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Numerous studies demonstrate that neuroinflammation is a key player in the progression of Alzheimer’s disease (AD). Interleukin (IL)-1β is a main inducer of inflammation and therefore a prime target for therapeutic options. The inactive IL-1β precursor requires processing by the the nucleotide-binding oligomerization domain-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome into a mature and active form. Studies have shown that IL-1β is up-regulated in brains of patients with AD, and that genetic inactivation of the NLRP3 inflammasome improves behavioral tests and synaptic plasticity phenotypes in a murine model of the disease. In the present study, we analyzed the effect of pharmacological inhibition of the NLRP3 inflammasome using dapansutrile (OLT1177), an oral NLRP3-specific inhibitor that is safe in humans. Six-month-old WT and APP/PS1 mice were fed with standard mouse chow or OLT1177-enriched chow for 3 mo. The Morris water maze test revealed an impaired learning and memory ability of 9-mo-old APP/PS1 mice (P = 0.001), which was completely rescued by OLT1177 fed to mice (P = 0.008 to untreated APP/PS1). Furthermore, our findings revealed that 3 mo of OLT1177 diet can rescue synaptic plasticity in this mouse model of AD (P = 0.007 to untreated APP/PS1). In addition, microglia were less activated (P = 0.07) and the number of plaques was reduced in the cortex (P = 0.03) following NLRP3 inhibition with OLT1177 administration. We also observed an OLT1177 dose-dependent normalization of plasma metabolic markers of AD to those of WT mice. This study suggests the therapeutic potential of treating neuroinflammation with an oral inhibitor of the NLRP3 inflammasome.

Psoriasis is an immune-mediated inflammatory skin disease that involves mainly T helper (Th)17, Th1 and Th22 lymphocytes, which cause hyper-proliferation of the epidermis with aberrant differentiation of keratinocytes, and local production of chemokines and cytokines. These fuel a self-amplifying loop where these products act on T cells to perpetuate cutaneous inflammatory processes. Among the various inflammatory mediators involved, interleukin (IL)-36 cytokines are important for the recruitment and activation of neutrophils and Th17 cells in psoriatic skin. In particular, IL-36s induce chemokines and cytokines interfere with differentiation/cornification programs in the epidermis, as well as promote pathological angiogenesis and endothelial cell activation. IL-36 cytokines belong to the IL-1 family, and comprise IL-36α, IL-36β, and IL-36γ agonists as well as IL-36 receptor antagonist and IL-38 antagonists. IL-36 cytokines are up-regulated in psoriatic epidermis, and their expression is strongly induced by TNF-α and IL-17. Contrarily, IL-38 antagonist is downregulated, and its impaired expression may be relevant to the dysregulated inflammatory processes induced by IL-36. Here, we discuss on the pathogenic mechanisms leading to the altered balance of IL-36 agonists/antagonists and the significance of this dysregulation in psoriasis. Collection of the information will provide a theoretical basis for the development of novel therapeutic strategies based on IL-36 agonist/antagonist manipulation in psoriasis.

Around the tenth day after diagnosis, ~20% of patients with coronavirus disease 2019 (COVID-19)–associated pneumonia evolve toward severe oxygen dependence (stage 2b) and acute respiratory distress syndrome (stage 3) associated with systemic inflammation often termed a “cytokine storm.” Because interleukin-1 (IL-1) blocks the production of IL-6 and other proinflammatory cytokines, we treated COVID-19 patients early in the disease with the IL-1 receptor antagonist, anakinra.We retrospectively compared 22 patients from three different centers in France with stages 2b and 3 COVID-19–associated pneumonia presenting with acute severe respiratory failure and systemic inflammation who received either standard-of-care treatment alone (10 patients) or combined with intravenous anakinra (12 patients). Treatment started at 300 mg·d−1 for 5 d, then tapered with lower dosing over 3 d. Both populations were comparable for age, comorbidities, clinical stage, and elevated biomarkers of systemic inflammation. All of the patients treated with anakinra improved clinically (P < 0.01), with no deaths, significant decreases in oxygen requirements (P < 0.05), and more days without invasive mechanical ventilation (P < 0.06), compared with the control group. The effect of anakinra was rapid, as judged by significant decrease of fever and C-reactive protein at day 3. A mean total dose of 1,950 mg was infused with no adverse side effects or bacterial infection. We conclude that early blockade of the IL-1 receptor is therapeutic in acute hyperinflammatory respiratory failure in COVID-19 patients.

