Effect of calcium ions on human calcitonin. Possible implications for bone resorption by osteoclasts

Evaluation of the Potential Cytoprotective Effect of Melatonin in Comparison with Vitamin E and Trolox against Cd2+-Induced Toxicity in SH-SY5Y, HCT 116, and HepG2 Cell Lines

Cadmium (Cd) toxicity poses a significant threat to cellular health, leading to oxidative stress and cell damage. Antioxidant agents, particularly those of natural origin, have been studied as a potential alternative for mitigating heavy metal toxicity. This study aimed to evaluate the cytoprotective effects of the antioxidant melatonin (MLT) in comparison with Vitamin E (VitE) and Trolox against Cd2+-induced cellular toxicity. The MTT assay was employed to assess cell viability in neuronal SH-SY5Y, colorectal HCT 116, and hepatic HepG2 cell lines. The results showed that all three antioxidants offered some level of protection against Cd toxicity, with Vitamin E proving to be the most effective. MLT also demonstrated a substantial cytoprotective effect, especially at the highest Cd concentration of 30 µM. These findings suggest that MLT, alongside Vit E and Trolox, could be valuable in mitigating the detrimental effects of Cd exposure by reducing the oxidative stress in these cellular models.

A systematic review on fluoride-induced epigenetic toxicity in mammals

Fluoride, one of the global groundwater contaminants, is ubiquitous in our day-to-day life from various natural and anthropogenic sources. Numerous in vitro, in vivo, and epidemiological studies are conducted to understand the effect of fluoride on biological systems. A low concentration of fluoride is reported to increase oral health, whereas chronic exposure to higher concentrations causes fluoride toxicity (fluorosis). It includes dental fluorosis, skeletal fluorosis, and fluoride toxicity in soft tissues. The mechanism of fluoride toxicity has been reviewed extensively. However, epigenetic regulation in fluoride toxicity has not been reviewed. This systematic review summarizes the current knowledge regarding fluoride-induced epigenetic toxicity in the in vitro, in vivo, and epidemiological studies in mammalian systems. We examined four databases for the association between epigenetics and fluoride exposure. Out of 932 articles (as of 31 March 2022), 39 met our inclusion criteria. Most of the studies focused on different genes, and overall, preliminary evidence for epigenetic regulation of fluoride toxicity was identified. We further highlight the need for epigenome studies rather than candidate genes and provide recommendations for future research. Our results indicate a correlation between fluoride exposure and epigenetic processes. Further studies are warranted to elucidate and confirm the mechanism of epigenetic alterations mediated fluoride toxicity.

DNA methylation and fluoride exposure in school-age children: Epigenome-wide screening and population-based validation

Excessive fluoride exposure and epigenetic change can induce numerous adverse health outcomes, but the role of epigenetics underneath the harmful health effects induced by fluoride exposure is unclear. In such gap, we evaluated the associations between fluoride exposure and genome-wide DNA methylation, and identified that novel candidate genes associated with fluoride exposure. A total of 931 school-age children (8-12 years) in Tongxu County of Henan Province (China) were recruited in 2017. Urinary fluoride (UF) concentrations were measured using the national standardized ion selective electrode method. Participants were divided into a high fluoride-exposure group (HFG) and control group (CG) according to the UF concentrations. Candidate differentially methylated regions (DMRs) were screened by Infinium-Methylation EPIC BeadChip of DNA samples collected from 16 participants (eight each from each group). Differentially methylated genes (DMGs) containing DMRs associated with skeletal and neuronal development influenced by fluoride exposure were confirmed using MethylTarget™ technology from 100 participants (fifty each from each group). DMGs were verified by quantitative methylation specific PCR from 815 participants. Serum levels of hormones were measured by auto biochemical analyzer. The mediation analysis of methylation in the effect of fluoride exposure on hormone levels was also performed. A total of 237 differentially methylated sites (DMSs) and 212 DMRs were found in different fluoride-exposure groups in the epigenome-wide phase. Methylation of the target sequences of neuronatin (NNAT), calcitonin-related polypeptide alpha (CALCA) and methylenetetrahydrofolate dehydrogenase 1 showed significant difference between the HFG and CG. Each 0.06% (95% CI: -0.11%, -0.01%) decreased in NNAT methylation status correlated with each increase of 1.0 mg/L in UF concentration in 815 school-age children using QMSP. Also, each 1.88% (95% CI: 0.04%, 3.72%) increase in CALCA methylation status correlated with each increase of 1.0 mg/L in UF concentration. The mediating effect of NNAT methylation was found in alterations of ACTH levels influenced by fluoride exposure, with a β value of 11.7% (95% CI: 3.4%, 33.4%). In conclusion, long-term fluoride exposure affected the methylation pattern of genomic DNA. NNAT and CALCA as DMGs might be susceptible to fluoride exposure in school-age children.

Finely-Tuned Calcium Oscillations in Osteoclast Differentiation and Bone Resorption

Calcium (Ca²⁺) plays an important role in regulating the differentiation and function of osteoclasts. Calcium oscillations (Ca oscillations) are well-known phenomena in receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclastogenesis and bone resorption via calcineurin. Many modifiers are involved in the fine-tuning of Ca oscillations in osteoclasts. In addition to macrophage colony-stimulating factors (M-CSF; CSF-1) and RANKL, costimulatory signaling by immunoreceptor tyrosine-based activation motif-harboring adaptors is important for Ca oscillation generation and osteoclast differentiation. DNAX-activating protein of 12 kD is always necessary for osteoclastogenesis. In contrast, Fc receptor gamma (FcRγ) works as a key controller of osteoclastogenesis especially in inflammatory situation. FcRγ has a cofactor in fine-tuning of Ca oscillations. Some calcium channels and transporters are also necessary for Ca oscillations. Transient receptor potential (TRP) channels are well-known environmental sensors, and TRP vanilloid channels play an important role in osteoclastogenesis. Lysosomes, mitochondria, and endoplasmic reticulum (ER) are typical organelles for intracellular Ca²⁺ storage. Ryanodine receptor, inositol trisphosphate receptor, and sarco/endoplasmic reticulum Ca²⁺ ATPase on the ER modulate Ca oscillations. Research on Ca oscillations in osteoclasts has still many problems. Surprisingly, there is no objective definition of Ca oscillations. Causality between Ca oscillations and osteoclast differentiation and/or function remains to be examined.

