Liver biopsy is the current reliable way of evaluating liver fibrosis. However, no specific sera biomarker could be applied in clinical diagnosis. As the pivotal role of osteopontin (OPN) reported in ...numerous liver diseases, thrombin‐cleaved OPN (Thr‐OPN) exposes an integrin‐binding motif that promoted biological functions. Herein, we investigated the potential of Thr‐OPN in liver fibrosis. Using patient samples, mouse models and hepatic stellate cells (HSCs), we analyzed the involvement of Thr‐OPN in liver fibrosis. The result showed that, first, Thr‐OPN level was significantly higher in patients with liver cirrhosis than that in patients with chronic hepatitis B and healthy controls. Thr‐OPN level was positively correlated with liver fibrosis degree in clinical samples. Then in mouse models, it showed a similar correlation between hepatic Thr‐OPN levels and liver fibrosis degree. Thr‐OPN peptides exacerbated liver fibrosis in OPN‐deficient mice, whereas the neutralization of Thr‐OPN alleviated liver fibrosis in wild‐type mice. Furthermore, when compared with full‐length OPN (FL‐OPN), Thr‐OPN exhibited a greater ability to promote HSC activation, proliferation, and migration via mitogen‐activated protein (MAP) kinase and nuclear factor (NF)‐κB pathways. In conclusion, Thr‐OPN, not FL‐OPN, was critically involved in the exacerbation of liver fibrosis by α9 and α4 integrins via MAP kinase and NF‐κB signaling pathway, thus representing a novel diagnostic biomarker and treatment target for liver cirrhosis.
Thrombin‐cleaved osteopontin (Thr‐OPN), not full‐length OPN (FL‐OPN), was critically involved in the pathogenesis of liver fibrosis by α9 and α4 integrins via mitogen‐activated protein (MAP) kinase and nuclear factor (NF‐κB) signaling pathway, thus representing a novel diagnostic biomarker and treatment target for liver cirrhosis.
Classically, osteopontin (OPN) has been described as a secreted glycophosprotein. Indeed, most data concerning its physiological and pathological roles are mainly related to the secreted OPN (sOPN). ...However, there are several instances in which intracellular OPN (iOPN) has been described, presenting some specific roles in distinct experimental models, such as in the immune system, cancer cells, and neurological disorders. We herein aimed to highlight and discuss some of these secreted and intracellular roles of OPN and their putative clinical and biological impacts. Moreover, by consolidating data from the OPN protein database, we also analyzed the occurrence of signal peptide (SP) sequences and putative subcellular localization, especially concerning currently known OPN splicing variants (OPN-SV). Comprehending the roles of OPN in its distinct cellular and tissue environments may provide data regarding the additional applications of this protein as biomarkers and targets for therapeutic purposes, besides further describing its pleiotropic roles.
Abstract Atherosclerosis is a chronic inflammatory process of the vessel wall with systemic correlates. It is now well established that patients' outcome is tightly linked to atherosclerotic plaque ...stability, potentially more so than to the mere plaque size. Osteopontin (OPN) is an integrin-binding ligand, N-linked glycoprotein, which was recognized as a significant participant in the atherosclerotic inflammatory milieu. Evidence from several genetic mouse models suggests that OPN is an enhancer of atherosclerosis. This may be mediated by its capacity to enhance inflammation in the atherosclerotic plaque. Interestingly, OPN may also possess potentially protective vascular effects, such as attenuation of vascular calcification. In humans circulating levels of OPN were found to be independently associated with the severity of coronary atherosclerosis. Moreover, several studies report that high plasma OPN levels were associated with increased risk for major adverse cardiac events. This review aims to critically assess current understanding of the role of OPN in the atherosclerotic process, from animal models to clinical practice. Specific focus is given to evaluating whether OPN could serve as a marker for monitoring coronary atherosclerosis severity, and in parallel, assess the evidence for its role as a mediator in the pathogenic pathways leading to atherosclerotic vascular disease.
