ALDH2 Activity Research Articles

Gualou Xiebai Banxia Decoction Suppresses Cardiac Apoptosis in Mice after Myocardial Infarction through Activation of Acetaldehyde Dehydrogenase 2.

Cardiac apoptosis has been reported to be involved in the development of Heart failure (HF) after Myocardial infarction (MI). As a traditional Chinese medicine with cardioprotective properties, Gualou Xiebai Banxia Decoction (GXBD) is therapeutically effective in treating MI. However, whether GXBD regulates cardiac apoptosis in HF after MI remains unknown, and the underlying mechanisms still unclear. This study aimed to explore the effects and potential mechanisms of GXBD on cardiac apoptosis after MI. The MI model was constructed by ligating the left anterior descending coronary artery (LAD) in mice. The cardioprotective effects of GXBD were determined by echocardiography, masson staining, and hematoxylin and eosin (HE) staining. Bioinformatics analysis and network Pharmacology were used to explore the underlying molecular mechanisms of GXBD in MI. The effects of GXBD on apoptosis as well as the ALDH2 were examined by TUNEL staining, Immunohistochemistry (IHC), and Western blot (WB). Additionally, the effects of GXBD on oxidative stress, apoptosis and the ALDH2 in cardiomyocytes (H9c2) were investigated using reactive oxygen species (ROS) detection, Hoechst33342/PI stainingand and WB. Moreover, the effects of suppressing and overexpressing ALDH2 in H9c2 cells were further examined. Target prediction analysis showed that ALDH2 was a key target of GXBD which could ameliorate myocardial infarction. GXBD dose-dependently reduced cardiomyocyte apoptosis and ventricular dysfunction. In vivo experiments, GXBD activated ALDH2 enzymatic activity and inhibited the expression levels of Bax, Bcl-2, Cleaved Caspase 3, and Caspase 9. In vitro experiments, GXBD inhibited apoptosis in H9c2 cells. ALDH2 activation enhanced these inhibitory effects of GXBD while silencing of ALDH2 significantly reversed these inhibitory effects of GXBD. GXBD exerts inhibitory effects on oxidative stress and cardiomyocyte apoptosis in mice after MI, suppresses H9c2 oxidative stress and apoptosis through activation of the enzyme activity of ALDH2.

Aldehyde dehydrogenase-2 deficiency aggravates neuroinflammation, nociception, and motor impairment in a mouse model of multiple sclerosis

Aldehyde dehydrogenase-2 deficiency (ALDH2∗2) found in 36 % of Han Chinese, affects approximately 8 % of the world population. ALDH2 is a mitochondrial key enzyme in detoxifying reactive aldehydes to less reactive forms. Studies demonstrate a potential link between ALDH2∗2 mutation and neurodegenerative diseases. Multiple sclerosis (MS) is an incurable and disabling neurodegenerative autoimmune disease that induces motor, and cognitive impairment, and hypersensitivity, including chronic pain. Accumulating evidence suggests that reactive aldehydes, such as 4-hydroxynonenal (4-HNE), contribute to MS pathogenesis. Here, using knock-in mice carrying the inactivating point mutation in ALDH2, identical to the mutation found in Han Chinese, we showed that the impairment in ALDH2 activity heightens motor disabilities, and hypernociception induced by experimental autoimmune encephalomyelitis (EAE). The deleterious clinical signs are followed by glial cell activation in the spinal cord and increased 4-HNE levels in the spinal cord and serum. Importantly, the pharmacological ALDH2 activation by Alda-1 ameliorates EAE-induced hypernociception and motor impairment in both wild-type and ALDH2∗2KI mice. Reduced hypernociception was associated with less early growth response protein 1 (EGR1), neuronal and glial activation, and reactive aldehyde accumulation in the spinal cord and serum. Taken together, our data suggest that the mitochondrial enzyme ALDH2 plays a role in regulating clinical, cellular, and molecular responses associated with EAE. This indicates that ALDH2 could serve as a molecular target for MS control, with ALDH2 activators, like Alda-1 as potential neuroprotective candidates. Furthermore, ALDH2∗2 carriers may be at increased risk of developing more accentuated MS symptoms.

Alda-1 Ameliorates Oxidative Stress-Induced Cardiomyocyte Damage by Inhibiting the Mitochondrial ROS/TXNIP/NLRP3 Pathway.

