|Thannhauser, Theodore - Ted|
|Lei, Xin Gen|
Submitted to: Journal of Free Radical Biology and Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2008
Publication Date: 5/20/2008
Citation: Zhu, J., Zhang, X., Roneker, C.A., Mcclung, J.P., Zhang, S., Thannhauser, T.W., Ripoll, D.R., Sun, Q., Lei, X. 2008. ROLE OF COPPER,ZINC-SUPEROXIDE DISMUTASE IN CATALYZING NITROTYROSINE FORMATION IN MURINE LIVER. Journal of Free Radical Biology and Medicine. 45:611-618. Interpretive Summary: The phenomenon of protein nitration is of great biological importance due to its potential to in activate or alter the function of the modified proteins. Protein nitration has been implicated in the development of certain diseases such as amyotrophic lateral scleorsis, Alzheimer disease and acetaminophen-induced hepatotoxicity. The catalytic role of copper, zinc superoxide dismutaste (SOD1) in in vitro protein nitration has been known for more than 10 years. Nevertheless, despite the potential pathological implications, this evidence has been largely dismissed or ignored due to the lack of any direct experimental evidence linking SOD1 and protein nitration in vivo. Such evidence has been difficult to obtain due to the short biological half-life of the reactants and the lack of specific in vivo models. However, the development of SOD1 knockout mice (SOD1 -/-) and the demonstration that certain substances (such as acetaminophen and lipopolysaccharide) can induce protein nitration in tissues have provided the opportunity to study the role of SOD1 on protein nitration in vivo. The data presented demonstrates that SOD1 activity is essential for the catalysis of acetaminophen and lipopolysaccharide-induced hepatic protein nitration in mice in vivo. This activity appears to be directed, is due to the SOD1 activity alone and is not directly related to NO concentration, peroxynitrite availability or secondary alterations associated with the SOD1 -/- phenotype.
Technical Abstract: The solely known function of Cu,Zn-superoxide dismutase (SOD1) is to catalyze the dismutation of superoxide anion into hydrogen peroxide. Our objective was to determine if SOD1 catalyzed murine liver protein nitration induced by acetaminophen (APAP) and lipopolysaccharide (LPS). Liver and plasma samples were collected from young adult SOD1 knockout mice (SOD1-/-) and wild-type (WT) mice at 5 or 6 h after an ip injection of saline, APAP or LPS. Hepatic nitrotyrosine formation was induced by APAP and LPS only in the WT mice. The lack of hepatic protein nitration in the SOD1-/- mice was not directly related to plasma nitrite and nitrate concentrations. Similar genotype differences were seen in liver homogenates treated with a bolus of peroxynitrite. Adding the holo, but not the apo-SOD1 enzyme into the liver homogenates enhanced the reaction in an activity-dependent fashion and nearly eliminated the genotype difference at the high doses. Mass Spectrometry showed 4 more nitrotyrosine residues in bovine serum albumin and 10 more nitrated protein candidates in the SOD1-/- liver homogenates by peroxynitrite in the presence of SOD1. In conclusion, the diminished hepatic protein nitration mediated by APAP or LPS in the SOD1-/- mice was due to the lack of SOD1 activity per se.