title: Edema-inducing activity of phospholipase A2 purified from human synovial fluid and inhibition by aristolochic acid.
abstract: A neutral-active, Ca2+-dependent phospholipase A2 (PLA2) purified 11,000-fold from human synovial fluid (HSF) induced edema when injected into the mouse foot pad. The edema produced by HSF-PLA2 was dose-dependent and was positively correlated with the dose-dependent in vitro expression of PLA2 activity. Maximum edema was achieved within 45 min after the injection and persisted for at least 6 h. Aristolochic acid [8-methoxy-6-nitrophenanthro(3,4-d)-1,3-dioxole-5-carboxylic acid], a major chemical component derived from various species of Aristolochia plant, produced a dose-dependent inhibition of in vitro phospholipid hydrolysis by HSF-PLA2, porcine pancreatic PLA2, snake venom (Naja naja) PLA2, and PLA2 isolated from human platelet. The sensitivity of these PLA2s to inhibition by aristolochic acid varied markedly: HSF-PLA2 greater than N. naja PLA2 greater than human platelet PLA2 greater than porcine pancreatic PLA2. The inhibition of HSF-PLA2 by aristolochic acid was independent of substrate concentration (18-144 microM) and Ca2+ concentration (0.1-4.0 mM). These observations indicate that inhibition of HSF-PLA2 by aristolochic acid may result from direct interaction with the enzyme. When aristolochic acid was mixed with HSF-PLA2 and then injected into the mouse foot pad, edema was inhibited in a dose-dependent manner and was positively correlated with in vitro inhibition of PLA2 activity. Alkylation of HSF-PLA2 with p-bromophenacyl bromide concomitantly inhibited both enzyme and edema-inducing activity. These results clearly demonstrate that the neutral-active, Ca2+-dependent PLA2 isolated from human synovial fluid is proinflammatory and that catalytic activity is positively correlated with in vivo proinflammatory effects.
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298-0614.
authors.forename: B S
authors.initials: BS
authors.lastname: Vishwanath
authors.forename: A A
authors.initials: AA
authors.lastname: Fawzy
authors.forename: R C
authors.initials: RC
authors.lastname: Franson
mesh_terms: D000098:Acetophenones / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D034341:Aristolochic Acids; D004487:Edema / Q000139:chemically induced* / Q000188:drug therapy; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D010616:Phenanthrenes / Q000378:metabolism / Q000494:pharmacology*; D010740:Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000633:toxicity*; D013582:Synovial Fluid / Q000378:metabolism*
chemical_list: D000098:Acetophenones; D034341:Aristolochic Acids; D010616:Phenanthrenes; C000228:aristolochic acid I; D010740:Phospholipases; C006821:4-bromophenacyl bromide