Aldehyde dehydrogenase 2 activation in heart failure restores mitochondrial function and improves ventricular function and remodelling

ALDH2 delays ventricular pressure overload-induced heart failure by promoting cardiomyocyte proliferation in mice

The adult mammalian heart is a terminally differentiated organ in which the majority of cardiomyocytes are in a state of cell cycle arrest, rendering them incapable of effectively proliferating to replace damaged cells. ALDH2, an enzyme known for alleviating oxidative stress, has been demonstrated to play a critical role in cardiac protection. However, whether ALDH2 regulates cardiomyocyte proliferation has not been conclusively established. We found that activation of ALDH2 activity significantly promotes cardiomyocyte proliferation and extends the proliferation window during early postnatal development in neonatal mice. Furthermore, administration of Alda-1 to activate ALDH2 in adult mice subjected to transverse aortic constriction markedly enhanced cardiomyocyte proliferation and delayed the onset of pressure overload-induced heart failure. In summary, our findings identify ALDH2 as a potential target for regulating cardiomyocyte proliferation and offer a novel therapeutic approach for treating heart failure.

Lipidomic insights on abdominal aortic aneurysm and peripheral arterial disease

Abdominal aortic aneurysm (AAA) and peripheral arterial disease (PAD) are two cardiovascular diseases associated with considerable morbidity, mortality and quality of life impairment. As they are multifactorial diseases, several factors contribute to their pathogenesis, including oxidative stress and lipid peroxidation, and these may have key roles in the development of these pathologies. Alterations of the lipid metabolism and lipid profile have been reported in cardiovascular diseases but to a lesser extent in AAA and PAD. Modifications in the profile of some molecular lipid species, in particular, native phospholipid and triglyceride species were mainly reported for AAA, while alterations in the fatty acid profile were noticed in the case of PAD. Oxidized phospholipids were also reported for AAA. Although AAA and PAD have a common atherosclerotic root, lipidomics demonstrates the existence of distinct lipid. Lipidomic research regarding AAA and PAD is still scarce and should be set in motion to increase the knowledge on the lipid changes that occur in these diseases, contributing not only to the discovery of new biomarkers for diagnosis and prognosis assessment but also to tailor precision medicine in the clinical field.

XBP1s-EDEM2 Prevents the Onset and Development of HFpEF by Ameliorating Cardiac Lipotoxicity

BACKGROUND

Morbidity and mortality of heart failure with preserved ejection fraction (HFpEF) is increased in metabolic disorders. However, options for preventing and treating these prevalent outcomes are limited. Intramyocardial lipotoxicity contributes to cardiac dysfunction. Here, we investigate the mechanisms underlying endoplasmic reticulum degradation enhancing EDEM2 (endoplasmic reticulum degradation-enhancing alpha-mannosidase-like protein 2) regulation of cardiac lipid homeostasis and assess strategies that inhibit the incidence and progression of HFpEF.

METHODS

Metabolic stress was induced in C57BL/6 male mice using a high-fat diet and Nω-nitro-l-arginine methyl ester. The recombinant adeno-associated virus 9 delivery system was used for loss- and gain-of-function studies. Palmitic acid and oleic acid stimulation of rat cardiomyocytes and human induced pluripotent stem cell-derived cardiomyocytes imitated a condition of high lipids in vitro. Molecular mechanisms were investigated via RNA sequencing, mass spectrometry proteomics, lipidomic analyses, transmission electron microscopy, histology, and luciferase reporter assays.

RESULTS

In the human heart, we first detected lipid overload accompanied by a reduction of XBP1 (X-box binding protein 1) under metabolic stress. Thereafter, a decrease in EDEM2 was confirmed in human and mouse HFpEF hearts. Given that the spliced form of XBP1 (XBP1s) is a transcription factor, EDEM2 was identified as its new target in cardiomyocytes. EDEM2 knockdown mice manifested lipid droplet accumulation and higher levels of triglycerides and diglycerides in the myocardium, aggravating oxidative stress, hypertrophy, and the onset and progression of HFpEF under metabolic stress. XBP1s ablation mice displayed a similar myocardial lipid disturbance and cardiac phenotypes, which were reversed by EDEM2 overexpression. Mechanistically, the findings obtained from rat cardiomyocytes and human induced pluripotent stem cell-derived cardiomyocytes demonstrated that, in the presence of EDEM2, SEC23A mediated intracellular translocation of ATGL (adipose triglyceride lipase) under fatty acid stimulation, inhibiting ATGL degradation and excessive intracellular lipid droplets. Furthermore, the functional studies supported that EDEM2 prevention of lipid overload occurred in an ATGL-dependent manner. Therapeutically, cardiac XBP1s or EDEM2 restoration mitigated lipid deposition and preserved lipid profiles in the myocardium, thus preventing the development of HFpEF.

CONCLUSIONS

We demonstrate a cardioprotective mechanism regulating myocardial lipid homeostasis. The findings provide a promising therapeutic target to prevent and treat HfpEF, a condition with limited treatment options.

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.

Metabolic pathways for removing reactive aldehydes are diminished in the skeletal muscle during heart failure

Muscle wasting is a serious complication in heart failure patients. Oxidative stress and inflammation are implicated in the pathogenesis of muscle wasting. Oxidative stress leads to the formation of toxic lipid peroxidation products, such as 4-hydroxy-2-nonenal (HNE), which covalently bind with proteins and DNA and activate atrophic pathways. Whether the formation of lipid peroxidation products and metabolic pathways that remove these toxic products are affected during heart failure-associated skeletal muscle wasting has never been studied. Male C57BL/6J mice were subjected to sham and transverse aortic constriction (TAC) surgeries for 4, 8 or 14 weeks. Different skeletal muscle beds were weighed, and the total cross-sectional area of the gastrocnemius muscle was measured via immunohistochemistry. Muscle function and muscle stiffness were measured by a grip strength meter and atomic force microscope, respectively. Atrophic and inflammatory marker levels were measured via qRT‒PCR. The levels of acrolein and HNE-protein adducts, aldehyde-removing enzymes, the histidyl dipeptide-synthesizing enzyme carnosine synthase (CARNS), and amino acid transporters in the gastrocnemius muscle were measured via Western blotting and qRT‒PCR. Histidyl dipeptides and histidyl dipeptide aldehyde conjugates in the Gastrocnemius and soleus muscles were analyzed by LC/MS-MS. Body weight, gastrocnemius muscle and soleus muscle weights and the total cross-sectional area of the gastrocnemius muscle were decreased after 14 weeks of TAC. Heart weight, cardiac function, grip strength and muscle stiffness were decreased in the TAC-operated mice. Expression of the atrophic and inflammatory markers Atrogin1 and TNF-α, respectively, was increased ~ 1.5-2fold in the gastrocnemius muscle after 14 weeks of TAC (p < 0.05 and p = 0.004 vs sham). The formation of HNE and acrolein protein adducts was increased, and the expression of the aldehyde-removing enzyme aldehyde dehydrogenase (ALDH2) was decreased in the gastrocnemius muscle of TAC mice. Carnosine (sham: 5.76 ± 1.3 vs TAC: 4.72 ± 0.7 nmol/mg tissue, p = 0.04) and total histidyl dipeptide levels (carnosine and anserine; sham: 11.97 ± 1.5 vs TAC: 10.13 ± 1.4 nmol/mg tissue, p < 0.05) were decreased in the gastrocnemius muscle of TAC mice. Depletion of histidyl dipeptides diminished the aldehyde removal capacity of the atrophic gastrocnemius muscle. Furthermore, CARNS and TAUT protein expression were decreased in the atrophic gastrocnemius muscle. Our data reveals that reduced expression of ALDH2 and depletion of histidyl dipeptides in the gastrocnemius muscle during heart failure leads to the accumulation of toxic aldehydes and might contribute to muscle wasting.

