Streptozotocin Aggravated Osteopathology and Insulin Induced Osteogenesis Through Co-treatment with Fluoride

Exosomal miR-150 partially attenuated acute lung injury by mediating microvascular endothelial cells and MAPK pathway

BACKGROUND

Acute lung injury (ALI) is a respiratory disease with high morbidity and mortality rates. Currently, there is no effective treatment to complement mechanical ventilation. Exosomes and microRNAs (miRNAs) are promising agents for the management of this disease.

METHODS

Exosomes were isolated from mouse bone marrow stromal stem cells (BMSCs). The levels of two miRNAs, miR-542-3P and miR-150, in exosomes were determined using RT-PCR, and miR-150 was selected for further study. ALI model was established in mice using lipopolysaccharides, and then, they were treated with saline, exosomes, miRNA agomirs, or miRNA antagomirs. The concentrations of TNF-α, IL-6, and IL-1β and the number of neutrophils and macrophages in the bronchoalveolar lavage fluid were measured. The wet/dry weight ratio of the lung tissue was calculated, and tissue pathology and apoptosis were observed using hematoxylin and eosin and terminal deoxynucleotidyl transferase dUTP nick-end labeling staining. CD34 and VE-cadherin expression was detected using immunofluorescence. Proteins associated with apoptosis and MAPK signaling were detected using Western blotting, and miR-150 expression in lung tissue was evaluated using RT-PCR.

RESULTS

We successfully isolated BMSCs and exosomes and showed that the level of miR-150 was significantly higher than that of miR-542-3p. Exosomes and miR-150 reduced inflammation and lung edema while maintaining the integrity of the alveolar structure. They also mitigated microvascular endothelial cell injury by regulating the caspase-3, Bax/Bcl-2, and MAPK signaling.

CONCLUSIONS

Exosomal miR-150 attenuates lipopolysaccharide-induced ALI through the MAPK pathway.

Progress of Signaling Pathways, Stress Pathways and Epigenetics in the Pathogenesis of Skeletal Fluorosis

Fluorine is widely dispersed in nature and has multiple physiological functions. Although it is usually regarded as an essential trace element for humans, this view is not held universally. Moreover, chronic fluorosis, mainly characterized by skeletal fluorosis, can be induced by long-term excessive fluoride consumption. High concentrations of fluoride in the environment and drinking water are major causes, and patients with skeletal fluorosis mainly present with symptoms of osteosclerosis, osteochondrosis, osteoporosis, and degenerative changes in joint cartilage. Etiologies for skeletal fluorosis have been established, but the specific pathogenesis is inconclusive. Currently, active osteogenesis and accelerated bone turnover are considered critical processes in the progression of skeletal fluorosis. In recent years, researchers have conducted extensive studies in fields of signaling pathways (Wnt/β-catenin, Notch, PI3K/Akt/mTOR, Hedgehog, parathyroid hormone, and insulin signaling pathways), stress pathways (oxidative stress and endoplasmic reticulum stress pathways), epigenetics (DNA methylation and non-coding RNAs), and their inter-regulation involved in the pathogenesis of skeletal fluorosis. In this review, we summarised and analyzed relevant findings to provide a basis for comprehensive understandings of the pathogenesis of skeletal fluorosis and hopefully propose more effective prevention and therapeutic strategies.

The pathogenesis of endemic fluorosis: Research progress in the last 5 years

Fluorine is one of the trace elements necessary for health. It has many physiological functions, and participates in normal metabolism. However, fluorine has paradoxical effects on the body. Many studies have shown that tissues and organs of humans and animals appear to suffer different degrees of damage after long-term direct or indirect exposure to more fluoride than required to meet the physiological demand. Although the aetiology of endemic fluorosis is clear, its specific pathogenesis is inconclusive. In the past 5 years, many researchers have conducted in-depth studies into the pathogenesis of endemic fluorosis. Research in the areas of fluoride-induced stress pathways, signalling pathways and apoptosis has provided further extensive knowledge at the molecular and genetic level. In this article, we summarize the main results.

