Moriyama T, Kawada N, Ando A, Yamauchi A, Horio M, Nagata K, Imai E, Hori M
First Department of Medicine, Osaka University School of Medicine, Faculty of Health and Sport Sciences, Japan.
Kidney Int. 1998 Jul;54(1):110-9. doi: 10.1046/j.1523-1755.1998.00964.x.
Unilateral ureteral obstruction (UUO) is a well established experimental model of renal injury leading to interstitial fibrosis. The molecular and cellular mechanism(s) of interstitial fibrosis in UUO are beginning to be elucidated. In the progression of interstitial fibrosis in UUO, up-regulation of collagen synthesis is commonly observed. HSP47 is a collagen-binding stress protein and is thought to be a collagen-specific molecular chaperone, which plays a pivotal role during the biosynthesis and secretion of collagen molecules in the endoplasmic reticulum. The synthesis of HSP47 has been demonstrated to always parallel that of collagen in physiological and pathophysiological conditions. It is well recognized that renin-angiotensin system (RAS) is enhanced in the setting of UUO and that enhanced RAS has been implicated in the pathogenesis of interstitial fibrosis in the obstructed kidneys.
To investigate the role of HSP47 in the progression of interstitial fibrosis in mouse UUO, the expression of HSP47 was examined by Northern blotting, immunohistochemistry and in situ hybridization in the obstructed kidneys. To test the possible involvement of enhanced RAS on the HSP47 expression, we examined the effects of lisinopril, an angiotensin converting enzyme inhibitor, on interstitial fibrosis. HSP47 and type I collagen mRNA expression.
By Northern blot analysis, HSP47 mRNA was significantly up-regulated at 12 hours (about twice that of sham operated kidneys) after the onset of ureteral obstruction, further increased and stayed at the increased level until seven days (about 8 times that of sham operated kidneys). HSP47 mRNA and protein expression were observed in the periglomerular and peritubular interstitial regions of the obstructed kidneys. Distribution of smooth muscle alpha actin and type I collagen immunoreactivity were similar to the HSP47 distribution pattern, suggesting that HSP47 was up-regulated in the myofibroblasts. Lisinopril ameliorated the expansion of cortical interstitium in the obstructed kidneys at four and seven days after ureteral obstruction. HSP47 mRNA expression was suppressed at four and seven days, whereas type I collagen mRNA was suppressed only at seven days after the onset of ureteral obstruction.
These results demonstrate the early and persistent up-regulation of HSP47 during the progression of interstitial fibrosis in mouse UUO kidneys, and further suggest the potential role of HSP47 in the pathogenesis of interstitial fibrosis in the obstructed kidneys. Partial suppression of HSP47 mRNA expression by lisinopril at day 4 and day 7 after ureteral obstruction suggests that there are other immediate trigger(s) that induce the HSP47 mRNA expression. Identification of the molecular mechanism of HSP47 induction during UUO may give an insight into the novel aspects of the molecular pathophysiology of interstitial fibrosis in obstructive nephropathy.
单侧输尿管梗阻（UUO）是一种成熟的导致肾间质纤维化的肾损伤实验模型。UUO 肾间质纤维化的分子和细胞机制正逐渐被阐明。在 UUO 肾间质纤维化进展过程中，通常可观察到胶原合成上调。热休克蛋白 47（HSP47）是一种胶原结合应激蛋白，被认为是一种胶原特异性分子伴侣，在内质网中胶原分子的生物合成和分泌过程中起关键作用。已证实在生理和病理生理条件下，HSP47 的合成始终与胶原的合成平行。众所周知，在 UUO 情况下肾素 - 血管紧张素系统（RAS）增强，且增强的 RAS 与梗阻性肾脏间质纤维化的发病机制有关。
为研究 HSP47 在小鼠 UUO 肾间质纤维化进展中的作用，通过 Northern 印迹法、免疫组织化学和原位杂交检测梗阻性肾脏中 HSP47 的表达。为检测增强的 RAS 对 HSP47 表达的可能影响，我们研究了血管紧张素转换酶抑制剂赖诺普利对间质纤维化、HSP47 和 I 型胶原 mRNA 表达的影响。
通过 Northern 印迹分析，输尿管梗阻开始后 12 小时，HSP47 mRNA 显著上调（约为假手术肾脏的两倍），进一步升高并维持在升高水平直至第 7 天（约为假手术肾脏的 8 倍）。在梗阻性肾脏的肾小球周围和肾小管周围间质区域观察到 HSP47 mRNA 和蛋白表达。平滑肌α肌动蛋白和 I 型胶原免疫反应性的分布与 HSP47 分布模式相似，表明 HSP47 在肌成纤维细胞中上调。输尿管梗阻后第 4 天和第 7 天，赖诺普利改善了梗阻性肾脏皮质间质的扩张。输尿管梗阻开始后第 4 天和第 7 天，HSP47 mRNA 的表达受到抑制，而 I 型胶原 mRNA 仅在第 7 天受到抑制。
这些结果表明在小鼠 UUO 肾脏间质纤维化进展过程中 HSP47 早期且持续上调，并进一步提示 HSP47 在梗阻性肾脏间质纤维化发病机制中的潜在作用。输尿管梗阻后第 4 天和第 7 天赖诺普利对 HSP47 mRNA 表达的部分抑制表明存在其他诱导 HSP47 mRNA 表达的直接触发因素。确定 UUO 期间 HSP47 诱导的分子机制可能有助于深入了解梗阻性肾病间质纤维化分子病理生理学的新方面。