Evaluation of supplementary carnosine accumulation and distribution: an initial analysis of participants in the Nucleophilic Defense Against PM Toxicity (NEAT) clinical trial

Carnosine is an endogenous dipeptide that buffers intracellular pH and quenches toxic products of lipid peroxidation. Used as a dietary supplement, it also supports exercise endurance. However, the accumulation and distribution of carnosine after supplementation has not been rigorously evaluated. To do this, we randomized a cohort to receive daily supplements of either placebo or carnosine (2 g/day). Blood and urine samples were collected twice over the subsequent 12 week supplementation period and we measured levels of red blood cell (RBC) carnosine, urinary carnosine, and urinary carnosine-propanol and carnosine-propanal conjugates by LC/MS-MS. We found that, when compared with placebo, supplementation with carnosine for 6 or 12 weeks led to an approximate twofold increase in RBC carnosine, while levels of urinary carnosine increased nearly sevenfold. Although there were no changes in the urinary levels of carnosine propanol, carnosine propanal increased nearly twofold. RBC carnosine levels were positively associated with urinary carnosine and carnosine propanal levels. No adverse reactions were reported by those in the carnosine or placebo arms, nor did carnosine supplementation have any effect on kidney, liver, and cardiac function or blood electrolytes. In conclusion, irrespective of age, sex, or BMI, oral carnosine supplementation in humans leads to its increase in RBC and urine, as well as an increase in urinary carnosine-propanal. RBC carnosine may be a readily accessible pool to estimate carnosine levels. Clinical trial registration: This study is registered with ClinicalTrials.gov (Nucleophilic Defense Against PM Toxicity (NEAT Trial)-Full Text View-ClinicalTrials.gov), under the registration: NCT03314987.

Role of mitochondria in inflammatory lung diseases

Mitochondria play a significant and varied role in inflammatory lung disorders. Mitochondria, known as the powerhouse of the cell because of their role in producing energy, are now recognized as crucial regulators of inflammation and immunological responses. Asthma, chronic obstructive pulmonary disease, and acute respiratory distress syndrome are characterized by complex interactions between immune cells, inflammatory substances, and tissue damage. Dysfunctional mitochondria can increase the generation of reactive oxygen species (ROS), triggering inflammatory pathways. Moreover, mitochondrial failure impacts cellular signaling, which in turn affects the expression of molecules that promote inflammation. In addition, mitochondria have a crucial role in controlling the behavior of immune cells, such as their activation and differentiation, which is essential in the development of inflammatory lung diseases. Their dynamic behavior, encompassing fusion, fission, and mitophagy, also impacts cellular responses to inflammation and oxidative stress. Gaining a comprehensive understanding of the intricate correlation between mitochondria and lung inflammation is essential in order to develop accurate treatment strategies. Targeting ROS generation, dynamics, and mitochondrial function may offer novel approaches to treating inflammatory lung diseases while minimizing tissue damage. Additional investigation into the precise contributions of mitochondria to lung inflammation will provide significant knowledge regarding disease mechanisms and potential therapeutic approaches. This review will focus on how mitochondria in the lung regulate these processes and their involvement in acute and chronic lung diseases.

Aldehyde Dehydrogenase 2 Deficiency Aggravates Lung Fibrosis through Mitochondrial Dysfunction and Aging in Fibroblasts

Idiopathic pulmonary fibrosis, a fatal interstitial lung disease, is characterized by fibroblast activation and aberrant extracellular matrix accumulation. Effective therapeutic development is limited because of incomplete understanding of the mechanisms by which fibroblasts become aberrantly activated. Here, we show aldehyde dehydrogenase 2 (ALDH2) in fibroblasts as a potential therapeutic target for pulmonary fibrosis. A decrease in ALDH2 expression was observed in patients with idiopathic pulmonary fibrosis and bleomycin-treated mice. ALDH2 deficiency spontaneously induces collagen accumulation in the lungs of aged mice. Furthermore, young ALDH2 knockout mice exhibited exacerbated bleomycin-induced pulmonary fibrosis and increased mortality compared with that in control mice. Mechanistic studies revealed that transforming growth factor (TGF)-β1 induction and ALDH2 depletion constituted a positive feedback loop that exacerbates fibroblast activation. TGF-β1 down-regulated ALDH2 through a TGF-β receptor 1/Smad3-dependent mechanism. The subsequent deficiency in ALDH2 resulted in fibroblast dysfunction that manifested as impaired mitochondrial autophagy and senescence, leading to fibroblast activation and extracellular matrix production. ALDH2 overexpression markedly suppressed fibroblast activation, and this effect was abrogated by PTEN-induced putative kinase 1 (PINK1) knockdown, indicating that the profibrotic effects of ALDH2 are PINK1- dependent. Furthermore, ALDH2 activated by N-(1,3-benzodioxol-5-ylmethyl)-2,6-dichlorobenzamide (Alda-1) reversed the established pulmonary fibrosis in both young and aged mice. In conclusion, ALDH2 expression inhibited the pathogenesis of pulmonary fibrosis. Strategies to up-regulate or activate ALDH2 expression could be potential therapies for pulmonary fibrosis.

Deciphering the mitochondria-inflammation axis: Insights and therapeutic strategies for heart failure

Heart failure (HF) is a clinical syndrome resulting from left ventricular systolic and diastolic dysfunction, leading to significant morbidity and mortality worldwide. Despite improvements in medical treatment, the prognosis of HF patients remains unsatisfactory, with high rehospitalization rates and substantial economic burdens. The heart, a high-energy-consuming organ, relies heavily on ATP production through oxidative phosphorylation in mitochondria. Mitochondrial dysfunction, characterized by impaired energy production, oxidative stress, and disrupted calcium homeostasis, plays a crucial role in HF pathogenesis. Additionally, inflammation contributes significantly to HF progression, with elevated levels of circulating inflammatory cytokines observed in patients. The interplay between mitochondrial dysfunction and inflammation involves shared risk factors, signaling pathways, and potential therapeutic targets. This review comprehensively explores the mechanisms linking mitochondrial dysfunction and inflammation in HF, including the roles of mitochondrial reactive oxygen species (ROS), calcium dysregulation, and mitochondrial DNA (mtDNA) release in triggering inflammatory responses. Understanding these complex interactions offers insights into novel therapeutic approaches for improving mitochondrial function and relieving oxidative stress and inflammation. Targeted interventions that address the mitochondria-inflammation axis hold promise for enhancing cardiac function and outcomes in HF patients.

ALDH2 polymorphism and myocardial infarction: From alcohol metabolism to redox regulation

Acute myocardial infarction (AMI) remains a leading cause of death worldwide. Increased formation of reactive oxygen species (ROS) during the early reperfusion phase is thought to trigger lipid peroxidation and disrupt redox homeostasis, leading to myocardial injury. Whilst the mitochondrial enzyme aldehyde dehydrogenase 2 (ALDH2) is chiefly recognised for its central role in ethanol metabolism, substantial experimental evidence suggests an additional cardioprotective role for ALDH2 independent of alcohol intake, which mitigates myocardial injury by detoxifying breakdown products of lipid peroxidation including the reactive aldehydes, malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). Epidemiological evidence suggests that an ALDH2 mutant variant with reduced activity that is highly prevalent in the East Asian population increases AMI risk. Additional studies have uncovered a strong association between coronary heart disease and this ALDH2 mutant variant. It appears this enzyme polymorphism (in particular, in ALDH2*2/2 carriers) has the potential to have wide-ranging effects on thiol reactivity, redox tone and therefore numerous redox-related signaling processes, resilience of the heart to cope with lifestyle-related and environmental stressors, and the ability of the whole body to achieve redox balance. In this review, we summarize the journey of ALDH2 from a mitochondrial reductase linked to alcohol metabolism, via pre-clinical studies aimed at stimulating ALDH2 activity to reduce myocardial injury to clinical evidence for its protective role in the heart.

