Structural and Functional Remodeling of Mitochondria in Cardiac Diseases

Valosin-containing protein acts as a target and mediator of S-nitrosylation in the heart through distinct mechanisms

S-nitrosylation (SNO) is an emerging paradigm of redox signaling protecting cells against oxidative stress in the heart. Our previous studies demonstrated that valosin-containing protein (VCP), an ATPase-associated protein, is a vital mediator protecting the heart against cardiac stress and ischemic injury. However, the molecular regulations conferred by VCP in the heart are not fully understood. In this study, we explored the potential role of VCP in cardiac protein SNO using multiple cardiac-specific genetically modified mouse models and various analytical techniques including biotin switch assay, liquid chromatography, mass spectrometry, and western blotting. Our results showed that cardiac-specific overexpression of VCP led to an overall increase in the levels of SNO-modified cardiac proteins in the transgenic (TG) vs. wild-type (WT) mice. Mass spectrometry analysis identified mitochondrial proteins involved in respiration, metabolism, and detoxification as primary targets of SNO modification in VCP-overexpressing mouse hearts. Particularly, we found that VCP itself underwent SNO modification at a specific cysteine residue in its N-domain. Additionally, our study demonstrated that glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a key enzyme in glycolysis, also experienced increased SNO in response to VCP overexpression. While deletion of inducible nitric oxide synthase (iNOS) in VCP TG mice did not affect VCP SNO, it did abolish SNO modification in mitochondrial complex proteins, suggesting a dual mechanism of regulation involving both iNOS-dependent and independent pathways. Overall, our findings shed light on post-translational modification of VCP in the heart, unveiling a previously unrecognized role for VCP in regulating cardiac protein SNO and offering new insights into its function in cardiac protection.

Mitochondrial network dynamics in pulmonary disease: Bridging the gap between inflammation, oxidative stress, and bioenergetics

Once thought of in terms of bioenergetics, mitochondria are now widely accepted as both the orchestrator of cellular health and the gatekeeper of cell death. The pulmonary disease field has performed extensive efforts to explore the role of mitochondria in regulating inflammation, cellular metabolism, apoptosis, and oxidative stress. However, a critical component of these processes needs to be more studied: mitochondrial network dynamics. Mitochondria morphologically change in response to their environment to regulate these processes through fusion, fission, and mitophagy. This allows mitochondria to adapt their function to respond to cellular requirements, a critical component in maintaining cellular homeostasis. For that reason, mitochondrial network dynamics can be considered a bridge that brings multiple cellular processes together, revealing a potential pathway for therapeutic intervention. In this review, we discuss the critical modulators of mitochondrial dynamics and how they are affected in pulmonary diseases, including chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), acute lung injury (ALI), and pulmonary arterial hypertension (PAH). A dysregulated mitochondrial network plays a crucial role in lung disease pathobiology, and aberrant fission/fusion/mitophagy pathways are druggable processes that warrant further exploration. Thus, we also discuss the candidates for lung disease therapeutics that regulate mitochondrial network dynamics.

Functional, structural, and molecular remodelling of the goldfish (Carassius auratus) heart under moderate hypoxia

The goldfish (Carassius auratus) is known for its physiologic ability to survive even long periods of oxygen limitation (hypoxia), adapting the cardiac performance to the requirements of peripheral tissue perfusion. We here investigated the effects of short-term moderate hypoxia on the heart, focusing on ventricular adaptation, in terms of hemodynamics and structural traits. Functional evaluations revealed that animals exposed to 4 days of environmental hypoxia increased the hemodynamic performance evaluated on ex vivo cardiac preparations. This was associated with a thicker and more vascularized ventricular compact layer and a reduced luminal lacunary space. Compared to normoxic animals, ventricular cardiomyocytes of goldfish exposed to hypoxia showed an extended mitochondrial compartment and a modulation of proteins involved in mitochondria dynamics. The enhanced expression of the pro-fission markers DRP1 and OMA1, and the modulation of the short and long forms of OPA1, suggested a hypoxia-related mitochondria fission. Our data propose that under hypoxia, the goldfish heart undergoes a structural remodelling associated with a potentiated cardiac activity. The energy demand for the highly performant myocardium is supported by an increased number of mitochondria, likely occurring through fission events.

