Tat mediation of HIV-associated mood disorders via functional deficits in brain

描述(申请人提供)：抑郁和焦虑是一种普遍存在的情绪障碍，症状被描述为“神经艾滋病”，并对艾滋病毒阳性患者的治疗和福祉构成重大问题。不幸的是，将HIV相关神经病理与神经元回路功能障碍和行为情绪障碍的进展联系起来的生物学机制还没有被很好地理解。最近的证据表明，TAT等HIV辅助蛋白可能会从HIV感染的细胞传播到整个大脑，产生神经毒性和神经元活动的变化，这可能是行为变化的原因。我们假设TAT蛋白的表达足以导致神经退化和调节情绪的神经回路功能障碍，导致抑郁和焦虑样行为的增加。该建议利用GT-TG转基因小鼠及其多西环素基因诱导策略在大脑中控制、选择性地表达TAT蛋白。诱导的GT-TG双基因小鼠将被用来通过行为和成像研究来验证这一假设，即TAT介导的抑郁和焦虑样行为的增加与TAT诱导的与抑郁和焦虑相关的区域的大脑结构和功能的改变相关，包括杏仁核、前扣带回、眶前皮质和海马体。对这些小鼠的行为学研究将通过强迫游泳压力和社交厌恶测试来评估TAT的表达如何影响抑郁样行为。行为学实验还将使用开阔场地、高架迷宫、明暗盒子、声学惊吓和大理石埋藏测试来检验TAT表达对焦虑样行为的影响。对TAT mRNA和蛋白水平的检测将使TAT的表达与观察到的行为变化相关联。在初步研究中，TAT诱导的小鼠在社交互动中比未诱导的小鼠花费更少的时间，而在强迫游泳压力测试中花费更多的时间不动，这表明TAT介导的抑郁样行为的增加。TAT诱导的小鼠也表现出与焦虑相关的行为增加，在露天环境中花费的时间更少，大理石埋葬的时间增加了3倍。同时，我们将使用超高磁场下的体外磁共振成像(MRI)和TUNEL染色检测TAT诱导的动物的脑组织结构和细胞死亡。初步的体外结构成像研究证明，在表达Tat的小鼠中，杏仁核和海马区的灰质密度显著减少。此外，我们将使用BOLD功能磁共振结合皮质酮的挑战来确定与情绪障碍相关的大脑区域的功能变化，这些变化是由于不同水平的TAT蛋白的诱导和暴露时间以及对挑战剂量的皮质酮的反应引起的。总体而言，该项目试图证明，可以在TAT诱导的动物的大脑回路中检测到功能和结构缺陷，从而确定TAT可能调节神经艾滋病特有的情绪障碍的机制。

DESCRIPTION (provided by applicant): Depression and anxiety are prevalent mood disorders symptomatic of the syndrome described as "NeuroAIDS," and pose significant problems for the treatment and well-being of HIV-positive patients. Unfortunately, the biological mechanisms linking HIV-related neuropathology to the dysfunction of neuronal circuitry and the progression of behavioral mood disorders are not well understood. Recent evidence suggests that HIV-accessory proteins such as Tat may spread throughout the brain from HIV-infected cells, producing neurotoxicity and changes in neuronal activity that could account for the behavioral changes. We hypothesize that Tat protein expression is sufficient to produce neurodegeneration and dysfunction of neuronal circuitry mediating mood, resulting in an increase of depression- and anxiety-like behaviors. This proposal utilizes the GT-tg transgenic mouse and its doxycycline-gene induction strategy for a controlled, selective expression of Tat protein in the brain. Induced GT-tg bigenic mice will be used to test the hypothesis with behavioral and imaging studies that Tat-mediated increases in depression- and anxiety-like behaviors are correlated with Tat-induced alterations in brain structure and function in regions associated with depression and anxiety, including the amygdala, anterior cingulate, orbitofrontal cortex and hippocampus. Behavioral studies with these mice will assess how Tat expression affects depression-like behaviors with the forced swim stress and social aversion tests. Behavioral experiments also will examine effects of Tat expression on anxiety-like behaviors using the open field, elevated plus maze, light-dark box, acoustic startle and marble burying tests. Assays of Tat mRNA and protein levels will correlate expression of Tat to the observed changes in behavior. In preliminary studies, Tat-induced mice spent less time than uninduced littermates in social interactions and more time immobile in forced swim stress tests, suggestive of a Tat-mediated increase in depression-like behavior. Tat-induced mice also demonstrated increased anxiety-related behaviors, with less time spent in open-field environments and a 3-fold increase in marble burying. Concurrently, we will examine the effects of Tat protein on brain structure and cell death using ex vivo magnetic resonance imaging (MRI) at ultra high magnetic field strength and TUNEL staining for apoptosis in Tat-induced animals. Preliminary ex vivo structural imaging studies documented significant reductions in the grey matter density of amygdala and hippocampus in Tat-expressing mice. Additionally, we will use BOLD functional MRI with corticosterone challenge to identify functional changes in brain regions associated with mood disorders resulting from varying levels of induction and duration of exposure to Tat protein and the response to a challenge dose of corticosterone. Overall, this project seeks to prove that functional and structural deficits can be detected in the brain circuitry of Tat-induced animals, thereby defining mechanisms by which Tat may mediate the mood disorders characteristic of NeuroAIDS.