Calcium and Vitamin D Supplementation Effectively Alleviates Dental and Skeletal Fluorosis and Retain Elemental Homeostasis in Mice

Drug molecules beyond chemical biology: fluorescence- and DFT-based investigations for fluoride ion sensing and the trace detection of chloroform

Excessive unmonitored use of fluoride has remained a threatening issue for a long time now as its long-term use is linked to several health issues. Similarly, chloroform is a highly carcinogenic solvent that requires proper monitoring. The increasing demand for a convenient, selective and sensitive fluoride and chloroform sensor intrigued us to utilize etoricoxib (ECX) as a sensor as it is highly safe and easily available. The photophysical properties of ECX, which were previously unexplored, were now studied with increasing water fractions and a significant aggregation-induced emission enhancement (AIEE) was seen through fluorescence spectroscopy. ECX was also successfully used for the trace level detection of chloroform through a significant emission enhancement. Similarly, the ECX-based sensor successfully detected fluoride ions by showing enhancement in emission intensity with maximum emission wavelength at 373 nm. Through fluorescence titration experiments, the effects of different conditions and interfering species on the sensing efficiency of ECX were studied, and the results showed that the sensor was highly selective and sensitive towards fluoride, with a limit of detection of 20 nM. Other than fluorescence spectroscopy, the type of interaction between the sensor and analyte was also studied through UV-Vis spectroscopy, revealing a non-covalent type of interaction, which was further validated through DFT studies. Frontier molecular orbital (FMO) analysis was performed along with density of state (DOS) studies to investigate the energy levels of the orbitals. Non-covalent interaction (NCI) and natural bond orbital (NBO) analysis provided information about the types of interaction and charge transfer. ECX has the potential to be used for real-time sensing applications and could be used for sensing moisture and fluoride in real samples.

Skeletal fluorosis: an uncommon cause, yet a rescue treatment?

PURPOSE

Skeletal fluorosis (SF) results from chronic exposure to fluoride (F-) causing excessive aberrantly mineralized brittle bone tissue, fractures, and exostoses. There is no established treatment other than avoiding the source of F-. Still, excess F- can persist in bone for decades after exposure ceases.

CASE PRESENTATION

A 50-year-old woman presented with multiple, recurrent, low AQ2 trauma fractures yet high radiologic bone mineral density. Serum F- was elevated, and osteomalacia was documented by non-decalcified transiliac biopsy. She reported intermittently "huffing" a keyboard cleaner containing F- (difluoroethane) for years. Following cessation of her F- exposure, we evaluated the administration of the parathyroid hormone analog, abaloparatide, hoping to increase bone remodeling and diminish her skeletal F- burden.

CONCLUSION

Due to the prolonged half-life of F- in bone, SF can cause fracturing long after F- exposure stops. Anabolic therapy approved for osteoporosis, such as abaloparatide, may induce mineralized bone turnover to replace the poorly mineralized osteomalacic bone characteristic of SF and thereby diminish fracture risk. Following abaloparatide treatment for our patient, there was a decrease in bone density as well as a reduction in F- levels.

Sodium Fluoride Exposure Induces Developmental Toxicity and Cardiotoxicity in Zebrafish Embryos

Fluorosis is a worldwide public health problem, in which the heart is an important target organ. However, studies on its toxicological mechanism in embryonic development are limited. This study assessed the toxicity of sodium fluoride (NaF) toward zebrafish embryos. We determined the mortality, hatching rate, phenotypic malformation, heart function, and morphology of zebrafish embryos after exposure to NaF. Subsequently, the molecular mechanism was revealed using high-throughput RNA sequencing analysis. The expression levels of key genes for heart development were detected using quantitative real-time reverse transcription PCR. The 50% lethal concentration (LC50) value of NaF toward zebrafish embryos at 96 h post-fertilization was 335.75 mg/L. When the concentration of NaF was higher than 200 mg/L, severe deformities, such as pericardial edema, yolk sac edema, spine curvature, shortened body length, reduced head area, and eye area, were observed. The heart rate of the embryos exposed to NaF decreased in a dose-dependent fashion. The distance between the sinus venosus and bulbus arteriosus was significantly increased in the NaF-exposed group compared with that in the control group. The stroke volume and cardiac output decreased significantly in the NaF groups. Compared with the control group, the expression levels of Gata4, Tbx5a, Hand2, Tnnt2c, Nppa, and Myh6 were significantly increased in the NaF-treated group. Through transcriptome sequencing, 1354 differentially expressed genes (DEGs) were detected in the NaF (200 mg/L) treated groups, including 1253 upregulated genes and 101 downregulated genes. Gene ontology functional analysis and Kyoto Encyclopedia of Genes and Genomes pathway analyses of the DEGs showed that cardiac-related pathways, such as actin cytoskeleton regulation, Jak-Stat, PI3k-Akt, and Ras, were activated in the NaF-exposed group. This study revealed the underlying mechanism of fluoride-induced cardiac morphological and functional abnormalities and provides clues for the clinical prevention and treatment of fluorosis.

