Psoriasis and extra domain A fibronectin loops

Carnosic acid inhibits integrin expression and prevents pulmonary metastasis of melanoma

Carnosic acid is a naturally occurring, plant-derived polyphenolic abietane diterpene with antitumor properties. However, its underlying mechanisms are still unclear. Therefore, we investigated the effects of carnosic acid on lung metastasis in a murine melanoma model. C57BL/6 mice were intravenously injected with B16-BL6 cells, followed by carnosic acid treatment. Lung weights were recorded, and tumor cell colonies were counted at the end of the experiment. Integrin expression was evaluated using flow cytometry and cell adhesion assays. Lung weights were significantly lower in the carnosic acid group than in the control group, indicating the suppression of metastasis. Carnosic acid suppressed α4 integrin expression in B16-BL6 cells and inhibited α4 and α9 integrin-dependent cell adhesion. Thus, our data suggest that carnosic acid prevents lung metastasis, possibly by suppressing integrin expression. Our findings support the clinical application of carnosic acid as a potential natural antitumor agent, offering a complementary approach to conventional therapies.

Shielding and nurturing: Fibronectin as a modulator of cancer drug resistance

Resistance to chemotherapy and targeted therapies constitute a common hallmark of most cancers and represent a dominant factor fostering tumor relapse and metastasis. Fibronectin, an abundant extracellular matrix glycoprotein, has long been proposed to play an important role in the pathobiology of cancer. Recent research has unraveled the role of Fibronectin in the onset of chemoresistance against a variety of antineoplastic drugs including DNA-damaging agents, hormone receptor antagonists, tyrosine kinase inhibitors, microtubule destabilizing agents, etc. The current review summarizes the role played by Fibronectin in mediating drug resistance against diverse anticancer drugs. We have also discussed how the aberrant expression of Fibronectin drives the oncogenic signaling pathways ultimately leading to drug resistance through the inhibition of apoptosis, promotion of cancer cell growth and proliferation.

Induction of pro-inflammatory genes by fibronectin DAMPs in three fibroblast cell lines: Role of TAK1 and MAP kinases

Changes in the organization and structure of the fibronectin matrix are believed to contribute to dysregulated wound healing and subsequent tissue inflammation and tissue fibrosis. These changes include an increase in the EDA isoform of fibronectin as well as the mechanical unfolding of fibronectin type III domains. In previous studies using embryonic foreskin fibroblasts, we have shown that fibronectin's EDA domain (FnEDA) and the partially unfolded first Type III domain (FnIII-1c) function as Damage Associated Molecular Pattern (DAMP) molecules to stimulate the induction of inflammatory cytokines by serving as agonists for Toll-Like Receptor-4 (TLR4). However, the role of signaling molecules downstream of TLR-4 such as TGF-β Activated Kinase 1 (TAK1) and Mitogen activated protein kinases (MAPK) in regulating the expression of fibronectin DAMP induced inflammatory genes in specific cell types is not known. In the current study, we evaluate the molecular steps regulating the fibronectin driven induction of inflammatory genes in three human fibroblast cell lines: embryonic foreskin, adult dermal, and adult kidney. The fibronectin derived DAMPs each induce the phosphorylation and activation of TAK1 which results in the activation of two downstream signaling arms, IKK/NF-κB and MAPK. Using the specific inhibitor 5Z-(7)-Oxozeanol as well as siRNA, we show TAK1 to be a crucial signaling mediator in the release of cytokines in response to fibronectin DAMPs in all three cell types. Finally, we show that FnEDA and FnIII-1c induce several pro-inflammatory cytokines whose expression is dependent on both TAK1 and JNK MAPK and highlight cell-type specific differences in the gene-expression profiles of the fibroblast cell-lines.

