Mechanisms of action of drugs that prevent experimental diabetic retinopathy

描述(由申请人提供)：我们工作的最终目标是开发预防糖尿病视网膜病变的药物策略。通过逐步更广泛地实施强化血糖控制，预防已经触手可及，我们预计，增加有效地预先清除残余高血糖的组织影响并长期服用安全的药物将使预防成为现实。临床上没有可用的辅助药物，也没有关于可能有效预防人类糖尿病视网膜病变的药物类型的严格的积极或消极信息。因此，我们试图从预防实验性糖尿病视网膜病变的药物中了解到，为了防止糖尿病引起的威胁视力的损害，必须在视网膜血管中沉默哪些分子过程。我们测试了两种具有不同作用机制的药物(一种醛糖还原酶抑制剂和中低浓度的阿司匹林)，理由是这两种药物的共同分子靶点将识别有待进一步研究的候选致病途径。实验表明，在大鼠中，糖尿病改变了视网膜血管中多个基因的表达，(Ii)转化生长因子-β途径是受糖尿病影响最大的单一功能途径，(Iii)两种药物既有共同的靶点，也有私人靶点，其中转化生长因子-β途径是两个共同的功能靶点之一。考虑到转化生长因子-β通路的过度活跃可以解释糖尿病视网膜病变的大部分血管组织病理学，并且基于更多的关于糖尿病视网膜血管中转化生长因子-β信号的增加的结果，我们计划检验这一假说，即过度的转化生长因子-β信号有助于糖尿病视网膜病变的特征性血管病变。该项目特别令人兴奋的是，有机会使用一种名为SM16的新型转化生长因子受体I型受体激酶小分子抑制剂，它具有口服活性，这是翻译步骤最吸引人的特点。我们的目标是在糖尿病大鼠身上开发和验证一种基于SM16的药物策略，用于无创、长期和靶向地预防视网膜血管中过度的转化生长因子-β信号。准确的目标是在不降低基本的转化生长因子-β活性的情况下，使转化生长因子-β信号恢复到控制值。我们将使用该抑制剂来了解过度的转化生长因子-β信号对糖尿病视网膜血管的分子影响。然后，我们将测试通过去除这些影响，视网膜毛细血管是否受到细胞死亡和重塑的保护，这些细胞死亡和重塑导致它们在糖尿病中最终死亡。在同一批大鼠中，我们还将检查SM16在典型肾脏病理发展过程中的作用。最后，我们将研究人类糖尿病视网膜血管(尸眼)中的转化生长因子-β途径。结合临床前研究的积极结果和人类糖尿病视网膜，将确定过度的转化生长因子-β信号是糖尿病视网膜病变血管病理的一个因素，并将刺激研究和开发药物，以安全地调节人类转化生长因子-β的活性。此外，这些研究有望为抗转化生长因子治疗在其他病理领域的应用创造一个范例。公共卫生相关性：这些研究提出了解决糖尿病视网膜病变的建议，这是糖尿病最常见和最可怕的并发症。我们试图确定在视网膜病变发展的早期阶段活跃的过程，以便我们可以开发出预防糖尿病对视网膜血管造成损害的最佳药物策略。这项工作现在发现了一种名为转化生长因子-β的多功能生长因子在糖尿病视网膜病变中的可能作用。已知转化生长因子-β参与多种血管病变，但以前从未与糖尿病视网膜病变有关。该项目旨在测试减少糖尿病引起的转化生长因子-β的增加是否会保护视网膜血管免受损伤并最终死亡。这个项目之所以令人兴奋，有三个原因。首先，它将测试一种新的转化生长因子-β抑制剂，这种抑制剂可以口服，因此将加速潜在的临床应用。其次，如果结果表明糖尿病引起的过量转化生长因子-β活性恢复到正常水平，实际上确实保护了视网膜血管，我们将有一个精确的分子靶点来测试人类糖尿病视网膜病变的预防。第三，从糖尿病和非糖尿病人的肾脏疾病，到遗传综合征中的血管畸形，再到高血压和动脉粥样硬化中的异常血管壁重构，转化生长因子-β与多种血管病理有关，因此，开发调节转化生长因子-β活性的药物策略将在几个医学领域引起人们的兴趣和使用。

DESCRIPTION (provided by applicant): The ultimate goal of our work is to develop drug strategies for the prevention of diabetic retinopathy. Prevention has been brought within reach by the progressively wider implementation of intensive glycemic control, and we anticipate that the addition of drugs that are effective in pre-emptying the tissue effects of residual hyperglycemia and are safe for long-term administration will make prevention a reality. There are no adjunct drugs usable clinically, and there are no rigorous positive or negative information on the type of drugs that may be effective in the prevention of human diabetic retinopathy. We thus sought to learn from drugs that prevent experimental diabetic retinopathy which molecular processes must be silenced in the retinal vessels in order to prevent the sight-threatening damage induced by diabetes. We tested two drugs with different mechanisms of action (an aldose reductase inhibitor and aspirin at low-intermediate concentrations) reasoning that molecular targets common to the two drugs would identify candidate pathogenic pathways to be investigated further. The experiments showed that, in rats, (i) diabetes changes the expression of multiple genes in retinal vessels, (ii) the TGF-¿ pathway was the single functional pathway mostly affected by diabetes, and (iii) the two drugs had private as well as common targets, with the TGF- ¿ pathway being one of the two common functional targets. Given that overactivity of the TGF- ¿ pathway could explain much of the vascular histopathology of diabetic retinopathy, and based on additional results