Claudin 11 regulates bone homeostasis via bidirectional EphB4-EphrinB2 signaling

Abstract

Claudins (Cldns) are well-established components of tight junctions (TJs) that play a pivotal role in the modulation of paracellular permeability. Several studies have explored the physiologic aspects of Cldn family members in bone metabolism. However, the effect of Cldn11, a major component of central nervous system myelin, on bone homeostasis has not been reported. In this study, we demonstrate that Cldn11 is a potential target for bone disease therapeutics as a dual modulator of osteogenesis enhancement and osteoclastogenesis inhibition. We found that Cldn11 played a negative role in the receptor activator of nuclear factor kappa B ligand-induced osteoclast (OC) differentiation and function by downregulating the phosphorylated form of extracellular signal-regulated kinase (ERK), Bruton’s tyrosine kinase, and phospholipase C gamma 2, in turn impeding c-Fos and nuclear factor in activated T cell c1 expression. The enhancement of osteoblast (OB) differentiation by positive feedback of Cldn11 was achieved through the phosphorylation of Smad1/5/8, ERK, and c-Jun amino-terminal kinase. Importantly, this Cldn11-dependent dual event in bone metabolism arose from targeting EphrinB2 ligand reverse signaling in OC and EphB4 receptor forward signaling in OB. In agreement with these in vitro effects, subcutaneous injection of Cldn11 recombinant protein exerted anti-resorbing effects in a lipopolysaccharide-induced calvarial bone loss mouse model and increased osteogenic activity in a calvarial bone formation model. These findings suggest that Cldn11 is a novel regulator in bone homeostasis.

The Natural Product 6-Gingerol Inhibits Inflammation-Associated Osteoclast Differentiation via Reduction of Prostaglandin E2 Levels

“…IL-1 is known to enhance the osteoclast-supporting activity of POBs by up-regulating RANKL expression and down-regulating expression of its decoy receptor, OPG [ 5 , 22 ]. Therefore, we examined whether 6-gingerol affects IL-1-induced RANKL and OPG expression in POBs.…”

Magnolol Inhibits Osteoclast Differentiation via Suppression of RANKL Expression

“…Because IL-1 has been shown to increase RANKL expression and decrease expression of its decoy receptor OPG on osteoblasts [ 6 , 13 ], we next investigated whether magnolol might modulate RANKL and OPG expression in osteoblasts through real-time polymerase chain reaction (PCR) analysis and enzyme-linked immunosorbent assay (ELISA). Magnolol (1.25–10 μm) significantly inhibited IL-induced RANKL mRNA levels in a dose-dependent manner ( p < 0.01, Figure 3 A); thereby, excess production of RANKL was also markedly reduced by magnolol ( p < 0.01, Figure 3 B).…”

Dual Oxidase Maturation Factor 1 Positively Regulates RANKL-Induced Osteoclastogenesis via Activating Reactive Oxygen Species and TRAF6-Mediated Signaling

“…BMCs were isolated from 5-week-old male ICR mice by flushing the femurs and tibias with α-MEM supplemented with 10% FBS and 1% antibiotics [ 26 ]. BMCs were cultured on culture dishes in α-MEM supplemented with 10% FBS and M-CSF (10 ng/mL) for 1 day.…”

“…The retroviral vector (pMX), pMX-Duoxa1-IRES-EGFP, and mouse negative control (siControl) and Duoxa1 (siDuoxa1) siRNAs were ordered and synthesized by Bioneer Co. (Daejeon, Korea). The transfection assay of retroviral genes and siRNA was performed as previously described [ 26 ]. Plat-E retroviral packaging cells were seeded in culture dish before 1 day transfection.…”

“…Mature OCs were prepared from the co-culture of BMCs and primary osteoblasts (OBs) as described previously [ 26 ]. Briefly, BMCs (1 × 10 7 cells) and primary OBs (1 × 10 6 cells) were incubated in collagen gel-coated culture dishes in the presence of 10 −8 M VitD 3 and 10 −6 M PGE 2 for 10–12 days.…”