TNFα Increases RANKL Expression via PGE₂-Induced Activation of NFATc1

Sorbitol Destroyed Intestinal Microfold Cells (M Cells) Development through Inhibition of PDE4-Mediated RANKL Expression

Objective

Microfold cells (M cells) are specific intestinal epithelial cells for monitoring and transcytosis of antigens, microorganisms, and pathogens in the intestine. However, the mechanism for M-cell development remained elusive.

Materials and Methods

Real-time polymerase chain reaction, immunofluorescence, and western blotting were performed to analyze the effect of sorbitol-regulated M-cell differentiation in vivo and in vitro, and luciferase and chromatin Immunoprecipitation were used to reveal the mechanism through which sorbitol-modulated M-cell differentiation.

Results

Herein, in comparison to the mannitol group (control group), we found that intestinal M-cell development was inhibited in response to sorbitol treatment as evidenced by impaired enteroids accompanying with decreased early differentiation marker Annexin 5, Marcksl1, Spib, sox8, and mature M-cell marker glycoprotein 2 expression, which was attributed to downregulation of receptor activator of nuclear factor kappa-В ligand (RANKL) expression in vivo and in vitro. Mechanically, in the M-cell model, sorbitol stimulation caused a significant upregulation of phosphodiesterase 4 (PDE4) phosphorylation, leading to decreased protein kinase A (PKA)/cAMP-response element binding protein (CREB) activation, which further resulted in CREB retention in cytosolic and attenuated CREB binds to RANKL promoter to inhibit RANKL expression. Interestingly, endogenous PKA interacted with CREB, and this interaction was destroyed by sorbitol stimulation. Most importantly, inhibition of PDE4 by dipyridamole could rescue the inhibitory effect of sorbitol on intestinal enteroids and M-cell differentiation and mature in vivo and in vitro.

Conclusion

These findings suggested that sorbitol suppressed intestinal enteroids and M-cell differentiation and matured through PDE4-mediated RANKL expression; targeting to inhibit PDE4 was sufficient to induce M-cell development.

Parkinson's disease-derived α-synuclein assemblies combined with chronic-type inflammatory cues promote a neurotoxic microglial phenotype

Parkinson's disease (PD) is a common age-related neurodegenerative disorder characterized by the aggregation of α-Synuclein (αSYN) building up intraneuronal inclusions termed Lewy pathology. Mounting evidence suggests that neuron-released αSYN aggregates could be central to microglial activation, which in turn mounts and orchestrates neuroinflammatory processes potentially harmful to neurons. Therefore, understanding the mechanisms that drive microglial cell activation, polarization and function in PD might have important therapeutic implications. Here, using primary microglia, we investigated the inflammatory potential of pure αSYN fibrils derived from PD patients. We further explored and characterized microglial cell responses to a chronic-type inflammatory stimulation combining PD patient-derived αSYN fibrils (FPD), Tumor necrosis factor-α (TNFα) and prostaglandin E2 (PGE2) (TPFPD). We showed that FPD hold stronger inflammatory potency than pure αSYN fibrils generated de novo. When combined with TNFα and PGE2, FPD polarizes microglia toward a particular functional phenotype departing from FPD-treated cells and featuring lower inflammatory cytokine and higher glutamate release. Whereas metabolomic studies showed that TPFPD-exposed microglia were closely related to classically activated M1 proinflammatory cells, notably with similar tricarboxylic acid cycle disruption, transcriptomic analysis revealed that TPFPD-activated microglia assume a unique molecular signature highlighting upregulation of genes involved in glutathione and iron metabolisms. In particular, TPFPD-specific upregulation of Slc7a11 (which encodes the cystine-glutamate antiporter xCT) was consistent with the increased glutamate response and cytotoxic activity of these cells toward midbrain dopaminergic neurons in vitro. Together, these data further extend the structure-pathological relationship of αSYN fibrillar polymorphs to their innate immune properties and demonstrate that PD-derived αSYN fibrils, TNFα and PGE2 act in concert to drive microglial cell activation toward a specific and highly neurotoxic chronic-type inflammatory phenotype characterized by robust glutamate release and iron retention.

