title: 4-Hydroxy-2-nonenal-mediated impairment of intracellular proteolysis during oxidative stress. Identification of proteasomes as target molecules.
abstract: Oxidative stress is associated with important pathophysiological events in a variety of diseases. It has been postulated that free radicals and lipid peroxidation products generated during the process may be responsible for these effects because of their ability to damage cellular components such as membranes, proteins, and DNA. In the present study, we provide evidence that oxidative stress causes a transient impairment of intracellular proteolysis via covalent binding of 4-hydroxy-2-nonenal (HNE), a major end product of lipid peroxidation, to proteasomes. A single intraperitoneal treatment with the renal carcinogen, ferric nitrilotriacetate, caused oxidative stress, as monitored by accumulation of lipid peroxidation products and 8-hydroxy-2'-deoxyguanosine, in the kidney of mice. In addition, transient accumulation of HNE-modified proteins in the kidney was also found by competitive enzyme-linked immunosorbent assay and immunohistochemical analyses. This and the observation that the HNE-modified proteins were significantly ubiquitinated suggested a crucial role of proteasomes in the metabolism of HNE-modified proteins. In vitro incubation of the kidney homogenates with HNE indeed resulted in a transient accumulation of HNE-modified proteins, whereas the proteasome inhibitor significantly suppressed the time-dependent elimination of HNE-modified proteins. We found that, among three proteolytic activities (trypsin, chymotrypsin, and peptidylglutamyl peptide hydrolase activities) of proteasomes, both trypsin and peptidylglutamyl peptide hydrolase activities in the kidney were transiently diminished in accordance with the accumulation of HNE-modified proteins during oxidative stress. The loss of proteasome activities was partially ascribed to the direct attachment of HNE to the protein, based on the detection of HNE-proteasome conjugates by an immunoprecipitation technique. These results suggest that HNE may contribute to the enhanced accumulation of oxidatively modified proteins via an impairment of ubiquitin/proteasome-dependent intracellular proteolysis.
authors.affiliation: Laboratory of Food and Biodynamics, Nagoya University Graduate School of Bioagricultural Sciences, Nagoya 464-8601, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Okada
authors.forename: C
authors.initials: C
authors.lastname: Wangpoengtrakul
authors.forename: T
authors.initials: T
authors.lastname: Osawa
authors.forename: S
authors.initials: S
authors.lastname: Toyokuni
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
authors.forename: K
authors.initials: K
authors.lastname: Uchida
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000447:Aldehydes / Q000494:pharmacology*; D000818:Animals; D003546:Cysteine Endopeptidases / Q000502:physiology*; D005290:Ferric Compounds / Q000494:pharmacology; D008297:Male; D051379:Mice; D009097:Multienzyme Complexes / Q000502:physiology*; D009571:Nitrilotriacetic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D018384:Oxidative Stress; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000378:metabolism*
chemical_list: D000447:Aldehydes; D005290:Ferric Compounds; D009097:Multienzyme Complexes; D011506:Proteins; D000255:Adenosine Triphosphate; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C027576:4-hydroxy-2-nonenal; D009571:Nitrilotriacetic Acid; C020326:ferric nitrilotriacetate