ML264 inhibits osteosarcoma growth and metastasis via inhibition of JAK2/STAT3 and WNT/ß-catenin signalling pathways.

Osteosarcoma, the most common bone malignancy, has a high morbidity rate and poor prognosis. Krüppel-like factor 5 (KLF5) is a key transcriptional regulator of cellular proliferation whose overexpression is observed in osteosarcoma cell lines (U2OS, 143B, MG63 and SAOS2). ML264, a small-molecule inhibitor of KLF5, exerts antiproliferative effects in colorectal cancer; however, its function in osteosarcoma remains unknown. Here, we explored the possible antitumour effects of ML264 on 143B and U2OS cell lines and murine tumour xenograft model. ML264 suppressed proliferation and clonogenic ability of osteosarcoma cells in a dose-dependent manner. Moreover, ML264 induced G0/G1 cell cycle arrest, with no influence on apoptosis, and inhibited the migratory and invasive abilities of osteosarcoma cells, as demonstrated by wound-healing and Transwell assays. Exposure to ML264 reduced the mRNA and protein levels of molecules associated with epithelial-mesenchymal transition phenotype, including N-cadherin, vimentin, Snail, matrix metalloproteinase (MMP) 9 and MMP13. Inhibition of signal transducer and activator of transcription (STAT) 3 phosphorylation and Wnt signalling was also observed. In the murine model of osteosarcoma, tumour growth was efficiently suppressed following a 10-day treatment with ML264. Collectively, our findings demonstrate the potential value of ML264 as a novel anticancer drug for osteosarcoma.

Activating ß-catenin/Pax6 axis negatively regulates osteoclastogenesis by selectively inhibiting phosphorylation of p38/MAPK.

Balance of osteoclast formation is regulated by the receptor activator of NF-κB ligand and extracellular negative regulators such as IFN-γ and IFN-ß. However, very little is known about the intrinsic negative regulatory factors of osteoclast differentiation. Recently, the paired-box homeodomain transcription factor Pax6 was shown to negatively regulate receptor activator of NF-κB ligand-mediated osteoclast differentiation. However, the mechanism underlying this regulation is still unclear. In this study, we show that a p38 inhibitor (VX-745) up-regulates the expression of Pax6 during osteoclast differentiation. Subsequently, we found that ß-catenin could bind to the proximal region of Pax6 promoter to induce its expression, and this action could be impaired by p38-induced ubiquitin-mediated degradation of ß-catenin. Our results suggest that Pax6 is regulated by a novel p38/ß-catenin pathway. Pax6 can further regulate the nuclear translocation of NF of activated T cells, cytoplasmic 1. Our study indicates that this novel p38/ß-catenin/Pax6 axis contributes to negative regulation of osteoclastogenesis. In addition, our study proposes a novel approach to treat osteoclast-related diseases through the use of VX-745 complemented with the ß-catenin activator SKL2001.-Jie, Z., Shen, S., Zhao, X., Xu, W., Zhang, X., Huang, B., Tang, P., Qin, A., Fan, S., Xie, Z. Activating ß-catenin/Pax6 axis negatively regulates osteoclastogenesis by selectively inhibiting phosphorylation of p38/MAPK.

Glabridin inhibits osteosarcoma migration and invasion via blocking the p38- and JNK-mediated CREB-AP1 complexes formation.

Osteosarcoma is the most common bone malignancy, and it seriously affects the quality of life of affected children and adolescents. Glabridin (GLA), a major component of licorice root extract, has been reported to exert antitumor effects against a variety of tumor types; however, its effects on osteosarcoma have not been elucidated. In the current study, we investigate the effects and potential antimetastatic mechanisms of GLA on osteosarcoma in vitro and in vivo. Flow cytometry showed that GLA induced G2/M cell cycle phase arrest and promoted cell apoptosis. Transwell and wound-healing assays showed that GLA significantly decreased the migration and invasion of osteosarcoma cells. Further western blotting and quantitative real-time polymerase chain reaction showed that the expression of matrix metalloproteinase (MMP)-2 and MMP-9 in MG63 and HOS cells were reduced after GLA treatment. Moreover, western blotting demonstrated that GLA downregulated the phosphorylation of p38 mitogen-activated protein kinases and c-Jun N-terminal kinase. A coimmunoprecipitation assay illustrated that formation of cAMP response element-binding protein (CREB)-activating protein 1 (AP1) complexes and the DNA binding activities of CREB and AP1 in MG63 and HOS cells were impaired following treatment with GLA. Finally, GLA inhibited tumor growth and suppressed osteosarcoma cell metastasis in vivo. Overall, our findings highlight the potential of GLA as a therapeutic agent for the prevention and treatment of tumor metastasis.

