Enhanced IL-10 Production by TLR4- and TLR2-Primed Dendritic Cells upon TLR Restimulation

High prevalence of dermatophytosis of the feet in acral melanoma of the foot

The clinical characteristics and pathogenesis of acral melanoma of the foot (AMF) have not been sufficiently elucidated. Clinical or subclinical persistent inflammation of the feet is caused by dermatophytosis of the feet (DPF). Persistent inflammation is potentially associated with oncogenesis. Moreover, diabetes has been reported to be associated with the development of dermatophytosis and cancer. The present study aimed to elucidate the clinical association between DPF and AMF, with consideration of diabetes. The medical records of 114 Japanese patients were retrospectively examined and divided into an AMF group (n = 30) and a control group consisting of patients with foot diseases other than melanoma (n = 84). Microscopic DPF screening was performed on all patients who reported symptoms in the foot, with or without AMF. Patients underwent a microscopic test to detect the presence of dermatophytes, and the diagnosis of DPF was made based on a positive result. In the AMF group, 18 (60.0%) and eight (26.7%) patients had DPF and diabetes, respectively. Four patients (13.3%) had both DPF and diabetes. In the control group, 25 (29.8%) and 11 (13.1%) patients had DPF and diabetes, respectively. Five patients (6.0%) had both DPF and diabetes. Univariate analyses showed a significantly higher prevalence of DPF in the AMF group than in the control group (odds ratio, 3.540; p = 0.003, Pearson χ2 test). Furthermore, multivariate analyses of sex, body mass index, DPF, and diabetes revealed DPF as a significant factor associated with AMF (odds ratio, 4.285; p = 0.002, logistic regression analysis). The hyperkeratotic type of DPF was more frequently observed in patients with AMF than in control patients (odds ratio, 11.083; p < 0.001, Pearson χ2 test). In conclusion, the present study found a significantly higher prevalence of DPF, especially its hyperkeratotic type, in patients with AMF. DPF may be associated with AMF pathogenesis.

Regulation of IL-10 expression and function by JAK-STAT in CD8+ T cells

IL-10 is a pleiotropic cytokine that plays a significant role in antiviral and antitumor immunity. Potent CD8+ T cells express IL-10 after stimulation by strong TCR signaling, which promotes the killing effect of CD8+ T cells. However, the regulation of IL-10 expression in CD8+ T cells and its signaling pathway to enhance CD8+ T cell function are largely unknown. In this study, we investigated the JAK-STAT signaling molecules that regulate IL-10 expression in CD8+ T cells and the JAK-STAT signaling pathway that IL-10 enhances the function of CD8+ T cells through its receptor, using small molecule inhibitors and CRISPR-Cas9 gene editing. Our findings provide new insights and a theoretical basis for the immunotherapy of tumors.

The Streptococcus virulence protein PepO triggers anti-tumor immune responses by reprograming tumor-associated macrophages in a mouse triple negative breast cancer model

BACKGROUND

The efficacy of current surgery and chemotherapy for triple negative breast cancer (TNBC) is limited due to heterogenous and immunosuppressive tumor microenvironment (TME). Tumor associated macrophages (TAMs), which are regarded as an M2 tumor-promoting phenotype, are crucial in the development of the immunosuppressive TME. Targeting TAM reprograming is a promising strategy in anti-tumor therapy since reprogramming techniques provide the opportunity to actively enhance the antitumor immunological activity of TAM in addition to eliminating their tumor-supportive roles, which is rarely applied in TNBC clinically. However, how to drive M2 macrophages reprogramming into M1 with high potency remains a challenge and the molecular mechanisms how M2 macrophages polarized into M1 are poorly understood. Here, we identified a new immunoregulatory molecular PepO that was served as an immunoregulatory molecule governed the transformation of tumor-promoting M2 to tumor-inhibitory M1 cells and represented an effective anti-tumor property.

RESULTS

At the present study, we identified a new immunoregulatory molecular PepO, as a harmless immunoregulatory molecule, governed the transformation of tumor-promoting M2 to tumor-inhibitory M1 cells efficiently. PepO-primed M2 macrophages decreased the expression of tumor-supportive molecules like Arg-1, Tgfb, Vegfa and IL-10, and increased the expression of iNOS, Cxcl9, Cxcl10, TNF-α and IL-6 to inhibit TNBC growth. Moreover, PepO enhanced the functions of macrophages related to cell killing, phagocytosis and nitric oxide biosynthetic process, thereby inhibiting the development of tumors in vivo and in vitro. Mechanistically, PepO reprogramed TAMs toward M1 by activating PI3K-AKT-mTOR pathway via TLR4 and suppressed the function of M2 by inhibiting JAK2-STAT3 pathway via TLR2. The PI3K inhibitor LY294002 abrogated the role of PepO in switching M2 macrophages into M1 and in inhibiting TNBC growth in vivo. And PepO failed to govern the M2 macrophages to reprogram into M1 macrophages and inhibit TNBC when TLR2 or TLR4 was deficient. Moreover, PepO enhanced the antitumor activity of doxorubicin and the combination exerted a synergistic effect on TNBC suppression.

CONCLUSIONS

Our research identified a possible macrophage-based TNBC immunotherapeutic approach and suggested a novel anticancer immunoregulatory molecular called PepO.

Myeloid differentiation protein-2 has a protective role in house dust mite-mediated asthmatic characteristics with the proinflammatory regulation of airway epithelial cells and dendritic cells

BACKGROUND

Myeloid differentiation protein-2 (MD-2) is a lipopolysaccharide-binding protein involved in lipopolysaccharide signalling via Toll-like receptor 4 (TLR4). TLR4 plays an essential role in HDM-mediated allergic airway inflammation. Moreover, MD-2 is structurally similar to Der f 2, a major allergen from house dust mite (HDM).

OBJECTIVES

We aimed to clarify the role of MD-2 in the pathogenesis of HDM-mediated allergic airway inflammation.

METHODS

Wild-type (WT), TLR4 knockout and MD-2 knockout mice were subjected to intranasal instillation of HDM extract, and asthmatic features were evaluated. We also evaluated gene sets regulated by MD-2 in HDM-treated airway epithelial cells and examined the function of dendritic cells from lymph nodes and from lungs.

RESULTS

Aggravated allergic airway inflammation with increased airway hyperresponsiveness was observed in MD-2 knockout mice compared with WT and TLR4 knockout mice. Global gene expression analysis revealed an MD-2 regulated proinflammatory response and reconstituted TLR4 signalling in airway epithelial cells. The ability of dendritic cells to evoke an allergic immune response was enhanced in MD-2 knockout mice.

CONCLUSIONS & CLINICAL RELEVANCE

MD-2 plays a protective role in HDM-induced airway allergy with the proinflammatory regulation of airway epithelial cells and dendritic cells. MD-2 may serve as a therapeutic target in the treatment of asthma.

Dectin-1-Mediated Production of Pro-Inflammatory Cytokines Induced by Yeast β-Glucans in Bovine Monocytes

Yeast-derived products containing β-glucans have long been used as feed supplements in domesticated animals in an attempt to increase immunity. β-glucans are mainly recognized by the cell surface receptor CLEC7A, also designated Dectin-1. Although the immune mechanisms elicited through Dectin-1 activation have been studied in detail in mice and humans, they are poorly understood in other species. Here, we evaluated the response of bovine monocytes to soluble and particulate purified β-glucans, and also to Zymosan. Our results show that particulate, but not soluble β-glucans, can upregulate the surface expression of costimulatory molecules CD80 and CD86 on bovine monocytes. In addition, stimulated cells increased production of IL-8 and of TNF, IL1B, and IL6 mRNA expression, in a dose-dependent manner, which correlated positively with CLEC7A gene expression. Production of IL-8 and TNF expression decreased significantly after CLEC7A knockdown using two different pairs of siRNAs. Overall, we demonstrated here that bovine monocytes respond to particulate β-glucans, through Dectin-1, by increasing the expression of pro-inflammatory cytokines. Our data support further studies in cattle on the induction of trained immunity using dietary β-glucans.

Tropisetron balances immune responses via TLR2, TLR4 and JAK2/STAT3 signalling pathway in LPS-stimulated PBMCs

Numerous documents have been stated that tropisetron, an antagonist of the 5-HT3 receptor and α7nAChR agonist, modulates immune responses. However, the mechanistic basis for this aspect of tropisetron action is largely unknown. Here, the immuno-modulatory effects of tropisetron are investigated, focusing on the possible molecular targets and the mechanisms. Aside from the well-characterized role in immune signalling, JAK2/STAT3, TLR2 and TLR4 are signal transducers linked to both immuno-modulatory actions of acetylcholine and serotonin. Therefore, we evaluated their involvement in the immunoregulatory effects of tropisetron. To test the hypothesis, we assessed the expression of pro-/anti-inflammatory cytokines including TNF-α, IL-1β, IL-17 and IL-10 following tropisetron treatment in lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMCs) derived from healthy subjects. Tropisetron up-regulates the transcription of TLR2, TLR4, JAK2 and STAT3 genes. Tropisetron also increases the expression of target pro-inflammatory cytokines, although considerably suppresses the pro-inflammatory cytokines (IL-1β, IL-17 and TNF-α) levels in media. Tropisetron notably promotes both IL-10 gene expression and secretion. These findings confirm the antiphlogistic properties of tropisetron. The present data also shed light on a new aspect of tropisetron immune-modulatory action that engaged TLR2, TLR4 and JAK2/STAT3 signalling cascades.