Novel one-pot strategy for fabrication of a pH-Responsive bone-targeted drug self-frame delivery system for treatment of osteoporosis

Osteoporosis (OP) is a systemic metabolic orthopedic disorder prevalent in elderly people, that is characterized by a decrease in bone mass. Although many therapeutics have been adopted for OP treatment, many of them are still not well satisfied clinical requirements and therefore development of novel therapeutics is of great significance. In this work, a novel bone-targeting drug self-frame delivery system (DSFDS) with high drug loading efficiency and pH responsive drug release was fabricated by condensation of curcumin (Cur), amino group terminated polyethylene glycol (NH₂-PEG), and alendronate (ALN) using hexachlorocyclotriphosphonitrile (HCCP) as the linker. The final product named as HCCP-Cur-PEG-ALN (HCPA NPs) displayed excellent water dispersity with small size (181.9 ​± ​25.9 ​nm). Furthermore, the drug loading capacity of Cur can reach 25.8%, and Cur can be released from HCPA NPs under acidic environment. Owing to the introduction of ALN, HCPA NPs exhibited strong binding to HAp in vitro and excellent bone-targeting effect in vivo. Results from cellular and biochemical analyses revealed that HCPA NPs could effectively inhibit the formation and differentiation function of osteoclasts. More importantly, we also demonstrated that HCPA NPs could effectively reduce bone loss in OVX mice with low toxicity to major organs. The above results clearly demonstrated that HCPA NPs are promising for OP treatment. Given the simplicity and well designability of fabrication strategy, explicit therapy efficacy and low toxicity of HCPA NPs, we believe that this work should be of great interest for fabrication of various DSFDS to deal with many diseases.

AA. The effect of Hyperhomocysteinemia on the Osteoclasts activity in Male New Zealand White Rabbits

Methionine is a specific amino acid which contains sulfur, and can be used to make proteins, found in fish, meat, and dairy products, the excess intake of L-methionine lead to elevated homocysteine (Hcy) level that known as Hyperhomocysteinemia (HHcy). Increased Hcy plasma may represent an independent risk factor for osteoporotic fractures, and therefore may also negatively affect bone metabolism. This study was designed to examine the impact of Hcy on osteoclast activity in Male Rabbits, following methionine overload. To achieve this study's aims, we recruiting (20) males of New Zealand white rabbits that were divided into (10/group) control group and a group treated with methionine. Then after the intubation of methionine overload, we measured the "Receptor Activator of Nuclear factor Kappa-b" (RANK) and "Receptor Activator of Nuclear factor Kappa-b ligand" (RANK-L) levels in the blood, in addition to histological examination of the trabecular structure of femur bone. The results show a significant (p≤0.001) increase in serum RANK and RANK-L levels of methionine treated group in comparison with the control group. The histological examination of the trabecular structure of femur bone shows an increase in osteoclasts percentage, activity, and large resorption pits in the methionine treated group. The HHcy that was induced by methionine overload, caused an increase in osteoclast activity and numbers in male rabbits suggested a mechanistic role for bone resorption by Hcy. Future research clarifying the mechanistic function of elevated concentrations of Hcy in osteoporosis may have important therapeutic implications.

FGF2 positively regulates osteoclastogenesis via activating the ERK-CREB pathway

Fibroblast growth factor 2 (FGF2) plays crucial roles in the growth and development of several tissues. However, its function in bone homeostasis remains controversial. Here, we found that exogenous FGF2 supplementation inhibited the mineralization of bone marrow stromal cells (BMSCs), at least partially, via up-regulating the gene expression of osteoclastogenesis. The FGF receptor (FGFR) allosteric antagonist SSR128129E modestly, whereas the FGFR tyrosine kinase inhibitor AZD4547 significantly antagonized the effects of FGF2. Mechanistically, FGF2 stimulated ERK phosphorylation, and the ERK signaling inhibitor PD325901 strongly blocked FGF2 enhancement of osteoclastogenesis. Moreover, the phosphorylation of CREB was also activated in response to FGF2, thereby potentiating the interaction of p-CREB with the promoter region of Rankl gene. Notably, FGF2-deficient BMSCs exhibited higher mineralization capability and lower osteoclastogenic gene expression. Correspondingly, FGF2-knockout mice showed increased bone mass and attenuated expression of osteoclast-related markers, which were associated with moderate inhibition of the ERK signaling. In conclusion, FGF2 positively regulates osteoclastogenesis via stimulating the ERK-CREB pathway. These findings establish the importance of FGF2 in bone homeostasis, hinting the potential use of FGF2/ERK/CREB specific inhibitors to fight against bone-related disorders, such as osteoporosis.