Calcium supplementation attenuates fluoride-induced bone injury via PINK1/Parkin-mediated mitophagy and mitochondrial apoptosis in mice

Excessive consumption of fluoride can cause skeletal fluorosis. Mitophagy has been identified as a novel target for bone disorders. Meanwhile, calcium supplementation has shown great potential for mitigating fluoride-related bone damage. Hence, this study aimed to elucidate the association between mitophagy and skeletal fluorosis and the precise mechanisms through which calcium alleviates these injuries. A 100 mg/L sodium fluoride (NaF) exposure model in Parkin knockout (Parkin-/-) mice and a 100 mg/L NaF exposure mouse model with 1% calcium carbonate (CaCO3) intervention were established in the current study. Fluoride exposure caused the impairment of mitochondria and activation of PTEN-induced putative kinase1 (PINK1)/E3 ubiquitin ligase Park2 (Parkin)-mediated mitophagy and mitochondrial apoptosis in the bones, which were restored after blocking Parkin. Additionally, the intervention model showed fluoride-exposed mice exhibited abnormal bone trabecula and mechanical properties. Still, these bone injuries could be effectively attenuated by adding 1% calcium to their diet, which reversed fluoride-activated mitophagy and apoptosis. To summarize, fluoride can activate bone mitophagy through the PINK1/Parkin pathway and mitochondrial apoptosis. Parkin-/- and 1% calcium provide protection against fluoride-induced bone damage. Notably, this study provides theoretical bases for the prevention and therapy of animal and human health and safety caused by environmental fluoride contamination.

Chronic exposure to environmentally relevant concentration of fluoride impairs osteoblast's collagen synthesis and matrix mineralization: Involvement of epigenetic regulation in skeletal fluorosis

Globally, 200 million people are suffering from toxic manifestations of Fluoride(F), dental and skeletal fluorosis; unfortunately, there is no treatment. To unravel the pathogenesis of skeletal fluorosis, we established fluorosis mice by treating environmentally relevant concentration of F (15 ppm NaF) through drinking water for 4 months. As in skeletal fluorosis, locomotor disability, crippling deformities occur and thus, our hypothesis was F might adversely affects collagen which gives the bone tensile strength. This work inevitably had to be carried out on osteoblast cells, responsible for synthesis, deposition, and mineralization of bone matrix. Isolated osteoblast cells were confirmed by ALP activity and mineralized nodules formation. Expression of collagen Col1a1, Col1a2, COL1A1 was significantly reduced in treated mice. Further, a study revealed the involvement of epigenetic regulation by promoter hypermethylation of Col1a1; expressional alterations of transcription factors, calcium channels and other genes e.g., Cbfa-1, Tgf-β1, Bmp1, Sp1, Sp7, Nf-Kb p65, Bmp-2, Bglap, Gprc6a and Cav1.2 are associated with impairment of collagen synthesis, deposition and decreased mineralization thus, enfeebling bone health. This study indicates the possible association of epigenetic regulation in skeletal fluorosis. However, no association was found between polymorphisms in the Col1a1 (RsaI, HindIII) and Col1a2 (RsaI, HindIII) genes with fluorosis in mice.

