TGF-β down-regulates IL-1α-induced TLR2 expression in murine hepatocytes

Monocytes enhance the inflammatory response to TLR2 stimulation in aortic valve interstitial cells through paracrine up-regulation of TLR2 level

Background and Objectives: Chronic valvular inflammation associated with monocyte infiltration promotes calcific aortic valve disease (CAVD) progression. Further, innate immunity in aortic valve interstitial cells (AVICs), mediated by Toll-like receptors (TLRs), up-regulates cellular inflammatory, fibrogenic and osteogenic activities. Currently, the pro-inflammatory communication between monocytes and AVICs and the underlying mechanism are unclear. We hypothesized that monocytes up-regulate AVIC inflammatory activity. This study sought to characterize the interaction between monocytes and AVICs and to elucidate the mechanism underlying cell-to-cell communication.

Methods and Results: AVICs, monocytes and co-cultures were exposed to a low concentration of TLR2 activator Pam3CSK4 (0.03 µg/ml). The TLR2 activator at this dose induced a marked increase in AVIC production of ICAM-1 and VCAM-1 only when co-cultured with monocytes. Adding conditioned medium from Pam3CSK4-treated monocytes (Pam3 CM, containing 0.1 µg/ml of Pam3CSK4) to AVIC culture (30% vol/vol; diluting Pam3CSK4 to 0.03 µg/ml) greatly increased the expression of adhesion molecules while adding conditioned medium from untreated monocytes (control CM) had no effect. Inhibition or knockdown of TLR2 in AVICs markedly reduced ICAM-1 and VCAM-1 expression induced by Pam3 CM. Further, Pam3 CM increased TLR2 levels in AVICs. Multiplex-ELISA analysis of Pam3 CM identified greater levels of TNF-α. Neutralization of TNF-α abolished the effect of Pam3 CM on AVIC TLR2 levels, resulting in marked attenuation of its potency in the induction of adhesion molecule expression.

Conclusions: This study demonstrates that activated monocytes use paracrine signaling to sensitize AVICs for inflammatory responses to a low level of TLR2 activator. The mechanism of sensitization involves up-regulation of AVIC TLR2 levels by TNF-α from monocytes. Infiltrated monocytes in aortic valve tissue may exacerbate valvular inflammation by rendering AVICs hypersensitive to TLR2 activators.

The TGFβ-SMAD3 pathway inhibits IL-1α induced interactions between human pancreatic stellate cells and pancreatic carcinoma cells and restricts cancer cell migration

BACKGROUND

The most abundant cells in the extensive desmoplastic stroma of pancreatic adenocarcinomas are the pancreatic stellate cells, which interact with the carcinoma cells and strongly influence the progression of the cancer. Tumor stroma interactions induced by IL-1α/IL-1R1 signaling have been shown to be involved in pancreatic cancer cell migration. TGFβ and its receptors are overexpressed in pancreatic adenocarcinomas. We aimed at exploring TGFβ and IL-1α signaling and cross-talk in the stellate cell cancer cell interactions regulating pancreatic adenocarcinoma cell migration.

METHODS

Human pancreatic stellate cells were isolated from surgically resected pancreatic adenocarcinomas and cultured in the presence of TGFβ or pancreatic adenocarcinoma cell lines. The effects of TGFβ were blocked by inhibitors or amplified by silencing the endogenous inhibitor of SMAD signaling, SMAD7. Pancreatic stellate cell responses to IL-1α or to IL-1α-expressing pancreatic adenocarcinoma cells (BxPC-3) were characterized by their ability to stimulate migration of cancer cells in a 2D migration model.

RESULTS

In pancreatic stellate cells, IL-1R1 expression was found to be down-regulated by TGFβ and blocking of TGFβ signaling re-established the expression. Endogenous inhibition of TGFβ signaling by SMAD7 was found to correlate with the levels of IL-1R1, indicating a regulatory role of SMAD7 in IL-1R1 expression. Pancreatic stellate cells cultured in the presence of IL-1α or in co-cultures with BxPC-3 cells enhanced the migration of cancer cells. This effect was blocked after treatment of the pancreatic stellate cells with TGFβ. Silencing of stellate cell expression of SMAD7 was found to suppress the levels of IL-1R1 and reduce the stimulatory effects of IL-1α, thus inhibiting the capacity of pancreatic stellate cells to induce cancer cell migration.

CONCLUSIONS

TGFβ signaling suppressed IL-1α mediated pancreatic stellate cell induced carcinoma cell migration. Depletion of SMAD7 upregulated the effects of TGFβ and reduced the expression of IL-1R1, leading to inhibition of IL-1α induced stellate cell enhancement of carcinoma cell migration. SMAD7 might represent a target for inhibition of IL-1α induced tumor stroma interactions.