Thermosensitive Polysaccharide Hydrogel As a Versatile Platform for Prolonged Salmon Calcitonin Release and Calcium Regulation

The common pathological characteristic of osteoporosis and hypercalcemia is the disorder of calcium homeostasis. Currently, salmon calcitonin (sCT), a clinical regenerative medicine, is an attractive chioice to regulate calcium metabolism for alleviation of osteoporosis and hypercalcemia. Unfortunately, serum sCT is quickly cleared in vivo, leading to its short half-life. Here, we designed a versatile hydrogel, based on salmon calcitonin-oxidized calcium alginate (sCT-OCA) conjugate and hydroxypropyl chitin (HPCH). The release profile showed that sCT could be released from HPCH hydrogels loaded with sCT-OCA conjugate (sCT-OCA-HPCH) for at least 28 days with conformation stability. The cellular test demonstrated that the biocompatible sCT-OCA-HPCH, compared with sCT formulation, had capacity in up-regulating alkaline phosphatase activity (∼63% increase) and promoting calcium to deposit into extracellular matrix (∼42% increase). These results indicated that thermosensitive sCT-OCA-HPCH hydrogel herein is a versatile platform for many applications such as calcium metabolism regulation, osteoporosis treatment, and hypercalcemia therapy.

Glucagon-like peptide 2 decreases osteoclasts by stimulating apoptosis dependent on nitric oxide synthase

OBJECTIVES

Glucagon-like peptide 2 (GLP2) is involved in the regulation of energy absorption and metabolism. Despite the importance of the GLP2 signalling mechanisms on osteoclast, little has been studied on how GLP2 works during osteoclastogenesis.

MATERIALS AND METHODS

RAW264.7 cells were infected with rLV-Green-GLP2. The induction of osteoclasts was performed by RANKL. TRAP were detected by RT-PCR, Western blotting and staining. Total nitric oxide and total NOS activity were measured. Cells apoptosis was detected by Hoest33258 and Annix V staining. Animal test, chromatin immunoprecipitation (CHIP), co-immunoprecipitation(IP) and luciferase reporter assay were also performed.

RESULTS

We indicate that GLP2 is associated with osteoporosis-related factors in aged rats, including BALP, TRAP, IL6, TNFα, Nitric Oxide (NO), iNOS, calcitonin and occludin. Moreover, GLP2 is demonstrated to result in negative action during proliferation of tartrate-resistant acid phosphatase-positive (TRAP+) osteoclasts. Furthermore, GLP2 decreases osteoclasts induced from monocyte/macrophage cells RAW264.7 as well as the serum TRAP activity in aged rats. Mechanistic investigations reveal GLP2 enhances the expression of iNOS through stimulating the activity of TGFβ-Smad2/3 signalling in osteoclasts. In particular, inhibition of TGFβ fully abrogates this function of GLP2 in osteoclasts. Strikingly, overexpression of GLP2 significantly increases the product of nitric oxide via iNOS which promotes apoptosis of osteoclasts by decreasing bcl2 or increasing caspase3. Thereby, the ability of GLP2 to regulate apoptosis depends on TGFβ-Smad2/3-iNOS-NO signalling pathway since total NOS inhibitor L-NMMA specifically inhibits the actions by GLP2.

CONCLUSIONS

GLP2 induces apoptosis via TGFβ-Smad2/3 signalling, which contributes to the inhibition of the proliferation of osteoclasts and which may provide potential therapeutic targets for the treatment of osteoporosis.

Comparison in Adherence to Osteoporosis Guidelines according to Bone Health Status in Korean Adult

BACKGROUND

Osteoporosis one of the most serious disease to decrease the quality of life and cause economic loss. Thus, prevention of osteoporosis has become an important health concern. The study examined in adherence to osteoporosis guidelines and compared the levels of adherence to osteoporosis guidelines between bone health status in Korean adult.

METHODS

This study used data from a nationally represented sample of Koreans (n=3,419) from 2008 to 2011 Korea National Health and Nutrition Examination Survey. We were divided into three groups by T-score: normal, osteopenia and osteoporosis. Assessment of adherence level was based on 5 components of osteoporosis guidelines, considering intake of sodium, calcium and protein, smoking and regular exercise.

RESULTS

The sex, body mass index, income and educational level did not significantly differ between three groups. Deficient intake of calcium was significantly associated with a threefold greater odds in osteoporosis group (OR 3.6; 95% confidence interval [CI] 2.52-5.22). Excessive protein intake was significantly increased the risk only in osteoporosis group compared to the normal group (OR 1.71; 95% CI 1.15-2.62). Smoking increased the risk in osteoporosis group compared to the normal group (OR 2.88; 95% CI 1.75-4.76), osteoporosis group compared to the osteopenia group (OR 2.69; 95% CI 1.61-4.55).

CONCLUSIONS

Nutritional factor (intake of calcium and protein) and lifestyle-related factor (smoking and exercise) must be accompanied the management for bone health. An adherence of guidelines is considered very important for the prevention of osteoporosis.