Osteopontin, a coordinator of host defense system: a cytokine or an extracellular adhesive protein?

Both Full-Length and Protease-Cleaved Products of Osteopontin Are Elevated in Infectious Diseases

Circulating full-length osteopontin (FL-OPN) is elevated in plasma from patients with various infectious diseases, such as adult T-cell leukemia, Mycobacterium tuberculosis (TB), hepatitis virus infection, leptospirosis, acquired immune deficiency syndrome (AIDS), AIDS/TB, and coronavirus disease 2019 (COVID-19). Proteolysis of OPN by thrombin, matrix metalloproteases, caspase 8/3, cathepsin D, plasmin, and enterokinase generates various cleaved OPNs with a variety of bioactivities by binding to different target cells. Moreover, OPN is susceptible to gradual proteolysis. During inflammation, one of the cleaved fragments, N-terminal thrombin-cleaved OPN (trOPN or OPN-Arg¹⁶⁸ [OPN-R]), induces dendritic cell (DC) adhesion. Further cleavage by carboxypeptidase B2 or carboxypeptidase N removes Arg¹⁶⁸ from OPN-R to OPN-Leu¹⁶⁷ (OPN-L). Consequently, OPN-L decreases DC adhesion. In particular, the differences in plasma level over time are observed between FL-OPN and its cleaved OPNs during inflammation. We found that the undefined OPN levels (mixture of FL-OPN and cleaved OPN) were elevated in plasma and reflected the pathology of TB and COVID-19 rather than FL-OPN. These infections are associated with elevated levels of various proteases. Inhibition of the cleavage or the activities of cleaved products may improve the outcome of the therapy. Research on the metabolism of OPN is expected to create new therapies against infectious diseases.

Neutralizing antibody against osteopontin attenuates non-alcoholic steatohepatitis in mice

Previously, we reported that an extracellular matrix protein, osteopontin (OPN), is involved in various autoimmune diseases using a neutralizing polyclonal antibody against OPN generated in rabbits. However, the antibody cannot be used for long-term mouse models of chronic inflammatory disease because of the induction of antibodies against anti-OPN rabbit IgG. In this study, we generated a new antibody, anti-mouse OPN mouse IgG (35B6). 35B6 inhibited the cell adhesion of mouse and human OPN to Chinese Hamster Ovary (CHO) cells or CHO cells expressing α4 or α9 integrin. It was reported that OPN is highly expressed and has an important role in a chronic liver disease, non-alcoholic steatohepatitis (NASH). 35B6 injection twice a week for 8 weeks attenuated liver inflammation and fibrosis in a NASH mouse model, suggesting 35B6 is beneficial for the treatment of NASH. 35B6 was preferable to the rabbit anti-OPN antibody for investigating the in vivo function of OPN in mouse models of long-term disease.

Mycobacterium avium subsp. hominissuis effector MAVA5_06970 promotes rapid apoptosis in secondary-infected macrophages during cell-to-cell spread

Mycobacterium avium subsp. hominissuis is an opportunistic intracellular pathogen associated with disease in patients either immunosuppression or chronic lung pathology. Once in the host, M. avium preferentially infects and replicates within the phagocytic cells. The host driven macrophage apoptosis appears to be an essential aspect of innate immunity during bacterial infection; however, the existing evidence suggests that M. avium has evolved adaptive approaches to trigger the phagocyte apoptosis, exit apoptotic cells or via ingestion of infected apoptotic bodies subsequently infect neighboring macrophages. By evaluating 4,000 transposon mutants of M. avium in THP-1 cells, we identified clones that can trigger a new form of early host cell apoptosis, which is only observed upon entry into the “secondary-infected” macrophages. Inactivation of MAVA5_06970 gene lead to significant attenuation in intracellular growth within macrophages and mice, and impaired M. avium to induce rapid apoptosis in the “secondary-infected” cells as measured by Annexin V-FITC detection assay. Complementation of MAVA5_06970 gene corrected the attenuation as well as apoptotic phenotypes. The MAVA5_06970 gene encodes for a secreted protein. Using the pull-down assay and then confirmed with the yeast two-hybrid screen, we found that MAVA5_06970 effector interacts with the Secreted Phosphoprotein 1, the cytokine also known as Osteopontin. This interaction enhances the THP-1 cell apoptosis and, consequently, restricts the production of interleukin-12 that likely may limit the activation of the type I immunity pathway in vivo. This work identified a key virulence effector of M. avium that contributes to the cell-to-cell spread of the pathogen.

Osteopontin in the host response to Leishmania amazonensis

BACKGROUND

Leishmania (L.) spp are intracellular eukaryotic parasites responsible for cutaneous or visceral leishmaniasis, replicating predominantly in macrophages (MF). In C57BL/6 mice virulence with L. amazonensis has been associated with inhibition of Th1 immune responses and an uncontrolled lesion development, whereas DBA/2 mice control any lesion. Parasitic clearance by the MFs requires the activation of proper immune responses. One of the immune related genes expressed in immune cells including MF, codes for osteopontin (OPN). OPN is a secreted glycoprotein, acting as an immune regulator. Its implication in promoting Th1 immunity in response to infectious microorganisms and its known protective effect against viral and bacterial infections via activation of the immune response, render OPN a molecule of interest in the study of the host response to L. amazonensis.

RESULTS

We examined the host response to L. amazonensis of opn mutant and wild type C57BL/6 mice. Bone marrow derived MFs were infected with the parasites in vitro, and opn mutant and wild type mice were inoculated in vivo by intradermal injection in the ears. The DBA/2 strain known to control L. amazonensis infection was also used for comparison. Our data indicate that the parasites increased opn gene expression and OPN protein while parasitic proliferation was contained in the presence of OPN. In the presence of parasites the expression of inflammation-related transcripts was inhibited. Interleukin-1-beta (IL-1β), and transcripts of the NLR-family (NLRC4, NLRP3) were down regulated after L. amazonensis infection. In the absence of OPN, the inhibition by the parasites of IL-1β transcripts was less efficient and a pyroptosis-like cell phenotype was detected in vitro, suggesting a central role of OPN in the host-response to L. amazonensis. Similarly, in vivo, in the absence of OPN, while the clinical inflammatory phenotype is more severe, an increase of these transcripts was observed.

CONCLUSIONS

L. amazonensis infection induces opn gene expression and protein, which in turn participates in shaping the host response to the parasites, seemingly by decreasing the activation of inflammation. OPN, further evaluated as a target for Leishmaniasis control represents an additional interest in improving vaccination strategies against the parasites.

Osteopontin is indispensable for activation of astrocytes in injured mouse brain and primary culture

OBJECTIVES

Osteopontin (OPN) is an inflammatory cytokine inducer involved in cell proliferation and migration in inflammatory diseases or tumors. To investigate the function of OPN in astrocyte activation during brain injury, we compared OPN-deficient (OPN/KO) with wild-type (WT) mouse brains after stab wound injury and primary culture of astrocytes.

METHODS

Primary cultures of astrocytes were prepared from either WT or OPN/KO postnatal mouse brains. Activation efficiency of astrocytes in primary culture was accessed using Western blotting by examining the protein levels of glial fibrillary acidic protein (GFAP) and tenascin-C (TN-C), which are markers for reactive astrocytes, following lipopolysaccharide (LPS) stimulation. Furthermore, the stab wound injury on the cerebral cortex as a brain traumatic injury model was used, and activation of astrocytes and microglial cells was investigated using immunofluorescent analysis on fixed brain sections.

RESULTS

Primary cultures of astrocytes prepared from WT or OPN/KO postnatal mouse brains showed that only 25% of normal shaped astrocytes in a flask were produced in OPN/KO mice. The expression levels of both GFAP and TN-C were downregulated in the primary culture of astrocytes from OPN/KO mice compared with that from WT mice. By the immunofluorescent analysis on the injured brain sections, glial activation was attenuated in OPN/KO mice compared with WT mice.

DISCUSSION

Our data suggest that OPN is essential for proper astrocytic generation in vitro culture prepared from mouse cerebral cortex. OPN is indispensable for astrocyte activation in the mouse brain injury model and in LPS stimulated primary culture.

ABBREVIATIONS

AQP4: aquaporin 4; BBB: blood brain barrier; BrdU: bromo-deoxy uridine; CNS: central nervous system; GFAP: glial fibllirary acidic protein; IgG: immunoglobulin G; LPS: lipopolysaccharide; OPN: osteopontin; OPN/KO: osteopontin-deficient; TN-C: tenascin-C.

