AMP-dependent kinase and autophagic flux are involved in aldehyde dehydrogenase-2-induced protection against cardiac toxicity of ethanol

TFEB activator protects against ethanol toxicity-induced cardiac injury by restoring mitophagy and autophagic flux

Excessive alcohol consumption is a major cause of alcoholic cardiomyopathy (ACM) and myocardial injury. This study aims to investigate the role of transcription factor EB (TFEB) in ethanol-induced cardiac anomalies using a murine model, AC16 human cardiomyocytes, and human plasma. Wild-type mice treated with a TFEB activator (Compound 1) or vehicle (25 mg/kg/d) were challenged with or without ethanol (3 g/kg/d, i.p.) for three consecutive days. Cardiac geometry and function were evaluated by echocardiography. The expressions of TFEB, molecules related to mitochondria, markers of apoptosis, mitophagy and lysosomes were examined in heart tissues and AC16 cardiomyocytes. Mitochondrial function, lysosome activity, and their localizations were measured in AC16 cardiomyocytes. Levels of TFEB and autophagic markers were also detected in human serum from healthy individuals and patients with ACM. Ethanol administration in mice induced severe cardiac dysfunction accompanied by upregulated P62 and LC3B, downregulated TFEB, lysosomal markers and mitophagy-associated receptors in heart tissues. Ethanol toxicity also led to reduced mitochondrial and lysosomal activity. Interestingly, TFEB activation mitigated the detrimental effects caused by ethanol. Inhibition of autophagy abolished the anti-apoptotic effect of TFEB in AC16 cells. In conclusion, TFEB is beneficial in ethanol-induced cardiac anomalies by reducing apoptosis, recovering lysosomal activity, and restoring proper mitophagy and autophagic flux.

AdipoRon ameliorates chronic ethanol induced cardiac necroptosis by reducing ceramide mediated mtROS

Chronic ethanol (EtOH) consumption has been widely recognized as a significant contributor to cardiotoxicity. However, no specific treatment is currently available to ameliorate chronic ethanol induced cardiotoxicity. Adiponectin receptor agonist AdipoRon exerts protective effects in multiple organs through alleviating lipotoxicity. Our previous study showed that chronic ethanol consumption increased de novo ceramide synthesis and necroptosis in myocardium. In this study, we investigated the role of AdipoRon on ceramide metabolism and necroptosis in chronic ethanol-treated myocardium. Eight-week-old C57/BL6J mice were fed with a Lieber-Decarli diet containing vehicle or AdipoRon for 12 weeks. Cardiac function, histology and oxidative stress were assessed. We found that chronic ethanol treatment decreased expression of AdipoR2 in myocardium and H9c2 cells, whereas AdipoRon improved cardiac function, reduced myocardium ceramide levels and suppressed necroptosis. By pharmacological interventions, RNA interference and point mutations in AdipoR2, we demonstrated that AdipoRon reduced ceramide levels through PPARα mediated lipid metabolism rather than AdipoR2's ceramidase activity. Using transmission electron microscope and reactive oxygen species (ROS) staining, we showed that chronic ethanol induced myocardium mitochondria damage and mitochondrial reactive oxygen species (mtROS) accumulation. Meanwhile, we found that AdipoRon ameliorated chronic ethanol induced cardiac necroptosis via the SIRT3-SOD2-mtROS pathway. Moreover, C6 ceramide treatment recapitulated chronic ethanol in inducing mtROS and necroptosis, whereas the ceramide synthesis inhibitors myriocin (MYR) and fumonisin B1 (FB1) attenuated chronic ethanol induced mtROS and necroptosis. Collectively, AdipoRon ameliorates chronic ethanol induced cardiac necroptosis by reducing ceramide de novo synthesis and mtROS, which highlights the therapeutic potential of targeting ceramide metabolism and oxidative stress pathways in treating ethanol induced cardiotoxicity.

Advances in Factors Affecting ALDH2 Activity and its Mechanisms

Aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial enzyme primarily involved in the detoxification of alcohol-derived aldehyde and endogenous toxic aldehydes. It exhibits widespread expression across various organs and exerts a broad and significant impact on diverse acute cardiovascular diseases, including acute coronary syndrome, acute aortic dissection, hypoxic pulmonary hypertension, and heart failure. The ALDH2 rs671 variant represents the most prevalent genetic variant in East Asian populations, with carriage rates ranging from 30 to 50% among the Chinese population. Given its widespread presence in the body, the wide range of diseases it affects, and its high rate of variation, it can serve as a crucial tool for the precise prevention and treatment of acute cardiovascular diseases, while offering individualized medication guidance. This review aims to provide a comprehensive overview of the latest advancements in factors affecting ALDH2 activity, encompassing post-transcriptional modifications, modulators of ALDH2, and relevant clinical drugs.

Alda-1 attenuation of binge alcohol-caused atrial arrhythmias through a novel mechanism of suppressed c-Jun N-terminal Kinase-2 activity

Holiday Heart Syndrome (HHS) is caused by excessive binge alcohol consumption, and atrial fibrillation (AF) is the most common arrhythmia among HHS patients. AF is associated with substantial morbidity and mortality, making its prevention and treatment of high clinical interest. This study defines the anti-AF action of Alda-1 (an established cardioprotective agent) and the underlying mechanisms of the action in our well-characterized HHS and cellular models. We found that Alda-1 effectively eliminated binge alcohol-evoked Ca2+ triggered activities (Ca2+ waves, prolonged Ca2+ transient diastolic decay) and arrhythmia inducibility in intact mouse atria. We then demonstrated that alcohol impaired human RyR2 channels (isolated from organ donors' hearts). The functional role of alcohol-caused RyR2 channel dysfunction in Ca2+ triggered arrhythmic activities was evidenced in a unique transgenic mouse model with a loss-of-function mutation (RyR2E4872Q+/-). Alda-1 is known to activate aldehyde dehydrogenase 2 (ALDH2), a key enzyme in alcohol detoxification. However, we found an increased level of ALDH2 and a preserved normal balance of pro- vs anti-apoptotic signaling in binge alcohol exposed hearts and H9c2 differentiated myocytes, which suggests that the link of alcohol-ALDH2-apoptosis is unlikely to be a key factor leading to binge alcohol-evoked arrhythmogenicity. We have previously reported that binge alcohol-activated stress response kinase JNK2 causatively drives Ca2+-triggered atrial arrhythmogenicity. Here, we found that JNK2-specific inhibition in either isolated human RyR2 channels or intact mouse atria abolished alcohol-evoked RyR2 channel dysfunction and Ca2+ triggered arrhythmic activities, suggesting a strong alcohol-JNK2-RyR2 interaction in atrial arrhythmogenicity. Furthermore, we revealed, for the first time, that Alda-1 suppresses JNK2 (but not JNK1) enzyme activity independently of ALDH2, which in turn alleviates binge alcohol-evoked Ca2+ triggered atrial arrhythmogenesis. Our findings provide novel mechanistic insights into the anti-arrhythmic action of Alda-1 and suggest that Alda-1 represents a potential preventative agent for AF management for HHS patients.

Elevated levels of alcohol dehydrogenase aggravate ethanol-evoked cardiac remodeling and contractile anomalies through FKBP5-yap-mediated regulation of ferroptosis and ER stress

Alcohol intake provokes severe organ injuries including alcoholic cardiomyopathy with hallmarks of cardiac remodeling and contractile defects. This study examined the toxicity of facilitated ethanol metabolism in alcoholism-evoked changes in myocardial morphology and contractile function, insulin signaling and various cell death domains using cardiac-selective overexpression of alcohol dehydrogenase (ADH). WT and ADH mice were offered an alcohol liquid diet for 12 weeks prior to assessment of cardiac geometry, function, ER stress, apoptosis and ferroptosis. Alcohol intake provoked pronounced glucose intolerance, cardiac remodeling and contractile anomalies with apoptosis, ER stress, and ferroptosis, the effects were accentuated by ADH with the exception of global glucose intolerance. Hearts from alcohol ingesting mice displayed dampened insulin-stimulated phosphorylation of insulin receptor (tyr1146) and IRS-1 (tyrosine) along with elevated IRS-1 serine phosphorylation, the effect was augmented by ADH. Alcohol challenge dampened phosphorylation of Akt and GSK-3β, and increased phosphorylation of c-Jun and JNK, the effects were accentuated by ADH. Alcohol challenge promoted ER stress, FK506 binding protein 5 (FKBP5), YAP, apoptosis and ferroptosis, the effects were exaggerated by ADH. Using a short-term ethanol challenge model (3 g/kg, i.p., twice in three days), we found that inhibition of FKBP5-YAP signaling or facilitated ethanol detoxification by Alda-1 alleviated ethanol cardiotoxicity. In vitro study revealed that the ethanol metabolite acetaldehyde evoked cardiac contractile anomalies, lipid peroxidation, and apoptosis, the effects of which were mitigated by Alda-1, inhibition of ER stress, FKBP5 and YAP. These data suggest that facilitated ethanol metabolism via ADH exacerbates alcohol-evoked myocardial remodeling, functional defects, and insulin insensitivity possibly through a FKBP5-YAP-associated regulation of ER stress and ferroptosis.

