Dextran Sulfate, Beta Cell Preservation and Immune Regulation in Type 1 Diabetes

1型糖尿病(T1D)，患病率约为200/10万，发病率一直在以2%-5%的速度增长 过去几年，在全世界范围内，这种疾病对受影响的个人、对制定有效的预防和治疗方法以及对整个公共卫生倡议构成了相当大的挑战。专注于保护功能性β细胞、获得免疫耐受性和诱导β细胞再生的治疗是该疾病治疗的优先事项。硫酸葡聚糖(DS)是细菌多糖葡聚糖的聚阴离子衍生物。我们实验室的初步研究表明，低分子DS(5-8 kDa)是体外培养的β细胞抵抗细胞因子和内质网应激的生存剂。然而，这些效应涉及的分子机制尚不清楚。此外，DS是否在促炎环境中保护β细胞功能也是未知的。抑制共刺激信号PD-1/PD-L1的上调提供了负面刺激，影响T淋巴细胞的激活，促进外周耐受的维持。初步研究表明，DS体外处理脾细胞后，DC、B细胞和巨噬细胞表达PD-L1的数量显著增加。DS还可增加表达PD-1的活化的CD4+和CD8+T细胞的数量。这表明DS可能有助于在易发生自身免疫的环境中维持外周耐受。为了验证丹参对T1D的治疗效果，我们在自发的T1D小鼠模型NOD小鼠上分析了丹参对糖尿病的预防和逆转作用。DS治疗可损害糖尿病前期NOD小鼠的β细胞死亡，保护β细胞质量，防止T1D的发展。更重要的是，对早发性糖尿病NOD小鼠进行DS治疗可以逆转约70%的小鼠的糖尿病。DS治疗保留了完整的胰岛，周围环绕着大量的免疫细胞，这表明胰岛渗透受损，细胞因子产生减少和/或提高了β细胞的存活。有趣的是，用针对PD-L1的阻断mAb治疗NOD小鼠，完全取消了DS在糖尿病发生中的预防作用。总之，这些研究表明DS对T1D有很好的治疗效果，它潜在地保留了功能性的β细胞，获得了免疫耐受，并促进了β细胞的再生。我们的假设是，DS通过在胰岛炎症环境中有利于胰岛β细胞的存活和维持功能而逆转T1D，并通过 调节免疫系统以增强耐受性。为了确定我们的假设是否正确，我们将开发以下特定目标：特定目标1.确定DS在T1D背景下对β细胞存活和功能的影响及其分子机制。具体目的2.分析硫酸葡聚糖(DS)单独或联合肝细胞生长因子(HGF)治疗NOD小鼠糖尿病的疗效。 具体目的3.对DS诱导的人T细胞反应的免疫调节作用进行解剖和分层。拟议的研究将提供有关DS对T1D和T1D的治疗潜力的重要信息。 这种硫酸多糖的有益作用涉及的细胞和分子机制。

Type 1 diabetes (T1D), with a prevalence of ~200/100,000 and an incidence that has been increasing by 2-5% worldwide over the past few years, poses a considerable challenge to afflicted individuals, to the development of effective prevention and treatment regimens, and to public health initiatives at large. Therapies focused on preserving functional beta cells; gaining immune tolerance; and inducing beta cell regeneration are a priority for the treatment of the disease. The sulfated polysaccharide Dextran Sulfate (DS) is a polyanionic derivative of the bacterial polysaccharide dextran. Preliminary studies from our lab suggest that low molecular weight DS (5-8kDa) is a prosurvival agent for the beta cell in vitro against cytokines and ER stress. However, the molecular mechanisms involved in these effects are unknown. In addition, whether DS protects beta cell function in a proinflammatory environment is also unknown. Upregulation of the inhibitory co-stimulatory signal PD-1/PD-L1 provides negative stimuli influencing T lymphocyte activation and promoting the maintenance of peripheral tolerance. Preliminary studies indicate that DS treatment of splenocytes in vitro leads to a significant increase in the number of DCs, B cells and macrophages expressing PD-L1. DS also increases the number of activated CD4+ and CD8+ T cells expressing PD-1. This suggests that DS could help to maintain peripheral tolerance in a setting predisposed to autoimmunity. To test the efficacy of DS for T1D treatment, we have analyzed the effect of DS in the prevention and reversal of diabetes in the NOD mouse, the spontaneous mouse model of T1D. DS treatment impairs beta cell death, preserves beta cell mass and prevents the development of T1D in pre-diabetic NOD mice. More importantly, DS treatment of early onset diabetic NOD mice reverses diabetes in ~70% of the mice. DS treatment preserves beta cell mass with intact islets surrounded by massive number of immune cells, suggesting islet infiltration impairment, decreased cytokine production and/or enhanced beta cell survival. Interestingly, treatment of NOD mice with a blocking mAb against PD-L1 completely abrogated the preventive effects of DS in diabetes development. Collectively, these studies suggest a promising therapeutic effect of DS for T1D by potentially preserving functional beta cells, gaining immune tolerance and enhancing beta cell regeneration. Our hypothesis is that DS reverses T1D by favoring the survival and maintaining the function of the beta cell in an islet inflammation environment, and by modulating the immune system to enhance tolerance. To determine whether our hypothesis is correct, we will develop the following Specific Aims: Specific Aim 1. To determine the effect and molecular mechanisms mediated by DS on beta cell survival and function in the context of T1D. Specific Aim 2. To analyze the efficacy of dextran sulfate (DS) treatment alone or in combination with hepatocyte growth factor (HGF) for reversing diabetes in NOD mice. Specific Aim 3. To dissect and stratify DS-induced immunomodulatory effects on human T cell responses. The proposed studies will provide significant information regarding the therapeutic potential of DS for T1D and the cellular and molecular mechanisms involved in the beneficial effects of this sulfated polysaccharide.