Cancer-associated Fibroblast-derived IL-6 Promotes Head and Neck Cancer Progression via the Osteopontin-NF-kappa B Signaling Pathway

Osteopontin (OPN), a chemokine-like protein, plays a crucial role in the proliferation and metastasis of various cancers. However, how tumor stroma modulates the expression of neoplastic OPN and the multifaceted roles of OPN in head and neck cancer (HNC) are unclear. In this study, we tried to investigate the bridging role of OPN between tumor stroma and cancer cells.

Methods: Immunohistochemical staining and quantitative real-time PCR were used to detect OPN expression in HNC tissues, and the correlations between OPN expression and clinicopathologic features were then analyzed. We used a co-culture assay to study the modulatory role of IL-6 on OPN expression and immunoprecipitation analysis was used to determine the endogenous interaction between OPN and integrin αvβ3. Furthermore, a xenograft assay was carried out to confirm the tumor-promoting role and the potential therapeutic value of OPN in HNC.

Results: We found that OPN was significantly up-regulated in HNCs, and the elevated OPN was correlated with poor prognosis. Moreover, we identified IL-6 secreted by cancer-associated fibroblasts (CAFs) as the major upstream molecule that triggers the induction of neoplastic OPN. As such, during the interaction of fibroblasts and cancer cells, the increased neoplastic OPN induced by stromal IL-6 accelerated the growth, migration and invasion of cancer cells. More importantly, we also showed that soluble OPN could promote HNC progression via the integrin αvβ3-NF-kappa B pathway, and the combination of OPN and IL-6 had a better prognostic and diagnostic performance in HNC than either molecule alone.

Conclusion: Our study identified a novel modulatory role for OPN in HNC progression and further demonstrated that the combination of OPN and IL-6 might be a promising prognostic and diagnostic indicator as well as a potential cancer therapeutic target.

Evaluation of matricellular proteins in systemic and local immune response to Mycobacterium tuberculosis infection

Matricellular proteins such as osteopontin (OPN), galectin-9 (Gal-9), and tenascin-C (TN-C) are expressed not only under normal physiological conditions, but also during infection, inflammation and tumorigenesis. Plasma concentrations of matricellular proteins were studied to determine their diagnostic value as potential markers of tuberculosis (TB) activity. It was found that concentrations of OPN and TN-C were higher in patients with active TB than in healthy controls and individuals with latent infection. Moreover, LTBI patients had higher concentrations of OPN than did healthy controls. Gal-9 concentrations did not differ significantly between groups. Concentrations of matricellular proteins were higher in pleural fluid than in the plasma of patients with TB. Expression of matricellular proteins was also investigated in TB granulomas and other granulomatous diseases. Positive OPN and Gal-9 staining was observed in TB and sarcoidosis granulomas, but not in Crohn disease granulomas. The fibrotic ring around granulomas stained positive for TN-C in TB and sarcoidosis, but not in Crohn disease. Of the three matricellular proteins studied, OPN and TN-C may serve as reliable plasma markers for monitoring TB activity, whereas Gal-9 seems to be expressed more at the site of infection than in the systemic circulation.

Multiple low-affinity interactions support binding of human osteopontin to integrin αXβ2

Integrin α(X)β(2) (also known as complement receptor 4, p150,95, or CD11c/CD18) is expressed in the cell membrane of myeloid leukocytes. α(X)β(2) has been reported to bind a large number of structurally unrelated ligands, often with a shared molecular character in the presence of polyanionic stretches in poorly folded proteins or glucosaminoglycans. Nevertheless, it is unclear what chemical sources of polyanionicity enable the binding by α(X)β(2). Osteopontin (OPN) is an intrinsically disordered protein, which facilitates phagocytosis via the integrin α(X)β(2). Unlike for other integrins, neither the RGD nor the SVVYGLR motifs account for this binding, and the molecular basis of OPN binding by α(X)β(2) remains uncharacterized. Here, we show that the monovalent interactions between the ligand-binding domain of α(X)β(2) and OPN, its fragments, or caseins are weak, with dissociation constants higher than 10(-5)M but with high apparent stoichiometries. From comparison with cell adhesion studies, the discrimination between α(X)β(2) ligands and non-ligands appears to rely on these apparent stoichiometries in a way, which involves glutamate rather than aspartate side chains. Surprisingly, the extensive, negatively charged phosphorylation of OPN is not contributing to α(X)β(2) binding. Furthermore, synchrotron radiation circular spectroscopy excludes that the phosphorylation affects the general folding of OPN. Taken together, our quantitative analyses reveal a mode of ligand recognition by integrin α(X)β(2), which seem to differ in principles considerably from other OPN receptors.

Current and potential applications of host-defense peptides and proteins in urology

The use of antibiotics has become increasingly disfavored as more multidrug resistant pathogens are on the rise. A promising alternative to the use of these conventional drugs includes antimicrobial peptides or host-defense peptides. These peptides typically consist of short amino acid chains with a net cationic charge and a substantial portion of hydrophobic residues. They mainly target the bacterial cell membrane but are also capable of translocating through the membrane and target intracellular components, making it difficult for bacteria to gain resistance as multiple essential cellular processes are being targeted. The use of these peptides in the field of biomedical therapies has been examined, and the different approaches to using them under various settings are constantly being discovered. In this review, we discuss the current and potential applications of these host-defense peptides in the field of urology. Besides the use of these peptides as antimicrobial agents, the value of these biological molecules has recently been expanded to their use as antitumor and anti-kidney-stone agents.

A novel cryptic binding motif, LRSKSRSFQVSDEQY, in the C-terminal fragment of MMP-3/7-cleaved osteopontin as a novel ligand for α9β1 integrin is involved in the anti-type II collagen antibody-induced arthritis

Osteopontin (OPN) is a multifunctional protein that has been linked to various intractable inflammatory diseases. One way by which OPN induces inflammation is the production of various functional fragments by enzyme cleavage. It has been well appreciated that OPN is cleaved by thrombin, and/or matrix metalloproteinase-3 and -7 (MMP-3/7). Although the function of thrombin-cleaved OPN is well characterized, little is known about the function of MMP-3/7-cleaved OPN. In this study, we found a novel motif, LRSKSRSFQVSDEQY, in the C-terminal fragment of MMP-3/7-cleaved mouse OPN binds to α9β1 integrin. Importantly, this novel motif is involved in the development of anti-type II collagen antibody-induced arthritis (CAIA). This study provides the first in vitro and in vivo evidence that OPN cleavage by MMP-3/7 is an important regulatory mechanism for CAIA.

Dissection of the human multipotent adult progenitor cell secretome by proteomic analysis

Multipotent adult progenitor cells (MAPCs) are adult adherent stromal stem cells currently being assessed in acute graft versus host disease clinical trials with demonstrated immunomodulatory capabilities and the potential to ameliorate detrimental autoimmune and inflammation-related processes. Our previous studies documented that MAPCs secrete factors that play a role in regulating T-cell activity. Here we expand our studies using a proteomics approach to characterize and quantify MAPC secretome components secreted over 72 hours in vitro under steady-state conditions and in the presence of the inflammatory triggers interferon-γ and lipopolysaccharide, or a tolerogenic CD74 ligand, RTL1000. MAPCs differentially responded to each of the tested stimuli, secreting molecules that regulate the biological activity of the extracellular matrix (ECM), including proteins that make up the ECM itself, proteins that regulate its construction/deconstruction, and proteins that serve to attach and detach growth factors from ECM components for redistribution upon appropriate stimulation. MAPCs secreted a wide array of proteases, some detectable in their zymogen forms. MAPCs also secreted protease inhibitors that would regulate protease activity. MAPCs secreted chemokines and cytokines that could provide molecular guidance cues to various cell types, including neutrophils, macrophages, and T cells. In addition, MAPCs secreted factors involved in maintenance of a homeostatic environment, regulating such diverse programs as innate immunity, angiogenesis/angiostasis, targeted delivery of growth factors, and the matrix-metalloprotease cascade.

Osteopontin gene polymorphisms as predictors for the efficacy of interferon therapy in chronic hepatitis C Egyptian patients with genotype 4

This study aimed to determine the relationship between osteopontin gene polymorphisms and its protein level and the efficacy of interferon-based therapies in Hepatitis C virus (HCV) patients. Hundreds HCV patients genotype 4, treated with pegylated interferon alfa-2b plus ribavirin and 60 healthy subjects were enrolled. All individuals were subjected to clinical and laboratory parameters, including hepatitis markers and HCV quantitation by real-time polymerase chain reaction. Single nucleotide polymorphisms (SNPs) of osteopontin (OPN) gene (nucleotide -155, -443 and -1748) were analysed by direct sequencing in addition to estimation of serum level of OPN. SNP at -443 (C/C versus C/T, T/T) was found to represent predictors for treatment response by univariate logistic regression analysis. OPN serum level was independent predictors for treatment response by both univariate and multivariate logistic regression analysis. SNP at nucleotide -443 and serum OPN protein levels could be used as useful markers to predict the efficacy of treatment.

