Division of Nephrology, University of São Paulo School of Medicine, Sao Paulo, Brazil.
Nephrol Dial Transplant. 2010 Jun;25(6):1795-803. doi: 10.1093/ndt/gfp719. Epub 2010 Jan 6.
Subsequent ischaemic episodes may induce renal resistance. P21 is a cell cycle inhibitor that may be induced by oxygen-free radicals and may have a protective effect in ischaemic acute kidney injury (AKI). This study aimed at evaluating the role of oxidative stress and p21 on tubular resistance in a model of acquired resistance after renal ischaemia and in isolated renal tubules.
Wistar rats were divided into: Group 1--sham; Group 2--sham operated and after 2 days submitted to 45-min ischaemia; and Group 3--45-min ischaemia followed after 2 days by a second 45-min ischaemia. Plasma urea was evaluated on Days 0, 2 and 4. Serum creatinine, creatinine clearance and oxidants (thiobarbituric acid-reactive substances) were determined 48 h after the second procedure (Day 4). Histology, immunohistochemistry for lymphocytes (CD3), macrophages (ED1), proliferation (PCNA) and apoptosis (TUNEL) were also evaluated. Rat proximal tubules (PTs) were isolated by collagenase digestion and Percoll gradient from control rats and rats previously subjected to 35 min of ischaemia. PTs were submitted to 15-min hypoxia followed by 45-min reoxygenation. Cell injury was assessed by lactate dehydrogenase release and hydroperoxide production (xylenol orange).
Ischaemia induced AKI in Group 2 and 3 rats. Subsequent ischaemia did not aggravate renal injury, demonstrating renal resistance (Group 3). Renal function recovery was similar in Group 2 and 3. Plasma and urine oxidants were similar among in Group 2 and 3. Histology disclosed acute tubular necrosis in Group 2 and 3. Lymphocyte infiltrates were similar among all groups whereas macrophages infiltrate was greater in Group 3. Cell proliferation was greater in Group 2 compared with Group 3. Apoptosis was similar in groups 2 and 3. The p21 expression was increased only in Group 3 whereas it was similar in groups 1 and 2. PTs from the ischaemia group were sensitive to hypoxia but resistant to reoxygenation injury which was followed by lower hydroperoxide production compared to control PT.
Renal resistance induced by ischaemia was associated with cell mechanism mediators involving oxidative stress and increased p21 expression.
继发的缺血事件可能会导致肾脏抵抗。P21 是一种细胞周期抑制剂，可能由氧自由基诱导，对缺血性急性肾损伤（AKI）可能有保护作用。本研究旨在评估氧化应激和 p21 在肾缺血后获得性抵抗模型及分离的肾小管中对管状阻力的作用。
Wistar 大鼠分为三组：第 1 组——假手术；第 2 组——假手术，术后 2 天行 45 分钟缺血；第 3 组——45 分钟缺血，2 天后再次行 45 分钟缺血。分别于第 0、2、4 天检测血尿素。术后 48 小时（第 4 天）检测血清肌酐、肌酐清除率和氧化剂（硫代巴比妥酸反应物质）。还评估了组织学、淋巴细胞（CD3）、巨噬细胞（ED1）、增殖（PCNA）和凋亡（TUNEL）的免疫组化。用胶原酶消化和聚蔗糖梯度法从对照组和先前经历 35 分钟缺血的大鼠中分离出近端肾小管（PT）。将 PT 置于 15 分钟缺氧后再氧合 45 分钟。通过乳酸脱氢酶释放和过氧化物生成（二甲氧基苯酚橙）评估细胞损伤。
第 2 组和第 3 组大鼠缺血引起 AKI。随后的缺血并没有加重肾损伤，表明肾脏具有抵抗性（第 3 组）。第 2 组和第 3 组肾功能恢复相似。第 2 组和第 3 组血浆和尿液氧化剂相似。第 2 组和第 3 组均有急性肾小管坏死。所有组的淋巴细胞浸润相似，而第 3 组的巨噬细胞浸润更多。第 2 组的细胞增殖大于第 3 组。第 2 组和第 3 组的凋亡相似。只有第 3 组的 p21 表达增加，而第 1 组和第 2 组的 p21 表达相似。缺血组的 PT 对缺氧敏感，但对再氧合损伤有抵抗性，与对照组 PT 相比，过氧化物生成较低。
缺血诱导的肾脏抵抗与涉及氧化应激和增加 p21 表达的细胞机制介质有关。
