Osteopontin and the skin: multiple emerging roles in cutaneous biology and pathology

31-GEP (DecisionDx): a review of clinical utility and performance in a Mayo Clinic cohort

BACKGROUND

Cutaneous melanoma (CM) is a significant health concern because of its high metastatic potential. Gene Expression Profile (GEP) testing, particularly the 31-GEP test (DecisionDx-Melanoma), has been increasingly used for risk stratification in CM patients. This study aimed to evaluate the clinical utility and performance of the 31-GEP test in a real-world setting.

METHODS

Patients with CM who underwent 31-GEP testing from August 2014 to August 2022 at our institution were identified through searches of electronic health records. The study analyzed the influence of 31-GEP testing on clinical decision-making related to sentinel lymph node biopsy (SLNB), medical oncology referral, and postdiagnosis surveillance. Kaplan-Meier curves and Cox proportional hazard models were used to elucidate the test's performance, focusing on relapse-free survival (RFS) and melanoma-specific survival (MSS).

RESULTS

The study included 65 CM patients. Dermatologists ordered more than 80% of 31-GEP tests. In 81.5% of cases, 31-GEP results did not alter standard clinical management. SLNB decisions were unaffected in 92% of patients with pre-SLNB 31-GEP results. Among patients with stage I-IIA melanoma, 25% of those with high-risk 31-GEP results were referred to medical oncology. Contrary to expectations, the rate of nodal metastasis was higher in low-risk than in high-risk 31-GEP cases. Survival analysis showed overlapping RFS and MSS curves between different 31-GEP classes, suggesting limited prognostic value.

CONCLUSIONS

The 31-GEP test has a limited impact on clinical management decisions and shows limited prognostic value.

Structural extracellular matrix-mediated molecular signaling in wound repair and tissue regeneration

The extracellular matrix (ECM) is a complex, non-cellular network of molecules that offers structural support for cells and tissues. The ECM is composed of various structural components, including collagen, fibronectin, laminin, perlecan, nidogen, tenascin, and fibulin, which are capable of binding to each other and to cell-to-adhesion receptors, endowing the ECM with unique physical and biochemical properties that are essential for its function in maintaining health and managing disease. Over the past three decades, extensive research has shown that the core of the ECM can significantly impact cellular events at the molecular level. Structural modifications have also been strongly associated with tissue repair. Through interactions with cells, matrix proteins regulate critical processes such as cell proliferation and differentiation, migration, and apoptosis, essential for maintaining tissue homeostasis, formation, and regeneration. This review emphasizes the interlocking networks of ECM macromolecules and their primary roles in tissue regeneration and wound repair. Through studying ECM dynamics, researchers have discovered molecular signaling pathways that demonstrate how the ECM influences protein patterns and open up more possibilities for developing therapeutics that target the ECM to enhance wound repair and tissue regeneration.

The Role of Osteopontin in Psoriasis-A Scoping Review

Psoriasis is a chronic systemic disease with an immunological basis and a complex pathophysiology. The chronic inflammatory status of psoriasis is associated with several comorbidities, such as metabolic syndrome, obesity, and cardiovascular disease. The development of psoriasis is influenced by osteopontin, a glycoprotein that influences physiological and pathological reactions by modulating Th1 and Th17 cellular responses, stimulating keratinocyte proliferation, regulating cellular apoptosis, and promoting angiogenesis. The recent identification of immune pathways involved in psoriasis development has facilitated the development of biological treatments; however, a better understanding of the intricate relationship between underlying inflammatory processes, psoriasis development, and accompanying comorbidities is needed for improved disease management.

Epithelial-like transport of mineral distinguishes bone formation from other connective tissues

We review unique properties of bone formation including current understanding of mechanisms of bone mineral transport. We focus on formation only; mechanism of bone degradation is a separate topic not considered. Bone matrix is compared to other connective tissues composed mainly of the same proteins, but without the specialized mechanism for continuous transport and deposition of mineral. Indeed other connective tissues add mechanisms to prevent mineral formation. We start with the epithelial-like surfaces that mediate transport of phosphate to be incorporated into hydroxyapatite in bone, or in its ancestral tissue, the tooth. These include several phosphate producing or phosphate transport-related proteins with special expression in large quantities in bone, particularly in the bone-surface osteoblasts. In all connective tissues including bone, the proteins that constitute the protein matrix are mainly type I collagen and γ-carboxylate-containing small proteins in similar molar quantities to collagen. Specialized proteins that regulate connective tissue structure and formation are surprisingly similar in mineralized and non-mineralized tissues. While serum calcium and phosphate are adequate to precipitate mineral, specialized mechanisms normally prevent mineral formation except in bone, where continuous transport and deposition of mineral occurs.

Downregulation of RUNX1-Activated Osteopontin Facilitates Burn Wound Healing by Activating the MAPK Pathways

Burn wounds require intervention to ensure timely progression to reduce morbidity and mortality. The migrative and proliferative capabilities of keratinocytes are impaired in wounds. Matrix metalloproteinases (MMPs) can degrade the extracellular matrix (ECM), allowing epithelial cells to migrate. As reported, osteopontin can regulate cell migration, cell adhesion, and ECM invasion in endothelial and epithelial cells, and its expression is significantly increased in chronic wounds. Therefore, this study investigates the biological functions of osteopontin and its related mechanisms involved in burn wounds. We established cellular and animal models of burn injury. Levels of osteopontin, RUNX1, MMPs, collagen I, CK19, PCNA, and pathway-associated proteins were measured by RT-qPCR, western blotting, and immunofluorescence staining. Cell viability and migration were examined by CCK-8 and wound scratch assays. Histological changes were analyzed by hematoxylin and eosin staining and Masson's trichrome staining. For in vitro analysis, osteopontin silencing facilitated the growth and migration of HaCaT cells and promoted ECM degradation in HaCaT cells. Mechanistically, RUNX1 bound to osteopontin promoter, and RUNX1 upregulation attenuated the promoting efficacy of osteopontin silencing on cell growth and migration and ECM degradation. Additionally, RUNX1-activated osteopontin inactivated the MAPK signaling pathway. For in vivo analysis, osteopontin depletion facilitated burn wound healing by promoting reepithelialization and ECM degradation. In conclusion, RUNX1 activates the osteopontin expression at the transcriptional level and osteopontin depletion facilitates the recovery of burn wounds by promoting the migration of keratinocytes and reepithelization and ECM degradation by activating the MAPK pathway.

