De Simone Roberta, Ajmone-Cat Maria Antonietta, Carnevale Daniela, Minghetti Luisa
Department of Cell Biology and Neurosciences, Section of Degenerative and Inflammatory Neurological Diseases, Istituto Superiore di Sanità, Rome, Italy.
J Neuroinflammation. 2005 Jan 25;2(1):4. doi: 10.1186/1742-2094-2-4.
Nicotinic acetylcholine (Ach) receptors are ligand-gated pentameric ion channels whose main function is to transmit signals for the neurotransmitter Ach in peripheral and central nervous system. However, the alpha7 nicotinic receptor has been recently found in several non-neuronal cells and described as an important regulator of cellular function. Nicotine and ACh have been recently reported to inhibit tumor necrosis factor-alpha (TNF-alpha) production in human macrophages as well as in mouse microglial cultures. In the present study, we investigated whether the stimulation of alpha7 nicotinic receptor by the specific agonist nicotine could affect the functional state of activated microglia by promoting and/or inhibiting the release of other important pro-inflammatory and lipid mediator such as prostaglandin E2. METHODS: Expression of alpha7 nicotinic receptor in rat microglial cell was examined by RT-PCR, immunofluorescence staining and Western blot. The functional effects of alpha7 receptor activation were analyzed in resting or lipopolysaccharide (LPS) stimulated microglial cells pre-treated with nicotine. Culture media were assayed for the levels of tumor necrosis factor, interleukin-1beta, nitric oxide, interleukin-10 and prostaglandin E2. Total RNA was assayed by RT-PCR for the expression of COX-2 mRNA. RESULTS: Rat microglial cells express alpha7 nicotinic receptor, and its activation by nicotine dose-dependently reduces the LPS-induced release of TNF-alpha, but has little or no effect on nitric oxide, interleukin-10 and interleukin-1beta. By contrast, nicotine enhances the expression of cyclooxygenase-2 and the synthesis of one of its major products, prostaglandin E2. CONCLUSIONS: Since prostaglandin E2 modulates several macrophage and lymphocyte functions, which are instrumental for inflammatory resolution, our study further supports the existence of a brain cholinergic anti-inflammatory pathway mediated by alpha7 nicotinic receptor that could be potentially exploited for novel treatments of several neuropathologies in which local inflammation, sustained by activated microglia, plays a crucial role.
烟碱型乙酰胆碱（Ach）受体是配体门控的五聚体离子通道，其主要功能是在周围和中枢神经系统中传递神经递质Ach的信号。然而，最近在几种非神经元细胞中发现了α7烟碱型受体，并将其描述为细胞功能的重要调节因子。最近有报道称，尼古丁和乙酰胆碱可抑制人巨噬细胞以及小鼠小胶质细胞培养物中肿瘤坏死因子-α（TNF-α）的产生。在本研究中，我们调查了特异性激动剂尼古丁对α7烟碱型受体的刺激是否会通过促进和/或抑制其他重要的促炎和脂质介质（如前列腺素E2）的释放来影响活化小胶质细胞的功能状态。
通过逆转录聚合酶链反应（RT-PCR）、免疫荧光染色和蛋白质印迹法检测大鼠小胶质细胞中α7烟碱型受体的表达。在用尼古丁预处理的静息或脂多糖（LPS）刺激的小胶质细胞中分析α7受体激活的功能效应。检测培养基中肿瘤坏死因子、白细胞介素-1β、一氧化氮、白细胞介素-10和前列腺素E2的水平。通过RT-PCR检测总RNA中环氧合酶-2（COX-2）mRNA的表达。
大鼠小胶质细胞表达α7烟碱型受体，尼古丁对其激活呈剂量依赖性地降低LPS诱导的TNF-α释放，但对一氧化氮、白细胞介素-10和白细胞介素-1β几乎没有影响。相比之下，尼古丁可增强环氧合酶-2的表达及其主要产物之一前列腺素E2的合成。
由于前列腺素E2可调节多种巨噬细胞和淋巴细胞功能，这些功能对炎症消退至关重要，我们的研究进一步支持存在由α7烟碱型受体介导的脑胆碱能抗炎途径，这可能为几种神经病理学的新治疗方法提供潜在途径，在这些神经病理学中，由活化小胶质细胞维持的局部炎症起着关键作用。