Fibronectin Functions as a Selective Agonist for Distinct Toll-like Receptors in Triple-Negative Breast Cancer

The microenvironment of tumors is characterized by structural changes in the fibronectin matrix, which include increased deposition of the EDA isoform of fibronectin and the unfolding of the fibronectin Type III domains. The impact of these structural changes on tumor progression is not well understood. The fibronectin EDA (FnEDA) domain and the partially unfolded first Type III domain of fibronectin (FnIII-1c) have been identified as endogenous damage-associated molecular pattern molecules (DAMPs), which induce innate immune responses by serving as agonists for Toll-Like Receptors (TLRs). Using two triple-negative breast cancer (TNBC) cell lines MDA-MB-468 and MDA-MB-231, we show that FnEDA and FnIII-1c induce the pro-tumorigenic cytokine, IL-8, by serving as agonists for TLR5 and TLR2, the canonical receptors for bacterial flagellin and lipoprotein, respectively. We also find that FnIII-1c is not recognized by MDA-MB-468 cells but is recognized by MDA-MB-231 cells, suggesting a cell type rather than ligand specific utilization of TLRs. As IL-8 plays a major role in the progression of TNBC, these studies suggest that tumor-induced structural changes in the fibronectin matrix promote an inflammatory microenvironment conducive to metastatic progression.

Mechanotransduction in Skin Inflammation

In the process of mechanotransduction, the cells in the body perceive and interpret mechanical stimuli to maintain tissue homeostasis and respond to the environmental changes. Increasing evidence points towards dysregulated mechanotransduction as a pathologically relevant factor in human diseases, including inflammatory conditions. Skin is the organ that constantly undergoes considerable mechanical stresses, and the ability of mechanical factors to provoke inflammatory processes in the skin has long been known, with the Koebner phenomenon being an example. However, the molecular mechanisms and key factors linking mechanotransduction and cutaneous inflammation remain understudied. In this review, we outline the key players in the tissue's mechanical homeostasis, the available data, and the gaps in our current understanding of their aberrant regulation in chronic cutaneous inflammation. We mainly focus on psoriasis as one of the most studied skin inflammatory diseases; we also discuss mechanotransduction in the context of skin fibrosis as a result of chronic inflammation. Even though the role of mechanotransduction in inflammation of the simple epithelia of internal organs is being actively studied, we conclude that the mechanoregulation in the stratified epidermis of the skin requires more attention in future translational research.

COVID-19 and Toll-Like Receptor 4 (TLR4): SARS-CoV-2 May Bind and Activate TLR4 to Increase ACE2 Expression, Facilitating Entry and Causing Hyperinflammation

Causes of mortality from COVID-19 include respiratory failure, heart failure, and sepsis/multiorgan failure. TLR4 is an innate immune receptor on the cell surface that recognizes pathogen-associated molecular patterns (PAMPs) including viral proteins and triggers the production of type I interferons and proinflammatory cytokines to combat infection. It is expressed on both immune cells and tissue-resident cells. ACE2, the reported entry receptor for SARS-CoV-2, is only present on ~1-2% of the cells in the lungs or has a low pulmonary expression, and recently, the spike protein has been proposed to have the strongest protein-protein interaction with TLR4. Here, we review and connect evidence for SARS-CoV-1 and SARS-CoV-2 having direct and indirect binding to TLR4, together with other viral precedents, which when combined shed light on the COVID-19 pathophysiological puzzle. We propose a model in which the SARS-CoV-2 spike glycoprotein binds TLR4 and activates TLR4 signalling to increase cell surface expression of ACE2 facilitating entry. SARS-CoV-2 also destroys the type II alveolar cells that secrete pulmonary surfactants, which normally decrease the air/tissue surface tension and block TLR4 in the lungs thus promoting ARDS and inflammation. Furthermore, SARS-CoV-2-induced myocarditis and multiple-organ injury may be due to TLR4 activation, aberrant TLR4 signalling, and hyperinflammation in COVID-19 patients. Therefore, TLR4 contributes significantly to the pathogenesis of SARS-CoV-2, and its overactivation causes a prolonged or excessive innate immune response. TLR4 appears to be a promising therapeutic target in COVID-19, and since TLR4 antagonists have been previously trialled in sepsis and in other antiviral contexts, we propose the clinical trial testing of TLR4 antagonists in the treatment of severe COVID-19. Also, ongoing clinical trials of pulmonary surfactants in COVID-19 hold promise since they also block TLR4.

