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Progression of tuberculosis is tightly linked to a disordered immune balance, resulting in inability of the host to restrict intracellular bacterial replication and its subsequent dissemination. The immune response is mainly characterized by an orchestrated recruitment of inflammatory cells secreting cytokines. This response results from the activation of innate immunity receptors that trigger downstream intracellular signaling pathways involving adaptor proteins such as the TIR-containing adaptor protein (Tirap). In humans, resistance to tuberculosis is associated with a loss-of-function in Tirap. Here, we explore how genetic deficiency in Tirap impacts resistance to Mycobacterium tuberculosis (Mtb) infection in a mouse model and ex vivo . Interestingly, compared to wild type littermates, Tirap heterozygous mice were more resistant to Mtb infection. Upon investigation at the cellular level, we observed that mycobacteria were not able to replicate in Tirap-deficient macrophages compared to wild type counterparts. We next showed that Mtb infection induced Tirap expression which prevented phagosomal acidification and rupture. We further demonstrate that the Tirap-mediated anti-tuberculosis effect occurs through a Cish-dependent signaling pathway. Our findings provide new molecular evidence about how Mtb manipulates innate immune signaling to enable intracellular replication and survival of the pathogen, thus paving the way for host-directed approaches to treat tuberculosis.

Toll‐like receptors transduce their signals through the adaptor molecule MyD88 and members of the IL‐1R‐associated kinase family (IRAK‐1, 2, M and 4). IRAK‐1 and IRAK‐2, known to form Myddosomes with MyD88–IRAK‐4, mediate TLR7‐induced TAK1‐dependent NFκB activation. IRAK‐M was previously known to function as a negative regulator that prevents the dissociation of IRAKs from MyD88, thereby inhibiting downstream signalling. However, we now found that IRAK‐M was also able to interact with MyD88–IRAK‐4 to form IRAK‐M Myddosome to mediate TLR7‐induced MEKK3‐dependent second wave NFκB activation, which is uncoupled from post‐transcriptional regulation. As a result, the IRAK‐M‐dependent pathway only induced expression of genes that are not regulated at the post‐transcriptional levels (including inhibitory molecules SOCS1, SHIP1, A20 and IκBα), exerting an overall inhibitory effect on inflammatory response. On the other hand, through interaction with IRAK‐2, IRAK‐M inhibited TLR7‐mediated production of cytokines and chemokines at translational levels. Taken together, IRAK‐M mediates TLR7‐induced MEKK3‐dependent second wave NFκB activation to produce inhibitory molecules as a negative feedback for the pathway, while exerting inhibitory effect on translational control of cytokines and chemokines. IRAK‐M was reported to inhibit TLR signalling. Now, IRAK‐M is shown to activate NFκB via interaction with MyD88/IRAK‐4 leading to the induction of a negative feedback loop that limits the inflammatory response.

The role of interleukin‐1 (IL‐1), a pro‐inflammatory cytokine, in parturition is typically noted by changes in its concentrations. Studying the expression of its receptor family, IL‐1 receptor (IL‐1R) 1, IL‐1R2, IL‐1R accessory protein (IL‐1RAcP), and its predominantly brain isoform, IL‐1RAcPb, during late gestation in the uterus in the Long‐Evans rat is another. We assessed changes in their mRNA and protein relative abundance in the uterus and compared IL‐1RAcP and IL‐1RAcPb mRNA abundance in uterus, cervix, ovaries, placenta, and whole blood of Long‐Evans rats during late gestation or in RU486 and progesterone‐treated dams using quantitative real‐time PCR and western immunoblotting. IL‐1R1, IL‐1RAcP, and IL‐1RAcPb mRNA abundance significantly increased in the uterus at delivery whereas IL‐1R2 mRNA abundance significantly decreased. IL‐1R1 protein increased at term and IL‐1R2 protein decreased at term compared to nonpregnant uteri. IL1‐RAcPb mRNA abundance was less than IL‐1RAcP, but in the lower uterine segment it was the highest of all tissues examined. RU486 stimulated preterm delivery and an increase in IL‐1R1 mRNA abundance whereas progesterone administration extended pregnancy and suppressed the increase in IL‐1R1. These data suggest that changes in uterine sensitivity to IL‐1 occur during late gestation and suggest another level of regulation for the control of delivery. The roles for IL‐1RAcP and IL‐1RAcPb need to be determined, but may relate to different intracellular signaling pathways. IL‐1R1 (A), IL‐1RAcP (C), and IL‐1RAcPb (D) mRNA abundance significantly increased in the rat uterus at delivery, whereas IL‐1R2 (B) mRNA abundance significantly decreased. Changes in uterine sensitivity to IL‐1 occur during late gestation and suggest another level of regulation for the control of delivery.

