Albumin induces endoplasmic reticulum stress and apoptosis in renal proximal tubular cells
Albumin induces endoplasmic reticulum stress and apoptosis in renal proximal tubular cells
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DOI：
10.1038/sj.ki.5001704
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发表时间：
2006-10-01
影响因子：
19.6
通讯作者：
Nangaku, M.
中科院分区：
文献类型：
--
作者：
Ohse, T.;Inagi, R.;Nangaku, M.
慢性蛋白尿似乎是肾小管间质损害的关键因素。最近的研究强调了内质网（ER）应激的致病作用，这是由错误折叠的蛋白质在ER中的积累，细胞外应激等引起的。在本研究中，我们研究了ER应激和ER应激诱导的近端肾小管细胞（PTC）凋亡。用牛血清白蛋白（BSA）培养永生化大鼠PTC（IRPTC）。IRPTC的存活率随BSA负荷的增加而呈时间依赖性下降.定量实时聚合酶链反应分析显示，与对照相比，40 mg/ml BSA使ER应激标志物（葡萄糖调节蛋白78（GRP 78）和氧调节蛋白150（ORP 150））的mRNA分别增加7.7倍和4.6倍。Western blot和免疫荧光法检测白蛋白超载时IRPTC中ORP 150和GRP 78的表达增加。这些体外观察结果得到了体内研究的支持，体内研究表明，ER应激蛋白在实验性蛋白尿大鼠的PTC中上调。此外，ER应激诱导的细胞凋亡和caspase-12的激活在白蛋白超载的IRPTC和实验性蛋白尿大鼠的肾脏中观察到增加。我们证实，凋亡性细胞死亡减弱与半胱天冬酶-3抑制剂或钙蛋白酶抑制剂共孵育。这些结果表明，ER应激诱导的凋亡途径有助于肾小管细胞的蛋白尿的侮辱。总之，暴露于高蛋白负荷的肾小管细胞会遭受ER应激。ER应激随后可能会通过激活caspase-12导致肾小管损伤。
Chronic proteinuria appears to be a key factor in tubulointerstitial damage. Recent studies have emphasized a pathogenic role of endoplasmic reticulum (ER) stress which is induced by the accumulation of misfolded proteins in ER, extracellular stress, etc. In the present study, we investigated ER stress and ER stress-induced apoptosis in proximal tubular cells (PTCs). Immortalized rat PTCs (IRPTCs) were cultured with bovine serum albumin (BSA). The viability of IRPTCs decreased proportionately with BSA overload in a time- dependent manner. Quantitative real-time polymerase chain reaction analysis revealed that 40mg/ml BSA increases mRNA of ER stress markers by 7.7- and 4.6-fold (glucose-regulated protein 78 (GRP78) and oxygen-regulated protein 150 (ORP150), respectively) as compared to control. The increased expression of ORP150 and GRP78 in IRPTCs with albumin overload was detected by Western blot and immunofluorescence study. These in vitro observations were supported by in vivo studies, which demonstrated that ER stress proteins were upregulated at PTCs in experimental proteinuric rats. Furthermore, increased ER stress- induced apoptosis and activation of caspase-12 were observed in IRPTCs with albumin overload and kidneys of experimental proteinuric rats. We confirmed that apoptotic cell death was attenuated by co- incubation with caspase-3 inhibitor or calpain inhibitors. These results indicate that the ER stress-induced apoptosis pathway contributed to the insult of tubular cells by proteinuria. In conclusion, renal tubular cells exposed to high protein load suffer from ER stress. ER stress may subsequently lead to tubular damage by activation of caspase-12.