The contact of human macrophages with extracellular matrix proteins selectively induces expression of proinflammatory cytokines

Fibronectin stimulates Escherichia coli phagocytosis by microglial cells

Microglia express Toll-like receptors (TLRs) that recognize invading pathogens as well as endogenous proteins such as fibronectin under nonphysiological conditions. Here, we demonstrated that fibronectin stimulates murine microglia in culture in a dose-dependent manner: microglial cells secreted proinflammatory cytokines and chemokines and increased phagocytosis of Escherichia coli DH5alpha and E. coli K1 strains. Low levels of fibronectin exerted a synergistic effect on the release of proinflammatory compounds by microglia co-stimulated with agonists for TLR1/2 (Pam(3)CSK(4)) or TLR9 (CpG DNA), but not in combination with the TLR4 agonist lipopolysaccharide (LPS). Phagocytosis of bacterial strains was moderately enhanced when microglia was co-stimulated with high concentrations of fibronectin and one pathogen-derived TLR agonist. In conclusion, fibronectin increased proinflammatory and phagocytotic functions in microglia and partially synergized with microbial TLR agonists.

Human immune responses to porcine xenogeneic matrices and their extracellular matrix constituents in vitro

Several tissue engineering approaches for the treatment of cardiovascular diseases are based on a xenogeneic extracellular matrix. However, the application of engineered heart valves has failed in some patients, causing severe signs of inflammation by so far undetermined processes. Therefore we investigated the immune-mediated responses to porcine valve matrices (native, decellularized and glutaraldehyde-fixed) and to purified xenogeneic extracellular matrix proteins (ECMp). The induction of human immune responses in vitro was evaluated by analyzing the co-stimulatory effects of matrices and ECMp collagen and elastin on the proliferation of immune cell sub-populations via CFSE-based proliferation assays. The pattern of cytokine release was also determined. In porcine matrix punches we demonstrated strong immune responses with the native as well as the decellularized type, in contrast to attenuated effects with glutaraldehyde-fixed matrices. Furthermore, our results indicate that collagen type I (porcine and human) and human elastin were able to elicit proliferation in co-stimulation with anti-CD3 antibody, accompanied by a strong release of Th1 cytokines (IFN-gamma, TNF-alpha). In contrast, porcine elastin did not elicit any response at all. This low immunogenic potential of porcine elastin suggests its suitability for the creation of new tissue engineering heart valve scaffolds in the future.

Influence of extracellular matrix on cytokine stimulated pro-labour gene expression in human uterine myocytes

Cellular function is modulated by the interaction with the extracellular matrix within the myometrium. We formed the hypothesis that the cytokine-stimulated pro-labour gene expression by human uterine smooth muscle cells would be increased by growing the cells on collagen-coated plates. Primary cultures of human uterine smooth muscle cells grown on uncoated plates and on plates coated with collagen were exposed to the inflammatory cytokines (tumor necrosis factor-alpha, interleukin-1beta and interleukin-6) and assessed the messenger RNA expression of oxytocin receptor, interleukin-8, prostaglandin H synthase type-2 and prostaglandin F(2) alpha receptor. Basal pro-labour gene expression was unaffected by collagen coating and the response to the inflammatory cytokines was similar for oxytocin receptor and prostaglandin H synthase type-2, but appeared to be reduced for interleukin-8 and enhanced for FP. Collagen coating made no significant impact on basal integrin expression and interleukin-1beta induced phosphorylation of extracellular-regulated-kinase1/2 and RelA subunit of nuclear factor-kappa B (p65). We conclude that growing human uterine smooth muscle cells on collagen-coated plates may modulate the pro-labour gene response to the inflammatory cytokines.

Macrophage-secreted factors promote a profibrotic phenotype in human preadipocytes

White adipose tissue (WAT) in obese humans is characterized by macrophage accumulation the effects of which on WAT biology are not fully understood. We previously demonstrated that macrophage-secreted factors impair preadipocyte differentiation and induce inflammation, and we described the excessive fibrotic deposition in WAT from obese individuals. Microarray analysis revealed significant overexpression of extracellular matrix (ECM) genes in inflammatory preadipocytes. We show here an organized deposition of fibronectin, collagen I, and tenascin-C and clustering of the ECM receptor alpha5 integrin, characterizing inflammatory preadipocytes. Anti-alpha5 integrin-neutralizing antibody decreased proliferation of these cells, underlining the importance of the fibronectin/integrin partnership. Fibronectin-cultured preadipocytes exhibited increased proliferation and expression of both nuclear factor-kappaB and cyclin D1. Small interfering RNA deletion of nuclear factor-kappaB and cyclin D1 showed that these factors link preadipocyte proliferation with inflammation and ECM remodeling. Macrophage-secreted molecules increased preadipocyte migration through an increase in active/phosphorylated focal adhesion kinase. Gene expression and neutralizing antibody experiments suggest that inhibin beta A, a TGF-beta family member, is a major fibrotic factor. Interactions between preadipocytes and macrophages were favored in a three-dimensional collagen I matrix mimicking the fibrotic context of WAT. Cell-rich regions were immunostained for preadipocytes, proliferation, and macrophages in the vicinity of fibrotic WAT from obese individuals. In conclusion, an inflammatory environment leads to profound modifications of the human preadipocyte phenotype, producing fibrotic components with increased migration and proliferation. This phenomenon might play a role in facilitating the constitution of quiescent preadipocyte pools and eventually in the maintenance and aggravation of increased fat mass in obesity.