Transcriptomics provides mechanistic indicators of fluoride toxicology on endochondral ossification in the hind limb of Bufo gargarizans

Endochondral ossification, the process by which most of the bone is formed, is regulated by many specific groups of molecules and extracellular matrix components. Hind limb of Bufo gargarizans is a model to study endochondral ossification during metamorphosis. Chinese toad (Bufo gargarizans) were exposed to different fluoride concentrations (0, 1, 5, 10 and 20 mg L^-1) from G3 to G42. The development of hind limb of B. gargarizans was observed using the double staining methodology. The transcriptome of hind limb of B. gargarizans was conducted using RNA-seq approach, and differentially expressed gene was also validated. In addition, the location of Sox9 and Ihh in the growth cartilage was determined using in situ hybridization. Our results showed that 5 mg L^-1 stimulated bone mineralization, while 10 and 20 mg L^-1 exposure could inhibit the tibio-fibula, tarsus and metacarpals ossification. Besides, 10 mg F/L treatment could down-regulate Ihh, Sox9, D2, D3, TRα, TRβ, Wnt10, FGF3 and BMP6 expression, while up-regulate ObRb and HHAT mRNA expression in the hind limb of B. gargarizans. Transcript level changes of Ihh, Sox9, D2, D3, TRα, TRβ, Wnt10, FGF3 and BMP6 were consistent with the results of RT-qPCR. In situ hybridization revealed that Ihh was expressed in prehypertrophic chondrocytes, while Sox9 was abundantly expressed in proliferous, prehypertrophic and hypertrophic chondrocytes. However, 10 mg F-/L did not cause any affect in the location of the Ihh and Sox9 mRNA. Therefore, high concentration of fluoride could affect the ossification-related genes mRNA expression and then inhibit the endochondral ossification. The present study thus will greatly contribute to our understanding of the effect of environmental contaminant on ossification in amphibian.

Fluoride Regulate Osteoblastic Transforming Growth Factor-β1 Signaling by Mediating Recycling of the Type I Receptor ALK5

This study aimed to preliminary investigate the role of activin receptor-like kinase (ALK) 5 as one of TGF-βR1 subtypes in bone turnover and osteoblastic differentiation induced by fluoride. We analyzed bone mineral density and the expression of genes related with transforming growth factor-β1(TGF-β1) signaling and bone turnover in rats treated by different concentrations of fluoride with or without SB431542 in vivo. Moreover, MTT assay, alkaline phosphatase staining, RT-PCR, immunocytochemical analysis and western blot analysis were used to detect the influence on bone marrow stem cells (BMSC) after stimulating by varying concentration of fluoride with or without SB431542 in vitro. The in vivo study showed SB431542 treatment affected bone density and gene expression of rats, which indicated TGF-β1 and ALK5 might take part in fluoride-induced bone turnover and bone formation. The in vitro study showed low concentration of fluoride improved BMSC cells viability, alkaline phosphatase activity, and osteocalcin protein expression which were inhibited by high concentration of fluoride. The gene expression of Runx2 and ALK5 in cells increased after low concentration fluoride treatment which was also inhibited by high concentration of fluoride. Fluoride treatment inhibited gene and protein expression of Samd3 (except 1 mgF-/L). Compared with fluoride treatment alone, cells differentiation was inhibited with SB431542 treatment. Moreover, the expression of Runx2, ALK5 and Smad3 were influenced by SB431542 treatment. In conclusion, this preliminary study indicated that fluoride regulated osteoblastic TGFβ1 signaling in bone turnover and cells differentiation via ALK5.

Effects of fluoride on insulin signaling and bone metabolism in ovariectomized rats

Fluoride is an essential trace element for the maintenance of bone health owing to its capacity to stimulate proliferation and osteoblastic activity that can lead to increased bone formation. However, excessive sodium fluoride (NaF) intake can impair carbohydrate metabolism thereby promoting hyperglycemia, insulin resistance, and changes in insulin signaling. Thus, this study aimed to evaluate the effect of chronic treatment with NaF in bone metabolism, insulin signaling, and plasma concentrations of glucose, insulin, tumor necrosis factor-α (TNF-α), osteocalcin (OCN), and fluoride in ovariectomized rats. Thirty-two ovariectomized Wistar rats were randomly distributed into two groups: Control (OVX-C) and those undergoing treatment with NaF (50mg F/L) in drinking water for 42days (OVX-F). Glucose and insulin levels were assessed, followed by homeostasis model assessment of insulin resistance (HOMA-IR). Akt serine phosphorylation was evaluated by western blotting. Plasma concentrations of TNF-α and OCN were evaluated by ELISA. The left and right tibia was collected for immunohistochemical and histomorphometric analysis, respectively. Chronic treatment with NaF promoted insulin resistance, decreased insulin signal, increased plasma concentration of insulin, fluoride, OCN and TNF-α, decreased trabecular bone area of the tibia, and caused changes in bone metabolism markers in ovariectomized rats. These results suggest the need for caution in the use of NaF for the treatment of osteoporosis, especially in postmenopausal woman.