The role of mitochondria in cardiac development and protection

Identification of VDAC1 as a cardioprotective target of Ginkgolide B

Ginkgolide B (GB), a compound derived from Ginkgo biloba, exhibits significant cardioprotective properties, although its precise molecular target has yet to be identified. In this study, we synthesized a biotin-labeled GB probe (GB-biotin) to identify the molecular targets of GB. Our experiments demonstrated that treatment with GB or GB-biotin reduced mitochondrial injury, restored mitochondrial membrane potential, and decreased cell apoptosis in a concentration-dependent manner. Additionally, GB increased mitochondrial oxygen consumption rate, indicating improved mitochondrial bioenergetics. Proteomic analysis revealed that the voltage-dependent anion channel 1 (VDAC1) is a key protein that interacts with GB-biotin. This finding was further confirmed through cellular thermal shift assay (CETSA) and molecular docking, which revealed hydrogen bond formation between GB and VDAC1. Furthermore, overexpression of VDAC1 diminished the protective effects of GB, highlighting the crucial role of VDAC1 in GB-mediated cardioprotection. These findings identify VDAC1 as a therapeutic target for GB in vitro, providing valuable insights into the cardioprotective mechanisms of GB and the development of novel cardioprotective strategies.

Targeted mitochondrial function for cardiac fibrosis: An epigenetic perspective

Mitochondria, commonly referred to as "energy factories"of cells, play a crucial role in the function and survival of cardiomyocytes. However, as research on cardiac fibrosis has advanced, mitochondrial dysfunction(including changes in energy metabolism, calcium ion imbalance, increased oxidative stress, and apoptosis)is now recognized as a significant pathophysiological pathway involved in cardiac remodeling and progression, which also negatively affects the function and structure of the heart. In recent years, research focusing on targeting mitochondria has gained significant attention, offering new approaches for treating cardiac fibrosis. Targeted mitochondrial therapy for cardiac fibrosis represents an emerging therapeutic strategy that aims to inhibit cardiac fibroblast proliferation or protect cardiomyocytes from damage by enhancing mitochondrial function. However, current research on epigenetic treatments for cardiac fibrosis through mitochondrial targeting remains limited. This review explores the relationship between mitochondrial dysfunction and cardiac fibrosis, as well as the epigenetic regulatory mechanisms involved in targeted mitochondrial therapy for cardiac fibrosis.

Di-(2-ethylhexyl) Phthalate Exposure Induces Developmental Toxicity in the Mouse Fetal Heart via Mitochondrial Dysfunction

Congenital heart disease (CHD) is a major cause of infant mortality and morbidity, with growing interest in the role of environmental factors in its etiology. Di-(2-ethylhexyl) phthalate (DEHP), an environmental endocrine disruptor, has been implicated in the development of CHD. This study aimed to investigate the effects of DEHP exposure on fetal heart development in mice. Pregnant mice exposed to DEHP exhibited increased fetal malformations, decreased fetal weight, and reduced crown-rump length.f Transcriptomic analysis revealed the downregulation of genes involved in aerobic respiration and mitochondrial ATP synthesis. Functional assays demonstrated reduced mitochondrial respiration, decreased ATP production, elevated reactive oxygen species levels, and lowered mitochondrial membrane potential in DEHP-exposed fetal cardiomyocytes. These findings underscore the detrimental effects of DEHP on fetal cardiac health and provide insights into the molecular mechanisms underlying DEHP-induced CHD. Understanding these mechanisms is crucial for developing preventive strategies against environmental toxicants that affect fetal cardiac development.

Micropeptide MPM regulates cardiomyocyte proliferation and heart growth via the AKT pathway

The role of micropeptide in cardiomyocyte proliferation remains unknown. We found that MPM (micropeptide in mitochondria) was highly expressed in cardiomyocytes. Compared to MPM+/+ mice, MPM knockout (MPM-/-) mice exhibited reduction in left ventricular (LV) mass, myocardial thickness and LV fractional shortening. RNA-sequencing analysis in H9c2, a rat cardiomyocyte cell line, identified downregulation of cell cycle-promoting genes as the most significant alteration in MPM-silencing cells. Consistently, gain- and loss-of-function analyses in H9c2 cells revealed that cardiomyocyte proliferation was repressed by silencing MPM but was promoted by overexpressing MPM. Moreover, the cardiomyocytes in the hearts of MPM-/- mice displayed reduced proliferation rates. Mechanism investigations disclosed that MPM is crucial for AKT activation in cardiomyocytes. We also identified an interaction between MPM and PTPMT1, and found that silencing PTPMT1 attenuated the effect of MPM in activating the AKT pathway, whereas inhibition of the AKT pathway abrogated the role of MPM in promoting cardiomyocyte proliferation. Collectively, these results indicate that MPM may promote cardiomyocyte proliferation and thus heart growth by interacting with PTPMT1 to activate the AKT pathway. Our findings identify the novel function and regulatory network of MPM and highlight the importance of micropeptides in cardiomyocyte proliferation and heart growth.

High-intensity interval training and moderate-intensity continuous training alleviate vascular dysfunction in spontaneously hypertensive rats through the inhibition of pyroptosis

Evidence-based guidelines suggest that High-Intensity Interval Training (HIIT) is more beneficial than aerobic exercise for patients with cardiovascular disease, but the differences in underlying pathophysiological mechanisms require further confirmation. The comparison between HIIT and Moderate-Intensity Continuous Training (MICT) in regulating vascular dysfunction in spontaneously hypertensive rats (SHR), along with their underlying mechanisms, has not been previously reported. The purpose of this study is to provide an experimental basis for exercise prescription therapy in hypertensive patients. In this study, six-week-old male SHR were randomly assigned to a HIIT group, MICT group, or sedentary group. Wistar Kyoto rats (WKY) of the same age were used as the control group. The weight, heart rate, and blood pressure of the rats were monitored weekly throughout twelve weeks of treadmill training. At the end of the protocol, serum and aortic vascular tissues were collected for further vascular function tests and molecular and biochemical analyses. The results show that MICT is more favorable for weight control than HIIT, while both forms of exercise offer equal protection against hypertension. However, MICT demonstrates a greater benefit in preserving vascular morphology, whereas HIIT is more effective in reducing oxidative stress. Both HIIT and MICT ameliorate vascular dysfunction in SHR by suppressing nucleotide-binding domain and leucine-rich repeat pyrin-domain containing protein 3 (NLRP3)-induced pyroptosis. The superior effect of HIIT on vascular dysfunction may be related to the inhibition of oxidative stress injury through AMPKα-SIRT1 activation. This study provides insight into the dose-effect relationship of exercise for cardiovascular health and offers foundational evidence for the development of exercise prescription therapies.

Exogenous Nucleotides Mitigate Cardiac Aging in SAMP8 Mice by Modulating Energy Metabolism Through AMPK Pathway

BACKGROUND

Cardiovascular disease (CVD) is the predominant cause of mortality, with aging being a significant risk factor. Nucleotides (NTs), essential for numerous biological functions, are particularly vital under conditions like aging, starvation, and nutrient deficiency. Although the antiaging benefits of exogenous NTs have been recognized in various systems, their cardiac-specific effects are not well understood. This study, therefore, investigated the impact of exogenous NTs on cardiac aging and delved into the potential mechanisms.

METHODS

Senescence-accelerated mouse prone-8 (SAMP8) mice were utilized, randomly assigned to one of three groups: a control group (Control), a low-dose NTs group (NTs_L), and a high-dose NTs group (NTs_H). Meanwhile, senescence-accelerated mouse resistant 1 (SAMR1) mice were set up as the SAMR1 group. Following a 9-month intervention, cardiac tissues were subjected to analysis.

RESULTS

The results showed that NTs improved the morphological structure of the cardiac tissue, enhanced the antioxidant capacity, and mitigated inflammation. Metabolomics analysis revealed that the high-dose NT intervention improved cardiac tissue energy metabolism, potentially through activating the AMPK pathway, enhanced mitochondrial biogenesis, and increased TFAM protein expression.

CONCLUSIONS

Together, these results indicate that exogenous NTs exert beneficial effects on the cardiac tissues of SAMP8 mice, potentially mitigating the cardiac aging process.

Mitochondrial non-energetic function and embryonic cardiac development

The initial contraction of the heart during the embryonic stage necessitates a substantial energy supply, predominantly derived from mitochondrial function. However, during embryonic heart development, mitochondria influence beyond energy supplementation. Increasing evidence suggests that mitochondrial permeability transition pore opening and closing, mitochondrial fusion and fission, mitophagy, reactive oxygen species production, apoptosis regulation, Ca2+ homeostasis, and cellular redox state also play critical roles in early cardiac development. Therefore, this review aims to describe the essential roles of mitochondrial non-energetic function embryonic cardiac development.

Gastrodin exerts perioperative myocardial protection by improving mitophagy through the PINK1/Parkin pathway to reduce myocardial ischemia-reperfusion injury

BACKGROUND

Although blood flow is restored after treatment of myocardial infarction (MI), myocardial ischemia and reperfusion (I/R) can cause cardiac injury, which is a leading cause of heart failure. Gastrodin (GAS) exerts protective effects against brain, heart, and kidney I/R. However, its pharmacological mechanism in myocardial I/R injury (MIRI) remains unclear.

PURPOSE

GAS regulates autophagy in various diseases, such as acute hepatitis, vascular dementia, and stroke. We hypothesized that GAS could repair mitochondrial damage and regulate autophagy to protect against MIRI.

