Cyclic Compressive Stress Regulates Apoptosis in Rat Osteoblasts: Involvement of PI3K/Akt and JNK MAPK Signaling Pathways

Taenia solium cysticerci's extracellular vesicles Attenuate the AKT/mTORC1 pathway for Alleviating DSS-induced colitis in a murine model

The excretory-secretory proteome plays a pivotal role in both intercellular communication during disease progression and immune escape mechanisms of various pathogens including cestode parasites like Taenia solium. The cysticerci of T. solium causes infection in the central nervous system known as neurocysticercosis (NCC), which affects a significant population in developing countries. Extracellular vesicles (EVs) are 30-150-nm-sized particles and constitute a significant part of the secretome. However, the role of EV in NCC pathogenesis remains undetermined. Here, for the first time, we report that EV from T. solium larvae is abundant in metabolites that can negatively regulate PI3K/AKT pathway, efficiently internalized by macrophages to induce AKT and mTOR degradation through auto-lysosomal route with a prominent increase in the ubiquitination of both proteins. This results in less ROS production and diminished bacterial killing capability among EV-treated macrophages. Due to this, both macro-autophagy and caspase-linked apoptosis are upregulated, with a reduction of the autophagy substrate sequestome 1. In summary, we report that T. solium EV from viable cysts attenuates the AKT-mTOR pathway thereby promoting apoptosis in macrophages, and this may exert immunosuppression during an early viable stage of the parasite in NCC, which is primarily asymptomatic. Further investigation on EV-mediated immune suppression revealed that the EV can protect the mice from DSS-induced colitis and improve colon architecture. These findings shed light on the previously unknown role of T. solium EV and the therapeutic role of their immune suppression potential.

Periodic Mechanical Stress Inhibits the Development of Osteoarthritis via Regulating ATF3-Akt Axis

Purpose

The development of osteoarthritis (OA) has been linked to mechanical factors. Studies suggest that periodic mechanical stress (PMS) may be a factor contributing to cartilage repair and the onset of OA. Therefore, this study was designed to explore the effects and underlying mechanisms of PMS on OA development.

Patients and Methods

Firstly, surgery and interleukin (IL)-1β were used for the establishment of rat/cell models of OA, respectively. Subsequently, activating transcription factor (ATF) 3 expression was knocked down in OA rats, and OA chondrocytes were treated with different heights (0, 1, 2, 4, 8 cm) of PMS or si-ATF. Safranin O staining was used to observe the histological changes in the rat knee joint, and enzyme-linked immunosorbent assay (ELISA) was performed to detect levels of tumor necrosis factor (TNF)-α, IL-6, and IL-8 in vivo and in vitro. Further, the expression of extracellular matrix (ECM) proteins in the rat knee joint was assessed immunohistochemistry. Flow cytometry was used to evaluate chondrocyte apoptosis. Lastly, Western blot was performed to detect the expression of related proteins of the protein kinase B (Akt) signaling pathway and ECM.

Results

The OA rat model was successfully constructed. Further experiments indicated that the knockdown of ATF3 not only alleviated joint swelling, pain, inflammatory response and pathological damage, but also promoted ECM synthesis and the phosphorylation of Akt in OA rats. In vitro experiments showed that PMS (4 cm) effectively inhibited cell apoptosis, decreased the levels of TNF-α, IL-6 and IL-8, promoted ECM synthesis, and activated the Akt signaling pathway in osteoarthritic chondrocytes. However, ATF3 overexpression reversed the positive effects of PMS on osteoarthritic chondrocytes.

Conclusion

PMS can effectively inhibit the development of OA, and its protective effects may be attributed to the down-regulation of ATF3 expression and activation of the Akt signaling pathway.

Reactive oxygen species-mediated endoplasmic reticulum stress contributes to osteocyte death induced by orthodontic compressive force

During orthodontic tooth movement (OTM), osteocytes, the most mechanosensitive cells in alveolar bone, suffer the heavy orthodontic force and initiate alveolar bone resorption on the compression side. However, the inherent mechanisms of compressive force-induced osteocyte death are not fully understood. In this study, we established an OTM model on Sprague-Dawley rats by inserting coil springs to investigate osteocyte damage on the compression side of alveolar bone. We then applied compressive force on the MLO-Y4 osteocyte-like cell line in vitro to explore whether the reactive oxygen species (ROS)-mediated endoplasmic reticulum stress (ERS) pathway is involved in compressive force-induced osteocyte death. We found that the orthodontic force caused apparent alveolar bone loss, osteocyte death, and elevated serum sclerostin and receptor activator of NF-κB ligand (RANKL) levels in rats. In vitro, compressive force inhibited cell viability but increased the LDH leakage and loss of mitochondrial membrane potential in MLO-Y4 cells. Simultaneously, it activated protein kinase RNA-like endoplasmic reticulum kinase (PERK), eukaryotic translation initiation factor 2 (eIF2α), and their downstream pro-apoptotic ERS signaling proteins and caused significant osteocyte apoptosis, which can be blocked by ERS inhibitor salubrinal. Moreover, the compressive force elevated intracellular ROS levels, while the ROS scavenger N-acetyl-L-cysteine (NAC) alleviated ERS and apoptosis in loaded osteocytes. These results suggest that the orthodontic compressive force induced osteocyte apoptosis via the ROS-mediated ERS pathway. This study first proposes the ERS pathway as a new potential pathway for regulating the rate of OTM based on osteocyte death. RESEARCH HIGHLIGHTS: The orthodontic force increases osteocyte death in rat alveolar bone. The compressive force causes osteocyte apoptosis by the endoplasmic reticulum stress (ERS) pathway in vitro. The ROS scavenger NAC blocked compressive force-induced ERS and osteocyte apoptosis.

