Platelet activating factor and endotoxin increase the enzyme activity and gene expression of type II phospholipase A2 in the rat intestine. Role of polymorphonuclear leukocytes.
Type II phospholipase A2 (PLA2-II) may regulate eicosanoid synthesis; is involved in various inflammatory processes, septic shock, and inflammatory bowel disease; and is up-regulated by LPS and inflammatory cytokines in vitro. We have previously shown that the platelet-activating factor (PAF)-induced intestinal injury is attenuated by peptido-leukotriene antagonists, suggesting a role of PLA2. The purpose of this study is to examine the regulation of intestinal PLA2-II by PAF and LPS. Using synthesized competitor RNA as competitor, we quantified PLA2-II transcripts by competitive reverse transcription-PCR. We found that PLA2-II gene is constitutively expressed in the rat ileum. PAF at a dose (1.5 micrograms/kg) below that causing intestinal injury rapidly up-regulated intestinal PLA2-II at both transcriptional and post-transcriptional levels, almost tripling its transcripts and significantly increasing enzyme activity in 30 min. LPS (5 mg/kg) also up-regulated PLA2-II. This effect could not be blocked by PAF antagonist. Depletion of circulating polymorphonuclear leukocytes (PMNs) abolished the effect of PAF on PLA2-II gene expression and enzyme activation. In contrast, PMN depletion prevented LPS-induced PLA2-II enzyme activity but enhanced the gene expression. We conclude that: 1) both PAF and LPS induce gene transcription and enzyme activation of PLA2-II in the small intestine; 2) PAF up-regulates PLA2-II via PMN activation; 3) LPS effect is independent of endogenous PAF formation; and 4) different pathways exist for PAF and LPS in the regulation of intestinal PLA2-II gene expression in vivo.
Tan
X D
XD
Department of Pathology, Children's Memorial Hospital, Chicago, IL 60614, USA.
Wang
H
H
Gonzalez-Crussi
F X
FX
Chang
H
H
Gonzalez-Crussi
F
F
Hsueh
W
W
D000818:Animals; D001483:Base Sequence; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D007421:Intestine, Small / Q000201:enzymology*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D010741:Phospholipases A / Q000187:drug effects / Q000235:genetics*; D054467:Phospholipases A2; D010972:Platelet Activating Factor / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology*
D008070:Lipopolysaccharides; D010972:Platelet Activating Factor; D010741:Phospholipases A; D054467:Phospholipases A2