Pyroptosis in platelets: Thrombocytopenia and inflammation

OBJECTIVE

The purpose of this manuscript was to conclude the role of platelets in immune inflammation and discuss the complex mechanisms of pyroptosis in platelets as well as their related diseases.

METHODS

This article reviewed the existing literature to see the development of pyroptosis in platelets.

RESULTS

Platelets have been shown to be capable of activating inflammasomes assembled from NOD-like receptor family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a CARD (ASC) and caspase-1. Recently, they were also implicated in pyroptosis. Cleaved by caspase-1, N-terminal gasdermin D (N-GSDMD) could form pores in the cell membrane, inducing nonselective intracellular substance release. This programmed cell death induced thrombocytopenia and inflammatory cytokine release such as IL-1β and IL-18, promoting platelet aggregation, vaso-occlusion, endothelial permeability and cascaded inflammatory response.

CONCLUSION

Pyroptosis in platelets contributes to thrombocytopenia and inflammation.

IL-1R8: A molecular brake of anti-tumor and anti-viral activity of NK cells and ILC

Interleukin-1 receptor family members (ILRs) and Toll-Like Receptors (TLRs) play pivotal role in immunity and inflammation and are expressed by most cell types including cells of both the innate and adaptive immune system. In this context, IL-1 superfamily members are also important players in regulating function and differentiation of adaptive and innate lymphoid cells. This system is tightly regulated in order to avoid uncontrolled activation, which may lead to detrimental inflammation contributing to autoimmune or allergic responses. IL-1R8 (also known as TIR8 or SIGIRR) is a member of the IL-1R family that acts as a negative regulator dampening ILR and TLR signaling and as a co-receptor for human IL-37. Human and mouse NK cells, that are key players in immune surveillance of tumors and infections, express high level of IL-1R8. In this review, we will summarize our current understanding on the structure, expression and function of IL-1R8 and we will also discuss the emerging role of IL-1R8 as an important checkpoint regulating NK cells function in pathological conditions including cancer and viral infections.

Flow Cytometry Analysis of IL-1 Receptors and Toll-Like Receptors on Platelets and Platelet-Derived Extracellular Vesicles

Flow cytometry is largely used for the immunophenotyping and quantification of several cell types or related components including platelets and extracellular vesicles. Platelets and platelet-derived extracellular vesicles (PEVs) are receiving increased interest in inflammatory diseases including sepsis. Thus, in this chapter, we will describe protocols for the flow cytometry analysis of platelets, platelet/neutrophils hetero aggregates, and PEVs mainly focusing on the evaluation of the surface expression of some IL-1 receptor (ILR) and Toll-like receptor (TLR) family members.

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.

Molecular characterization and functional analysis of DIGIRR from golden pompano (Trachinotus ovatus)

Mammalian single immunoglobulin (Ig) interleukin-1 receptor related molecule (SIGIRR), an important member of the Toll/interleukin-1 receptor (TIR) family, plays important balancing roles in the inflammatory responses. In the present study, the double Ig interleukin-1 receptor related molecule (DIGIRR), the homologous of SIGIRR, was characterized in golden pompano (Trachinotus ovatus) (termed as trDIGIRR). The full-length cDNA of trDIGIRR was 2,167 bp with an open reading frame (ORF) of 1,572 bp encoding 523 amino acids. The trDIGIRR contained several conserved domains including a signal peptide, two Ig domains, a transmembrane domain and a TIR domain, and shared high sequence identities with its teleost counterparts. Realtime qPCR analysis revealed that the trDIGIRR was distributed in all tissues examined, with high expressions in intestine, liver and head kidney. The expressions of trDIGIRR were induced by Vibrio alginolyticus, lipopolysaccharide (LPS) and polyinosinic-polycytidylic acid (poly I:C) challenge. Further analysis revealed that trDIGIRR was mainly located in the cytoplasm. In addition, the co-immunoprecipitation (co-IP) assay identified that trDIGIRR could interact with myeloid differentiation factor 88 (MyD88), but not interact with TIR domain containing adaptor protein inducing interferon-β (TRIF). Our results provide basis for studying the immune role of fish DIGIRR.

