Molecular Imaging of neuroHIv using animals models of disease

2017年使用转基因大鼠的研究总结： 1. HIV转基因大鼠中的多巴胺能功能障碍：我们先前报道了与年龄匹配的对照组相比，成年Tg大鼠脑中的D2/3受体显著降低，在背侧纹状体（DS）和腹侧纹状体（VS）中，使用18F-fallypride PET成像。 在较年轻的动物中，D2/3受体的减少仅在DS中显著，这表明随着年龄的增长，神经/多巴胺能损伤有持续的趋势。 我们在免疫荧光上看到的TH降低（多巴胺合成的早期步骤）和在PET上看到的突触后受体密度降低（D2/3）的组合支持了该动物模型中多巴胺能神经元功能障碍/丧失的概念。我们的结论是，18F-fallypride可以检测多巴胺能系统功能障碍的Tg大鼠，并可能是一个合理的成像生物标志物，以评估神经保护的方法。然而，我们想使用另一种PET配体18F-FP-CMT进一步评估多巴胺能系统的突触前组分。使用两组大鼠（5-8月龄和15-18月龄），我们发现15-18月龄Tg大鼠的18F-FP-CMT和18F-Fallypride结合电位（BPND）值显著低于年龄匹配的WT大鼠（分别为p< 0.0001和0.001）。然而，5-8月龄大鼠的18F-FP-CMT BPND值无显著差异。在Tg大鼠中，18 F-FP-CMT BPND的纵向年龄相关性降低加剧。 我们的结论是，有突触前和突触后多巴胺能功能障碍/损失相比，WT大鼠在老年Tg。我们认为这与Tg大鼠血清和脑中存在的病毒蛋白的神经毒性有关。 2. 氧化应激在tg大鼠神经病理学中的作用：HIV相关的神经认知障碍（HAND）仍然是一个普遍存在的问题，并且已经报道了HIV患者中因衰老引起的神经认知障碍的进展。 HAND的特征在于细胞水平上活性氧（ROS）和活性氮物质（RNS）的增加。运动和行为功能障碍是常见的症状之一，据信氧化和亚硝化应激有助于导致神经认知障碍的机制变化。 我们先前的成像、组织学、运动和行为评估支持随着HIV-1 Tg大鼠年龄的增长多巴胺能功能失调。 本研究的目的是证明与多巴胺能功能障碍的HIV-1转基因（HIV-1 Tg）大鼠脑内的神经解剖区域内的氧化和亚硝化应激的存在。我们发现，与年龄匹配的野生型大鼠相比，HIV-1 Tg大鼠基底神经节神经元中突触前多巴胺能神经元损失、纹状体NADPH氧化酶-4（Nox 4）和神经元型一氧化氮合酶（nNOS）表达增加以及3-硝基酪氨酸（3-NT）修饰的神经丝蛋白相关增加的病理学一致。这些异常在9月龄大鼠中观察到，但在3月龄大鼠中未观察到。最后，这种自由基介导的神经元病理学的增加没有显著诱导转录因子Nrf 2和Nrf 2响应性硫氧还蛋白和谷胱甘肽抗氧化系统的氧化还原适应。 我们的研究结果表明，在老化的HIV-1转基因大鼠，可能是由于慢性暴露于HIV-1蛋白和缺乏适当的氧化还原适应，亚硝化应激和3-NT修饰的基底节神经元的神经丝蛋白是加速可能有助于结构的变化，多巴胺能神经元和继发性多巴胺能功能障碍。我们准备了一份手稿并提交给了美国病理学杂志。 使用SIV感染猴的研究总结： 1. 我们假设11 C-DASB结合将在SIV感染中受到影响（相对于接种前扫描）。我们使用的是感染了神经毒性SIV毒株SIVsm 804 E的恒河猴。我们已经完成了在接种前后使用11 C-DASB在猴中获得靶向SERT的PET成像，以检测SIV感染影响下的肾上腺素能系统状态。我们发现，当我们比较最后一个时间点成像（11 C-DASB PET）与接种前扫描时，接种SIV的大多数动物（7只中有6只）的5-羟色胺转运蛋白（SERT）水平/表达增加。我们准备了一份手稿并提交给艾滋病杂志。 2. 我们也在研究SIV感染猴的神经炎症变化的演变，使用外周病毒血症和疾病控制（模拟最佳治疗的HIV+患者）作为协变量。为了实现这一目标，我们已经完成了18F-DPA-714 PET成像，作为SIV感染猴体内小胶质细胞活化（神经炎症）的生物标志物。与我们的预期不同，我们在猴中使用18F-DPA 714 PET成像没有发现增加的转运蛋白表达（5/5显示接种后结合减少而不是结合增加）。我们认为这与通过CSF病毒载量测量的CNS受累的严重程度相关。我们还发现，由于大脑中的高病毒载量，许多脑细胞正在死亡。我们已经准备了一份手稿并提交给艾滋病。

Summary of studies using the transgenic rats in 2017: 1. Dopaminergic dysfunction in HIV transgenic rat: We have previously reported significantly decreased D2/3 receptors in the adult Tg rat brains compared to age-matched controls, in both the dorsal striatum (DS) and ventral striatum (VS), using 18F-fallypride PET imaging. In younger animals, the decrease in D2/3 receptors was only significant in the DS, suggesting that there was a continuous trend of neurological/dopaminergic damage that worsens with age. The combination of decreased TH that we saw on immunofluorescence (early step in dopamine synthesis) and decreased post synaptic receptor density (D2/3) seen on PET supported the notion of dopaminergic neuronal dysfunction/loss in this animal model. We concluded that 18F-fallypride can detect dopaminergic system dysfunction in the Tg rats and may be a reasonable imaging biomarker to evaluate neuroprotective approaches. We wanted however to further evaluate the pre-synaptic component of the dopaminergic system using another PET ligand, 18F-FP-CMT. Using two groups of rats (5-8 Month-old and 15-18 Month-old), we found that the 18F-FP-CMT and 18F-Fallypride binding potential (BPND) values were significantly lower in 15-18 month-old Tg compared to age-matched WT rats (p< 0.0001 and 0.001, respectively). 18F-FP-CMT BPND values in 5-8 month-old rats, however, were not significantly different. Longitudinal age-related decrease in 18F-FP-CMT BPND was exacerbated in the Tg rat. We concluded that there is both presynaptic and postsynaptic dopaminergic dysfunction/loss in older Tg compared to WT rats. We believe this to be related to neurotoxicity of viral proteins present in the Tg rats serum and brain. 