摘要：

The present study hypothesized thatsuperoxide (O 2 − ·) importantly contributes to theregulation of hypoxia-inducible factor (HIF)-1 expression atposttranscriptional levels in renal medullary interstitial cells(RMICs) of rats. By Western blot analysis, it was found that incubationof RMICs with O 2 − · generators xanthine/xanthine oxidase and menadione significantly inhibited the hypoxia- or CoCl 2 -induced increase in HIF-1 levels and completelyblocked the increase in HIF-1 levels induced by ubiquitin-proteasome inhibition with CBZ-LLL in the nuclear extracts from these cells. Undernormoxic conditions, a cell-permeable O 2 − · dismutase(SOD) mimetic, 4-hydroxyl-tetramethylpiperidin-oxyl (TEMPOL) andPEG-SOD, significantly increased HIF-1 levels in RMICs. Twomechanistically different inhibitors of NAD(P)H oxidase, diphenyleneiodonium and apocynin, were also found to increase HIF-1 levels in these renal cells. Moreover, introduction of an anti-senseoligodeoxynucleotide specific to NAD(P)H oxidase subunit,p22 phox, into RMICs markedly increased HIF-1 levels. In contrast, the OH· scavenger tetramethylthiourea had noeffect on the accumulation of HIF-1 in these renal cells. ByNorthern blot analysis, scavenging or dismutation ofO 2 − · by TEMPOL and PEG-SOD was found to increase themRNA levels of an HIF-1 -targeted gene, heme oxygenase-1. Theseresults indicate that increased intracellular O 2 − ·levels induce HIF-1 degradation independently ofH 2 O 2 and OH· radicals in RMICs. NAD(P)H oxidase activity may importantly contribute to this posttranscriptional regulation of HIF-1 in these cells under physiological conditions.

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