Distinct microenvironmental cues stimulate divergent TLR4-mediated signaling pathways in macrophages

Chemical characterization, antioxidant activity and activation of macrophages RAW264.7 via MAPK signaling pathway of the exopolysaccharide from Penicillium EF-2

BACKGROUND

Microbial exopolysaccharides represent a significant source of polysaccharides, with their production unconstrained by temporal or spatial limitations. Penicillium, a filamentous fungus widely recognized for its medicinal food applications, is known to produce exopolysaccharides that exhibit cancer-inhibitory properties.

RESULTS

In the present study, exopolysaccharides from Penicillium EF-2 (EPS) were extracted and structurally characterized using ion chromatograph, infrared spectroscopy and NMR. The in vitro antioxidant and immunomodulatory activities were also investigated. EPS has a molecular weight of 111.47 kDa, is primarily composed of mannose, glucose and galactose, possesses a crystalline region, and exhibits excellent thermal properties. In free radical scavenging assays, EPS demonstrated robust in vitro antioxidant activity. Furthermore, EPS activated the mitogen-activated protein kinase pathway, enhancing the immunomodulatory capacity of macrophages.

CONCLUSION

EPS has excellent antioxidant and biological activities. The present study provides a theoretical basis for the utilization of EPS and offers new ideas for active sources of Penicillium fermented foods. © 2025 Society of Chemical Industry.

Integrated proteomics and phosphoproteomics profiling dynamic signaling networks underlying two distinct types of macrophage activation

Macrophages play a crucial role in antimicrobial host defense and those with differential maturation/differentiation status differ in inflammatory responses. Herein, GM-CSF and M-CSF primed mouse bone marrow derived macrophages (GM-BMDMs, GM and M-BMDMs, M), the well-established macrophage models in vitro, were utilized and their dynamic signaling changes in response to gram-negative bacteria component LPS treatment were analyzed using both 4D label-free proteomics and phosphoproteomics. Protein changes maintained relatively constant within or across GM and M macrophages post LPS challenge while phospho-protein exhibited more diverse and transient changes. Early induction of phospho-mediated GTPase activities, mRNA processing, and protein-mediated metabolic changes like oxidative phosphorylation (OXPHOS)/mitochondria function was identified at 1 h and maintained until 6 h post LPS treatment in GM and M while canonical TLR mediated MyD88-dependent and -independent pathways were activated at 3 and 6 h, individually at protein levels. Classical and novel phospho-sites for MyD88 and TRIF signaling pathways were also detected by phosphoproteomics. Comprehensively, the integrated protein and phospho-protein trend analysis was conducted and the core protein-phospho-protein network for the early phase actin reorganization, phagocytosis, and TLR signaling in both GM and M were presented. Taken together, these data described differences and similarities between these two types of macrophages in terms of their inflammatory responses to LPS.

The Soluble Cytoplasmic Tail of CD45 (ct-CD45) Regulates Dendritic Cell Activation and Function via TLR4 Signaling

The soluble cytoplasmic tail of the prototypic receptor-like protein tyrosine phosphatase (PTP) CD45 (ct-CD45) is cleaved and released into the human plasma by activated phagocytes. Released ct-CD45 was found to inhibit T cell proliferation and cytokine production via engagement of Toll-like receptor 4 (TLR4). In this study, we analyzed the impact of the ct-CD45/TLR4 pathway on the function of human monocyte-derived dendritic cells (DCs). We could demonstrate that activation of DCs by ct-CD45 upregulated the expression of certain cell surface markers (e.g., CD71 and CD86) and induced IL-10 production via TLR4. Yet, in contrast to stimulation with LPS, other typical cell surface markers and cytokines were not upregulated or induced in DCs by ct-CD45. The T cell proliferation-stimulatory capacity of DCs was not modulated by ct-CD45 treatment. However, treatment of DCs with ct-CD45 modulated the cytokine profile in co-cultured T cells. While IFN-γ production induced by DCs was strongly inhibited, the release of IL-4 was increased in T cells upon stimulation with ct-CD45-treated DCs. In contrast, ct-CD45-stimulated DCs induced IL-2 and IL-10 production in co-cultured T cells comparable to untreated DCs. In summary, we could demonstrate that ct-CD45 acts as an immunoregulatory factor for DCs via a non-canonical TLR4-dependent activation pathway.

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.

Intestinal E. coli-produced yersiniabactin promotes profibrotic macrophages in Crohn's disease

Inflammatory bowel disease (IBD)-associated fibrosis causes significant morbidity. Mechanisms are poorly understood but implicate the microbiota, especially adherent-invasive Escherichia coli (AIEC). We previously demonstrated that AIEC producing the metallophore yersiniabactin (Ybt) promotes intestinal fibrosis in an IBD mouse model. Since macrophages interpret microbial signals and influence inflammation/tissue remodeling, we hypothesized that Ybt metal sequestration disrupts this process. Here, we show that macrophages are abundant in human IBD-fibrosis tissue and mouse fibrotic lesions, where they co-localize with AIEC. Ybt induces profibrotic gene expression in macrophages via stabilization and nuclear translocation of hypoxia-inducible factor 1-alpha (HIF-1α), a metal-dependent immune regulator. Importantly, Ybt-producing AIEC deplete macrophage intracellular zinc and stabilize HIF-1α through inhibition of zinc-dependent HIF-1α hydroxylation. HIF-1α+ macrophages localize to sites of disease activity in human IBD-fibrosis strictures and mouse fibrotic lesions, highlighting their physiological relevance. Our findings reveal microbiota-mediated metal sequestration as a profibrotic trigger targeting macrophages in the inflamed intestine.

Development of immunocompetent full thickness skin tissue constructs to model skin fibrosis for high-throughput drug screening

The lack of the immune component in most of the engineered skin models remains a challenge to study the interplay between different immune and non-immune cell types of the skin. Immunocompetent humanin vitroskin models offer potential advantages in recapitulatingin vivolike behavior which can serve to accelerate translational research and therapeutics development for skin diseases. Here we describe a three-dimensional human full-thickness skin (FTS) equivalent incorporating polarized M1 and M2 macrophages from human peripheral CD14+monocytes. This macrophage-incorporated FTS model demonstrates discernible immune responses with physiologically relevant cytokine production and macrophage plasticity under homeostatic and lipopolysaccharide stimulation conditions. M2-incorporated FTS recapitulates skin fibrosis phenotypes with transforming growth factor-β1 treatment as reflected by significant collagen deposition and myofibroblast expression, demonstrating a M2 potentiation effect. In conclusion, we successfully biofabricated an immunocompetent FTS with functional macrophages in a high-throughput (HT) amenable format. This model is the first step towards a HT-assay platform to develop new therapeutics for skin diseases.

Cellular and microenvironmental cues that promote macrophage fusion and foreign body response

During the foreign body response (FBR), macrophages fuse to form foreign body giant cells (FBGCs). Modulation of FBGC formation can prevent biomaterial degradation and loss of therapeutic efficacy. However, the microenvironmental cues that dictate FBGC formation are poorly understood with conflicting reports. Here, we identified molecular and cellular factors involved in driving FBGC formation in vitro. Macrophages demonstrated distinct fusion competencies dependent on monocyte differentiation. The transition from a proinflammatory to a reparative microenvironment, characterised by specific cytokine and growth factor programmes, accompanied FBGC formation. Toll-like receptor signalling licensed the formation of FBGCs containing more than 10 nuclei but was not essential for cell-cell fusion to occur. Moreover, the fibroblast-macrophage crosstalk influenced FBGC development, with the fibroblast secretome inducing macrophages to secrete more PDGF, which enhanced large FBGC formation. These findings advance our understanding as to how a specific and timely combination of cellular and microenvironmental factors is required for an effective FBR, with monocyte differentiation and fibroblasts being key players.

