Effect Of Apolipoprotein E On Microglial Inflammatory Response In Spinal Cord Slice Model Of Neuromyelitis Opica

Objective To explore the effect of apolipoprotein E(Apo E)on microglial inflammatory response in neuromyelitis optica-like(NMO-like)lesions via the ex vivo spinal cord slice model.Methods Vibratome-cut transverse spinal cord slices from postnatal day 7wild-type mice and Apo E-/-mice on a C57BL/6 background of 300 μ m thickness were cultured on transwell porous supports.After 7 days in culture,some slices were exposed to NMO-Ig G and complement to induce NMO-like lesions(Apo E-/-NMO group and WT-NMO group),some were exposed to LPS for 24 h prior to NMO-Ig G and complement for activating microglia(Apo E-/-NMO+LPS group and WT-NMO+LPS group).C groups,indicating no added NMO-Ig G and complement and LPS groups,indicating only LPS was added were also established.Slices were cultured for another 3 days,and then examined for AQP4,GFAP and Iba1 immunoreactivity.The m RNA level of TNF-α,IL-6,IL-10 and i NOS of the slices was detected by RT-PCR.The concentration of cytokines(TNF-α,IL-6,IL-10)and NO in culture medium of slices was detected by ELISA and method of nitrate reductase,respectively.Results(1)Spinal cord slice cultures incubated with NMO-Ig G and complement produced NMO-like lesions,showing marked loss of AQP4 and GFAP staining.The NMO lesion score was higher in NMO+LPS groups than NMO groups(P<0.05).The NMO lesion score was no difference between Apo E-/-NMO group and WT-NMO group(P > 0.05),but it was higher in Apo E-/-NMO+LPS group than WT-NMO+LPS group(P<0.05).(2)LPS activated microglia throughout the slices as seen by Iba1 staining in NMO+LPS groups.Both the concentration and m RNA levels of TNF-α,IL-6,and NO/i NOS were higher in Apo E-/-NMO+LPS group than WT-NMO+LPS group(P<0.05).However,both the m RNA levels and concentration of IL-10 were no significant differences between Apo E-/-NMO+LPS group and WT-NMO+LPS group(P>0.05).(3)Unexpectedly,loss of AQP4 and GFAP staining was also seen in LPS groups,however,the NMO lesion score was no difference between LPS groups and C groups.(P>0.05).Conclusion(1)Lack of Apo E has no directly effect on the NMO lesions induced by NMO-Ig G and complement in the ex vivo spinal cord slice model.(2)Microglia mediated inflammatory response may be involved in the pathogenesis of NMO.(3)Apo E may serve as a protective role in NMO lesions,likely through its inhibitory effect on microglial inflammatory response.