Exposure to Carbon Ions Triggers Proinflammatory Signals and Changes in Homeostasis and Epidermal Tissue Organization to a Similar Extent as Photons

The increasing application of charged particles in radiotherapy requires a deeper understanding of early and late side effects occurring in skin, which is exposed in all radiation treatments. We measured cellular and molecular changes related to the early inflammatory response of human skin irradiated with carbon ions, in particular cell death induction and changes in differentiation and proliferation of epidermal cells during the first days after exposure. Model systems for human skin from healthy donors of different complexity, i.e., keratinocytes, coculture of skin cells, 3D skin equivalents, and skin explants, were used to investigate the alterations induced by carbon ions (spread-out Bragg peak, dose-averaged LET 100 keV/μm) in comparison to X-ray and UV-B exposure. After exposure to ionizing radiation, in none of the model systems, apoptosis/necrosis was observed. Carbon ions triggered inflammatory signaling and accelerated differentiation of keratinocytes to a similar extent as X-rays at the same doses. High doses of carbon ions were more effective than X-rays in reducing proliferation and inducing abnormal differentiation. In contrast, changes identified following low-dose exposure (≤0.5 Gy) were induced more effectively after X-ray exposure, i.e., enhanced proliferation and change in the polarity of basal cells.

Termination of immune activation: an essential component of healthy host immune responses

The ideal immune response is rapid, proportionate and effective. Crucially, it must also be finite. An inflammatory response which is disproportionate or lasts too long risks injury to the host; chronic un-regulated inflammation in autoimmune diseases is one example of this. Thus, mechanisms to regulate and ultimately terminate immune responses are central to a healthy immune system. Despite extensive knowledge of what drives immune responses, our understanding of mechanisms of immune termination remains relatively sparse. It is clear that such processes are more complex than a one-dimensional homeostatic balance. Recent discoveries have revealed ever more nuanced mechanisms of signal termination, such as intrinsically self-limiting signals, multiple inhibitory mechanisms acting in tandem and activating proteins behaving differently in a variety of contexts. This review will summarise some important mechanisms, including termination by immunoreceptor tyrosine-based inhibitory motifs (ITIM), inhibition by soluble antagonists, receptor endocytosis or ubiquitination, and auto-inhibition by newly synthesised intracellular inhibitory molecules. Several recent discoveries showing immunoreceptor tyrosine-based activation motifs transducing inhibitory signals, ITIM mediating activating responses and the possible roles of immunoreceptor tyrosine-based switch motifs will also be explored.

Evaluation of the effects of chitin nanofibrils on skin function using skin models

Chitins are highly crystalline structures that are predominantly found in crustacean shells. Alpha-chitin is composed of microfibers, which are made up of nanofibrils that are 2-5 nm in diameter and 30 nm in length and embedded in a protein matrix. Crystalline nanofibrils can also be prepared by acid treatment. We verified the effect of chitin nanofibrils (NF) and nanocrystals (NC) on skin using a three-dimensional skin culture model and Franz cells. The application of NF and NC to skin improved the epithelial granular layer and increased granular density. Furthermore, NF and NC application to the skin resulted in a lower production of TGF-β compared to that of the control group. NF and NC might have protective effects to skin. Therefore, their potential use as components of skin-protective formulations merits consideration.

IL-1β promotes TGF-β1 and IL-2 dependent Foxp3 expression in regulatory T cells

Earlier, we have shown that GM-CSF-exposed CD8α− DCs that express low levels of pro-inflammatory cytokines IL-12 and IL-1β can induce Foxp3+ Tregs leading to suppression of autoimmunity. Here, we examined the differential effects of IL-12 and IL-1β on Foxp3 expression in T cells when activated in the presence and absence of DCs. Exogenous IL-12 abolished, but IL-1β enhanced, the ability of GM-CSF-exposed tolerogenic DCs to promote Foxp3 expression. Pre-exposure of DCs to IL-1β and IL-12 had only a modest effect on Foxp3− expressing T cells; however, T cells activated in the absence of DCs but in the presence of IL-1β or IL-12 showed highly significant increase and decrease in Foxp3+ T cell frequencies respectively suggesting direct effects of these cytokines on T cells and a role for IL-1β in promoting Foxp3 expression. Importantly, purified CD4+CD25+ cells showed a significantly higher ability to maintain Foxp3 expression when activated in the presence of IL-1β. Further analyses showed that the ability of IL-1β to maintain Foxp3 expression in CD25+ T cells was dependent on TGF-β1 and IL-2 expression in Foxp3+Tregs and CD25− effectors T cells respectively. Exposure of CD4+CD25+ T cells to IL-1β enhanced their ability to suppress effector T cell response in vitro and ongoing experimental autoimmune thyroidits in vivo. These results show that IL-1β can help enhance/maintain Tregs, which may play an important role in maintaining peripheral tolerance during inflammation to prevent and/or suppress autoimmunity.

