Changes in expression of Toll-like receptor 4 mRNA and its down-stream cytokines mRNA in spinal cord in a rat model of incisional pain / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the changes in the expression of Toll-like receptor 4 (TLR4) mRNA and its down-stream cytokines IL-1β and TNF-α mRNA in spinal cord in a rat model of incisional pain.Methods Fifty-eight male Sprague-Dawley rats,weighing 180-220 g,were used in this study.A 1-cm longitudinal incision was made through skin,fascia and muscle of the plantar aspect of the hindpaw in isoflurane-anesthetized rats.Mechanical paw withdrawal threshold to yon Frey filament stimulation (MWT) on the operated and non-operated sides was measured before operation and at 0.5,1,2,6 and 12 h and 1,2,3,5 and 7 days after operation.Six rats were chosen and sacrificed before operation and at 2 and 8 h and 1,2,3,5 and 7 days after operation.Their lumbar segments (L4-6) of the spinal cord were removed for determination of the expression of TLR4,IL-1β and TNF-α mRNA by real-time PCR.Results Compared with the baseline value before operation,MWT on the operated side was significantly decreased at 0.5 h-5 days after operation,and the expression of TLR4,IL-1β and TNFα mRNA was up-regulated at 2 and 8 h and 1,2 and 3 days after operation (P ＜ 0.05),and no significant change was found in MWT on the non-operated side (P ＞ 0.05).MWT on the operated side was lowest at 2 h after operation and then gradually increased,the expression of TLR4 mRNA peaked on 1 day after operation,and the expression of IL-1 and TNF-α mRNA peaked at 8 h after operation (P ＜ 0.05).The TLR4 mRNA expression was negatively correlated with MWT on the operative side (r =-0.484,P ＜ 0.05),and IL-1 mRNA and TNF-α mRNA expression was positively correlated with TLR4 mRNA (r =0.294 and 0.540,respectively,P ＜ 0.05).Conclusion The expression of TLR4 mRNA and its down-stream cytokines IL-1β and TNF-α(mRNA in spinal cord is up-regulated,this change is involved in the maintenace of incisional pain,but it does not play an important role.