Alda-1 functions as an agonist of aldehyde dehydrogenase (ALDH2) within the mitochondria, contributing to the preservation of mitochondrial structure and function. This study aimed to determine whether Alda-1 inhibited the accumulation of mitochondrial reactive oxygen species (mtROS) and improved cardiomyocyte damage under oxidative stress. Cardiomyocytes derived from human induced pluripotent embryonic stem cells (iPSC-CMs) and human AC16 cardiomyocytes were chosen for the experiments. Oxidative stress was induced in both cardiomyocyte types using hydrogen peroxide (H2O2), a commonly employed agent. The mtROS accumulation and mitochondrial functional status were assessed by measuring the ROS content, mitochondrial membrane potential, and mitochondrial respiratory chain function. Co-IP experiments were used to analyze whether mtROS promoted protein interactions between TXNIP and NLRP3 and induced NLRP3 inflammasome activation. The results showed that Alda-1 mitigated damage to mitochondrial structure and function under oxidative stress, concurrently reducing the accumulation of mtROS. Co-IP experiments revealed that elevated mtROS levels attenuated the protein interaction between TXNIP and TRX while intensifying the interaction between TXNIP and NLRP3. Consequently, this triggers activation of the NLRP3 inflammasome, leading to cardiomyocyte damage. In contrast, TXNIP knockdown inhibited H2O2-induced myocardial injury and enhanced the therapeutic effects of Alda-1. Collectively, the results show that, in an H2O2 environment, Alda-1 increased the production of ALDH2 activity in cardiomyocytes, hindered the production of mtROS, disrupted the interaction between TXNIP and NLRP3, and alleviated myocardial damage during oxidative stress.

The aldehyde dehydrogenase 2 rs671 variant enhances amyloid β pathology

In the ALDH2 rs671 variant, a guanine changes to an adenine, resulting in a dramatic decrease in the catalytic activity of the enzyme. Population-based data are contradictory about whether this variant increases the risk of Alzheimer’s disease. In East Asian populations, the prevalence of the ALDH2 rs671 variant is 30–50%, making the National Human Brain Bank for Development and Function (the largest brain bank in East Asia) an important resource to explore the link between the ALDH2 rs671 polymorphism and Alzheimer’s disease pathology. Here, using 469 postmortem brains, we find that while the ALDH2 rs671 variant is associated with increased plaque deposits and a higher Aβ40/42 ratio, it is not an independent risk factor for Alzheimer’s disease. Mechanistically, we show that lower ALDH2 activity leads to 4-HNE accumulation in the brain. The (R)−4-HNE enantiomer adducts to residue Lys53 of C99, favoring Aβ40 generation in the Golgi apparatus. Decreased ALDH2 activity also lowers inflammatory factor secretion, as well as amyloid β phagocytosis and spread in brains of patients with Alzheimer’s disease. We thus define the relationship between the ALDH2 rs671 polymorphism and amyloid β pathology, and find that ALDH2 rs671 is a key regulator of Aβ40 or Aβ42 generation.

The Effect of HIF1-α/NF-κB/MMP2 Signaling Pathways Mediated by ALDH2 on Chronic Intermittent Hypoxia Induced Myocardial Injury in Rats

(1) Objective: To investigate the effect of HIF1-α/NF-κB/MMP2 signaling pathways mediated by ALDH2 on chronic intermittent hypoxia induced myocardial injury in rats. (2) Methods: Thirty SD rats were randomly assigned to three groups (10 rats in each group): control group (CONTROL), chronic intermittent hypoxia group (CIH), and CIH + ALDH2 group. Rats in the CIH + ALDH2 group were established by an intraperitoneal injection of the ALDH2 activator, Alda-1 (20 mg/kg), once a day for three consecutive days. After three months, changes in ventricular function were determined by ultrasound. The expressions of HIF1-α, NF-κB, and MMP2 proteins were detected by protein blotting, and the concentration of 4-HNE in myocardial tissue was measured. (3) Results: Compared with the control group, echocardiography showed that rats in the CIH group had significantly reduced myocardial function, elevated protein levels of HIF1-α, NF-κB, and MMP2 in myocardial tissues, and increased the expression of 4-HNE in myocardial tissues (P<0.01); Compared with the CIH group, rats in the CIH + ALDH2 group showed significant improvement in myocardial function, decreased protein levels of HIF1-α, NF-κB, and MMP2 in myocardial tissue, and decreased the expression of 4-HNE in myocardial tissue (P<0.01). (4) Conclusion: Chronic intermittent hypoxia increases the expression of HIF1-α to damage the myocardium and affect cardiac function, and ALDH2 inhibits the expression of HIF1-α to protect the myocardium.