Effect of SH2B1 on glucose metabolism during pressure overload-induced cardiac hypertrophy and cardiac dysfunction

This study mainly explored the effect and mechanism of Src homology 2 (SH2) B adaptor protein 1 (SH2B1) on cardiac glucose metabolism during pressure overload-induced cardiac hypertrophy and dysfunction. A pressure-overloaded cardiac hypertrophy model was constructed, and SH2B1-siRNA was injected through the tail vein. Haematoxylin and eosin (H&E) staining was used to detect myocardial morphology. ANP, BNP, β-MHC and the diameter of myocardial fibres were quantitatively measured to evaluate the degree of cardiac hypertrophy, respectively. GLUT1, GLUT4, and IR were detected to assess cardiac glucose metabolism. Cardiac function was determined by echocardiography. Then, glucose oxidation and uptake, glycolysis and fatty acid metabolism were assessed in Langendorff perfusion of hearts. Finally, PI3K/AKT activator was used to further explore the relevant mechanism. The results showed that during cardiac pressure overload, with the aggravation of cardiac hypertrophy and dysfunction, cardiac glucose metabolism and glycolysis increased, and fatty acid metabolism decreased. After SH2B1-siRNA transfection, cardiac SH2B1 expression was knocked down, and the degree of cardiac hypertrophy and dysfunction was alleviated compared with the Control-siRNA transfected group. Simultaneously, cardiac glucose metabolism and glycolysis were reduced, and fatty acid metabolism was enhanced. The SH2B1 expression knockdown mitigated the cardiac hypertrophy and dysfunction by reducing cardiac glucose metabolism. After using PI3K/AKT activator, the effect of SH2B1 expression knockdown on cardiac glucose metabolism was reversed during cardiac hypertrophy and dysfunction. Collectively, SH2B1 regulated cardiac glucose metabolism by activating the PI3K/AKT pathway during pressure overload-induced cardiac hypertrophy and cardiac dysfunction.

Ruscogenin Alleviates Myocardial Ischemia via Myosin IIA-Dependent Mitochondrial Fusion and Fission Balance

Ruscogenin (RUS), a major effective steroidal sapogenin derived from Ophiopogon japonicas, has been reported to alleviate myocardial ischemia (MI), but its cardioprotective mechanism is still not completely clear. In this study, we observed that RUS markedly reduced MI-induced myocardial injury, as evidenced by notable reductions in infarct size, improvement in biochemical markers, alleviation of cardiac pathology, amelioration of mitochondrial damage, and inhibition of myocardial apoptosis. Moreover, RUS notably suppressed oxygen-glucose deprivation (OGD)-triggered cell injury and apoptosis. Notably, RUS demonstrated a considerable decrease of the interaction between myosin IIA and F-actin, along with the restoration of mitochondrial fusion and fission balance. We further confirmed that the effects of RUS on MI were mediated by myosin IIA using siRNA and overexpression techniques. The inhibition of myosin IIA resulted in a significant improvement of mitochondrial fusion and fission imbalance, while simultaneously counteracting the beneficial effects of RUS. By contrast, overexpression of myosin IIA aggravated the imbalance between mitochondrial fusion and fission and partially weakened the protection of RUS. These findings suggest that myosin IIA is essential or even a key functional protein in the cardioprotection of RUS. Overall, our results have elucidated an undiscovered mechanism involving myosin IIA-dependent mitochondrial fusion and fission balance for treating MI. Furthermore, our study has uncovered a novel mechanism underlying the protective effects of RUS.

Flt3 Activation Mitigates Mitochondrial Fragmentation and Heart Dysfunction through Rebalanced L-OPA1 Processing by Hindering the Interaction between Acetylated p53 and PHB2 in Cardiac Remodeling