SIGIRR Downregulation and Interleukin-1 Signaling Intrinsic to Renal Cell Carcinoma

Renal cell carcinoma is highly inflamed, and tumor cells are embedded into a microenvironment enriched with IL1. While inflammatory pathways are well characterized in the immune system, less is known about these same pathways in epithelial cells; it is unclear if and how innate immune signals directly impact on cancer cells, and if we could we manipulate these for therapeutic purposes. To address these questions, we first focused on the inflammatory receptors belonging to the IL1- and Toll-like receptor family including negative regulators in a small cohort of 12 clear cell RCC (ccRCC) patients’ samples as compared to their coupled adjacent normal tissues. Our data demonstrated that renal epithelial cancer cells showed a specific and distinctive pattern of inflammatory receptor expression marked by a consistent downregulation of the inhibitory receptor SIGIRR mRNA. This repression was confirmed at the protein level in both cancer cell lines and primary tissues. When we analyzed in silico data of different kidney cancer histotypes, we identified the clear cell subtype as the one where SIGIRR was mostly downregulated; nonetheless, papillary and chromophobe tumor types also showed low levels as compared to their normal counterpart. RNA-sequencing analysis demonstrated that IL1 stimulation of the ccRCC cell line A498 triggered an intrinsic signature of inflammatory pathway activation characterized by the induction of distinct “pro-tumor” genes including several chemokines, the autocrine growth factor IL6, the atypical co-transcription factor NFKBIZ, and the checkpoint inhibitor PD-L1. When we looked for the macroareas most represented among the differentially expressed genes, additional clusters emerged including pathways involved in cell differentiation, angiogenesis, and wound healing. To note, SIGIRR overexpression in A498 cells dampened IL1 signaling as assessed by a reduced induction of NFKBIZ. Our results suggest that SIGIRR downregulation unleashes IL1 signaling intrinsic to tumor cells and that manipulating this pathway may be beneficial in ccRCC.

IL-1R8 as Pathoimmunological Marker for Severity of Canine Chronic Enteropathy

Chronic enteropathy (CE) is a severe multifactorial gastrointestinal disease that affects dogs and is driven by poorly characterized inflammatory pathways. Imbalance of pro-inflammatory response regulators, including IL-1R8, may be due to different factors, among which the infection with Helicobacteraceae is known to lead to a vicious circle in which excessive pro-inflammatory signaling and gastrointestinal injury reinforce each other and boost the disease. We investigated the expression of IL-1R8 in large intestine biopsies of dogs with or without clinical signs of CE and with previously assessed enterohepatic Helicobacter spp. colonization status by mean of quantitative real-time PCR. Our study revealed that IL-1R8 is downregulated in both acutely (p = 0.0074) and chronically (p = 0.0159) CE affected dogs compared to healthy controls. The data also showed that IL-1R8 expression tends to decrease with colonization by Helicobacter spp. Interestingly, a negative correlation was detected between the level of expression of IL-1R8 and the severity of macroscopic lesions identified by endoscopy and the crypt hyperplasia score. We further compared the expression levels between males and females and found no statistically significant difference between the two groups. No significant difference was observed in IL-1R8 expression profiles with the age of the animals either. Interestingly, an association was uncovered between IL-1R8 expression level and dog breed. Together, our data advance knowledge on gastrointestinal pathoimmunology in dogs and highlight the potential utilization of IL-1R8 as a diagnostic, prognostic and therapeutic biomarker for canine chronic enteropathy.

Negative Regulation of the IL-1 System by IL-1R2 and IL-1R8: Relevance in Pathophysiology and Disease

Interleukin-1 (IL-1) is a primary cytokine of innate immunity and inflammation. IL-1 belongs to a complex family including ligands with agonist activity, receptor antagonists, and an anti-inflammatory cytokine. The receptors for these ligands, the IL-1 Receptor (IL-1R) family, include signaling receptor complexes, decoy receptors, and negative regulators. Agonists and regulatory molecules co-evolved, suggesting the evolutionary relevance of a tight control of inflammatory responses, which ensures a balance between amplification of innate immunity and uncontrolled inflammation. IL-1 family members interact with innate immunity cells promoting innate immunity, as well as with innate and adaptive lymphoid cells, contributing to their differentiation and functional polarization and plasticity. Here we will review the properties of two key regulatory receptors of the IL-1 system, IL-1R2, the first decoy receptor identified, and IL-1R8, a pleiotropic regulator of different IL-1 family members and co-receptor for IL-37, the anti-inflammatory member of the IL-1 family. Their complex impact in pathology, ranging from infections and inflammatory responses, to cancer and neurologic disorders, as well as clinical implications and potential therapeutic exploitation will be presented.