The Toll-interleukin 1 receptor superfamily includes the genes interleukin 1 receptor-like 1 ( IL1RL1 ), Toll like receptors ( TLRs ), myeloid differentiation primary-response 88 ( MyD88 ), and MyD88 adaptor-like ( TIRAP ). This study describes the interaction between MyD88, TIRAP and IL1RL1 against Helicobacter pylori infection. Cases and controls were genotyped at the polymorphic sites MyD88 rs6853, TIRAP rs8177374 and IL1RL1 rs11123923. The results show that specific combinations of IL1RL1 - TIRAP (AA-CT; P: 2,8 × 10 –17 ) and MyD88 - TIRAP - IL1RL1 (AA-CT-AA; P: 1,4 × 10 –8 ) – but not MyD88 alone—act synergistically against Helicobacter pylori. Nuclear magnetic resonance (NMR) clearly discriminates cases from controls by highlighting significantly different expression levels of several metabolites (tyrosine, tryptophan, phenylalanine, branched-chain amino acids, short chain fatty acids, glucose, sucrose, urea, etc.). NMR also identifies the following dysregulated metabolic pathways associated to Helicobacter pylori infection: phenylalanine and tyrosine metabolism, pterine biosynthesis, starch and sucrose metabolism, and galactose metabolism. Furthermore, NMR discriminates between the cases heterozygous at the  IL1RL1 locus from those homozygous at the same locus. Heterozygous patients are characterized by high levels of lactate, and IL1RL1 —both associated with anti-inflammatory activity—and low levels of the pro-inflammatory molecules IL-1β, TNF-α, COX-2, and IL-6.

Obesity is an epidemic condition linked to cardiovascular disease severity and mortality. Fat localization and type represent cardiovascular risk estimators. Importantly, visceral fat secretes adipokines known to promote low-grade inflammation that, in turn, modulate its secretome and cardiac metabolism. In this regard, IL-33 regulates the functions of various immune cells through ST2 binding and—following its role as an immune sensor to infection and stress—is involved in the pro-fibrotic remodeling of the myocardium. Here we further investigated the IL-33/ST2 effects on cardiac remodeling in obesity, focusing on molecular pathways linking adipose-derived IL-33 to the development of fibrosis or hypertrophy. We analyzed the Zucker Fatty rat model, and we developed in vitro models to mimic the adipose and myocardial relationship. We demonstrated a dysregulation of IL-33/ST2 signaling in both adipose and cardiac tissue, where they affected Epac proteins and myocardial gene expression, linked to pro-fibrotic signatures. In Zucker rats, pro-fibrotic effects were counteracted by ghrelin-induced IL-33 secretion, whose release influenced transcription factor expression and ST2 isoforms balance regulation. Finally, the effect of IL-33 signaling is dependent on several factors, such as cell types’ origin and the balancing of ST2 isoforms. Noteworthy, it is reasonable to state that considering IL-33 to have a unique protective role should be considered over-simplistic.

