Control of retrovirus CNS disease by redox modulation

逆转录病毒tsl是Moloney小鼠白血病病毒的一种突变体，就像人类的HIV感染一样，在小鼠中引起进行性神经免疫退行性（NID）综合征。由tsl感染中枢神经系统导致神经细胞丧失，并伴有胶质瘤和海绵状病变。由于神经胶质细胞而非神经元被病毒感染，因此与艾滋病毒一样，tsl的神经致病机制很可能是间接的。我们之前证明，tsl前体包膜蛋白的积累发生在tsl感染星形胶质细胞的内质网（ER）中。这种积累伴随着tsl感染的星形胶质细胞的细胞死亡。我们还观察到tsl感染小鼠中枢神经系统病变区域星形细胞和神经元中细胞内钙的积累和NFkappaB的激活。因此，我们假设星形细胞内质网中tsl前体包膜蛋白的过度积累激活了内质网过载反应，导致过量的Ca2+释放，使线粒体解偶，导致有毒活性氧（ROS）的释放。在tsl感染小鼠的中枢神经系统中，半胱氨酸水平显著降低。半胱氨酸缺乏的一个后果是细胞内谷胱甘肽的减少，而谷胱甘肽在细胞中提供主要的抗氧化防御。这与我们最近发现的tsl降低了受感染星形胶质细胞和中枢神经系统中过氧化氢酶的水平，表明星形胶质细胞和中枢神经系统对氧化应激的防御不足。氧化损伤的星形胶质细胞可能无法支持神经元的发育，星形胶质细胞释放ROS也可能导致神经元膜损伤。这两种影响都可能导致神经元死亡。谷胱甘肽前体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tsl诱导的星形细胞死亡，并延长体内tsl诱导的神经变性的潜伏期。基于这些初步观察，我们建议：1)确定tsl是否诱导培养的星形胶质细胞和中枢神经系统中硫醇缺乏和氧化损伤，2)阐明tsl介导的星形胶质细胞和神经元中硫醇缺乏和氧化还原应激的机制，以及3)确定(a) NAC, (b) α -硫辛酸/二氢硫辛酸，(c)生成过氧化氢酶的过氧化物酶体增殖剂，如PBA，以及(d)其他抗氧化剂，如氧噻唑烷-4-羧酸盐（OTC），单独或联合使用，可以预防或改善tsl诱导的星形细胞损伤和中枢神经系统的神经变性。这个项目的重点是一个特征良好的动物模型。它解决了对我们理解逆转录病毒诱导的脑病中硫醇缺乏和氧化应激的关键问题。它也为控制逆转录病毒引起的神经退行性变提供了治疗依据

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