STUDY DESIGN

Male C57BL/6 mice and H9C2 cells were subjected to I/R and hypoxia-reoxygenation (H/R) injury after GAS administration, respectively, to assess the impact of GAS on cardiomyocyte phenotypes, heart, and mitochondrial structure and function. The effect of GAS on cardiac function and mitochondrial structure in patients undergoing cardiac surgery has been observed in clinical practice.

METHODS

The effects of GAS on cardiac structure and function, mitochondrial structure, and expression of related molecules in an animal model of MIRI were evaluated using immunohistochemical staining, enzyme-linked immunosorbent assay (ELISA), transmission electron microscopy, western blotting, and gene sequencing. Its effects on the morphological, molecular, and functional phenotypes of cardiomyocytes undergoing H/R were observed using immunohistochemical staining, real-time quantitative PCR, and western blotting.

RESULTS

GAS significantly reduces myocardial infarct size and improves cardiac function in MIRI mice in animal models and increases cardiomyocyte viability and reduces cardiomyocyte damage in cellular models. In clinical practice, myocardial injury was alleviated with better cardiac function in patients undergoing cardiac surgery after the application of GAS; improvements in mitochondria and autophagy activation were also observed. GAS primarily exerts cardioprotective effects through activation of the PINK1/Parkin pathway, which promotes mitochondrial autophagy to clear damaged mitochondria.

CONCLUSION

GAS can promote mitophagy and preserve mitochondria through PINK1/Parkin, thus indicating its tremendous potential as an effective perioperative myocardial protective agent.

Role of mitochondrial ribosomal protein L7/L12 (MRPL12) in diabetic ischemic heart disease

BACKGROUND

Myocardial infarction (MI) is a significant cause of death in diabetic patients. Growing evidence suggests that mitochondrial dysfunction contributes to heart failure in diabetes. However, the molecular mechanisms of mitochondrial dysfunction mediating heart failure in diabetes are still poorly understood.

METHODS

We examined MRPL12 levels in right atrial appendage tissues from diabetic patients undergoing coronary artery bypass graft (CABG) surgery. Using AC-16 cells overexpressing MRPL12 under normal and hyperglycemic conditions we performed mitochondrial functional assays OXPHOS, bioenergetics, mitochondrial membrane potential, ATP production and cell death.

RESULTS

We observed elevated MRPL12 levels in heart tissue samples from diabetic patients with ischemic heart disease compared to non-diabetic patients. Overexpression of MRPL12 under hyperglycemic conditions did not affect oxidative phosphorylation (OXPHOS) levels, cellular ATP levels, or cardiomyocyte cell death. However, notable impairment in mitochondrial membrane potential (MMP) was observed under hyperglycemic conditions, along with alterations in both basal respiration oxygen consumption rate (OCR) and maximal respiratory capacity OCR.

CONCLUSIONS

Overall, our results suggest that MRPL12 may have a compensatory role in the diabetic myocardium with ischemic heart disease, suggesting that MRPL12 may implicate in the pathophysiology of MI in diabetes.

Peptide PDRPS6 attenuates myocardial ischemia injury by improving mitochondrial function

Mitochondrial dynamics play a crucial role in myocardial ischemia-reperfusion (I/R) injury, where an imbalance between fusion and fission processes occurs. However, effective measures to regulate mitochondrial dynamics in this context are currently lacking. Peptide derived from the 40 S ribosomal protein S6 (PDRPS6), a peptide identified via peptidomics, is associated with hypoxic stress. This study aimed to investigate the function and mechanism of action of PDRPS6 in I/R injury. In vivo, PDRPS6 ameliorated myocardial tissue injury and cardiomyocyte apoptosis and decreased cardiac function induced by I/R injury in rats. PDRPS6 supplementation significantly reduced apoptosis in vitro. Mechanistically, PDRPS6 improved mitochondrial function by decreasing reactive oxygen species (ROS) levels, maintaining mitochondrial membrane potential (MMP), and inhibiting mitochondrial fission. Pull-down assay analyses revealed that phosphoglycerate mutase 5 (PGAM5) may be the target of PDRPS6, which can lead to the dephosphorylation of dynamin-related protein1 (Drp1) at ser616 site. Overexpression of PGAM5 partially eliminated the effect of PDRPS6 on improving mitochondrial function. These findings suggest that PDRPS6 supplementation is a novel method for treating myocardial injuries caused by I/R.

The characterization of protein lactylation in relation to cardiac metabolic reprogramming in neonatal mouse hearts

In mammals, the neonatal heart can regenerate upon injury within a short time after birth, while adults lose this ability. Metabolic reprogramming has been demonstrated to be critical for cardiomyocyte proliferation in the neonatal heart. Here, we reveal that cardiac metabolic reprogramming could be regulated by altering global protein lactylation. By performing 4D label-free proteomics and lysine lactylation (Kla) omics analyses in mouse hearts at postnatal days 1, 5, and 7, 2297 Kla sites from 980 proteins are identified, among which 1262 Kla sites from 409 proteins are quantified. Functional clustering analysis reveals that the proteins with altered Kla sites are mainly involved in metabolic processes. The expression and Kla levels of proteins in glycolysis show a positive correlation while a negative correlation in fatty acid oxidation. Furthermore, we verify the Kla levels of several differentially modified proteins, including ACAT1, ACADL, ACADVL, PFKM, PKM, and NPM1. Overall, our study reports a comprehensive Kla map in the neonatal mouse heart, which will help to understand the regulatory network of metabolic reprogramming and cardiac regeneration.

Cardioprotective response and senescence in aged sEH null female mice exposed to LPS

Deterioration of physiological systems, like the cardiovascular system, occurs progressively with age impacting an individual's health and increasing susceptibility to injury and disease. Cellular senescence has an underlying role in age-related alterations and can be triggered by natural aging or prematurely by stressors such as the bacterial toxin lipopolysaccharide (LPS). The metabolism of polyunsaturated fatty acids by CYP450 enzymes produces numerous bioactive lipid mediators that can be further metabolized by soluble epoxide hydrolase (sEH) into diol metabolites, often with reduced biological effects. In our study, we observed age-related cardiac differences in female mice, where young mice demonstrated resistance to LPS injury, and genetic deletion or pharmacological inhibition of sEH using trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid attenuated LPS-induced cardiac dysfunction in aged female mice. Bulk RNA-sequencing analyses revealed transcriptomics differences in aged female hearts. The confirmatory analysis demonstrated changes to inflammatory and senescence gene markers such as Il-6, Mcp1, Il-1β, Nlrp3, p21, p16, SA-β-gal, and Gdf15 were attenuated in the hearts of aged female mice where sEH was deleted or inhibited. Collectively, these findings highlight the role of sEH in modulating the aging process of the heart, whereby targeting sEH is cardioprotective.NEW & NOTEWORTHY Soluble epoxide hydrolase (sEH) is an essential enzyme for converting epoxy fatty acids to their less bioactive diols. Our study suggests deletion or inhibition of sEH impacts the aging process in the hearts of female mice resulting in cardioprotection. Data indicate targeting sEH limits inflammation, preserves mitochondria, and alters cellular senescence in the aged female heart.

Alcohol exposure during pregnancy induces cardiac mitochondrial damage in offspring mice

BACKGROUND

Prenatal alcohol exposure (PAE) has been linked to congenital heart disease and fetal alcohol syndrome. The heart primarily relies on mitochondria to generate energy, so impaired mitochondrial function due to alcohol exposure can significantly affect cardiac development and function. Our study aimed to investigate the impact of PAE on myocardial and mitochondrial functions in offspring mice.

METHODS

We administered 30% alcohol (3 g/kg) to pregnant C57BL/6 mice during the second trimester. We assessed cardiac function by transthoracic echocardiography, observed myocardial structure and fibrosis through staining tests and electron transmission microscopy, and detected cardiomyocyte apoptosis with dUTP nick end labeling assay and real-time quantitative PCR. Additionally, we measured the reactive oxygen species content, ATP level, and mitochondrial DNA copy number in myocardial mitochondria. Mitochondrial damage was evaluated by assessing the level of mitochondrial membrane potential and the opening degree of mitochondrial permeability transition pores.

RESULTS

Our findings revealed that PAE caused cardiac systolic dysfunction, ventricular enlargement, thinned ventricular wall, cardiac fibrosis in the myocardium, scattered loss of cardiomyocytes, and disordered arrangement of myocardial myotomes in the offspring. Furthermore, we observed a significant increase in mitochondrial reactive oxygen species content, a decrease in mitochondrial membrane potential, ATP level, and mitochondrial DNA copy number, and sustained opening of mitochondrial permeability transition pores in the heart tissues of the offspring.

CONCLUSIONS

These results indicated that PAE had adverse effects on the cardiac structure and function of the newborn mice and could trigger oxidative stress in their myocardia and contribute to mitochondrial dysfunction.

Mitochondrial DNA Stress-Mediated Health Risk to Dibutyl Phthalate Contamination on Zebrafish (Danio rerio) at Early Life Stage

Plastics contaminations are found globally and fit the exposure profile of the planetary boundary threat. The plasticizer of dibutyl phthalate (DBP) leaching has occurred and poses a great threat to human health and the ecosystem for decades, and its toxic mechanism needs further comprehensive elucidation. In this study, environmentally relevant levels of DBP were used for exposure, and the developmental process, oxidative stress, mitochondrial ultrastructure and function, mitochondrial DNA (mtDNA) instability and release, and mtDNA-cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling pathway with inflammatory responses were measured in zebrafish at early life stage. Results showed that DBP exposure caused developmental impairments of heart rate, hatching rate, body length, and mortality in zebrafish embryo. Additionally, the elevated oxidative stress damaged mitochondrial ultrastructure and function and induced oxidative damage to the mtDNA with mutations and instability of replication, transcription, and DNA methylation. The stressed mtDNA leaked into the cytosol and activated the cGAS-STING signaling pathway and inflammation, which were ameliorated by co-treatment with DBP and mitochondrial reactive oxygen species (ROS) scavenger, inhibitors of cGAS or STING. Furthermore, the larval results suggest that DBP-induced mitochondrial toxicity of energy disorder and inflammation were involved in the developmental defects of impaired swimming capability. These results enhance the interpretation of mtDNA stress-mediated health risk to environmental contaminants and contribute to the scrutiny of mitochondrial toxicants.