Rapid tumor vaccine using Toll-like receptor-activated ovarian cancer ascites monocytes

Background

Novel therapeutic strategies in ovarian cancer (OC) are needed as the survival rate remains dismally low. Although dendritic cell-based cancer vaccines are effective in eliciting therapeutic responses, their complex and costly manufacturing process hampers their full clinical utility outside specialized clinics. Here, we describe a novel approach of generating a rapid and effective cancer vaccine using ascites-derived monocytes for treating OC.

Methods

Using the ID8 mouse ovarian tumor model and OC patient samples, we isolated ascites monocytes and evaluated them with flow cytometry, Luminex cytokine and chemokine array analysis, ex vivo cocultures with T cells, in vivo tumor challenge and T cell transfer experiments, RNA-sequencing and mass spectrometry.

Results

We demonstrated the feasibility of isolating ascites monocytes and restoring their ability to function as bona fide antigen-presenting cells (APCs) with Toll-like receptor (TLR) 4 lipopolysaccharide and TLR9 CpG-oligonucleotides, and a blocking antibody to interleukin-10 receptor (IL-10R Ab) in the ID8 model. The ascites monocytes were laden with tumor antigens at a steady state in vivo. After a short 48 hours activation, they upregulated maturation markers (CD80, CD86 and MHC class I) and demonstrated strong ex vivo T cell stimulatory potential and effectively suppressed tumor and malignant ascites in vivo. They also induced protective long-term T cell memory responses. To evaluate the translational potential of this approach, we isolated ascites monocytes from stage III/IV chemotherapy-naïve OC patients. Similarly, the human ascites monocytes presented tumor-associated antigens (TAAs), including MUC1, ERBB2, mesothelin, MAGE, PRAME, GPC3, PMEL and TP53 at a steady state. After a 48-hour treatment with TLR4 and IL-10R Ab, they efficiently stimulated oligoclonal tumor-associated lymphocytes (TALs) with strong reactivity against TAAs. Importantly, the activated ascites monocytes retained their ability to activate TALs in the presence of ascitic fluid.

Conclusions

Ascites monocytes are naturally loaded with tumor antigen and can perform as potent APCs following short ex vivo activation. This novel ascites APC vaccine can be rapidly prepared in 48 hours with a straightforward and affordable manufacturing process, and would be an attractive therapeutic vaccine for OC.

Galectin 3 protects from cisplatin-induced acute kidney injury by promoting TLR-2-dependent activation of IDO1/Kynurenine pathway in renal DCs

Strategies targeting cross-talk between immunosuppressive renal dendritic cells (DCs) and T regulatory cells (Tregs) may be effective in treating cisplatin (CDDP)-induced acute kidney injury (AKI). Galectin 3 (Gal-3), expressed on renal DCs, is known as a crucial regulator of immune response in the kidneys. In this study, we investigated the role of Gal-3 for DCs-mediated expansion of Tregs in the attenuation of CDDP-induced AKI. Methods: AKI was induced in CDDP-treated wild type (WT) C57BL/6 and Gal-3 deficient (Gal-3^-/-) mice. Biochemical, histological analysis, enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, real-time PCR, magnetic cell sorting, flow cytometry and intracellular staining of renal-infiltrated immune cells were used to determine the differences between CDDP-treated WT and Gal-3^-/- mice. Newly synthesized selective inhibitor of Gal-3 (Davanat) was used for pharmacological inhibition of Gal-3. Recombinant Gal-3 was used to demonstrate the effects of exogenously administered soluble Gal-3 on AKI progression. Pam3CSK4 was used for activation of Toll-like receptor (TLR)-2 in DCs. Cyclophosphamide or anti-CD25 antibody were used for the depletion of Tregs. 1-Methyl Tryptophan (1-MT) was used for pharmacological inhibition of Indoleamine 2,3-dioxygenase-1 (IDO1) in TLR-2-primed DCs which were afterwards used in passive transfer experiments. Results: CDDP-induced nephrotoxicity was significantly more aggravated in Gal-3^-/- mice. Significantly reduced number of immunosuppressive TLR-2 and IDO1-expressing renal DCs, lower serum levels of KYN, decreased presence of IL-10-producing Tregs and significantly higher number of inflammatory IFN-γ and IL-17-producing neutrophils, Th1 and Th17 cells were observed in the CDDP-injured kidneys of Gal-3^-/- mice. Pharmacological inhibitor of Gal-3 aggravated CDDP-induced AKI in WT animals while recombinant Gal-3 attenuated renal injury and inflammation in CDDP-treated Gal-3^-/- mice. CDDP-induced apoptosis, driven by Bax and caspase-3, was aggravated in Gal-3^-/- animals and in WT mice that received Gal-3 inhibitor (CDDP+Davanat-treated mice). Recombinant Gal-3 managed to completely attenuate CDDP-induced apoptosis in CDDP-injured kidneys of Gal-3^-/- mice. Genetic deletion as well as pharmacological inhibition of Gal-3 in renal DCs remarkably reduced TLR-2-dependent activation of IDO1/KYN pathway in these cells diminishing their capacity to prevent transdifferentiation of Tregs in inflammatory Th1 and Th17 cells. Additionally, Tregs generated by Gal-3 deficient DCs were not able to suppress production of IFN-γ and IL-17 in activated neutrophils. TLR-2-primed DCs significantly enhanced capacity of Tregs for attenuation of CDDP-induced AKI and inflammation and expression of Gal-3 on TLR-2-primed DCs was crucially important for their capacity to enhance nephroprotective and immunosuppressive properties of Tregs. Adoptive transfer of TLR-2-primed WTDCs significantly expanded Tregs in the kidneys of CDDP-treated WT and Gal-3^-/- recipients resulting in the suppression of IFN-γ and IL-17-driven inflammation and alleviation of AKI. Importantly, this phenomenon was not observed in CDDP-treated WT and Gal-3^-/- recipients of TLR-2-primed Gal-3^-/-DCs. Gal-3-dependent nephroprotective and immunosuppressive effects of renal DCs was due to the IDO1-induced expansion of renal Tregs since either inhibition of IDO1 activity in TLR-2-primed DCs or depletion of Tregs completely diminished DCs-mediated attenuation of CDDP-induced AKI. Conclusions: Gal-3 protects from CDDP-induced AKI by promoting TLR-2-dependent activation of IDO1/KYN pathway in renal DCs resulting in increased expansion of immunosuppressive Tregs in injured kidneys. Activation of Gal-3:TLR-2:IDO1 pathway in renal DCs should be further explored as new therapeutic approach for DC-based immunosuppression of inflammatory renal diseases.

Infection of Dendritic Cells With Mycobacterium avium subspecies hominissuis Exhibits a Functionally Tolerogenic Phenotype in Response to Toll-Like Receptor Agonists via IL-10/Cox2/PGE2/EP2 Axis

Mycobacterium avium subspecies hominissuis (MAH) is the most common agent causing nontuberculous mycobacterial disease in humans. It mainly causes chronic and slowly progressive pulmonary disease (PD), which requires a long-term treatment and allows opportunistic co-infection by common pulmonary pathogens such as Pseudomonas aeruginosa, Staphylococcus aureus, and Aspergillus spp., thereby resulting in alteration of host immune response. In the present study, we investigated the phenotypical and functional alterations of dendritic cells (DCs), a bridge antigen-presenting cell between innate and adaptive immunity, following MAH infection in response to various toll-like receptor (TLR) agonists mimicking co-infection conditions, along with subsequent T cell response. Interestingly, MAH-infected DCs produced interleukin (IL)-10 significantly and decreased the level of IL-12p70 in response to Poly I:C and LPS, although not so in response to Pam3CSK4, imiquimod, or CpG oligodeoxynucleotide, thereby indicating that the TLR3 and TLR4 agonists functionally altered MAH-infected DCs toward a tolerogenic phenotype. Moreover, IL-10-producing tolerogenic DCs were remarkably induced by MAH and P. aeruginosa co-infection. To precisely elucidate how these TLR agonists induce tolerogenic DCs upon MAH infection, we sought to clarify the major mechanisms involved, using LPS, which caused the greatest increase in IL-10 production by the TLR agonists. Increased IL-10 stimulated the creation of tolerogenic DCs by significantly reducing MHC class II expression and MHC class II-antigen presentation, eventually inhibiting CD4⁺ T cell proliferation, along with decreased IFN-γ and IL-2. The tolerogenic phenotypes of MAH/LPS-treated DCs were restored by anti-IL-10 neutralization, validating the induction of tolerogenicity by IL-10. Interestingly, IL-10-producing-tolerogenic DCs were observed after infection with live MAH, rather than with inactivated or dead MAH. In addition, TLR2^-/- and TLR4^-/- DCs confirmed the association of IL-10 production with TLR2 and TLR4 signaling; IL-10 production synergistically increased when both TLR4 and TLR2 were involved. Expression of Cox2 and PGE2 increased along with IL-10 while that of IL-10 was inhibited by their selective inhibitors celecoxib and anti-EP2 antibody, respectively. Thus, the tolerogenic phenotypes of MAH/LPS-treated DCs were proven to be induced by Cox-2/PGE2-dependent EP2 signaling as the main mechanism. These findings may provide important clues that the tolerogenic cascade in MAH-infected DCs induced by TLR 4 signaling can alter host immune response.

