Down-regulation Of Osteopontin Research Articles

Osteopontin drives neuroinflammation and cell loss in MAPT-N279K frontotemporal dementia patient neurons

Frontotemporal dementia (FTD) is an incurable group of early-onset dementias that can be caused by the deposition of hyperphosphorylated tau in patient brains. However, the mechanisms leading to neurodegeneration remain largely unknown. Here, we combined single-cell analyses of FTD patient brains with a stem cell culture and transplantation model of FTD. We identified disease phenotypes in FTD neurons carrying the MAPT-N279K mutation, which were related to oxidative stress, oxidative phosphorylation, and neuroinflammation with an upregulation of the inflammation-associated protein osteopontin (OPN). Human FTD neurons survived less and elicited an increased microglial response after transplantation into the mouse forebrain, which we further characterized by single nucleus RNA sequencing of microdissected grafts. Notably, downregulation of OPN in engrafted FTD neurons resulted in improved engraftment and reduced microglial infiltration, indicating an immune-modulatory role of OPN in patient neurons, which may represent a potential therapeutic target in FTD.

Regulatory roles of Osteopontin in lung epithelial inflammation and epithelial-telocyte interaction.

Lung epithelial cells play important roles in lung inflammation and injury, although mechanisms remain unclear. Osteopontin (OPN) has essential roles in epithelial damage and repair and in lung cancer biological behaviours. Telocyte (TC) is a type of interstitial cell that interacts with epithelial cells to alleviate acute inflammation and lung injury. The present studies aim at exploring potential mechanisms by which OPN regulates the epithelial origin lung inflammation and the interaction of epithelial cells with TCs in acute and chronic lung injury. The lung disease specificity of OPN and epithelial inflammation were defined by bioinformatics. We evaluated the regulatory roles of OPN in OPN-knockdown or over-expressed bronchial epithelia (HBEs) challenged with cigarette smoke extracts (CSE) or in animals with genome OPN knockout (gKO) or lung conditional OPN knockout (cKO). Acute lung injury and chronic obstructive pulmonary disease (COPD) were induced by smoking or lipopolysaccharide (LPS). Effects of OPN on PI3K subunits and ERK were assessed using the inhibitors. Spatialization and distribution of OPN, OPN-positive epithelial subtypes, and TCs were defined by spatial transcriptomics. The interaction between HBEs and TCs was assayed by the co-culture system. Levels of OPN expression increased in smokers, smokers with COPD, and smokers with COPD and lung cancer, as compared with healthy nonsmokers. LPS and/or CSE induced over-production of cytokines from HBEs, dependent upon the dysfunction of OPN. The severity of lung inflammation and injury was significantly lower in OPN-gKO or OPN-cKO mice. HBEs transferred with OPN enhanced the expression of phosphoinositide 3-kinase (PI3K)CA/p110α, PIK3CB/p110β, PIK3CD/p110δ, PIK3CG/p110γ, PIK3R1, PIK3R2 or PIK3R3. Spatial locations of OPN and OPN-positive epithelial subtypes showed the tight contact of airway epithelia and TCs. Epithelial OPN regulated the epithelial communication with TCs, and the down-regulation of OPN induced more alterations in transcriptomic profiles than the up-regulation. Our data evidenced that OPN regulated lung epithelial inflammation, injury, and cell communication between epithelium and TCs in acute and chronic lung injury. The conditional control of lung epithelial OPN may be an alternative for preventing and treating epithelial-origin lung inflammation and injury.

OPN Promotes Cell Proliferation and Invasion through NF-κB in Human Esophageal Squamous Cell Carcinoma.