Echinacea purpurea (L.) Moench Polysaccharide Alleviates DSS-Induced Colitis in Rats by Restoring Th17/Treg Balance and Regulating Intestinal Flora

Echinacea purpurea is popularly used as a food supplement or nutritional supplement for its immune regulatory function against various threats. As one of its promising components, Echinacea purpurea (L.) Moench polysaccharide (EPP) has a wide range of biological activities. To evaluate the effect of EPP as a dietary supplement on ulcerative colitis (UC), this study used sodium dextran sulfate (DSS) to induce a UC model, extracted EPP using the ethanol subsiding method, and then supplemented with EPP by gavage for 7 days. Then, we evaluated the efficacy of EPP on DSS rats in terms of immunity, anti-inflammation, and intestinal flora. The result showed that EPP could alleviate colonic shortening and intestinal injury in rats with DSS-induced colitis, decrease the disease activity index (DAI) score, downregulate serum levels of inflammatory cytokines, and contribute to the restoration of the balance between the T helper cells 17 (Th17) and the regulatory T cells (Treg) in the spleen and mesenteric lymph nodes (MLNs). Meanwhile, EPP could downregulate the expression of Toll-like receptors 4 (TLR4), myeloid differentiation factor 88 (MyD88), and nuclear factor kappa-B (NF-κB) in colon tissue. In addition, the results of 16SrRNA sequencing showed that EPP also had a regulatory effect on intestinal flora of UC rats. These results indicate that EPP might achieve a beneficial effect on UC rats as a dietary supplement through restoring Th17/Treg balance, inhibiting the TLR4 signaling pathway and regulating intestinal flora, suggesting its possible application as a potential functional food ingredient alleviating UC.

Deoxynivalenol increases pro-inflammatory cytokine secretion and reduces primary bile acid transport in an inflamed intestinal in vitro co-culture model

The fungal secondary metabolite deoxynivalenol (DON) that can contaminate cereal-based food products not only induces inflammation but also reduces bile acid absorption by a healthy human intestine. Bile acid malabsorption is commonly observed in individuals with an inflamed intestine. Here we studied the effects of DON on inflammation and primary bile acid transport using an in vitro model for an inflamed intestine. An inflamed intestinal in vitro model was established by co-culturing a Caco-2 cell-layer and LPS-pre-stimulated THP-1 macrophages in Transwells. We observed a decreased transport of 5 primary bile acids across inflamed co-cultures compared to healthy co-cultures but not of chenodeoxycholic acid. DON exposure further reduced the transport of the affected primary bile acids across the inflamed co-cultures. DON exposure also enhanced the secretion of pro-inflammatory cytokines in the inflamed co-cultures, while it did not increase the pro-inflammatory cytokines secretion from LPS-pre-stimulated THP-1 monocultures. Exposure of Caco-2 cell-layers to pro-inflammatory cytokines or THP-1 conditioned media partly mimicked the DON-induced effects of the co-culture model. Local activation of intestinal immune cells reinforces the direct pro-inflammatory effects of DON on intestinal epithelial cells. This affects the bile acid intestinal kinetics in an inflamed intestine.

Surface immunogenic protein from Streptococcus agalactiae and Fissurella latimarginata hemocyanin are TLR4 ligands and activate MyD88- and TRIF dependent signaling pathways

The development of vaccine adjuvants is of interest for the management of chronic diseases, cancer, and future pandemics. Therefore, the role of Toll-like receptors (TLRs) in the effects of vaccine adjuvants has been investigated. TLR4 ligand-based adjuvants are the most frequently used adjuvants for human vaccines. Among TLR family members, TLR4 has unique dual signaling capabilities due to the recruitment of two adapter proteins, myeloid differentiation marker 88 (MyD88) and interferon-β adapter inducer containing the toll-interleukin-1 receptor (TIR) domain (TRIF). MyD88-mediated signaling triggers a proinflammatory innate immune response, while TRIF-mediated signaling leads to an adaptive immune response. Most studies have used lipopolysaccharide-based ligands as TLR4 ligand-based adjuvants; however, although protein-based ligands have been proven advantageous as adjuvants, their mechanisms of action, including their ability to undergo structural modifications to achieve optimal immunogenicity, have been explored less thoroughly. In this work, we characterized the effects of two protein-based adjuvants (PBAs) on TLR4 signaling via the recruitment of MyD88 and TRIF. As models of TLR4-PBAs, we used hemocyanin from Fissurella latimarginata (FLH) and a recombinant surface immunogenic protein (rSIP) from Streptococcus agalactiae. We determined that rSIP and FLH are partial TLR4 agonists, and depending on the protein agonist used, TLR4 has a unique bias toward the TRIF or MyD88 pathway. Furthermore, when characterizing gene products with MyD88 and TRIF pathway-dependent expression, differences in TLR4-associated signaling were observed. rSIP and FLH require MyD88 and TRIF to activate nuclear factor kappa beta (NF-κB) and interferon regulatory factor (IRF). However, rSIP and FLH have a specific pattern of interleukin 6 (IL-6) and interferon gamma-induced protein 10 (IP-10) secretion associated with MyD88 and TRIF recruitment. Functionally, rSIP and FLH promote antigen cross-presentation in a manner dependent on TLR4, MyD88 and TRIF signaling. However, FLH activates a specific TRIF-dependent signaling pathway associated with cytokine expression and a pathway dependent on MyD88 and TRIF recruitment for antigen cross-presentation. Finally, this work supports the use of these TLR4-PBAs as clinically useful vaccine adjuvants that selectively activate TRIF- and MyD88-dependent signaling to drive safe innate immune responses and vigorous Th1 adaptive immune responses.

Integrating bioinformatic resources to identify characteristics of rheumatoid arthritis-related usual interstitial pneumonia

BACKGROUND

Rheumatoid arthritis (RA) is often accompanied by a common extra-articular manifestation known as RA-related usual interstitial pneumonia (RA-UIP), which is associated with a poor prognosis. However, the mechanism remains unclear. To identify potential mechanisms, we conducted bioinformatics analysis based on high-throughput sequencing of the Gene Expression Omnibus (GEO) database.

RESULTS

Weighted gene co-expression network analysis (WGCNA) analysis identified 2 RA-positive related modules and 4 idiopathic pulmonary fibrosis (IPF)-positive related modules. A total of 553 overlapped differentially expressed genes (DEG) were obtained, of which 144 in the above modules were further analyzed. The biological process of "oxidative phosphorylation" was found to be the most relevant with both RA and IPF. Additionally, 498 up-regulated genes in lung tissues of RA-UIP were screened out and enriched by 7 clusters, of which 3 were closely related to immune regulation. The analysis of immune infiltration showed a characteristic distribution of peripheral immune cells in RA-UIP, compared with IPF-UIP in lung tissues.

CONCLUSIONS

These results describe the complex molecular and functional landscape of RA-UIP, which will help illustrate the molecular pathological mechanism of RA-UIP and identify new biomarkers and therapeutic targets for RA-UIP in the future.

Upadacitinib inhibits corneal inflammation and neovascularization by suppressing M1 macrophage infiltration in the corneal alkali burn model

Alkali burn-induced corneal inflammation and subsequent corneal neovascularization (CNV) are major causes of corneal opacity and vision loss. M1 macrophages play a central role in inflammation and CNV. Therefore, modulation of M1 macrophage polarization is a promising strategy for corneal alkali burns. Here, we illustrate the effect and underlying mechanisms of upadacitinib on corneal inflammation and CNV induced by alkali burns in mice. The corneas of BALB/c mice were administered with 1 M NaOH for 30 s and randomly assigned to the vehicle group and the upadacitinib-treated group. Corneal opacity and corneal epithelial defects were assessed clinically. Quantitative real-time PCR (qRT-PCR), immunohistochemistry, and western blot analysis were performed to detect M1 macrophage polarization and CD31⁺ corneal blood vessels. The results showed that upadacitinib notably decreased corneal opacity, and promoted corneal wound healing. On day 7 and 14 after alkali burns, upadacitinib significantly suppressed CNV. Corneal alkali injury caused M1 macrophage recruitment in the cornea. In contrast to the vehicle, upadacitinib suppressed M1 macrophage infiltration and decreased the mRNA expression levels of inducible nitric oxide synthase (iNOS), monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, IL-1β, and vascular endothelial growth factor A (VEGF-A) in alkali-injured corneas. Moreover, upadacitinib dose-dependently inhibited M1 macrophage polarization by suppressing interferon (IFN)-γ-/lipopolysaccharide-stimulated STAT1 activation in vitro. Our findings reveal that upadacitinib can efficiently alleviate alkali-induced corneal inflammation and neovascularization by inhibiting M1 macrophage infiltration. These data demonstrate that upadacitinib is an effective drug for the treatment of corneal alkali burns.

Toll-like receptor triggering in systemic sclerosis: time to target

SSc is an autoimmune disease that has features of vascular abnormalities, inflammation and skin and lung fibrosis. Toll-like receptors (TLRs) are sentinel receptors that serve to recognize pathogens or internal danger signals leading to downstream signalling pathways that ultimately lead to inflammation and modification of adaptive immunity. Inflammation and fibrosis appear intricately connected in this disease and TLR ligation on fibroblasts can directly activate these cells to produce copious amounts of collagen, a hallmark of disease. The presence of damage-associated molecular patterns in association with fibrosis has been highlighted. Given their prominent role in disease, this review discusses the evidence of their expression and role in disease pathogenesis and possible therapeutic intervention to mitigate fibrosis.

