Background: Massage therapy is widely used to alleviate pain, however, its molecular mechanisms, particularly those integrating Traditional Chinese Medicine (TCM) with mechanobiology, remain inadequately elucidated. This study investigates the novel hypothesis that coordinated signaling between cannabinoid receptor-1 (CB1) and the Epac1-Piezo2 axis underlies massage-induced analgesia in inflammatory pain.
Methods: Female C57BL/6 mice (8-10 weeks) were randomly allocated into three groups (n=6/group): Control group: Received a 25-µL intramuscular microinjection of saline into the right tibialis anterior muscle; CFA group: Inflammatory hyperalgesia was established via 25-µL intramuscular CFA (complete Freund's adjuvant) microinjection. Model validation was performed 48 hours post-CFA administration by assessing ipsilateral hindlimb edema, erythema, exudation, and mechanical hyperalgesia using von Frey filament testing. Massage group: CFA mice received daily ipsilateral ST36/GB34 acupressure for 14 days starting 24h post-modeling. Thermal and mechanical hyperalgesia were assessed via hot plate and von Frey tests. CB1 (Western blot), Epac1 (IHC), and Piezo2 (IF) levels in L4-6 DRGs were analyzed.
Results: Acupoint massage (targeting ST36 and GB34) significantly elevated mechanical and thermal pain thresholds in CFA-induced inflammatory pain mice. Western blot analysis revealed upregulation of CB1 protein expression in L4-6 DRGs. Notably, massage downregulated Epac1 and Piezo2 protein levels, suggesting that the analgesic mechanism involves modulation of the CB1, Epac1, and Piezo2 signaling pathways.
Conclusion: These findings demonstrate that massage therapy attenuates inflammatory pain, potentially through activation of cannabinoid type 1 (CB1) receptors and modulation of the Epac1/Piezo2 signaling axis. This study provides mechanistic insights into the analgesic properties of massage treatment.
Keywords: Epac1; Piezo2; analgesic; cannabinoid receptor-1; inflammation; massage.
© 2025 Liu et al.