Heavy Metal Scavenger Metallothionein Rescues Against Cold Stress-Evoked Myocardial Contractile Anomalies Through Regulation of Mitophagy

Cold stress prompts an increased prevalence of cardiovascular morbidity yet the underneath machinery remains unclear. Oxidative stress and autophagy appear to contribute to cold stress-induced cardiac anomalies. Our present study evaluated the effect of heavy metal antioxidant metallothionein on cold stress (4 °C)-induced in cardiac remodeling and contractile anomalies and cell signaling involved including regulation of autophagy and mitophagy. Cold stress (3 weeks) prompted interstitial fibrosis, mitochondrial damage (mitochondrial membrane potential and TEM ultrastructure), oxidative stress (glutathione, reactive oxygen species and superoxide), lipid peroxidation, protein injury, elevated left ventricular (LV) end systolic and diastolic diameters, decreased fractional shortening, ejection fraction, Langendorff heart function, cardiomyocyte shortening, maximal velocities of shortening/relengthening, and electrically stimulated intracellular Ca2+ rise along with elongated relaxation duration and intracellular Ca2+ clearance, the responses of which were overtly attenuated or mitigated by metallothionein. Levels of apoptosis, cell death (Bax and loss of Bcl2, IL-18), and autophagy (LC3BII-to-LC3BI ratio, Atg7 and Beclin-1) were overtly upregulated with comparable p62 under cold stress. Cold stress also evoked elevated mitophagy (decreased TOM20, increased Parkin and FUNDC1 with unaltered BNIP3). Cold stress overtly dampened phosphorylation of autophagy/mitophagy inhibitory molecules Akt and mTOR, stimulated and suppressed phosphorylation of ULK1 and eNOS, respectively, in the absence of altered pan protein levels. Cold stress-evoked responses in cell death, autophagy, mitophagy and their regulatory domains were overtly attenuated or ablated by metallothionein. Suppression of autophagy and mitophagy with 3-methyladenine, bafilomycin A1, cyclosporine A, and liensinine rescued hypothermia-instigated cardiomyocyte LC3B puncta formation and mechanical anomalies. Our findings support a protective nature for metallothionein in deep hypothermia-evoked cardiac abnormalities associated with regulation of autophagy and mitophagy.

ALDH2 mitigates LPS-induced cardiac dysfunction, inflammation, and apoptosis through the cGAS/STING pathway

BACKGROUND

Sepsis is a severe syndrome of organ dysfunction that often leads to cardiac dysfunction and endangers life. The role of mitochondrial aldehyde dehydrogenase 2 (ALDH2) in LPS-induced myocardial injury is unclear. The purpose of this study was to assess the role of ALDH2 in lipopolysaccharide (LPS)-induced myocardial injury and the regulatory mechanism and to identify potential therapeutic strategies for treating this condition.

METHODS

An in vivo model was established by 12 h of LPS (10 mg/kg, intraperitoneal injection) stimulation, and an in vitro model was generated by stimulating H9C2 cells with LPS (10 μg/ml) for 12 h. We then used the ALDH2 activator Alda-1 and the ALDH2 inhibitor daidzin to assess their effects on LPS-induced cardiac injury. Cardiac function in mice was evaluated by using cardiac ultrasound. We used various methods to evaluate inflammation, apoptosis, and oxidative stress, including ELISA, flow cytometry, JC-1 staining, Western blotting, and DCFH-DA staining. Additionally, we used a small interfering RNA (siRNA) to knock down cyclic GMP-AMP synthase (cGAS) to further investigate the relationship between ALDH2 and cGAS in LPS-induced cardiac injury.

RESULTS

LPS-induced cardiac dysfunction and increased the levels of the cardiac injury markers creatine kinase-MB (CKMB) and lactate dehydrogenase (LDH) in vivo. This change was accompanied by an increase in reactive oxygen species (ROS) levels, which exacerbated the oxidative stress response and regulated apoptosis through cleaved caspase-3, BAX, BCL-2. The expression of inflammatory cytokines such as IL-6/IL-1β/TNF-α was also upregulated. However, these effects were reversed by pretreatment with Alda-1 via the inhibition of cGAS/stimulator of interferon genes (STING) signaling pathway. Interestingly, LPS, Alda-1 and daidzin altered the activity of ALDH2 but did not regulate its protein expression. Knocking down cGAS in H9C2 cardiomyocytes alleviated LPS-induced cardiac inflammation, apoptosis, and ROS production and weakened the synergistic effect of daidzin.

CONCLUSION

We demonstrated that ALDH2 alleviated LPS-induced cardiac dysfunction, inflammation, and apoptosis through the cGAS/STING signaling pathway, thereby protecting against LPS-induced cardiac injury. This study identifies a novel therapeutic approach for treating sepsis-induced cardiomyopathy (SIC).

Deficiency of aldehyde dehydrogenase 2 aggravates ethanol-induced cytotoxicity in N2a cells via CaMKII/Drp1-mediated mitophagy

Chronic alcohol abuse causes brain damage and has been associated with an increased risk of Alzheimer's disease. The toxic metabolite of alcohol, acetaldehyde, which is converted to acetate by aldehyde dehydrogenase 2 (ALDH2), has been shown to induce excessive mitochondrial fragmentation and dysfunction leading to neurotoxicity. However, it is still unclear how alcohol affects mitochondrial function in ALDH2-deficient cells. The present study investigated the association between abnormal mitochondrial dynamics, mitophagy and cytotoxicity in ALDH2-deficient N2a cells treated with ethanol. It was found that ethanol induced dynamin-related protein 1 (Drp1)-mediated mitochondrial fragmentation and impaired mitochondrial function, causing excessive mitophagy and cytotoxicity in ALDH2-deficient N2a cells while inducing Ca2+ influx and activating Ca2+/calmodulin-dependent protein kinase II (CaMKII). Inhibition of Ca2+ overload or CaMKII activation prevented Drp1 phosphorylation and ameliorated ethanol-induced mitophagy and cytotoxicity, indicating that Ca2+-dependent CaMKII activation was critical for mediating Drp1-dependent excessive mitochondrial fission and mitophagy in ALDH2-deficient N2a cells. The results of the present study suggested that prevention of intracellular Ca2+ overload might be beneficial for preventing neurotoxicity associated with alcohol abuse in individuals with defective ALDH2.

The role of aldehyde dehydrogenase 2 in cardiovascular disease

Aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial enzyme involved in the detoxification of alcohol-derived acetaldehyde and endogenous aldehydes. The inactivating ALDH2 rs671 polymorphism, present in up to 8% of the global population and in up to 50% of the East Asian population, is associated with increased risk of cardiovascular conditions such as coronary artery disease, alcohol-induced cardiac dysfunction, pulmonary arterial hypertension, heart failure and drug-induced cardiotoxicity. Although numerous studies have attributed an accumulation of aldehydes (secondary to alcohol consumption, ischaemia or elevated oxidative stress) to an increased risk of cardiovascular disease (CVD), this accumulation alone does not explain the emerging protective role of ALDH2 rs671 against ageing-related cardiac dysfunction and the development of aortic aneurysm or dissection. ALDH2 can also modulate risk factors associated with atherosclerosis, such as cholesterol biosynthesis and HDL biogenesis in hepatocytes and foam cell formation and efferocytosis in macrophages, via non-enzymatic pathways. In this Review, we summarize the basic biology and the clinical relevance of the enzymatic and non-enzymatic, tissue-specific roles of ALDH2 in CVD, and discuss the future directions in the research and development of therapeutic strategies targeting ALDH2. A thorough understanding of the complex roles of ALDH2 in CVD will improve the diagnosis, management and prognosis of patients with CVD who harbour the ALDH2 rs671 polymorphism.

Deficiency in Beclin1 attenuates alcohol-induced cardiac dysfunction via inhibition of ferroptosis

BACKGROUND

Binge drinking leads to compromised mitochondrial integrity and contractile function in the heart although little effective remedy is readily available. Given the possible derangement of autophagy in ethanol-induced cardiac anomalies, this study was designed to examine involvement of Beclin1 in acute ethanol-induced cardiac contractile dysfunction, in any, and the impact of Beclin1 haploinsufficiency on ethanol cardiotoxicity with a focus on autophagy-related ferroptosis.

METHODS

WT and Beclin1 haploinsufficiency (BECN^+/-) mice were challenged with ethanol for one week (2 g/kg, i.p. on day 1, 3 and 7) prior to assessment of cardiac injury markers (LDH, CK-MB), cardiac geometry, contractile and mitochondrial integrity, oxidative stress, lipid peroxidation, apoptosis and ferroptosis.

RESULTS

Ethanol exposure compromised cardiac geometry and contractile function accompanied with upregulated Beclin1 and autophagy, mitochondrial injury, oxidative stress, lipid peroxidation and apoptosis, and ferroptosis (GPx4, SLC7A11, NCOA4). Although Beclin1 deficiency did not affect cardiac function in the absence of ethanol challenge, it alleviated ethanol-induced changes in cardiac injury biomarkers, cardiomyocyte area, interstitial fibrosis, echocardiographic and cardiomyocyte mechanical properties along with mitochondrial integrity, oxidative stress, lipid peroxidation, apoptosis and ferroptosis. Ethanol challenge evoked pronounced ferroptosis (downregulated GPx4, SLC7A11 and elevated NCOA4, lipid peroxidation), the effect was alleviated by Beclin1 haploinsufficiency. Inhibition of ferroptosis using LIP-1 rescued ethanol-induced cardiac mechanical anomalies. In vitro study noted that ferroptosis induction using erastin abrogated Beclin1 haploinsufficiency-induced response against ethanol.

CONCLUSIONS

In sum, our data suggest that Beclin1 haploinsufficiency benefits acute ethanol challenge-induced myocardial remodeling and contractile dysfunction through ferroptosis-mediated manner.