Evaluation of Toll-like receptor expression profile in patients with psoriasis vulgaris

TLRs are thought to play a role in the pathophysiology of such dermatological diseases as leprosy, acne and psoriasis. The study included 20 patients with plaque psoriasis, as well as 20 healthy age- and gender-matched control subjects. Real-time polymerase chain reaction evaluation was made of the messenger RNA expression of TLRs 1-10 in lesional tissue and peripheral blood mononuclear cell samples in psoriasis patients. TLR 3, 5, 6, 7, 9 and 10 lesional tissue mRNA expressions were increased significantly when compared to the expression levels in the PBMCs of the same patients (p = 0.0082, p = 0.0176, p = 0.0239, p = 0.0261, p = 0.0223, p = 0.0206). A comparison of the TLR expression in the PBMCs of healthy subjects and the PBMCs of patients with psoriasis showed a significant increase in the TLR 1, 8 and 10 mRNA expressions in the patient group (p < 0.0001, p < 0.0001, p = 0.0035). The TLR 5 mRNA expression was significantly higher in the control group than in the patient group (p = 0.0037). To the best of our knowledge, this is the first study in literature to evaluate mRNA TLR expression levels in the lesional tissue and PBMCs of patients with psoriasis.

Re-investigating the Basement Membrane Zone of Psoriatic Epidermal Lesions: Is Laminin-511 a New Player in Psoriasis Pathogenesis?

Psoriasis is a complex chronic inflammatory skin disease characterized by epidermal thickening on the basis of increased keratinocyte proliferation and insufficient apoptosis. Laminins are important components of the basement membrane (BM) and impact on epidermal keratinocyte growth/apoptosis. Although several laminins are involved in the pathogenesis of psoriasis, it is still controversial about the expression patterns of laminin isoforms and which laminins are important in the development of psoriasis. Because laminin-511 and -332 are key BM components in human skin, and laminin-511 stimulates human hair follicle growth, we asked whether the BM zone in psoriasis shows any laminin-related abnormalities. This showed that the BM expression of laminin-511 and -332 was significantly increased within the skin lesion of psoriasis. Immunofluorescence microscopy revealed that laminin-511, -332, and collagen type IV proteins were also significantly increased in psoriasis-like skin lesions of Imiquimod-treated mice. Transmission electron microscopy showed a few gaps of lamina densa, and its thickness was significantly increased. Finally, laminin-511 treatment significantly stimulated the proliferation and inhibited apoptosis of HaCaT cells, while laminin-α5 chain gene knockdown decreased proliferation and induced apoptosis. These phenomenological observations raise the question of whether laminin-511-controlled keratinocyte growth/death may be a previously overlooked player in the pathogenesis of psoriatic epidermal lesions.

Integration of Canonical and Noncanonical Pathways in TLR4 Signaling: Complex Regulation of the Wound Repair Program

Significance: Chronic inflammation and maladaptive repair contribute to the development of fibrosis that negatively impacts quality of life and organ function. The toll-like receptor (TLR) system is a critical node in the tissue response to both exogenous (pathogen-associated) and endogenous (damage-associated) molecular pattern factors (PAMPs and DAMPs, respectively). The development of novel TLR ligand-, pathway-, and/or target gene-specific therapeutics may have clinical utility in the management of the exuberant inflammatory/fibrotic tissue response to injury without compromising the host defense to pathogens. Recent Advances: DAMP ligands, released upon wounding, and microbial-derived PAMPs interact with several TLRs, and their various coreceptor partners, engaging downstream pathways that include Src family kinases, the epidermal growth factor receptor, integrins and the tumor suppressor phosphatase and tensin homolog (PTEN). Toll-like receptor 4 (TLR4) activation enhances cellular responses to the potent profibrotic cytokine transforming growth factor-β1 (TGF-β1) by attenuating the expression of receptors that inhibit TGF-β1 signaling. Critical Issues: Common as well as unique pathways may be activated by PAMP and DAMP ligands that bind to the repertoire of TLRs on various cell types. Dissecting mechanisms underlying ligand-dependent engagement of this complex, highly interactive, network will provide for adaptation of new and focused therapies directed to the regulation of pathologically significant profibrotic genes. Inherent in this diversity are therapeutic opportunities to modulate the pathophysiologic consequences of persistent TLR signaling. The recently identified involvement of receptor and nonreceptor kinase pathways in TLR signaling may present novel opportunities for pharmacologic intervention. Future Directions: Clarifying the identity and function of DAMP-activated TLR complexes or ligand-binding partners, as well as their engaged downstream effectors and target genes, are key factors in the eventual design of pathway-specific treatment modalities. Such approaches may be tailored to address the spectrum of TLR-initiated pathologies (including localized and persistent inflammation, maladaptive repair/fibrosis) and, perhaps, even titrated to achieve patient-unique beneficial clinical outcomes.

