Role of high-mobility group B1 in myocardial injury induced by coronary microembolization in rats.

OBJECTIVE: This study aimed to explore the effects of high-mobility group B1 (HMGB1) on coronary microembolization (CME)-induced myocardial inflammation, myocardial apoptosis, and cardiac function injury in rats. METHODS: Forty Sprague-Dawley rats were divided into sham operation group (sham group), microembolization group (CME group), CME + HMGB1 siRNA (HMGB1 siRNA) group, and CME + scrambled siRNA (control siRNA) group (10 rats in each group). The CME model group was constructed by injecting microembolism spheres into the apex of the left ventricle after clamping the ascending aorta. The sham group was constructed by injecting the same amount of saline. The HMGB1 siRNA group was injected with HMGB1 siRNA transfection complex via the tail vein 72 hours before CME modeling. The control siRNA group was injected with the same amount of scrambled siRNA mixture through the tail vein 72 hours before CME modeling. The cardiac function, serum cardiac troponin I level, and apoptotic index were examined 12 hours after the surgery. The levels of HMGB1, nuclear factor-κB (NF-κB) p65, glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), cleaved caspase-12, cleaved caspase-3, tumor necrosis factor-α (TNF-α), and interleukin 1ß (IL-1ß) were detected. RESULTS: Myocardial dysfunction, enhanced serum cardiac troponin I level, and apoptotic index were induced following CME. Moreover, CME increased the expression of HMGB1, NF-κB p65, GRP78, CHOP, cleaved caspase-12, cleaved caspase-3, TNF-α, and IL-1ß. HMGB1 siRNA reversed these effects, whereas scrambled siRNA had no effect. CONCLUSIONS: Inhibition of HMGB1 expression reduced CME-induced myocardial injury and improved cardiac function. Hence, it may serve as a new target for preventing and treating the CME-induced myocardial injury.