Activation of aldehyde dehydrogenase 2 protects ethanol-induced osteonecrosis of the femoral head in rat model

OBJECTIVES

Osteonecrosis of the femoral head (ONFH) is a devastating disease characterized by destructive bone structures, enlarged adipocyte accumulation and impaired vascularization. The aldehyde dehydrogenase 2 (ALDH 2) is the limiting enzyme for ethanol metabolism with many physiological functions. The aim was investigated the potential protective role of activated ALDH 2 by Alda-1 for ethanol-induced ONFH.

MATERIALS AND METHODS

The ethanol-induced ONFH in rat was performed to explore the protective of Alda-1 by various experimental methods. Subsequently, the effect of Alda-1 and ethanol on the osteogenic and adipogenic differentiation was investigated via multiple cellular and molecular methods. Finally, the effect of Alda-1 and ethanol on the neo-vascularization was detected in Human umbilical vein endothelial cells (HUVECs) and ONFH model.

RESULTS

Firstly, radiographical and pathological measurements indicated that alda-1 protected ethanol-induced ONFH. Moreover, ethanol significantly inhibited the proliferation and osteogenic differentiation of BMSCs, whereas Alda-1 could distinctly rescue it by PI3K/AKT signalling. Secondly, ethanol remarkably promoted the lipid vacuoles formation of BMSCs, while Alda-1 significantly retarded it on BMSCs by AMPK signalling pathway. Finally, ethanol significantly inhibited proliferation and growth factor level resulting in reduced angiogenesis, whereas Alda-1 could rescue the effect of ethanol. Additionally, Alda-1 significantly reduced the occurrence of ONFH and promoted vessel number and distribution in alcoholic ONFH.

CONCLUSIONS

Alda-1 activation of ALDH 2 was highly demonstrated to protect ethanol-induced ONFH by triggering new bone formation, reducing adipogenesis and stimulating vascularization.

Aldehyde dehydrogenase 2 alleviates monosodium iodoacetate-induced oxidative stress, inflammation and apoptosis in chondrocytes via inhibiting aquaporin 4 expression

BACKGROUND

Knee osteoarthritis (KOA) is a common cause of disability among the elderly. We aimed to explore the effects of aldehyde dehydrogenase (ALDH) 2 on the progression of KOA and identifying the potential mechanisms.

METHODS

First, ALDH2 expression in knee joint effusion of patients with KOA and the levels of oxidative stress-related markers were determined. After ALDH2 overexpression in monosodium iodoacetate (MIA)-treated SW1353 cells, cell viability was tested with CCK-8 assay. Subsequently, oxidative stress and inflammation-associated factors were measured. Meanwhile, cell apoptosis was assessed with TUNEL staining and expression of apoptosis-related proteins was detected by western blotting. To analyze the mechanism of ALDH2 in KOA, aquaporin 4 (AQP4) expression was determined using western blotting following ALDH2-upregulation. Subsequently, AQP4 was overexpressed to evaluate the changing of oxidative stress, inflammation and apoptosis in SW1353 cells exposed to MIA with ALDH2 overexpression.

RESULTS

Results indicated that knee joint effusion with higher ALDH2 expression displayed lower oxidative stress. In addition, significantly upregulated ALDH2 expression was observed in MIA-treated SW1353 cells. ALDH2 overexpression oxidative stress, inflammation and apoptosis in SW1353 cells exposed to MIA. Moreover, MIA-triggered elevated expression of AQP4, which was reduced by ALDH2 overexpression. By contrast, AQP4-upregulation abrogated the inhibitory effects of ALDH2 on oxidative stress, inflammation and apoptosis in MIA-induced SW1353 cells.

CONCLUSIONS

ALDH2 inactivates the expression of AQP4, by which mechanism the MIA-induced oxidative stress, inflammation and apoptosis injuries were alleviated, which provides a novel insight for understanding the mechanism of KOA and a promising target for the treatment of this disease.

Tanshinone IIA alleviates acute ethanol-induced myocardial apoptosis mainly through inhibiting the expression of PDCD4 and activating the PI3K/Akt pathway

Myocardial apoptosis contributes to acute ethanol-induced cardiac injury. Improving immoderate apoptosis has become the potential therapeutic strategy for acute ethanol-induced heart damage. Previous studies reported that Tanshinone IIA (Tan IIA), a key ingredient extracted from Salvia miltiorrhiza Bunge, performed an anti-apoptotic role against acute ethanol-related cell damage. In this study, we investigated whether Tan IIA protected the acute ethanol-induced cardiac damage in vivo and in vitro. C57BL/6 mice were treated with acute ethanol and then treated with Tan IIA. The results showed that Tan IIA significantly improved heart function and blocked myocardial apoptosis. Acute ethanol exposure induced H9C2 cells apoptosis. Treatment with Tan IIA abrogated acute ethanol-induced H9C2 cells apoptosis. Mechanistically, Tan IIA inhibited apoptosis by downregulating the programmed cell death protein 4 (PDCD4) expression and activating the phosphoinositide 3-kinase (PI3K)/Akt pathway. Furthermore, PDCD4 overexpression abrogated Tan IIA-mediated anti-apoptotic role and activation on the PI3K/Akt pathway. Interestingly, the PI3K inhibitor (LY294002) application significantly attenuated the main protective effects of Tan IIA. In conclusion, Tan IIA improves acute ethanol-induced myocardial apoptosis mainly through regulating the PDCD4 expression and activating the PI3K/Akt signaling pathway. We provide evidence that Tan IIA is a new treatment approach for acute ethanol-induced heart damage.

Ethanol, neurosteroids and cellular stress responses: Impact on central nervous system toxicity, inflammation and autophagy

Alcohol intake can impair brain function, in addition to other organs such as the liver and kidney. In the brain ethanol can be detrimental to memory formation, through inducing the integrated stress response/endoplasmic reticulum stress/unfolded protein response and the molecular mechanisms linking stress to other events such as NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammation and autophagy. This literature review aims to provide an overview of our current understanding of the molecular mechanisms involved in ethanol-induced damage with endoplasmic reticulum stress, integrated stress response, NLRP3 inflammation and autophagy, while discussing the impact of neurosteroids and oxysterols, including allopregnanolone, 25-hydroxycholesterol and 24S-hydroxycholesterol, on the central nervous system.

Deletion of the E3 ubiquitin ligase, Parkin, exacerbates chronic alcohol intake-induced cardiomyopathy through an Ambra1-dependent mechanism

BACKGROUND AND PURPOSE

Chronic alcohol consumption contributes to contractile dysfunction and unfavourable geometric changes in myocardium, accompanied by altered autophagy and disturbed mitochondrial homeostasis. The E3 ubiquitin ligase Parkin encoded by PARK2 gene maintains a fundamental role in regulating mitophagy and mitochondrial homeostasis, although little is known of its role in the aetiology of alcoholic cardiomyopathy. Here we assessed the effects of Parkin deletion in chronic alcohol-evoked cardiotoxicity.

EXPERIMENTAL APPROACH

Following alcohol (4%) or control diet intake for 8 weeks, adult male wild-type (WT) and PARK2 knockout (Parkin^-/- ) mice were examined using echocardiography. Cardiomyocyte mechanical properties, morphology of myocardium, and mitochondrial damage were also evaluated. Autophagy and mitophagy levels were assessed by LC3B and GFP-LC3 puncta, and lysosome-dependent autophagic flux was scrutinized using GFP-mRFP-LC3 puncta and Bafilomycin A1 treatment.

KEY RESULTS

Chronic alcohol exposure provoked unfavourable geometric changes in myocardium and led to mitochondrial dysfunction and cardiac contractile defects, effects further exacerbated by Parkin knockout. Chronic alcohol exposure provoked autophagy and PINK1/Parkin-mediated mitophagy without affecting lysosome-dependent autophagic flux, the effects of which were diminished by Parkin deletion. Parkin adenovirus infection in neonatal rat cardiomyocytes further increased autophagy and protected against alcohol-induced myocardial injury, effects blocked by siRNA for Ambra1 (Autophagy and Beclin1 regulator 1). Immunofluorescence staining and co-immunoprecipitation assays showed interactions between Parkin and Ambra1.

CONCLUSIONS AND IMPLICATIONS

Parkin was essential for cardiac homeostasis in alcohol challenge, accompanied by increased autophagy/mitophagy and maintenance of mitochondrial integrity through its interaction with Ambra1.

Alda-1 Attenuates Hyperoxia-Induced Acute Lung Injury in Mice

Acute lung injury (ALI), a milder form of acute respiratory distress syndrome (ARDS), is a leading cause of mortality in older adults with an increasing prevalence. Oxygen therapy, is a common treatment for ALI, involving exposure to a high concentration of oxygen. Unfortunately, hyperoxia induces the formation of reactive oxygen species which can cause an increase in 4-HNE (4-hydroxy 2 nonenal), a toxic byproduct of lipid peroxidation. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) serves as an endogenous shield against oxidative stress-mediated damage by clearing 4-HNE. Alda-1 [(N-(1, 3 benzodioxol-5-ylmethyl)-2, 6- dichloro-benzamide)], a small molecular activator of ALDH2, protects against reactive oxygen species-mediated oxidative stress by promoting ALDH2 activity. As a result, Alda-1 shields against ischemic reperfusion injury, heart failure, stroke, and myocardial infarction. However, the mechanisms of Alda-1 in hyperoxia-induced ALI remains unclear. C57BL/6 mice implanted with Alzet pumps received Alda-1 in a sustained fashion while being exposed to hyperoxia for 48 h. The mice displayed suppressed immune cell infiltration, decreased protein leakage and alveolar permeability compared to controls. Mechanistic analysis shows that mice pretreated with Alda-1 also experience decreased oxidative stress and enhanced levels of p-Akt and mTOR pathway associated proteins. These results show that continuous delivery of Alda-1 protects against hyperoxia-induced lung injury in mice.

