-based studies have shown that alcohol flushing education and awareness could reduce alcohol consumption, indicating that a promising model for community-based public health campaign. In Taiwan, we have successfully created such a model by establishing a non-profitable advocacy group (Taiwan Alcohol Intolerance Education Society, TAIES) and collaborate with community leaders, universities, hospitals, volunteers, and government health promotion agencies to educate the public. Educational materials such as fliers, posters, animation videos, interviews were produced and disseminated widely in public exhibitions, conferences, university/community outreach events and via government websites and news/social media. Results: An interview with a popular social media influencer reached more than 500,000 viewers within one week. A national “Taiwan No Alcohol Day” on May 9th (59 =無酒, a homophone in Chinese) was also launched to raise awareness since 2019. ‘No Alcohol Day’ received endorsements from the government and more than 150 organizations. A pilot study to incorporate ALDH2 genetic test and education in oral cancer prevention program in Taiwan has been initiated. Conclusion: Our public health campaign model demonstrated wide reach and strong community and government support. Similar public health campaign on alcohol flushing and cancer risk should also be translated and disseminated in other East Asian countries and to the nearly 19 million Asian Americans in the U.S. Citation Format: Che-Hong Chen, Daria Mochly-Rosen, Su-I Hou. A Model of Public Health Campaign on the Awareness of Alcohol Flushing and Prevention of Upper Aerodigestive Tract Cancers in East Asia [abstract]. In: Proceedings of the 11th Annual Symposium on Global Cancer Research; Closing the Research-to-Implementation Gap; 2023 Apr 4-6. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(6_Suppl):Abstract nr 2.

The “Asian flush syndrome”: ALDH2 Deficiency and Long-term Health Consequences

Harmful use of alcohol leads to roughly 3 million deaths worldwide every year, and is linked to the development of roughly 230 different types of disease (World Health Organization, 2016). As alcohol has the ability to diffuse through cell membranes, its toxicity can heavily impact almost all organs within the human body. A large proportion of the East Asian population experiences the “Asian flush syndrome” post-drinking, which induces characteristic facial-flushing symptoms caused by an aldehyde dehydrogenase (ALDH2) enzyme deficiency due to an ALDH2 gene mutation. In the past, investigations on links between ALDH2 deficiencies and long-term health consequences have been conducted with conclusive evidence that confirm that “Asian flushers'' have a predisposed risk for various diseases, including cancer and cardiovascular disease. This literature review systematically compiles research that explains the mechanisms behind ALDH2 deficient communities and increased health risks to esophageal cancer, cardiovascular disease, and Alzhiemer’s disease. Furthermore, it shows that risk levels for disease are compounded when alcohol intake is increased. The preventative measures and social factors are also considered, including recommendations for further interventions to increase awareness and decrease alcohol intake in affected individuals.

Protective effects of isoflavones on alcoholic liver diseases: Computational approaches to investigate the inhibition of ALDH2 with isoflavone analogues.

Excessive and chronic alcohol intake can lead to the progression of alcoholic liver disease (ALD), which is a major cause of morbidity and mortality worldwide. ALD encompasses a pathophysiological spectrum such as simple steatosis, alcoholic steatohepatitis (ASH), fibrosis, alcoholic cirrhosis, and hepatocellular carcinoma (HCC). Aldehyde dehydrogenase (ALDH2) is the most vital enzyme that produces acetate from acetaldehyde and is expressed at high levels in the liver, kidneys, muscles, and heart. The ALDH2*2 allele is found in up to 40% of East Asian populations, and has a significant impact on alcohol metabolism. Interestingly, several studies have shown that individuals with ALDH2 deficiency are more susceptible to liver inflammation after drinking alcohol. Furthermore, there is growing evidence of an association between ALDH2 deficiency and the development of cancers in the liver, stomach, colon, and lung. Isoflavone analogues are low molecular-weight compounds derived from plants, similar in structure and activity to estrogen in mammals, known as phytoestrogens. Recent studies have reported that isoflavone analogues have beneficial effects on the progression of ALD. This mini-review summarizes the current knowledge about the roles of isoflavone analogues in ALD and discusses the therapeutic potential of isoflavone analogues in liver pathophysiology. In particular, we highlight the significance of computational approaches in this field.