Osteopontin and Regulatory T Cells in Effector Phase of Allergic Contact Dermatitis

Studies have shown that osteopontin (OPN) and regulatory T cells play a role in allergic contact dermatitis (ACD), but the mechanisms responsible for their function are poorly understood. The study aimed to determine CD4 T lymphocytes producing intracellular osteopontin (iOPN T cells) and assess the selected T lymphocyte subsets including regulatory T cells in the blood of patients with ACD. Twenty-six patients with a disseminated form of allergic contact dermatitis and 21 healthy controls were enrolled in the study. Blood samples were taken twice: in the acute phase of the disease and during remission. The samples were analyzed by the flow cytometry method. Patients with acute ACD showed significantly higher percentage of iOPN T cells compared with healthy controls which persisted during remission. An increase in the percentage of CD4CD25 and a reduced percentage of regulatory T lymphocytes (CD4CD25highCD127low) were also found in the patients with acute stage of ACD. The percentage of CD4CD25 T lymphocytes showed a positive correlation with the EASI index. The increase in the iOPN T cells can indicate their participation in acute ACD. The decreased percentage of regulatory T lymphocytes in the acute stage of ACD may be related to the transformation of Tregs into CD4CD25 T cells. It may also indicate their increased recruitment to the skin. The positive correlation between the percentage of CD4CD25 lymphocytes and the EASI index may be indirect evidence for the importance of activated lymphocytes-CD4CD25 in addition to CD8 lymphocytes as effector cells in ACD.

Hyperbaric oxygen therapy augments ciprofloxacin effect against Pseudomonas aeruginosa biofilm infected chronic wounds in a mouse model

Introduction

Chronic wounds have a compromised microcirculation which leads to restricted gas exchange. The majority of these hypoxic wounds is infested with microorganisms congregating in biofilms which further hinders the antibiotic function. We speculate whether this process can be counteracted by hyperbaric oxygen therapy (HBOT).

Methodology

Twenty-eight BALB/c mice with third-degree burns were included in the analyses. Pseudomonas aeruginosa embedded in seaweed alginate beads was injected under the eschar to mimic a biofilm infected wound. Challenged mice were randomized to receive either 4 days with 1 x ciprofloxacin combined with 2 × 90 min HBOT at 2.8 standard atmosphere daily, 1 x ciprofloxacin as monotherapy or saline as placebo. The mice were clinically scored, and wound sizes were estimated by planimetry daily. Euthanasia was performed on day 8. Wounds were surgically removed in toto, homogenized and plated for quantitative bacteriology. Homogenate supernatants were used for cytokine analysis.

Results

P. aeruginosa was present in all wounds at euthanasia. A significant lower bacterial load was seen in the HBOT group compared to either the monotherapy ciprofloxacin group (p = 0.0008), or the placebo group (p < 0.0001). IL-1β level was significantly lower in the HBOT group compared to the placebo group (p = 0.0007). Both treatment groups had higher osteopontin levels than the placebo group (p = 0.002 and p = 0.004). The same pattern was seen in the S100A9 analysis (p = 0.01 and p = 0.008), whereas no differences were detected between the S100A8, the VEGF or the MMP8 levels in the three groups.

Conclusion

These findings show that HBOT improves the bactericidal activity of ciprofloxacin against P. aeruginosa wound biofilm in vivo. HBOT in addition to ciprofloxacin also modulates the host response to a less inflammatory phenotype.

Matricellular proteins in cutaneous wound healing

Cutaneous wound healing is a complex process that encompasses alterations in all aspects of the skin including the extracellular matrix (ECM). ECM consist of large structural proteins such as collagens and elastin as well as smaller proteins with mainly regulative properties called matricellular proteins. Matricellular proteins bind to structural proteins and their functions include but are not limited to interaction with cell surface receptors, cytokines, or protease and evoking a cellular response. The signaling initiated by matricellular proteins modulates differentiation and proliferation of cells having an impact on the tissue regeneration. In this review we give an overview of the matricellular proteins that have been found to be involved in cutaneous wound healing and summarize the information known to date about their functions in this process.

An integrin axis induces IFN-β production in plasmacytoid dendritic cells

Type I interferon (IFN) production by plasmacytoid dendritic cells (pDCs) has been mainly studied in the context of Toll-like receptor (TLR) activation. In the current report, we reveal that, in the absence of TLR activation, the integrin-binding SLAYGLR motif of secreted osteopontin (sOpn) induces IFN-β production in murine pDCs. This process is mediated by α4β1 integrin, indicating that integrin triggering may act as a subtle danger signal leading to IFN-β induction. The SLAYGLR-mediated α4 integrin/IFN-β axis is MyD88 independent and operates via a PI3K/mTOR/IRF3 pathway. Consequently, SLAYGLR-treated pDCs produce increased levels of type I IFNs following TLR stimulation. Intratumoral administration of SLAYGLR induces accumulation of IFN-β-expressing pDCs and efficiently suppresses melanoma tumor growth. In this process, pDCs are crucial. Finally, SLAYGLR enhances pDC development from bone marrow progenitors. These findings open new questions on the roles of sOpn and integrin α4 during homeostasis and inflammation. The newly identified integrin/IFN-β axis may be implicated in a wide array of immune responses.

Transcriptomics Analysis Indicates Trifarotene Reverses Acne-Related Gene Expression Changes

Background and Objectives: Trifarotene is a topical retinoid selective for retinoic acid receptor gamma that was recently approved for treatment of acne vulgaris. We performed a gene expression analysis to identify the molecular and cellular impact of trifarotene treatment on acne papules. Methods: In this open-label prospective study, subjects with moderate inflammatory acne of the back were treated with trifarotene 0.005% or vehicle cream on dedicated areas for 27 days, and 4 biopsies were collected from each subject (1 from skin without a visible acne lesion and three at the site of an acne papule: one baseline, one after vehicle treatment, and one after trifarotene treatment). Large scale gene expression profiling of the biopsies was performed using Affymetrix technology, treatment-specific gene expression profiles were generated using statistical modeling, and pathway analysis was performed. Using single-cell RNAseq data, in silico deconvolution of transcriptomics data was performed to identify cellular signatures. Results: We discovered a unique set of 67 genes modulated by trifarotene that are primarily involved in cellular migration, inflammation, and extracellular matrix reorganization. Changes in cellular expression were similar in both trifarotene-treated and spontaneously-resolving lesions. However, only trifarotene treatment impacted SPP1⁺ macrophages, a subset of highly proliferative macrophages recently identified in fibrotic tissue. Conclusions: These results show that trifarotene has a novel action in acne treatment by affecting epidermal and immune components of acne pathogenesis.