A critical assessment of the potential of pharmacological modulation of aldehyde dehydrogenases to treat the diseases of bone loss

Chronic alcoholism (CA) decreases bone mass and increases the risk of hip fracture. Alcohol and its main metabolite, acetaldehyde impairs osteoblastogenesis by increasing oxidative stress. Aldehyde dehydrogenase (ALDH) is the rate-limiting enzyme in clearing acetaldehyde from the body. The clinical relevance of ALDH in skeletal function has been established by the discovery of single nucleotide polymorphism, SNP (rs671) in the ALDH2 gene giving rise to an inactive form of the enzyme (ALDH2*2) that causes increased serum acetaldehyde and osteoporosis in the affected individuals. Subsequent mouse genetics studies have replicated human phenotype in mice and confirmed the non-redundant role of ALDH2 in bone homeostasis. The activity of ALDH2 is amenable to pharmacological modulation. ALDH2 inhibition by disulfiram (DSF) and activation by alda-1 cause reduction and induction of bone formation, respectively. DSF also inhibits peak bone mass accrual in growing rats. On the other hand, DSF showed an anti-osteoclastogenic effect and protected mice from alcohol-induced osteopenia by inhibiting ALDH1a1 in bone marrow monocytes. Besides DSF, there are several classes of ALDH inhibitors with disparate skeletal effects. Alda-1, the ALDH2 activator induced osteoblast differentiation by increasing bone morphogenic protein 2 (BMP2) expression via ALDH2 activation. Alda-1 also restored ovariectomy-induced bone loss. The scope of structure-activity based studies with ALDH2 and the alda-1-like molecule could lead to the discovery of novel osteoanabolic molecules. This review will critically discuss the molecular mechanism of the ethanol and its principal metabolite, acetaldehyde in the context of ALDH2 in bone cells, and skeletal homeostasis.

Aldh2 gene reduces oxidative stress in the bladder by regulating the NF-κB pathway in a mouse model of ketamine-induced cystitis

Aldehyde dehydrogenase 2 (aldh2) serves an important role in the development of organ injury. Therefore, the present study investigated the effects of aldh2 on the oxidative stress response in a mouse model of ketamine-induced cystitis (KIC). A total of 60 8-week-old male Institute of Cancer Research wild-type (WT) mice and 45 aldh2 knock-out (KO) mice were randomized to receive low-dose ketamine (30 mg/kg), high-dose ketamine (60 mg/kg) or normal saline (controls). At 4, 8 and 12 weeks post-injection, bladder tissues were harvested and used to investigate the protective mechanisms of aldh2 on bladder function. The results demonstrated that aldh2 KO mice exhibited significant weight loss following chronic ketamine injection compared with that in WT mice. Furthermore, ketamine treatment increased the urination rate (P<0.05), pathological score (P<0.05), levels of the oxidative stress product malondialdehyde (P<0.05) in addition to reducing the expression of the anti-oxidative stress enzyme superoxide dismutase (P<0.05) and glutathione-SH (P<0.05). Oxidative stress in aldh2 KO mice was also found to significantly enhance the expression of proteins associated with the NF-κB signaling pathway, which promoted the expression of inducible nitric oxide synthase (P<0.05) and cyclooxygenase-2 (P<0.05) further. Finally, aldh2 KO mice demonstrated higher severity of fibrosis in the submucosal and muscular layers of the bladder. In conclusion, the present study suggests that aldh2 serves a protective role in preventing inflammation and fibrosis in KIC.

Parkin deficiency accentuates chronic alcohol intake-induced tissue injury and autophagy defects in brain, liver and skeletal muscle

Alcoholism leads to organ injury including mitochondrial defect and apoptosis with evidence favoring a role for autophagy dysregulation in alcoholic damage. Parkin represents an autosomal recessive inherited gene for Parkinson's disease and an important member of selective autophagy for mitochondria. The association between Parkinson's disease and alcoholic injury remains elusive. This study aimed to examine the effect of parkin deficiency on chronic alcohol intake-induced organ injury in brain, liver and skeletal muscle (rectus femoris muscle). Adult parkin-knockout (PRK-/-) and wild-type mice were placed on Liber-De Carli alcohol liquid diet (4%) for 12 weeks prior to assessment of liver enzymes, intraperitoneal glucose tolerance, protein carbonyl content, apoptosis, hematoxylin and eosin morphological staining, and mitochondrial respiration (cytochrome c oxidase, NADH:cytochrome c reductase and succinate:cytochrome c reductase). Autophagy protein markers were monitored by western blot analysis. Our data revealed that chronic alcohol intake imposed liver injury as evidenced by elevated aspartate aminotransferase and alanine transaminase, glucose intolerance, elevated protein carbonyl formation, apoptosis, focal inflammation, necrosis, microvesiculation, autophagy/mitophagy failure and dampened mitochondrial respiration (complex IV, complexes I and III, and complexes II and III) in the brain, liver and rectus femoris skeletal muscle. Although parkin ablation itself did not generate any notable effects on liver enzymes, insulin sensitivity, tissue carbonyl damage, apoptosis, tissue morphology, autophagy or mitochondrial respiration, it accentuated alcohol intake-induced tissue damage, apoptosis, morphological change, autophagy/mitophagy failure and mitochondrial injury without affecting insulin sensitivity. These data suggest that parkin plays an integral role in the preservation against alcohol-induced organ injury, apoptosis and mitochondrial damage.

Aldehyde dehydrogenase 2 protects against abdominal aortic aneurysm formation by reducing reactive oxygen species, vascular inflammation, and apoptosis of vascular smooth muscle cells

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is an enzyme that detoxifies aldehydes by converting them to carboxylic acids. ALDH2 deficiency is known to increase oxidative stress. Increased oxidative stress plays a pivotal role in abdominal aortic aneurysm (AAA) pathogenesis. Reactive oxygen species (ROS) promote degradation of the extracellular matrix (ECM) and vascular smooth muscle cell (VSMC) apoptosis. Reducing oxidative stress by an ALDH2 activator could have therapeutic potential for limiting AAA development. We hypothesized that ALDH2 deficiency could increase the risk for AAA by decreasing ROS elimination and that an ALDH2 activator could provide an alternative option for AAA treatment. The National Center for Biotechnology (NCBI) Gene Expression Omnibus (GEO) database was used. Human aortic smooth muscle cells (HASMCs) were used for the in vitro experiments. Gene-targeted ALDH2*2 KI knock-in mice on a C57BL/6J background and apolipoprotein E knockout (ApoE KO) mice were obtained. An animal model of AAA was constructed using osmotic minipumps to deliver 1000 ng/kg/min angiotensin II (AngII) for 28 days. Patients with AAA had significantly lower ALDH2 expression levels than normal subjects. ALDH2*2 KI mice were susceptible to AngII administration, exhibiting significantly increased AAA incidence rates and increased aortic diameters. Alda-1, an ALDH2 activator, reduced AngII-induced ROS production, NF-kB activation, and apoptosis in HASMCs. Alda-1 attenuated AngII-induced aneurysm formation and decreased aortic expansion in ApoE KO mice. We concluded that ALDH2 deficiency is associated with the development of AAAs in humans and a murine disease model. ALDH2 deficiency increases susceptibility to AngII-induced AAA formation by attenuating anti-ROS effects and increasing VSMC apoptosis and vascular inflammation. Alda-1 was shown to attenuate the progression of experimental AAA in a murine model.

Cardiac Toxicity From Ethanol Exposure in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Alcohol use prior to and during pregnancy remains a significant societal problem and can lead to developmental fetal abnormalities including compromised myocardia function and increased risk for heart disease later in life. Alcohol-induced cardiac toxicity has traditionally been studied in animal-based models. These models have limitations due to physiological differences from human cardiomyocytes (CMs) and are also not suitable for high-throughput screening. We hypothesized that human-induced pluripotent stem cell-derived CMs (hiPSC-CMs) could serve as a useful tool to study alcohol-induced cardiac defects and/or toxicity. In this study, hiPSC-CMs were treated with ethanol at doses corresponding to the clinically relevant levels of alcohol intoxication. hiPSC-CMs exposed to ethanol showed a dose-dependent increase in cellular damage and decrease in cell viability, corresponding to increased production of reactive oxygen species. Furthermore, ethanol exposure also generated dose-dependent increased irregular Ca2+ transients and contractility in hiPSC-CMs. RNA-seq analysis showed significant alteration in genes belonging to the potassium voltage-gated channel family or solute carrier family, partially explaining the irregular Ca2+ transients and contractility in ethanol-treated hiPSC-CMs. RNA-seq also showed significant upregulation in the expression of genes associated with collagen and extracellular matrix modeling, and downregulation of genes involved in cardiovascular system development and actin filament-based process. These results suggest that hiPSC-CMs can be a novel and physiologically relevant system for the study of alcohol-induced cardiac toxicity.