Genetic and molecular mechanisms of chemical atherogenesis

Injury to the cellular components of the vascular wall and blood by endogenous and exogenous chemicals has been associated with atherosclerosis in humans and experimental systems. The genetic and molecular mechanisms responsible for initiation and promotion of atherosclerotic changes include modulation of extracellular matrix-integrin axis, genes involved in the regulation of growth and differentiation and possibly, genomic stability. This review summarizes seminal studies over the past 20 years that shed light on critical gene-gene and gene-environment interactions mediating the atherogenic response to chemical injury.

The interrelated role of fibronectin and interleukin-1 in biomaterial-modulated macrophage function

Macrophages play a critical role in mediating the host response to biomaterials, perhaps most notably by guiding the host inflammatory response through the release of inflammatory molecules such as the cytokine interleukin-1 (IL-1). The extent of the macrophage response following interaction with the biomaterial surface contributes greatly to device efficacy, yet the molecular mechanisms of this interaction are still unclear. The extracellular matrix (ECM) protein fibronectin (FN) is recognized by macrophages and frequently used in biomaterial modification to elicit greater cellular adhesion and tissue integration. Macrophage interaction with FN and other ECM molecules on the biomaterial surface has been shown to induce a variety of inflammatory responses, thus both FN and IL-1 can be utilized as model molecules to better understand the mechanisms of material-mediated macrophage responses. This literature review presents a comprehensive survey of past and current research on the interrelated role of IL-1, FN, and FN-derivatives in determining biomaterial-modulated macrophage function.

Intramyocardial synthesis of pro- and anti-inflammatory cytokines in infants with congenital cardiac defects

OBJECTIVES

We sought to test the hypothesis that cytokines would be expressed in the myocardium of infants with congenital cardiac defects and to identify the signaling pathways involved.

BACKGROUND

Mechanical stress upregulates pro-inflammatory cytokines in the myocardium.

METHODS

Fifteen infants with tetralogy of Fallot (TOF) (n = 7) or with ventricular septal defects (VSDs) (n = 8) were investigated. Concentrations of pro- and anti-inflammatory cytokines and of the inducible nitric oxide synthase (iNOS) were measured by enzyme-linked immunosorbent assay and/or Western blotting in the right ventricular myocardium taken during cardiac surgery. Activation of the nuclear factor-kappa-B (NF-kappa-B) and p38 mitogen-activated protein kinase (MAPK) pathways was assessed by electrophoretic mobility shift assay with supershift and/or Western blotting, respectively.

RESULTS

The pro-inflammatory cytokines tumor necrosis factor (TNF)-alpha, interleukin (IL)-1-beta, and IL-6 and the anti-inflammatory cytokine IL-10 were detected in the myocardium of all patients. Concentrations of the pro-inflammatory cytokines and also of phosphorylated p38 MAPK were higher in patients with TOF than in those with VSD and correlated with the degree of pressure overload of the right ventricle. Levels of phosphorylated I-kappa-B-alpha, iNOS, and IL-10 were similar in patients with TOF and in those with VSD.

CONCLUSIONS

Our results show intramyocardial synthesis of pro-inflammatory cytokines in infants with congenital cardiac defects. This is associated with activation of both the NF-kappa-B and p38 MAPK pathways. The latter could be particularly important for the transduction of mechanical signals in the infant's myocardium. Synthesis of IL-10 indicates an intramyocardial anti-inflammatory potential in this age group.

Modulation of proliferation, differentiation and cytokine secretion of murine B-1b cells by proteins of the extracellular matrix

At least three B cell subsets, B-1a (Ly-1B), B-1b and B-2, are present in the mouse periphery. B-1a and B1-b cells represent a small population in the adult spleen and are abundant in the peritonial and pleural cavities. It has been demonstrated in our laboratory that B-1b cells spontaneously proliferated in stationary cultures of adherent peritonial cells. Further, that these cells migrate to a non-specific inflammatory focus. Based on these findings, it was investigated whether components of the extracellular matrix (ECM) might selectively influence the adherence, proliferation and cytokine production of these cells in vitro. Results showed that collagen induced a higher level of B-1b cells differentiation into adherent phagocytic cells. It was observed that only fibronectin induced higher level of proliferation than other matrix components. The analysis of cytokine production has shown that the presence of laminin stimulated B-1b cells led to high levels of IL-10 production and fibronectin and collagen induced the production of high levels of TNF-alpha. The combination of fibronectin, collagen and laminin induced higher levels of IL-1beta. These results demonstrate that differentiation, proliferation and cytokine production by B-1b cells are markedly influenced by ECM components.

Silica, Hyaluronate, and Alveolar Macrophage Functional Differentiation

Background

Silicosis is mediated by macrophages, their soluble mediators, and extracellular matrix molecules. In this study, we investigated the effects of silica and/or hyaluronate (HA) on several alveolar macrophage responses.

Methods

We evaluated glycosaminoglycan (GAG) production by radiolabeled precursors, nitric oxide (NO) release by its oxidation product, phagocytic activity by Candida albicans internalization, and the secretion of two fibrogenic cytokines, tumor necrosis factor (TNF)-α and transforming growth factor (TGF)-β, by specific assays.

Results

Silica significantly reduced GAG secretion, particularly HA secretion. Alone, it decreased Candida uptake; associated with HA, it enhanced the reduction. Silica and Candida reduced NO release, which was not significantly affected when silica- or Candida-exposed cells were also treated with HA. TNF-α and TGF-β activities were stimulated by silica but reduced by HA.

Conclusions

The results suggest that silica and HA modify alveolar macrophage functional differentiation. Silica- and HA-induced modifications of the microenvironment could determine whether the response proceeds toward healing and repair or toward lung chronic pathology.