Study On The Effects Of Low-Dose LPS Pretreatment On Inflammation In EIU Rats

Purpose: The EIU model is a commonly used and important research model for studying acute anterior uveitis.In this study,we established an EIU model in rats and studied the effects of low-dose lipopolysaccharide(LPS)pretreatment on inflammation in EIU rats,in order to explore the protective mechanism of endotoxin tolerance in EIU rats after low-dose LPS pretreatment.Methods: Ten adult male Wistar rats weighing approximately 180-200 g were subcutaneously injected with 1 mg/kg LPS under the right footpad in order to induce EIU model.60 Wistar rats of the same standard were divided into three groups randomly and evenly: normal control(NC)group,endotoxin tolerance(ET)group and endotoxin-induced uveitis(EIU)group,with 20 rats in each group.Rats of the ET group were subcutaneously injected with 0.1 mg/kg LPS in the right footpad daily for five consecutive days to induce endotoxin tolerance,while rats in the NC and EIU groups were given an equal volume of saline solution daily.On the sixth day,rats of the ET and EIU groups were subcutaneously injected with 1 mg/kg LPS in the right footpad to induce anterior uveitis,while rats in the NC group were given an equal volume of saline solution.At the same time of the seventh day,the degree of anterior segment inflammation of rats was observed under a slit lamp microscope,photographed and scored,besides the degree of intraocular inflammation which histopathological sections of enucleated eyes showed in rats was scored.The clinical and histopathological scores of the anterior segment were statistically analyzed by Kruskal-Wallis rank sum test.Aqueous humor of rats in each group was extracted to detect the concentrations of cytokines IL-6 and TNF-α in aqueous humor by ELISA,and the results were analyzed by ANOVA.Results: In the experiment,the anterior segment response of rats was observed and scored under a slit lamp microscope,and histopathological sections were observed and scored.In the NC group,the aqueous humor was clear,and there were no significant inflammation in the anterior chamber under the slit lamp microscope and histopathological sections.In the EIU group,under the slit lamp microscope there was significant ciliary congestion,iris vessel dilation and fibrin exudation in the pupil area,and ciliary body edema with inflammatory cell infiltration was observed in the histopathological sections.Compared with the EIU group,the inflammation was significantly inhibited in the ET group: only iris vessel dilation was observed under the slit lamp microscope,and there were no other significant inflammatory reactions.In the histopathological sections,there was less inflammatory cell infiltration and mild ciliary body edema.According to the rank sum test of the photographic score and histopathological score of the anterior segment of clinical symptoms,the difference was statistically significant(P<0.05),and the inflammation of the ET group was statistically significantly lower than that of the EIU group.Meanwhile,the concentrations of cytokines IL-6 and TNF-α in aqueous humor were detected by enzyme-linked immunosorbent assay: The mean concentrations of IL-6 in the aqueous humor of the NC,EIU and ET groups were 8.55 pg/m L,26.88 pg/m L and 14.01pg/m L,respectively.The mean concentrations of TNF-α in the aqueous humor of the three groups were 51.38 pg/m L,453.88 pg/m L and 313.67 pg/m L,respectively.It was observed that the expression of inflammatory factors in the aqueous humor of the ET group rats was significantly lower than that in the EIU group rats after low-dose LPS pretreatment,and the difference was statistically significant(P<0.05).Conclusion: Low-dose LPS pretreatment may reduce the anterior chamber inflammation of EIU rats by reducing the expression of cytokines IL-6 and TNF-α in aqueous humor.