Aldehyde dehydrogenase 2 preserves mitochondrial morphology and attenuates hypoxia/reoxygenation-induced cardiomyocyte injury

BACKGROUND

Disturbance of mitochondrial fission and fusion (termed mitochondrial dynamics) is one of the leading causes of ischemia/reperfusion (I/R)-induced myocardial injury. Previous studies showed that mitochondrial aldehyde dehydrogenase 2 (ALDH2) conferred cardioprotective effect against myocardial I/R injury and suppressed I/R-induced excessive mitophagy in cardiomyocytes. However, whether ALDH2 participates in the regulation of mitochondrial dynamics during myocardial I/R injury remains unknown.

METHODS

In the present study, we investigated the effect of ALDH2 on mitochondrial dynamics and the underlying mechanisms using the H9c2 cells exposed to hypoxia/reoxygenation (H/R) as an in vitro model of myocardial I/R injury.

RESULTS

Cardiomyocyte apoptosis was significantly increased after oxygen-glucose deprivation and reoxygenation (OGD/R), and ALDH2 activation largely decreased the cardiomyocyte apoptosis. Additionally, we found that both ALDH2 activation and overexpression significantly inhibited the increased mitochondrial fission after OGD/R. Furthermore, we found that ALDH2 dominantly suppressed dynamin-related protein 1 (Drp1) phosphorylation (Ser616) and adenosine monophosphate-activated protein kinase (AMPK) phosphorylation (Thr172) but not interfered with the expression levels of mitochondrial shaping proteins.

CONCLUSIONS

We demonstrate the protective effect of ALDH2 against cardiomyocyte H/R injury with a novel mechanism on mitochondrial fission/fusion.

Mechanisms Underlying Muscle Protein Imbalance Induced by Alcohol

Both acute intoxication and longer-term cumulative ingestion of alcohol negatively impact the metabolic phenotype of both skeletal and cardiac muscle, independent of overt protein calorie malnutrition, resulting in loss of skeletal muscle strength and cardiac contractility. In large part, these alcohol-induced changes are mediated by a decrease in protein synthesis that in turn is governed by impaired activity of a protein kinase, the mechanistic target of rapamycin (mTOR). Herein, we summarize recent advances in understanding mTOR signal transduction, similarities and differences between the effects of alcohol on this central metabolic controller in skeletal muscle and in the heart, and the effects of acute versus chronic alcohol intake. While alcohol-induced alterations in global proteolysis via activation of the ubiquitin-proteasome pathway are equivocal, emerging data suggest alcohol increases autophagy in muscle. Further studies are necessary to define the relative contributions of these bidirectional changes in protein synthesis and autophagy in the etiology of alcoholic myopathy in skeletal muscle and the heart.

CD74 knockout attenuates alcohol intake-induced cardiac dysfunction through AMPK-Skp2-mediated regulation of autophagy

CD74, a non-polymorphic type II transmembrane glycoprotein and MHC class II chaperone, is the cell surface receptor for the inflammatory cytokine macrophage migration inhibitory factor (MIF) and participates in inflammatory signaling regulation. This study examined the potential role of CD74 in binge drinking-induced cardiac contractile dysfunction. WT and CD74 knockout mice were exposed to ethanol (3 g/kg/d, i.p., for 3 days). Echocardiography, cardiomyocyte function, histological staining and autophagy signaling including AMPK, mTOR, and AMPK downstream signals Skp2 and Sirt1 were evaluated. Our results revealed that ethanol challenge overtly compromised echocardiographic, cardiomyocyte contractile, intracellular Ca²⁺ and ultrastructural properties along with overt apoptosis, inflammation (elevated MIF, IL-1β and IL-6) and mitochondrial O₂^- production (p < 0.01), the effect of which was reconciled by CD74 ablation (p < 0.01 vs. ethanol group) with the exception of MIF expression. Ethanol challenge upregulated autophagy (p < 0.001), promoted AMPK phosphorylation and Sirt1 levels (p < 0.003) while suppressing mTOR phosphorylation and Skp2 levels (p < 0.02). These effects were reversed by CD74 ablation. In vitro studies demonstrated that short-term ethanol challenge compromised cardiomyocyte contractile function and facilitated GFP-Puncta formation, which were mitigated by CD74 knockout (p < 0.0001). Moreover, the CD74 ablation-offered beneficial effects against ethanol-induced cardiomyocyte dysfunction, and GFP-Puncta formation were nullified by the AMPK activator AICAR, the Skp2 inhibitor C1 or the Sirt1 activator SRT1720 (p < 0.0001). Taken together, our data revealed that CD74 ablation counteracts acute ethanol challenge-induced myocardial dysfunction, inflammation and apoptosis possibly through an AMPK-mTOR-Skp2-mediated regulation of autophagy.

Mitochondrial Aldehyde Dehydrogenase in Myocardial Ischemic and Ischemia-Reperfusion Injury

Myocardial ischemia-reperfusion (IR) injury during acute myocardial infarction or open-heart surgery would promote oxidative stress, leading to the accumulation of reactive aldehydes that cause cardiac damage. It has been well demonstrated that aldehyde dehydrogenase (ALDH)-2 is an important cardioprotective enzyme for its central role in the detoxification of reactive aldehydes. ALDH2 activation by small molecule activators is a promising approach for cardioprotection for myocardial IR injury.

ALDH2 and Stroke: A Systematic Review of the Evidence

Cerebral stroke is one of the leading causes of mortality and disability worldwide. The prevalence of cerebral stroke is the result of the synergistic effect of genetic susceptibility and numerous vascular risk factors, including hypertension, diabetes, excessive alcohol intake, obesity, and dyslipidemia. Mitochondrial aldehyde dehydrogenase (ALDH2) is a vital enzyme metabolizing various acetaldehyde and toxic aldehydes. The ALDH2 enzymatic activity is severely decreased in the individuals with ALDH2*2 gene mutation, especially in East Asians. Increasing epidemiological surveys have revealed that ALDH2 genetic polymorphism is closely associated with the increasing incidence of cardiovascular risk factors and cerebral stroke. Evidence from experimental studies has also suggested that ALDH2 facilitates the clearance of reactive aldehydes and reduces the size of cerebral infarct. Therefore, targeting ALDH2 may represent a promising avenue for protection against stroke injury. This review will mainly focus on clinical and epidemiological evidence and the underlying molecular mechanisms involved in the protective effect of ALDH2 in stroke-related injury.

Mechanisms of cardiac ethanol toxicity and novel treatment options

Ethanol can acutely and chronically alter cardiomyocyte and whole-organ function in the heart. Importantly, ethanol acutely and chronically predisposes to arrhythmias, while chronic abuse can induce heart failure. However, the molecular mechanisms of ethanol toxicity in the heart are incompletely understood. In this review, we summarize the current mechanistic knowledge on cardiac ethanol toxicity, with a focus on druggable pathways. Ethanol effects on excitation-contraction coupling, oxidative stress, apoptosis, and cardiac metabolism, as well as effects of ethanol metabolites will be discussed. Important recent findings have been gained by investigation of acute ethanol effects. These include a renewed focus on reactive oxygen species (ROS) and induction of SR Ca²⁺ leak by CaMKII-mediated pathways downstream of ROS. Furthermore, a clinical outlook into potential novel treatment options is provided.

Opposing effects of intracellular versus extracellular adenine nucleotides on autophagy: implications for β-cell function

AMPK-mTORC1 signaling senses nutrient availability, thereby regulating autophagy. Surprisingly, we found that, in β-cells, the AMPK activator 5-amino-4-imidazolecarboxamide ribofuranoside (AICAR) inhibited, rather than stimulated, autophagy. AICAR is an intermediate in the generation of inosine monophosphate, with subsequent conversion to other purine nucleotides. Adenosine regulated autophagy in a concentration-dependent manner: at high concentrations, it mimicked the AICAR effect on autophagy, whereas at low concentrations it stimulated autophagy through its cognate A₁ receptor. Adenosine regulation of autophagy was independent of AMPK or mTORC1 activity. Adenosine kinase (ADK) is the principal enzyme for metabolic adenosine clearance. ADK knockdown and pharmacological inhibition of the enzyme markedly stimulated autophagy in an adenosine A₁ receptor-dependent manner. High-concentration adenosine increased insulin secretion in a manner sensitive to treatment with the autophagy inducer Tat-beclin1, and inhibition of autophagy augmented secretion. In conclusion, high concentrations of AICAR or adenosine inhibit autophagy, whereas physiological concentrations of adenosine or inhibition of adenosine clearance by ADK stimulate autophagy via the adenosine receptor. Adenosine might thus be an autocrine regulator of autophagy, independent of AMPK-mTORC1 signaling. Adenosine regulates insulin secretion, in part, through modulation of autophagy.

Role of autophagy and regulatory mechanisms in alcoholic cardiomyopathy

Alcoholism is accompanied with a high incidence of cardiac morbidity and mortality due to the development of alcoholic cardiomyopathy, manifested as dilation of one or both ventricles, reduced ventricular wall thickness, myofibrillary disarray, interstitial fibrosis, hypertrophy and contractile dysfunction. Several theories have been postulated for the etiology of alcoholic cardiomyopathy including ethanol/acetaldehyde toxicity, mitochondrial production of reactive oxygen species, oxidative injury, apoptosis, impaired myofilament Ca²⁺ sensitivity and protein synthesis, altered fatty acid extraction and deposition, as well as accelerated protein catabolism. In particular, buildup of long-lived or dysfunctional organelles has been reported to contribute to cardiac structural and functional damage following alcoholism. Removal of cell debris and defective organelles by autophagy is essential to the maintenance of cardiac homeostasis in physiological and pathological conditions. However, insufficient understanding is currently available with regards to the involvement of autophagy in the pathogenesis of alcoholic cardiomyopathy. This review summarizes the recent findings on the pathophysiological role of dysregulated autophagy in one set and development of alcoholic cardiomyopathy. A thorough understanding of how autophagy is affected in alcoholism, and subsequently, contributes to the pathogenesis of alcoholic heart injury, will offer therapeutic guidance towards the management of alcoholic cardiomyopathy.

