New Bitongling Ameliorates Joint Tissue Damage in Collagen-Induced Arthritis Mice by Suppressing Mapt Expression: A...

Rheumatoid arthritis (RA) affects 1% of the global population, with joint destruction leading to disability. While current biologics (eg, TNF-α inhibitors) and small-molecule therapies (eg, JAK inhibitors) have significantly improved symptom control and slowed radiographic progression in many patients, unresolved challenges remain in simultaneously addressing mitochondrial dysfunction and synovial inflammation-the core drivers of joint destruction. This study aimed to investigate the molecular mechanism by which New Bitongling (NBTL) mitigates joint damage in collagen-induced arthritis (CIA) mice through regulation of the microtubule-associated protein tau (Mapt).

Male C57BL/6 mice (6 weeks old, specific pathogen-free) were used to establish the collagen-induced arthritis (CIA) model and randomly assigned to three groups: control, model, and NBTL intervention. Clinical symptoms were evaluated using the arthritis index (AI), paw swelling volume (measured by water displacement), and behavioral tests (sucrose preference test and open-field test). Histopathological changes were assessed via hematoxylin-eosin (HE) and Safranin O-Fast Green staining. Molecular mechanisms were analyzed using Western blotting, flow cytometry, and mitochondrial membrane potential (JC-1 staining) assays. Western blotting analyzed apoptosis-related proteins and the Sirtuin 1 (Sirt1)/Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) pathway, flow cytometry measured reactive oxygen species (ROS) levels, and JC-1 fluorescence staining evaluated mitochondrial membrane potential. Genome-wide sequencing identified Mapt as the key target, with functional validation conducted through siRNA knockdown and adeno-associated virus (AAV) Mapt overexpression. Statistical analyses included repeated-measures Analysis of Variance (ANOVA) with Tukey's post-hoc test and P<0.05 was considered significant.

NBTL treatment significantly reduced AI scores, paw swelling, and joint deformities while improving behavioral indicators. Histological analysis revealed attenuated synovial inflammation, pannus formation, and bone erosion in the NBTL group. Moreover, pro-inflammatory mediators were downregulated in NBTL-treated mice, accompanied by reduced Bax/cleaved-caspase3 and elevated Bcl-2 expression (P<0.05). NBTL restored mitochondrial membrane potential, activated the Sirt1/PGC-1α pathway, reduced ROS levels, and decreased oxidative stress damage (P<0.05). Mapt overexpression exacerbated joint damage, whereas Mapt silencing or NBTL intervention reversed these effects. Genome-wide sequencing confirmed that NBTL modulates mitochondrial homeostasis and inflammatory responses via Mapt inhibition.

This study demonstrates that New bitongling ameliorates joint damage in collagen-induced arthritis mice by suppressing microtubule-associated protein tau expression, restoring mitochondrial function, and modulating synovial inflammation. These findings provide preclinical evidence supporting further investigation of New bitongling as a novel therapeutic agent for rheumatoid arthritis.