RAS-RH up-regulates the level of miR-126 and inhibits the opening of mPTP in a rat model of coronary microvascular disease.

Background: Coronary microvascular dysfunction (CMVD) significantly impairs cardiac function and worsens prognosis in patients with cardiovascular diseases, yet no definitively effective pharmacological treatment currently exists. Endothelial cell injury stands as the core pathogenic mechanism of CMVD, however, the molecular mechanisms underlying X-ray radiation-induced endothelial damage remain poorly understood. Although our research group has previously demonstrated that RAS-RH possesses pro-angiogenic properties, its therapeutic potential and mechanistic basis in treating CMVD remain unexplored. Aim This study aims to investigate the potential mechanism by which RAS-RH mitigates radiation-induced coronary microcirculation dysfunction through the inhibition of mitochondrial membrane permeability transition pore (mPTP) opening in endothelial cells.

Methods: We employed a comprehensive set of techniques, including transthoracic echocardiography, coronary microvessel casting technique, carstairs and heidenhain staining, immunohistochemistry, enzyme-linked immunosorbent assay, Western blot, fluorescence in situ hybridization, transmission electron microscopy, TUNEL assay, and flow cytometry, to systematically evaluate cardiac function, coronary vascular structure, myocardial pathological changes, ultrastructural damage, apoptosis, and protein marker expression in an animal model.

Results: In the CMVD rat model, X-ray radiation induced cardiac dysfunction, accompanied by elevated levels of vasoactive substances (TXA₂, ET-1, and vWF) and reduced nitric oxide (NO) production. Coronary vascular injury worsened, evidenced by decreased vascular volume, narrowed lumen diameter, and shortened vessel length. Additionally, capillary density was reduced, myocardial ischemia was exacerbated, and intravascular thrombosis was aggravated. At the molecular level, mPTP-related proteins (CypD, VDAC, F₁F₀-ATPase and ANT) exhibited abnormal expression, while apoptosis-related proteins (Cytc, AIF, caspase-9, and caspase-3) were upregulated, leading to increased apoptotic severity. Ultrastructural damage in cardiomyocytes and telocytes was aggravated, and miR-126 expression was downregulated. These findings suggest that X-ray radiation induces CMVD by triggering excessive mPTP opening in endothelial cells. Notably, interventions with RAS-RH, miR-126 agomir and RAS-RH + miR-126 agomir significantly ameliorated these pathological changes to varying degrees. This demonstrates that RAS-RH mitigates X-ray radiation-induced CMVD by upregulating miR-126 to suppress mPTP overactivation.

Conclusion: RAS-RH effectively ameliorates X-ray radiation-induced CMVD by modulating miR-126 expression to inhibit pathological opening of the mPTP in endothelial cells. This finding provides novel mechanistic evidence supporting RAS-RH as a therapeutic strategy for CMVD.