钠-氢交换蛋白1小干扰RNA对抗霉素A诱导人肾小管上皮细胞缺血再灌注损伤的保护机制

目的 通过构建钠-氢交换蛋白1（NHE-1）小干扰RNA (siRNA)抑制肾小管上皮细胞NHE-1的表达，探讨其对细胞缺血再灌注损伤的保护作用机制。 方法 根据人NHE-1全长基因序列设计并合成NHE-1-siRNA，转染人肾小管上皮细胞系（HKC），以无关siRNA转染组作为对照。利用10 μmol/L 抗霉素A诱导细胞来模拟缺血缺氧环境。用RT-PCR、Western印迹法检测NHE-1的表达。用BCECF/AM、Fluo-3/AM和SBFI-AM标记HKC，通过激光共聚焦显微镜分别检测其细胞内pHi、Ca2+和Na+浓度的变化。用Hoechst 33342染色技术及Annexin V/PI 染色结合流式细胞仪技术检测细胞凋亡情况。利用荧光探针JC-1检测细胞线粒体膜电位的变化。 结果 特异性NHE-1-siRNA能有效抑制HKC的NHE-1表达，与无关siRNA转染组相比，NHE-1-siRNA转染组NHE-1 mRNA和蛋白表达水平明显下调(均P < 0.05)。抗霉素A刺激后，2组细胞NHE-1 mRNA及蛋白表达水平显著上调，而NHE-1-siRNA转染组低于无关siRNA转染组；同时NHE-1-siRNA转染组细胞凋亡率（8.9%±2.9%）明显低于抗霉素A处理组（18.8%±3.2%）和抗霉素A+无关siRNA转染组（17.4%±3.6%）（均P < 0.05）；NHE-1-siRNA转染组线粒体膜电位明显增高；与无关siRNA转染组相比较，NHE-1-siRNA转染组经抗霉素A处理后，细胞内钠离子、氢离子及钙离子增高的幅度较低（P < 0.05）。 结论 NHE-1-siRNA可抑制肾小管上皮细胞内NHE-1的表达，对抗霉素A诱导肾小管上皮细胞的缺血再灌性损伤有一定的保护作用。其机制可能通过抑制NHE-1表达，延缓细胞内Na+的积聚，减轻细胞内钙离子的超载，抑制损伤细胞的线粒体膜电位下降，减少细胞的凋亡。

Protective mechanism of NHE-1-siRNA on human renal tubular epithelial cell from ischemic reperfusion injury induced by antimycin A

Objective To explore the mechanism of protecting cells from ischemic reperfusion injury by constructing specific small interference RNA (siRNA) to inhibit Na+-H+exchanger-1 (NHE-1) expression in human renal tubular epithelial cell (HKC). Methods The siRNA was designed and synthesized based on human NHE-1 complete sequence,and was transfected into HKC.The irrespective siRNA transfected group was used as control.The cells were treated with 10 μmol/L antimyein A to induce ischemia and anoxyaemia environment.NHE-1expression was examined by RT-PCR and Western blot.The intraeellular pH (pHi),Ca2+ or Na+ concentrations were detected by BCECF/AM,Fluo-3/AM and SBFI-AM,respectively,combining with laser eonfocal assay system.Nucleic morphology was determined by Hoechst 33342.Cellular apoptosis was examined by Annexin V/PI staining and flow eytometry.Fluorescent probe JC-1 was used to detect the change of mitechondrial transmembrane potential. Results The specific siRNA could efficiently inhibit NHE-1 expression in HKC.Compared with the irrespective siRNA transfected group,the mRNA and protein expression of NHE-1 was significantly down-regulated in NHE-1 siRNA transfeeted group (all P＜0.05).After treatment with antimyein A,the mRNA and protein expression of NHE-1 was significantly up-regulated in both groups,however,it was less than that in irrespective siBNA transfected group.At the same time,the ratio of apoptosis decreased (8.9% +2.9% vs 18.8%±3.2% , 17.4%±3.6% ,P＜0.05) and mitochondrial transmembrane potential rose significantly in NHE-1 siRNA transfected group as compared to irrespective siRNA transfected group and antimycin A group.The intracellular Na+,H+ and Ca2+concentrations increased in NHE-1 siRNA transfected group treated with antimyein A,but their levels were lower than those in irrespective siRNA transfected group with the same treatment(P＜0.05). Conclusions The synthesized siBNA can inhibit the expression of NHE-1 and can protect HKC from isehemia reperfasion injury induced by antimyein A.The mechanism might be via suppressing the expression of NHE-1 to delay intracelluar Na+ accumulation,attenuate intracellular Ca2+ overloading,and inhibit the decrease of mitechondrion transmembrane potential and reduce cellular apoptosis.