title: Transcriptional regulation of heme oxygenases by HIF-1alpha in renal medullary interstitial cells.
abstract: The present study was designed to test the hypothesis that hypoxia-inducible factor-1alpha (HIF-1alpha)-mediated transcriptional activation contributes to increased expression of heme oxygenase (HO) genes in renal medullary interstitial cells (RMICs). By Northern blot analysis, HO-1 mRNA expression was found to significantly increase in response to reduction of PO(2) in culture medium. However, HO-2 mRNA was not altered by hypoxia. This hypoxia-induced upregulation of HO-1 mRNA was significantly blocked by HIF-1alpha inhibition with ferrous ammonium sulfate. To further determine the role of HIF-1alpha in the activation of HO-1, the inducers of HIF-1alpha were used to address whether induction of HIF-1alpha stimulates HO-1 mRNA expression. Both desferrioxamine and CoCl(2) markedly increased HIF-1alpha mRNA and protein levels and resulted in the upregulation of HO-1 mRNA but not HO-2. Furthermore, inhibition of HIF-1alpha degradation by CBZ-LLL, an inhibitor of ubiquitin-proteasome, significantly increased HIF-1alpha protein and HO-1 mRNA but not HO-2 in these cells. Using cis-element oligodeoxynucleotide transfection to specifically decoy HIF-1alpha and block HIF-1alpha binding, increased mRNA expression of HO-1 in response to hypoxia and CoCl(2) was attenuated. In vitro nuclear run-on assays further confirmed that hypoxia and alterations of HIF-1alpha mRNA or protein levels significantly affected the formation of HO-1 mRNA. Taken together, our results indicate that HO-1, but not HO-2, is transcriptionally activated by hypoxia through HIF-1alpha-mediated mechanism in RMICs. This hypoxia-induced transcriptional activation may be one of the important mechanisms mediating increased expression of HO-1 in the renal medulla.
authors.affiliation: Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
authors.forename: Z Z
authors.initials: ZZ
authors.lastname: Yang
authors.forename: A P
authors.initials: AP
authors.lastname: Zou
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D015687:Cell Hypoxia; D003035:Cobalt / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics* / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism; D007679:Kidney Medulla / Q000201:enzymology*; D007976:Leupeptins / Q000494:pharmacology; D008297:Male; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D014157:Transcription Factors / Q000378:metabolism / Q000494:pharmacology*; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007527:Isoenzymes; D007976:Leupeptins; D012333:RNA, Messenger; D014157:Transcription Factors; C098734:carbobenzoxy-leucyl-leucyl-leucine; D003035:Cobalt; D006419:Heme Oxygenase (Decyclizing); C018021:cobaltous chloride