Differential post-transcriptional regulation of IL-10 by TLR2 and TLR4-activated macrophages

The effect of microbial metabolites from colonic protein fermentation on bacteria-induced cytokine production in dendritic cells

Compared to the well-defined immune-modulating effect of butyrate, the understanding of the effect of other protein fermentation metabolites is limited. This study aimed to investigate the impact of protein-derived metabolites (valerate, branched-chain fatty acids, ammonium, phenol, p-Cresol, indole, and hydrogen sulfide) on cytokine production in murine bone marrow-derived dendritic cells (BMDCs) stimulated with lipopolysaccharides (LPS), Lactobacillus acidophilus NCFM, or Staphylococcus aureus USA300. Some of the metabolites, but not the short-chain fatty acids (SCFAs), strongly affected cell viability. After short-term treatment and depending on the microbial stimulus, SCFAs affected the cytokine profile similarly but weaker than butyrate, as reflected by inhibition of IL-12p70 and IL-10 but enhanced IL-23 (LPS and S. aureus USA300) and IL-1β production. Compared to butyrate, valerate exhibited a weaker and slower effect on cytokine expression. Two-day treatment with valerate and butyrate resulted in similar effects, that is, LPS-induced IL-12 abrogation and IL-10 enhancement, increased aryl hydrocarbon receptor (Ahr) expression, and after LPS stimulation, increased expression of dual specificity phosphatase 1 (Dusp1). In conclusion, SCFAs exhibited low toxicity and modulated microbially stimulated BMDCs. Valerate and butyrate showed the strongest effect, which was dependent on the specific microbial stimulation and the course of the SCFA treatment. Our work adds knowledge regarding the role of protein-derived metabolites from gut bacterial fermentation on the immune system.

miRNA-Mediated Fine Regulation of TLR-Induced M1 Polarization

Macrophage polarization to the M1 spectrum is induced by bacterial cell wall components through stimulation of Toll-like family (TLR) receptors. By orchestrating the expression of relevant mediators of the TLR cascade, as well as associated pathways and feedback loops, macrophage polarization is coordinated to ensure an appropriate immune response. This is central to the successful control of pathogens and the maintenance of health. Macrophage polarization is known to be modulated at both the transcriptional and post-transcriptional levels. In recent years, the miRNA-based post-transcriptional regulation of M1 polarization has received increasing attention from the scientific community. Comparative studies have shown that TLR stimulation alters the miRNA profile of macrophages and that macrophages from the M1 or the M2 spectrum differ in terms of miRNAs expressed. Simultaneously, miRNAs are considered critical post-transcriptional regulators of macrophage polarization. In particular, miRNAs are thought to play a regulatory role in the switch between the early proinflammatory response and the resolution phase. In this review, we will discuss the current state of knowledge on the complex interaction of transcriptional and post-transcriptional regulatory mechanisms that ultimately determine the functionality of macrophages.

Biological characteristics and pathogenicity of a Staphylococcus aureus strain with an incomplete hemolytic phenotype isolated from bovine milk

Staphylococcus aureus is a common pathogen capable of infecting both humans and animals and causing various severe diseases. Here, we aimed to determine the biological features and pathogenicity of S. aureus strain Sa9, of the incomplete hemolysis phenotype, isolated from bovine milk. Sa9 was classified as ST97 by multilocus sequence typing, and it showed increased β-hemolysin expression and lower Hla and Hld expression levels compared with that in the S. aureus USA300 strain LAC. RT-PCR and ELISA results showed that the expression levels of inflammatory cytokines were higher in Sa9-induced mouse primary peritoneal macrophages compared with those induced by the LAC strain. However, the Sa9 strain also mediated anti-inflammatory effects by upregulating IL-10 and IFN-β in macrophages, which were not apparently induced by S. aureus culture supernatants. Phagocytosis and whole-blood survival assays were also performed to assess the in vitro survival of bacteria, and the virulence was evaluated in mice. Although the Sa9 strain showed lower ability of intracellular survival in macrophages than LAC, similar multiplication in human whole blood and pathogenicity toward mice were observed. Taken together, we report that the distinctive immune response induced by the S. aureus strain with an incomplete hemolysis phenotype occurs in cattle, and its potential pathogenicity and risk of transmission to humans require attention.

Imbalanced Inflammatory Responses in Preterm and Term Cord Blood Monocytes and Expansion of the CD14+CD16+ Subset upon Toll-like Receptor Stimulation

Developmentally regulated features of innate immunity are thought to place preterm and term infants at risk of infection and inflammation-related morbidity. Underlying mechanisms are incompletely understood. Differences in monocyte function including toll-like receptor (TLR) expression and signaling have been discussed. Some studies point to generally impaired TLR signaling, others to differences in individual pathways. In the present study, we assessed mRNA and protein expression of pro- and anti-inflammatory cytokines in preterm and term cord blood (CB) monocytes compared with adult controls stimulated ex vivo with Pam3CSK4, zymosan, polyinosinic:polycytidylic acid, lipopolysaccharide, flagellin, and CpG oligonucleotide, which activate the TLR1/2, TLR2/6, TLR3, TLR4, TLR5, and TLR9 pathways, respectively. In parallel, frequencies of monocyte subsets, stimulus-driven TLR expression, and phosphorylation of TLR-associated signaling molecules were analyzed. Independent of stimulus, pro-inflammatory responses of term CB monocytes equaled adult controls. The same held true for preterm CB monocytes-except for lower IL-1β levels. In contrast, CB monocytes released lower amounts of anti-inflammatory IL-10 and IL-1ra, resulting in higher ratios of pro-inflammatory to anti-inflammatory cytokines. Phosphorylation of p65, p38, and ERK1/2 correlated with adult controls. However, stimulated CB samples stood out with higher frequencies of intermediate monocytes (CD14⁺CD16⁺). Both pro-inflammatory net effect and expansion of the intermediate subset were most pronounced upon stimulation with Pam3CSK4 (TLR1/2), zymosan (TR2/6), and lipopolysaccharide (TLR4). Our data demonstrate robust pro-inflammatory and yet attenuated anti-inflammatory responses in preterm and term CB monocytes, along with imbalanced cytokine ratios. Intermediate monocytes, a subset ascribed pro-inflammatory features, might participate in this inflammatory state.