IL-1R8 silencing improves the anti-tumor function of freshly isolated human NK cells

The inhibitory receptor interleukin-1 receptor 8 (IL-1R8) has been recently recognized to be expressed also by human natural killer (NK) cells. This study was aimed to design and optimize IL-1R8 silencing conditions in human NK cells to precisely establish the activity of such receptor in these cells. Electroporation of freshly isolated or IL-2-cultured NK cells with small interfering RNA (siRNA), resulted in a marked, even though variable, IL-1R8-silencing. Although the expression profile revealed downregulation of most genes involved in several intracellular pathways, some genes related to proliferation, expression of some chemokine receptors, antibody-dependent cell cytotoxicity and cytotoxic activity were upregulated in IL-1R8-silenced NK cells. Furthermore, upon IL-15 activation, the majority of genes involved in NK cell function were upregulated in IL-1R8-siRNA—compared with control—siRNA-transfected NK cells. More importantly, in agreement with these findings, the reduction of IL-1R8 gene expression levels resulted in enhanced expression of NK cell activation markers, production of cytokines and chemokines, and cytotoxic activity against several NK cell targets with different susceptibility to NK-mediated lysis. Similar results were obtained following stimulation with IL-18. All together these data, deeply impacting on the main effector functions of human NK cells, can lead to a better understanding of IL-1R8-mediated regulation on these cells and to the design of new strategies for improving NK cell-mediated anti-tumor responses.

The probable role and therapeutic potential of the PI3K/AKT signaling pathway in SARS-CoV-2 induced coagulopathy

Coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), is associated with a high mortality rate. The majority of deaths in this disease are caused by ARDS (acute respiratory distress syndrome) followed by cytokine storm and coagulation complications. Although alterations in the level of the number of coagulation factors have been detected in samples from COVID-19 patients, the direct molecular mechanism which has been involved in this pathologic process has not been explored yet. The PI3K/AKT signaling pathway is an intracellular pathway which plays a central role in cell survival. Also, in recent years the association between this pathway and coagulopathies has been well clarified. Therefore, based on the evidence on over-activity of the PI3K/AKT signaling pathway in SARS-CoV-2 infection, in the current review, the probable role of this cellular pathway as a therapeutic target for the prevention of coagulation complications in patients with COVID-19 is discussed.

Platelet Behavior Contributes to Neuropathologies: A Focus on Alzheimer's and Parkinson's Disease

The functions of platelets are broad. Platelets function in hemostasis and thrombosis, inflammation and immune responses, vascular regulation, and host defense against invading pathogens, among others. These actions are achieved through the release of a wide set of coagulative, vascular, inflammatory, and other factors as well as diverse cell surface receptors involved in the same activities. As active participants in these physiological processes, platelets become involved in signaling pathways and pathological reactions that contribute to diseases that are defined by inflammation (including by pathogen-derived stimuli), vascular dysfunction, and coagulation. These diseases include Alzheimer's and Parkinson's disease, the two most common neurodegenerative diseases. Despite their unique pathological and clinical features, significant shared pathological processes exist between these two conditions, particularly relating to a central inflammatory mechanism involving both neuroinflammation and inflammation in the systemic environment, but also neurovascular dysfunction and coagulopathy, processes which also share initiation factors and receptors. This triad of dysfunction-(neuro)inflammation, neurovascular dysfunction, and hypercoagulation-illustrates the important roles platelets play in neuropathology. Although some mechanisms are understudied in Alzheimer's and Parkinson's disease, a strong case can be made for the relevance of platelets in neurodegeneration-related processes.

