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.

Intracellular IL-1 Receptor Antagonist Isoform 1 Released from Keratinocytes upon Cell Death Acts as an Inhibitor for the Alarmin IL-1α.

The inflammatory effects of IL-1α/β are controlled by IL-1R antagonist (IL-1Ra). One IL-1Ra isoform is secreted, whereas three other isoforms (intracellular IL-1Ra [icIL-1Ra] 1, 2, and 3) are supposed to remain intracellular because of the absence of a signal peptide. In contrast to the well-characterized function of the secreted isoform, the biological role of the intracellular isoforms remains largely unclear.

β Cell-Specific Deletion of the IL-1 Receptor Antagonist Impairs β Cell Proliferation and Insulin Secretion.

Interleukin-1 receptor antagonist (IL-1Ra) is elevated in the circulation during obesity and type 2 diabetes (T2D) but is decreased in islets from patients with T2D. The protective role of local IL-1Ra was investigated in pancreatic islet β cell (βIL-1Ra)-specific versus myeloid-cell (myeloIL-1Ra)-specific IL-1Ra knockout (KO) mice. Deletion of IL-1Ra in β cells, but not in myeloid cells, resulted in diminished islet IL-1Ra expression.

Unopposed IL-18 signaling leads to severe TLR9-induced macrophage activation syndrome in mice.

The term macrophage activation syndrome (MAS) defines a severe, potentially fatal disorder characterized by overwhelming inflammation and multiorgan involvement. Interleukin-18 (IL-18) is a proinflammatory cytokine belonging to the IL-1 family, the activity of which is regulated by its endogenous inhibitor IL-18 binding protein (IL-18BP). Elevated IL-18 levels have been reported in patients with MAS.

Deficiency in IL-1 Receptor Type 2 Aggravates K/BxN Serum Transfer-Induced Arthritis in Mice but Has No Impact on Systemic Inflammatory Responses.

The biological activity of IL-1 is tightly regulated by the specific receptor antagonist (IL-1Ra) and the decoy receptor IL-1 receptor type 2 (IL-1R2). The role of IL-1Ra has been well demonstrated in IL-1Ra-deficient mice. In contrast, the role of endogenous IL-1R2 remains widely unknown.

Granzyme A Contributes to Inflammatory Arthritis in Mice Through Stimulation of Osteoclastogenesis.

Objective: Granzyme A (GzmA) levels are elevated in the plasma and synovium of patients with rheumatoid arthritis (RA), suggesting involvement of this protease in the pathogenesis of the disease. GzmA contributes to sepsis by regulating the production of proinflammatory cytokines. The purpose of this study was to evaluate the contribution of GzmA to the pathogenesis of RA in vivo and to examine the possibility that GzmA acting via tumor necrosis factor (TNF) stimulates osteoclastogenesis.

Interleukin-36 potently stimulates human M2 macrophages, Langerhans cells and keratinocytes to produce pro-inflammatory cytokines.

Interleukin (IL)-36 cytokines belong to the IL-1 family and include three agonists, IL-36 α, β and γ and one inhibitor, IL-36 receptor antagonist (IL-36Ra). IL-36 and IL-1 (α and β) activate similar intracellular pathways via their related heterodimeric receptors, IL-36R/IL-1RAcP and IL-1R1/IL-1RAcP, respectively. However, excessive IL-36 versus IL-1 signaling induces different phenotypes in humans, which may be related to differential expression of their respective receptors.

Atherosclerosis severity is not affected by a deficiency in IL-33/ST2 signaling.

Interleukin (IL)-33 is a cytokine of the IL-1 family, which signals through the ST2 receptor. Previous work demonstrated that the systemic administration of recombinant IL-33 reduces the development of atherosclerosis in apolipoprotein E-deficient (ApoE(-/-)) mice by inducing a Th1-to-Th2 shift. The objective of our study was to examine the role of endogenous IL-33 and ST2 in atherosclerosis.

The interleukin (IL)-1 cytokine family--Balance between agonists and antagonists in inflammatory diseases.

The interleukin (IL)-1 family of cytokines comprises 11 members, including 7 pro-inflammatory agonists (IL-1α, IL-1β, IL-18, IL-33, IL-36α, IL-36β, IL-36γ) and 4 defined or putative antagonists (IL-1R antagonist (IL-1Ra), IL-36Ra, IL-37, and IL-38) exerting anti-inflammatory activities. Except for IL-1Ra, IL-1 cytokines do not possess a leader sequence and are secreted via an unconventional pathway. In addition, IL-1β and IL-18 are produced as biologically inert pro-peptides that require cleavage by caspase-1 in their N-terminal region to generate active proteins.

Severe neutrophil-dominated inflammation and enhanced myelopoiesis in IL-33-overexpressing CMV/IL33 mice.

IL-33 is a cytokine of the IL-1 family, which signals through the ST2 receptor. Previous studies emphasized a role for IL-33 in shaping innate and adaptive immune responses. IL-33 was also reported to modulate myelopoiesis and myeloid cell activity.

Secretory lysosomes of mouse mast cells store and exocytose active caspase-3 in a strictly granzyme B dependent manner.

In this study, we report that cytoplasmic granules from in vivo and in vitro derived mouse mast cells (MCs) contain active granzyme B (gzmB) and caspase-3, which is consistent with recent findings. Studying WT and gzmB-deficient mice, we observed that BM-derived MCs (BMMCs) from both strains contain cytosolic pro-caspase-3, but only WT BMMCs expressed active caspase-3 limited to their secretory lysosomes. Confocal microscopy revealed colocalization of active caspase-3 and gzmB in these cytoplasmic granules.