The Programmed Death-1 Pathway Counter-Regulates Inflammation-Induced Osteoclast Activity in Clinical and Experimental Settings

Objective

The programmed death-1 (PD-1) pathway is essential for maintaining self-tolerance and plays an important role in autoimmunity, including rheumatoid arthritis (RA). Here, we investigated how membrane-bound and soluble (s)PD-1 influence bone homeostasis during chronic inflammation, exemplified in RA.

Methods

Bone mineral density and bone microstructure were examined in PD-1 and PD-L1 knockout (KO) mice and compared with wild-type (WT) mice. Receptor activator of nuclear factor kappa-B ligand (RANKL) was measured in serum, and the expression examined on activated bone marrow cells. Osteoclast formation was examined in cells from murine spleen and bone marrow and from human synovial fluid cells. sPD-1 was measured in chronic and early (e)RA patients and correlated to markers of disease activity and radiographic scores.

Results

PD-1 and PD-L1 KO mice showed signs of osteoporosis. This was supported by a significantly reduced trabecular bone volume fraction and deteriorated microstructure, as well as increased osteoclast formation and an increased RANKL/OPG ratio. The recombinant form of sPD-1 decreased osteoclast formation in vitro, but was closely associated with disease activity markers in eRA patients. Sustained elevated sPD-1 levels indicated ongoing inflammation and were associated with increased radiographic progression.

Conclusion

The PD-1 pathway is closely associated with bone homeostasis, and lacking members of this pathway causes a deteriorated bone structure. The immunological balance in the microenvironment determines how the PD-1 pathway regulates osteoclast formation. In eRA patients, sPD-1 may serve as a biomarker, reflecting residual but clinically silent disease activity and radiographic progression.

Multiomics characteristics of neurogenesis-related gene are dysregulated in tumor immune microenvironment

The success of immunotherapy was overshadowed by its low response rate, and the hot or cold tumor microenvironment was reported to be responsible for it. However, due to the lack of an appropriate method, it is still a huge challenge for researchers to understand the molecular differences between hot and cold tumor microenvironments. Further research is needed to gain deeper insight into the molecular characteristics of the hot/cold tumor microenvironment. A large-scale clinical cohort and single-cell RNA-seq technology were used to identify the molecular characteristics of inflamed or noninflamed tumors. With single-cell RNA sequencing technology, we provided a novel method to dissect the tumor microenvironment into a hot/cold tumor microenvironment to help us understand the molecular differences between hot and cold tumor microenvironments. Compared with cold tumors, hot tumors highly expressed B cell-related genes, such as MS4A1 and CXCR5, neurogenesis-related miRNA such as MIR650, and immune molecule-related lncRNA such as MIR155HG and LINC00426. In cold tumors, the expression of genes related to multiple biological processes, such as the neural system, was significantly upregulated, and methylome analysis indicated that the promoter methylation level of genes related to neurogenesis was significantly reduced. Finally, we investigated the pan-cancer prognostic value of the cold/hot microenvironment and performed pharmacogenomic analysis to predict potential drugs that may have the potential to convert the cold microenvironment into a hot microenvironment. Our study reveals the multiomics characteristics of cold/hot microenvironments. These molecular characteristics may contribute to the understanding of immune exclusion and the development of microenvironment-targeted therapy.

Denosumab Therapy for Giant-cell Tumor of the Lumbar Spine: A Case Report and Immunohistochemical Examination

Introduction

Denosumab, a monoclonal antibody that inhibits the receptor activator of nuclear factor-kappa (RANK) ligand, has been reported to reduce tumor size and progression, promote bone mineralization reconstruction, and increase bone density in patients with giant-cell tumor of bone (GCTB). However, information regarding the histopathological findings of spinal GCTB following denosumab therapy and the time course of the treatment is limited.