Metabolic Pathways for Removing Reactive Aldehydes are Diminished in Atrophic Muscle During Heart Failure

Background

Muscle wasting is a serious complication in heart failure patients, and oxidative stress is involved in the pathogenesis of muscle wasting. Oxidative stress leads to the formation of toxic lipid peroxidation products, such as 4-hydroxy-2-nonenal (HNE) and acrolein, which causemuscle wasting. In tissues, these toxic aldehydes are metabolically removed by enzymes such asaldo keto reductases and endogenous nucleophiles, such as glutathione and carnosine. Whether these metabolic pathways could be affected in skeletal muscle during heart failure has never been studied.

Methods

Male wild-type C57BL/6J mice were subjected to a pressure overload model of hypertrophy by transaortic constriction (TAC) surgery, and echocardiography was performed after 14 weeks. Different skeletal muscle beds were weighed and analyzed for atrophic and inflammatory markers, Atrogin1 and TRIM63, TNF-α and IL-6, respectively, by RT-PCR. Levels of acrolein and HNE-protein adducts, aldehyde-removing enzymes, aldose reductase (AKR1B1) and aldehyde dehydrogenase 2 (ALDH2) were measured by Western blotting, and histidyl dipeptides and histidyl dipeptide aldehyde conjugates were analyzed by LC/MS-MS in the gastrocnemius and soleus muscles of sham- and TAC-operated mice. Furthermore, histidyl dipeptide synthesizing enzyme carnosine synthase (CARNS) and amino acid transporters (PEPT2 and TAUT)wasmeasured in the gastrocnemius muscles of the sham and TAC-operated mice.

Results

TAC-induced heart failure decreases body weight and gastrocnemius and soleus muscle weights. The expression of the atrophic and inflammatory markers Atrogin1 and TNF-α, respectively, wasincreased (~1.5-2-fold), and the formation of HNE and acrolein-protein adducts was increased in the gastrocnemius muscle of TAC-operated mice. The expression of AKR1B1 remained unchanged, whereas ALDH2 was decreased, in the gastrocnemius muscle of TAC mice. Similarly, in the atrophic gastrocnemius muscle, levels of total histidyl dipeptides (carnosine and anserine) and, in particular,carnosine were decreased. Depletion of histidyl dipeptides diminished the aldehyde removal capacity of the atrophic gastrocnemius muscle. Furthermore, the expression of CARNS and TAUT wasdecreased in the atrophic gastrocnemius muscle.

Conclusions

Collectively, these results show that metabolic pathways involved in the removal of lipid peroxidation products and synthesis of histidyl dipeptides are diminished in atrophic skeletal muscle during heart failure, which could contribute to muscle atrophy.

4-Hydroxynonenal impairs miRNA maturation in heart failure via Dicer post-translational modification

BACKGROUND AND AIMS

Developing novel therapies to battle the global public health burden of heart failure remains challenging. This study investigates the underlying mechanisms and potential treatment for 4-hydroxynonenal (4-HNE) deleterious effects in heart failure.

METHODS

Biochemical, functional, and histochemical measurements were applied to identify 4-HNE adducts in rat and human failing hearts. In vitro studies were performed to validate 4-HNE targets.

RESULTS

4-HNE, a reactive aldehyde by-product of mitochondrial dysfunction in heart failure, covalently inhibits Dicer, an RNase III endonuclease essential for microRNA (miRNA) biogenesis. 4-HNE inhibition of Dicer impairs miRNA processing. Mechanistically, 4-HNE binds to recombinant human Dicer through an intermolecular interaction that disrupts both activity and stability of Dicer in a concentration- and time-dependent manner. Dithiothreitol neutralization of 4-HNE or replacing 4-HNE-targeted residues in Dicer prevents 4-HNE inhibition of Dicer in vitro. Interestingly, end-stage human failing hearts from three different heart failure aetiologies display defective 4-HNE clearance, decreased Dicer activity, and miRNA biogenesis impairment. Notably, boosting 4-HNE clearance through pharmacological re-activation of mitochondrial aldehyde dehydrogenase 2 (ALDH2) using Alda-1 or its improved orally bioavailable derivative AD-9308 restores Dicer activity. ALDH2 is a major enzyme responsible for 4-HNE removal. Importantly, this response is accompanied by improved miRNA maturation and cardiac function/remodelling in a pre-clinical model of heart failure.

CONCLUSIONS

4-HNE inhibition of Dicer directly impairs miRNA biogenesis in heart failure. Strikingly, decreasing cardiac 4-HNE levels through pharmacological ALDH2 activation is sufficient to re-establish Dicer activity and miRNA biogenesis; thereby representing potential treatment for patients with heart failure.

Mitochondrial Calcium Overload Plays a Causal Role in Oxidative Stress in the Failing Heart

Heart failure is a serious global health challenge, affecting more than 6.2 million people in the United States and is projected to reach over 8 million by 2030. Independent of etiology, failing hearts share common features, including defective calcium (Ca2+) handling, mitochondrial Ca2+ overload, and oxidative stress. In cardiomyocytes, Ca2+ not only regulates excitation-contraction coupling, but also mitochondrial metabolism and oxidative stress signaling, thereby controlling the function and actual destiny of the cell. Understanding the mechanisms of mitochondrial Ca2+ uptake and the molecular pathways involved in the regulation of increased mitochondrial Ca2+ influx is an ongoing challenge in order to identify novel therapeutic targets to alleviate the burden of heart failure. In this review, we discuss the mechanisms underlying altered mitochondrial Ca2+ handling in heart failure and the potential therapeutic strategies.

Apoptosis and heart failure: The role of non-coding RNAs and exosomal non-coding RNAs

Heart failure is a condition that affects the cardio vascular system and occurs if the heart cannot adequately pump the oxygen and blood to the body. Myocardial infarction, reperfusion injury, and this disease is the only a few examples of the numerous cardiovascular illnesses that are impacted by the closely controlled cell deletion process known as apoptosis. Attention has been paid to the creation of alternative diagnostic and treatment modalities for the condition. Recent evidences have shown that some non-coding RNAs (ncRNAs) influence the stability of proteins, control of transcription factors, and HF apoptosis through a variety of methods. Exosomes make a significant paracrine contribution to the regulation of illnesses as well as to the communication between nearby and distant organs. However, it has not yet been determined whether exosomes regulate the cardiomyocyte-tumor cell interaction in ischemia HF to limit the vulnerability of malignancy to ferroptosis. Here, we list the numerous ncRNAs in HF that are connected to apoptosis. In addition, we emphasize the significance of exosomal ncRNAs in the HF.

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.

Improving mitochondrial function in preclinical models of heart failure: therapeutic targets for future clinical therapies?

INTRODUCTION

Heart failure is a complex clinical syndrome resulting from the unsuccessful compensation of symptoms of myocardial damage. Mitochondrial dysfunction is a process that occurs because of an attempt to adapt to the disruption of metabolic and energetic pathways occurring in the myocardium. This, in turn, leads to further dysfunction in cardiomyocyte processes. Currently, many therapeutic strategies have been implemented to improve mitochondrial function, but their effectiveness varies widely.

AREAS COVERED

This review focuses on new models of therapeutic strategies targeting mitochondrial function in the treatment of heart failure.

EXPERT OPINION

Therapeutic strategies targeting mitochondria appear to be a valuable option for treating heart failure. Currently, the greatest challenge is to develop new research models that could restore the disrupted metabolic processes in mitochondria as comprehensively as possible. Only the development of therapies that focus on improving as many dysregulated mitochondrial processes as possible in patients with heart failure will be able to bring the expected clinical improvement, along with inhibition of disease progression. Combined strategies involving the reduction of the effects of oxidative stress and mitochondrial dysfunction, appear to be a promising possibility for developing new therapies for a complex and multifactorial disease such as heart failure.