Systemic TLR2 tolerance enhances central nervous system remyelination

Background

Multiple sclerosis (MS) is a central nervous system (CNS) autoimmune disease characterized by both inflammatory demyelination and impaired remyelination. Studies indicate that Toll-like receptor 2 (TLR2) signaling contributes to both the inflammatory component and the defective remyelination in MS. While most MS therapeutics target adaptive immunity, we recently reported that reducing TLR2 signaling in innate immune cells by inducing TLR2 tolerance attenuates adoptively transferred experimental autoimmune encephalomyelitis. Given that previous reports suggest TLR2 signaling also inhibits myelin repair, the objective of this study was to assess how reducing TLR2 signaling through TLR2 tolerance induction affects CNS myelin repair.

Methods

Chow containing 0.2% cuprizone was fed to male and female wild-type (WT) C57BL/6 mice or TLR2-deficient (TLR2^−/−) mice for 5 weeks to induce demyelination. During a 2-week remyelination period following discontinuation of cuprizone, WT mice received either low dose TLR2 ligands to induce systemic TLR2 tolerance or vehicle control (VC). Remyelination was evaluated via electron microscopy and immunohistochemical analysis of microglia and oligodendrocytes in the corpus callosum. Statistical tests included 2-way ANOVA and Mann-Whitney U analyses.

Results

Inducing TLR2 tolerance in WT mice during remyelination significantly enhanced myelin recovery, restoring unmyelinated axon frequency and myelin thickness to baseline levels compared to VC-treated mice. Mechanistically, enhanced remyelination in TLR2 tolerized mice was associated with a shift in corpus callosum microglia from a pro-inflammatory iNOS⁺ phenotype to a non-inflammatory/pro-repair Arg1⁺ phenotype. This result was confirmed in vitro by inducing TLR2 tolerance in WT microglia cultures. TLR2^−/− mice, without TLR2 tolerance induction, also significantly enhanced myelin recovery compared to WT mice, adding confirmation that reduced TLR2 signaling is associated with enhanced remyelination.

Discussion

Our results suggest that reducing TLR2 signaling in vivo by inducing TLR2 tolerance significantly enhances myelin repair. Furthermore, the enhanced remyelination resulting from TLR2 tolerance induction is associated with a shift in corpus callosum microglia from a pro-inflammatory iNOS⁺ phenotype to a non-inflammatory/pro-repair Arg1⁺ phenotype. While deletion of TLR2 would be an impractical approach in vivo, reducing innate immune signaling through TLR2 tolerance induction may represent a novel, two-pronged approach for treating both inflammatory and myelin repair components of MS.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1540-2) contains supplementary material, which is available to authorized users.

Galectin-3 Regulates Indoleamine-2,3-dioxygenase-Dependent Cross-Talk between Colon-Infiltrating Dendritic Cells and T Regulatory Cells and May Represent a Valuable Biomarker for Monitoring the Progression of Ulcerative Colitis

Galectin-3 regulates numerous biological processes in the gut. We investigated molecular mechanisms responsible for the Galectin-3-dependent regulation of colon inflammation and evaluated whether Galectin-3 may be used as biomarker for monitoring the progression of ulcerative colitis (UC). The differences in disease progression between dextran sodium sulphate-treated wild type and Galectin-3-deficient mice were investigated and confirmed in clinical settings, in 65 patients suffering from mild, moderate, and severe colitis. During the induction phase of colitis, Galectin-3 promoted interleukin-1β-induced polarization of colonic macrophages towards inflammatory phenotype. In the recovery phase of colitis, Galectin-3 was required for the immunosuppressive function of regulatory dendritic cells (DCs). Regulatory DCs in Galectin-3:Toll-like receptor-4:Kynurenine-dependent manner promoted the expansion of colon-infiltrated T regulatory cells (Tregs) and suppressed Th1 and Th17 cell-driven colon inflammation. Concentration of Galectin-3 in serum and stool samples of UC patients negatively correlated with clinical, endoscopic, and histological parameters of colitis. The cutoff serum values of Galectin-3 that allowed the discrimination of mild from moderate and moderate from severe colitis were 954 pg/mL and 580 pg/mL, respectively. Fecal levels of Galectin-3 higher than 553.44 pg/mL indicated attenuation of UC. In summing up, Galectin-3 regulates the cross-talk between colon-infiltrating DCs and Tregs and represents a new biomarker for monitoring the progression of UC.

Expression of Toll-like receptors and costimulatory molecules in splenic B cells in a normal and abortion-prone murine pregnancy model

PROBLEM

The regulatory role of B lymphocytes in the pregnancy-induced maternal immune response is not well recognized. B lymphocytes function as antigen-presenting cells (APCs) and regulate Toll-like receptors and costimulatory molecule expression in response to intrinsic and extrinsic signals. Therefore, the aim of this study was to determine the expression of TLR2, TLR4, TLR9, and MHC class II and the costimulatory molecules CD80, CD86, and CD40 in splenic B cells in a normal and abortion-prone murine pregnancy model.

METHODS OF STUDY

The expression level of these molecules on female splenic B cells was investigated using real-time PCR and flow cytometry. The analysis was performed on the 3rd and 14th day of normal (CBA/JxBALB/c) and abortion-prone (CBA/JxDBA/2J) murine pregnancy.

RESULTS

The expression of Tlr9, Cd86, and H2-Ab1 in splenic B cells on the 3rd day after mating was upregulated, whereas Tlr2 was downregulated in abortion-prone females. On day 14, we observed lower expression levels of Tlr4 and Cd80 and higher expression levels of Cd86 in CBA/J females mated with DBA/2J males. At the protein level, the differences were observed only on day 3 of pregnancy. TLR4 and CD40 molecules were upregulated in splenic B cells, while TLR9 and CD86 were downregulated in abortion-prone mice.

CONCLUSION

Differential expression of TLRs and costimulatory molecules in splenic B cells in abortion-prone and normal pregnancies suggests the involvement of these cells in the regulation of the immune response at the periphery in pregnant females.

Interleukin-10 negatively modulates extracellular signal-regulated kinases 1 and 2 in aorta from hypertensive mouse induced by angiotensin II infusion

The activation of extracellular signal-regulated kinase 1 and 2 (ERK 1/2) pathway promotes increased vascular contractility in angiotensin II (Ang II)-induced hypertensive mice. Interleukin-10 (IL-10) is an immune-regulatory cytokine with the ability to prevent vascular hypercontractility during hypertension. We hypothesized that IL-10 would downregulate vascular ERK 1/2 activation during Ang II-induced hypertension. Wild-type (WT) or IL-10 knockout (IL-10-/- ) mice received Ang II infusion (90 ηg.min) or vehicle (saline), via osmotic mini-pumps (0.25 μL/h for 14 days), whereas another WT group were infused with exogenous IL-10 (0.5 ηg/min, 14 days) simultaneously, or not, with Ang II. Aortic rings were mounted in a myograph, and concentration-response curves to phenylephrine were evaluated, in the presence or absence of ERK 1/2 inhibitor (PD98059, 10 μm, 40 min). Protein expression of vascular ERK 1/2 was determined by Western blot. Ang II infusion increased the maximal contractile response in both WT and IL-10-/- mice. Concomitant infusion of IL-10 and Ang II prevented hypercontractility in the vasculature. Exogenous IL-10 infusion prevented ERK 1/2 activation and hypercontractility, induced by Ang II. These findings suggest that IL-10 negatively modulates ERK 1/2 activation and prevents hypercontractility during Ang II-induced hypertension.

Identification of a TLR2 Inhibiting Wheat Hydrolysate

SCOPE

Wheat hydrolysates are used in medical nutrition to provide undernourished patients a readily digestible protein source, for instance to recover from chemotherapy-induced intestinal mucosal inflammation. Since many hydrolysates of different sources can modulate the immune system, likely via Toll-like receptors (TLRs), it is hypothesized that also wheat hydrolysates might interact with TLR signaling, which could be a way to prevent intestinal inflammation and damage.

METHODS AND RESULTS

The capacity of three wheat hydrolysates to modulate immunity by interfering with TLR signaling is determined. All wheat hydrolysates have TLR modulating effects but only one has strong TLR2 inhibiting effects, attenuating both TLR2/1 and TLR2/6 signaling in a reporter cell system. This is likely induced by direct TLR2-ectodomain binding, as confirmed by ELISA. Furthermore, this TLR2 blocking hydrolysate reduces IL-6 production in human dendritic cells. Application of reversed-phase-ultra HPLC combined with MS reveals that the presence of peptide WQIPEQSR is associated with the observed TLR2 inhibiting capacity.