Case Report

We report the case of a 58-year-old woman with progressive low back pain for 3 months before admission. Radiological and histological examinations revealed L4 GCTB. The patients received 10 courses of denosumab, and the tumor was subsequently resected. The therapy resulted in reduction of tumor mass and replacement of the lesions with bone tissue, particularly at the extravertebral and intracanal mass lesions. Histological examination of resected vertebra revealed a notable decrease in the number of RANK-positive and cyclooxygenase-2-positive cells. However, few RANK-positive cells were present around the woven bone.

Conclusion

Denosumab therapy for spinal GCTB is effective for reducing the tumor stage, surgical complications, and neurological impairment progression; however, it does not lead to total elimination of GCT cells, and careful consideration is needed in terms of the surgical procedure and post-operative denosumab therapy.

Leptin reduces in vitro cementoblast mineralization and survival as well as induces PGE2 release by ERK1/2 commitment

Objectives

Juvenile obesity is a complex clinical condition that is present more and more frequently in the daily orthodontic practice. Over-weighted patients have an impaired bone metabolism, due in part to their increased levels of circulating adipokines. Particularly, leptin has been reported to play a key role in bone physiology. Leptin is ubiquitously present in the body, including blood, saliva, and crevicular fluid. If, and to what extent, it could influence the reaction of cementoblasts during orthodontic-induced forces is yet unknown.

Material and methods

OCCM-30 cementoblasts were cultivated under compressive forces using different concentrations of leptin. The expression of ObR, Runx-2, Osteocalcin, Rank-L, Sost, Caspase 3, 8, and 9 were analyzed by RT-PCR. Western blots were employed for protein analysis. The ERK1/2 antagonist FR180204 (Calbiochem) was used and cPLA2 activation, PGE2, and cytochrome C release were further evaluated.

Results

In vitro, when compressive forces are applied, leptin promotes ERK1/2 phosphorylation, as well as upregulates PGE2 and caspase 3 and caspase 9 on OCCM cells. Blockade of ERK1/2 impairs leptin-induced PGE2 secretion and reduced caspase 3 and caspase 9 expression.

Conclusions

Leptin influences the physiological effect of compressive forces on cementoblasts, exerting in vitro a pro-inflammatory and pro-apoptotic effect.

Clinical relevance

Our findings indicate that leptin exacerbates the physiological effect of compressive forces on cementoblasts promoting the release of PGE2 and increases the rate of cell apoptosis, and thus, increased levels of leptin may influence the inflammatory response during orthodontically induced tooth movement.

Etoricoxib prevents progression of osteolysis in repeated intra-articular monosodium urate-induced gouty arthritis in rats

Deposition of monosodium urate (MSU) crystals in the joint or synovium is the major factor in Gouty arthritis (GA). The clinical features of chronic and recurrent GA include pain and the subsequent development of chronic tophaceous GA with multiple tophi deposits accompanied by osteolysis. The majority of previous animal studies have focused on MSU-induced acute GA without making observations regarding osteolysis. In the study, intra-articular injections of MSU into the knee (2 times/week for 10 weeks) was used to induce chronic and recurrent attacks of GA that in turn induced progressive osteolysis. Moreover, we also evaluated whether the clinical, nonsteroidal anti-inflammatory drug (NSAID) etoricoxib attenuated the osteoclastogenesis of progressive osteolysis. The knee morphometry and the expression of osteoclastogenesis-related proteins (cathepsin K and matrix metalloproteinase-9 and -13) in the knee were examined by micro-CT and immunohistochemistry, respectively. Results showed that oral etoricoxib not only significantly attenuated the nociceptive behaviors of the rats but that it also inhibited the expression of osteoclastogenesis-related proteins in their knee joints in chronic and recurrent attacks of GA. Our findings thus suggest that NSAIDs not only inhibit nociception but also prevent the progression of osteolysis in chronic and repeated attacks of GA.