IL-37 is a member of the IL-1 family with profound anti-inflammatory functions. Nold and colleagues identify the receptor for IL-37 and clarify the molecular nature of the anti-inflammatory pathway induced by this cytokine. Interleukin 37 (IL-37) and IL-1R8 (SIGIRR or TIR8) are anti-inflammatory orphan members of the IL-1 ligand family and IL-1 receptor family, respectively. Here we demonstrate formation and function of the endogenous ligand-receptor complex IL-37–IL-1R8–IL-18Rα. The tripartite complex assembled rapidly on the surface of peripheral blood mononuclear cells upon stimulation with lipopolysaccharide. Silencing of IL-1R8 or IL-18Rα impaired the anti-inflammatory activity of IL-37. Whereas mice with transgenic expression of IL-37 (IL-37tg mice) with intact IL-1R8 were protected from endotoxemia, IL-1R8-deficient IL-37tg mice were not. Proteomic and transcriptomic investigations revealed that IL-37 used IL-1R8 to harness the anti-inflammatory properties of the signaling molecules Mer, PTEN, STAT3 and p62(dok) and to inhibit the kinases Fyn and TAK1 and the transcription factor NF-κB, as well as mitogen-activated protein kinases. Furthermore, IL-37–IL-1R8 exerted a pseudo-starvational effect on the metabolic checkpoint kinase mTOR. IL-37 thus bound to IL-18Rα and exploited IL-1R8 to activate a multifaceted intracellular anti-inflammatory program.

Objective and designType 2 diabetes is a pandemic disease characterized by hyperglycemia, ineffective insulin use, and insulin resistance and affecting 1 in 11 people worldwide. Inflammation-related insulin resistance is thought to play an important role in the etiology of the disease. TLR4 is the central receptor of the natural immune system and has an important role as a trigger of the inflammatory response. The IRAK1 and TIRAP are members of the TLR4 pathway and involved in the TLR4-mediated inflammatory response. Genetic variants in the TLR4 gene or in the IRAK1 and TIRAP genes may have an important role in the development of insulin resistance and type 2 diabetes by disrupting the inflammatory response. In this direction, we aimed to investigate the relationship among TLR4 and IRAK1, TIRAP gene variants, and type 2 diabetes and insulin resistance, and investigate how these variants affect inflammatory factors (TNF-α, IL-6, MCP-1, and IL-1β).Subjects and methodsIn our study, a total of seven variations on the genes of TLR4 (rs4986790, rs4986791), IRAK1 (rs1059703, rs3027898, rs7061789), and TIRAP (rs8177374, rs8177400) were genotyped by the MassARRAY® Iplex GOLD SNP genotyping in 100 type 2 diabetic patients and 100 non-diabetic individual. The TLR4 rs4986790 and rs4986791 variation was confirmed by PCR–RFLP method also. The serum IL1-β, IL6, MCP-1, and TNF-α levels were measured using enzyme-linked immunosorbent assay kits.Results and conclusionAs a result of our study, no correlation was found among TLR4, IRAK1, and TIRAP gene variants and the risk of type 2 diabetes and insulin resistance. However, TNF-α, IL-6, MCP-1, and IL-1β levels were also associated with diabetes and insulin resistance (p > 0.05). Although the gene variants were not significant in type 2 diabetes and insulin resistance groups, IRAK1, TLR4, and TIRAP gene variants were found to be associated with TNF-α, IL-6, MCP-1, and IL-1β levels.