Immunogenetics of drug-induced skin blistering disorders. Part II: Synthesis

The overall immunopathogenesis relevant to a large series of disorders caused by a drug or its associated hyperimmune condition is discussed based upon examining the genetics of severe drug-induced bullous skin problems (sporadic idiosyncratic adverse events including Stevens–Johnson syndrome and Toxic epidermal necrolysis). New results from an exemplar study on shared precipitating and perpetuating inner causes with other related disease phenotypes including aphtous stomatitis, Behçets, erythema multiforme, Hashimoto’s thyroiditis, pemphigus, periodic fevers, Sweet’s syndrome and drug-induced multisystem hypersensitivity are presented. A call for a collaborative, wider demographic profiling and deeper immunotyping in suggested future work is made.

Dose-dependent cross-talk between the transforming growth factor-beta and interleukin-1 signaling pathways

Some tumor cell lines secrete high concentrations of TGFbeta or IL-1. Similarly high concentrations of each of these cytokines cross-activate the other pathway: TGFbeta activates NFkappaB, and IL-1beta activates Smads. The IL-1 signaling components IRAK, MyD88, TRAF6, and TAK1 are all required for cross-activation of NFkappaB by TGFbeta. Knockdown experiments revealed that both TGFbeta receptor subunits are required for IL-1beta to activate Smads, and the IL-1 receptor is required for TGFbeta to activate NFkappaB. Coimmunoprecipitations showed that either TGFbeta or IL-1beta stimulate ligand-dependent association of all three receptor subunits. Furthermore, cross-talk between the TGFbeta and IL-1 signaling pathways leads to dose-dependent cross-control of gene expression. These interactions provide new insight into biological responses to IL-1 and TGFbeta in the proximity of tumors that secrete high concentrations of these factors and probably also at sites of inflammation, where the local concentrations of these cytokines are likely to be high.

Macrophage migration inhibitory factor contributes to host defense against acute Trypanosoma cruzi infection

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that is involved in the host defense against several pathogens. Here we used MIF-/- mice to determine the role of endogenous MIF in the regulation of the host immune response against Trypanosoma cruzi infection. MIF-/- mice displayed high levels of blood and tissue parasitemia, developed severe heart and skeletal muscle immunopathology, and succumbed to T. cruzi infection faster than MIF+/+ mice. The enhanced susceptibility of MIF-/- mice to T. cruzi was associated with reduced levels of proinflammatory cytokines, such as tumor necrosis factor alpha, interleukin-12 (IL-12), IL-18, gamma interferon (IFN-gamma), and IL-1beta, in their sera and reduced production of IL-12, IFN-gamma, and IL-4 by spleen cells during the early phase of infection. At all time points, antigen-stimulated splenocytes from MIF+/+ and MIF-/- mice produced comparable levels of IL-10. MIF-/- mice also produced significantly less Th1-associated antigen-specific immunoglobulin G2a (IgG2a) throughout the infection, but both groups produced comparable levels of Th2-associated IgG1. Lastly, inflamed hearts from T. cruzi-infected MIF-/- mice expressed increased transcripts for IFN-gamma, but fewer for IL-12 p35, IL-12 p40, IL-23, and inducible nitric oxide synthase, compared to MIF+/+ mice. Taken together, our findings show that MIF plays a role in controlling acute T. cruzi infection.

Estrogen stimulates transcription of human immunodeficiency virus type 1 (HIV-1)

Gene expression from human immunodeficiency virus (HIV) provirus is a crucial step for the viral replication. Here we examined a potential role of 17beta-estradiol (E2) in HIV-1 transcription. Transient luciferase expression studies revealed that E2 activated HIV-LTR reporter gene in HEK293 cells when the cells were co-transfected with estrogen receptor alpha (ERalpha) but not ERbeta expression plasmid. This E2 effect was abrogated by a specific antagonist to ER, ICI 182,780, indicating that it was mediated by ERalpha. Mutation analysis revealed that Sp1 binding site but not nuclear factor-kappa B (NF-kappaB) binding site of HIV-1 LTR is critical to the E2 effect. In addition, whereas E2 could not induce DNA-binding activity of NF-kappaB, E2 could augment both Sp1 DNA-binding and transcriptional activity. These findings suggest a contribution of estrogen for HIV-1 replication through ERalpha by augmenting Sp1 DNA-binding and transcriptional activity.