MicroRNA-543 promotes ovariectomy-induced osteoporosis through inhibition of AKT/p38 MAPK signaling pathway by targeting YAF2.

The present study aimed to determine the roles of miRNA-543 in osteoporosis in rats induced by ovariectomy. The osteoporosis rat model was established by ovariectomy induction. MiRNA-543 expression in osteoblasts was measured by quantitative real-time polymerase chain reaction. The cell proliferation and apoptosis were measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and flow cytometry assays, respectively. Western blot analysis was conducted to examine the expression of YAF-2 and AKT signaling. TargetScan analysis and dual-luciferase reporter assay were performed to determine the target gene of miRNA-543. MiRNA-543 was significantly upregulated in osteoporosis rat model. Overexpression of miRNA-543 significantly suppressed cell growth and promoted apoptosis in osteoblasts, whereas downregulation of miRNA-543 significantly enhanced cell growth and inhibited apoptosis. MiRNA-543 upregulation significantly inhibited YAF-2 expression and suppressed the phosphorylation and expression of AKT and p38 mitogen-activated protein kinases (MAPK) in osteoblasts. Furthermore, YAF-2 knockdown enhanced the effects of miRNA-543 on apoptosis in osteoblasts. AKT inhibitor MK2206 and p38 MAPK inhibitor SB203580 also enhanced the effects of miRNA-543 on apoptosis in osteoblasts. Our findings revealed that inhibition of miRNA-543 could protect osteoblasts against ovariectomy-induced osteoporosis through AKT/p38 MAPK signaling pathway by targeting YAF2.

The PPAR-γ antagonist T007 inhibits RANKL-induced osteoclastogenesis and counteracts OVX-induced bone loss in mice.

BACKGROUND: Osteoclasts are key determinant cellular components implicated in the development and progression of disorders driven by bone damage. Herein, we studied the upshot of T007, an antagonist of peroxisome proliferator-activated receptor-gamma (PPARγ), on osteoclastogenesis using cell and animal models. RESULTS: The in vitro assays revealed that T007 hindered the osteoclastogenesis caused by the treatment with the receptor activator of nuclear factor-κB ligand (RANKL) through inhibiting the levels of PPARγ in cells. The PPARγ siRNA partially reproduced the inhibitory action of T007. The opposite findings were produced after PPARγ overexpression. Furthermore, T007 prevented from bone loss in a mouse model of osteoporosis induced by ovariectomy (OVX). These findings implied that T007 is a potential efficient drug for the prophylaxis and cure of osteoclast-related disorders. CONCLUSIONS: Taken together, our findings demonstrated that T007 impedes osteoclastogenesis and will be useful for the therapy of bone related diseases, essentially osteoporosis.

FTO-mediated SMAD2 m6A modification protects cartilage against Osteoarthritis.

N6-methyladenosine (m6A) modification is one of the most prevalent forms of epigenetic modification and plays an important role in the development of degenerative diseases such as osteoarthritis (OA). However, the evidence concerning the role of m6A modification in OA is insufficient. Here, m6A modification was increased in human OA cartilage and degenerated chondrocytes. Among all of the m6A enzymes, the expression of the demethylase fat mass and obesity-associated protein (FTO) decreased dramatically. Conditional knockout of FTO in chondrocytes accelerates OA progression. FTO transcription is regulated by runt-related transcription factor-1 (RUNX1). Reduced FTO elevates m6A modification at the adenosine N6 position in SMAD family member 2 (SMAD2) mRNA, whose stability is subsequently modulated by the recruited m6A reader protein YTH N6-methyladenosine RNA binding protein F2 (YTHDF2). Collectively, these findings reveal the function and mechanism of the m6A family member FTO in OA progression. Therefore, reducing m6A modification to increase SMAD2 stability by activating FTO might be a potential therapeutic strategy for OA treatment.