Mitochondrial aldehyde dehydrogenase rescues against diabetic cardiomyopathy through GSK3β-mediated preservation of mitochondrial integrity and Parkin-mediated mitophagy.

Mitochondrial aldehyde dehydrogenase (ALDH2) offers proven cardiovascular benefit, although its impact on diabetes remains elusive. This study examined the effects of ALDH2 overexpression and knockout on diabetic cardiomyopathy and the mechanism involved with a focus on mitochondrial integrity. Mice challenged with streptozotocin (STZ, 200mg/kg, via intraperitoneal injection) exhibited pathological alterations, including reduced respiratory exchange ratio, dampened fractional shortening and ejection fraction, increased left ventricular end-systolic and diastolic diameters, cardiac remodeling, cardiomyocyte contractile anomalies, intracellular Ca2+ defects, myocardial ultrastructural injury, oxidative stress, apoptosis, and mitochondrial damage, which were overtly attenuated or accentuated by ALDH2 overexpression or knockout, respectively. Diabetic patients also exhibited reduced plasma ALDH2 activity, cardiac remodeling, and diastolic dysfunction. In addition, STZ challenge altered expression levels of mitochondrial proteins (PGC-1α and UCP2) and Ca2+ regulatory proteins (SERCA, Na+-Ca2+ exchanger, and phospholamban), dampened autophagy and mitophagy (LC3B ratio, TOM20, Parkin, FUNDC1, and BNIP3), disrupted phosphorylation of Akt, GSK3β, and Foxo3a, and elevated PTEN phosphorylation, most of which were reversed or worsened by ALDH2 overexpression or knockout, respectively. Furthermore, the novel ALDH2 activator torezolid, as well as the classical ALDH2 activator Alda-1, protected against STZ- or high glucose-induced in vivo or in vitro cardiac anomalies, which was nullified by inhibition of Akt, GSK3β, Parkin, or mitochondrial coupling. Our data discerned a vital role for ALDH2 in diabetic cardiomyopathy possibly through regulation of Akt and GSK3β activation, Parkin mitophagy, and mitochondrial function.

Retraction: Isoflurane Preconditioning Confers Cardioprotection by Activation of ALDH2.

Retraction: Isoflurane Preconditioning Confers Cardioprotection by Activation of ALDH2.

A common East-Asian ALDH2 mutation causes metabolic disorders and the therapeutic effect of ALDH2 activators

Obesity and type 2 diabetes have reached pandemic proportion. ALDH2 (acetaldehyde dehydrogenase 2, mitochondrial) is the key metabolizing enzyme of acetaldehyde and other toxic aldehydes, such as 4-hydroxynonenal. A missense Glu504Lys mutation of the ALDH2 gene is prevalent in 560 million East Asians, resulting in reduced ALDH2 enzymatic activity. We find that male Aldh2 knock-in mice mimicking human Glu504Lys mutation were prone to develop diet-induced obesity, glucose intolerance, insulin resistance, and fatty liver due to reduced adaptive thermogenesis and energy expenditure. We find reduced activity of ALDH2 of the brown adipose tissue from the male Aldh2 homozygous knock-in mice. Proteomic analyses of the brown adipose tissue from the male Aldh2 knock-in mice identifies increased 4-hydroxynonenal-adducted proteins involved in mitochondrial fatty acid oxidation and electron transport chain, leading to markedly decreased fatty acid oxidation rate and mitochondrial respiration of brown adipose tissue, which is essential for adaptive thermogenesis and energy expenditure. AD-9308 is a water-soluble, potent, and highly selective ALDH2 activator. AD-9308 treatment ameliorates diet-induced obesity and fatty liver, and improves glucose homeostasis in both male Aldh2 wild-type and knock-in mice. Our data highlight the therapeutic potential of reducing toxic aldehyde levels by activating ALDH2 for metabolic diseases.

SNHG3/miR-330-5p/ HSD11B1 alleviates myocardial ischemia-reperfusion injury by regulating the ERK/p38 signaling pathway.