Genetically predicted dietary macronutrient intakes and atrial fibrillation risk: a Mendelian randomization study

BACKGROUND AND AIM

Previous observational investigations have indicated a potential association between relative dietary macronutrient intakes and atrial fibrillation and flutter (AF) risk. In this study, we employed Mendelian Randomization (MR) to evaluate the presence of causality and to elucidate the specific causal relationship.

METHODS

We employed six, five, and three single nucleotide polymorphisms (SNPs) as instrumental variables for relative carbohydrate, protein, and fat intake, identified from a genome-wide association study that included 268,922 individuals of European descent. Furthermore, we acquired summary statistics for genome-wide association studies on AF from the FinnGen consortium, which involved 22,068 cases and 116,926 controls. To evaluate the causal estimates, we utilized the random effect inverse variance weighted method (IVW) and several other MR methods, including MR-Egger, weighted median, and MR-PRESSO, to confirm the robustness of our findings.

RESULTS

Our analysis indicates a convincing causal relationship between genetically predicted relative carbohydrate and protein intake and reduced AF risk. Inverse variance weighted analysis results for carbohydrates (OR = 0.29; 95% CI (0.14, 0.59); P < 0.001) and protein (OR = 0.47; 95% CI (0.26, 0.85); P = 0.01) support this association. Our MR analysis did not identify a significant causal relationship between relative fat intake and AF risk.

CONCLUSION

Our study provides evidence supporting a causal relationship between higher relative protein and carbohydrate intake and a lower risk of atrial fibrillation (AF).

Integrated Stress Response Potentiates Ponatinib-Induced Cardiotoxicity

BACKGROUND

Mitochondrial dysfunction is a primary driver of cardiac contractile failure; yet, the cross talk between mitochondrial energetics and signaling regulation remains obscure. Ponatinib, a tyrosine kinase inhibitor used to treat chronic myeloid leukemia, is among the most cardiotoxic tyrosine kinase inhibitors and causes mitochondrial dysfunction. Whether ponatinib-induced mitochondrial dysfunction triggers the integrated stress response (ISR) to induce ponatinib-induced cardiotoxicity remains to be determined.

METHODS

Using human induced pluripotent stem cells-derived cardiomyocytes and a recently developed mouse model of ponatinib-induced cardiotoxicity, we performed proteomic analysis, molecular and biochemical assays to investigate the relationship between ponatinib-induced mitochondrial stress and ISR and their role in promoting ponatinib-induced cardiotoxicity.

RESULTS

Proteomic analysis revealed that ponatinib activated the ISR in cardiac cells. We identified GCN2 (general control nonderepressible 2) as the eIF2α (eukaryotic translation initiation factor 2α) kinase responsible for relaying mitochondrial stress signals to trigger the primary ISR effector-ATF4 (activating transcription factor 4), upon ponatinib exposure. Mechanistically, ponatinib treatment exerted inhibitory effects on ATP synthase activity and reduced its expression levels resulting in ATP deficits. Perturbed mitochondrial function resulting in ATP deficits then acts as a trigger of GCN2-mediated ISR activation, effects that were negated by nicotinamide mononucleotide, an NAD+ precursor, supplementation. Genetic inhibition of ATP synthase also activated GCN2. Interestingly, we showed that the decreased abundance of ATP also facilitated direct binding of ponatinib to GCN2, unexpectedly causing its activation most likely because of a conformational change in its structure. Importantly, administering an ISR inhibitor protected human induced pluripotent stem cell-derived cardiomyocytes against ponatinib. Ponatinib-treated mice also exhibited reduced cardiac function, effects that were attenuated upon systemic ISRIB administration. Importantly, ISRIB does not affect the antitumor effects of ponatinib in vitro.

CONCLUSIONS

Neutralizing ISR hyperactivation could prevent or reverse ponatinib-induced cardiotoxicity. The findings that compromised ATP production potentiates GCN2-mediated ISR activation have broad implications across various cardiac diseases. Our results also highlight an unanticipated role of ponatinib in causing direct activation of a kinase target despite its role as an ATP-competitive kinase inhibitor.

The role of metabolism in cardiac development

Metabolism is the fundamental process that sustains life. The heart, in particular, is an organ of high energy demand, and its energy substrates have been studied for more than a century. In recent years, there has been a growing interest in understanding the role of metabolism in the early differentiation of pluripotent stem cells and in cancer research. Studies have revealed that metabolic intermediates from glycolysis and the tricarboxylic acid cycle act as co-factors for intracellular signal transduction, playing crucial roles in regulating cell behaviors. Mitochondria, as the central hub of metabolism, are also under intensive investigation regarding the regulation of their dynamics. The metabolic environment of the fetus is intricately linked to the maternal metabolic status, and the impact of the mother's nutrition and metabolic health on fetal development is significant. For instance, it is well known that maternal diabetes increases the risk of cardiac and nervous system malformations in the fetus. Another notable example is the decrease in the risk of neural tube defects when pregnant women are supplemented with folic acid. These examples highlight the profound influence of the maternal metabolic environment on the fetal organ development program. Therefore, gaining insights into the metabolic environment within developing fetal organs is critical for deepening our understanding of normal organ development. This review aims to summarize recent findings that build upon the historical recognition of the environmental and metabolic factors involved in the developing embryo.

Tetrahydrocurcumin ameliorates postinfarction cardiac dysfunction and remodeling by inhibiting oxidative stress and preserving mitochondrial function via SIRT3 signaling pathway

BACKGROUND

Myocardial infarction (MI) often leads to sudden cardiac death. Persistent myocardial ischemia increases oxidative stress and impairs mitochondrial function, contributing significantly to postinfarction cardiac dysfunction and remodeling, and the subsequent progression to heart failure (HF). Tetrahydrocurcumin (THC), isolated from the rhizome of turmeric, has antioxidant properties and has been shown to protect against cardiovascular diseases. However, its effects on HF after MI are poorly understood.

PURPOSE

The objective was the investigation of the pharmacological effects of THC and its associated mechanisms in the pathogenesis of HF after MI.

METHODS

A total of 120 mice (C57BL/6, male) were used for the in vivo experiments. An MI mouse model was created by permanent ligation of the left anterior descending coronary artery. The mice received oral dose of THC at 120 mg/kg/d and the effects on MI-induced myocardial injury were evaluated by assessment of cardiac function, histopathology, myocardial oxidative levels, and mitochondrial function. Molecular mechanisms were investigated by intraperitoneal injection of 50 mg/kg of the SIRT3 selective inhibitor 3-TYP. Meanwhile, mouse neonatal cardiomyocytes were isolated and cultured in a hypoxic incubator to verify the effects of THC in vitro. Lastly, SIRT3 and Nrf2 were silenced using siRNAs to further explore the regulatory mechanism of key molecules in this process.

RESULTS

The mouse hearts showed significant impairment in systolic function after MI, together with enlarged infarct size, increased myocardial fibrosis, cardiac hypertrophy, and apoptosis of cardiomyocytes. A significant reversal of these changes was seen after treatment with THC. Moreover, THC markedly reduced reactive oxygen species generation and protected mitochondrial function, thus mitigating oxidative stress in the post-MI myocardium. Mechanistically, THC counteracted reduced Nrf2 nuclear accumulation and SIRT3 signaling in the MI mice while inhibition of Nrf2 or SIRT3 reversed the effects of THC. Cell experiments showed that Nrf2 silencing markedly reduced SIRT3 levels and deacetylation activity while inhibition of SIRT3 signaling had little impact on Nrf2 expression.

CONCLUSION

This is the first demonstration that THC protects against the effects of MI. THC reduced both oxidative stress and mitochondrial damage by regulating Nrf2-SIRT3 signaling. The results suggest the potential of THC in treating myocardial ischemic diseases.

Characterizing Early Cardiac Metabolic Programming via 30% Maternal Nutrient Reduction during Fetal Development in a Non-Human Primate Model

Intra-uterine growth restriction (IUGR) is a common cause of fetal/neonatal morbidity and mortality and is associated with increased offspring predisposition for cardiovascular disease (CVD) development. Mitochondria are essential organelles in maintaining cardiac function, and thus, fetal cardiac mitochondria could be responsive to the IUGR environment. In this study, we investigated whether in utero fetal cardiac mitochondrial programming can be detectable in an early stage of IUGR pregnancy. Using a well-established nonhuman IUGR primate model, we induced IUGR by reducing by 30% the maternal diet (MNR), both in males (MNR-M) and in female (MNR-F) fetuses. Fetal cardiac left ventricle (LV) tissue and blood were collected at 90 days of gestation (0.5 gestation, 0.5 G). Blood biochemical parameters were determined and heart LV mitochondrial biology assessed. MNR fetus biochemical blood parameters confirm an early fetal response to MNR. In addition, we show that in utero cardiac mitochondrial MNR adaptations are already detectable at this early stage, in a sex-divergent way. MNR induced alterations in the cardiac gene expression of oxidative phosphorylation (OXPHOS) subunits (mostly for complex-I, III, and ATP synthase), along with increased protein content for complex-I, -III, and -IV subunits only for MNR-M in comparison with male controls, highlight the fetal cardiac sex-divergent response to MNR. At this fetal stage, no major alterations were detected in mitochondrial DNA copy number nor markers for oxidative stress. This study shows that in 90-day nonhuman primate fetuses, a 30% decrease in maternal nutrition generated early in utero adaptations in fetal blood biochemical parameters and sex-specific alterations in cardiac left ventricle gene and protein expression profiles, affecting predominantly OXPHOS subunits. Since the OXPHOS system is determinant for energy production in mitochondria, our findings suggest that these early IUGR-induced mitochondrial adaptations play a role in offspring's mitochondrial dysfunction and can increase predisposition to CVD in a sex-specific way.