Modulation of bone turnover aberration: A target for management of primary osteoporosis in experimental rat model

Osteoporosis is a skeletal degenerative disease characterised by abnormal bone turnover with scant bone formation and overabundant bone resorption. The present approach was intended to address the potency of nanohydroxyapatite (nHA), chitosan/hydroxyapatite nanocomposites (nCh/HA) and silver/hydroxyapatite nanoparticles (nAg/HA) to modulate bone turnover deviation in primary osteoporosis induced in the experimental model. Characterisation techniques such as TEM, zeta-potential, FT-IR and XRD were used to assess the morphology, the physical as well as the chemical features of the prepared nanostructures. The in vivo experiment was conducted on forty-eight adult female rats, randomised into 6 groups (8 rats/group), (1) gonad-intact, (2) osteoporotic group, (3) osteoporotic + nHA, (4) osteoporotic + nCh/HA, (5) osteoporotic + nAg/HA and (6) osteoporotic + alendronate (ALN). After three months of treatment, serum sclerostin (SOST), bone alkaline phosphatase (BALP) and bone sialoprotein (BSP) levels were quantified using ELISA. Femur bone receptor activator of nuclear factor-kappa B (NF-κB) ligand (RANKL) and cathepsin K (CtsK) mRNA levels were evaluated by quantitative RT-PCR. Moreover, alizarin red S staining was applied to determine the mineralisation intensity of femur bone. Findings in the present study indicated that treatment with nHA, nCh/HA or nAg/HA leads to significant repression of serum SOST, BALP and BSP levels parallel to a significant down-regulation of RANKL and CtsK gene expression levels. On the other side, significant enhancement in the calcification intensity of femur bone has been noticed. The outcomes of this experimental setting ascertained the potentiality of nHA, nCh/HA and nAg/HA as promising nanomaterials in attenuating the excessive bone turnover in the primary osteoporotic rat model. The mechanisms behind the efficacy of the investigated nanostructures involved the obstacle of serum and tissue indices of bone resorption besides the strengthening of bone mineralisation.

Effects of Placenta-Derived Mesenchymal Stem Cells on the Particulate Matter-Induced Damages in Human Middle Ear Epithelial Cells

This study was aimed at investigating the effects of placenta-derived mesenchymal stem cells (PL-MSCs) on particulate matter- (PM-) exposed human middle ear epithelial cells (HMEECs). HMEECs were treated with 300 μg/ml PM for 24 hours. The PL-MSCs were cocultured with PM-treated HMEECs. Cells were harvested on days 0, 1, and 4, and the expression of the inflammatory genes TNFα, COX2, IL1β, IL6, and MUC5B in HMEECs and anti-inflammatory genes PTGES, TGFβ, and VEGF in PL-MSCs was examined by qRT-PCR. The culture media were collected to measure the secreted PGE2 level using an enzyme-linked immunosorbent assay. The mRNA expression of TNFα, COX2, IL1β, IL6, and MUC5B in HMEECs increased following PM treatment. PM-treated HMEECs cocultured with PL-MSCs showed alleviated inflammatory reactions represented by lower mRNA expression levels of MUC5B, TNFα, IL1β, and IL6 compared to monocultured PM-treated HMEECs. The mRNA expression levels of PGE2, TGFβ, and VEGF were elevated in cocultured PL-MSCs compared to those of control PL-MSCs. The medium of PM-treated HMEECs cocultured with PL-MSCs exhibited increased PGE2 levels. The increased inflammatory response in PM-treated HMEECs was reversed using PL-MSCs. The PGE2, TGFβ, and VEGF were the mediators of the anti-inflammatory effects of PL-MSCs.