CONCLUSION

The study demonstrates TLR2-inhibiting capacities of a wheat hydrolysate. The findings provide a good start for further research to investigate whether this hydrolysate might contribute to the management of intestinal mucosal inflammation in cancer patients receiving chemotherapy.

Modulating toll-like receptor-mediated inflammatory responses following exposure of whole cell and lipopolysaccharide component from Porphyromonas gingivalis in wistar rat models

Objective:

To explore host innate inflammatory response and the signal pathway induced by Porphyromonas gingivalis by measuring level of toll-like receptor 2 (TLR2) and TLR4 activity.

Materials and Methods:

Animal experimental study with pretest-posttest controlled group design were done between January 1 and December 10, 2016.. Total of 28 wistar rats had been used, randomized into 7 groups, each were given various dose of intra-sulcural injection of Porphyromonas gingivalis lipopolysaccharide.

Statistical Analysis:

Normality were measured by Shapiro–Wilk test, while statistical analysis made by ANOVA, t test, Pearson, and linear regression model..

Results:

At day 0, no significant difference TLR2 and TLR4 level were measured. At day 4, there is a slight difference between TLR2 and TLR4 level in each group. At day 11, there is a significant difference between TLR2 and TLR4 level in each group. Group with exposure of whole cell will develop greater TLR2 but lower TLR4 level. In the contrary, group with exposure of LPS will develop greater TLR4 but lower TLR2 level.

Conclusion:

Our data supported that P. gingivalis played a vital role in the pathogenesis of pathogen-induced inflammatory responses in which TLR2 and TLR4 have different molecular mechanisms following recognition of pathogens and inflammatory response.

Toll-like receptor 2 dominance over Toll-like receptor 4 in stressful conditions for its detrimental role in the heart

It has been suggested that Toll-like receptor (TLR)4 promotes IL-10-mediated cardiac cell survival, whereas another receptor, TLR2, from the same family, is detrimental. Here, we examined the interactive role of these two innate signaling molecules under stressful conditions, including IL-10 knockout (IL-10−/−) mice, global ischemia-reperfusion (I/R) injury in rat hearts, and in vitro short hairpin RNA experimental models in the presence or absence of IL-10 (10 ng/ml). Circulating and myocardial levels of TNF-α as well as apoptosis and fibrosis were higher in IL-10−/− mice. The increase in TLR2 in IL-10−/− hearts indicated its negative regulation by IL-10. Ex vivo I/R also caused a marked upregulation of TLR2 and TNF-α as well as apoptotic and fibrotic signals. However, a 40-min reperfusion with IL-10 triggered an increase in TLR4 expression and improved recovery of cardiac function. The increase in IL-1 receptor-associated kinase (IRAK)-M and IRAK-2 activity during I/R injury suggested their role in TLR2 signaling. In vitro inhibition of TLR4 activity as a consequence of RNA inhibition-mediated suppression of myeloid differentiation gene (MyD)88 suggested MyD88-dependent activation of TLR4. The inclusion of IL-10 during reperfusion also downregulated the expression of IRAK-2, TNF-α receptor-associated factor 1-interacting protein (TRAIP) and apoptotic signals, caspase-3, and the Bax-to-Bcl-xL ratio. IL-10 reduced the TNF-α receptor-associated increase in TRAIP-induced apoptosis during I/R injury, which led to an increase in IL-1β to mitigate transforming growth factor-β receptor type I-mediated fibrosis. The IL-10 mitigation of these changes suggests that the stimulation through TLR4 signaling promotes IRAK-4 and phosphorylates IRAK-1 instead of IRAK-2 and may be an important therapeutic approach in restoring heart health in stress.

NEW & NOTEWORTHY Under stress conditions such as downregulation of the IL-10 gene or ischemia-reperfusion injury, Toll-like receptor (TLR)4 and IL-1 receptor-associated kinase (IRAK)-1 activation is suppressed, along with the upregulation of TLR-2 and IRAK-2, resulting in fibrosis and apoptosis. It is suggested that IL-10 helps to maintain heart function during stress via myeloid differentiation gene 88/IRAK-4/IRAK-1-dependent TLR4 signaling.

Few-Layer Graphene Kills Selectively Tumor Cells from Myelomonocytic Leukemia Patients

In the cure of cancer, a major cause of today's mortality, chemotherapy is the most common treatment, though serious frequent challenges are encountered by current anticancer drugs. We discovered that few-layer graphene (FLG) dispersions have a specific killer action on monocytes, showing neither toxic nor activation effects on other immune cells. We confirmed the therapeutic application of graphene on an aggressive type of cancer that is myelomonocytic leukemia, where the monocytes are in their malignant form. We demonstrated that graphene has the unique ability to target and boost specifically the necrosis of monocytic cancer cells. Moreover, the comparison between FLG and a common chemotherapeutic drug, etoposide, confirmed the higher specificity and toxicity of FLG. Since current chemotherapy treatments of leukemia still cause serious problems, these findings open the way to new and safer therapeutic approaches.

Immune transcriptome reveals the mincle C-type lectin receptor acts as a partial replacement for TLR4 in lipopolysaccharide-mediated inflammatory response in barramundi (Lates calcarifer)

Fish represent the most diverse and abundant extant vertebrate infraclass. They are also one of the earliest divergent phyla with adaptive immunity based on antigen recognition by MHC and immunoglobulin. The aquaculture industry, which currently provides more than half of the fish for human consumption globally, has successfully exploited the adaptive immune system of fish through mass vaccination programs. However, vaccination against highly diverse antigens, mostly carbohydrates, such as capsular polysaccharides and lipopolysaccharide (LPS) is challenging. Fish have a subdued innate response to LPS, but adaptive response is generally high and type-specific. To better understand the link between initial innate response and early onset of adaptive immunity to carbohydrate antigens in the perciform barramundi (Lates calcarifer), an immune transcriptome was prepared from pronephros and spleen following vaccination with LPS and peptidoglycan. From 163,661 transcripts derived by Illumina mRNA-Seq, most grouped in neuronal, endocrine or immune system categories, suggesting a close relationship between the three systems. Moreover, digestive enzyme transcripts in spleen appeared to be highly inducible in barramundi. Most of the known TLRs were transcribed in the barramundi spleen and HK transcriptome, with the notable exception of TLR4, which is primarily responsible for LPS recognition in mammals. Several C-type lectin receptors were also identified, including CD209, CD205, and CLEC4E (Mincle). As Mincle has been shown to bind LPS and is abundant on dendritic cells, its role in response to LPS in barramundi was further investigated. A high dose of LPS induced TNF-alpha expression via Mincle. However, IL-6 regulation, whilst still regulated in response to LPS, did not depend upon the Mincle pathway, suggesting other routes of activation. This study thus suggests that Mincle acts as a partial substitute for TLR4 in barramundi in the processing of LPS.

Lipopolysaccharide-primed heterotolerant dendritic cells suppress experimental autoimmune uveoretinitis by multiple mechanisms

Exposure of bone‐marrow‐derived dendritic cells (BMDC) to high‐dose ultrapure lipopolysaccharide for 24 hr (LPS‐primed BMDC) enhances their potency in preventing inter‐photoreceptor retinoid binding protein: complete Freund's adjuvant‐induced experimental autoimmune uveoretinitis (EAU). LPS‐primed BMDC are refractory to further exposure to LPS (= endotoxin tolerance), evidenced here by decreased phosphorylation of TANK‐binding kinase 1, interferon regulatory factor 3 (IRF3), c‐Jun N‐terminal kinase and p38 mitogen‐activated protein kinase as well as impaired nuclear translocation of nuclear factor κB (NF‐κB) and IRF3, resulting in reduced tumour necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6), IL‐12 and interferon‐β secretion. LPS‐primed BMDC also show reduced surface expression of Toll‐like receptor‐4 and up‐regulation of CD14, followed by increased apoptosis, mediated via nuclear factor of activated T cells (NFATc)‐2 signalling. LPS‐primed BMDC are not only homotolerant to LPS but are heterotolerant to alternative pathogen‐associated molecular pattern ligands, such as mycobacterial protein extract (Mycobacterium tuberculosis). Specifically, while M. tuberculosis protein extract induces secretion of IL‐1β, TNF‐α and IL‐6 in unprimed BMDC, LPS‐primed BMDC fail to secrete these cytokines in response to M. tuberculosis. We propose that LPS priming of BMDC, by exposure to high doses of LPS for 24 hr, stabilizes their tolerogenicity rather than promoting immunogenicity, and does so by multiple mechanisms, namely (i) generation of tolerogenic apoptotic BMDC through CD14:NFATc signalling; (ii) reduction of NF‐κB and IRF3 signalling and downstream pro‐inflammatory cytokine production; and (iii) blockade of inflammasome activation.