Aldehyde Dehydrogenase 2 Protects the Kidney from Ischemia-Reperfusion Injury by Suppressing the IκBα/NF-κB/IL-17C Pathway.

Ischemia-reperfusion injury (IRI) is an important cause of delayed functional recovery after transplantation. This study is aimed at investigating the molecular mechanism of ALDH2 in a kidney ischemia-reperfusion model based on RNA-seq. We performed kidney ischemia-reperfusion in ALDH2-/- and WT mice and evaluated kidney function and morphology using SCr, HE staining, TUNEL staining, and TEM. We used RNA-seq to compare mRNA expression in ALDH2-/- and WT mice after IR, and then, we verified the related molecular pathways by PCR and western blotting. In addition, activators and inhibitors of ALDH2 were used to alter the activity of ALDH2. Finally, we established a model of hypoxia and reoxygenation in HK-2 cells and clarified the role of ALDH2 in IR by interfering with ALDH2 and using an NF-κB inhibitor. After kidney ischemia-reperfusion, the SCr value increased significantly, kidney tubular epithelial cells were damaged, and the apoptosis rate increased. In the microstructure, mitochondria were swollen and deformed, and ALDH2 deficiency aggravated these changes. The NF-κB pathway and IL-17 pathway were significantly enriched in ALDH2-/- mice compared with WT mice according to KEGG enrichment analysis of the RNA-seq data. The PCR results showed that the mRNA expression levels of IκBα and IL-17B, C, D, E, and F were significantly higher than those in the WT-IR group. Western blot verification results showed that ALHD2 knockdown resulted in increased phosphorylation of IκBα, increased phosphorylation of NF-κB, and increased expression of IL-17C. When we used ALDH2 agonists, the number of lesions and the expression levels of the corresponding proteins were reduced. Knockdown of ALDH2 in HK-2 cells resulted in a higher proportion of apoptotic cells after hypoxia and reoxygenation, but inhibiting the phosphorylation of NF-κB prevented the increase in apoptosis and reduced the protein expression level of IL-17C. ALDH2 deficiency can lead to the aggravation of kidney ischemia-reperfusion injury. RNA-seq analysis and validation by PCR and western blotting revealed that this effect may be due to the promotion of IκBα/NF-κB p65 phosphorylation during ischemia-reperfusion caused by ALDH2 deficiency, which then leads to an increase in inflammatory factors, including IL-17C. Thus, cell death is promoted, and kidney IRI is eventually aggravated. We link ALDH2 deficiency with inflammation, revealing a new idea for ALDH2-related research.

AD-9308 ameliorates the impacts of 4-HNE on the progress of pulmonary arterial hypertension in aldehyde dehydrogenase 2*1*2 knock-in mice

Abstract Endothelial dysfunctions play a critical role on the development of pulmonary arterial hypertension (PAH). It has been reported that the one-year mortality rate is still up to 15% even with PAH-targeted therapy, implying that there may be untargeted pathways. 4-hydroxynenonal (4-HNE), an unsaturated aldehyde, is highly induced in the lungs of PAH animals and its serum levels were also reported to be higher in PAH patients. 4-HNE is metabolized by mitochondrial aldehyde dehydrogenase (ALDH2), which is dysfunctional in near 40% of East Asian people. Currently, the impacts of 4-HNE on endothelial dysfunctions in the development of PAH are unclear. In terms of translational medicine, we proposed that modulation of 4-HNE level may alleviate the progress of PAH patients with ALDH2 deficiency. We found that 4-HNE alone was not sufficient to induce pulmonary artery endothelial cell (PAEC) functional changes, including proliferation, migration and tube formation, whereas their effects emerge from the depletion of ALDH2. We further mimicked human ALDH2 functional deficiency by using daidzin (DZN), an inhibitor which is able to block the substrate binding site of ALDH2. ALDH2 functional inhibition alone did not induce any PAEC functional change, while an add-on of 4-HNE impaired PAEC functions. In addition, 4-HNE significantly reduced eNOS activity with combined DZN treatment. Consistent with the mechanism of ALDH2 activity-mediated angiogensis, ALDH2 enhancers Alda-1 and AD-5591 completely reverse the anti-angiogenic effects of 4-HNE in the presence of DZN. To further confirm whether ALDH2 functional deficiency impact on PAH development in mammals, heterozygous ALDH2*1/*2 transgenic and wild-type mice were subjected to chronic hypoxia to induce PAH. ALDH2*1/*2 transgenic mice had similar right ventricular systolic pressure (RVSP) as wild-type mice. However, after exposure to chronic hypoxia, ALDH2*1/*2 transgenic mice indeed developed a significantly higher RVSP than that in wild-type mice. Furthermore, we demonstrated that 4-HNE expression was profoundly enhanced in ALDH2*1/*2 transgenic mice by chronic hypoxia-induced PAH with pulmonary artery smooth muscle cell hyperplasia. More importantly, we found that AD-9308, an enhancer of ALDH2 significantly decreased hypoxia-induced RVSP elevation in heterozygous ALDH2*1/*2 transgenic mice. Taken together, our data demonstrate that 4-HNE and ALDH2 functional deficiency potentially contribute to PAH development and worsening, and that ALDH2 enhancers may be promising as a PAH adjunct therapy, particularly for patients with ALDH2 nonfunctional alleles. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ministry of Science and Technology, Taiwan

