A novel Mn(2+)-doped core/shell quantum dot-based intracellular probe for fluoride anions sensing in MC3T3-E1 osteoblastic cells.

In this paper, 3-aminobenzeneboronic acid functionalized Mn(2+)-doped ZnTe/ZnSe quantum dots (APBA-dQDs) were prepared. The APBA functional groups had strong binding ability with F(-), resulting in the quenchment of dQDs photoluminescence (PL). Under the optimal condition, the fluorescence intensity of APBA-dQDs was related linearly to the concentration of F(-) in the range of 0.25-1.5µmol/L with a detection limit of 0.1µmol/L. The selectivity of fluorescence quenching of APBA-dQDs for F(-) was enhanced. Moreover, the proposed methodology for the sensing of F(-) at EM 560nm in MC3T3-E1 osteoblastic cells was demonstrated and got a satisfactory results. The results indicate that the APBA-dQDs are promising candidates for intracellular in MC3T3-E1 osteoblastic cells. To the best of our knowledge, it was the first report of F(-) sensing by using the quenched fluorescence of APBA-dQDs in non-cancerous cells.

Fluoride Affects Calcium Homeostasis by Regulating Parathyroid Hormone, PTH-Related Peptide, and Calcium-Sensing Receptor Expression.

Parathyroid hormone (PTH), PTH-related peptide (PTHrP), and calcium-sensing receptor (CaSR) play important roles in maintaining calcium homeostasis. Here, we study the effect of fluoride on expression of PTH, PTHrP, and CaSR both in vitro and in vivo. MC3T3-E1 cells and Sprague-Dawley rats were treated with different concentrations of fluoride. Then, the free calcium ion concentration in cell culture supernatant and serum were measured by biochemical analyzer. The expression of PTH, PTHrP, and CaSR was analyzed by qRT-PCR and Western blot. We found that the low dose of fluoride increased ionized calcium (i[Ca(2+)]) and the high dose of fluoride decreased i[Ca(2+)] in cell culture supernatant. The low dose of fluoride inhibited the PTH and PTHrP expression in MC3T3-E1 cells. The high dose of fluoride improved the PTHrP expression in MC3T3-E1 cells. Interestingly, we found that NaF decreased serum i[Ca(2+)] in rats. Fluoride increased CaSR expression at both messenger RNA (mRNA) and protein levels in MC3T3-E1 cells and rats. The expression of PTHrP protein was inhibited by fluoride in rats fed regular diet and was increased by fluoride in rats fed low-calcium diet. Fluoride also increased the expression of PTH, NF-kappaB ligand (RANKL), and osteoprotegerin (OPG) in rats. The ratio of RANKL/OPG in rats fed low-calcium food in presence or absence of fluoride was significantly increased. These results indicated that fluoride might be able to affect calcium homeostasis by regulating PTH, PTHrP, and CaSR.

Fluoride affects calcium homeostasis and osteogenic transcription factor expressions through L-type calcium channels in osteoblast cell line.

Osteoblast L-type voltage-dependent calcium channels (VDCC) play important roles in maintaining intracellular homeostasis and influencing multiple cellular processes. In particular, they contribute to the activities and functions of osteoblasts (OBs). In order to study how L-type VDCC modulate calcium ion (Ca(2+)) homeostasis and the expression of osteogenic transcription factors in OBs exposed to fluoride, MC3T3-E1 cells were exposed to a gradient of concentrations of fluoride (0, 2.0, 5.0, 10.0 mg/L) in combination with 10 µM nifedipine, a specific inhibitor of VDCC, for 48 h. We examined messenger RNA (mRNA) and protein levels of Cav1.2, the main subunit of VDCC, and c-fos, c-jun, runt-related transcription factor 2 (Runx2), osterix (OSX), and intracellular free Ca(2+) ([Ca(2+)]i) concentrations in MC3T3-E1 cells. Our results showed that [Ca(2+)]i levels increased in a dose-dependent manner with increase in concentration of fluoride. Meantime, results indicated that lower concentrations of fluoride (less than 5 mg/L, especially 2 mg/L) can lead to high expression of Cav1.2 and enhance osteogenic function, while high concentration of fluoride (10 mg/L) can induce decreased Cav1.2 and osteogenic transcriptional factors in MC3T3E1 cells exposed to fluoride. However, the levels of [Ca(2+)]i, Cav1.2, c-fos, c-jun, Runx2, and OSX induced by fluoride were significantly altered and even reversed in the presence of nifedipine. These results demonstrate that L-type calcium channels play a crucial role in Ca(2+) homeostasis and they affect the expression of osteogenic transcription factors in fluoride-treated osteoblasts.

Fluoride-induced oxidative stress in three-dimensional culture of OS732 cells and rats.

Exposure to excessive fluoride poses a threat to human health, including increased susceptibility to developing the skeletal fluorosis. Despite its recognized importance as an endemic disease, little is known about how fluoride directly impacts on osteoblasts. We previously reported that fluoride-stimulating monolayer-cultured osteoblast proliferation or inhibiting cell viability depended on fluoride-exposure concentration and period, both accompanied with active oxidative stress. The purpose of this study was to provide extra insight into skeletal fluorosis by comparing their regulation of oxidative stress in rats and OS732 cells (a human osteoblast-like cell line) cultured in the three-dimensional approach. Our in vivo and in vitro studies proved that exposure to fluoride promoted varying extents of oxidative stress. Three-dimensional cultured OS732 cells revealed the action of fluoride on cell viability from excitatory to inhibitory trend according to fluoride-exposure concentration and time. The study provided insight into the mechanism of skeletal fluorosis. Also, this study distinguished itself by identifying oxidative stress as a potential modulator of osteogenesis in skeletal fluorosis.