TIR8/SIGIRR is an Interleukin-1 Receptor/Toll Like Receptor Family Member with Regulatory Functions in Inflammation and Immunity

Application of chitosan as nano carrier in the treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD), encompassing ulcerative colitis (UC) and Crohn's disease (CD), is characterized by persistent and recurrent gastrointestinal inflammation. Conventional IBD therapies often involve the use of antibiotics, NSAIDs, biological agents, and immunomodulators. While these medications can mitigate acute inflammatory symptoms, their long-term efficacy is frequently compromised due to cumulative toxic effects. In recent years, significant attention has shifted toward nanoparticle (NP)-based therapies as potential alternatives for IBD management. Various drug delivery strategies, including those targeting microbiota interactions, ligand-receptor binding, pH sensitivity, biodegradability, pressure response, and specific charge and size parameters, have been explored and optimized in animal studies. This review provides a comprehensive overview of the current landscape of chitosan NP-mediated drug delivery systems for IBD treatment. Additionally, it will discuss the prevailing challenges and propose future research directions to advance chitosan NP-based therapeutic strategies for IBD.

From periphery to center stage: 50 years of advancements in innate immunity

Over the past 50 years in the field of immunology, something of a Copernican revolution has happened. For a long time, immunologists were mainly concerned with what is termed adaptive immunity, which involves the exquisitely specific activities of lymphocytes. But the other arm of immunity, so-called "innate immunity," had been neglected. To celebrate Cell's 50th anniversary, we have put together a review of the processes and components of innate immunity and trace the seminal contributions leading to the modern state of this field. Innate immunity has joined adaptive immunity in the center of interest for all those who study the body's defenses, as well as homeostasis and pathology. We are now entering the era where therapeutic targeting of innate immune receptors and downstream signals hold substantial promise for infectious and inflammatory diseases and cancer.

Recurrent urinary tract infection genetic risk: a systematic review and gene network analysis

INTRODUCTION AND HYPOTHESIS

The development of recurrent urinary tract infections (rUTIs) is not completely understood. This review is aimed at investigating the connection between genetics and rUTIs and summarizing the results of studies that have documented variations in gene expression among individuals with rUTIs compared with healthy individuals.

METHODS

A systematic search was conducted in Cochrane, Ovid, and PubMed, limiting the results to articles published between 1 January 2000, and 5 July 2022. Only studies comparing the difference in gene expression between individuals with rUTI and healthy individuals utilizing molecular techniques to measure gene expression in blood or urine samples were included in this systematic review. Gene network and pathways analyses were performed using Cytoscape software, with input data obtained from our systematic review of differentially expressed genes in rUTIs.

RESULTS

Six studies met our criteria for inclusion. The selected studies used molecular biology methods to quantify gene expression data from blood specimens. The analysis revealed that gene expressions of CXCR1 and TLR4 decreased, whereas CXCR2, TRIF, and SIGIRR increased in patients with rUTI compared with healthy controls. The analysis demonstrated that the most significant pathways were associated with TLR receptor signaling and tolerance, I-kappa B kinase/NF-kappa B signaling, and MyD88-independent TLR signaling.

CONCLUSIONS

This systematic review uncovered gene expression variations in several candidate genes and identified a number of underlying biological pathways associated with rUTIs. These findings could shift the treatment and prevention strategies for rUTIs.

Regulatory effect of IL-38 on NF-κB pathway in systemic lupus erythematosus

BACKGROUND

IL-38 is a newly identified cytokine that exhibits immunosuppression effects. However, there are few studies focusing on the effects and mechanisms of IL-38 in the systemic lupus erythematosus (SLE).

AIM

We investigated the effects and mechanisms of IL-38 on NF-κB signaling pathway in SLE.

METHODS

Levels of IL-38, IL-36R, IL-1RAcP, IKKα/β, NF-κB, TNF-α and anti-dsDNA antibody levels in peripheral blood of SLE patients, and in peripheral blood and kidney tissues of MRL/lpr mice, were examined with real-time PCR, ELISA, Western blot and immunohistochemistry. Pathological changes of kidney were detected with PAS staining. Recombinant human IL-38 protein and IL-38 siRNA were used to intervene the PBMCs of SLE patients and MRL/lpr mice.

RESULTS

The mRNA and protein levels of IL-38 in peripheral blood of SLE patients decreased and were positively correlated. The mRNA and protein levels of IKKα/β, NF-κB, and TNF-α increased, especially in patients with active SLE. There was a negative correlation between IL-38 and the levels of IKKα/β, NF-κB and TNF-α in SLE patients. In vitro experiments showed that the levels of IKKα/β, NF-κB and TNF-α, and anti-dsDNA antibodies decreased in PBMCs of SLE patients after treatment with human recombinant IL-38 protein. These effects were reversed after IL-38 siRNA intervention. Consistent results were obtained on IL-38, IKKα/β, NF-κB, and TNF-α in MRL/lpr lupus mice after treatment with IL-38 protein or IL-38 shRNA. Additionally, kidney function (reflected by creatinine and blood urea nitrogen), anti-dsDNA antibody, complement C3, and urinary protein levels decreased after treatment with IL-38 protein but increased after IL-38 shRNA treatment. PAS staining showed IL-38 protein treatment induced mild hyperplasia of glomerular mesangial cells and a small amount of lymphocyte infiltration. However, these were aggravated after IL-38 shRNA treatment.

CONCLUSION

IL-38 may be involved in the occurrence and development of SLE by regulating the NF-κB signaling pathway. This study only discussed the relationship between IL-38 and NF-κB, and more biological functions of IL-38 need to be further studied.

SIGIRR-caspase-8 signaling mediates endothelial apoptosis in Kawasaki disease

BACKGROUND

Kawasaki disease (KD) is a kind of vasculitis with unidentified etiology. Given that the current diagnosis and therapeutic strategy of KD are mainly dependent on clinical experiences, further research to explore its pathological mechanisms is warranted.

METHODS

Enzyme linked immunosorbent assay (ELISA) was used to measure the serum levels of SIGIRR, TLR4 and caspase-8. Western blotting was applied to determine protein levels, and flow cytometry was utilized to analyze cell apoptosis. Hematoxylin eosin (HE) staining and TUNEL staining were respectively used to observe coronary artery inflammation and DNA fragmentation.

RESULTS

In this study, we found the level of SIGIRR was downregulated in KD serum and KD serum-treated endothelial cells. However, the level of caspase-8 was increased in serum from KD patients compared with healthy control (HC). Therefore, we hypothesized that SIGIRR-caspase-8 signaling may play an essential role in KD pathophysiology. In vitro experiments demonstrated that endothelial cell apoptosis in the setting of KD was associated with caspase-8 activation, and SIGIRR overexpression alleviated endothelial cell apoptosis via inhibiting caspase-8 activation. These findings were also recapitulated in the Candida albicans cell wall extracts (CAWS)-induced KD mouse model.

CONCLUSION

Our data suggest that endothelial cell apoptosis mediated by SIGIRR-caspase-8 signaling plays a crucial role in coronary endothelial damage, providing potential targets to treat KD.

Systematic Analysis of IL-1 Cytokine Signaling Suppression by HPV16 Oncoproteins

The human papillomavirus (HPV) E6 and E7 oncogenes are expressed at all stages of HPV-mediated carcinogenesis and are essential drivers of cancers caused by high-risk HPV. Some of the activities of HPV E6 and E7, such as their interactions with host cellular tumor suppressors, have been characterized extensively. There is less information about how high-risk HPV E6 and E7 alter cellular responses to cytokines that are present in HPV-infected tissues and are an important component of the tumor microenvironment. We used several models of HPV oncoprotein activity to assess how HPV16 E6 and E7 alter the cellular response to the proinflammatory cytokine IL-1β. Models of early stage HPV infection and of established HPV-positive head and neck cancers exhibited similar dysregulation of IL-1 pathway genes and suppressed transcriptional responses to IL-1β treatment. Such overlap in cell responses supports that changes induced by HPV16 E6 and E7 early in infection could persist and contribute to a dysregulated immune environment throughout carcinogenesis. HPV16 E6 and E7 also drove the upregulation of several suppressors of IL-1 cytokine signaling, including SIGIRR, both in primary keratinocytes and in cancer cells. SIGIRR knockout was insufficient to increase IL-1β-dependent gene expression in the presence of HPV16 E6 and E7, suggesting that multiple suppressors of IL-1 signaling contribute to dampened IL-1 responses in HPV16-positive cells. IMPORTANCE Human papillomavirus (HPV) infection is responsible for nearly 5% of the worldwide cancer burden. HPV-positive tumors develop over years to decades in tissues that are subject to frequent stimulation by proinflammatory cytokines. However, the effects of HPV oncoproteins on the cellular response to cytokine stimulation are not well defined. We analyzed IL-1 cytokine signaling in several models of HPV biology and disease. We found that HPV16 E6 and E7 oncoproteins mediate a broad and potent suppression of cellular responses to IL-1β in models of both early and late stages of carcinogenesis. Our data provide a resource for future investigation of IL-1 signaling in HPV-positive cells and cancers.