Mouse neutrophils express the decoy type 2 interleukin-1 receptor (IL-1R2) constitutively and in acute inflammatory conditions.

The proinflammatory activities of IL-1 are tightly controlled at different levels. IL-1R2 acts as a decoy receptor and has been shown to regulate the biological effects of IL-1 in vitro and in vivo. However, little is known about its natural expression in the mouse in physiologic and pathologic conditions.

The severity of experimental arthritis is independent of IL-36 receptor signaling.

Introduction: Interleukin (IL)-36 refers to three related IL-1 family cytokines, IL-36α, IL-36β, and IL-36γ, that bind to the IL-36 receptor (IL-36R). IL-36 exerts proinflammatory effects in skin and lung and stimulates T cell responses. In the present study, we examined the expression and function of IL-36R and its ligands in experimental arthritis.

Disease severity in K/BxN serum transfer-induced arthritis is not affected by IL-33 deficiency.

Introduction: Interleukin (IL)-33 is a cytokine of the IL-1 family, which signals through the ST2 receptor. Previous work suggested implication of the IL-33/ST2 axis in the pathogenesis of human and mouse arthritis. Here, we directly investigated the role of endogenous IL-33 in K/BxN serum transfer-induced arthritis by using IL-33 knockout (KO) mice.

IL-36 signaling amplifies Th1 responses by enhancing proliferation and Th1 polarization of naive CD4+ T cells.

The interleukin-1 (IL-1) superfamily of cytokines comprises a set of pivotal mediators of inflammation. Among them, the action of IL-36 cytokines in immune responses has remained elusive. In a recent study, we demonstrated a direct effect of IL-36 on immune cells.

Articular inflammation is controlled by myeloid cell-derived interleukin 1 receptor antagonist during the acute phase of arthritis in mice.

Objectives: To define the cell type (myeloid vs other cells) specific effect of interleukin 1 (IL-1) receptor antagonist (IL-1Ra) deficiency on the acute inflammatory phase of arthritis.

Methods: Arthritis was induced by K/BxN serum transfer in wild-type (WT), IL-1Ra-deficient (IL-1Ra(-/-)) and conditional knockout mice. In the latter, IL-1Ra production was specifically targeted in myeloid cells (IL-1Ra(ΔM)) or in both hepatocytes and myeloid cells (IL-1Ra(ΔH+M)).

IL-36R ligands are potent regulators of dendritic and T cells.

IL-36α (IL-1F6), IL-36β (IL-1F8), and IL-36γ (IL-1F9) are members of the IL-1 family of cytokines. These cytokines bind to IL-36R (IL-1Rrp2) and IL-1RAcP, activating similar intracellular signals as IL-1, whereas IL-36Ra (IL-1F5) acts as an IL-36R antagonist (IL-36Ra). In this study, we show that both murine bone marrow-derived dendritic cells (BMDCs) and CD4(+) T lymphocytes constitutively express IL-36R and respond to IL-36α, IL-36β, and IL-36γ.

Granzyme B-induced and caspase 3-dependent cleavage of gelsolin by mouse cytotoxic T cells modifies cytoskeleton dynamics.

Granule-associated perforin and granzymes (gzms) are key effector molecules of cytotoxic T lymphocytes (Tc cells) and natural killer cells and play a critical role in the control of intracellular pathogens and cancer. Based on the notion that many gzms, including A, B, C, K, H, and M exhibit cytotoxic activity in vitro, all gzms are believed to serve a similar function in vivo. However, more recent evidence supports the concept that gzms are not unidimensional but, rather, possess non-cytotoxic potential, including stimulation of pro-inflammatory cytokines and anti-viral activities.

The biology of cytotoxic cell granule exocytosis pathway: granzymes have evolved to induce cell death and inflammation.

The granule exocytosis pathway of cytotoxic lymphocytes (Tc and NK cells) is critical for control of tumor development and viral infections. Granule-associated perforin and granzymes are key components in Tc cell-mediated function(s). On the basis of studies that showed granzymes A, B, C, K and M, to induce apoptosis in vitro, all granzymes were thought to also induce cell death in vivo.

Quiescent and activated mouse granulocytes do not express granzyme A and B or perforin: similarities or differences with human polymorphonuclear leukocytes?

Polymorphonuclear leukocytes have been shown to use a multitude of effector functions to combat pathogens and tumors, including enzymes, defensins, and toxic products such as oxygen radicals and nitrogen oxides. Recent studies provided evidence for the expression of granzymes (gzms) and perforin (perf) within the cytotoxic arsenal of human neutrophils, the validity of which was questioned by 2 subsequent studies. We have now used cytology, intracellular flow cytometry, enzymatic assays, immunoelectron microscopy, and quantitative reverse transcriptase-polymerase chain reaction to obtain evidence of the presence of gzms and/or perf in mouse Gr-1+ granulocyte populations.

Perforin and Fas act together in the induction of apoptosis, and both are critical in the clearance of lymphocytic choriomeningitis virus infection.

In this report we questioned the current view that the two principal cytotoxic pathways, the exocytosis and the Fas ligand (FasL)/Fas-mediated pathway, have largely nonoverlapping biological roles. For this purpose we have analyzed the response of mice that lack Fas as well as granzyme A (gzmA) and gzmB (FasxgzmAxB(-/-)) to infection with lymphocytic choriomeningitis virus (LCMV). We show that FasxgzmAxB(-/-) mice, in contrast to B6, Fas(-/-), and gzmAxB(-/-) mice, do not recover from a primary infection with LCMV, in spite of the expression of comparable numbers of LCMV-immune and gamma interferon-producing cytotoxic T lymphocytes (CTL) in all mouse strains tested.