Cappoli Natalia, Mezzogori Daniele, Tabolacci Elisabetta, Coletta Isabella, Navarra Pierluigi, Pani Giovambattista, Dello Russo Cinzia
Institute of Pharmacology, Università Cattolica del S. Cuore, Roma.
Institute of Human Physiology, Università Cattolica del S. Cuore, Roma.
EXCLI J. 2019 Sep 6;18:779-798. doi: 10.17179/excli2019-1715. eCollection 2019.
Emerging evidence suggests the potential use of rapamycin in treatment of several neurological disorders. The drug readily crosses the blood brain barrier and may exert direct immunomodulatory effects within the brain. Microglia are the main innate immune cells of the brain, thus critically involved in the initiation and development of inflammatory processes at this level. However, there are conflicting data from rodent studies about the pharmacological effects of rapamycin on microglial inflammatory responses. Considering that rodent microglia display relevant biochemical and pharmacological differences compared to human microglia, in the present study we studied the effects of rapamycin in an experimental model of human microglia, the human microglial clone 3 (HMC3) cell line. Rapamycin was tested in the nM range both under basal conditions and in cells activated with a pro-inflammatory cytokine cocktail, consisting in a mixture of interferon-γ and interleukin-1β (II). The drug significantly increased II stimulatory effect on interleukin-6 (IL-6) expression and release in the HMC3 cells, while reducing the production of free oxygen radicals (ROS) both under basal conditions and in cells activated with II. Consistently with its known molecular mechanism of action, rapamycin reduced the extent of activation of the so-called 'mechanistic' target of rapamycin complex 1 (mTORC1) kinase and the total amount of intracellular proteins. In contrast to rodent cells, rapamycin did not alter human microglial cell viability nor inhibited cell proliferation. Moreover, rapamycin did not exert any significant effect on the morphology of the HMC3 cells. All together these data suggest that the inhibition of mTORC1 in human microglia by rapamycin results in complex immunomodulatory effects, including a significant increase in the expression and release of the pro-inflammatory IL-6.
新出现的证据表明雷帕霉素在治疗几种神经系统疾病方面具有潜在用途。该药物能够轻易穿过血脑屏障，并可能在脑内发挥直接的免疫调节作用。小胶质细胞是脑内主要的固有免疫细胞，因此在这一水平的炎症过程的启动和发展中起着关键作用。然而，关于雷帕霉素对小胶质细胞炎症反应的药理作用，啮齿动物研究的数据存在矛盾。鉴于与人类小胶质细胞相比，啮齿动物小胶质细胞表现出相关的生化和药理差异，在本研究中，我们在人类小胶质细胞的实验模型——人类小胶质细胞克隆3（HMC3）细胞系中研究了雷帕霉素的作用。在基础条件下以及在用促炎细胞因子混合物（由干扰素-γ和白细胞介素-1β（IL）组成）激活的细胞中，对纳摩尔范围内的雷帕霉素进行了测试。该药物显著增强了IL对HMC3细胞中白细胞介素-6（IL-6）表达和释放的刺激作用，同时在基础条件下以及在用IL激活的细胞中均减少了活性氧（ROS）的产生。与其已知的分子作用机制一致，雷帕霉素降低了所谓的雷帕霉素复合物1（mTORC1）激酶的激活程度以及细胞内蛋白质的总量。与啮齿动物细胞不同，雷帕霉素并未改变人类小胶质细胞的活力，也未抑制细胞增殖。此外，雷帕霉素对HMC3细胞的形态没有产生任何显著影响。所有这些数据表明，雷帕霉素对人类小胶质细胞中mTORC1的抑制会导致复杂的免疫调节作用，包括促炎细胞因子IL-6的表达和释放显著增加。