Investigation of the Effects of Monomeric and Dimeric Stilbenoids on Bacteria-Induced Cytokines and LPS-Induced ROS Formation in Bone Marrow-Derived Dendritic Cells

Stilbenoids are anti-inflammatory and antioxidant compounds, with resveratrol being the most investigated molecule in this class. However, the actions of most other stilbenoids are much less studied. This study compares five monomeric (resveratrol, piceatannol, pterostilbene, pinostilbene, and trimethoxy-resveratrol) and two dimeric (dehydro-δ-viniferin and trans-δ-viniferin) stilbenoids for their capability to modulate the production of bacteria-induced cytokines (IL-12, IL-10, and TNF-α), as well as lipopolysaccharide (LPS)-induced reactive oxygen species (ROS), in murine bone marrow-derived dendritic cells. All monomeric species showed dose-dependent inhibition of E. coli-induced IL-12 and TNF-α, whereas only resveratrol and piceatannol inhibited IL-10 production. All monomers, except trimethoxy-resveratrol, inhibited L. acidophilus-induced IL-12, IL-10, and TNF-α production. The dimer dehydro-δ-viniferin remarkably enhanced L. acidophilus-induced IL-12 production. The contrasting effect of resveratrol and dehydro-δ-viniferin on IL-12 production was due, at least in part, to a divergent inactivation of the mitogen-activated protein kinases by the two stilbenoids. Despite having moderate to high total antioxidant activity, dehydro-δ-viniferin was a weak inhibitor of LPS-induced ROS formation. Conversely, resveratrol and piceatannol potently inhibited LPS-induced ROS formation. Methylated monomers showed a decreased antioxidant capacity compared to resveratrol, also depending on the methylation site. In summary, the immune-modulating effect of the stilbenoids depends on both specific structural features of tested compounds and the stimulating bacteria.

Inflammatory phenotype, clinicopathologic variables, and effects of long-term methylene blue in dogs with hereditary methemoglobinemia caused by cytochrome b5 reductase deficiency

OBJECTIVE

To determine whether dogs with cytochrome b5 reductase (CYB5R) deficiency have a constitutive proinflammatory phenotype, characterize hematologic and serum chemistry results, and describe changes in methemoglobin (MetHb) levels and serum C-reactive protein (CRP) concentrations after long-term per os (PO) methylene blue (MB) therapy.

ANIMALS

21 client-owned dogs (CYB5R deficient, n = 10; healthy controls, 11).

PROCEDURES

In this prospective, case-control study, methemoglobin levels were measured using a blood gas analyzer with co-oximetry. Plasma tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10) concentrations were measured using a canine-specific multiplex bead-based assay. Serum CRP concentrations were measured with a canine-specific commercial ELISA kit. Serum CRP concentration and MetHb levels were measured in 6 dogs with CYB5R deficiency after ≥ 60 days of PO MB therapy.

RESULTS

As expected, MetHb levels were higher in dogs with CYB5R deficiency compared to controls (P < .001). Plasma TNF-α, IL-6, IL-10, and serum CRP concentrations were no different between CYB5R-deficient and control dogs. Dogs with CYB5R deficiency had lower absolute lymphocyte (P = .005) and eosinophil counts (P = .04) and higher alanine transaminase (P = .04) and alkaline phosphatase activity (P = .02) than controls, but these changes were not clinically relevant. Methemoglobin levels decreased after PO MB therapy (P = .03).

CLINICAL RELEVANCE

These results suggest that otherwise healthy dogs with CYB5R deficiency do not have a constitutive proinflammatory phenotype and clinically relevant abnormalities in hematologic and serum chemistry panels are not expected. Dogs with decreased quality of life attributed to methemoglobinemia from CYB5R deficiency might benefit from PO MB therapy.

Rab7l1 plays a role in regulating surface expression of toll like receptors and downstream signaling in activated macrophages

Rab GTPases are known for controlling intracellular membrane traffic in a GTP-dependent manner. Rab7l1, belonging to family of Rab GTPases, is important for both endosomal sorting and retrograde transport. In our previous study, we identified a novel role of Rab7l1 in phagosome maturation. However, its role in regulating macrophage innate-effector signaling and cytokine response is not clearly understood. In this study, we have demonstrated that upon treatment of Rab7l1-knocked-down (Rab7l1-KD) THP-1 macrophages with lipopolysaccharide (LPS) and Pam₃CSK₄ has led to higher induction levels of tumor necrosis factor-alpha (TNF-α) and interleukin-10 (IL-10) as compared to the control cells that received scrambled shRNA. Similar results were observed in Rab7l1-KD RAW 264.7 and Balb/c peritoneal macrophages. The phospho-ERK 1/2 (extracellular signal-regulated kinase 1/2) and phospho-p38 MAPK (mitogen-activated protein kinase) levels, known to be responsible for higher induction of TNF-α and IL-10 respectively, were higher in Rab7l1-KD THP-1 macrophages which also displayed higher nuclear translocation of p50/p65 nuclear factor kappa B (NF-κB) upon stimulation with LPS. Surface expression levels of toll-like receptor 2 (TLR2), TLR4 and CD14 receptors were higher in Rab7l1-KD THP-1 macrophages as compared to the control cells. However, intracellular levels of these receptors were lower in Rab7l1-KD THP-1 macrophages as compared to the control group. Together, our study suggests that Rab7l1 has a role in regulating MAPK signaling and cytokine effector responses in macrophages by regulating the surface expression of membrane receptors.

Precision-cut rat placental slices as a model to study sex-dependent inflammatory response to LPS and Poly I:C

Introduction

Maternal inflammation in pregnancy represents a major hallmark of several pregnancy complications and a significant risk factor for neurodevelopmental and neuropsychiatric disorders in the offspring. As the interface between the mother and the fetus, the placenta plays a crucial role in fetal development and programming. Moreover, studies have suggested that the placenta responds to an inflammatory environment in a sex-biased fashion. However, placenta-mediated immunoregulatory mechanisms are still poorly understood.

Methods

Therefore, we have developed a model of ex vivo precision-cut placental slices from the rat term placenta to study acute inflammatory response. Rat placental slices with a precise thickness of 200 µm were generated separately from male and female placentas. Inflammation was stimulated by exposing the slices to various concentrations of LPS or Poly I:C for 4 and 18 hours.

Results

Treatment of placental slices with LPS significantly induced the expression and release of proinflammatory cytokines TNF-α, IL-6, and IL-1β. In contrast, Poly I:C treatment resulted in a less-pronounced inflammatory response. Interestingly, the female placenta showed higher sensitivity to LPS than male placenta. Anti-inflammatory agents, curcumin, 1α,25- dihydroxyvitamin D3, and progesterone attenuated the LPS-induced proinflammatory cytokine response at both mRNA and protein levels.

Discussion

We conclude that rat placental slices represent a novel alternative model to study the role of sexual dimorphism in the acute inflammatory response and immune activation in pregnancy.

