School of Medicine, University of Electronic Science and Technology of China, Chengdu, 610054, China.
Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, USA.
J Neuroimmune Pharmacol. 2018 Sep;13(3):330-344. doi: 10.1007/s11481-018-9779-4. Epub 2018 Mar 1.
Chronic neuroinflammation still remains a common underlying feature of HIV-infected patients on combined anti-retroviral therapy (cART). Previous studies have reported that despite near complete suppression of virus replication by cART, cytotoxic viral proteins such as HIV trans-activating regulatory protein (Tat) continue to persist in tissues such as the brain and the lymph nodes, thereby contributing, in part, to chronic glial activation observed in HIV-associated neurological disorders (HAND). Understanding how the glial cells cross talk to mediate neuropathology is thus of paramount importance. MicroRNAs (miR) also known as regulators of gene expression, have emerged as key paracrine signaling mediators that regulate disease pathogenesis and cellular crosstalk, through their transfer via the extracellular vesicles (EV). In the current study we have identified a novel function of miR-9, that of mediating microglial migration. We demonstrate that miR-9 released from Tat-stimulated astrocytes can be taken up by microglia resulting in their migratory phenotype. Exposure of human astrocytoma (A172) cells to HIV Tat resulted in induction and release of miR-9 in the EVs, which, was taken up by microglia, leading in turn, increased migration of the latter cells, a process that could be blocked by both an exosome inhibitor GW4869 or a specific target protector of miR-9. Furthermore, it was also demonstrated that EV miR-9 mediated inhibition of the expression of target PTEN, via its binding to the 3'UTR seed sequence of the PTEN mRNA, was critical for microglial migration. To validate the role of miR-9 in this process, microglial cells were treated with EVs loaded with miR-9, which resulted in significant downregulation of PTEN expression with a concomitant increase in microglial migration. These findings were corroborated by transfecting microglia with a specific target protector of PTEN, that blocked miR-9-mediated downregulation of PTEN as well as microglial migration. In vivo studies wherein the miR-9 precursor-transduced microglia were transplanted into the striatum of mice, followed by assessing their migration in response to a stimulus administered distally, further validated the role of miR-9 in mediating microglial migration. Collectively, our findings provide evidence that glial crosstalk via miRs released from EVs play a vital role in mediating disease pathogenesis and could provide new avenues for development of novel therapeutic strategies aimed at dampening neuropathogenesis.
慢性神经炎症仍然是接受联合抗逆转录病毒治疗(cART)的 HIV 感染患者的常见潜在特征。先前的研究报告表明,尽管 cART 几乎完全抑制了病毒复制,但 HIV 反式激活调节蛋白(Tat)等细胞毒性病毒蛋白仍持续存在于大脑和淋巴结等组织中,从而部分导致了 HIV 相关神经障碍(HAND)中观察到的慢性神经胶质激活。因此,了解神经胶质细胞如何相互作用以介导神经病理学非常重要。microRNAs(miR)也称为基因表达调节剂,已成为关键的旁分泌信号介质,通过其通过细胞外囊泡(EV)的转移来调节疾病发病机制和细胞串扰。在本研究中,我们确定了 miR-9 的新功能,即介导小胶质细胞迁移。我们证明,Tat 刺激的星形胶质细胞释放的 miR-9 可以被小胶质细胞摄取,从而导致其迁移表型。将人类星形细胞瘤(A172)细胞暴露于 HIV Tat 会导致 EV 中 miR-9 的诱导和释放,而后者则被小胶质细胞摄取,从而导致后者细胞的迁移增加,该过程可以被外泌体抑制剂 GW4869 或 miR-9 的特定靶标保护剂阻断。此外,还证明了 EV miR-9 通过与 PTEN mRNA 的 3'UTR 种子序列结合来抑制靶标 PTEN 的表达,这对于小胶质细胞迁移至关重要。为了验证 miR-9 在该过程中的作用,用负载 miR-9 的 EV 处理小胶质细胞,导致 PTEN 表达显著下调,同时小胶质细胞迁移增加。用 PTEN 的特定靶标保护剂转染小胶质细胞,阻断 miR-9 介导的 PTEN 下调以及小胶质细胞迁移,证实了这些发现。体内研究中,将 miR-9 前体转导的小胶质细胞移植到小鼠纹状体中,然后评估它们对远端给予刺激的迁移反应,进一步验证了 miR-9 在介导小胶质细胞迁移中的作用。总之,我们的研究结果提供了证据,表明 EV 释放的神经胶质细胞通过 miR 进行的串扰在介导疾病发病机制方面起着至关重要的作用,并为开发旨在抑制神经发病机制的新型治疗策略提供了新途径。
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