Melatonin Inhibits Osteoclastogenesis and Osteolytic Bone Metastasis: Implications for Osteoporosis

Melatonin prevents cadmium-induced osteoporosis by affecting the osteoblast and osteoclast differentiation and pyroptosis in duck

Cadmium (Cd), is a highly toxic environmental pollutant, which seriously threatens the health of poultry and humans. The occurrence of osteoporosis is the main manifestation of cadmium toxicity. Pyroptosis plays an important role in the development of osteoporosis. Melatonin has been shown to affect preserving bone health. However, the underlying mechanism has not been elucidated. In the present study, these functions of melatonin have been investigated in duck bone tissue and osteoblast during cadmium exposure. In vivo, the studies suggest that melatonin protects against cadmium-induced duck osteoporosis by improving the osteogenesis function, inhibiting bone resorption, and suppressing the occurrence of pyroptosis. In vitro, the findings demonstrated that melatonin alleviated the inhibition effect of cadmium on duck bone marrow-derived mesenchymal stem cells (BMSC) osteogenic differentiation, and suppressed the cadmium-induced osteoclast differentiation. In addition, we also found that melatonin prevents cytokines release of lactate dehydrogenase (LDH), interleukin-18 (IL-18), and interleukin-1β (IL-1β) by cadmium-induced, and reduces the expression of n-terminal Gasdermin D (N-GSDMD), alleviates the osteoblast death rate. In short, melatonin as a potential therapeutic agent has bright prospects in cadmium-induced bone toxicity.

A sponge-like nanofiber melatonin-loaded scaffold accelerates vascularized bone regeneration via improving mitochondrial energy metabolism

Electrospun nanofibers have been widely employed in bone tissue engineering for their ability to mimic the micro to nanometer scale network of the native bone extracellular matrix. However, the dense fibrous structure and limited mechanical support of these nanofibers pose challenges for the treatment of critical size bone defects. In this study, we propose a facile approach for creating a three-dimensional scaffold using interconnected electrospun nanofibers containing melatonin (Scaffold@MT). The hypothesis posited that the sponge-like Scaffold@MT could potentially enhance bone regeneration and angiogenesis by modulating mitochondrial energy metabolism. Melatonin-loaded gelatin and poly-lactic-acid nanofibers were fabricated using electrospinning, then fragmented into shorter fibers. The sponge-like Scaffold@MT was created through a process involving homogenization, low-temperature lyophilization, and chemical cross-linking, while maintaining the microstructure of the continuous nanofibers. The incorporation of short nanofibers led to a low release of melatonin and increased Young's modulus of the scaffold. Scaffold@MT demonstrated positive biocompatibility by promoting a 14.2 % increase in cell proliferation. In comparison to the control group, Scaffold@MT significantly enhanced matrix mineralization by 3.2-fold and upregulated the gene expression of osteoblast-specific markers, thereby facilitating osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs). Significantly, Scaffold@MT led to a marked enhancement in the mitochondrial energy function of BMMSCs, evidenced by elevated adenosine triphosphate (ATP) production, mitochondrial membrane potential, and protein expression of respiratory chain factors. Furthermore, Scaffold@MT promoted the migration of human umbilical vein endothelial cells (HUVECs) and increased tube formation by 1.3 times compared to the control group, accompanied by an increase in vascular endothelial growth factor (VEGFA) expression. The results of in vivo experiments indicate that the implantation of Scaffold@MT significantly improved vascularized bone regeneration in a distal femur defect in rats. Micro-computed tomography analysis conducted 8 weeks post-surgery revealed that Scaffold@MT led to optimal development of new bone microarchitecture. Histological and immunohistochemical analyses demonstrated that Scaffold@MT facilitated bone matrix deposition and new blood vessel formation at the defect site. Overall, the utilization of melatonin-loaded nanofiber sponges exhibits significant promise as a scaffold that promotes bone growth and angiogenesis, making it a viable option for the repair of critical-sized bone defects.