Reversing an Oncogenic Epithelial-to-Mesenchymal Transition Program in Breast Cancer Reveals Actionable Immune Suppressive Pathways

Approval of checkpoint inhibitors for treatment of metastatic triple negative breast cancer (mTNBC) has opened the door for the use of immunotherapies against this disease. However, not all patients with mTNBC respond to current immunotherapy approaches such as checkpoint inhibitors. Recent evidence demonstrates that TNBC metastases are more immune suppressed than primary tumors, suggesting that combination or additional immunotherapy strategies may be required to activate an anti-tumor immune attack at metastatic sites. To identify other immune suppressive mechanisms utilized by mTNBC, our group and others manipulated oncogenic epithelial-to-mesenchymal transition (EMT) programs in TNBC models to reveal differences between this breast cancer subtype and its more epithelial counterpart. This review will discuss how EMT modulation revealed several mechanisms, including tumor cell metabolism, cytokine milieu and secretion of additional immune modulators, by which mTNBC cells may suppress both the innate and adaptive anti-tumor immune responses. Many of these pathways/proteins are under preclinical or clinical investigation as therapeutic targets in mTNBC and other advanced cancers to enhance their response to chemotherapy and/or checkpoint inhibitors.

Assessing SPP1/Osteopontin (OPN) Splice Variants and Their Association to Nonmelanoma Skin Cancer by Absolute Quantification: Identification of OPN-5 Subvariants and Their Protein Coding Potential

The study evaluated whether SPP1/osteopontin (OPN) splice variants are differentially expressed in nonmelanoma skin cancer compared to normal skin. The absolute number of mRNA molecules of OPN-a predominated in normal skin and nonmelanoma skin cancer compared to OPN-b, OPN-c, and OPN-5. However, mRNAs of OPN-a, OPN-b, and OPN-c were expressed in higher levels in cutaneous squamous cell carcinomas (cSCCs) and basal cell carcinomas relative to normal skin. Additionally, OPN-5 expression was higher than OPN-b and OPN-c, and OPN-c, in normal skin and nonmelanoma skin cancer, respectively. Furthermore, we identified four OPN-5 splice variants, which were cloned and analyzed for protein expression.

Integrin-α9β1 as a Novel Therapeutic Target for Refractory Diseases: Recent Progress and Insights

Integrins refer to heterodimers consisting of subunits α and β. They serve as receptors on cell membranes and interact with extracellular ligands to mediate intracellular molecular signals. One of the least-studied members of the integrin family is integrin-α9β1, which is widely distributed in various human tissues and organs. Integrin-α9β1 regulates the physiological state of cells through a variety of complex signaling pathways to participate in the specific pathological processes of some intractable diseases. In recent years, an increasing amount of research has focused on the role of α9β1 in the molecular mechanisms of different refractory diseases and its promising potential as a therapeutic target. Accordingly, this review introduces and summarizes recent research related to integrin-α9β1, describes the synergistic functions of α9β1 and its corresponding ligands in cancer, autoimmune diseases, nerve injury and thrombosis and, more importantly, highlights the potential of α9β1 as a distinctive target for the treatment of these intractable diseases.

Inference and analysis of cell-cell communication using CellChat

Understanding global communications among cells requires accurate representation of cell-cell signaling links and effective systems-level analyses of those links. We construct a database of interactions among ligands, receptors and their cofactors that accurately represent known heteromeric molecular complexes. We then develop CellChat, a tool that is able to quantitatively infer and analyze intercellular communication networks from single-cell RNA-sequencing (scRNA-seq) data. CellChat predicts major signaling inputs and outputs for cells and how those cells and signals coordinate for functions using network analysis and pattern recognition approaches. Through manifold learning and quantitative contrasts, CellChat classifies signaling pathways and delineates conserved and context-specific pathways across different datasets. Applying CellChat to mouse and human skin datasets shows its ability to extract complex signaling patterns. Our versatile and easy-to-use toolkit CellChat and a web-based Explorer ( http://www.cellchat.org/ ) will help discover novel intercellular communications and build cell-cell communication atlases in diverse tissues.

Osteopontin Serum Concentration and Metabolic Syndrome in Male Psoriatic Patients

Psoriasis (Ps) is an immune-mediated inflammatory skin disease that is widely associated with the clinical features of metabolic syndrome (MetS), including hypertension, abdominal obesity, insulin resistance, type 2 diabetes and dyslipidemia. Osteopontin (OPN), a multifunctional protein involved in the modulation of inflammatory processes, may contribute to the development of atherosclerosis and MetS. Therefore, the aim of the study was the assessment of the correlation between OPN concentration in the peripheral blood and the presence of MetS as well as its particular components in the Ps patients. The study comprised 107 male Ps patients (50 patients with MetS and 57 without MetS) and 38 healthy volunteers (HVs). The concentration of OPN in serum was determined using enzyme-linked immunosorbent assay (ELISA) method. Fasting blood glucose and lipid profile components: total cholesterol (total CHOL), high-density lipoprotein cholesterol (HDL-CHOL), low-density lipoprotein cholesterol (LDL-CHOL), triglycerides (TG) were examined. Ps patients with MetS had significantly higher obesity, systolic blood pressure, TG, CHOL/HDL, LDL/HDL and TG/HDL ratios than Ps patients without MetS. OPN serum concentration was significantly higher in the Ps patients than in the HVs (p = 0.022) but not significantly different between the Ps patients with and without MetS (p = 0.275). OPN serum concentration in Ps patients correlated negatively with total CHOL (p = 0.004) and TG (p = 0.009). OPN is increased in Ps patients and may serve as a biomarker of some lipid abnormalities in them.

An osteopontin-derived peptide inhibits human hair growth at least in part by decreasing fibroblast growth factor-7 production in outer root sheath keratinocytes

BACKGROUND

Given that unwanted hair growth (hirsutism, hypertrichosis) can cause major psychological distress, new pharmacological treatment strategies with safe and effective hair growth inhibitors that do not destroy the hair follicle (HF) and its stem cells need to be developed.

OBJECTIVES

To establish if osteopontin-derived fragments may modulate human hair growth given that human HFs express the multifunctional, immunomodulatory glycoprotein, osteopontin.

METHODS

Our hypothesis was tested ex vivo and in vivo by using a newly generated, toxicologically well-characterized, modified osteopontin-derived peptide (FOL-005), which binds to the HF.

RESULTS

In organ-cultured human HFs and scalp skin, and in human scalp skin xenotransplants onto SCID mice, FOL-005 treatment (60 nmol L^-1 to 3 μmol L^-1 ) significantly promoted premature catagen development without reducing the number of keratin 15-positive HF stem cells or showing signs of drug toxicity. Genome-wide DNA microarray, quantitative reverse-transcriptase polymerase chain reaction and immunohistochemistry revealed decreased expression of the hair growth promoter, fibroblast growth factor-7 (FGF7) by FOL-005, while cotreatment of HFs with recombinant FGF7 partially abrogated FOL-005-induced catagen promotion.

