Isoproterenol-induced hypertrophy of neonatal cardiac myocytes and H9c2 cell is dependent on TRPC3-regulated CaV1.2 expression

Isoproterenol induced cardiac hypertrophy: A comparison of three doses and two delivery methods in C57BL/6J mice

Heart Failure (HF) continues to be a complex public health issue with increasing world population prevalence. Although overall mortality has decreased for HF and hypertrophic cardiomyopathy (HCM), a precursor for HF, their prevalence continues to increase annually. Because the etiology of HF and HCM is heterogeneous, it has been difficult to identify novel therapies to combat these diseases. Isoproterenol (ISP), a non-selective β-adrenoreceptor agonist, is commonly used to induce cardiotoxicity and cause acute and chronic HCM and HF in mice. However, the variability in dose and duration of ISP treatment used in studies has made it difficult to determine the optimal combination of ISP dose and delivery method to develop a reliable ISP-induced mouse model for disease. Here we examined cardiac effects induced by ISP via subcutaneous (SQ) and SQ-minipump (SMP) infusions across 3 doses (2, 4, and 10mg/kg/day) over 2 weeks to determine whether SQ and SMP ISP delivery induced comparable disease severity in C57BL/6J mice. To assess disease, we measured body and heart weight, surface electrocardiogram (ECG), and echocardiography recordings. We found all 3 ISP doses comparably increase heart weight, but these increases are more pronounced when ISP was administered via SMP. We also found that the combination of ISP treatment and delivery method induces contrasting heart rate, RR interval, and R and S amplitudes that may place SMP treated mice at higher risk for sustained disease burden. Mice treated via SMP also had increased heart wall thickness and LV Mass, but mice treated via SQ showed greater increase in gene markers for hypertrophy and fibrosis. Overall, these data suggest that at 2 weeks, mice treated with 2, 4, or 10mg/kg/day ISP via SQ and SMP routes cause similar pathological heart phenotypes but highlight the importance of drug delivery method to induce differing disease pathways.

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

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

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

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

Prohibitin1 maintains mitochondrial quality in isoproterenol-induced cardiac hypertrophy in H9C2 cells

BACKGROUND INFORMATION

Various types of stress initially induce a state of cardiac hypertrophy (CH) in the heart. But, persistent escalation of cardiac stress leads to progression from an adaptive physiological to a maladaptive pathological state. So, elucidating molecular mechanisms that can attenuate CH is imperative in developing cardiac therapies. Previously, we showed that Prohibitin1 (PHB1) has a protective role in CH-induced oxidative stress. Nevertheless, it is unclear how PHB1, a mitochondrial protein, has a protective role in CH. Therefore, we hypothesized that PHB1 maintains mitochondrial quality in CH. To test this hypothesis, we used Isoproterenol (ISO) to induce CH in H9C2 cells overexpressing PHB1 and elucidated mitochondrial quality control pathways.

RESULTS

We found that overexpressing PHB1 attenuates ISO-induced CH and restores mitochondrial morphology in H9C2 cells. In addition, PHB1 blocks the pro-hypertrophic IGF1R/AKT pathway and restores the mitochondrial membrane polarization in ISO-treated cells. We observed that overexpressing PHB1 promotes mitochondrial biogenesis, improves mitochondrial respiratory capacity, and triggers mitophagy.

CONCLUSION

We conclude that PHB1 maintains mitochondrial quality in ISO-induced CH in H9C2 cells.

SIGNIFICANCE

Based on our results, we suggest that small molecules that induce PHB1 in cardiac cells may prove beneficial in developing cardiac therapies.

Puerarin ameliorates myocardial remodeling of spontaneously hypertensive rats through inhibiting TRPC6-CaN-NFATc3 pathway

Puerarin (Pue) has been widely used in the treatment of hypertension and cardiovascular diseases, but the basic mechanism of Pue on myocardial remodeling (MR) of hypertension is not clear. The purpose of this study was to investigate the effect and mechanism of Pue on MR and provide the basis for the clinical application. Thirty male spontaneously hypertensive rats (SHR) and six male Wistar Kyoto rats (WKY) aged 3 months were used in this study, SHR rats were randomly divided into 5 groups, Pue (40 or 80 mg/kg/d, ip) and telmisartan (TELMI) (30 mg/kg/d, ig) were administrated for 12 weeks. We used Echocardiography to detect the cardiac function. Morphology and structure of myocardium were observed. H9C2 cells were subjected to 1 μM Ang Ⅱ in vitro, 100 μM Pue, 0.5 μM Calmodulin-dependent calcineurin (CaN) inhibitor Cyclosporin A (CsA) and 1 μM specific transient receptor potential channel 6 (TRPC6) inhibitor SAR7334 were used in H9C2 cells. Long-term administration of Pue could significantly improve cardiac function, improve morphology and structure of myocardium in vivo. Pue could reduce MR related proteins expression (ACTC1, TGF-β1, CTGF, β-MHC and BNP), attenuate ROS, restore MMP and decrease Ca²⁺-overload in vitro. Further study indicated that Pue could decrease TRPC6 expression and inhibit nuclear factor of activated T cells 3 (NFATc3) nuclear translocation in vitro. These results suggested that puerarin could ameliorate myocardial remodeling through inhibiting TRPC6-CaN-NFATc3 in spontaneously hypertensive rats.

Qishen Yiqi dropping pills improve isoproterenol-induced cardiomyocyte hypertrophy by regulating X-inactive specific transcript (XIST) expression in rats

Background

This study aimed to explore the potential mechanism of Qishen Yiqi dropping pills (QYDPs) in the treatment of chronic heart failure (CHF) by regulating the expression of lncRNAs during CHF.

Methods

Differences in the expression of the long non-coding RNA (lncRNA), X-inactive specific transcript (XIST), in an isoproterenol (ISO)-induced cardiomyocyte hypertrophy model treated with QYDPs was analyzed by reverse transcription quantitative polymerase chain reaction (RT-qPCR). A cell counting kit-8 (CCK8) assay, flow cytometry (FCM), and enzyme linked immunosorbent assay (ELISA) were used to analyze the protective effects of QYDPs on the proliferation rate, apoptosis, myocardial enzyme, oxidative stress, and inflammation of cardiomyocytes, as well as the molecular mechanism of XIST.

Results

Our results showed that in the ISO-induced cardiomyocyte hypertrophy model, XIST expression and apoptosis were increased, the cell proliferation rate was decreased, and myocardial enzyme levels increased [i.e., increased lactate dehydrogenase (LDH) and creatine kinase (CK) levels]. Furthermore, cellular oxidative stress [i.e., increased malondialdehyde (MDA) levels and decreased superoxide dismutase (SOD) levels] and inflammatory response [i.e., increased interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α protein secretion] were also promoted. QYDP treatment effectively mitigated the effects of ISO induction. Subsequently, we found that suppressing XIST expression reversed the effect of ISO induction, whereas overexpression (ov) of XIST enhanced the effect of ISO induction. Finally, this study confirmed that QYDP treatment improved the ISO-induced decrease in proliferation, apoptosis, and promotion of oxidative stress and inflammatory response in cardiomyocytes, whereas ov of XIST partially negated the effect of QYDPs.

Conclusions

QYDPs protected H9c2 cells from ISO-induced damage by downregulating XIST expression.

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.