Frequent detection of anti-tubercular-glycolipid-IgG and -IgA antibodies in healthcare workers with latent tuberculosis infection in the Philippines

Anti-tubercular-glycolipid-IgG (TBGL-IgG) and -IgA (TBGL-IgA) antibodies, and the QuantiFERON-TB Gold test (QFT) were compared in healthcare workers (HCWs, n = 31) and asymptomatic human immunodeficiency virus-carriers (HIV-AC, n = 56) in Manila. In HCWs, 48%, 51%, and 19% were positive in QFT, TBGL-IgG, and -IgA, respectively. The TBGL-IgG positivity was significantly higher (P = 0.02) in QFT-positive than QFT-negative HCWs. Both TBGL-IgG- and -IgA-positive cases were only found in QFT-positive HCWs (27%). The plasma IFN-γ levels positively correlated with TBGL-IgA titers (r = 0.74, P = 0.005), but not TBGL-IgG titers in this group, indicating that mucosal immunity is involved in LTBI in immunocompetent individuals. The QFT positivity in HIV-AC was 31% in those with CD4+ cell counts >350/μL and 12.5% in low CD4 group (<350/μL). 59 % and 29% were positive for TBGL-IgG and -IgA, respectively, in HIV-AC, but no association was found between QFT and TBGL assays. TBGL-IgG-positive rates in QFT-positive and QFT-negative HIV-AC were 61% and 58%, and those of TBGL-IgA were 23% and 30%, respectively. The titers of TBGL-IgA were associated with serum IgA (P = 0.02) in HIV-AC. Elevations of TBGL-IgG and -IgA were related to latent tuberculosis infection in HCWs, but careful interpretation is necessary in HIV-AC.

Quinolone-induced upregulation of osteopontin gene promoter activity in human lung epithelial cell line A549

Quinolones, in addition to their antibacterial activities, act as immunomodulators. Osteopontin (OPN), a member of the extracellular matrix proteins, was found to play a role in the immune and inflammatory response. We found that quinolones significantly enhanced OPN secretion, namely, garenoxacin (220%), moxifloxacin (62%), gatifloxacin (82%), sparfloxacin, (79%), and sitafloxacin (60%). Enhancement of OPN secretion was shown to be due to the effect of quinolones on the OPN gene promoter activity. We also examined the role of quinolones on apoptosis and found that sparfloxacin decreased the late apoptosis of A549 cells, but garenoxacin did not show the antiapoptotic effect. The antiapoptotic effects of quinolones do not appear to be associated with OPN elevation.

Pretreatment of endothelial progenitor cells with osteopontin enhances cell therapy for peripheral vascular disease

Tissue necrosis resulting from critical limb ischemia (CLI) leads to amputation in a significant number of patients. Autologous cell therapy using angiogenic cells such as endothelial progenitor cells (EPCs) holds promise as a treatment for CLI but a limitation of this treatment is that the underlying disease etiology that resulted in CLI may also contribute to dysfunction of the therapeutic EPCs. This study aimed to elucidate the mechanism of EPC dysfunction using diabetes mellitus as a model and to determine whether correction of this defect in dysfunctional EPCs ex vivo would improve the outcome after cell transplantation in the murine hind limb ischemia model. EPC dysfunction was confirmed in a homogenous population of patients with type 1 diabetes mellitus and a microarray study was preformed to identify dysregulated genes. Notably, the secreted proangiogenic protein osteopontin (OPN) was significantly downregulated in diabetic EPCs. Furthermore, OPN-deficient mice showed impaired recovery following hind limb ischemia, suggesting a critical role for OPN in postnatal neovascularization. EPCs isolated from OPN KO mice showed decreased ability to adhere to endothelial cells as well as impaired angiogenic potential. However, this dysfunction was reversed upon exposure to recombinant OPN, suggesting that OPN may act in an autocrine manner on EPCs. Indeed, exposure of OPN knockout (KO) EPCs to OPN was sufficient to induce the secretion of angiogenic proteins (IL-6, TGF-α, and FGF-α). We also demonstrated that vascular regeneration following hind limb ischemia in OPN KO mice was significantly improved upon injection of EPCs preexposed to OPN. We concluded that OPN acts in an autocrine manner on EPCs to induce the secretion of angiogenic proteins, thereby playing a critical role in EPC-mediated neovascularization. Modification of cells by exposure to OPN may improve the efficacy of autologous EPC transplantation via the enhanced secretion of angiogenic proteins.

Osteopontin levels are elevated in patients with asthma

Osteopontin (OPN) plays a role in T cell-mediated immunity, but its involvement in Th2-associated allergic responses, especially asthma, has not been investigated. This cross-sectional case-control study was designed to determine whether serum OPN levels are elevated in asthma patients and whether these correlated with disease severity. Serum samples were obtained from patients with mild (n = 42), moderate (n = 48) and severe (n = 39) asthma, and 41 healthy control subjects. OPN protein concentrations were measured by enzyme-linked immuno sorbent assay and were found to be significantly higher in all three asthma patient groups compared with healthy controls. There was no significant association between OPN concentration and disease severity. The data suggest a role for OPN in the pathogenesis of asthma. Further studies are needed to clarify the involvement of OPN in various aspects of asthma.

Osteopontin and endostatin concentrations in peripheral blood of patients with adrenal tumors undergoing unilateral adrenalectomy

Peripheral blood osteopontin (OPN) and endostatin (END) levels were studied in 35 patients with adrenal cortex tumors and 10 patients with pheochromocytoma before unilateral adrenalectomy, as well as in 10 healthy subjects (controls). Thirty days after surgery, OPN and END were evaluated again in 16 patients with adrenal cortex tumors and 4 female patients with pheochromocytoma. Before surgery, OPN blood concentrations increased in the group of patients with adrenal cortex carcinomas as compared to controls (p < 0.001) and the group with Conn syndrome (p < 0.05); they did not change after surgery. Before adrenalectomy, OPN blood levels in pheochromocytoma patients were also lower than in Conn syndrome subjects (p < 0.05). After adrenalectomy, the normal concentrations of END decreased only in the group of patients with hormonally inactive cortical adenomas (p < 0.05). We were unable to demonstrate any relationships between removed tumor volumes and OPN or END blood levels.

Expression profile of the matricellular protein osteopontin in primary open-angle glaucoma and the normal human eye

PURPOSE. To characterize the role of osteopontin (OPN) in primary open-angle glaucoma (POAG) and normal eyes. METHODS. OPN quantification was performed by enzyme-linked immunosorbent assay in aqueous humor (AH) obtained from human donor eyes (POAG and normal) and surgical samples (POAG and elective cataract removal). OPN expression and localization in whole eye tissue sections and primary normal human trabecular meshwork (NTM) cells were studied by Western blot and immunohistochemistry. Latanoprost-free acid (LFA)-treated NTM cells were analyzed for OPN gene and protein expression. Intraocular pressure was measured by tonometry, and central corneal thickness was measured by optical coherence tomography in young OPN(-/-) and wild-type mice. RESULTS. OPN levels were significantly reduced in donor POAG AH compared with normal AH (0.54 ± 0.18 ng/μg [n = 8] vs. 0.77 ± 0.23 ng/μg [n = 9]; P = 0.039). A similar trend was observed in surgical AH (1.05 ± 0.31 ng/μg [n = 20] vs. 1.43 ± 0.88 ng/μg [n = 20]; P = 0.083). OPN was present in the trabecular meshwork, corneal epithelium and endothelium, iris, ciliary body, retina, vitreous humor, and optic nerve. LFA increased OPN gene expression, but minimal change in OPN protein expression was observed. No difference in intraocular pressure (17.5 ± 2.0 mm Hg [n = 56] vs. 17.3 ± 1.9 mm Hg [n = 68]) but thinner central corneal thickness (91.7 ± 3.6 μm [n = 50] vs. 99.2 ± 5.5 μm [n = 70]) was noted between OPN(-/-) and wild-type mice. CONCLUSIONS. OPN is widely distributed in the human eye and was found in lower concentrations in POAG AH. Reduction of OPN in young mice does not affect IOP.