CONCLUSIONS

With caveats in mind, our study identifies this osteopontin-derived peptide as an effective, novel inhibitory principle for human hair growth ex vivo and in vivo, which deserves systematic clinical testing in hirsutism and hypertrichosis. What's already known about this topic? The treatment of unwanted hair growth (hypertrichosis, hirsutism) lacks pharmacological intervention, with only few and often unsatisfactory treatments available. Osteopontin is prominently expressed in human HFs and has been reported to be elevated during catagen in the murine hair cycle. What does this study add? We tested the effects on hair growth of a novel, osteopontin-derived fragment (FOL-005) ex vivo and in vivo. In human hair follicles, high-dose FOL-005 significantly reduces hair growth both ex vivo and in vivo. What is the translational message? High-dose FOL-005 may provide a new therapeutic opportunity as a treatment for unwanted hair growth.

Upregulation of intratumoral HLA class I and peritumoral Mx1 in ulcerated melanomas

Before the era of immune checkpoint blockade, a meta-analysis encompassing fifteen trials reported that adjuvant IFN-α significantly reduces the risk of relapse and improves survival of ulcerated melanoma (UM) with no benefit for higher doses compared to lower doses. IFNa2b affects many cell intrinsic features of tumor cells and modulates the host innate and cognate immune responses. To better understand the biological traits associated with ulceration that could explain the efficacy of prophylactic type 1 IFN, we performed immunohistochemical analysis of various molecules (major histocompatibility complex class I and class II, MX Dynamin Like GTPase 1 (MX1), inducible Nitric-Oxide Synthase (iNOS) or CD47) in two retrospective cohorts of melanoma patients, one diagnosed with a primary cutaneous melanoma (1995-2013, N = 172, among whom 49% were ulcerated melanoma (UM)) and a second one diagnosed with metastatic melanoma amenable to lymph node resection (EORTC 18952 and 18991 trials, N = 98, among whom 44% were UM). We found that primary and metastatic UM exhibit higher basal expression of MHC class I molecules, independently of Breslow thickness, histology and lymphocytic infiltration compared with NUM and that primary UM harbored higher constitutive levels of the antiviral protein Mx1 at the border of tumor beds than NUM. These findings suggest that UM expand in a tumor microenvironment where chronic exposure to type 1 IFN could favor a response to exogenous IFNs.

Role of osteopontin in dendritic cell shaping of immune responses

Osteopontin (OPN) is a pleiotropic cytokine produced both by immune and non-immune cells and active on different cellular targets. OPN production has been associated with several pathological conditions, including autoimmune diseases (e.g. lupus, multiple sclerosis and rheumatoid arthritis) and cancer. Emerging evidence suggests that the role of OPN has been underestimated, as it seems to be working at multiple levels of immune regulation, such as the shaping of T cell effector responses, the regulation of the tumor microenvironment, and the functional interaction with mesenchymal stromal cells. In this context, dendritic cells (DCs) play a crucial role being both an important source and a cellular target for OPN action. DC family is composed by several cell subsets endowed with specific immune functions. OPN exerts its biological functions through multiple receptors and is produced in different intracellular and secreted forms. OPN production by DC subsets is emerging as a crucial mechanism of regulation in normal and pathological conditions and starts to be exploited as a therapeutic target. This review will focus on the role of DC-derived OPN in shaping immune response and on the complex role of this cytokines in the regulation in immune response.

Unraveling the ECM-Immune Cell Crosstalk in Skin Diseases

The extracellular matrix (ECM) is a complex network of proteins and proteoglycans secreted by keratinocytes, fibroblasts and immune cells. The function of the skin ECM has expanded from being a scaffold that provides structural integrity, to a more dynamic entity that is constantly remodeled to maintain tissue homeostasis. The ECM functions as ligands for cell surface receptors such as integrins, dystroglycans, and toll-like receptors (TLRs) and regulate cellular signaling and immune cell dynamics. The ECM also acts as a sink for growth factors and cytokines, providing critical cues during epithelial morphogenesis. Dysregulation in the organization and deposition of ECMs lead to a plethora of pathophysiological conditions that are exacerbated by aberrant ECM-immune cell interactions. In this review, we focus on the interplay between ECM and immune cells in the context of skin diseases and also discuss state of the art therapies that target the key molecular players involved.

Intracellular osteopontin negatively regulates toll-like receptor 4-mediated inflammatory response via regulating GSK3β and 4EBP1 phosphorylation

Toll-like receptors (TLRs) play an important role in host defense against invading pathogens. By initiating a signal transduction cascade, TLRs lead to the release of pro-inflammatory cytokines. However, the inappropriate activation of TLR signaling could result in inflammatory disorders or autoimmune diseases. Osteopontin (OPN) has been reported to be an inflammatory cytokine participating in cell-mediated immunity. However, the role of OPN in TLR-mediated immune responses is poorly understood. In the present study, OPN-deficient (OPN-/-) macrophages exhibited significantly higher levels of pro-inflammatory cytokines after stimulation with lipopolysaccharide (LPS). Our study also demonstrated that the intracellular OPN (iOPN) isoform acted as a negative regulator to inhibit LPS-induced inflammatory responses. Compared to WT macrophages, OPN-/- macrophages had lower Akt phosphorylation levels and higher GSK3β phosphorylation levels, which were downregulated by p-Akt. Moreover, as a down-stream target of Akt, 4EBP1 was hypo-phosphorylated in OPN-/- macrophages compared to 4EBP1 in WT macrophages. These findings reveal that iOPN can regulate GSK3β and 4EBP1 phosphorylation to inhibit TLR4-mediated inflammatory responses.

Extracellular matrix contribution to skin wound re-epithelialization

The ability of skin to act as a barrier is primarily determined by cells that maintain the continuity and integrity of skin and restore it after injury. Cutaneous wound healing in adult mammals is a complex multi-step process that involves overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodeling. Under favorable conditions, epidermal regeneration begins within hours after injury and takes several days until the epithelial surface is intact due to reorganization of the basement membrane. Regeneration relies on numerous signaling cues and on multiple cellular processes that take place both within the epidermis and in other participating tissues. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here we focus on the involvement of the extracellular matrix proteins that impact epidermal regeneration during wound healing.