Recent studies have shown that FMS-like receptor tyrosine kinase 3 (Flt3) has a beneficial effect on cardiac maladaptive remodeling. However, the role and mechanism of Flt3 in mitochondrial dynamic imbalance under cardiac stress remains poorly understood. This study aims to investigate how Flt3 regulates p53-mediated optic atrophy 1 (OPA1) processing and mitochondrial fragmentation to improve cardiac remodeling. Mitochondrial fragmentation in cardiomyocytes was induced by isoprenaline (ISO) and H2O2 challenge, respectively, in vitro. Cardiac remodeling in mice was established by ligating the left anterior descending coronary artery or by chronic ISO challenge, respectively, in vivo. Our results demonstrated that the protein expression of acetylated-p53 (ac-p53) in mitochondria was significantly increased under cell stress conditions, facilitating the dissociation of PHB2-OPA1 complex by binding to prohibitin 2 (PHB2), a molecular chaperone that stabilizes OPA1 in mitochondria. This led to the degradation of the long isoform of OPA1 (L-OPA1) that facilitates mitochondrial fusion and resultant mitochondrial network fragmentation. This effect was abolished by a p53 K371R mutant that failed to bind to PHB2 and impeded the formation of the ac-p53-PHB2 complex. The activation of Flt3 significantly reduced ac-p53 expression in mitochondria via SIRT1, thereby hindering the formation of the ac-p53-PHB2 complex and potentiating the stability of the PHB2-OPA1 complex. This ultimately inhibits L-OPA1 processing and leads to the balancing of mitochondrial dynamics. These findings highlight a novel mechanism by which Flt3 activation mitigates mitochondrial fragmentation and dysfunction through the reduction of L-OPA1 processing by dampening the interaction between ac-p53 and PHB2 in cardiac maladaptive remodeling.

Remodeling of Mitochondria in Cancer and Other Diseases

Mitochondria are highly dynamic and responsive organelles capable of fission and fusion and are a hub of diverse signaling pathways that are fundamental to cellular homeostasis, energy production, metabolism, survival, and death [...].

Long-term administration of Western diet induced metabolic syndrome in mice and causes cardiac microvascular dysfunction, cardiomyocyte mitochondrial damage, and cardiac remodeling involving caveolae and caveolin-1 expression

BACKGROUND

Long-term consumption of an excessive fat and sucrose diet (Western diet, WD) has been considered a risk factor for metabolic syndrome (MS) and cardiovascular disease. Caveolae and caveolin-1 (CAV-1) proteins are involved in lipid transport and metabolism. However, studies investigating CAV-1 expression, cardiac remodeling, and dysfunction caused by MS, are limited. This study aimed to investigate the correlation between the expression of CAV-1 and abnormal lipid accumulation in the endothelium and myocardium in WD-induced MS, and the occurrence of myocardial microvascular endothelial cell dysfunction, myocardial mitochondrial remodeling, and damage effects on cardiac remodeling and cardiac function.

METHODS

We employed a long-term (7 months) WD feeding mouse model to measure the effect of MS on caveolae/vesiculo-vacuolar organelle (VVO) formation, lipid deposition, and endothelial cell dysfunction in cardiac microvascular using a transmission electron microscopy (TEM) assay. CAV-1 and endothelial nitric oxide synthase (eNOS) expression and interaction were evaluated using real-time polymerase chain reaction, Western blot, and immunostaining. Cardiac mitochondrial shape transition and damage, mitochondria-associated endoplasmic reticulum membrane (MAM) disruption, cardiac function change, caspase-mediated apoptosis pathway activation, and cardiac remodeling were examined using TEM, echocardiography, immunohistochemistry, and Western blot assay.

RESULTS

Our study demonstrated that long-term WD feeding caused obesity and MS in mice. In mice, MS increased caveolae and VVO formation in the microvascular system and enhanced CAV-1 and lipid droplet binding affinity. In addition, MS caused a significant decrease in eNOS expression, vascular endothelial cadherin, and β-catenin interactions in cardiac microvascular endothelial cells, accompanied by impaired vascular integrity. MS-induced endothelial dysfunction caused massive lipid accumulation in the cardiomyocytes, leading to MAM disruption, mitochondrial shape transition, and damage. MS promoted brain natriuretic peptide expression and activated the caspase-dependent apoptosis pathway, leading to cardiac dysfunction in mice.

CONCLUSION

MS resulted in cardiac dysfunction, remodeling by regulating caveolae and CAV-1 expression, and endothelial dysfunction. Lipid accumulation and lipotoxicity caused MAM disruption and mitochondrial remodeling in cardiomyocytes, leading to cardiomyocyte apoptosis and cardiac dysfunction and remodeling.

The effect of high intensity interval training with genistein supplementation on mitochondrial function in the heart tissue of elderly rats

INTRODUCTION

For the most part, heart disease increases with age; on the other hand, although the role of exercise and antioxidants in the health of the elderly has been reported, the simultaneous effect of these two interventions is a new research topic. Thus, the aim of this study was to evaluate the effect of eight weeks of high intensity interval training (HIIT) and genistein (G) supplementation on oxidative stress, apoptosis and mitochondrial biogenesis in the heart tissue of elderly rats.

