Benedictine University, Biological Sciences, Lisle, IL 60532
Estrogen is protective on bone, inducing bone formation and inhibiting bone resorption by stimulating apoptosis of osteoclasts. Previous studies in our lab have demonstrated that cadmium can act anti-estrogenically on bone, causing bone loss, by delaying the induction of estrogen-induced osteoclast apoptosis. Other studies in the literature have demonstrated that divalent cationic metals, including cadmium, act estrogenically on reproductive tissues. The objective of our study was to determine whether other divalent cationic metals could work similar to that of cadmium on bone. The divalent metals, SnCl2, and CuCl2, were used to determine whether they could also inhibit estrogen-induced apoptosis in differentiated osteoclasts in culture. The RAW 264.7 mouse macrophage cell line was differentiated with RANK ligand for five days before incubation with a control, metal, estradiol, or metal + estradiol solution for 24 hours. Osteoclasts were exposed to estradiol solutions at concentrations of 1 μM and metal solutions at 0.1 μM. The trivalent metal chromium chloride was used as a negative control. Fluorescent microscopy analysis of DAPI-stained multinucleated osteoclasts indicated that divalent metal + estradiol treatments decrease apoptosis from the levels induced by estradiol only treatments as seen with cadmium. Preliminary research of earlier timepoints of apoptosis using various apoptosis indicators have shown that the effects of divalent cationic metals on estrogen-induced apoptosis begin as early as two hours after treatment. These results support the hypothesis that the anti-estrogenic effect of cadmium can be extended to divalent cationic metals in general. As divalent cationic metals exist as environmental contaminants, their effects on bone can be added to the list of endocrine disruptors.
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