Cellular localization of the inhibitory action of abruquinone A against respiratory burst in rat neutrophils.
1. The possible mechanisms of action of the inhibitory effect of abruquinone A on the respiratory burst in rat neutrophils in vitro was investigated. 2. Abruquinone A caused an irreversible and a concentration-dependent inhibition of formylmethionylleucyl-phenylalanine (fMLP) plus dihydrocytochalasin B (CB)- and phorbol 12-myristate 13-acetate (PMA)-induced superoxide anion (O2.-) generation with IC50 values of 0.33 +/- 0.05 microgram ml-1 and 0.49 +/- 0.04 microgram ml-1, respectively. 3. Abruquinone A also inhibited O2 consumption in neutrophils in response to fMLP/CB and PMA. However, abruquinone A did not scavenge the generated O2.- in xanthine-xanthine oxidase system and during dihydroxyfumaric acid (DHF) autoxidation. 4. Abruquinone A inhibited both the transient elevation of [Ca2+]i in the absence of [Ca2+]o (IC50 7.8 +/- 0.2 micrograms ml-1) and the generation of inositol trisphosphate (IP3) (IC50 10.6 +/- 2.0 micrograms ml-1) in response to fMLP. 5. Abruquinone A did not affect the enzyme activaties of neutrophil cytosolic protein kinase C (PKC) and porcine heart protein kinase A (PKA). 6. Abruquinone A had no effect on intracellular guanosine 3':5'-cyclic monophosphate (cyclic GMP) levels but decreased the adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels. 7. The cellular formation of phosphatidic acid (PA) and phosphatidylethanol (PEt) induced by fMLP/ CB was inhibited by abruquinone A with IC50 values of 2.2 +/- 0.6 micrograms ml-1 and 2.5 +/- 0.3 micrograms ml-1, respectively. Abruquinone A did not inhibit the fMLP/CB-induced protein tyrosine phosphorylation but induced additional phosphotyrosine accumulation on proteins of 73-78 kDa in activated neutrophils. 8. Abruquinone A inhibited both the O2.- generation in PMA-activated neutrophil particulate NADPH oxidase (IC50 0.6 +/- 0.1 microgram ml-1) and the iodonitrotetrazolium violet (INT) reduction in arachidonic acid (AA)-activated cell-free system (IC50 1.5 +/- 0.2 micrograms ml-1) 9. Collectively, these results indicate that the inhibition of respiratory burst in rat neutrophils by abruquinone A is mediated partly by the blockade of phospholipase C (PLC) and phospholipase D (PLD) pathways, and by suppressing the function of NADPH oxidase through the interruption of electron transport.
Hsu
M F
MF
Department of Biochemistry, China Medical College, Taichung, Taiwan, Republic of China.
Raung
S L
SL
Tsao
L T
LT
Kuo
S C
SC
Wang
J P
JP
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D001578:Benzopyrans / Q000494:pharmacology*; D016227:Benzoquinones / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D018836:Inflammation Mediators / Q000037:antagonists & inhibitors; D007295:Inositol Phosphates / Q000096:biosynthesis; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors; D009504:Neutrophils / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D016897:Respiratory Burst / Q000187:drug effects*; D013481:Superoxides / Q000378:metabolism
D000894:Anti-Inflammatory Agents, Non-Steroidal; D001578:Benzopyrans; D016227:Benzoquinones; D018836:Inflammation Mediators; D007295:Inositol Phosphates; D013481:Superoxides; C093391:abruquinone A; D000242:Cyclic AMP; D019255:NADPH Oxidases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D006152:Cyclic GMP; D010100:Oxygen