4-Hydroxy-2-nonenal cytotoxicity in renal proximal tubular cells: protein modification and redox alteration.

4-Hydroxy-2-nonenal (HNE), one of the major products of membrane lipid peroxidation, has been shown recently to be present in a form covalently attached to proteins in the renal proximal tubules of rats treated with a renal carcinogen, ferric nitrilotriacetate (Toyokuni, S., et al. (1994) Proc. Natl. Acad. Sci. USA 91, 2616-2620; Uchida, K., et al. (1995) Arch. Biochem. Biophys. 317, 405-411). In the present study, the mechanism of HNE cytotoxicity was studied using the renal tubular epithelial cells (LLC-PK1), focusing on the protein modification and alteration of cellular redox status induced by HNE. Upon treatment with HNE for 2 h, the LLC-PK1 cells were found to be resistant to the low concentration (10 microM) of HNE, while HNE at higher concentrations (> or = 50 microM) mediated cell death. The cytotoxicity of HNE appeared to be correlated with the HNE modification of cellular proteins. Among a number of proteins modified by HNE, a glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase was detected as one of the major targets of HNE in the cells. On the other hand, exposure of LLC-PK1 cells to HNE resulted in rapid reduction of cellular glutathione (GSH) levels, suggesting that HNE influenced primarily the redox status of the cells. Depletion of GSH with buthionine sulfoximine, a potent suppressor of GSH biosynthesis, before HNE treatment caused the cells to be sensitive to HNE cytotoxicity and to HNE modification of cellular proteins, whereas the increase in intracellular GSH levels by treatment with N-acetylcysteine before HNE treatment resulted in a dose-dependent inhibition of HNE-mediated protein modification. These results suggest that intracellular GSH is a determinant on cellular resistance against the HNE-mediated cytotoxicity.