Investigation of causal relationships between cortical structure and osteoporosis using two-sample Mendelian randomization

The mutual interaction between bone characteristics and brain had been reported previously, yet whether the cortical structure has any relevance to osteoporosis is questionable. Therefore, we applied a two-sample bidirectional Mendelian randomization analysis to investigate this relationship. We utilized the bone mineral density measurements of femoral neck (n = 32,735) and lumbar spine (n = 28,498) and data on osteoporosis (7300 cases and 358,014 controls). The global surficial area and thickness and 34 specific functional regions of 51,665 patients were screened by magnetic resonance imaging. For the primary estimate, we utilized the inverse-variance weighted method. The Mendelian randomization-Egger intercept test, MR-PRESSO, Cochran's Q test, and "leave-one-out" sensitivity analysis were conducted to assess heterogeneity and pleiotropy. We observed suggestive associations between decreased thickness in the precentral region (OR = 0.034, P = 0.003) and increased chance of having osteoporosis. The results also revealed suggestive causality of decreased bone mineral density in femoral neck to declined total cortical surface area (β = 1400.230 mm2, P = 0.003), as well as the vulnerability to osteoporosis and reduced thickness in the Parstriangularis region (β = -0.006 mm, P = 0.002). Our study supports that the brain and skeleton exhibit bidirectional crosstalk, indicating the presence of a mutual brain-bone interaction.

Unveiling the Protective Role of Melatonin in Osteosarcoma: Current Knowledge and Limitations

Melatonin, an endogenous neurohormone produced by the pineal gland, has received increased interest due to its potential anti-cancer properties. Apart from its well-known role in the sleep-wake cycle, extensive scientific evidence has shown its role in various physiological and pathological processes, such as inflammation. Additionally, melatonin has demonstrated promising potential as an anti-cancer agent as its function includes inhibition of tumorigenesis, induction of apoptosis, and regulation of anti-tumor immune response. Although a precise pathophysiological mechanism is yet to be established, several pathways related to the regulation of cell cycle progression, DNA repair mechanisms, and antioxidant activity have been implicated in the anti-neoplastic potential of melatonin. In the current manuscript, we focus on the potential anti-cancer properties of melatonin and its use in treating and managing pediatric osteosarcoma. This aggressive bone tumor primarily affects children and adolescents and is treated mainly by surgical and radio-oncological interventions, which has improved survival rates among affected individuals. Significant disadvantages to these interventions include disease recurrence, therapy-related toxicity, and severe/debilitating side effects that the patients have to endure, significantly affecting their quality of life. Melatonin has therapeutic effects when used for treating osteosarcoma, attributed to its ability to halt cancer cell proliferation and trigger apoptotic cell death, thereby enhancing chemotherapeutic efficacy. Furthermore, the antioxidative function of melatonin alleviates harmful side effects of chemotherapy-induced oxidative damage, aiding in decreasing therapeutic toxicities. The review concisely explains the many mechanisms by which melatonin targets osteosarcoma, as evidenced by significant results from several in vitro and animal models. Nevertheless, if further explored, human trials remain a challenge that could shed light and support its utility as an adjunctive therapeutic modality for treating osteosarcoma.

A novel link between melatonin and circ_0005753/PTBP1/TXNIP regulatory network in the modulation of osteogenic potential in mesenchymal stem cells

Labeled with pluripotent potential, the transplantation of bone marrow mesenchymal stem cells (BMSCs) is considered as a promising strategy for treating osteoporosis (OP). Melatonin (MEL) has been investigated to be an essential regulator involved in bone metabolism, as well as BMSCs differentiation. Circular RNAs (circRNAs) are a unique kind of non-coding RNA and play an important regulatory role in OP. However, whether circRNAs are implicated in the effects of MEL on BMSCs osteogenic differentiation remains largely indeterminate. Expression of circ_0005753 in human BMSCs with MEL treatment, clinical specimens diagnosed with OP, either with ovariectomy (OVX)-induced mice, was measured by RT-qPCR. Western blot was conducted to analyze protein levels of osteogenesis-related molecules (Opg, RUNX2, ALP, BMP4) and TXNIP. RNA immunoprecipitation (RIP) and RNA pull-down assays were performed to validate the binding relationship among circ_0005753, PTBP1, and TXNIP. Alkaline phosphatase (ALP) and alizarin red staining (ARS) were performed to evaluate osteogenic capacity of BMSCs. OP mouse model was established by ovariectomy, as evaluated pathologic changes via hematoxylin-eosin (HE), Masson, and Immunohistochemistry (IHC) staining. Expression of circ_0005753 was remarkably decreased during MEL-induced osteogenic differentiation of BMSCs. Interestingly, not only circ_0005753 knockdown significantly promoted osteogenic differentiation of BMSCs, but circ_0005753 overexpression also weakened osteogenic differentiation induced by MEL treatment. Mechanistically, circ_0005753 maintained the stabilization of TXNIP mRNA via recruiting PTBP1. Additionally, reinforced circ_0005753 abrogated MEL-mediated protective effects on OP pathogenesis in a mouse model. This work shows that MEL facilitates osteogenic differentiation of BMSCs via the circ_0005753/PTBP1/TXNIP axis, which may shed light on the development of a novel therapeutic strategy to prevent OP.