ALDH2 variance in disease and populations.

ABSTRACTThe ALDH2*2 missense variant that commonly causes alcohol flushing reactions is the single genetic polymorphism associated with the largest number of traits in humans. The dysfunctional ALDH2 variant affects nearly 8% of the world population and is highly concentrated among East Asians. Carriers of the ALDH2*2 variant commonly present alterations in a number of blood biomarkers, clinical measurements, biometrics, drug prescriptions, dietary habits and lifestyle behaviors, and they are also more susceptible to aldehyde-associated diseases, such as cancer and cardiovascular disease. However, the interaction between alcohol and ALDH2-related pathology is not clearly delineated. Furthermore, genetic evidence indicates that the ALDH2*2 variant has been favorably selected for in the past 2000-3000 years. It is therefore necessary to consider the disease risk and mechanism associated with ALDH2 deficiency, and to understand the possible beneficial or protective effect conferred by ALDH2 deficiency and whether the pleiotropic effects of ALDH2 variance are all mediated by alcohol use.

Aldehyde dehydrogenase 2 protects against sympathetic excitation-induced cardiac fibrosis

Sympathetic stimulated-cardiac fibrosis imposes great significance on both disease progression and survival in the pathogenesis of many cardiovascular diseases. However, there are few effective therapies targeting it clinically. The cardioprotective effect of aldehyde dehydrogenase 2 (ALDH2) has been explored in many pathological conditions, whether it can exert benefit effects on chronic sympathetic stimulus-induced cardiac fibrosis remains unclear. In this study, we determined to explore the role of ALDH2 on isoproterenol (ISO)-induced cardiac fibroblasts (CF) proliferation and cardiac fibrosis. It was found that ALDH2 enzymatic activity was impaired in ISO-induced HCF proliferation and Aldh2 deficiency promoted mouse CF proliferation. Alda-1, an ALDH2 activator, exerted obvious suppressive effect on ISO-induced HCF proliferation, together with the induction of cell cycle arrest at G0/G1 phase and decreased expression of cyclin E1 and cyclin-dependent kinase 2 (CDK2). Mechanistically, the inhibitory role of Alda-1 on HCF proliferation was achieved by decreasing mitochondrial reactive oxygen species (ROS) production, which was partially reversed by rotenone, an inducer of ROS. In addition, wild-type mice treated with Alda-1 manifested with reduced fibrosis and better cardiac function after ISO pump. In summary, Alda-1 alleviates sympathetic excitation-induced cardiac fibrosis via decreasing mitochondrial ROS accumulation, highlighting ALDH2 activity as a promising drug target of cardiac fibrosis.