Raspberry polyphenols alleviate neurodegenerative diseases: through gut microbiota and ROS signals

Neurodegenerative diseases are neurological disorders that become more prevalent with age, usually caused by damage or loss of neurons or their myelin sheaths, such as Alzheimer's disease and epilepsy. Reactive oxygen species (ROS) are important triggers for neurodegenerative disease development, and mitigation of oxidative stress caused by ROS imbalance in the human body is important for the treatment of these diseases. As a widespread delicious fruit, the raspberry is widely used in the field of food and medicine because of its abundant polyphenols and other bioactive substances. Polyphenols from a wide variety of raspberry sources could alleviate neurodegenerative diseases. This review aims to summarize the current roles of these polyphenols in maintaining neurological stability by regulating the composition and metabolism of the intestinal flora and the gut-brain axis signal transmission. Especially, we discuss the therapeutic effects on neurodegenerative diseases of raspberry polyphenols through intestinal microorganisms and ROS signals, by means of summary and analysis. Finally, methods of improving the digestibility and utilization of raspberry polyphenols are proposed, which will provide a potential way for raspberry polyphenols to guarantee the health of the human nervous system.

Mitochondrial quality control in cardiac fibrosis: Epigenetic mechanisms and therapeutic strategies

Cardiac fibrosis (CF) is considered an ultimate common pathway of a wide variety of heart diseases in response to diverse pathological and pathophysiological stimuli. Mitochondria are characterized as isolated organelles with a double-membrane structure, and they primarily contribute to and maintain highly dynamic energy and metabolic networks whose distribution and structure exert potent support for cellular properties and performance. Because the myocardium is a highly oxidative tissue with high energy demands to continuously pump blood, mitochondria are the most abundant organelles within mature cardiomyocytes, accounting for up to one-third of the total cell volume, and play an essential role in maintaining optimal performance of the heart. Mitochondrial quality control (MQC), including mitochondrial fusion, fission, mitophagy, mitochondrial biogenesis, and mitochondrial metabolism and biosynthesis, is crucial machinery that modulates cardiac cells and heart function by maintaining and regulating the morphological structure, function and lifespan of mitochondria. Certain investigations have focused on mitochondrial dynamics, including manipulating and maintaining the dynamic balance of energy demand and nutrient supply, and the resultant findings suggest that changes in mitochondrial morphology and function may contribute to bioenergetic adaptation during cardiac fibrosis and pathological remodeling. In this review, we discuss the function of epigenetic regulation and molecular mechanisms of MQC in the pathogenesis of CF and provide evidence for targeting MQC for CF. Finally, we discuss how these findings can be applied to improve the treatment and prevention of CF.

Nono deficiency impedes the proliferation and adhesion of H9c2 cardiomyocytes through Pi3k/Akt signaling pathway

Congenital heart disease (CHD) is the most common type of birth defect and the main noninfectious cause of death during the neonatal stage. The non-POU domain containing, octamer-binding gene, NONO, performs a variety of roles involved in DNA repair, RNA synthesis, transcriptional and post-transcriptional regulation. Currently, hemizygous loss-of-function mutation of NONO have been described as the genetic origin of CHD. However, essential effects of NONO during cardiac development have not been fully elucidated. In this study, we aim to understand role of Nono in cardiomyocytes during development by utilizing the CRISPR/Cas9 gene editing system to deplete Nono in the rat cardiomyocytes H9c2. Functional comparison of H9c2 control and knockout cells showed that Nono deficiency suppressed cell proliferation and adhesion. Furthermore, Nono depletion significantly affected the mitochondrial oxidative phosphorylation (OXPHOS) and glycolysis, resulting in H9c2 overall metabolic deficits. Mechanistically we demonstrated that the Nono knockout impeded the cardiomyocyte function by attenuating phosphatidyl inositol 3 kinase-serine/threonine kinase (Pi3k/Akt) signaling via the assay for transposase-accessible chromatin using sequencing in combination with RNA sequencing. From these results we propose a novel molecular mechanism of Nono to influence cardiomyocytes differentiation and proliferation during the development of embryonic heart. We conclude that NONO may represent an emerging possible biomarkers and targets for the diagnosis and treatment of human cardiac development defects.

AKAP1 Regulates Mitochondrial Dynamics during the Fatty-Acid-Promoted Maturation of Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes as Indicated by Proteomics Sequencing

Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are cells with promising applications. However, their immaturity has restricted their use in cell therapy, disease modeling, and other studies. Therefore, the current study focused on inducing the maturation of CMs. We supplemented hiPSC-CMs with fatty acids (FAs) to promote their phenotypic maturity. Proteomic sequencing was performed to identify regulators critical for promoting the maturation of hiPSC-CMs. AKAP1 was found to be significantly increased in FA-treated hiPSC-CMs, and the results were verified. Therefore, we inhibited AKAP1 expression in the FA-treated cells and analyzed the outcomes. FA supplementation promoted the morphological and functional maturation of the hiPSC-CMs, which was accompanied by the development of a mitochondrial network. Proteomic analysis results revealed that AKAP1 expression was significantly higher in FA-treated hiPSC-CMs than in control cells. In addition, increased phosphorylation of the mitochondrial dynamin Drp1 and an increased mitochondrial fusion rate were found in FA-treated hiPSC-CMs. After AKAP1 was knocked down, the level of DRP1 phosphorylation in the cell was decreased, and the mitochondrial fusion rate was reduced. FA supplementation effectively promoted the maturation of hiPSC-CMs, and in these cells, AKAP1 regulated mitochondrial dynamics, possibly playing a significant role.

Protection of melatonin treatment and combination with traditional antibiotics against septic myocardial injury

BACKGROUND

Heart failure is a common complication of sepsis with a high mortality rate. It has been reported that melatonin can attenuate septic injury due to various properties. On the basis of previous reports, this study will further explore the effects and mechanisms of melatonin pretreatment, posttreatment, and combination with antibiotics in the treatment of sepsis and septic myocardial injury.

METHODS AND RESULTS

Our results showed that melatonin pretreatment showed an obvious protective effect on sepsis and septic myocardial injury, which was related to the attenuation of inflammation and oxidative stress, the improvement of mitochondrial function, the regulation of endoplasmic reticulum stress (ERS), and the activation of the AMPK signaling pathway. In particular, AMPK serves as a key effector for melatonin-initiated myocardial benefits. In addition, melatonin posttreatment also had a certain degree of protection, while its effect was not as remarkable as that of pretreatment. The combination of melatonin and classical antibiotics had a slight but limited effect. RNA-seq detection clarified the cardioprotective mechanism of melatonin.

CONCLUSION

Altogether, this study provides a theoretical basis for the application strategy and combination of melatonin in septic myocardial injury.

A conditional knockout rat resource of mitochondrial protein-coding genes via a DdCBE-induced premature stop codon

Hundreds of pathogenic variants of mitochondrial DNA (mtDNA) have been reported to cause mitochondrial diseases, which still lack effective treatments. It is a huge challenge to install these mutations one by one. We repurposed the DddA-derived cytosine base editor to incorporate a premature stop codon in the mtProtein-coding genes to ablate mitochondrial proteins encoded in the mtDNA (mtProteins) instead of installing pathogenic variants and generated a library of both cell and rat resources with mtProtein depletion. In vitro, we depleted 12 of 13 mtProtein-coding genes with high efficiency and specificity, resulting in decreased mtProtein levels and impaired oxidative phosphorylation. Moreover, we generated six conditional knockout rat strains to ablate mtProteins using Cre/loxP system. Mitochondrially encoded ATP synthase membrane subunit 8 and NADH:ubiquinone oxidoreductase core subunit 1 were specifically depleted in heart cells or neurons, resulting in heart failure or abnormal brain development. Our work provides cell and rat resources for studying the function of mtProtein-coding genes and therapeutic strategies.

Relationship between ferroptosis and mitophagy in cardiac ischemia reperfusion injury: a mini-review

Cardiovascular diseases (CVD), with high morbidity and mortality, seriously affect people's life and social development. Clinically, reperfusion therapy is typically used to treat ischemic cardiomyopathy, such as severe coronary heart disease and acute myocardial infarction. However, reperfusion therapy can lead to myocardial ischemia reperfusion injury (MIRI), which can affect the prognosis of patients. Studying the mechanisms of MIRI can help us improve the treatment of MIRI. The pathological process of MIRI involves many mechanisms such as ferroptosis and mitophagy. Ferroptosis can exacerbate MIRI, and regulation of mitophagy can alleviate MIRI. Both ferroptosis and mitophagy are closely related to ROS, but there is no clear understanding of the relationship between ferroptosis and mitophagy. In this review, we analyzed the relationship between ferroptosis and mitophagy according to the role of mTOR, NLPR3 and HIF. In addition, simultaneous regulation of mitophagy and ferroptosis may be superior to single therapy for MIRI. We summarized potential drugs that can regulate mitophagy and/or ferroptosis, hoping to provide reference for the development of drugs and methods for MIRI treatment.