Studies have found that microRNAs (miRNAs) participate in the pathogenesis of myocardial ischemia-reperfusion injury (MIRI). miR-330-5p alleviated cerebral IR injury and regulated myocardial damage. However, the mechanism of the effect of miR-330-5p on MIRI needs to be further studied. The study aimed to explore the role and mechanism of miR-330-5p in MIRI. The oxygen-glucose deprivation reperfusion (OGD/R) model was constructed in cardiomyocytes to simulate MIRI in vitro. QRT-PCR was used for the detection of gene expression. ELISA was used for evaluation of the levels of aldehyde dehydrogenase 2 family member (ALDH2), 4-hydroxynonenal (4-HNE), and malondialdehyde (MDA). Flow cytometry was used to evaluate apoptosis. Western blot was employed for protein determination. Bioinformatic analysis was performed for predicting the targets of miR-330-5p. miR-330-5p was found to be down-regulated in MIRI-induced cardiomyocytes (Model group). miR-330-5p mimic enhanced ALDH2 activity, inhibited apoptosis, and suppressed 4-HNE and MDA of MIRI-induced cardiomyocytes. miR-330-5p inhibited ERK expression while increasing the p38 expression. Bioinformatic analysis showed HSD11B1 to be a target of miR-330-5p. HSD11B1 expression was inhibited by miR-330-5p mimic while increased by miR-330-5p inhibitor in MIRI-induced cardiomyocytes. Hydroxysteroid 11-beta dehydrogenase 1 (HSD11B1) overexpression reversed the effect of miR-330-5p on ALDH2, 4-HNE, MDA, apoptosis, and ERK/p38 signaling pathway. Furthermore, lncRNA small nucleolar RNA host gene 3 (SNHG3) was the upstream lncRNA of miR-330-5p. SNHG3 decreased miR-330-5p expression and increased HSD11B1 expression. SNHG3/miR-330-5p alleviated MIRI in vitro by targeting HSD11B1 to regulate the ERK/p38 signaling pathway.

Abstract P3173: Exposure Of Mitochondria Isolated From Left Ventricular Myocardium Of Dogs With Moderate Heart Failure To 4-hydroxy-2-nonenal (4-hne) Worsens Existing Mitochondrial Dysfunction

Background: Reactive oxygen species (ROS) generated by dysfunction of mitochondria (MITO) of the failing heart plays an important role in lipid peroxidation of polyunsaturated fatty acids in cell and MITO membranes resulting in the production of aldehydes, such as malondialdehyde and 4-hydroxy-2-nonenal (4-HNE). MITO aldehyde dehydrogenase-2 (mALDH2) is a key enzyme for the detoxification of endogenous aldehyde substrates through NAD dependent oxidation. We previously showed that mALDH2 expression and activity are markedly reduced in MITO of failing LV cardiomyocytes, a maladaptation that can lead to considerable accumulation of 4-HNE in MITO. It is unclear whether such an accumulation of 4-HNE can further exacerbate MITO dysfunction resulting in further limitation to ATP formation via oxidative phosphorylation. Hypothesis: This study tested the hypothesis that exposure of MITO isolated from failing hearts to exogenous 4-HNE can result in further deterioration of MITO function. Methods: Freshly isolated MITO from LV myocardium of dogs with moderate heart failure (HF, LV ejection fraction ~40%) were incubated for 1 hour in absence (baseline) and presence of 4-HNE at concentrations of 3 and 30 μM. MITO energetic parameters namely ADP-stimulated respiration (ADPresp), maximal respiratory capacity (MRC) and ATP-linked respiration (ATPresp) were evaluated using an XFe96 analyzer (Seahorse Biosciences). Results: Compared to baseline, exposure of MITO to 3 μM 4-HNE has no significant effects on any of the MITO energetic measures. However, exposure of MITO to 30 μM 4-HNE resulted in significant reduction of ADPresp (490 ± 37 vs. 179 ± 7 OCR pmols/O 2 /min, p<0.05), significant reduction of MRC (334 ± 56 vs. 124 ± 18 OCR pmols/O 2 /min, p<0.05), and significant reduction of ATPresp (48 ± 10 vs. 20 ± 12 OCR pmols/O 2 /min, p<0.05). Conclusions: Exposure of MITO from failing myocardium to elevated levels of 4-HNE can lead to marked deterioration of MITO function that can result in a further reduction of ATP leading to progression of LV dysfunction. Limiting the accumulation of 4-HNE through pharmacologic normalization of ALDH2 activity can potentially represent a therapeutic target for retarding the progression of LV dysfunction toward intractable HF.

