Induction of Heme Oxygenase-1 Can Halt and Even Reverse Renal Tubule-Interstitial Fibrosis

BackgroundThe tubule-interstitial fibrosis is the hallmark of progressive renal disease and is strongly associated with inflammation of this compartment. Heme-oxygenase-1 (HO-1) is a cytoprotective molecule that has been shown to be beneficial in various models of renal injury. However, the role of HO-1 in reversing an established renal scar has not yet been addressed.
AimWe explored the ability of HO-1 to halt and reverse the establishment of fibrosis in an experimental model of chronic renal disease.
MethodsSprague-Dawley male rats were subjected to unilateral ureteral obstruction (UUO) and divided into two groups: non-treated and Hemin-treated. To study the prevention of fibrosis, animals were pre-treated with Hemin at days -2 and -1 prior to UUO. To investigate whether HO-1 could reverse established fibrosis, Hemin therapy was given at days 6 and 7 post-surgery. After 7 and/or 14 days, animals were sacrificed and blood, urine and kidney tissue samples were collected for analyses. Renal function was determined by assessing the serum creatinine, inulin clearance, proteinuria/creatininuria ratio and extent of albuminuria. Arterial blood pressure was measured and fibrosis was quantified by Picrosirius staining. Gene and protein expression of pro-inflammatory and pro-fibrotic molecules, as well as HO-1 were performed.
ResultsPre-treatment with Hemin upregulated HO-1 expression and significantly reduced proteinuria, albuminuria, inflammation and pro-fibrotic protein and gene expressions in animals subjected to UUO. Interestingly, the delayed treatment with Hemin was also able to reduce renal dysfunction and to decrease the expression of pro-inflammatory molecules, all in association with significantly reduced levels of fibrosis-related molecules and collagen deposition. Finally, TGF-β protein production was significantly lower in Hemin-treated animals.
ConclusionTreatment with Hemin was able both to prevent the progression of fibrosis and to reverse an established renal scar. Modulation of inflammation appears to be the major mechanism behind HO-1 cytoprotection.

研究背景：肾小管间质纤维化是进行性肾病的标志性病理特征，且与该区域的炎症反应密切相关。血红素氧合酶-1（Heme-oxygenase-1, HO-1）是一种具有细胞保护作用的分子，在多种肾损伤模型中已被证实具有获益效果。然而，HO-1在逆转已形成的肾瘢痕中的作用尚未得到阐明。
研究目的：本研究旨在探讨HO-1在慢性肾病实验模型中阻断并逆转纤维化进程的能力。
实验方法：将雄性Sprague-Dawley大鼠建立单侧输尿管梗阻（Unilateral Ureteral Obstruction, UUO）模型，并随机分为两组：未治疗组与Hemin处理组。为研究纤维化的预防作用，我们于UUO造模前第2天和第1天对大鼠进行Hemin预处理。为探究HO-1能否逆转已形成的肾纤维化，我们于术后第6天和第7天给予Hemin治疗。分别于造模后7天和/或14天处死大鼠，采集血液、尿液及肾组织样本用于后续分析。肾功能评估指标包括血清肌酐、菊糖清除率、尿蛋白/尿肌酐比值及尿白蛋白水平。同时检测动脉血压，并通过天狼星红（Picrosirius）染色定量纤维化程度。此外，还检测了促炎、促纤维化分子及HO-1的基因与蛋白表达水平。
实验结果：Hemin预处理可上调HO-1的表达，并显著降低UUO模型大鼠的尿蛋白、尿白蛋白水平，减轻炎症反应及促纤维化分子的蛋白与基因表达。值得注意的是，延迟给予Hemin治疗同样能够改善肾功能不全，降低促炎分子的表达，同时显著减少纤维化相关分子水平与胶原沉积。最终，Hemin处理组大鼠的转化生长因子-β（Transforming Growth Factor-β, TGF-β）蛋白表达水平显著降低。
研究结论：Hemin治疗既可预防纤维化进展，也可逆转已形成的肾瘢痕。对炎症反应的调控似乎是HO-1发挥细胞保护作用的主要机制。