An Experimental Study On The Role Of CD55in Mice Suffering From Diabetic Neuropathic Pain

Backround：The diabetic neuropathic pain(DNP)is one of the most common chronic complicationof diabetes, and is one of the most common kind of the neuropathic pain（NPP）in clinical.The clinical features of DNP manifested as spontaneous pain, hyperalgesia and allodynia.Distal limb pain in patients suffering from DNP is severe and long-lasting, and the standardanalgesic therapy is unsatisfactory. There is growing recognition that NPP is closelyassociated with abnormal complement activation. The activation of complement proteinplay an important role in the formation and development of the NPP models. By the effectsof a series of program relevant to complement3, the pain state was promoted，maintainedand amplified by complement3. After the complement inhibitors cut down the expression ofcomplement，the symptoms of NPP can be reversed. However, the startup mechanism ofabnormal complement activation is unclear. Complement regulatory proteins can inactivatecomplement rapidly, then terminate the complement cascade, and which can determine thestrength of the complement cascade. Therefore, we speculate that CRP might play importantrole in the mechanisms with abnormal activation.Current studies on NPP are mainly focuses on peripheral nerve injury models, such asCCI model、SNL model and so on. But whether the happening of DNP is related to theabnormal complement activation or not we have no idea. And there were no researchs pointedout that changes of CRP could start the abnormal activation.Objective：In the study，we used different doses of STZ to induce DNP models，and observed therate of mice suffering from diabetic，the ratio of NPP and the28d survival in the model miceand then chose the optimal dose. In addition, by observing the mRNA and protein ofcomplement3and CD55in dorsal horn of spinal cord in mice with NPP，to look for "trigger point" in the pathogenesis of NPP..Methods：This study consisted of three parts as follows.(1) To investigate the optimal dose of streptozocin to induce diabetic neuropathicpain in C57BL/6J mice. Eighty-five healthy adult male C57BL/6J mice, with body weight18-20g, were divided into normal control group (n=10) and5experimental groups (n=15)randomly. The blood glucose levels of mice and the mechanical and thermal pain threshold ofmice were recorded at pre-injection of STZ and3,7,14,21days after injection. In additionobserved the survival rate of mice in28days.(2) The expression of mRNA and protein of Complent3in spinal dorsal horn inmice with diabetic neuropathic pain. Ninety healthy adult male C57BL/6J mice wererandomly divided into six groups as normal control group,DM3,7,14,21,28d group. Theblood glucose levels,the mechanical and thermal pain threshold were measured in differenttime according the set times, while the mRNA and protein of Complement3were determinedby methods of RT-PCR and immunohistochemistry.(3) The expression of mRNA and protein of CD55in spinal dorsal horn in mice withdiabetic neuropathic pain. The experimental groups and methods of measurement aresimilar to those in the second part.Results：(1) We indentified the mice with blood glucose level higher than16.7mmol/L in3,7,14,21day after injection of STZ as successful DNP model mice. Diabetic mice showedseveral special characteristics: the rough fur, more water intaking, more urine output, and theweight loss. Some mice in DM group exhibited typical hyperalgesia, and the mechanical andthermal pain threshold decreased significantly. In those five DM groups, all of mice showeddiabetes characteristics, the highest success rate of mice with DNP was in group C, and the28days survival rate of group E was lowest than others.(2) Compared with the control group,the expression of protein of Complement3in spinal dorsal horn increased in21day after STZinjection, and the expression of mRNA increased in14day which is earlier than proteinexpression.(3) Compared with the control group, the expression of mRNA and protein ofCD55in spinal dorsal horn decreased at7day after STZ injection and continue to28day, besides, the expression of mRNA and protein of CD55showed progressive decrease.Conclusion：(1) The optimal dose of injection of STZ to make DNP mice was120mg/kg whichinduced the highest successful rate of models.(2) The same as peripheral nerve injury models,the occurrence and development of DNP was closely related to abnormal activation of thecomplement.(3) The expression of mRNA and protein of CD55in spinal dorsal horndecreased earlier than Complement3. CD55may be one of the upstream mechanism ofabmormal activation of complement in the pathogenesis of NPP.