ferric-ammonium-citrate and Osteoporosis

To analyze the effect of ferric ammonium citrate on iron accumulation, bone turnover and bone density in ovariectomized rat models with osteoporosis, 40 female SD rats were randomized into four groups, that were, sham-operated, model, low and high-dose ferric ammonium citrate groups (i.e. low and high-dose groups) respectively, each of them had ten rats. Except for the sham-operated group, bilateral ovariectomy was performed in the other groups to establish models with osteoporosis; one week after the operation, those in the low and high-dose groups were given 90 mg/kg and 180 mg/kg ferric ammonium citrate, respectively. Those in the other two groups received isodose saline for nine weeks, with the frequency of twice per week. The changes in bone tissue morphology, serum ferritin concentration, tibial iron content, serum osteocalcin, carboxyl terminal peptide (β - CTX), bone density, bone volume fraction and trabecular thickness were compared. Results showed that the rats in the low and high-dose groups contained a higher concentration of serum ferritin and tibial iron content compared to the other groups (P < 0.05). In contrast to the model group, the bone trabeculae in the low and high-dose groups were sparse in morphology and increased in spacing. It was obvious that the rats contained more osteocalcin and β - CTX in the model group, the low and high-dose groups versus the sham-operated group (P < 0.05), and those had more β - CTX in the high-dose group versus the model group and the low-dose group (P < 0.05). The bone density, bone volume fraction and trabecular thickness of the rats in the model group, the low and high-dose groups showed lower versus the sham-operated group (P < 0.05); those in the low and high-dose groups significantly presented lower bone density and bone volume fraction versus the model group (P < 0.05). Iron accumulation can aggravate osteoporosis in ovariectomized rats, and its mechanism may be associated with accelerating bone turnover, promoting bone absorption, reducing bone density and sparsely trabecular structure. Therefore, it is particularly important to understand iron accumulation in postmenopausal osteoporosis patients.

Topics: Animals; Bone Density; Bone Remodeling; Collagen; Female; Ferritins; Humans; Iron; Osteocalcin; Osteoporosis; Ovariectomy; Rats; Rats, Sprague-Dawley

Iron overload has recently been associated with the changes in the bone microstructure that occur in osteoporosis. However, the effect of iron overload on osteoblasts is unclear. The purpose of this study was to explore the function of divalent metal transporter 1 (DMT1) in the pathological processes of osteoporosis. Osteoblast hFOB1.19 cells were cultured in medium supplemented with different concentrations (0, 50, 100, 200, 300, 400, 500 μmol/L) of ferric ammonium citrate (FAC) as a donor of ferric ions. We used western blotting and immunofluorescence to determine the levels of DMT1 after treatment with FAC. Apoptosis was evaluated by detecting the levels of cleaved caspase 3, BCL2, and BAX with western blotting. Autophagy was evaluated by detecting the levels of LC3 with western blotting and immunofluorescence. Beclin-1 expression was also assessed with western blotting. The autophagy inhibitor 3-methyladenine was used to determine whether autophagy affects the apoptosis induced by FAC. Our results show that FAC increased the levels of DMT1, upregulated the expression of BCL2, and downregulated the apoptosis-related proteins cleaved caspase 3 and BAX. Both LC3I/LC3II levels and beclin-1 were also increased, indicating that FAC increases the accumulation of autophagosomes in hFOB1.19 cells. FAC-induced autophagy was increased by the apoptosis inhibitor 3-MA but was reduced in DMT1 shRNA hFOB1.19 cells. These results suggest that the increased expression of DMT1 induces iron overload and iron overload induces osteoblast autophagy and apoptosis, thus affecting the pathological processes of osteoporosis. Clarifying the mechanisms underlying the effects of DMT1 will allow the identification of novel targets for the prevention and treatment of osteoporosis.

Topics: Apoptosis; Autophagy; bcl-2-Associated X Protein; Caspase 3; Ferric Compounds; Gene Expression Regulation; Humans; Iron; Iron Overload; Osteoblasts; Osteoporosis; Oxidative Stress; Proto-Oncogene Proteins c-bcl-2; Quaternary Ammonium Compounds; Transcription Factors