Effect of CCL2 neutralizing antibody on pain behaviour and spinal microglia activation in rat bone cancer model

Objective To investigate the role of CCL2 in pain facilitation and spinal mechanisms in the rat model of bone cancer pain.Methods The bone cancer pain model was developed by inoculating.Walker 256 mammary gland carcinoma cells into the rat tibia medullary cavity.SD female rats were divided into 5 groups randomly ( n =8):sham group( group Ⅰ),sham + CCL2 antibody group( group Ⅱ),BCP group( group Ⅲ),BCP +control lgG group ( group Ⅳ),BCP + CCL2 antibody group ( group Ⅴ ).VonFrey threshold was measured one day before operation and 1 st,3 rd,5th,7th,10th,14th,21 st after operation.CCL2 antibody or control lgG was injected intrathecally from 10th to 12th day.The expression of the spinal Iba-1 ( microglial marker) in rat lumbar4-5 was detected by immunohistochemistry assay.Results From the 10th to 21st day after operation,the PMWT of group Ⅲ rats were ( 1.78 ±0.38)g,( 1.70 ±0.17)g,( 1.35 ±0.07 )g;group Ⅳ rats were (2.99 ±0.67)g,(2.52 ±0.75)g,(1.13±0.07)g ; and group Ⅴ rats were (5.88±0.66)g,(7.81 ±0.75)g,(6.19±0.53)g.Compared with group Ⅲ,the PMWT of group Ⅴ was remarkly higher (P＜0.01) ; group Ⅳ had no obvious statistical significance (P＞0.05).At the 14th day after operation,the MOD of group Ⅲ,Ⅳ and Ⅴ rats were (151.3 ±10.8 ),( 149.2 ± 10.6),(74.5 ± 5.0),Compared with group Ⅲ,the MOD of group Ⅴ was significantly increased (P＜0.01 ),group Ⅳ had no obvious statistical significance (P ＞ 0.05 ).Conclusion Intrathecal injection of CCL2 antibody can remarkly attenuate established pain facilitation of tibial bone cancer pain rats,and significantly suppress the expression of Iba-1.It suggests that CCL2 is involved in the bone cancer pain via activation of spinal microglia. Key words: Bone cancer pain;  Hyperalgesic;  Microglia;  CCL2;  Spinal mechanism