Osteopontin improves adhesion and migration of human primary renal cortical epithelial cells during wound healing

The aim of the present study was to investigate the effect of osteopontin (OPN) on adhesion and migration in human primary renal cortical epithelial cells during wound healing and Transwell assays. MTT assay was used to examine the cell viability and western blot analysis was used to examine the expression of cytoskeletal proteins and cell adhesion molecules. The results showed that overexpression of OPN had positive effects on the viability, proliferation, adhesion and migration of the human primary renal cortical epithelial cells. In addition, the integrity of the cell membrane and cytoskeleton of the epithelial cells was negatively affected by knockdown of OPN expression. The Transwell migration and a wound healing assays performed using OPN-knockdown cells suggested that OPN had a significant impact on cell migration (P=0.0421) and wound healing (P=0.0333). Therefore, OPN may be a potential target for the therapeutic modulation of skin repair to improve the healing rate and quality of wound healing.

Neuroimmunological Implications of AQP4 in Astrocytes

The brain has high-order functions and is composed of several kinds of cells, such as neurons and glial cells. It is becoming clear that many kinds of neurodegenerative diseases are more-or-less influenced by astrocytes, which are a type of glial cell. Aquaporin-4 (AQP4), a membrane-bound protein that regulates water permeability is a member of the aquaporin family of water channel proteins that is expressed in the endfeet of astrocytes in the central nervous system (CNS). Recently, AQP4 has been shown to function, not only as a water channel protein, but also as an adhesion molecule that is involved in cell migration and neuroexcitation, synaptic plasticity, and learning/memory through mechanisms involved in long-term potentiation or long-term depression. The most extensively examined role of AQP4 is its ability to act as a neuroimmunological inducer. Previously, we showed that AQP4 plays an important role in neuroimmunological functions in injured mouse brain in concert with the proinflammatory inducer osteopontin (OPN). The aim of this review is to summarize the functional implication of AQP4, focusing especially on its neuroimmunological roles. This review is a good opportunity to compile recent knowledge and could contribute to the therapeutic treatment of autoimmune diseases through strategies targeting AQP4. Finally, the author would like to hypothesize on AQP4’s role in interaction between reactive astrocytes and reactive microglial cells, which might occur in neurodegenerative diseases. Furthermore, a therapeutic strategy for AQP4-related neurodegenerative diseases is proposed.

Role of Osteopontin in Psoriasis: An Immunohistochemical Study

Background:

Osteopontin (OPN) has been postulated to have a role in several T-helper (Th) 1 and Th 17-mediated diseases including psoriasis (PS), through multiple mechanisms sharing in the onset and worsening of PS, OPN shares in induction of keratinocyte proliferation through inhibiting keratinocyte apoptosis, OPN acts as a proinflammatory agent that participates in the upregulation of Th cell lineages, among which are the Th 1 and Th 17 cells.

Aims and Objectives:

The aim of this study was to explore the possible role of OPN in the pathogenesis of PS.

Materials and Methods:

This case–control study was carried out on 18 patients of chronic plaque PS (mean age 37.61 ± 14.48) and a control group of 18 apparently healthy volunteers (mean age 41.11 ± 11.02 years). Severity of PS was assessed using the PS area and severity index score. Two skin biopsies were taken from psoriatic patients. The first was taken from the lesional skin and the other from a counter apparently healthy site.

Results:

Our results showed statistically significant differences in the expression of OPN, between lesional and nonlesional skin as well as between nonlesional skin and control group (P ≤ 0.001). In addition, there was a significant difference in the expression of OPN, between control and lesional group.

Conclusions:

OPN involvement in PS enlarges the list of cytokines able to stimulate the inflammatory response in this disease, anti-OPN antibodies, may eventually become a useful therapeutic approach in PS.

Serum osteopontin levels in disseminated allergic contact dermatitis

PURPOSE

The aim of the study was to evaluate serum osteopontin (OPN) concentrations in patients with disseminated form of allergic contact dermatitis (ACD), and to assess the relationship between serum OPN level and disease severity.

PATIENTS AND METHODS

Twenty-four patients with numerous allergic contact dermatitis lesions and twenty-two age- and sex-matched healthy subjects as a control group were enrolled in the study. Serum osteopontin levels were measured in the ACD patients twice: in the acute stage and during disease remission by ELISA.

RESULTS

Serum OPN concentrations were significantly increased in patients with disseminated ACD examined in the acute stage as compared to healthy subjects and ACD patients during remission (p<0.01 and p<0.001, respectively). In the ACD patients with extensive skin lesions (EASI>10), OPN serum levels were significantly higher than in those with mild disease (EASI<10).

CONCLUSIONS

Acute disseminated ACD is characterized by elevated serum concentrations of osteopontin, with levels depending on ACD severity, which indicates its role in the elicitation phase of allergic contact dermatitis. The possibility of inhibition of OPN activity may create a new therapeutic perspective in severe forms of this troublesome skin disease.

Assessment of serum levels of osteopontin, selenium and prolactin in patients with psoriasis compared with healthy controls, and their association with psoriasis severity

BACKGROUND

The association between psoriasis and cardiovascular diseases is well documented, but the underlying mechanisms remain unknown. Overexpression of osteopontin (OPN) has been reported in the plasma of patients with psoriasis, with increased cardiovascular risk factors in these patients. Selenium compounds are effective in downregulating OPN expression.

OBJECTIVE

We investigated the levels of OPN, selenium and prolactin (PRL) in psoriasis, and their association with metabolic status in patients to identify a possible link between these markers and observed comorbidities.

METHODS

Plasma samples from 40 patients with psoriasis and 40 age- and sex-matched healthy controls (HCs) were collected for ELISA. The clinical significance of plasma OPN, selenium and PRL levels in patients compared with controls was analysed in relation to metabolic disorders.

RESULTS

There was no significant difference in median serum selenium levels between the two groups. Serum levels of PRL were not significantly different from those of HCs, but levels of OPN were significantly higher in patients with psoriasis than in HCs.

CONCLUSIONS

High plasma OPN is a predictor for occurrence of psoriasis. Our study showed that serum selenium and PRL were not decreased in patients with psoriasis, but there was a negative statistically significant correlation between OPN and selenium in all participants.

The role of osteopontin expression in melanoma progression

It was shown that osteopontin (OPN), a glycophosphoprotein, plays divergent roles in cancer progression. In addition to multiple intra- and extracellular functions, it facilitates migration of tumour cells, has crucial role in cell adhesion and is associated with increased metastasis formation. In previous studies, we performed global gene expression profiling on a series of primary melanoma samples and found that OPN was significantly overexpressed in ulcerated melanomas. The major purpose of this study was to define OPN expression in primary melanomas with differing biological behaviours. OPN mRNA expression was analysed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) in primary melanoma tissues. Immunohistochemistry was performed using a tissue microarray. Cox regression tests were used for survival analysis. Greater than 50 % of the tissues exhibited high protein expression that was significantly associated with tumour thickness and metastasis. OPN mRNA expression was significantly increased in thicker melanomas and lesions with an ulcerated surface. Increased expression was primarily detected in advanced-stage tumours. A multivariate Cox regression analysis revealed that high OPN expression, tumour thickness and metastasis were significantly associated with reduced relapse-free survival. In summary, high OPN mRNA and protein expression were associated with a less favourable clinical outcome of primary melanoma patients. We determined that OPN is a significant predictive factor for the survival of primary melanoma patients. Based on our and others data, the high expression of OPN may have a crucial stimulatory role in tumour progression and metastasis formation, which, thus, have been proposed as potential targets for cancer diagnosis and therapy.