Commentary: Aldehyde dehydrogenase, redox balance and exercise physiology: What is missing?

Aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial enzyme involved in reactive aldehyde detoxification. Approximately 560 million people (about 8% of the world's population) carry a point mutation in the aldehyde dehydrogenase 2 gene (ALDH2), identified as ALDH2*2, which leads to decreased ALDH2 catalytic activity. ALDH2*2 variant is associated with an accumulation of toxic reactive aldehydes and consequent disruption of cellular metabolism, which contributes to the establishment and progression of several degenerative diseases. Consequences of aldehyde accumulation include impaired mitochondrial functional, hindered anabolic signaling in the skeletal muscle, impaired cardiovascular and pulmonary function, and reduced osteoblastogenesis. Considering that aldehydes are endogenously produced through redox processes, it is expected that conditions that have a high energy demand, such as exercise, might be affected by impaired aldehyde clearance in ALDH2*2 individuals. Despite the large body of evidence supporting the importance of ALDH2 to ethanol metabolism, redox homeostasis and overall health, specific research investigating the impact of ALDH2*2 on phenotypes relevant to exercise performance are notoriously scarce. In this commentary, we highlight the consolidated knowledge on the impact of ALDH2*2 on physiological processes that are relevant to exercise.

ALDH2 attenuates ischemia and reperfusion injury through regulation of mitochondrial fusion and fission by PI3K/AKT/mTOR pathway in diabetic cardiomyopathy

The function of mitochondrial fusion and fission is one of the important factors causing ischemia-reperfusion (I/R) injury in diabetic myocardium. Aldehyde dehydrogenase 2 (ALDH2) is abundantly expressed in heart, which involved in the regulation of cellular energy metabolism and stress response. However, the mechanism of ALDH2 regulating mitochondrial fusion and fission in diabetic myocardial I/R injury has not been elucidated. In the present study, we found that the expression of ALDH2 was downregulated in rat diabetic myocardial I/R model. Functionally, the activation of ALDH2 resulted in the improvement of cardiac hemodynamic parameters and myocardial injury, which were abolished by the treatment of Daidzin, a specific inhibitor of ALDH2. In H9C2 cardiomyocyte hypoxia-reoxygenation model, ALDH2 regulated the dynamic balance of mitochondrial fusion and fission and maintained mitochondrial morphology stability. Meanwhile, ALDH2 reduced mitochondrial ROS levels, and apoptotic protein expression in cardiomyocytes, which was associated with the upregulation of phosphorylation (p-PI3K_Tyr458, p-AKT_Ser473, p-mTOR). Moreover, ALDH2 suppressed the mitoPTP opening through reducing 4-HNE. Therefore, our results demonstrated that ALDH2 alleviated the ischemia and reperfusion injury in diabetic cardiomyopathy through inhibition of mitoPTP opening and activation of PI3K/AKT/mTOR pathway.

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.

Effect of Xuefu Zhuyu Capsule on Myocardial Infarction: Network Pharmacology and Experimental Verification

Background

Myocardial infarction (MI) is the most severe manifestation of cardiovascular disease. Xuefu Zhuyu Capsule (XFC), a proprietary Chinese medicine, is widely used in various cardiovascular diseases. At present, the molecular mechanism of XFC remains unclear.

Objective

To explore the mechanism of anti-MI effects of XFC by combining network pharmacology and experiments.

Methods

TCMSP, GeneCards, and DisGeNET databases were used to find the target of XFC. PPI analysis was performed by the STRING database. KEGG and GO analyses were performed by Metascape Database. Molecular docking was performed by Autodock Vina. HE staining, echocardiography, immunofluorescence, and TUNEL were performed to verify the prediction results.

Results

Network pharmacology showed that quercetin, kaempferol, β-sitosterol, luteolin, and baicalein were the main active ingredients of XFC. TNF, IL6, TP53, VEGFA, JUN, CASP3, and SIRT1 were the main targets of XFC. KEGG results showed that key genes were mainly enriched in lipid and atherosclerosis, PI3K-Akt signaling pathway, MAPK signaling pathway, and NF-κB signaling pathway. HE staining showed that XFC could improve the morphology of myocardial tissue. Echocardiography showed that XFC could improve cardiac function. TUNEL showed that XFC could reduce cardiomyocyte apoptosis. Immunofluorescence showed that XFC could reduce the expression of α-smooth muscle actin (α-SMA) and increase the expression of CD31. In addition, we found that XFC may exert its therapeutic effects through SIRT1.

Conclusion

This study demonstrated that SIRT1 may be the target of XFC in the treatment of MI. The active ingredients of XFC and SIRT1 can be stably bound. XFC could inhibit apoptosis, promote angiogenesis, and improve myocardial fibrosis through SIRT1.

Trimethylamine oxide induces pyroptosis of vascular endothelial cells through ALDH2/ROS/NLRP3/GSDMD pathway

OBJECTIVES

Trimethylamine oxide (TMAO) is a metabolite of intestinal flora and is known to promote the progression of atherosclerotic plaques. However, how TMAO works, including its effect on vascular endothelial cells, is not fully understood. This study aims to explore the biological role of TMAO in human umbilical vein endothelial cells (HUVECs) and the underlying mechanism.

METHODS

Cell pyroptosis and the loss of plasma membrane integrity were induced under TMAO stimulation in HUVECs. The plasma membrane integrity of the cells was measured by Hoechst 33342/propidium iodide (PI) staining and lactate dehydrogenase leakage assay, and the changes in cell morphology were observed by atomic force microscope. The expression of proteins related to pyroptosis was determined by Western blotting or immunofluorescence. Mitochondrial acetaldehyde dehydrogenase 2 (ALDH2) activity in HUVECs was measured by the ALDH2 activity assay kit, and the level of reactive oxygen species (ROS) was detected by fluorescent probe DCFH-DA.

RESULTS

TMAO induced pyroptotic cell death, manifesting by the presence of propidium iodide-positive cells, the leakage of lactate dehydrogenase, the production of N-terminal gasdermin D (GSDMD-N), and the formation of plasma membrane pores. Moreover, TMAO induced elevated expression of inflammasome components, nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC), and caspase-1 in cells. TMAO significantly inhibited ALDH2 activity and increased intracellular ROS production. However, the activation of ALDH2 by pharmacological manipulation attenuated TMAO-induced inflammasome activation and GSDMD-N production.

CONCLUSIONS

TMAO induces pyroptosis of vascular endothelial cells through the ALDH2/ROS/NLRP3/GSDMD signaling pathway, which may be a potential therapeutic target for improving the treatment of atherosclerosis.

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.

Integrated Gut-Heart Axis and Network Pharmacology to Reveal the Mechanisms of the Huoxue Wentong Formula Against Myocardial Ischemia

Background

Myocardial ischemia (MI) is a major public health problem with high mortality and morbidity worldwide. Huoxue Wentong formula (HX), a traditional Chinese medicine (TCM) formula, exhibits unambiguous effects on treating MI and preventing cardiovascular diseases. However, the molecular mechanism of the therapeutic effects of HX on MI remains largely unknown.

Objective

This study combined microbiology, metabolomics, and network pharmacology to explore the relationship between the gut microbiota and its metabolites in MI rats and the efficacy of HX.

Methods

First, the MI rat model was established by ligation of left anterior descending. Echocardiography, Masson's staining, and hematoxylin and eosin staining were used to evaluate the effect of HX on MI. Then, fecal metabolomics and 16S rRNA sequencing were used to obtain the microbial and metabolic characteristics of HX on MI. After that, network pharmacology was used to predict the target and action pathway of HX in treating MI. Finally, the relationship between fecal metabolites and target was explored through bioinformatics.