Targeting liver aldehyde dehydrogenase-2 prevents heavy but not moderate alcohol drinking

Aldehyde dehydrogenase 2 (ALDH2), a key enzyme for detoxification the ethanol metabolite acetaldehyde, is recognized as a promising therapeutic target to treat alcohol use disorders (AUDs). Disulfiram, a potent ALDH2 inhibitor, is an approved drug for the treatment of AUD but has clinical limitations due to its side effects. This study aims to elucidate the relative contribution of different organs in acetaldehyde clearance through ALDH2 by using global- (Aldh2-/-) and tissue-specific Aldh2-deficient mice, and to examine whether liver-specific ALDH2 inhibition can prevent alcohol-seeking behavior. Aldh2-/- mice showed markedly higher acetaldehyde concentrations than wild-type (WT) mice after acute ethanol gavage. Acetaldehyde levels in hepatocyte-specific Aldh2 knockout (Aldh2Hep-/-) mice were significantly higher than those in WT mice post gavage, but did not reach the levels observed in Aldh2-/- mice. Energy expenditure and motility were dramatically dampened in Aldh2-/- mice, but moderately decreased in Aldh2Hep-/- mice compared to controls. In the 2-bottle paradigm and the drinking-in-the-dark model, Aldh2-/- mice drank negligible volumes from ethanol-containing bottles, whereas Aldh2Hep-/- mice showed reduced alcohol preference at high but not low alcohol concentrations. Glial cell- or neuron-specific Aldh2 deficiency did not affect voluntary alcohol consumption. Finally, specific liver Aldh2 knockdown via injection of shAldh2 markedly decreased alcohol preference. In conclusion, although the liver is the major organ responsible for acetaldehyde metabolism, a cumulative effect of ALDH2 from other organs likely also contributes to systemic acetaldehyde clearance. Liver-targeted ALDH2 inhibition can decrease heavy drinking without affecting moderate drinking, providing molecular basis for hepatic ALDH2 targeting/editing for the treatment of AUD.

Abstract 4360: ALDH2 and the TGF-β/SMAD3 adaptor, Sptbn1 suppress hepatic steatosis and obesity

Abstract Background: Previously we have demonstrated that TGF-β-deficient mutants derived from the loss of Smad3 and the Smad adaptor β2SP (Sptbn1) phenocopy a human cancer stem cell syndrome, are exquisitely sensitive to alcohol, with dysregulation DNA damage repair and have raised levels of aldehyde dehydrogenase (ALDH2). Moreover, β2SP and β2SP/Smad3 mutant mice develop multiple liver abnormalities that include steatosis, chronic hepatitis, inflammation, and cancer. ALDH2 is a key intermediate enzyme for aldehyde and alcohol metabolism. We, therefore, hypothesized that disruption of TGF-β signaling combined with ALDH2 deficiency would increase the susceptibility of liver cancer. Methods: Aldh2 knockout mice were intercrossed with Sptbn1 heterozygous knockout mice to explore the role of Aldh2 and Sptbn1 in liver steatosis and liver cancer. Conditional knockout of Sptbn1 mice was generated by the intercross of Albumin-Cre mice with mice carrying Loxp sites flanked exons of Sptbn1. Sptbn1 conditional mice were fed with high-fat diet or chow diet. Further analysis included blood lipid panel analysis and tissue profiles including western and RNA analysis, lipidomics and metabolomics analysis of liver tissues from the mutant mice and wild-type controls. Results: Interestingly, we found that Aldh2-/-Sptbn1+/- mice on a normal diet demonstrated early signs of truncal obesity. Within 6 months of age, we observed a greater than 23% increase in body weight, with predominantly abdominal fat accumulation in Aldh2-/-Sptbn1+/- mice compared to Aldh2-/- mice or wild type (WT) mice (Aldh2-/-Sptbn1+/- vs Aldh2-/- or WT, p<0.05). A marked increase in zone 3 hepatic micro and macro-steatosis with some inflammation was observed in liver tissues of mutant Aldh2-/-Sptbn1+/- mice as well as the conditional Sptbn1 knockout (Alb-Cre+Sptbn1F/+) mice in a high-fat diet. In addition to significant increased blood glucose levels in Aldh2-/-Sptbn1+/- mice compared with Aldh2-/- mice (165±23 VS 135±13, p<0.05), further analysis revealed that the fatty liver phenotype accompanied with abnormal expression of genes related to glucose uptake, metabolisms and homeostasis as demonstrated by decrease of glucose transporter and increased expression of Ceramide which is known to promote insulin resistance. Moreover, we also observed disruption of lipid metabolism as demonstrated by significantly increased serum and liver triglyceride and cholesterol ester levels in Aldh2-/-Sptbn1+/- mice. Conclusions: Our data suggest that the TGF-β pathway plays an important role in maintaining normal glucose metabolism homeostasis and patients with SPTBN1 and ALDH2 defects may have increased susceptibility to obesity as well as fatty liver (NASH), and cancer. Citation Format: Shuyun Rao, Sobia Zaidi, Wilma Jogunoori, Shoujun Gu, Jon White, Bibhuti Mishra, Chu-Xia Deng, Patricia Latham, Lopa Mishra. ALDH2 and the TGF-β/SMAD3 adaptor, Sptbn1 suppress hepatic steatosis and obesity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4360.

