Chen Cheng-Hsien, Chen Tso-Hsiao, Wu Mei-Yi, Chen Jia-Rung, Hong Li-Yu, Zheng Cai-Mei, Chiu I-Jen, Lin Yuh-Feng, Hsu Yung-Ho
Division of Nephrology, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan.
Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
Mol Med. 2016 Mar;21(1):886-889. doi: 10.2119/molmed.2015.00196. Epub 2015 Nov 23.
Peroxisome proliferator-activated receptor (PPAR)-α is a transcription factor that has been reported to inhibit gentamicin-induced apoptosis in renal tubular cells. However, the antiapoptotic mechanism of PPARα is still unknown. In this study, we found that PPARα overexpression induced Na/H exchanger-1 (NHE1) expression in the rat renal tubular cells NRK-52E. Beraprost, a PPARα ligand, also increased NHE1 expression in the renal tubules in normal mice, but not in PPARα knockout mice. Chromatin immunoprecipitation assays revealed that two PPARα binding elements were located in the rat NHE1 promoter region. Na/H exchanger activity also increased in the PPARα-overexpressed cells. Flow cytometry showed that the PPARα-overexpressed cells were resistant to apoptosis-induced shrinkage. Cariporide, a selective NHE1 inhibitor, inhibited the antiapoptotic effect of PPARα in the gentamicin-treated cells. The interaction between NHE1 and ezrin/radixin/moesin (ERM) and between ERM and phosphatidylinositol 4,5-bisphosphate in the PPARα-overexpressed cells was more than in the control cells. ERM short interfering RNA (siRNA) transfection inhibited the PPARα-induced antiapoptotic effect. PPARα overexpression also increased the phosphoinositide 3-kinase (PI3K) expression, which is dependent on NHE1 activity. Increased PI3K further increased the phosphorylation of the prosurvival kinase Akt in the PPARα-overexpressed cells. Wortmannin, a PI3K inhibitor, inhibited PPARα-induced Akt activity and the antiapoptotic effect. We conclude that PPARα induces NHE1 expression and then recruits ERM to promote PI3K/Akt-mediated cell survival in renal tubular cells. The application of PPARα activation reduces the nephrotoxicity of gentamicin and may expand the clinical use of gentamicin.
过氧化物酶体增殖物激活受体（PPAR）-α是一种转录因子，据报道其可抑制庆大霉素诱导的肾小管细胞凋亡。然而，PPARα的抗凋亡机制仍不清楚。在本研究中，我们发现PPARα过表达可诱导大鼠肾小管细胞NRK-52E中钠/氢交换体-1（NHE1）的表达。PPARα配体贝拉前列腺素也可增加正常小鼠肾小管中NHE1的表达，但在PPARα基因敲除小鼠中则无此作用。染色质免疫沉淀试验表明，大鼠NHE1启动子区域存在两个PPARα结合元件。在PPARα过表达的细胞中，钠/氢交换体活性也增加。流式细胞术显示，PPARα过表达的细胞对凋亡诱导的细胞收缩具有抗性。选择性NHE1抑制剂卡立泊来德可抑制PPARα在庆大霉素处理细胞中的抗凋亡作用。在PPARα过表达的细胞中，NHE1与埃兹蛋白/根蛋白/膜突蛋白（ERM）之间以及ERM与磷脂酰肌醇4,5-二磷酸之间的相互作用比对照细胞中更强。ERM小干扰RNA（siRNA）转染可抑制PPARα诱导的抗凋亡作用。PPARα过表达还可增加磷脂酰肌醇3-激酶（PI3K）的表达，这依赖于NHE1的活性。PI3K的增加进一步增强了PPARα过表达细胞中促存活激酶Akt的磷酸化。PI3K抑制剂渥曼青霉素可抑制PPARα诱导的Akt活性及抗凋亡作用。我们得出结论，PPARα诱导NHE1表达，然后募集ERM以促进肾小管细胞中PI3K/Akt介导的细胞存活。PPARα激活剂的应用可降低庆大霉素的肾毒性，并可能扩大庆大霉素的临床应用。