Negative Effects of SIGIRR on TRAF6 Ubiquitination in Acute Lung Injury In Vitro

In this study, the effects of single immunoglobin IL-1 receptor-related protein (SIGIRR) on tumor necrosis factor- (TNF-) receptor-associated factor 6 (TRAF6) ubiquitination in acute lung injury (ALI) were evaluated in both alveolar epithelial cells and alveolar macrophage cells in vitro. Our results found that SIGIRR negatively regulated TRAF6 ubiquitination and such SIGIRR inhibition could enhance the TRAF6 expression in both alveolar epithelial cells (AECs) and alveolar macrophage cells (AMCs). SIGIRR knockdown may increase NF-κB activity via TRAF6 regulation by the classical but not the nonclassical NF-κB signaling pathway. Such modulation between TRAF6 and SIGIRR could affect cytokine secretion and exacerbate the immune response; the IL-8, NFKB1, and NFKBIA mRNA levels were reduced after SIGIRR overexpression. The current study reveals the molecular mechanisms of the negative regulatory roles of SIGIRR on the innate immune response related to the LPS/TLR-4 signaling pathway and provides evidence for strategies to clinically treat inflammatory diseases.

Galactosaminogalactan secreted from Aspergillus fumigatus and Aspergillus flavus induces platelet activation

Platelets are meanwhile recognized as versatile elements within the immune system and appear to play a key role in the innate immune response to pathogens including fungi. Previous experiments revealed platelet activation by direct contact with the hyphal-associated polysaccharide galactosaminogalactan (GAG). Since secreted fungal products may also be relevant and trigger immune reactions or thrombosis, we screened culture supernatants (SN) of human-pathogenic fungi for their capacity to activate platelets. For that purpose, platelets were incubated with SN from various fungal species; platelet activation and GAG deposition on the surface of platelets were detected by flow cytometry and electron and confocal microscopy, Culture supernatants of Aspergillus fumigatus and flavus isolates were potent platelet stimulators in a dose- and time-dependent manner, while SN of other Aspergillus species and all tested mucormycete species did not significantly induce platelet activation. The capacity of culture SN to activate platelets was dependent on fungal production of GAG and deposition of secreted GAG on the platelet surface; supernatants from mucormycetes or mutants of A. fumigatus lacking GAG secretion did not affect platelet activity. These results suggest that invading fungi can stimulate platelets not only locally through direct interactions with fungal hyphae, but can also act over a certain distance through secreted GAG.

The TLR9 agonist (GNKG168) induces a unique immune activation pattern in vivo in children with minimal residual disease positive acute leukemia: Results of the TACL T2009-008 phase I study

Background: Preclinical studies show that TLR9 agonists can eradicate leukemia by induction of immune responses in vivo against AML and ALL. These studies demonstrated that TLR9 agonists induce an immediate NK response followed by adaptive T and B cells responses resulting in long term anti-leukemia immunity. Methods: The Therapeutic Advances in Childhood Leukemia and Lymphoma Phase I consortium performed a pilot study on 3 patients with MRD positive acute leukemia after an initial remission on conventional chemotherapy (TACL T2009-008) with the TLR 9 agonist (GNKG168). To guide future trial development, we evaluated the impact of GNKG168 by Nanostring on the expression 608 genes before and 8 days after initiation of GNKG168 therapy. Results: Twenty-three out of 578 markers on the nanostring panel showed significant difference (p ≤ 0.05). We focused on 8 markers that had the greatest differences with p < 0.01. Two genes were increased, promyelocytic leukemia protein (PML) and H-RAS, and 6 were decreased, Single Ig and TIR Domain containing (SIGIRR, IL1R8), interleukin 1 receptor 1 (IL1RL1, ST2), C-C Motif chemokine receptor 8 (CCR8), interleukin 7 R (IL7R), cluster of differentiation 8B (CD8B), and cluster of differentiation 3 (CD3D). Tumor inhibitory pathways were downregulated including the SIGIRR (IL1R8), important in IL-37 signaling and NK cell inhibition. TLR9 can induce IL-33, which is known to downregulate ST2 (IL1RL1) a receptor for IL-33. Conclusion: GNKG168 therapy is associated with immunologic changes in pediatric leukemia patients. Further work with a larger sample size is required to assess the impact of these changes on disease treatment and persistence of leukemia remission.