Validation of Alcohol Flushing Questionnaire to Identify ALDH2 Status in a Case-Control Study of Head and Neck Cancer.

Carriers of the ALDH2*2 allele have impaired alcohol metabolism and are more susceptible to the development of alcohol-related cancers, including head and neck cancer (HNC). Screening for ALDH2*2 allele may identify high-risk individuals for alcohol health education. Although genotyping of ALDH2 is the most accurate way to identify ALDH2 deficiency, it may not be practical due to the cost and requirement for genotyping service. This study evaluated the accuracy of the alcohol flushing questionnaire to identify ALDH2 deficiency in a case-control study of HNC conducted in Taiwan using data collected from 904 patients with HNC and 1,078 controls. Overall, alcohol flushing questionnaire had a high sensitivity (89%) of identifying ALDH2*2 carriers among the control subjects and a good sensitivity (79%) among the patients with HNC. The sensitivity of the alcohol flushing questionnaire in identifying ALDH2*2 carriers was affected by alcohol use, with a lower sensitivity among individuals who consumed alcohol, particularly among current regular (drinking alcohol once per week or more) alcohol drinkers. The current validation study showed that the alcohol flushing questionnaire may be a reasonable method to identify ALDH2-deficient individuals. However, current regular users of alcohol who reported no alcohol flushing may need to undergo genotyping of ALDH2 for a more accurate assessment of the ALDH2 status.

Targeting ALDH2 for Therapeutic Interventions in Chronic Pain-Related Myocardial Ischemic Susceptibility.

Clinical observations have demonstrated a link between chronic pain and increased ischemic heart disease mortality, but the mechanisms remain elusive. Reactive aldehydes have recently been confirmed as a new player in pain pathologies, while our previous study demonstrated that reactive aldehydes (4-HNE) induced carbonyl stress contributing to myocardial ischemic intolerance. The aim of this study was to explore whether chronic pain increases susceptibility to myocardial ischemia/reperfusion (MI/R) injury and to investigate the underlying mechanisms focusing on toxic aldehyde and carbonyl stress.Methods: Chronic pain was induced by chronic compression of the dorsal root ganglion (CCD). After 2 weeks CCD, aldehyde dehydrogenase (ALDH2) KO or wild-type (WT) littermate mice were then subjected to in vivo MI/R.Results: In CCD-WT mice, heightened nociception paralleled circulating aldehyde (4-HNE) accumulation and cardiac protein carbonylation. Mechanistically, CCD-induced 4-HNE overload provoked cardiac Sirtuin 1 (SIRT1) carbonylative inactivation and inhibited Liver kinase B1 (LKB1) - AMP-activated protein kinase (LKB1-AMPK) interaction, which resulted in exacerbated MI/R injury and higher mortality compared with non-CCD WT mice. ALDH2 deficiency further aggravated CCD-induced susceptibility to MI/R injury. Exogenous 4-HNE exposure in peripheral tissue mimicked chronic pain-induced aldehyde overload, elicited sustained allodynia and increased MI/R injury. However, cardiac-specific ALDH2 upregulation by AAV9-cTNT-mediated gene delivery significantly ameliorated chronic pain-induced SIRT1 carbonylative inactivation and decreased MI/R injury (minor infarct size, less apoptosis, and improved cardiac function).Conclusion: Collectively, chronic pain-enhanced carbonyl stress promotes myocardial ischemic intolerance by SIRT1 carbonylative inactivation and impairment of LKB1-AMPK interaction. ALDH2 activation and prevention of protein carbonylation may be a potential therapeutic target for myocardial ischemic vulnerability in chronic pain patients. Our results newly provided overlapping cellular mechanisms of chronic pain and myocardial dysfunction interplay.