Key Points Interleukin-1 (IL-1) is a master cytokine in the pathogenesis of several diseases, inducing multiple pathways of inflammation. Inflammation is part of every disease, acute or chronic. Diseases in which monocytes and/or macrophages and neutrophils have a dominant role are called autoinflammatory diseases. By contrast, diseases in which T lymphocytes have a major role are termed autoimmune diseases. Autoimmune diseases are treated with glucocorticoids, immunosuppressive drugs as well as various anti-cytokine-based therapeutics that target the immune system. Autoinflammatory diseases are uniquely responsive to IL-1-blocking therapies and are less responsive to immunosuppressors. There are two forms of IL-1: IL-1α and IL-1β. Both trigger inflammation by binding to the same receptor. The IL-1 receptor antagonist anakinra binds to the IL-1 receptor and blocks the activity of both IL-1α and IL-1β. A broad spectrum of acute and inflammatory diseases are treated with anakinra. Neutralizing monoclonal antibodies to IL-1α, IL-1β and the IL-1 receptor have been developed to decrease the activity of IL-1. An orally active inhibitor of caspase 1, the enzyme that processes IL-1β into an active cytokine, has also been developed. Blocking IL-1 in individuals with rare inherited diseases reverses generalized as well as local inflammation. Common inflammatory diseases such as arthritis, gout, type 2 diabetes, dry eye syndrome and heart failure are also responsive to IL-1 blocking. The future of IL-1 drug development will involve an expansion of disease indications through controlled trials. Blockade of the pro-inflammatory cytokine interleukin-1 (IL-1) is emerging as an effective approach for the treatment of an increasing number of diseases. Here, Dinarello and colleagues discuss the pathogenic roles of IL-1, present therapeutic strategies aimed at modulating the activity of this cytokine and review clinical trial data for multiple indications. Interleukin-1 (IL-1) is a highly active pro-inflammatory cytokine that lowers pain thresholds and damages tissues. Monotherapy blocking IL-1 activity in autoinflammatory syndromes results in a rapid and sustained reduction in disease severity, including reversal of inflammation-mediated loss of sight, hearing and organ function. This approach can therefore be effective in treating common conditions such as post-infarction heart failure, and trials targeting a broad spectrum of new indications are underway. So far, three IL-1-targeted agents have been approved: the IL-1 receptor antagonist anakinra, the soluble decoy receptor rilonacept and the neutralizing monoclonal anti-IL-1β antibody canakinumab. In addition, a monoclonal antibody directed against the IL-1 receptor and a neutralizing anti-IL-1α antibody are in clinical trials.

Interleukin-1β (IL-1β)–mediated inflammation suppresses antitumor immunity, leading to the generation of a tumor-permissive environment, tumor growth, and progression. Here, we demonstrate that nucleotide-binding domain, leucine-rich containing family, pyrin domain-containing-3 (NLRP3) inflammasome activation in melanoma is linked to IL-1β production, inflammation, and immunosuppression. Analysis of cancer genome datasets (TCGA and GTEx) revealed greater NLRP3 and IL-1β expression in cutaneous melanoma samples (n = 469) compared to normal skin (n = 324), with a highly significant correlation between NLRP3 and IL-1β (P < 0.0001). We show the formation of the NLRP3 inflammasome in biopsies of metastatic melanoma using fluorescent resonance energy transfer analysis for NLRP3 and apoptosis-associated speck-like protein containing a CARD. In vivo, tumor-associated NLRP3/IL-1 signaling induced expansion of myeloid-derived suppressor cells (MDSCs), leading to reduced natural killer and CD8⁺ T cell activity concomitant with an increased presence of regulatory T (Treg) cells in the primary tumors. Either genetic or pharmacological inhibition of tumor-derived NLRP3 by dapansutrile (OLT1177) was sufficient to reduce MDSCs expansion and to enhance antitumor immunity, resulting in reduced tumor growth. Additionally, we observed that the combination of NLRP3 inhibition and anti–PD-1 treatment significantly increased the antitumor efficacy of the monotherapy by limiting MDSC-mediated T cell suppression and tumor progression. These data show that NLRP3 activation in melanoma cells is a protumor mechanism, which induces MDSCs expansion and immune evasion. We conclude that inhibition of NLRP3 can augment the efficacy of anti–PD-1 therapy.