Saga of monokines in shaping tumour-immune microenvironment: Origin to execution

Cellular communication mediated by cytokines is an important mechanism dictating immune responses, their cross talk and final immune output. Cytokines play a major role in dictating the immune outcome to cancer by regulating the events of development, differentiation and activation of innate immune cells. Cytokines are pleiotropic in nature, hence understanding their role individually or as member of network cytokines is critical to delineate their role in tumour immunity. Tumour systemically manipulates the immune system to evade and escape immune recognition for their uncontrollable growth and metastasis. The developing tumour comprise a large and diverse set of myeloid cells which are vulnerable to manipulation by the tumour-microenvironment. The innate immune cells of the monocytic lineage skew the fate of the adaptive immune cells and thus dictating cancer elimination or progression. Targeting cells at tumour cite is preposterous owing to their tight network, poor reach and abundance of immunosuppressive mechanisms. Monocytic lineage-derived cytokines (monokines) play crucial role in tumour regression or progression by either directly killing the tumour cells with TNFα or promoting its growth by TGFβ. In addition, the monokines like IL-12, IL-1β, IL-6, IL-10 and TGFβ direct the adaptive immune cells to secrete anti-tumour cytokines, TNFα, IFNγ, perforin and granzyme or pro-tumour cytokines, IL-10 and TGFβ. In this review, we elucidate the roles of monokines in dictating the fate of tumour by regulating responses at various stages of generation, differentiation and activation of immune cells along with the extensive cross talk. We have attempted to delineate the synergy and antagonism of major monokines among themselves or with tumour-derived or adaptive immune cytokines. The review provides an update on the possibilities of placing monokines to potential practical use as cytokine therapy against cancer.

Mechanisms of Immune Checkpoint Inhibitor-Mediated Colitis

Immune checkpoint inhibitors (ICIs) have provided tremendous clinical benefit in several cancer types. However, systemic activation of the immune system also leads to several immune-related adverse events. Of these, ICI-mediated colitis (IMC) occurs frequently and is the one with the highest absolute fatality. To improve current treatment strategies, it is important to understand the cellular mechanisms that induce this form of colitis. In this review, we discuss important pathways that are altered in IMC in mouse models and in human colon biopsy samples. This reveals a complex interplay between several types of immune cells and the gut microbiome. In addition to a mechanistic understanding, patients at risk should be identifiable before ICI therapy. Here we propose to focus on T-cell subsets that interact with bacteria after inducing epithelial damage. Especially, intestinal resident immune cells are of interest. This may lead to a better understanding of IMC and provides opportunities for prevention and management.

Tofacitinib Suppresses IL-10/IL-10R Signaling and Modulates Host Defense Responses in Human Macrophages

Jak inhibitors are increasingly used in dermatology. Despite broad inhibitory effects on cytokine signaling cascades, they only modestly increase the risk for infectious diseases. To address the molecular mechanisms underlying this unexpected clinical observation, we investigated how tofacintib (tofa), a first-in-class Jak inhibitor, regulates host defense responses in toll-like receptor 4-activated human macrophages. Specifically, we asked whether tofa inhibits anti-inflammatory IL-10 signaling, thereby counteracting the downregulation of inflammatory, host-protective pathways. We found that tofa blocked macrophage responses to IL-10 at the level of signal transducer and activator of transcription 3 phosphorylation. Furthermore, toll-like receptor 4-induced, autocrine/paracrine IL-10/IL-10R activation promoted the expression of hepcidin, the master regulator of iron metabolism, resulting in intracellular iron sequestration. In contrast, autocrine/paracrine IL-10/IL-10R activation repressed the expression of cathelicidin antimicrobial peptide as well as antigen-presenting molecules, thus together, inducing a pathogen-favoring environment. Although tofa further repressed cathelicidin, it prevented the induction of intracellular HAMP and restored the expression of antigen-presentation molecules in toll-like receptor 4-activated macrophages. Our study supports the concept that induction of IL-10/IL-10R signaling drives a complex immune evasion strategy of intracellular microbes. Moreover, we conclude that tofa has diverging effects on macrophage host response pathways, and we identify the toll-like receptor 4-IL-10-signal transducer and activator of transcription 3-HAMP axis as a potential therapeutic target to counteract immune evasion.

Physiologically relevant aspirin concentrations trigger immunostimulatory cytokine production by human leukocytes

Acetylsalicylic acid is a globally used non-steroidal anti-inflammatory drug (NSAID) with diverse pharmacological properties, although its mechanism of immune regulation during inflammation (especially at in vivo relevant doses) remains largely speculative. Given the increase in clinical perspective of Acetylsalicylic acid in various diseases and cancer prevention, this study aimed to investigate the immunomodulatory role of physiological Acetylsalicylic acid concentrations (0.005, 0.02 and 0.2 mg/ml) in a human whole blood of infection-induced inflammation. We describe a simple, highly reliable whole blood assay using an array of toll-like receptor (TLR) ligands 1–9 in order to systematically explore the immunomodulatory activity of Acetylsalicylic acid plasma concentrations in physiologically relevant conditions. Release of inflammatory cytokines and production of prostaglandin E₂ (PGE₂) were determined directly in plasma supernatant. Experiments demonstrate for the first time that plasma concentrations of Acetylsalicylic acid significantly increased TLR ligand-triggered IL-1β, IL-10, and IL-6 production in a dose-dependent manner. In contrast, indomethacin did not exhibit this capacity, whereas cyclooxygenase (COX)-2 selective NSAID, celecoxib, induced a similar pattern like Acetylsalicylic acid, suggesting a possible relevance of COX-2. Accordingly, we found that exogenous addition of COX downstream product, PGE₂, attenuates the TLR ligand-mediated cytokine secretion by augmenting production of anti-inflammatory cytokines and inhibiting release of pro-inflammatory cytokines. Low PGE₂ levels were at least involved in the enhanced IL-1β production by Acetylsalicylic acid.

Ivacaftor partially corrects airway inflammation in a humanized G551D rat

Animal models have been highly informative for understanding the pathogenesis and progression of cystic fibrosis (CF) lung disease. In particular, the CF rat models recently developed have addressed mechanistic causes of the airway mucus defect characteristic of CF, and how these may change when cystic fibrosis transmembrane conductance regulator (CFTR) activity is restored using new modulator therapies. We hypothesized that inflammatory changes to the airway would develop spontaneously and progressively, and that these changes would be resolved with modulator therapy. To test this, we used a humanized-CFTR rat expressing the G551D variant that responds to the CFTR modulator ivacaftor. Markers typically found in the CF lung were assessed, including neutrophil influx, small airway histopathology, and inflammatory cytokine concentration. Young hG551D rats did not express inflammatory cytokines at baseline but did upregulate these in response to inflammatory trigger. As the hG551D rats aged, histopathology worsened, accompanied by neutrophil influx into the airway and increasing concentrations of TNF-α, IL-1α, and IL-6 in the airways. Ivacaftor administration reduced concentrations of these cytokines when administered to the rats at baseline but was less effective in the rats that had also received inflammatory stimulus. Therefore, we conclude that administration of ivacaftor resulted in an incomplete resolution of inflammation when rats received an external trigger, suggesting that CFTR activation may not be enough to resolve inflammation in the lungs of patients with CF.