METHODS

In this experimental study, 40 elderly female Sprague-Dawley rats aged 20 ± 2 months and weighing 250 ± 30 g were randomly divided into five groups of eight animals, including: (1) control (C), (2) sham (Sh), (3) HIIT, (4) HIIT + G and (5) G. Also, to evaluate the effect of time passage on the variables, 8 healthy young rats were included in the healthy young control group. HIIT protocol was performed for eight weeks, three sessions with an intensity of 95-90 % VO_2max at high intensity intervals and 45-45 % VO_2max at low intensity intervals. Ge was received daily at a dose of 60 mg/kg peritoneally. Data analysis was performed using one-way ANOVA with Tukey's post hoc test (P ≤ 0.05).

RESULTS

In the HIIT and HIIT + G groups, levels of Bax, Bax/Bcl-2 ratio, MDA, PAB, GSSG were lower and levels of PGC-1α, TFAM, GSH, GSH/GSSG ratio and NDUFS7 were higher than the control and sham groups (P ≤ 0.05). In the HIIT + G group, levels of Bcl-2 were significantly higher than the control group (P ≤ 0.05). In the HIIT + G group, levels of Bax, GSSG, Bax/Bcl-2 ratio, and PAB were lower, and levels of GSH/GSSG ratio, Bcl-2, PGC-1α, TFAM and NDUFS7 were higher than the G consumption group (P ≤ 0.05). In the HIIT + G group, levels of PGC-1α and TFAM were significantly higher and levels of MDA and PAB were lower than the HIIT group (P ≤ 0.05).

CONCLUSION

Both HIIT and G consumption seem to have beneficial effects on reducing oxidative stress; in addition, the interaction of these two variables on the improvement of apoptosis and mitochondrial biogenesis is more favorable than the effect of either one alone. However, more studies are needed on different pathways of apoptosis following G administration.

Therapeutic non-invasive brain treatments in Alzheimer's disease: recent advances and challenges

Alzheimer's disease (AD) is one of the major neurodegenerative diseases and the most common form of dementia. Characterized by the loss of learning, memory, problem-solving, language, and other thinking abilities, AD exerts a detrimental effect on both patients' and families' quality of life. Although there have been significant advances in understanding the mechanism underlying the pathogenesis and progression of AD, there is no cure for AD. The failure of numerous molecular targeted pharmacologic clinical trials leads to an emerging research shift toward non-invasive therapies, especially multiple targeted non-invasive treatments. In this paper, we reviewed the advances of the most widely studied non-invasive therapies, including photobiomodulation (PBM), transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), and exercise therapy. Firstly, we reviewed the pathological changes of AD and the challenges for AD studies. We then introduced these non-invasive therapies and discussed the factors that may affect the effects of these therapies. Additionally, we review the effects of these therapies and the possible mechanisms underlying these effects. Finally, we summarized the challenges of the non-invasive treatments in future AD studies and clinical applications. We concluded that it would be critical to understand the exact underlying mechanisms and find the optimal treatment parameters to improve the translational value of these non-invasive therapies. Moreover, the combined use of non-invasive treatments is also a promising research direction for future studies and sheds light on the future treatment or prevention of AD.

Cardiac Mitochondria Dysfunction in Dyslipidemic Mice

Dyslipidemia triggers many severe pathologies, including atherosclerosis and chronic inflammation. Several lines of evidence, including our studies, have suggested direct effects of dyslipidemia on cardiac energy metabolism, but details of these effects are not clear. This study aimed to investigate how mild dyslipidemia affects cardiac mitochondria function and vascular nucleotide metabolism. The analyses were performed in 3- and 6-month-old knock-out mice for low-density lipoprotein receptor (Ldlr−/−) and compared to wild-type C57Bl/6J mice (WT). Cardiac isolated mitochondria function was analyzed using Seahorse metabolic flux analyzer. The mechanical function of the heart was measured using echocardiography. The levels of fusion, fission, and mitochondrial biogenesis proteins were determined by ELISA kits, while the cardiac intracellular nucleotide concentration and vascular pattern of nucleotide metabolism ecto-enzymes were analyzed using reverse-phase high-performance liquid chromatography. We revealed the downregulation of mitochondrial complex I, together with a decreased activity of citrate synthase (CS), reduced levels of nuclear respiratory factor 1 and mitochondrial fission 1 protein, as well as lower intracellular adenosine and guanosine triphosphates’ pool in the hearts of 6-month Ldlr−/− mice vs. age-matched WT. The analysis of vascular ecto-enzyme pattern revealed decreased rate of extracellular adenosine monophosphate hydrolysis and increased ecto-adenosine deaminase activity (eADA) in 6-month Ldlr−/− vs. WT mice. No changes were observed in echocardiography parameters in both age groups of Ldlr−/− mice. Younger hyperlipidemic mice revealed no differences in cardiac mitochondria function, CS activity, intracellular nucleotides, mitochondrial biogenesis, and dynamics but exhibited minor changes in vascular eADA activity vs. WT. This study revealed that dysfunction of cardiac mitochondria develops during prolonged mild hyperlipidemia at the time point corresponding to the formation of early vascular alterations.