Evaluation of Coronary Flow Level with Mots-C in Patients with STEMI Undergoing Primary PCI

BACKGROUND

The protective effects of mitochondrial open reading frame of the 12S rRNA-c (MOTS-C) on cardiovascular diseases have been shown in numerous studies. However, there is little documentation of the relationship between MOTS-C and coronary blood flow in ST-segment elevation myocardial infarction (STEMI).

OBJECTIVE

We aimed to investigate the role of MOTS-C, which is known to have cytoprotective properties in the pathogenesis of the no-reflow phenomenon, by comparing the coronary flow rate and MOTS-C levels in patients with STEMI submitted to primary PCI.

METHODS

52 patients with STEMI and 42 patients without stenosis >50% in the coronary arteries were included in the study. The STEMI group was divided into two groups according to post-PCI TIMI (Thrombolysis In Myocardial Infarction) flow grade:(i) No-reflow: grade 0, 1, and 2 and (ii) grade 3(angiographic success). A p value of <0.05 was considered significant.

RESULTS

MOTS-C levels were significantly lower in the STEMI group compared to the control group (91.9 ± 8.9 pg/mL vs. 171.8±12.5 pg/mL, p<0.001). In addition, the Receiver Operating Characteristics (ROC) curve analysis indicated that serum MOTS-C levels had a diagnostic value in predicting no-reflow (Area Under the ROC curve [AUC]:0.95, 95% CI:0.856-0.993, p<0.001). A MOTS-C ≥84.15 pg/mL measured at admission was shown to have 95.3% sensitivity and 88.9% specificity in predicting no-reflow.

CONCLUSION

MOTS-C is a strong and independent predictor of no-reflow and in-hospital MACE in patients with STEMI. It was also noted that low MOTS-C levels may be an important prognostic marker of and may have a role in the pathogenesis of STEMI.

Spermidine Alleviates Intrauterine Hypoxia-Induced Offspring Newborn Myocardial Mitochondrial Damage in Rats by Inhibiting Oxidative Stress and Regulating Mitochondrial Quality Control

Background

Intrauterine hypoxia (IUH) increases the risk of cardiovascular diseases in offspring. As a reactive oxygen species (ROS) scavenger, polyamine spermidine (SPD) is essential for embryonic and fetal survival and growth. However, further studies on the SPD protection and mechanisms for IUH-induced heart damage in offspring are required.

Objectives

This study aimed to investigate the preventive effects of prenatal SPD treatment on IUH-induced heart damage in newborn offspring rats and its underlying mitochondrial-related mechanism.

Methods

The rat model of IUH was established by exposure to 10% O₂ seven days before term. Meanwhile, for seven days, the pregnant rats were given SPD (5 mg.kg^-1.d^-1; ip). The one-day offspring rats were sacrificed to assess several parameters, including growth development, heart damage, cardiomyocytes proliferation, myocardial oxidative stress, cell apoptosis, and mitochondrial function, and have mitochondrial quality control (MQC), including mitophagy, mitochondrial biogenesis, and mitochondrial fusion/fission. In in vitro experiments, primary cardiomyocytes were subjected to hypoxia with or without SPD for 24 hours.

Results

IUH decreased body weight, heart weight, cardiac Ki67 expression, the activity of SOD, and the CAT and adenosine 5'-triphosphate (ATP) levels and increased the BAX/BCL2 expression, and TUNEL-positive nuclei numbers. Furthermore, IUH also caused mitochondrial structure abnormality, dysfunction, and decreased mitophagy (decreased number of mitophagosomes), declined mitochondrial biogenesis (decreased expression of SIRT-1, PGC-1α, NRF-2, and TFAM), and led to fission/fusion imbalance (increased percentage of mitochondrial fragments, increased DRP1 expression, and decreased MFN2 expression) in the myocardium. Surprisingly, SPD treatment normalized the variations in the IUH-induced parameters. Furthermore, SPD also prevented hypoxia-induced ROS accumulation, mitochondrial membrane potential decay, and the mitophagy decrease in cardiomyocytes.

Conclusion

Maternal SPD treatment caused IUH-induced heart damage in newborn offspring rats by improving the myocardial mitochondrial function via anti-oxidation and anti-apoptosis, and regulating MQC.

PTEN-induced putative kinase 1 regulates mitochondrial quality control and is essential for the maturation of human induced pluripotent stem cell-derived cardiomyocytes

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have attracted attention in the field of regenerative medicine due to their potential ability to repair damaged hearts. However, the immature phenotype of these cells limits their clinical application. Cardiomyocyte maturation is accompanied by changes in mitochondrial quality. PTEN-induced putative kinase 1 (PINK1) has been linked to mitochondrial quality control. However, whether the changes in mitochondrial quality in hiPSC-CMs are associated with PINK1, and the impact of PINK1 on hiPSC-CMs development are not clear. In this study, we found that knockdown of PINK1 in hiPSC-CMs resulted in mitochondrial fragmentation and impaired mitochondrial functions such as mitophagy and mitochondrial biogenesis. PINK1 deletion also inhibited the maturation of hiPSC-CMs, reverting them to a naive structural and functional state. We found that restoring the mitochondrial structure did not completely rescue the mitochondrial dysfunction caused by PINK1 deletion, while activation of PINK1 kinase activity using kinetin promoted mitochondrial fusion, increased the mitochondrial membrane potential and ATP production, and maintained the development and maturation of hiPSC-CMs. In conclusion, PINK1 regulates the mitochondrial structure and function of hiPSC-CMs, and is essential for the maturation of hiPSC-CMs.

Adaptive and Pathological Outcomes of Radiation Stress-Induced Redox Signaling

Significance: Ionizing radiation can damage cells either directly or through oxidative damage caused by ionization. Although radiation exposure from natural sources is very limited, ionizing radiation in nuclear disaster zones and long spaceflights causes inconspicuous, yet measurable physiological effects in men and animals, whose significance remains poorly known. Understanding the physiological impacts of ionizing radiation has a wide importance due to the increased use of medical imaging and radiotherapy. Recent Advances: Radiation exposure has been traditionally investigated from the perspective of DNA damage and its consequences. However, recent studies from Chernobyl as well as spaceflights have provided interesting insights into oxidative stress-induced metabolic alterations and disturbances in the circadian regulation. Critical Issues: In this review, we discuss the physiological consequences of radiation exposure in the light of oxidative stress signaling. Radiation exposure likely triggers many converging or interconnecting signaling pathways, some of which mimic mitochondrial dysfunction and might explain the observed metabolic changes. Future Directions: Better understanding of the different radiation-induced signaling pathways might help to devise strategies for mitigation of the long-term effects of radiation exposure. The utility of fibroblast growth factor 21 (FGF21) as a radiation exposure biomarker and the use of radiation hormesis as a method to protect astronauts on a prolonged spaceflight, such as a mission to Mars, should be investigated. Antioxid. Redox Signal. 37, 336-348.

Metabolic Disruption by Naturally Occurring Mycotoxins in Circulation: A Focus on Vascular and Bone Homeostasis Dysfunction

Naturally occurring food/feed contaminants have become a significant global issue due to animal and human health implications. Despite risk assessments and legislation setpoints on the mycotoxins' levels, exposure to lower amounts occurs, and it might affect cell homeostasis. However, the inflammatory consequences of this possible everyday exposure to toxins on the vascular microenvironment and arterial dysfunction are unexplored in detail. Circulation is the most accessible path for food-borne toxins, and the consequent metabolic and immune shifts affect systemic health, both on vascular apparatus and bone homeostasis. Their oxidative nature makes mycotoxins a plausible underlying source of low-level toxicity in the bone marrow microenvironment and arterial dysfunction. Mycotoxins could also influence the function of cardiomyocytes with possible injury to the heart. Co-occurrence of mycotoxins can modulate the metabolic pathways favoring osteoblast dysfunction and bone health losses. This review provides a novel insight into understanding the complex events of coexposure to mixed (low levels) mycotoxicosis and subsequent metabolic/immune disruptions contributing to chronic alterations in circulation.

A reduced form of nicotinamide riboside protects the cochlea against aminoglycoside-induced ototoxicity by SIRT1 activation

BACKGROUND

Nicotinamide adenine dinucleotide (NAD⁺), a coenzyme that plays crucial roles in many cellular processes, is a potential therapeutic target for various diseases. Dihydronicotinamide riboside (NRH), a novel reduced form of nicotinamide riboside, has emerged as a potent NAD⁺ precursor. Here, we studied the protective effects and underlying mechanism of NRH on aminoglycoside-induced ototoxicity.

METHODS

Auditory function and hair-cell (HC) morphology were examined to assess the effects of NRH on kanamycin-induced hearing loss. The pharmacokinetic parameters of NRH were measured in plasma and the cochlea using liquid chromatography tandem mass spectrometry. NAD⁺ levels in organ explant cultures were assessed to compare NRH with known NAD⁺ precursors. Immunofluorescence analysis was performed to detect reactive oxygen species (ROS) and apoptosis. We analyzed SIRT1 and 14-3-3 protein expression. EX527 and resveratrol were used to investigate the role of SIRT1 in the protective effect of NRH against kanamycin-induced ototoxicity.

RESULTS

NRH alleviated kanamycin-induced HC damage and attenuated hearing loss in mice. NRH reduced gentamicin-induced vestibular HC loss. Compared with NAD and NR, NRH produced more NAD⁺ in cochlear HCs and significantly ameliorated kanamycin-induced oxidative stress and apoptosis. NRH rescued the aminoglycoside-induced decreases in SIRT1 and 14-3-3 protein expression. Moreover, EX527 antagonized the protective effect of NRH on kanamycin-induced HC loss by inhibition of SIRT1, while resveratrol alleviated HC damage caused by EX527.

