Binding and bioeffects of Ipriflavone on a human preosteoclastic cell line

Effects of grape seed proanthocyanidins extract on mandibles in developing rats

OBJECTIVE

Grape seed proanthocyanidins extract (GSPE), a flavonoid, has a beneficial effect on physical health, which may include the health of bone. The purpose of the present study was to investigate the effects of GSPE on mandibular bone by examining trabecular and cortical bone density, mineral content, and non-invasive bone strength in low-calcium diet rats.

MATERIALS AND METHODS

Wistar male rats at 5 weeks old (n = 40) were divided into control (A), low-calcium diet (B), low-calcium diet plus standard diet (C), and low-calcium diet plus standard diet with supplementary GSPE (D) groups. Following 3 weeks of a calcium-restricted diet, group D rats were given 3 mg of GSPE as supplement in 100 g of a standard diet for the next 3 weeks. Following the 6-week experimental period, mandibular bones were examined using peripheral quantitative computed tomography (pQCT).

RESULTS

There were no significant differences in body weight or trabecular bone area among the four groups. Trabecular bone density, and trabecular bone mineral content, cortical bone density, cortical bone cross-sectional area, and cortical bone mineral content were significantly higher in group D than in C. Further, Stress-strain index (SSI) values of xSSI and ySSI in group D were significantly higher than in C, although there was no significant difference in pSSI value between those two groups.

CONCLUSION

Our results suggest that GSPE treatment caused an increase in both bone formation and bone strength in rat mandibles.

Fluid shear stress increases interleukin-11 expression in human osteoblast-like cells: its role in osteoclast induction

It is unclear how mechanical stress influences bone cells. Mechanical stress causes fluid shear stress (FSS) in the bone. Osteoblast lineage cells are thought to sense FSS and regulate bone remodeling. We therefore investigated the effects of FSS on human osteoblast-like osteosarcoma cells: SaOS-2 cells in vitro. The conditioned medium of the SaOS-2 cells after 24 h of FSS (24 h-FSS CM) showed such osteoclastic phenotype inductions as significantly increasing the number of tartrate-resistant acid phosphatase (TRAP) positive multinuclear cells in rat bone marrow cells and TRAP-positive cells in human preosteoclastic cells: FLG 29.1 cells. An enzyme-linked immunosorbent assay showed interleukin-11 (IL-11) protein to increase 7-fold in the 24 h-FSS CM. A Northern analysis showed that IL-11 mRNA increased 4-fold in the SaOS-2 cells after 6 h-FSS; however, no IL-6 mRNA expression was detected. Furthermore, the anti-human IL-11 antibody significantly neutralized the osteoclastic phenotype induction of the 24 h-FSS CM. The IL-11 mRNA up-regulation in SaOS-2 cells by the 6 h-FSS was not inhibited by the anti-human transforming growth factor-beta1 antibody, but it was significantly inhibited by indomethacin. An enzymeimmunoassay showed prostaglandin E2 to increase 7-fold in the 1 h-FSS CM. These findings thus suggest that FSS induces osteoblasts to produce IL-11 (mediated by prostaglandins) and thus stimulates bone remodeling.

Inhibition of parathyroid hormone-stimulated resorption in cultured fetal rat long bones by the main metabolites of ipriflavone

Ipriflavone is an isoflavone derivative used in the prevention and treatment of postmenopausal and senile osteoporosis in humans. To assess the potential contribution of the main in vivo ipriflavone metabolites (M1, M2, M3, and M5) on the pharmacological properties of the drug, we investigated their effect on osteoclastic resorption induced by the well-known stimulator of bone resorption bovine parathyroid hormone fragment 1-34 (bPTH 1-34). The study was carried out using fetal rat long bones in stationary cultures. The amount of osteoclastic resorption was determined by assaying for 5 days the release from bones in the media of previously incorporated 45Ca. All metabolites were effective at inhibiting osteoclastic resorption. Maximal potency was shown by M3, characterized by a significant effect at 10 microM (P < 0.01) and by an IC50 value of 17 microM. M2 was about threefold less potent than M3 (IC50 = 46 microM). M1 and M5 were the least active compounds with an IC50 value of 117 and 200 microM, respectively. The present evidence indicates that metabolites of ipriflavone, in particular M3 and M2, inhibit bPTH 1-34-induced bone resorption in fetal rat long bones. Accordingly, they may play an important role in the pharmacological effects of the drug.

Interactions between ipriflavone and the estrogen receptor

Estrogen replacement therapy is effective in the prevention of postmenopausal osteoporosis, and a direct action of 17-beta-estradiol (17 beta E2) on osteoblastic and osteoclastic cells has been demonstrated. The inhibition of bone resorption by ipriflavone (IP), an isoflavone derivative devoid of estrogenic properties but active in potentiating the effects of estrogen on bone tissue, has been shown in in vitro and in vivo studies and confirmed by clinical data. To investigate the molecular mechanisms that underlie IP effect, we studied the possible interactions of IP and its four main in vivo metabolites (I, II, III, and V) with the estrogen receptor (ER) in the human preosteoclastic cell line FLG 29.1, whose growth and function are modulated by the compound. In parallel experiments, the human breast cancer cell line MCF7 was also analyzed. IP binding sites were demonstrated in the nuclear fraction of FLG 29.1 cells. 17 beta E2 and other steroid compounds failed to displace IP binding to intact FLG 29.1 cells. Similarly, IP and metabolites I, III, and V were not able to displace 17 beta E2 binding to intact MCF7 cells, whereas metabolite II showed an IC50 of 61 nM. 17 beta E2 binding to FLG 29.1 cells was increased after preincubation with metabolites I, III, and V. IP and its metabolites did not induce ER-dependent gene expression in FLG 29.1 and MCF7 cells transfected with a reporter gene and an estrogen response element (ERE).(ABSTRACT TRUNCATED AT 250 WORDS)