Integrins in Wound Healing

Significance: Regulation of cell adhesions during tissue repair is fundamentally important for cell migration, proliferation, and protein production. All cells interact with extracellular matrix proteins with cell surface integrin receptors that convey signals from the environment into the nucleus, regulating gene expression and cell behavior. Integrins also interact with a variety of other proteins, such as growth factors, their receptors, and proteolytic enzymes. Re-epithelialization and granulation tissue formation are crucially dependent on the temporospatial function of multiple integrins. This review explains how integrins function in wound repair. Recent Advances: Certain integrins can activate latent transforming growth factor beta-1 (TGF-β1) that modulates wound inflammation and granulation tissue formation. Dysregulation of TGF-β1 function is associated with scarring and fibrotic disorders. Therefore, these integrins represent targets for therapeutic intervention in fibrosis. Critical Issues: Integrins have multifaceted functions and extensive crosstalk with other cell surface receptors and molecules. Moreover, in aberrant healing, integrins may assume different functions, further increasing the complexity of their functionality. Discovering and understanding the role that integrins play in wound healing provides an opportunity to identify the mechanisms for medical conditions, such as excessive scarring, chronic wounds, and even cancer. Future Directions: Integrin functions in acute and chronic wounds should be further addressed in models better mimicking human wounds. Application of any products in acute or chronic wounds will potentially alter integrin functions that need to be carefully considered in the design.

Increased osteopontin expression is associated with progression from vulvar precancerous lesions to vulvar squamous cell carcinoma

PURPOSE

Vulvar squamous cell carcinoma (VSCC) contributes to about 3-5% of all gynecological cancers. Vulvar intraepithelial neoplasia (VIN) and vulvar lichen sclerosus (VLS) are regarded as precancerous lesions. Early detection and treatment of precancerous lesions may prevent development of VSCC. Osteopontin (OPN) has been shown to be involved in many physiological and pathological processes, such as tumor progression, by promoting cancer cell invasion and metastasis. As a result of these findings, OPN has been described as a potential marker for tumor progression in some malignancies. In this study, we investigated the expression of OPN in vulvar tissue specimens and compared its expression between different histopathological grades.

METHODS

In the present study, the expression patterns of OPN in 80 paraffin-embedded tissue specimens, including 25 VSCC samples, 21 VIN lesions and 21 VLS, in addition to 13 normal vulvar samples, were examined by the immunohistochemical method and chromogenic in situ hybridization.

RESULTS

The intensity of OPN expression steadily increased according to the pathological grades. In addition, OPN staining was found in the extracellular matrix in VSCC.

CONCLUSIONS

Expression levels of OPN increased from VLS and VIN to VSCC, and steadily increased with the pathological stage of VSCC. Our results suggest that OPN may be associated with the progression of VSCC.

miR-126&126* restored expressions play a tumor suppressor role by directly regulating ADAM9 and MMP7 in melanoma

The abnormal expression of several microRNAs has a causal role in tumorigenesis with either antineoplastic or oncogenic functions. Here we demonstrated that miR-126 and miR-126* play a tumor suppressor role in human melanoma through the direct or indirect repression of several key oncogenic molecules. The expression levels of miR-126&126* were elevated in normal melanocytes and primary melanoma cell lines, whereas they markedly declined in metastatic cells. Indeed, the restored expression of miR-126&126* in two advanced melanoma cell lines was accompanied by a significant reduction of proliferation, invasion and chemotaxis in vitro as well as of growth and dissemination in vivo. In accordance, the reverse functional effects were obtained by knocking down miR-126&126* by transfecting antisense LNA oligonucleotides in melanoma cells. Looking for the effectors of these antineoplastic functions, we identified ADAM9 and MMP7, two metalloproteases playing a pivotal role in melanoma progression, as direct targets of miR-126&126*. In addition, as ADAM9 and MMP7 share a role in the proteolytic cleavage of the HB-EGF precursor, we looked for the effectiveness of this regulatory pathway in melanoma, confirming the decrease of HB-EGF activation as a consequence of miR-126&126*-dependent downmodulation of ADAM9 and MMP7. Finally, gene profile analyses showed that miR-126&126* reexpression was sufficient to inactivate other key signaling pathways involved in the oncogenic transformation, as PI3K/AKT and MAPK, and to restore melanogenesis, as indicated by KIT/MITF/TYR induction. In view of this miR-126&126* wide-ranging action, we believe that the replacement of these microRNAs might be considered a promising therapeutic approach.

Rapid decrease of plasma galectin-9 levels in patients with acute HIV infection after therapy

Acute HIV-1 infection is often diagnosed as infectious mononucleosis and the symptoms resolve spontaneously after varying periods of time. After the infection of HIV-1 through the mucosa, the characteristic clinical symptoms and laboratory markers of acute HIV-1 infection appear in each patient through a complicated virus-host interaction. To understand the host responses, we measured two unique proinflammatory cytokines, galectin-9 (Gal-9) and osteopontin (OPN). A β-galactoside-binding mammalian lectin, Gal-9, reduces pro-inflammatory type-1 helper T (Th1) cells and Th17 cells and increases anti-inflammatory regulatory T cells. The plasma level of Gal-9 is known to be associated with HIV-1 viral load in chronic HIV-1 infection. On the contrary, osteopontin induces Th1/Th17 cells and promotes tissue inflammation. OPN is synthesized by variety of cells in the body, and dendritic cells are known to synthesize OPN in HIV-1 infected individuals. It was hypothesized that Gal-9 and/or OPN could be not only immune-modulators but also novel biomarkers of acute HIV-1 infection. We experienced 3 patients with acute HIV-1 and measured the levels of Gal-9 and OPN periodically before and after antiretroviral treatment. The results showed that the plasma levels of Gal-9 were extremely elevated [more than 2,300 pg/ml (normal range < 46 pg/ml)] in all three acute HIV-1 infected individuals and decreased rapidly after treatment. The changes in the OPN levels were less marked. In conclusion, the plasma levels of Gal-9 may be predictive of a severe inflammation status during the acute phase of HIV-1 infection and could be a potential biomarker during acute infection.

