Peroxynitrite regulates ER stress-mediated Ca(2+) flux to mitochondria characterizing cardiac microvascular ischemia-reperfusion injury associated with hyperhomocysteinemia.

BACKGROUND: Homocysteine (Hcy) is not only associated with the development of chronic cardiovascular diseases like atherosclerosis, but may also participate in the acute cardiovascular events. However, the exact mechanism of the latter remains elusive. The present study aims to further investigate the mechanism of cardiac microvascular endothelial cells (CMECs) death after I/R induction in the presence of Hcy and explore new therapeutic strategies. METHODS: By generating the hypoxia/reoxygenation (H/R) human cardiac microvascular endothelial cell (HCMEC) model and the I/R models in rats with hyperhomocysteinemia (HHcy), the mechanisms of endothelial cell injury associated with HHcy were investigated. RESULTS: We demonstrated that ONOO(-), generated by the combination of Hcy and Cu(2+) during I/R, induces ER stress and the subsequent ER-mitochondria Ca(2+) transfer via IP3R-mediated Ca(2+) release in CMECs. The cytosolic/mitochondrial Ca(2+) oscillations and mitochondrial Ca(2+) overload promote mROS generation, provoke LMP, and ultimately drive CMEC necroptosis. Our study further demonstrates the IP3R inhibitor 2-APB (5 mg/kg) significantly reduced infarct size by 29.14%, and improved cardiac function in HHcy rats (HHcyR), as evidenced by increased LVEF (35.71% → 55.32%), elevated LVFS (31.44% → 48.54%), and reduced LVEDd (6.98 mm → 5.80 mm). CONCLUSIONS: Altogether, our results reveal the pathological role of Hcy in acute cardiovascular events. We show that HHcy aggravates cardiac microvascular I/R injury via ONOO(-)-driven ER stress that triggers IP3R-mediated Ca(2+) mis-handling, culminating in mitochondrial dysfunction and necroptosis. These data identify IP3R-dependent Ca(2+) transfer as a tractable pathway for HHcy-complicated reperfusion injury.