Differential expression of the inflammasome complex genes in systemic lupus erythematosus

Decoding the connection between SLE and DNA Sensors: A comprehensive review

Systemic lupus erythematosus (SLE) is recognized as a prevalent autoimmune disorder characterized by a multifaceted pathogenesis potentially influenced by a combination of environmental factors, genetic predisposition, and hormonal regulation. The continuous study of immune system activation is especially intriguing. Analysis of blood samples from individuals with SLE reveals an abnormal increase in interferon levels, along with the existence of anti-double-stranded DNA antibodies. This evidence suggests that the development of SLE may be initiated by innate immunity. The presence of abnormal dsDNA fragments can activate DNA sensors within cells, particularly immune cells, leading to the initiation of downstream signaling cascades that result in the upregulation of relevant cytokines and the subsequent initiation of adaptive immune responses, such as B cell differentiation and T cell activation. The intricate pathogenesis of SLE results in DNA sensors exhibiting a wide range of functions in innate immune responses that are subject to variation based on cell types, developmental processes, downstream effector signaling pathways and other factors. The review aims to reorganize how DNA sensors influence signaling pathways and contribute to the development of SLE according to current studies, with the aspiration of furnishing valuable insights for future investigations into the pathological mechanisms of SLE and potential treatment approaches.

Ursolic acid alleviates lupus nephritis by suppressing SUMO1-mediated stabilization of NLRP3

BACKGROUND

Systemic lupus erythematosus (SLE) is a multi-system autoimmune disease that affects multiple organs and cause a wide range of severe clinical manifestations, including lupus nephritis (LN), which is a major risk factor for morbidity and mortality in individual with SLE. Ursolic acid (UA) is a natural compound with favorable anti-inflammatory properties and has been employed to treat multiple disease, including inflammatory diseases, diabetes, and Parkinson's disease. However, its therapeutic potential on LN and the underlying mechanisms remains unclear.

PURPOSE

This aim of this study was to investigate the impact of UA on LN and its underlying mechanism.

METHODS

MRL/lpr lupus-prone mouse model was used and UA was administered orally for 8 weeks. Dexamethasone was used as a positive control. After 8 weeks of administration, the spleen-to-body-weight ratio, renal function, urine albumin excretion, cytokines levels, and the deposition of immune complex were measured. The primary mouse glomerular mesangial cells (GMCs) and SV40-MES-13 were stimulated by lipopolysaccharide (LPS), either alone or in combination with nigericin, to establish an in vitro model. The activation of NLRP3 inflammasome were investigated both in vivo and in vitro using qRT-PCR, immunoblotting, and immunofluorescence.

RESULTS

Our results revealed that UA prominently alleviated LN in MRL/lpr lupus-prone mice, leading to a significant reduction in proteinuria production, infiltration of immune cells infiltration, and histopathological damage in the renal tissue. In addition, UA exerted inhibitory effects on the secretion of IL-1β, IL-18, and caspase-1, pyroptosis, and ASC speck formation in primary mouse GMCs and SV40-MES-13 cells. Furthermore, UA facilitated the degradation of NLRP3 by suppressing SUMO1-mediated SUMOylation of NLRP3.

CONCLUSION

UA possess a therapeutical effect on LN in MRL/lpr mice by enhancing the degradation of NLRP3 through inhibition of SUMO1-mediated SUMOylation of NLRP3. Our findings provide a basis for proposing UA as a potential candidate for the treatment of LN.

Type I interferon regulates interleukin-1beta and IL-18 production and secretion in human macrophages

Inflammasomes are immune complexes whose activation leads to the release of pro-inflammatory cytokines IL-18 and IL-1β. Type I IFNs play a role in fighting infection and stimulate the expression of IFN-stimulated genes (ISGs) involved in inflammation. Despite the importance of these cytokines in inflammation, the regulation of inflammasomes by type I IFNs remains poorly understood. Here, we analysed RNA-sequencing data from patients with monogenic interferonopathies and found an up-regulation of several inflammasome-related genes. To investigate the effect of type I IFN on the inflammasome, we treated human monocyte-derived macrophages with IFN-α and observed an increase in CASP1 and GSDMD mRNA levels over time, whereas IL1B and NLRP3 were not directly correlated to IFN-α exposure time. IFN-α treatment reduced the release of mature IL-1β and IL-18, but not caspase-1, in response to ATP-mediated NLRP3 inflammasome activation, suggesting regulation occurs at cytokine expression levels and not the inflammasome itself. However, more studies are required to investigate how regulation by IFN-α occurs and impacts NLRP3 and other inflammasomes at both transcriptional and post-translational levels.