Integrin αVβ3 Signaling in the Progression of Osteoarthritis Induced by Excessive Mechanical Stress

Osteoarthritis (OA) is believed to be linked with cartilage degeneration, subchondral bone sclerosis, and synovial inflammation that lead to joint failure, and yet treatment that can effectively reverse the pathological process of the disease still not exists. Recent evidence suggests excessive mechanical stress (eMS) as an essential role in the pathogenesis of OA. Increased levels of integrin αVβ3 have been detected in osteoarthritic cartilage and were previously implicated in OA pathogenesis. However, the role of integrin αVβ3 in the process of eMS-induced OA remains unclear. Here, histologic and proteomic analyses of osteoarthritic cartilage in a rat destabilization of the medial meniscus model demonstrated elevated expression of integrin αVβ3 as well as more serious cartilage degeneration in the medial weight-bearing area. Furthermore, results of in vitro study demonstrated that eMS led to a significant increase of integrin αVβ3 expression and phosphorylation of downstream signaling molecules such as FAK and ERK, as well as upregulated expressions of inflammatory and degradative mediators. In addition, we found that inhibition of integrin αVβ3 could alleviate chondrocyte inflammation triggered by eMS both in vivo and in vitro. Our findings suggest a central role for upregulation of integrin αVβ3 signaling in OA pathogenesis and demonstrate that activation of integrin αVβ3 signaling in cartilage contributes to inflammation and joint destruction in eMS-induced OA. Taken together, our data presented here provide a possibility for targeting integrin αVβ3 signaling pathway as a disease-modifying therapy.

Controlled therapeutic delivery of CO from carbon monoxide-releasing molecules (CORMs)

Carbon monoxide (CO) has been regarded as a "silent killer" for its toxicity toward biological systems. However, a low concentration of endogenously produced CO has shown a number of therapeutic benefits such as anti-inflammatory, anti-proliferative, anti-apoptosis, and cytoprotective activities. Carbon monoxide-releasing molecules (CORMs) have been developed as alternatives to direct CO inhalation, which requires a specialized setting for strict dose control. CORMs are efficient CO donors, with central transition metals (such as ruthenium, iron, cobalt, and manganese) surrounded by CO as a ligand. CORMs can stably store and subsequently release their CO payload in the presence of certain triggers including solvent, light, temperature, and ligand substitution. However, CORMs require appropriate delivery strategies to improve short CO release half-life and target specificity. Herein, we highlighted the therapeutic potential of inhalation and CORMs-delivered CO. The applications of conjugate and nanocarrier systems for controlling CO release and improving therapeutic efficacy of CORMs are also described in detail. The review concludes with some of the hurdles that limit clinical translation of CORMs. Keeping in mind the tremendous potential and growing interest in CORMs, this review would be helpful for designing controlled CO release systems for clinical applications.

Cinnamophilin overcomes cancer multi-drug resistance via allosterically modulating human P-glycoprotein on both drug binding sites and ATPase binding sites

Cancer multi-drug resistance (MDR) caused by P-glycoprotein (P-gp) efflux is a critical unresolved clinical concern. The present study analyzed the effect of cinnamophilin on P-gp inhibition and MDR reversion. The effect of cinnamophilin on P-gp was investigated through drug efflux assay, ATPase assay, MDR1 shift assay, and molecular docking. The cancer MDR-reversing ability and mechanisms were analyzed through cytotoxicity and combination index (CI), cell cycle, and apoptosis experiments. P-gp efflux function was significantly inhibited by cinnamophilin without influencing the drug's expression or conformation. Cinnamophilin uncompetitively inhibited the efflux of doxorubicin and rhodamine 123 and exhibited a distinct binding behavior compared with verapamil, the P-gp standard inhibitor. The half maximal inhibitory concentration of cinnamophilin for doxorubicin and rhodamine 123 efflux was 12.47 and 11.59 μM, respectively. In regard to P-gp energy consumption, verapamil-stimulated ATPase activity was further enhanced by cinnamophilin at concentrations of 0.1, 1, 10, and 20 μM. In terms of MDR reversion, cinnamophilin demonstrated synergistic cytotoxic effects when combined with docetaxel, vincristine, or paclitaxel. The CI was < 0.7 in all experimental combination treatments. The present study showed that cinnamophilin possesses P-gp-modulating effects and cancer MDR resensitizing ability.

Exercise improves bone formation by upregulating the Wnt3a/β-catenin signalling pathway in type 2 diabetic mice

BACKGROUND

The bone formation ability of type 2 diabetes is inhibited, and exercise can effectively improve the bone formation of T2DM. However, whether exercise can mediate the Wnt3a/β-catenin pathway to improve the mechanism of bone formation and metabolism still needs further research.

METHODS

A T2DM mouse model was established by a high-fat diet and STZ injection, and the mice were trained with swimming and downhill running exercise. Alizarin red staining is used to observe the changes of the left femoral trabecular bone; micro-CT is used to analyze the trabecular and cortical BMD, BV/TV, BS/BV, BS/TV, Tb.Th, Tb.Sp; the ALP staining of skull was used to observe the changes in ALP activity of bone tissues at the skull herringbone sutures; ALP staining was performed to observe the changes in the number of OBs and ALP activity produced by differentiation; Quantitative PCR was used to detect mRNA expression; Western blot was used to detect protein expression levels.