Designed PKC-targeting bryostatin analogs modulate innate immunity and neuroinflammation

Neuroinflammation characterizes multiple neurologic diseases, including primary inflammatory conditions such as multiple sclerosis and classical neurodegenerative diseases. Aberrant activation of the innate immune system contributes to disease progression, but drugs modulating innate immunity, particularly within the central nervous system (CNS), are lacking. The CNS-penetrant natural product bryostatin-1 attenuates neuroinflammation by targeting innate myeloid cells. Supplies of natural bryostatin-1 are limited, but a recent scalable good manufacturing practice (GMP) synthesis has enabled access to it and its analogs (bryologs), the latter providing a path to more efficacious, better tolerated, and more accessible agents. Here, we show that multiple synthetically accessible bryologs replicate the anti-inflammatory effects of bryostatin-1 on innate immune cells in vitro, and a lead bryolog attenuates neuroinflammation in vivo, actions mechanistically dependent on protein kinase C (PKC) binding. Our findings identify bryologs as promising drug candidates for targeting innate immunity in neuroinflammation and create a platform for evaluation of synthetic PKC modulators in neuroinflammatory diseases.

Silencing of Ac45 Simultaneously Inhibits Osteoclast-Mediated Bone Resorption and Attenuates Dendritic Cell-Mediated Inflammation through Impairing Acidification and Cathepsin K Secretion

Endodontic disease is characterized by inflammation and destruction of periapical tissues, leading to severe bone resorption and tooth loss. ATP6AP1 (Ac45) has been implicated in human immune diseases, yet the mechanism underlying how Ac45 regulates immune response and reaction in inflammatory diseases remains unknown. We generated endodontic disease mice through bacterial infection as an inflammatory disease model and used adeno-associated virus (AAV)-mediated Ac45 RNA interference knockdown to study the function of Ac45 in periapical inflammation and bone resorption. We demonstrated that the AAV small hairpin RNA targeting Ac45 (AAV-sh-Ac45) impaired cellular acidification, extracellular acidification, and bone resorption. Our results showed that local delivery of AAV-sh-Ac45 in periapical tissues in bacterium-induced inflammatory lesions largely reduced bone destruction, inhibited inflammation, and dramatically reduced mononuclear immune cells. T-cell, macrophage, and dendritic cell infiltration in the periapical lesion was dramatically reduced, and the periodontal ligament was protected from inflammation-induced destruction. Furthermore, AAV-sh-Ac45 significantly reduced osteoclast formation and the expression of proinflammatory cytokines, such as tumor necrosis factor alpha, interleukin-10 (IL-10), IL-12, IL-1α, IL-6, and IL-17. Interestingly, AAV-sh-Ac45 impaired mature cathepsin K secretion more significantly than that by AAV-sh-C1 and AAV-sh-CtsK Unbiased genome-wide transcriptome sequencing analysis of Ctsk ^-/- dendritic cells stimulated with lipopolysaccharide demonstrated that the ablation of Ctsk dramatically reduced dendritic cell-mediated inflammatory signaling. Taken together, our results indicated that AAV-sh-Ac45 simultaneously inhibits osteoclast-mediated bone resorption and attenuates dendritic cell-mediated inflammation through impairing acidification and cathepsin K secretion. Thus, Ac45 may be a novel target for therapeutic approaches to attenuate inflammation and bone erosion in endodontic disease and other inflammation-related osteolytic diseases.

NK Cell IL-10 Production Requires IL-15 and IL-10 Driven STAT3 Activation

Natural killer (NK) cells can produce IFNγ or IL-10 to regulate inflammation and immune responses but the factors driving NK cell IL-10 secretion are poorly-defined. Here, we identified NK cell-intrinsic STAT3 activation as vital for IL-10 production during both systemic Listeria monocytogenes (Lm) infection and following IL-15 cytokine/receptor complex (IL15C) treatment for experimental cerebral malaria (ECM). In both contexts, conditional Stat3 deficiency in NK cells abrogated production of IL-10. Initial NK cell STAT3 phosphorylation was driven by IL-15. During Lm infection, this required capture or presentation of IL-15 by NK cell IL-15Rα. Persistent STAT3 activation was required to drive measurable IL-10 secretion and required NK cell expression of IL-10Rα. Survival-promoting effects of IL-15C treatment in ECM were dependent on NK cell Stat3 while NK cell-intrinsic deficiency for Stat3, Il15ra, or Il10ra abrogated NK cell IL-10 production and increased resistance against Lm. NK cell Stat3 deficiency did not impact production of IFNγ, indicating the STAT3 activation initiated by IL-15 and amplified by IL-10 selectively drives the production of anti-inflammatory IL-10 by responding NK cells.

Exclusive Temporal Stimulation of IL-10 Expression in LPS-Stimulated Mouse Macrophages by cAMP Inducers and Type I Interferons

Expression of the key anti-inflammatory cytokine IL-10 in lipopolysaccharide (LPS)-stimulated macrophages is mediated by a delayed autocrine/paracrine loop of type I interferons (IFN) to ensure timely attenuation of inflammation. We have previously shown that cAMP synergizes with early IL-10 expression by LPS, but is unable to amplify the late type I IFN-dependent activity. We now examined the mechanism of this synergistic transcription in mouse macrophages at the promoter level, and explored the crosstalk between type I IFN signaling and cAMP, using the β-adrenergic receptor agonist, isoproterenol, as a cAMP inducer. We show that silencing of the type I IFN receptor enables isoproterenol to synergize with LPS also at the late phase, implying that autocrine type I IFN activity hinders synergistic augmentation of LPS-stimulated IL-10 expression by cAMP at the late phase. Furthermore, IL-10 expression in LPS-stimulated macrophages is exclusively stimulated by either IFNα or isoproterenol. We identified a set of two proximate and inter-dependent cAMP response element (CRE) sites that cooperatively regulate early IL-10 transcription in response to isoproterenol-stimulated CREB and that further synergize with a constitutive Sp1 site. At the late phase, up-regulation of Sp1 activity by LPS-stimulated type I IFN is correlated with loss of function of the CRE sites, suggesting a mechanism for the loss of synergism when LPS-stimulated macrophages switch to type I IFN-dependent IL-10 expression. This report delineates the molecular mechanism of cAMP-accelerated IL-10 transcription in LPS-stimulated murine macrophages that can limit inflammation at its onset.

