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，与人类感染HIV一样，会在小鼠中引起进行性神经免疫退行性变(NID)综合征。TSL感染中枢神经系统会导致神经元丢失，并伴有胶质细胞增厚和海绵状病变。由于感染病毒的是胶质细胞，而不是神经元，因此TSL的神经致病机制很可能是间接的，就像HIV的机制一样。我们先前证明TSL前体包膜蛋白在感染TSL的星形胶质细胞的内质网(ER)中积聚。这种积聚伴随着TSL感染的星形胶质细胞的细胞死亡。我们还观察了TSL感染小鼠中枢神经系统病变区域星形胶质细胞和神经元内钙离子的积聚和NFkappaB的激活。因此，我们推测，星形细胞内质网中TSL前体包膜蛋白的过度积累激活了ER超载反应，导致过量的钙释放，从而解偶联线粒体，导致有毒的活性氧物种(ROS)的释放。在感染TSL的小鼠的中枢神经系统中，半胱氨酸水平显着降低。半胱氨酸缺乏的一个后果是细胞内谷胱甘肽的减少，谷胱甘肽在细胞中提供主要的抗氧化防御。再加上我们最近的发现，TSL降低了被感染的星形胶质细胞和中枢神经系统中的过氧化氢酶水平，表明星形胶质细胞和中枢神经系统对氧化应激的防御是不足的。氧化损伤的星形胶质细胞可能无法支持发育中的神经元，星形胶质细胞释放ROS也可能导致神经细胞膜的损伤。这两种效应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氢酶增殖物，已被证明在体外可以改善TSL诱导的星形胶质细胞死亡，并在体内延长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是否导致培养的星形胶质细胞和中枢神经系统的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的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)产生过氧化氢酶的过氧化酶体增殖物，如PBA，和(D)其他抗氧化剂，如恶唑烷-4-羧酸盐(OTC)，单独或联合使用，能预防或改善TSL诱导的中枢神经系统星形胶质细胞损伤和神经变性。这个项目的重点是一个很有特色的动物模型。它解决了对我们理解逆转录病毒引起的脑病中的硫醇缺乏和氧化应激至关重要的问题。这也为控制逆转录病毒引起的神经变性提供了治疗依据。

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