CYP2J2-derived EETs attenuated ethanol-induced myocardial dysfunction through inducing autophagy and reducing apoptosis

Chronic excessive drinking leads to myocardial contractile dysfunction and dilated cardiomyopathy, where ethanol toxicity plays an essential role. Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acids to form epoxyeicosatrienoic acids (EETs), which exert beneficial roles in the cardiovascular system, but their role in alcoholic cardiomyopathy is elusive. This study was designed to evaluate the effects and mechanisms of CYP2J2 gene delivery on ethanol-induced myocardial dysfunction with focus on autophagy and apoptosis. C57BL/6 J mice were challenged with a 4% Lieber-DeCarli ethanol liquid diet for 8 weeks, before which rAAV9-CYP2J2 was injected via the tail vein. Cardiac function was assessed using echocardiography, hemodynamic measurement, and cardiac histology. The results showed that chronic ethanol intake led to cardiac dilation, contractile dysfunction, cardiomyocyte hypertrophy, oxidative stress, and cardiomyocyte apoptosis, while CYP2J2 overexpression ameliorated these effects. Additionally, chronic ethanol consumption triggered myocardial autophagosome formation, but impaired autophagic flux via disrupting autophagosome-lysosome fusion, as evidenced by increased LC3 II/I, Beclin-1 and SQSTM1 levels, but reduced LAMP-2 expression. Interestingly, rAAV9-CYP2J2 treatment exerted cardioprotection via restoring autophagic flux in the alcoholic myocardium. Similarly, exogenous 11,12-EET addition significantly restored ethanol-induced neonatal rat cardiomyocyte autophagic flux impairment and inhibited apoptosis, both of which were mediated by AMPK/mTOR signaling pathway in vitro. In conclusion, our data suggest that CYP2J2-derived EETs attenuate ethanol-induced myocardial dysfunction through inducing autophagy and reducing apoptosis.

The potential of aldehyde dehydrogenase 2 as a therapeutic target in cardiovascular disease

INTRODUCTION

Mitochondrial aldehyde dehydrogenase (ALDH-2) plays a major role in the ethanol detoxification pathway by removing acetaldehyde. Therefore, ALDH-2 inhibitors such as disulfiram represent the first therapeutic targeting of ALDH-2 for alcoholism therapy. Areas covered: Recently, ALDH-2 was identified as an essential bioactivating enzyme of the anti-ischemic organic nitrate nitroglycerin, bringing ALDH-2 again into the focus of clinical interest. Mechanistic studies on the nitroglycerin bioactivation process revealed that during bioconversion of nitroglycerin and in the presence of reactive oxygen and nitrogen species the active site thiols of ALDH-2 are oxidized and the enzyme activity is lost. Thus, ALDH-2 activity represents a useful marker for cardiovascular oxidative stress, a concept, which has been meanwhile supported by a number of animal disease models. Mechanistic studies on the protective role of ALDH-2 in different disease processes identified the detoxification of 4-hydroxynonenal by ALDH-2 as a fundamental process of cardiovascular, cerebral and antioxidant protection. Expert opinion: The most recent therapeutic exploitation of ALDH-2 includes activators of the enzyme such as Alda-1 but also cell-based therapies (ALDH-bright cells) that deserve further clinical characterization in the future.

SR Ca2+-leak and disordered excitation-contraction coupling as the basis for arrhythmogenic and negative inotropic effects of acute ethanol exposure

AIMS

Ethanol has acute negative inotropic and arrhythmogenic effects. The underlying mechanisms, however, are largely unknown. Sarcoplasmic reticulum Ca²⁺-leak is an important mechanism for reduced contractility and arrhythmias. Ca²⁺-leak can be induced by oxidative stress and Ca²⁺/Calmodulin-dependent protein kinase II (CaMKII). Therefore, we investigated the influence of acute ethanol exposure on excitation-contraction coupling in atrial and ventricular cardiomyocytes.

METHODS AND RESULTS

Isolated human atrial and murine atrial or ventricular cardiomyocytes were preincubated for 30 min and then superfused with control solution or solution containing ethanol. Ethanol had acute negative inotropic and positive lusitropic effects in human atrial muscle strips and murine ventricular cardiomyocytes. Accordingly, Ca²⁺-imaging indicated lower Ca²⁺-transient amplitudes and increased SERCA2a activity, while myofilament Ca²⁺-sensitivity was reduced. SR Ca²⁺-leak was assessed by measuring Ca²⁺-sparks. Ethanol induced severe SR Ca²⁺-leak in human atrial cardiomyocytes (calculated leak: 4.60 ± 0.45 mF/F₀ vs 1.86 ± 0.26 in control, n ≥ 80). This effect was dose-dependent, while spontaneous arrhythmogenic Ca²⁺-waves increased ~5-fold, as investigated in murine cardiomyocytes. Delayed afterdepolarizations, which can result from increased SR Ca²⁺-leak, were significantly increased by ethanol. Measurements using the reactive oxygen species (ROS) sensor CM-H₂DCFDA showed increased ROS-stress in ethanol treated cells. ROS-scavenging with N-acetylcysteine prevented negative inotropic and positive lusitropic effects in human muscle strips. Ethanol-induced Ca²⁺-leak was abolished in mice with knockout of NOX2 (the main source for ROS in cardiomyocytes). Importantly, mice with oxidation-resistant CaMKII (Met281/282Val mutation) were protected from ethanol-induced Ca²⁺-leak.

CONCLUSION

We show for the first time that ethanol acutely induces strong SR Ca²⁺-leak, also altering excitation-contraction coupling. Acute negative inotropic effects of ethanol can be explained by reduced systolic Ca²⁺-release. Mechanistically, ROS-production via NOX2 and oxidative activation of CaMKII appear to play central roles. This provides a mechanism for the arrhythmogenic and negative inotropic effects of ethanol and suggests a druggable target (CaMKII).

Inhibition of advanced glycation endproduct (AGE) rescues against streptozotocin-induced diabetic cardiomyopathy: Role of autophagy and ER stress

Diabetes mellitus leads to oxidative stress and contractile dysfunction in the heart. Although several rationales have been speculated, the precise mechanism behind diabetic cardiomyopathy remains elusive. This study was designed to assess the role of inhibition of advanced glycation endproducts (AGE) in streptozotocin (STZ)-induced diabetic cardiac dysfunction. Cardiac contractile function was assessed in normal C57BL/6 and STZ (200mg/kg, single injection and maintained for 2 wks)-induced diabetic mice treated with or without the AGE inhibitor aminoguanidine (50mg/kg/d in drinking water) for 2 weeks using echocardiography and IonOptix MyoCam techniques. Diabetes compromised cardiac contractile function shown as reduced fractional shortening and ejection fraction, enlarged left ventricular end systolic/diastolic diameters, decreased peak shortening, maximal velocity of shortening/relengthening, prolonged shortening and relengthening duration as well as impaired intracellular Ca²⁺ homeostasis, the effects of which were alleviated or reversed by aminoguanidine treatment. Diabetes also inhibited autophagy, increased ER stress and phosphorylation of pro-hypertrophic signaling molecules Akt and mTOR, the effect of which was reversed by aminoguanidine. In vitro study revealed that methylglyoxal-derived AGE (MG-AGE) incubation in isolated cardiomyocytes promoted oxidation of sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA2a) and production of superoxide, the effects of which were negated by the autophagy inducer rapamycin, the ER stress chaperone TUDCA or the antioxidant N-acetylcysteine. Taken together, these data revealed that inhibition of AGE formation rescues against experimental diabetes-induced cardiac remodeling and contractile dysfunction possible through regulation of autophagy and ER stress.

ULK1-regulated autophagy: A mechanism in cellular protection for ALDH2 against hyperglycemia

Mitochondrial aldehyde dehydrogenase 2 (ALDH2), an important enzyme in the elimination of toxic aldehydes, is involved in cardioprotection against diabetes mellitus. This study was designed to examine the mechanism behind ALDH2-offered protection against high glucose exposure with a focus on autophagy. H9C2 cells were cultured with normal or high glucose medium in the presence or absence of the ALDH2 agonist Alda-1. GFP-LC3 puncta and immunofluorescence were employed to assess autophagosome formation. Western blotting was applied to evaluate autophagy protein markers Atg5, LC3, p62, ULK1 phosphorylation and ALDH2. JC-1 staining was used to monitor mitochondrial membrane potential and mitochondrial injury. CCK-8 and TUNEL assays were employed for apoptosis and cell viability. Our results indicated that high glucose promoted cell death and decreased cell viability. Levels of autophagy protein marker Atg5, and LC3B were decreased and level of p62 was elevated in hyperglycemic condition, the effects of which were reversed by ALHD2. High glucose lowered mitochondrial membrane potential, the effect of which was accentuated by ULK1 knock-down. All these high glucose-induced responses were negated by Alda-1 along with upregulated autophagy. The autophagy inhibitor 3-MA and lysosomal inhibitor bafilomycin A1 cancelled off whereas autophagy inducer rapamycin mimicked the Alda-1-offered protection against high glucose. High glucose suppressed phosphorylation of ULK1, the effect of which was mitigated by Alda-1. Knock-down of ULK1 using siRNA negated Alda-1-induced upregulation of autophagosome accumulation and LC3 expression. High glucose-dampened autophagy was also confirmed using GFP-LC3 puncta, and immunofluorescence. Taken together, these data suggested that ULK1 played a crucial role in ALDH2-offered protective effect against high glucose exposure-induced cardiomyocyte injury through regulation of autophagy.