Tenascin-C: A Key Regulator in Angiogenesis during Wound Healing

(1) Background: Injury repair is a complex physiological process in which multiple cells and molecules are involved. Tenascin-C (TNC), an extracellular matrix (ECM) glycoprotein, is essential for angiogenesis during wound healing. This study aims to provide a comprehensive review of the dynamic changes and functions of TNC throughout tissue regeneration and to present an up-to-date synthesis of the body of knowledge pointing to multiple mechanisms of TNC at different restoration stages. (2) Methods: A review of the PubMed database was performed to include all studies describing the pathological processes of damage restoration and the role, structure, expression, and function of TNC in post-injury treatment; (3) Results: In this review, we first introduced the construction and expression signature of TNC. Then, the role of TNC during the process of damage restoration was introduced. We highlight the temporal heterogeneity of TNC levels at different restoration stages. Furthermore, we are surprised to find that post-injury angiogenesis is dynamically consistent with changes in TNC. Finally, we discuss the strategies for TNC in post-injury treatment. (4) Conclusions: The dynamic expression of TNC has a significant impact on angiogenesis and healing wounds and counters many negative aspects of poorly healing wounds, such as excessive inflammation, ischemia, scarring, and wound infection.

Immunopathogenesis of Sjogren's syndrome: Current state of DAMPs

Sjögren's syndrome (SS) is a systemic autoimmune disorder with an estimated global prevalence of 0.3 to 1/1000 persons. This disease has a female predilection and mainly affects salivary and lacrimal glands. The distinctive pathological hallmark of SS is focal lymphocyte infiltration in affected glands, accompanied by the production of autoantibodies and inflammatory cytokines leading to epithelial damage and disease progression. Danger-associated molecular patterns (DAMPs) as alarmins have been demonstrated to promote lymphocyte recruitment in several inflammatory and autoimmune diseases. Here we summarize that the levels of DAMPs were increased in the periphery and affected tissues in SS as the stimulators, DAMPs sensed by pattern recognition receptors (PRRs, the same sensors for PAMPs) initiated the inflammatory and autoimmune response constituting a vicious autoimmunity loop leading to disease exacerbation. Thus, DAMPs are involved in the immunopathogenesis of SS and inhibition of these DAMPs may serve as a novel therapeutic strategy for SS.

Advances on the roles of tenascin-C in cancer

The roles of the extracellular matrix molecule tenascin-C (TNC) in health and disease have been extensively reviewed since its discovery over 40 years ago. Here, we will describe recent insights into the roles of TNC in tumorigenesis, angiogenesis, immunity and metastasis. In addition to high levels of expression in tumors, and during chronic inflammation, and bacterial and viral infection, TNC is also expressed in lymphoid organs. This supports potential roles for TNC in immunity control. Advances using murine models with engineered TNC levels were instrumental in the discovery of important functions of TNC as a danger-associated molecular pattern (DAMP) molecule in tissue repair and revealed multiple TNC actions in tumor progression. TNC acts through distinct mechanisms on many different cell types with immune cells coming into focus as important targets of TNC in cancer. We will describe how this knowledge could be exploited for cancer disease management, in particular for immune (checkpoint) therapies.

Breast cancer microenvironment and obesity: challenges for therapy

Women with obesity who develop breast cancer have a worsened prognosis with diminished survival rates and increased rates of metastasis. Obesity is also associated with decreased breast cancer response to endocrine and chemotherapeutic treatments. Studies utilizing multiple in vivo models of obesity as well as human breast tumors have enhanced our understanding of how obesity alters the breast tumor microenvironment. Changes in the complement and function of adipocytes, adipose-derived stromal cells, immune cells, and endothelial cells and remodeling of the extracellular matrix all contribute to the rapid growth of breast tumors in the context of obesity. Interactions of these cells enhance secretion of cytokines and adipokines as well as local levels of estrogen within the breast tumor microenvironment that promote resistance to multiple therapies. In this review, we will discuss our current understanding of the impact of obesity on the breast tumor microenvironment, how obesity-induced changes in cellular interactions promote resistance to breast cancer treatments, and areas for development of treatment interventions for breast cancer patients with obesity.

Tenascin-C in fibrosis in multiple organs: Translational implications

Systemic sclerosis (SSc, scleroderma) is a complex disease with a pathogenic triad of autoimmunity, vasculopathy, and fibrosis involving the skin and multiple internal organs [1]. Because fibrosis accounts for as much as 45% of all deaths worldwide and appears to be increasing in prevalence [2], understanding its pathogenesis and progression is an urgent scientific challenge. Fibroblasts and myofibroblasts are the key effector cells executing physiologic tissue repair on one hand, and pathological fibrogenesis leading to chronic fibrosing conditions on the other. Recent studies identify innate immune signaling via toll-like receptors (TLRs) as a key driver of persistent fibrotic response in SSc. Repeated injury triggers the in-situ generation of "damage-associated molecular patterns" (DAMPs) or danger signals. Sensing of these danger signals by TLR4 on resident cells elicits potent stimulatory effects on fibrotic gene expression and myofibroblast differentiation triggering the self-limited tissue repair response to self-sustained pathological fibrosis characteristic of SSc. Our unbiased survey for DAMPs associated with SSc identified extracellular matrix glycoprotein tenascin-C as one of the most highly up-regulated ECM proteins in SSc skin and lung biopsies [3,4]. Furthermore, tenascin C is responsible for driving sustained fibroblasts activation, thereby progression of fibrosis [3]. This review summarizes recent studies examining the regulation and complex functional role of tenascin C, presenting tenascin-TLR4 axis in pathological fibrosis, and novel anti-fibrotic approaches targeting their signaling.

Tenascin-C is a driver of inflammation in the DSS model of colitis

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Increased tenascin-C staining appeared to predominantly occur in damaged ulcerated areas.

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Tenascin-C knock-out mice were partly protected from DSS induced colitis.

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Mice deficient in tenascin-C had areas of + ve EpCAM staining indicating that crypt and epithelial integrity was maintained.

Inflammatory Bowel Disease (IBD) is a grouping of chronic inflammatory disorders of the gut. Tenascin-C is a pro-inflammatory, extracellular matrix protein found upregulated in IBD patients and whilst a pathological driver of chronic inflammation, its precise role in the etiology of IBD is unknown. To study tenascin-C’s role in colitis pathology we investigated its expression in a murine model of IBD. Wild-type (WT) or tenascin-C knockout (KO) male mice were left untreated or treated with dextran sodium sulphate (DSS) in their drinking water. Tenascin-C was upregulated at the mRNA level in the colitic distal colon of day eight DSS treated mice, coinciding with significant increases in gross and histological pathology. Immunohistochemistry localized this increase in tenascin-C to areas of inflammation and ulceration in the mucosa. Tenascin-C KO mice exhibited reduced gross pathology in comparison. These differences also extended to the histopathological level where reduced colonic inflammation and tissue damage were found in KO compared to WT mice. Furthermore, the severity of the distal colon lesions were less in the KO mice after 17 days of recovery from DSS treatment. This study demonstrates a role for tenascin-C as a driver of inflammatory pathology in a murine model of IBD and thus suggests neutralizing its pro-inflammatory activity could be explored as a therapeutic strategy for treating IBD.

Induction of IDO1 and Kynurenine by Serine Proteases Subtilisin, Prostate Specific Antigen, CD26 and HtrA: A New Form of Immunosuppression?

Several serine proteases have been linked to autoimmune disorders and tumour initiation although the mechanisms are not fully understood. Activation of the kynurenine pathway enzyme indoleamine-2,3-dioxygenase (IDO1) modulates cellular activity in the brain, tolerogenesis in the immune system and is a major checkpoint in cancer development. We now report that IDO1 mRNA and IDO1 protein expression (generating kynurenine) are induced in human monocyte-derived macrophages by several chymotryptic serine proteases with direct links to tumorigenesis, including Prostate Specific Antigen (PSA), CD26 (Dipeptidyl-peptidase-4, CD26/DPP-4), High Temperature Requirement protein-A (HtrA), and the bacterial virulence factor subtilisin. These proteases also induce expression of the pro-inflammatory cytokine genes IL1B and IL6. Other serine proteases tested: bacterial glu-C endopeptidase and mammalian Pro-protein Convertase Subtilase-Kexin-3 (PCSK3, furin), urokinase plasminogen activator (uPA), cathepsin G or neutrophil elastase, did not induce IDO1, indicating that the reported effects are not a general property of all serine proteases. The results represent a novel mechanism of activating immunosuppressive IDO1 and inducing kynurenine generation which, together with the production of inflammatory cytokines, would contribute to tumour initiation and progression, providing a new target for drug development. In addition, the proteasomal S20 serine protease inhibitor carfilzomib, used in the treatment of myeloma, prevented the induction of IDO1 and cytokine gene expression, potentially contributing to its clinical anti-cancer activity.