Osteopontin (OPN) is a phosphorylated glycoprotein. There is increasing evidence that the OPN gene played a major role in the progression of solid organ tumors. However, few studies have clarified how OPN regulated the functional role of human esophageal squamous cell carcinoma (ESCC). This study was designed to investigate the effect of OPN in esophageal squamous cell carcinoma. First, we screened Eca-109 and KYSE-510 cells to construct OPN silencing and overexpression models. Endogenous OPN of Eca-109 and KYSE-510 were knocked down or overexpressed using small interfering RNAs. QRT-PCR, Western blot, flow cytometry, and CCK-8 were used to detect the function of Eca-109 and KYSE-510 cells. Tumor formation in nude mice was used to measure tumor growth after OPN inhibition. Eca-109 and KYSE-510 cells contain the si-OPN arrest cell cycle in the S-phase and increase apoptosis. These changes were OPN downregulation of the NF-κB pathway that significantly reduced the protein levels of TNF-α, IL-1β, and p-p65. However, the activity of Eca-109 and KYSE-510 cells was enhanced in OPN overexpressing cells. Then, the in vivo tumor formation experiment in nude mice showed that the tumor volume and weight of nude mice after silencing OPN were significantly reduced. This study contributed to understanding the vital role of OPN in ESCC development and progression. This could be a promising molecular target for developing new ESCC diagnostic and therapeutic strategies.

Osteopontin silencing attenuates bleomycin-induced murine pulmonary fibrosis by regulating epithelial–mesenchymal transition

Idiopathic pulmonary fibrosis (IPF) is the most common and most deadly form of interstitial lung disease. Osteopontin (OPN), a matricellular protein with proinflammatory and profibrotic properties, plays a major role in several fibrotic diseases, including IPF; OPN is highly upregulated in patients’ lung samples. In this study, we knocked down OPN in a bleomycin (BLM)-induced pulmonary fibrosis (PF) mouse model using small interfering RNA (siRNA) to determine whether the use of OPN siRNA is an effective therapeutic strategy for IPF. We found that fibrosing areas were significantly smaller in specimens from OPN siRNA-treated mice. The number of alveolar macrophages, neutrophils, and lymphocytes in bronchoalveolar lavage fluid was also reduced in OPN siRNA-treated mice. Regarding the expression of epithelial–mesenchymal transition (EMT)-related proteins, the administration of OPN-siRNA to BLM-treated mice upregulated E-cadherin expression and downregulated vimentin expression. Moreover, in vitro, we incubated the human alveolar adenocarcinoma cell line A549 with transforming growth factor (TGF)-β1 and subsequently transfected the cells with OPN siRNA. We found a significant upregulation of Col1A1, fibronectin, and vimentin after TGF-β1 stimulation in A549 cells. In contrast, a downregulation of Col1A1, fibronectin, and vimentin mRNA levels was observed in TGF-β1-stimulated OPN knockdown A549 cells. Therefore, the downregulation of OPN effectively reduced pulmonary fibrotic and EMT changes both in vitro and in vivo. Altogether, our results indicate that OPN siRNA exerts a protective effect on BLM-induced PF in mice. Our results provide a basis for the development of novel targeted therapeutic strategies for IPF.

Red Rooibos Tea Stimulates Osteoblast Mineralization in a Dose-Dependent Manner

Most studies show a positive association between higher tea intake and bone mineral density (BMD), while associations with fracture are inconclusive. Although a few studies have investigated the potential effects of rooibos tea on the bone cell metabolism, only 1 or 2 doses were tested or specific flavonoids were evaluated in isolation. A dose-response study is needed to comprehensively identify whether a level that modulates bone cell activity is associated with dietary or supplemental levels of red rooibos (RR) tea. We investigated if RR tea stimulates mineralization in a dose-dependent manner. Mineralization was induced in Saos-2 cells in the presence of RR tea (0.1–10 µg/mL of polyphenols) or control (dH2O) for 5 days. Cell activity, mRNA, protein expression and activity of key regulators of mineralization were measured. A positive dose-dependent relationship was observed between RR tea concentration and mineralization accompanied with similar trends in cell activity. With high concentrations of tea, protein expression of enzymes directly regulating mineralization (ALP and NPP1) were unchanged but ALP activity was significantly elevated. Osteopontin (OPN) was significantly downregulated midway through mineralization while sclerostin (SOST) was upregulated in response to higher concentrations of RR tea. In conclusion, RR tea stimulated osteoblast mineralization in a dose-dependent manner and were accompanied with downregulation of OPN, increased ALP activity, and increased cell activity.