The administration of Alda-1, an activator of ALDH2, inhibits relapse-like ethanol intake in female alcohol-preferring UChB rats

AimsAlcohol relapse is a main limitation for the treatment of alcohol use disorders. Previous studies have shown that Alda-1, a pharmacological activator of ALDH2, inhibits both acquisition and chronic ethanol intake in rats; however, its effects on relapse-like ethanol intake are unknown. The aim of this study was to assess the effect of Alda-1 on post-deprivation and reaccess relapse-like ethanol intake in alcohol-preferring UChB rats. We also aimed to assess the possible mechanisms associated with the effects of Alda-1 by measuring the levels of glutamate transporter (GLT-1), oxidative stress and neuroinflammation markers in different regions of the mesocorticolimbic system. Main methodsIn Experiment I, UChB female rats were exposed for 100 days to voluntary ethanol intake followed by 2-weeks of ethanol withdrawal and 1 week of ethanol reaccess. Alda-1 (25 mg/kg, intragastric, i.g) or vehicle was administered daily for 14 days during the withdrawal/re-access period. Experiment II was similar to Experiment I, but after the withdrawal period, ethanol re-access was not allowed, and Alda-1 was administered during the last week of withdrawal. At the end of both experiments, the levels of GLT-1, oxidative stress (GSH, MDA), and neuroinflammation markers (GFAP, Iba-1) were assessed in nucleus accumbens and/or hippocampus. Key findingsThe results showed that Alda-1 administration markedly blocked (90 %, p < 0.001) relapse-like ethanol intake in UChB rats. Alda-1 increased Iba-1 reactivity (microglial marker) in the NAc of ethanol-deprived rats. Alda-1 administration did not influence the levels of GLT-1, oxidative stress markers (MDA, GSH) or GFAP reactivity in the mesocorticolimbic system. SignificanceThese preclinical findings support the use of activators of ALDH2, such as Alda-1, as a potential pharmacological strategy in the treatment of alcohol relapse.

The effect of vitamin C on nitroglycerin-mediated vasodilation in individuals with and without the aldehyde dehydrogenase 2 polymorphism.

To mediate its pharmacodynamic effects, glyceryl trinitrate (GTN) requires bioactivation, by which it releases nitric oxide or a nitric oxide moiety. The exact mechanism of GTN bioactivation remains uncertain. Mitochondrial aldehyde dehydrogenase (ALDH-2) has been proposed as the primary enzyme responsible for this bioactivation process. Evidence for the importance of ALDH-2 in GTN bioactivation has been inconsistent, particularly in human models. An alternative hypothesis suggests that decreased ALDH-2 activity leads to accumulation of reactive cytotoxic aldehydes, which either inhibit the vasoactive product(s) of GTN or impair other enzymatic pathways involved in the bioactivation of GTN. We investigated the effect of supplemental vitamin C on vascular responses to GTN in healthy volunteers of East Asian descent, of whom 12 with and 12 without the ALDH-2 polymorphism participated. Subjects underwent 2 sequential brachial artery infusions of GTN at rates of 5, 11 and 22 nmol/min, separated by a 30-min washout period. The GTN infusions were carried out in the presence and absence of vitamin C using a randomized, crossover design. Venous occlusion plethysmography was used to measure forearm blood flow responses to GTN. Compared to subjects with functional ALDH-2, the variant group exhibited blunted hemodynamic responses to intra-arterial GTN infusions, although this reduction in response was not statically significant. Contrary to our hypothesis, vitamin C had an inhibitory effect on GTN mediated vasodilation as compared to GTN during saline in both groups. We conclude that vitamin C did not augment the acute vascular response to GTN in those with the ALDH-2 polymorphism.

ALDH2 activation attenuates oxygen-glucose deprivation/reoxygenation-induced cell apoptosis, pyroptosis, ferroptosis and autophagy.