NLRP3 inflammasome and its role in autoimmune diseases: A promising therapeutic target

The NOD-like receptor protein 3 (NLRP3) inflammasome is a protein complex that regulates innate immune responses by activating caspase-1 and the inflammatory cytokines IL-1β and IL-18. Numerous studies have highlighted its crucial role in the pathogenesis and development of inflammatory bowel disease, rheumatoid arthritis, systemic lupus erythematosus, autoimmune thyroid diseases, and other autoimmune diseases. Therefore, investigating the underlying mechanisms of NLRP3 in disease and targeted drug therapies holds clinical significance. This review summarizes the structure, assembly, and activation mechanisms of the NLRP3 inflammasome, focusing on its role and involvement in various autoimmune diseases. This review also identifies studies where the involvement of the NLRP3 inflammasome in the disease mechanism within the same disease appears contradictory, as well as differences in NLRP3-related gene polymorphisms among different ethnic groups. Additionally, the latest therapeutic advances in targeting the NLRP3 inflammasome for autoimmune diseases are outlined, and novel clinical perspectives are discussed. Conclusively, this review provides a consolidated source of information on the NLRP3 inflammasome and may guide future research efforts that have the potential to positively impact patient outcomes.

Human Umbilical Cord Mesenchymal Stem Cells Repair Endothelial Injury and Dysfunction by Regulating NLRP3 to Inhibit Endothelial Cell Pyroptosis in Kawasaki Disease

Vascular endothelial inflammation and endothelial dysfunction are the main causes of endothelial injury in Kawasaki disease (KD). Human umbilical cord-derived mesenchymal stem cells (Huc-MSCs) have multiple functions in immune regulation. This study examined whether Huc-MSCs inhibited endothelial inflammation and improved endothelial function in KD through constructing cell and in vivo animal KD vasculitis models. The pyroptosis factor NOD-like receptor protein 3 (NLRP3) was involved in the inflammatory process in the acute phase of KD. After tail vein injection of Huc-MSCs, inflammatory cell infiltration and the expression of pyroptosis-related proteins in the LCWE-induced KD mouse vasculitis model were significantly reduced. In vitro, NLRP3-dependent pyroptosis successfully induced human umbilical vein endothelial cell (HUVEC) damage. Huc-MSCs effectively increased the abilities of impaired HUVECs to proliferate, migrate, invade, and form vessel-like tubes, while inhibiting their apoptosis, suggesting that Huc-MSCs can reduce inflammation and improve vascular endothelial function by inhibiting the NLRP3-dependent pyroptosis pathway in KD, providing a possibility and novel target for KD endothelial injury and dysfunction.

New Potentiality of Bioactive Substances: Regulating the NLRP3 Inflammasome in Autoimmune Diseases

The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is an essential component of the human innate immune system, and is closely associated with adaptive immunity. In most cases, the activation of the NLRP3 inflammasome requires priming and activating, which are influenced by various ion flux signals and regulated by various enzymes. Aberrant functions of intracellular NLRP3 inflammasomes promote the occurrence and development of autoimmune diseases, with the majority of studies currently focused on rheumatoid arthritis, systemic lupus erythematosus and systemic sclerosis. In recent years, a number of bioactive substances have shown new potentiality for regulating the NLRP3 inflammasome in autoimmune diseases. This review provides a concise overview of the composition, functions, and regulation of the NLRP3 inflammasome. Additionally, we focus on the newly discovered bioactive substances for regulating the NLRP3 inflammasome in autoimmune diseases in the past three years.

Study of NLRP3 Single Nucleotide Polymorphisms in Juvenile Systemic Lupus Erythematosus (JSLE)

Juvenile systemic lupus erythematosus (JSLE) is a multifaceted multifactorial disorder with an unclear etiopathogenesis. Environmental factors, genetic factors, and dysregulated and defective immune system responses are known to have a role in JSLE etiopathogenesis. NLRP3 inflammasome, as an important contributor to immune-mediated inflammatory responses, is assumed to be involved in JSLE etiopathogenesis. To determine whether the NLRP3 genetic variants are altered in patients with JSLE. Fifty-three patients diagnosed with JSLE and 56 healthy sex-matched controls were studied. NLRP3 (C/G rs10754558, C/T rs3806265, C/T rs4612666, A/C rs35829419) gene polymorphisms were evaluated using a TaqMan single-nucleotide polymorphism assay. C allele at position rs3806265 was detected in higher frequencies in patients than in the control group (37.74% vs 23.21%, P-value = .028). At the genotype level at the same position, CT has a significantly higher frequency in patients than the healthy subjects (75.47% vs 46.43%, P-value = .003). The NLRP3 rs3806265 CT genotype was detected at a higher frequency in patients with JSLE than in the healthy control group.

