Redox regulation of HIF-1alpha levels and HO-1 expression in renal medullary interstitial cells.
The present study hypothesized that superoxide (O2(-)*) importantly contributes to the regulation of hypoxia-inducible factor (HIF)-1alpha expression at posttranscriptional levels in renal medullary interstitial cells (RMICs) of rats. By Western blot analysis, it was found that incubation of RMICs with O2(-)* generators xanthine/xanthine oxidase and menadione significantly inhibited the hypoxia- or CoCl(2)-induced increase in HIF-1alpha levels and completely blocked the increase in HIF-1alpha levels induced by ubiquitin-proteasome inhibition with CBZ-LLL in the nuclear extracts from these cells. Under normoxic conditions, a cell-permeable O2(-)* dismutase (SOD) mimetic, 4-hydroxyl-tetramethylpiperidin-oxyl (TEMPOL) and PEG-SOD, significantly increased HIF-1alpha levels in RMICs. Two mechanistically different inhibitors of NAD(P)H oxidase, diphenyleneiodonium and apocynin, were also found to increase HIF-1alpha levels in these renal cells. Moreover, introduction of an anti-sense oligodeoxynucleotide specific to NAD(P)H oxidase subunit, p22(phox), into RMICs markedly increased HIF-1alpha levels. In contrast, the OH* scavenger tetramethylthiourea had no effect on the accumulation of HIF-1alpha in these renal cells. By Northern blot analysis, scavenging or dismutation of O2(-)* by TEMPOL and PEG-SOD was found to increase the mRNA levels of an HIF-1alpha-targeted gene, heme oxygenase-1. These results indicate that increased intracellular O2(-)* levels induce HIF-1alpha degradation independently of H(2)O(2) and OH* radicals in RMICs. NAD(P)H oxidase activity may importantly contribute to this posttranscriptional regulation of HIF-1alpha in these cells under physiological conditions.
Yang
Zhi-Zhang
ZZ
Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
Zhang
Andrew Y
AY
Yi
Fu-Xian
FX
Li
Pin-Lan
PL
Zou
Ai-Ping
AP
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D015687:Cell Hypoxia / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism; D002469:Cell Separation; D003035:Cobalt / Q000494:pharmacology; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D016166:Free Radical Scavengers / Q000494:pharmacology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007679:Kidney Medulla / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007976:Leupeptins / Q000494:pharmacology; D008297:Male; D019255:NADPH Oxidases / Q000378:metabolism; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis*; D015533:Transcriptional Activation; D024483:Vitamin K 3 / Q000494:pharmacology; D014969:Xanthine Oxidase / Q000494:pharmacology
D018076:DNA, Complementary; D016166:Free Radical Scavengers; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007976:Leupeptins; D020319:Oligodeoxyribonucleotides, Antisense; D017382:Reactive Oxygen Species; D014157:Transcription Factors; C098734:carbobenzoxy-leucyl-leucyl-leucine; D003035:Cobalt; D024483:Vitamin K 3; D014969:Xanthine Oxidase; D019255:NADPH Oxidases; C018021:cobaltous chloride