OBJECTIVETo study the effect of NADPH oxidase on hypoxia-inducible factor (HIF)-1alpha and endothelin (ET)-1 expression in human umbilical endothelia cells (HUVECs) and its possible mechanism.

METHODSTwenty-five bottles of HUVECs culture fluid were randomly assigned into five groups: group A (normoxic control), group B (hypoxic), group C (NADPH oxidase inhibitor apocynin + normoxic), group D (H2O2 which can degrade HIF-1alpha rapidly+hypoxic) and group E (H2O2+apocynin+normoxic), with five bottles in each group. The culture supernates were collected and the total protein was extracted 3 hrs after treatment. Western Blot and ELISA were used to detect the HIF-1alpha protein expression in HUVECs and the ET-1 level in the culture supernates respectively.

RESULTSThere was a lower expression of HIF-1alpha protein (0.336 +/- 0.012) and lower ET-1 levels (5.87 +/- 2.22 pg/mL) in group A. The HIF-1alpha protein expression in groups B and C (0.773 +/- 0.018 and 0.888 +/- 0.022) and ET-1 levels (95.38 +/- 8.06 and 33.67 +/- 4.21 pg/mL) were noticeably higher than in group A (P < 0.05). The groups D and E had the HIF-1alpha protein expression levels similar to group A, but the ET-1 levels in group D (108.43 +/- 8.38 pg/mL) and group E (109.66 +/- 5.80 pg/mL) were significantly higher than in group A (P < 0.05).

CONCLUSIONSHypoxia or apocynin can increase the HIF-1alpha and ET-1 expression in HUVECs. H2O2 can inhibit the HIF-1alpha expression but increase the ET-1levels. It is speculated that NADPH oxidase as an oxygen sensor regulates the HIF-1alpha expression by changing the intracellular redox reaction and that except HIF-1, H2O2 might contribute to ET-1 synthesis and release.