Salidroside improved cerebrovascular vasodilation in streptozotocin-induced diabetic rats through restoring the function of BK_Ca channel in smooth muscle cells

Vessel disease is a kind of severe complication in diabetic patients. However, few pharmacologic agents can directly recover diabetic vascular function. Salidroside (SAL), a major ingredient from Rhodiola rosea, has been found to have an obvious hypoglycemic effect and a beneficial protection on vascular function in diabetes. However, whether SAL is a suitable treatment for diabetes has not so far been evaluated and the underlying mechanisms remain unknown. The present work aims to (1) investigate the potential effects of SAL on cerebrovascular relaxation in streptozotocin-induced diabetic rats or when exposed to acute hyperglycemia condition and (2) examine whether function of the BK_Ca channel is involved in SAL treatment for diabetic vascular relaxation. Our results indicate that chronic administration of 100 mg/kg/day SAL not only improves cerebrovascular relaxation but also increases BK_Ca β1-subunit expressions at both protein and mRNA levels and enhances BK_Ca whole-cell and single-channel activities in cerebral VSMCs of diabetic rats. Correspondingly, acute application of 100 μM SAL induces cerebrovascular relaxation by activation of the BK_Ca channel. Furthermore, SAL activated the BK_Ca channel mainly through acting on the β1-subunit in HEK293 cells transfected with hSloα+β1 constructs. We concluded that SAL improved vasodilation in diabetic rats through restoring the function of the BK_Ca-β1 subunit in cerebrovascular smooth muscle cells, which may be the underlying mechanism responsible for the vascular protection of SAL in diabetes.