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劳动年龄人口中主要的视力威胁疾病。它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一种新的方法。我们观察到，用(+)-pentazocine ((+)-PTZ)（一种高度特异性的sR1配体）治疗的Ins2Akita/+糖尿病视网膜病变小鼠模型中，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，现在被认为是一种结合内质网应激蛋白BiP （GRP78）的分子伴侣。触发sr1结合的因子现在才被确定。我们有初步数据显示，氧化应激与糖尿病视网膜病变有关，可诱导sR1丝氨酸磷酸化，并增加其与视网膜神经节细胞中BiP的结合。我们的数据表明(+)-PTZ使sR1去磷酸化并使其与BiP分离。我们观察到，在Ins2Akita/+小鼠的视网膜中，BiP（和其他内质网应激基因）的表达增加，当小鼠给予(+)-PTZ时，其表达降低。此外，(+)-PTZ上调in2akita /+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将验证(+)-PTZ通过最小化氧化应激/调节内质网应激反应并通过调节sR1磷酸化来提供神经保护的假设。（+）-PTZ被认为是sR1的高特异性配体。因此，我们预测(+)-PTZ神经保护仅通过其与sR1的相互作用介导；然而，这还没有经过检验。我们已经建立了一个sR1敲除小鼠群体，这将使我们能够明确地确定sR1是否需要(+)-PTZ提供神经保护。Aim 2将验证(+)-PTZ仅通过激活sR1介导其神经保护作用的假设，而sR1的缺失将增加视网膜对糖尿病诱导的细胞应激的易变性。除了这些机制研究，我们必须在我们的发现的临床适用性方面取得进展。到目前为止，我们仅在糖尿病发病时给予(+)-PTZ，并观察到糖尿病小鼠的视网膜神经保护作用。我们不知道(+)-PTZ是否可以在糖尿病发病后给予视网膜神经保护。这在临床上是相关的，因为很少有视网膜病变患者在发病时就开始治疗。确定在发病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sR1配体是否有希望在人类视网膜病变中发挥神经保护作用。

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.