Abstract
The biological significance of the heme oxygenase (HO) system's response to stress reflects functions of its products—CO and bile pigments. CO is a messenger molecule, whereas bile pigments are antioxidants and modulators of cell signaling. Presently, an unexpected mechanism for sustained suprainduction of renal HO-1 following ischemia/reperfusion injury is described. Inhibition of nitric-oxide synthase (NOS) activity by Nω-nitro-l-arginine methyl ester (l-NAME) at the resumption of reperfusion of rat kidney subjected to bilateral ischemia (30 min) was as effective as the most potent HO-1 inducer, the spin trap agent n-tert-butyl-α-phenyl nitrone (PBN), in causing sustained suprainduction of HO-1 mRNA. PBN forms stable radicals of oxygen and nitrogen. Twenty-four hours after reperfusion, HO-1 mRNA measured ∼30-fold that of the control in the presence of l-NAME treatment; in its absence, the transcript increased to only ∼5-fold. At 4 h in the presence or absence of the l-NAME HO-1, mRNA was increased by ∼30-fold. The transcript was translated to active protein as indicated by Western blotting, immunohistochemistry, and activity analyses. l-NAME was not effective given 1 h after resumption of reperfusion. Suprainduction was restricted to the kidney and not detected in the heart and aorta; ferritin expression in the kidney was not effected. It is reasoned that in tissue directly insulted by ischemia/reperfusion, increased production of NO radicals promotes the loss of HO-1 transcript. Because the absence of NO radicals and presence of PBN had a similar effect on HO-1, we propose that suprainduction of the gene is mainly caused by O2 radicals formed on reperfusion. Inhibition of NOS is potentially useful for sustained induction of HO-1 in organs that will be subjected to oxidative-stress insult.
Footnotes
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This study was supported by National Institutes of Health Grants NS 41043, DK393087, and ES04066.
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DOI: 10.1124/jpet.102.048686.
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ABBREVIATIONS: HO, heme oxygenase; NOS, nitric-oxide synthase; PBN, n-tert-butyl-α-phenyl nitrone; l-NAME, Nω-nitro-l-arginine methyl ester; GST, glutathione S-transferase.
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↵1 Current address: Graduate School of Peking, University Health Science Center, Beijing, China.
- Received January 2, 2003.
- Accepted April 3, 2003.
- The American Society for Pharmacology and Experimental Therapeutics
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