Interleukin-1β mediates high glucose induced phenotypic transition in human aortic endothelial cells

BACKGROUND: Previous studies have shown that high glucose (HG) induced endothelial cell (EC) damage via a phenotypic transition of EC. There is increasing evidence suggesting the role of inflammatory cytokines in mediated HG-induced EC damage. However, little is known about the potential role of interleukin-1β (IL-1β) in the process. The aim of present study was to investigate whether IL-1β mediated HG–induced phenotypic transition in human aortic endothelial cells (HAECs) and to determine the possible underlying mechanism. METHODS: Primary HAECs were exposed to normal glucose (NG, 5.5 nM), high glucose (HG,30 nM), IL-1β (10 ng/ml), HG + IL-1β (10 ng/ml) and HG + anti-IL-1β antibodies (1000 ng/ml) or HG + IL-1β small interfering RNA (siRNA). Pathological changes were investigated using confocal microscopy and electron microscopy. Confocal microscopy was performed to detect the co-expression of CD31 and fibroblast specific protein 1 (FSP1). To study the effect of protein kinase C-β (PKCβ) activation on IL-1β in HAECs, HAECs were stimulated with 30 nM PMA (PKCβ activator) and 0.3 μM PKCβ inhibition (LY317615) for 48 h in the NG or HG group. The expressions of PKCβ and IL-1β were detected by RT-PCR and Western blot. And the concentration of IL-1β in the supernatant of HAECs was measured by ELISA. The expressions of FSP1, a-SMA and CD31 were detected by Western blot. RESULTS: It was shown that the HG resulted in significant increase in the expressions of PKCβ and IL-1β in dose-and time-dependent manners. The HG or exogenous IL-1β alone inhibited the expression of CD31 and markly increased the expressions of FSP1 and α-SMA. Furthermore, we observed that the HG and IL-1β synergistically increased FSP1 and a-SMA expressions compared with the HG or IL-1β alone group (P < 0.05). Confocal microscopy revealed a colocalization of CD31 and FSP1 and that some cells acquired spindle-shaped morphologies and a loss of CD31 staining. Electron microscopy showed that the HG resulted in the increased microfilamentation and a roughened endoplasmic reticulum structure in the cytoplasm. However, the changes above were attenuated by the intervention of anti-IL-1β antibodies or IL-1β siRNA (P < 0.05). In addition, the PMA induced the expressions of PKCβ and IL-1β in HAECs. The PKCβ activation may mediate the effect of the HG on IL-1β production, which could be attenuated by the PKCβ selective inhibitor (LY317615) (P < 0.05). CONCLUSIONS: Our findings suggested that HG-induced phenotypic transition of HAECs might require IL-β activation via the PKCβ pathway.