Parkinson's Disease: A Systemic Inflammatory Disease Accompanied by Bacterial Inflammagens

Parkinson’s disease (PD) is a well-known neurodegenerative disease with a strong association established with systemic inflammation. Recently, the role of the gingipain protease group from Porphyromonas gingivalis was implicated in Alzheimer’s disease and here we present evidence, using a fluorescent antibody to detect gingipain R1 (RgpA), of its presence in a PD population. To further elucidate the action of this gingipain, as well as the action of the lipopolysaccharide (LPS) from P. gingivalis, low concentrations of recombinant RgpA and LPS were added to purified fluorescent fibrinogen. We also substantiate previous findings regarding PD by emphasizing the presence of systemic inflammation via multiplex cytokine analysis, and demonstrate hypercoagulation using thromboelastography (TEG), confocal and electron microscopy. Biomarker analysis confirmed significantly increased levels of circulating proinflammatory cytokines. In our PD and control blood analysis, our results show increased hypercoagulation, the presence of amyloid formation in plasma, and profound ultrastructural changes to platelets. Our laboratory analysis of purified fibrinogen with added RgpA, and/or LPS, showed preliminary data with regards to the actions of the protease and the bacterial membrane inflammagen on plasma proteins, to better understand the nature of established PD.

The intestinal microbiota and cardiovascular disease

The intestinal microbiota of human hosts is the community of microorganisms living in the small and, mainly, the large intestine of humans. This microbial ecosystem has co-evolved with humans across the millennia, has come to play an important interactive role in human physiology and has been aptly called our forgotten organ. Significant properties of the microbiota benefiting its host include energy harvest from food sources indigestible by humans, protection from pathogen colonization, and vitamin synthesis. Mounting evidence has linked changes in the composition or metabolic profiles of the microbiota with human disease, including disorders of the cardiovascular spectrum. Although cause and effect mechanisms are as yet essentially unproven in the relevant literature, the established associations point to the importance of the microbiota in the pathophysiology of cardiovascular disease (CVD). In this review, we first summarize key information on the gut microbial communities and the elaborate tools developed to analyse their structure and metabolic functions. Ecological terms are explained and analytical techniques are simplified, to enhance the understanding of published studies. Statistical methods used in microbial analysis are also described in simple terms. We then present published literature on the association of the compositional and functional changes of the microbiota with CVD, including heart failure, hypertension, and atherosclerosis. Each section of the review deals with the underlying pathophysiology of the relevant associations, connecting the observational and mechanistic aspects. Finally, we discuss the challenges that remain to be met before this field of research can generate knowledge which can impact everyday clinical practice.

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.

Toll-like receptor-mediated inflammation markers are strongly induced in heart tissue in patients with cardiac disease under both ischemic and non-ischemic conditions

BACKGROUND

A sustained low grade inflammatory state is a recognized feature of various diseases, including cardiovascular disease. This state of chronic inflammation involves activation of Toll-like receptor (TLR) signaling. However, little is known regarding the genetic profile of TLR components in cardiac tissue from patients with cardiac disease.

METHODS

In this study we investigated the genetic profile of 84 TLR markers in a unique set of cardiac tissue from patients that had undergone either coronary artery bypass grafting (CABG) or aortic valve replacement (AVR). In addition, we compared the gene data from the cardiac tissue with the same gene profile in blood as well as circulating cytokines to elucidate possible targets in blood that could be used to estimate the inflammatory state of the heart in cardiac disease.

RESULTS

We found a marked upregulation of TLR-induced inflammation in cardiac tissue from both patient groups compared to healthy controls. The inflammation appeared to be primarily mediated through TLR1, 3, 7, 8 and 10, resulting in a marked induction of mediators of the innate immune response. Furthermore, the gene expression data in combination with unbiased multivariate analysis suggested a difference in inflammatory response in ischemic cardiac tissue compared to non-ischemic cardiac tissue. Serum levels of IL-13 were significantly elevated in both CABG and AVR patients compared to controls, whereas other cytokines did not appear to coincide with cardiac TLR-induced inflammation.