Integrative genomics identifies gene signature associated with melanoma ulceration

Background

Despite the extensive research approaches applied to characterise malignant melanoma, no specific molecular markers are available that are clearly related to the progression of this disease. In this study, our aims were to define a gene expression signature associated with the clinical outcome of melanoma patients and to provide an integrative interpretation of the gene expression -, copy number alterations -, and promoter methylation patterns that contribute to clinically relevant molecular functional alterations.

Methods

Gene expression profiles were determined using the Affymetrix U133 Plus2.0 array. The NimbleGen Human CGH Whole-Genome Tiling array was used to define CNAs, and the Illumina GoldenGate Methylation platform was applied to characterise the methylation patterns of overlapping genes.

Results

We identified two subclasses of primary melanoma: one representing patients with better prognoses and the other being characteristic of patients with unfavourable outcomes. We assigned 1,080 genes as being significantly correlated with ulceration, 987 genes were downregulated and significantly enriched in the p53, Nf-kappaB, and WNT/beta-catenin pathways. Through integrated genome analysis, we defined 150 downregulated genes whose expression correlated with copy number losses in ulcerated samples. These genes were significantly enriched on chromosome 6q and 10q, which contained a total of 36 genes. Ten of these genes were downregulated and involved in cell-cell and cell-matrix adhesion or apoptosis. The expression and methylation patterns of additional genes exhibited an inverse correlation, suggesting that transcriptional silencing of these genes is driven by epigenetic events.

Conclusion

Using an integrative genomic approach, we were able to identify functionally relevant molecular hotspots characterised by copy number losses and promoter hypermethylation in distinct molecular subtypes of melanoma that contribute to specific transcriptomic silencing and might indicate a poor clinical outcome of melanoma.

Osteopontin as a two-sided mediator in acute neuroinflammation in rat models

Osteopontin (OPN) plays an important role in the initiation of inflammation, affecting cell adhesion, chemotaxis, immune regulation, and protection against apoptosis, depending on its intracellular or extracellular localization. Although OPN in inflammation of the autoimmune central nervous system is proinflammatory, recent studies have shown that OPN during the induction stage of inflammation may also participate in neuroprotection and neurite growth. The present review examines the dual roles of OPN, specifically, its proinflammatory and subsequent neuroprotective roles, in acute neuroinflammation in rat models, including experimental autoimmune encephalomyelitis, brain injury, and autoimmune neuritis. All of these models are characterized by acute neuroinflammation, followed by remodeling of neural tissues.

Phosphorylation of osteopontin in osteoarthritis degenerative cartilage and its effect on matrix metalloprotease 13

The purpose of this study is to observe the differences of osteopontin (OPN) phosphorylation in osteoarthritis (OA) cartilage and normal cartilage, and evaluate the possible correlations between the OPN phosphorylation and MMP-13 expression. Degenerative cartilage (n = 29) and normal cartilage (n = 10) were identified by hematoxylin-eosin, safranin-O staining and modified Mankin score. The phosphorylation level of OPN in OA cartilage and normal cartilage was detected by immunoprecipitation. Chondrocytes were treated with phospho-OPN, OPN or buffer. Quantitative reverse transcription polymerase chain reaction (qPCR) and ELISA were used to assess the expression of MMP-13 in different treatments. The OD values of phosphorylation of OPN in normal cartilage and OA cartilage were 137.89 ± 10.59 and 153.52 ± 8.80, respectively, (P = 0.000). Chondrocytes treated with OPN showed a higher MMP-13 expression at gene and protein level compared with control group. Chondrocytes treated with phospho-OPN showed the highest MMP-13 expression in gene and protein. In conclusion, our results revealed a higher phosphorylation level of OPN in OA cartilage than in normal cartilage. We found OPN leads to elevated expression of MMP-13 (both at gene level and protein level), and phospho-OPN had a more obvious upregulation effect on MMP-13 expression than nonphospho-OPN. Further studies are needed to reveal the mechanism of OPN phosphorylation on cartilage degeneration.

Knockdown of osteopontin reduces the inflammatory response and subsequent size of postsurgical adhesions in a murine model

Adhesions between organs after abdominal surgery remain a significant unresolved clinical problem, causing considerable postoperative morbidity. Osteopontin (OPN) is a cytokine up-regulated after cell injury and tissue repair. Our previous studies have shown that blocking OPN expression at sites of cutaneous wounding resulted in reduced granulation tissue and scarring. We hypothesize that it may be possible to similarly reduce inflammation-associated fibrosis that causes small-bowel adhesions after abdominal surgery. By using a mouse model, we deliver OPN antisense oligodeoxynucleotides via Pluronic gel to the surface of injured, juxtaposed small bowel and show a significant reduction of inflammatory cell influx to the developing adhesion and a dramatic reduction in the resulting adhesion size. A significant reduction in α-smooth muscle actin expression and collagen deposition within the mature adhesion is also demonstrated. We see no impact on mortality, and the healing of serosal injury to intact bowel appeared normal given the reduced inflammatory response. Our studies suggest that dampening OPN levels might be a potentially important target for anti-adhesion therapeutics.

DNAJB6 chaperones PP2A mediated dephosphorylation of GSK3β to downregulate β-catenin transcription target, osteopontin

Elevated levels of the oncoprotein, osteopontin (OPN), are associated with poor outcome of several types of cancers including melanoma. We have previously reported an important involvement of DNAJB6, a member of heat-shock protein 40 (HSP40) family, in negatively impacting tumor growth. The current study was prompted by our observations reported here which revealed a reciprocal relationship between DNAJB6 and OPN in melanoma specimens. The 'J domain' is the most conserved domain of HSP40 family of proteins. Hence, we assessed the functional role of the J domain in activities of DNAJB6. We report that the J domain of DNAJB6 is involved in mediating OPN suppression. Deletion of the J domain renders DNAJB6 incapable of impeding malignancy and suppressing OPN. Our mechanistic investigations reveal that DNAJB6 binds HSPA8 (heat-shock cognate protein, HSC70) and causes dephosphorylation of glycogen synthase kinase 3β (GSK3β) at Ser 9 by recruiting protein phosphatase, PP2A. This dephosphorylation activates GSK3β, leading to degradation of β-catenin and subsequent loss of TCF/LEF (T cell factor1/lymphoid enhancer factor1) activity. Deletion of the J domain abrogates assembly of this multiprotein complex and renders GSK3β inactive, thus, stabilizing β-catenin, a transcription co-activator for OPN expression. Our in-vitro and in-vivo functional analyses show that silencing OPN expression in the background of deletion of the J domain renders the resultant tumor cells less malignant despite the presence of stabilized β-catenin. Thus, we have uncovered a new mechanism for regulation of GSK3β activity leading to inhibition of Wnt/β-catenin signaling.

