Transforming growth factor beta1, MicroRNAs and Diabetic Nephropathy

描述(申请人提供)：糖尿病肾病是糖尿病的主要并发症之一，可导致终末期肾脏疾病。糖尿病肾病的主要特征包括肾小球硬化增加和细胞外基质(ECM)沉积导致的系膜细胞增宽。尽管一些生化途径和关键的促纤维化因子，如转化生长因子-β1和细胞外基质蛋白胶原参与了糖尿病肾病的发病机制，但其微妙的分子和核机制尚不清楚。我们最近发现了系膜细胞(MC)中转化生长因子-β的关键基因靶标与称为microRNAs(MiRs)的一类非编码小RNA的成员之间的一种新的联系。越来越多的证据表明，miRs在基因调控中发挥着重要作用，因为它们可以通过与靶基因的mRNAs结合来抑制靶基因的表达。虽然已经预测了MIR的几个目标，但要确定它们的生物学和疾病相关性，还需要做很多工作。在正常和疾病条件下调节MIR的机制也不清楚。我们建议在数字域名的背景下探讨这些方面。我们发现，转化生长因子β下调了涉及胶原调节的关键抑制因子，并且这些因子也被肾脏和MC中表达的两个特定的MIR靶向和下调。经转化生长因子-β处理的肾小球系膜细胞和糖尿病小鼠肾小球中这些miRs的表达增加。此外，我们观察到这些MIR可以触发调节和前馈机制，从而增强胶原的表达。因此，我们提出了一种新的假说，即糖尿病肾病中转化生长因子-β的增加会导致关键的MIR及其靶基因的异常产生和作用，从而导致肾小球硬化的加重。具体目标1将研究转化生长因子β上调MC中主miR及其下游效应物miR的转录机制。特异性目标2将评估下游miR的特异性基因靶点，以及它如何参与转化生长因子-β介导的胶原调节。具体目标3将通过评估抗miR寡核苷酸在糖尿病小鼠中的治疗潜力，并通过检测miR基因敲除小鼠的糖尿病肾病进展来测试体内功能相关性。我们的初步结果揭示了迄今为止尚未探索的新的转化生长因子-β的作用机制。通过破译肾脏中这些难以捉摸的小RNA的生物学功能，这项最先进的研究可能会在肾脏研究领域开辟新的天地，并产生重大影响。他们还可以为治疗糖尿病肾病的新疗法铺平道路。公共卫生相关性：糖尿病在美国非常普遍，也是一个主要的医疗保健问题。它与糖尿病肾病等明显加速和衰弱的并发症有关，这一事实进一步放大了这一点。该项目建议确定新的相关机制，这些新机制可能导致开发急需的新疗法，以降低糖尿病肾病的发病率和死亡率。

DESCRIPTION (provided by applicant): Diabetic nephropathy (DN) is one of the major complications of diabetes that can lead to end stage renal disease. Key features of DN include increased glomerulosclerosis and mesangial cell widening due to extracellular matrix (ECM) deposition. Although several biochemical pathways and key profibrotic factors, such as transforming growth factor-beta 1 (TGF-¿) and the ECM protein collagen, have been implicated in the pathogenesis of DN, the subtle molecular and nuclear mechanisms regulating them are unclear. We recently uncovered a novel connection between key gene targets of TGF-¿ in mesangial cells (MCs) and members of a family of small non-coding RNAs called micro-RNAs (miRs). Increasing evidence shows that miRs play important roles in gene regulation since they can suppress the expression of target genes by binding to their mRNAs. Although several targets of miRs have been predicted, much needs to be done to determine their biological and disease relevance. The mechanisms by which miRs are regulated under normal and disease conditions are also not clear. We propose to explore these aspects in the context of DN. We discovered that TGF-¿ downregulates key repressive factors involved in collagen regulation, and that these factors are also targeted and downregulated by two specific miRs expressed in the kidney and MCs. The expressions of these miRs are increased in MCs treated with TGF-¿ and also in the glomeruli of diabetic mice. Furthermore, we observed that these miRs can trigger regulatory and feed forward mechanisms that enhance the expression of collagen. We therefore put forward the novel hypothesis that increased TGF-¿ in DN leads to the aberrant production and actions of key miRs and their target genes which result in enhanced glomerulosclerosis. Specific Aim 1 will examine the transcriptional mechanisms by which TGF-¿ upregulates a master miR and its downstream effector miR in MCs. Specific Aim 2 will evaluate the specific gene target of the downstream miR and how it contributes to TGF-¿ mediated collagen regulation. Specific Aim 3 will test the in vivo functional relevance by evaluating the therapeutic potential of anti-miR oligo-nucleotides in diabetic mice, and by examining the progression of DN in a miR knockout mouse. Our preliminary results have uncovered novel hitherto unexplored mechanisms of action of TGF-¿. This state-of-the-art study could break new ground and have a major impact in the field of renal research by deciphering the biological functions of these elusive small RNAs in the kidney. They could also pave the way for novel new therapies for diabetic kidney disease. PUBLIC HEALTH RELEVANCE: Diabetes is highly prevalent in the USA and a major healthcare problem. This is further magnified by the fact that it is associated with significantly accelerated and debilitating complications such as diabetic nephropathy. This project proposes to identify novel new mechanisms involved that could lead to the development of sorely needed newer therapies to reduce the morbidity and mortality of diabetic nephropathy.