Functional identification of the zebrafish Interleukin-1 receptor in an embryonic model of Il-1β-induced systemic inflammation

Interleukin-1β (IL-1β) is a potent proinflammatory cytokine that plays a vital role in the innate immune system. To observe the innate immune response in vivo, several transgenic zebrafish lines have been developed to model IL-1β-induced inflammation and to visualize immune cell migration and proliferation in real time. However, our understanding of the IL-1β response in zebrafish is limited due to an incomplete genome annotation and a lack of functional data for the cytokine receptors involved in the inflammatory process. Here, we use a combination of database mining, genetic analyses, and functional assays to identify zebrafish Interleukin-1 receptor, type 1 (Il1r1). We identified putative zebrafish il1r1 candidate genes that encode proteins with predicted structures similar to human IL1R1. To examine functionality of these candidates, we designed highly effective morpholinos to disrupt gene expression in a zebrafish model of embryonic Il-1β-induced systemic inflammation. In this double transgenic model, ubb:Gal4-EcR, uas:il1βmat , the zebrafish ubiquitin b (ubb) promoter drives expression of the modified Gal4 transcription factor fused to the ecdysone receptor (EcR), which in turn drives the tightly-regulated expression and secretion of mature Il-1β only in the presence of the ecdysone analog tebufenozide (Teb). Application of Teb to ubb:Gal4-EcR, uas:il1βmat embryos causes premature death, fin degradation, substantial neutrophil expansion, and generation of reactive oxygen species (ROS). To rescue these deleterious phenotypes, we injected ubb:Gal4-EcR, uas:il1βmat embryos with putative il1r1 morpholinos and found that knockdown of only one candidate gene prevented the adverse effects caused by Il-1β. Mosaic knockout of il1r1 using the CRISPR/Cas9 system phenocopied these results. Taken together, our study identifies the functional zebrafish Il1r1 utilizing a genetic model of Il-1β-induced inflammation and provides valuable new insights to study inflammatory conditions specifically driven by Il-1β or related to Il1r1 function in zebrafish.

IL-1 family cytokines serve as 'activity recognition receptors' for aberrant protease activity indicative of danger

Members of the extended IL-1 cytokine family play key roles as instigators of inflammation in numerous infectious and sterile injury contexts and are highly enriched at barrier surfaces such as the skin, lungs and intestinal mucosa. Because IL-1 family cytokines do not possess conventional ER-golgi trafficking and secretory signals, these cytokines are typically released into the extracellular space due to tissue damage resulting in necrosis, or pathogen detection resulting in pyroptosis. The latter feature, in combination with other factors, suggests that IL-1 family cytokines serve as canonical damage-associated molecular patterns (DAMPs), which instigate inflammation in response to tissue damage. However, IL-1 family cytokines also require a proteolytic activation step and diverse intracellular, extracellular and non-self proteases have been identified that are capable of processing and activating members of this family. This suggests that IL-1 family members function as sentinels for aberrant protease activity, which is frequently associated with infection or tissue damage. Here, we overview the diversity of proteases implicated in the activation of IL-1 family cytokines and suggest that this ancient cytokine family may have evolved to complement 'pattern recognition receptors', by serving as 'activity recognition receptors' enabling the detection of aberrant enzyme activity indicative of 'danger'.

The emerging roles of IL-36, IL-37, and IL-38 in diabetes mellitus and its complications

Diabetes mellitus is a metabolic disease caused by a combination of genetics and environmental factors. The importance of the inflammatory response occurring in the pancreas and adipose tissue in the occurrence and progression of diabetes has been gradually accepted. Excess blood glucose and free fatty acids produce large amounts of inflammatory cytokines and chemokines through oxidative stress and endoplasmic reticulum stress. There is sufficient evidence that proinflammatory mediators, such as interleukin (IL)-1β, IL-6, macrophage chemotactic protein-1, and tumor necrosis factor-α, are engaged in the insulin resistance in peripheral adipose tissue and the apoptosis of pancreatic β-cells. IL-36, IL-37, and IL-38, as new members of the IL-1 family, play an indispensable effect in the regulation of immune system homeostasis and are involved in the pathogenesis of inflammatory and autoimmune diseases. Recently, the abnormal expression of IL-36, IL-37, and IL-38 in diabetes has been reported. In this review, we discuss the emerging functions, potential mechanisms, and future research directions on the role of IL-36, IL-37, and IL-38 in diabetes mellitus and its complications.

IL-33, an Alarmin of the IL-1 Family Involved in Allergic and Non Allergic Inflammation: Focus on the Mechanisms of Regulation of Its Activity

Interleukin-33 (IL-33) is a member of the interleukin-1 (IL-1) family that is expressed in the nuclei of endothelial and epithelial cells of barrier tissues, among others. It functions as an alarm signal that is released upon tissue or cellular injury. IL-33 plays a central role in the initiation and amplification of type 2 innate immune responses and allergic inflammation by activating various target cells expressing its ST2 receptor, including mast cells and type 2 innate lymphoid cells. Depending on the tissue environment, IL-33 plays a wide variety of roles in parasitic and viral host defense, tissue repair and homeostasis. IL-33 has evolved a variety of sophisticated regulatory mechanisms to control its activity, including nuclear sequestration and proteolytic processing. It is involved in many diseases, including allergic, inflammatory and infectious diseases, and is a promising therapeutic target for the treatment of severe asthma. In this review, I will summarize the literature around this fascinating pleiotropic cytokine. In the first part, I will describe the basics of IL-33, from the discovery of interleukin-33 to its function, including its expression, release and signaling pathway. The second part will be devoted to the regulation of IL-33 protein leading to its activation or inactivation.

The citrullinated/native index of autoantibodies against hnRNP-DL predicts an individual "window of treatment success" in RA patients

BACKGROUND

There is a need for biomarker to identify patients "at risk" for rheumatoid arthritis (risk-RA) and to better predict the therapeutic response and in this study we tested the hypothesis that novel native and citrullinated heterogeneous nuclear ribonucleoprotein (hnRNP)-DL autoantibodies could be possible biomarkers.

METHODS

Using protein macroarray and ELISA, epitope recognition against hnRNP-DL was analysed in sera from different developed RA disease and diagnosed SLE patients. Toll-like receptor (TLR) 7/9 and myeloid differentiation primary response gene 88 (MyD88)-dependency were studied in sera from murine disease models. HnRNP-DL expression in cultivated cells and synovial tissue was analysed by indirect immunofluorescence, immunoblot and immunohistochemistry.

RESULTS

HnRNP-DL was highly expressed in stress granules, citrullinated in the rheumatoid joint and targeted by autoantibodies either as native or citrullinated proteins in patient subsets with different developed RA disease. Structural citrullination dependent epitopes (SCEs) of hnRNP-DL were detected in 58% of the SLE patients although 98% of these sera were α-CCP-2-negative. To obtain a specific citrullinated signal value, we subtracted the native antibody value from the citrullinated signal. The citrullinated/native index of autoantibodies against hnRNP-DL (CNDL-Index) was identified as a new value for an "individual window of treatment success" in early RA and for the detection of RF IgM/α-CCP-2 seronegative RA patients (24-46%). Negative CNDL-index was found in SLE patients, risk-RA and early RA cohorts such as EIRA where the majority of these patients are DAS28-responders to methotrexate (MTX) treatment (87%). High positive CNDL-values were associated with more severe RA, shared epitope and parenchymal changes in the lung. Specifically, native α-hnRNP-DL is TLR7/9-dependent, associated with pain and ROC analysis revealed an association to initial MTX or etanercept treatment response, especially in seronegative RA patients.

CONCLUSION

CNDL-index defines people at risk to develop RA and the "window of treatment success" thereby closing the sensitivity gap in RA.

IL-37b alleviates endothelial cell apoptosis and inflammation in Kawasaki disease through IL-1R8 pathway

Kawasaki disease (KD) is an acute vasculitis of pediatric populations that may develop coronary artery aneurysms if untreated. It has been regarded as the principal cause of acquired heart disease in children of the developed countries. Interleukin (IL)-37, as one of the IL-1 family members, is a natural suppressor of inflammation that is caused by activation of innate and adaptive immunity. However, detailed roles of IL-37 in KD are largely unclear. Sera from patients with KD displayed that IL-37 level was significantly decreased compared with healthy controls (HCs). QRT-PCR and western blot analyses showed that the expression level of IL-37 variant, IL-37b, was remarkably downregulated in human umbilical vein endothelial cells (HUVECs) exposed to KD sera-treated THP1 cells. Therefore, we researched the role of IL-37b in the context of KD and hypothesized that IL-37b may have a powerful protective effect in KD patients. We first observed and substantiated the protective role of IL-37b in a mouse model of KD induced by Candida albicans cell wall extracts (CAWS). In vitro experiments demonstrated that IL-37b alleviated endothelial cell apoptosis and inflammation via IL-1R8 receptor by inhibiting ERK and NFκB activation, which were also recapitulated in the KD mouse model. Together, our findings suggest that IL-37b play an effective protective role in coronary endothelial damage in KD, providing new evidence that IL-37b is a potential candidate drug to treat KD.