Vanillic acid attenuates H2O2-induced injury in H9c2 cells by regulating mitophagy via the PINK1/Parkin/Mfn2 signaling pathway

Vanillic acid, a phenolic compound mainly obtained from the foot of Picrorhiza scrophulariiflora Pennell, has been demonstrated to possess a cardiovascular-protective effect in previous studies. However, there is lack of research on vanillic acid protecting cardiomyocytes from oxidative stress injury by mediating mitophagy. In the present study, oxidative stress injury in the H9c2 cell line was induced by H₂O₂. Our results confirmed that vanillic acid mitigated apoptosis and injury triggered by oxidative stress, evidenced by the decline in production of reactive oxygen species and malondialdehyde and level of lactate dehydrogenase and the increase of superoxide dismutase and glutathione. The use of vanillic acid could also improve the polarization of mitochondrial membrane potential and decrease the cellular calcium level. After treatment by vanillic acid, impaired autophagy flux and mitophagy were improved, and the length of mitochondria was restored. Vanillic acid increased the expression of PINK1, Parkin, Mfn2, and the ratio of LC3-II/LC3-I and decreased the expression of p62. But, under the intervention of mitophagy inhibitor 3-MA, vanillic acid could not change the expression of PINK1/Parkin/Mfn2 and downstream genes to affect cell autophagy, mitophagy, and mitochondrial function. Our findings suggested that vanillic acid activated mitophagy to improve mitochondrial function, in which the PINK1/Parkin/Mfn2 pathway could be the potential regulatory mechanism.

Vaspin Ameliorates Cardiac Remodeling by Suppressing Phosphoinositide 3-Kinase/Protein Kinase B Pathway to Improve Oxidative Stress in Heart Failure Rats

ABSTRACT

This study aimed to explore whether vaspin could alleviate cardiac remodeling through attenuating oxidative stress in heart failure rats and to determine the associated signaling pathway. Cardiac remodeling was induced by myocardial infarction, transverse aortic constriction, or angiotensin (Ang) II infusion in vivo, and the neonatal rat cardiomyocytes (NRCMs) and neonatal rat cardiac fibroblasts (NRCFs) were treated with Ang II. Vaspin treatment alleviated fibrosis in myocardial infarction, transverse aortic constriction, and Ang II-treated rats. The Ang II-induced increases of atrial natriuretic peptide and brain natriuretic peptide in NRCMs and Ang II-induced increases of collagen I and collagen III in NRCFs were reduced after vaspin treatment. Vaspin administration inhibited the Ang II-induced increases of phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) pathway, superoxide anions, malondialdehyde, and NADPH oxidases activity in NRCMs and NRCFs. The overexpression of PI3K, Akt, or NADPH oxidases 1 reversed the attenuating effects of vaspin on Ang II-induced elevation of atrial natriuretic peptide and brain natriuretic peptide in NRCMs, as well as Ang II-induced increases of collagen I and collagen III in NRCFs. The administration of wortmannin (PI3K inhibitor) or MK2206 (Akt inhibitor) inhibited the oxidative stress induced by Ang II in NRCMs and NRCFs. The above results suggest that vaspin can alleviate cardiac dysfunction and remodeling in heart failure rats. Vaspin attenuates Ang II-induced hypertrophy of NRCMs and fibrosis of NRCFs through suppressing PI3K/Akt pathway to alleviate oxidative stress.

Tumstatin (69-88) alleviates heart failure via attenuating oxidative stress in rats with myocardial infarction

Background

This study aimed to elucidate the effects of tumstatin (69–88) on heart failure and the underlying mechanism.