Downregulation of osteopontin inhibits browning of white adipose tissues through PI3K-AKT pathway in C57BL / 6 mice

Brown adipose tissue (BAT) plays important roles in regulating energy homeostasis and combating obesity. Accordingly, increasing the abundance and/or activating BAT would be effective and promising approaches to combat obesity and obesity-relative diseases. Our previous data in vitro have shown that osteopontin (OPN) induces the brown adipogenesis in 3T3-L1 cells via a phosphatidylinositol 3 kinase (PI3K)-AKT pathway. However, it is currently unknown whether OPN exerts such an effect on animals in vivo. Therefore, in the study we sought to investigate the pro-browning effects of OPN and to explore its underlying mechanisms by transfecting with Ad-GFP-aP2-OPN-shRNA to specifically down-regulate the OPN of white adipose tissue (WAT) in mice. Our present results show that downregulation of OPN in WAT exacerbates obesity and inhibits WAT-browning. Moreover, immunohistochemical results also exhibit that the downregulation of OPN significantly diminishes the expression and sub-cellular localization of UCP-1, PRDM16 and PGC-1α. Besides, the western blotting results reveal that the expression levels of PI3K, AKT-pS473 and PPARγ markedly reduce. Consequently, we conclude that the downregulation of OPN inhibits the browning of WAT through inhibiting the expression of PPARγ mediated by the PI3K-AKT pathway. The findings suggest that OPN is involved in regulation of WAT-browning and regulating its expression would become a potential strategy to combat obesity and obesity-relative metabolic diseases.

Targeting ER\u03b2 in Macrophage Reduces Crown-like Structures in Adipose Tissue by Inhibiting Osteopontin and HIF-1\u03b1

Proinflammatory processes in adipose tissue contribute to development of breast cancer and insulin resistance. Crown-like structures (CLS) are histologic hallmarks of the proinflammatory process in adipose tissue. CLS are microscopic foci of dying adipocytes surrounded by macrophages mostly derived from monocytes in blood. Estrogen receptor β (ERβ) is expressed in microglia, macrophages within the central nervous system (CNS), where it evokes an anti-inflammatory response. The present study investigates the function of ERβ in macrophages within CLS. We report that even though monocytes in the blood have no detectable levels of ERβ, macrophages in CLS do express ERβ. In ERβ−/− mice, there was a significant increase in the number of CLS in both subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT). CLS in these mice were dominated by pro-inflammatory macrophages (M1 macrophages) with higher expression of osteopontin (OPN) and an increase in number of proliferating macrophages. In mice made obese by Western diet, treatment with an ERβ selective agonist (LY3201) reduced the number of CLS in both SAT and VAT with downregulation of OPN, activated hypoxia-inducible factor-1α (HIF-1α), proliferation and upregulation prolyl hydroxylase 2 (PHD2), the enzyme which prevents activation of HIF1α, in macrophages. We conclude that ERβ expression is induced in macrophages in CLS within adipose tissue where it plays a pivotal role in suppression of CLS. Thus ERβ agonists may be used to alleviate CLS-related breast cancer and insulin resistance in adipose tissue.