Systemic blood osteopontin, endostatin, and E-selectin concentrations after vertical banding surgery in severely obese adults

BACKGROUND

Obesity is associated with endothelial dysfunction and increased inflammation as well as with expansion of the capillary bed in regional adipose deposits, and a balance between these factors is involved in angiogenesis. Osteopontin (OPN) is a proinflammatory cytokine involved in regulating immune processes and mediating chronic inflammation. Its level is usually elevated in the plasma and adipose tissue of obese subjects. E-selectin, an adhesion molecule which is released by dysfunctional endothelial cells, is believed to be a marker of an early atherosclerotic process. Endostatin (END), an angiogenesis inhibitor, is present in the blood of obese subjects. The most effective treatment to achieve weight loss in morbidly obese subjects is bariatric surgery. The aim of the study was to evaluate and compare the circulating concentrations of OPN, E-selectin and END as well as the insulin resistance (HOMA-IR) of severely obese patients with metabolic syndrome before and after vertical banded gastroplasty (VBG).

MATERIAL AND METHODS

The test cohorts comprised eight males and 20 females (total 28 patients) aged from 20 to 59 years with simple obesity and the presence of metabolic syndrome, both before and 3, 6, 12, 24 months after bariatric surgery (six patients were also checked after 36 and four after 48 months).

RESULTS

Bariatric surgery significantly reduced (over 24 months) body weight, BMI, waist circumference, HOMA-IR and blood concentrations of CRP. Plasma OPN gradually increased after VBG and E-selectin in systemic blood decreased. We did not observe any differences in END concentrations from 12 to 48 months after surgery.

CONCLUSION

VBG improves metabolic syndrome parameters, decreases E-selectin and gradually increases OST blood concentrations but it does not have any significant influence on END levels.

Osteopontin, intrinsic tissue regulator of intractable inflammatory diseases

Within classical extracellular matrix (ECM) proteins, there are a unique group of proteins that should be regarded as a distinct functional group of molecules. Matricellular proteins including osteopontin (OPN) and tenascin-c (TN-C) are highly expressed at the pathological foci of various inflammatory diseases. Unlike classical ECM proteins, these are soluble proteins and induce cell motility and persistent inflammation rather than providing a scaffold for stable cell adhesion. Osteopontin is a pleiotropic cytokine expressed by various cells. Two forms of OPN are present. A secreted form of OPN (sOPN) is involved in generation of T helper type 1 (Th1) and Th17 cells that are pathogenic T cells for various autoimmune diseases. An intracellular form of OPN (iOPN) is a critical regulator for Toll like receptor-9 (TLR-9) and/or TLR-7-dependent interferon-α (IFN-α) expression by plasmacytoid dendritic cells (DCs) and Th17 development. Indeed, both OPN and TN-C deficient mice are resistant to various Th1- and/or Th17-related autoimmune diseases. Interestingly, thrombin-cleaved forms of sOPN and TN-C share a common integrin receptor, α9β1, and α9β1 integrin-mediated signaling is involved in the pathogenesis of various autoimmune diseases. Thus, OPN, TN-C and its common receptor, α9β1 integrin may serve as potential therapeutic targets for various intractable inflammatory diseases.

Association of circulating osteopontin levels with clinical outcomes in postoperative biliary atresia

PURPOSE

Biliary atresia (BA) is one of the most serious liver disorders in children. The aims of the present study were to investigate circulating levels of osteopontin in BA children compared with healthy controls and to evaluate the relationship between circulating osteopontin and therapeutic outcome of BA patients.

METHODS

Fifty-nine BA patients post-Kasai operation and 13 healthy children were recruited. The patients were divided into two groups according to their serum total bilirubin levels (TB < 2, jaundice-free vs. TB ≥ 2 mg/dL, persistent jaundice) and alanine aminotransferase (ALT < 45, normal ALT vs. ALT ≥ 45 IU/L, elevated ALT). Plasma osteopontin levels were analyzed using commercial enzyme-linked immunosorbent assay.

RESULTS

The circulating osteopontin was higher in BA children compared with that of healthy controls (146.9 ± 19.1 vs. 28.0 ± 8.4 ng/mL, P = 0.001). The BA patients with persistent jaundice had more increased plasma osteopontin levels than those without jaundice (157.8 ± 47.9 vs. 27.5 ± 6.4 ng/mL, P = 0.001). Furthermore, plasma osteopontin levels in BA patients with elevated ALT were significantly higher than those with normal ALT (103.2 ± 29.2 vs. 24.5 ± 7.9 ng/mL, P = 0.01). In addition, circulating osteopontin was positively correlated with serum total bilirubin (r = 0.526, P < 0.001) and with serum ALT (r = 0.575, P < 0.001). Subsequent analysis showed that the BA patients with portal hypertension had more elevated plasma osteopontin compared to those without portal hypertension (116.7 ± 31.1 vs. 19.5 ± 9.3 ng/mL, P = 0.01).

CONCLUSION

Increased circulating osteopontin was associated with the development of hepatic dysfunction and portal hypertension in BA patients. Circulating osteopontin may serve as a possible marker reflecting disease severity and monitoring the disease progression in postoperative BA patients.

Osteopontin expression and relation to streptococcal disease severity in mice

Osteopontin (OPN) is a phosphorylated glycoprotein that has been implicated in a number of infectious diseases. However, the role of OPN in Streptococcus pyogenes infection is unknown. To investigate whether OPN is involved in S. pyogenes infection, we first examined the plasma OPN levels after local injection of S. pyogenes. OPN expression was significantly increased at 2 h post-infection and increased thereafter. A correlation was found between plasma OPN levels and the development of S. pyogenes infection. The plasma OPN level in severe S. pyogenes infection was higher than during a normal infection. Levels of OPN were found to correlate with the severity of S. pyogenes infection. We also found that OPN production was suppressed by interleukin-6 and enhanced by tumour necrosis factor-alpha in immunocompetent cells. Collectively, these findings demonstrate that the OPN level may provide clues to the severity of S. pyogenes infection in the early phase of the infection.

Regulatory role of DC-derived osteopontin in systemic allergen sensitization

Osteopontin (OPN) is a secreted phosphoglycoprotein with a wide range of functions, and is involved in various pathophysiological conditions. However, the role of OPN in IgE and Th2-associated allergic responses remains incompletely defined. The aim of this study was to elucidate the role of OPN in systemic allergen sensitization in mice. When compared with OPN(+/+) mice, significantly increased levels of OVA-induced IgE were found in OPN(-/-) mice. OPN(-/-) DC demonstrated an increased capacity to enhance Th2 cytokine production in CD4+ T cells from sensitized OPN(+/+) mice. Furthermore, significantly reduced levels of IL-12p70 expression were seen in LPS-stimulated OPN(-/-) DC as compared with the WT DC, and the reduction was reversible by the addition of recombinant OPN (rOPN). rOPN was able to suppress OVA-induced IL-13 production in the cultures of CD4 and OPN(-/-) DC, but this inhibitory activity was neutralized by the addition of anti-IL-12 Ab. In addition, administration of rOPN in vivo suppressed OVA-specific IgE production; however, this suppressive effect was abrogated in IL-12-deficient mice. These results indicate that DC-derived OPN plays a regulatory role in the development of systemic allergen sensitization, which is mediated, at least in part, through the production of endogenous IL-12.

Biological variation and reference intervals for circulating osteopontin, osteoprotegerin, total soluble receptor activator of nuclear factor kappa B ligand and high‐sensitivity C‐reactive protein

OBJECTIVE

Monitoring inflammatory diseases and osteoclastogenesis with osteopontin (OPN), osteoprotegerin (OPG), total soluble receptor activator of nuclear factor kappa B ligand (total sRANKL) and high-sensitivity C-reactive protein (hsCRP) has recently attracted increased interest. The purpose of our study was to determine reference intervals, variability caused by sampling time, biological variation and stability after repeated freeze-thaw cycles of circulating levels of OPN, OPG, total sRANKL and hsCRP.

MATERIAL AND METHODS

Plasma OPN and plasma OPG concentrations were determined with sandwich ELISA; serum total sRANKL concentration was determined using a two-site sandwich ELISA; and hsCRP was analysed by turbidimetry in 300 Danish blood donors (183 M and 117 F) with a median age of 43 years (range 18-64 years). Variability due to biological variation and sampling time was studied in serial samples from 38 healthy subjects.

