Modulation of Inhibitory Synapses by HIV-1 Proteins and Cannabinoids

描述（由申请人提供）：在许多神经退行性疾病中，包括HIV-1相关痴呆（HAD）在内的细胞死亡之前，树突形态的改变，如树突修剪和突触丢失。HAD患者的认知能力下降与兴奋性突触连接的丧失密切相关。暴露于hiv -1感染细胞释放的蛋白质后，兴奋性突触的丧失发生在导致细胞死亡之前，并通过不同的机制导致细胞死亡。突触丢失是可逆的。因此，兴奋性突触的丧失似乎是应对HIV-1蛋白诱导的过度兴奋性输入的一种机制。然而，神经元网络由兴奋性和抑制性突触连接组成，两者之间的动态相互作用决定了网络的总体兴奋性。抑制性突触在HAD患者认知能力下降中的相对影响尚不清楚。这一建议的前提是，更好地了解当神经网络暴露于HIV-1蛋白时抑制性突触连接如何变化，将最终改善我们对HAD的理解和治疗。本研究的重点是抑制性突触后密度以及暴露于HIV-1蛋白后抑制性突触连接如何变化。初步研究表明，当神经元培养物暴露于HIV-1蛋白中时，抑制性突触数量增加，而兴奋性突触明显减少，这表明抑制性突触可能会扩大规模，以抵消HIV-1诱导的网络兴奋性增加。拟议研究的目标是建立在这个基础上

DESCRIPTION (provided by applicant): Alterations in dendritic morphology such as dendritic pruning and synapse loss precede cell death in many neurodegenerative disorders, including HIV-1 associated dementia (HAD). Cognitive decline in patients with HAD is closely correlated with loss of excitatory synaptic connections. Loss of excitatory synapses following exposure to proteins released by HIV-1-infected cells occurs prior to and via a mechanism distinct from that leading to cell death. Synapse loss is reversible. Thus, loss of excitatory synapses appears to be a mechanism to cope with excess excitatory input induced by HIV-1 proteins. Neuronal networks, however, are comprised of both excitatory and inhibitory synaptic connections, and the dynamic interaction between the two defines the overall excitability of the network. The relative influence of inhibitory synapses in contributing to cognitive decline in HAD remains unclear. The premise of this proposal is that a better understanding of how inhibitory synaptic connections change when neural networks are exposed to HIV-1 proteins will ultimately improve how we understand and treat HAD. The focus of this study is the inhibitory post-synaptic density and how inhibitory synaptic connections change following exposure to HIV-1 proteins. Preliminary studies demonstrated that inhibitory synapse numbers increase when neuronal cultures are exposed to HIV-1 proteins as opposed to the marked decrease of excitatory synapses, suggesting that inhibitory synapses may scale to counteract HIV-1- induced increases in network excitability. The goal of the proposed research is to build on this foundation by to determine factors that modulate HIV-1 protein-induced changes in inhibitory synapses, mechanisms underlying the restoration of inhibitory synapses following exposure to HIV-1 proteins, and the possible role of cannabinoids in modulating these changes. Effort will be centered on three inter-related Specific Aims: (1) Determine the relationship between HIV-1 neurotoxin-induced alterations in excitatory and inhibitory synaptic connections. The hypothesis that inhibitory synaptic connections increase to compensate for network over- excitation induced by exposure to HIV-1 proteins will be tested. (2) Examine the ability of inhibitory synapses to return to basal levels following exposure to HIV-1 proteins. The hypothesis that stimuli known to induce recovery of excitatory synapses following HIV-1-induced loss will restore inhibitory synapses back to basal levels will be tested. (3) Investigate the effects of cannabinoids on HIV-1 protein-induced alterations in inhibitory synapses. The hypothesis that activation of cannabinoid receptors will protect from HIV-1 protein- induced increases in inhibitory synapses will be tested. These specific aims will be carried out using live-cell confocal imaging to count postsynaptic densities, presynaptic syGCaMP2 imaging to assess network excitability, and pharmacology to determine the mechanism responsible. The insights gleaned from these studies will enhance our understanding of how inhibitory synapses respond to exposure to HIV-1 proteins, while offering new insights into possible pharmacotherapies targeting inhibitory synapses to treat HAD.