Lactobacillus fermentum (MTCC-5898) alleviates Escherichia coli-induced inflammatory responses in intestinal epithelial cells by modulating immune genes and NF-κB signalling

AIM

Dietary intervention using probiotic bacteria has emerged as a promising preventive strategy in addressing foodborne infections or gastrointestinal disorders. This study investigated the immunomodulatory effects of Lactobacillus fermentum (MTCC-5898) on Escherichia coli-induced inflammatory responses in intestinal epithelial cells.

METHODS AND RESULTS

The immune response of intestinal cells (Caco-2) in the presence of probiotic Lact. fermentum was determined during exclusion, competition and displacement of E. coli as the inflammatory agent. To achieve this objective, transcriptional modulation of key immune-related genes (cytokines, pattern recognition receptors and NF-κB), release of cytokines and nuclear translocation of the NF-κB subunit p-65 were studied. Expression of pro-inflammatory cytokines IL-8, TNF-α, IFN-ϒ and IL-23 was high in E. coli-exposed intestinal cells. However, overexpression of these E. coli-induced pro-inflammatory cytokines was prevented by Lact. fermentum during exclusion and competition assays. It also modulated the transcriptional expression of regulatory cytokines (IL-10 and TGF-β), pattern recognition receptors (TLR-2 and TLR-4) and genes associated with master inflammatory regulators (NF-κB and SIGIRR) to reduce E. coli-induced inflammation. The protective effect of Lact. fermentum was further confirmed by suppression of nuclear translocation of cytoplasmic NF-κB subunit (p-65).

CONCLUSION

Lactobacillus fermentum alleviated E. coli-induced inflammatory responses by modulating the NF-κB signalling besides pro-inflammatory and regulatory cytokines expression.

SIGNIFICANCE AND IMPACT OF THE STUDY

Lactobacillus fermentum holds significant promise as a potent nutraceutical that prevents and manages inflammatory gut-associated dysfunctions.

A negative feedback loop involving NF-κB/TIR8 regulates IL-1β-induced epithelial- myofibroblast transdifferentiation in human tubular cells

Renal tubular epithelial-myofibroblast transdifferentiation (EMT) plays a central role in the development of renal interstitial fibrosis (RIF). The profibrotic cytokine interleukin (IL)-1 and the IL-1 receptor (IL-1R) also participate in RIF development, and Toll/IL-1R 8 (TIR8), a member of the Toll-like receptor superfamily, has been identified as a negative regulator of IL-1R signaling. However, the functions of TIR8 in IL-1-induced RIF remain unknown. Here, human embryonic kidney epithelial cells (HKC) and unilateral ureteric obstruction (UUO)-induced RIF models on SD rats were used to investigate the functions of TIR8 involving IL-1β-induced EMT. We showed that IL-1β primarily triggers TIR8 expression by activating nuclear factor-κB (NF-κB) in HKC cells. Conversely, high levels of TIR8 in HKC cells repress IL-1β-induced NF-κB activation and inhibit IL-1β-induced EMT. Moreover, in vitro and in vivo findings revealed that TIR8 downregulation facilitated IL-1β-induced NF-κB activation and contributed to TGF-β1-mediated EMT in renal tubular epithelial cells. These results suggested that TIR8 exerts a protective role in IL-1β-mediated EMT and potentially represents a new target for RIF treatment.

Interleukin-37 regulates innate immune signaling in human and mouse colonic organoids

Intestinal epithelial cells (IEC) reside in close proximity to the gut microbiota and are hypo-responsive to bacterial products, likely to prevent maladaptive inflammatory responses. This is in part due to their strong expression of Single Ig IL-1 related receptor (SIGIRR), a negative regulator of interleukin (IL)-1 and toll-like receptor signaling. IL-37 is an anti-inflammatory cytokine that inhibits innate signaling in diverse cells by signaling through SIGIRR. Despite the strong expression of SIGIRR by IEC, few studies have examined whether IL-37 can suppress their innate immune signaling. We characterized innate immune responses of human and murine colonoids to bacteria (FliC, LPS) and host (IL-1β) products and the role of IL-37/SIGIRR in regulating these responses. We demonstrated that human colonoids responded only to FliC, but not to LPS or IL-1β. While colonoids derived from different donors displayed significant inter-individual variability in the magnitude of their innate responses to FliC stimulation, all colonoids released a variety of chemokines. Interestingly, IL-37 attenuated these responses through inhibition of p38 and NFκB signaling pathways. We determined that this suppression by IL-37 was SIGIRR dependent, in murine organoids. Along with species-specific differences in IEC innate responses, we show that IL-37 can promote IEC hypo-responsiveness by suppressing inflammatory signaling.

IL-1 Family Antagonists in Mouse and Human Skin Inflammation

Interleukin (IL)-1 family cytokines initiate inflammatory responses, and shape innate and adaptive immunity. They play important roles in host defense, but excessive immune activation can also lead to the development of chronic inflammatory diseases. Dysregulated IL-1 family signaling is observed in a variety of skin disorders. In particular, IL-1 family cytokines have been linked to the pathogenesis of psoriasis and atopic dermatitis. The biological activity of pro-inflammatory IL-1 family agonists is controlled by the natural receptor antagonists IL-1Ra and IL-36Ra, as well as by the regulatory cytokines IL-37 and IL-38. These four anti-inflammatory IL-1 family members are constitutively and highly expressed at steady state in the epidermis, where keratinocytes are a major producing cell type. In this review, we provide an overview of the current knowledge concerning their regulatory roles in skin biology and inflammation and their therapeutic potential in human inflammatory skin diseases. We further highlight some common misunderstandings and less well-known observations, which persist in the field despite recent extensive interest for these cytokines.

Comparison of the response of mammary gland tissue from two divergent lines of goat with high and low milk somatic cell scores to an experimental Staphylococcus aureus infection

Mastitis represents one of the major economic and health threats to the livestock sector associated with reduction in milk quality, loss of production and is a major reason for culling. Somatic cell score (SCS) is used as a criterion in breeding programmes to select cows genetically less susceptible to mastitis. The relevance of SCS as a predictor of udder health and susceptibility to mastitis is still untested in goats. In this study, two lines of French Alpine goats selected for extreme breeding values for somatic cell scores, one line with high SCS (HSCS) and the other with low SCS (LSCS), were used to test the hypothesis that the mammary response and function differed between the lines. The aim of the present study was to investigate differences in the early immune response in caprine mammary gland tissues challenged with Staphylococcus aureus, one of the main pathogens responsible for the intra-mammary infection in small ruminants, using transcriptomic and histopathology analyses. The comparison between HSCS and LSCS goat lines, showed differences in the response at the histological level for inflammation, presence of neutrophils and micro-abscess formation, and at the molecular level in the expression of CXCL8, IL-6, NFKBIZ and IL-1β. CXCL8 and CXCL2 genes, which showed a higher level of expression in the experimentally infected HSCS line. The molecular data and histopathology both suggested that following S. aureus infection, mobilization, recruitment, infiltration, and chemotaxis of neutrophil, leads to a more severe inflammation in the HSCS compared to LSCS animals. Our results represent an initial basis for further studies to unravel the genetic basis of early mastitis inflammatory responses and the selection of dairy animals more resistant to bacterial mastitis.

IL-37-induced activation of glycogen synthase kinase 3β promotes IL-1R8/Sigirr phosphorylation, internalization, and degradation in lung epithelial cells

Interleukin (IL)-37 diminishes a variety of inflammatory responses through ligation to its receptor IL-1R8/Sigirr. Sigirr is a Toll like receptor/IL-1R family member. We have shown that Sigirr is not stable in response to IL-37 treatment. IL-37-induced Sigirr degradation is mediated by the ubiquitin-proteasome system, and the process is reversed by a deubiquitinase, USP13. However, the molecular mechanisms by which USP13 regulates Sigirr stability have not been revealed. In this study, we investigate the roles of glycogen synthesis kinase 3β (GSK3β) in Sigirr phosphorylation and stability. IL-37 stimulation induced Sigirr phosphorylation and degradation, as well as activation of GSK3β. Inhibition of GSK3β attenuated IL-37-induced Sigirr phosphorylation, while exogenous expressed GSK3β promoted Sigirr phosphorylation at threonine (T)372 residue. Sigirr association with GSK3β was detected. Amino acid residues 51-101 in GSK3β were identified as the Sigirr binding domain. These data indicate that GSK3β mediates IL-37-induced threonine phosphorylation of Sigirr. Further, we investigated the role of GSK3β-mediated phosphorylation of Sigirr in Sigirr degradation. Inhibition of GSK3β attenuated IL-37-induced Sigirr degradation, while T372 mutant of Sigirr was resistant to IL-37-mediated degradation. Furthermore, inhibition of Sigirr phosphorylation prevented Sigirr internalization and association with USP13, suggesting GSK3β promotes Sigirr degradation through disrupting Sigirr association with USP13.

