Regulatory mechanism of CaMKII δ mediated by RIPK3 on myocardial fibrosis and reversal effects of RIPK3 inhibitor GSK'872

Background: Myocardial fibrosis (MF) remains a prominent challenge in heart disease. The role of receptor-interacting protein kinase 3 (RIPK3)-mediated necroptosis is evident in the pathogenesis of numerous heart diseases. Concurrently, the activation of Ca2+/calmodulin-dependent protein kinase (CaMKII) is pivotal in cardiovascular disease (CVD). This study aimed to evaluate the impact and underlying mechanisms of RIPK3 on myocardial injury in MF and to elucidate the potential involvement of CaMKII. Methods: Building upon our previous research methods [1], wild-type (WT) mice and RIPK3 knockout (RIPK3 -/-) mice underwent random assignment for transverse aortic constriction (TAC) in vivo. Four weeks post-procedure, the MF model was effectively established. Parameters such as the extent of MF, myocardial injury, RIPK3 expression, necroptosis, CaMKII activity, phosphorylation of mixed lineage kinase domain-like protein (MLKL), mitochondrial ultrastructural details, and oxidative stress levels were examined. Cardiomyocyte fibrosis was simulated in vitro using angiotensin II on cardiac fibroblasts. Results: TAC reliably produced MF, myocardial injury, CaMKII activation, and necroptosis in mice. RIPK3 depletion ameliorated these conditions. The RIPK3 inhibitor, GSK'872, suppressed the expression of RIPK3 in myocardial fibroblasts, leading to improved fibrosis and inflammation, diminished CaMKII oxidation and phosphorylation levels, and the rectification of CaMKIIδ alternative splicing anomalies. Furthermore, GSK'872 downregulated the expressions of RIPK1, RIPK3, and MLKL phosphorylation, attenuated necroptosis, and bolstered the oxidative stress response. Conclusions: Our data suggested that in MF mice, necroptosis was augmented in a RIPK3-dependent fashion. There seemed to be a positive correlation between CaMKII activation and RIPK3 expression. The adverse effects on myocardial fibrosis mediated by CaMKII δ through RIPK3 could potentially be mitigated by the RIPK3 inhibitor, GSK'872. This offered a fresh perspective on the amelioration and treatment of MF and myocardial injury.