Role of SIRT3 in bone homeostasis and its application in preventing and treating bone diseases

Bone homeostasis refers to the balance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption and the maintenance of stable bone mass. SIRT3 is a class of mitochondrial protein deacetylase that influences various mitochondrial functions and is involved in the mechanisms underlying resistance to aging; regulation of bone marrow mesenchymal stem cells, osteoblasts, and osteoclasts; and development of osteoporosis, osteoarthritis, and other bone diseases. Moreover, exercise affects bones through SIRT3. Thus, studies on SIRT3 may provide insights for the treatment of bone diseases. Although SIRT3 can exert multiple effects on bone, the specific mechanism by which it regulates bone homeostasis remains unclear. By evaluating the relevant literature, this review discusses the structure and function of SIRT3, reveals the role and associated mechanisms of SIRT3 in regulating bone homeostasis and mediating bone health during exercise, and highlights the potential pharmacological value of SIRT3 in treating bone diseases.

Daytime administration of melatonin has better protective effects on bone loss in ovariectomized rats

OBJECTIVE

To explore the difference in the protective effects of intraperitoneal injection of exogenous melatonin of daytime or nighttime on bone loss in ovariectomized (OVX) rats.

METHODS

After bilateral ovariectomy and sham surgery, 40 rats were randomly divided into four groups: sham operation group (Sham), ovariectomy (OVX), and daytime melatonin injection group (OVX + DMLT, 9:00, 30 mg/kg/d) and nighttime injection of melatonin (OVX + NMLT, 22:00, 30 mg/kg/d). After 12 weeks of treatment, the rats were sacrificed. The distal femur, blood and femoral marrow cavity contents were saved. The rest of the samples were tested by Micro-CT, histology, biomechanics and molecular biology. Blood was used for bone metabolism marker measurements. CCK-8, ROS, and Cell apoptosis are performed using MC3E3-T1 cells.

RESULTS

Compared with treatment at night, the bone mass of the OVX rats was significantly increased after the daytime administration. All microscopic parameters of trabecular bone increased, only Tb.Sp decreased. Histologically, the bone microarchitecture of the OVX + DMLT was also more dense than the bone microarchitecture of the OVX + LMLT. In the biomechanical experiment, the femur samples of the day treatment group were able to withstand greater loads and deformation. In molecular biology experiments, bone formation-related molecules increased, while bone resorption-related molecules decreased. After treatment with melatonin administration at night, the expression of MT-1β was significantly decreased. In cell experiments, the MC3E3-T1 cells treated with low-dose MLT had higher cell viability and greater efficiency in inhibiting ROS production than the MC3E3-T1 cells treated with high-dose MLT, which in turn more effectively inhibited apoptosis.

CONCLUSION

Daytime administration of melatonin acquires better protective effects on bone loss than night in OVX rats.

Bifidobacterium lactis Probio-M8 improves bone metabolism in patients with postmenopausal osteoporosis, possibly by modulating the gut microbiota

PURPOSE

Postmenopausal osteoporosis (PMO) is usually managed by conventional drug treatment. However, prolonged use of these drugs cause side effects. Gut microbiota may be a potential target for treatment of PMO. This work was a three-month intervention trial aiming to evaluate the added effect of probiotics as adjunctive treatment for PMO.