The Hajdu Cheney mutation sensitizes mice to the osteolytic actions of tumor necrosis factor α

Hajdu Cheney syndrome (HCS) is characterized by craniofacial developmental abnormalities, acro-osteolysis, and osteoporosis and is associated with gain-of-NOTCH2 function mutations. A mouse model of HCS termed Notch2^tm1.1Ecan harboring a mutation in exon 34 of Notch2 replicating the one found in HCS was used to determine whether the HCS mutation sensitizes the skeleton to the osteolytic effects of tumor necrosis factor α (TNFα). TNFα injected over the calvarial vault caused a greater increase in osteoclast number, osteoclast surface, and eroded surface in Notch2^tm1.1Ecan mice compared with littermate WT controls. Accordingly, the effect of TNFα on osteoclastogenesis was greatly enhanced in cultures of bone marrow-derived macrophages (BMMs) from Notch2^tm1.1Ecan mice when compared with the activity of TNFα in control cultures. TNFα induced the expression of Notch2 and Notch2 mutant mRNA by ∼2-fold, possibly amplifying the NOTCH2-dependent induction of osteoclastogenesis. The effect of TNFα on osteoclastogenesis in Notch2^tm1.1Ecan mutants depended on NOTCH2 activation because it was reversed by anti-NOTCH2 negative regulatory region and anti-jagged 1 antibodies. The inactivation of Hes1 prevented the TNFα effect on osteoclastogenesis in the context of the Notch2^tm1.1Ecan mutation. In addition, the induction of Il1b, but not of Tnfa and Il6, mRNA by TNFα was greater in Notch2^tm1.1Ecan BMMs than in control cells, possibly contributing to the actions of TNFα and NOTCH2 on osteoclastogenesis. In conclusion, the HCS mutation enhances TNFα-induced osteoclastogenesis and the inflammatory bone-resorptive response possibly explaining the acro-osteolysis observed in affected individuals.

RANKL inhibition improves muscle strength and insulin sensitivity and restores bone mass

Receptor activator of Nfkb ligand (RANKL) activates, while osteoprotegerin (OPG) inhibits, osteoclastogenesis. In turn a neutralizing Ab against RANKL, denosumab improves bone strength in osteoporosis. OPG also improves muscle strength in mouse models of Duchenne's muscular dystrophy (mdx) and denervation-induce atrophy, but its role and mechanisms of action on muscle weakness in other conditions remains to be investigated. We investigated the effects of RANKL inhibitors on muscle in osteoporotic women and mice that either overexpress RANKL (HuRANKL-Tg+), or lack Pparb and concomitantly develop sarcopenia (Pparb-/-). In women, denosumab over 3 years improved appendicular lean mass and handgrip strength compared to no treatment, whereas bisphosphonate did not. HuRANKL-Tg+ mice displayed lower limb force and maximal speed, while their leg muscle mass was diminished, with a lower number of type I and II fibers. Both OPG and denosumab increased limb force proportionally to the increase in muscle mass. They markedly improved muscle insulin sensitivity and glucose uptake, and decrease anti-myogenic and inflammatory gene expression in muscle, such as myostatin and protein tyrosine phosphatase receptor-γ. Similarly, in Pparb-/-, OPG increased muscle volume and force, while also normalizing their insulin signaling and higher expression of inflammatory genes in skeletal muscle. In conclusions, RANKL deteriorates, while its inhibitor improves, muscle strength and insulin sensitivity in osteoporotic mice and humans. Hence denosumab could represent a novel therapeutic approach for sarcopenia.

Activation of RANK/RANKL/OPG Pathway Is Involved in the Pathophysiology of Fibrous Dysplasia and Associated With Disease Burden

