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Effect of chronic alcohol administration on catalase expression.
Andres Caro, Shameela Khimani, Zacchary Branscum and Grover Miller
Chemistry Department, Hendrix College, Conway, AR 72032
Background and Objective: Chronic alcohol intake induces hepatic oxidative stress, characterized
by increased concentration of reactive oxygen species including hydrogen peroxide. Hepatic
hydrogen peroxide is detoxified by catalase, an enzyme that catalyzes the dismutation of
hydrogen peroxide into molecular oxygen and water. The effects of chronic alcohol on hepatic
catalase activity are not clear, with reports of increased catalase and decreased catalase activity.
In this work, we evaluated the effect of chronic alcohol administration on hepatic catalase activity.
Methods: Mice received a liquid ethanol diet for 21 days, with ethanol at 36% calories; pair-fed
control mice received an isocaloric liquid diet without ethanol.
Results: Hepatic catalase activity increased three-fold in alcohol-fed mice with respect to the
controls. Catalase mRNA levels measured by reverse-transcriptase PCR and protein levels
evaluated by western blot did not change after alcohol administration. Because catalase activity
can be upregulated by phosphorylation on critical serine/threonine or tyrosine residues, the
phosphorylation state of catalase was evaluated by immunoblotting for phospho serine/threonine
or tyrosine residues in immunoprecipitated catalase. Preliminary experiments did not show
significant differences in phosphorylation between hepatic catalase isolated from ethanol- and
control-fed animals.
Discussion and Conclusions: These results suggest that alcohol administration induces hepatic
catalase activity as part of an antioxidant response. The mechanism for this induction might
involve post-translational modifications, which are currently being evaluated by proteomic
techniques.
Grant Support: The study was supported by grants from the National Center for Research
Resources (5P20RR16460-11) and the National Institute of General Medical Sciences (8P20
GM103429-11).