RESULTS

The 95th percentiles in the donors were 76 microg/L for OPN, 4.2 pmol/L for OPG, 40.2 nmol/L for total sRANKL and 12 mg/L for hsCRP. The overall medians for both genders were 51 microg/L, 2.2 pmol/L, 0.66 nmol/L and 1.0 mg/L, respectively. We found a significant correlation between hsCRP and OPN (rho = 0.173; p<0.003). The biological within-subject variations were calculated to be 8.2 % for OPN, 8.8% for total sRANKL and 50% for hsCRP.

CONCLUSIONS

Reference intervals have been established with a high analytic performance for OPN and an acceptable analytic performance for OPG and total sRANKL. The study revealed low biological variation for OPN and total sRANKL and high biological variation for hsCRP.

Osteopontin: role in extracellular matrix deposition and myocardial remodeling post-MI

Remodeling after myocardial infarction (MI) associates with left ventricular (LV) dilation, decreased cardiac function and increased mortality. The dynamic synthesis and breakdown of extracellular matrix (ECM) proteins play a significant role in myocardial remodeling post-MI. Expression of osteopontin (OPN) increases in the heart post-MI. Evidence has been provided that lack of OPN induces LV dilation which associates with decreased collagen synthesis and deposition. Inhibition of matrix metalloproteinases, key players in ECM remodeling process post-MI, increased ECM deposition (fibrosis) and improved LV function in mice lacking OPN after MI. This review summarizes--1) signaling pathways leading to increased expression of OPN in the heart; 2) the alterations in the structure and function of the heart post-MI in mice lacking OPN; and 3) mechanisms involved in OPN-mediated ECM remodeling post-MI.

DLC1 suppresses distant dissemination of human hepatocellular carcinoma cells in nude mice through reduction of RhoA GTPase activity, actin cytoskeletal disruption and down-regulation of genes involved in metastasis

The process of cell dissemination from the primary tumors to distant sites is the most harmful event during cancer progression, and the leading cause of cancer death. We have previously demonstrated that restoration of DLC1 tumor suppressor gene expression in the DLC1-negative Focus and 7703K human hepatocellular carcinoma (HCC) cell lines induced caspase-3 mediated apoptosis, reduced cell growth in vitro and tumorigenicity in vivo and diminished the ability to migrate through Matrigel, a property suggestive of metastatic potential in vivo. We now show that subcutaneous tumors developing after inoculation of Focus and 7703K cells into nude mice disseminate cells to liver and lung, and this process is markedly suppressed by restoration of DLC1 expression. Inhibition of tumor cell dissemination was associated with lower levels of RhoA activity, an increase in rounded cells and a reduction in actin stress fibers and focal adhesion molecules that are of critical importance in cancer cell invasion and metastasis. In addition, DLC1 down-regulated the expression of osteopontin and matrix metalloproteinase-9, which are highly up-regulated in most primary HCC with associated metastases. These observations implicate the DLC1 gene in suppression of HCC cell dissemination and identify novel cellular and genetic alterations that contribute to prevention of metastasis, a life-threatening event in cancer progression.

Chronic alcohol consumption generates a vulnerable immune environment during early SIV infection in rhesus macaques

BACKGROUND

Alcohol consumption is a common problem in HIV-infected individuals, and the effects of alcohol may alter the efficiency of the immune response, potentially aggravating the disease as well as affecting end organs, such as the brain. However, the elements of the virus-host interaction that are modulated by ethanol are poorly dissected.

METHODS

Ethanol intake was conditioned in rhesus macaques prior to SIV infection, in order to mimic this common human behavior, and allow the evaluation of aspects of the virus-immune system interactions during acute time-points, when important facets of the infection are set up and when virus reproducibly enters the brain.

RESULTS

Although ethanol had a limited effect on the acute plasma viral load, it resulted in reduced circulating memory CD4(+) T cells and increased levels of monocytes expressing the viral coreceptor CCR5. In organs, ethanol consumption impacted immune cells in the liver as well as lymphoid and other nonlymphoid tissues, where CD4(+) T cells were predominantly affected.

CONCLUSION

Overall, the consumption of alcohol causes immune cell alterations that can contribute to the generation of a disease susceptible environment upon SIV infection.

Elevated plasma osteopontin level is predictive of cirrhosis in patients with hepatitis B infection

BACKGROUND

Osteopontin (OPN) was shown to play an important role in the pathogenesis of various inflammatory and fibrotic processes and elevated in fibrotic liver of mouse model. However, the significance of OPN in hepatitis B virus (HBV)-induced liver cirrhosis (LC) remains unclear and is therefore evaluated in this study.

METHODS

Thirty-nine patients with HBV-induced LC, 30 patients with HBV infection but without cirrhosis, 11 patients with HBV-related hepatocellular carcinoma (HCC) and 14 additional healthy controls were enrolled in this study. Plasma levels of OPN were measured with enzyme-linked immunosorbent assay and the relationship between OPN and clinical parameters was evaluated.

RESULTS

When compared to HBV infection group (median 2.16 ng/ml), plasma levels of OPN were significantly increased in cirrhosis (4.52 ng/ml, p < 0.001) and cancer group (13.38 ng/ml, p < 0.001). The OPN level was correlated with the severity of liver damage according to Child-Pugh classification (p = 0.003). It showed at least comparable sensitivity and specificity to predict cirrhosis as aspartate aminotransferase to platelet ratio index, a previously established non-invasive serum marker of cirrhosis.

CONCLUSIONS

These data suggest that OPN could be used to evaluate the existence of LC, as OPN has previously been reported to be increased in the HCC; this unique feature makes OPN a promising candidate for prediction biomarker in the long-time surveillance of patients with HBV infection to evaluate the risk of cirrhosis and cancer.

The role of osteopontin in tumor progression and metastasis in breast cancer

The use of cancer biomarkers to anticipate the outlines of disease has been an emerging issue, especially as cancer treatment has made such positive steps in the last few years. Progress in the development of consistent malignancy markers is imminent because advances in genomics and bioinformatics have allowed the examination of immense amounts of data. Osteopontin is a phosphorylated glycoprotein secreted by activated macrophages, leukocytes, and activated T lymphocytes, and is present in extracellular fluids, at sites of inflammation, and in the extracellular matrix of mineralized tissues. Several physiologic roles have been attributed to osteopontin, i.e., in inflammation and immune function, in mineralized tissues, in vascular tissue, and in kidney. Osteopontin interacts with a variety of cell surface receptors, including several integrins and CD44. Binding of osteopontin to these cell surface receptors stimulates cell adhesion, migration, and specific signaling functions. Overexpression of osteopontin has been found in a variety of cancers, including breast cancer, lung cancer, colorectal cancer, stomach cancer, ovarian cancer, and melanoma. Moreover, osteopontin is present in elevated levels in the blood and plasma of some patients with metastatic cancers. Therefore, suppression of the action of osteopontin may confer significant therapeutic activity, and several strategies for bringing about this suppression have been identified. This review looks at the recent advances in understanding the possible mechanisms by which osteopontin may contribute functionally to malignancy, particularly in breast cancer. Furthermore, the measurement of osteopontin in the blood or tumors of patients with cancer, as a way of providing valuable prognostic information, will be discussed based on emerging clinical data.

Increased osteopontin levels in the vitreous of patients with diabetic retinopathy

PURPOSE

Osteopontin (OPN) has diverse functions such as cell adhesion, chemoattraction, immunomodulation, and angiogenesis. The aim of this study is to analyze the OPN levels in vitreous fluid obtained from diabetic retinopathy (DR) and non-DR patients.

METHODS

Nineteen patients out of 11 with DR and 8 without DR underwent pars plana vitrectomy and vitreous fluid was obtained simultaneously. Two distinct sandwich enzyme-linked immunosorbent assay systems (systems 1 and 2) were applied, which have been developed in our laboratories to quantify the OPN concentrations in vitreous fluid.

RESULTS

The non-thrombin-cleaved full-length OPN levels in the vitreous fluid were 921.63 +/- 45.38 ng/ml in DR and 632.80 +/- 83.43 ng/ml in non-DR using system 1. Also, vitreous thrombin-cleaved and noncleaved OPN levels were increased to 2,109.22 +/- 151.651 and 1,651.13 +/- 229.82 ng/ml in patients with DR and non-DR using system 2. The vitreous OPN levels were significantly higher in DR than those in non-DR (p < 0.01 by system 1 and p < 0.05 by system 2).

CONCLUSION

Thrombin-cleaved and noncleaved vitreous OPN levels in patients with DR were increased compared with control subjects, suggesting that OPN plays a potential role in the pathogenesis of diabetic retinal ischemia.