The soluble cytoplasmic tail of CD45 regulates T-cell activation via TLR4 signaling

The soluble cytoplasmic tail of CD45 (ct-CD45) is a cleavage fragment of CD45, that is generated during the activation of human phagocytes. Upon release to the extracellular space, ct-CD45 binds to human T cells and inhibits their activation in vitro. Here, we studied the potential role of TLR4 as a receptor for ct-CD45. Treatment of Jurkat TLR4/CD14 reporter cells with ct-CD45 induced the upregulation of the reporter gene NFκB-eGFP and could be blocked by inhibitors of TLR4 signaling. Conversely, ct-CD45 did not promote the NFκB-controlled eGFP induction in reporter cells expressing TLR1, TLR2, and TLR6 transgenes and did not lead to the activation of the transcription factors NFκB, AP-1, and NFAT in a Jurkat reporter cell line expressing endogenous TLR5. Moreover, ct-CD45 binds to recombinant TLR4 in an in vitro assay and this association was reduced in the presence of oxidized 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphorylcholine. Blockade of TLR4 with mAb HTA125 partially reversed the ct-CD45-mediated inhibition of T-cell proliferation. Interestingly, targeting of TLR4 with mAb W7C11 also suppressed T-cell proliferation. In summary, the results of this study demonstrate that ct-CD45 acts via a noncanonical TLR4 activation pathway on T cells, which modulates TCR signaling.

Tenascin C Has a Modest Protective Effect on Acute Lung Pathology during Methicillin-Resistant Staphylococcus aureus-Induced Pneumonia in Mice

Tenascin C (TNC) is an extracellular matrix protein with immunomodulatory properties that plays a major role during tissue injury and repair. TNC levels are increased in patients with pneumonia and pneumosepsis, and they are associated with worse outcomes. Methicillin-resistant Staphylococcus aureus (MRSA) is a Gram-positive bacterium that is a major causative pathogen in nosocomial pneumonia and a rising cause of community-acquired pneumonia. To study the role of TNC during MRSA-induced pneumonia, TNC sufficient (TNC+/+) and TNC-deficient (TNC-/-) mice were infected with MRSA via the airways and euthanized after 6, 24, and 48 h for analysis. Pulmonary transcription of TNC peaked at 6 h, while immunohistochemistry revealed higher protein levels at later time points. Although TNC deficiency was not associated with changes in bacterial clearance, TNC-/- mice showed increased levels of TNF-α and IL-6 in bronchoalveolar lavage fluid during the acute phase of infection when compared with TNC+/+ mice. In addition, TNC-/- mice showed more severe pulmonary pathology at 6, but not at 24 or 48 h, after infection. Together, these data suggest that TNC plays a moderate protective role against tissue pathology during the acute inflammatory phase, but not during the bacterial clearance phase, of MRSA-induced pneumonia. These results argue against an important role of TNC on disease outcome during MRSA-induced pneumonia. IMPORTANCE Recently, the immunomodulatory properties of TNC have drawn substantial interest. However, to date most studies made use of sterile models of inflammation. In this study, we examine the pathobiology of MRSA-induced pneumonia in a model of TNC-sufficient and TNC-deficient mice. We have studied the immune response and tissue pathology both during the initial insult and also during the resolution phase. We demonstrate that MRSA-induced pneumonia upregulates pulmonary TNC expression at the mRNA and protein levels. However, the immunomodulatory role of TNC during bacterial pneumonia is distinct from models of sterile inflammation, indicating that the function of TNC is context dependent. Contrary to previous descriptions of TNC as a proinflammatory mediator, TNC-deficient mice seem to suffer from enhanced tissue pathology during the acute phase of infection. Nonetheless, besides its role during the acute phase response, TNC does not seem to play a major role in disease outcome during MRSA-induced pneumonia.

Evolving Perspectives on Innate Immune Mechanisms of IPF

While epithelial-fibroblast interactions are viewed as the primary drivers of Idiopathic Pulmonary Fibrosis (IPF), evidence gleaned from animal modeling and human studies implicates innate immunity as well. To provide perspective on this topic, this review synthesizes the available data regarding the complex role of innate immunity in IPF. The role of substances present in the fibrotic microenvironment including pathogen associated molecular patterns (PAMPs) derived from invading or commensal microbes, and danger associated molecular patterns (DAMPs) derived from injured cells and tissues will be discussed along with the proposed contribution of innate immune populations such as macrophages, neutrophils, fibrocytes, myeloid suppressor cells, and innate lymphoid cells. Each component will be considered in the context of its relationship to environmental and genetic factors, disease outcomes, and potential therapies. We conclude with discussion of unanswered questions and opportunities for future study in this area.

Immune-Intrinsic Myd88 Directs the Production of Antibodies With Specificity for Extracellular Matrix Components in Primary Sjögren's Syndrome

Primary Sjögren's syndrome is an autoimmune disease that is predominantly seen in women. The disease is characterized by exocrine gland dysfunction in combination with serious systemic manifestations. At present, the causes of pSS are poorly understood. Pulmonary and renal inflammation are observed in pSS mice, reminiscent of a subset of pSS patients. A growing body of evidence indicates that inflammation mediated by Damage-Associated Molecular Patterns (DAMPs) contributes to autoimmunity, although this is not well-studied in pSS. Degraded extracellular matrix (ECM) constituents can serve as DAMPs by binding pattern-recognition receptors and activating Myd88-dependent signaling cascades, thereby exacerbating and perpetuating inflammatory cascades. The ECM components biglycan (Bgn) and decorin (Dcn) mediate sterile inflammation and both are implicated in autoimmunity. The objective of this study was to determine whether these ECM components and anti-ECM antibodies are altered in a pSS mouse model, and whether this is dependent on Myd88 activation in immune cells. Circulating levels of Bgn and Dcn were similar among pSS mice and controls and tissue expression studies revealed pSS mice had robust expression of both Bgn and Dcn in the salivary tissue, saliva, lung and kidney. Sera from pSS mice displayed increased levels of autoantibodies directed against ECM components when compared to healthy controls. Further studies using sera derived from conditional knockout pSS mice demonstrated that generation of these autoantibodies relies, at least in part, on Myd88 expression in the hematopoietic compartment. Thus, this study demonstrates that ECM degradation may represent a novel source of chronic B cell activation in the context of pSS.

Tenascin-C in Heart Diseases-The Role of Inflammation

Tenascin-C (TNC) is a large extracellular matrix (ECM) glycoprotein and an original member of the matricellular protein family. TNC is transiently expressed in the heart during embryonic development, but is rarely detected in normal adults; however, its expression is strongly up-regulated with inflammation. Although neither TNC-knockout nor -overexpressing mice show a distinct phenotype, disease models using genetically engineered mice combined with in vitro experiments have revealed multiple significant roles for TNC in responses to injury and myocardial repair, particularly in the regulation of inflammation. In most cases, TNC appears to deteriorate adverse ventricular remodeling by aggravating inflammation/fibrosis. Furthermore, accumulating clinical evidence has shown that high TNC levels predict adverse ventricular remodeling and a poor prognosis in patients with various heart diseases. Since the importance of inflammation has attracted attention in the pathophysiology of heart diseases, this review will focus on the roles of TNC in various types of inflammatory reactions, such as myocardial infarction, hypertensive fibrosis, myocarditis caused by viral infection or autoimmunity, and dilated cardiomyopathy. The utility of TNC as a biomarker for the stratification of myocardial disease conditions and the selection of appropriate therapies will also be discussed from a clinical viewpoint.