Results

HX can improve the cardiac function and ameliorated myocardial fibrosis in MI rats. Moreover, HX can affect the gut microbiota community and metabolites of MI rats, especially Bacteroides, Deferribacteres, Ruminococcus_sp._zagget7, Acidobacteria, daidzein, L-lactic acid, and malate. Network pharmacology found that HX can function through tumor necrosis factor (TNF), tumor protein p53 (TP53), interleukin 6 (IL6), vascular endothelial growth factor A (VEGFA), fos proto-oncogene (FOS), bcl2-associated X (BAX), myeloperoxidase (MPO), PI3K-Akt signaling pathways, and HIF-1 signaling pathway. The mechanism study showed that the anti-MI effect of HX was related to valine, leucine, and isoleucine biosynthesis, fatty acid biosynthesis, and arachidonic acid metabolism.

Conclusion

This study demonstrates that HX treated MI rats in a multitarget and multipathway manner. Its mechanism is related to the change of gut microbiota and the regulation of valine, leucine and isoleucine biosynthesis, fatty acid biosynthesis, and arachidonic acid metabolism.

Nitrated fatty acid, 10-nitrooleate protects against hyperoxia-induced acute lung injury in mice

The antioxidant and anti-inflammatory effects of electrophilic nitrated fatty acid (NFA); 10-nitrooleate, have been reported. The present study investigated whether 10-nitrooleate has a protective role against hyperoxic-induced acute lung injury (HALI). Using a C57BL/6 mice model of HALI, we investigated the protective effect of 10-nitrooleate. C57BL/6 mice were administered with NFA intratracheally, exposed to hyperoxia for 48 h to induce HALI, and kept at room air for 24 h. Bronchoalveolar lavage (BAL) fluid and lung samples were collected after 24 h of post hyperoxia to analyze markers associated with HALI. Intratracheal (IT) and intraperitoneal (IP) administration of NFA notably attenuated hyperoxia-induced infiltration of inflammatory cells, alveolar-capillary leakage, upregulation of proinflammatory cytokine levels (IL-6 and TNFα) into the BAL fluid, and resolution of inflammation in the lung. Western blot analyses showed that 10-nitrooleate reduced the expression of the inflammatory transcription factor NFκB p65 subunit and increased antioxidant proteins HO-1 and NQO1 expression in the lung tissues compared to vehicle-treated animals. Moreover, 10-nitrooleate reversed the hyperoxia-induced expression of mitophagy-associated markers (PINK1 and p62/SQSTM1), thereby protecting the HALI/ acute respiratory distress syndrome (ARDS). IT and IP delivery of 10-nitrooleate reduces hyperoxia-induced ALI/ARDS by regulating the antioxidant pathways and restoring the mitochondrial homeostasis by regulating mitophagy. It is suggested that NFAs can be further evaluated as supplementary therapy for critically ill patients like COVID-19/ARDS.

Mitochondrial Fusion, Fission, and Mitophagy in Cardiac Diseases: Challenges and Therapeutic Opportunities

Significance: Mitochondria play a critical role in the physiology of the heart by controlling cardiac metabolism, function, and remodeling. Accumulation of fragmented and damaged mitochondria is a hallmark of cardiac diseases. Recent Advances: Disruption of quality control systems that maintain mitochondrial number, size, and shape through fission/fusion balance and mitophagy results in dysfunctional mitochondria, defective mitochondrial segregation, impaired cardiac bioenergetics, and excessive oxidative stress. Critical Issues: Pharmacological tools that improve the cardiac pool of healthy mitochondria through inhibition of excessive mitochondrial fission, boosting mitochondrial fusion, or increasing the clearance of damaged mitochondria have emerged as promising approaches to improve the prognosis of heart diseases. Future Directions: There is a reasonable amount of preclinical evidence supporting the effectiveness of molecules targeting mitochondrial fission and fusion to treat cardiac diseases. The current and future challenges are turning these lead molecules into treatments. Clinical studies focusing on acute (i.e., myocardial infarction) and chronic (i.e., heart failure) cardiac diseases are needed to validate the effectiveness of such strategies in improving mitochondrial morphology, metabolism, and cardiac function. Antioxid. Redox Signal. 36, 844-863.

New Insights Into the Role of Mitochondria Quality Control in Ischemic Heart Disease

IHD is a significant cause of mortality and morbidity worldwide. In the acute phase, it's demonstrated as myocardial infarction and ischemia-reperfusion injury, while in the chronic stage, the ischemic heart is mainly characterised by adverse myocardial remodelling. Although interventions such as thrombolysis and percutaneous coronary intervention could reduce the death risk of these patients, the underlying cellular and molecular mechanisms need more exploration. Mitochondria are crucial to maintain the physiological function of the heart. During IHD, mitochondrial dysfunction results in the pathogenesis of ischemic heart disease. Ischemia drives mitochondrial damage not only due to energy deprivation, but also to other aspects such as mitochondrial dynamics, mitochondria-related inflammation, etc. Given the critical roles of mitochondrial quality control in the pathological process of ischemic heart disease, in this review, we will summarise the efforts in targeting mitochondria (such as mitophagy, mtROS, and mitochondria-related inflammation) on IHD. In addition, we will briefly revisit the emerging therapeutic targets in this field.

Activation of Aldehyde Dehydrogenase 2 Ameliorates Glucolipotoxicity of Pancreatic Beta Cells

Chronic hyperglycemia and hyperlipidemia hamper beta cell function, leading to glucolipotoxicity. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) detoxifies reactive aldehydes, such as methylglyoxal (MG) and 4-hydroxynonenal (4-HNE), derived from glucose and lipids, respectively. We aimed to investigate whether ALDH2 activators ameliorated beta cell dysfunction and apoptosis induced by glucolipotoxicity, and its potential mechanisms of action. Glucose-stimulated insulin secretion (GSIS) in MIN6 cells and insulin secretion from isolated islets in perifusion experiments were measured. The intracellular ATP concentrations and oxygen consumption rates of MIN6 cells were assessed. Furthermore, the cell viability, apoptosis, and mitochondrial and intracellular reactive oxygen species (ROS) levels were determined. Additionally, the pro-apoptotic, apoptotic, and anti-apoptotic signaling pathways were investigated. We found that Alda-1 enhanced GSIS by improving the mitochondrial function of pancreatic beta cells. Alda-1 rescued MIN6 cells from MG- and 4-HNE-induced beta cell death, apoptosis, mitochondrial dysfunction, and ROS production. However, the above effects of Alda-1 were abolished in Aldh2 knockdown MIN6 cells. In conclusion, we reported that the activator of ALDH2 not only enhanced GSIS, but also ameliorated the glucolipotoxicity of beta cells by reducing both the mitochondrial and intracellular ROS levels, thereby improving mitochondrial function, restoring beta cell function, and protecting beta cells from apoptosis and death.

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

Background

Aldehyde 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 Results

Three 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.

Conclusions

Low 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.

Mitochondrial proteins in heart failure: The role of deacetylation by SIRT3

Heart failure (HF) is still the leading cause of death worldwide, occurring with a variety of complex mechanisms. However, most intervention for HF do not directly target the pathological mechanisms underlying cell damage in failing cardiomyocytes. Mitochondria are involved in many physiological processes, which is an important guarantee for normal heart function. Mitochondrial dysfunction is considered to be the critical node of the development of HF. Strict modulation of the mitochondrial function can ameliorate the myocardial injury and protect cardiac function. Acetylation plays an important role in mitochondrial protein homeostasis, and SIRT3, the most important deacetylation protein in mitochondria, is involved in the maintenance of mitochondrial function. SIRT3 can delay the progression of HF by improving mitochondrial function. Herein we summarize the interaction between SIRT3 and proteins related to mitochondrial function including oxidative phosphorylation (OXPHOS), fatty acid oxidation (FAO), mitochondrial biosynthesis, mitochondrial quality control. In addition, we also sum up the effects of this interaction on HF and the research progress of treatments targeting SIRT3, so as to find potential HF therapeutic for clinical use in the future.