Osteopontin in Vascular Disease Lok, Zoe Shin Yee; Lyle, Alicia N
Arteriosclerosis, thrombosis, and vascular biology,
04/2019, Volume:
39, Issue:
4
Journal Article
Peer reviewed
Open access
Inflammatory cytokines are necessary for an acute response to injury and the progressive healing process. However, when this acute response does not resolve and becomes chronic, the same proteins ...that once promoted healing then contribute to chronic inflammatory pathologies, such as atherosclerosis. OPN (Osteopontin) is a secreted matricellular cytokine that signals through integrin and CD44 receptors, is highly upregulated in acute and chronic inflammatory settings, and has been implicated in physiological and pathophysiologic processes. Evidence from the literature suggests that OPN may fit within the Goldilocks paradigm with respect to cardiovascular disease, where acute increases are protective, attenuate vascular calcification, and promote postischemic neovascularization. In contrast, chronic increases in OPN are clinically associated with an increased risk for a major adverse cardiovascular event, and OPN expression is a strong predictor of cardiovascular disease independent of traditional risk factors. With the recent finding that humans express multiple OPN isoforms as the result of alternative splicing and that these isoforms have distinct biologic functions, future studies are required to determine what OPN isoform(s) are expressed in the setting of vascular disease and what role each of these isoforms plays in vascular disease progression. This review aims to discuss our current understanding of the role(s) of OPN in vascular disease pathologies using evidence from in vitro, animal, and clinical studies. Where possible, we discuss what is known about OPN isoform expression and our understanding of OPN isoform contributions to cardiovascular disease pathologies.
Osteopontin (OPN) is a multifunctional cytokine that impacts cell proliferation, survival, drug resistance, invasion, and stem like behavior. Due to its critical involvement in regulating cellular ...functions, its aberrant expression and/or splicing is functionally responsible for undesirable alterations in disease pathologies, specifically cancer. It is implicated in promoting invasive and metastatic progression of many carcinomas. Due to its autocrine and paracrine activities OPN has been shown to be a crucial mediator of cellular cross talk and an influential factor in the tumor microenvironment. OPN has been implicated as a prognostic and diagnostic marker for several cancer types. It has also been explored as a possible target for treatment. In this article we hope to provide a broad perspective on the importance of OPN in the pathophysiology of cancer.
•A comprehensive review of the literature on OPN•Role of OPN in the critical hallmarks of cancer•Focus on the role of cancer cell-derived OPN as well as host-derived OPN•OPN as a drug target, a marker of disease progression and response to therapy
Liver fibrosis is associated with significant collagen-I deposition largely produced by activated hepatic stellate cells (HSCs); yet, the link between hepatocyte damage and the HSC profibrogenic ...response remains unclear. Here we show significant induction of osteopontin (OPN) and high-mobility group box-1 (HMGB1) in liver fibrosis. Since OPN was identified as upstream of HMGB1, we hypothesised that OPN could participate in the pathogenesis of liver fibrosis by increasing HMGB1 to upregulate collagen-I expression.
Patients with long-term hepatitis C virus (HCV) progressing in disease stage displayed enhanced hepatic OPN and HMGB1 immunostaining, which correlated with fibrosis stage, whereas it remained similar in non-progressors. Hepatocyte cytoplasmic OPN and HMGB1 expression was significant while loss of nuclear HMGB1 occurred in patients with HCV-induced fibrosis compared with healthy explants. Well-established liver fibrosis along with marked induction of HMGB1 occurred in CCl
-injected
transgenic yet it was less in wild type and almost absent in
mice.
ablation in hepatocytes (
) protected mice from CCl
-induced liver fibrosis. Coculture with hepatocytes that secrete OPN plus HMGB1 and challenge with recombinant OPN (rOPN) or HMGB1 (rHMGB1) enhanced collagen-I expression in HSCs, which was blunted by neutralising antibodies (Abs) and by
or
ablation. rOPN induced acetylation of HMGB1 in HSCs due to increased NADPH oxidase activity and the associated decrease in histone deacetylases 1/2 leading to upregulation of collagen-I. Last, rHMGB1 signalled via receptor for advanced glycation end-products and activated the PI3K-pAkt1/2/3 pathway to upregulate collagen-I.