The role of osteopontin in tendon tissue remodeling after denervation-induced mechanical stress deprivation

It has been shown that musculoskeletal tissues undergo dynamic tissue remodeling by a process that is quite sensitive to the mechanical environment. However, the detailed molecular mechanism underlying this process remains unclear. We demonstrate here that after denervation-induced mechanical stress deprivation, tendons undergo dynamic tissue remodeling as evidenced by a significant reduction of the collagen fibril diameter. Importantly, the transient up-regulation of osteopontin (OPN) expression was characteristic during the early phase of tendon tissue remodeling. Following this dynamic change of OPN expression, matrix metalloproteinase (MMP)-13 expression was induced, which presumably accounts for the morphological changes of tendon by degrading tendon collagen fibrils. The modulation of MMP-13 expression by OPN was specific, since the expression of MMP-2, which is also known to be involved in tissue remodeling, did not alter in the tendons under the absence or presence of OPN. We also demonstrate that the modulation of MMP-13 expression by OPN is due to the signaling through cell surface receptors for OPN. Thus, we conclude that OPN plays a crucial role in conveying the effect of denervation-induced mechanical stress deprivation to the tendon fibroblasts to degrade the extracellular matrices by regulating MMP-13 expression in tendon fibroblasts.

Osteopontin: a potential biomarker for successful bee venom immunotherapy and a potential molecule for inhibiting IgE-mediated allergic responses

Venom immunotherapy (VIT) is proven to be curative for insect allergy, but the mechanisms and the biomarkers associated with clinical efficacy remain elusive. We report herein the discovery of a leading candidate biomarker, osteopontin (OPN), for VIT. From cDNA microarray and clustering analyses, an increased expression of OPN was found in patients who completed 5-6 years of VIT and discontinued therapy for 3-6 years as compared with the untreated group. A significantly higher level of serum OPN was found in the completed treatment group as compared with the untreated group. Following VIT, kinetically increased levels of OPN associated with reduced venom specific IgE levels were noted in subjects with large local allergic reactions to venom. These findings together with the fact that OPN is involved in Th1-associated immune response strongly suggest a role of OPN as a functional biomarker for VIT.

Interleukin-10 and Th2 cytokines differentially regulate osteopontin expression in human monocytes and dendritic cells

Osteopontin (OPN) is a pleiotrophic phosphoprotein involved in homeostatic and pathophysiologic responses. It is known to be a chemotactic cytokine for dendritic cells (DCs), a critical cell type in both innate and adaptive immune responses. We report herein a contrasting role of interleukin-10 (IL-10) and Th2 cytokines in the regulation of OPN expression in human monocytes and monocyte-derived DCs (Mo-DCs). Our results showed first that the expression of OPN in monocytes and Mo-DCs was induced in a time-dependent and dose-dependent manner by IL-10 but was inhibited by IL-4 or IL-13. Further, the basal level of OPN expression was also inhibited by IL-4. This inhibitory effect of IL-4 was associated with a faster decay of OPN transcripts and a decreased proximal promoter activity of OPN in IL-4-treated cells. These results demonstrate a novel role of IL-10 and Th2 cytokines in the regulation of DC function through their contrasting regulatory activities on the expression of OPN.

Lack of osteopontin improves cardiac function in streptozotocin-induced diabetic mice

The purpose of this study was to investigate the role of osteopontin (OPN) in diabetic hearts. Diabetes was induced in wild-type (WT) and OPN knockout (KO) mice by using streptozotocin (150 mg/kg) injection. Left ventricular (LV) structural and functional remodeling was studied 30 and 60 days after induction of diabetes. Induction of diabetes increased OPN expression in cardiac myocytes. Heart weight-to-body weight ratio was increased in both diabetic (D) groups. Lung wet weight-to-dry weight ratio was increased only in the WT-D group. Peak left ventricular (LV) developed pressures measured using Langendorff perfusion analyses were reduced to a greater extent in WT-D versus KO-D group. LV end-diastolic pressure-volume curve exhibited a significant leftward shift in WT-D but not in KO-D group. LV end-diastolic diameter, percent fractional shortening, and the ratio of peak velocity of early and late filling (E/A wave) were significantly reduced in WT-D mice as analyzed by echocardiography. The increase in cardiac myocyte apoptosis and fibrosis was significantly higher in the WT-D group. Expression of atrial natriuretic peptide and transforming growth factor-beta1 was significantly increased in the WT-D group. Induction of diabetes increased protein kinase C (PKC) phosphorylation in both groups. However, phosphorylation of PKC-betaII was significantly higher in the WT-D group, whereas phosphorylation of PKC-zeta was significantly higher in the KO-D group. Levels of peroxisome proliferator-activated receptor-gamma were significantly decreased in the WT-D group but not in the KO-D group. Thus increased expression of OPN may play a deleterious role during streptozotocin-induced diabetic cardiomyopathy with effects on cardiac fibrosis, hypertrophy, and myocyte apoptosis.

Regular expression of osteopontin in granular cell tumor: distinctive feature among Schwannian cell tumors

For further characterization of S-100 protein-positive granular cell tumor (GCT), the expression of osteopontin (OPN) in the tumor cells was compared with other types of Schwannian cell tumors. Twenty GCT, three amputation neuromas, 12 neurilemmomas (NM) and three malignant peripheral nerve sheath tumors (MPNST) were used. In addition, two granular cell epulides were employed because of histological similarity to that of GCT. Immunohistochemistry by anti-OPN-monoclonal antibody revealed OPN-immunoreactivity in tumor cells of all GCT and stromal macrophages in neurilemmomas and one MPNST, but neither in amputation neuromas nor in granular cell epulides. All nine GCT studied by in situ hybridization (ISH) and all three GCT analyzed by reverse transcription-polymerase chain reaction (RT-PCR) were positive for OPN mRNA. In contrast, seven NM and three amputation neuromas were negative for OPN mRNA by either ISH or RT-PCR, while macrophages infiltrated in these tumors had OPN mRNA consistently. Double immunostaining for OPN and CD68, a lysosome-associated glycoprotein, showed their colocalization in tumor cells of GCT, suggesting a possible degradation of OPN by lysosomes. In conclusion, GCT among Schwannian cell tumors consistently express OPN, but its biological significance requires further investigation.

Inhibition of tumor formation by snake venom disintegrin

The metastasis of tumor cells to bone involves migration, invasion and adhesion to bone. Breast and prostate cancer cells have predilection for spreading to bone. Snake venom-derived arginine-glycine-aspartic acid (RGD)-containing disintegrins (e.g. rhodostomin) have been demonstrated to inhibit cell adhesion. Here, we found that rhodostomin inhibited the adhesion of breast and prostate carcinoma cells to both unmineralized and mineralized bone extracellular matrices in a dose-dependent manner, without affecting the viability of tumor cells. In addition, rhodostomin also inhibited the migration and invasion of breast and prostate carcinoma cells. It specifically inhibited the binding of monoclonal antibody (MoAb) 7E3, which recognizes integrin alphavbeta3, to tumor cells, but not those of other MoAbs against other integrin subunits such as alpha2, alpha3, alpha5 and beta1. As breast cancer cells MDA-MB-231 were locally injected into tibia in nude mice, histological examination of the tibia of control group revealed that most of the cancellous bone had been replaced by the breast cancer cells after 28 days' inoculation. In contrast, co-administration of trigramin with cancer cells markedly inhibited tumor growth and bone destruction. Taken together, disintegrins strongly inhibit the adhesion, migration, invasion of tumor cells and also tumor growth of human breast cancer cells in bone as well. Therefore, disintegrins may be developed as alternate therapy for bone metastasis of cancer cells.

High plasma concentrations of osteopontin in patients with interstitial pneumonia

Osteopontin (OPN) produced by alveolar macrophages functions as a fibrogenic cytokine in the development of bleomycin (BLM)-induced murine pulmonary fibrosis, and OPN mRNA is expressed on lung tissues from patients with idiopathic pulmonary fibrosis (IPF). The present study investigates plasma OPN levels in human interstitial pneumonia (IP) and their relationships with disease severity by analyzing the correlation between plasma OPN concentrations and pulmonary functions. The concentrations of OPN in plasma were measured in 17 patients with IP, in 9 with sarcoidosis and in 20 healthy controls using an antigen-capture enzyme-linked immunosorbent assay. The concentrations of OPN in plasma were significantly higher in IP patients than in those with sarcoidosis or in controls. Based on a Receiver Operating Characteristic curve analysis, cut-off points between 300 and 380 ng/ml discriminated between IP and control subjects with 100% sensitivity and 100% specificity. In such case, the sensitivity for sarcoidosis decreased (55.5-33.3%) in cut-offs with 100% specificity. Plasma OPN levels inversely and closely correlated with arterial oxygen tension (PaO2) in patients with IP. Immunohistochemically, OPN was localized predominantly in macrophages and airway epithelium. These findings suggest that plasma OPN levels were found to be associated with the presence of IP, and that OPN play an important role in the development of IP.

