- Osteocytes can tolerate the toxic dose of fluoride, and PTH [Parathyroid hormone] administration significantly reduced osteocytes viability.
- PTH aggravated effect of fluoride on osteoclastogenesis related molecules in osteocytes.
- PTH administration hardly amplified the stimulating effect of fluoride on osteoclastogenesis.
- The impact of fluoride on osteocyte-driven osteoclast differentiation was stronger than that of PTH.
- The RANK-JNK-NFAtc1 signaling pathway was involved in fluoride affected osteocyte-driven osteoclastogenesis.
Excessive systemic uptake of inorganic fluorides causes disturbances of bone homeostasis. The mechanism of skeletal fluorosis is still uncertain. This study aimed to study the effect of fluoride on osteocyte-driven osteoclastogenesis and probe into the role of PTH in this process. IDG-SW3 cells seeded in collagen–coated constructs were developed into osteocyte-like cells through induction of mineral agents. Then, osteocyte-like cells were exposed to fluoride in the presence or absence of parathyroid hormone (PTH). Cell viability and their capacity to produce receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG) and sclerostin (SOST) were detected by MTT and Western blot assays, respectively. Finally, a transwell coculture system using osteocyte-like cells seeded in the low compartment, and osteoclast precursors added in the inserts was developed to observe the osteocyte-driven osteoclasogenesis response to fluoride with or without PTH, and the expression of molecules involved in this mechanism were measure by real time RT-PCR. Results showed that osteocytes withstood a toxic dose of fluoride, and yet PTH administration significantly reduced osteocytes viability. PTH amplified the effect of fluoride on the expression of osteoclastogenesis-related molecules in osteocyte, but did not enlarged the stimulating effect of fluoride on osteoclastogenesis drove by osteocyte coculture. Gene expression levels of TRAP, RANK, JNK and NFAtc1 significantly increased in fluoride affected osteoclast precursor cocultured with osteocyte-like cells. The impact of fluoride on osteocyte-driven osteoclast differentiation was stronger than that of PTH. In conclusion, osteocyte played a pivotal role on the mechanism underlying fluoride-affected osteoclastogenesis in which RANK-JNK-NFATc1 signaling pathway was involved, and PTH had a significant impact in this process.
*Original abstract online at https://www.sciencedirect.com/science/article/pii/S0300483X20300688?via%3Dihub
Is the severity of osteosclerosis of fluorosis proportional to the dose of fluoride intake?
Histomorphometric study was made on a series of sections of undecalcified epiphyseal femoral specimens from rats with experimental fluorosis. The results revealed osteosclerosis in Group A (5 ppm) being more severe than that in Group B (25 ppm). With the increase of fluoride dose, the parameters fell down instead of
PTH (1–34) affects bone turnover governed by osteocytes exposed to fluoride
Highlights • Osteocytes endured high dose of fluoride exposure.• Fluoride inhibited expression of SOST/Sclerostin in osteocytes.• Fluoride modulated ratio of RANKL/OPG in osteocytes.• Fluoride regulated Wnt/?-catenin signaling in osteocytes.• PTH(1–34) participated in fluoride-modulating SOST and RANKL expression in osteocytes. Exposure to fluoride from environmental sources remains an overlooked, but serious public health
Effect of fluoride on osteoclast formation at various levels of receptor activator of nuclear factor Kappa-B ligand (RANKL).
Receptor activator of nuclear factor kappa-B ligand (RANKL) acting on osteoblasts is an essential cytokine for osteoclast formation. Recent studies have shown that fluoride (F) can stimulate RANKL expression of osteoblasts. However, the effect of F under various levels of RANKL on osteoclast formation is not clear. In this study,
Fluoride-mediated apoptosis and disordering of cell cycle distributions during in vitro organ culture of mouse fetal long bones.
Effects of fluoride (as NaF) on cell cycle, DNA content, and apoptosis of mouse fetal long bone cultures were examined and analyzed by flow cytometry (FCM). The results showed that NaF at 2.5–5.0 µg/mL (2.5–5.0 ppm) had only slight effects on the DNA content and cell cycle distributions. At 10.0
Fluorosis increases the risk of postmenopausal osteoporosis by stimulating interferon y
Estrogen deficiency in postmenopausal women frequently activates osteoclasts (OC), accelerates bone resorption, and leads to osteoporosis (OP). Previous studies have demonstrated that interferon y (IFNy) could increase bone resorption and may be involved in postmenopausal OP. Fluorosis also increased the risk of fractures and dental fluorosis, and fluoride may enhance osteoclast formation and
Related Studies :
As demonstrated by the studies below, skeletal fluorosis may produce adverse symptoms, including arthritic pains, clinical osteoarthritis, gastrointestinal disturbances, and bone fragility, before the classic bone change of fluorosis (i.e., osteosclerosis in the spine and pelvis) is detectable by x-ray. Relying on x-rays, therefore, to diagnosis skeletal fluorosis will invariably fail to protect those individuals who are suffering from the pre-skeletal phase of the disease. Moreover, some individuals with clinical skeletal fluorosis will not develop an increase in bone density, let alone osteosclerosis, of the spine. Thus, relying on unusual increases in spinal bone density will under-detect the rate of skeletal fluoride poisoning in a population.
Skeletal Fluorosis: The Misdiagnosis Problem
It is a virtual certainty that there are individuals in the general population unknowingly suffering from some form of skeletal fluorosis as a result of a doctor's failure to consider fluoride as a cause of their symptoms. Proof that this is the case can be found in the following case reports of skeletal fluorosis written by doctors in the U.S. and other western countries. As can be seen, a consistent feature of these reports is that fluorosis patients--even those with crippling skeletal fluorosis--are misdiagnosed for years by multiple teams of doctors who routinely fail to consider fluoride as a possible cause of their disease.
Fluoride & Osteoarthritis
While the osteoarthritic effects that occurred from fluoride exposure were once considered to be limited to those with skeletal fluorosis, recent research shows that fluoride can cause osteoarthritis in the absence of traditionally defined fluorosis. Conventional methods used for detecting skeletal fluorosis, therefore, will fail to detect the full range of people suffering from fluoride-induced osteoarthritis.
Fluoride & Osteoclasts
It is well established that fluoride exposure can increase bone formation by increasing the proliferation of osteoblasts. Less clear is fluoride's impact on bone resorption and the cells (osteoclasts) that resorb bone. Many have assumed that fluoride's main effect on bone resorption and osteoclasts is an inhibitory one (i.e., less
Fluoride's Effect on Osteoblasts (Bone-Forming Cells)
As noted by the National Research Council, "[p]erhaps the single clearest effect of fluoride on the skeleton is its stimulation of osteoblast proliferation." (NRC 2006). Osteoblasts are bone-forming cells. "Stimulatory effects of fluoride on osteoblasts result in formation of osteoid, which subsequently undergoes mineralization." (Fisher RL, et al. 1989). If the new
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