Department of Orthopedic Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, China.
PLoS One. 2013;8(1):e54593. doi: 10.1371/journal.pone.0054593. Epub 2013 Jan 17.
Clinical evidence indicates that late acute renal failure (ARF) predicts high mortality in severely burned patients but the pathophysiology of late ARF remains undefined. This study was designed to test the hypothesis that sustained reactive oxygen species (ROS) induced late ARF in a severely burned rat model and to investigate the signaling mechanisms involved.
Rats were exposed to 100°C bath for 15 s to induce severe burn injury (40% of total body surface area). Renal function, ROS generation, tubular necrosis and apoptosis, and phosphorylation of MAPK and Akt were measured during 72 hours after burn.
Renal function as assessed by serum creatinine and blood urea nitrogen deteriorated significantly at 3 h after burn, alleviated at 6 h but worsened at 48 h and 72 h, indicating a late ARF was induced. Apoptotic cells and cleavage caspase-3 in the kidney went up slowly and turned into significant at 48 h and 72 h. Tubular cell ROS production shot up at 6 h and continuously rose during the 72-h experiment. Scavenging ROS with tempol markedly attenuated tubular apoptosis and renal dysfunction at 72 h after burn. Interestingly, renal p38 MAPK phosphorylation elevated in a time dependent manner whereas Akt phosphorylation increased during the first 24 h but decreased at 48 h after burn. The p38 MAPK specific inhibitor SB203580 alleviated whereas Akt inhibitor exacerbated burn-induced tubular apoptosis and renal dysfunction. Furthermore, tempol treatment exerted a duplex regulation through inhibiting p38 MAPK phosphorylation but further increasing Akt phosphorylation at 72 h postburn.
These results demonstrate that sustained renal ROS overproduction induces continuous tubular cell apoptosis and thus a late ARF at 72 h after burn in severely burned rats, which may result from ROS-mediated activation of p38 MAPK but a late inhibition of Akt phosphorylation.
临床证据表明，迟发性急性肾衰竭（ARF）预测严重烧伤患者的高死亡率，但迟发性 ARF 的病理生理学仍未确定。本研究旨在测试以下假设：在严重烧伤大鼠模型中，持续的活性氧（ROS）诱导迟发性 ARF，并研究涉及的信号转导机制。
大鼠暴露于 100°C 水浴中 15 秒，以诱导严重烧伤（全身表面积的 40%）。烧伤后 72 小时内测量肾功能、ROS 生成、肾小管坏死和凋亡以及 MAPK 和 Akt 的磷酸化。
烧伤后 3 小时血清肌酐和血尿素氮明显恶化，6 小时后缓解，但 48 小时和 72 小时后恶化，表明发生迟发性 ARF。肾脏中凋亡细胞和裂解半胱天冬酶-3 缓慢增加，48 小时和 72 小时时明显增加。肾小管细胞 ROS 生成在 6 小时时急剧增加，并在 72 小时的实验过程中持续上升。用 tempol 清除 ROS 可明显减轻烧伤后 72 小时肾小管凋亡和肾功能障碍。有趣的是，肾 p38 MAPK 磷酸化呈时间依赖性增加，而 Akt 磷酸化在烧伤后前 24 小时增加，但在 48 小时后减少。p38 MAPK 特异性抑制剂 SB203580 减轻了 Akt 抑制剂加剧的烧伤诱导的肾小管凋亡和肾功能障碍。此外，tempol 治疗在烧伤后 72 小时通过抑制 p38 MAPK 磷酸化和进一步增加 Akt 磷酸化发挥双重调节作用。
这些结果表明，持续的肾 ROS 过度产生诱导持续的肾小管细胞凋亡，从而导致严重烧伤大鼠烧伤后 72 小时发生迟发性 ARF，这可能是由于 ROS 介导的 p38 MAPK 激活，但 Akt 磷酸化的晚期抑制所致。