Luteolin induces caspase-dependent apoptosis via inhibiting the AKT/osteopontin pathway in human hepatocellular carcinoma SK-Hep-1 cells

AimsLuteolin, a naturally occurring flavonoid, possesses anti-cancer effects including induction of apoptosis. This study investigated the involvement of osteopontin (OPN) in luteolin-induced apoptosis in human hepatocellular carcinoma (HCC) SK-Hep-1 cells with high OPN expression. Main methodsMTT assay was used to determine the cell viability. Cell cycle analysis was performed to identify apoptosis. Apoptosis was confirmed by detecting cytoplasmic histone-associated-DNA-fragments using a cell death detection ELISAPLUS kit. The expression of proteins was evaluated by Western blot. Reverse transcriptase-polymerase chain reaction was employed to detect the expression of mRNA. Key findingsCytotoxic effect of luteolin was higher in cancer cell line SK-Hep-1 cells than in normal cell line AML12 cells. Luteolin led a significantly increase in apoptosis accompanied by activation of caspase 8, −9 and −3 and cleavage of poly (ADP-ribose) polymerase (PARP), which was completely blocked by Z-VAD-FMK, a pan caspase inhibitor. Luteolin significantly downregulated the expression of X-linked inhibitor of apoptosis (XIAP), Mcl-1 and Bid. Furthermore, luteolin effectively decreased OPN expression at both mRNA and protein level. Exogenous OPN markedly blocked apoptosis induction, caspases activation, PARP cleavage, downregulation of XIAP and Mcl-1 in luteolin-treated cells. Luteolin impaired the AKT pathway by inhibiting the phosphorylation of AKT. SC79, an AKT activator, blocked apoptosis induction, caspases activation, PARP cleavage, downregulation of OPN, XIAP, Mcl-1 and Bid in luteolin-treated cells. SignificanceThese results demonstrated that luteolin inhibits the AKT/OPN pathway, thereby inducing caspase-dependent apoptosis in human HCC SK-Hep-1 cells with little toxicity.

The prognostic value of osteopontin in limited-stage small cell lung cancer patients and its mechanism.

Osteopontin (OPN) is known to be overexpressed in numerous carcinomas. Although abundant OPN has been reported to be correlated with poor survival in non-small cell lung cancer (NSCLC) but their clinical and prognostic significance in SCLC remains unknown. In this study, RNA-sequencing was used to obtain gene expression data in SCLC tissue samples and OPN expression levels were then investigated using qPCR, immunohistochemical and Western blot. We found OPN was one of the most upregulated genes. Besides, the correlation of OPN with tumor clinicopathological characteristics was evaluated and we found OPN was associated with advanced tumor stages. In addition, Kaplan-Meier survival analysis and Cox analyses revealed OPN expression was an independent predictor for overall survival (OS) (P= 0.013) and progression-free survival (PFS) (P=0.008). A high level of OPN was correlated with pT classification and pN classification (P<0.05). Moreover, In vitro experiments, by test the biological function of OPN via colony formation, wound healing, Transwell assays, and western blotting, we found that overexpression of OPN induced cell proliferation, migration, and invasion; down-regulation of OPN inhibited these. Overexpression of OPN stimulates epithelial-mesenchymal transition (EMT) whereas OPN silencing prevents the EMT. In conclusion: OPN appears to contribute to the malignant mechanism of SCLC and is a promising and significant prognostic predictor in patients with SCLC. Specific silence of OPN could be a future direction to develop a novel therapeutic strategy for SCLC patients.

124 CHANGES IN GENE EXPRESSION FOLLOWING EXPOSURE OF BOVINE ENDOMETRIAL EPITHELIAL CELLS (bEEC) TO ESCHERICHIA COLI LPS; THEIR POSSIBLE EFFECT ON IMPLANTATION