The cAMP Pathway Amplifies Early MyD88-Dependent and Type I Interferon-Independent LPS-Induced Interleukin-10 Expression in Mouse Macrophages

Interleukin-10 (IL-10) is a key anti-inflammatory cytokine, secreted by macrophages and other immune cells to attenuate inflammation. Autocrine type I interferons (IFNs) largely mediate the delayed expression of IL-10 by LPS-stimulated macrophages. We have previously shown that IL-10 is synergistically expressed in macrophages following a costimulus of a TLR agonist and cAMP. We now show that the cAMP pathway directly upregulates IL-10 transcription and plays an important permissive and synergistic role in early, but not late, LPS-stimulated IL-10 mRNA and protein expression in mouse macrophages and in a mouse septic shock model. Our results suggest that the loss of synergism is not due to desensitization of the cAMP inducing signal, and it is not mediated by a positive crosstalk between the cAMP and type I IFN pathways. First, cAMP elevation in LPS-treated cells decreased the secretion of type I IFN. Second, autocrine/paracrine type I IFNs induce IL-10 promoter reporter activity only additively, but not synergistically, with the cAMP pathway. IL-10 promoter reporter activity was synergistically induced by cAMP elevation in macrophages stimulated by an agonist of either TLR4, TLR2/6, or TLR7, receptors which signal via MyD88, but not by an agonist of TLR3 which signals independently of MyD88. Moreover, MyD88 knockout largely reduced the synergistic IL-10 expression, indicating that MyD88 is required for the synergism displayed by LPS with cAMP. This report delineates the temporal regulation of early cAMP-accelerated vs. late type I IFN-dependent IL-10 transcription in LPS-stimulated murine macrophages that can limit inflammation at its onset.

Mycobacterium bovis BCG promotes IL-10 expression by establishing a SYK/PKCα/β positive autoregulatory loop that sustains STAT3 activation

Mycobacterium ensures its survival inside macrophages and long-term infection by subverting the innate and adaptive immune response through the modulation of cytokine gene expression profiles. Different Mycobacterium species promote the expression of TGFβ and IL-10, which, at the early stages of infection, block the formation of the phagolysosome, thereby securing mycobacterial survival upon phagocytosis, and at later stages, antagonize IFNγ production and functions. Despite the key role of IL-10 in mycobacterium infection, the signal transduction pathways leading to IL-10 expression in infected macrophages are poorly understood. Here, we report that Mycobacterium bovis BCG promotes IL-10 expression and cytokine production by establishing a SYK/PKCα/β positive feedback loop that leads to STAT3 activation.

Exosomes from differentially activated macrophages influence dormancy or resurgence of breast cancer cells within bone marrow stroma

Breast cancer (BC) cells (BCCs) can retain cellular quiescence for decades, a phenomenon referred to as dormancy. BCCs show preference for the bone marrow (BM) where they can remain dormant for decades. Targeting BCCs within the BM is a challenge since the dormant BCCs reside within BM stroma, also residence for hematopoietic stem cells (HSCs). Dormant BCCs could behave as cancer stem cells (CSCs). The CSCs and HSCs are similar by function and also, by commonly expressed genes. The method by which dormant BCCs transition into clinically metastatic cells remains unclear. This study tested the hypothesis that macrophages (MΦs) within BM stroma, facilitates dormancy or reverse this state into metastatic cells. MΦs exhibiting an M2 phenotype constitute ~10% of cultured BM stroma. The M2 MΦs form gap junctional intercellular communication (GJIC) with CSCs, resulting in cycling quiescence, reduced proliferation and carboplatin resistance. In contrast, MΦs expressing the M1 phenotype reversed BC dormancy. Activation of M2a MΦs via the toll-like receptor 4 (TLR4) switched to M1 phenotype. The switch can occur by direct activation of M2a MΦs, or indirectly through activation of mesenchymal stem cells. M1 MΦ-derived exosomes activated NFкB to reverse quiescent BCCs to cycling cells. Using an in vivo model of BC dormancy, injected Mi MOs sensitized BCCs to carboplatin and increased host survival. In summary, we have shown how BM stromal MΦs, through exosomes, regulate the behavior of BCCs, by either inducing or reversing dormancy.

Mycobacterium tuberculosis Mannose-Capped Lipoarabinomannan Induces IL-10-Producing B Cells and Hinders CD4+Th1 Immunity

The importance of Th1/interferon (IFN)-γ-mediated responses in mycobacterial infection has been well established. However, little is known about B cell-mediated immunity during Mycobacterium tuberculosis (Mtb) infection. Interleukin (IL)-10-producing B cells (B10 cells), a subset of B regulatory cells (Bregs), are implicated in modulating the immune response. Herein, we found that B10 cells were significantly increased in patients with tuberculosis. Furthermore, mannose-capped lipoarabinomannan (ManLAM), a major surface lipoglycan component from Mtb, induced a significant increase in B10 cells, which enriched in CD5⁺ B1a B cells. ManLAM induced IL-10 production mainly by activating MyD88/PI3K/AKT/Ap-1 and K63-linked ubiquitination of NF-κB essential modulator/nuclear factor kappa-light-chain-enhancer of activated B cells signaling pathways in B cells via Toll-like receptor 2. IL-10 production by ManLAM-treated B cells further inhibited CD4⁺ Th1 polarization, leading to increased susceptibility to mycobacterial infection compared with ManLAM-treated IL-10^−/− B group. Thus, we report a new immunoregulation mechanism in which Mtb ManLAM-induced B10 cells negatively regulate host anti-TB cellular immunity.

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Mtb mannose-capped lipoarabinomannan (ManLAM) induces IL-10 production in B cells

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ManLAM-induced B10 cells enrich in CD5⁺ B1a B cells

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ManLAM binding with TLR2 triggers MyD88 signaling pathways of B cells

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ManLAM-induced B10 cells hinder CD4⁺Th1 immunity during Mtb infection in mice

Protective effects of guggulsterone against colitis are associated with the suppression of TREM-1 and modulation of macrophages

Triggering receptor expressed on myeloid cells 1 (TREM-1)-expressing intestinal macrophages are significantly increased in the colons of patients with inflammatory bowel disease (IBD). We focused here on the effects of guggulsterone on macrophage modulation in colitis as a potential therapeutic molecule in human IBD and explore the underlying mechanisms. Gene expression in macrophages was examined and wound-healing assay using HT-29 cells was performed. Colitis in wild-type and IL-10-, Toll-like receptor 4 (TLR4)-, and myeloid differentiation primary response 88 (MyD88)-deficient mice was induced via the administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS) into the colon. In both in vitro and in vivo experiments, guggulsterone suppressed intestinal inflammation amplified by TREM-1 stimulation, in which the suppression of NF-κB, activating protein-1, and proteasome pathways was involved. In the TNBS-induced colitis model, guggulsterone reduced disease activity index scores and TREM-1 expression, stimulated IL-10 production, and improved survival in wild-type mice. These effects were not observed in IL-10-, TLR4-, and MyD88-deficient mice. Guggulsterone also suppressed M1 polarization, yet induced the M2 phenotype in macrophages from IBD patients as well as from mice. These findings indicate that guggulsterone blocks the hyperactivation of macrophages via TREM-1 suppression and induces M2 polarization via IL-10 mediated by the TLR4 signaling pathway. Furthermore, this study provides a new rationale for the therapeutic potential of guggulsterone in the treatment of IBD. NEW & NOTEWORTHY We found that guggulsterone attenuates triggering receptor expressed on myeloid cells 1 (TREM-1)-mediated hyperactivation of macrophages and polarizes macrophages toward the M2 phenotype. This was mediated by IL-10 and partly Toll-like receptor 4 signaling pathways. Overall, these data support that guggulsterone as a natural plant sterol modulates macrophage phenotypes in colitis, which may be of novel therapeutic importance in inflammatory bowel disease treatment.