Psoriasis is a chronic inflammatory disorder of the skin affecting approximately 2% of the world's population. Accumulating evidence has revealed that the IL-23/IL-17/IL-22 pathway is key for development of skin immunopathology. However, the role of keratinocytes and their crosstalk with immune cells at the onset of disease remains poorly understood. Here, we show that IL-36R-deficient (Il36r-/-) mice were protected from imiquimod-induced expansion of dermal IL-17-producing γδ T cells and psoriasiform dermatitis. Furthermore, IL-36R antagonist-deficient (Il36rn-/-) mice showed exacerbated pathology. TLR7 ligation on DCs induced IL-36-mediated crosstalk with keratinocytes and dermal mesenchymal cells that was crucial for control of the pathological IL-23/IL-17/IL-22 axis and disease development. Notably, mice lacking IL-23, IL-17, or IL-22 were less well protected from disease compared with Il36r-/- mice, indicating an additional distinct activity of IL-36 beyond induction of the pathological IL-23 axis. Moreover, while the absence of IL-1R1 prevented neutrophil infiltration, it did not protect from acanthosis and hyperkeratosis, demonstrating that neutrophils are dispensable for disease manifestation. These results highlight a central and unique IL-1-independent role for IL-36 in control of the IL-23/IL-17/IL-22 pathway and development of psoriasiform dermatitis.

Exacerbations of asthma and COPD are a major cause of morbidity and mortality and are responsible for significant health care costs. This study further investigates interleukin (IL)-1 pathway activation and its relationship with exacerbations of asthma and COPD. In this prospective cohort study, 95 participants with stable asthma (n=35) or COPD (n=60) were recruited and exacerbations recorded over the following 12 months. Gene expressions of IL-1 pathway biomarkers, including the IL-1 receptors ( , , and ), and signaling molecules ( , , and ), were measured in sputum using real-time quantitative polymerase chain reaction. Mediators were compared between the frequent (≥2 exacerbations in the 12 months) and infrequent exacerbators, and the predictive relationships investigated using receiver operating characteristic curves and area under the curve (AUC) values. Of the 95 participants, 89 completed the exacerbation follow-up, where 30 participants (n=22 COPD, n=8 asthma) had two or more exacerbations. At the baseline visit, expressions of IRAK2, IRAK3, PELI1, and IL1R1 were elevated in participants with frequent exacerbations of both asthma and COPD combined and separately. In the combined population, sputum gene expression of IRAK3 (AUC=75.4%; <0.001) was the best predictor of future frequent exacerbations, followed by IL1R1 (AUC=72.8%; <0.001), PELI1 (AUC=71.2%; <0.001), and IRAK2 (AUC=68.6; =0.004). High IL-1 pathway gene expression was associated with frequent prior year exacerbations and correlated with the number and severity of exacerbations. The upregulation of IL-1 pathway mediators is associated with frequent exacerbations of obstructive airway disease. Further studies should investigate these mediators as both potential diagnostic biomarkers predicting at-risk patients and novel treatment targets.

Toll-like receptor (TLR) 4 belongs to the TLR family of receptors inducing pro-inflammatory responses to invading pathogens. TLR4 is activated by lipopolysaccharide (LPS, endotoxin) of Gram-negative bacteria and sequentially triggers two signaling cascades: the first one involving TIRAP and MyD88 adaptor proteins is induced in the plasma membrane, whereas the second engaging adaptor proteins TRAM and TRIF begins in early endosomes after endocytosis of the receptor. The LPS-induced internalization of TLR4 and hence also the activation of the TRIF-dependent pathway is governed by a GPI-anchored protein, CD14. The endocytosis of TLR4 terminates the MyD88-dependent signaling, while the following endosome maturation and lysosomal degradation of TLR4 determine the duration and magnitude of the TRIF-dependent one. Alternatively, TLR4 may return to the plasma membrane, which process is still poorly understood. Therefore, the course of the LPS-induced pro-inflammatory responses depends strictly on the rates of TLR4 endocytosis and trafficking through the endo-lysosomal compartment. Notably, prolonged activation of TLR4 is linked with several hereditary human diseases, neurodegeneration and also with autoimmune diseases and cancer. Recent studies have provided ample data on the role of diverse proteins regulating the functions of early, late, and recycling endosomes in the TLR4-induced inflammation caused by LPS or phagocytosis of E. coli. In this review, we focus on the mechanisms of the internalization and intracellular trafficking of TLR4 and CD14, and also of LPS, in immune cells and discuss how dysregulation of the endo-lysosomal compartment contributes to the development of diverse human diseases.