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: Z Z Yang, A P Zou
• Journal: American journal of physiology. Renal physiology (Am J Physiol Renal Physiol) Vol. 281 Issue 5 Pg. F900-8 (Nov 2001) ISSN: 1931-857X [Print] United States
• PMID: 11592948 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Hypoxia-Inducible Factor 1, alpha Subunit
• Isoenzymes
• Leupeptins
• RNA, Messenger
• Transcription Factors
• carbobenzoxy-leucyl-leucyl-leucine
• Cobalt
• Heme Oxygenase (Decyclizing)
• cobaltous chloride

Topics

• Animals
• Blotting, Northern
• Blotting, Western
• Cell Hypoxia
• Cobalt (pharmacology)
• Gene Expression Regulation, Enzymologic (drug effects)
• Heme Oxygenase (Decyclizing) (genetics, metabolism)
• Hypoxia-Inducible Factor 1, alpha Subunit
• Isoenzymes (genetics, metabolism)
• Kidney Medulla (enzymology)
• Leupeptins (pharmacology)
• Male
• RNA, Messenger (analysis)
• Rats
• Rats, Wistar
• Transcription Factors (metabolism, pharmacology)
• Transcription, Genetic
• Transfection