Heme Oxygenase-1(HO-1) Is Involved In Vincristine-induced Pain

Objective The chemotherapy drug vincristine(VCR) can induce neuropathic pain(chemotherapy-induced pain), manifested as hyperalgesia and allodynia. The chemotherapy-induced pain affected the quality of life of cancer patients and the effecacy of chemotherapy seriously. Heme oxygenase-1(HO-1) is the rate-limiting enzyme in the catabolism heme. The catabolism of heme and HO-1 overexpression may directly or indirectly inhibit the chain reaction of inflammation and stress. Here we investigated whether and how HO-1 is involved in VCR-induced pain.Methods Chemotherapy pain was induced by intraperitoneal injection of VCR(0.1mg/kg, daily, for 5 consecutive days) into mice. Spinal lumbar enlargement(L4-6 segments) of mice were harvested at different time points after VCR injection. The expression of HO-1, GFAP(astrocyte marker), IBA-1(microglia marker), MCP-1, and TNF-α m RNA was tested by Real-Time quantitative PCR. The expression of GFAP, IBA-1 and HO-1 and the distribution of HO-1 was tested by immunofluorescence. The HO-1 inhibitor(Sn PP) and inducer(COPP) were intraperitoneally injected. The pain behavior was tested. The expression of HO-1 and MAPKs were examined by Western Blot. The expression of HO-1, GFAP, IBA-1, MCP-1, TNF-α m RNA in the spinal cord were tested by Real-Time quantitative PCR; The expression of GFAP, IBA-1 in the spinal cord were examined by immunofluorescence; The expression of HO-1 and MAPKs were checked by Western blot. The HO-1 overexpression lentivirus(LV-HO-1) and the control(LV-CON) were injected into the spinal cord. The effect on mechanical allodynia and thermal hyperalgesia were tested by behavioral tests. The expression of HO-1 was checked by RT-PCR and Western blot after lentivirus intraspinal injection.Results( 1) The mechanical allodynia and thermal hyperalgesia were induced after injection of VCR in the mice, began from 6 d and maintained for more than 28 d.(2) The expression of HO-1 mRNA and HO-1 protein did not change significantly after VCR injection; Double immunofluorescence showed that HO-1 were double labeled with neuronal marker(NeuN), the astrocyte marker(GFAP) and the microglia marker(CD11b). The result indicated that HO-1 was expressed in all three cell types in the spinal cord, with a major distribution in astrocytes.(3) VCR induced GFAP and IBA-1 mRNA upregulation in the spinal cord; Immunofluorescence showed glial cell were activated.(4) The HO-1 inducer(COPP) attenuated the mechanical and thermal hyperalgesia induced by VCR in a dose dependent manner, whereas the inhibitor(SnPP) had no effect. The expression of HO-1 mRNA and protein were increased by COPP.(5) The HO-1 overexpression lentivirus(LV-HO-1) significantly and persistently alleviated VCR-induced mechanical and thermal hyperalgesia after intraspinal injection. The expression of HO-1 mRNA and protein were increased by LV-HO-1.(6) RT-PCR and immunofluorescence showed that COPP reduced glial cells activation.(7) VCR induced the activation of MAPKs, which was reduced by COPP.(8) VCR also increased the expression of MCP-1 and TNF-α mRNA, which was decreased by COPP.Conclusions Intraperitoneal injection of VCR induced persistent pain and accompanied by the activation of glial cells and MAPKs, and the increase of inflammatory cytokines TNF-α, chemokine MCP-1 expression in the spinal cord. The exogenous increase of HO-1 in the spinal cord relieved the hyperalgesia induced by VCR, reduced the activation of glial cells and MAPKs, and decreased the expression of TNF-α and MCP-1 in the spinal cord. The HO-1 inhibitor had no effect on the pain behavior. These results indicate that HO-1 overexpression attenuated the chemotherapy pain induced by vincristine. Targeting HO-1 may be an effective method for the treatment of pain caused by vincristine.