Lipopolysaccharide (LPS) is a component of the outer membrane of gram-negative bacteria and is involved in postpartum uterine infection in cattle. Lipopolysaccharide causes inflammation of the endometrium and the activation of immune and pro-inflammatory pathways in uterine cells has been well documented. This study was performed to investigate the effects of LPS on epithelial cells from whole-genome information, and this abstract focuses on genes and pathways involved in the regulation of implantation. Following in vitro culture of bovine endometrial epithelial cells (bEEC), passage 4 epithelial cell samples from 3 cows were exposed to 0, 2, and 8 µg mL−1 LPS (Sigma L2630, Escherichia coli O111:B4, Sigma Chemical Co., St. Louis, MO, USA) for 24 h. At time 0 and at 24 h for each LPS dosage, RNA was extracted by using the All prep DNA/RNA Universal kit (Qiagen, Valencia, CA, USA). Samples were analysed by RNA sequencing performed in the SciLife Laboratory in Uppsala. Differentially expressed genes (DEG) were identified by using Ensemble genes as a reference. No DEG were found between 2 and 8 µg mL−1 LPS-treated samples and at 24 h 2035 DEG were identified (Benjamini-Hochberg adjusted P-value &lt; 0.05) between controls and samples treated with 2 µg mL−1 LPS. Gene ontology analysis did show that DEG were associated to immune response (up), response to stress and external stimuli (up), catalytic activity (up), cell cycle, anatomical structures especially cell membrane, and adhesion (down) pathways. In the latest, numerous specific genes in relation with implantation were highly deregulated. This includes down-regulation of 8 members of the cadherin superfamily. On the contrary, 4 members of the mucin family were strongly up-regulated by LPS (MUC1, MUC13, MUC16, F1MUC1). Molecules such as plakophilins and desmogleins involved in desmosomes, in tight junctions, and in the control of cell adhesion were also deregulated. Specific changes occurred in immune response related with implantation [strong up-regulation of the immunoglobulin superfamily members such ICAM1 (or CD54) and down-regulation of ALCAM]. A set of 10 molecules belonging to the family of integrins and their binding partners were also deregulated [for instance, down-regulation of osteopontin (SPP1)]. In addition, LPS deregulated a large set of genes binding the above molecules (such as galectins LGALS1, S3, S9) and more than 20 transcripts coding for cytokines and their receptors. A large series of interferon-induced genes (IFITS) and genes coding for interferon-induced trans membrane proteins (IFITM) were highly up-regulated by LPS. This may be of functional importance due to the fact that all those genes are normally up-regulated by interferon tau from embryonic origin. The above results show that the function of endometrial epithelial cells is profoundly affected by LPS and that most of the key signals involved in implantation are deregulated. It is likely that these LPS-induced changes strongly perturb lately endometrial responsiveness to embryos at the time of implantation. Research was done with the financial support of FP7 project “Prolific” and RMUTSV (Thailand).

Identification of brefelamide as a novel inhibitor of osteopontin that suppresses invasion of A549 lung cancer cells.

The contribution of aberrant osteopontin(OPN) expression to tumor progression and metastasis has been documented in a wide spectrum of malignancies, and targeted inhibition of OPN has therefore emerged as an attractive strategy for cancer therapy. Transcription of OPN is regulated by various transcription factors, and our recently published study demonstrated that downregulation of OPN is an important event in the TGF‑β cytostatic program. We report here that brefelamide exerts an inhibitory effect on OPN expression and function in A549 human lung carcinoma cells. The promoter, RNA, and protein levels of OPN were decreased in brefelamide‑treated A549 cells, which was accompanied by reduced invasive abilityinvitro. OPN inhibition by brefelamide was largely abrogated by disruption of a putative TGF‑β inhibitory element in the OPN promoter. Treatment with brefelamide induced Smad4 expression, and knockdown of Smad4 by RNA interference partially diminished the inhibitory effect of brefelamide on OPN. These results indicate that brefelamide inhibited OPN‑mediated cell invasion through restoration of the OPN repression by TGF‑β/Smad signaling. Together with the reported antiproliferative property, our findings suggest that brefelamide might serve as a potential candidate for the development of a new antitumor and antimetastatic agent.

Influence of cyclosporine A on glomerular growth and the effect of mizoribine and losartan on cyclosporine nephrotoxicity in young rats.