Single immunoglobulin and Toll‑interleukin‑1 receptor domain containing molecule protects against severe acute pancreatitis in vitro by negatively regulating the Toll‑like receptor‑4 signaling pathway: A clinical and experimental study

Single immunoglobulin and Toll-interleukin-1 receptor domain-containing molecule (SIGIRR) is a specific inhibitor of IL-1R and Toll-like receptor (TLR) signaling and considered a potential target for the treatment of inflammatory diseases. Pathogenic mechanisms associated with the TLR4 signaling pathway have a critical role in the development of severe acute pancreatitis (SAP). The aim of the present study was to determine the role of SIGIRR in the regulation of TLR4 signaling during the progression of SAP. Pancreatitis-associated ascitic fluid (PAAF) was collected from patients with SAP. Murine RAW264.7 macrophages were transfected with a SIGIRR overexpression plasmid and co-cultured with the PAAF from the donors in order to evaluate the effect of SIGIRR in vitro. The mRNA expression of TLR4, SIGIRR and other key downstream signaling molecules was quantified using semi-quantitative PCR with agarose gel electrophoresis. Furthermore, the levels of pro-inflammatory cytokines in the culture supernatant were detected using ELISA. In contrast to SIGIRR, the mRNA expression levels of TLR4, myeloid differentiation factor 88 (MyD88), IL-1R-associated kinase-1 (IRAK-1) and TNF receptor-associated factor-6 (TRAF-6) were significantly increased in RAW264.7 cells following treatment with PAAF. Furthermore, TLR4, MyD88, IRAK-1 and TRAF-6 mRNA levels were significantly downregulated following SIGIRR overexpression and PAAF treatment in RAW264.7 cells. The levels of IL-2, IL-12, IL-17 and IFN-γ in the culture supernatant were also significantly decreased, while IL-10 levels were increased. Overall, SIGIRR negatively regulated the TLR4 signaling pathway to protect against the development of SAP in an in vitro model. Therefore, SIGIRR may represent a promising therapeutic target for SAP.

A Flowable Placental Formulation Prevents Bleomycin-Induced Dermal Fibrosis in Aged Mice

Fibrosis, the thickening and scarring of injured connective tissue, leads to a loss of organ function. Multiple cell types, including T-cells, macrophages, fibrocytes, and fibroblasts/myofibroblasts contribute to scar formation via secretion of inflammatory factors. This event results in an increase in oxidative stress and deposition of excessive extracellular matrix (ECM), characteristic of fibrosis. Further, aging is known to predispose connective tissue to fibrosis due to reduced tissue regeneration. In this study, we investigated the anti-fibrotic activity of a flowable placental formulation (FPF) using a bleomycin-induced dermal fibrosis model in aged mice. FPF consisted of placental amnion/chorion- and umbilical tissue-derived ECM and cells. The mice were injected with either FPF or PBS, followed by multiple doses of bleomycin. Histological assessment of FPF-treated skin samples revealed reduced dermal fibrosis, inflammation, and TGF-β signaling compared to the control group. Quantitative RT-PCR and Next Generation Sequencing analysis of miRNAs further confirmed anti-fibrotic changes in the FPF-treated group at both the gene and transcriptional levels. The observed modulation in miRNAs was associated with inflammation, TGF-β signaling, fibroblast proliferation, epithelial-mesenchymal transition and ECM deposition. These results demonstrate the potential of FPF in preventing fibrosis and may be of therapeutic benefit for those at higher risk of fibrosis due to wounds, aging, exposure to radiation and genetic predisposition.

Porcine Circovirus Type 2 Induces Single Immunoglobulin Interleukin-1 Related Receptor (SIGIRR) Downregulation to Promote Interleukin-1β Upregulation in Porcine Alveolar Macrophage

Multisystemic inflammation in pigs affected by porcine circovirus type 2 (PCV2) indicates the disordered expression of inflammatory cytokines. However, the PCV2-induced expression profile of inflammation cytokines and its regulating mechanism remain poorly understood. In this study, inflammatory cytokines and receptors in porcine alveolar macrophages (PAMs) after PCV2 infection were profiled in vitro by an RT² Profiler^TM PCR array assay. The regulatory mechanism of interleukin-1β (IL-1β) expression was investigated. Results showed that 49 of 84 inflammation cytokines and receptors were differentially expressed (p < 0.05, absolute fold change ≥2) in PAMs at different stages post-PCV2 infection. Moreover, the overexpression of single-immunoglobulin interleukin-1 related receptor (SIGIRR) or the blocking of NF-κB activation by its inhibitor markedly decreased IL-1β secretion. This finding suggested that PCV2-induced overexpression of IL-1β was associated with the downregulation of SIGIRR and the activation of NF-κB. Furthermore, the excessive activity of NF-κB in SIGIRR-knockout PAMs cell line, indicating that SIGIRR negatively regulated IL-1β production by inhibiting the activation of NF-κB. Overall, PCV2-induced downregulation of SIGIRR induction of NF-κB activation is a critical process in enhancing IL-1β production in PAMs. This study may provide insights into the underlying inflammatory response that occurs in pigs following PCV2 infection.

Potential role of IL-37 signaling pathway in feedback regulation of autoimmune Hashimoto thyroiditis

IL-37, the anti-inflammatory cytokine of the IL-1 family, plays several key roles in the regulation of autoimmune diseases. Yet, its role in Hashimoto's thyroiditis (HT) is not clear. In the present study, we found that, in tissues from HT patients, most of the follicular epithelial cells were positive for both IL-37 and single Ig IL-1-related receptor (SIGIRR) by immunohistochemical staining, while the infiltrating lymphocytes and other inflammatory cells hardly expressed any. Meanwhile, mRNA expression levels of IL-37 in peripheral blood mononuclear cells (PBMC) of HT patients were significantly higher than those in normal controls measured by quantitative real-time PCR. Finally, we studied the possible role of IL-37 in IFN-γ-stimulated rat FRTL-5 cells. The results showed that IL-1β, TNF-α, and MCP-1 mRNA levels were significantly decreased, while the expression of IL-4 mRNA was dramatically up-regulated in IFN-γ-stimulated rat thyroid cell line FRTL-5 pre-treated with IL-37. The current study, for the first time, demonstrated that the IL-37 network is involved in Hashimoto's thyroiditis, and IL-37 signaling pathway may ameliorate the excessive autoimmune responses in this chronic lymphocytic thyroiditis.

Genome-Wide Association Study in Mexican Holstein Cattle Reveals Novel Quantitative Trait Loci Regions and Confirms Mapped Loci for Resistance to Bovine Tuberculosis

Bovine tuberculosis (bTB) is a disease of cattle that represents a risk to public health and causes severe economic losses to the livestock industry. Recently, genetic studies, like genome-wide association studies (GWAS) have greatly improved the investigation of complex diseases identifying thousands of disease-associated genomic variants. Here, we present evidence of genetic variants associated with resistance to TB in Mexican dairy cattle using a case-control approach with a selective DNA pooling experimental design. A total of 154 QTLRs (quantitative trait loci regions) at 10% PFP (proportion of false positives), 42 at 5% PFP and 5 at 1% PFP have been identified, which harbored 172 annotated genes. On BTA13, five new QTLRs were identified in the MACROD2 and KIF16B genes, supporting their involvement in resistance to bTB. Six QTLRs harbor seven annotated genes that have been previously reported as involved in immune response against Mycobacterium spp: BTA (Bos taurus autosome) 1 (CD80), BTA3 (CTSS), BTA 3 (FCGR1A), BTA 23 (HFE), BTA 25 (IL21R), and BTA 29 (ANO9 and SIGIRR). We identified novel QTLRs harboring genes involved in Mycobacterium spp. immune response. This is a first screening for resistance to TB infection on Mexican dairy cattle based on a dense SNP (Single Nucleotide Polymorphism) chip.

