Astrocytic expression of GFAP and serum levels of IL-1β and TNF-α in rats treated with different pain relievers

ABSTRACT Pro-inflammatory cytokines and glial cells, especially microglial cells, have been implicated in persistent pain sensitization. Less is known about the role of astrocytes in pain regulation. This study aimed to observe the expression of the astrocytic biomarker glial fibrillary acidic protein (GFAP) and the serum levels of interleukin 1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) after short-term administration of central pain relievers in rats not submitted to noxious stimuli. Male Wistar rats were divided into five groups, receiving for nine days- (1) amitriptyline (Amt-10 mg/kg/day, by gavage); (2) gabapentin (Gb-60 mg/kg/day, by gavage; (3) methadone (Me-4.5 mg/kg/day, intraperitoneal route [IP]); (4) morphine (Mo-10 mg/kg/day, IP); or (5) 0.9% saline solution, IP. Brain samples were collected for immunohistochemical study of GFAP expression in the mesencephalon and nucleus accumbens (NAc). The area of GFAP-positive cells was calculated using MetaMorph software and serum levels of IL-1β and TNF-α were measured by enzyme-linked immunosorbent assay. Serum TNF-α levels were decreased in the groups treated with Mo, Me and Gb, but not in the Amt-treated group. IL-1β decreased only in rats treated with Me. The astrocytic expression of GFAP was decreased in the brainstem with all drugs, while it was increased in the NAc with Amt, Me and Mo.

摘要 促炎细胞因子与神经胶质细胞（尤其是小胶质细胞）已被证实参与持续性疼痛敏化的病理过程。目前针对星形胶质细胞在疼痛调控中的作用仍知之甚少。本研究旨在观察未接受伤害性刺激的大鼠，在短期给予中枢性止痛药后，其星形胶质细胞生物标志物胶质纤维酸性蛋白（glial fibrillary acidic protein，GFAP）的表达水平，以及血清白细胞介素1β（interleukin 1 beta，IL-1β）与肿瘤坏死因子α（tumor necrosis factor alpha，TNF-α）的含量变化。
将雄性Wistar大鼠随机分为5组，连续给药9天：(1) 阿米替林（Amt-10 mg/kg/天，灌胃给药）；(2) 加巴喷丁（Gb-60 mg/kg/天，灌胃给药）；(3) 美沙酮（Me-4.5 mg/kg/天，腹腔注射（intraperitoneal route，IP））；(4) 吗啡（Mo-10 mg/kg/天，腹腔注射）；(5) 0.9%生理盐水，腹腔注射。
采集脑组织样本，针对中脑与伏隔核（nucleus accumbens，NAc）内GFAP的表达开展免疫组织化学分析；采用MetaMorph软件定量计算GFAP阳性细胞的面积，并通过酶联免疫吸附试验检测血清IL-1β与TNF-α的水平。
结果显示，吗啡、美沙酮与加巴喷丁处理组的血清TNF-α水平显著降低，而阿米替林处理组未出现该变化；仅美沙酮处理组的血清IL-1β水平有所下降。所有药物处理组的脑干内GFAP星形胶质细胞表达均受到抑制，而阿米替林、美沙酮与吗啡处理组的伏隔核内GFAP表达则出现上调。