Regulation of lipoxygenase-1 and Dectin-1 on interleukin-10 in mouse Aspergillus fumigatus keratitis

AIM

To investigate the regulation of lipoxygenase (LOX)-1 and Dectin-1 on interleukin-10 (IL-10) production in mice with Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

The corneas of C57BL/6 mice were pretreated with LOX-1 inhibitor Poly(I) or Dectin-1 siRNA separately before the infection of A. fumigatus. Polymerase chain reaction (PCR) and Western blot were used to detect the expression of IL-10.

RESULTS

The mRNA and protein expressions of IL-10 were significantly increased in mice with A. fumigatus keratitis. Compared with the group pretreated with sterile water before infection, Poly(I) pretreatment suppressed IL-10 expression significantly. Compared with the group pretreated with scrambled siRNA before infection, Dectin-1 siRNA pretreatment significantly reduced IL-10 expression in response to A. fumigatus infection.

CONCLUSION

LOX-1 and Dectin-1 regulate IL-10 production in mouse A. fumigatus keratitis.

Toll-like receptor agonists partially restore the production of pro-inflammatory cytokines and type I interferon in Sézary syndrome

Sézary syndrome (SS) carries a poor prognosis, and infections represent the most frequent cause of death in SS patients. Toll-like receptors (TLRs) are a family of innate immune receptors that induce protective immune responses against infections. We sought to evaluate the ability of TLR agonists to induce inflammatory cytokine, Th2 cytokine, and type I interferon (IFN-I) production by peripheral blood mononuclear cells (PBMC) of untreated SS patients. We detected impaired IL-6, IL-10 and IL-13 secretion by PBMC induced by the agonists for TLR5, TLR3, TLR7 and TLR9 in SS patients, while it was partially recovered by TLR2/TLR4 and TLR7/8 agonists TNF secretion was restored following stimulation with TLR2/TLR4 agonists. IFN-γ was scarcely produced upon TLR activation in SS cells, albeit TLR 7/8 (CL097) enhanced their secretion at lower levels than the control group. TLR9 agonist efficiently induced IFN-I in SS patients, although this positive regulation was not observed for other cytokines, in direct contrast to the broad activity of CL097. Among the TLR agonists, TLR4 was able to induce pro-inflammatory, IL-10 and Th2 secretion, while TLR7-8 agonist induced the inflammatory cytokines, IFN-I and IFN-γ. These findings reveal a dysfunctional cytokine response upon both extracellular and intracellular TLR activation in SS patients, which was partially restored by TLRs agonists.

Understanding Progressive Multifocal Leukoencephalopathy Risk in Multiple Sclerosis Patients Treated with Immunomodulatory Therapies: A Bird's Eye View

The increased use of newer potent immunomodulatory therapies for multiple sclerosis (MS), including natalizumab, fingolimod, and dimethyl fumarate, has expanded the patient population at risk for developing progressive multifocal leukoencephalopathy (PML). These MS therapies shift the profile of lymphocytes within the central nervous system (CNS) leading to increased anti-inflammatory subsets and decreased immunosurveillance. Similar to MS, PML is a demyelinating disease of the CNS, but it is caused by the JC virus. The manifestation of PML requires the presence of an active, genetically rearranged form of the JC virus within CNS glial cells, coupled with the loss of appropriate JC virus-specific immune responses. The reliability of metrics used to predict risk for PML could be improved if all three components, i.e., viral genetic strain, localization, and host immune function, were taken into account. Advances in our understanding of the critical lymphocyte subpopulation changes induced by these MS therapies and ability to detect viral mutation and reactivation will facilitate efforts to develop these metrics.

Increased Endovascular Staphylococcus aureus Inoculum Is the Link Between Elevated Serum Interleukin 10 Concentrations and Mortality in Patients With Bacteremia

Background

Cell wall peptidoglycan stimulates interleukin 10 (IL-10) production in Staphylococcus aureus bacteremia (SaB) animal models, but clinical data are not available. This study evaluates the impact of intravascular bacterial cell numbers (ie, the level of bacteremia), in patients at the time of clinical presentation on IL-10 production and its association with S. aureus bacteremia (SaB) mortality.

Methods

Blood and isolates were collected in 133 consecutive SaB patients. Serum IL-10 was quantified by an electrochemoluminescence assay. Bacterial inoculum was measured in patient sera with elevated (n = 8) or low (n = 8) IL-10 using a magnetic bacterial capture assay. Staphylococcus aureus from these 2 groups were introduced into whole blood ex vivo to determine IL-10 production with variable inocula.

Results

IL-10 serum concentration was higher in SaB patient mortality (n = 27) vs survival (n = 106) (median, 36.0 pg/mL vs 10.4 pg/mL, respectively, P < .001). Patients with elevated IL-10 more often had endovascular SaB sources. The inoculum level of SaB was higher in patients with elevated serum IL-10 vs patients with low IL-10 (35.5 vs 0.5 median CFU/mL; P = .044). Ex vivo studies showed that 108 CFU/mL yielded greater IL-10 than did 103 CFU/mL (4.4 ± 1.8 vs 1.0 ± 0.6 pg/mL; P < .01).

Conclusions

Elevated IL-10 serum concentrations at clinical presentation of SaB were highly associated with mortality. High intravascular peptidoglycan concentration, driven by a higher level of bacteremia, is a key mediator of IL-10 anti-inflammatory response that portends poor clinical outcome. Using IL-10 as an initial biomarker, clinicians may consider more aggressive antimicrobials for rapid bacterial load reduction in high-risk SaB patients.

Inhibition of cyclin-dependent kinase 5 affects early neuroinflammatory signalling in murine model of amyloid beta toxicity

BACKGROUND

Cyclin-dependent kinase 5 (Cdk5) belongs to the family of proline-directed serine/threonine kinases and plays a critical role in neuronal differentiation, migration, synaptogenesis, plasticity, neurotransmission and apoptosis. The deregulation of Cdk5 activity was observed in post mortem analysis of brain tissue of Alzheimer's disease (AD) patients, suggesting the involvement of Cdk5 in the pathomechanism of this neurodegenerative disease. However, our recent study demonstrated the important function of Cdk5 in regulating inflammatory reaction.

