Hewitson Tim D, Mookerjee Ishanee, Masterson Rosemary, Zhao Chongxin, Tregear Geoffrey W, Becker Gavin J, Samuel Chrishan S
Howard Florey Institute, University of Melbourne, Parkville, Victoria 3010, Australia.
Endocrinology. 2007 Feb;148(2):660-9. doi: 10.1210/en.2006-0814. Epub 2006 Nov 9.
Relaxin is a naturally occurring regulator of collagen turnover. In this study, we determined the role of endogenous relaxin in the pathogenesis of primary tubulointerstitial fibrosis after unilateral ureteric obstruction (UUO). Four- to 6-wk-old relaxin (RLX) gene-knockout (RLX(-/-)) and age-matched wild-type (RLX(+/+)) mice, with equivalent baseline collagen levels, were subjected to UUO. Obstructed and contralateral kidneys were collected at d 0, 3, and 10 after surgery and analyzed for changes in inflammatory and fibrosis-related markers. UUO was associated with a progressive increase in fibrosis in all obstructed, but not contralateral kidneys. The increase in total collagen (hydroxyproline analysis) was associated with more alpha-smooth muscle actin (alpha-SMA) staining (myofibroblasts) and interstitial collagen sub-types (SDS-PAGE; types I, III, and V), whereas gelatin zymography demonstrated increased expression of matrix metalloproteinase-2 after surgery. By d 10 after UUO, there was a 5-fold decrease in RLX mRNA expression (quantitative RT-PCR) in RLX(+/+) animals. Total collagen and alpha-SMA expression were significantly greater in the obstructed kidneys of RLX(-/-) mice 3 d after UUO (both P < 0.05 vs. RLX(+/+) D3 after UUO), but comparable to that in RLX(+/+) animals 10 d after UUO. Administration of recombinant H2 relaxin to RLX(-/-) mice 4 d before UUO ameliorated the increase in collagen and alpha-SMA expression (both P < 0.05 vs. untreated RLX(-/-) mice) by d 3 after UUO. Expression of monocyte chemoattractant protein-1 and macrophage infiltration (inflammation) in addition to that of matrix metalloproteinases was unaffected by genotype after UUO. These combined data demonstrate that endogenous RLX acts as a modulating factor in tubulointerstitial fibrosis, a hallmark of progressive renal disease. This is likely to be via direct effects on renal myofibroblast function.
松弛素是一种天然存在的胶原蛋白代谢调节因子。在本研究中，我们确定了内源性松弛素在单侧输尿管梗阻（UUO）后原发性肾小管间质纤维化发病机制中的作用。将4至6周龄、基线胶原蛋白水平相当的松弛素（RLX）基因敲除（RLX(-/-)）小鼠和年龄匹配的野生型（RLX(+/+)）小鼠进行UUO手术。在手术后第0、3和10天收集梗阻侧和对侧肾脏，分析炎症和纤维化相关标志物的变化。UUO与所有梗阻侧肾脏（而非对侧肾脏）的纤维化逐渐增加有关。总胶原蛋白（羟脯氨酸分析）的增加与更多α-平滑肌肌动蛋白（α-SMA）染色（肌成纤维细胞）和间质胶原蛋白亚型（SDS-PAGE；I、III和V型）相关，而明胶酶谱分析显示手术后基质金属蛋白酶-2的表达增加。在UUO后第10天，RLX(+/+)动物中RLX mRNA表达（定量RT-PCR）下降了5倍。在UUO后3天，RLX(-/-)小鼠梗阻侧肾脏中的总胶原蛋白和α-SMA表达显著更高（与UUO后第3天的RLX(+/+)小鼠相比均P < 0.05），但与UUO后10天的RLX(+/+)动物相当。在UUO前4天给RLX(-/-)小鼠注射重组H2松弛素，可改善UUO后第3天胶原蛋白和α-SMA表达的增加（与未治疗的RLX(-/-)小鼠相比均P < 0.05）。UUO后，单核细胞趋化蛋白-1的表达、巨噬细胞浸润（炎症）以及基质金属蛋白酶的表达均不受基因型影响。这些综合数据表明内源性RLX在肾小管间质纤维化（进行性肾脏疾病的一个标志）中起调节因子的作用。这可能是通过对肾肌成纤维细胞功能的直接影响实现的。