Osteopontin modulates myocardial hypertrophy in response to chronic pressure overload in mice

Osteopontin (OPN) expression increases in the heart during hypertrophy and heart failure. Here, we studied the role of OPN in pressure overload-induced hypertrophy and analyzed the signaling pathways involved in hypertrophy. Aortic banding (AB) was performed in a group of wild-type (WT) and OPN knockout (KO) mice to induce pressure overload. Left ventricular (LV) structural and functional remodeling was studied 1 month after AB. AB increased OPN and beta1 integrin (a receptor for OPN) protein expression in WT-AB group. Hypertrophic response as measured by increased heart weight-to-body weight ratio and myocyte cross-sectional area was significantly increased in WT-AB and KO-AB groups when compared with their respective shams. However, the increase was significantly higher in WT-AB. Re-expression of atrial natriuretic factor was only detected in WT-AB group. LV end-diastolic pressure-volume curve obtained using Langendorff perfusion analysis exhibited a leftward shift in WT-AB group, not in KO-AB. LV-developed pressures measured over a range of LV volumes were significantly increased in WT-AB, not in KO-AB mice. Increased phosphorylation of c-Jun N-terminal kinases, p38 kinase, Akt, and glycogen synthase kinase-3beta was significantly higher in WT-AB when compared with KO-AB group. Increased OPN expression may play an essential role in modulating compensatory cardiac hypertrophy in response to chronic pressure overload.

Transgenic mice expressing osteopontin in hepatocytes as a model of autoimmune hepatitis

Osteopontin, a crucial factor for Th1 immune response, is expressed in stellate cells and macrophages activated in injured liver. To clarify the role of osteopontin in inflammatory changes in the liver, we attempted to establish transgenic mice expressing osteopontin in hepatocytes. Mouse osteopontin cDNA, cloned from concanavalin-A-stimulated spleen cells in C57BL/6 mice, was constructed into the vector containing serum amyloid-P component promoter. This construction was microinjected into fertilized eggs of C57BL/6 mice, and 4 lines of the transgenic mice were obtained. Western blotting and immunohistochemistry revealed that osteopontin was expressed in hepatocytes, but not in non-parenchymal cells, in the transgenic mice. The mean osteopontin concentrations in the liver and plasma in the mice were 13 and 2.6 times higher than those in negative littermates. Antinuclear antibody was positive in the plasma in 50% of the transgenic mice. In the transgenic mice later than 12 weeks of age, mononuclear cell infiltration in the liver developed, and these cells were positive for CD8 and HLA-DR. Plasma ALT activity was increased with focal necrosis in hepatic lobules in the transgenic mice later than 24 weeks of age. The transgenic mice expressing osteopontin in hepatocytes may be useful as a model of autoimmune hepatitis.

Osteopontin is up-regulated in human decidual stromal cells

OBJECTIVE

To analyze expression and regulation of osteopontin in human stromal endometrial and decidual cells.

DESIGN

Study by immunohistochemistry, RNase protection assay, and in vitro study.

SETTING

Academic research unit.

PATIENT(S)

Twenty-five fertile women.

INTERVENTION(S)

Expression of osteopontin mRNA and protein was analyzed by RNase protection assay (RPA) and immunohistochemistry in secretory endometrium and decidua. Regulation of osteopontin expression in endometrial epithelial cell and stromal cells was analyzed by incubation with 17beta-estrogen, progesterone, IL-1beta, IL-6, and LIF and by incubation with cell culture supernatants of decidual natural killer cells. Furthermore, osteopontin expression was studied in stromal cells, decidualized in vitro.

MAIN OUTCOME MEASURE(S)

mRNA and protein expression and regulation of endometrial stromal osteopontin.

RESULT(S)

Osteopontin mRNA and protein are expressed at increasing concentrations in human secretory endometrium and in decidua. High concentrations in total decidua were due to high osteopontin concentrations in decidualized stromal cells. Osteopontin mRNA and protein expression was not regulated by incubation of endometrial epithelial and stromal cells with steroids, cytokines, and natural killer cell supernatant for 6 and 24 hours. In contrast, decidualization of stromal cells for 7, 14, and 21 days resulted in significant up-regulation of osteopontin mRNA and protein.

CONCLUSION(S)

Osteopontin is expressed at high concentrations in secretory endometrium in epithelial cells and in decidua in stromal cells. Decidual stromal expression of osteopontin is up-regulated by decidualization.

ERK1/2 and JNKs, but not p38 kinase, are involved in reactive oxygen species-mediated induction of osteopontin gene expression by angiotensin II and interleukin-1beta in adult rat cardiac fibroblasts

Osteopontin (OPN), also called cytokine Eta-1, expressed in the myocardium co-incident with heart failure plays an important role in post myocardial infarction (MI) remodeling by promoting collagen synthesis and accumulation. Angiotensin II (Ang II) and inflammatory cytokines are increased in the heart following MI. We studied the involvement of mitogen-activated protein kinases (ERK1/2, JNKs, p38 kinase) and reactive oxygen species (ROS) in Ang II- and cytokine-induced OPN gene expression in adult rat cardiac fibroblasts. Ang II alone increased OPN mRNA (3.3 +/- 0.3-folds; P < 0.05; n = 7), while interleukin-1beta (IL-1beta), tumor necrosis factor (TNF-alpha), and interferon-gamma (IFN-gamma) had no effect. A combination of Ang II with IL-1beta or TNF-alpha, not IFN-gamma, increased OPN mRNA more than Ang II alone. Nitric oxide donor, S-nitrosoacetylpenicillamine (SNAP), alone or in combination with Ang II had no effect. Diphenylene iodonium (DPI), inhibitor of NAD(P)H oxidase, and tiron, superoxide scavenger, inhibited Ang II- and Ang II+ IL-1beta-stimulated increases in OPN mRNA. Ang II activated ERK1/2 within 5 min of treatment, not JNKs. IL-1beta activated ERK1/2 and JNKs within 15 min of treatment. A combination of Ang II and IL-1beta activated ERK1/2 within 5 min of treatment. None of these stimuli activated p38 kinase. DPI almost completely inhibited Ang II + IL-1beta-stimulated activation of ERK1/2, while partially inhibiting JNKs. PD98059, ERK1/2 pathway inhibitor, and SP600125, JNKs inhibitor, partially inhibited Ang II + IL-1beta-stimulated increases in OPN mRNA. A combination of PD98059 and SP600125 almost completely inhibited Ang II + IL-1beta-stimulated increases in OPN mRNA. Thus, Ang II alone increases OPN expression, while IL-1beta and TNF-alpha act synergistically with Ang II to increase OPN mRNA possibly via NO independent mechanisms. The synergistic increase in OPN mRNA involves ROS-mediated activation of ERK1/2 and JNKs, not P38 kinase, pathways in cardiac fibroblasts.

Genetic polymorphims in promoter region of osteopontin gene may be a marker reflecting hepatitis activity in chronic hepatitis C patients

BACKGROUND AND AIMS

Osteopontin, an extracellular matrix protein with RGD motif, is shown to be a cytokine essential for Th1 immune response initiation. Genetic polymorphisms in the osteopontin gene (OPN) determine the magnitude of immunity against rickettsial infection in mice. Similar polymorphisms, if present also in human beings, might affect hepatitis activity in those infected with HCV.

METHODS

Blood was collected from 176 patients with chronic hepatitis C. SNPs in the promoter region of OPN were analyzed in 20 patients by direct sequencing of DNA fragments amplified by PCR and in 156 patients by Invader assay. Ninety-five patients compatible to evaluation criteria were classified into three groups depending on maximal serum ALT levels during the observation periods at least for 2 years as follows; lower than 30IU/L (low-activity group), between 30 and 80IU/L with no hepatoprotective treatment (medium-activity group), and higher than 80IU/L irrespective of hepatoprotective treatment (high-activity group).

RESULTS

There were 16, 19, and 60 patients in the low-, medium-, and high-activity groups, respectively. Four SNPs (nt -155, -443, -616, and -1748) were detected in the promoter region of OPN. Among them, the SNP at nt -443 (C or T) was a novel one and showed an association with hepatitis activity in our patients: T/T homozygosity was found in 2 (13%), 8 (42%), and 25 (44%), and C/T heterozygosity in 12 (75%), 8 (42%), and 23 (40%), in the low-, medium-, and high-activity groups, respectively. The other 3 SNPs already known showed linkage disequilibrium with D(') and r(2) greater than 0.937 to each other without correlation to disease activity.

