Vishwanath B S, Frey F J, Escher G, Reichen J, Frey B M
Division of Nephrology, Department of Medicine, University of Berne, Switzerland.
J Clin Invest. 1996 Jul 15;98(2):365-71. doi: 10.1172/JCI118801.
Maintenance of renal function in liver cirrhosis requires increased synthesis of arachidonic acid derived prostaglandin metabolites. Arachidonate metabolites have been reported to be involved in modulation of liver damage. The purpose of the present study was to establish whether the first enzyme of the prostaglandin cascade synthesis, the phospholipase A2(PLA2) is altered in liver cirrhosis induced by bile duct excision. The mRNA of PLA2(group I and II) and annexin-I a presumptive inhibitor of PLA2 enzyme was measured by PCR using glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as an internal standard. The mean mRNA ratio of group II PLA2/GAPDH was increased in liver tissue by 126% (P < 0.001) and in kidney tissue by 263% (P < 0.006) following induction of liver cirrhosis. The increase in group II PLA2 mRNA in cirrhotic animals was reflected by an increase in PLA2 protein and enzyme activity in both liver and kidney tissues. Since the mRNA of group I PLA2 was not detectable and Group IV PLA2 activity measured in liver and kidney tissue samples was very low and not changed following induction of cirrhosis, it is likely that the major PLA2 activity measured in liver and kidney corresponds to group II PLA2 enzyme. The mean mRNA ratio of annexin-I/GAPDH was increased in liver tissue by 115% (P < 0.05) but unchanged in kidney tissue following induction of cirrhosis. The protein content of annexin-I and -V were not affected by bile duct excision in liver and kidney tissue indicating that upregulation of group II PLA2 activity was not due to downregulation of annexin-I or -V. Group II PLA2 activity of glomerular mesangial cells stimulated by interleukin-1 beta was enhanced by bile juice and various bile salts. In conclusion, activity of group II PLA2 is upregulated partly due to enhanced transcription and translation in cirrhosis and is furthermore augmented by elevated levels of bile salts.
肝硬化患者肾功能的维持需要增加花生四烯酸衍生的前列腺素代谢产物的合成。据报道，花生四烯酸代谢产物参与了肝损伤的调节。本研究的目的是确定前列腺素级联合成的第一种酶——磷脂酶A2（PLA2）在胆管切除诱导的肝硬化中是否发生改变。以甘油醛-3-磷酸脱氢酶（GAPDH）作为内标，通过PCR测定PLA2（I组和II组）和膜联蛋白-I（一种推测的PLA2酶抑制剂）的mRNA。肝硬化诱导后，肝组织中II组PLA2/GAPDH的平均mRNA比值增加了126%（P<0.001），肾组织中增加了263%（P<0.006）。II组PLA2 mRNA在肝硬化动物中的增加反映在肝和肾组织中PLA2蛋白和酶活性的增加。由于未检测到I组PLA2的mRNA，且在肝和肾组织样本中测得的IV组PLA2活性非常低，且在肝硬化诱导后未发生变化，因此肝和肾中测得的主要PLA2活性可能对应于II组PLA2酶。肝硬化诱导后，肝组织中膜联蛋白-I/GAPDH的平均mRNA比值增加了115%（P<0.05），但肾组织中未发生变化。肝和肾组织中膜联蛋白-I和-V的蛋白质含量不受胆管切除的影响，这表明II组PLA2活性的上调不是由于膜联蛋白-I或-V的下调。胆汁和各种胆盐可增强白细胞介素-1β刺激的肾小球系膜细胞的II组PLA2活性。总之，II组PLA2的活性部分由于肝硬化中转录和翻译的增强而上调，并且进一步被胆盐水平的升高所增强。