IL-10 Controls Early Microglial Phenotypes and Disease Onset in ALS Caused by Misfolded Superoxide Dismutase 1

While reactive microgliosis is a hallmark of advanced stages of amyotrophic lateral sclerosis (ALS), the role of microglial cells in events initiating and/or precipitating disease onset is largely unknown. Here we provide novel in vivo evidence of a distinct adaptive shift in functional microglial phenotypes in preclinical stages of superoxide dismutase 1 (SOD1)-mutant-mediated disease. Using a mouse model for live imaging of microglial activation crossed with SOD1(G93A) and SOD1(G37R) mouse models, we discovered that the preonset phase of SOD1-mediated disease is characterized by development of distinct anti-inflammatory profile and attenuated innate immune/TLR2 responses to lipopolysaccharide (LPS) challenge. This microglial phenotype was associated with a 16-fold overexpression of anti-inflammatory cytokine IL-10 in baseline conditions followed by a 4.5-fold increase following LPS challenge. While infusion of IL-10R blocking antibody, initiated at day 60, caused a significant increase in markers of microglial activation and precipitated clinical onset of disease, a targeted overexpression of IL-10 in microglial cells, delivered via viral vectors expressed under CD11b promoter, significantly delayed disease onset and increased survival of SOD1(G93A) mice. We propose that the high IL-10 levels in resident microglia in early ALS represent a homeostatic and compensatory "adaptive immune escape" mechanism acting as a nonneuronal determinant of clinical onset of disease. Significance statement: We report here for the first time that changing the immune profile of brain microglia may significantly affect clinical onset and duration of disease in ALS models. We discovered that in presymptomatic disease microglial cells overexpress anti-inflammatory cytokine IL-10. Given that IL-10 is major homeostatic cytokine and its production becomes deregulated with aging, this may suggest that the capacity of microglia to adequately produce IL-10 may be compromised in ALS. We show that blocking IL-10 increased inflammation and precipitated clinical disease onset, whereas overexpression of IL-10 in microglia using a gene therapy approach significantly delayed disease onset and increased survival of ALS mice. Based on our results, we propose that targeted overexpression of IL-10 in microglia may have therapeutic potential in ALS.

Identification of Barramundi (Lates calcarifer) DC-SCRIPT, a Specific Molecular Marker for Dendritic Cells in Fish

Antigen presentation is a critical step bridging innate immune recognition and specific immune memory. In mammals, the process is orchestrated by dendritic cells (DCs) in the lymphatic system, which initiate clonal proliferation of antigen-specific lymphocytes. However, fish lack a classical lymphatic system and there are currently no cellular markers for DCs in fish, thus antigen-presentation in fish is poorly understood. Recently, antigen-presenting cells similar in structure and function to mammalian DCs were identified in various fish, including rainbow trout (Oncorhynchus mykiss) and zebrafish (Danio rerio). The present study aimed to identify a potential molecular marker for DCs in fish and therefore targeted DC-SCRIPT, a well-conserved zinc finger protein that is preferentially expressed in all sub-types of human DCs. Putative dendritic cells were obtained in culture by maturation of spleen and pronephros-derived monocytes. DC-SCRIPT was identified in barramundi by homology using RACE PCR and genome walking. Specific expression of DC-SCRIPT was detected in barramundi cells by Stellaris mRNA FISH, in combination with MHCII expression when exposed to bacterial derived peptidoglycan, suggesting the presence of DCs in L. calcarifer. Moreover, morphological identification was achieved by light microscopy of cytospins prepared from these cultures. The cultured cells were morphologically similar to mammalian and trout DCs. Migration assays determined that these cells have the ability to move towards pathogens and pathogen associated molecular patterns, with a preference for peptidoglycans over lipopolysaccharides. The cells were also strongly phagocytic, engulfing bacteria and rapidly breaking them down. Barramundi DCs induced significant proliferation of responder populations of T-lymphocytes, supporting their role as antigen presenting cells. DC-SCRIPT expression in head kidney was higher 6 and 24 h following intraperitoneal challenge with peptidoglycan and lipopolysaccharide and declined after 3 days relative to PBS-injected controls. Relative expression was also lower in the spleen at 3 days post challenge but increased again at 7 days. As DC-SCRIPT is a constitutively expressed nuclear receptor, independent of immune activation, this may indicate initial migration of immature DCs from head kidney and spleen to the injection site, followed by return to the spleen for maturation and antigen presentation. DC-SCRIPT may be a valuable tool in the investigation of antigen presentation in fish and facilitate optimisation of vaccines and adjuvants for aquaculture.

TLR signaling-induced CD103-expressing cells protect against intestinal inflammation

BACKGROUND

Toll-like receptor (TLR) expression in patients with inflammatory bowel disease is increased when compared with healthy controls. However, the impact of TLR signaling during inflammatory bowel disease is not fully understood.

METHODS

In this study, we used a murine model of acute phase inflammation in bone marrow chimeric mice to investigate in which cell type TLR2/4 signal induction is important in preventing intestinal inflammation and how intestinal dendritic cells are influenced. Mice were either fed with wild-type bacteria, able to initiate the TLR2/4 signaling cascade, or with mutant strains with impaired signal induction capacity.

RESULTS

The induction of the TLR2/4 signal cascade in epithelial cells resulted in inflammation in bone marrow chimeric mice, whereas induction in hematopoietic cells had an opposed function. Furthermore, feeding of wild-type bacteria prevented disease; however, differing signal induction of bacteria had no effect on lamina propria dendritic cell activation. In contrast, functional TLR2/4 signals resulted in increased frequencies of CD103-expressing lamina propria and mesenteric lymph node dendritic cells, which were able to ameliorate disease.

CONCLUSIONS

The TLR-mediated amelioration of disease, the increase in CD103-expressing cells, and the beneficial function of TLR signal induction in hematopoietic cells indicate that the increased expression of TLRs in patients with inflammatory bowel disease might result in counterregulation of the host and serve in preventing disease.

Exposure to High Doses of Lipopolysaccharide during Ovalbumin Sensitization Prevents the Development of Allergic Th2 Responses to a Dietary Antigen

Food allergies are driven by aberrant T helper (Th) 2 cells. Lipopolysaccharide (LPS) influences the development of Th2-mediated diseases, but its role in food allergy and tolerance remains unclear. To address this issue, we established mouse models presenting allergic or tolerant responses to ovalbumin (OVA). Mice sensitized with crude OVA developed Th2 responses including acute diarrhea, increases in serum OVA-specific IgE, dominant production of serum OVA-specific IgG1, increases in Th2-type cytokines and proliferation of mast cells in duodenal and colonic tissues. Sensitization of mice with crude OVA and LPS abrogated Th2-type responses observed in allergic mice. The level of OVA-specific proliferation in mesenteric lymph node CD4⁺ T cells was comparable in allergic and tolerant mice, indicating that the tolerance is not caused by anergy and apoptosis of antigen-primed T cells. Expression of Th1- and Th2-type cytokines was suppressed in whole spleen cells and/or purified spleen CD4⁺ T cells of tolerant mice, indicating that the tolerance was not caused by the shift from Th2 to Th1. On the other hand, interleukin (IL)-10, a regulatory cytokine produced by regulatory T cells, was upregulated in whole spleen cells and purified spleen CD4⁺ T cells of tolerant mice. Furthermore, spleen CD4⁺ T cells from tolerant mice suppressed the growth of CD4⁺ T cells from DO11.10 mice in co-culture. These results indicate that tolerance is induced in allergic mice by simultaneous exposure to LPS during sensitization with OVA and that a population of T cells producing IL-10 plays an important role in the tolerance induction.

Porphyromonas gingivalis exacerbates ligature-induced, RANKL-dependent alveolar bone resorption via differential regulation of Toll-like receptor 2 (TLR2) and TLR4

Toll-like receptors (TLRs) play a key role in the innate immune responses to periodontal pathogens in periodontal disease. The present study was performed to determine the roles of TLR2 and TLR4 signaling in alveolar bone resorption, using a Porphyromonas gingivalis-associated ligature-induced periodontitis model in mice. Wild-type (WT), Tlr2(-/-), and Tlr4(-/-) mice (8 to 10 weeks old) in the C57/BL6 background were used. Silk ligatures were applied to the maxillary second molars in the presence or absence of live P. gingivalis infection. Ligatures were removed from the second molars on day 14, and mice were kept for another 2 weeks before sacrifice for final analysis (day 28). On day 14, there were no differences in alveolar bone resorption and gingival RANKL expression between mice treated with ligation plus P. gingivalis infection and mice treated with ligation alone. Gingival interleukin-1β (IL-1β) and tumor necrosis factor alpha (TNF-α) expression was increased, whereas IL-10 expression was decreased in WT and Tlr2(-/-) mice but not in Tlr4(-/-) mice. On day 28, WT and Tlr4(-/-) mice treated with ligation plus P. gingivalis infection showed significantly increased bone loss and gingival RANKL expression compared to those treated with ligation alone, whereas such an increase was diminished in Tlr2(-/-) mice. Gingival TNF-α upregulation and IL-10 downregulation were observed only in WT and Tlr4(-/-) mice, not in Tlr2(-/-) mice. In all mice, bone resorption induced by ligation plus P. gingivalis infection was antagonized by local anti-RANKL antibody administration. This study suggests that P. gingivalis exacerbates ligature-induced, RANKL-dependent periodontal bone resorption via differential regulation of TLR2 and TLR4 signaling.

