| Objectives: Diabetic peripheral neuropathy (DPN) is one of the diabetic chroniccomplications. Among the diabetics, its clinical incidence is believed to be as high as80～100%. The pathogenesis of DPN is thought of multiple factors, such as metabolicabnormalities and microvasculopathy due mainly to the hyperglycemia: Up till now,the real pathogenesis remains unclear while the therapy based upon the mechanismsas mentioned above seems to failure to effectively prevent the progression of DPN.Our reasearches had proved that there were autoimmune injuries to the multipleorgans in STZ-induced diabetes rats, at the same time, the deposition of several kindsof immunoglobulin and complement was demonstrated in the kidney, skin and muscleof the diabetic by biopsy. We speculate that diabetes and its chronic complicationsmay be the results of autoimmune leisions to multiple organs, infection-immune-inflammation-organ leision-functional dysfunction is the common rule of the diseases.There is no doubt, however, that varieties of antibody circulating in the serum ofpatients with DPN, and complement decreased in the circulation also, suggest thatimmunological mechanisms may be involved in the pathogenesis of DPN. It is quiteof doubt if these antibodies correlate with DPN, because the pathogenesis currentlyadopted in the clinical practice seem to be ineffective. Nuclear factor-κB(NF-κB) isthe most important downstream transcription regulatory factor of oxidative stresspathway, and the key position between oxidative stress and inflammation. There isdoubt that if local oxidative stress of nerve tissues is the consequence ofimmunological injury, and if oxidative stress and NF-κB activation can be suppressedby CsA.There was reported that tumor necrosis factor-α(TNF-α) participated thepathogenesis of diabetic retinopathy and diabetic nephropathy, and the progression of diabetic retinopathy can be delayed by suppress the expression of TNF-αin the retina,so it is doubt that if the expression of TNF-αcan also be suppressed by CsA. For thetime being, there has been no report at all whether immunodepressive agents canblock the cascade of the pathogenesis of DPN.In the present study, STZ-induced diabetic rats were used as animal model. Ourfirst objective was to observe the abnormal desposition of immunoglobulins andcomplement C3b in spinal, dorsal root ganglion(DRG) and sciatic nerve and todiscuss the etiology of DPN related to the autoimmune injuries, and to evaluate thetherapeutic effect of CsA on DPN. Secondly, oxidative stress and expression ofNF-κB and TNF-αwere also investigated to elucidate if the inflammation could beprevented when the autoimmune injuries had been blocked if it was present.Materials and methods: 90 male rats were randomly divided into controlgroup(CON) and diabetic group(DM) which were also randomly divided into fourgroups,such as,low doses of CsA-treated group(ML),middle doses of CsA-treatedgroup(MM),high doses of CsA-treated group(MH) and insulin intensive therapygroup(MI).The diabetic rat models were made by intravenous administration 50mg/kgof STZ, ML, MM, MH group according 0.5mg/kg·d,1 mg/kg·d and 2 mg/kg·dsubcutaneous injected CsA, MI group subcutaneous injected isophane insulin 2-6U/d according to glycemia level, sacrified after 16 weeks modeling. Hepatic function,renal function, serum insulin, C-reactive protein and urine albumin were investigated.The morphology changes of spinal, DRG and sciatic nerve were observed to judge thetherapeutic effects of CsA and insulin.The deposition of immunoglobulins and C3b were detected in the spinal, DRGand sciatic nerve by immunohistochemistry and immunofluorescence. The level ofmalonaldehyde(MDA),total superoxide dismutase(SOD), CuZn-superoxide dimutase(CuZn-SOD),catalyse(CAT)and glutathione perioxidase(GSH-Px)of neural systemwere measured. In the above-mentioned three locations, the expression of NF-κB wasevaluated by immunohistochemistry, and the expression of TNF-αwas detected by immunohistochemistry and RT-PCR.Results: All the rats treated with STZ fully demonstrated the clinicalmanifestations of DM eventually,and morphology observations showed that diabeticrat has DPN in 16 weeks after modeling. All the doses of CsA we adopted had notshown any impairment on the hepatic function and renal function. Area ratio of axonalto myelin sheet of DM group was significantly decreased than that of CON group,both middile and high doses of CsA and insulin therapy can prohibit the tendency, yetlow doses of CsA had no effect on the ratio.Compared with the CON group, it was quite obvious that the deposition of IgG,IgA and IgM was remarkably increased in spinal, DRG and sciatic nerve of DM group,and a significantly negative association between IOD of IgA,IgG, C3b deposited onthe nerve and the area ratio of axonal to myelin sheet. Middle and high doses of CsAcan significantly reduce the deposition of all three immunoglobulins and C3b, lowdoses of CsA only had significant effect on part of these indexes, and there were noevidence show that insulin therapy can reduce the deposition of immunoglobulins andcomplement.In the above-mentioned three locations, the level of MDA was increased andT-SOD, CuZn-SOD, CAT, GSH-Px were decreased, the protein expression of NF-κBand TNF-αwere increased, and mRNA of TNF-αalso raised up. Both middle andhigh doses of CsA and insulin therapy can reduce the level of oxidative stress andexpression of NF-κB. The protein and mRNA expression of TNF-αwere significantlyreduced by middle and high doses of CsA therapy, while insulin therapy had no effecton it.Conclusions: 16 weeks after modeling, there were abnormal immunoglobulinsand C3b deposition in spinal, DRG and sciatic nerve of STZ induced diabetic rat,suggested that humoral immune reaction participated the pathogenesis of DPN. 1mg/kg·d and 2 mg/kg·d CsA therapy can significantly decrease the deposition ofimmunoglubulins and C3b, yet insulin therapy can not ameliorate immune abnormality.The pathway of oxidative stress and NF-κB was activated, and downstreaminflammatory factor TNF-αhighly expressed in spinal, DRG and sciatic nerve ofSTZ-induced diabetic rats in 16 weeks after modeling. 1 mg/kg·d and 2 mg/kg·dCsA therapy can significantly suppress all these abnormalities, suggested that bothimmunological injuries and hyperglycemia were possible causes of oxidative stress,while CsA gained advantage effects on suppression the inflammatory factors.The progression of DPN was significantly suppressed by both 1 mg/kg·d and 2mg/kg·d CsA therapy, and there was no obviously hepatic and renal injuries in ratsreceived above doses of CsA therapy during 16 weeks.
|
PDF Full Text Request