title: Evidence for the involvement of protein kinase C inhibition by norathyriol in the reduction of phorbol ester-induced neutrophil superoxide anion generation and aggregation.
abstract: Norathyriol, a xanthone aglycone, inhibited superoxide anion (O2-) generation and O2 consumption in phorbol 12-myristate 13-acetate (PMA)-activated rat neutrophils in a concentration-dependent manner. In addition, norathyriol inhibited PMA- but enhanced formylmethionyl-leucyl-phenylalanine (fMLP)-induced neutrophil aggregation. Norathyriol suppressed neutrophil cytosolic protein kinase C as well as rat brain protein kinase C over the same range of concentrations at which it inhibited the respiratory burst. Norathyriol did not affect [3H]phorbol 12,13-dibutyrate ([3H]PDB) binding to neutrophil cytosolic protein kinase C, but effectively attenuated trypsin-treated rat brain protein kinase C activity. Moreover, norathyriol was found to be a noncompetitive inhibitor with respect to ATP and peptide substrate (N-terminal acetylated, amino acid sequence 4-14 of the myelin basic protein, Ac-MBP-(4-14)). Unlike staurosporine, norathyriol did not affect porcine heart protein kinase A activity. On the immunoblot analysis of protein kinase C subcellular distribution, the PMA-induced translocation of protein kinase C-beta from the cytosol to the membrane was not affected by norathyriol. These results show that the inhibition by a plant product, norathyriol, of PMA-induced respiratory burst and aggregation is, at least partly, attributed to the direct suppression of protein kinase C activity through blockade of the catalytic region, but is not due to interference with the membrane translocation of protein kinase C during PMA-induced cell activation.
authors.affiliation: Department of Medical Research, Taichung Veterans General Hospital, Taiwan.
authors.forename: J P
authors.initials: JP
authors.lastname: Wang
authors.forename: S L
authors.initials: SL
authors.lastname: Raung
authors.forename: L T
authors.initials: LT
authors.lastname: Tsao
authors.forename: C N
authors.initials: CN
authors.lastname: Lin
mesh_terms: D000818:Animals; D002449:Cell Aggregation / Q000187:drug effects; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects* / Q000502:physiology; D015240:Phorbol 12,13-Dibutyrate / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051381:Rats; D016897:Respiratory Burst / Q000187:drug effects*; D013481:Superoxides / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000008:administration & dosage; D014357:Trypsin; D014966:Xanthenes / Q000494:pharmacology*
chemical_list: D014966:Xanthenes; D013481:Superoxides; C069053:norathyriol; D015240:Phorbol 12,13-Dibutyrate; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D014357:Trypsin; D013755:Tetradecanoylphorbol Acetate