Excessive glucocorticoids combined with RANKL promote the differentiation of bone marrow macrophages (BMM) into osteoclasts and accelerate the progression of osteoporosis by activating the SYK/SHP2/NF-κB signaling pathway

Abstract

The primary objective of this study was to explore the extensive implications and complex molecular interactions arising from the confluence of excessive glucocorticoids and RANKL on the differentiation process of BMM into osteoclasts, profoundly impacting osteoporosis development. The methodology encompassed X-ray analysis and HE staining for evaluating bone loss in mice, while immunohistochemical staining was utilized to observe phosphorylated SHP2 (p-SHP2) expression. The assessment of several phosphorylated and total protein expression levels, including NF-κB, SHP2, SYK, JAK2, TAK1, NFATC1, c-fos, and Cathepsin K, was conducted via Western blotting. Additional experiments, involving CCK8 and monoclonal proliferation assays, were undertaken to determine BMM proliferation capacity. Immunofluorescence staining facilitated the quantification of TRAP fluorescence intensity. In vivo analysis revealed that glucocorticoid surplus triggers SHP2 signaling pathway activation, accelerating osteoporosis progression. Western blot results demonstrated that SHP2 inhibition could decrease the expression of specific proteins such as p-NF-κB and p-SHP2, with minimal effects on p-SYK levels. In vitro findings indicated that glucocorticoid and RANKL interaction activates the SHP2 pathway through NF-κB and SYK pathways, enhancing expressions of p-JAK2, p-TAK1, NFATC1, c-fos, and Cathepsin K, thereby promoting BMM to osteoclast transformation. Conclusion: Excessive glucocorticoids and RANKL interaction advance osteoclast differentiation from BMM by activating the SYK/SHP2/NF-κB signaling pathway, expediting osteoporosis progression.