CONCLUSIONS

We propose that cardiac disease in humans may be mediated by local cardiac TLR signaling under both ischemic and non-ischemic conditions.

The Role of Human Platelet Preparation for Toll-Like Receptors 2 and 4 Related Platelet Responsiveness

Background  Like immune cells, platelets express the repertoire of toll-like receptors (TLR), among them TLR2 and TLR4, which are important for the recognition of bacterial patterns. Receptor-mediated functional effects in platelets have been investigated, but reliable conclusions are tampered due to heterogeneous study designs with variable platelet preparation methods. This study compares TLR2- and TLR4-dependent platelet responsiveness in platelet-rich plasma (PRP) and in washed platelets (WPs).

Material and Methods  Fresh peripheral blood samples from healthy donors served for the preparation of PRP and WP. Basal and agonist-stimulated TLR2 and TLR4 expression levels were evaluated by flow cytometry. Light transmission aggregometry was used to investigate functional effects of TLR2 and TLR4 stimulation with Pam3CSK4 or LPS (lipopolysaccharides from Escherichia coli ) as ligands. The capacity of chemokine release was determined by immunoassays.

Results  Pam3CSK4 and LPS (in combination with thrombin) were able to induce aggregation in WP, but not in PRP, with threshold concentrations of 15 µg/mL. Basal expression levels of TLR2 and TLR4 were higher in WP than in PRP, increasing several-fold rapidly and persistently upon platelet activation with potent agonists. Pam3CSK4 (15 µg/mL) or LPS led to the submaximal release of RANTES, PF4, PDGF, NAP-2, and sCD40L from WP. In PRP, secretory effects are less pronounced for RANTES, PDGF, or PF4, and not detectable for NAP-2 or sCD40L.

Conclusion  The effects mediated by TLR2 and TLR4 stimulation are dependent on platelet preparation, an important issue for experimental designs and for manufacturing of platelet concentrates in transfusion medicine.

Interleukin-1 and Related Cytokines in the Regulation of Inflammation and Immunity

Forty years after its naming, interleukin-1 (IL-1) is experiencing a renaissance brought on by the growing understanding of its context-dependent roles and advances in the clinic. Recent studies have identified important roles for members of the IL-1 family-IL-18, IL-33, IL-36, IL-37, and IL-38-in inflammation and immunity. Here, we review the complex functions of IL-1 family members in the orchestration of innate and adaptive immune responses and their diversity and plasticity. We discuss the varied roles of IL-1 family members in immune homeostasis and their contribution to pathologies, including autoimmunity and auto-inflammation, dysmetabolism, cardiovascular disorders, and cancer. The trans-disease therapeutic activity of anti-IL-1 strategies argues for immunity and inflammation as a metanarrative of modern medicine.

Tuning inflammation and immunity by the negative regulators IL-1R2 and IL-1R8

Interleukin-1 receptor family members (ILRs) and Toll-Like Receptors (TLRs) are key players in immunity and inflammation and are tightly regulated at different levels. Most cell types, including cells of the innate and adaptive immune system express ILRs and TLRs. In addition, IL-1 family members are emerging as key players in the differentiation and function of innate and adaptive lymphoid cells. IL-1R2 and IL-1R8 (also known as TIR8 or SIGIRR) are members of the ILR family acting as negative regulators of the IL-1 system. IL-1R2 binds IL-1 and the accessory protein IL-1RAcP without activating signaling and can be released as a soluble form (sIL-1R2), thus modulating IL-1 availability for the signaling receptor. IL-1R8 dampens ILR- and TLR-mediated cell activation and it is a component of the receptor recognizing human IL-37. Here, we summarize our current understanding of the structure and function of IL-1R2 and IL-1R8, focusing on their role in different pathological conditions, ranging from infectious and sterile inflammation, to autoimmunity and cancer-related inflammation. We also address the emerging evidence regarding the role of IL-1R8 as a crucial checkpoint molecule in NK cells in anti-cancer and antiviral activity and the potential therapeutic implications of IL-1R8 blockade in specific pathological contexts.