Aberrant inflammasome activation as a driving force of human autoimmune skin disease

Autoimmune skin diseases are understood as conditions in which the adaptive immune system with autoantigen-specific T cells and autoantibody-producing B cells reacting against self-tissues plays a crucial pathogenic role. However, there is increasing evidence that inflammasomes, which are large multiprotein complexes that were first described 20 years ago, contribute to autoimmune disease progression. The inflammasome and its contribution to the bioactivation of interleukins IL-1β and IL-18 play an essential role in combating foreign pathogens or tissue damage, but may also act as a pathogenic driver of myriad chronic inflammatory diseases when dysfunctionally regulated. Inflammasomes containing the NOD-like receptor family members NLRP1 and NLRP3 as well as the AIM2-like receptor family member AIM2 have been increasingly investigated in inflammatory skin conditions. In addition to autoinflammatory diseases, which are often associated with skin involvement, the aberrant activation of the inflammasome has also been implied in autoimmune diseases that can either affect the skin besides other organs such as systemic lupus erythematosus and systemic sclerosis or are isolated to the skin in humans. The latter include, among others, the T-cell mediated disorders vitiligo, alopecia areata, lichen planus and cutaneous lupus erythematosus as well as the autoantibody-driven blistering skin disease bullous pemphigoid. Some diseases are characterized by both autoinflammatory and autoimmune responses such as the chronic inflammatory skin disease psoriasis. Further insights into inflammasome dysregulation and associated pathways as well as their role in forming adaptive immune responses in human autoimmune skin pathology could potentially offer a new field of therapeutic options in the future.

The regulation of self-tolerance and the role of inflammasome molecules

Inflammasome molecules make up a family of receptors that typically function to initiate a proinflammatory response upon infection by microbial pathogens. Dysregulation of inflammasome activity has been linked to unwanted chronic inflammation, which has also been implicated in certain autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, type 1 diabetes, systemic lupus erythematosus, and related animal models. Classical inflammasome activation-dependent events have intrinsic and extrinsic effects on both innate and adaptive immune effectors, as well as resident cells in the target tissue, which all can contribute to an autoimmune response. Recently, inflammasome molecules have also been found to regulate the differentiation and function of immune effector cells independent of classical inflammasome-activated inflammation. These alternative functions for inflammasome molecules shape the nature of the adaptive immune response, that in turn can either promote or suppress the progression of autoimmunity. In this review we will summarize the roles of inflammasome molecules in regulating self-tolerance and the development of autoimmunity.

Mitochondrial bioenergetic changes in systemic lupus erythematosus immune cell subsets: Contributions to pathogenesis and clinical applications

The association of dysregulated metabolism in systemic lupus erythematosus (SLE) pathogenesis has prompted investigations into metabolic rewiring and the involvement of mitochondrial metabolism as a driver of disease through NLRP3 inflammasome activation, disruption of mitochondrial DNA maintenance, and pro-inflammatory cytokine release. The use of Agilent Seahorse Technology to gain functional in situ metabolic insights of selected cell types from SLE patients has identified key parameters that are dysregulated during disease. Mitochondrial functional assessments specifically can detect dysfunction through oxygen consumption rate (OCR), spare respiratory capacity, and maximal respiration measurements, which, when coupled with disease activity scores could show potential as markers of disease activity. CD4+ and CD8 + T cells have been assessed in this way and show that oxygen consumption rate, spare respiratory capacity, and maximal respiration are blunted in CD8 + T cells, with results not being as clear cut in CD4 + T cells. Additionally, glutamine, processed by mitochondrial substrate level phosphorylation is emerging as a key role player in the expansion and differentiation of Th1, Th17, ϒδ T cells, and plasmablasts. The role that circulating leukocytes play in acting as bioenergetic biomarkers of diseases such as diabetes suggests that this may also be a tool to detect preclinical SLE. Therefore, the metabolic characterization of immune cell subsets and the collection of metabolic data during interventions is also essential. The delineation of the metabolic tuning of immune cells in this way could lead to novel strategies in treating metabolically demanding processes characteristic of autoimmune diseases such as SLE.

