HDAC9 Inhibits Osteoclastogenesis via Mutual Suppression of PPARγ/RANKL Signaling

Abstract Recent studies suggest that the class II histone deacetylase (HDAC)9 plays important roles in physiology such as metabolism and immunity. Here, we report that HDAC9 also controls bone turnover by suppressing osteoclast differentiation and bone resorption. HDAC9 expression is down-regulated during osteoclastogenesis. Ex vivo osteoclast differentiation is accelerated by HDAC9 deletion but diminished by HDAC9 overexpression. HDAC9 knockout mice exhibit elevated bone resorption and lower bone mass. Bone marrow transplantation reveal that the osteoclastogenic defects are intrinsic to the hematopoietic lineage, because the excessive bone resorption phenotype can be conferred in wild-type (WT) mice receiving HDAC9-null bone marrow, and rescued in HDAC9-null mice receiving WT bone marrow. Mechanistically, HDAC9 forms a negative regulatory loop with peroxisome proliferator-activated receptor gamma (PPARg) and receptor activator of nuclear factor kappa-B ligand (RANKL) signaling. On one hand, PPARγ and nuclear factor κB suppress HDAC9 expression, on the other hand, HDAC9 inhibits PPARγ activity in synergy with silencing mediator of retinoic acid and thyroid hormone receptors (SMRT)/NCoR corepressors. These findings identify HDAC9 as a novel, important and physiologically relevant modulator of bone remodeling and skeletal homeostasis.

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Stimulation of Resorption in Cultured Mouse Calvarial Bones by Thiazolidinediones

Endocrinology ◽

10.1210/en.2005-0601 ◽

2005 ◽

Vol 146 (10) ◽

pp. 4349-4361 ◽

Cited By ~ 21

Author(s):

A. M. Schwab ◽

S. Granholm ◽

E. Persson ◽

B. Wilkes ◽

U. H. Lerner ◽

...

Keyword(s):

Mrna Expression ◽

Osteoclast Differentiation ◽

Cathepsin K ◽

Nuclear Factor Κb ◽

Tartrate Resistant Acid Phosphatase ◽

Peroxisome Proliferator ◽

Nuclear Factor ◽

Activated T Cells ◽

Peroxisome Proliferator Activated Receptor ◽

Stimulation Of

Dosage-dependent release of 45Ca was observed from prelabeled mouse calvarial bones after treatment with two thiazolidinediones, troglitazone and ciglitazone. Release of 45Ca by ciglitazone was decreased by the osteoclast inhibitors acetazolamide, calcitonin, 3-amino-1-hydroxypropylidene-1,1-bisphosphonate, and IL-4, but not affected by the peroxisome proliferator-activated receptor γ antagonist, GW 9662, the mitotic inhibitor, hydroxyurea, or indomethacin. Enhanced expression of receptor activator of nuclear factor-κB ligand (RANKL) mRNA and protein and decreased osteoprotegerin (OPG) mRNA and protein were noted after ciglitazone treatment of calvariae. Ciglitazone and RANKL each caused increased mRNA expression of osteoclast markers: calcitonin receptor, tartrate-resistant acid phosphatase, cathepsin K, matrix metalloproteinase-9, integrin β3, and nuclear factor of activated T cells 2. OPG inhibited mRNA expression of RANKL stimulated by ciglitazone, mRNA expression of osteoclast markers stimulated by ciglitazone and RANKL, and 45Ca release stimulated by troglitazone and ciglitazone. Increased expression of IL-1α mRNA by ciglitazone was not linked to resorption stimulated by the thiazolidinedione. Ciglitazone did not increase adipogenic gene expression but enhanced osteocalcin mRNA in calvariae. In addition to exhibiting sensitivity to OPG, data indicate that stimulation of osteoclast differentiation and activity by thiazolidinediones may occur by a nonperoxisome proliferator-activated receptor γ-dependent pathway that does not require cell proliferation, prostaglandins, or IL-1α but is characterized by an increased RANKL to OPG ratio.

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GPR109A mediates the effects of hippuric acid on regulating osteoclastogenesis and bone resorption in mice

Communications Biology ◽

10.1038/s42003-020-01564-2 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Jin-Ran Chen ◽

Haijun Zhao ◽

Umesh D. Wankhade ◽

Sree V. Chintapalli ◽

Can Li ◽

...

Keyword(s):

Bone Marrow ◽

Bone Resorption ◽

Bone Mass ◽

Hippuric Acid ◽

Ex Vivo ◽

Marrow Cell ◽

Osteoclast Differentiation ◽

Bone Homeostasis ◽

Wild Type ◽

Osteoclast Precursors

AbstractThe G protein-coupled receptor 109 A (GPR109A) is robustly expressed in osteoclastic precursor macrophages. Previous studies suggested that GPR109A mediates effects of diet-derived phenolic acids such as hippuric acid (HA) and 3-(3-hydroxyphenyl) propionic acid (3-3-PPA) on promoting bone formation. However, the role of GPR109A in metabolic bone homeostasis and osteoclast differentiation has not been investigated. Using densitometric, bone histologic and molecular signaling analytic methods, we uncovered that bone mass and strength were significantly higher in tibia and spine of standard rodent diet weaned 4-week-old and 6-month-old GPR109A gene deletion (GPR109A−/−) mice, compared to their wild type controls. Osteoclast numbers in bone and in ex vivo bone marrow cell cultures were significantly decreased in GPR109A−/− mice compared to wild type controls. In accordance with these data, CTX-1 in bone marrow plasma and gene expression of bone resorption markers (TNFα, TRAP, Cathepsin K) were significantly decreased in GPR109A−/− mice, while on the other hand, P1NP was increased in serum from both male and female GPR109A−/− mice compared to their respective controls. GPR109A deletion led to suppressed Wnt/β-catenin signaling in osteoclast precursors to inhibit osteoclast differentiation and activity. Indeed, HA and 3-3-PPA substantially inhibited RANKL-induced GPR109A expression and Wnt/β-catenin signaling in osteoclast precursors and osteoclast differentiation. Resultantly, HA significantly inhibited bone resorption and increased bone mass in wild type mice, but had no additional effects on bone in GPR109A−/− mice compared with their respective untreated control mice. These results suggest an important role for GPR109A during osteoclast differentiation and bone resorption mediating effects of HA and 3-3-PPA on inhibiting bone resorption during skeletal development.

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