Redox signaling in heart failure and therapeutic implications

Heart failure is a growing health burden worldwide characterized by alterations in excitation-contraction coupling, cardiac energetic deficit and oxidative stress. While current treatments are mostly limited to antagonization of neuroendocrine activation, more recent data suggest that also targeting metabolism may provide substantial prognostic benefit. However, although in a broad spectrum of preclinical models, oxidative stress plays a causal role for the development and progression of heart failure, no treatment that targets reactive oxygen species (ROS) directly has entered the clinical arena yet. In the heart, ROS derive from various sources, such as NADPH oxidases, xanthine oxidase, uncoupled nitric oxide synthase and mitochondria. While mitochondria are the primary source of ROS in the heart, communication between different ROS sources may be relevant for physiological signalling events as well as pathologically elevated ROS that deteriorate excitation-contraction coupling, induce hypertrophy and/or trigger cell death. Here, we review the sources of ROS in the heart, the modes of pathological activation of ROS formation as well as therapeutic approaches that may target ROS specifically in mitochondria.

Aldehyde Dehydrogenase 2 Protects Against Lipopolysaccharide-Induced Myocardial Injury by Suppressing Mitophagy

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Sepsis-induced circulatory and cardiac dysfunction is associated with high mortality rates. Mitophagy, a specific form of autophagy, is excessively activated in lipopolysaccharide-induced myocardial injury. The present study investigated whether aldehyde dehydrogenase 2 (ALDH2) regulates mitophagy in sepsis-induced myocardial dysfunction. After lipopolysaccharide administration, cardiac dysfunction, inflammatory cell infiltration, biochemical indicators of myocardial cell injury, and cardiomyocyte apoptosis were ameliorated in mice by ALDH2 activation or overexpression. In contrast, cardiac dysfunction and cardiomyocyte apoptosis were exacerbated in mice followed ALDH2 inhibition. Moreover, ALDH2 activation or overexpression regulated mitophagy by suppressing the expression of phosphatase and tensin homolog-induced putative kinase 1 (PINK1)/Parkin, by preventing the accumulation of 4-hydroxy-trans-nonenal. Conversely, ALDH2 inhibition promoted the expression of LC3B by increasing 4-hydroxy-trans-2-nonenal accumulation. Consequently, ALDH2 may protect the heart from lipopolysaccharide-induced injury by suppressing PINK1/Parkin-dependent mitophagy.

Effect of doxorubicin on cardiac lipid metabolism-related transcriptome and the protective activity of Alda-1

The use of doxorubicin (DOX) as an antineoplastic drug is compromised by its cardiotoxicity risk. Although several mechanisms have been proposed for DOX-induced cardiac dysfunction, there is still increased interest in assessing its effects. Likewise, it is important to find protocols that can prevent or minimize the side effects of DOX without hindering its antitumor activity. Thus, this study was designed to investigate the molecular mechanisms underlying DOX cardiotoxicity, with a special focus on cardiac energy metabolism and the ability of Alda-1 (ALDH2 agonist) to prevent DOX-induced cardiac alterations. We explored the effects of DOX on the histological morphology of the myocardium, on lipid profile, and on the expression of genes related to fatty acid metabolism, in the presence and absence of Alda-1 (8 mg/kg body weight; b.wt.). Two DOX treatment protocols were used: a single dose of DOX (4 mg/kg b.wt.); four doses of DOX (4 mg/kg b.wt.), one dose/week, for 4 weeks. Treatment with DOX caused a progressive injury in the cardiac tissue and an increase in the blood total cholesterol, high-density lipoproteins, very low-density lipoproteins and triglyceride, as well as an up-regulation of FABP4 (DOX and DOX + Alda-1 groups) and Slc27a2 (in DOX-treated animals). Alda-1 administration promoted reduction in the severity of the histopathological injuries (after single dose of DOX) and Slc27a2 overexpression was restored. In conclusion, the study revealed novel insights regarding the development of DOX-mediated cardiomyopathy, indicating a relationship between DOX exposure and FABP4 and Slc27a2 overexpression, and confirmed the cardioprotective effect of Alda-1.

Mitochondria-associated membrane-modulated Ca2+ transfer: A potential treatment target in cardiac ischemia reperfusion injury and heart failure

Effective Ca²⁺ dependent mitochondrial energy supply is imperative for proper cardiac contractile activity, while disruption of Ca²⁺ homeostasis participates in the pathogenesis of multiple human diseases. This phenomenon is particularly prominent in cardiac ischemia and reperfusion (I/R) and heart failure, both of which require strict clinical intervention. The interface between endoplasmic reticula (ER) and mitochondria, designated the mitochondria-associated membrane (MAM), is now regarded as a crucial mediator of Ca²⁺ transportation. Thus, interventions targeting this physical and functional coupling between mitochondria and the ER are highly desirable. Increasing evidence supports the notion that restoration, and maintenance, of the physiological contact between these two organelles can improve mitochondrial function, while inhibiting cell death, thereby sufficiently ameliorating I/R injury and heart failure development. A better understanding regarding the underlying mechanism of MAM-mediated transport will pave the way for identification of novel treatment approaches for heart disease. Therefore, in this review, we summarize the crucial functions and potential mechanisms of MAMs in the pathogenesis of I/R and heart failure.

Detoxification of Reactive Aldehydes by Alda-1 Treatment Ameliorates Experimental Autoimmune Encephalomyelitis in Mice

Reactive aldehydes are generated as a toxic end-product of lipid peroxidation under inflammatory oxidative stress condition which is a well-established phenomenon in the pathogenesis of multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Alda-1, a selective agonist of mitochondrial aldehyde dehydrogenase 2 (ALDH2), is known to detoxify the reactive aldehydes. In this study, we investigated the effect of Alda-1 on CNS myelin pathology associated with reactive aldehydes and mitochondrial/peroxisomal dysfunctions in a mouse model of EAE. Daily treatment of EAE mice with Alda-1, starting at the peak of disease, ameliorated the clinical manifestation of disease along with the improvement of motor functions. Accordingly, Alda-1 treatment improved demyelination and neuroaxonal degeneration in EAE mice. EAE mice had increased levels of reactive aldehyde species, such as 4-hydroxynonenal (4-HNE), malondialdehyde (MDA), and acrolein (ACL) in the spinal cords and these levels were significantly reduced in Alda-1-treated EAE mice. Furthermore, Alda-1 treatment improved the loss of mitochondrial (OXPHOS) and peroxisomal (PMP70 and catalase) proteins as well as mitochondrial/peroxisomal proliferation factors (PGC-1α and PPARs) in the spinal cords of EAE mice. Taken together, this study demonstrates the therapeutic efficacy of ALDH2-agonist Alda-1 in the abatement of EAE disease through the detoxification of reactive aldehydes, thus suggesting Alda-1 as a potential therapeutic intervention for MS.