Gene editing of the extra domain A positive fibronectin in various tumors, amplified the effects of CRISPR/Cas system on the inhibition of tumor progression

Background

The low efficiency of clustered, regularly interspaced, palindromic repeats-associated Cas (CRISPR/Cas) system editing genes in vivo limits the application. A components of the extracellular matrix (ECM), the extra domain A positive fibronectin (EDA+FN), may be a target for CRISPR/Cas system for the pro-oncogenic effects. The exclusion of EDA exon would alter the microenvironment and inhibit tumor progression, even the frequency of gene editing is still limited.

Results

The pro-oncogenic effects were confirmed by the exclusion of EDA exon from the fibronectin gene, as illustrated by the down-regulated proliferation, migration and invasion of CNE-2Z or SW480 cells (P<0.05). Furthermore, although the efficacy of EDA exon knockout through CRISPR/Cas system was shown to be low in vivo, the EDA+FN protein levels decrease obviously, inhibiting the tumor growth rate significantly (P<0.05), which was accompanied by a decrease in Ki-67 expression and microvessel numbers, and increased E-cadherin or decreased Vimentin expression (P<0.05).

Methods and materials

Human nasopharyngeal carcinoma cell line CNE-2Z, and the colorectal carcinoma cell line SW480 were transfected with CRISPR/Cas9 plasmids targeting EDA exon. The effects of the exclusion of EDA on the cell proliferation, motility and epithelial-mesenchymal transition (EMT) were investigated, and the western blot and real-time PCR were performed to analyze the underlying mechanisms. Furthermore, CRISPR/Cas9 plasmids were injected into xenograft tumors to knockout EDA exon in vivo, and tumor growth, cell proliferation, EMT rate, or vascularization were investigated using western blot, PCR and immunohistochemistry.

Conclusion

CRISPR/Cas system targeting ECM components was shown to be an effective method for the inhibition of tumor progression, as these paracrine or autocrine molecules are necessary for various tumor cells. This may represent a novel strategy for overcoming the drug evasion or resistance, in addition, circumventing the low efficiency of CRISPR/Cas system in vivo.

Integrin α4β1 and TLR4 Cooperate to Induce Fibrotic Gene Expression in Response to Fibronectin's EDA Domain

Alternative splicing of fibronectin increases expression of the EDA⁺ isoform of fibronectin (EDA⁺Fn), a damage-associated molecular pattern molecule, which promotes fibro-inflammatory disease through the activation of toll-like receptors. Our studies indicate that the fibronectin EDA domain drives two waves of gene expression in human dermal fibroblasts. The first wave, seen at 2 hours, consisted of inflammatory genes, VCAM1, and tumor necrosis factor. The second wave, evaluated at 24 hours, was composed of the fibrosis-associated cytokines IL-10 and IL-13 and extracellular matrix genes fibronectin and osteopontin. Gene expression was coordinately regulated by the α4β1 integrin and the innate immune receptor toll-like receptor 4. Additionally, we found a significant toll-like receptor 4/α4β1-dependent enrichment in the ratio of EDA⁺Fn to total fibronectin in response to EDA, consistent with EDA⁺Fn initiating further production of EDA⁺Fn. Our data also suggest that the EDA/α4β1 integrin interaction primes the cell for an enhanced response to toll-like receptor 4 ligands. Our studies provide evidence that remodeling of the fibronectin matrix in injured or diseased tissue elicits an EDA-dependent fibro-inflammatory response in dermal fibroblasts. The data suggest a paradigm of damage-associated molecular pattern-based signaling whereby damage-associated molecular pattern binding integrins cooperate with innate immune receptors to stimulate inflammation and fibrosis.

