Protective effect of shikonin in myocardial ischemia/reperfusion injury in rats by inhibition of autophagy through the Hippo pathway.

Shikonin is widely acknowledged as a bioactive substance extracted from the root of lithospermum erythrorhizon with multifunction. It alleviates ischemic/reperfusion (I/R) injury in liver and brain. Due to the similar pathogenesis of I/R and hypoxia/reoxygenation (H/R)-stimulated injury, we aimed to explore the potential pharmacological effects of Shikonin on the myocardial injury. The rats with myocardial I/R injury and the primary cardiomyocytes with H/R-stimulated injury were taken as in vivo and in vitro models. 2,3,5-Triphenyltetrazolium chloride staining and ELISA kits were used for detection of myocardial infarction and cardiac injury. Hematoxylin and eosin and immunohistochemistry staining were used to analyze the effect of Shikonin on autophagy histology. Western blot was performed to detect the proteins related to autophagy and Hippo pathway. The results showed that SHK reduces the size of myocardial infarction, improved cardiac function, suppressed the expression of autophagy-related proteins, and reduced the amount of autophagosomes. The underlying mechanism is to activate Hippo pathway. In vitro assay also suggested that SHK enhanced the cell viability, reduced the apoptotic rates in rat primary cardiomyocytes. Collectively, our results demonstrated that SHK protects against myocardial I/R injury by inhibiting autophagy, of which the underlying molecular mechanism is to activate the Hippo signaling pathway.