RESULTS

When the Wnt3a/β-catenin pathway in the bones of T2DM mice was inhibited, the bone formation ability of the mice was significantly reduced, resulting in the degradation of the bone tissue morphology and structure. Swimming caused the significant increase in body weight and Runx2 mRNA expression, while downhill running could significantly decrease the body weight of the mice, while the tibia length, wet weight, and the trabecular morphological structure of the distal femur and the indexes of bone histomorphology were significantly improved by activating the Wnt3a/β-catenin pathway.

CONCLUSIONS

Bone formation is inhibited in T2DM mice, leading to osteoporosis. Downhill running activates the Wnt3a/β-catenin pathway in the bones of T2DM mice, promotes OB differentiation and osteogenic capacity, enhances bone formation metabolism, and improves the bone morphological structure.

Targeting autophagy in ischemic stroke: From molecular mechanisms to clinical therapeutics

Stroke constitutes the second leading cause of death and a major cause of disability worldwide. Stroke is normally classified as either ischemic or hemorrhagic stroke (HS) although 87% of cases belong to ischemic nature. Approximately 700,000 individuals suffer an ischemic stroke (IS) in the US each year. Recent evidence has denoted a rather pivotal role for defective macroautophagy/autophagy in the pathogenesis of IS. Cellular response to stroke includes autophagy as an adaptive mechanism that alleviates cellular stresses by removing long-lived or damaged organelles, protein aggregates, and surplus cellular components via the autophagosome-lysosomal degradation process. In this context, autophagy functions as an essential cellular process to maintain cellular homeostasis and organismal survival. However, unchecked or excessive induction of autophagy has been perceived to be detrimental and its contribution to neuronal cell death remains largely unknown. In this review, we will summarize the role of autophagy in IS, and discuss potential strategies, particularly, employment of natural compounds for IS treatment through manipulation of autophagy.

Platyphyllenone Induces Autophagy and Apoptosis by Modulating the AKT and JNK Mitogen-Activated Protein Kinase Pathways in Oral Cancer Cells

Platyphyllenone is a type of diarylheptanoid that exhibits anti-inflammatory and chemoprotective effects. However, its effect on oral cancer remains unclear. In this study, we investigated whether platyphyllenone can promote apoptosis and autophagy in SCC-9 and SCC-47 cells. We found that it dose-dependently promoted the cleavage of PARP; caspase-3, -8, and -9 protein expression; and also led to cell cycle arrest at the G2/M phase. Platyphyllenone up-regulated LC3-II and p62 protein expression in both SCC-9 and SCC-47 cell lines, implying that it can induce autophagy. Furthermore, the results demonstrated that platyphyllenone significantly decreased p-AKT and increased p-JNK1/2 mitogen-activated protein kinase (MAPK) signaling pathway in a dose-dependent manner. The specific inhibitors of p-JNK1/2 also reduced platyphyllenone-induced cleavage of PARP, caspase-3, and caspase -8, LC3-II and p62 protein expression. These findings are the first to demonstrate that platyphyllenone can induce both autophagy and apoptosis in oral cancers, and it is expected to provide a therapeutic option as a chemopreventive agent against oral cancer proliferation.

Phyllanthin inhibits MOLT-4 leukemic cancer cell growth and induces apoptosis through the inhibition of AKT and JNK signaling pathway

Among cancers, leukemia is a multistep progression that involves genetic modifications of normal hematopoietic progenitor cells to cancerous cells. In recent times, leukemia cases and their mortality rate have increased rapidly. Therefore, the immense need for a therapeutic approach is crucial that can control this type of cancer. Phyllanthin is a lignan compound constituent from the Phyllanthus species and has numerous beneficial effects as a dietary component. The present study aims to determine the impact of phyllanthin on the MOLT-4 cytotoxic effect. MOLT-4 cells and MS-5 cells were cultured at different concentrations of phyllanthin (5, 10, 25, 50, 75, and 100 μM/ml), and the viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. The level of reactive oxygen species, the membrane potential of mitochondria, apoptosis by 2',7'-dichlorofluorescin-diacetate (DCF-DA), rhodamine, acridine orange (AO)/ethidium bromide (EB), 4',6-diamidino-2-phenylindole (DAPI)/propidium iodide (PI) staining, gene expression of signaling molecules, and protein levels were assessed by reverse-transcription polymerase chain reaction and western blot analysis. Phyllanthin did not show toxicity toward MS-5 cells and significantly decreased the cell viability of MOLT-4 cells with an IC₅₀ value of 25 µM/ml. Also, phyllanthin induced the production of reactive oxygen species and led to the loss of mitochondrial membrane potential. AO/EB and DAPI/PI staining fluorescent image confirmed the induction of apoptosis by phyllanthin treatment. The messenger RNA (mRNA) expression of cell cycle regulator cyclin D1, antiapoptotic gene Bcl-2, NF-κB, and TNF-α decreased, but the proapoptotic Bax mRNA expression was increased. The phosphorylated protein levels of p-PI3K1/2, p-ERK1/2, and p-AKT were decreased, whereas the levels of p-p38 and p-JNKT1/2 increased. Our results confirmed that phyllanthin inhibits the MOLT-4 cells, increases apoptosis, and inhibits MOLT-4 migration and cell invasion. Therefore, phyllanthin can be used as a potential target for leukemia treatment.

