The expression of brain cyclooxygenase-2 is down-regulated in the cytosolic phospholipase A2 knockout mouse.
We examined brain phospholipase A2 (PLA2) activity and the expression of enzymes metabolizing arachidonic acid (AA) in cytosolic PLA2 knockout () mice to see if other brain PLA2 can compensate for the absence of cPLA2 alpha and if cPLA2 couples with specific downstream enzymes in the eicosanoid biosynthetic pathway. We found that the rate of formation of prostaglandin E2 (PGE2), an index of net cyclooxygenase (COX) activity, was decreased by 62% in the compared with the control mouse brain. The decrease was accompanied by a 50-60% decrease in mRNA and protein levels of COX-2, but no change in these levels in COX-1 or in PGE synthase. Brain 5-lipoxygenase (5-LO) and cytochrome P450 epoxygenase (cyp2C11) protein levels were also unaltered. Total and Ca2+-dependent PLA2 activities did not differ significantly between and control mice, and protein levels of type VI iPLA2 and type V sPLA2, normalized to actin, were unchanged. These results show that type V sPLA2 and type VI iPLA2 do not compensate for the loss of brain cPLA2 alpha, and that this loss has significant downstream effects on COX-2 expression and PGE2 formation, sparing other AA oxidative enzymes. This suggests that cPLA2 is critical for COX-2-derived eicosanoid production in mouse brain.
Bosetti
Francesca
F
Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892, USA. frances@mail.nih.gov
Weerasinghe
Gayani R
GR
D058927:5-Lipoxygenase-Activating Proteins; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000166:cytology / Q000201:enzymology*; D002352:Carrier Proteins / Q000378:metabolism; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D000072467:Cytochrome P450 Family 2; D003600:Cytosol / Q000201:enzymology; D015232:Dinoprostone / Q000378:metabolism; D015536:Down-Regulation; D015971:Gene Expression Regulation, Enzymologic; D024601:Glyceraldehyde 3-Phosphate Dehydrogenase (NADP+) / Q000235:genetics / Q000378:metabolism; D054513:Group IV Phospholipases A2; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010741:Phospholipases A / Q000235:genetics / Q000378:metabolism*; D054467:Phospholipases A2; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D011459:Prostaglandins E, Synthetic / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D039181:Steroid 16-alpha-Hydroxylase / Q000378:metabolism
D058927:5-Lipoxygenase-Activating Proteins; C548593:Alox5ap protein, mouse; C548594:Alox5ap protein, rat; D002352:Carrier Proteins; D007527:Isoenzymes; D008565:Membrane Proteins; D011459:Prostaglandins E, Synthetic; D012333:RNA, Messenger; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C496512:Ptgs1 protein, mouse; D024601:Glyceraldehyde 3-Phosphate Dehydrogenase (NADP+); D010741:Phospholipases A; D054513:Group IV Phospholipases A2; D054467:Phospholipases A2; D015232:Dinoprostone