CONCLUSIONS

NRH ameliorates aminoglycoside-induced ototoxicity by inhibiting HC apoptosis by activating SIRT1 and decreasing ROS. NRH is an effective therapeutic option for aminoglycoside-induced ototoxicity.

Dibutyltin dichloride exposure affects mouse oocyte quality by inducing spindle defects and mitochondria dysfunction

Dibutyltin dichloride (DBTCl) is a widespread environmental pollutant that is frequently employed as a light and heat sustainer for polyvinyl chloride (PVC) plastics and is a teratogen in vivo. Nevertheless, its destructiveness in mammalian oocytes remains unclear. This study highlighted the consequences of DBTCl vulnerability on mouse oocyte. Our results revealed that exposure to 5.0 mg/kg/day of DBTCl for ten days reduced the number of mature follicles and oocytes in the ovaries and inhibited the meiotic maturation of oocytes. Single-cell transcriptomic analysis indicated that DBTCl exposure interfered with the expression of more than 400 genes in oocytes, including those involved in multiple biological pathways. Specifically, DBTCl exposure impaired spindle assembly and chromosome alignment. In addition, DBTCl exposure caused mitochondrial dysfunction, which led to the accumulation of reactive oxygen species (ROS) and induced apoptosis. In summary, our study illustrates that mitochondrial dysfunction and redox perturbation are the major causes of the reduced quality of oocytes exposed to DBTCl.

Diminazene Aceturate, an angiotensin converting enzyme 2 (ACE2) activator, promotes cardioprotection in ischemia/reperfusion-induced cardiac injury

This study aimed to investigate whether the Diminazene Aceturate (DIZE), an angiotensin-converting enzyme 2 (ACE2) activator, can revert cardiac dysfunction in ischemia reperfusion-induced (I/R) injury in animals and examine the mechanism underlying this effect. Wistar rats systemically received DIZE (1 mg/kg) for thirty days. Cardiac function in isolated rat hearts was evaluated using the Langendorff technique. After I/R, ventricular non-I/R and I/R samples were used to evaluate ATP levels. Mitochondrial function was assessed using cardiac permeabilized fibers and isolated cardiac mitochondria. Cardiac cellular electrophysiology was evaluated using the patch clamp technique. DIZE protected the heart after I/R from arrhythmia and cardiac dysfunction by preserving ATP levels, independently of any change in coronary flow and heart rate. DIZE improved mitochondrial function, increasing the capacity for generating ATP and reducing proton leak without changing the specific citrate synthase activity. The activation of the ACE2 remodeled cardiac electrical profiles, shortening the cardiac action potential duration at 90 % repolarization. Additionally, cardiomyocytes from DIZE-treated animals exhibited reduced sensibility to diazoxide (K_ATP agonist) and a higher K_ATP current compared to the controls. DIZE was able to improve mitochondrial function and modulate cardiac electrical variables with a cardio-protective profile, resulting in direct myocardial cell protection from I/R injury.

Targeting the multifaceted roles of mitochondria in intracerebral hemorrhage and therapeutic prospects

Intracerebral hemorrhage (ICH) is a severe, life-threatening subtype of stoke that constitutes a crucial health and socioeconomic problem worldwide. However, the current clinical treatment can only reduce the mortality of patients to a certain extent, but cannot ameliorate neurological dysfunction and has a high recurrence rate. Increasing evidence has demonstrated that mitochondrial dysfunction occurs in the early stages of brain injury and participates in all stages of secondary brain injury (SBI) after ICH. As the energy source of cells, various pathobiological processes that lead to SBI closely interact with the mitochondria, such as oxidative stress, calcium overload, and neuronal injury. In this review, we discussed the structure and function of mitochondria and the abnormal morphological changes after ICH. In addition, we discussed recent research on the involvement of mitochondrial dynamics in the pathological process of SBI after ICH and introduced the pathological variations and related molecular mechanisms of mitochondrial dysfunction in the occurrence of brain injury. Finally, we summarized the latest progress in mitochondrion-targeted agents for ICH, which provides a direction for the development of emerging therapeutic strategies targeting the mitochondria after ICH.

Clemastine protects against sepsis-induced myocardial injury in vivo and in vitro

Sepsis-induced myocardial dysfunction (SIMD) is associated with high morbidity and mortality rates; however, it lacks targeted therapies. Modulating cardiomyocyte autophagy maintains intracellular homeostasis during SIMD. Clemastine, a histamine receptor inhibitor, promotes autophagy and other effective biological functions. Nevertheless, the effect of clemastine on SIMD remains unclear. This study aimed to explore the underlying mechanism of clemastine in cardiomyocyte injury in cecum ligation and perforation (CLP)-induced rats and lipopolysaccharide (LPS)-stimulated H9c2 cells. Clemastine (10 mg/kg, 30 mg/kg, and 50 mg/kg) was intraperitoneally injected after 30 min of CLP surgery. Serum cTnI levels and the 7-day survival rate were evaluated. Echocardiograms and H&E staining were used to evaluate cardiac function and structure. TEM was used to detect the mitochondrial ultrastructure and autophagosomes. Clemastine significantly improved the survival rate and reduced cTnI production in serum. Clemastine ameliorated cellular apoptosis, improved mitochondrial ultrastructure both in vivo and in vitro, increased ATP content, decreased dynamin-related protein 1 (DRP1) expression, and decreased mitochondrial ROS levels. Additionally, clemastine treatment increased autophagosome concentration, LC3II/LC3I rate, and Beclin 1 expression. However, 3-methyladenine (3-MA), an autophagy inhibitor, could abolish the effect of clemastine on alleviating myocardial apoptosis. In conclusion, clemastine protected against cardiac structure destruction and function dysfunction, mitochondrial damage, apoptosis, and autophagy in vivo and in vitro. Moreover, clemastine attenuated myocardial apoptosis by promoting autophagy. This study provides a novel favorable perspective for SIMD therapy.

Mitochondrial DNA Depletion Syndrome and Its Associated Cardiac Disease

Mitochondria is a ubiquitous, energy-supplying (ATP-based) organelle found in nearly all eukaryotes. It acts as a “power plant” by producing ATP through oxidative phosphorylation, providing energy for the cell. The bioenergetic functions of mitochondria are regulated by nuclear genes (nDNA). Mitochondrial DNA (mtDNA) and respiratory enzymes lose normal structure and function when nuclear genes encoding the related mitochondrial factors are impaired, resulting in deficiency in energy production. Massive generation of reactive oxygen species and calcium overload are common causes of mitochondrial diseases. The mitochondrial depletion syndrome (MDS) is associated with the mutations of mitochondrial genes in the nucleus. It is a heterogeneous group of progressive disorders characterized by the low mtDNA copy number. TK2, FBXL4, TYPM, and AGK are genes known to be related to MDS. More recent studies identified new mutation loci associated with this disease. Herein, we first summarize the structure and function of mitochondria, and then discuss the characteristics of various types of MDS and its association with cardiac diseases.

Substrate-dependent differential regulation of mitochondrial bioenergetics in the heart and kidney cortex and outer medulla

The kinetics and efficiency of mitochondrial oxidative phosphorylation (OxPhos) can depend on the choice of respiratory substrates. Furthermore, potential differences in this substrate dependency among different tissues are not well-understood. Here, we determined the effects of different substrates on the kinetics and efficiency of OxPhos in isolated mitochondria from the heart and kidney cortex and outer medulla (OM) of Sprague-Dawley rats. The substrates were pyruvate+malate, glutamate+malate, palmitoyl-carnitine+malate, alpha-ketoglutarate+malate, and succinate±rotenone at saturating concentrations. The kinetics of OxPhos were interrogated by measuring mitochondrial bioenergetics under different ADP perturbations. Results show that the kinetics and efficiency of OxPhos are highly dependent on the substrates used, and this dependency is distinctly different between heart and kidney. Heart mitochondria showed higher respiratory rates and OxPhos efficiencies for all substrates in comparison to kidney mitochondria. Cortex mitochondria respiratory rates were higher than OM mitochondria, but OM mitochondria OxPhos efficiencies were higher than cortex mitochondria. State 3 respiration was low in heart mitochondria with succinate but increased significantly in the presence of rotenone, unlike kidney mitochondria. Similar differences were observed in mitochondrial membrane potential. Differences in H2O2 emission in the presence of succinate±rotenone were observed in heart mitochondria and to a lesser extent in OM mitochondria, but not in cortex mitochondria. Bioenergetics and H2O2 emission data with succinate±rotenone indicate that oxaloacetate accumulation and reverse electron transfer may play a more prominent regulatory role in heart mitochondria than kidney mitochondria. These studies provide novel quantitative data demonstrating that the choice of respiratory substrates affects mitochondrial responses in a tissue-specific manner.

MicroRNA-223-3p Protect Against Radiation-Induced Cardiac Toxicity by Alleviating Myocardial Oxidative Stress and Programmed Cell Death via Targeting the AMPK Pathway

Objectives: Radiotherapy improves the survival rate of cancer patients, yet it also involves some inevitable complications. Radiation-induced heart disease (RIHD) is one of the most serious complications, especially the radiotherapy of thoracic tumors, which is characterized by cardiac oxidative stress disorder and programmed cell death. At present, there is no effective treatment strategy for RIHD; in addition, it cannot be reversed when it progresses. This study aims to explore the role and potential mechanism of microRNA-223-3p (miR-223-3p) in RIHD.

