The role of visfatin in intermittent hypoxia-induced inflammation and endothelial dysfunction in ea.hy926 cells

Abstract

INTRODUCTION: Intermittent hypoxia (IH), a hallmark feature in obstructive sleep apnoea (OSA) may be the main culprit underlying endothelial dysfunction. Visfatin is a multifaceted adipokine, whose extracellular form can exert various effects on the vascular endothelium including inflammation, proliferation, etc. However, little is known about the role of visfatin in inflammation and endothelial dysfunction induced by IH. METHODS: IH exposure was performed in the hypoxic chamber (O2 levels: 1% for 10 mins and 21% for 5 mins in one complete cycle and 5% CO2). Intermittent normoxia (IN; 21% O2 and 5% CO2) exposure was carried out simultaneously in control cell cultures. Endothelial EA.hy926 cells were exposed to IN or IH for 96 cycles with two concentrations of visfatin (10 ng/mL and 100 ng/mL). Supernatants were collected after treatment to measure the levels of inflammation-associated markers interleukin-8 (IL-8), macrophage chemoattractant protein-1 (MCP-1), and transforming growth factor beta 1 (TGF-β1) using enzyme-linked immunosorbent assay. Cellular proteins were extracted to determine the expression of nitric oxide synthase (eNOS) and its activity in terms of phosphorylation at ser1177 (p-eNOS [Ser1177]) using Western blot. RESULTS: IH exposure induced elevation of IL-8 and MCP-1 levels and reduction of TGF-β1 level (P<0.05). Visfatin attenuated IH-induced elevation of IL-8 and MCP-1 levels and reduction of TGF-β1 level in a dose-dependent manner. Western blot analysis revealed that IH exposure significantly suppressed p-eNOS expression but not eNOS expression in EA.hy926 cells. In the presence of visfatin, no differences were found in the basal expression of p-eNOS and eNOS or in IH-induced suppression of p-eNOS. CONCLUSION: These results provided evidence that visfatin might play a pivotal role in IH-induced endothelial inflammation but not in reversing endothelial dysfunction in OSA.