Modulating ALDH2 reveals a differential dependence on ROS for hypertrophy and SR Ca2+ release in aldosterone-treated cardiac myocytes

Growing evidence links high aldosterone levels with atrial fibrillation and other heart diseases. Here, we have investigated the functional consequences of culturing adult rat atrial myocytes with aldosterone, at the level of cell size, homeostasis of Ca2+, reactive oxygen species (ROS), and nitrogen oxide (NO). The protein levels of NO synthase (NOS), aldehyde dehydrogenase 2 (ALDH2), NADPH oxidase (NOX), and Na+-Ca2+ exchanger (NCX) were also studied. Aldosterone did not alter the expression of these proteins, except for the NCX, which was enhanced by nearly 100%. Additionally, the hormone inhibited and stimulated, respectively, the production of NO and ROS (the effect on ROS appeared after 24 h of treatment and reached a maximum by 4-6 days, with an EC50 of 1.2 nM). These changes in reactive species generation were blunted by tetrahydrobiopterin (BH4, a NOS cofactor), suggesting the involvement of an uncoupled NOS. An activator (Alda-1) and an inhibitor (daidzin) of ALDH2 were used, to determine if this enzyme activity is related to aldosterone effects, through possible modulation of ROS. Aldosterone produced a ∼10% increase in cell size and, remarkably, this hypertrophic effect, along with the corresponding changes in ROS and NO, were all mimicked by daidzin and prevented by Alda-1. Something different happened with SR Ca2+ release. Aldosterone increased both the magnitude of Ca2+ transients and the incidence of spontaneous Ca2+ oscillations, but these actions were not reproduced by daidzin. Moreover, rather than being prevented, they were further promoted by Alda-1, which also increased the rate of SR Ca2+ reuptake. These results suggest that NOS and ALDH2 may prevent some adverse consequences of aldosteronism (in the case of ALDH2, at the expense of exacerbating SR Ca2+ release). Our data also suggest a hierarchical model in which aldosterone promotes: SR Ca2+ release, then ROS production, and finally hypertrophy.

Lipid Peroxidation in Atherosclerotic Cardiovascular Diseases

Significance: Atherosclerotic cardiovascular diseases (ACVDs) continue to be a primary cause of mortality worldwide in adults aged 35-70 years, occurring more often in countries with lower economic development, and they constitute an ever-growing global burden that has a considerable socioeconomic impact on society. The ACVDs encompass diverse pathologies such as coronary artery disease and heart failure (HF), among others. Recent Advances: It is known that oxidative stress plays a relevant role in ACVDs and some of its effects are mediated by lipid oxidation. In particular, lipid peroxidation (LPO) is a process under which oxidants such as reactive oxygen species attack unsaturated lipids, generating a wide array of oxidation products. These molecules can interact with circulating lipoproteins, to diffuse inside the cell and even to cross biological membranes, modifying target nucleophilic sites within biomolecules such as DNA, lipids, and proteins, and resulting in a plethora of biological effects. Critical Issues: This review summarizes the evidence of the effect of LPO in the development and progression of atherosclerosis-based diseases, HF, and other cardiovascular diseases, highlighting the role of protein adduct formation. Moreover, potential therapeutic strategies targeted at lipoxidation in ACVDs are also discussed. Future Directions: The identification of valid biomarkers for the detection of lipoxidation products and adducts may provide insights into the improvement of the cardiovascular risk stratification of patients and the development of therapeutic strategies against the oxidative effects that can then be applied within a clinical setting.

The effect of ALDH2 rs671 gene mutation on clustering of cardiovascular risk factors in a big data study of Chinese population: associations differ between the sexes

BACKGROUND

The ALDH2 rs671 genetic polymorphism has been linked with cardiovascular diseases (CVDs), but comprehensive epidemiological studies are lacking. An observational, retrospective big data study was carried out to evaluate the associations between this polymorphism and clustering cardiovascular risk factors (CRFs) in a Chinese population.

METHODS

A total of 13,101 individuals (8431 males and 4670 females) were enrolled. Genetic polymorphism was assessed using gene mutation detection kits, coupled with an automatic fluorescent analyzer. Other data were obtained from the records of the Department of Health Care at Peking Union Medical College Hospital.

RESULTS

Comparing the concentrations of common biochemical analytes, including BMI, SBP, DBP, ALT, AST, γ-GT, TBil, Cr, Glu, TC, TG, and HDL-C among individuals with the GG, GA, and AA genotypes of ALDH2 rs671, we found significant differences in males (all p < 0.001), but not in females. For males, the frequencies of hypertension, diabetes, and obesity were significantly higher for GG than for GA or AA (all p < 0.05). However, there was no significant difference for dyslipidemia, and no significant associations were observed for all frequencies in females. The prevalence of individuals with 1-4 CRFs was significantly higher among GG males than those carrying GA or AA, and fewer GG males had non-CRFs (all p < 0.05).

CONCLUSION

Polymorphisms of ALDH2 rs671 are associated with clustering CRFs, especially hypertension and diabetes in males, but not in females. These associations are likely mediated by alcohol intake, which is also associated with this gene.

Precision Medicine Considerations for the Management of Heart Disease and Stroke in East Asians

Heart disease is the leading cause of death in Asian Americans. Importantly, people of East Asian descent are more likely to carry a loss-of-function point mutation in aldehyde dehydrogenase 2 (ALDH2), ALDH2*2, which reduces ALDH2 enzymatic activity by at least 40% relative to wild type ALDH2. Given the role of ALDH2 in removing toxic aldehydes from the cell, ALDH2 is intimately involved in the cardioprotective mechanisms of ischemic preconditioning and the pathophysiology of ischemia reperfusion injury. The ALDH2*2 variant is associated with an increased incidence of coronary artery disease, myocardial infarction, and stroke. Furthermore, this variant is associated with insensitivity to nitroglycerin, which is commonly prescribed in patients with cardiovascular disease. In this review, we discuss the genetic susceptibility and pathophysiology associated with the ALDH2*2 variant in regards to cardiovascular disease. We also present the considerations for the management of heart disease and stroke specific to East Asians carrying the ALDH2*2 genetic variant.

Alda-1 attenuates hyperoxia-induced mitochondrial dysfunction in lung vascular endothelial cells

Acute lung injury (ALI) is a major cause of morbidity and mortality worldwide, especially in aged populations. Mitochondrial damage is one of the key features of ALI. Hyperoxia-induced lung injury model in mice has been widely used for ALI study because it features many ALI phenotypes including, but not limited to, mitochondrial and vascular endothelial cell damage. Recently, accumulating evidence has shown that mitochondrial aldehyde dehydrogenase 2 (ALDH2) has a protective effect against oxidative stress mediated cell damage in epithelial cells. However, it is not known whether ALDH2 protects against oxidative stress in vascular endothelial cells. In this current study, we attempted to find the capacity of Alda-1 [(N-(1,3benzodioxol-5-ylmethyl)-2,6- dichloro-benzamide), an ALDH2 activator] to protect against oxidative stress in human microvascular endothelial cells (HMVEC). HMVEC pretreated with Alda-1 prior to hyperoxic exposure vs non-treated controls showed i) lower 4-hydroxynonenal (4-HNE) levels, ii) significantly decreased expressions of Bax and Cytochrome C, iii) partially restored activity and expression of ALDH2 and iv) significantly improved mitochondrial membrane potential. These results suggest that ALDH2 protein in lung vascular endothelial cells is a promising therapeutic target for the treatment of ALI and that Alda-1 is a potential treatment option.

