Session Title: Cytokines, Mediators, and Gene Regulation
Session Type: Abstract Submissions (ACR)
Background/Purpose: Interleukin-1β (IL-1β) and thapsigargin (TG)-augmented endoplasmic reticulum (ER) stress modulate the receptor activator of nuclear factor kappa-B ligand (RANKL)-mediated osteoclastogenesis. However, the mechanism by which IL-1β and TG affect osteoclastogenesis remains elusive. Thus, we investigated the relationships between RANKL-mediated osteoclast specific pathways and ER stress relevant signals in osteoclast differentiation of bone marrow-derived cells.
Methods: Bone marrow cells (BMCs) were obtained from 5-week-old male ICR mice. The cells were cultured to be differentiated into osteoclasts with macrophage-colony stimulating factor (M-CSF) and RANKL in the presence or absence of IL-1β, thapsigargin (TG, ER stress inducer), or 4-phenylbutyric acid (PBA, ER stress inhibitor). The formation of osteoclasts was evaluated by tartrate-resistant acid phosphatase (TRAP) staining and resorption pit assay with dentine slice. The molecular mechanisms of IL-1β and ER stress in osteoclastogenesis of BMCs were investigated using reverse transcription-polymerase chain reaction (RT-PCR) and immunoblotting. Osteoclast specific and ER stress relevant signaling molecules were analyzed. Transfections of small interfering RNA (siRNA) for glucose-regulated protein 78 (GRP78), protein kinase RNA-like ER kinase (PERK) and inositol-requiring enzyme 1 (IRE1) were performed to knockdown ER stress initiating signals to verify the relationships between osteoclast specific pathways and ER stress signals.
Results: The formation of osteoclasts was increased by IL-1β and TG augmented ER stress. PBA significantly inhibited IL-1β and TG induced osteoclats formation. The expressions of osteoclast specific pathways such as c-Fos and NFATc1, and ER stress associated signals such as PERK, IRE1, GRP78, and eIF2α were significantly increased by IL-1β and TG which was inhibited by PBA. Inhibition of ER stress initiating signals by siRNA inhibited the expression of above mentioned osteoclast specific signals, thus reduced IL-1β and/or TG-induced osteoclastogenesis.
Conclusion: IL-1β and/or TG-augmented ER stress significantly increased osteoclast formation which was inhibited by PBA. The mechanisms were mainly associated with up-regulation of ER stress signals such as GRP78, PERK, p-eIF2α and IRE1. Thus the modulation of ER stress signals affecting osteoclast formation might be a new therapeutic strategy to prevent inflammatory and destructive arthritis diseases such as rheumatoid arthritis (RA) and diverse osteoporotic diseases.
M. J. Hong,
M. S. Sung,
E. G. Lee,
Y. K. Hong,
C. H. Lee,
M. S. Lee,
W. H. Yoo,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/receptor-activator-of-nuclear-factor-eb-ligand-mediated-osteoclastogenesis-is-augmented-by-interleukin-1a-via-up-regulation-of-endoplasmic-reticulum-stress-signals/