CCN1 promotes IL-1β production in keratinocytes by activating p38 MAPK signaling in psoriasis

CCN1, an extracellular protein also known as cysteine-rich protein 61 (Cyr61), is a novel pro-inflammatory factor involved in the pathogenesis of rheumatoid arthritis. As an inflammatory disease, psoriasis is characterized by keratinocyte activation-induced epidermal hyperplasia and cytokine-mediated inflammation. We demonstrated in our previous study that CCN1 promoted keratinocyte activation in psoriasis. However, the role of CCN1 in regulating inflammation in psoriasis is still unknown. Here, we showed that CCN1 increased inflammatory cytokine IL-1β production in keratinocytes. Furthermore, endogenous ATP and caspase-1 were required for mature IL-1β production stimulated by CCN1 in keratinocytes. After binding to the receptor of integrin α6β1, CCN1 activated the downstream p38 MAPK signaling pathway, thus inducing the expression of IL-1β. In addition, we inhibited CCN1 function in mouse models of psoriasis, and decreased IL-1β production was observed in vivo. Overall, we showed that CCN1 increased IL-1β production via p38 MAPK signaling, indicating a role for CCN1 protein in regulating inflammation in psoriasis.

Purification of Human Plasma/Cellular Fibronectin and Fibronectin Fragments

A method is described for the purification of plasma fibronectins based on a combination of gelatin- and arginine-Sepharose chromatography steps. Cellular fibronectin can be purified from an osteosarcoma fibroblast cell line by affinity chromatography using a monoclonal antibody anti-fibronectin as ligand. Furthermore, we also provide a protocol for the purification of fibronectin domains obtained by fractionation of thermolysin-digested plasma fibronectin on ion-exchange/gel filtration chromatography columns. Assessment of the fibronectin purity is performed by SDS-PAGE, while the ligand binding activities of specific fibronectin domains are determined by ELISA.

Detection of Soluble ED-A(+) Fibronectin and Evaluation as Novel Serum Biomarker for Cardiac Tissue Remodeling

Background and Aims. Fibronectin containing the extra domain A (ED-A⁺ Fn) was proven to serve as a valuable biomarker for cardiac remodeling. The study was aimed at establishing an ELISA to determine ED-A⁺ Fn in serum of heart failure patients. Methods. ED-A⁺ Fn was quantified in serum samples from 114 heart failure patients due to ischemic (ICM, n = 44) and dilated (DCM, n = 39) cardiomyopathy as well as hypertensive heart disease (HHD, n = 31) compared to healthy controls (n = 12). Results. In comparison to healthy volunteers, heart failure patients showed significantly increased levels of ED-A⁺ Fn (p < 0.001). In particular in ICM patients there were significant associations between ED-A⁺ Fn serum levels and clinical parameters, for example, increased levels with rising NYHA class (p = 0.013), a negative correlation with left ventricular ejection fraction (p = 0.026, r: −0.353), a positive correlation with left atrial diameter (p = 0.008, r: 0.431), and a strong positive correlation with systolic pulmonary artery pressure (p = 0.002, r: 0.485). In multivariate analysis, ED-A⁺ Fn was identified as an independent predictor of an ischemic heart failure etiology. Conclusions. The current study could clearly show that ED-A⁺ Fn is a promising biomarker in cardiovascular diseases, especially in heart failure patients due to an ICM. We presented a valid ELISA method, which could be applied for further studies investigating the value of ED-A⁺ Fn.

Degranulating Neutrophils Promote Leukotriene B4 Production by Infected Macrophages To Kill Leishmania amazonensis Parasites

Neutrophils mediate early responses against pathogens, and they become activated during endothelial transmigration toward the inflammatory site. In the current study, human neutrophils were activated in vitro with immobilized extracellular matrix proteins, such as fibronectin (FN), collagen, and laminin. Neutrophil activation by FN, but not other extracellular matrix proteins, induces the release of the granules' contents, measured as matrix metalloproteinase 9 and neutrophil elastase activity in culture supernatant, as well as reactive oxygen species production. Upon contact with Leishmania amazonensis-infected macrophages, these FN-activated neutrophils reduce the parasite burden through a mechanism independent of cell contact. The release of granule proteases, such as myeloperoxidase, neutrophil elastase, and matrix metalloproteinase 9, activates macrophages through TLRs, leading to the production of inflammatory mediators, TNF-α and leukotriene B4 (LTB4), which are involved in parasite killing by infected macrophages. The pharmacological inhibition of degranulation reverted this effect, abolishing LTB4 and TNF production. Together, these results suggest that FN-driven degranulation of neutrophils induces the production of LTB4 and TNF by infected macrophages, leading to the control of Leishmania infection.