DNAJB6 chaperones PP2A mediated dephosphorylation of GSK3β to downregulate β-catenin transcription target, osteopontin

Elevated levels of the oncoprotein, osteopontin (OPN), are associated with poor outcome of several types of cancers including melanoma. We have previously reported an important involvement of DNAJB6, a member of heat-shock protein 40 (HSP40) family, in negatively impacting tumor growth. The current study was prompted by our observations reported here which revealed a reciprocal relationship between DNAJB6 and OPN in melanoma specimens. The 'J domain' is the most conserved domain of HSP40 family of proteins. Hence, we assessed the functional role of the J domain in activities of DNAJB6. We report that the J domain of DNAJB6 is involved in mediating OPN suppression. Deletion of the J domain renders DNAJB6 incapable of impeding malignancy and suppressing OPN. Our mechanistic investigations reveal that DNAJB6 binds HSPA8 (heat-shock cognate protein, HSC70) and causes dephosphorylation of glycogen synthase kinase 3β (GSK3β) at Ser 9 by recruiting protein phosphatase, PP2A. This dephosphorylation activates GSK3β, leading to degradation of β-catenin and subsequent loss of TCF/LEF (T cell factor1/lymphoid enhancer factor1) activity. Deletion of the J domain abrogates assembly of this multiprotein complex and renders GSK3β inactive, thus, stabilizing β-catenin, a transcription co-activator for OPN expression. Our in-vitro and in-vivo functional analyses show that silencing OPN expression in the background of deletion of the J domain renders the resultant tumor cells less malignant despite the presence of stabilized β-catenin. Thus, we have uncovered a new mechanism for regulation of GSK3β activity leading to inhibition of Wnt/β-catenin signaling.

[The gene ontology and electro localization of ovine skin derived EST-SSR markers]

Abstract: In order to study the potential gene function of ovine EST-SSR markers, nine original EST of Ovine Skin Derived polymorphic EST-SSR loci, which were developed in an early study by our lab, were ontology annotated and Electro localized. The results revealed that the original ESTs of the six loci had high homology with known genes and three of them probably played an important role in wool traits. Compared with its cDNA library, 8 loci were located on chromosomes of cattle. The homology of chromosomes between cattle and sheep was estimated based on the similarity coefficients calculated by positioning markers. Additionally, NJ clustering tree was establishedto serve for electro localization of ovine EST-SSR markers. Finally, 8 EST-SSR markers were successfully positioned on ovine chromosomes. The results from this study not only provide references for further studies on genetic mapping, in silico cloning of key genes for wool traits, but also are helpful to the researchs of chromosome evolution in animal.

Host-derived osteopontin maintains an acute inflammatory response to suppress early progression of extrinsic cancer cells

The matricellular protein osteopontin (OPN), expressed in various cancer types and elevated in the blood of cancer patients, is thought to have different functions when derived from host versus cancer cells. To assess the effect of host-derived OPN on growth of cancers of epithelial origin, we established a line of cutaneous squamous cell carcinoma (SCC) cells, named ONSC, which lacks the OPN gene and develops SCC in syngeneic wild-type (WT) and OPN-null mice. At 8 and/or 10 week after subcutaneous injection of ONSC cells in mice, however, there was a lower tumor incidence in WT mice, suggesting that host-derived OPN is associated with suppression of early growth of extrinsic cancer cells. Histological, immunohistochemical, biochemical and hematological analyses were performed on the tumor microenvironment and blood from tumor-bearing mice during the first week after implantation. Host-derived OPN suppression of extrinsic ONSC cell progression is likely mediated through elicitation of an early innate inflammatory response, through its function as a chemoattractant and/or by enhancing survival of inflammatory cells. Further, consistent with a previous report, the serum levels of host-derived OPN, which are elevated during the early phase of tumor growth in mice implanted with ONSC, appear to reflect an anti-tumor progression effect.

Downregulation of osteopontin is associated with fluoxetine amelioration of monocrotaline-induced pulmonary inflammation and vascular remodelling

1. Osteopontin (OPN) has emerged as a key factor in inflammatory activation and cardiovascular remodelling. The aim of the present study was to investigate the involvement of OPN in fluoxetine amelioration of monocrotaline (MCT)-induced pulmonary inflammation and vascular remodelling in rats. 2. Wistar rats were divided into control, MCT and two fluoxetine-treated groups. Pulmonary arterial hypertension (PAH) was induced by a single injection of MCT (60 mg/kg, i.p.). Fluoxetine (2 and 10 mg/kg) was administered via the intragastric route once a day for 21 days. On Day 22, pulmonary haemodynamic measurements were undertaken, followed by ELISA, western blotting and immunohistochemistry. 3. Monocrotaline caused pulmonary inflammation and vascular remodelling and significantly enhanced OPN expression in the plasma, lungs and pulmonary arteries. Fluoxetine decreased pulmonary arterial pressure and ameliorated pulmonary inflammation and pulmonary vascular remodelling. At 10 mg/kg, fluoxetine significantly inhibited MCT-induced increases in the expression of serotonin transporter (SERT) and phosphorylated extracellular signal-regulated kinase 1/2 and downregulated the expression of OPN, macrophage inflammatory protein-1β and matrix metalloproteinase 2/tissue inhibitor of metalloproteinase 2. Although 2 mg/kg fluoxetine tended to ameliorate some MCT-induced changes in the lung, the differences did not always reach statistical significance. Linear regression analysis showed that there was a positive correlation between plasma OPN concentrations and mean pulmonary arterial pressure, as well as percentage medial wall thickness and percentage wall area in the pulmonary artery. 4. In conclusion, the amelioration by fluoxetine of MCT-induced pulmonary inflammation and vascular remodelling is associated with downregulation of OPN expression in rats.

Intracellular osteopontin (iOPN) and immunity

Osteopontin (OPN) is a protein involved in various pathophysiological events. OPN has been studied as a secreted protein, but recent reports showed that OPN can be found in the cytoplasm and the nucleus. Therefore, some OPN molecules are not secreted and stay in cells. Such intracellular OPN (iOPN) has biological functions distinct from secreted OPN (sOPN). iOPN is involved in cytoskeletal rearrangement and in signal transduction pathways downstream of innate immune receptors, such as Toll-like receptors (TLRs), as an adaptor or scaffolding protein. Although sOPN and iOPN are generated from the same Opn mRNA species, biological outcomes mediated by two isoforms can be different. It would be necessary to delineate which isoform of OPN is responsible for pathophysiological events.