CONCLUSIONS

OPN promoter region SNP at nt -433 may be a useful marker reflecting hepatitis activity in chronic hepatitis C patients.

Osteopontin inhibits interleukin-1beta-stimulated increases in matrix metalloproteinase activity in adult rat cardiac fibroblasts: role of protein kinase C-zeta

We have shown that osteopontin (OPN), an extracellular matrix protein, plays an important role in post myocardial infarction (MI) remodeling by promoting collagen synthesis and accumulation. Interleukin-1beta (IL-1beta), increased in the heart following MI, increases matrix metalloproteinase (MMP) activity in cardiac fibroblasts in vitro. Here, we show that OPN alone has no effect on MMP activity or expression. However, it reduces IL-1beta-stimulated increases in MMP activity and expression in adult rat cardiac fibroblasts. Pretreatment with bovine serum albumin had no effect on MMP activity or protein content, whereas GRGDS (glycine-arginine-glycine-aspartic acid-serine)-pentapeptide (which interrupts binding of RGD-containing proteins to cell surface integrins) and monoclonal antibody m7E3 (a rat beta3 integrins antagonist) inhibited the effects of OPN. Inhibition of PKC using chelerythrine inhibited the activities of both MMP-2 and MMP-9. Stimulation of cells using IL-1beta increased phosphorylation and translocation of PKC to membrane fractions, which was inhibited by OPN. OPN inhibited IL-1beta-stimulated increases in translocation of PKC-zeta from cytosolic to membrane fractions. Furthermore, the levels of phospho-PKC-zeta were lower in the cytosolic fractions of OPN knock-out mice hearts as compared with wild type 6 days post-MI. Inhibition of PKC-zeta using PKC-zeta pseudosubstrate inhibited IL-1beta-stimulated increases in MMP-2 and MMP-9 activities. These observations suggest that OPN, acting via beta3 integrins, inhibits IL-1beta-stimulated increases in MMP-2 and MMP-9 activity, at least in part, via the involvement of PKC-zeta. Thus, OPN may play a key role in collagen deposition during myocardial remodeling following MI by modulating cytokine-stimulated MMP activity.

Comparative analysis of effects of cytokine gene adjuvants on DNA vaccination against Mycobacterium tuberculosis heat shock protein 65

DNA-based vaccines generate potent cellular immunity as well as humoral immunity. It seems evident that cytokines play a crucial role in generation of effector T cell subsets and in determining the magnitude of the response by DNA vaccines. In this study, we compared the effects of several TH1 cytokine genes as adjuvant in DNA vaccination using mycobacterial Hsp65 as a model antigen. Our results demonstrated that although the overall immune response to Hsp65 was enhanced by co-injection of Hsp65 DNA with cytokine genes, each cytokine gene was shown to affect different immune response elements. Co-injection of Hsp65 DNA with IL-12 or GM-CSF led to an increase in IFN-gamma production and represented potent protections against Mycobacterium tuberculosis challenge, while that with Eta-1, IL-12 or IL-18 gene led to an elevated IgG2a/IgG1 ratio. Interestingly, co-administration of Flt3L gene was shown to enhance the Ag-specific CTL response. These results show that the direction and magnitude of immune response in DNA vaccination against Hsp65 of M. tuberculosis could be modulated in different ways by co-injection of an appropriate cytokine gene as adjuvant.

High plasma osteopontin level and its relationship with interleukin-12-mediated type 1 T helper cell response in tuberculosis

Osteopontin (OPN, also known as Eta-1), a noncollagenous matrix protein produced by macrophages and T lymphocytes, is expressed in granulomatous lesions caused by Mycobacterium tuberculosis infection. In the present study, we compared plasma concentrations of OPN in patients with active pulmonary tuberculosis with those of healthy control subjects and patients with sarcoidosis, another disease associated with granuloma formation. Plasma OPN levels were significantly higher in patients with tuberculosis (n = 48) than in control subjects (n = 34) and patients with sarcoidosis (n = 20). OPN levels correlated well with severity of pulmonary tuberculosis, as indicated by the size of lung lesions on chest X-ray films. Furthermore, chemotherapy resulted in a significant fall in plasma OPN levels. In patients with tuberculosis, plasma OPN concentrations correlated significantly with those of interleukin (IL)-12. In vitro experiments showed that OPN production by peripheral blood mononuclear cells infected with Mycobacterium bovis bacillus Calmette-Guérin preceded the synthesis of IL-12 and interferon-gamma and that the neutralizing anti-OPN monoclonal antibody significantly reduced the production of IL-12 and interferon-gamma. Our results suggest that OPN may be involved in the pathologic process associated with active pulmonary tuberculosis by inducing IL-12-mediated type 1 T helper cell responses.

Transcriptional regulation of osteopontin and the metastatic phenotype: evidence for a Ras-activated enhancer in the human OPN promoter

Elevated osteopontin (OPN) transcription often correlates with increased metastatic potential of transformed cells, and in several model systems OPN--whether produced by the tumor cells or by stromal cells - has been shown to enhance metastatic ability. Sequence elements in the OPN promoter have been identified on the basis of their ability to interact with protein factors associated with the tumorigenic process in one or more cell lineages. One of these is a Ras-activated enhancer (RAE) that binds a protein, the Ras-response factor (RRF), whose ability to form a complex with the RAE is stimulated by Ras signaling in fibroblasts and epithelial cells. Another is the T cell factor-4 binding site, which in the OPN promoter can retard OPN transcription when bound by the Tcf-4 protein. In Rama 37 rat mammary epithelial cells Tcf-4 suppresses OPN transcription and the metastatic phenotype. A third promoter segment consists of two sequences in the -94 to -24 region of the human OPN promoter able to bind several known transcription factors, including Sp1, Myc and Oct-1, which may act synergistically to stimulate OPN transcription in malignant astrocytic cells. Although expression of other genes may also be regulated by these transcription factors, evidence suggests that often OPN alone can stimulate metastasis. In this communication we address two issues: (1) How does OPN facilitate the metastatic phenotype? (2) What mechanisms are responsible for the increase in OPN transcription in metastatic cells?

Osteopontin is involved in the formation of epithelioid granuloma and bile duct injury in primary biliary cirrhosis

Recently, it was shown that osteopontin (OPN) is involved as a chemoattractant cytokine in the recruitment of macrophages and T lymphocytes in the granulomas of diverse etiologies and also plays an important role in the production of autoantibodies and development of autoimmune diseases. Primary biliary cirrhosis (PBC) is characterized by immune-mediated bile duct damage with frequent epithelioid granulomas. In this study, the expression of OPN was immunohistochemically examined in 25 PBC and 52 control livers. Epithelioid cells within granuloma in PBC expressed OPN variably. These cells were also positive for CD68, suggesting their histiocyte/macrophage lineage. In addition, strong expression of OPN was seen in the cytoplasm of mononuclear cells infiltrating around granulomas and also damaged bile ducts in PBC. The number of such positive mononuclear cells and the ratio of OPN-positive cells/total infiltrating cells in portal tracts were higher in PBC than in controls. The majority of these OPN-positive cells were found to be IgG- or IgM-producing plasma cells. These suggest that in PBC, OPN is an important immune molecule in portal tracts, and contributes to the recruitment of mononuclear cells into epithelioid granuloma and also participates in bile duct injury via B-cell differentiation and plasma cell expansion.

Tumors associated with oncogenic osteomalacia express genes important in bone and mineral metabolism

Oncogenic osteomalacia (OOM) is associated with primitive mesenchymal tumors that secrete phosphaturic factors resulting in low serum concentrations of phosphate and calcitriol, phosphaturia, and defective bone mineralization. To identify overexpressed genes in these tumors, we compared gene expression profiles of tumors resected from patients with OOM and histologically similar control tumors using serial analysis of gene expression (SAGE). Three hundred and sixty-four genes were expressed at least twofold greater in OOM tumors compared with control tumors. A subset of 67 highly expressed genes underwent validation with an extended set of OOM and control tumors using array analysis or reverse-transcription polymerase chain reaction (RT-PCR). Ten of these validated genes were consistently overexpressed in all OOM tumors relative to control tumors. Strikingly, genes with roles in bone matrix formation, mineral ion transport, and bone mineralization were highly expressed in the OOM tumors.