During liver fibrosis, the increase in OPN induces HMGB1, which acts as a downstream alarmin driving collagen-I synthesis in HSCs.
Clonal myeloproliferation and development of bone marrow (BM) fibrosis are the major pathogenetic events in myelofibrosis (MF). The identification of novel antifibrotic strategies is of utmost ...importance since the effectiveness of current therapies in reverting BM fibrosis is debated. We previously demonstrated that osteopontin (OPN) has a profibrotic role in MF by promoting mesenchymal stromal cells proliferation and collagen production. Moreover, increased plasma OPN correlated with higher BM fibrosis grade and inferior overall survival in MF patients. To understand whether OPN is a druggable target in MF, we assessed putative inhibitors of OPN expression in vitro and identified ERK1/2 as a major regulator of OPN production. Increased OPN plasma levels were associated with BM fibrosis development in the Romiplostim-induced MF mouse model. Moreover, ERK1/2 inhibition led to a remarkable reduction of OPN production and BM fibrosis in Romiplostim-treated mice. Strikingly, the antifibrotic effect of ERK1/2 inhibition can be mainly ascribed to the reduced OPN production since it could be recapitulated through the administration of anti-OPN neutralizing antibody. Our results demonstrate that OPN is a novel druggable target in MF and pave the way to antifibrotic therapies based on the inhibition of ERK1/2-driven OPN production or the neutralization of OPN activity.
Background
Osteopontin (OPN) is a pleiotropic glycoprotein expressed in various cell types in animals and in humans, including bone, immune, smooth muscle, epithelial and endothelial cells. Moreover, ...OPN is found in kidneys (in the thick ascending limbs of the loop of Henle and in distal nephrons) and urine. The protein plays an important role in mineralization and bone resorption. In addition, OPN is involved in the regulation of immunity and inflammation, angiogenesis and apoptosis. It was demonstrated that OPN and some OPN gene polymorphic variants are associated with the pathogenesis and progression of multiple disorders, such as cancer, autoimmune, neurodegenerative and cardiovascular diseases. Moreover, recent studies suggested that OPN is associated with the pathogenesis of renal failure.
Methods
In this review, I briefly discussed the role of OPN and its gene polymorphisms in kidney physiology, as well as in various kidney diseases.
Findings and Conclusion
Most studies reported that OPN expression is elevated in urolithiasis, and also in acute and chronic kidney diseases, and in renal allograft dysfunction. Moreover, it was demonstrated that polymorphic variants of the OPN gene may be associated with renal failure. However, some reports suggested that OPN is essential for tubulogenesis, and that it inhibits calcium oxalate crystal formation and retention, nitric oxide synthesis, cell apoptosis and promotes cell regeneration.
Thus, further studies are required to fully understand the role of OPN in kidney physiology and pathology. Eventually, these studies may result in the identification of OPN as a valuable marker for renal dysfunction prognosis and treatment.
Lung cancers with activating KRAS mutations are characterized by treatment resistance and poor prognosis. In particular, the basis for their resistance to radiation therapy is poorly understood. ...Here, we describe a radiation resistance phenotype conferred by a stem-like subpopulation characterized by mitosis-like condensed chromatin (MLCC), high CD133 expression, invasive potential, and tumor-initiating properties. Mechanistic investigations defined a pathway involving osteopontin and the EGFR in promoting this phenotype. Osteopontin/EGFR-dependent MLCC protected cells against radiation-induced DNA double-strand breaks and repressed putative negative regulators of stem-like properties, such as CRMP1 and BIM. The MLCC-positive phenotype defined a subset of KRAS-mutated lung cancers that were enriched for co-occurring genomic alterations in TP53 and CDKN2A. Our results illuminate the basis for the radiation resistance of KRAS-mutated lung cancers, with possible implications for prognostic and therapeutic strategies.
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