Chrono-moxibustion adjusts circadian rhythm of CLOCK and BMAL1 in adjuvant-induced arthritic rats

The clinical symptoms of rheumatoid arthritis (RA) have significant circadian rhythms, with morning stiffness and joint pain. Moxibustion is effective in the treatment of RA, while the underlying therapeutic mechanisms remain limited. Thus, we explored whether moxibustion could adjust the circadian rhythm of RA by modulating the core clock genes CLOCK and BMAL1 at the molecular level.

144 Sprague Dawley rats were randomly divided into four groups: control group (group A), model group (group B), 7-9 am moxibustion treatment group (group C), and 5-7 pm moxibustion treatment group (group D). Each group was divided into 6 time points (0 am, 4 am, 8 am, 12 N, 6 pm, and 8 pm) with an equal number of rats at each time point. Except for group A, all rats were injected with Freund's Complete Adjuvant (FCA) 0.15 ml on the right foot pad to establish the RA model. The rats of the two moxibustion treatment groups were respectively subjected to moxibustion at 7-9 am and 5-7 pm. After 3 weeks of treatment, the tissues were collected at 6 time points during the next 24 hours. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to test the mRNA expression of CLOCK and BMAL1 in the hypothalamus and synovial tissues. CLOCK and BMAL1 protein expression in synovial tissues were detected with western blot.

Compared to group A, group B showed significantly down-regulated expression levels of CLOCK and BMLA1 at synovial tissue (P < 0.05), while no statistically significant difference was found in the hypothalamus (P > 0.05). The expression levels of CLOCK and BMLA1 were up-regulated in the moxibustion treatment groups in different tissues, especially in synovial tissue (P < 0.05) compared to group B. Nevertheless, no difference was observed between groups C and D (P > 0.05).

Moxibustion could treat RA by modulating clock core genes CLOCK and BMAL1 to regulate the circadian rhythm. However, there was no significant difference between the 7-9 am moxibustion treatment group and the 5-7 pm moxibustion treatment group. This study provides a basis for research on moxibustion in the treatment of RA.