Background Parkinson’s disease (PD) is characterized by a progressive degeneration of dopaminergic neurons, which leads to irreversible loss of peripheral motor functions. Death of dopaminergic neurons induces an inflammatory response in microglial cells, which further exacerbates neuronal loss. Reducing inflammation is expected to ameliorate neuronal loss and arrest motor dysfunctions. Because of the contribution of the NLRP3 inflammasome to the inflammatory response in PD, we targeted NLRP3 using the specific inhibitor OLT1177 ® . Methods We evaluated the effectiveness of OLT1177 ® in reducing the inflammatory response in an MPTP neurotoxic model of PD. Using a combination of in vitro and in vivo studies, we analyzed the effects of NLRP3 inhibition on pro-inflammatory markers in the brain, α-synuclein aggregation, and dopaminergic neuron survival. We also determined the effects of OLT1177 ® on locomotor deficits associated with MPTP and brain penetrance. Results Treatment with OLT1177 ® prevented the loss of motor function, reduced the levels of α-synuclein, modulated pro-inflammatory markers in the nigrostriatal areas of the brain, and protected dopaminergic neurons from degeneration in the MPTP model of PD. We also demonstrated that OLT1177 ® crosses the blood–brain barrier and reaches therapeutic concentrations in the brain. Conclusions These data suggest that targeting the NLRP3 inflammasome by OLT1177 ® may be a safe and novel therapeutic approach to arrest neuroinflammation and protect against neurological deficits of Parkinson’s disease in humans.

Background Activation of the NLRP3 inflammasome in gout amplifies the inflammatory response and mediates further damage. In the current study, we assessed the therapeutic effect of OLT1177, an orally active NLRP3 inflammasome inhibitor that is safe in humans, in murine acute arthritis models. Methods Zymosan or monosodium urate (MSU) crystals were injected intra-articularly (i.a.) into mouse knee joints to induce reactive or gouty arthritis. Joint swelling, articular cell infiltration, and synovial cytokines were evaluated 25 hours and 4 hours following zymosan or MSU challenge, respectively. OLT1177 was administrated intraperitoneally by oral gavage or in the food by an OLT1177-enriched diet. Results OLT1177 reduced zymosan-induced joint swelling ( p  < 0.001), cell influx ( p  < 0.01), and synovial levels of interleukin (IL)-1β, IL-6, and chemokine (C-X-C motif) ligand 1 (CXCL1) ( p  < 0.05), respectively, when compared with vehicle-treated mice. Plasma OLT1177 levels correlated ( p  < 0.001) dose-dependently with reduction in joint inflammation. Treatment of mice with OLT1177 limited MSU crystal articular inflammation ( p  > 0.0001), which was associated with decreased synovial IL-1β, IL-6, myeloperoxidase, and CXCL1 levels ( p  < 0.01) compared with vehicle-treated mice. When administrated orally 1 hour after MSU challenge, OLT1177 reduced joint inflammation, processing of IL-1β, and synovial phosphorylated c-Jun N-terminal kinase compared with the vehicle group. Mice were fed an OLT1177-enriched diet for 3 weeks and then challenged i.a. with MSU crystals. Joint swelling, synovial IL-1β, and expression of Nlrp3 and Il1b were significantly reduced in synovial tissues in mice fed an OLT1177-enriched diet when compared with the standard diet group. Conclusions Oral OLT1177 is highly effective in ameliorating reactive as well as gouty arthritis.

