BML-111 inhibits osteoclast differentiation by suppressing the MAPK and NF-κB pathways, alleviating deterioration of the knee joints in a CIA rat model

Irreversible destruction of joints is the hallmark of rheumatoid arthritis (RA). Osteoclasts are the only bone-resorbing cells and play an important role in joint rebuilding. BML-111 (5(S),6(R),7-trihydroxyheptanoic acid methyl ester, C₈ H₁₆ O₅ ) is a synthetic lipoxin A4 agonist with antioxidant and anti-inflammatory properties. The present study aimed to investigate the effect of BML-111 on osteoclasts in vivo and in vitro, to investigate its therapeutic effect on joint destruction in RA. Cell Counting Kit-8 assay and flow cytometry were used to exclude cytotoxic effects of BML-111 to bone marrow-derived macrophages (BMMs). Then, osteoclasts were differentiated in vitro from BMMs by used macrophage colony-stimulating factor and receptor activator of nuclear factor-κB ligand, and osteoclasts were observed following tartrate-resistant acid phosphatase staining with or without BML-111 treatment. Meanwhile, absorption pit assay and immunofluorescence staining of the fibrous actin ring were used to observe osteoclast function. Moreover, we examined mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) activation. We established collagen-induced arthritis in a rat model and, after treatment with BML-111, joint swelling was measured and the knee joints were processed for histology. We also examined serum and tissue for osteoclastogenesis-related markers. BML-111 inhibited osteoclast formation and differentiation in a time- and concentration-dependent manner, and downregulated the expression levels of MAPK and NF-κB in vitro. Meanwhile, BML-111 effectively alleviated joint structural damage and inhibited osteoclast formation in vivo. BML-111 inhibited osteoclast formation and differentiation in vitro and in vivo, and delayed the progression of joint destruction.