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

描述（由申请人提供）：糖尿病视网膜病变是美国工作年龄人群中主要的视力威胁性疾病。它影响视网膜血管和神经元。我们最近发现的强大的σ受体1（sR 1）的配体在体内的神经保护作用，可能会提供一种新的方法来治疗这种疾病的神经元死亡。我们已经观察到，当用（+）-喷他佐辛（（+）-PTZ）（一种高度特异性的sR 1配体）治疗糖尿病视网膜病变的Ins 2Akita/+小鼠模型时，视网膜结构得到了显著的保护。sR 1最初被认为是阿片受体，现在已知作为分子伴侣结合ER应激蛋白BiP（GRP 78）。触发sR 1结合的因素现在才被确定。我们有初步的数据表明，氧化应激，这是牵连在糖尿病视网膜病变，诱导磷酸化的丝氨酸在sR 1和增加其结合到BiP在视网膜神经节细胞。我们的数据表明，（+）-PTZ去磷酸化sR 1和解离它从BiP。我们已经观察到Ins 2Akita/+小鼠视网膜中BiP（和其他ER应激基因）的表达增加，当给小鼠施用（+）-PTZ时，其表达降低。此外，（+）-PTZ上调Ins 2Akita/+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质。基于这些数据，目标1将检验以下假设：（+）-PTZ通过最小化氧化应激/调节ER应激反应来赋予神经保护，并且其通过调节sR 1磷酸化来实现。（+）-PTZ被认为是sR 1的高度特异性配体。因此，我们预测（+）-PTZ神经保护作用仅通过其与sR 1的相互作用介导;然而，这尚未得到验证。我们已经建立了一个sR 1基因敲除小鼠的群体，其可用性将使我们能够明确地确定sR 1是否是（+）-PTZ赋予神经保护所必需的。目的2将检验以下假设：（+）-PTZ仅通过激活sR 1介导其神经保护作用，而sR 1的缺失将增加视网膜对糖尿病诱导的细胞应激的脆弱性。除了这些机制研究之外，我们还必须在我们研究结果的临床适用性方面取得进展。到目前为止，我们仅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。我们不知道如果在糖尿病发作后给予（+）-PTZ是否可以赋予视网膜神经保护。这在临床上是相关的，因为患有视网膜病的人的治疗在疾病发作时开始是罕见的。在疾病发生后确定有效的干预战略至关重要。目的3将检验糖尿病发作后给予（+）-PTZ可以预防糖尿病视网膜病变中神经元细胞死亡的假设。这些目标的完成将使我们能够实现我们的长期目标，即确定sR 1配体是否有希望在人类视网膜病变中发挥神经保护作用。 公共卫生相关性：糖尿病视网膜病变是美国工作年龄段失明的主要原因。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，最显著的是神经节细胞。我们有令人兴奋的数据表明，药物（+）-喷他佐辛，它针对一种独特的蛋白质称为西格玛受体1，有深刻的神经保护作用，对神经节细胞死亡的小鼠模型糖尿病视网膜病变。拟议的项目将扩展这些发现，以了解这种保护的机制，最终目标是确定（+）-喷他佐辛是否可能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.