A novel synthetic lipopeptide is allergy-protective by the induction of LPS-tolerance

BACKGROUND

Exposure to the environment of traditional farms can protect children from some allergic disease. Due to this exposure, TLR2 expression in these children is increased. TLR2 ligands derived from gram-positive bacteria are found in the dust of these farms.

OBJECTIVES

We proved whether a synthetic lipopeptide binding to the TLR1/2 heterodimer is able to protect from allergic disease in two different murine models of allergy. We also investigated the immunological mechanisms underlying the protective properties of the lipopeptide.

METHODS

We synthesized a lipopeptide derived from a germination lipoprotein of Bacillus cereus (LPGerD). We evaluated the immunomodulatory activity of LPGerD in a murine model of systemic sensitization (OVA/Alum) and in a model in which mice were sensitized with OVA pulsed bone-marrow-derived dendritic cells (BMDCs) via the airways. Furthermore, the induction of LPS tolerance was studied.

RESULTS

Treatment of mice with LPGerD in a mouse model of asthma led to protection against sensitization and airway inflammation. Similarly, bone-marrow-derived dendritic cells (BMDCs) pre-treated with LPGerD were not able to prime mice for allergic immune response. We observed that pre-treatment with LPGerD led to the induction of a LPS-tolerant state in BMDCs. These cells secreted markedly lower amounts of pro-inflammatory cytokines upon LPS stimulation. Furthermore, we observed an up-regulation of IRAK-M mRNA in BMDCs pre-treated with LPGerD.

CONCLUSIONS AND CLINICAL RELEVANCE

Our results suggest that induction of a LPS-tolerant state in antigen-presenting cells (APCs) may contribute to the protective effect of a farming environment. TLR2 agonists similar to those appearing in cowshed dust extracts, such as our synthetic LPGerD, lead to the ignorance of the LPS stimulus, which is important for the activation of APCs to mount a Th2 immune response. This substance might be a promising candidate for allergy-preventive treatments as LPGerD had only low pro-inflammatory characteristics.

NF-κB1 inhibits NOD2-induced cytokine secretion through ATF3-dependent mechanisms

Regulation of microbially induced cytokine secretion is critical in intestinal immune homeostasis. NOD2, the Crohn's disease-associated bacterial peptidoglycan sensor, activates the NF-κB pathway. After chronic NOD2 stimulation in human macrophages, cytokine secretion is significantly attenuated, similar to the situation in the intestinal environment. We find that NF-κB1 (p105/p50) expression is upregulated with chronic NOD2 stimulation and is required for attenuation of cytokine secretion in vitro in human macrophages and in vivo in mice. Upon chronic NOD2 stimulation, regulation of both activating (H3K4Me2 and H4Ac) and inhibitory (H3K27Me3) histone modifications was observed within cytokine gene promoters; these outcomes were NF-κB1 dependent. In addition to enhanced binding to cytokine gene promoters with chronic NOD2 stimulation, NF-κB1 bound to the promoter of the transcriptional repressor, ATF3. ATF3 was then induced and bound to cytokine gene promoters; both features were impaired upon NF-κB1 knockdown. Restoring ATF3 expression under NF-κB1 knockdown conditions restored NOD2-mediated cytokine downregulation. Finally, NF-κB1 and ATF3 cooperate with other inhibitory pathways, including IRAKM and secreted mediators, to downregulate cytokine secretion after chronic NOD2 stimulation. Therefore, we identify NF-κB1 and ATF3 as critical mechanisms through which NOD2 downregulates cytokines and contributes to intestinal immune homeostasis.

Signaling mechanism for Aspergillus fumigatus tolerance in corneal fibroblasts induced by LPS pretreatment

TLRs, particularly TLR2 and TLR4, play primary roles in inflammatory responses triggered by Aspergillus fumigatus and lead to the activation of signaling pathways that initiate host defense responses. We previously demonstrated that LPS, a ligand of TLR4, can induce tolerance of A. fumigatus hyphae in telomerase-immortalized human stroma fibroblasts (THSFs). In the present study we investigated the role of TLR4, TLR2 and their downstream signaling pathways in this activity. The THSFs were pretreated with low-dose LPS and then exposed to A. fumigatus hyphae. It was demonstrated that enhanced expression of TLR4, but not of TLR2, was associated with LPS pretreatment. Inhibition of TLR4 with monoclonal Ab prevented reduction of pro-inflammatory cytokine secretion in LPS-pretreated THSFs. Pretreatment of THSFs with low-dose LPS caused an impaired response of the MyD88-dependent classical and MAPK signaling pathway upon subsequent A. fumigatus challenge, while expression of signaling molecules in the MyD88-independent Toll-IL-1 receptor domain-containing adaptor inducing IFN-β pathway was increased in THSFs pretreated with LPS. These results indicated that TLR4 mediates attenuated cytokine production induced by LPS pretreatment, and regulation of MyD88-dependent and MyD88-independent pathways may contribute to the development of A. fumigatus hyphae tolerance in LPS-pretreated THSFs.

Regulation of innate immune function in bovine oviduct epithelial cells in culture: the homeostatic role of epithelial cells in balancing Th1/Th2 response

This study aimed to investigate the role of epithelial cells in regulating innate immunity in bovine oviduct epithelial cell (BOEC) culture. We studied the effect of Escherichia coli lipopolysaccharide (LPS) and its interaction with ovarian steroids, estradiol (E2) and progesterone (P4), and luteinizing hormone (LH) at concentrations observed during the preovulatory period on immune responses in BOEC culture. Immunohistochemistry of oviduct tissue showed intensive expression of Toll-like receptor-4 (TLR-4) and TLR-2 in epithelial cells. A dose of 10 ng/ml LPS stimulated TLR-4, cyclooxygenase-2 (COX-2), nuclear factor kappa B inhibitor A (NFKBIA), interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α) expression, indicating an early pro-inflammatory response. A dose of 100 ng/ml LPS did not induce expression of these genes but stimulated TLR-2, IL-10,IL-4 and microsomal prostaglandin E synthase-1 (mPGES-1) expression and PGE2 secretion, indicating an anti-inflammatory response. Ovarian steroids and LH completely block LPS (10 ng/ml)-induced TLR-4, IL-1β and TNF-α expression as well as LPS (100 ng/ml)-induced TLR-2 expression. Taken together, this study suggests the existence of an early signaling system to respond to infection in the BOEC. In addition, ovarian steroids and LH may play a critical role in inducing homeostasis and in controlling hyperactive pro-inflammatory responses detrimental to epithelial cells, sperm and the embryo.

An fc gamma receptor-mediated upregulation of the production of interleukin 10 by intravenous immunoglobulin in bone-marrow-derived mouse dendritic cells stimulated with lipopolysaccharide in vitro

Intravenous immunoglobulin (IVIG), a highly purified immunoglobulin fraction prepared from pooled plasma of several thousand donors, increased anti-inflammatory cytokine IL-10 production, while decreased proinflammatory cytokine IL-12p70 production in bone-marrow-derived mouse dendritic cells (BMDCs) stimulated with lipopolysaccharide (LPS). The changes of cytokine production were confirmed with the transcription levels of these cytokines. To study the mechanisms of this bidirectional effect, we investigated changes of intracellular molecules in the LPS-induced signaling pathway and observed that IVIG upregulated ERK1/2 phosphorylation while downregulated p38 MAPK phosphorylation. Using chemical inhibitors specific to protein kinases involved in activation of Fc gamma receptors (FcγRs), which mediate IgG signals, we found that hyperphosphorylation of ERK1/2 and Syk phosphorylation occurred after stimulation of BMDC with LPS and IVIG, and the increasing effect on IL-10 production was abolished by these inhibitors. Furthermore, an antibody specific to FcγRI, one of FcγRs involved in immune activation, inhibited IVIG-induced increases in IL-10 production, but not IL-12p70 decreases, whereas the anti-IL-10 antibody restored the decrease in IL-12p70 induced by IVIG. These findings suggest that IVIG induced the upregulation of IL-10 production through FcγRI activation, and IL-10 was indispensable to the suppressing effect of IVIG on the production of IL-12p70 in LPS-stimulated BMDC.