METHODS

Since the role of Cdk5 in regulation of inflammatory signalling in AD is unknown, we investigated the involvement of Cdk5 in neuroinflammation induced by single intracerebroventricular (icv) injection of amyloid beta protein (Aβ) oligomers in mouse. The brain tissue was analysed up to 35 days post injection. Roscovitine (intraperitoneal administration) was used as a potent Cdk5 inhibitor. The experiments were also performed on human neuroblastoma SH-SY5Y as well as mouse BV2 cell lines treated with exogenous oligomeric Aβ.

RESULTS

Our results demonstrated that single injection of Aβ oligomers induces long-lasting activation of microglia and astrocytes in the hippocampus. We observed also profound, early inflammatory response in the mice hippocampus, leading to the significant elevation of pro-inflammatory cytokines expression (e.g. TNF-α, IL-1β, IL-6). Moreover, Aβ oligomers elevated the formation of truncated protein p25 in mouse hippocampus and induced overactivation of Cdk5 in neuronal cells. Importantly, administration of roscovitine reduced the inflammatory processes evoked by Aβ in the hippocampus, leading to the significant decrease of cytokines level.

CONCLUSIONS

These studies clearly show the involvement of Cdk5 in modulation of brain inflammatory response induced by Aβ and may indicate this kinase as a novel target for pharmacological intervention in AD.

Interferon-β regulates the production of IL-10 by toll-like receptor-activated microglia

Pattern recognition receptors, such as toll‐like receptors (TLRs), perceive tissue alterations and initiate local innate immune responses. Microglia, the resident macrophages of the brain, encode TLRs which primary role is to protect the tissue integrity. However, deregulated activation of TLRs in microglia may lead to chronic neurodegeneration. This double role of microglial responses is often reported in immune‐driven neurologic diseases, as in multiple sclerosis (MS). Consequently, strategies to manipulate microglia inflammatory responses may help to ameliorate disease progression. In this context, the anti‐inflammatory cytokine interleukin (IL)‐10 appears as an attractive target. In this study, we investigated how activation of microglia by TLRs with distinct roles in MS impacts on IL‐10 production. We found that activation of TLR2, TLR4, and TLR9 induced the production of IL‐10 to a greater extent than activation of TLR3. This was surprising as both TLR3 and IL‐10 play protective roles in animal models of MS. Interestingly, combination of TLR3 triggering with the other TLRs, enhanced IL‐10 through the modulation of its transcription, via interferon (IFN)‐β, but independently of IL‐27. Thus, in addition to the modulation of inflammatory responses of the periphery described for the axis TLR3/IFN‐β, we now report a direct modulation of microglial responses. We further show that the presence of IFN‐γ in the microenvironment abrogated the modulation of IL‐10 by TLR3, whereas that of IL‐17 had no effect. Considering the therapeutic application of IFN‐β in MS, our study bears important implications for the understanding of the cytokine network regulating microglia responses in this setting.

Defects in early cell recruitment contribute to the increased susceptibility to respiratory Klebsiella pneumoniae infection in diabetic mice

Diabetes is associated with increased susceptibility to Klebsiella pneumoniae and poor prognosis with infection. We demonstrate accelerated mortality in mice with streptozotocin-induced diabetes following tracheal instillation of K. pneumoniae. Diabetic mice recruited fewer granulocytes to the alveolar airspace and had reduced early production of CXCL1, CXCL2, IL-1β and TNF-α following tracheal instillation of K. pneumoniae-lipopolysaccharide. Additionally, TLR2 and TIRAP expression following K. pneumoniae-lipopolysaccharide exposure was decreased in hyperglycemic mice. These findings indicate that impaired innate sensing and failure to rapidly recruit granulocytes to the site of infection is a mechanism for diabetic susceptibility to respiratory K. pneumoniae infection.

Porphyromonas gingivalis Outer Membrane Vesicles Induce Selective Tumor Necrosis Factor Tolerance in a Toll-Like Receptor 4- and mTOR-Dependent Manner

Porphyromonas gingivalis is an important member of the anaerobic oral flora. Its presence fosters growth of periodontal biofilm and development of periodontitis. In this study, we demonstrated that lipophilic outer membrane vesicles (OMV) shed from P. gingivalis promote monocyte unresponsiveness to live P. gingivalis but retain reactivity to stimulation with bacterial DNA isolated from P. gingivalis or AIM2 ligand poly(dA·dT). OMV-mediated tolerance of P. gingivalis is characterized by selective abrogation of tumor necrosis factor (TNF). Neutralization of interleukin-10 (IL-10) during OMV challenge partially restores monocyte responsiveness toP. gingivalis; full reactivity toP. gingivalis can be restored by inhibition of mTOR signaling, which we previously identified as the major signaling pathway promoting Toll-like receptor 2 and Toll-like receptor 4 (TLR2/4)-mediated tolerance in monocytes. However, despite previous reports emphasizing a central role of TLR2 in innate immune recognition of P. gingivalis, our current findings highlight a selective role of TLR4 in the promotion of OMV-mediated TNF tolerance: only blockade of TLR4-and not of TLR2-restores responsiveness toP. gingivalis Of further note, OMV-mediated tolerance is preserved in the presence of cytochalasin B and chloroquine, indicating that triggering of surface TLR4 is sufficient for this effect. Taking the results together, we propose that P. gingivalis OMV contribute to local immune evasion of P. gingivalis by hampering the host response.

HIV-tuberculosis-associated immune reconstitution inflammatory syndrome is characterized by Toll-like receptor and inflammasome signalling

Patients with HIV-associated tuberculosis (TB) initiating antiretroviral therapy (ART) may develop immune reconstitution inflammatory syndrome (TB-IRIS). No biomarkers for TB-IRIS have been identified and the underlying mechanisms are unclear. Here we perform transcriptomic profiling of the blood samples of patients with HIV-associated TB. We identify differentially abundant transcripts as early as week 0.5 post ART initiation that predict downstream activation of proinflammatory cytokines in patients who progress to TB-IRIS. At the characteristic time of TB-IRIS onset (week 2), the signature is characterized by over-representation of innate immune mediators including TLR signalling and TREM-1 activation of the inflammasome. In keeping with the transcriptional data, concentrations of plasma cytokines and caspase-1/5 are elevated in TB-IRIS. Inhibition of MyD88 adaptor and group 1 caspases reduces secretion of cytokines including IL-1 in TB-IRIS patients. These data provide insight on the pathogenesis of TB-IRIS and may assist the development of specific therapies.

Some patients with HIV-associated tuberculosis develop an immune reconstitution inflammatory syndrome (TB-IRIS) in response to antiretroviral therapy. Here the authors identify genes differentially expressed in patients likely to progress to TB-IRIS and find activation of Toll-like receptor and inflammasome pathways.

