Control of retrovirus CNS disease by redox modulation

逆转录病毒tsl是Moloney鼠白血病病毒的突变体，与人类HIV感染一样，在小鼠中引起进行性神经免疫变性（NID）综合征。 在中枢神经系统感染tsl导致神经元损失与神经胶质增生和海绵状病变。 由于病毒感染的是神经胶质细胞而不是神经元，因此tsl的神经致病机制与HIV的机制一样，很可能是间接的。我们以前证明，积累的tsl前体包膜蛋白发生在内质网（ER）的tsl感染的星形胶质细胞。 这种积累伴随着受tsl感染的星形胶质细胞的细胞死亡。 我们还观察到在tsl感染的小鼠的CNS中的病变区域中的星形胶质细胞和神经元中的细胞内钙积累和NF κ B的活化。 因此，我们假设星形胶质细胞ER中tsl前体包膜蛋白的过度积累激活ER过载反应，导致过量的Ca 2+释放，其使线粒体解偶联，引起毒性活性氧（ROS）的释放。 在受感染小鼠的CNS中，半胱氨酸水平显著降低。 半胱氨酸缺乏的后果是细胞内谷胱甘肽的减少，其在细胞中提供主要的抗氧化防御。 这与我们最近发现tsl降低感染的星形胶质细胞和CNS中的过氧化氢酶水平一起表明星形胶质细胞和CNS中对氧化应激的防御是缺陷的。 氧化损伤的星形胶质细胞可能无法支持发育中的神经元，并且星形胶质细胞释放的ROS也可能导致神经元膜的损伤。 这两种效应都可能导致神经元死亡。谷氨酸前体N-乙酰半胱氨酸或激活过氧化氢酶产生的过氧化物酶体增殖剂已被证明可以改善体外的tsl诱导的星形胶质细胞死亡，并延长体内tsl诱导的神经变性的潜伏期。 因此，根据这些初步意见，我们建议：1）确定tsl是否在培养的和CNS中的星形胶质细胞中诱导硫醇缺乏和氧化损伤，2）阐明在培养的和CNS中的星形胶质细胞和神经元中tsl介导的硫醇缺乏和氧化还原应激的潜在机制，和3）确定（a）NAC，（B）α-硫辛酸/二氢硫辛酸，（c）过氧化物酶体增殖物，例如PBA，其产生过氧化氢酶，和（d）其它抗氧化剂，例如氧代噻唑烷-4-羧酸酯（OTC），单独或组合，可以预防或改善CNS中的TSI诱导的星形胶质细胞损伤和神经变性。 该项目的重点是一个良好的表征动物模型。 它解决了关键问题，我们的理解，在逆转录病毒引起的脑病巯基缺乏和氧化应激。 它也为控制逆转录病毒引起的神经变性提供了治疗原理

The retrovirus tsl, a mutant of Moloney murine leukemia virus, like HIV infection in human, causes a progressive neuroimmunodegenerative (NID) syndrome in mice. Infection in the central nervous system by tsl results in neuronal loss with gliosis and spongiform lesions. Since glial cells but not neurons are infected with the virus, the neuropathogenic mechanism of tsl, like those of HIV, are most likely indirect. We previously demonstrated that accumulation of tsl precursor envelope proteins occurs in the endoplasmic reticulum (ER) of tsl infected astrocytes. This accumulation is accompanied by cell death in tsl-infected astrocytes. We also observed intracellular calcium accumulation and activation of NFkappaB in both astrocytes and neurons m the area of lesions in the CNS of tsl- infected mice. We therefore hypothesize that the excessive accumulation of tsl precursor envelope proteins in the astrocytic ER activates ER overload response resulting in excessive Ca2+ release that uncouples mitochondria causing release of toxic reactive oxygen species (ROS). In the CNS of tsl-infected mice there is a significant reduction of cysteine levels. A consequence of cysteine deficiency is the decrease in intracellular glutathione, which provides the major antioxidant defense in cells. This together with our recent finding that tsl decreases catalase levels in infected astrocytes and CNS suggests that the defense against oxidative stress in astrocytes and in the CNS is deficient. The oxidative damaged astrocytes may fail to support the developing neurons, and the release of ROS from astrocytes may also result in damage to neuronal membrane. Both of these effects could in turn result in neuronal death. Glutathione precursor N-acetyl cysteine, or peroxisome proliferator that activate production of catalase, have been shown to ameliorate both the tsl-induced astrocytic death in vitro and to prolong the latency period of tsl-induced neurodegeneration in vivo. Based on these preliminary observations we therefore propose here to: 1) Determine whether tsl induces thiol deficiency and oxidative damage in astrocytes in culture and in the CNS, 2) Elucidate the mechanisms underlying tsl-mediated thiol deficiency and redox stress in astrocytes and neurons in culture and in the CNS, and 3) Determine whether (a) NAC, (b) alpha-lipoic acid/dihydrolipoic acid, (c) peroxisome proliferators, such as PBA, that generate catalase, and (d) other antioxidants, e.g. Oxothiazolidine-4-carboxylate (OTC), either alone or in combination, can prevent or ameliorate tsl-induced astrocyte damage and neurodegeneration in the CNS. This project is focused on a well-characterized animal model. It addresses questions critical to our understanding of thiol deficiency and oxidative stress in retroviral-induced encephalopathy. It also provides a therapeutic rationale for controlling retroviral- induced neurodegeneration