The Inhibitory Effect of WenxinKeli on H9C2 Cardiomyocytes Hypertrophy Induced by Angiotensin II through Regulating Autophagy Activity

Objectives

We investigated the role of cardiomyocyte autophagy and its regulatory mechanisms by WenxinKeli (WXKL) in cells subjected to hypertrophy.

Methods

H9C2 cardiomyocytes were divided into 8 groups. Cytoskeletal proteins as well as endogenously expressed autophagy marker proteins were studied by confocal imaging. Western blotting was used to assess the levels of light chain-3 (LC3) and mechanistic target of rapamycin (mTOR). The cell viability assay was used to detect the content of ATP. Flow cytometry was used to detect apoptotic cardiomyocytes.

Results

(1) Compared with the control group, the length and width of cells in the Angiotensin II (AngII) group were significantly increased, while those in the 3-methyladenine (3-MA) and the WXKL groups were decreased. (2) Compared with AngII group, the expression of LC3 II/I protein in the 3-MA and WXKL groups was downregulated, while the expression of mTOR protein was upregulated. (3) Compared with the AngII group, the cardiomyocytes in the WXKL group showed increased ATP and decreased apoptosis rate and number of autophagosome.

Conclusions

We propose a novel role of WXKL as a likely inhibitor of cardiac hypertrophy by regulation of pathological autophagy.

Alcoholic Cardiomyopathy: Disrupted Protein Balance and Impaired Cardiomyocyte Contractility

Alcoholic cardiomyopathy (ACM) can develop after consumption of relatively large amounts of alcohol over time or from acute binge drinking. Of the many factors implicated in the etiology of ACM, chronic perturbation in protein balance has been strongly implicated. This review focused on recent contributions (since 2010) in the area of protein metabolism and cardiac function related to ACM. Data reviewed include that from in vitro and preclinical in vivo animal studies where alcohol or an oxidative metabolite was studied and outcome measures in either cardiomyocytes or whole heart pertaining to protein synthesis or degradation were reported. Additionally, studies on the contractile properties of cardiomyocytes were also included to link signal transduction with function. Methodological differences including the potential impact of sex, dosing, and duration/timing of alcohol administration are addressed. Acute and chronic alcohol consumption decreases cardiac protein synthesis and/or activation of proteins within the regulatory mammalian/mechanistic target of rapamycin complex pathway. Albeit limited, evidence suggests that myocardial protein degradation via the ubiquitin pathway is not altered, while autophagy may be enhanced in ACM. Alcohol impairs ex vivo cardiomyocyte contractility in relation to its metabolism and expression of proteins within the growth factor pathway. Dysregulation of protein metabolism, including the rate of protein synthesis and autophagy, may contribute to contractile deficits and is a hallmark feature of ACM meriting additional sex-inclusive, methodologically consistent studies.

Complex inhibition of autophagy by mitochondrial aldehyde dehydrogenase shortens lifespan and exacerbates cardiac aging

Autophagy, a conservative degradation process for long-lived and damaged proteins, participates in a cascade of biological processes including aging. A number of autophagy regulators have been identified. Here we demonstrated that mitochondrial aldehyde dehydrogenase (ALDH2), an enzyme with the most common single point mutation in humans, governs cardiac aging through regulation of autophagy. Myocardial mechanical and autophagy properties were examined in young (4months) and old (26-28months) wild-type (WT) and global ALDH2 transgenic mice. ALDH2 overexpression shortened lifespan by 7.7% without affecting aging-associated changes in plasma metabolic profiles. Myocardial function was compromised with aging associated with cardiac hypertrophy, the effects were accentuated by ALDH2. Aging overtly suppressed autophagy and compromised autophagy flux, the effects were exacerbated by ALDH2. Aging dampened phosphorylation of JNK, Bcl-2, IKKβ, AMPK and TSC2 while promoting phosphorylation of mTOR, the effects of which were exaggerated by ALDH2. Co-immunoprecipitation revealed increased dissociation between Bcl-2 and Beclin-1 (result of decreased Bcl-2 phosphorylation) in aging, the effect of which was exacerbated with ALDH2. Chronic treatment of the autophagy inducer rapamycin alleviated aging-induced cardiac dysfunction in both WT and ALDH2 mice. Moreover, activation of JNK and inhibition of either Bcl-2 or IKKβ overtly attenuated ALDH2 activation-induced accentuation of cardiomyocyte aging. Examination of the otherwise elderly individuals revealed a positive correlation between cardiac function/geometry and ALDH2 gene mutation. Taken together, our data revealed that ALDH2 enzyme may suppress myocardial autophagy possibly through a complex JNK-Bcl-2 and IKKβ-AMPK-dependent mechanism en route to accentuation of myocardial remodeling and contractile dysfunction in aging. This article is part of a Special Issue entitled: Genetic and epigenetic control of heart failure - edited by Jun Ren & Megan Yingmei Zhang.

Activation of ALDH2 with Low Concentration of Ethanol Attenuates Myocardial Ischemia/Reperfusion Injury in Diabetes Rat Model

The aim of this paper is to observe the change of mitochondrial aldehyde dehydrogenase 2 (ALDH2) when diabetes mellitus (DM) rat heart was subjected to ischemia/reperfusion (I/R) intervention and analyze its underlying mechanisms. DM rat hearts were subjected to 30 min regional ischemia and 120 min reperfusion in vitro and pretreated with ALDH2 activator ethanol (EtOH); cardiomyocyte in high glucose (HG) condition was pretreated with ALDH2 activator Alda-1. In control I/R group, myocardial tissue structure collapse appeared. Compared with control I/R group, left ventricular parameters, SOD activity, the level of Bcl-2/Bax mRNA, ALDH2 mRNA, and protein expressions were decreased and LDH and MDA contents were increased, meanwhile the aggravation of myocardial structure injury in DM I/R group. When DM I/R rats were pretreated with EtOH, left ventricular parameters, SOD, Bcl-2/Bax, and ALDH2 expression were increased; LDH, MDA, and myocardial structure injury were attenuated. Compared with DM + EtOH I/R group, cyanamide (ALDH2 nonspecific blocker), atractyloside (mitoPTP opener), and wortmannin (PI3K inhibitor) groups all decreased left ventricular parameters, SOD, Bcl-2/Bax, and ALDH2 and increased LDH, MDA, and myocardial injury. When cardiomyocyte was under HG condition, CCK-8 activity and ALDH2 protein expression were decreased. Alda-1 increased CCK-8 and ALDH2. Our findings suggested enhanced ALDH2 expression in diabetic I/R rats played the cardioprotective role, maybe through activating PI3K and inhibiting mitoPTP opening.

Autophagy and ethanol neurotoxicity

Excessive ethanol exposure is detrimental to the brain. The developing brain is particularly vulnerable to ethanol such that prenatal ethanol exposure causes fetal alcohol spectrum disorders (FASD). Neuronal loss in the brain is the most devastating consequence and is associated with mental retardation and other behavioral deficits observed in FASD. Since alcohol consumption during pregnancy has not declined, it is imperative to elucidate the underlying mechanisms and develop effective therapeutic strategies. One cellular mechanism that acts as a protective response for the central nervous system (CNS) is autophagy. Autophagy regulates lysosomal turnover of organelles and proteins within cells, and is involved in cell differentiation, survival, metabolism, and immunity. We have recently shown that ethanol activates autophagy in the developing brain. The autophagic preconditioning alleviates ethanol-induced neuron apoptosis, whereas inhibition of autophagy potentiates ethanol-stimulated reactive oxygen species (ROS) and exacerbates ethanol-induced neuroapoptosis. The expression of genes encoding proteins required for autophagy in the CNS is developmentally regulated; their levels are much lower during an ethanol-sensitive period than during an ethanol-resistant period. Ethanol may stimulate autophagy through multiple mechanisms; these include induction of oxidative stress and endoplasmic reticulum stress, modulation of MTOR and AMPK signaling, alterations in BCL2 family proteins, and disruption of intracellular calcium (Ca2+) homeostasis. This review discusses the most recent evidence regarding the involvement of autophagy in ethanol-mediated neurotoxicity as well as the potential therapeutic approach of targeting autophagic pathways.

Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress

Organic nitrates, such as nitroglycerin (GTN), isosorbide-5-mononitrate and isosorbide dinitrate, and pentaerithrityl tetranitrate (PETN), when given acutely, have potent vasodilator effects improving symptoms in patients with acute and chronic congestive heart failure, stable coronary artery disease, acute coronary syndromes, or arterial hypertension. The mechanisms underlying vasodilation include the release of •NO or a related compound in response to intracellular bioactivation (for GTN, the mitochondrial aldehyde dehydrogenase [ALDH-2]) and activation of the enzyme, soluble guanylyl cyclase. Increasing cyclic guanosine-3',-5'-monophosphate (cGMP) levels lead to an activation of the cGMP-dependent kinase I, thereby causing the relaxation of the vascular smooth muscle by decreasing intracellular calcium concentrations. The hemodynamic and anti-ischemic effects of organic nitrates are rapidly lost upon long-term (low-dose) administration due to the rapid development of tolerance and endothelial dysfunction, which is in most cases linked to increased intracellular oxidative stress. Enzymatic sources of reactive oxygen species under nitrate therapy include mitochondria, NADPH oxidases, and an uncoupled •NO synthase. Acute high-dose challenges with organic nitrates cause a similar loss of potency (tachyphylaxis), but with distinct pathomechanism. The differences among organic nitrates are highlighted regarding their potency to induce oxidative stress and subsequent tolerance and endothelial dysfunction. We also address pleiotropic effects of organic nitrates, for example, their capacity to stimulate antioxidant pathways like those demonstrated for PETN, all of which may prevent adverse effects in response to long-term therapy. Based on these considerations, we will discuss and present some preclinical data on how the nitrate of the future should be designed.

