Effect of water extracts of Rhizopus delemar on the stimulus coupled responses of neutrophils and their modulation by various protein kinase inhibitors

Human peripheral blood polymorphonuclear leukocytes were preincubated with water extracts from Rhizopus delemar. The water extracts significantly inhi bited arachidonic acid induced superoxide generation, whereas enhanced supe roxide generation induced by phorbol 12-myristate 13-acetate but not those induced by N-formyl-methionyl-leucyl-phenylalanine. Superoxide generation i nduced by water extracts was inhibited by staurosporine, an inhibitor of pr otein kinase C, and was enhanced by genistein, an inhibitor of tyrosine kin ase. The water extracts incubated with phorbol 12-myristate 13-acetate mark edly increased phosphorylation of serine residue of 28.5 kDa protein with t ime and the phosphorylation depended on the concentration of the water extr acts, whereas the water extracts incubated with arachidonic acid decreased the phosphorylation of serine residue of 38 and 42 kDa proteins. The phosph orylation of 28.5 kDa protein induced by the water extracts was inhibited b y staurosporine, an inhibitor of protein kinase C, but was not inhibited by genistein, an inhibitor of tyrosine kinase. (C) 1999 Elsevier Science B.V. All rights reserved.