Abnormal regulation of fibronectin production by fibroblasts in psoriasis

BACKGROUND

Data indicate that in psoriasis, abnormalities are already present in nonlesional skin. Transforming growth factor-β and keratinocyte growth factor (KGF), together with fibronectin and α5β1 integrin, were suggested to play a crucial role in the pathogenesis of psoriasis by influencing inflammation and keratinocyte hyperproliferation.

OBJECTIVES

To investigate the expression of KGF, fibroblast growth factor receptor (FGFR)2, fibronectin (FN) and extra domain A (EDA)-positive FN in healthy and nonlesional psoriatic skin, and to study the effect of KGF on the regulation of FN and EDA(+) FN production by fibroblasts.

METHODS

Healthy, nonlesional psoriatic skin and lesional psoriatic skin were immunostained for α5 integrin, KGF, FGFR2, EDA(+) FN and signal transducer and activator of transcription (STAT)1. KGF-treated cell cultures were analysed for FN and EDA(+) FN mRNA and protein by real-time reverse-transcriptase polymerase chain reaction and flow cytometry, respectively. The major downstream signalling of KGF was investigated by blocking experiments using inhibitors of mitogen-activated protein kinase (MAPK) kinase (MEK1), AKT1/2, STAT1 and STAT3.

RESULTS

The expression of α5 integrin, EDA(+) FN, KGF and its receptor FGFR2 is elevated in psoriatic nonlesional skin compared with healthy skin. KGF mildly induced EDA(+) FN, but not FN expression in healthy fibroblasts through MAPK signalling. Fibroblasts express the FGFR2-IIIc splice variant. STAT1 negatively regulates both FN and EDA(+) FN expression in healthy fibroblasts, and this regulation is compromised in fibroblasts derived from nonlesional psoriatic dermis. We detected active STAT1 in healthy and lesional skin, similarly to a previous report. However, in the nonlesional skin STAT1 activation was absent in tissues far away from lesions.

CONCLUSIONS

The production of FN and EDA(+) FN by fibroblasts and the signalling of STAT1 are abnormally regulated in psoriatic nonlesional skin.

Urinary oncofetal ED-A fibronectin correlates with poor prognosis in patients with bladder cancer

The extracellular matrix protein fibronectin (FN) contributes to the structural integrity of tissues as well as the adhesive and migratory functions of cells. While FN is abundantly expressed in adult tissues, the expression of several alternatively spliced FN isoforms is restricted to embryonic development, tissue remodeling and cancer. These FN isoforms, designated ED-A and ED-B, are frequently expressed by cancer cells, tumor-associated fibroblasts and newly forming blood vessels. Using a highly sensitive collagen-based indirect ELISA, we evaluated the correlation of urinary ED-A and ED-B at time of cystectomy with overall survival in patients with high-grade bladder cancer (BCa). Detectable levels of total FN as well as ED-A and ED-B were found in urine from 85, 73 and 51 % of BCa patients, respectively. The presence of urinary ED-A was a significant independent predictor of 2-year overall survival (OS) after adjusting for age, tumor stage, lymph node stage, and urinary creatinine by multivariable Logistic Regression (p = 0.029, OR = 4.26, 95 % CI 1.16-15.71) and improved accuracy by 3.6 %. Furthermore, detection of ED-A in the urine was a significant discriminator of survival specifically in BCa patients with negative lymph node status (Log-Rank, p = 0.006; HR = 5.78, 95 % CI 1.39-24.13). Lastly, multivariable Cox proportional hazards analysis revealed that urinary ED-A was an independent prognostic indicator of 5-year OS rate for patients with BCa (p = 0.04, HR = 2.20, 95 % CI 1.04-4.69). Together, these data suggest that cancer-derived, alternatively spliced FN isoforms can act as prognostic indicators and that additional studies are warranted to assess the clinical utility of ED-A in BCa.