Fibrous dysplasia of bone (FD) is a mosaic disease caused by mutations in GNAS. Constitutive activation of the α-subunit of the G_s stimulatory protein (Gαs) leads to dysregulated proliferation of bone marrow stromal cells (BMSCs), generating expansile lesions of fibrotic tissue and abnormal bone. Local bone remodeling regulation by BMSCs is also altered, and FD tissue is characterized by abundant osteoclast-like cells that may be essential for lesion expansion. Animal models show local expression of RANKL in bone lesions, and treatment with the RANKL neutralizing antibody denosumab decreased lesion expansion rate in a patient with aggressive FD. However, the role of RANKL/osteoprotegerin (OPG) in FD pathophysiology is not yet understood. We measured serum levels of RANKL, OPG, and inactive RANKL-OPG complexes in FD patients of known disease burden and in healthy volunteers (HVs). RANK, RANKL, and Ki67 immunohistochemistry were assessed in FD tissue. Cultured FD and HV BMSCs were stimulated with prostaglandin E₂ (PGE₂ ) and 1,25 vitamin D₃ to increase RANKL expression, and media levels of RANKL and OPG were measured. Osteoclastogenic induction by FD or HV BMSCs was assessed in co-cultures with HV peripheral monocytes. FD patients showed a 16-fold increase in serum RANKL compared to HVs. OPG was moderately increased (24%), although RANKL/OPG ratio was 12-fold higher in FD patients than in HVs. These measurements were positively correlated with the skeletal burden score (SBS), a validated marker of overall FD burden. No differences in serum inactive RANKL-OPG complexes were observed. In FD tissue, RANKL+ and Ki67+ fibroblastic cells were observed near RANK+ osteoclasts. High levels of RANKL were released by FD BMSCs cultures, but were undetectable in HV cultures. FD BMSC released less OPG than HV BMSCs. FD, but not HV BMSCs, induced osteoclastogenesis in monocyte co-cultures, which was prevented by denosumab addition. These data are consistent with the role of RANKL as a driver in FD-induced osteoclastogenesis. © 2018 American Society for Bone and Mineral Research.

Aminothiazoles inhibit osteoclastogenesis and PGE2 production in LPS-stimulated co-cultures of periodontal ligament and RAW 264.7 cells, and RANKL-mediated osteoclastogenesis and bone resorption in PBMCs

Inflammatory mediator prostaglandin E₂ (PGE₂ ) contributes to bone resorption in several inflammatory conditions including periodontitis. The terminal enzyme, microsomal prostaglandin E synthase-1 (mPGES-1) regulating PGE₂ synthesis is a promising therapeutic target to reduce inflammatory bone loss. The aim of this study was to investigate effects of mPGES-1 inhibitors, aminothiazoles TH-848 and TH-644, on PGE₂ production and osteoclastogenesis in co-cultures of periodontal ligament (PDL) and osteoclast progenitor cells RAW 264.7, stimulated by lipopolysaccharide (LPS), and bone resorption in RANKL-mediated peripheral blood mononuclear cells (PBMCs). PDL and RAW 264.7 cells were cultured separately or co-cultured and treated with LPS alone or in combination with aminothiazoles. Multinucleated cells stained positively for tartrate-resistant acid phosphatase (TRAP) were scored as osteoclast-like cells. Levels of PGE₂ , osteoprotegerin (OPG) and interleukin-6, as well as mRNA expression of mPGES-1, OPG and RANKL were analysed in PDL cells. PBMCs were treated with RANKL alone or in combination with aminothiazoles. TRAP-positive multinucleated cells were analysed and bone resorption was measured by the CTX-I assay. Aminothiazoles reduced LPS-stimulated osteoclast-like cell formation both in co-cultures and in RAW 264.7 cells. Additionally, aminothiazoles inhibited PGE₂ production in LPS-stimulated cultures, but did not affect LPS-induced mPGES-1, OPG or RANKL mRNA expression in PDL cells. In PBMCs, inhibitors decreased both osteoclast differentiation and bone resorption. In conclusion, aminothiazoles reduced the formation of osteoclast-like cells and decreased the production of PGE₂ in co-cultures as well as single-cell cultures. Furthermore, these compounds inhibited RANKL-induced bone resorption and differentiation of PBMCs, suggesting these inhibitors for future treatment of inflammatory bone loss such as periodontitis.

GATA4 represses RANKL in osteoblasts via multiple long-range enhancers to regulate osteoclast differentiation