The aim of this study was to evaluate the influence of cyclosporine A (CsA) on glomerular growth and the effect of mizoribine (MZR) and losartan (LSAR) on CsA-induced nephropathy in young rats. Six-week-old male Sprague-Dawley rats maintained on a low salt diet were given CsA (15 mg/kg), CsA and LSRT (30 mg/kg/day), CsA and MZR (5 mg/kg), or a combination of CsA, LSRT, and MZR for 4 and 7 weeks (two experiments) and compared with control group (olive oil-treated). Histopathology and glomerular size, inflammatory and fibrotic factors were studied. The score of acute CsA toxicity significantly decreased in the CsA + MZR group compared to the CsA group (p < 0.01). MZR and MZR + LSRT reduced tubulointerstitial fibrosis and TGF-β1 mRNA expression at 7 weeks. Osteopontin (OPN) mRNA expression was decreased at 7 weeks in MZR + LSRT (p < 0.01). Glomerular area decreased CsA group and recovered in MZR (p < 0.01) and MZR + LSRT (p < 0.01) at 7weeks. This study demonstrated that MZR and LSRT had suppressive effects on inflammatory process in chronic CsA nephropathy and led to improvement of tubular damage, tubulointerstitial fibrosis and arteriolopathy by down regulation of OPN and TGF-β1 and glomerular size contraction.

Down-regulation of osteopontin mediates a novel mechanism underlying the cytostatic activity of TGF-β.

Loss of a cytostatic response to TGF-β has been implicated in multiple hyper-proliferative disorders, including cancer. Although several key genes involved in the cytostatic activity of TGF-β have in the past been identified, its exact mode of action is yet to be elucidated. A comprehensive understanding of the mechanisms underlying the cytostatic activity of TGF-β may open up new avenues for the development of therapeutic strategies. Quantitative real-time RT-PCR was used to assess osteopontin (OPN) gene expression in human hepatoma-derived Huh-7 and lung adenocarcinoma-derived A549 cells. Reporter assays using an OPN promoter-luciferase construct and its mutated counterparts were performed to assess its transcriptional activity. Binding of Smad4 to the OPN gene promoter was investigated using chromatin immunoprecipitation (CHIP). The putative role of Smad4 in OPN gene expression down-regulation was also assessed using a shRNA-mediated knockdown strategy. The anti-proliferative effect of TGF-β on different cancer-derived cell lines was determined using the cell proliferation reagent WST-1. We found that the OPN expression levels dose-dependently decreased in TGF-β-treated Huh-7 and A549 cells. Our reporter assays indicated that this TGF-β-induced repression occurred at the transcriptional level, and could largely be abrogated by disruption of an element (TIE2) similar to the TGF-β inhibitory element found in other TGF-β-repressed genes. Our CHIP assay revealed that the Smad protein complex specifically binds to the OPN gene promoter, and that the TGF-β-mediated inhibition of OPN was lost upon shRNA-mediated knockdown of Smad4. Moreover, we found that the deregulation of OPN gene expression by TGF-β occurred concomitantly with loss of the TGF-β anti-proliferative response, whereas a neutralizing anti-OPN antibody partially restored this response. Our results indicate that the OPN gene is a direct target of Smad-mediated TGF-β signaling, implying that OPN expression inhibition serves as a novel mechanism underlying the cytostatic activity of TGF-β.

Gla-rich protein acts as a calcification inhibitor in the human cardiovascular system.