Methods: Mice were injected with miR-223-3p mimic, inhibitor, or their respective controls in the tail vein and received a single dose of 20 Gy whole-heart irradiation (WHI) for 16 weeks after 3 days to construct a RIHD mouse model. To inhibit adenosine monophosphate activated protein kinase (AMPK) or phosphodiesterase 4D (PDE4D), compound C (CompC) and AAV9-shPDE4D were used.

Results: WHI treatment significantly inhibited the expression of miR-223-3p in the hearts; furthermore, the levels of miR-223-3p decreased in a radiation time-dependent manner. miR-223-3p mimic significantly relieved, while miR-223-3p inhibitor aggravated apoptosis, oxidative damage, and cardiac dysfunction in RIHD mice. In addition, we found that miR-223-3p mimic improves WHI-induced myocardial injury by activating AMPK and that the inhibition of AMPK by CompC completely blocks these protective effects of miR-223-3p mimic. Further studies found that miR-223-3p lowers the protein levels of PDE4D and inhibiting PDE4D by AAV9-shPDE4D blocks the WHI-induced myocardial injury mediated by miR-223-3p inhibitor.

Conclusion: miR-223-3p ameliorates WHI-induced RIHD through anti-oxidant and anti-programmed cell death mechanisms via activating AMPK by PDE4D regulation. miR-223-3p mimic exhibits potential value in the treatment of RIHD.

Early-onset dietary restriction maintains mitochondrial health, autophagy and ER function in the left ventricle during aging

Dietary restriction (DR) exerts healthy benefits, including heart functions. However, the cardioprotective role of DR is till controversial among researchers due to the variation of DR conditions. The present study focuses on the protective effect of early-onset DR on cardiac injury using mitochondrial structure and expression of protein associated with mitochondrial homeostasis, autophagy and endoplasmic reticulum (ER) function as measures.

METHODS

Two-month-old mice were fed with a breeding diet ad libitum (AL) or DR (60% of AL) for 3 (Young) or 20 (Aged) months.

RESULTS

Body weight increased with aging, whereas DR treatment kept body weight consistent. DR mice exhibited a higher relative heart weight than AL mice. DR mice displayed lower plasma glucose levels, compared with AL groups. Furthermore, Aged-AL, but not Aged-DR mice, had increased collagen content and morphological distortions in the left ventricle (LV). Aged-DR mice had a higher ATP and lower TBARS in the LV than Aged-AL mice. Mitochondrial morphology was detected by electron microscopy; Aged-AL mice had increased abnormal morphology of mitochondria. Treatment with DR reduced abnormal mitochondrial accumulation. Aging elevated the protein expressions of mitochondrial functions and ER-induced apoptosis. Aging downregulated autophagy-related proteins and chaperones in the heart. Dietary restriction reversed those protein expressions.

CONCLUSIONS

The present study demonstrated a beneficial effect of early onset DR on cardiac aging. The age-dependent mitochondrial dysfunction and protein quality control dysregulation was significantly reversed by long-term DR, demonstrating a concordance with the beneficial effect in the heart.

Proteomic analysis of the heart in normal aging mice

Aging induces pathological cardiovascular changes such as cardiac dysfunction and arteriosclerosis. With aging, heart cells, especially, become more susceptible to lethal damage. In this report, we tried to understand the precise mechanism of myocardial change resulting from aging by examining the heart proteome in aging mice using two-dimensional gel electrophoresis (2DE). The proteins were stained with fluorescence dyes (SYPRO Ruby and Pro-Q Diamond) and identified by subsequent MALDI-TOF-MS / MS. As a result, markedly altered levels of 14 proteins and 7 phosphoproteins were detected in the hearts of 3-, 7-, 11-, and 20-month-old mice. The functions of these identified proteins and phosphoproteins were energy metabolism, muscle contraction, glycolysis, and cytoskeletal support. Additionally, the results of Western blotting confirmed changes in the expression of FTH, CPNE5, and SUCLA2. These findings showed that aging modified the expression of proteins and phosphoproteins in the heart. We suggest that changes in the expression of these proteins are critical to the development of cardiac dysfunction resulting from aging. J. Med. Invest. 69 : 217-223, August, 2022.

Mitochondrial calpain-1 activates NLRP3 inflammasome by cleaving ATP5A1 and inducing mitochondrial ROS in CVB3-induced myocarditis

Treatment options for myocarditis are currently limited. Inhibition of calpains has been shown to prevent Coxsackievirus B3 (CVB3)-induced cardiac injuries, but the underlying mechanism of action of calpains has not been elucidated. We investigated whether NOD-, LRR-, and pyrin domain-containing 3 (NLRP3) inflammasome participated in CVB3-induced myocarditis, and investigated the effects of calpain-1 on CVB3-induced cardiac injury. NLRP3 inflammasome was activated in CVB3-infected hearts, evidenced by elevated protein levels of NLRP3, N-terminal domain of Gasdermin D, and cleaved caspase-1, and the increased co-localization of NLRP3 and apoptosis-associated speck-like protein. The intraperitoneal administration of MCC950, a selective inhibitor of the NLRP3 inflammasome, led to decreased levels of serum creatine kinase-MB, cardiac troponin I, lactate dehydrogenase, interleukin-18, interleukin-1β, prevention of the infiltration of inflammatory cells, and improvement of cardiac function under CVB3 infection. Transgenic mice overexpressing the endogenous calpain inhibitor calpastatin (Tg-CAST mice) exhibited not only decreased apoptosis, inflammation, fibrosis, and enhanced cardiac function but also inhibition of NLRP3 inflammasome and pyroptosis. The selective inhibition of calpain-1 using PD151746 protected cardiomyocytes in vitro from CVB3 infection by downregulating NLRP3 inflammasome and, thus, preserved cell viability. Mechanistically, we showed that mitochondrial dysfunction preceded inflammatory response after CVB3 treatment and elimination of mitochondrial reactive oxygen species (ROS) using mitochondria-targeted antioxidants (mito-TEMPO) recapitalized the phenotype observed in Tg-CAST mice. Furthermore, the promotion or inhibition of calpain-1 activation in vitro regulated the mitochondrial respiration chain. Mito-TEMPO reversed calpain-1-mediated NLRP3 inflammation activation and cell death. We also found that mitochondrial calpain-1, which was increased after CVB3 stimulation, activated the NLRP3 inflammasome and resulted in cell death. Furthermore, ATP synthase-α (ATP5A1) was revealed to be the cleaving target of calpain-1 after CVB3 treatment. Downregulating ATP5A1 using ATP5A1-small interfering RNA impaired mitochondrial function, decreased cell viability, and induced NLRP3 inflammasome activation. In conclusion, CVB3 infection induced calpain-1 accumulation in mitochondria, and led to subsequent ATP5A1 cleavage, mitochondrial ROS overproduction, and impaired mitochondrial function, eventually causing NLRP3 inflammasome activation and inducing pyroptosis. Therefore, our findings established the role of calpain in viral myocarditis and unveiled its underlying mechanism of its action. Calpain appears as a promising target for the treatment of viral myocarditis.

Substrate- and Calcium-Dependent Differential Regulation of Mitochondrial Oxidative Phosphorylation and Energy Production in the Heart and Kidney

Mitochondrial dehydrogenases are differentially stimulated by Ca2+. Ca2+ has also diverse regulatory effects on mitochondrial transporters and other enzymes. However, the consequences of these regulatory effects on mitochondrial oxidative phosphorylation (OxPhos) and ATP production, and the dependencies of these consequences on respiratory substrates, have not been investigated between the kidney and heart despite the fact that kidney energy requirements are second only to those of the heart. Our objective was, therefore, to elucidate these relationships in isolated mitochondria from the kidney outer medulla (OM) and heart. ADP-induced mitochondrial respiration was measured at different CaCl2 concentrations in the presence of various respiratory substrates, including pyruvate + malate (PM), glutamate + malate (GM), alpha-ketoglutarate + malate (AM), palmitoyl-carnitine + malate (PCM), and succinate + rotenone (SUC + ROT). The results showed that, in both heart and OM mitochondria, and for most complex I substrates, Ca2+ effects are biphasic: small increases in Ca2+ concentration stimulated, while large increases inhibited mitochondrial respiration. Furthermore, significant differences in substrate- and Ca2+-dependent O2 utilization towards ATP production between heart and OM mitochondria were observed. With PM and PCM substrates, Ca2+ showed more prominent stimulatory effects in OM than in heart mitochondria, while with GM and AM substrates, Ca2+ had similar biphasic regulatory effects in both OM and heart mitochondria. In contrast, with complex II substrate SUC + ROT, only inhibitory effects on mitochondrial respiration was observed in both the heart and the OM. We conclude that the regulatory effects of Ca2+ on mitochondrial OxPhos and ATP synthesis are biphasic, substrate-dependent, and tissue-specific.

