[Hydrogen alleviates collagen-induced arthritis (CIA) in mice by inhibiting IL-22 levels]

Objective To investigate the therapeutic effect and mechanism of hydrogen (H₂) on collagen-induced arthritis (CIA) in mice. Methods DBA/1 mice were randomly divided into normal control group, CIA group and CIA mice treated with H₂ group (H₂ treated group), with 6 mice in each group. Following the preparation of CIA mouse model, the H₂ treated group received H₂ inhalation therapy (300 mL/L, 3 hours/d) for 15-60 days. The arthritis score were assessed and HE staining of joint were evaluated by referring to the pathology score; The number of CD4⁺IL-22⁺ cells in spleen and joint was observed by flow cytometry and immunohistochemical staining; ELISA was conducted to assess the levels of interleukin 22 (IL-22) in serum and joint; Western blotting was performed to examine the expression of phosphorylated STAT3 (p-STAT3) and phosphorylated NF-κB (p-NF-κB) in joint between the three groups. Results In the CIA group, both the arthritis score and pathology score were higher than control group, while they dropped after H₂ treatment. In addition, compared with control group, CIA group showed higher proportion of CD4⁺IL-22⁺ cells and higher level of IL-22 which then interestingly decreased after H₂ therapy. Besides, the p-STAT3 and p-NF-κB were elevated in CIA mice compared with control group, and H₂ treatment significantly inhibited them. Conclusion H₂ can reduce the levels of CD4⁺IL-22⁺ cells and IL-22, and alleviate arthritis symptoms in CIA mice by inhibiting STAT3/NF-κB pathway.