O-GlcNAc / Akt pathway regulates glucose metabolism and reduces apoptosis in liver of piglets with acute cold stress

Cold stress is one of the serious factors restricting the development of animal husbandry in cold areas. Cold exposure can easily lead to cold stress, slow growth and even death of newborn animals. O-GlcNAcylation modification can act as type of "stress receptor" and"nutrition sensor" in a variety of stress responses, however, it is not clear how O-GlcNAcylation can regulate glucose metabolism in the liver of piglets under cold stress. In this study, piglets 21 days of age were exposed to 4 °C for 4 h or 8 h in a phytotron. Serum cortisol and other stress hormones were used to assess body status to establish a cold stress piglet model. The changes of glycogen in liver were detected by PAS. FDP and PA were also measured to study the glycolysis level of liver. To characterize potential mechanisms of O-GlcNAcylation on the livers of cold stress piglets, AKT, GSK3β, GS, PFKFB2, AS160 and their corresponding phosphorylation were determined by Western blotting. Results show O-GlcNAcylation increased and apoptosis levels increased in the liver following cold exposure during excessive CORT or metabolic dysfunction. It is suggested that the acute cold exposure of piglets induced a sequential change in the level of O-GlcNAcylation, which may be one of the factors mediating liver cell apoptosis and glucose metabolism regulation by the O-GlcNAc/AKT pathway. These findings provide new insight into the mechanisms of the cold stress response, which can facilitate the development of new strategies to combat the effects of hypothermia.

Potential effect of adrenomedullin on metabolic and endocrinal dysfunctions in the experimentally induced polycystic ovary: Targeting implication of endoplasmic reticulum stress

This study investigated the potential effect of adrenomedullin (ADM) on metabolic and endocrinal dysfunctions in experimentally induced polycystic ovary. Twenty-four female Wistar rats were allocated into three groups: control; polycystic ovary syndrome (PCOS) in which PCOS was induced by letrozole, orally in a dose of 1 mg/kg once daily for 3 weeks; and ADM group in which ADM was injected intraperitonally in a dose of 3.5/μg/twice daily for 4 weeks. At the end of the experimental period, the serum sex hormone profile, ADM, fasting glucose, insulin, homeostatic model assessment of insulin resistance, and lipid parameters were determined. Ovarian tissue homogenates were used to determine malondialdehyde, total antioxidant capacity, glutathione peroxidase activity, tumor necrosis factor α, interleukin 6, B cell lymphoma-2 (Bcl-2), and Bcl-2 associated X protein. The profibrotic growth factors, including transforming growth factor β1 and connective tissue growth factor, were determined; and also, the relative gene expression of endoplasmic reticulum (ER) stress, including (Xbox-binding protein-1 [XBP-1], activating transcription factor 6 [ATF6], and homologous protein [CHOP]), serine/threonine kinase 1 (Akt1), phosphatidylinositol 3-kinase (PI3K), and peroxisome proliferator-activated receptor γ (PPAR-γ) were determined. Finally, histopathological analysis of the ovaries was evaluated. PCOS group exhibited increased ER stress, suppressing of PI3K/Akt1 and PPAR-γ pathways, imbalance of sex hormonal profile, hyperglycemia, insulin resistance, dyslipidemia, increased profibrotic factors, and abnormal ovarian histopathological picture, while ADM treatment alleviated these disturbances occurring in the PCOS model. We concluded that ADM mitigated PCOS via attenuating the ER stress, in addition to activation of PI3K/Akt1 and PPAR-γ pathways, its antioxidant, anti-inflammatory, antiapoptotic, and antifibrotic properties.

Role of microRNAs in Pressure Ulcer Immune Response, Pathogenesis, and Treatment

Pressure ulcers are preventable, yet highly prevalent, chronic wounds that have significant patient morbidity and high healthcare costs. Like other chronic wounds, they are characterized by impaired wound healing due to dysregulated immune processes. This review will highlight key biochemical pathways in the pathogenesis of pressure injury and how this signaling leads to impaired wound healing. This review is the first to comprehensively describe the current literature on microRNA (miRNA, miR) regulation of pressure ulcer pathophysiology.

Regulation of Autophagic Signaling by Mechanical Loading and Inflammation in Human PDL Fibroblasts

Autophagy (cellular self-consumption) is a crucial adaptation mechanism during cellular stress conditions. This study aimed to examine how this important process is regulated in human periodontal ligament (PDL) fibroblasts by mechanical and inflammatory stress conditions and whether the mammalian target of rapamycin (mTOR) signaling pathway is involved. Autophagy was quantified by flow cytometry. Qualitative protein phosphorylation profiling of the mTOR pathway was carried out. Effects of mTOR regulation were assessed by quantification of important synthesis product collagen 1, cell proliferation and cell death with real-time PCR and flow cytometry. Autophagy as a response to mechanical or inflammatory treatment in PDL fibroblasts was dose and time dependent. In general, autophagy was induced by stress stimulation. Phosphorylation analysis of mTOR showed regulatory influences of mechanical and inflammatory stimulation on crucial target proteins. Regulation of mTOR was also detectable via changes in protein synthesis and cell proliferation. Physiological pressure had cell-protective effects (p = 0.025), whereas overload increased cell death (p = 0.003), which was also promoted in long-term inflammatory treatment (p < 0.001). Our data provide novel insights about autophagy regulation by mechanical and inflammatory stress conditions in human PDL fibroblasts. Our results suggest some involvement of the mTOR pathway in autophagy and cell fate regulation under the named conditions.