Vascular and valvular calcifications are pathological processes regulated by resident cells, and depending on a complex interplay between calcification promoters and inhibitors, resembling skeletal metabolism. Here, we study the role of the vitamin K-dependent Gla-rich protein (GRP) in vascular and valvular calcification processes. Immunohistochemistry and quantitative polymerase chain reaction showed that GRP expression and accumulation are upregulated with calcification simultaneously with osteocalcin and matrix Gla protein (MGP). Using conformation-specific antibodies, both γ-carboxylated GRP and undercarboxylated GRP species were found accumulated at the sites of mineral deposits, whereas undercarboxylated GRP was predominant in calcified aortic valve disease valvular interstitial cells. Mineral-bound GRP, MGP, and fetuin-A were identified by mass spectrometry. Using an ex vivo model of vascular calcification, γ-carboxylated GRP but not undercarboxylated GRP was shown to inhibit calcification and osteochondrogenic differentiation through α-smooth muscle actin upregulation and osteopontin downregulation. Immunoprecipitation assays showed that GRP is part of an MGP-fetuin-A complex at the sites of valvular calcification. Moreover, extracellular vesicles released from normal vascular smooth muscle cells are loaded with GRP, MGP, and fetuin-A, whereas under calcifying conditions, released extracellular vesicles show increased calcium loading and GRP and MGP depletion. GRP is an inhibitor of vascular and valvular calcification involved in calcium homeostasis. Its function might be associated with prevention of calcium-induced signaling pathways and direct mineral binding to inhibit crystal formation/maturation. Our data show that GRP is a new player in mineralization competence of extracellular vesicles possibly associated with the fetuin-A-MGP calcification inhibitory system. GRP activity was found to be dependent on its γ-carboxylation status, with potential clinical relevance.

Role of osteopontin in osteosarcoma.

The primary bone malignancy osteosarcoma (OS) is a painful health burden, of which treatment remains a challenging problem. Identification of specific tumor biomarkers may help to investigate and develop the novel effective therapeutic approaches that have specific molecular target for the treatment of patients with OS. Osteopontin (OPN), a phosphorylated glycoprotein, is involved in many biological processes, such as biomineralization, bone remodeling and immune responses and has recently been reported to be associated with OS pathogenesis. Interestingly, both of the up- and down-regulation of OPN are involved in OS. During OS development, genetic or epigenetic disruption causes reduced expression of RUNX2 and OPN through the up-regulation of notch signaling pathway, leading to the development of OS. On the other hand, during hypoxic condition, upregulation of OPN induces the glucose uptake into hypoxic OS cells which is responsible for the OS cell proliferation and drug resistance. Recent evidences show that targeting OPN might be an important tool in OS therapeutics. This review has focused on the association of abnormal OPN expression with the pathogenesis of OS, the efficiency of OPN as a diagnostic tool for OS and the therapeutic aspects of OS by targeting OPN.

Downregulation of osteopontin enhances the sensitivity of glioma U251 cells to temozolomide and cisplatin by targeting the NF-κB/Bcl‑2 pathway.

Glioma is resistant to the apoptotic effects of chemotherapy and the mechanism underlying its chemoresistance is not currently understood. In a previous study, we reported that osteopontin (OPN) was overexpressed in glioma tissues and had an important anti‑apoptotic effect. Furthermore, overexpression of OPN was observed following chemotherapy. To elucidate whether OPN plays a role in chemotherapy resistance and to investigate its downstream signaling pathway, this study used small interfering RNA (siRNA) to silence the expression of OPN in U251 human neuronal glioma astrocytoma cells. OPN downregulation in U251 cells enhanced the apoptotic effects induced by temozolomide (TMZ) and cisplatin (DDP). Furthermore, OPN siRNA suppressed the nuclear factor κ‑light‑chain‑enhancer of activated B cells (NF‑κB) activation and B cell lymphoma 2 (Bcl‑2) expression that was induced by chemotherapy. Taken together, these results demonstrated that the expression levels of OPN are involved in glioma chemoresistance. Knockdown of OPN through siRNA enhanced the effects of TMZ and DDP chemotherapy by targeting the NF‑κB/Bcl‑2 pathway.

Osteopontin deficiency aggravates hepatic injury induced by ischemia-reperfusion in mice.

