Attenuating effect of chrysin on experimental autoimmune uveitis and its mechanism

Background

Chrysin has many biological activities, and its anti-inflammatory effect has been confirmed. However, whether it can treat experimental autoimmune uveitis (EAU) is still not elucidated.

Objective

This study was to investigate the therapeutic effect of chrysin on EAU and explore the potential mechanism.

Methods

EAU animal models were established in 30 SPF C57BL/6J mice by the subcutaneous injection and ball pad injection of interphotoreceptor retinoid binding protein_1-20 (IRBP_1-20)/complete Freund adjuvant (CFA), and then the models were randomized into the model control group and chrysin-treated group. Chrysin solution dissolved by 10 μl dimethyl sulfoxide (DMSO)+ 140 μl PBS was administrated by gavaging in the mice with the dose 25 mg/kg from 3 days before immunization through 21 days everyday in the chrysin group, and equal volume of solvent was used in the same way in the model control group. Retinas were examined by indirect ophthalmoscope once per day, and inflammation and pathological scores of retina were performed based on the criteria of Caspi on the 21st day after injection. The apoptosis of retinal cells was assayed by TUNEL staining, and the relative expressions of pro-inflammatory cytokines interferon-γ (IFN-γ), interleukin-17A (IL-17A), IL-6 and tumor necrosis factor-α (TNF-α) and signal transducer and activator of transcription 1 (STAT1), STAT3, p-STAT1, p-STAT3 in mouse retinas were detected by Western blot.

Results

Compared with the model control group, the inflammation scores and pathological scores of retinal inflammation were significantly reduced in the chrysin group (inflammation scores: 0.50±0.45 vs 1.58±0.92, t=2.600, P=0.026; pathologic scores: 0.58±0.38 vs 1.83±0.75, t=3.638, P=0.005). The infiltration of a large number of inflammatory cells, retinal vasculitis and granulomatous lesions were found in mouse retinas in the model control group, however, the morphology of mouse retinas in the chrysin group was normal based on hematoxylin-eosin staining. The number of apoptotic cells was remarkable lessened in the chrysin group compared with the model control group under the fluorescence microscope. Western blot assay resolved that significantly down-regulation in the expressions of IFN-γ, IL-17A, IL-6 and TNF-α was seen in the chrysin group in comparison with the model control group (t=7.802, P=0.001; t=14.906, P=0.000; t=10.241, P=0.001; t=3.304, P=0.030), and the relative expression levels of STAT1, STAT3, p-STAT1 and p-STAT3 were considerably lower in the chrysin group than those in the model control group (t=8.965, P=0.001; t=8.358, P=0.001; t=4.864, P=0.031; t=4.730, P=0.009).

Conclusions

Chrysin or chrysin-like flavonoids ameliorate intraocular inflammatory symptoms in EAU mice by inhibiting the activity of STAT signal pathway.

Flavonoids/pharmacology; Immunosuppressive agents/pharmacology; Autoimmune diseases; Uveitis/immunology; Disease models, animal; Signal transducer and activator of transcription; T-lymphocytes/drug effects