ConBr lectin modulates MAPKs and Akt pathways and triggers autophagic glioma cell death by a mechanism dependent upon caspase-8 activation

Glioblastoma multiforme is the most aggressive type of glioma, with limited treatment and poor prognosis. Despite some advances over the last decade, validation of novel and selective antiglioma agents remains a challenge in clinical pharmacology. Prior studies have shown that leguminous lectins may exert various biological effects, including antitumor properties. Accordingly, this study aimed to evaluate the mechanisms underlying the antiglioma activity of ConBr, a lectin extracted from the Canavalia brasiliensis seeds. ConBr at lower concentrations inhibited C6 glioma cell migration while higher levels promoted cell death dependent upon carbohydrate recognition domain (CRD) structure. ConBr increased p38^MAPK and JNK and decreased ERK1/2 and Akt phosphorylation. Moreover, ConBr inhibited mTORC1 phosphorylation associated with accumulation of autophagic markers, such as acidic vacuoles and LC3 cleavage. Inhibition of early steps of autophagy with 3-methyl-adenine (3-MA) partially protected whereas the later autophagy inhibitor Chloroquine (CQ) had no protective effect upon ConBr cytotoxicity. ConBr also augmented caspase-3 activation without affecting mitochondrial function. Noteworthy, the caspase-8 inhibitor IETF-fmk attenuated ConBr induced autophagy and C6 glioma cell death. Finally, ConBr did not show cytotoxicity against primary astrocytes, suggesting a selective antiglioma activity. In summary, our results indicate that ConBr requires functional CRD lectin domain to exert antiglioma activity, and its cytotoxicity is associated with MAPKs and Akt pathways modulation and autophagy- and caspase-8- dependent cell death.

Morusin Suppresses Cancer Cell Invasion and MMP-2 Expression through ERK Signaling in Human Nasopharyngeal Carcinoma

The most important cause of treatment failure of nasopharyngeal carcinoma (NPC) patients is metastasis, including regional lymph nodes or distant metastasis, resulting in a poor prognosis and challenges for treatment. In the present study, we investigated the in vitro anti- tumoral properties of morusin on human nasopharyngeal carcinoma HONE-1, NPC-39, and NPC-BM cells. Our study revealed that morusin suppressed the migration and invasion abilities of the three NPC cells. Gelatin zymography assay and Western blotting demonstrated that the enzyme activity and the level of matrix metalloproteinases-2 (MMP-2) protein were downregulated by the treatment of morusin. Mitogen-activated protein kinase proteins were examined to identify the signaling pathway, which showed that phosphorylation of ERK1/2 was inhibited after the treatment of morusin. In summary, our data showed that morusin inhibited the migration and invasion of NPC cells by suppressing the expression of MMP-2 by downregulating the ERK1/2 signaling pathway, suggesting that morusin may be a potential candidate for chemoprevention or adjuvant therapy of NPC.

β1 integrin, ILK and mTOR regulate collagen synthesis in mechanically loaded tendon cells

Tendons are specialized tissues composed primarily of load-responsive fibroblasts (tenocytes) embedded in a collagen-rich extracellular matrix. Habitual mechanical loading or targeted exercise causes tendon cells to increase the stiffness of the extracellular matrix; this adaptation may occur in part through collagen synthesis or remodeling. Integrins are likely to play an important role in transmitting mechanical stimuli from the extracellular matrix to tendon cells, thereby triggering cell signaling pathways which lead to adaptive regulation of mRNA translation and protein synthesis. In this study, we discovered that mechanical stimulation of integrin β1 leads to the phosphorylation of AKT, an event which required the presence of integrin-linked kinase (ILK). Repetitive stretching of tendon cells activates the AKT and mTOR pathways, which in turn regulates mRNA translation and collagen expression. These results support a model in which integrins are an upstream component of the mechanosensory cellular apparatus, regulating fundamental tendon cell functions relevant to exercise-induced adaptation and mechanotherapy.

Fluid shear stress induces Runx-2 expression via upregulation of PIEZO1 in MC3T3-E1 cells

Mechanically induced biological responses in bone cells involve a complex biophysical process. Although various mechanosensors have been identified, the precise mechanotransduction pathway remains poorly understood. PIEZO1 is a newly discovered mechanically activated ion channel in bone cells. This study aimed to explore the involvement of PIEZO1 in mechanical loading (fluid shear stress)-induced signaling cascades that control osteogenesis. The results showed that fluid shear stress increased PIEZO1 expression in MC3T3-E1 cells. The fluid shear stress elicited the key osteoblastic gene Runx-2 expression; however, PIEZO1 silencing using small interference RNA blocked these effects. The AKT/GSK-3β/β-catenin pathway was activated in this process. PIEZO1 silencing impaired mechanically induced activation of the AKT/GSK-3β/β-catenin pathway. Therefore, the results demonstrated that MC3T3-E1 osteoblasts required PIEZO1 to adapt to the external mechanical fluid shear stress, thereby inducing osteoblastic Runx-2 gene expression, partly through the AKT/GSK-3β/β-catenin pathway.

