Kasuno Kenji, Nakamura Hajime, Ono Takahiko, Muso Eri, Yodoi Junji
Department of Biological Responses, Institute for Virus Research, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Kidney Int. 2003 Oct;64(4):1273-82. doi: 10.1046/j.1523-1755.2003.00224.x.
Thioredoxin (TRX) is a small protein with redox-regulating functions. Although TRX is known to be induced in response to various forms of oxidative stress, including ischemia/reperfusion injury, the induction and the specific role of this protein in the kidney have not been fully investigated.
Renal ischemia/reperfusion was induced by the clipping and release of renal arteries in C57BL/6 and human thioredoxin-overexpressing transgenic (hTRX-Tg) mice. TRX protein was detected by immunohistochemistry, Western blotting, and enzyme-linked immunosorbent assay (ELISA). TRX mRNA was detected by in situ hybridization and Northern blotting. Renal functions were evaluated by measuring the levels of blood urea nitrogen and serum creatinine in these mice.
With ischemia/reperfusion, endogenous murine TRX was rapidly depleted from the cytosol in the cortical proximal tubuli and detected in the urinary lumen, whereas it was spread diffusely in all segments of the tubular epithelial cells in sham-operated mice. The urinary excretion of TRX increased transiently after ischemia/reperfusion and recovered to the control level in 72 hours. In the medullary thick ascending limb (mTAL), however, TRX was specifically retained in the cytosol. A similar distribution change of transgenic hTRX was observed in the kidney of hTRX-Tg. These hTRX-Tg mice were more resistant to the injury to the mTAL and functional deterioration caused by ischemia/reperfusion, compared with wild-type mice.
The present findings suggest that TRX is retained in mTAL and secreted from proximal tubuli into urine during renal ischemia/reperfusion. The mTAL-specific retention of TRX may have a protective effect against renal ischemia/reperfusion injury.
硫氧还蛋白（TRX）是一种具有氧化还原调节功能的小蛋白。尽管已知TRX可在包括缺血/再灌注损伤在内的各种形式的氧化应激反应中被诱导产生，但该蛋白在肾脏中的诱导情况及其具体作用尚未得到充分研究。
通过夹闭和松开C57BL/6小鼠及人硫氧还蛋白过表达转基因（hTRX-Tg）小鼠的肾动脉来诱导肾缺血/再灌注。通过免疫组织化学、蛋白质印迹法和酶联免疫吸附测定（ELISA）检测TRX蛋白。通过原位杂交和Northern印迹法检测TRX mRNA。通过测量这些小鼠的血尿素氮和血清肌酐水平来评估肾功能。
在缺血/再灌注时，内源性小鼠TRX在皮质近端小管的胞质溶胶中迅速耗尽，并在尿腔中被检测到，而在假手术小鼠的肾小管上皮细胞的所有节段中TRX呈弥漫性分布。缺血/再灌注后TRX的尿排泄量短暂增加，并在72小时内恢复到对照水平。然而，在髓质厚升支（mTAL）中，TRX特异性保留在胞质溶胶中。在hTRX-Tg小鼠的肾脏中观察到转基因hTRX有类似的分布变化。与野生型小鼠相比，这些hTRX-Tg小鼠对缺血/再灌注引起的mTAL损伤和功能恶化更具抵抗力。
目前的研究结果表明，在肾缺血/再灌注期间，TRX保留在mTAL中，并从近端小管分泌到尿液中。TRX在mTAL中的特异性保留可能对肾缺血/再灌注损伤具有保护作用。
