Abstract: Objective: To preliminarily study the anti-inflammatory effect of Streptococcus salivarius (Ss) by using a chronic inflammation model of oral cavity. Methods: Seventy-five C57BL/6 mice were randomly divided into 5 groups with 15 mice in each group. The first group was the blank control (CON) group; the second group was the chronic inflammation (CI) group; the third group was the Streptococcus salivarius treatment (CI+SS) group; the fourth group was the glucocorticoid treatment (CI+GC) group; and the fifth group was the Streptococcus salivarius alone (CON+SS) group. The mice were sacrificed after 4 weeks, and the buccal mucosa of the lesion was stained with HE to observe its pathological changes and inflammatory cell infiltration. The mRNA expressions of IL-1β, IL-6, TNF-α, IL-10, IL-17 and Foxp3 were detected by qRT-PCR, and the protein expression of IL-6 in the lesions was detected by immunofluorescence staining. Then, 45 C57BL/6 mice were randomly divided into 3 groups with 15 mice in each group. The first group was the CON group; the second group was the CI group; and the third group was the CI+SS group. After 4 weeks of treatment, the blood was collected. The expression levels of IL-17A in serum were detected by ELISA, and the ratio of Th17/Treg cells in peripheral blood was detected by flow cytometry. Results: Compared with the CI group, the CI+SS group had less local inflammatory cell infiltration, less expressions of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α, and decreased IL-6 positive cells (P＜0.001). The expressions of IL-10, IL-17, and Foxp3 in the lesions of the CI+SS group were decreased (P＜0.01), the expression of serum IL-17A was decreased (P＜0.001), and the ratio of Th17/Treg cells in peripheral blood was decreased (P<0.001). Conclusion: Ss has a therapeutic effect on local inflammation of the oral mucosa, possibly by improving the imbalance of Th17/Treg differentiation to maintain local immune balance.

Key words: Streptococcus salivarius, chronic inflammation, treatment