TGFβ1 Regulates Human RANKL-Induced Osteoclastogenesis via Suppression of NFATc1 Expression

Abstract

Osteoclasts are multinucleated giant cells responsible for bone resorption. Various mediators involved in osteoclast differentiation have been investigated as possible therapeutic targets for osteoporosis and rheumatoid arthritis (RA). Although transforming growth factor beta1 (TGFβ1) has been described as one such multifunctional cytokine essential for bone remodeling, its effect on osteoclastogenesis remains controversial. Therefore, we sought to examine the effect of TGFβ1 on osteoclast generation induced by receptor activator of nuclear factor (NF)-κB ligand (RANKL) in humans. Peripheral blood monocytes, isolated using magnetic bead sorting, were cultured with macrophage-colony stimulating factor (M-CSF) or RANKL with or without TGFβ1. Tartrate-resistant acid phosphatase (TRAP) staining, as well as bone resorption assays, revealed that TGFβ1 suppressed RANKL-mediated human osteoclast development. Real-time reverse transcription PCR and Western blotting revealed that TGFβ1 reduced the gene and protein expression of nuclear factor of activated T cells, cytoplasmic 1 (NFATc1), the master regulator of osteoclast differentiation, respectively. Luciferase assays indicated that TGFβ1 inhibited the NF-κB p65-stimulated promoter activity of NFATc1. Immunofluorescence analysis demonstrated that TGFβ1 abrogated RANKL-induced nuclear translocation of p65. Thus, TGFβ1 regulates human RANKL-induced osteoclastogenesis via downregulation of NFATc1 by blocking nuclear translocation of NF-κB, suggesting that TGFβ1 may be a potential therapeutic target for RA.

Increased FURIN expression in rheumatoid arthritis patients and its anti‐inflammatory effect

“…21,22 However, a recent report showed that TGF-β1 suppresses human RANKL-induced human osteoclast development and bone resorption and identified a potential therapeutic target for RA. 23 We believe that the opposing effects of TGF-β1 may be due to difference in the experimental cells used in previous studies. 23 Macrophages are the major source of IL-1β and contribute to tissue destruction and pain in RA patients.…”

“…23 We believe that the opposing effects of TGF-β1 may be due to difference in the experimental cells used in previous studies. 23 Macrophages are the major source of IL-1β and contribute to tissue destruction and pain in RA patients. In this study, LPS and ATP treatment contributed to the inflammatory environment in THP-1-derived macrophages, and IL-1β and caspase-1 levels were higher following the inhibition of FURIN expression.…”

“…Additionally, a positive feedback loop between FURIN and TGF‐β1 has been reported in synoviocytes, which upregulates “A disintegrin and metalloprotease with thrombospondin motif‐4” (ADAMTS‐4); this eventually leads to the destruction of arthritis 21,22 . However, a recent report showed that TGF‐β1 suppresses human RANKL‐induced human osteoclast development and bone resorption and identified a potential therapeutic target for RA 23 . We believe that the opposing effects of TGF‐β1 may be due to difference in the experimental cells used in previous studies 23 …”

Communications Between Bone Marrow Macrophages and Bone Cells in Bone Remodeling

“…Nuclear factor of activated T cells cytoplasmic 1 (NFATc1) is a master regulator of osteoclast differentiation (Okamoto and Takayanagi, 2011 ). Some studies have shown that TGF-β1 directly down-regulates NFATc1 activity by blocking the p65 in the receptor activator and then inhibits the generation and bone resorption of osteoclasts ( Figure 2 ) (Tokunaga et al, 2020 ). Recently, the role of the NEMO protein (a core component of the NF-kB signaling pathway) in mouse bone marrow macrophages was investigated that if the lysine-270 (NEMO-Lys270) in NEMO protein was mutated to Ala, the NF-kB signal in bone marrow macrophages would lose control, leading to the accelerated production of osteoclasts (Adapala et al, 2020 ).…”

Synovial Fluid Interleukin-16 Contributes to Osteoclast Activation and Bone Loss through the JNK/NFATc1 Signaling Cascade in Patients with Periprosthetic Joint Infection

“…The RANKL-induced osteoclast activation was mediated by MAPK signaling [25][26][27][28]. Thus, we evaluated whether MAPK signaling has a role in IL-16-mediated osteoclast activation.…”