Human HIF1A adenoviral particles

Fetoplacental endothelial cells are exposed to physiological normoxic conditions (approximately 2-8% O₂) in vivo. Under these conditions, cells are thought to sense changes in O₂ primarily through hypoxia-inducible factor 1 alpha (HIF1A). However, little is known about the role of HIF1A in regulating these cellular responses in human umbilical vein endothelial cells (HUVECs) under physiological normoxic conditions. Here, researchers investigated the role of HIF1A in regulating these cellular responses in human umbilical vein endothelial cells (HUVECs). HIF1A adenovirus infection of SCN cells increased HIF1A protein expression, enhanced FGF2- and VEGFA-stimulated cell proliferation by 2.4- and 2.0-fold, respectively, and promoted VEGFA-stimulated cell migration by 1.4-fold. HIF1A adenoviral infection of SCN cells did not affect basal or FGF2- and VEGFA-induced ERK1/2 activation, but it reduced basal AKT1 phosphorylation. Interestingly, knockdown of HIF1A in PCN cells by specific HIF1A siRNA transfection did not alter FGF2- and VEGFA-stimulated cell proliferation and migration, or ERK1/2 activation. However, it inhibited FGF2-induced AKT1 activation by approximately 50%. These data suggest that HIF1A regulates cell proliferation and migration, as well as ERK1/2 and AKT1 activation, in different ways in PCN and SCN-HUVEC.

To investigate whether HIF1A regulates ERK1/2 and AKT1 activation in SCN-HUVECs, the researchers examined the phosphorylation of ERK1/2 and AKT1 after Ad-HIF1A infection by Western blotting. In cells infected with Ad-HIF1A and Ad-GFP, stimulation with FGF2 or VEGFA for up to 10 minutes increased the phosphorylation of ERK1/2 (Thr202/Tyr204). However, Ad-HIF1A infection neither further enhanced this phosphorylation induced by FGF2 and VEGFA (Figure 1A) nor altered basal ERK1/2 phosphorylation (Figure 1C). In contrast, Ad-HIF1A infection in SCN-HUVECs inhibited the basal phosphorylation of AKT1 by 63% without affecting total AKT1 protein levels (Figure 3C). Stimulation with FGF2 or VEGFA for up to 10 minutes did not significantly induce AKT1 phosphorylation (Ser473) in HUVECs infected with Ad-GFP (Figure 1B). However, infection with Ad-HIF1A enhanced FGF2-induced AKT1 phosphorylation, but not VEGFA-induced AKT1 phosphorylation (Figure 1B). These data suggest that in SCN-HUVECs, HIF1A regulates ERK1/2 and AKT1 activation in different ways in response to FGF2 and VEGFA.

Figure 1. Effects of HIF1A overexpression on ERK1/2 and AKT1 phosphorylation in SCN-HUVECs. (Jiang Y Z, et al., 2014)