Alkhunaizi A M, Yaqoob M M, Edelstein C L, Gengaro P E, Burke T J, Nemenoff R A, Schrier R W
Department of Medicine, University of Colorado Health Sciences Center, Denver, USA.
Kidney Int. 1996 Mar;49(3):620-5. doi: 10.1038/ki.1996.89.
Free fatty acids (FFA) and lysophospholipids accumulate during hypoxia (H) in rat proximal tubular epithelial cells partly as a result of increased phospholipase A2 (PLA2) activity. The role of FFA in mediating hypoxic injury and modulating PLA2 activity is not clear. In the present study, the effect of several FFA including arachidonic acid (AA, 20:4) on hypoxia-induced injury and PLA2 activity was assessed in freshly isolated rat proximal tubules. Hypoxia (H) was induced in the presence of either an unsaturated free fatty acid (uFFA) [AA or linoleic acid (LA, 18:2)] or a saturated FFA (sFFA) [palmitic (PA, 16:0) or myristic acid (MA, 14:0)]. Cell membrane injury was assessed by measuring lactate dehydrogenase release (LDH). AA markedly reduced LDH release during hypoxia in a dose dependent manner, while sFFA had no protective effect. LA showed similar protection to that observed with AA. AA did not affect buffer calcium concentration, buffer pH, intracellular pH or intracellular calcium concentration. Neither inhibiting the cyclooxygenase pathway with indomethacin, nor the lipoxygenase pathway with nordihydroguaiaretic acid (NDGA) had any effect on the AA observed cytoprotection. In vitro PLA2 activity in the control tubular extracts was compared to that following addition of AA or PA. PLA2 activity decreased significantly with AA but not with PA in a dose dependent manner. These data suggest that: (1) AA protects against hypoxic injury in rat proximal tubules. (2) This cytoprotection is not specific for AA and other uFFA have a similar effect. (3) AA significantly inhibits PLA2 activity, (4) AA induced cytoprotection may be related to a negative feedback inhibition of PLA2 activity.
在大鼠近端肾小管上皮细胞中，缺氧（H）期间游离脂肪酸（FFA）和溶血磷脂会积累，部分原因是磷脂酶A2（PLA2）活性增加。FFA在介导缺氧损伤和调节PLA2活性中的作用尚不清楚。在本研究中，在新鲜分离的大鼠近端肾小管中评估了几种FFA（包括花生四烯酸（AA，20:4））对缺氧诱导的损伤和PLA2活性的影响。在不饱和游离脂肪酸（uFFA）[AA或亚油酸（LA，18:2）]或饱和FFA（sFFA）[棕榈酸（PA，16:0）或肉豆蔻酸（MA，14:0）]存在的情况下诱导缺氧（H）。通过测量乳酸脱氢酶释放（LDH）来评估细胞膜损伤。AA以剂量依赖性方式显著降低缺氧期间的LDH释放，而sFFA没有保护作用。LA显示出与AA相似的保护作用。AA不影响缓冲液钙浓度、缓冲液pH、细胞内pH或细胞内钙浓度。用吲哚美辛抑制环氧化酶途径或用去甲二氢愈创木酸（NDGA）抑制脂氧合酶途径均对观察到的AA细胞保护作用没有任何影响。将对照肾小管提取物中的体外PLA2活性与添加AA或PA后的活性进行比较。PLA2活性随AA以剂量依赖性方式显著降低，但随PA则没有降低。这些数据表明：（1）AA可保护大鼠近端肾小管免受缺氧损伤。（2）这种细胞保护作用并非AA所特有，其他uFFA也有类似作用。（3）AA显著抑制PLA2活性，（4）AA诱导的细胞保护作用可能与对PLA2活性的负反馈抑制有关。