Mitochondria damage in ambient particulate matter induced cardiotoxicity: Roles of PPAR alpha/PGC-1 alpha signaling

Particulate matter (PM) had been associated with cardiotoxicity, while the mechanism of toxicity has yet to be elucidated, with mitochondria dysfunction as a potential candidate. To investigate the potential cardiotoxic effects of ambient PM exposure and assess the damage to cardiac mitochondria, C57/B6 mice were exposed to filtered air or real ambient PM for three or six weeks. Furthermore, to reveal the role of peroxisome proliferators-activated receptor alpha (PPAR alpha) in PM exposure induced cardiotoxicity/mitochondria damage, animals were also co-treated with PPAR alpha agonist WY 14,643 or PPAR alpha antagonist GW 6471. Cardiotoxicity was assessed with echocardiography and histopathology, while mitochondria damage was evaluated with mitochondria membrane potential measurement and transmission electron microscopy. Potential impacts of PM exposure to PPAR alpha signaling were detected with co-immunoprecipitation and western blotting. The results indicated that exposure to ambient PM exposure induced cardiotoxicity in C57/B6 mice, including altered cardiac functional parameters and morphology. Cardiac mitochondria damage is detected, in the form of compromised mitochondria membrane potential and morphology. Molecular investigations revealed disruption of PPAR alpha interaction with peroxisome proliferator-activated receptor gamma coactivator-1A (PGC-1a) as well as altered expression levels of PPAR alpha downstream genes. Co-treatment with WY 14,643 alleviated the observed toxicities, while co-treatment with GW 6471 had mixed results, exaggerating most cardiotoxicity and mitochondrial damage endpoints but alleviating some cardiac functional parameters. Interestingly, WY 14,643 and GW 6471 co-treatment seemed to exhibit similar regulative effects towards PPAR alpha signaling in animals exposed to PM. In conclusion, ambient PM exposure indeed induced cardiotoxicity in C57/B6 mice, in which cardiac mitochondria damage and disrupted PPAR alpha signaling are contributors.

Troglitazone-Induced PRODH/POX-Dependent Apoptosis Occurs in the Absence of Estradiol or ERβ in ER-Negative Breast Cancer Cells

Simple Summary

PRODH/POX (proline dehydrogenase/proline oxidase) is a mitochondrial enzyme that catalyzes proline degradation generating reactive oxygen species (ROS). Estrogens limit proline availability for PRODH/POX by stimulating collagen biosynthesis. It has been considered that estrogens determine efficiency of troglitazone (TGZ)-induced PRODH/POX-dependent apoptosis in breast cancer cells. The studies were performed in wild-type and PRODH/POX-silenced estrogen-dependent MCF-7 cells and estrogen-independent MDA-MB-231 cells. DNA and collagen biosynthesis were determined by radiometric method, ROS production was measured by fluorescence assay, protein expression was determined by Western blot and proline concentration by LC/MS analysis. We found that: i/TGZ-induced apoptosis in MDA-MB-231 occurs only in the absence of estradiol or ERβ, ii/the process is mediated by PRODH/POX, iii/and is facilitated by proline availability for PRODH/POX by TGZ-dependent inhibition of collagen biosynthesis (proline utilizing process). The data suggest that combined TGZ and anti-estrogen treatment could be considered in experimental therapy of ER negative breast cancers.

Abstract

The impact of estradiol on troglitazone (TGZ)-induced proline dehydrogenase/proline oxidase (PRODH/POX)-dependent apoptosis was studied in wild-type and PRODH/POX-silenced estrogen receptor (ER) dependent MCF-7 cells and ER-independent MDA-MB-231 cells. DNA and collagen biosynthesis were determined by radiometric method, prolidase activity evaluated by colorimetric method, ROS production was measured by fluorescence assay. Protein expression was determined by Western blot and proline concentration by LC/MS analysis. PRODH/POX degrades proline yielding reactive oxygen species (ROS). Estrogens stimulate collagen biosynthesis utilizing free proline and limiting its availability for PRODH/POX-dependent apoptosis. TGZ cytotoxicity was highly pronounced in wild-type MDA-MB-231 cells cultured in medium without estradiol or in the cells cultured in medium with estradiol but deprived of ERβ (by ICI-dependent degradation), while in PRODH/POX-silenced cells the process was not affected. The TGZ cytotoxicity was accompanied by increase in PRODH/POX expression, ROS production, expression of cleaved caspase-3, caspase-9 and PARP, inhibition of collagen biosynthesis, prolidase activity and decrease in intracellular proline concentration. The phenomena were not observed in PRODH/POX-silenced cells. The data suggest that TGZ-induced apoptosis in MDA-MB-231 cells cultured in medium without estradiol or deprived of ERβ is mediated by PRODH/POX and the process is facilitated by proline availability for PRODH/POX by TGZ-dependent inhibition of collagen biosynthesis. It suggests that combined TGZ and antiestrogen treatment could be considered in experimental therapy of estrogen receptor negative breast cancers.

Environmental Alterations during Embryonic Development: Studying the Impact of Stressors on Pluripotent Stem Cell-Derived Cardiomyocytes

Non-communicable diseases (NCDs) sauch as diabetes, obesity and cardiovascular diseases are rising rapidly in all countries world-wide. Environmental maternal factors (e.g., diet, oxidative stress, drugs and many others), maternal illnesses and other stressors can predispose the newborn to develop diseases during different stages of life. The connection between environmental factors and NCDs was formulated by David Barker and colleagues as the Developmental Origins of Health and Disease (DOHaD) hypothesis. In this review, we describe the DOHaD concept and the effects of several environmental stressors on the health of the progeny, providing both animal and human evidence. We focus on cardiovascular diseases which represent the leading cause of death worldwide. The purpose of this review is to discuss how in vitro studies with pluripotent stem cells (PSCs), such as embryonic and induced pluripotent stem cells (ESC, iPSC), can underpin the research on non-genetic heart conditions. The PSCs could provide a tool to recapitulate aspects of embryonic development “in a dish”, studying the effects of environmental exposure during cardiomyocyte (CM) differentiation and maturation, establishing a link to molecular mechanism and epigenetics.

Endocrine Influence on Cardiac Metabolism in Development and Regeneration

Mammalian cardiomyocytes mostly utilize oxidation of fatty acids to generate ATP. The fetal heart, in stark contrast, mostly uses anaerobic glycolysis. During perinatal development, thyroid hormone drives extensive metabolic remodeling in the heart for adaptation to extrauterine life. These changes coincide with critical functional maturation and exit of the cell cycle, making the heart a post-mitotic organ. Here, we review the current understanding on the perinatal shift in metabolism, hormonal status, and proliferative potential in cardiomyocytes. Thyroid hormone and glucocorticoids have roles in adult cardiac metabolism, and both pathways have been implicated as regulators of myocardial regeneration. We discuss the evidence that suggests these processes could be interrelated and how this can help explain variation in cardiac regeneration across ontogeny and phylogeny, and we note what breakthroughs are still to be made.

ATPAF1 deficiency impairs ATP synthase assembly and mitochondrial respiration

ATP11p and ATP12p are two nuclear-encoded mitochondrial chaperone proteins required for assembling the F1Fo-ATP synthase F1 sector. ATPAF1 and ATPAF2 are the mammalian homologs of ATP11p and ATP12p. However, the biochemical and physiological relevance of ATPAF1 and ATPAF2 in animal tissues with high energy-dependence remains unclear. To explore the in vivo role of ATP assembly and the effects of ATP synthase deficiency in animals, we have generated knockout (KO) mouse models of these assembly factors using CRISPR/Cas9 technology. While the Atpaf2-KO mice were embryonically lethal, Atpaf1-KO mice grew to adulthood but with smaller body sizes and elevated blood lactate later in life. We specifically investigated how ATPAF1 deficiency may affect ATP synthase biogenesis and mitochondrial respiration in the mouse heart, an organ highly energy-dependent. Western blots and Blue-Native electrophoresis (BN-PAGE) demonstrated a decreased F1 content and ATP synthase dimers in the Atpaf1-KO heart. Mitochondria from ATPAF1-deficient hearts showed ultrastructural abnormalities with condensed degenerated mitochondria, loss of cristae, and impaired respiratory capacity. ATP synthase deficiency also leads to impaired autophagy and mitochondrial dynamic. Consequently, decreased cardiac function was exhibited in adult Atpaf1-KO mice. The results provide strong support that ATPAF1 is essential for ATP synthase assembly and mitochondrial oxidative phosphorylation, thus playing a crucial role in maintaining cardiac structure and function in animals.

Evidences for the mechanism of Shenmai injection antagonizing doxorubicin-induced cardiotoxicity

BACKGROUND

Doxorubicin (DOX) is a widely used antitumor drug. However, its clinical application is limited for its serious cardiotoxicity. The mechanism of DOX-induced cardiotoxicity is attributed to the increasing of cell stress in cardiomyocytes, then following autophagic and apoptotic responses. Our previous studies have demonstrated the protective effect of Shenmai injection (SMI) on DOX-induced cardiotoxicity via regulation of inflammatory mediators for releasing cell stress.

PURPOSE

To further investigate whether SMI attenuates the DOX-induced cell stress in cardiomyocytes, we explored the mechanism underlying cell stress as related to Jun N-terminal kinase (JNK) activity and the regulation of autophagic flux to determine the mechanism by which SMI antagonizes DOX-induced cardiotoxicity.

STUDY DESIGN

The DOX-induced cardiotoxicity model of autophagic cell death was established in vitro to disclose the protected effects of SMI on oxidative stress, autophagic flux and JNK signaling pathway. Then the autophagic mechanism of SMI antagonizing DOX cardiotoxicity was validated in vivo.

RESULTS

SMI was able to reduce the DOX-induced cardiomyocyte apoptosis associated with inhibition of activation of the JNK pathway and the accumulation of reactive oxygen species (ROS). Besides, SMI antagonized DOX cardiotoxicity, regulated cardiomyocytes homeostasis by restoring DOX-induced cardiomyocytes autophagy. Under specific circumstances, SMI depressed autophagic process by reducing the Beclin 1-Bcl-2 complex dissociation which was activated by DOX via stimulating the JNK signaling pathway. At the same time, SMI regulated lysosomal pH to restore the autophagic flux which was blocked by DOX in cardiomyocytes.

CONCLUSION

SMI regulates cardiomyocytes apoptosis and autophagy by controlling JNK signaling pathway, blocking DOX-induced apoptotic pathway and autophagy formation. SMI was also found to play a key role in restoring autophagic flux for counteracting DOX-damaged cardiomyocyte homeostasis.