Osteopontin (OPN) is a multifunctional protein involved in hepatic steatosis, inflammation, fibrosis and cancer progression. However, its role in hepatic injury induced by ischemia–reperfusion (I–R) has not yet been investigated. We show here that hepatic warm ischemia for 45 min followed by reperfusion for 4 h induced the upregulation of the hepatic and systemic level of OPN in mice. Plasma aspartate aminotransferase and alanine aminotransferase levels were strongly increased in Opn−/− mice compared with wild-type (Wt) mice after I–R, and histological analysis of the liver revealed a significantly higher incidence of necrosis of hepatocytes. In addition, the expression levels of inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNFα), interleukin 6 (IL6) and interferon-γ were strongly upregulated in Opn−/− mice versus Wt mice after I–R. One explanation for these responses could be the vulnerability of the OPN-deficient hepatocyte. Indeed, the downregulation of OPN in primary and AML12 hepatocytes decreased cell viability in the basal state and sensitized AML12 hepatocytes to cell death induced by oxygen–glucose deprivation and TNFα. Further, the downregulation of OPN in AML12 hepatocytes caused a strong decrease in the expression of anti-apoptotic Bcl2 and in the ATP level. The hepatic expression of Bcl2 also decreased in Opn−/− mice versus Wt mice livers after I–R. Another explanation could be the regulation of the macrophage activity by OPN. In RAW macrophages, the downregulation of OPN enhanced iNOS expression in the basal state and sensitized macrophages to inflammatory signals, as evaluated by the upregulation of iNOS, TNFα and IL6 in response to lipopolysaccharide. In conclusion, OPN partially protects from hepatic injury and inflammation induced in this experimental model of liver I–R. This could be due to its ability to partially prevent death of hepatocytes and to limit the production of toxic iNOS-derived NO by macrophages.

Osteopontin: Versatile modulator of liver diseases

Osteopontin (OPN) is a multifunctional protein, involved in pathological conditions including inflammation, immunity, angiogenesis, fibrosis and cancer progression in various tissues. Hepatic inflammation and fibrosis induced by feeding with a diet deficient in methionine and choline (MCD diet) were markedly attenuated in OPN knockout mice when compared with wild-type mice in the model of non-alcoholic steatohepatitis (NASH). Hepatic cholangiocytes, myofibroblastic stellate cells and natural killer T cells were suggested to secret OPN in mice fed an MCD diet. Plasma and hepatic OPN levels were significantly higher in patients with NASH with advanced fibrosis than in those with early fibrosis. Hepatic OPN mRNA level was correlated with hepatic neutrophil infiltration and fibrosis in patients with alcoholic liver diseases. In those with hepatocellular carcinoma (HCC), OPN levels in plasma and HCC were prognostic factors after liver resection or transplantation. Downregulation of OPN inhibited tumor growth and lung metastasis in nude mice implanted with HCC cells. The single nucleotide polymorphism in the promoter region of the OPN gene was shown to be associated with activity of hepatitis in chronic hepatitis C patients, prognosis in patients with HCC, and growth and lung metastasis of HCC xenografts in nude mice. OPN was reported to be a downstream effecter of Hedgehog pathway, which modulates hepatic fibrosis and carcinogenesis. This review focuses on the roles of OPN in hepatic inflammation, fibrosis and cancer progression. Further elucidation of cellular interactions and molecular mechanisms associated with OPN actions may contribute to development of novel strategies for treatment of the liver diseases.

Down regulation of osteopontin interferes with HCV replication by inhibition of WNT signalling in vitro

Down regulation of osteopontin interferes with HCV replication by inhibition of WNT signalling in vitro

Downregulation of osteopontin in the mouse salivary gland after X-ray irradiation

Objectives Radiation-induced xerostomia is a frequent consequence of radiotherapy for head and neck cancer, but its mechanisms remain unclear. Osteopontin (OPN), a highly phosphorylated glycoprotein, has been shown to be involved in the modulation of inflammatory and tissue repair processes and to be expressed in the salivary gland.