Molecular Imaging of neuroHIv using animals models of disease

2017年转基因大鼠研究综述： 1.HIV转基因大鼠的多巴胺能功能障碍：我们此前曾报道，与年龄匹配的对照组相比，成年转基因大鼠脑内背侧纹状体(DS)和腹侧纹状体(VS)的D2/3受体显著减少。在较年轻的动物中，D2/3受体的减少仅在DS中显著，这表明存在神经/多巴胺能损伤的持续趋势，并随着年龄的增长而恶化。我们在免疫荧光上看到的TH减少(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)相结合，支持在这个动物模型中多巴胺能神经元功能障碍/丢失的概念。我们的结论是，18F-FolyPride可以检测到TG大鼠的多巴胺能系统功能障碍，并可能成为评价神经保护措施的一个合理的成像生物标志物。然而，我们希望使用另一种PET配体18F-FP-CMT进一步评估多巴胺能系统的突触前成分。用两组大鼠(5-8月龄和15-18月龄)，我们发现15-18月龄大鼠的18F-FP-CMT和18F-FallyPride结合势(BPND)值显著低于同龄WT大鼠(P&lt；分别为0.0001和0.001)。而5~8月龄大鼠的18F-FP-CMT BPND值无显著差异。在TG大鼠中，18F-FP-CMT BPND的纵向年龄相关性下降加剧。我们的结论是，与WT大鼠相比，老年TG大鼠存在突触前和突触后多巴胺能功能障碍/丢失。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大鼠神经病理中的作用：HIV相关性神经认知障碍(HAND)仍然是一个普遍存在的问题，已有报道称HIV携带者因年龄增长而导致神经认知障碍的进展。HAND的特征是细胞水平上的活性氧(ROS)和活性氮物种(RNS)的增加。运动和行为障碍是常见的症状之一，人们认为氧化和亚硝化应激导致机械性改变，导致神经认知功能障碍。我们之前的成像、组织学、运动和行为评估支持随着HIV-1TG大鼠年龄的增长，多巴胺能功能的失调。本研究的目的是证明在HIV-1转基因(HIV-1TG)大鼠脑内与多巴胺能功能障碍相关的神经解剖区域内存在氧化和亚硝化应激。我们发现，与年龄匹配的野生型大鼠相比，HIV-1TG大鼠基底节神经元突触前多巴胺能神经元丢失，纹状体NADPH氧化酶-4(NOX4)和神经元型一氧化氮合酶(NNOS)表达增加，3-硝基酪氨酸(3-NT)修饰的神经丝蛋白增加。这些异常在9月龄大鼠中可见，而在3月龄大鼠中未见。最后，这种自由基介导的神经元病理的增加发生在没有显著诱导转录因子Nrf2以及Nrf2反应的硫氧还蛋白和谷胱甘肽抗氧化系统的氧化还原适应的情况下。我们的发现提示，在衰老的HIV-1 TG大鼠中，可能由于长期暴露于HIV-1蛋白和缺乏适当的氧化还原适应，亚硝化应激和基底节神经元神经丝蛋白的3-NT修饰加速，可能导致多巴胺能神经元的结构变化和继发性多巴胺能功能障碍。 使用受SIV感染的猴子的研究摘要： 1.我们假设11C-DASB结合在SIV感染时会受到影响(关于接种前的扫描)。我们使用的是感染了神经毒力SIV毒株SIVsm804E的恒河猴。我们用11C-DASB在猴体内完成了免疫前后靶向SERT的PET成像，以检测SIV感染下的5-羟色胺能系统状态。当我们比较最后的时间点成像(11C-DASB PET)和接种前的扫描时，我们发现大多数接种SIV的动物(7只动物中有6只)5-羟色胺转运体(SERT)水平/表达增加。目前，我们正在研究病毒对SERT表达的潜在表观遗传效应，并准备一份手稿。 2.我们还在以外周病毒血症和疾病控制(模拟最佳治疗的HIV+患者)为协变量，研究SIV感染猴子的神经炎性变化的演变。为了实现这一目标，我们已经完成了18F-DPA-714PET成像，作为体内感染SIV的猴子小胶质细胞激活(神经炎症)的生物标志物。与我们的预期不同，我们没有发现18F-DPA714 PET成像在猴子体内的转位蛋白表达增加(5/5在接种后显示结合减少，而不是增加)。我们认为这与脑脊液病毒载量测量的中枢神经系统受累的严重程度有关。我们现在是

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 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 are investigating a potential epigenetic effect of the virus on SERT expression at this point and preparing a manuscript. 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 are now