The TLR4 agonist fibronectin extra domain A is cryptic, exposed by elastase-2; use in a fibrin matrix cancer vaccine

Fibronectin (FN) is an extracellular matrix (ECM) protein including numerous fibronectin type III (FNIII) repeats with different functions. The alternatively spliced FN variant containing the extra domain A (FNIII EDA), located between FNIII 11 and FNIII 12, is expressed in sites of injury, chronic inflammation, and solid tumors. Although its function is not well understood, FNIII EDA is known to agonize Toll-like receptor 4 (TLR4). Here, by producing various FN fragments containing FNIII EDA, we found that FNIII EDA's immunological activity depends upon its local intramolecular context within the FN chain. N-terminal extension of the isolated FNIII EDA with its neighboring FNIII repeats (FNIII 9-10-11) enhanced its activity in agonizing TLR4, while C-terminal extension with the native FNIII 12-13-14 heparin-binding domain abrogated it. In addition, we reveal that an elastase 2 cleavage site is present between FNIII EDA and FNIII 12. Activity of the C-terminally extended FNIII EDA could be restored after cleavage of the FNIII 12-13-14 domain by elastase 2. FN being naturally bound to the ECM, we immobilized FNIII EDA-containing FN fragments within a fibrin matrix model along with antigenic peptides. Such matrices were shown to stimulate cytotoxic CD8⁺ T cell responses in two murine cancer models.

The α4β1 integrin and the EDA domain of fibronectin regulate a profibrotic phenotype in dermal fibroblasts

Prompt deposition of fibronectin-rich extracellular matrix is a critical feature of normal development and the host-response to injury. Fibronectin isoforms that include the EDA and EDB domains are prominent in these fibronectin matrices. We now report using human dermal fibroblast cultures that the EDA domain of fibronectin or EDA-derived peptides modeled after the C-C' loop promote stress fiber formation and myosin-light chain phosphorylation. These changes are accompanied by an increase in fibronectin synthesis and fibrillogenesis. These effects are blocked by pretreating cells with either siRNA or blocking antibody to the α4 integrin. Our data indicate that the interaction between the α4β1 integrin and the EDA domain of fibronectin helps to drive tissue fibrosis by promoting a contractile phenotype and an increase in fibronectin synthesis and deposition.

Role of toll-like receptors in systemic sclerosis

Accumulative evidence demonstrates the crucial role of evolutionary conserved Toll-like receptors (TLRs) in identifying microbial or viral compounds. TLRs are also able to recognise endogenous molecules which are released upon cell damage or stress and have been shown to play a key role in numerous autoimmune diseases including systemic sclerosis (SSc). A classic feature of SSc, is vascular injury manifested as Raynaud's phenomenon and ischaemia of the skin, resulting in the release of endogenous TLR ligands during inflammation and local tissue damage. These locally released TLR ligands bind TLRs possibly complexed to autoantibodies, and initiate intracellular signalling pathways and may be one of the mechanisms that initiate and drive autoimmunity and subsequent fibrosis. Activation of the immune system results in interferon (IFN) sensitive gene transcription. There is also an IFN gene signature in SSc peripheral blood. TLRs may represent the link between immune activation, common in SSc, and tissue fibrosis. Therefore, a better understanding of the mechanisms of TLR-mediated pathogenesis and therapies targeting individual TLRs, may provide a more specific approach of treating multi-systemic autoimmune diseases. This review aims to integrate the current knowledge of TLR function in the autoimmune disorders with particular emphasis on SSc. We suggest the TLR system as a new therapeutic target.

Increased gene expression of Toll-like receptor 4 on peripheral blood mononuclear cells in patients with psoriasis

BACKGROUND

A role for the innate immune system in driving the autoimmune T cell cascade in psoriasis has been proposed. Toll-like receptors-(TLR)-2 and -4 play a role in inflammation, atherosclerosis, and their specific role in psoriasis remains unclear.

OBJECTIVE

To evaluate TLR2 and TLR4 gene expression levels in peripheral blood mononuclear cells from psoriatic patients.

METHODS

Changes in TLR2 ⁄ 4 gene expressions were evaluated using quantitative real-time reverse transcription polymerase chain reaction in peripheral blood mononuclear cells, from twenty-one patients with severe psoriasis, and analysed whether there was any correlation with cytokine plasma levels (T-helper 0-, T-helper 1-, T-helper 2- or regulatory T cells-type), or Calprotectin and with S100A8 and S100A9 gene expression levels. Eleven non-psoriatic healthy controls were analysed.