GATA4 is a transcription factor that is responsible for tissue-specific gene regulation in many tissues, and more recent studies showed that it is necessary for osteoblast differentiation. Previously, we showed that in vivo deletion of Gata4 using Cre-recombinase under the control of the Col1a1 2.3 kb promoter, showed significantly reduced trabecular bone properties. To understand the role of GATA4 in more differentiated cells, GATA4^fl/fl mice were crossed with mice expressing Cre-recombinase under the control of the osteocalcin promoter. MicroCT analysis of trabecular bone properties of the femur and tibia from 14-week-old female osteocalcin-Cre/GATA4^fl/fl (OCN-cKO) mice showed a significant reduction in percentage bone volume, a decrease in trabecular number and an increase in trabecular spacing. In vivo, histomorphometric analysis revealed a decrease in the number of osteoblasts and an increase in the number of osteoclasts in the tibiae of OCN-cKO mice. In vivo and in vitro systems correlated a decrease in Gata4 mRNA with increased RANKL gene expression. To determine if RANKL is a direct target of GATA4, chromatin immunoprecipitation (ChIP)-sequencing was performed, and it demonstrated that GATA4 is recruited to seven enhancers near RANKL. Furthermore, when Gata4 is knocked down, the chromatin at the RANKL region is further opened, as detected by a reduction in histone 3 lysine 27 trimethylation (H3K27me3) and an increase in histone 3 lysine 4 dimethylation (H3K4me2) in the RANKL locus. In vitro, TRAP staining of cells from bone marrow cultures from Gata4 knockout cells show that the increased levels of RANKL are sufficient for osteoclast formation. Together, the data suggest that GATA4 directly represses RANKL expression via seven cis-regulatory regions and plays an important role in maintaining proper bone development and osteoclast formation.

Improving knowledge on the activation of bone marrow fibroblasts in MGUS and MM disease through the automatic extraction of genes via a nonnegative matrix factorization approach on gene expression profiles

Background

Multiple myeloma (MM) is a cancer of terminally differentiated plasma that is part of a spectrum of blood diseases. The role of the micro-environment is crucial for MM clonal evolution.

Methods

This paper describes the analysis carried out on a limited number of genes automatically extracted by a nonnegative matrix factorization (NMF) based approach from gene expression profiles of bone marrow fibroblasts of patients with monoclonal gammopathy of undetermined significance (MGUS) and MM.

Results

Automatic exploration through NMF, combined with a motivated post-processing procedure and a pathways analysis of extracted genes, allowed to infer that a functional switch is required to lead fibroblasts to acquire pro-tumorigenic activity in the progression of the disease from MGUS to MM.

Conclusion

The extracted biologically relevant genes may be representative of the considered clinical conditions and may contribute to a deeper understanding of tumor behavior.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1589-1) contains supplementary material, which is available to authorized users.

Isoproterenol Increases RANKL Expression in a ATF4/NFATc1-Dependent Manner in Mouse Osteoblastic Cells

Sympathetic nervous system stimulation-induced β-adrenergic signal transduction is known to induce bone loss and increase of osteoclast activity. Although isoproterenol, a nonspecific β-adrenergic receptor agonist, has been shown to increase receptor activator of NF-κB ligand (RANKL), the details of the regulatory mechanisms remain unclear. In the present study, we investigated the role of the nuclear factor of activated T-cells (NFAT) in isoproterenol-induced RANKL expression in C2C12 and in primary cultured mouse calvarial cells. Isoproterenol increased nuclear factor of activated T-cells cytoplasmic 1 (NFATc1) and RANKL expressions at both mRNA and protein levels and increased NFAT reporter activity. NFATc1 knockdown blocked isoproterenol-mediated RANKL expression. Isoproterenol also promoted cAMP response element-binding protein 1 (CREB1) and activating transcription factor 4 (ATF4) phosphorylation. Isoproterenol-mediated transcriptional activation of NFAT was blocked by protein kinase A (PKA) inhibitor H89. Isoproterenol-induced CREB1, ATF4, NFATc1, and RANKL expressions were suppressed by H89. Mutations in cAMP response element-like or NFAT-binding element suppressed isoproterenol-induced RANKL promoter activity. Chromatin immunoprecipitation analysis demonstrated that isoproterenol increased NFAT-binding and ATF4-binding activities on the mouse RANKL promoter, but did not increase CREB1-binding activity. Association of NFATc1 and ATF4 was not observed in a co-immunoprecipitation study. ATF4 knockdown suppressed isoproterenol-induced NFAT binding to the RANKL promoter, whereas NFATc1 knockdown did not suppress isoproterenol-induced ATF4 binding to the RANKL promoter. ATF4 knockdown suppressed isoproterenol-induced expressions of NFATc1 and RANKL. These results suggest that isoproterenol increases RANKL expression in an ATF4/NFATc1-dependent manner.