Pretreatment with the ALDH2 activator Alda‑1 protects rat livers from ischemia/reperfusion injury by inducing autophagy

Hepatic ischemia/reperfusion injury (HIRI) is a complex pathophysiological process that often leads to poor clinical prognosis. Clinically, the effective means to alleviate HIRI are limited. The aim of the present study was to investigate whether Alda-1, an activator of mitochondrial aldehyde dehydrogenase 2 (ALDH2), had a protective effect on HIRI and to investigate the mechanisms underlying this protective effect. Sprague-Dawley rats were treated with Alda-1 or Daidzin, an ALDH2 inhibitor, 30 min before partial (70%) warm liver ischemia to induce HIRI. The 48 rats were randomly divided into four groups: Sham, ischemia injury (IR), IR-Alda-1, and IR-Daidzin. After 6 and 24 h of reperfusion, serum and liver tissue samples were collected and stored for further experiments. Alanine aminotransferase, aspartate aminotransferase and hematoxylin & eosin staining was used to evaluate the liver damage. Western blotting and reverse transcription-quantitative PCR were used to detect the expression of related proteins and mRNA. TUNEL staining was used to observe the apoptosis of liver cells. Transmission electron microscopy was used to detect the mitochondrial injuries. Alda-1 pretreatment ameliorated the HIRI-induced damage to the liver function and reduced histological lesions. Alda-1 also increased ALDH2 activity after HIRI. Moreover, the pretreatment with Alda-1 reduced the accumulation of toxic aldehyde 4-hydroxy-2-nonenal, decreased the production of reactive oxygen species and malondialdehyde, reversed the damage to the liver mitochondria, attenuated hepatocyte apoptosis and inhibited the HIRI-induced inflammatory response, including high-mobility group box 1/toll-like receptor 4 signaling. Alda-1 also induced autophagy by upregulating autophagy-related 7 and Rab7 increasing the microtubule associated protein 1 light chain 3 αII/I ratio and inhibiting p62 expression. ALDH2-induced autophagy was dependent on the activation of the AKT/mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) signaling pathways. In conclusion, the findings of the present study suggested that Alda-1 may protect the liver against HIRI-induced damage, including hepatic enzyme injury, acetaldehyde accumulation, oxidative stress, hepatocyte apoptosis and inflammation. Alda-1 may confer this protection by inducing autophagy through the AKT/mTOR and AMPK signaling pathways. Therefore, ALDH2 could represent a potential pharmacological target in the clinical treatment of HIRI.

Different Expression of Aldehyde Dehydrogenases 1A1 and 2 in Oral Leukoplakia With Epithelial Dysplasia and in Oral Squamous Cell Carcinoma

Oral potentially malignant disorders (OPMD) may develop malignant characteristics and transform into oral squamous cell carcinoma (OSCC) in a range of 1% to 2% of cases. Chronic alcohol consumption is associated with carcinogenesis, but its mechanism has not yet been fully elucidated. ALDH1A1 and 2, isoenzymes responsible for aldehyde oxidation involved in ethanol metabolism may be associated with the development of malignant head and neck neoplasms. The aim of this study was to analyze the expression of ALDH1A1 and ALDH2 in oral leukoplakia with epithelial dysplasia (OLP) and OSCC. A retrospective study was conducted on 27 cases of OLP and 30 cases of OSCC. Clinical data were obtained from medical records, and all cases were classified as mild, moderate, and severe for OLP, and well-differentiated, moderately differentiated, or poorly differentiated for OSCC cases. The ALDH1A1 and ALDH2 expression in OLP and OSCC was evaluated by the immunohistochemical technique. There was predominance of the male sex, in both OLP and OSCC cases. Oral tongue was the most affected site in both groups. OLP showed positive protein expression of ALDH1A1 in all cases, both basal and suprabasal epithelial layers, whereas ALDH2 showed less protein expression. In OSCC, the immunohistochemical reaction for ALDH1A1 expression was negative in 70%, whereas ALDH2 expression was positive in all cases. This study demonstrated the gradual loss of ALDH1A1 expression in OSCC in comparison with OLP, and the increased ALDH2 expression in OSCC.

ALDH2 Activation Inhibited Cardiac Fibroblast-to-Myofibroblast Transformation Via the TGF-β1/Smad Signaling Pathway

Pathological stimulus-triggered differentiation of cardiac fibroblasts plays a major role in the development of myocardial fibrosis. Aldehyde dehydrogenase 2 (ALDH2) was reported to exert a protective role in cardiovascular disease, and whether ALDH2 is involved in cardiac fibroblast differentiation remains unclear. In this study, we used transforming growth factor-β1 (TGF-β1) to induce the differentiation of human cardiac fibroblasts (HCFs) and adopted ALDH2 activator Alda-1 to verify the influence of ALDH2 on HCF differentiation. Results showed that ALDH2 activity was obviously impaired when treating HCFs with TGF-β1. Activation of ALDH2 with Alda-1 inhibited the transformation of HCFs into myofibroblasts, demonstrated by the decreased smooth muscle actin (α-actin) and periostin expression, reduced HCF-derived myofibroblast proliferation, collagen production, and contractility. Moreover, application of Smad2/3 inhibitor alleviated TGF-β1-induced HCF differentiation and improved ALDH2 activity, which was reversed by the application of ALDH2 inhibitor daidzin. Finally, Alda-1-induced HCF alterations alleviated neonatal rat cardiomyocyte hypertrophy, supported by the immunostaining of α-actin. To summarize, activation of ALDH2 enzymatic activity inhibited the differentiation of cardiac fibroblasts via the TGF-β1/Smad signaling pathway, which might be a promising strategy to relieve myocardial fibrosis of various causes.

Aldehyde dehydrogenase 2 protects cardiomyocytes against lipotoxicity via the AKT/glycogen synthase kinase 3 beta pathways

Aldehyde dehydrogenase 2, a mitochondrial matrix enzyme, plays a crucial role in protecting the heart against stress, such as ischemia reperfusion and alcohol injury. The present study aimed to investigate the effect of aldehyde dehydrogenase 2 on lipotoxic cardiomyopathy and to explore the possible mechanisms in vitro. Primary cardiomyocytes in the lipotoxic group were treated with oxidatively modified low-density lipoprotein (50 mg/L) for 24 h. Overexpression of aldehyde dehydrogenase 2 was achieved using the aldehyde dehydrogenase 2 activator, Alda-1 (20 μM). We found that cardiomyocyte apoptosis was attenuated by aldehyde dehydrogenase 2 overexpression. In addition, aldehyde dehydrogenase 2 overexpression inhibited the expression of BCL2 associated X, apoptosis regulator (BAX) and caspase 3, while it enhanced protein kinase B (AKT) and glycogen synthase kinase 3 beta (GSK-3β) phosphorylation. The results suggested that aldehyde dehydrogenase 2 is cardioprotective against lipotoxic cardiomyopathy, probably by reducing apoptosis through the AKT/glycogen synthase kinase 3 beta (GSK-3β) pathway. Our findings partially revealed the molecular mechanism of aldehyde dehydrogenase 2's cardioprotective effect against lipotoxic injury, and suggest a new therapeutic strategy to treat lipotoxic cardiomyopathy.

β2 -adrenoceptor activation improves skeletal muscle autophagy in neurogenic myopathy

β2 -adrenoceptor agonists improve autophagy and re-establish proteostasis in cardiac cells; therefore, suggesting autophagy as a downstream effector of β2 -adrenoceptor signaling pathway. Here, we used the pharmacological and genetic tools to determine the autophagy effect of sustained β2 -adrenoceptor activation in rodents with neurogenic myopathy, which display impaired skeletal muscle autophagic flux. Sustained β2 -adrenoceptor activation using Formoterol (10 μg kg-1  day-1 ), starting at the onset of neurogenic myopathy, prevents disruption of autophagic flux in skeletal muscle 14 days after sciatic nerve constriction. These changes are followed by reduction of the cytotoxic protein levels and increased skeletal muscle cross-sectional area and contractility properties. Of interest, sustained administration of Formoterol at lower concentration (1 μg kg-1  day-1 ) induces similar improvements in skeletal muscle autophagic flux and contractility properties in neurogenic myopathy, without affecting the cross-sectional area. Sustained pharmacological inhibition of autophagy using Chloroquine (50 mg kg-1  day-1 ) abolishes the beneficial effects of β2 -adrenoceptor activation on the skeletal muscle proteostasis and contractility properties in neurogenic myopathy. Further supporting an autophagy mechanism for β2 -adrenoceptor activation, skeletal muscle-specific deletion of ATG7 blunts the beneficial effects of β2 -adrenoceptor on skeletal muscle proteostasis and contractility properties in neurogenic myopathy in mice. These findings suggest autophagy as a critical downstream effector of β2 -adrenoceptor signaling pathway in skeletal muscle.