Renoprotective Effects of Valproic Acid and Dexamethasone in Acute Kidney Ischemia-Reperfusion Injury

Introduction: Renal ischemia-reperfusion (IR) causes acute kidney injury (AKI) with high mortality and morbidity. The objective of this study was to ameliorate kidney IR injury and identify novel biomarkers for kidney injury and repair. Methods: Left renal ischemia was induced in rats by clamping renal artery for 45 minutes, followed by reperfusion and right nephrectomy. Thirty minutes prior to ischemia, rats (n=8/group) received Valproic Acid (150 mg/kg; VPA), Dexamethasone (3 mg/kg; Dex) or Vehicle (Saline) intraperitoneally. Animals were sacrificed at 3h, 24h or 120h post- IR and blood, urine and kidney were collected. Results: Serum creatinine (mg/dL) at 24 h IR in VPA (2.7±1.8) and Dex (2.3±1.2) was reduced (P<0.05) compared to Vehicle (3.8±0.5). At 3h post-IR, urine albumin (mg/ml) was higher in Vehicle (1.47±0.10), VPA (0.84±0.62) and Dex (1.04±0.73) compared to uninjured/untreated control (0.14±0.26) group. At 24h post-IR urine Lipocalin-2 (µg/ml) was significantly higher (P<0.05) in VPA, Dex and Vehicle groups (9.61-11.36) compared to uninjured/untreated control (0.67±o.29); also, Kidney Injury Molecule-1 (KIM-1; ng/ml) was significantly higher in VPA, Dex and Vehicle groups (13.7-18.7) compared uninjured/untreated control (1.7±1.9). KIM-1 levels were significantly (P<0.05) higher in all groups compared to uninjured/untreated control levels. Histopathology at 3h post IR demonstrated (P<0.05) reduction in ischemic injury in the renal cortex in VPA (Grade 1.6± 1.5) compared to Vehicle (Grade 2.9±1.1) group. Inflammatory cytokines IL1ß and IL6 were down-regulated in VPA and Dex groups. BCL2 was higher in VPA group. DNA microarray analysis demonstrated reduced stress response and injury, and improved recovery related gene expression in the kidneys of VPA treated animals. Conclusions: VPA administration reduced kidney IR injury and improved regeneration. KIM-1 and Lipocalin-2 appear to be promising early urine biomarkers of acute ischemic kidney injury.Introduction: 肾缺血再灌注（Renal ischemia-reperfusion, IR）可引发急性肾损伤（Acute Kidney Injury, AKI），具有较高的病死率与致残率。本研究旨在减轻肾脏IR损伤，并筛选用于肾脏损伤与修复的新型生物标志物。 Methods: 通过夹闭大鼠肾动脉45分钟构建左侧肾缺血模型，随后实施再灌注并摘除右侧肾脏。缺血前30分钟，各组大鼠（每组n=8）分别腹腔注射丙戊酸（Valproic Acid, VPA，150 mg/kg）、地塞米松（Dexamethasone, Dex，3 mg/kg）或溶剂（生理盐水）。分别于缺血再灌注（IR）后3小时、24小时或120小时处死动物，采集血液、尿液及肾脏组织样本。 Results: 缺血再灌注后24小时，丙戊酸组（2.7±1.8）与地塞米松组（2.3±1.2）的血清肌酐值（mg/dL）较溶剂组（3.8±0.5）显著降低（P<0.05）。缺血再灌注后3小时，溶剂组（1.47±0.10）、丙戊酸组（0.84±0.62）与地塞米松组（1.04±0.73）的尿白蛋白水平（mg/ml）均高于未损伤未处理对照组（0.14±0.26）。缺血再灌注后24小时，丙戊酸、地塞米松及溶剂组的尿脂质运载蛋白-2（Lipocalin-2，µg/ml）水平（9.61~11.36）显著高于未损伤未处理对照组（0.67±0.29，P<0.05）；同时，肾损伤分子-1（Kidney Injury Molecule-1, KIM-1，ng/ml）水平在丙戊酸、地塞米松及溶剂组（13.7~18.7）亦显著高于未损伤未处理对照组（1.7±1.9，P<0.05）。缺血再灌注后3小时的组织病理学检测显示，与溶剂组（评分2.9±1.1）相比，丙戊酸组大鼠肾皮质缺血损伤评分（1.6±1.5）显著降低（P<0.05）。丙戊酸与地塞米松组的炎症因子IL-1β及IL-6表达均下调。丙戊酸组的B细胞淋巴瘤因子2（BCL2）表达水平升高。基因芯片（DNA microarray）分析显示，丙戊酸处理组大鼠肾脏的应激反应与损伤相关基因表达降低，而修复相关基因表达得到改善。 Conclusions: 腹腔注射丙戊酸可减轻肾脏IR损伤并促进肾脏再生。KIM-1与脂质运载蛋白-2（Lipocalin-2）有望成为急性缺血性肾损伤的早期尿液生物标志物。