Effect of Rho-Kinase and Autophagy on Remote Ischemic Conditioning-Induced Cardioprotection in Rat Myocardial Ischemia/Reperfusion Injury Model

Rnd3 protects against doxorubicin-induced cardiotoxicity through inhibition of PANoptosis in a Rock1/Drp1/mitochondrial fission-dependent manner

Doxorubicin, a representative drug of the anthracycline class, is widely used in cancer treatment. However, Doxorubicin-induced cardiotoxicity (DIC) presents a significant challenge in its clinical application. Mitochondrial dysfunction plays a central role in DIC, primarily through disrupting mitochondrial dynamics. This study aimed to investigate the impact of Rnd3 (a Rho family GTPase 3) on DIC, with a focus on mitochondrial dynamics. Cardiomyocyte-specific Rnd3 transgenic mice (Rnd3-Tg) and Rnd3LSP/LSP mice (N-Tg) were established for in vivo experiments, and adenoviruses harboring Rnd3 (Ad-Rnd3) or negative control (Ad-Control) were injected in the myocardium for in vitro experiments. The DIC model was established using wild-type, N-Tg, and Rnd3-Tg mice, with subsequent intraperitoneal injection of Dox for 4 weeks. The molecular mechanism was explored through RNA sequencing, immunofluorescence staining, co-immunoprecipitation assay, and protein-protein docking. Dox administration induced significant mitochondrial injury and cardiac dysfunction, which was ameliorated by Rnd3 overexpression. Further, the augmentation of Rnd3 expression mitigated mitochondrial fragmentation which is mediated by dynamin-related protein 1 (Drp1), thereby ameliorating the PANoptosis (pyroptosis, apoptosis, and necroptosis) response induced by Dox. Mechanically, the interaction between Rnd3 and Rho-associated kinase 1 (Rock1) may impede Rock1-induced Drp1 phosphorylation at Ser616, thus inhibiting mitochondrial fission and dysfunction. Interestingly, Rock1 knockdown nullified the effects of Rnd3 on cardiomyocytes PANoptosis, as well as Dox-induced cardiac remodeling and dysfunction elicited by Rnd3. Rnd3 enhances cardiac resilience against DIC by stabilizing mitochondrial dynamics and reducing PANoptosis. Our findings suggest that the Rnd3/Rock1/Drp1 signaling pathway represents a novel target for mitigating DIC, and modulating Rnd3 expression could be a strategic approach to safeguarding cardiac function in patients undergoing Dox treatment. The graphical abstract illustrated the cardioprotective role of Rnd3 in DIC. Rnd3 directly binds to Rock1 in cytoplasm and ameliorates mitochondrial fission by inhibiting Drp1 phosphorylation at ser616, thereby alleviating PANoptosis (apoptosis, pyroptosis, and necroptosis) in DIC.

Effects of Renal Denervation on Ouabain-Induced Hypertension in Rats

Background

Ouabain, a Na+, K+-ATPase inhibitor, is elevated in hypertensive patients. Evidence suggests ouabain contributes to hypertension mainly through activation of the sympathetic nervous system (SNS). Renal nerves play a vital role in the regulation of SNS activity, so we hypothesize that renal denervation may attenuate the development of ouabain-induced hypertension.

Methods and Results

Forty Sprague-Dawley rats were divided into following groups (n = 10 each): control group (sham surgery plus intraperitoneal saline injection), RDN group (renal denervation (RDN) plus intraperitoneal saline injection), ouabain group (sham surgery plus intraperitoneal ouabain injection), and ouabain + RDN group (RDN plus intraperitoneal ouabain injection). After eight weeks, compared with the control group, rats in the ouabain group exhibited elevated blood pressure (P < 0.05), increased plasma epinephrine, norepinephrine, angiotensin II, and aldosterone levels (P < 0.05). These indexes could be significantly ameliorated by RDN. RDN also reduced the thickening of aortic tunica media and downregulated the expression of proliferating cell nuclear antigen (PCNA) in the thoracic aorta induced by ouabain. Masson staining and echocardiography showed that myocardial fibrosis and increased left ventricular mass in the ouabain group could be attenuated by RDN.

Conclusions

The present study reveals that renal nerves play an important role in the development of ouabain-induced hypertension. RDN could inhibit the pressor effect and the myocardial remodeling induced by ouabain potentially via inhibiting catecholamine release and vascular smooth muscle cell proliferation. Clinical studies are needed to explore whether RDN may exhibit better antihypertensive effects on hypertensive patients with high plasma ouabain levels as compared to those with normal plasma ouabain levels.

Interaction of Cardiovascular Nonmodifiable Risk Factors, Comorbidities and Comedications With Ischemia/Reperfusion Injury and Cardioprotection by Pharmacological Treatments and Ischemic Conditioning

Preconditioning, postconditioning, and remote conditioning of the myocardium enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and the potential to provide novel therapeutic paradigms for cardioprotection. While many signaling pathways leading to endogenous cardioprotection have been elucidated in experimental studies over the past 30 years, no cardioprotective drug is on the market yet for that indication. One likely major reason for this failure to translate cardioprotection into patient benefit is the lack of rigorous and systematic preclinical evaluation of promising cardioprotective therapies prior to their clinical evaluation, since ischemic heart disease in humans is a complex disorder caused by or associated with cardiovascular risk factors and comorbidities. These risk factors and comorbidities induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury and responses to cardioprotective interventions. Moreover, some of the medications used to treat these comorbidities may impact on cardioprotection by again modifying cellular signaling pathways. The aim of this article is to review the recent evidence that cardiovascular risk factors as well as comorbidities and their medications may modify the response to cardioprotective interventions. We emphasize the critical need for taking into account the presence of cardiovascular risk factors as well as comorbidities and their concomitant medications when designing preclinical studies for the identification and validation of cardioprotective drug targets and clinical studies. This will hopefully maximize the success rate of developing rational approaches to effective cardioprotective therapies for the majority of patients with multiple comorbidities. SIGNIFICANCE STATEMENT: Ischemic heart disease is a major cause of mortality; however, there are still no cardioprotective drugs on the market. Most studies on cardioprotection have been undertaken in animal models of ischemia/reperfusion in the absence of comorbidities; however, ischemic heart disease develops with other systemic disorders (e.g., hypertension, hyperlipidemia, diabetes, atherosclerosis). Here we focus on the preclinical and clinical evidence showing how these comorbidities and their routine medications affect ischemia/reperfusion injury and interfere with cardioprotective strategies.