Effects of Lactobacillus Salivary on Spleen T Cells and Inflammatory Factors in a Rat Model of Type II Collagen Induced Arthritis Running Title: Effects Exploration of Lactobacillus Salivary

To explore the therapeutic effect and role of Lactobacillus salivarius on rheumatoid arthritis. A Collagen induced arthritis (CIA) model was constructed in male Sprague Dawley (SD) rats by adopting bovine type II collagen as immunogen. The modeled rats (24 SD rats) were randomly divided into the CIA model group, salivary lactobacillus group, and methotrexate group, and 8 rats in each group with healthy group. Both the healthy group and CIA group were administered bacterial culture medium; the salivary lactobacillus group administered salivary lactobacillus. The methotrexate group given methotrexate medication, and each group was continuously operated by gavage for 4 weeks. After that, evaluated arthritis index, thickness of the affected foot, pathological changes in the naked joint tissue, and histopathological staining. Moreover, the content of T helper cell 17 (Th17) and regulatory T cells (Treg) in the spleen were also detected, and included the levels of expression of interleukin-1 β (IL-1 β), Interleukin-10 (IL-10), Interleukin-17 (IL-17), Interleukin-2 (IL-2), Interleukin-6 (IL-6), Interleukin-8 (IL-8), γ Interferon (IFN- γ), and Tumor Necrosis Factor- α (TNF- α) in the serum of each group. Compared with the CIA model group, the arthritis index score, onset foot thickness, spleen Th17 cells, the content of inflammatory factors above were significantly decreased (P < 0.05) in the salivary lactobacillus group and methotrexate group. The level of Th17 cells significantly increased (F-value: 238.918, P < 0.05), and the content of Treg cells significantly increased (CIA group: 9.47 ± 0.30, Salivary Lactobacillus group: 13.04 ± 0.47, Methotrexate group: 22.41 ± 0.33, P = 0.003 < 0.05); while the Th17/Treg cell ratio in both the salivary lactobacillus group and the methotrexate group was decreased (CIA group: 0.62 ± 0.03, salivary lactobacillus group: 0.29 ± 0.11, methotrexate group: 0.15 ± 0.03, P = 0.004 < 0.05). However, there was no significant difference in the content of spleen Th17 cells, Th17/Treg ratio, and total joint pathology score (P = 0.54 > 0.05) between the salivary lactobacillus group and the methotrexate group. Lactobacillus salivarius has immune regulatory and anti-inflammatory effects on CIA model SD rats, and the corresponding mechanism of action is mainly reflected in the regulation of Th17 and Treg cell balance, and inhibiting the expression of inflammatory factors.