IL-38: A New Player in Inflammatory Autoimmune Disorders

Interleukin (IL)-38, a newly discovered IL-1 family cytokine, is expressed in several tissues and secreted by various cells. IL-38 has recently been reported to exert an anti-inflammatory function by binding to several receptors, including interleukin-36 receptor (IL-36R), interleukin-1 receptor accessory protein-like 1 (IL-1RAPL1), and interleukin-1 receptor 1 (IL-1R1) to block binding with other pro-inflammatory cytokines and inhibit subsequent signaling pathways; thereby regulating the differentiation and function of T cells, peripheral blood mononuclear cells, macrophages, and dendritic cells. Inflammatory autoimmune diseases, which are common immune-mediated inflammatory syndromes, are characterized by an imbalance between T helper cells (Ths), especially Th1s and Th17s, and regulatory T cells (Tregs). Recent findings have shown that abnormal expression of IL-38 in inflammatory autoimmune diseases, such as rheumatoid arthritis, psoriatic arthritis, systemic lupus erythematosus, primary Sjogren's syndrome, psoriasis, inflammatory bowel disease, hidradenitis suppurativa, ankylosing spondylitis, and glaucoma, involves Th1s, Th17s, and Tregs. In this review, the expression, regulation, and biological function of IL-38 are discussed, as are the roles of IL-38 in various inflammatory autoimmune disorders. Current data support that the IL-38/IL-36R and/or IL-38/IL-1RAPL1 axis primarily play an anti-inflammatory role in the development and resolution of inflammatory autoimmune diseases and indicate a possible therapeutic benefit of IL-38 in these diseases.

Staphylococcus aureus intra-mammary infection affects the expression pattern of IL-R8 in goat

IL-1R8 is a member of Interleukin-1 receptor family acting as a negative regulator of inflammation reliant on ILRs and TLRs activation. IL-1R8 role has never been evaluated in acute bacterial mastitis. We first investigated IL-1R8 sequence conservation among different species and its pattern of expression in a wide panel of organs from healthy goats. Then, modulation of IL-1R8 during natural and experimental mammary infection was evaluated and compared in blood, milk and mammary tissues from healthy and Staphylococcus aureus infected goats. IL-1R8 has a highly conserved sequence among vertebrates. Goat IL-1R8 was ubiquitously expressed in epithelial and lymphoid tissues with highest levels in pancreas. IL-1R8 was down-regulated in epithelial mammary cells following S. aureus infection. Interestingly it was up-regulated in leukocytes infiltrating the infected mammary tissues suggesting that it could represent a target of S. aureus immune evasion.

IL-36, IL-37, and IL-38 Cytokines in Skin and Joint Inflammation: A Comprehensive Review of Their Therapeutic Potential

The interleukin (IL)-1 family of cytokines is composed of 11 members, including the most recently discovered IL-36α, β, γ, IL-37, and IL-38. Similar to IL-1, IL-36 cytokines are initiators and amplifiers of inflammation, whereas both IL-37 and IL-38 display anti-inflammatory activities. A few studies have outlined the role played by these cytokines in several inflammatory diseases. For instance, IL-36 agonists seem to be relevant for the pathogenesis of skin psoriasis whereas, despite being expressed within the synovial tissue, their silencing or overexpression do not critically influence the course of arthritis in mice. In this review, we will focus on the state of the art of the molecular features and biological roles of IL-36, IL-37, and IL-38 in representative skin- and joint-related inflammatory diseases, namely psoriasis, rheumatoid arthritis, and psoriatic arthritis. We will then offer an overview of the therapeutic potential of targeting the IL-36 axis in these diseases, either by blocking the proinflammatory agonists or enhancing the physiologic inhibitory feedback on the inflammation mediated by the antagonists IL-37 and IL-38.

Production of functional human interleukin 37 using plants

KEY MESSAGE

We demonstrate for the first time that a fully bioactive human IL-37, a newly discovered cytokine acting as a fundamental inhibitor of innate immunity, can be recombinantly produced in plant cells. Interleukin 37 (IL-37), a newly discovered member of the interleukin (IL)-1 family of cytokines, plays a pivotal role in limiting innate inflammation and suppressing acquired immune responses, thus holding high potential for treating a wide array of human inflammatory and autoimmune disorders. In this study, we have developed transgenic plants as a novel expression platform for production of human IL-37 (IL-37). Plant transformation vectors synthesizing various forms of the b isoform of IL-37, including an unprocessed full-length precursor form (proIL-37b), a mature form (matIL-37b) and an IL-37 fusion protein in which IL-37b was fused to soybean agglutinin (SBA-IL-37b), have been constructed and introduced into tobacco plants. The expression of all forms of IL-37b was driven by a strong constitutive 35S promoter. Transgenic tobacco plants were generated with each of these constructs. Depending on the form of IL-37b being produced, the expression level of proIL-37b reached approximately 1% of TSP, while matIL-37b expression was substantially lower (0.01% TSP). Fusion to SBA substantially increased the expression of matIL-37b, with the expression level of fusion protein accounting for 1% of TSP. Functional analysis using a cell-based in vitro assay showed that plant-made matIL-37b and proIL-37b are both biologically active, but plant-made matIL-37b exhibited significantly greater biological activity than proIL-37b. These results demonstrate that plants have great potential of being a green bioreactor for low-cost, large-scale production of biologically active IL-37.

Increased ratio of Th17 cells to SIGIRR+CD4+ T cells in peripheral blood of patients with SLE is associated with disease activity

To investigate the clinical significance of the ratio of T helper cell 17 (Th17) cells to single immunoglobulin IL-1-related receptor (SIGIRR)⁺ cluster of differentiation (CD4)⁺ T cells in patients with systemic lupus erythematosus (SLE), novel data and data from previous studies were analyzed. The frequency of Th17 cells in peripheral blood mononuclear cells (PBMCs) and their correlation with clinical data were evaluated in 48 patients with SLE and 38 healthy controls through flow cytometry. Compared with healthy controls, the percentage of Th17 cells was significantly increased in the PBMCs of patients with SLE (Z=-5.82, P<0.001). Compared with inactive SLE (ISLE), the percentage of Th17 cells in active SLE (ASLE) were significantly increased (Z=-4.26, P<0.0001). Compared with patients without lupus nephritis, the frequency of Th17 cells was significant increased (Z=-2.20, P=0.028). The frequency of Th17 cells was inversely correlated with the frequency of SIGIRR⁺CD4⁺ T cells (r=-0.61, P<0.001). The ratio of Th17 cells to SIGIRR⁺CD4⁺ T cells in ASLE was significantly increased compared with healthy controls or patients with ISLE (P<0.001) and was inversely correlated with complement component 3 and complement component 4, and positively correlated with SLE disease activity index and 24-h proteinuria (P<0.05). In summary, increased numbers of Th17 cells and decreased numbers of SIGIRR⁺CD4⁺ T cells in patients with SLE suggested that SIGIRR⁺CD4⁺ T and Th17 cells may be involved in the pathogenesis of SLE.

Effects of Sodium Houttuyfonate on Pulmonary Inflammation in COPD Model Rats

The anti-inflammatory effect of sodium houttuyfonate (SH), an herbal-originated drug that used in China clinically, was investigated on chronic obstructive pulmonary disease (COPD) inflammatory model rats induced by combination usage of cigarette smoke (CS) and lipopolysaccharide (LPS). The morphology of the lung tissue, the expression levels of cytokines in the bronchoalveolar lavage fluid (BALF), the protein levels of TLR4, NF-κB p65, and SIGIRR, and the mRNA levels of TLR4, MyD88, NF-κB p65, and SIGIRR in lung tissues were investigated, respectively. After treated by SH (24.3 mg/kg), the abnormal morphology changes of lung tissues in COPD rats, such as neutrophil infiltration and airway obstruction, were considerably alleviated, as well as both proinflammatory cytokines, TNF-α and IL-1β, significantly decreased in BALF. The mRNA level of TLR4, MyD88, and NF-κB p65 and protein expression of TLR4 and NF-κB p65 in lung tissues decreased significantly after SH treatment, while both SIGIRR mRNA and protein levels increased significantly. These results suggest that SH markedly attenuated the pulmonary inflammation induced by CS and LPS and protected the lung tissue in COPD model rat. The anti-inflammatory effects were related to suppress the TLR4/NF-κB pathway dependent on MyD88. TIR8/SIGIRR might contribute to the protective effects of SH on pulmonary inflammation.

Dichotomous function of IL-33 in health and disease: From biology to clinical implications

Interleukin (IL)-33 is a cytokine that is released from epithelial and endothelial cells at barrier surfaces upon tissue stress or damage to operate as an alarmin. IL-33 has been primarily implicated in the induction of T helper (Th) 2 type immune responses. Therefore, IL-33 has attracted a lot of interest as a potential therapeutic target in asthma and other allergic diseases. Over the years, it has become clear that IL-33 has a much broader activity and also contributes to Th1 immunity, expanding the possibilities for therapeutic modulation of IL-33 activity to multiple inflammatory diseases. However, more recently IL-33 has also been shown to mediate immunosuppression and tissue repair by activating regulatory T cells (Treg) and promoting M2 macrophage polarization. These pleiotropic activities of IL-33 illustrate the need for a tight molecular regulation of IL-33 activity, and have to be taken into account when IL-33 or its receptor is targeted for therapeutic modulation. Here we review the multiple molecular mechanisms that regulate IL-33 activity and describe how IL-33 can shape innate and adaptive immune responses by promoting Th1, Th2 and Treg function. Finally, we will discuss the possibilities for therapeutic modulation of IL-33 signaling as well as possible safety issues.

