Therapeutic effects of Melittin acupoint injection on rheumatoid arthritis through autophagy activation and PI3K/AKT/mTOR pathway inhibition.

BACKGROUND

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that leads to cartilage degradation and bone destruction, significantly impacting daily life. Melittin acupoint injection (MAI) is a promising traditional Chinese medicine treatment, but its molecular mechanisms are not fully understood. This study aimed to investigate the therapeutic effects of MAI on RA and elucidate its underlying mechanisms.

METHODS

A collagen-induced arthritis (CIA) mouse model was established using bovine type II collagen, administered every other day for 28 days. The mice were randomly divided into a CIA model group (MO group), melittin acupoint subcutaneous injection group (ST group), melittin acupoint intramuscular injection group (IT group), and methotrexate group (MTX group), with an additional normal control group (NC group) established. Each group contained 8 mice, all of which were treated for 28 days. Therapeutic outcomes were assessed by measuring body weight, swollen joint count (SJC), arthritis index (AI), ankle circumference, and plantar thickness. Radiological and histological changes were analyzed with micro-computed tomography (CT) imaging and pathological staining. Cytokine levels were measured via enzyme-linked immunosorbent assay (ELISA), and autophagy levels were assessed using immunofluorescence staining. The phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) signaling pathway and autophagy status were examined through western blot (WB) and immunofluorescence techniques.

RESULTS

MAI significantly improved clinical symptoms in CIA mice by reducing plantar thickness, AI scores, and swollen joints (P<0.05). Histopathological analysis showed decreased inflammatory cell infiltration, synovial proliferation, and cartilage damage (P<0.01). Micro-CT and immunohistochemistry revealed reduced inflammation, bone destruction, and cartilage erosion, along with decreased tumor necrosis factor-α (TNF-α) expression (P<0.05). MAI also lowered serum levels of interleukin (IL)-1β (P<0.05), IL-17A, and TNF-α (P<0.01), while increasing IL-10 levels (P<0.05). Immunofluorescence indicated increased microtubule-associated protein 1 light chain 3 beta (LC3B) fluorescence intensity (P<0.05). WB analysis showed elevated levels of Unc-51-like autophagy activating kinase 1 (ULK1), beclin-1 (P<0.01), and microtubule-associated protein 1 light chain 3 II (LC3II) (P<0.05), and reduced phosphorylation of PI3K, AKT, and mTOR (P<0.05).

CONCLUSIONS

MAI alleviates RA symptoms by inhibiting the PI3K/AKT/mTOR pathway and promoting autophagy.