Choi Hyun B, Ryu Jae K, Kim Seung U, McLarnon James G
Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada.
J Neurosci. 2007 May 2;27(18):4957-68. doi: 10.1523/JNEUROSCI.5417-06.2007.
We investigated the involvement and roles of the ionotropic purinergic receptor P2X(7)R in microglia in mediating lipopolysaccharide (LPS)-induced inflammatory responses and neuronal damage in rat striatum. A detailed in vivo study showed that LPS injection into striatum markedly increased the expression of P2X(7)R in microglia compared with control (saline)-injected animals. Additionally, LPS injection upregulated a broad spectrum of proinflammatory mediators, including inducible nitric oxide synthase (nitric oxide production marker), 3-nitrotyrosine (peroxynitrite-mediated nitration marker), 4-hydroxynonenal (lipid peroxidation marker), and 8-hydroxy-2'-deoxyguanosine (oxidative DNA damage marker), and reduced neuronal viability. The P2X(7)R antagonist oxidized ATP (oxATP) was effective in attenuating expressions of all inflammatory mediators and in addition inhibited LPS-induced activation of the cellular signaling factors p38 mitogen-activated protein kinase and transcriptional factor nuclear factor kappaB. Most importantly, in vivo, oxATP blockade of P2X(7)R also reduced numbers of caspase-3-positive neurons and increased neuronal survival in LPS-injected brain. In vitro, LPS stimulation of cultured human microglia enhanced cellular expressions of a host of proinflammatory factors, including cyclooxygenase-2, interleukin-1beta (IL-1beta), IL-6, IL-12, and tumor necrosis factor-alpha; all factors were inhibited by oxATP. A novel finding was that LPS potentiated intracellular Ca(2+) mobilization induced by the P2X(7)R ligand 2',3'-O-(4-benzoyl-benzoyl) ATP, which could serve as a mechanistic link for P2X(7)R amplification of inflammatory responses. Our results suggest critical roles for P2X(7)R in mediating inflammation and inhibition of this subtype purinergic receptor as a novel therapeutic approach to reduce microglial activation and confer neuroprotection in inflamed and diseased brain.
我们研究了离子型嘌呤能受体P2X(7)R在小胶质细胞中介导脂多糖（LPS）诱导的大鼠纹状体炎症反应和神经元损伤中的作用。一项详细的体内研究表明，与注射生理盐水的对照动物相比，向纹状体注射LPS可显著增加小胶质细胞中P2X(7)R的表达。此外，注射LPS上调了多种促炎介质的表达，包括诱导型一氧化氮合酶（一氧化氮产生标志物）、3-硝基酪氨酸（过氧亚硝酸盐介导的硝化标志物）、4-羟基壬烯醛（脂质过氧化标志物）和8-羟基-2'-脱氧鸟苷（氧化性DNA损伤标志物），并降低了神经元活力。P2X(7)R拮抗剂氧化ATP（oxATP）可有效减弱所有炎症介质的表达，此外还可抑制LPS诱导的细胞信号因子p38丝裂原活化蛋白激酶和转录因子核因子κB的激活。最重要的是，在体内，oxATP对P2X(7)R的阻断还减少了注射LPS的脑中半胱天冬酶-3阳性神经元的数量，并提高了神经元的存活率。在体外，LPS刺激培养的人小胶质细胞可增强多种促炎因子的细胞表达，包括环氧合酶-2、白细胞介素-1β（IL-1β）、IL-6、IL-12和肿瘤坏死因子-α；所有这些因子均被oxATP抑制。一个新发现是，LPS增强了由P2X(7)R配体2',3'-O-（4-苯甲酰苯甲酰）ATP诱导的细胞内[Ca(2+)]i动员，这可能是P2X(7)R放大炎症反应的一个机制联系。我们的结果表明，P2X(7)R在介导炎症中起关键作用，抑制这种亚型的嘌呤能受体作为一种新的治疗方法，可减少小胶质细胞的激活，并在炎症和患病脑中提供神经保护。