METHODS

Forty patients with PMO were randomized into probiotic (n = 20; received Bifidobacterium animalis subsp. lactis Probio-M8 [Probio-M8], calcium, calcitriol) and placebo (n = 20; received placebo material, calcium, calcitriol) groups. The bone mineral density of patients was measured at month 0 (0 M; baseline) and month 3 (3 M; after three-month intervention). Blood and fecal samples were collected 0 M and 3 M. Only 15 and 12 patients from Probio-M8 and placebo groups, respectively, provided complete fecal samples for gut microbiota analysis.

RESULTS

No significant change was observed in the bone mineral density of patients at 3 M. Co-administering Probio-M8 improved the bone metabolism, reflected by an increased vitamin D3 level and decreased PTH and procalcitonin levels in serum at 3 M. Fecal metagenomic analysis revealed modest changes in the gut microbiome in both groups at 3 M. Interestingly, Probio-M8 co-administration affected the gut microbial interactive correlation network, particularly the short-chain fatty acid-producing bacteria. Probio-M8 co-administration significantly increased genes encoding some carbohydrate metabolism pathways (including ABC transporters, the phosphotransferase system, and fructose and mannose metabolism) and a choline-phosphate cytidylyltransferase.

CONCLUSIONS

Co-administering Probio-M8 with conventional drugs/supplements was more efficacious than conventional drugs/supplements alone in managing PMO. Our study shed insights into the beneficial mechanism of probiotic adjunctive treatment.

REGISTRATION NUMBER OF CLINICAL TRIAL

Chinese Clinical Trial Registry (identifier number: ChiCTR1800019268).

GPR84 potently inhibits osteoclastogenesis and alleviates osteolysis in bone metastasis of colorectal cancer

The expression of GPR84 in bone marrow-derived monocytes/macrophages (BMMs) can inhibit osteoclast formation; however, its role in bone metastasis of colorectal cancer (CRC) is still unknown. To investigate the effects of GPR84 on bone metastasis of CRC, the murine CRC cell line MC-38 was injected into tibial bone marrow. We found that the expression of GPR84 in BMMs was gradually downregulated during bone metastasis of CRC, and the activation of GPR84 significantly prevented osteoclastogenesis in the tumor microenvironment. Mechanistically, the MAPK pathway mediated the effects of GPR84 on osteoclast formation. Moreover, we found that IL-11 at least partly inhibited the expression of GPR84 in the tumor microenvironment through the inactivation of STAT1. Additionally, activation of GPR84 could prevent osteolysis during bone metastasis of CRC. Our results suggest that CRC cells downregulate the expression of GPR84 in BMMs to promote osteoclastogenesis in an IL-11-dependent manner. Thus, GPR84 could be a potential therapeutic target to attenuate bone destruction induced by CRC metastasis.

A Review on the Molecular Mechanisms of Action of Natural Products in Preventing Bone Diseases

The drugs used for treating bone diseases (BDs), at present, elicit hazardous side effects that include certain types of cancers and strokes, hence the ongoing quest for the discovery of alternatives with little or no side effects. Natural products (NPs), mainly of plant origin, have shown compelling promise in the treatments of BDs, with little or no side effects. However, the paucity in knowledge of the mechanisms behind their activities on bone remodeling has remained a hindrance to NPs’ adoption. This review discusses the pathological development of some BDs, the NP-targeted components, and the actions exerted on bone remodeling signaling pathways (e.g., Receptor Activator of Nuclear Factor κ B-ligand (RANKL)/monocyte/macrophage colony-stimulating factor (M-CSF)/osteoprotegerin (OPG), mitogen-activated protein kinase (MAPK)s/c-Jun N-terminal kinase (JNK)/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), Kelch-like ECH-associated protein 1 (Keap-1)/nuclear factor erythroid 2–related factor 2 (Nrf2)/Heme Oxygenase-1 (HO-1), Bone Morphogenetic Protein 2 (BMP2)-Wnt/β-catenin, PhosphatidylInositol 3-Kinase (PI3K)/protein kinase B (Akt)/Glycogen Synthase Kinase 3 Beta (GSK3β), and other signaling pathways). Although majority of the studies on the osteoprotective properties of NPs against BDs were conducted ex vivo and mostly on animals, the use of NPs for treating human BDs and the prospects for future development remain promising.