Abstract 302: Chronic Neuropathic Pain Increases Susceptibility to Myocardial Ischemia/Reperfusion Injury by Sirt1 Carbonylative Inactivation

Pain is not a symptom that exists alone, but whether chronic pain enhances susceptibility to myocardial ischemia/reperfusion (MI/R) injury and the underlying mechanisms remain unknown. Reactive aldehydes contribute to pain pathologies and cardiac injury, suggesting that aldehyde dehydrogenase (ALDH2), which detoxifies aldehydes, may regulate chronic pain related MI/R injury. In this study, chronic neuropathic pain was induced by chronic compression of the dorsal root ganglion (CCD). CCD for 2 weeks, ALDH2 KO or wild-type (WT) littermates were subjected to in vivo MI/R. CCD-WT mice exhibited heightened nociception and correlated with circulating aldehyde (4-HNE) accumulation and cardiac protein carbonylation. CCD induced 4-HNE overload provoked cardiac SIRT1 carbonylative inactivation and impairment the cardioprotection of LKB1-mediated AMPK activation, which resulting in enhanced MI/R injury and higher mortality compare with pain free WT mice. Chronic neuropathic pain enhanced susceptibility to MI/R injury was further exacerbated by ALDH2 deficiency in which associated with more impaired SIRT1-LKB1-AMPK signaling. However, treatment of CCD-WT mice with ALDH2-selective activator (Alda-1) or cardiac specific ALDH2 upregulation by AAV9-cTNT-mediated gene delivery significantly reduced chronic neuropathic pain-induced SIRT1 carbonylative inactivation and decreased MI/R injury (minor infarct size, less apoptosis, and elevated cardiac function). These results strongly suggest that elevated reactive aldehyde concentration, like that observed in the presence of chronic pain, may render cardiomyocytes more susceptible to MI/R injury by SIRT1 carbonylative inactivation and impairment the cardioprotection of LKB1-mediated AMPK activation. ALDH2 activation blocked reactive aldehyde overproduction induced carbonyl stress and attenuated myocardial ischemic vulnerability in chronic pain individual. Keywords: chronic pain; myocardial ischemia/reperfusion; ALDH2; 4-HNE; carbonylation

Mitochondrial ALDH2 Deficiency Promotes Fibrosis and Reactive Oxygen Species Formation in the Myocardium of Aged Mice

Enhanced fibrosis and reactive oxygen species (ROS) generation are two major features of aged heart. Since a loss-of-function mutation of ALDH2 was found in nearly half of East Asian population, we explored the impact of ALDH2 deficiency on the process of aging in the heart. We found that the body weight increased profoundly in aged wild-type (WT) mice but not in ALDH2 knockout (KO) mice. However, the ratio of heart weight to body weight increased significantly only in KO mice. Echocardiographic assessment showed that left ventricular ejection fraction of aged WT mice was significantly decreased, which was further aggravated by ALDH2 deficiency. Further study revealed that the compromised cardiac function of aged KO mice might be resulted from PI3K/Akt pathway-mediated fibrosis formation, as shown by remarkable upregulation of collagen I, transforming growth factor-β, and α-smooth muscle actin expression. Aging-induced ROS generation was quantified by the expression of 4-hydroxy-2-nonenal-adducted proteins, which was notably increased in the myocardium of aged KO mice. Besides, the expression of cleaved caspase-3 and 8-oxoguanine DNA glycosylase also increased significantly in the myocardium of aged KO mice. Further study demonstrated that increased ROS generation stimulated a prominent upregulation of ROS scavenger SOD2 expression in the myocardium of aged WT mice but not in KO mice. Our findings suggest that mitochondrial ALDH2 deficiency accelerates aging in the heart by increasing fibrosis formation and oxidative stress.