Regulatory actions of Toll-like receptor 2 (TLR2) and TLR4 in Leishmania donovani infection in the liver

In livers of susceptible but self-curing C57BL/6 mice, intracellular Leishmania donovani infection enhanced Toll-like receptor 4 (TLR4) and TLR2 gene expression. In the liver, infected TLR4(-/-) mice showed reduced gamma interferon (IFN-γ), tumor necrosis factor (TNF), and inducible nitric oxide synthase (iNOS) mRNA expression, higher-level and slowly resolving infection, delayed granuloma formation, and little response to low-dose chemotherapy; in serum, the ratio of IFN-γ to interleukin 10 (IL-10) activity was decreased by 50%. In contrast, in TLR2(-/-) mice, control of liver infection, parasite killing, and granuloma assembly were accelerated and chemotherapy's efficacy enhanced. In livers of infected TLR2(-/-) mice, mRNA expression was not increased for inflammatory cytokines or iNOS or decreased for IL-10; however, the serum IFN-γ/IL-10 ratio was increased 6.5-fold and minimal responses to IL-10 receptor blockade suggested downregulated IL-10. In established infection in wild-type mice, blockading TLR2 induced parasite killing and triggering TLR4 strengthened resistance and promoted chemotherapy's effect. Thus, in experimental L. donovani infection in the liver, TLR4 signaling upregulates and TLR2 signaling downregulates macrophage antileishmanial activity, making both receptors potential therapeutic targets in visceral leishmaniasis for engagement (TLR4) or blockade (TLR2).

Interleukin-10 activates Toll-like receptor 4 and requires MyD88 for cardiomyocyte survival

Toll-like receptors (TLRs) are important in a variety of inflammatory diseases including acute cardiac disorders. TLR4 innate signaling regulates the synthesis of anti-inflammatory cytokine, interleukin-10 (IL-10) upon TLR4 agonists' re-stimulation. Anti-apoptotic action of IL-10 in cardiac dysfunction is generally accepted but its protective mechanism through TLR4 is not yet understood. We studied the effect of IL-10 in the activation of TLR4 downstream signals leading to cardiomyocytes survival. IL-10 caused a significant increase in the expression of CD14, MyD88 and TLR4. TLR4 activation led to the translocation of the interferon regulatory factor 3 (IRF3) into the nucleus. Phosphorylation of IRF3 enhanced mRNA synthesis for IL-1β but not TNF-α and was elevated even after removal of IL-10 stimulation. Furthermore, degradation of inhibitory kappa B (IκB) kinase (Ikk) suggested that IκBβ was the main activating kinase for IRF3-regulated NF-κB activation and phosphorylation of p65. Phosphorylated NF-κB p65 was translocated into the nucleus. Concomitantly, an increase in Bcl-xL activity inhibited Bax and the proteolytic activity of caspase 3 as well as a decrease in PARP cleavage. An inhibition of MyD88, modulated the above listed responses to IL-10 as there was a decrease in TLR4 and IRF3 and an increase in TNF-α mRNA. This was associated with a decrease in NF-κB p65, Bcl-xL mRNA and protein levels as well as there was an activation of Bax and PARP cleavage independent of caspase 3 activation. These data in cardiomyocytes suggest that IL-10 induced anti-apoptotic signaling involves upregulation of TLR4 through MyD88 activation.

Pattern recognition receptors: sentinels in innate immunity and targets of new vaccine adjuvants

The innate immune system plays an essential role in the host's first line of defense against microbial invasion, and involves the recognition of distinct pathogen-associated molecular patterns by pattern recognition receptors (PRRs). Activation of PRRs triggers cell signaling leading to the production of proinflammatory cytokines, chemokines and Type 1 interferons, and the induction of antimicrobial and inflammatory responses. These innate responses are also responsible for instructing the development of an appropriate pathogen-specific adaptive immune response. In this review, the focus is on different classes of PRRs that have been identified, including Toll-like receptors, nucleotide-binding oligomerization domain-like receptors, and the retinoic acid-inducible gene-I-like receptors, and their importance in host defense against infection. The role of PRR cooperation in generating optimal immune responses required for protective immunity and the potential of targeting PRRs in the development of a new generation of vaccine adjuvants is also discussed.

IRAK-M modulates expression of IL-10 and cell surface markers CD80 and MHC II after bacterial re-stimulation of tolerized dendritic cells

BACKGROUND

As essential components of the innate immune system, dendritic cells (DCs) can interact directly with pathogens as well as participate in the adaptive immune response. In cells closely related to DCs such as macrophages and monocytes, prior exposure to minute amounts of endotoxin can lead to a refractory period where subsequent exposure to higher doses fails to induce an inflammatory response; little research has investigated this effect on DCs. This study tested if murine bone marrow-derived dendritic cells (BM-DCs) respond to endotoxin- and bacterial sonicate-induced tolerance by decreased inflammatory and increased anti-inflammatory response, and the role of IRAK-M, an intracellular negative regulator of TLR signaling, in this tolerance.

RESULTS

Tolerized BM-DCs exhibited a significant drop in TNF-α and IL-12p70 production and increased IL-10 expression compared to untolerized cells. BM-DCs also showed the ability to develop heterotolerance, in which the LPS exposure alone was able to induce tolerance to Helicobacter pylori sonicate and TLR2 agonist Pam3Cys. Furthermore, the expression of IRAK-M was increased after restimulation of tolerized BM-DCs as determined qPCR and Western blot. IRAK-M exhibited a suppressive effect on surface expression of major histocompatibilty complex class II (MHC II) and CD80 in LPS-tolerized BM-DCs. IL-10 expression in bacterial sonicate-tolerized IRAK-M-/- BM-DCs was altered as compared to wild type BM-DCs, with tolerance-induced expression of IL-10 mitigated in tolerized IRAK-M-/- BM-DCs.

CONCLUSION

Along with endotoxin, bacterial sonicate is able to induce refractory tolerance in BM-DCs, and IRAK-M plays a role in modulating cell surface expression of MHC class II and CD80 and release of IL-10 during this tolerance.

Role of interleukin 10 transcriptional regulation in inflammation and autoimmune disease

Interleukin 10 (IL-10) is a cytokine with potent anti-inflammatory properties that plays a central role in limiting host immune response to pathogens, thereby preventing damage to the host and maintaining normal tissue homeostasis. Dysregulation of IL-10 is associated with enhanced immunopathology in response to infection as well as increased risk for development of many autoimmune diseases. Thus a fundamental understanding of IL-10 gene expression is critical for our comprehension of disease progression and resolution of host inflammatory response. In this review, we discuss modes of regulation of IL-10 gene expression in immune effector cell types, including signal transduction, epigenetics, promoter architecture, and post-transcriptional regulation, and how aberrant regulation contributes to immunopathology and disease progression.

Inhibition of autoimmune diabetes by TLR2 tolerance

We have reported that apoptotic β cells undergoing secondary necrosis, called "late apoptotic (LA) β cells," stimulated APCs and induced diabetogenic T cell priming through TLR2, which might be one of the initial events in autoimmune diabetes. Indeed, diabetogenic T cell priming and the development of autoimmune diabetes were significantly inhibited in TLR2-null NOD mice, suggesting the possibility that TLR2 blockade could be used to inhibit autoimmune diabetes. Because prolonged TLR stimulation can induce TLR tolerance, we investigated whether repeated TLR2 administration affects responses to LA β cells and inhibits autoimmune diabetes in NOD mice by inducing TLR2 tolerance. Treatment of primary peritoneal macrophages with a TLR2 agonist, Pam3CSK(4), suppressed cytokine release in response to LA insulinoma cells or further TLR2 stimulation. The expression of signal transducer IRAK-1 and -4 proteins was decreased by repeated TLR2 stimulation, whereas expression of IRAK-M, an inhibitory signal transducer, was enhanced. Chronic Pam3CSK(4) administration inhibited the development of diabetes in NOD mice. Diabetogenic T cell priming by dendritic cells and upregulation of costimulatory molecules on dendritic cells by in vitro stimulation were attenuated by Pam3CSK(4) administration in vivo. Pam3CSK(4) inhibited diabetes after adoptive transfer of diabetogenic T cells or recurrence of diabetes after islet transplantation by pre-existing sensitized T cells. These results showed that TLR2 tolerance can be achieved by prolonged treatment with TLR2 agonists, which could inhibit priming of naive T cells, as well as the activity of sensitized T cells. TLR2 modulation could be used as a novel therapeutic modality against autoimmune diabetes.

Toll Like Receptors Signaling Pathways as a Target for Therapeutic Interventions

This review summarizes the key role of Toll-Like Receptor (TLRs) molecules for igniting the immune system. Activated by a broad spectrum of pathogens, cytokines or other specific molecules, TLRs trigger innate immune responses. Published data demonstrate that the targeting and suppression of TLRs and TLR-related proteins with particular inhibitors may provide pivotal treatments for patients with cancer, asthma, sepsis, Crohn's disease and thrombosis. Many drugs that target cytokines act in the late phases of the activated pathways, after the final peptides, proteins or glycoproteins are formed in the cell environment. TLR activity occurs in the early activation of cellular pathways; consequently inhibiting them might be most beneficial in the treatment of human diseases.

Rectal administration of lipopolysaccharide and ovalbumin ameliorates acute murine colitis

BACKGROUND

Repeated challenges of lipopolysaccharide (LPS) could reduce the expression of proinflammatory cytokines in vitro, and oral administration of ovalbumin (OVA) induces mucosal tolerance in vivo. However, the effect of local administration of LPS and OVA on experimental colitis in vivo remains unknown.