Generation of Transgenic Mice that Conditionally Overexpress Tenascin-C

Tenascin-C (TNC) is an extracellular matrix glycoprotein that is expressed during embryogenesis. It is not expressed in normal adults, but is up-regulated under pathological conditions. Although TNC knockout mice do not show a distinct phenotype, analyses of disease models using TNC knockout mice combined with in vitro experiments revealed the diverse functions of TNC. Since high TNC levels often predict a poor prognosis in various clinical settings, we developed a transgenic mouse that overexpresses TNC through Cre recombinase-mediated activation. Genomic walking showed that the transgene was integrated into and truncated the Atp8a2 gene. While homozygous transgenic mice showed a severe neurological phenotype, heterozygous mice were viable, fertile, and did not exhibit any distinct abnormalities. Breeding hemizygous mice with Nkx2.5 promoter-Cre or α-myosin heavy chain promoter Cre mice induced the heart-specific overexpression of TNC in embryos and adults. TNC-overexpressing mouse hearts did not have distinct histological or functional abnormalities. However, the expression of proinflammatory cytokines/chemokines was significantly up-regulated and mortality rates during the acute stage after myocardial infarction were significantly higher than those of the controls. Our novel transgenic mouse may be applied to investigations on the role of TNC overexpression in vivo in various tissue/organ pathologies using different Cre donors.

Macrophages and Extracellular Matrix in Breast Cancer: Partners in Crime or Protective Allies?

Solid cancers such as breast tumors comprise a collection of tumor, stromal and immune cells, embedded within a network of tumor-specific extracellular matrix. This matrix is associated with tumor aggression, treatment failure, chemo- and radio-resistance, poor survival and metastasis. Recent data report an immunomodulatory role for the matrix in cancer, via the creation of niches that control the migration, localization, phenotype and function of tumor-infiltrating immune cells, ultimately contributing to escape of immune surveillance. Macrophages are crucial components of the immune infiltrate in tumors; they are associated with a poor prognosis in breast cancer and contribute to shaping the anti-tumor immune response. We and others have described how matrix molecules commonly upregulated within the tumor stroma, such as tenascin-C, fibronectin and collagen, exert a complex influence over macrophage behavior, for example restricting or enhancing their infiltration into the tumor, and driving their polarization towards or away from a pro-tumoral phenotype, and how in turn macrophages can modify matrix production in the tumor to favor tumor growth and metastasis. Targeting specific domains of matrix molecules to reinstate an efficient anti-tumor immune response, and effectively control tumor growth and spread, is emerging as a promising field offering a new angle for cancer therapy. Here, we review current knowledge on the interactions between tumor-associated macrophages and matrix molecules that occur within the tumor microenvironment of breast cancer, and discuss how these pathways can be targeted for new immunotherapies for hard to treat, desmoplastic tumors.

HAMLET a human milk protein-lipid complex induces a pro-inflammatory phenotype of myeloid cells

HAMLET is a protein‐lipid complex with a specific and broad bactericidal and tumoricidal activity, that lacks cytotoxic activity against healthy cells. In this study, we show that HAMLET also has general immune‐stimulatory effects on primary human monocyte‐derived dendritic cells and macrophages (Mo‐DC and Mo‐M) and murine RAW264.7 macrophages. HAMLET, but not its components alpha‐lactalbumin or oleic acid, induces mature CD14^low/–CD83⁺ Mo‐DC and M1‐like CD14⁺CD86⁺⁺ Mo‐M surface phenotypes. Concomitantly, inflammatory mediators, including IL‐2, IL‐6, IL‐10, IL‐12 and MIP‐1α, were released in the supernatant of HAMLET‐stimulated cells, indicating a mainly pro‐inflammatory phenotype. The HAMLET‐induced phenotype was mediated by calcium, NFκB and p38 MAPK signaling in Mo‐DCs and calcium, NFκB and ERK signaling in Mo‐M as inhibitors of these pathways almost completely blocked the induction of mature Mo‐DCs and M1‐like Mo‐M. Compared to unstimulated Mo‐DCs, HAMLET‐stimulated Mo‐DCs were more potent in inducing T cell proliferation and HAMLET‐stimulated macrophages were more efficient in phagocytosis of Streptococcus pneumoniae in vitro. This indicates a functionally activated phenotype of HAMLET‐stimulated DCs and macrophages. Combined, we propose that HAMLET has a two‐fold anti‐bacterial activity; one inducing direct cytotoxic activity, the other indirectly mediating elimination of bacteria by activation of immune cells of the myeloid lineage.

Metformin regulates inflammation and fibrosis in diabetic kidney disease through TNC/TLR4/NF-κB/miR-155-5p inflammatory loop

BACKGROUND

Type 2 diabetes mellitus (T2DM) is significantly increasing worldwide, and the incidence of its complications is also on the rise. One of the main complications of T2DM is diabetic kidney disease (DKD). The glomerular filtration rate (GFR) and urinary albumin creatinine ratio (UACR) increase in the early stage. As the disease progresses, UACR continue to rise and GFR begins to decline until end-stage renal disease appears. At the same time, DKD will also increase the incidence and mortality of cardiovascular and cerebrovascular diseases. At present, the pathogenesis of DKD is not very clear. Therefore, exploration of the pathogenesis of DKD to find a treatment approach, so as to delay the development of DKD, is essential to improve the prognosis of DKD.

AIM

To detect the expression of tenascin-C (TNC) in the serum of T2DM patients, observe the content of TNC in the glomerulus of DKD rats, and detect the expression of TNC on inflammatory and fibrotic factors in rat mesangial cells (RMCs) cultured under high glucose condition, in order to explore the specific molecular mechanism of TNC in DKD and bring a new direction for the treatment of DKD.

METHODS

The expression level of TNC in the serum of diabetic patients was detected by enzyme-linked immunosorbent assay (ELISA), the protein expression level of TNC in the glomerular area of DKD rats was detected by immunohistochemistry, and the expression level of TNC in the rat serum was detected by ELISA. Rat glomerular mesangial cells were cultured. Following high glucose stimulation, the expression levels of related proteins and mRNA were detected by Western blot and polymerase chain reaction, respectively.

RESULTS

ELISA results revealed an increase in the serum TNC level in patients with T2DM. Increasing UACR and hypertension significantly increased the expression of TNC (P < 0.05). TNC expression was positively correlated with glycosylated haemoglobin (HbA1c) level, body mass index, systolic blood pressure, and UACR (P < 0.05). Immunohistochemical staining showed that TNC expression in the glomeruli of rats with streptozotocin-induced diabetes was significantly increased compared with normal controls (P < 0.05). Compared with normal rats, serum level of TNC in diabetic rats was significantly increased (P < 0.05), which was positively correlated with urea nitrogen and urinary creatinine (P < 0.05). The levels of TNC, Toll-like receptor-4 (TLR4), phosphorylated nuclear factor-κB p65 protein (Ser536) (p-NF-κB p65), and miR-155-5p were increased in RMCs treated with high glucose (P < 0.05). The level of TNC protein peaked 24 h after high glucose stimulation (P < 0.05). After TNC knockdown, the levels of TLR4, p-NF-κB p65, miR-155-5p, connective tissue growth factor (CTGF), and fibronectin (FN) were decreased, revealing that TNC regulated miR-155-5p expression through the TLR4/NF-κB p65 pathway, thereby regulating inflammation (NF-κB p65) and fibrosis (CTGF and FN) in individuals with DKD. In addition, metformin treatment may relive the processes of inflammation and fibrosis in individuals with DKD by reducing the levels of the TNC, p-NF-κB p65, CTGF, and FN proteins.

CONCLUSION

TNC can promote the occurrence and development of DKD. Interfering with the TNC/TLR4/NF-κB p65/miR-155-5p pathway may become a new target for DKD treatment.

Immunomodulatory Role of the Extracellular Matrix Within the Liver Disease Microenvironment

Chronic liver disease when accompanied by underlying fibrosis, is characterized by an accumulation of extracellular matrix (ECM) proteins and chronic inflammation. Although traditionally considered as a passive and largely architectural structure, the ECM is now being recognized as a source of potent damage-associated molecular pattern (DAMP)s with immune-active peptides and domains. In parallel, the ECM anchors a range of cytokines, chemokines and growth factors, all of which are capable of modulating immune responses. A growing body of evidence shows that ECM proteins themselves are capable of modulating immunity either directly via ligation with immune cell receptors including integrins and TLRs, or indirectly through release of immunoactive molecules such as cytokines which are stored within the ECM structure. Notably, ECM deposition and remodeling during injury and fibrosis can result in release or formation of ECM-DAMPs within the tissue, which can promote local inflammatory immune response and chemotactic immune cell recruitment and inflammation. It is well described that the ECM and immune response are interlinked and mutually participate in driving fibrosis, although their precise interactions in the context of chronic liver disease are poorly understood. This review aims to describe the known pro-/anti-inflammatory and fibrogenic properties of ECM proteins and DAMPs, with particular reference to the immunomodulatory properties of the ECM in the context of chronic liver disease. Finally, we discuss the importance of developing novel biotechnological platforms based on decellularized ECM-scaffolds, which provide opportunities to directly explore liver ECM-immune cell interactions in greater detail.