Deficiency in adiponectin exaggerates cigarette smoking exposure-induced cardiac contractile dysfunction: Role of autophagy

Second hand smoke is an independent risk factor for cardiovascular disease. Adiponectin (APN), an adipose-derived adipokine, has been shown to offer cardioprotective effect through an AMPK-dependent manner. This study was designed to evaluate the impact of adiponectin deficiency on second hand smoke-induced cardiac pathology and underlying mechanisms using a mouse model of side-stream smoke exposure. Adult wild-type (WT) and adiponectin knockout (APNKO) mice were placed in a chamber exposed to cigarette smoke for 1 hour daily for 40 days. Echocardiographic, cardiomyocyte function, and intracellular Ca2+ handling were evaluated. Autophagy and apoptosis were examined using western blot. 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA) staining was used to evaluate reactive oxygen species (ROS) generation. Masson trichrome staining was employed to measure interstitial fibrosis. Our data revealed that adiponectin deficiency provoked smoke exposure-induced cardiomyopathy (compromised fractional shortening, disrupted cardiomyocyte function and intracellular Ca2+ homeostasis, apoptosis and ROS generation). In addition, these detrimental effects of side-stream smoke were accompanied by defective autophagolysosome formation, the effect of which was exacerbated by adiponectin deficiency. Blocking autophagolysosome formation using bafilomycin A1 (BafA1) negated the cardioprotective effect of rapamycin against smoke extract. Induction of autophagy using rapamycin and AMPKα activation using AICAR rescued against smoke extract-induced myopathic anomalies in APNKO mice. Our data suggest that adiponectin serves as an indispensable cardioprotective factor against side-stream smoke exposure-induced myopathic changes possibly through facilitating autophagolysosome formation.

Alcohol abuse: critical pathophysiological processes and contribution to disease burden

Alcohol abuse; the most common and costly form of drug abuse, is a major contributing factor to many disease categories. The alcohol-attributable disease burden is closely related to the average volume of alcohol consumption, with dose-dependent relationships between amount and duration of alcohol consumption and the incidence of diabetes mellitus, hypertension, cardiovascular disease, stroke, and pneumonia. The frequent occurrence of alcohol use disorders in the adult population and the significant and widespread detrimental organ system effects highlight the importance of recognizing and further investigating the pathophysiological mechanisms underlying alcohol-induced tissue and organ injury.

Mitochondrial aldehyde dehydrogenase activity protects against lipopolysaccharide‑induced cardiac dysfunction in rats

Myocardial dysfunction in sepsis is associated with an increased risk of mortality. The mitochondrial aldehyde dehydrogenase (ALDH2) enzyme is crucial for protecting the heart from ischemic injury. The aim of the present study was to determine the role of ALDH2 in cardiac dysfunction induced by lipopolysaccharide (LPS). Male rats were treated intraperitoneally with LPS, and their stroke volume and cardiac output were evaluated using an M‑mode echocardiograph. The expression levels and activity of ALDH2, nitric oxide content and inducible nitric oxide synthase (iNOS) activity, and the opening of the mitochondrial permeability transition pore (MPTP) were also evaluated. Treatment with LPS (5, 10, or 20 mg/kg) resulted in a steady decrease in cardiac output and stroke volume. The ALDH2 activity was decreased in a dose‑dependent manner; however, the ALDH2 protein expression levels remained unchanged. Alda‑1, a specific activator of ALDH2, increased the activity of ALDH2 and lessened LPS‑induced cardiac dysfunction. A marked opening of the MPTP was observed 12 h following treatment with LPS, which was prevented by Alda‑1. The improvement in cardiac function in response to treatment with Alda‑1, was partially prevented by treatment with the MPTP inhibitor atractyloside. LPS treatment induced an increase in iNOS activation and inhibition of ALDH2 activity. The iNOS selective inhibitor, aminoguanidine, partially reversed the LPS‑induced ALDH2 activity decrease and MPTP opening. These results indicate that ALDH2 activity may have a role in protecting against LPS‑induced cardiac dysfunction. The potential mechanism may involve inhibition of MPTP opening and iNOS expression.

Autophagy in alcohol-induced multiorgan injury: mechanisms and potential therapeutic targets

Autophagy is a genetically programmed, evolutionarily conserved intracellular degradation pathway involved in the trafficking of long-lived proteins and cellular organelles to the lysosome for degradation to maintain cellular homeostasis. Alcohol consumption leads to injury in various tissues and organs including liver, pancreas, heart, brain, and muscle. Emerging evidence suggests that autophagy is involved in alcohol-induced tissue injury. Autophagy serves as a cellular protective mechanism against alcohol-induced tissue injury in most tissues but could be detrimental in heart and muscle. This review summarizes current knowledge about the role of autophagy in alcohol-induced injury in different tissues/organs and its potential molecular mechanisms as well as possible therapeutic targets based on modulation of autophagy.

Antioxidant catalase rescues against high fat diet-induced cardiac dysfunction via an IKKβ-AMPK-dependent regulation of autophagy

Autophagy, a conservative degradation process for long-lived and damaged proteins, participates in a variety of biological processes including obesity. However, the precise mechanism of action behind obesity-induced changes in autophagy still remains elusive. This study was designed to examine the role of the antioxidant catalase in high fat diet-induced changes in cardiac geometry and function as well as the underlying mechanism of action involved with a focus on autophagy. Wild-type (WT) and transgenic mice with cardiac overexpression of catalase were fed low or high fat diet for 20 weeks prior to assessment of myocardial geometry and function. High fat diet intake triggered obesity, hyperinsulinemia, and hypertriglyceridemia, the effects of which were unaffected by catalase transgene. Myocardial geometry and function were compromised with fat diet intake as manifested by cardiac hypertrophy, enlarged left ventricular end systolic and diastolic diameters, fractional shortening, cardiomyocyte contractile capacity and intracellular Ca²⁺ mishandling, the effects of which were ameliorated by catalase. High fat diet intake promoted reactive oxygen species production and suppressed autophagy in the heart, the effects of which were attenuated by catalase. High fat diet intake dampened phosphorylation of inhibitor kappa B kinase β(IKKβ), AMP-activated protein kinase (AMPK) and tuberous sclerosis 2 (TSC2) while promoting phosphorylation of mTOR, the effects of which were ablated by catalase. In vitro study revealed that palmitic acid compromised cardiomyocyte autophagy and contractile function in a manner reminiscent of fat diet intake, the effect of which was significantly alleviated by inhibition of IKKβ, activation of AMPK and induction of autophagy. Taken together, our data revealed that the antioxidant catalase counteracts against high fat diet-induced cardiac geometric and functional anomalies possibly via an IKKβ-AMPK-dependent restoration of myocardial autophagy. This article is part of a Special Issue entitled: Autophagy and protein quality control in cardiometabolic diseases.

α,β-Unsaturated aldehyde crotonaldehyde triggers cardiomyocyte contractile dysfunction: role of TRPV1 and mitochondrial function

Recent evidence has suggested that cigarette smoking is associated with an increased prevalence of heart diseases. Given that cigarette smoking triggers proinflammatory response via stimulation of the capsaicin-sensitive transient receptor potential cation channel TRPV1, this study was designed to evaluate the effect of an essential α,β-unsaturated aldehyde from cigarette smoke crotonaldehyde on myocardial function and the underlying mechanism with a focus on TRPV1 and mitochondria. Cardiomyocyte mechanical and intracellular Ca2+ properties were evaluated including peak shortening (PS), maximal velocity of shortening/relengthening (±dL/dt), time-to-PS (TPS), time-to-90% relengthening (TR90), fura-2 fluorescence intensity (FFI), intracellular Ca2+ decay and SERCA activity. Apoptosis and TRPV1 were evaluated using Western blot analysis. Production of reactive oxygen species (ROS) and DNA damage were measured using the intracellular fluoroprobe 5-(6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate and 8-hydroxy-2'-deoxyguanosine (8-OHdG), respectively. Our data revealed that crotonaldehyde interrupted cardiomyocyte contractile and intracellular Ca2+ property including depressed PS, ±dL/dt, ΔFFI and SERCA activity, as well as prolonged TR90 and intracellular Ca2+ decay. Crotonaldehyde exposure increased TRPV1 and NADPH oxidase levels, promoted apoptosis, mitochondrial injury (decreased aconitase activity, PGC-1α and UCP-2) as well as production of ROS and 8-OHdG. Interestingly, crotonaldehyde-induced cardiac defect was obliterated by the ROS scavenger glutathione and the TRPV1 inhibitor capsazepine. Capsazepine (not glutathione) ablated crotonaldehyde-induced mitochondrial damage. Capsazepine, glutathione and the NADPH inhibitor apocynin negated crotonaldehyde-induced ROS accumulation. Our data suggest a role of crotonaldehyde compromises cardiomyocyte mechanical function possibly through a TRPV1- and mitochondria-dependent oxidative stress mechanism.