Urea and hypertonicity increase expression of heme oxygenase-1 in murine renal medullary cells

• Published in: American journal of physiology. Renal physiology Vol. 281; no. 5; pp. F983 - F991
• Main Authors: Tian, W, Bonkovsky, H L, Shibahara, S, Cohen, D M
• Format: Journal Article
• Language: English
• Published: United States 01.11.2001
• Subjects: 3T3 Cells; Animals; beta-Galactosidase - genetics; Cell Line; Chickens; Fluoresceins - metabolism; Gene Expression - drug effects; Half-Life; Heme Oxygenase (Decyclizing) - genetics; Heme Oxygenase (Decyclizing) - metabolism; Heme Oxygenase-1; Humans; Immunoblotting; Kidney Medulla - enzymology; Membrane Proteins; Mice; Oxidative Stress; Promoter Regions, Genetic; RNA, Messenger - analysis; Saline Solution, Hypertonic - pharmacology; Spectrometry, Fluorescence; Transfection; Urea - pharmacology
• ISSN: 1931-857X; 1522-1466
• DOI: 10.1152/ajprenal.0358.2000

Epithelial cells derived from the mammalian kidney medulla are responsive to urea at the levels of signal transduction and gene regulation. Hybridization of RNA harvested from control- and urea-treated murine inner medullary collecting duct (mIMCD3) cells with a cDNA expression array encoding stress-responsive genes suggested that heme oxygenase (HO)-1 mRNA was upregulated by urea. RNase protection assay confirmed this upregulation; hypertonicity also increased HO-1 mRNA expression but neither hypertonic NaCl nor urea were effective in the nonrenal 3T3 cell line. The effect on HO-1 expression appeared to be transcriptionally mediated on the basis of mRNA half-life studies and reporter gene analyses using the promoters of both human and chicken HO-1. Although urea signaling resembles that of heavy metal signaling in other contexts, the effect of urea on HO-1 transcription was independent of the cadmium response element in this promoter. Urea-inducible HO-1 expression was sensitive to antioxidants but not to scavengers of nitric oxide. Urea also upregulated HO-1 protein expression and pharmacological inhibition of HO-1 action with zinc protoporphyrin-sensitized mIMCD3 cells to the adverse effects of hypertonicity but not to urea. Coupled with the prior observation of others that HO-1 expression increases along the renal corticomedullary gradient, these data suggest that HO-1 expression may comprise an element of the adaptive response to hypertonicity and/or urea in renal epithelial cells.