Materials and methods

Myocardial infarction (MI) was induced by ligating the left coronary artery in rats to trigger heart failure.

Results

Tumstatin (69–88) can reduce cardiac insufficiency in rats with heart failure. The increased cardiac fibrosis in MI rat was attenuated by tumstatin (69–88). Increase of cardiac atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in rats with myocardial infarction, and Ang II-treated NRCMs or H9C2 cells was inhibited by tumstatin (69–88). In the heart of MI rats, and Ang II-treated NRCMs or H9C2 cells, the superoxide anions and NADPH oxidase (Nox) activity rose and the superoxide dismutase (SOD) activity was reduced, which was inhibited by tumstatin (69–88). Diethyldithiocarbamate, an SOD inhibitor, increased the ANP and BNP in NRCMs or H9C2 cells. Tumstatin (69–88) inhibited the Ang II-induced raises of ANP and BNP in NRCMs or H9C2 cells, which was reversed by DETC.

Conclusions

These results indicate that tumstatin (69–88) alleviates cardiac dysfunction of heart failure. Tumstatin (69–88) improves the hypertrophy of cardiomyocytes via attenuation of oxidative stress. Tumstatin (69–88) may be a potential drug for heart failure in the future.

Assessing Drug-Induced Mitochondrial Toxicity in Cardiomyocytes: Implications for Preclinical Cardiac Safety Evaluation

Drug-induced cardiotoxicity not only leads to the attrition of drugs during development, but also contributes to the high morbidity and mortality rates of cardiovascular diseases. Comprehensive testing for proarrhythmic risks of drugs has been applied in preclinical cardiac safety assessment for over 15 years. However, other mechanisms of cardiac toxicity have not received such attention. Of them, mitochondrial impairment is a common form of cardiotoxicity and is known to account for over half of cardiovascular adverse-event-related black box warnings imposed by the U.S. Food and Drug Administration. Although it has been studied in great depth, mitochondrial toxicity assessment has not yet been incorporated into routine safety tests for cardiotoxicity at the preclinical stage. This review discusses the main characteristics of mitochondria in cardiomyocytes, drug-induced mitochondrial toxicities, and high-throughput screening strategies for cardiomyocytes, as well as their proposed integration into preclinical safety pharmacology. We emphasize the advantages of using adult human primary cardiomyocytes for the evaluation of mitochondrial morphology and function, and the need for a novel cardiac safety testing platform integrating mitochondrial toxicity and proarrhythmic risk assessments in cardiac safety evaluation.

The potential of remdesivir to affect function, metabolism and proliferation of cardiac and kidney cells in vitro

Remdesivir is a prodrug of a nucleoside analog and the first antiviral therapeutic approved for coronavirus disease. Recent cardiac safety concerns and reports on remdesivir-related acute kidney injury call for a better characterization of remdesivir toxicity and understanding of the underlying mechanisms. Here, we performed an in vitro toxicity assessment of remdesivir around clinically relevant concentrations (C_max 9 µM) using H9c2 rat cardiomyoblasts, neonatal mouse cardiomyocytes (NMCM), rat NRK-52E and human RPTEC/TERT1 cells as cell models for the assessment of cardiotoxicity or nephrotoxicity, respectively. Due to the known potential of nucleoside analogs for the induction of mitochondrial toxicity, we assessed mitochondrial function in response to remdesivir treatment, early proteomic changes in NMCM and RPTEC/TERT1 cells and the contractile function of NMCM. Short-term treatments (24 h) of H9c2 and NRK-52E cells with remdesivir adversely affected cell viability by inhibition of proliferation as determined by significantly decreased ³H-thymidine uptake. Mitochondrial toxicity of remdesivir (1.6–3.1 µM) in cardiac cells was evident by a significant decrease in oxygen consumption, a collapse of mitochondrial membrane potential and an increase in lactate secretion after a 24–48-h treatment. This was supported by early proteomic changes of respiratory chain proteins and intermediate filaments that are typically involved in mitochondrial reorganization. Functionally, an impedance-based analysis showed that remdesivir (6.25 µM) affected the beat rate and contractility of NMCM. In conclusion, we identified adverse effects of remdesivir in cardiac and kidney cells at clinically relevant concentrations, suggesting a careful evaluation of therapeutic use in patients at risk for cardiovascular or kidney disease.