Mitochondrial aldehyde dehydrogenase-2 deficiency compromises therapeutic effect of ALDH bright cell on peripheral ischemia

The autologous ALDH bright (ALDHbr) cell therapy for ischemic injury is clinically safe and effective, while the underlying mechanism remains elusive. Here, we demonstrated that the glycolysis dominant metabolism of ALDHbr cells is permissive to restore blood flow in an ischemic hind limb model compared with bone marrow mononuclear cells (BMNCs). PCR array analysis showed overtly elevated Aldh2 expression of ALDHbr cells following hypoxic challenge. Notably, ALDHbr cells therapy induced blood flow recovery in this model was reduced in case of ALDH2 deficiency. Moreover, significantly reduced glycolysis flux and increased reactive oxygen species (ROS) levels were detected in ALDHbr cell from Aldh2-/- mice. Compromised effect on blood flow recovery was also noticed post transplanting the human ALDHbr cell from ALDH2 deficient patients (GA or AA genotypes) in this ischemic hindlimb mice model. Taken together, our findings illustrate the indispensable role of ALDH2 in maintaining glycolysis dominant metabolism of ALDHbr cell and advocate that patient's Aldh2 genotype is a prerequisite for the efficacy of ALDHbr cell therapy for peripheral ischemia.

Mitochondrial aldehyde dehydrogenase 2 deficiency aggravates energy metabolism disturbance and diastolic dysfunction in diabetic mice.

ALDH2 deficiency exacerbates diastolic dysfunction in early diabetic hearts. ALDH2 deficiency triggers decompensation of metabolic reserves and energy metabolism disturbances in early diabetic hearts. ALDH2 deficiency potentiates oxidative stress and AMPK phosphorylation induced by diabetes via post-translational regulation of LKB1. Diabetic patients with ALDH2 mutations are predisposed to worse diastolic dysfunction.

ALDH2 Deficiency Promotes Ethanol-Induced Gut Barrier Dysfunction and Fatty Liver in Mice.

Acetaldehyde, the toxic ethanol (EtOH) metabolite, disrupts intestinal epithelial barrier function. Aldehyde dehydrogenase (ALDH) detoxifies acetaldehyde into acetate. Subpopulations of Asians and Native Americans show polymorphism with loss-of-function mutations in ALDH2. We evaluated the effect of ALDH2 deficiency on EtOH-induced disruption of intestinal epithelial tight junctions and adherens junctions, gut barrier dysfunction, and liver injury. Wild-type and ALDH2-deficient mice were fed EtOH (1 to 6%) in Lieber-DeCarli diet for 4weeks. Gut permeability invivo was measured by plasma-to-luminal flux of FITC-inulin, tight junction and adherens junction integrity was analyzed by confocal microscopy, and liver injury was assessed by the analysis of plasma transaminase activity, histopathology, and liver triglyceride. EtOH feeding elevated colonic mucosal acetaldehyde, which was significantly greater in ALDH2-deficient mice. ALDH2(-/-) mice showed a drastic reduction in the EtOH diet intake. Therefore, this study was continued only in wild-type and ALDH2(+/-) mice. EtOH feeding elevated mucosal inulin permeability in distal colon, but not in proximal colon, ileum, or jejunum of wild-type mice. In ALDH2(+/-) mice, EtOH-induced inulin permeability in distal colon was not only higher than that in wild-type mice, but inulin permeability was also elevated in the proximal colon, ileum, and jejunum. Greater inulin permeability in distal colon of ALDH2(+/-) mice was associated with a more severe redistribution of tight junction and adherens junction proteins from the intercellular junctions. In ALDH2(+/-) mice, but not in wild-type mice, EtOH feeding caused a loss of junctional distribution of tight junction and adherens junction proteins in the ileum. Histopathology, plasma transaminases, and liver triglyceride analyses showed that EtOH-induced liver damage was significantly greater in ALDH2(+/-) mice compared to wild-type mice. These data demonstrate that ALDH2 deficiency enhances EtOH-induced disruption of intestinal epithelial tight junctions, barrier dysfunction, and liver damage.