title: Daphnoretin-induced respiratory burst in rat neutrophils is, probably, mainly through protein kinase C activation.
abstract: Daphnoretin, a dicoumarin isolated from Wikstroemia indica C.A. Mey. (Thymelaceae), induced superoxide anion (O2-) formation in rat neutrophils in a concentration-dependent manner. Addition of staurosporine reduced daphnoretin-induced respiratory burst. Removal of extracellular free Ca2+ by EGTA did not affect the respiratory burst of neutrophils in response to daphnoretin. Prior exposure of neutrophils to phorbol 12-myristate 13-acetate (PMA) or daphnoretin reduced the O2- formation caused by a subsequent challenge with PMA and daphnoretin, but potentiated the response caused by a subsequent addition of formyl-Met-Leu-Phe (fMLP). Like PMA, daphnoretin did not increase the [Ca2+]i during cell activation. In neutrophil suspension, daphnoretin increased the membrane associated protein kinase C activity. In the presence of Ca2+ and phosphatidyl-serine, daphnoretin also activated protein kinase C isolated from cytosolic fraction of resting neutrophils. Staurosporine inhibited the direct activation of protein kinase C caused by daphnoretin as well as by PMA. Daphnoretin reduced the [3H]Phorbol-12,13-dibutyrate ([3H]PDB) binding to the neutrophil cytosolic protein kinase C in a concentration-dependent manner with an IC50 value of 1.77 +/- 0.37 microM. These results indicate that daphnoretin, like PMA, may direct activation of protein kinase C which in turn activated NADPH oxidase and elicited respiratory burst.
authors.affiliation: Department of Medical Research, Taichung Veterans General Hospital, Taiwan, China.
authors.forename: J P
authors.initials: JP
authors.lastname: Wang
authors.forename: S L
authors.initials: SL
authors.lastname: Raung
authors.forename: Y H
authors.initials: YH
authors.lastname: Kuo
authors.forename: C M
authors.initials: CM
authors.lastname: Teng
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D003374:Coumarins / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D015240:Phorbol 12,13-Dibutyrate / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016897:Respiratory Burst / Q000187:drug effects; D013481:Superoxides / Q000378:metabolism
chemical_list: D003374:Coumarins; D013481:Superoxides; C035316:daphnoretin; D015240:Phorbol 12,13-Dibutyrate; D004533:Egtazic Acid; D011493:Protein Kinase C; D002118:Calcium