Restrained Mitf-associated autophagy by Mulberroside A ameliorates osteoclastogenesis and counteracts OVX-Induced osteoporosis in mice.

Bone and mineral metabolism homeostasis accounts for the maintenance of normal skeletal remodeling. However, with aging and changes in hormone levels, over-activated osteoclasts disrupt homeostasis, induce osteoporosis, and even cause osteoporotic fractures, leading to an enormous economic burden. Despite the rapid development of pharmacological therapy for osteoporosis, safer and more effective treatments remain to be explored. Here, we demonstrate that Mulberroside A (Mul-A), a natural component extracted from mulberry bark and branches, effectively suppresses osteoclastogenesis in vitro and counteracts bone loss caused by ovariectomy (OVX). The mechanism underlying this effect involves the repression of autophagic flux during osteoclastogenesis by Mul-A, which can be attributed to the restrained expression of microphthalmia-related transcription factor (Mitf) and its nuclear translocation. Importantly, Mitf overexpression partially reverses the inhibitory effects of Mul-A on autophagy and osteoclastogenesis. Moreover, applying two autophagy agonizts, rapamycin and Torin 1, attenuates the osteoclastogenic regulatory role of Mul-A. Collectively, our study demonstrates that Mul-A damages osteoclast differentiation and ameliorates osteoporosis caused by estrogen deficiency by modulation of Mitf-associated autophagy, indicating its therapeutic potential against osteoporosis.

Pexmetinib suppresses osteoclast formation and breast cancer induced osteolysis via P38/STAT3 signal pathway.

Breast cancer metastases to the bone can lead to a series of bone-related events that seriously affect the quality of life. Pexmetinib, a novel p38 mitogen-activated protein kinase (p38) inhibitor that has been evaluated in phase I clinical trials for myelodysplastic syndrome, but the effects of Pexmetinib on breast cancer induced osteolysis haven't been explored. Here, we found that Pexmetinib inhibited receptor activator of nuclear factor-κB ligand-induced osteoclast formation and bone resorption in vitro. Pexmetinib suppressed p38-mediated signal transducer and activator of transcription 3 (STAT3), which direct regulated transcription of the nuclear factor of activated T cells 1 (NFATc1), leading to reduced osteoclast formation. Moreover, Pexmetinib exerted anti-tumor effects in breast cancer cells in vitro via suppressing p38-mediated STAT3 activation and matrix metalloproteinases (MMPs) expression. Furthermore, Pexmetinib suppressed breast cancer-associated osteolysis in vivo. These results suggest that Pexmetinib may be a promising drug for the treatment of breast cancer-induced osteolysis.

USP1 inhibition suppresses the progression of osteosarcoma via destabilizing TAZ.

Mutations and altered expression of deubiquitinating enzymes (DUBs) profoundly influence tumor progression. Ubiquitin-specific protease 1 (USP1) is a well-characterized human DUB reportedly overexpressed in and associated with maintaining the mesenchymal stem cell status of osteosarcoma (OS); however, the potential mechanisms of USP1 in OS remain poorly understood. In this study, we identified that USP1 directly interacts with Transcriptional Co-Activator With PDZ-Binding Motif (TAZ) in OS cell lines, and with mechanistic analysis indicating that the anti-OS effects of USP1 inhibition could be partially attributed to TAZ instability, with its reduced nuclear accumulation responsible for a subsequent decrease in the expression of downstream genes associated with the Hippo signaling pathway. Moreover, pharmacological inhibition USP1 by ML323 presented the similar effects on Hippo signaling pathway and suppressed OS growth and metastasis both in vitro and in vivo. Taken together, our results revealed a novel molecular mechanism underlying the function of USP1 in OS and a potential role of ML323 as a therapeutic strategy for the clinical treatment of OS.