documenting increased TGF- ¿ signaling in diabetic retinal vessels, we plan to test the hypothesis that excess TGF- ¿ signaling contributes to the characteristic vascular pathology of diabetic retinopathy. The project is made especially exciting by the opportunity to use a new small molecule inhibitor of TGF- ¿ type I receptor kinase, named SM16, that is orally active, a most appealing feature for translational steps. We aim to develop and validate in diabetic rats a drug strategy based on SM16 for non-invasive, long-term, and on-target prevention of the excess TGF- ¿ signaling in retinal vessels. The precise aim is to bring TGF- ¿ signaling back to control values without reducing basal TGF- ¿ activity. We will use the inhibitor to learn the molecular effects of excess TGF- ¿ signaling on diabetic retinal vessels. We will then test whether by taking away such effects, the retinal capillaries are protected from the cell death and remodeling that lead to their final demise in diabetes. In the same rats we will also examine the effects of SM16 on the development of the typical renal pathology. Finally, we will examine the TGF- ¿ pathway in human diabetic retinal vessels (postmortem eyes). A combination of positive results in the preclinical studies and the human diabetic retina will identify excess TGF- ¿ signaling as a contributor to the vascular pathology of diabetic retinopathy and will stimulate investigation and development of drugs to modulate safely TGF- ¿ activity in humans. In addition, the studies are poised to generate a paradigm for applications of anti-TGF- ¿ therapy to other pathologies. PUBLIC HEALTH RELEVANCE: The studies proposed address diabetic retinopathy, the most common and dreaded complication of diabetes. We seek to identify processes that are active at early stages of the development of retinopathy, so that we may develop the best drug strategy for prevention of the damage inflicted by diabetes to the retinal vessels. Such work has now uncovered a possible role in diabetic retinopathy of a multifunctional growth factor named TGF- ¿. TGF- ¿ has been known to be involved in several vascular pathologies, but has never before been associated with diabetic retinopathy. This project intends to test whether reducing the increased TGF- ¿ caused by diabetes will protect the retinal vessels from damage and ultimately death. The project is exciting for three reasons. First, it will test a new inhibitor of TGF- ¿ that can be administered by mouth, and therefore would accelerate potential clinical application. Second, if the results show that returning to normal levels the excess TGF- ¿ activity caused by diabetes does in fact protect the retinal vessels, we will have a precise molecular target to be brought to test for the prevention of human diabetic retinopathy. Third, being TGF- ¿ implicated in multiple vascular pathologies - from kidney disease in diabetic and nondiabetic individuals, to vascular malformations in genetic syndromes, to abnormal vascular wall remodeling in hypertension and atherosclerosis -, the development of drug strategies to modulate the activity of TGF- ¿ will find interest and use in several fields of medicine.