It is previously reported that aldehyde dehydrogenase 2 family member (ALDH2) shows neuroprotective effects in cerebral ischemia/reperfusion injury. However, whether the protective effects are through mediating the programmed cell death is yet to be fully elucidated. In vitro oxygen-glucose deprivation/reoxygenation (OGD/R) model was established in HT22 cells and mouse cortical neurons. Subsequently, ALDH2 expression were assessed by qRT-PCR and western blot. The methylation status was examined by methylation-specific PCR (MS-PCR). Then, ALDH2 expression was promoted and suppressed to explore the role of ALDH2 in OGD/R-treated cells. CCK-8 assay was applied to detect cell viability, and flow cytometry was applied to evaluate cell apoptosis. Western blot was applied to detect the apoptosis-related proteins (Caspase 3, Bcl-2 and Bax), necroptosis-related proteins (RIP3 and MLKL), pyroptosis-related proteins (NLRP3 and GSDMD), ferroptosis-related protein (ACSL4 and GPX4), and autophagy-related proteins (LC3B, and p62). IL-1β and IL-18 production was evaluated by ELISA assay. Reactive oxygen species production and Fe2+ content were evaluated by the corresponding detection kit. In OGD/R-treated cells, ALDH2 expression was decreased, which was due to the hypermethylation of ALDH2 in the promoter region. ALDH2 overexpression improved cell viability and ALDH2 knockdown suppressed cell viability in OGD/R-treated cells. We also found that ALDH2 overexpression attenuated OGD/R-induced cell apoptosis, pyroptosis, ferroptosis and autophagy, while ALDH2 knockdown facilitated the OGD/R-induced cell apoptosis, pyroptosis, ferroptosis and autophagy. Collectively, our results implied that ALDH2 attenuated OGD/R-induced cell apoptosis, pyroptosis, ferroptosis and autophagy to promote cell viability in HT22 cells and mouse cortical neurons.

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.

Acetaldehyde dehydrogenase 2 activation attenuates sepsis-induced brain injury through NLRP3 inflammasome regulation

ObjectiveAcetaldehyde dehydrogenase 2 (ALDH2) plays an important part in neuroprotection; however, its effect on sepsis-induced brain injury is nuclear. Our aim is to investigate the potential effect and mechanism of ALDH2 in this condition. MethodsWe established an animal model using cecal ligation and perforation (CLP). Twenty-four rats were divided into sham group (n = 6), CLP group (n = 6), CLP + Alda-1 group (n = 6) and CLP + Cyanamide (CYA) group (n = 6). Vital signs were monitored, and arterial blood gas analysis, hippocampal histological staining and ALDH2 activity analysis were conducted. Western blot analysis and enzyme-linked immunosorbent assays were also carried out. Lipopolysaccharide (LPS)-treated HT22 cells were employed as an in vitro model of sepsis-induced brain injury, with and without pretreatment with Alda-1 or CYA, to further examine the potential mechanisms. Real-time quantitative polymerase chain reaction and western blot were used to determine the levels of pyrin domain-containing 3 (NLRP3) inflammasome. ResultsWe found hippocampal cell injury in the CLP group (p < 0.05), with decreased ALDH2 activity (p < 0.05) and suspected overexpression of NLRP3/caspase-1 axis (p < 0.05). In the group pretreated with Alda-1, there were increased ALDH2 activity (p < 0.05), decreased hippocampal cell damage (p < 0.05), and reduced protein levels of NLRP3, apoptosis-associated speck like protein containing a caspase recruitment domain (ASC), cleaved caspase-1 and Gasdermin D (GSDMD) (p < 0.05). The levels of interleukin 18 (IL-18) and interleukin 1β (IL-1β) were also reduced (p < 0.05). In the group pretreated with CYA, ALDH2 activity was further declined, the cell injury grade increased, and the elevated levels of pyroptosis-related proteins aggravated (p < 0.05). LPS treatment decreased the cell viability and ALDH2 activity of the HT22 cells (p < 0.05), along with increased mRNA levels of the NLRP3 inflammasome, as well as IL-1β and IL-18 (p < 0.05). Western blot further revealed elevated levels of NLRP3, ASC, cleaved caspase-1 and GSDMD (p < 0.05). In the LPS+Alda-1 group, there were increased cell viability (p < 0.05), elevated ALDH2 activity (p < 0.05), and reduced levels of NLRP3 inflammasome and pyroptosis-related proteins (p < 0.05). In the CYA+LPS group, cell viability and ALDH2 activity were further declined (p < 0.05), while levels of NLRP3 /caspase-1 axis were increased (p < 0.05). ConclusionsThe activation of ALDH2 can attenuate sepsis-induced brain injury, hypothetically through regulation of the NLRP3/caspase-1 signaling pathway. Therefore, ALDH2 could potentially be considered as a new therapeutic target for the treatment of sepsis-induced brain injury.

Aldehyde Dehydrogenase 2 Activator Augments the Beneficial Effects of Empagliflozin in Mice with Diabetes-Associated HFpEF.