The SFRP1 Inhibitor WAY-316606 Attenuates Osteoclastogenesis Through Dual Modulation of Canonical Wnt Signaling.

Osteoporosis, a noteworthy age-related disease induced by imbalanced osteogenesis and osteoclastogenesis, is a serious economic burden on both individuals and society. Small molecule drugs with dual effects on both bone resorption and mineralization are pressingly needed. Secreted frizzled-related protein 1 (SFRP1), a well-known extracellular repressor of canonical Wnt signaling, has been reported to regulate osteogenesis. Global SFRP1 knockout mice show significantly elevated bone mass. Although osteoclasts (OCs) express and secrete SFRP1, the role of SFRP1 produced by OCs in osteoclastogenesis and osteoporosis remains unclear. In this work, the levels of SFRP1 were found to be increased in patients with osteoporosis compared with healthy controls. Pharmacological inhibition of SFRP1 by WAY-316606 (WAY)- attenuated osteoclastogenesis and bone resorption in vitro. The expressions of OC-specific genes were suppressed by the SFRP1 inhibitor, WAY. Mechanistically, both extracellular and intracellular SFRP1 could block activation of the canonical Wnt signaling pathway, and WAY reverse the silent status of canonical Wnt through dual effects, leading to osteoclastogenesis inhibition and osteogenesis promotion. Severe osteopenia was observed in the ovariectomized (OVX) mouse model, and WAY treatment effectively improved the OVX-induced osteoporosis. In summary, this work found that SFRP1 supports OC differentiation and function, which could be attenuated by WAY through dual modulation of canonical Wnt signaling, suggesting its therapeutic potential. © 2021 American Society for Bone and Mineral Research (ASBMR).

Mechanical force promotes dimethylarginine dimethylaminohydrolase 1-mediated hydrolysis of the metabolite asymmetric dimethylarginine to enhance bone formation.

Mechanical force is critical for the development and remodeling of bone. Here we report that mechanical force regulates the production of the metabolite asymmetric dimethylarginine (ADMA) via regulating the hydrolytic enzyme dimethylarginine dimethylaminohydrolase 1 (Ddah1) expression in osteoblasts. The presence of -394 4 N del/ins polymorphism of Ddah1 and higher serum ADMA concentration are negatively associated with bone mineral density. Global or osteoblast-specific deletion of Ddah1 leads to increased ADMA level but reduced bone formation. Further molecular study unveils that mechanical stimulation enhances TAZ/SMAD4-induced Ddah1 transcription. Deletion of Ddah1 in osteoblast-lineage cells fails to respond to mechanical stimulus-associated bone formation. Taken together, the study reveals mechanical force is capable of down-regulating ADMA to enhance bone formation.

Correlation Analysis Between Basic Diseases and Subsequent Vertebral Fractures After Percutaneous Kyphoplasty (PKP) for Osteoporotic Vertebral Compression Fractures.

BACKGROUND: Percutaneous kyphoplasty (PKP) is a widely accepted surgical treatment modality for painful osteoporotic vertebral compression fractures. The risk factors cause of subsequent vertebral fractures after PKP are debated. OBJECTIVES: To evaluate risk factors for the occurrence of new vertebral compression fractures after PKP. STUDY DESIGN: A retrospective study. SETTING: A single-center inpatient population. METHODS: A total of 921 patients (1,152 vertebrae) with PKP were investigated. Among those patients, 111 patients (155 levels) incurred refractures after PKP. RESULTS: The average bone mineral density was -3.27 in the "refracture"group and -3.00 in the "no fracture" group (P = 0.031). Morbidities of women were significantly higher in the "refracture" group (90.99%) compared with the "no fracture" group (81.73%) (P = 0.015). Among the basic diseases, several diseases (history of previously fracture, previously osteoporosis, gallstone disease, stomach disease, and ovariectomy) are associated with refractures after PKP (P < 0.05). And antiosteoporotic treatment (calcium + vitamin D or zoledronate) after PKP can also significantly reduce the occurrence of refracture (P < 0.000). In addition, logistic regression analysis also showed that most of the above contents had significant correlation with the refracture after PKP (P < 0.05), except for gallstone disease (P = 0.362). LIMITATIONS: Retrospective study, single center. CONCLUSION: Osteoporosis is the main cause of refracture after PKP. Elderly women were found to be more susceptible than elderly men to refracture. Patients with a history of previously fracture, previously osteoporosis, stomach ulcer, and ovariectomy are more likely to be refracture. Antiosteoporosis treatment (calcium + vitamin D or zoledronate) after PKP can reduce the risk of refracture.