Myeloid Sirtuin 2 Expression Does Not Impact Long-Term Mycobacterium tuberculosis Control

Sirtuins (Sirts) regulate several cellular mechanisms through deacetylation of several transcription factors and enzymes. Recently, Sirt2 was shown to prevent the development of inflammatory processes and its expression favors acute Listeria monocytogenes infection. The impact of this molecule in the context of chronic infections remains unknown. We found that specific Sirt2 deletion in the myeloid lineage transiently increased Mycobacterium tuberculosis load in the lungs and liver of conditional mice. Sirt2 did not affect long-term infection since no significant differences were observed in the bacterial burden at days 60 and 120 post-infection. The initial increase in M. tuberculosis growth was not due to differences in inflammatory cell infiltrates in the lung, myeloid or CD4⁺ T cells. The transcription levels of IFN-γ, IL-17, TNF, IL-6 and NOS2 were also not affected in the lungs by Sirt2-myeloid specific deletion. Overall, our results demonstrate that Sirt2 expression has a transitory effect in M. tuberculosis infection. Thus, modulation of Sirt2 activity in vivo is not expected to affect chronic infection with M. tuberculosis.

Increased expression of TLR2 in CD4(+) T cells from SLE patients enhances immune reactivity and promotes IL-17 expression through histone modifications

The innate immune system has been shown to play an important pathologic role in systemic lupus erythematosus (SLE). TLR2, a PRR, recognizes exogenous PAMPs, and endogenous damage-associated molecular patterns and has been implicated in the initiation and maintenance of the perpetuated inflammatory reactions in autoimmune diseases. Here, we report increased expression of TLR2 in CD4(+) and CD8(+) T cells, CD19(+) B cells, and CD14(+) monocytes from SLE patients. Conventional treatment, such as hydroxychloroquine and corticosteroids, showed no effect on TLR2 expression in CD4(+) T cells from SLE patients. In vitro stimulation of TLR2 in CD4(+) T cells from SLE patients increased CD40L and CD70 expression, as well as secretion of IL-6, IL-17A, IL-17F, and TNF-α, while Foxp3 transcription decreased. This effect was reversed by TLR2 siRNA. Moreover, TLR2 activation upregulated H3K4 tri-methylation and H4 acetylation levels while downregulated H3K9 tri-methylation level in the IL-17A promoter region. In addition, it also increased H4 acetylation levels and decreased H3K9 tri-methylation levels in the IL-17F promoter region. In summary, our findings demonstrate that increased expression of TLR2 contributes to immune reactivity and promotes IL-17A and IL-17F expression through histone modifications in SLE.

NMDA-receptor antagonists block B-cell function but foster IL-10 production in BCR/CD40-activated B cells

BACKGROUND

B cells are important effectors and regulators of adaptive and innate immune responses, inflammation and autoimmunity, for instance in anti-NMDA-receptor (NMDAR) encephalitis. Thus, pharmacological modulation of B-cell function could be an effective regimen in therapeutic strategies. Since the non-competitive NMDAR antagonist memantine is clinically applied to treat advanced Alzheimer`s disease and ketamine is supposed to improve the course of resistant depression, it is important to know how these drugs affect B-cell function.

RESULTS

Non-competitive NMDAR antagonists impaired B-cell receptor (BCR)- and lipopolysaccharide (LPS)-induced B-cell proliferation, reduced B-cell migration towards the chemokines SDF-1α and CCL21 and downregulated IgM and IgG secretion. Mechanistically, these effects were mediated through a blockade of Kv1.3 and KCa3.1 potassium channels and resulted in an attenuated Ca(2+)-flux and activation of Erk1/2, Akt and NFATc1. Interestingly, NMDAR antagonist treatment increased the frequency of IL-10 producing B cells after BCR/CD40 stimulation.

CONCLUSIONS

Non-competitive NMDAR antagonists attenuate BCR and Toll-like receptor 4 (TLR4) B-cell signaling and effector function and can foster IL-10 production. Consequently, NMDAR antagonists may be useful to target B cells in autoimmune diseases or pathological systemic inflammation. The drugs' additional side effects on B cells should be considered in treatments of neuronal disorders with NMDAR antagonists.

Neuroimmunological communication via CGRP promotes the development of a regulatory phenotype in TLR4-stimulated macrophages

Environmental signals shape the phenotype and function of activated macrophages. Here, we show that the neuropeptide calcitonin gene-related peptide (CGRP), which is released from sensory nerves, modulates the phenotype of TLR4-activated murine macrophages by enhancing expression of the regulatory macrophage markers IL-10, sphingosine kinase 1 (SPHK1), and LIGHT (lymphotoxin-like, exhibits inducible expression and competes with HSV glycoprotein D for herpesvirus entry mediator, a receptor expressed by T lymphocytes). In contrast, CGRP inhibits production of cytokines characteristic of inflammatory macrophages and does not affect expression of wound-healing macrophage markers upon TLR4 engagement. In IL-4-stimulated macrophages, CGRP increased LIGHT expression, but failed to induce IL-10 and SPHK1. The stimulatory effect of CGRP on IL-10 production required activation of protein kinase A and was linked to prolonged phosphorylation of CREB and sustained nuclear accumulation of CRTC2 and CRTC3 (where CRTC is CREB-regulated transcriptional cofactor). CGRP enhanced expression of regulatory macrophage markers during the early, but not late, phase of LPS-stimulation and this effect was independent of autocrine type-I IFN activity. In contrast, autocrine type-I IFN activity and treatment of macrophages with IFN-β promoted late-phase IL-10 production, but had only minor influence on LIGHT and SPHK1 expression. Together, the results identify neuroimmunological communication through CGRP as a novel costimulatory pathway promoting the development of a regulatory phenotype of TLR4-stimulated macrophages. CGRP appears to act through a mechanism that involves sustained activation of CREB-dependent gene transcription.

Scaling of immune responses against intracellular bacterial infection

Macrophages detect bacterial infection through pattern recognition receptors (PRRs) localized at the cell surface, in intracellular vesicles or in the cytosol. Discrimination of viable and virulent bacteria from non-virulent bacteria (dead or viable) is necessary to appropriately scale the anti-bacterial immune response. Such scaling of anti-bacterial immunity is necessary to control the infection, but also to avoid immunopathology or bacterial persistence. PRR-mediated detection of bacterial constituents in the cytosol rather than at the cell surface along with cytosolic recognition of secreted bacterial nucleic acids indicates viability and virulence of infecting bacteria. The effector responses triggered by activation of cytosolic PRRs, in particular the RIG-I-induced simultaneous rapid type I IFN induction and inflammasome activation, are crucial for timely control of bacterial infection by innate and adaptive immunity. The knowledge on the PRRs and the effector responses relevant for control of infection with intracellular bacteria will help to develop strategies to overcome chronic infection.