To ameliorate diabetes mellitus-associated heart failure with preserved ejection fraction (HFpEF), we plan to lower diabetes-mediated oxidative stress-induced 4-hydroxy-2-nonenal (4HNE) accumulation by pharmacological agents that either decrease 4HNE generation or increase its detoxification.A cellular reactive carbonyl species (RCS), 4HNE, was significantly increased in diabetic hearts due to a diabetes-induced decrease in 4HNE detoxification by aldehyde dehydrogenase (ALDH) 2, a cardiac mitochondrial enzyme that metabolizes 4HNE. Therefore, hyperglycemia-induced 4HNE is critical for diabetes-mediated cardiotoxicity and we hypothesize that lowering 4HNE ameliorates diabetes-associated HFpEF. We fed a high-fat diet to ALDH2*2 mice, which have intrinsically low ALDH2 activity, to induce type-2 diabetes. After 4 months of diabetes, the mice exhibited features of HFpEF along with increased 4HNE adducts, and we treated them with vehicle, empagliflozin (EMP) (3 mg/kg/d) to reduce 4HNE and Alda-1 (10 mg/kg/d), and ALDH2 activator to enhance ALDH2 activity as well as a combination of EMP + Alda-1 (E + A), via subcutaneous osmotic pumps. After 2 months of treatments, cardiac function was assessed by conscious echocardiography before and after exercise stress. EMP + Alda-1 improved exercise tolerance, diastolic and systolic function, 4HNE detoxification and cardiac liver kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) pathways in ALDH2*2 mice with diabetes-associated HFpEF. This combination was even more effective than EMP alone. Our data indicate that ALDH2 activation along with the treatment of hypoglycemic agents may be a salient strategy to alleviate diabetes-associated HFpEF.

Effects of intracardiac delivery of aldehyde dehydrogenase 2 gene in myocardial salvage.

Intrinsic activity of aldehyde dehydrogenase (ALDH)2, a cardiac mitochondrial enzyme, is vital in detoxifying 4-hydroxy-2-nonenal (4HNE) like cellular reactive carbonyl species (RCS) and thereby conferring cardiac protection against pathological stress. It was also known that a single point mutation (E487K) in ALDH2 (prevalent in East Asians) known as ALDH2*2 reduces its activity intrinsically and was associated with increased cardiovascular diseases. We and others have shown that ALDH2 activity is reduced in several pathologies in WT animals as well. Thus, exogenous augmentation of ALDH2 activity is a good strategy to protect the myocardium from pathologies. In this study, we will test the efficacy of intracardiac injections of the ALDH2 gene in mice. We injected both wild type (WT) and ALDH2*2 knock-in mutant mice with ALDH2 constructs, AAv9-cTNT-hALDH2-HA tag-P2A-eGFP or their control constructs, AAv9-cTNT-eGFP. We found that intracardiac ALDH2 gene transfer increased myocardial levels of ALDH2 compared to GFP alone after 1 and 3 weeks. When we subjected the hearts of these mice to 30 min global ischemia and 90 min reperfusion (I-R) using the Langendorff perfusion system, we found reduced infarct size in the hearts of mice with ALDH2 gene vs GFP alone. A single time injection has shown increased myocardial ALDH2 activity for at least 3 weeks and reduced myocardial 4HNE adducts and infarct size along with increased contractile function of the hearts while subjected to I-R. Thus, ALDH2 overexpression protected the myocardium from I-R injury by reducing 4HNE protein adducts implicating increased 4HNE detoxification by ALDH2. In conclusion, intracardiac ALDH2 gene transfer is an effective strategy to protect the myocardium from pathological insults.

Aldh2 is a lineage-specific metabolic gatekeeper in melanocyte stem cells.

ABSTRACTMelanocyte stem cells (McSCs) in zebrafish serve as an on-demand source of melanocytes during growth and regeneration, but metabolic programs associated with their activation and regenerative processes are not well known. Here, using live imaging coupled with scRNA-sequencing, we discovered that, during regeneration, quiescent McSCs activate a dormant embryonic neural crest transcriptional program followed by an aldehyde dehydrogenase (Aldh) 2 metabolic switch to generate progeny. Unexpectedly, although ALDH2 is well known for its aldehyde-clearing mechanisms, we find that, in regenerating McSCs, Aldh2 activity is required to generate formate – the one-carbon (1C) building block for nucleotide biosynthesis – through formaldehyde metabolism. Consequently, we find that disrupting the 1C cycle with low doses of methotrexate causes melanocyte regeneration defects. In the absence of Aldh2, we find that purines are the metabolic end product sufficient for activated McSCs to generate progeny. Together, our work reveals McSCs undergo a two-step cell state transition during regeneration, and that the reaction products of Aldh2 enzymes have tissue-specific stem cell functions that meet metabolic demands in regeneration.