Oxidative Stress-Induced Hypermethylation of KLF5 Promoter Mediated by DNMT3B Impairs Osteogenesis by Diminishing the Interaction with ß-Catenin.

Aims: Emerging evidence suggests that the pathogenesis of osteoporosis, characterized by impaired osteogenesis, is shifting from estrogen centric to oxidative stress. Our previous studies have shown that the zinc-finger transcription factor krüppel-like factor 5 (KLF5) plays a key role in the degeneration of nucleus pulposus and cartilage. However, its role in osteoporosis remains unknown. We aimed to investigate the effect and mechanism of KLF5 on osteogenesis under oxidative stress. Results: First, KLF5 was required for osteogenesis and stimulated osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). KLF5 was hypermethylated and downregulated in ovariectomy-induced osteoporosis mice and in BMSCs treated with H2O2. Interestingly, DNA methyltransferases 3B (DNMT3B) upregulation mediated the hypermethylation of KLF5 induced by oxidative stress, thereby impairing osteogenic differentiation. The inhibition of KLF5 hypermethylation using DNMT3B siRNA or 5-AZA-2-deoxycytidine (5-AZA) protected osteogenic differentiation of BMSCs from oxidative stress. Regarding the downstream mechanism, KLF5 induced ß-catenin expression. More importantly, KLF5 promoted the nuclear translocation of ß-catenin, which was mediated by the armadillo repeat region of ß-catenin. Consistently, oxidative stress-induced KLF5 hypermethylation inhibited osteogenic differentiation by reducing the expression and nuclear translocation of ß-catenin. Innovation: We describe the novel effect and mechanism of KLF5 on osteogenesis under oxidative stress, which is linked to osteoporosis for the first time. Conclusion: Our results suggested that oxidative stress-induced hypermethylation of KLF5 mediated by DNMT3B impairs osteogenesis by diminishing the interaction with ß-catenin, which is likely to contribute to osteoporosis. Targeting the hypermethylation of KLF5 might be a new strategy for the treatment of osteoporosis. Antioxid. Redox Signal. 35, 1-20.

Lycorine Induces Apoptosis and G1 Phase Arrest Through ROS/p38 MAPK Signaling Pathway in Human Osteosarcoma Cells In Vitro and In Vivo.

STUDY DESIGN: Xenograft osteosarcoma mouse model. OBJECTIVE: We determined the effect of lycorine on osteosarcoma. SUMMARY OF BACKGROUND DATA: Osteosarcoma is an aggressive malignant neoplasm, is most prevalent in teenagers and adults and current treatment approaches have reached a survival plateau and attempts to improve osteosarcoma prognosis have proven unsuccessful. Thus there is clear evidence that development of new agents with high efficacy and fewer side effects to provide better prognostic outcome is urgently needed. METHODS: The toxicity, function and mechanism of lycorine (LY) on osteosarcoma were accessed in vitro by CCK-8 assay, flow cytometry, and western blotting and in vivo by the xenograft osteosarcoma mouse model. RESULTS: In this study, we found that LY exhibited dose-dependent and time-dependent cytotoxic effects on human osteosarcoma cell-lines SJSA-1 and U2OS, inducing G1 phase cell cycle arrest and cellular death via apoptosis. Mechanistically, LY treatment elevated ROS generation that activates the p38 mitogen-activated protein kinases (MAPKs) and p53-dependent apoptotic program. Inhibition of ROS generation by NAC or p38 MAPK signaling by SB203580 attenuated the p53-mediated cell cycle arrest and apoptosis induced by LY. In vivo administration of LY markedly reduced tumor growth with little organ-related toxicity in a mouse xenograft model of osteosarcoma. CONCLUSION: Collectively, our data suggests that LY exhibit therapeutic potential for the treatment of osteosarcoma. LEVEL OF EVIDENCE: N/A.

