趋化因子CCL2对骨癌痛大鼠痛行为的影响及其外周机制

Effects of CC chemokine ligand 2 on pain behavior in a rat model of bone cancer pain and its underlying peripheral mechanism

目的研究 CC 趋化因子配体 2(CC chemokine ligand 2,CCL2)对骨癌痛(bone cancer pain,BCP)大鼠痛行为的影响及其外周机制。方法在 SD 大鼠右侧后肢胫骨骨髓腔内注入 Walker256 乳腺癌细胞,建立 BCP 模型,假手术组注射等体积的生理盐水。检测 BCP 大鼠机械痛阈值,来判断 BCP 模型是否成功。采用免疫荧光染色的方法,检测 2 组大鼠 L4 和 L5 背根神经节(dorsal rootganglion,DRG)中 CCL2 的表达情况。术侧足底注射 CCL2(500 ng,25 μL),观察对 2 组大鼠术侧后肢抬腿和舔脚行为的影响。采用全细胞膜片钳的方法,考察 CCL2 对 2 组大鼠急性分离培养的 DRG 神经元膜电位的影响。结果术后 14 d,BCP 大鼠的机械刺激痛阈显著低于假手术组;其术侧 L4 和 L5 DRG 中 CCL2 的表达明显高于假手术组;足底注射 CCL2 后,BCP 大鼠右后肢的悬空时间显著多于假手术组;CCL2 引起 BCP 大鼠 DRG 神经元去极化的比例和幅度均显著高于假手术组。结论 CCL2 可易化 BCP 大鼠痛行为,其外周机制可能由 CCL2 诱导 DRG 神经元去极化,进而增强神经元兴奋性,提示 CCL2 在 BCP 的发生发展中发挥重要作用。

Objective To investigate the effects of CC chemokine ligand 2 (CCL2) on pain behavior in a rat model of bone cancer pain (BCP) and the underlying peripheral mechanisms. Methods BCP models were developed by inoculation of Walker256 mammary gland carcinoma cells into the tibia medullary cavities of right hind limbs SD rats. The same volume of saline was injected in sham operation (sham) group. The mechanical pain threshold was measured to judge the success of BCP model. Expression of CCL2 in L4 and L5 dorsal root ganglion (DRG) was detected by immunofluorescence staining. CCL2 (500 ng, 25 μL) was injected into plantar of the operated side to observe its effects on leg-raising and foot-licking behaviors of hind paws in BCP and sham rats. Whole-cell patch-clamp recording was used to investigate the effects of CCL2 on membrane potential of acutely dissociated DRG neurons from the two groups. Results Fourteen days after operation, the mechanical pain threshold in the right hind paws of BCP rats was significantly lower than that in sham rats. Compared with the Sham rats, the expression of CCL2 in L4 and L5 DRG of BCP rats was signi ficantly higher. Plantar injection of CCL2 increased paw lift time in BCP rats. The rate and amplitude of depolarization induced by CCL2 in BCP DRG neurons were significantly higher than those in sham neurons. Conclusion CCL2 facilitates pain behavior in BCP rats, and its peripheral mechanism maybe involves CCL2-induced neuron depolarization to enhance excitability of DRG neurons. These results indicate that CCL2 plays an important role in development of BCP.