Anti-Osteoclast Effect of Exportin-1 Inhibitor Eltanexor on Osteoporosis Depends on Nuclear Accumulation of IκBα–NF-κB p65 Complex

Abstract

Osteoporosis affects around 200 million people globally, with menopausal women accounting for the bulk of cases. In the occurrence and development of osteoporosis, a key role is played by osteoclasts. Excessive osteoclast-mediated bone resorption activity reduces bone mass and increases bone fragility, resulting in osteoporosis. Thus, considerable demand exists for designing effective osteoporosis treatments based on targeting osteoclasts. Eltanexor (Elt; KPT-8602) is a selective nuclear-export inhibitor that covalently binds to and blocks the function of the nuclear-export protein exportin-1 (XPO1), which controls the nucleus-to-cytoplasm transfer of certain critical proteins related to growth regulation and tumor suppression, such as p53, IκBα [nuclear factor-κB (NF-κB) inhibitor α] and FOXO1; among these proteins, IκBα, a critical component of the NF-κB signaling pathway that primarily governs NF-κB activation and transcription. How Elt treatment affects osteoclasts remains poorly elucidated. Elt inhibited the growth and activity of RANKL-induced osteoclasts in vitro in a dose-dependent manner, and Elt exerted no cell-killing effect within the effective inhibitory concentration. Mechanistically, Elt was found to trap IκBα in the nucleus and thus protect IκBα from proteasome degradation, which resulted in the blocking of the translocation of IκBα and NF-κB p65 and the consequent inhibition of NF-κB activity. The suppression of NF-κB activity, in turn, inhibited the activity of two transcription factors (NFATc1 and c-Fos) essential for osteoclast formation and led to the downregulation of genes and proteins related to bone resorption. Our study thus provides a newly identified mechanism for targeting in the treatment of osteoporosis.

Recent advances of NFATc1 in rheumatoid arthritis-related bone destruction: mechanisms and potential therapeutic targets

“…Chen et al found that Eltanexor (Elt), a selective nuclear-export inhibitor, prevented NF-κB activity by trapping IκBα in the nucleus and protecting it from proteasomal degradation, thereby impeding the translocation of IκBα and NF-κB p65. Consequently, the inhibition of NF-κB suppressed NFATc1 and c-Fos activity and resulted in the downregulation of genes and proteins associated with bone destruction (Chen et al 2022a ).…”

Unveiling the potential of Butylphthalide: inhibiting osteoclastogenesis and preventing bone loss

“…Nevertheless, regenerating damaged bone tissue in osteoporosis patients remains a therapeutic challenge. Conventional antiosteoporotic medications can improve conditions to some degree but cannot effectively repair affected areas, with long-term use incurring more side effects (Li J. et al, 2022;Chen et al, 2022;Long et al, 2022;Wu et al, 2022). Therefore, searching for a safe and efficacious osteoporosis drug is imperative.…”