Diabetic retinopathy: sigma receptor 1 (??R1) as a novel therapeutic target.

描述(申请人提供)：糖尿病视网膜病变是美国劳动年龄人口中威胁视力的主要疾病。它会影响视网膜血管系统和神经元。我们最近发现Sigma受体1(SR1)的配体在体内具有强大的神经保护作用，这可能为治疗这种疾病中的神经元死亡提供了一种新的方法。我们观察到，在糖尿病视网膜病变的Ins2Akita/+小鼠模型中，当用高度特异的SR1配体(+)-五唑辛((+)-PTZ)治疗时，这些小鼠的视网膜结构得到了显著的保存。SR1最初被认为是一种阿片受体，现在已知作为分子伴侣与内质网应激蛋白Bip(GRP78)结合。触发SR1结合的因素直到现在才被确定。我们的初步数据表明，与糖尿病视网膜病变有关的氧化应激诱导SR1丝氨酸的磷酸化，并增加其与视网膜神经节细胞中Bip的结合。我们的数据显示，(+)-PTZ使SR1去磷酸化，并使其与BiP解离。我们观察到在Ins2Akita/+小鼠的视网膜中Bip(和其他ER应激基因)的表达增加，当小鼠服用(+)-PTZ时，其表达降低。此外，(+)-PTZ上调了Ins2Akita/+小鼠视网膜中XCT的表达。XCT是调节抗氧化剂谷胱甘肽合成的关键蛋白。基于这些数据，Aim 1将测试(+)-PTZ通过最小化氧化应激/调节内质网应激反应而提供神经保护的假设，以及它通过调节SR1磷酸化来实现这一假设。(+)-PTZ被认为是SR1的高度特异性配体。因此，我们预测(+)-PTZ的神经保护作用仅通过其与SR1的相互作用来介导；然而，这一点尚未得到测试。我们已经建立了一个SR1基因敲除小鼠的群体，它的可用性将使我们能够明确地确定(+)-PTZ是否需要SR1来提供神经保护。目的2将验证(+)-PTZ仅通过激活SR1介导其神经保护作用的假设，并且SR1的缺失将增加视网膜对糖尿病诱导的细胞应激的易感性。除了这些机制研究，我们还必须在我们的研究结果的临床适用性方面取得进展。到目前为止，我们只在糖尿病发作时给予(+)-PTZ，并在糖尿病小鼠中观察到强大的视网膜神经保护作用。我们不知道(+)-PTZ如果在糖尿病发病后应用是否具有视网膜神经保护作用。这在临床上是有意义的，因为对患有视网膜病变的人类的治疗很少会在疾病发作时开始。确定在疾病发作后有效的干预策略至关重要。目的3将验证糖尿病发病后给予(+)-PTZ可以预防糖尿病视网膜病变中神经细胞死亡的假设。完成这些目标将使我们能够实现我们的长期目标，即确定SR1配体是否有希望在人类视网膜病变中提供神经保护。 公共卫生相关性：糖尿病视网膜病变是美国劳动年龄人群失明的主要原因。它是一种以视网膜血管改变和视网膜神经元死亡为特征的神经血管疾病。与糖尿病视网膜病变相关的神经元死亡涉及视网膜内细胞，最明显的是神经节细胞。我们有令人兴奋的数据表明，这种药物，(+)-五唑碱，针对一种名为Sigma Receptor 1的独特蛋白质，对糖尿病视网膜病变小鼠模型中的神经节细胞死亡具有深刻的神经保护作用。拟议的项目将扩大这些发现，以了解这种保护的机制，最终目标是确定(+)-五唑碱是否在临床上对人类视网膜病变有用。

DESCRIPTION (provided by applicant): Diabetic retinopathy is the major sight-threatening disease in the American working-aged population. It affects retinal vasculature and neurons. Our recent discovery of the powerful in vivo neuroprotective effects of a ligand for sigma receptor 1 (sR1) may offer a novel approach to treatment of neuronal death in this disease. We have observed remarkable preservation of retinal structure in the Ins2Akita/+ mouse model of diabetic retinopathy when the mice were treated with (+)-pentazocine ((+)-PTZ), a highly specific sR1 ligand. sR1, initially thought to be an opiate receptor, is now known to function as a molecular chaperone that binds the ER stress protein BiP (GRP78). Factors that trigger sR1-binding are only now being identified. We have preliminary data showing that oxidative stress, which is implicated in diabetic retinopathy, induces phosphorylation of serine in sR1 and increases its binding to BiP in retinal ganglion cells. Our data show that (+)-PTZ dephosphorylates sR1 and dissociates it from BiP. We have observed increased expression of BiP (and other ER stress genes) in retinas of Ins2Akita/+ mice, the expression of which is decreased when the mice are administered (+)-PTZ. In addition, (+)-PTZ upregulates the expression of xCT in the Ins2Akita/+ mouse retina. xCT is a key protein regulating synthesis of the antioxidant glutathione. Based on these data, Aim 1 will test the hypothesis that (+)-PTZ confers neuroprotection by minimizing oxidative stress/modulating the ER stress response and that it does so by regulating sR1 phosphorylation. (+)-PTZ is considered a highly specific ligand for sR1. Thus, we predict that (+)-PTZ neuroprotection is mediated solely through its interactions with sR1; however, this has not been tested. We have established a colony of sR1 knockout mice, the availability of which will permit us to determine definitively whether sR1 is required for (+)-PTZ to confer neuroprotection. Aim 2 will test the hypothesis that (+)-PTZ mediates its neuroprotective effects solely through activation of sR1 and absence of sR1 will increase retinal vulnerability to diabetes-induced cellular stress. In addition to these mechanistic studies, we must make progress regarding the clinical applicability of our findings. Thus far, we have administered (+)-PTZ only at diabetes onset and observed robust retinal neuroprotection in the diabetic mice. We do not know whether (+)-PTZ can confer retinal neuroprotection if administered after diabetes onset. This is relevant clinically since it would be rare that treatment of humans with retinopathy would commence at disease onset. Identification of intervention strategies that are effective following the onset of disease are of paramount importance. Aim 3 will test the hypothesis that administration of (+)-PTZ post-onset of diabetes can prevent neuronal cell death in diabetic retinopathy. Completion of these aims will allow us to achieve our long-range goal, which is to determine whether sR1 ligands hold promise for neuroprotection in human retinopathy. PUBLIC HEALTH RELEVANCE: Diabetic retinopathy is the leading cause of blindness in working-aged Americans. It is a neurovascular disease characterized by alterations of retinal vessels and death of retinal neurons. The neuronal death associated with diabetic retinopathy involves inner retinal cells, most notably ganglion cells. We have exciting data showing that the drug, (+)-pentazocine, which targets a unique protein called sigma receptor 1, has profound neuroprotective effects against ganglion cell death in a mouse model of diabetic retinopathy. The proposed project will extend these findings to understand the mechanism of this protection with the ultimate goal of determining whether (+)- pentazocine may be useful clinically for retinopathy in humans.