Montesinos M Carmen, Desai Avani, Cronstein Bruce N
Department of Pharmacology, Universidad de Valencia, Burjassot, Valencia, Spain.
Arthritis Res Ther. 2006;8(2):R53. doi: 10.1186/ar1914. Epub 2006 Mar 6.
Prior studies demonstrate that adenosine, acting at one or more of its receptors, mediates the anti-inflammatory effects of methotrexate in animal models of both acute and chronic inflammation. Both adenosine A2A and A3 receptors contribute to the anti-inflammatory effects of methotrexate treatment in the air pouch model of inflammation, and the regulation of inflammation by these two receptors differs at the cellular level. Because different factors may regulate inflammation at different sites we examined the effect of low-dose weekly methotrexate treatment (0.75 mg/kg/week) in a model of acute peritoneal inflammation in adenosine A2A receptor knockout mice and A3 receptor knockout mice and their wild-type littermates. Following intraperitoneal injection of thioglycollate there was no significant difference in the number or type of leukocytes, tumor necrosis factor alpha (TNF-alpha) and IL-10 levels that accumulated in the thioglycollate-induced peritoneal exudates in adenosine A2A knockout mice or wild-type control mice. In contrast, there were more leukocytes, TNF-alpha and IL-10 in the exudates of the adenosine A3 receptor-deficient mice. Low-dose, weekly methotrexate treatment increased the adenosine concentration in the peritoneal exudates of all mice studied, and reduced the leukocyte accumulation in the wild-type mice and A3 receptor knockout mice but not in the A2A receptor knockout mice. Methotrexate reduced exudate levels of TNF-alpha in the wild-type mice and A3 receptor knockout mice but not the A2A receptor knockout mice. More strikingly, IL-10, a critical regulator of peritoneal inflammation, was increased in the methotrexate-treated wild-type mice and A3 knockout mice but decreased in the A2A knockout mice. Dexamethasone, an agent that suppresses inflammation by a different mechanism, was similarly effective in wild-type mice, A2A mice and A3 knockout mice. These findings provide further evidence that adenosine is a potent regulator of inflammation that mediates the anti-inflammatory effects of methotrexate. Moreover, these data provide strong evidence that the anti-inflammatory effects of methotrexate and adenosine are mediated by different receptors in different inflammatory loci, an observation that may explain why inflammatory diseases of some organs but not of other organs respond to methotrexate therapy.
先前的研究表明，腺苷通过作用于其一种或多种受体，在急性和慢性炎症的动物模型中介导甲氨蝶呤的抗炎作用。腺苷A2A和A3受体均有助于甲氨蝶呤在气囊炎症模型中的抗炎作用，并且这两种受体在细胞水平上对炎症的调节有所不同。由于不同因素可能在不同部位调节炎症，我们在腺苷A2A受体敲除小鼠和A3受体敲除小鼠及其野生型同窝小鼠的急性腹膜炎症模型中，研究了低剂量每周甲氨蝶呤治疗（0.75mg/kg/周）的效果。腹腔注射巯基乙酸盐后，在腺苷A2A敲除小鼠或野生型对照小鼠的巯基乙酸盐诱导的腹膜渗出物中积累的白细胞数量或类型、肿瘤坏死因子α（TNF-α）和IL-10水平没有显著差异。相比之下，腺苷A3受体缺陷小鼠的渗出物中有更多的白细胞、TNF-α和IL-10。低剂量每周甲氨蝶呤治疗增加了所有研究小鼠腹膜渗出物中的腺苷浓度，并减少了野生型小鼠和A3受体敲除小鼠中的白细胞积聚，但在A2A受体敲除小鼠中没有。甲氨蝶呤降低了野生型小鼠和A3受体敲除小鼠中TNF-α的渗出物水平，但在A2A受体敲除小鼠中没有。更显著的是，IL-10是腹膜炎症的关键调节因子，在甲氨蝶呤治疗的野生型小鼠和A3敲除小鼠中增加，但在A2A敲除小鼠中减少。地塞米松是一种通过不同机制抑制炎症的药物，在野生型小鼠、A2A小鼠和A3敲除小鼠中同样有效。这些发现提供了进一步的证据，表明腺苷是炎症的有效调节因子，介导甲氨蝶呤的抗炎作用。此外，这些数据提供了有力的证据，表明甲氨蝶呤和腺苷的抗炎作用是由不同炎症部位的不同受体介导的，这一观察结果可能解释了为什么某些器官的炎症性疾病对甲氨蝶呤治疗有反应，而其他器官则没有。