Single-Immunoglobulin Interleukin-1-Related Receptor regulates vulnerability to TLR4-mediated necrotizing enterocolitis in a mouse model

BackgroundThe mechanisms underlying aberrant activation of intestinal Toll-like receptor 4 (TLR4) signaling in necrotizing enterocolitis (NEC) remain unclear. In this study, we examined the role of single-immunoglobulin interleukin-1 receptor-related molecule (SIGIRR), an inhibitor of TLR signaling, in modulating experimental NEC vulnerability in mice.MethodsExperimental NEC was induced in neonatal wild-type and SIGIRR-/- mice using hypoxia, formula-feeding, and lipopolysaccharide administration. Intestinal TLR canonical signaling, inflammation, apoptosis, and severity of experimental NEC were examined at baseline and after NEC induction in mice.ResultsSIGIRR is developmentally regulated in the neonatal intestine with a restricted expression after birth and a gradual increase by day 8. At baseline, breast-fed SIGIRR-/- mouse pups exhibited low-grade inflammation and TLR pathway activation compared with SIGIRR+/+ pups. With experimental NEC, SIGIRR-/- mice had significantly more intestinal interleukin (IL)-1β, KC (mouse homolog to IL-8), intercellular adhesion molecule-1 (ICAM-1), and interferon-beta (IFN-β) expression in association with the amplified TLR pathway activation. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining, cleaved caspase 3, and severity of intestinal injury with NEC were worse in SIGIRR-/- mice in comparison with SIGIRR+/+ mice.ConclusionSIGIRR is a negative regulator of TLR4 signaling in the developing intestine, and its insufficiency results in native intestinal TLR hyper-responsiveness conducive to the development of severe experimental NEC in mice.

IL-36 cytokines in autoimmunity and inflammatory disease

The inteleukin-36 (IL-36) cytokines include IL-36α, IL-36β, IL-36γ and IL-36Ra, which belong to the IL-1 family and exert pro-inflammatory effects on various target cells such as keratinocytes, synoviocytes, dendritic cells and T cells. Emerging evidence has suggested a role of IL-36 in the pathogenesis of many inflammatory diseases. Here, we provide a brief review on the activation of IL-36 family cytokines and their involvement in autoimmunity and inflammatory diseases, which will provide further insights in understanding the functions of IL-36 family cytokines in the pathophysiology of autoimmunity and inflammatory diseases.

What we have lost: Mastitis resistance in Holstein Friesians and in a local cattle breed

In Holstein Friesian dairy cows, selective pressure for increased milk production has led to a higher propensity to disease, including mastitis, when compared to less selected and lower producing dairy breeds. The biology underpinning the higher resistance to disease of such "local breeds" is not fully understood. With the aim of investigating the factors associated to this phenomenon, we applied a multidisciplinary approach to compare innate immune response patterns, metabolic parameters, milk protein profiles and the milk microbiota in Holstein Friesian and Rendena cows reared in the same farm and under the same management conditions. Quarter milk samples and blood plasma were collected from all cows at dry-off, 1day after calving, 7-10days after calving and 30days after calving. Quarter milk samples were subjected to bacteriological culture, characterization of the milk microbiota by 16S metagenomics, milk protein profiling by electrophoresis and densitometry, somatic cell counting, measurement of the inflammation marker cathelicidin and assessment of different innate immune-related mediators such as lysozyme, CD45, IL-1β, TNF-α, PTX3, IL-1R8. In parallel, the main inflammometabolic parameters were measured in blood plasma samples. Despite having relatively few animals (6 moderate-yielding Holstein Friesian and 4 low-yielding Rendena) some important differences were apparent. Holstein Friesian cows showed a more severe fat mobilization and systemic inflammatory response postpartum in comparison with Rendena cows, which had a greater postpartum muscle mass and an increased amino acid mobilization compared to Holstein Friesians. Upon bacteriological analysis, contagious bacteria such as Staphylococcus aureus and Streptococcus agalactiae were absent, but significant differences were seen in the general composition of the milk microbiota of the two breeds. Concerning the milk protein abundance profile, pronounced differences were seen in colostrum, with significantly higher amounts of immunoglobulins and other immune-related proteins in Rendena. Added to this, the expression of innate immune related genes such as PTX-3, IL-1β, TNF-α, and KRT5 expression in milk epithelial and leukocyte cell components, respectively, was lower in Holstein Friesian colostrum compared with Rendena. In conclusion, several differences were observed in the two breeds, in spite of the same farming conditions. The observations reported in this work present numerous pointers to the factors that may provide autochthonous, more rustic breeds with a higher resistance to disease.

Chemopreventive Strategies for Inflammation-Related Carcinogenesis: Current Status and Future Direction

A sustained and chronically-inflamed environment is characterized by the presence of heterogeneous inflammatory cellular components, including neutrophils, macrophages, lymphocytes and fibroblasts. These infiltrated cells produce growth stimulating mediators (inflammatory cytokines and growth factors), chemotactic factors (chemokines) and genotoxic substances (reactive oxygen species and nitrogen oxide) and induce DNA damage and methylation. Therefore, chronic inflammation serves as an intrinsic niche for carcinogenesis and tumor progression. In this article, we summarize the up-to-date findings regarding definitive/possible causes and mechanisms of inflammation-related carcinogenesis derived from experimental and clinical studies. We also propose 10 strategies, as well as candidate agents for the prevention of inflammation-related carcinogenesis.

Lack of IL-1R8 in neurons causes hyperactivation of IL-1 receptor pathway and induces MECP2-dependent synaptic defects

Inflammation modifies risk and/or severity of a variety of brain diseases through still elusive molecular mechanisms. Here we show that hyperactivation of the interleukin 1 pathway, through either ablation of the interleukin 1 receptor 8 (IL-1R8, also known as SIGIRR or Tir8) or activation of IL-1R, leads to up-regulation of the mTOR pathway and increased levels of the epigenetic regulator MeCP2, bringing to disruption of dendritic spine morphology, synaptic plasticity and plasticity-related gene expression. Genetic correction of MeCP2 levels in IL-1R8 KO neurons rescues the synaptic defects. Pharmacological inhibition of IL-1R activation by Anakinra corrects transcriptional changes, restores MeCP2 levels and spine plasticity and ameliorates cognitive defects in IL-1R8 KO mice. By linking for the first time neuronal MeCP2, a key player in brain development, to immune activation and demonstrating that synaptic defects can be pharmacologically reversed, these data open the possibility for novel treatments of neurological diseases through the immune system modulation.

DOI:http://dx.doi.org/10.7554/eLife.21735.001

Errors that occur while the brain is developing can lead to conditions such as autism and schizophrenia. They can also lead to rare disorders like Rett syndrome and MeCP2 duplication syndromes, which are characterized by severe cognitive and physical disabilities. Many people with these neurodevelopmental disorders have mutations in genes that encode proteins found at synapses, which are the junctions between neurons where the cells exchange information with one another. However, not everyone with these mutations develops a neurodevelopmental disorder, which indicates that other, non-genetic factors also play a part.

One of the main non-genetic factors that can influence the risk and severity of neurodevelopmental disorders is inflammation of the brain. Inflammation is a normal part of the body’s immune response to threats such as invading microorganisms or tissue damage. However, abnormal activation of the immune system in early life can trigger excessive inflammation. This increases the risk of a neurodevelopmental disorder, but it is not clear exactly how it does so.

Tomasoni et al. set out to test whether the missing link between inflammation and neurodevelopmental disorders might be damage to synapses. The experiments revealed that genetically modified mice with inflammation of the brain have abnormal synapses and are unable to learn properly. These mutant mice also have excessive levels of a protein that influences how synapses function called MeCP2, which is missing in the brains of people with Rett syndrome and abnormally increased in brains of patients affected by MeCP2 Duplication Syndrome. This is thus the first evidence that directly links inflammation of the brain to a synapse protein implicated in a disorder of brain development.

Tomasoni et al. also found that a drug called anakinra – which is used to treat an inflammatory disease called rheumatoid arthritis – reduced levels of MeCP2 in the mutant mice and improved their performance in cognitive tasks. Together, these results raise the possibility that anti-inflammatory medications may be beneficial in the treatment of neurodevelopment disorders.