RESULTS

A clear increase in TLR4 gene expression was observed (3.84 ± 0.93, n = 21) together with a moderate increase in TLR2 expression (1.522 ± 0.31, n = 21). Both TLR4 and TLR2 gene expressions were significantly augmented in psoriatic patients compared with controls (all P < 0.001). Correlations between TLR2 and S100A9 gene expressions (r = 0.5145, P = 0.0170, n = 21); and between TLR2 expression and plasma interleukin-2 (r = 0.5667, P = 0.0074); interleukin-4 (r = 0.4766, P = 0.0289), interleukin-10 (r = 0.4355, P = 0.0484) and interleukin-13 (r = 0.4603, P = 0.0358), were found. When patients with atheroma plaque were considered (n = 7), both TLR4 (3.47 ± 0.99, P = 0.0156) and TLR2 (1.63 ± 0.31, P = 0.0156) expressions were significantly increased vs. controls and correlated with plasma TNF-a (r = 0.8929, P = 0.0123, in both cases).

CONCLUSION

Differential TLR4 ⁄ 2 gene expressions on psoriatic peripheral blood mononuclear cells and correlations with regulatory and ⁄ or proinflammatory cytokines and ⁄ or damage-associated molecular pattern molecule S100A9 emphasize innate immune response role in psoriasis.

The extra domain A of fibronectin increases VEGF-C expression in colorectal carcinoma involving the PI3K/AKT signaling pathway

The extra domain A (EDA)-containing fibronectin (EDA-FN), an alternatively spliced form of the extracellular matrix protein fibronectin, is predominantly expressed in various malignancies but not in normal tissues. In the present study, we investigated the potential pro-lymphangiogenesis effects of extra domain A (EDA)-mediated vascular endothelial growth factor-C (VEGF-C) secretion in colorectal carcinoma (CRC). We detected the expressions of EDA and VEGF-C in 52 human colorectal tumor tissues and their surrounding mucosae by immunohistochemical analysis, and further tested the correlation between the expressions of these two proteins in aforementioned CRC tissues. Both EDA and VEGF-C were abundantly expressed in the specimens of human CRC tissues. And VEGF-C was associated with increased expression of EDA in human CRC according to linear regression analysis. Besides, EDA expression was significantly correlated with lymph node metastasis, tumor differentiation and clinical stage by clinicopathological analysis of tissue microarrays containing tumor tissues of 115 CRC patients. Then, human CRC cell SW480 was transfected with lentivectors to elicit expression of shRNA against EDA (shRNA-EDA), and SW620 was transfected with a lentiviral vector to overexpress EDA (pGC-FU-EDA), respectively. We confirmed that VEGF-C was upregulated in EDA-overexpressed cells, and downregulated in shRNA-EDA cells. Moreover, a PI3K-dependent signaling pathway was found to be involved in EDA-mediated VEGF-C secretion. The in vivo result demonstrated that EDA could promote tumor growth and tumor-induced lymphangiogenesis in mouse xenograft models. Our findings provide evidence that EDA could play a role in tumor-induced lymphangiogenesis via upregulating autocrine secretion of VEGF-C in colorectal cancer, which is associated with the PI3K/Akt-dependent pathway.

Extra domain A-positive fibronectin-positive feedback loops and their association with cutaneous inflammatory disease

Cutaneous inflammation can show Th1 or Th2 predominance, but the precise mechanisms by which such selectivity is determined are unknown. A recent study has demonstrated that Th1 cells, but not Th2 cells, produce an endogenous ligand for Toll-like receptor (TLR) 4, namely extradomain A+ fibronectin containing extra type III domain A (FnEDA+). As TLR4 stimulation leads to production of proinflammatory cytokines that recruit (via altered endothelial adhesion molecule expression and chemokine production) more Th1/Th17 cells, a positive feedback mechanism for Th1/Th17 inflammation exists. We propose that FnEDA+ positive feedback loops are a potential driver of Th1/Th17 inflammation. Conversely, the inflammatory EDA+ fibronectin loop is negatively regulated in atopic dermatitis, Th2 cytokines actively suppress TLR4 expression of Th1 cytokines, and recruited Th2 cells do not produce FnEDA+. In psoriasis, there are multiple FnEDA+ loops, comprising inflammatory, keratinocyte, and autoimmune loops. In allergic contact dermatitis, a single inflammatory loop operates. In atopic dermatitis, the FnEDA+ loop is actively suppressed by Th2 cytokines, and recruited Th2 cells do not "feedback" FnEDA+. We review endogenous ligands for TLR in relation to inflammatory disease, FnEDA+ function, and the potential role for FnEDA+ in psoriasis, allergic contact dermatitis, and atopic dermatitis.