Combination of KRAS gene silencing and PI3K inhibition for ovarian cancer treatment

The phosphoinositide 3-kinase (PI3K) and RAS signaling pathways are frequently co-activated and altered during oncogenesis. Owing to their regulatory cross-talk, the early attempts of targeting only one pathway have mostly ended up promoting the development of drug resistance. Here, we propose using small interfering RNA (siRNA) therapeutics to directly target the undruggable KRAS (siKRAS) in combination with the pan-PI3K inhibitor GDC-0941 (GDC) to simultaneously block both PI3K and RAS signaling, thereby exerting synergistic anti-tumor effects on ovarian cancers with PTEN deficiency and KRAS^G12D mutation. For successful delivery of siKRAS, tGC/psi-nanoparticle formulation of polymerized siRNA and thiol-modified glycol chitosan nanoparticle-was used for KRAS specific inhibition in vitro and in vivo. GDC or siKRAS monotherapy each impede downstream signaling, leading to some delay in cell proliferation and migration. When combined, however, they engender much higher inhibition of PI3K signaling and stimulation of apoptosis in an ovarian allograft model compared to monotherapies. Our results show the feasibility of developing new combination strategies for the management of multiple oncogenic mutations activating PI3K and RAS signaling.

Co-culture with synovial tissue in patients with rheumatoid arthritis suppress cell proliferation by regulating MAPK pathway in osteoblasts

There is growing evidence that synovial tissue affects osteoblasts although the mechanisms behind the aberrant bone metabolism in rheumatoid arthritis (RA) are unclear. The aim of this study is to preliminarily establish a co-culture system of rheumatoid arthritis-derived synovial tissue (RAS) and osteoblasts in vitro and to investigate the potential mechanism of RAS on osteoblasts. A consistent volume of approximately 85 mm³ of RAS was cultured isolated and co-cultured with Hfob1.19 cells for up to 21 days. Equal volume of normal synovial tissue (NS) was co-cultured as a control group. Cell proliferation, cell cycle and bone markers were valued and the mechanisms underlying MAPK pathway have been fully delineated. Our findings suggested that co-cultures with RAS exhibited decreased proliferation of Hfob1.19 cells. Moreover, gene and protein expressions of GLUT3 in cells were suppressed, and the cell cycle was also down-regulated. The expressions of related proteins of MAPKs (JNK and p38) signaling pathway were found to be inhibited. Rescue experiments demonstrated that co-cultures with RAS could decrease the growth and cell cycle of Hfob1.19 cells, which were reversed by p-JNK and p-p38 over expression. In conclusion, this study suggested that synovial tissue in patients with RA may negatively regulate osteoblasts proliferation by declining MAPK pathway.

[Pulsed electromagnetic fields stimulating osteogenic differentiation and maturation involves primary cilia-PI3K/AKT pathway]

OBJECTIVE

To study whether the pulsed electromagnetic fields (PEMF) promoting rat osteoblasts differentiation and maturation is related to the primary cilia and PI3K/AKT pathway, and to explore the mechanism of PEMF in promoting bone differentiation.

METHODS

Enzyme solution was used to obtain newborn SD rats calvarial osteoblasts (ROB), which were processed by 50 Hz 0.6 mT PEMF for 0, 0.5, 1, 1.5 and 2 h, detecting PI3K and AKT protein expression and changes in primary cilia length and incidence; with LY294002 blocking PI3K/AKT signaling pathways we observed whether PEMF promoted osteogenic differentiation of ROB was affected; by interfering IFT88 gene expression by RNAi to inhibit primary cilia we observed whether PI3K/AKT signaling pathway and osteogenic differentiation of ROB was affected. Osteogenic differentiation indexes included alkaline phosphatase (ALP) activity, Real-time PCR and Western blot detection of osteogenic related genes of BMP-2, COL-1 and OSX and calcified nodules number, etc..

RESULTS

After exposure to PEMF for 0, 0.5, 1, 1.5, and 2 h, the protein expression of PI3K and AKT in ROB were increased significantly (P<0.01) and the primary cilia became longer; and the protein expression of PI3K reached the highest level at 0.5 h, as the treatment time of PEMF increased, the PI3K protein expression decreased. AKT showed higher protein expression at 0.5 h and 1.5 h. After blocking the PI3K/AKT signaling pathway with the PI3K blocker LY294002, PEMF could no longer increase ALP activity and the gene expressions of BMP-2, COL-1, OSX which were osteogenically related. However, PEMF could increase the ALP activity and the osteogenically related gene expression in ROB before blocking. After RNAi interfered the primary cilia, PEMF could no longer increase the protein expression of PI3K, which indicated that PEMF could not activate the PI3K/AKT signaling pathway after primary cilia interfering; secondly, the effect of PEMF on enhancing ALP activity disappeared, it also decrease the gene expressions of BMP-2, COL-1, and OSX, and the ability of increasing the calcification nodule formation also disappeared, indicating that the ability of PEMF to promote osteoblast maturation and mineralization disappeared after primary cilia interference.

CONCLUSION

PEMF activated the PI3K/AKT signaling pathway through primary cilia on the surface of osteoblasts, then promoted bone formation activity and differentiation.

[Pulsed electromagnetic fields stimulating osteogenic differentiation and maturation involves primary cilia-PI3K/AKT pathway]

OBJECTIVE

To study whether the pulsed electromagnetic fields (PEMF) promoting rat osteoblasts differentiation and maturation is related to the primary cilia and PI3K/AKT pathway, and to explore the mechanism of PEMF in promoting bone differentiation.

