Involvement of reactive oxygen intermediates in lectin-induced protein-tyrosine phosphorylation of Syk in THP-1 cells.

Oxidative stress (H2O2) has been shown to be associated with tyrosine phosphorylation and activation of protein-tyrosine kinase Syk. In the present study, we examined the possibility that reactive oxygen intermediates (ROI) were involved in concanavalin A (Con A)-induced tyrosine phosphorylation in THP-1 cells. Rapid tyrosine phosphorylations of Syk, Fc gamma receptor(s) and phospholipase C gamma 2 (PLC gamma 2) were induced by Con A treatment in THP-1 cells. Pretreatment of cells with antioxidants N-acetylcysteine (NAC) and glutathione (GSH) almost completely blocked tyrosine phosphorylations of Syk, Fc gamma receptor(s) and PLC gamma 2. In addition, THP-1 cells showed significant levels of ROI from the early period of Con A treatment and the levels of ROI were inhibited by antioxidant treatment. These data suggest that ROI have an important role in Con A-induced protein-tyrosine kinase(s) signaling pathways.