2. Role of oxidative stress in the neuropathology of the tg rat: HIV-associated neurocognitive disorder (HAND) continues to be a widespread problem, and progression of neurocognitive impairment caused by aging in individuals with HIV has been reported. HAND is characterized by an increase in reactive oxygen (ROS), and reactive nitrogen species (RNS) at the cellular level. Motor and behavioral dysfunction are among the common symptoms and it is believed that oxidative and nitrosative stress contribute to mechanistic changes leading to neurocognitive impairment. Our previous imaging, histological, motor and behavioral assessments support a dysregulation in dopaminergic function as the HIV-1 Tg rat ages. The goal of this study was to demonstrate the presence of oxidative and nitrosative stress within the neuroanatomic areas associated with dopaminergic dysfunction in the HIV-1 transgenic (HIV-1 Tg) rat brain. We found pathology consistent with pre-synaptic dopaminergic neuronal loss, increases in striatal NADPH oxidase-4 (Nox4) and neuronal nitric oxide synthase (nNOS) expression with associated increase in 3-nitrotyrosine (3-NT) modified neurofilament proteins in the basal ganglia neurons of HIV-1 Tg rats compared to age-matched wild type rats. Those abnormalities were seen in the 9 month-old but not in the 3 month-old rats. Finally, this increase in free radical mediated neuronal pathology occurred without significant induction of the transcription factor Nrf2 and redox adaptation of the Nrf2 responsive thioredoxin and glutathione antioxidant system. Our findings suggest that in the aging HIV-1 Tg rat, possibly due to chronic exposure to HIV-1 proteins and lack of appropriate redox adaptation, nitrosative stress and 3-NT modification of neurofilament proteins of basal ganglia neurons is hastened possibly contributing to structural changes to dopaminergic neurons and secondary dopaminergic dysfunction. We have prepared a manuscript and submitted to American journal of pathology. Summary of studies using the SIV infected monkeys: 1. We hypothesized that 11C-DASB binding will be affected in SIV infection (with respect to pre-inoculation scans). We are using rhesus macaques infected with the neurovirulent SIV strain, SIVsm804E. We have finished acquiring PET imaging targeting SERT using 11C-DASB in monkeys before and after inoculation, in order to detect serotonergic system status under the effect of SIV infection. We found that the serotonin transporter (SERT) levels/expression increased in most animals (6 out of 7) that were inoculated with SIV when we compared the last time point imaging (11C-DASB PET) to the preinoculation scans. We have prepared a manuscript and submitted to journal of AIDS. 2. We are also investigating the evolution of neuroinflammatory changes in the SIV-infected monkeys using peripheral viremia and disease control (simulating optimally treated HIV+ patients) as covariants. Towards this goal, we have finished acquiring 18F-DPA-714 PET imaging as biomarker of microglial activation (neuroinflammation), in vivo, in the SIV-infected monkeys. Unlike our expectations, we did not find increased translocator protein expression using 18F-DPA714 PET imaging in the monkeys (5 out 5 showing decreased binding after inoculation rather than increased binding). We believe this correlates to the severity of CNS involvement as measured by CSF viral load. we also found that many brain cells were dying because of the high viral loads in the brain. We have prepared a manuscript and submitted to AIDS.