Tenascin-C Function in Glioma: Immunomodulation and Beyond

First identified in the 1980s, tenascin-C (TNC) is a multi-domain extracellular matrix glycoprotein abundantly expressed during the development of multicellular organisms. TNC level is undetectable in most adult tissues but rapidly and transiently induced by a handful of pro-inflammatory cytokines in a variety of pathological conditions including infection, inflammation, fibrosis, and wound healing. Persistent TNC expression is associated with chronic inflammation and many malignancies, including glioma. By interacting with its receptor integrin and a myriad of other binding partners, TNC elicits context- and cell type-dependent function to regulate cell adhesion, migration, proliferation, and angiogenesis. TNC operates as an endogenous activator of toll-like receptor 4 and promotes inflammatory response by inducing the expression of multiple pro-inflammatory factors in innate immune cells such as microglia and macrophages. In addition, TNC drives macrophage differentiation and polarization predominantly towards an M1-like phenotype. In contrast, TNC shows immunosuppressive function in T cells. In glioma, TNC is expressed by tumor cells and stromal cells; high expression of TNC is correlated with tumor progression and poor prognosis. Besides promoting glioma invasion and angiogenesis, TNC has been found to affect the morphology and function of tumor-associated microglia/macrophages in glioma. Clinically, TNC can serve as a biomarker for tumor progression; and TNC antibodies have been utilized as an adjuvant agent to deliver anti-tumor drugs to target glioma. A better mechanistic understanding of how TNC impacts innate and adaptive immunity during tumorigenesis and tumor progression will open new therapeutic avenues to treat brain tumors and other malignancies.

Tenascin-C in cardiac disease: a sophisticated controller of inflammation, repair, and fibrosis

Tenascin-C (TNC) is a large extracellular matrix glycoprotein classified as a matricellular protein that is generally upregulated at high levels during physiological and pathological tissue remodeling and is involved in important biological signaling pathways. In the heart, TNC is transiently expressed at several important steps during embryonic development and is sparsely detected in normal adult heart but is re-expressed in a spatiotemporally restricted manner under pathological conditions associated with inflammation, such as myocardial infarction, hypertensive cardiac fibrosis, myocarditis, dilated cardiomyopathy, and Kawasaki disease. Despite its characteristic and spatiotemporally restricted expression, TNC knockout mice develop a grossly normal phenotype. However, various disease models using TNC null mice combined with in vitro experiments have revealed many important functions for TNC and multiple molecular cascades that control cellular responses in inflammation, tissue repair, and even myocardial regeneration. TNC has context-dependent diverse functions and, thus, may exert both harmful and beneficial effects in damaged hearts. However, TNC appears to deteriorate adverse ventricular remodeling by proinflammatory and profibrotic effects in most cases. Its specific expression also makes TNC a feasible diagnostic biomarker and target for molecular imaging to assess inflammation in the heart. Several preclinical studies have shown the utility of TNC as a biomarker for assessing the prognosis of patients and selecting appropriate therapy, particularly for inflammatory heart diseases.

Scrodentoids H and I, a Pair of Natural Epimerides from Scrophularia dentata, Inhibit Inflammation through JNK-STAT3 Axis in THP-1 Cells

Background

Scrophularia dentata is an important medicinal plant and used for the treatment of exanthema and fever in Traditional Tibetan Medicine. Scrodentoids H and I (SHI), a pair of epimerides of C₁₉-norditerpenoids isolated from Scrophularia dentata, could transfer to each other in room temperature and were firstly reported in our previous work. Here, we first reported the anti-inflammatory effects of SHI on LPS-induced inflammation.

Purpose

To evaluate the anti-inflammatory property of SHI, we investigated the effects of SHI on LPS-activated THP-1 cells.

Methods

THP-1 human macrophages were pretreated with SHI and stimulated with LPS. Proinflammatory cytokines IL-1β and IL-6 were measured by RT-PCR and enzyme-linked immunosorbent assays (ELISA). The mechanism of action involving phosphorylation of ERK, JNK, P38, and STAT3 was measured by western Blot. The NF-κB promoter activity was evaluated by Dual-Luciferase Reporter Assay System in TNF-α stimulated 293T cells.

Results

SHI dose-dependently reduced the production of proinflammatory cytokines IL-1β and IL-6. The ability of SHI to reduce production of cytokines is associated with phosphorylation depress of JNK and STAT3 rather than p38, ERK, and NF-κB promoter.

Conclusions

Our experimental results indicated that anti-inflammatory effects of SHI exhibit attenuation of LPS-induced inflammation and inhibit activation through JNK/STAT3 pathway in macrophages. These results suggest that SHI might have a potential in treating inflammatory disease.

Tenascin-C inactivation impacts lung structure and function beyond lung development

Tenascin-C (TNC) is an extracellular matrix protein expressed at high levels during lung organogenesis. Later, TNC is only transiently de novo expressed to orchestrate tissue repair in pathological situations. We previously showed that TNC inactivation affects lung development and thus evaluated here the implications on lung function in newborn/adult mice. Respiratory function parameters were measured in anesthetized and mechanically ventilated wild-type (WT) and TNC-deficient mice at 5 (P5) and 90 (P90) days of age under basal conditions, as well as following high tidal volume (HTV) ventilation. At P5, TNC-deficient mice showed an increased static compliance (Cst) and inspiratory capacity (IC) relative to WT at baseline and throughout HTV. At P90, however, Cst and IC were only elevated at baseline. Control non-ventilated newborn and adult TNC-deficient mice showed similar lung morphology, but less alpha smooth muscle actin (α-SMA) around small airways. SMA + cells were decreased by 50% in adult TNC-deficient lungs and collagen layer thickened around small airways. Increased surfactant protein C (SP-C) and altered TGFβ and TLR4 signaling pathways were also detected. Thus, TNC inactivation-related defects during organogenesis led to persisting functional impairment in adulthood. This might be of interest in the context of pulmonary diseases with thickened airway smooth muscle layer or ventilation heterogeneity, like asthma and COPD.

McKeown-Longo P. Role of TLR4 Receptor Complex in the Regulation of the Innate Immune Response by Fibronectin

Chronic inflammation and subsequent tissue fibrosis are associated with a biochemical and mechanical remodeling of the fibronectin matrix. Due to its conformational lability, fibronectin is considerably stretched by the contractile forces of the fibrotic microenvironment, resulting in the unfolding of its Type III domains. In earlier studies, we have shown that a peptide mimetic of a partially unfolded fibronectin Type III domain, FnIII-1c, functions as a Damage Associated Molecular Pattern (DAMP) molecule to induce activation of a toll-like receptor 4 (TLR4)/NF-B pathway and the subsequent release of fibro-inflammatory cytokines from human dermal fibroblasts. In the current study, we evaluated the requirement of the canonical TLR4/MD2/CD14 receptor complex in the regulation of FnIII-1c induced cytokine release. Using dermal fibroblasts and human embryonic kidney (HEK) cells, we found that all the components of the TLR4/MD2/CD14 complex were required for the release of the fibro-inflammatory cytokine, interleukin 8 (IL-8) in response to both FnIII-1c and the canonical TLR4 ligand, lipopolysaccharide (LPS). However, FnIII-1c mediated IL-8 release was strictly dependent on membrane-associated CD14, while LPS could use soluble CD14. These findings demonstrate that LPS and FnIII-1c share a similar but not identical mechanism of TLR4 activation in human dermal fibroblasts.

