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Prostaglandin E2 strongly inhibits human osteoclast formation
Ikuko Take1, Yasuhiro Kobayashi, Yohei Yamamoto
1Graduate School of Oral Medicine, Matsumoto Dental University, Nagano, Japan.
Endocrinology
|September 10, 2005
Summary
Prostaglandin E(2) (PGE(2)) inhibits human osteoclast formation, unlike its effect in mice. This inhibition is mediated by EP2/EP4 receptor signals and involves the production of inhibitory factors from CD14(+) cells.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Prostaglandin E(2) (PGE(2)) is known to enhance osteoclast formation in mouse models.
- Osteoclasts are crucial for bone remodeling and their dysregulation is implicated in bone diseases.
Purpose of the Study:
- To investigate the effects of PGE(2) on human osteoclast formation.
- To elucidate the signaling pathways and mechanisms underlying PGE(2)'s action on human osteoclasts.
Main Methods:
- Human peripheral blood mononuclear cells were isolated and cultured to obtain CD14(+) cells.
- Osteoclast differentiation was induced using receptor activator of nuclear factor-kappaB ligand (RANKL) and macrophage colony-stimulating factor.
- Gene expression of PGE(2) receptors (EP1-4) was analyzed in CD14(+) cells and osteoclasts.
- Cyclic AMP (cAMP) production was measured following stimulation with PGE(2) and an EP2/4 agonist.
- The effects of PGE(2) and its agonists/antagonists on osteoclast formation were assessed in various culture systems, including co-cultures with SaOS4/3 cells.
Main Results:
- CD14(+) cells expressed EP2 and EP4 receptors for PGE(2).
- PGE(2) and an EP2/4 agonist inhibited RANKL-induced human osteoclast formation, mediated by EP2/4 signals and cAMP production.
- PGE(2) also inhibited parathyroid hormone (PTH)-induced osteoclast formation in co-cultures.
- A cyclooxygenase 2 inhibitor enhanced PTH-induced osteoclast formation.
- Conditioned medium from PGE(2)-treated CD14(+) cells inhibited osteoclast formation in both human and mouse cultures, suggesting the production of inhibitory factors.
Conclusions:
- PGE(2) inhibits human osteoclast formation via EP2/EP4 receptor signaling pathways.
- The mechanism involves cAMP stimulation and the potential production of osteoclastogenesis inhibitory factors.
- These findings contrast with the pro-osteoclastogenic effects of PGE(2) in mice, highlighting species-specific differences in immune and bone cell regulation.