Dissecting the interplay between the kynurenine pathway and extracellular vesicle signaling in schizophrenia

在精神分裂症患者的大脑中发现犬尿氨酸途径(KP)代谢产物L犬尿氨酸(KYN)和犬尿酸(KYNA)水平升高，并与这些人的认知障碍有关。KYN和KYNA可以结合和激活转录因子芳香烃受体(AHR)，后者在炎症和癌症中发挥关键作用。其他配体激活AHR可以诱导细胞外小泡(EV)的释放，特别是体外细胞释放小的外切体样小泡。然而，小胶质细胞和神经元(KP生理学中的关键细胞类型)对KP代谢物激活AHR的反应释放EV之前还没有被检测过。我们假设KP代谢物调节小胶质细胞和神经元释放EV，然后这些EV可以在细胞类型之间转移，以调节基因表达和改变细胞功能-最终影响精神分裂症的发病机制。因此，对于这个项目的初始部分，我们建议描述犬尿氨酸和KYNA对小胶质细胞和神经元释放EV的反应，并研究AHR和下游信号通路的参与。我们还将检查释放的电动汽车的miRNA和蛋白质含量，因为在不同刺激下激活细胞可以导致货物装入电动汽车的不同。这不仅潜在地改变了EV对受体细胞功能的影响，而且使EV成为有用的疾病生物标记物，因为它们的miRNA或蛋白质含量反映了它们被释放的细胞的含量。因此，本研究将研究释放的EVS的货物，EVS在小胶质细胞和神经元之间的转移以及它们对细胞功能的影响，如细胞存活/凋亡和基因表达的调节。还将评估细胞类型的特异性反应，如小胶质细胞释放炎性细胞因子，以及初级神经元中树突的形成和神经递质受体的表达。这项工作中有希望的发现在神经丰富的EVS中得到了验证，这些EV来自精神分裂症患者和Giorgii小组正在进行的工作中产生的对照组的血浆。这将使我们能够改进/扩展我们目前的工作，并以翻译相关的方式验证拟议项目的结果。

Increased levels of the kynurenine pathway (KP) metabolites L-kynurenine (KYN) and kynurenic acid (KYNA) have been found in the brains of patients with schizophrenia, and have been linked to cognitive impairment in these individuals. KYN and KYNA can bind and activate the transcription factor aryl hydrocarbon receptor (AHR), which has key roles in inflammation and cancer. Activation of the AHR by other ligands has been shown to induce extracellular vesicle (EV) release, in particular the release of small exosome-like vesicles from cells in vitro. However, the release of EVs from microglia and neurons - critical cell types in KP physiology - in response to AHR activation by KP metabolites has not been previously examined. We hypothesise that KP metabolites modulate the release of EVs from microglia and neurons, and that these EVs can then be transferred between cell types to regulate gene expression and modify cellular functions - ultimately impacting schizophrenia pathogenesis . For the initial part of this project we therefore propose to characterise the release of EVs from microglial cells and neurons in response to kynurenine and KYNA, and examine the involvement of AHR and downstream signalling pathways. We also will examine the miRNA and protein content of the released EVs, as activation of cells with different stimuli can result in the differential loading of cargo into EVs. This not only potentially alters the outcome of EV uptake on the function of the recipient cells, but also makes EVs useful biomarkers of disease as their miRNA or protein content reflects that of the cells they were released from. Therefore, this study will examine the cargo of the released EVs, the transfer of EVs between microglia and neurons and their effects on cellular functions such as cell survival/apoptosis and the regulation of gene expression. Cell-type specific responses such as the release of inflammatory cytokines from microglia, and dendrite formation and neurotransmitter receptor expression in primary neurons will also be assessed. Promising findings from this work validated in neuronally-enriched EVs derived from the plasma of individuals with schizophrenia and controls arising from ongoing work in the Giorgini group. This will permit us to refine/extend our current work and validate findings from the proposed project in a translationally relevant manner.