METHODS

Enzyme solution was used to obtain newborn SD rats calvarial osteoblasts (ROB), which were processed by 50 Hz 0.6 mT PEMF for 0, 0.5, 1, 1.5 and 2 h, detecting PI3K and AKT protein expression and changes in primary cilia length and incidence; with LY294002 blocking PI3K/AKT signaling pathways we observed whether PEMF promoted osteogenic differentiation of ROB was affected; by interfering IFT88 gene expression by RNAi to inhibit primary cilia we observed whether PI3K/AKT signaling pathway and osteogenic differentiation of ROB was affected. Osteogenic differentiation indexes included alkaline phosphatase (ALP) activity, Real-time PCR and Western blot detection of osteogenic related genes of BMP-2, COL-1 and OSX and calcified nodules number, etc..

RESULTS

After exposure to PEMF for 0, 0.5, 1, 1.5, and 2 h, the protein expression of PI3K and AKT in ROB were increased significantly (P<0.01) and the primary cilia became longer; and the protein expression of PI3K reached the highest level at 0.5 h, as the treatment time of PEMF increased, the PI3K protein expression decreased. AKT showed higher protein expression at 0.5 h and 1.5 h. After blocking the PI3K/AKT signaling pathway with the PI3K blocker LY294002, PEMF could no longer increase ALP activity and the gene expressions of BMP-2, COL-1, OSX which were osteogenically related. However, PEMF could increase the ALP activity and the osteogenically related gene expression in ROB before blocking. After RNAi interfered the primary cilia, PEMF could no longer increase the protein expression of PI3K, which indicated that PEMF could not activate the PI3K/AKT signaling pathway after primary cilia interfering; secondly, the effect of PEMF on enhancing ALP activity disappeared, it also decrease the gene expressions of BMP-2, COL-1, and OSX, and the ability of increasing the calcification nodule formation also disappeared, indicating that the ability of PEMF to promote osteoblast maturation and mineralization disappeared after primary cilia interference.

CONCLUSION

PEMF activated the PI3K/AKT signaling pathway through primary cilia on the surface of osteoblasts, then promoted bone formation activity and differentiation.

Effect of Mechanical Stretch on the DNCB-induced Proinflammatory Cytokine Secretion in Human Keratinocytes

Skin is exposed to various physico-chemical cues. Keratinocytes, a major component of the skin epidermis, directly interact with the surrounding extracellular matrix, and thus, biochemical and biophysical stimulations from the matrix regulate the function of keratinocytes. Although it was reported that inflammatory responses of skin were altered by an applied mechanical force, understanding how the keratinocytes sense the mechanical stimuli and regulate a cytokine secretion remains unclear. Here, we designed a device that is able to apply chemo-mechanical cues to keratinocytes and assess their proinflammatory cytokine IL-6 production. We showed that when chemical stimuli were applied with mechanical stimuli simultaneously, the IL-6 production markedly increased compared to that observed with a single stimulus. Quantitative structural analysis of cellular components revealed that the applied mechanical stretch transformed the cell morphology into an elongated shape, increased the cell size, and dictated the distribution of focal adhesion complex. Our results suggest that the mechanical cue-mediated modulation of focal adhesion proteins and actin cytoskeleton translates into intracellular signaling associated with the IL-6 production particularly in skin sensitization. Our study can be applied to understand proinflammatory responses of skin under altered biophysical environments of the skin.

The role of physical forces in osteoclastogenesis

The movements of life at every level from organs, tissues, cells to sub-cells, are all conducted in certain physical environments. In the human body, skeletal tissue among all connective tissues is influenced the most by physical forces. Studying the biological behavior of bone cells under different physical environments is helpful in further understanding bone homeostasis and metabolism. Among all bone cells, osteoclast (OC) and OC steered bone remodeling is one of the key points in bone metabolism. In the past few decades, people's understanding of OC was mostly limited to its involvement of bone resorption under physiological and pathological conditions. However, more and more studies started to focus on how physical forces affect the formation and differentiation of OC. This review tries to illustrate the knowledge up to date about how osteoclastogenesis is regulated by physical forces through direct and indirect ways, including fluid shear force, compressive force, and microgravity. The direct way describes the straightforward effects produced by different forces in osteoclastogenesis, whereas the indirect way describes the effects of different forces in osteoclastogenesis through regulation of other bone cells when a certain force is applied. Molecular mechanisms were analyzed and reviewed in both direct and indirect regulation by different forces. Finally, we discussed the status quo and tendency of related research, as well as other unresolved issues, and some future prospects.

New application of the commercial sweetener rebaudioside a as a hepatoprotective candidate: Induction of the Nrf2 signaling pathway

A large population of drug candidates have failed "from bench to bed" due to unwanted toxicities. We intend to develop an alternative approach for drug discovery, that is, to seek candidates from "safe" compounds. Rebaudioside A (Reb-A) is an approved commercial sweetener from Stevia rebaudiana Bertoni. We found that Reb-A protects against carbon tetrachloride (CCl₄)-induced oxidative injury in human liver hepatocellular carcinoma (HepG2) cells. Reb-A showed antioxidant activity on reducing cellular reactive oxygen species and malondialdehyde levels while increasing glutathione levels and superoxide dismutase and catalase activities. Reb-A treatment induced nuclear factor erythroid-derived 2-like 2 (Nrf2) activation and antioxidant response element activity, as well as the expression of heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase 1 (NQO1). Further mechanistic studies indicated that c-Jun N-terminal kinase (JNK), extracellular signal-regulated protein kinase (ERK), mitogen-active protein kinase (MAPK) and protein kinase C epsilon (PKCε) signaling was upregulated. Thus, the present in vitro study conclusively demonstrated that Reb-A is an activator of Nrf2 and is a potential candidate hepatoprotective agent. More importantly, the present study illustrated that seeking drug candidates from "safe" compounds is a promising strategy.