Mechanism of ALDH2 improves the neuronal damage caused by hypoxia/reoxygenation.

To investigate the protective effect and mechanism of ALDH2 on PC12 cells and brain nerve tissue injury under hypoxia. The hypoxia model of PC12 cells with low ALDH2 expression was established and screened. The eukaryotic expression vector of wild type pEGFP-N1-ALDH2 and blank plasmid pEGFP-N1 were constructed and transfected into PC12 hypoxia cells respectively. After reoxygenation culture, the morphology, quantity, ALDH2 expression level and apoptosis rate of the two groups were observed, and the role of ALDH2 in cell hypoxia injury was analyzed. Eighty SD rats were randomly divided into model group (ischemia-reperfusion injury group), Alda-1 group (intraperitoneal injection of alda-1 12 hours before and after modeling), DMSO group (intraperitoneal injection of dimethyl sulfoxide) and sham operation group, with 20 rats in each group. The neurobehavioral score, apoptosis rate of nerve cells, the content and activity of ALDH2 in active cerebral cortex and hippocampal CA1 area were compared. The number of PC12 cells in hypoxia group was lower than that in control group. The expression level of ALDH2 protein in PC12 cells after 4 hours of hypoxia was lower than that in normal culture group. The number of PC12 cells transfected with wild-type recombinant plasmid was significantly more than that of blank plasmid group. Compared with the hypoxia group, the pre apoptotic and post apoptotic cells in wild type transfection group decreased after hypoxia treatment. Compared with sham operation group, nerve injury and apoptosis were increased in group M and DMSO, while ALDH2 activity and expression did not change significantly. Compared with M group and DMSO group, the nerve injury and apoptosis in Alda-1 group were improved, ALDH2 activity was increased, and ALDH2 expression was not significantly changed in Alda-1 group. Increasing the expression of ALDH2 or enhancing the activity of ALDH2 can improve the injury of neurons induced by hypoxia/reoxygenation.

Diabetic Aldehyde Dehydrogenase 2 Mutant (ALDH2*2) Mice Are More Susceptible to Cardiac Ischemic-Reperfusion Injury Due to 4-Hydroxy-2-Nonenal Induced Coronary Endothelial Cell Damage.

BackgroundAldehyde dehydrogenase‐2 (ALDH2), a mitochondrial enzyme, detoxifies reactive aldehydes such as 4‐hydroxy‐2‐nonenal (4HNE). A highly prevalent E487K mutation in ALDH2 (ALDH2*2) in East Asian people with intrinsic low ALDH2 activity is implicated in diabetic complications. 4HNE‐induced cardiomyocyte dysfunction was studied in diabetic cardiac damage; however, coronary endothelial cell (CEC) injury in myocardial ischemia‐reperfusion injury (IRI) in diabetic mice has not been studied. Therefore, we hypothesize that the lack of ALDH2 activity exacerbates 4HNE‐induced CEC dysfunction which leads to cardiac damage in ALDH2*2 mutant diabetic mice subjected to myocardial IRI.Methods and ResultsThree weeks after diabetes mellitus (DM) induction, hearts were subjected to IRI either in vivo via left anterior descending artery occlusion and release or ex vivo IRI by using the Langendorff system. The cardiac performance was assessed by conscious echocardiography in mice or by inserting a balloon catheter in the left ventricle in the ex vivo model. Just 3 weeks of DM led to an increase in cardiac 4HNE protein adducts and, cardiac dysfunction, and a decrease in the number of CECs along with reduced myocardial ALDH2 activity in ALDH2*2 mutant diabetic mice compared with their wild‐type counterparts. Systemic pretreatment with Alda‐1 (10 mg/kg per day), an activator of both ALDH2 and ALDH2*2, led to a reduction in myocardial infarct size and dysfunction, and coronary perfusion pressure upon cardiac IRI by increasing CEC population and coronary arteriole opening.ConclusionsLow ALDH2 activity exacerbates 4HNE‐mediated CEC injury and thereby cardiac dysfunction in diabetic mouse hearts subjected to IRI, which can be reversed by ALDH2 activation.