Abstract: Objective To investigate the effects of HO/CO pathway on inflammation cytokines in a rat model of incisional pain. Methods Thirty-six rats were executed to collect ipsilateral spinal cord tissues for HO- 1 detection by Western blot assay, and cytokines tumor necrosis factor (TNF)- a, interleukin (IL)-1b, IL-6 and high mobility group box (HMGB)1 were detected by ELISA before and at 1, 4, 8, 12 and 24 h after establishing incisional pain model. Additionally, 36 rats without establishment of incisional pain model were used as control group. A total of 144 model rats of incisional pain were divided into incisional pain (IP) group, IP+hemin group (100 mg/kg hemin was injected by i.p. before operation), IP+ Znpp-IX group (45 μmoL/kg Znpp-IX was injected by i.p. before operation) and IP+CORM-2 group (10 mg/kg CORM-2 was injected by i.p. before operation). Values of paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) were detected, and expressions of TNF-a, IL-1 b, IL-6 and HMGB1 were measured by ELISA before and at 1, 4, 8, 12 and 24 h after operation. Results Compared with pre-operation of incisional pain in rats, expression levels of HO-1 protein and cytokines TNF-a, IL-1 b, IL-6 and HMGB1 were increased at 1, 4, 8, 12 and 24 h after operation (P＜ 0.05). Compared with control group, values of PWMT and PWTL were obviously decreased, and expression levels of IL-1β, TNF-α, IL-6 and HMGB1 were increased at 1, 4, 8, 12 and 24 h after operation in IP groups (P＜ 0.05). Compared with IP groups, values of PWMT and PWTL were significantly increased and cytokines TNF- a, IL-1 b, IL-6 and HMGB1 were decreased at 1, 4, 8, 12 and 24 h after operation in IP+hemin group and IP+CORM-2 group (P＜ 0.05). Values of PWMT and PWTL were decreased and cytokines TNF-α, IL-1β, IL-6 and HMGB1 were increased in IP+Znpp-IX group (P＜ 0.05). Conclusion Incisional pain can increase the expression of HO-1, and HO-1/CO pathway exists the regulatory effect on inflammatory cytokines in the rat model of incisional pain.

Key words: pain, postoperation, inflammation, disease models, animal, tumor necrosis factor-alpha, interleukin-1beta, high mobility group protein 1, heme oxygenase 1, HO-1/CO signal path