The Nrf2 activator RTA-408 attenuates osteoclastogenesis by inhibiting STING dependent NF-κb signaling.

The dysregulation of ROS production and osteoclastogenesis is involved in the progress of osteoporosis. To identify novel and effective targets to treat this disease, it is important to explore the underlying mechanisms. In our study, we firstly tested the effect of the Nrf2 activator RTA-408, a novel synthetic triterpenoid under clinical investigation for many diseases, on osteoclastogenesis. We found that it could inhibit osteoclast differentiation and bone resorption in a time- and dose-dependent manner. Further, RTA-408 enhanced the expression and activity of Nrf2 and significantly suppressed RANKL-induced reactive oxygen species (ROS) production. Nrf2 regulates the STING expression and STING induces the production of IFN-ß. Here, we found that RTA-408 could suppress STING expression, but that it does not affect Ifnb1 expression. RANKL-induced degradation of IκBα and the nuclear translocation of P65 was suppressed by RTA-408. Although this compound was not found to influence STING-IFN-ß signaling, it suppressed the RANKL-induced K63-ubiquitination of STING via inhibiting the interaction between STING and the E3 ubiquitin ligase TRAF6. Further, adenovirus-mediated STING overexpression rescued the suppressive effect of RTA-408 on NF-κB signaling and osteoclastogenesis. In vivo experiments showed that this compound could effectively attenuate ovariectomy (OVX)-induced bone loss in C57BL/6 mice by inhibiting osteoclastogenesis. Collectively, we show that RTA-408 inhibits NF-κB signaling by suppressing the recruitment of TRAF6 to STING, in addition to attenuating osteoclastogenesis and OVX-induced bone loss in vivo, suggesting that it could be a promising candidate for treating osteoporosis in the future.

The Novel p38 Inhibitor, Pamapimod, Inhibits Osteoclastogenesis and Counteracts Estrogen-Dependent Bone Loss in Mice.

Pamapimod (PAM) is a novel selective p38 mitogen-activated protein (MAP) kinase inhibitor proved to be effective in rheumatoid arthritis in phase 2 clinical trial. However, its effect on osteoclast-associated osteoporosis and the underlying mechanisms remain unclear. In this study, we showed that PAM suppressed receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation via inhibition of p38 phosphorylation and subsequent c-Fos and nuclear factor of activated T cells c1 (NFATc1) expression. In addition, the downregulated NFATc1 leads to reduced expression of its targeting gene disintegrin and metalloproteinase domain-containing protein 12 (ADAM12), which was further proven to be critical for osteoclastic bone resorption. Therefore, we treated ovariectomized (OVX) mice with PAM and revealed a protective effect of PAM on osteoporosis in vivo. In conclusion, our results demonstrated PAM can prevent OVX-induced bone loss through suppression of p38/NFATc1-induced osteoclast formation and NFATc1/ADAM12-associated bone resorption. © 2018 American Society for Bone and Mineral Research.

SREBP-2 aggravates breast cancer associated osteolysis by promoting osteoclastogenesis and breast cancer metastasis.

Bone is one of the most common sites of breast cancer metastasis and a major cause of high mortality in these patients. Thus, further understanding the molecular mechanisms regulating breast cancer-induced osteolysis is critical for the development of more effective treatments. In this study, we demonstrated that important roles sterol regulatory element-binding protein 2 (SREBP-2) play in osteoclast formation a function, and in breast cancer metastasis. SREBP-2 expression was found to be induced during the early stages of osteoclast formation under the control of the RANKL/cAMP-response element binding protein (CREB) signaling cascade. SREBP-2 is subsequently translocated into the nucleus where it participates with other transcriptional factors to induce the expression of NFATc1 required for mature osteoclast formation. Additionally, SREBP-2 was also found to be highly expressed in breast cancer tissues and correlated with a poor prognosis. SREBP-2 was similarly under the transcriptional control of CREB and its induction regulates the expression of matrix metalloproteinases (MMPs), key degradative enzymes involved in bone metastases by breast cancer cells. Accordingly, targeting of SREBP-2 with Fatostatin which specifically inhibits SCAP (SREBP cleavage-activating protein) and prevents SREBP activation, attenuated breast cancer-induced osteolysis in vivo. Collectively, our results suggest that SREBP-2 plays a critical role in regulating osteoclastogenesis and contributes to breast cancer-induced osteolysis. Thus, SREBP-2 inhibition is a potential therapeutic approach for breast cancer patients with osteolytic bone lesions.