Decades of evidence positioned IL-1β as a master regulatory cytokine in acute and chronic inflammatory diseases. Approved biologics aimed at inhibiting IL-1 signaling have shown efficacy but variable safety. More recently, targeting NLRP3 activation, an upstream mediator of IL-1β, has garnered the most attention. Aberrant NLRP3 activation has been demonstrated to participate in the progression of several pathological conditions from neurogenerative diseases to cardio-metabolic syndromes and cancer. Pharmacological and genetic strategies aimed to limit NLRP3 function have proven effective in many preclinical models of diseases. These evidences have lead to a significant effort in the generation and clinical testing of small orally active molecules that can target NLRP3. In this report, we discuss different properties of these molecules with translational potential and describe the technologies currently available to screen NLRP3 targeting molecules highlighting advantages and limitations of each method.

Key Points Toll-like receptors (TLRs) have an important role in chronic inflammation in rheumatic diseases, including rheumatoid arthritis, systemic lupus erythematosus, gout and Lyme disease The Toll–IL-1 receptor (TIR) domain triggers biological responses to IL-1 molecules and to TLR ligands Both microbial (such as lipopolysaccharide and DNA) and endogenous ligands have a role in chronic inflammation in rheumatic diseases Novel strategies to inhibit TLR signalling to treat chronic inflammation in rheumatic diseases include antibodies and small molecules that target TLR receptors and TLR signalling In the past few years, substantial progress has been made in our understanding of the role of Toll-like receptors (TLRs) in inflammatory diseases. Joosten and colleagues discuss the role of TLRs in the pathophysiology of rheumatic diseases and how TLRs and TLR signalling pathways can be targeted to treat these conditions. In the past few years, new developments have been reported on the role of Toll-like receptors (TLRs) in chronic inflammation in rheumatic diseases. The inhibitory function of TLR10 has been demonstrated. Receptors that enhance the function of TLRs, and several TLR inhibitors, have been identified. In addition, the role of the microbiome and TLRs in the onset of rheumatic diseases has been reported. We review novel insights on the role of TLRs in several inflammatory joint diseases, including rheumatoid arthritis, systemic lupus erythematosus, gout and Lyme arthritis, with a focus on the signalling mechanisms mediated by the Toll–IL-1 receptor (TIR) domain, the exogenous and endogenous ligands of TLRs, and the current and future therapeutic strategies to target TLR signalling in rheumatic diseases.

IL-37 is a fundamental inhibitor of innate immunity. Human IL-37 has a caspase-1 cleavage site and translocates to the nucleus upon LPS stimulation. Here, we investigated whether caspase-1 processing affects IL-37–mediated suppression of LPS-induced cytokines and the release from cells by analyzing a caspase-1 cleavage site mutant IL-37 (IL-37D20A). Nuclear translocation of IL-37D20A is significantly impaired compared with WT IL-37 in transfected cells. LPS-induced IL-6 was decreased in cells expressing WT IL-37 but not IL-37D20A. The function of IL-37 in transfected bone marrow-derived macrophages is nucleotide-binding oligomerization domain-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome-dependent, because IL-37 transfection in apoptosis-associated speck-like protein containing a carboxyl-terminal caspase recruitment domain- and NLRP3-deficient cells does not reduce levels of IL-6 and IL-1β upon LPS stimulation. IL-37–expressing macrophages release both precursor and mature IL-37, but only the externalization of mature IL-37 was dependent on ATP. Precursor and mature IL-37 was also secreted from human dendritic cells and peripheral blood mononuclear cells. To determine whether IL-37 is active in the extracellular compartment, we pretreated IL-37 transgenic mice with IL-37–neutralizing antibodies before LPS challenge. In IL-37–expressing mice, neutralizing IL-37 antibodies reversed the suppression of LPS-induced serum IL-6. In contrast, the addition of neutralizing antibody did not reverse suppression of LPS-induced IL-6 in mouse macrophages transfected with IL-37. Although caspase-1 is required for nuclear translocation of intracellular IL-37 and for secretion of mature IL-37, the release of the IL-37 precursor is independent of caspase-1 activation. IL-37 now emerges as a dual-function cytokine with intra- and extracellular properties for suppressing innate inflammation.