Activation of Myd88-Dependent TLRs Mediates Local and Systemic Inflammation in a Mouse Model of Primary Sjögren's Syndrome

Toll-like receptors (TLRs) are important mediators of chronic inflammation in numerous autoimmune diseases, although the role of these receptors in primary Sjögren's syndrome (pSS) remains incompletely understood. Previous studies in our laboratory established Myd88 as a crucial mediator of pSS, although the disease-relevant ligands and the upstream signaling events that culminate in Myd88 activation have yet to be established. The objective of this study was to identify specific Myd88-dependent TLR-related pathways that are dysregulated both locally and systemically in a mouse model of pSS [NOD.B10Sn-H2^b/J (NOD.B10)]. We performed RNA-sequencing on spleens derived from NOD.B10 mice. We then harvested salivary tissue and spleens from Myd88-sufficient and deficient C57BL/10 (BL/10) and NOD.B10 mice and performed flow cytometry to determine expression of Myd88-dependent TLRs. We cultured splenocytes with TLR2 and TLR4 agonists and measured production of inflammatory mediators by ELISA. Next, we evaluated spontaneous and TLR4-mediated inflammatory cytokine secretion in NOD.B10 salivary tissue. Finally, we assessed spontaneous Myd88-dependent cytokine secretion by NOD.B10 salivary cells. We identified dysregulation of numerous TLR-related networks in pSS splenocytes, particularly those employed by TLR2 and TLR4. We found upregulation of TLRs in both the splenic and salivary tissue from pSS mice. In NOD.B10 splenic tissue, robust expression of B cell TLR1 and TLR2 required Myd88. Splenocytes from NOD.B10 mice were hyper-responsive to TLR2 ligation and the endogenous molecule decorin modulated inflammation via TLR4. Finally, we observed spontaneous secretion of numerous inflammatory cytokines and this was enhanced following TLR4 ligation in female NOD.B10 salivary tissue as compared to males. The spontaneous production of salivary IL-6, MCP-1 and TNFα required Myd88 in pSS salivary tissue. Thus, our data demonstrate that Myd88-dependent TLR pathways contribute to the inflammatory landscape in pSS, and inhibition of such will likely have therapeutic utility.

Gene Expression Profiling of the Extracellular Matrix Signature in Macrophages of Different Activation Status: Relevance for Skin Wound Healing

The extracellular matrix (ECM) provides structural support for tissue architecture and is a major effector of cell behavior during skin repair and inflammation. Macrophages are involved in all stages of skin repair but only limited knowledge exists about macrophage-specific expression and regulation of ECM components. In this study, we used transcriptome profiling and bioinformatic analysis to define the unique expression of ECM-associated genes in cultured macrophages. Characterization of the matrisome revealed that most genes were constitutively expressed and that several genes were uniquely regulated upon interferon gamma (IFNγ) and dexamethasone stimulation. Among those core matrisome and matrisome-associated components transforming growth factor beta (TGFβ)-induced, matrix metalloproteinase 9 (MMP9), elastin microfibril interfacer (EMILIN)-1, netrin-1 and gliomedin were also present within the wound bed at time points that are characterized by profound macrophage infiltration. Hence, macrophages are a source of ECM components in vitro as well as during skin wound healing, and identification of these matrisome components is a first step to understand the role and therapeutic value of ECM components in macrophages and during wound healing.

Innate immunity and Toll-like receptor signaling in the pathogenesis of scleroderma: advances and opportunities for therapy

PURPOSE OF REVIEW

Systemic sclerosis (SSc) is an autoimmune connective tissue disease in which inflammation and cytokine dysregulation leads to skin fibrosis. Toll-like receptors (TLRs) are conserved pattern recognition receptors, recognizing pathogens danger-associated molecular patterns (DAMPs) that elicit a cascade of proinflammatory signaling. Recently, TLRs have been found to be critically important in SSc pathogenesis, with increased levels of the TLRs and their ligands present in the disease. Animal models have also been pivotal in delineating the role of these innate immune receptors in SSc. This current review examines the role of TLRs and the most recent evidence of the role of DAMPs and how these may be exploited therapeutically.

RECENT FINDINGS

Increasingly, studies have demonstrated the key roles of TLR4 and other intracellular TLRs in mediating fibrosis in SSc patients and animal models. TLR4 activation appears a key point and novel DAMPs, expressed upon tissue damage, appear critical in mediating the profibrotic effect through a downstream enhancement of transforming growth factor β. Deletion of Tenascin-C or a splice variant of fibronectin ameliorates animal models of skin fibrosis. Intracellular, nucleic acid sensing, TLR8 is critical in activating macrophages to secrete profibrotic molecules. The mechanism involves histone modification through epigenetic modifying enzymes.

SUMMARY

TLRs are key therapeutic targets in SSc.

Analysis of Potential Genes and Pathways Involved in the Pathogenesis of Acne by Bioinformatics

Acne is the eighth most frequent disease worldwide. Inflammatory response runs through all stages of acne. It is complicated and is involved in innate and adaptive immunity. This study aimed to explore the candidate genes and their relative signaling pathways in inflammatory acne using data mining analysis. Microarray data GSE6475 and GSE53795, including 18 acne lesion tissues and 18 matched normal skin tissues, were obtained. Differentially expressed genes (DEGs) were filtered and subjected to functional and pathway enrichment analyses. Protein-protein interaction (PPI) network and module analyses were also performed based on the DEGs. In this work, 154 common DEGs, including 145 upregulated and 9 downregulated, were obtained from two microarray profiles. Gene Ontology and pathway enrichment of DEGs were clustered using significant enrichment analysis. A PPI network containing 110 nodes/DEGs was constructed, and 31 hub genes were obtained. Four modules in the PPI network, which mainly participated in chemokine signaling pathway, cytokine-cytokine receptor interaction, and Fc gamma R-mediated phagocytosis, were extracted. In conclusion, aberrant DEGs and pathways involved in acne pathogenesis were identified using bioinformatic analysis. The DEGs included FPR2, ITGB2, CXCL8, C3AR1, CXCL1, FCER1G, LILRB2, PTPRC, SAA1, CCR2, ICAM1, and FPR1, and the pathways included chemokine signaling pathway, cytokine-cytokine receptor interaction, and Fc gamma R-mediated phagocytosis. This study could serve as a basis for further understanding the pathogenesis and potential therapeutic targets of inflammatory acne.

Human granulosa cells function as innate immune cells executing an inflammatory reaction during ovulation: a microarray analysis

Ovulation has been compared to a local inflammatory reaction. We performed an in silico study on a unique, PCR validated, transcriptome microarray study to evaluate if known inflammatory mechanisms operate during ovulation. The granulosa cells were obtained in paired samples at two different time points during ovulation (just before and 36 hours after ovulation induction) from nine women receiving fertility treatment. A total of 259 genes related to inflammation became significantly upregulated during ovulation (2-80 fold, p<0.05), while specific leukocyte markers were absent. The genes and pathway analysis indicated NF-KB-, MAPK- and JAK/STAT signalling (p<1.0E-10) as the major pathways involved in danger recognition and cytokine signalling to initiate inflammation. Upregulated genes further encoded enzymes in eicosanoid production, chemo-attractants, coagulation factors, cell proliferation factors involved in tissue repair, and anti-inflammatory factors to resolve the inflammation again. We conclude that granulosa cells, without involvement from the innate immune system, can orchestrate ovulation as a complete sterile inflammatory reaction.

Targeting early changes in the synovial microenvironment: a new class of immunomodulatory therapy?

OBJECTIVES

Controlled immune responses rely on integrated crosstalk between cells and their microenvironment. We investigated whether targeting proinflammatory signals from the extracellular matrix that persist during pathological inflammation provides a viable strategy to treat rheumatoid arthritis (RA).

METHODS

Monoclonal antibodies recognising the fibrinogen-like globe (FBG) of tenascin-C were generated by phage display. Clones that neutralised FBG activation of toll-like receptor 4 (TLR4), without impacting pathogenic TLR4 activation, were epitope mapped by crystallography. Antibodies stained synovial biopsies of patients at different stages of RA development. Antibody efficacy in preventing RA synovial cell cytokine release, and in modulating collagen-induced arthritis in rats, was assessed.

RESULTS

Tenascin-C is expressed early in the development of RA, even before disease diagnosis, with higher levels in the joints of people with synovitis who eventually developed RA than in people whose synovitis spontaneously resolved. Anti-FBG antibodies inhibited cytokine release by RA synovial cells and prevented disease progression and tissue destruction during collagen-induced arthritis.

CONCLUSIONS

Early changes in the synovial microenvironment contribute to RA progression; blocking proinflammatory signals from the matrix can ameliorate experimental arthritis. These data highlight a new drug class that could offer early, disease-specific immune modulation in RA, without engendering global immune suppression.