New Therapeutics Targeting Arterial Media Calcification: Friend or Foe for Bone Mineralization?

The presence of arterial media calcification, a highly complex and multifactorial disease, puts patients at high risk for developing serious cardiovascular consequences and mortality. Despite the numerous insights into the mechanisms underlying this pathological mineralization process, there is still a lack of effective treatment therapies interfering with the calcification process in the vessel wall. Current anti-calcifying therapeutics may induce detrimental side effects at the level of the bone, as arterial media calcification is regulated in a molecular and cellular similar way as physiological bone mineralization. This especially is a complication in patients with chronic kidney disease and diabetes, who are the prime targets of this pathology, as they already suffer from a disturbed mineral and bone metabolism. This review outlines recent treatment strategies tackling arterial calcification, underlining their potential to influence the bone mineralization process, including targeting vascular cell transdifferentiation, calcification inhibitors and stimulators, vascular smooth muscle cell (VSMC) death and oxidative stress: are they a friend or foe? Furthermore, this review highlights nutritional additives and a targeted, local approach as alternative strategies to combat arterial media calcification. Paving a way for the development of effective and more precise therapeutic approaches without inducing osseous side effects is crucial for this highly prevalent and mortal disease.

Melatonin suppresses the metastatic potential of osteoblastic prostate cancers by inhibiting integrin α2 β1 expression

Advanced prostate cancer often develops into bone metastasis, which is characterized by aberrant bone formation with chronic pain and lower chances of survival. No treatment exists as yet for osteoblastic bone metastasis in prostate cancer. The indolamine melatonin (N-acetyl-5-methoxytryptamine) is a major regulator of the circadian rhythm. Melatonin has shown antiproliferative and antimetastatic activities but has not yet been shown to be active in osteoblastic bone lesions of prostate cancer. Our study investigations reveal that melatonin concentration-dependently decreases the migratory and invasive abilities of two osteoblastic prostate cancer cell lines by inhibiting FAK, c-Src, and NF-κB transcriptional activity via the melatonin MT₁ receptor, which effectively inhibits integrin α₂ β₁ expression. Melatonin therapy appears to offer therapeutic possibilities for reducing osteoblastic bone lesions in prostate cancer.

Melatonin as an antioxidant agent in disease prevention: A biochemical focus

Abstract:

In the recent years, free radicals and oxidative stress have been found to be associated with aging, cancer, atherosclerosis, neurodegenerative disorders, diabetes, and inflammatory diseases. Confirming the role of oxidants in numerous pathological situations including cancer, developing antioxidants as therapeutic platforms is needed. It has been well established that melatonin and its derived metabolites function as endogenous free-radical scavengers and broad spectrum antioxidants. To achieve this function, melatonin can directly detoxify reactive oxygen and reactive nitrogen species and indirectly overexpress antioxidant enzymes while suppressing the activity of pro-oxidant enzymes. Many investigations have also confirmed the role of melatonin and its derivatives in different physiological processes and therapeutic functions such as controlling the circadian rhythm and immune functions. This review aimed to focus on melatonin as a beneficial agent for the stimulation of antioxidant enzymes and inhibition of lipid peroxidation and to evaluate its contribution to protection against oxidative damages. In addition, the clinical application of melatonin in several diseases is discussed. Finally, the safety and efficacy of melatonin in clinical backgrounds is also reviewed.

Osteoporosis: From Molecular Mechanisms to Therapies 3.0

Osteoporosis is a common skeletal disorder that occurs as a result of an imbalance between bone resorption and bone formation, with bone breakdown exceeding bone building. Bone resorption inhibitors, e.g., bisphosphonates, have been designed to treat osteoporosis. Teriparatide, an anabolic agent, stimulates bone formation and corrects the characteristic changes in the trabecular microarchitecture. However, these drugs are associated with significant side effects. It is therefore crucial that we continue to research the pathogenesis of osteoporosis and seek novel modes of therapy. This editorial summarizes and discusses the themes of the six articles published in our Special Issue “Osteoporosis: From Molecular Mechanisms to Therapies 3.0”, a continuation of our 2020 Special Issue "Osteoporosis: From Molecular Mechanisms to Therapies". These Special Issues detail important global scientific findings that contribute to our current understanding of osteoporosis.