胫骨癌痛大鼠脊髓细胞外信号调节激酶5活性的变化

Changes in activity of extracellular signal-regulated protein kinase 5 in spinal cord in a rat model of bone cancer pain

目的评价胫骨癌痛大鼠脊髓细胞外信号调节激酶5（ERK5）活性的变化。方法雌性未交配SD大鼠108只，体重160．180g，采用随机数字表法，将其分为3组（n=36）：对照组（C组）、假手术组（S组）和胫骨癌痛组（BCP组）。BCP组胫骨骨髓腔内注射Walker256乳腺癌细胞混悬液制备大鼠胫骨癌痛模型；S组胫骨骨髓腔内注射等容量生理盐水；C组不作任何处理。于接种前1d、接种后3、5、7、14和21d时，测定机械痛阈。C组和S组于接种后21d痛阈测定结束后随机处死6只大鼠，BCP组分别于接种后3、5、7、14和21d痛阈测定结束后随机处死6只大鼠，取脊髓组织，采用Westernblot法测定脊髓背角磷酸化ERK5（p-ERK5）、ERK5和Fos蛋白的表达。结果C组和S组各时点机械痛阈、脊髓背角p-ERK5、ERK5和Fos蛋白的表达差异无统计学意义（P〉0．05）。与C组和S组比较，BCP组接种后7—21d时机械痛阈下降，接种后5—21d时脊髓p-ERK5和Fos蛋白表达上调（P〈0．05），ERK5表达差异无统计学意义（P〉0．05）。结论大鼠胫骨骨髓腔内注射肿瘤细胞可能通过增强脊髓ERK5活性，导致其下游Fos蛋白的释放，从而诱发骨癌痛。

Objective To evaluate the changes in the activity of extracellular signal-regulated protein ki- nase 5 （ERK5） in the spinal cord in a rat model of bone cancer pain （BCP） .Methods One hundred and eight female Sprague-Dawley rats, weighing 160-180 g, were randomly divided into 3 groups （ n = 36 each） ： control group （group C）： sham operation （group S） and group BCP. In group BCP Walker 256 mammary gland cancer cell suspension （1 × 10^5 cells/ml） 5μl was injected into the left tibia, while in group S normal saline 5 μl was in- jected into the left tibia instead of cancer cell suspension. Group C underwent no treatment. Mechanical paw with- drawal threshold to von Frey filament stimulation （MWT） was measured at 1 day before inoculation and 3, 5, 7, 14 and 21 days after inoculation. Six rats were sacrificed after the last t of MWT in groups C and S or after measurement of MWT at 3, 5, 7, 14 and 21 days after inoculation in group BCP and the spinal cord was re- moved for determination of the expression of phosphorylated ERK5 （p-ERK5）, ERK5 and Fos protein in the spinal dorsal horn by Western blot analysis. Results There was no significant difference in the MWT and expression of p-ERKS, ERK5 and Fos protein at each time point between groups C and S （P 〉 0.05）. Compared with groups C and S, MWT was significantly decreased at 7-21 days after inoculation, the expression of p-ERK5 and Fos protein was significantly up-regulated at 5-21 days after inoculation （ P 〈 0.05）, and no significant change was found in the expression of ERK5 in group BCP （ P 〉 0.05）. Conclusion Intra-tibial inoculation of Walker-256 breast can-cer cells can increase the activity of ERK5 in the spinal cord in rats, leading to the increased release of Fos pro- tein, thus inducing BCP.