Effect of Phosphotyrosine Proteins on Phorbol Myristate Acetate-Induced NADPH Oxidase Activation in Guinea Pig Peritoneal Polymorphonuclear Leukocytes

Abstract

Phorbol myristate acetate (PMA)-induced superoxide radical (O(2)(-))-production in guinea pig peritoneal polymorphonuclear leukocytes (PMNs) was significantly lower than that in peripheral cells. To determine the role of phosphotyrosine proteins in the lower O(2)(-) production, the effect of ST638 and genistein, tyrosine kinase inhibitors, on PMA-induced O(2)(-) production in peritoneal PMNs was examined. PMA-induced O(2)(-)-production of the cells was increased by the pretreatment with ST638 or genistein, the increment depending on the inhibitor concentration. The p47phox level in the plasma membrane of PMA-stimulated PMNs was increased by the pretreatment with ST638, although the phosphorylated p47phox level in the cells was not altered by ST638. On the other hand, PMA-induced O(2)(-)-production of peripheral PMNs was not affected by the pretreatment with ST638, but that of cytochalasin B (CB)-primed peripheral PMNs significantly increased by further treatment with ST638. The phosphotyrosine protein level of peritoneal PMNs was higher than that of the peripheral cells, especially in cytosolic proteins including 50-60 and 70-85 kDa proteins, and that of the CB-primed peripheral cells was also higher than that of the intact cells in similar cytosolic proteins to those above. Further treatment of CB-primed peripheral cells with ST638 resulted in a lower level of phosphotyrosine proteins. These findings suggest that phosphorylation of some protein(s) at specific tyrosine residues inhibits the translocation of p47phox to the plasma membrane from the cytosol, resulting in lower O(2)(-)-generation in casein-induced peritoneal exudate PMNs.

Naturally Occurring and Synthetic Agents as Potential Anti-Inflammatory and Immunomodulants

“…The catalytic activity of this enzyme is dependent on assembly of all of its cytosolic components to the membrane. At resting state, these components are distributed between membrane and cytosol [77] but when the cell is exposed to appropriate inflammatory stimuli or agents like N-formyl-methionyl-leucyl-phenylalanine (fMLP) or phorobol myristate acetate (a protein kinase c activator) or opsonized zymosan, all the cytosolic components are translocated to membrane that catalyzes the oneelectron reduction of oxygen to at the expense of NADPH.…”