Protective effects of natural products against myocardial ischemia/reperfusion: Mitochondria-targeted therapeutics

Patients with ischemic heart disease receiving reperfusion therapy still need to face left ventricular remodeling and heart failure after myocardial infarction. Reperfusion itself paradoxically leads to further cardiomyocyte death and systolic dysfunction. Ischemia/reperfusion (I/R) injury can eliminate the benefits of reperfusion therapy in patients and causes secondary myocardial injury. Mitochondrial dysfunction and structural disorder are the basic driving force of I/R injury. We summarized the basic relationship and potential mechanisms of mitochondrial injury in the development of I/R injury. Subsequently, this review summarized the natural products (NPs) that have been proven to targeting mitochondrial therapeutic effects during I/R injury in recent years and related cellular signal transduction pathways. We found that these NPs mainly protected the structural integrity of mitochondria and improve dysfunction, such as reducing mitochondrial division and fusion abnormalities, improving mitochondrial Ca²⁺ overload and inhibiting reactive oxygen species overproduction, thereby playing a role in protecting cardiomyocytes during I/R injury. This data would deepen the understanding of I/R-induced mitochondrial pathological process and suggested that NPs are expected to be transformed into potential therapies targeting mitochondria.

Targeting calcium-mediated inter-organellar crosstalk in cardiac diseases

INTRODUCTION

Abnormal calcium signaling between organelles such as the sarcoplasmic reticulum (SR), mitochondria and lysosomes is a key feature of heart diseases. Calcium serves as a secondary messenger mediating inter-organellar crosstalk, essential for maintaining the cardiomyocyte function.

AREAS COVERED

This article examines the available literature related to calcium channels and transporters involved in inter-organellar calcium signaling. The SR calcium-release channels ryanodine receptor type-2 (RyR2) and inositol 1,4,5-trisphosphate receptor (IP₃R), and calcium-transporter SR/ER-ATPase 2a (SERCA2a) are illuminated. The roles of mitochondrial voltage-dependent anion channels (VDAC), the mitochondria Ca²⁺ uniporter complex (MCUC), and the lysosomal H⁺/Ca²⁺ exchanger, two pore channels (TPC), and transient receptor potential mucolipin (TRPML) are discussed. Furthermore, recent studies showing calcium-mediated crosstalk between the SR, mitochondria, and lysosomes as well as how this crosstalk is dysregulated in cardiac diseases are placed under the spotlight.

EXPERT OPINION

Enhanced SR calcium release via RyR2 and reduced SR reuptake via SERCA2a, increased VDAC and MCUC-mediated calcium uptake into mitochondria, and enhanced lysosomal calcium-release via lysosomal TPC and TRPML may all contribute to aberrant calcium homeostasis causing heart disease. While mechanisms of this crosstalk need to be studied further, interventions targeting these calcium channels or combinations thereof might represent a promising therapeutic strategy.

Functional Inhibition of Valosin-Containing Protein Induces Cardiac Dilation and Dysfunction in a New Dominant-Negative Transgenic Mouse Model

Valosin-containing protein (VCP) was found to play a vital protective role against cardiac stresses. Genetic mutations of VCP are associated with human dilated cardiomyopathy. However, the essential role of VCP in the heart during the physiological condition remains unknown since the VCP knockout in mice is embryonically lethal. We generated a cardiac-specific dominant-negative VCP transgenic (DN-VCP TG) mouse to determine the effects of impaired VCP activity on the heart. Using echocardiography, we showed that cardiac-specific overexpression of DN-VCP induced a remarkable cardiac dilation and progressively declined cardiac function during the aging transition. Mechanistically, DN-VCP did not affect the endogenous VCP (EN-VCP) expression but significantly reduced cardiac ATPase activity in the DN-VCP TG mouse hearts, indicating a functional inhibition. DN-VCP significantly impaired the aging-related cytoplasmic/nuclear shuffling of EN-VCP and its co-factors in the heart tissues and interrupted the balance of the VCP-cofactors interaction between the activating co-factors, ubiquitin fusion degradation protein 1 (UFD-1)/nuclear protein localization protein 4 (NPL-4) complex, and its inhibiting co-factor P47, leading to the binding preference with the inhibitory co-factor, resulting in functional repression of VCP. This DN-VCP TG mouse provides a unique functional-inactivation model for investigating VCP in the heart in physiological and pathological conditions.