Persistent protease-activated receptor 4 signaling mediates thrombin-induced microglial activation
Persistent protease-activated receptor 4 signaling mediates thrombin-induced microglial activation
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DOI：
10.1074/jbc.m302137200
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发表时间：
2003-08-15
影响因子：
4.8
通讯作者：
Festoff, BW
中科院分区：
文献类型：
--
作者：
Suo, ZM;Wu, M;Festoff, BW
凝血酶是凝血级联反应中的终极丝氨酸蛋白酶，是一种促炎因子，可引起脑小胶质细胞的增殖和激活。然而，其主要受体蛋白酶激活受体1(PAR1)的参与似乎仅限于促进小胶质细胞的增殖，而不是诱导炎症介质。在目前的研究中，我们现在报道凝血酶促进脑小胶质细胞炎症介质的作用是通过另一种凝血酶受体PAR4介导的。在这里，我们发现PAR4激动肽(PAR4AP，GYPGKF)，而不是PAR1AP(TRAP，SFLLRN)，不仅能在体外诱导培养的小鼠小胶质细胞产生肿瘤坏死因子-α(TNF-α)，而且在体内也能诱导大鼠皮质产生肿瘤坏死因子-α。通过特定的反义而不是正义的方法下调小胶质细胞培养中PAR4的表达，寡核苷酸降低了PAR4AP诱导的肿瘤坏死因子-α。机制研究表明，与PAR1信号通路相比，PAR4AP诱导的小胶质细胞产生的肿瘤坏死因子-α可能与PAR4AP诱导的小胶质细胞产生肿瘤坏死因子-α有关。综上所述，这些结果表明，PAR4激活介导了凝血酶对小胶质细胞的潜在有害影响，这意味着将PAR1作为潜在的抗炎靶点的观点应该转向PAR4，作为与神经创伤和神经退行性变相关的脑炎性疾病的更特异的治疗靶点。
We have previously reported that thrombin, the ultimate serine protease in the coagulation cascades, is a proinflammatory agent that causes proliferation and activation of brain microglial cells. However, participation of its principal receptor, the protease-activated receptor 1 (PAR1) appears to be limited to promoting microglial proliferation and not induction of inflammatory mediators. In the present study, we now report that thrombin action in promoting inflammatory mediators from brain microglia is mediated through another thrombin receptor, PAR4. Here we show that the PAR4 agonist peptide (PAR4AP, GYPGKF), but not the PAR1AP (TRAP, SFLLRN), induced tumor necrosis factor-alpha (TNF-alpha) production not only in cultured murine microglial cells in vitro but also in rat cortex in vivo. Down-regulation of PAR4 expression in microglial cultures by a specific antisense, but not a sense, oligonucleotide reduced PAR4AP- induced TNF-alpha. Mechanistic studies indicated that, in comparison with PAR1 signaling, prolonged increase of [Ca2+](i) and phosphorylation of p44/42 mitogen-activated protein kinases, as well as NFkappaB activation may be responsible for PAR4AP-induced TNF-alpha production in microglia. Taken together, these results demonstrate that PAR4 activation mediates the potentially detrimental effects of thrombin on microglia, implying that perspectives of exploiting PAR1 as a potential anti-inflammatory target should be shifted toward PAR4 as a much more specific therapeutic target in brain inflammatory conditions associated with neurotrauma and neurodegenerations.