Fluoride resistance capacity in mammalian cells involves global gene expression changes associate with ferroptosis

OBJECTIVE

The purpose of this study was to understand mouse osteoblast ferroptosis under high fluoride environment by stimulating fluoride levels to corresponding levels. In order to define the underlying mechanism of fluoride resistance in mammals and provide a theoretical basis for fluorosis treatment, high-throughput sequencing was applied to map the genetic changes of fluoride-resistant mouse osteoblasts and analyze the role of ferroptosis-related genes.

METHODS

Cell Counting Kit-8, Reactive Oxygen Species Assay Kit and C11 BODIPY 581/591 were used to monitor proliferation and ferroptosis of mouse osteoblasts MC3T3-E1 under high fluoride environment. Fluoride-tolerant MC3T3-E1 cells were developed by gradient fluoride exposure. The differentially expressed genes of fluorine-resistant MC3T3-E1 cells were identified by high-throughput sequencing.

RESULTS

MC3T3-E1 cells cultured in medium containing 20, 30, 60, 90 ppm F^- exhibited decreased viability and increased reactive oxygen species and lipid peroxidation levels in correlation with F^- concentrations. High-throughput RNA sequencing identified 2702 differentially expressed genes (DEGs) showed more than 2-fold difference in 30 ppm FR MC3T3-E1 cells, of which 17 DEGs were associated with ferroptosis.

CONCLUSION

High fluoride environment affected the content of lipid peroxides in the body and increased the level of ferroptosis, further, ferroptosis-related genes played specific roles in the fluoride resistance of mouse osteoblasts.

Challenges of fluoride pollution in environment: Mechanisms and pathological significance of toxicity - A review

Fluoride is an important trace element in the living body. A suitable amount of fluoride has a beneficial effect on the body, but disproportionate fluoride entering the body will affect various organs and systems, especially the liver, kidneys, nervous system, endocrine system, reproductive system, bone, and intestinal system. In recent years, with the rapid development of agriculture and industry, fluoride pollution has become one of the important factors of environmental pollution, and fluoride pollution in any form is becoming a serious problem. Although countries around the world have made great breakthroughs in controlling fluoride pollution, however fluorosis still exists. A large amount of fluoride accumulated in animals will not only produce the toxic effects, but it also causes cell damage and affect the normal physiological activities of the body. There is no systematic description of the damage mechanism of fluoride. Therefore, the study on the toxicity mechanism of fluoride is still in progress. This review summarizes the existing information of several molecular mechanisms of the fluoride toxicity comprehensively, aiming to clarify the toxic mechanism of fluoride on various body systems. We have also summerized the pathological changes of those organ systems after fluoride poisoning in order to provide some ideas and solutions to the reader for the prevention and control of modern fluoride pollution.

A simple pillar[5]arene assembled multi-functional material with ultrasensitive sensing, self-healing, conductivity and host-guest stimuli-responsive properties

Multi-functional materials have received wide attention due to their potential applications in various fields; therefore, developing a simple and easy strategy for the preparation of multi-functional materials is an interesting issue. In this work, a novel supramolecular gel, TP-QG, has been successfully constructed via the assembly of a simple methoxyl-pillar[5]arene host (TP) and a tripodal (tri-pyridine-4-yl)-amido-benzene guest (Q). Interestingly, TP-QG could act as a multi-functional material and showed strong fluorescence, good self-healing, host-guest stimuli-responsiveness and conductive properties. Due to these properties, TP-QG shows a fascinating application prospect. For instance, TP-QG could exhibit ultrasensitive fluorescence response for Fe³⁺ and F^- in water via the fluorescence "ON-OFF-ON" pathway; the lowest detection limit (LOD) of TP-QG for Fe³⁺ was 2.32 × 10^-10 M and the LOD of TP-QG-Fe for F^- was 4.30 × 10^-8 M. These properties permit TP-QG to act as not only a Fe³⁺ and F^- sensor, but also an "ON-OFF-ON" fluorescence display material and an efficient logic gate. Meanwhile, the xerogel of TP-QG could remove Fe³⁺ from water, and the adsorption ratio was 98.68%; the xerogel of TP-QG-Fe could also remove F^- from water; the removal ratio was about 87.92%. This work provides a feasible way to construct multi-functional smart materials by host-guest assembly.