AIMS

This study was performed to elucidate the effect of rectal administration of LPS and OVA on an acute murine colitis induced by dextran sulfate sodium (DSS).

METHODS

BALB/c mice were rectally administered LPS with or without OVA followed by 3% DSS. Colitis was assessed by disease activity index (DAI) including weight loss, stool consistency and rectal bleeding, and histopathology. Primary colon epithelial cells were isolated and the expression of Toll-like receptor 4 (TLR4) was examined using the Western blot analysis. IL-6, IFN-γ and IL-10 mRNA levels in colonic tissue were assessed using real-time RT-PCR.

RESULTS

LPS administration significantly attenuated the severity of acute DSS-induced colitis as assessed by DAI and histopathologic scoring compared with the control group. Combined treatment of LPS and OVA restored body weight loss and further ameliorated the severity of acute DSS colitis. LPS pretreatment regardless of OVA administration decreased TLR4 expression. LPS and OVA pretreatment reduced IL-6 and IFN-γ mRNA expression and increased IL-10 mRNA expression compared with controls.

CONCLUSION

Rectal administration of LPS attenuated acute murine colitis, possibly through TLR4 down-regulation, and combined treatment of OVA additionally ameliorated colonic inflammation associated with up-regulation of IL-10.

LPS response and endotoxin tolerance in Flt-3L-induced bone marrow-derived dendritic cells

Fms-like tyrosine kinase-3 ligand (Flt-3L) stimulates the differentiation of bone marrow cells into dendritic cells (DCs) and was used as an adjuvant therapy in the experimental model of burn wound sepsis. In this study, we describe the phenotypical characteristics of an Flt-3L-dependent DC culture (FLDC) system following LPS stimulation, which induces an inflammatory response, and after a second LPS stimulation, which induces tolerance. Priming of FLDCs with LPS via TLR4 has been shown to induce the activation of all three mitogen-activated protein kinase (MAPK) families and enhance NF-κB complex translocation into the nucleus. Stimulated FLDCs express all maturation markers and exhibit an increase in IL-12p40 production and to a lesser extent, IL-10 production. In contrast, LPS stimulation of tolerized FLDCs was not associated with TLR4 up-regulation and led to MAPK inhibition. The decrease in p38 and JNK activation was correlated with an impairment of IL-12p40 production. Endotoxin tolerance in FLDCs was associated with enhanced ERK1/2 activation, an increase in MKP-1 phosphatase expression, a decrease in NF-κB translocation to the nucleus and an increase in IL-10 production. Overall, DCs generated from bone marrow with Flt-3 ligand have similar characteristics to DC subtypes found in the steady state in vivo, which can acquire endotoxin tolerance in some circumstances.

Systemic cancer therapy with a small molecule agonist of toll-like receptor 7 can be improved by circumventing TLR tolerance

Topical application of small molecule Toll-like receptor 7 (TLR7) agonists is highly effective for the treatment of skin tumors, whereas their systemic application has been largely unsuccessful for cancer therapy. One reason may be that repeated systemic application of TLR ligands can induce a state of immune unresponsiveness, termed TLR tolerance. We show here that a single injection of the TLR7 agonist R848 in mice induces a short period of increased response to TLR stimulation followed by a state of hyporesponsiveness lasting several days. This state is characterized by inhibited secretion of the key cytokines interleukin (IL)-12p70 and IL-6 as well as by a block in IFN-α production. We show for the first time that at the cellular level, TLR7 tolerance occurs in both plasmacytoid and myeloid dendritic cells, two cell populations that play a critical role in the initiation and amplification of antitumor immune responses. We further show that TLR7 tolerance in plasmacytoid dendritic cells is accompanied by downregulation of the adaptor protein IL-1 receptor-associated kinase 1. On the basis of these findings, we have designed a novel strategy for the treatment of tumors by using cycles of repeated R848 injections separated by treatment-free intervals. We show in CT26 tumor-bearing mice that this protocol circumvents TLR7 tolerance and improves the efficacy of cancer immunotherapy.

Retroviral vectors induce epigenetic chromatin modifications and IL-10 production in transduced B cells via activation of toll-like receptor 2

The immune response toward viral vectors used for gene therapy and genetic vaccination appears to be critically important in determining the therapeutic outcome. However, the mechanisms that control the immune response following gene transfer are poorly understood. Unexpectedly, we found that integrating retroviral vector particles induce stable interleukin-10 (IL-10) production in murine (BALB/c H-2(d)) transduced B cells. This requires a novel mechanism whereby the interaction of retroviral vector particle with its cognate cellular receptor activates intracellular signaling pathways resulting in stable epigenetic modifications. Murine B cells exposed to retroviral vector particles triggered the colocalization of the retroviral cellular receptor [mouse cationic amino acid transporter 1 (mCAT1)] and Toll-like receptor 2 (TLR2) into lipid microrafts, which in turn activated TLR2 signaling pathways. TLR2 activation induced STAT3 phosphorylation and increased phosphorylated histone 3 (H3) at the STAT3-binding site of the IL-10 promoter. In addition, TLR2 activation during transduction activates nuclear factor of κ light polypeptide gene enhancer in B-cells inhibitor, α (NFKBIA), thereby preventing the translocation of the nuclear factor-κB (NF-κB) complex to the nucleus and the transcription of proinflammatory cytokines. These findings open new perspectives for controlling immune responses following gene therapy and genetic vaccination.

IL-10 enhances promoter activity of ILT4 gene and up-regulates its expression in THP-1 cells

This study examined the effect of IL-10 on immunoglobulin-like transcript (ILT4) expression of human monocytic leukemic cell line THP-1, especially the role of the ILT4 promoter activity. ILT4 promoter area was amplified by PCR, and was cloned into the eukaryotic expressing vector pGL3-Basic. The pGL3-ILTP obtained was tested by double endonuclease digestion and sequencing. Then, the recombinant plasmid was transfected into THP-1 cells by using lipofectamine. After culture with IL-10 for 12 h, the mRNA extracted from THP-1 cells was detected by RT-PCR and the protein was detected by FACS. The dual-luciferase reporter assay system was employed to detect the activity of ILT4 promoter with or without IL-10. The results showed that the activity of pGL3-ILTP was significantly increased and was more than ten times that of pGL3-Basic cells. After culture with IL-10 for 12 h, the expression of ILT4 protein and its mean fluorescence intensity (MFI) were increased. Moreover, the mRNA was remarkably higher than that of the control group. Dual-luciferase reporter assay revealed that ILT4 promoter was much more activated after being treated with IL-10. We were led to conclude that pGL3-ILTP containing ILT4 promoter was constructed successfully. The expression of ILT4 could be up-regulated by IL-10 both at the transcriptional and translational level. Furthermore, ILT4 promoter could be much more active after addition of IL-10. This study suggests that IL-10 up-regulates ILT4 expression on monocytes via increasing ILT4 gene promoter activity, which may have implication for inducing transplantation tolerance in clinical practice.

Enhanced dendritic cell antigen uptake via alpha2 adrenoceptor-mediated PI3K activation following brief exposure to noradrenaline

Although noradrenaline (NA), a stress-associated neurotransmitter, seems to affect the immune system, the precise mechanisms underlying NA-mediated immunoregulation are not fully understood. We examined the effect of NA on Ag uptake (endocytosis) by dendritic cells (DCs) using murine bone marrow-derived DCs and fluorescence-labeled endocytic tracers (dextran and OVA). Ag uptake by DCs notably increased following a very brief treatment (3 min) with NA. NA-induced endocytosis was completely blocked by treatment with α(2)-adrenoceptor antagonist yohimbine. Neither α(1)-adrenoceptor antagonist prazosin nor β-adrenoceptor antagonist propranolol affected NA-induced endocytosis by DCs. A selective α(2)-adrenoceptor agonist, azepexole (B-HT 933), also significantly increased endocytosis by DCs. Thus, the α(2)-adrenoceptor seems to be responsible for NA-induced DC endocytosis. In parallel, NA markedly activated intracellular signaling pathways of PI3K and ERK1/2 in DCs. NA-mediated activation of these pathways was completely inhibited by yohimbine treatment. Blocking PI3K activation significantly reduced NA-induced endocytosis by DCs. Based on these results, NA rapidly enhances Ag capture by DCs via α(2) adrenoceptor-mediated PI3K activation, which may be associated with immune enhancement following acute stress.

Toll-like receptors in inflammatory bowel diseases: a decade later

Differential alteration of Toll-like receptor (TLR) expression in inflammatory bowel disease (IBD) was first described 10 years ago. Since then, studies from many groups have led to the current concept that TLRs represent key mediators of innate host defense in the intestine, involved in maintaining mucosal as well as commensal homeostasis. Recent findings in diverse murine models of colitis have helped to reveal the mechanistic importance of TLR dysfunction in IBD pathogenesis. It has become evident that environment, genetics, and host immunity form a multidimensional and highly interactive regulatory triad that controls TLR function in the intestinal mucosa. Imbalanced relationships within this triad may promote aberrant TLR signaling, critically contributing to acute and chronic intestinal inflammatory processes in IBD colitis and associated cancer.