Genistein attenuates glucocorticoid-induced bone deleterious effects through regulation Eph/ephrin expression in aged mice

Abstract

Objective: This study was performed to investigate bone deteriorations and the involvement of skeletal Eph/ephrin signaling pathway of GIOP aged mice in response to the treatment of genistein.

Methods: The biomarkers in serum and urine were measured, tibias were taken for the measurement on gene and protein expression and histomorphology analysis, and femurs were taken for the measurement on bone Ca and three-dimensional architecture of trabecular bone.

Results: Genistein showed a greater increase in bone Ca, BMD and significantly increased FGF-23 and OCN, reduced TRACP-5b, PTH and CTX in GIOP mice. Genistein reversed DXM-induced trabecular deleterious effects and stimulated bone remodeling. The treatment of DXM group with genistein significantly elevated the ratio of OPG/RANKL. Moreover, genistein administration down-regulated the mRNA and protein expression of Eph A2 and ephrin A2 in tibia of the GIOP mice. In contrast, the mRNA and protein expression of Eph B4 and ephrin B2 were increased in mice treated by DXM with genistein as compared to the DXM single treatment.

Conclusions: DXM-induced trabecular bone micro-structure deterioration in aged mice was involved in the regulation of the Eph receptors and ephrin ligands. Genistein might represent a therapy with bone-forming as well as an anti-resorptive activity in GIOP mice. The underlying mechanism was mediated, at least partially, through regulation Eph/ephrin signaling.

Keywords: Eph/ephrin; bone; dexamethasone; genistein.

Figure 1

Hematoxylin and eosin staining of the proximal metaphysis of the tibia. Trabecular bone zone below growth plate was shown.

Figure 2

Biochemical parameters analysis. PTH, parathyroid hormone; FGF-23, fibroblast growth factor-23; TRACP-5b, tartrate resistant acid phosphatase-5b; OCN, Osteocalcin; CTX, C-terminal telopeptide of type I collagen. Values are expressed as mean ± SEM, n = 7-10 in each group. *P < 0.05, versus vehicle group; #P < 0.05, versus DXM group.

Figure 3

OPG/RANKL ratio in tibia. The mRNA expression of osteoprotegerin (OPG), receptor activator of nuclear factor-κB ligand (RANKL) (A) and the quantitative ratio of OPG/RANKL (B). Values are expressed as mean ± SEM, n = 6-7 in each group. *P < 0.05, versus vehicle group; #P < 0.05, versus DXM group.

Figure 4

mRNA and protein expression of Eph receptors and ephrins. The mRNA expression of erythropoietin-producing hepatocyte receptor A2 (Eph A2), erythropoietin-producing hepatocyte receptor B4 (Eph B4), Eph receptor interacting protein A2 (ephrin A2), Eph receptor interacting protein B4 (ephrin B4) in the tibia (A) and densitometric quantification (B), the protein expression of Eph A2, Eph B4, ephrin A2 and ephrin B4 in the tibia (C) and densitometric quantification (D). Values are expressed as mean ± SEM, n = 6-7 in each group. *P < 0.05, versus vehicle group; #P < 0.05, versus DXM group.