Tenascin-C protects against acute kidney injury by recruiting Wnt ligands

The development of acute kidney injury (AKI) is a complex process involving tubular, inflammatory, and vascular components, but less is known about the role of the interstitial microenvironment. We have previously shown that the extracellular matrix glycoprotein tenascin-C (TNC) is induced in fibrotic kidneys. In mouse models of AKI induced by ischemia-reperfusion injury (IRI) or cisplatin, TNC was induced de novo in the injured sites and localized to the renal interstitium. The circulating level of TNC protein was also elevated in AKI patients after cardiac surgery. Knockdown of TNC by shRNA in vivo aggravated AKI after ischemic or toxic injury. This effect was associated with reduced renal β-catenin expression, suggesting an impact on Wnt signaling. In vitro, TNC protected tubular epithelial cells against apoptosis and augmented Wnt1-mediated β-catenin activation. Co-immunoprecipitation revealed that TNC physically interacts with Wnt ligands. Furthermore, a TNC-enriched kidney tissue scaffold prepared from IRI mice was able to recruit and concentrate Wnt ligands from the surrounding milieu ex vivo. The ability to recruit Wnt ligands in this ex vivo model diminished after TNC depletion. These studies indicate that TNC is specifically induced at sites of injury and recruits Wnt ligands, thereby creating a favorable microenvironment for tubular repair and regeneration after AKI.

Extracellular vimentin modulates human dendritic cell activation

Vimentin is an intermediate filament protein traditionally considered to be an intracellular protein with a structural role. However, recent evidence suggests that vimentin can also be found outside the cell in disease conditions such as cancer, traumatic tissue injury, and inflammation. Extracellular vimentin was previously found to stimulate innate immunity by increasing monocyte and macrophage ability to kill bacteria. However, vimentin has also been previously found to decrease neutrophil infiltration into inflamed tissue. How extracellular vimentin affects the initiation of adaptive immune responses is unknown. Initiation of adaptive immunity involves priming of naïve T cells by antigen-presenting cells, the most effective of which are dendritic cells (DCs). In this study, we demonstrate how extracellular vimentin modulates lipopolysaccharide (LPS) - induced activation of human DCs. Using cytometric bead arrays, we show that extracellular vimentin decreases LPS-activated DC secretion of pro-inflammatory cytokines IL-6 and IL-12 while increasing secretion of the anti-inflammatory cytokine IL-10. Using flow cytometry, we show that extracellular vimentin does not significantly affect LPS-induced DC surface expression of MHC I (HLA-ABC) or MHC II (HLA-DR) presentation molecules, costimulatory factors (CD80, CD86), or the DC maturation marker (CD83). Further, LPS-stimulated DCs co-cultured with allogeneic naïve CD4 + T cells (Th0) induced less secretion of the pro-inflammatory Th1 effector cytokine IFN-γ in the presence of vimentin than in the presence of LPS alone. This result suggests that vimentin reduces Th1 differentiation. Taken together, our data suggest that extracellular vimentin may inhibit pro-inflammatory adaptive immune responses, by blocking DC secretion of pro-inflammatory cytokines. Thus, extracellular vimentin may play an important role in cancer or trauma-complications by inducing suppression of the adaptive immune response. In a positive sense, the presence of extracellular vimentin may prevent tissue-damage from contributing to the development of autoimmunity. Consequently, extracellular vimentin may become a novel drug target for treatment of a variety of pro- and anti-inflammatory disease conditions.

Heparan sulfate as a regulator of inflammation and immunity

Heparan sulfate is found on the surface of most cell types, as well as in basement membranes and extracellular matrices. Its strong anionic properties and highly variable structure enable this glycosaminoglycan to provide binding sites for numerous protein ligands, including many soluble mediators of the immune system, and may promote or inhibit their activity. The formation of ligand binding sites on heparan sulfate (HS) occurs in a tissue- and context-specific fashion through the action of several families of enzymes, most of which have multiple isoforms with subtly different specificities. Changes in the expression levels of these biosynthetic enzymes occur in response to inflammatory stimuli, resulting in structurally different HS and acquisition or loss of binding sites for immune mediators. In this review, we discuss the multiple roles for HS in regulating immune responses, and the evidence for inflammation-associated changes to HS structure.

A complex interplay between the extracellular matrix and the innate immune response to microbial pathogens

The role of the host extracellular matrix (ECM) in infection tends to be neglected. However, the complex interactions between invading pathogens, host tissues and immune cells occur in the context of the ECM. On the pathogen side, a variety of surface and secreted molecules, including microbial surface components recognizing adhesive matrix molecules and tissue-degrading enzymes, are employed that interact with different ECM proteins to effectively establish an infection at specific sites. Microbial pathogens can also hijack or misuse host proteolytic systems to modify the ECM, evade immune responses or process biologically active molecules such as cell surface receptors and cytokines that direct cell behaviour and immune defence. On the host side, the ECM composition and three-dimensional ultrastructure undergo significant modifications, which have a profound impact on the specific signals that the ECM conveys to immune cells at the forefront of infection. Unexpectedly, activated immune cells participate in the remodelling of the local ECM by synthesizing ECM glycoproteins, proteoglycans and collagen molecules. The close interplay between the ECM and the innate immune response to microbial pathogens ultimately affects the outcome of infection. This review explores and discusses recent data that implicate an active role for the ECM in the immune response to infection, encompassing antimicrobial activities, microbial recognition, macrophage activation, phagocytosis, leucocyte population balance, and transcriptional and post-transcriptional regulation of inflammatory networks, and may foster novel antimicrobial approaches.

Targeting TLRs and the inflammasome in systemic sclerosis

Systemic sclerosis (SSc) is an idiopathic autoimmune disease characterised by inflammation, vascular problems, cytokine dysregulation and ultimately fibrosis, which accounts for poor prognosis and eventual mortality. At present no curative treatments exist, hence there is an urgent need to better understand the aetiology and develop improved therapies accordingly. Although still widely debated, significant evidence points to upregulation of the innate immune response via the activity of Toll-like receptors (TLRs) and the NLRP3 inflammasome as the start points in a cascade of signaling events which drives excessive extracellular matrix protein production, causing fibrosis. Herein the recent breakthroughs which have implicated TLR signaling and the NLRP3 inflammasome in SSc and the novel therapeutic possibilities this introduces to the field will be discussed.

Autocrine GABA signaling distinctively regulates phenotypic activation of mouse pulmonary macrophages

In response to micro-environmental cues such as microbial infections or T-helper 1 and 2 (T_H1 and T_H2) cytokines, macrophages (Mϕs) develop into M1- or M2-like phenotypes. Phenotypic polarization/activation of Mϕs are also essentially regulated by autocrine signals. Type-A γ-aminobutyric acid receptor (GABA_AR)-mediated autocrine signaling is critical for phenotypic differentiation and transformation of various cell types. The present study explored whether GABA_AR signaling regulates lung Mϕ (LMϕ) phenotypic activation under M1/T_H1 and M2/T_H2 environments. Results showed that GABA_AR subunits were expressed by primary LMϕ of mice and the mouse Mϕ cell line RAW264.7. The expression levels of GABA_AR subunits in mouse LMϕs and RAW264.7 cells decreased or increased concurrently with classical (M1) or alternative (M2) activation, respectively. Moreover, activation or blockade of GABA_ARs distinctively influenced the phenotypic characteristics of Mϕ. These results suggested that microenvironments leading to LMϕ phenotypic polarization concurrently modulates autocrine GABA signaling and its role in Mϕ activation.

Mass Spectrometry-based Structural Analysis and Systems Immunoproteomics Strategies for Deciphering the Host Response to Endotoxin

One cause of sepsis is systemic maladaptive immune response of the host to bacteria and specifically, to Gram-negative bacterial outer-membrane glycolipid lipopolysaccharide (LPS). On the host myeloid cell surface, proinflammatory LPS activates the innate immune system via Toll-like receptor-4/myeloid differentiation factor-2 complex. Intracellularly, LPS is also sensed by the noncanonical inflammasome through caspase-11 in mice and 4/5 in humans. The minimal functional determinant for innate immune activation is the membrane anchor of LPS called lipid A. Even subtle modifications to the lipid A scaffold can enable, diminish, or abolish immune activation. Bacteria are known to modify their LPS structure during environmental stress and infection of hosts to alter cellular immune phenotypes. In this review, we describe how mass spectrometry-based structural analysis of endotoxin helped uncover major determinations of molecular pathogenesis. Through characterization of LPS modifications, we now better understand resistance to antibiotics and cationic antimicrobial peptides, as well as how the environment impacts overall endotoxin structure. In addition, mass spectrometry-based systems immunoproteomics approaches can assist in elucidating the immune response against LPS. Many regulatory proteins have been characterized through proteomics and global/targeted analysis of protein modifications, enabling the discovery and characterization of novel endotoxin-mediated protein translational modifications.