Targeting protein for Xenopus kinesin-like protein 2 knockdown enhances radiation sensitivity of human lung squamous carcinoma cell

The targeting protein for Xenopus kinesin-like protein 2 (TPX2) has been demonstrated to be associated with the tumourigenesis of many cancers. In the present study, we investigated the role and preliminary mechanism of TPX2 in the resistance of lung squamous carcinoma to radiation therapy. The results showed that SK-MES-1R and NCI-H226R cells were more resistant to X-ray irradiation than the parental cells (SK-MES-1 and NCI-H226). Moreover, TPX2 was upregulated in the radioresistant cells compared with the parental cells. TPX2 knockdown significantly decreased TPX2 expression in SK-MES-1 cells, while TPX2 overexpression increased TPX2 expression in NCI-H226 cells compared with the corresponding control cells. TPX2 knockdown enhanced the radiosensitivity of SK-MES-1 and promoted cell apoptosis following exposure to irradiation, whereas TPX2 overexpression decreased the radiosensitivity of NCI-H226 and inhibited cell apoptosis. In in vivo studies, the combination of TPX2 knockdown and irradiation significantly inhibited tumour growth, decreased tumour weight, downregulated TPX2 expression in tumour tissue and induced cell apoptosis in nude mice, while TPX2 overexpression exerted an opposite effect. Our results indicated that TPX2 was correlated with cell radioresistance and it might be served as a therapeutic target to enhance cell radiosensitivity in the radiation therapy of lung squamous carcinoma.

Mechanical Loading Improves Tendon-Bone Healing in a Rabbit Anterior Cruciate Ligament Reconstruction Model by Promoting Proliferation and Matrix Formation of Mesenchymal Stem Cells and Tendon Cells

Background/Aims: This study investigated the effect of mechanical stress on tendon-bone healing in a rabbit anterior cruciate ligament (ACL) reconstruction model as well as cell proliferation and matrix formation in co-culture of bone-marrow mesenchymal stem cells (BMSCs) and tendon cells (TCs). Methods: The effect of continuous passive motion (CPM) therapy on tendon-bone healing in a rabbit ACL reconstruction model was evaluated by histological analysis, biomechanical testing and gene expressions at the tendon-bone interface. Furthermore, the effect of mechanical stretch on cell proliferation and matrix synthesis in BMSC/TC co-culture was also examined. Results: Postoperative CPM therapy significantly enhanced tendon-bone healing, as evidenced by increased amount of fibrocartilage, elevated ultimate load to failure levels, and up-regulated gene expressions of Collagen I, alkaline phosphatase, osteopontin, Tenascin C and tenomodulin at the tendon-bone junction. In addition, BMSC/TC co-culture treated with mechanical stretch showed a higher rate of cell proliferation and enhanced expressions of Collagen I, Collagen III, alkaline phosphatase, osteopontin, Tenascin C and tenomodulin than that of controls. Conclusion: These results demonstrated that proliferation and differentiation of local precursor cells could be enhanced by mechanical stimulation, which results in enhanced regenerative potential of BMSCs and TCs in tendon-bone healing.

Mechanical Stress Regulates Osteogenesis and Adipogenesis of Rat Mesenchymal Stem Cells through PI3K/Akt/GSK-3β/β-Catenin Signaling Pathway

Osteogenesis and adipogenesis of bone marrow mesenchymal stem cells (BMSCs) are regarded as being of great importance in the regulation of bone remodeling. In this study, rat BMSCs were exposed to different levels of cyclic mechanical stress generated by liquid drops and cultured in general medium or adipogenic medium. Markers of osteogenic (Runx2 and Collagen I) and adipogenic (C/EBPα, PPARγ, and lipid droplets) differentiation were detected using Western blot and histological staining. The protein levels of members of the phosphatidylinositol 3-kinase (PI3K)/Akt/glycogen synthase kinase 3β (GSK-3β)/β-catenin signaling pathway were also examined. Results showed that small-magnitude stress significantly upregulated Runx2 and Collagen I and downregulated PPARγ and C/EBPα expression in BMSCs cultured in adipogenic medium, while large-magnitude stress reversed the effect when compared with unloading groups. The PI3K/Akt signaling pathway could be strongly activated by mechanical stimulation; however, large-magnitude stress led to decreased activation of the signaling pathway when compared with small-magnitude stress. Activation of β-catenin with LiCl led to increased expression of Runx2 and Collagen I and reduction of C/EBPα and PPARγ expression in BMSCs. Inhibition of PI3K/Akt signaling partially blocked the expression of β-catenin. Taken together, our results indicate that mechanical stress-regulated osteogenesis and adipogenesis of rat BMSCs are mediated, at least in part, by the PI3K/Akt/GSK-3β/β-catenin signaling pathway.