Apelin/APJ increased renal blood flow through endothelial BKCa channel induced p-eNOS and ET-1 in diabetic conditions.

Abstract

Renal hemodynamics damage, an important driving mechanism of diabetic nephropathy (DN), is related to many abnormal endothelial released molecules, such as endothelial nitrogen monoxide synthase (eNOS) and endothelin-1 (ET-1), caused by glomerular endothelial cells dysfunction. Apelin, as the endogenous ligand for APJ, was reported to be associated with endothelial cell dysfunction in diabetes. Therefore, it is hypothesized that apelin/APJ increased renal perfusion in DN through regulating endothelial released molecules. Diabetic models were replicated via injecting STZ intraperitoneally (40 mg/kg/day) for 5 consecutive days. Apelin-13 was infused with micro-osmotic pump at 30 μg/kg/day for 4 weeks. The results showed that apelin increased renal blood flow by increasing phosphorylated eNOS and decreasing ET-1 in diabetic mice, which were cancelled in endothelial-specific APJ knockout mice or whole-body large conductance Ca^2 +-activated K⁺ (BKCa) channel knockout rats. Additionally, apelin/APJ activated BKCa channel via increasing expression of BKCa subunits through PI3K/AKT/GSK-3β/Nrf2 pathway but not increasing intracellular Ca²⁺ concentration under high glucose conditions. In conclusion, this study revealed that apelin/APJ increased renal blood flow in early phase of DN via increasing p-eNOS and decreasing ET-1 in glomerular endothelial cells dependent on PI3K/AKT/GSK-3β/Nrf2 pathway induced expression of BKCa subunits.