The Effect Of TGF-β1 On TLR4,TLR9 Expression In C57BL/6 Mice With Experimental Autoimmune Encephalomyelitis

ObjectiveOur aim is to investgate the clinical effects of TGF-β1 on EAEmice model, as well as the mRNA expression alterations of TLR4 andTLR9 during the natural time course of MS in EAE mice and afterreceiving the intervention, as to further explore the role of TLR4 andTLR9 in MS pathologic mechanism and the effects of TGF-β1 on theirexpression.Methods72 adult female C57BL/6 mice were randomly divided into modelgroup,adjuvant-control group,intervention group and interventioncontrol group. Each of them were injected subcutaneously with 300 ug ofMOG35-55 peptide emulsified in 2.0 mg of CFA in the day 0 and day7, except that adjuvant-control group was immunized by PBS instead ofmMOG35-55. All mice then received intraperitonal injections with 250ng PTX at the time of immunization and 48 hours later. Interventiongroup was also injected subcutaneously with 1μg TGF-β1/100μ1PBS inthe day 0, 3, 5, 6, 8, 9, 11; intervention control group was treated inthe same way, only that their TGF-β1 injection was replaced by PBS. Weevaluated the severity of EAE model symptoms and its clinical course with Benson score standard.Finally, RT-PCR was performed todemonstrate the expression alteration of TLR4 and TLR9 mRNA of brainand spinal cord on four different time points in each group.Results1 In EAE model group, 15 mice out of 18 were successfully inducedto experience symptoms as expected, with 2 of them died for their severesickness. The symptoms initiated on day 14-20, maximized on day20-24, and reached their remission on day 28-32. While in interventiongroup, 16 mice out of 18 were successfully induced, with 1 of them died.Their symptoms initiated on day 13-17, maximized on day17-22, andreached their remission on day 22-24. Thus the peak period wasshortened though the onset was earlier in intervention group.2 The expression level of TLR4 and TLR9 mRNA was low in bothbrain and spinal cord in adjuvant-control group, while they wereelevated during all stages in both intervention control group and modelgroup.In model group, TLR4 mRNA expression level reached itsmaximum on the occurrence of symptoms, though it lowered duringpeak period and chronic stage. While in intervention group, TLR4mRNA expression level reached its maximum in peak period though itselevation occurred as soon as symptoms appeared. Compared to model group, TLR4 mRNA expression level lowered during all stages inintervention group, and the difference is statistically significant.TLR9 mRNA expression elevated as symptoms appeared, andreached its maximum in the peak period both in model group andintervention group, though TLR9 mRNA expression level was loweredduring all stages in intervention group。Conclusion1. TLR4 and TLR9 both played a pivotal role in the central nervoussystem pathogenesis of EAE model.2 TGF-β1 may impact the pathological and clinical course of EAEthrough down-regulating TLR4 and TLR9.