DOI:http://dx.doi.org/10.7554/eLife.21735.002

The inhibitory receptor toll interleukin-1R 8 (TIR8/IL-1R8/SIGIRR) is downregulated in chronic lymphocytic leukemia

Toll interleukin-1 receptor 8 (also known as TIR8, SIGIRR, or IL1R8) is a transmembrane receptor that inhibits inflammation. Accordingly, genetic inactivation of this protein exacerbates chronic inflammation and inflammation-associated tumors in mice. In particular, lack of TIR8 triggers leukemia progression in a mouse model of chronic lymphocytic leukemia (CLL), supporting its role as a novel tumor restrainer. The aim of this study was to measure the amount of TIR8 mRNA and protein in CLL cells, and to analyze its regulation of expression. Circulating leukemic cells expressed lower levels of TIR8 compared to normal B-lymphocytes. Treatment of CLL cells with Azacytidine restored higher levels of TIR8 suggesting that DNA methylation may be involved in modulating TIR8 expression, with implications for novel therapeutic strategies.

Pharmacological Tools to Activate Microglia and their Possible use to Study Neural Network Patho-physiology

BACKGROUND

Microglia are the resident immunocompetent cells of the CNS and also constitute a unique cell type that contributes to neural network homeostasis and function. Understanding microglia cell-signaling not only will reveal their diverse functions but also will help to identify pharmacological and non-pharmacological tools to modulate the activity of these cells.

METHODS

We undertook a search of bibliographic databases for peer-reviewed research literature to identify microglial activators and their cell-specificity. We also looked for their effects on neural network function and dysfunction.

RESULTS

We identified several pharmacological targets to modulate microglial function, which are more or less specific (with the proper control experiments). We also identified pharmacological targets that would require the development of new potent and specific modulators. We identified a wealth of evidence about the participation of microglia in neural network function and their alterations in pathological conditions.

CONCLUSION

The identification of specific microglia-activating signals provides experimental tools to modulate the activity of this heterogeneous cell type in order to evaluate its impact on other components of the nervous system, and it also helps to identify therapeutic approaches to ease some pathological conditions related to microglial dysfunction.

TLR ligands, but not modulators of histone modifiers, can induce the complex immune response pattern of endotoxin tolerance in mammary epithelial cells

Excessive stimulation of the TLR4 axis through LPS reduces the expression of some cytokine genes in immune cells, while stimulating the expression of immune defense genes during a subsequent bacterial infection. This endotoxin tolerance (ET) is mediated via epigenetic mechanisms. Priming the udder of cows with LPS was shown to induce ET in mammary epithelial cells (MEC), thereby protecting the udder against reinfection for some time. Seeking alternatives to LPS priming we tried to elicit ET by priming MEC with either lipopeptide (Pam2CSK4) via the TLR2/6 axis or inhibitors of histone-modifying enzymes. Pre-incubation of MEC with Pam2CSK4 enhanced baseline and induced expression of bactericidal (β-defensin; SLPI) and membrane protecting factors (SAA3, TGM3), while reducing the expression of cytokine- and chemokine-encoding genes (TNF, IL1β) after a subsequent pathogen challenge, the latter, however, not as efficiently as after LPS priming. Pre-treating MEC with various inhibitors of histone H3 modifiers (for demethylation, acetylation or deacetylation) all failed to induce any of the protective factors and only resulted in some dampening of cytokine gene expression after the re-challenge. Hence, triggering immune functions via the TLR axis, but not through those histone modifiers, induced the beneficial phenomenon of ET in MEC.

Cell death and inflammation: the case for IL-1 family cytokines as the canonical DAMPs of the immune system

It is well known that necrotic cells are capable of promoting inflammation through releasing so-called endogenous 'danger signals' that can promote activation of macrophages, dendritic cells, and other sentinel cells of the innate immune system. However, the identity of these endogenous proinflammatory molecules, also called damage-associated molecular patterns (DAMPs), has been debated since the 'danger model' was first advanced 20 years ago. While a relatively large number of molecules have been proposed to act as DAMPs, little consensus has emerged concerning which of these represent the key activators of sterile inflammation. Here I argue that the canonical DAMPs have long been hiding in plain sight, in the form of members of the extended IL-1 cytokine family (IL-1α, IL-1β, IL-18, IL-33, IL-36α, IL-36β, and IL-36γ). The latter cytokines possess all of the characteristics expected of endogenous DAMPs and initiate inflammation in a manner strikingly similar to that utilized by the other major category of inflammatory triggers, pathogen-associated molecular patterns (PAMPs). Furthermore, many PAMPs upregulate the expression of IL-1 family DAMPs, enabling robust synergy between these distinct classes of inflammatory triggers. Thus, multiple lines of evidence now suggest that IL-1 family cytokines represent the key initiators of necrosis-initiated sterile inflammation, as well as amplifiers of inflammation in response to infection-associated tissue injury.

Characterization of SIGIRR/IL-1R8 Homolog from Zebrafish Provides New Insights into Its Inhibitory Role in Hepatic Inflammation

Single Ig IL-1R-related molecule (SIGIRR, also called IL-1R8 or Toll/IL-1R [TIR]8), a negative regulator for Toll/IL-1R signaling, plays critical roles in innate immunity and various diseases in mammals. However, the occurrence of this molecule in ancient vertebrates and its function in liver homeostasis and disorders remain poorly understood. In this study, we identified a SIGIRR homology from zebrafish (Danio rerio [DrSIGIRR]) by using a number of conserved structural and functional hallmarks to its mammalian counterparts. DrSIGIRR was highly expressed in the liver. Ablation of DrSIGIRR by lentivirus-delivered small interfering RNA in the liver significantly enhanced hepatic inflammation in response to polyinosinic-polycytidylic acid [poly(I:C)] stimulation, as shown by the upregulation of inflammatory cytokines and increased histological disorders. In contrast, depletion of TIR domain-containing adaptor inducing IFN-β (TRIF) or administration of TRIF signaling inhibitor extremely abrogated the poly(I:C)-induced hepatic inflammation. Aided by the zebrafish embryo model, overexpression of DrSIGIRR in vivo significantly inhibited the poly(I:C)- and TRIF-induced NF-κB activations; however, knockdown of DrSIGIRR promoted such activations. Furthermore, pull-down and Duolink in situ proximity ligation assay assays showed that DrSIGIRR can interact with the TRIF protein. Results suggest that DrSIGIRR plays an inhibitory role in TRIF-mediated inflammatory reactions by competitive recruitment of the TRIF adaptor protein from its TLR3/TLR22 receptor. To our knowledge, this study is the first to report a functional SIGIRR homolog that existed in a lower vertebrate. This molecule is essential to establish liver homeostasis under inflammatory stimuli. Overall, the results will enrich the current knowledge about SIGIRR-mediated immunity and disorders in the liver.

Comparison of the pathogen species-specific immune response in udder derived cell types and their models

The outcome of an udder infection (mastitis) largely depends on the species of the invading pathogen. Gram-negative pathogens, such as Escherichia coli often elicit acute clinical mastitis while Gram-positive pathogens, such as Staphylococcus aureus tend to cause milder subclinical inflammations. It is unclear which type of the immune competent cells residing in the udder governs the pathogen species-specific physiology of mastitis and which established cell lines might provide suitable models. We therefore profiled the pathogen species-specific immune response of different cell types derived from udder and blood. Primary cultures of bovine mammary epithelial cells (pbMEC), mammary derived fibroblasts (pbMFC), and bovine monocyte-derived macrophages (boMdM) were challenged with heat-killed E. coli, S. aureus and S. uberis mastitis pathogens and their immune response was scaled against the response of established models for MEC (bovine MAC-T) and macrophages (murine RAW 264.7). Only E. coli provoked a full scale immune reaction in pbMEC, fibroblasts and MAC-T cells, as indicated by induced cytokine and chemokine expression and NF-κB activation. Weak reactions were induced by S. aureus and none by S. uberis challenges. In contrast, both models for macrophages (boMdM and RAW 264.7) reacted strongly against all the three pathogens accompanied by strong activation of NF-κB factors. Hence, the established cell models MAC-T and RAW 264.7 properly reflected key aspects of the pathogen species-specific immune response of the respective parental cell type. Our data imply that the pathogen species-specific physiology of mastitis likely relates to the respective response of MEC rather to that of professional immune cells.

CARD- and pyrin-only proteins regulating inflammasome activation and immunity

Membrane-bound and intracellular immune receptors respond to microbial pathogens by initiating signaling cascades that result in production of inflammatory cytokines and antimicrobial factors. These host responses need to be tightly regulated to prevent tissue damage and other harmful consequences of excessive inflammation. CARD-only proteins (COPs) and Pyrin-only proteins (POPs) are human- and primate-specific dominant negative inhibitors that modulate inflammatory and innate immune responses. In addition, several poxviruses encode POPs that interfere with inflammatory and host defense responses. COPs and POPs modulate inflammatory signaling at several checkpoints by sequestering key components of the inflammasome and NF-κB signaling cascades, thus hampering downstream signal transduction. Here, we review and discuss current understanding of the evolutionary history and molecular mechanisms by which roles of host- and virus-encoded COPs and POPs may regulate inflammatory and immune responses. In addition, we address their (patho)physiological roles and highlight topics for further research.

