Effect Of Apolipoprotein E Deficiency On The Expression Of NMDAR1 And NMDAR2B In The Invitro Model Of Neuromyelitis Optica

Purpose Neuromyelitis optica (NMO) is an autoimmune inflammatory demyelinating disease which primarily involve spinal cord and optic nerve,Complement dependent cytotoxicity ( CDC) induced by specific autoantibodies to AQP4 on astrocytes may be the most important pathologic mechanisms of NMO, however,in which the role of glutamate excitotoxicity is still controversial. Apolipoprotein E (ApoE) is the major apolipoprotein in central nervous system(CNS), ApoE deficiency could aggravate neurological deficit in in some pathological conditions,such as experimental autoimmune encephalomyelitis(EAE), however, whether it play a similar role in NMO is not very clear.The purpose of this research is to study whether is it possible that glutamate excitotoxicity take part in NMO pathogenic mechanism,and what role dose ApoE deficiency play in NMO.Methods Autoantibodies to aquaporin 4(AQP4-IgG, NMO-IgG) in blood plasma of NMO patients was detected by immunofluorescence assay, then,AQP4-IgG positive blood plasma was selected, NMO-IgG was purified,Freezd,dried and saved in -20 ? which would be used in the following experiments; 7-14 days aged wild type and ApoE gene knockout C57BL/6 mice were decapitated, the spinal cord of which were removed and cutted into 300?m slices,meanwhile, optic nerves were separated from adult mice, then all of them were cultured on trans-well and treated by puried IgG and complement,NMO-IgG and complemet were not added in control group.Colorimetric method and immunohistochemistry were used respectively to detect glutamate concentrations in the culture solution and GFAP,AQP4,NR1,NR2B expression of spinal cord and optic nerves .The defect of spinal cord slices was assessed. Western blot was employed to detect the protein expression of NRl and NR2B.Results We found that spinal cord slices and optic nerves which were intervened by NMO-IgG and complement expressed characteristic pathological changes of NMO: deletion of GFAP and AQP4 , which were not affected by deficiency of EAE. Compared to the normal control group, NMO-IgG and complement accompanied by apoE deficient or not could not induce increaseing glutamate concentration in culture medium of spinal cord slices and optic nerves(P > 0.05), but NMO-IgG and complement had increased the expression of NR1 and NR2B subunit in spinal cord and the optic nerves(P < 0.05),meanwhile, apoE deficient could have enhanced the increase of NR2B subunit expression (P<0.05) , however had no impact on NR 1 subunit expression (P>0.05).Conclusion these results hint that NMDA receptors may play a role in the NMO pathogenesis, NMDAR especially NR2B-containing NMDAR receptors may induce excitatory toxicity thus take part in NMO pathological changes which might give thinking direction of NMDAR antagonist agent especially NMDAR2B-selective antagonist in adjuvant treatment of NMO; however apoE deletion although could increase the NR2B expression but didn't affect the Complement dependent cytotoxicity (CDC) of NMO-IgG which was the main pathogenic mechanism of NMO so pathological changes in spinal cord and the optic nerves was not impacted. These results suggest that ApoE may have an impact on the excitotoxicity induced by NMDAR which might provide new mechanisms in other diseases that ApoE involved in .