Anti-inflammatory effect of Celastrol in the ocular tissues of mice with exper-imental autoimmune uveitis and its impact on microglia polarization / 眼科新进展

ABSTRACT

Objective To investigate the anti-inflammatory action of Celastrol in the ocular tissues of mice with ex-perimental autoimmune uveitis(EAU)and its effect on microglia polarization.Methods A total of 36 healthy B10.RⅢmice at 6-8 weeks of age were selected and randomly divided into the normal control group,EAU solvent control group and Celastrol intervention group,with 12 mice in each group.The interphotoreceptor retinoid-binding protein(IRBP)161-180 and Freund's complete adjuvant were mixed by thorough emulsification and injected subcutaneously into the bilateral thighs and tails of mice in the EAU solvent control group and the Celastrol intervention group with a total volume of 200 μL and 50 μg IRBP 161-180 in each mouse.On 7-14 days after immunization,mice in the Celastrol intervention group received a daily intraperitoneal injection of 0.5 mg·kg-1 Celastrol,and mice in the EAU solvent control group were injected with an equivalent dose of sterile Phosphate Buffered Saline solution.On the 14th day after immunization,the anterior segment of mice in each group was observed by slit-lamp microscope and Hematoxylin and Eosin(HE)staining of tissue sections was performed;the clinical and histopathological scores of mice in each group were obtained by reference to the Caspi grading standards;immunofluorescence staining was used to observe the activation of microglia in the eyes of mice;Western blot was used to detect the protein expression levels of inducible nitric oxide synthase(iNOS)and arginase-1(Argl)in the reti-na;quantitative real-time PCR was used to detect the relative mRNA expression of inflammatory factors in the retina,such as tumor necrosis factor(TNF)-α,interleukin(IL)-1β and IL-6.GraphPad Prism 9.0 was used for data analysis.Results On the 14th day after immunization,it was observed by the slit-lamp microscope that the anterior segment of mice in the EAU solvent control group was markedly congested with dilated iris blood vessels,corneal edema,and anterior chamber exudation;the inflammation in the anterior segment of mice in the Celastrol intervention group was markedly at-tenuated,and the iris blood vessels were seen to be mildly congested.Compared with the normal control group,the clini-cal scores of mice in the EAU solvent control group and the Celastrol intervention group were significantly elevated(both P＜0.05);the clinical scores of mice in the Celastrol intervention group were lower than those in the EAU solvent control group(P＜0.05).HE staining results showed that on the 14th day after immunization,mice in the EAU solvent control group showed severe retinal folds and detachment with diffuse infiltration of inflammatory cells,while mice in the Celastrol intervention group showed slight structural damage to the retina and a small amount of inflammatory cell infiltration.Com-pared with the normal control group,the histopathological scores of mice in the EAU solvent control group and the Celas-trol intervention group were significantly elevated(both P＜0.05);the histopathological scores of mice in the Celastrol in-tervention group were lower than those in the EAU solvent control group(P＜0.05).The intraocular Iba1+cell densities of mice in the normal control,EAU solvent control and Celastrol intervention groups were(1.00±0.12)％,(36.07± 4.57)％,and(1.83±0.36)％,respectively.Compared with the normal control group,the number of Iba1+cells in the eyes of mice in the EAU solvent control group and the Celastrol intervention group significantly increased(both P＜0.05);compared with the EAU solvent control group,the number of Iba1+cells in the eyes of mice in the Celastrol intervention group was significantly reduced(P＜0.05).Compared with the normal control group,the expression levels of iNOS and Arg1 proteins in the retinas of mice in the EAU solvent control group were significantly elevated(both P＜0.01);compared with the EAU solvent control group,the expression of iNOS protein in the retinas of mice in the Celastrol intervention group was significantly reduced(P＜0.01).Compared with the normal control group,the relative mRNA expressions of TNF-α.IL-1β,and IL-6 in the retinas of mice in the EAU solvent control group was significantly elevated(all P＜0.05);compared with the EAU solvent control group,the relative mRNA expressions of TNF-α,IL-1 β,and IL-6 in the retinas of mice in the Celastrol intervention group significantly decreased(all P＜0.05).Conclusion Celastrol inhibits Ml microglia activation and reduces the production of retinal inflammatory factors TNF-α,IL-1 β and IL-6 in EAU mice,thereby attenuating the in-flammatory reaction.