Hypoxia-induced hyperpermeability of rat glomerular endothelial cells involves HIF-2 alpha mediated changes in the expression of occludin and ZO-1

This study aimed to investigate the role of hypoxia-inducible factor-2 alpha (HIF-2 alpha) in the expression of tight junction proteins and permeability alterations in rat glomerular endothelial cells (rGENCs) under hypoxia conditions. The expression level of HIF-2 alpha and tight junction proteins (occludin and ZO-1) in rGENCs were examined following 5% oxygen density exposure at different treatment times. HIF-2 alpha lentivirus transfection was used to knockdown HIF-2 alpha expression. Cells were divided into four groups: 1) control group (rGENCs were cultured under normal oxygen conditions), 2) hypoxia group (rGENCs were cultured under hypoxic conditions), 3) negative control group (rGENCs were infected with HIF-2 alpha lentivirus negative control vectors and cultured under hypoxic conditions), and 4) Len group (rGENCs were transfected with HIF-2 alpha lentivirus and cultured under hypoxic conditions). The hypoxia, negative control, and Len groups were kept in a hypoxic chamber (5% O-2, 5% CO2, and 90% N-2) for 24 h and the total content of occludin and ZO-1, and the permeability of rGENCs were assessed. With increasing hypoxia time, the expression of HIF-2 alpha gradually increased, while the expression of occludin decreased, with a significant difference between groups. ZO-1 expression gradually decreased under hypoxia conditions, but the difference between the 24 and 48 h groups was not significant. The permeability of cells increased following 24-h exposure to hypoxia compared to the control group (P<0.01). The knockdown of HIF-2 alpha expression significantly increased occludin and ZO-1 content compared with hypoxia and negative control groups (P<0.01), while permeability was reduced (P<0.01). Hypoxia increased HIF-2 alpha content, inducing permeability of rGENCs through the reduced expression of occludin and ZO-1.