title: Basal protein phosphorylation is decreased and phosphatase activity increased by an antioxidant and a free radical trap in primary rat glia.
abstract: Reversible protein phosphorylation regulates a wide array of cellular functions. Cells respond to cytokines and various stressors via phosphorylation and thus activation of one or more of the mitogen-activated protein kinase (MAPK) pathways. Involvement of these signal transduction pathways has been implicated in numerous pathologies, including inflammation. Using a primary glia cell culture, we show here that the antioxidant N-acetylcysteine (NAC) and the nitrone-based free radical trap, alpha-phenyl-N-tert-butyl nitrone (PBN), reduce total basal protein phosphorylation in a concentration-dependent manner as assessed by phosphotyrosine analysis and by [gamma-32P]ATP transfer radioassay. In addition we show that NAC inhibits H2O2-induced phosphatase inactivation in glia cell lysate. The PBN- and NAC-induced reduction in protein phosphorylation is accompanied by an increase in phosphatase activity, suggesting that PBN and NAC reduce protein phosphorylation by globally augmenting oxidant-sensitive phosphatase activities. These results partly explain why certain antioxidants also possess anti-inflammatory actions.
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D000975:Antioxidants / Q000494:pharmacology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism; D003497:Cyclic N-Oxides; D004789:Enzyme Activation; D016166:Free Radical Scavengers / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007700:Kinetics; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009457:Neuroglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009589:Nitrogen Oxides / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction