Bosetti Francesca, Weerasinghe Gayani R
Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Neurochem. 2003 Dec;87(6):1471-7. doi: 10.1046/j.1471-4159.2003.02118.x.
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.
我们检测了胞质型磷脂酶A2（cPLA2）基因敲除小鼠脑内磷脂酶A2（PLA2）的活性以及代谢花生四烯酸（AA）的酶的表达，以探究其他脑内PLA2是否能补偿cPLA2α的缺失，以及cPLA2是否与类花生酸生物合成途径中的特定下游酶偶联。我们发现，与对照小鼠脑相比，前列腺素E2（PGE2）的生成速率（净环氧化酶（COX）活性的指标）在cPLA2基因敲除小鼠中降低了62%。这种降低伴随着COX-2的mRNA和蛋白水平下降50 - 60%，但COX-1或PGE合酶的这些水平没有变化。脑内5-脂氧合酶（5-LO）和细胞色素P450环氧化酶（cyp2C11）的蛋白水平也未改变。cPLA2基因敲除小鼠与对照小鼠之间的总PLA2活性和Ca2+依赖性PLA2活性没有显著差异，以肌动蛋白标准化后的VI型iPLA2和V型sPLA2的蛋白水平也没有变化。这些结果表明，V型sPLA2和VI型iPLA2不能补偿脑内cPLA2α的缺失，且这种缺失对COX-2的表达和PGE2的生成有显著的下游影响，而其他AA氧化酶未受影响。这表明cPLA2对小鼠脑内COX-2衍生的类花生酸生成至关重要。
