SB 203347, an inhibitor of 14 kDa phospholipase A2, alters human neutrophil arachidonic acid release and metabolism and prolongs survival in murine endotoxin shock.
Phospholipase A2 (PLA2) catalyzes the hydrolysis of the sn-2 fatty acyl group [predominantly arachidonic acid (AA)] of membrane phospholipids, the products of which are further metabolized, forming a variety of eicosanoids and/or platelet-activating factor. PLA2 activity is significantly enhanced during inflammation and therefore offers an intriguing target in designing anti-inflammatory drugs. SB 203347 (2-[2-[3,5-bis (trifluoromethyl) sulfonamido]-4- trifluoromethylphenoxy] benzoic acid) potently inhibits rh type II 14 kDa PLA2 (IC50 = 0.5 microM) but exhibits a 40-fold weaker inhibition of 85 kDa PLA2 (IC50 = 20 microM) using [3H]-AA E. coli as substrate. A specific interaction with rh type II 14 kDa PLA2 was confirmed both by observing the pH dependence of its IC50 and by demonstrating linear inhibition in a "scooting" kinetic model using radiolabeled phospholipid reporter substrate in a 1,2-dimyristoyl phosphatidylmethanol vesicle. Before evaluating the effect of SB 203347 on AA metabolism in intact human neutrophil, we showed that it fully inhibits PLA2 activity in acid extracted-intact human neutrophil homogenate (IC50 = 4.7 microM). SB 203347 inhibited A23187-induced intact human neutrophil AA mass release in a concentration-dependent manner (IC50 = 1 microM), which coincided with reductions in the biosynthesis of platelet-activating factor (IC50 = 1.5 microM) and leukotriene B4 (IC50 = 2.3 microM). Finally, SB 203347 prolonged survival in a mouse model of endotoxin shock delivered i.p. Taken together, the data support a role of cellular 14 kDa PLA2 in the formation of AA-derived proinflammatory lipid mediator.(ABSTRACT TRUNCATED AT 250 WORDS)
Marshall
L A
LA
Department of Inflammation & Respiratory Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania, USA.
Hall
R H
RH
Winkler
J D
JD
Badger
A
A
Bolognese
B
B
Roshak
A
A
Flamberg
P L
PL
Sung
C M
CM
Chabot-Fletcher
M
M
Adams
J L
JL
D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D002474:Cell-Free System; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D007975:Leukotriene B4 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000633:toxicity; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009504:Neutrophils / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010741:Phospholipases A / Q000037:antagonists & inhibitors*; D054467:Phospholipases A2; D010972:Platelet Activating Factor / Q000096:biosynthesis; D012772:Shock, Septic / Q000139:chemically induced / Q000378:metabolism* / Q000401:mortality; D013449:Sulfonamides / Q000494:pharmacology*; D017741:Survivors
D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D010972:Platelet Activating Factor; C095801:SB 203347; D013449:Sulfonamides; D007975:Leukotriene B4; D016718:Arachidonic Acid; D010741:Phospholipases A; D054467:Phospholipases A2; D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase