Expression of suppressor of cytokine signaling in retina of experimental autoimmune uveoretinitis

Abstract

To investigate the expression and significance of suppressor of cytokine signaling (SOCS) mRNA and protein in retina of rats with experimental autoimmune uveoretinitis (EAU). Research was designed with randomized controlled trials. Eighty Lewis rats were immunized with interphotoreceptor retinoid-binding protein (IRBP) to induce EAU. They were stratified randomly into two groups: nontreatment group (40 rats) and treatment group (40 rats). The treatment group was administered cyclosporine A 20 mg.kg(-1).day(-1) after immunization for 28 days, and the nontreatment group received saline buffer in the same way, ten normal Lewis rats without immunization and treatment as normal control group. The rats in both groups were stratified randomly into four sub-groups. Each sub-group had 10 rats and the rats were sacrificed at day 0, 7, 14, 21, 28 after immunization. All eyes were evaluated by slit-lamp microscopy. Retinas of rats were subjected to analysis of SOCS mRNA and protein expression using quantitative RT-PCR and western blot, respectively. IL-4, IL-12 and IFN-gamma in the serum were measured by ELISA. At day 14, the nontreatment group developed acute anterior uveitis and showed typical signs including aqueous flare, small or irregular pupil due to posterior synechiae and hypopyon, the score of inflammation was 1.5 +/- 0.5; but the treatment group did not suffer from severe anterior chamber inflammation, the score of inflammation was 0.5 +/- 0.3. The highest level of IL-4, IL-12 and IFN-gamma production occurred at day 14 (P < 0.05), followed by decline in the secretion of IL-12 and IFN-gamma secretion to the baseline at day 28, while the concentration of IL-4 did not decrease significantly in the nontreatment group (P > 0.05). IL-12 and IFN-gamma did not change significantly (P > 0.05) and IL-4 production reached the highest level at day 28 in the treatment group. Both SOCS1 and CIS mRNA increased to the highest level at day 14. Compared to normal controls, the copies of SOCS1 and CIS mRNA were 3.41 fold and 3.36 fold in the nontreatment group, and were only 1.44 fold and 1.73 fold in treatment group, respectively. Both SOCS3 and SOCS5 mRNA reached the highest level at day 28 after immunization in both groups. The copies of SOCS3 and SOCS5 mRNA were 1.95 fold and 3.16 fold in the nontreatment group, and were 1.59 fold and 3.58 fold in the treatment group, respectively. Marked increased expression of SOCS1 and CIS proteins in the nontreatment group as compared to normal controls was detected at 7, 14, 21 days; in the treatment group these proteins only increased significantly at day 14 (P < 0.05). Expression of SOCS3 and SOCS5 proteins in both groups were higher than those in normal controls (P > 0.05). Marked increased expression of SOCS1 of retina may involve in the development of a Th1 mediated immune response in EAU. CIS and SOCS3 of retina may play important roles in mitigating pathogenic effects of proinflammatory cytokines during different stages of EAU. Up-regulation of SOCS5 may have protective functions.