OBJECTIVE  To explore the molecular mechanism by which wheat-grain moxibustion exerts anti-inflammatory and analgesic effects on rheumatoid arthritis (RA) by regulating the ROS-NLRP3 inflammatory pathway.

  METHODS  47 male SD rats were randomly divided into control group, model group, model moxibustion group, ROS overexpression group and ROS overexpression moxibustion group by SPSS random program. There were 7 rats in the control group, and 10 rats in each of the other 4 groups. Rats in the control group were intradermally injected with sterile normal saline from the right posterior foot pad, while the rest were intradermally injected with Freund's complete adjuvant (FCA) Adjuvant to induce adjuvant arthritis (AA). After FCA modeling, ROS overexpression group and ROS overexpression moxibustion group were injected subcutaneously with rotenone oil solution (1.5 mg·kg^-1) on the second day after modeling to establish ROS overexpression model. The model moxibustion group and ROS overexpression moxibustion group were treated with wheat-grain moxibustion at Zusanli point and Shenshu point 7 days after modeling, with 5 grains on each point, alternating on both sides. Moxibustion treatment lasts for 6 days as a course of treatment, with a day off between the courses. There is a total of 3 courses of treatment. Control group and model group were fixed by the same method without moxibustion treatment. The swelling degree of the foot plantar, thermal pain threshold and arthritic flexion pain test score were observed before and after modeling and treatment. After treatment, samples were collected and ELISA was used to detect the changes of inflammatory factors IL-1β and IL-18 in serum of rats. The expressions of NLRP3 protein and ROS-related protein reactive oxygen regulatory Factor 1 (ROMO1) in ankle inflammatory tissue were detected by Western blot. The expression level of ROS-related ROMO1 mRNA in hypothalamus was detected by qPCR.

  RESULTS  The body mass of the ROS overexpression group did not significantly increase during the experimental period, while all other groups increased (P < 0.05). Compared with control group, the swelling degree of the right foot, the percentage increase of thermal pain threshold and the score of arthritic flexion pain test were significantly increased in the model group (P < 0.01), while the swelling degree, the percentage increase of thermal pain threshold and the score of arthritic flexion pain test were significantly decreased in the model moxibustion group after moxibustion (P < 0.01). Meanwhile, compared with control group, the expressions of NLRP3 and ROMO1 in inflammatory ankle tissue and the expressions of ROMO1 mRNA, IL-1β and IL-18 in hypothalamus in model group were significantly increased (P < 0.01), while the expressions of inflammatory pathways and inflammatory factors above in model moxibustion group were significantly decreased after moxibustion (P < 0.01). Compared with the ROS overexpression group, the ROS overexpression moxibustion group showed significant improvement in behavioral performance (degree of foot swelling, percentage increase of thermal pain threshold and score of arthritic flexion pain test) (P < 0.01). The expressions of NLRP3 and ROMO1 in the inflammatory tissue of ankle joint and the ROMO1 mRNA expression, IL-1β and IL-18 in hypothalamus were significantly decreased (P < 0.01).

  CONCLUSION  Wheat-grain moxibustion may inhibit ROS-NLRP3-IL-1β inflammatory pathways in AA model rats, thereby exerting anti-inflammatory and analgesic effects.