Allergic airway inflammation: unravelling the relationship between IL-37, IL-18Rα and Tir8/SIGIRR

The hallmarks of allergic bronchial asthma arise from chronic airway inflammation. Thus, elucidating the mechanisms regulating the maintenance of this chronic inflammatory response is key to understanding asthma pathogenesis. To date, it is not clear whether a predominance of proinflammatory factors or a reduced capacity of counterbalancing anti-inflammatory mediators is the pivotal factor predisposing individuals towards asthma development. The IL-1 cytokine family and its receptor systems comprise a variety of proinflammatory cytokines like IL-1β and IL-18 and anti-inflammatory molecules such as the Toll/interleukin-1 receptor 8/single Ig IL-1 receptor (IL-R)-related molecule (Tir8/SIGIRR) and the recently established cytokine IL-37. This article reviews the functions of these IL-1 cytokine family members in the regulation of allergic airway inflammation and asthma as they have been assessed clinically, in vitro and in mouse models.

A Structural View of Negative Regulation of the Toll-like Receptor-Mediated Inflammatory Pathway

Even though the Toll-like receptor (TLR) pathway is integral to inflammatory defense mechanisms, its excessive signaling may be devastating. Cells have acquired a cascade of strategies to regulate TLR signaling by targeting protein-protein interactions, or ubiquitin chains, but the details of the inhibition mechanisms are still unclear. Here, we provide the structural basis for the regulation of TLR signaling by constructing architectures of protein-protein interactions. Structural data suggest that 1) Toll/IL-1R (TIR) domain-containing regulators (BCAP, SIGIRR, and ST2) interfere with TIR domain signalosome formation; 2) major deubiquitinases such as A20, CYLD, and DUBA prevent association of TRAF6 and TRAF3 with their partners, in addition to removing K63-linked ubiquitin chains that serve as a docking platform for downstream effectors; 3) alternative downstream pathways of TLRs also restrict signaling by competing to bind common partners through shared binding sites. We also performed in silico mutagenesis analysis to characterize the effects of oncogenic mutations on the negative regulators and to observe the cellular outcome (whether there is/is not inflammation). Missense mutations that fall on interfaces and nonsense/frameshift mutations that result in truncated negative regulators disrupt the interactions with the targets, thereby enabling constitutive activation of the nuclear factor-kappa B, and contributing to chronic inflammation, autoimmune diseases, and oncogenesis.

SIGIRR/TIR8, an important regulator of TLR4 and IL-1R-mediated NF-κB activation, predicts biochemical recurrence after prostatectomy in low-grade prostate carcinomas

Single Ig IL-1-related receptor (SIGIRR) is a negative regulator of toll-like receptor 4 and IL-1-mediated activation of nuclear factor κ-light-chain enhancer of activated B cells. The purpose of this study was to qualitatively and quantitatively determine SIGIRR protein expression in human prostate tissues and associate SIGIRR expression with clinical parameters. SIGIRR expression was quantified in glandular prostate tissue using immunohistochemistry and multispectral imaging, and expression was evaluated in relation to clinicopathological features of benign prostatic hyperplasia and prostate cancer (PCa). Subgroupings of low Gleason score (≤ 6 and 3 + 4) and high Gleason score (4 + 3 and ≥ 8) were used for patient outcomes. SIGIRR was predominantly expressed in the cytoplasm and nucleus of the prostatic epithelium with little expression within the stroma. Compared with normal prostate, cytoplasmic SIGIRR expression was similar in benign prostatic hyperplasia, high-grade prostatic intraepithelial neoplasia, PCa, and metastases. A decrease in nuclear expression was found in metastasis samples (P = .04). Changes in SIGIRR expression were not associated with Gleason score, pathological stage, tumor volume, surgical margin status, or serum prostate-specific antigen (P > .05). Nuclear (P = .96) and cytoplasmic (P = .89) SIGIRR expressions were not related to patient outcomes in univariable analysis, but in the analysis of patients with low Gleason scores, high cytoplasmic SIGIRR expression was associated with biochemical recurrence in both univariable (P = .01) and multivariable (hazard ratio, 2.31 [95% confidence interval 1.05-5.06]; P = .04) analyses. Similarly, in multivariable analysis of only low-stage (pT2) tumors, SIGIRR independently predicted biochemical recurrence (P = .009). We conclude that SIGIRR predicts biochemical recurrence in patients with low Gleason score and low pathological stage PCa.

α-TLR2 antibody attenuates the Aβ-mediated inflammatory response in microglia through enhanced expression of SIGIRR

The immunoregulatory function of single-Ig-interleukin-1 related receptor (SIGIRR) is derived from its ability to constrain the inflammatory consequences of interleukin (IL)-1R and toll-like receptor (TLR)4 activation. This role extends to the brain, where SIGIRR deficiency increases the synaptic and cognitive dysfunction associated with IL-1R- and TLR4-mediated signalling. The current study set out to investigate the interaction between SIGIRR and TLR2 in brain tissue and the data demonstrate that the response to the TLR2 agonist, Pam3CysSK4 (Pam3Cys4), is enhanced in glial cells from SIGIRR(-/-) animals. Consistent with the view that β-amyloid peptide (Aβ) signals through activation of TLR2, the data also show that Aβ-induced changes are exaggerated in glia from SIGIRR(-/-) animals. We report that microglia, rather than astrocytes, are the primary glial cell expressing both TLR2 and SIGIRR. While Aβ increased TLR2 expression, it decreased SIGIRR expression in microglia. This was mimicked by direct activation of TLR2 with Pam3Cys4. We investigated the effect of an anti-TLR2 antibody (αTLR2) on the Aβ-induced inflammatory responses and demonstrate that it prevented the expression and release of the pro-inflammatory cytokines TNFα and IL-6 from microglia. In addition, application of αTLR2 alleviated the Aβ-mediated impairment in long-term potentiation (LTP) of hippocampal synaptic activity. The protective effects of αTLR2 were accompanied by an up-regulation in SIGIRR expression. We propose that a mechanism involving activation of PI3 kinase/Akt and the transcription factor peroxisome proliferator-activated receptor (PPAR)γ may facilitate this increase in SIGIRR. These findings highlight a novel role of SIGIRR as a negative regulator of TLR2-mediated inflammation in the brain.

Transcriptomic signatures in whole blood of patients who acquire a chronic inflammatory response syndrome (CIRS) following an exposure to the marine toxin ciguatoxin

Background

Ciguatoxins (CTXs) are polyether marine neurotoxins found in multiple reef-fish species and are potent activators of voltage-gated sodium channels. It is estimated that up to 500,000 people annually experience acute ciguatera poisoning from consuming toxic fish and a small percentage of these victims will develop a chronic, multisymptom, multisystem illness, which can last years, termed a Chronic Inflammatory Response Syndrome (CIRS). Symptoms of ciguatera CIRS include fatigue, cognitive deficits, neurologic deficits, pain and sensitivity to light. There are few treatment options for ciguatera CIRS since little is known about its pathophysiology.

Methods

This study characterizes the transcriptional profile in whole blood of 11 patients with ciguatera-induced CIRS and 11 normal controls run in duplicate using Agilent one color whole genome microarrays. Differential expression was determined by using a combination of moderated t-test p-value and fold change (FC). Significant genes were subjected to gene ontology, principal component analysis and SVM classification. Seven significant genes found by microarray were validated by PCR.

Results

Using a low stringency (p < 0.05 and FC > 1.4) and a high stringency (p < 0.01 and FC > 1.5) filter, the resulting gene sets of 185 and 55, respectively, showed clear separation of cases and controls by PCA as well as 100% classification accuracy by SVM, indicating that the gene profiles can separate patients from controls. PCR results of 7 genes showed a 95% correlation to microarray data. Several genes identified by microarray are important in wound healing (CD9, CD36, vWF and Factor XIII), adaptive immunity (HLA-DQB1, DQB2, IL18R1 and IL5RA) and innate immunity (GZMK, TOLLIP, SIGIRR and VIPR2), overlapping several areas shown to be disrupted in a mouse model of acute exposure to ciguatoxin. Another area of interest was differential expression of long, non-coding sequences, or lncRNA.

Conclusions

Disruptions of innate and adaptive immune mechanisms were recorded at both the genomic and proteomic level. A disruption in the HLA-T cell receptor axis could indicate HLA haplotype sensitivity for this chronic syndrome, as noted in many autoimmune conditions. Taken together, these indicators of illness provide additional insights into pathophysiology and potential therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0089-x) contains supplementary material, which is available to authorized users.