Treatment of experimental autoimmune uveoretinitis with different natural compounds

Uveitis is an important eye disease that potentially causes loss of sight. Although extensive studies have been conducted on uveitis, the exact pathogenesis remains to be determined. The effects of treatment with natural compounds on an experimental autoimmune uveoretinitis (EAU) rat model were examined in the present study. A total of 25 rats were divided into 5 groups: Alkaloids (n=5), saponins (n=5), flavonoids (n=5), phenols (n=5), and the normal saline group (n=5). The rats in each group were treated with an intraperitoneal injection of proper alkaloids (berberine hydrochloride), saponins (steroidal saponins), flavonoids (baicalein), or phenols (chlorogenic acid) or physiological saline, respectively. The rats' aqueous humour and crystalline lens was then observed under the slit lamp periodically, looking for signs of inflammation. After 2 weeks, the rats were sacrificed and the degree of pathological changes on their eyeballs under different treatment methods were determined using an optical microscope. The expression of the interleukin (IL)-17 gene in the ocular tissues of the rats was assessed via RT-PCR and western blot analysis. Apoptosis on the rats' retinal tissues was detected using flow cytometry. The results showed that rats injected with phenols (chlorogenic acid) had serious ocular vascular dilatation, iris hemorrhage and purulent exudation; those injected with alkaloids (berberine hydrochloride) and flavonoids (baicalein) had a more mild form of inflammation; and those administered saponins (steroidal saponins) had only mild inflammation signs. Following detection of IL-17 mRNA and protein expression levels in the ocular tissues of rats of the five groups, it was found that their expression was lowest in the saponin-treated group and the other differences in expression were all statistically significant (P<0.05). A comparison with other groups revealed that cell apoptosis in the eyes of rats in the saponin group was the most prominent, reflecting a beneficial decrease in the amount of inflammatory cells on the lesion. Based on these findings, natural compounds such as saponins (steroidal saponins), alkaloids (berberine hydrochloride), and flavonoids (baicalein), but not phenols (chlorogenic acid), can inhibit the clinical symptoms of EAU in rats to a certain extent and reduce cell apoptosis. The most promising results in the present study were obtained using steroidal saponins.