Administration of SB239063 Ameliorates Ovariectomy-Induced Bone Loss via Suppressing Osteoclastogenesis in Mice.

Activation of osteoclast formation and function is crucial for the development of osteolytic diseases such as osteoporosis. RANKL (receptor activator of nuclear factor-κB ligand) activates NF-κB (nuclear factor κB), MAPK (mitogen-activated protein kinase), and NFATc1 (nuclear factor of activated T-cells, cytoplasmic 1) signaling pathways to induce osteoclastogenesis. In this study, we demonstrated that SB239063, a p38-specific inhibitor, suppressed osteoclastogenesis and bone resorption via inhibiting phosphorylation of MEF2C (myocyte enhancer factor 2C) and subsequently leading to MEF2C degradation by ubiquitination. Knockdown of MEF2C impaired osteoclast formation due to decreased c-Fos expression. Furthermore, MEF2C can directly bind to the promoter region of c-Fos to initiate its transcription. Interestingly, overexpression of either MEF2C or c-Fos can partially rescue the inhibitory effect of SB239063 on osteoclastogenesis. In addition, in vivo data proved that SB239063 also played a preventive role in both LPS (lipopolysaccharide)- and OVX (ovariectomy)-induced bone loss in mice. In conclusion, our results show that SB239063 can be a potential therapy for osteolytic diseases, and a novel p38/MEF2C/c-Fos axis is essential for osteoclastogenesis.

Ascorbic Acid Attenuates Multifidus Muscles Injury and Atrophy After Posterior Lumbar Spine Surgery by Suppressing Inflammation and Oxidative Stress in a Rat Model.

STUDY DESIGN: A rat model of multifidus muscles injury and atrophy after posterior lumbar spine surgery. OBJECTIVE: We determined the effect of ascorbic acid (AA) on the postoperative multifidus muscles in rat model. SUMMARY OF BACKGROUND DATA: Previous studies show oxidative stress and inflammation are two main molecular mechanisms in multifidus muscle injury and atrophy after posterior lumbar surgery. AA may have a protective effect in postoperative multifidus muscles. METHODS: Rats were divided into sham surgery, control surgery, and surgery plus AA groups. Multifidus muscles of the control and AA groups were excised from the osseous structures. The muscles were retracted continuously for 2 hours. In the sham and AA groups, AA was administered via oral gavage daily in the first week. In each group, the oxidative stress was evaluated by measuring malondialdehyde (MDA) and Total superoxide dismutase (T-SOD). The inflammation, fat degeneration, or fibrosis of multifidus muscle were evaluated by quantitative real-time polymerase chain reaction (q-PCR), histology, or immunohistochemical analysis. RESULTS: T-SOD activity was significantly lower in the control group than that in the AA group in the first week. MDA levels were significantly higher in the AA group. Interleukin-6 and tumor necrosis factor-α in multifidus muscles also showed significant differences when treated with AA. The inflammation score on histology was significantly lower in the AA group postoperatively in the first week. In the long run, marker genes for fibrosis and fat degeneration, and fibrosis and fat degeneration scores, were significantly lower in the AA than the control group on days 14 and 28 postoperatively. CONCLUSION: In conclusion, AA attenuated the oxidative stress and inflammation response in the postoperative multifidus muscles, and remarkable differences were observed from the histological assessment and related marker genes expression. Our results provided important insight into the anti-inflammatory and anti-oxidative effects of AA in the postoperative multifidus muscles. LEVEL OF EVIDENCE: N/A.