Over-production of IFN-gamma and IL-12 in AhR-null mice

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates toxicity of environmental pollutants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin. The exposure to AhR agonists results in profound suppression of cellular and humoral immune responses and compromises host to infectious disease. Therefore, to define the role of AhR in the immune response, spleen cells from ovalbumin (OVA)-immunized and naïve mice were removed and stimulated in vitro with either OVA or mitogen concanavalin-A (Con A), respectively. Proliferation, CD19+, F4/80+, CD4+ and CD8+ T cells expansion and cytokines production were measured in C57BL/6-AhR-/- mice (AhR-/-) and compared with immune response in similarly immunized age-matched wild type (AhR+/+) mice. In response to OVA immunization, AhR-/- mice had similar levels of serum OVA-specific IgG2a, IgG1, and IgG2b compared with AhR+/+ animals. However, AhR-/- mice showed splenomegalia and an increase in B cells. No changes were observed on proliferation and IL-4 secretion, although AhR-/- cells produced more IFN-gamma and IL-12 than AhR+/+ cells. Similar results were observed with Con A stimulation, a decrease on IL-5 and no change on IL-2 secretion were observed on AhR-/- cells compared with AhR+/+ cells in response to Con A stimulation. High levels of IFN-gamma mRNA were detected in AhR-/- lymphocytes, but IL-4 mRNA levels in AhR-/- cells were similar to those in AhR+/+ mice. These data suggest that AhR may play an important role in the normal development and function of immune system by down-regulating IFN-gamma and IL-12 expression.

Interference with the IL-1-signaling pathway improves the toxicity profile of systemically applied adenovirus vectors

The safety of gene therapy vectors is a major concern when novel viral or nonviral therapeutics are proposed for applications in humans. Adenovirus (Ad) vectors have been extensively used as efficient gene delivery vehicles in vitro over the last two decades. However, upon i.v. application, they elicit robust innate and inflammatory responses that may be fatal for the host. To date, the primary cytokines and chemokines involved in the initiation of these host responses remain illusive. In this study, we demonstrate that IL-1 is a major mediator involved in the initiation of immediate host responses toward i.v. applied Ad vectors. Using mice in which IL-1 signaling was genetically eliminated (IL-1RI-KO), or wild-type animals for which signaling was blocked by anti-IL-1 Abs, we found that i.v. applied Ad vectors elicited dramatically reduced acute inflammatory responses when compared with control animals. Importantly, the efficiency of Ad gene transfer in vivo was not significantly affected by interfering with IL-1 signaling. Using an in situ hybridization technique, we found that hepatocytes and Kupffer cells trigger IL-1 transcription in liver tissue after i.v. Ad vector administration. We also found that expression of the MIP-2 chemokine gene (which is responsible for recruitment of neutrophils to the liver) depends on IL-1 activation. Our data indicate that immediate innate and inflammatory host responses toward i.v. applied Ad vectors can be pharmacologically controlled through interference with IL-1 signaling pathways.

IL-10 gene-deficient mice lack TGF-beta/Smad signaling and fail to inhibit proinflammatory gene expression in intestinal epithelial cells after the colonization with colitogenic Enterococcus faecalis

Nonpathogenic enteric bacterial species initiate and perpetuate experimental colitis in IL-10 gene-deficient mice (IL-10(-/-)). Bacteria-specific effects on the epithelium are difficult to dissect due to the complex nature of the gut microflora. We showed that IL-10(-/-) mice compared with wild-type mice fail to inhibit proinflammatory gene expression in native intestinal epithelial cells (IEC) after the colonization with colitogenic Gram-positive Enterococcus faecalis. Interestingly, proinflammatory gene expression was transient after 1 wk of E. faecalis monoassociation in IEC from wild-type mice, but persisted after 14 wk of bacterial colonization in IL-10(-/-) mice. Accordingly, wild-type IEC expressed phosphorylated NF-kappaB subunit RelA (p65) and phosphorylated Smad2 only at day 7 after bacterial colonization, whereas E. faecalis-monoassociated IL-10(-/-) mice triggered persistent RelA, but no Smad2 phosphorylation in IEC at days 3, 7, 14, and 28. Consistent with the induction of TLR2-mediated RelA phosphorylation and proinflammatory gene expression in E. faecalis-stimulated cell lines, TLR2 protein expression was absent after day 7 from E. faecalis-monoassociated wild-type mice, but persisted in IL-10(-/-) IEC. Of note, TGF-beta1-activated Smad signaling was associated with the loss of TLR2 protein expression and the inhibition of NF-kappaB-dependent gene expression in IEC lines. In conclusion, E. faecalis-monoassociated IL-10(-/-), but not wild-type mice lack protective TGF-beta/Smad signaling and fail to inhibit TLR2-mediated proinflammatory gene expression in the intestinal epithelium, suggesting a critical role for IL-10 and TGF-beta in maintaining normal epithelial cell homeostasis in the interplay with commensal enteric bacteria.