Association between NLRP3 rs10754558 and CARD8 rs2043211 Variants and Susceptibility to Chronic Kidney Disease

Nod-like receptor protein 3 (NLRP3) is a multi-protein complex belonging to the innate immune system, whose activation by danger stimuli promotes inflammatory cell death. Evidence supports the crucial role of NLRP3 inflammasome activation in the transition of acute kidney injury to Chronic Kidney Disease (CKD), by promoting both inflammation and fibrotic processes. Variants of NLRP3 pathway-related genes, such as NLRP3 itself and CARD8, have been associated with susceptibility to different autoimmune and inflammatory diseases. In this study, we investigated for the first time the association of functional variants of NLRP3 pathway-related genes (NLRP3-rs10754558, CARD8-rs2043211), with a susceptibility to CKD. A cohort of kidney transplant recipients, dialysis and CKD stage 3-5 patients (303 cases) and a cohort of elderly controls (85 subjects) were genotyped for the variants of interest and compared by using logistic regression analyses. Our analysis showed a significantly higher G allele frequency of the NLRP3 variant (67.3%) and T allele of the CARD8 variant (70.8%) among cases, compared with the control sample (35.9 and 31.2%, respectively). Logistic regressions showed significant associations (p < 0.001) between NLRP3 and CARD8 variants and cases. Our results suggest that the NLRP3 rs10754558 and CARD8 rs2043211 variants could be associated with a susceptibility to CKD.

Association of caspase-1 gene polymorphisms with rheumatoid arthritis risk in a Chinese Han population

The goals of present research are to investigate if the genetic polymorphisms in the caspase-1 (CASP1) gene are associated with the risk of rheumatoid arthritis (RA) and the clinical characteristics of the illness in Han patients from China. Our team studied the CASP1 rs2409062 A/G polymorphisms in 1095 healthy controls and 805 RA patients, while the genotype was identified via a custom-by-design 48-Plex single nucleotide polymorphism (SNP) scan™ Kit. The mRNA expression levels of the CASP1 in 40 RA cases and 40 healthy controls were detected by qRT-PCR, while blood plasma levels of the CASP1 in 40 RA cases and 40 paired controls measured via ELISA. Our research showed that the CASP1 rs2409062 A/G polymorphisms were related to an elevated risk for RA. By stratified analysis, our team discovered a remarkably elevated RA risk in females sufferers, age ≥ 55, CRP-positive, or DAS28 < 3.20. In contrast to the control group, the mean level of CASP1 protein in the plasma of RA cases rised significantly. Moreover, RA cases displayed significantly greater levels of CASP1 mRNA versus the control group (P < 0.05). Those outcomes reveal that the CASP1 rs2409062 A/G gene polymorphisms are associated with an elevated risk for RA in a Chinese Han population.

GBP5 Inhibition Ameliorates the Progression of Lupus Nephritis by Suppressing NLRP3 Inflammasome Activation

BACKGROUND

The inflammatory response and NLRP3 inflammasome activation are typical characteristics of lupus nephritis (LN). Guanylate-binding protein 5 (GBP5) has effects on the release of proinflammatory cytokines and the activation of NLRP3 inflammasome. However, it is largely unknown whether and how GBP5 contributes to the progression of LN.

METHODS

To detect the role of GBP5 in LN, MRL/lpr mice were administrated with the lentiviral vectors that knockdown GBP5 via tail vein. Proximal tubular epithelial HK-2 cells were treated with LPS and ATP to mimic the inflammatory response of LN in vitro.

RESULTS

GBP5 expression was increased in the renal cortical tissues of LN mice. The in vivo results showed that GBP5 inhibition prevented the progression of LN, as evidenced by the decreased levels of 24-hour proteinuria, blood urea nitrogen and creatinine, accompanied by the ameliorated renal pathological damages. The increased mRNA and protein levels of proinflammatory factors (IL-6, TNF-α, iNOS and COX-2) in the renal cortex of LN mice were suppressed by GBP5 knockdown. In vitro, we demonstrated that the treatment of LPS combined with ATP induced an increase in GBP5 mRNA and protein expression in HK-2 cells. Mechanically, knockdown of GBP5 inhibited the activation of NLRP3 inflammasome and the secretion of IL-1β and IL-18 both in vivo and in vitro.

CONCLUSION

Our findings reveal that GBP5 inhibition prevents the progression of LN, most likely by suppressing NLRP3 inflammasome activation. It provides a novel insight into the therapeutic interventions for LN.

A patent review of NLRP3 inhibitors to treat autoimmune diseases

INTRODUCTION

NOD-like receptor family pyrin domain containing 3 (NLRP3) can sense a plethora of exogenous and endogenous dangers. Upon activation, a multimeric protein complex, the NLRP3 inflammasome, is formed to initiate the innate immune responses. Emerging studies have implicated the pathophysiological roles of this protein complex in human disorders, highlighting that it represents a druggable target for therapeutics development.

AREAS COVERED

The current review summarizes the functional facets of the NLRP3 inflammasome, its association with autoimmune diseases, and recent patents on the development of NLRP3 inhibitors. Literature search was conducted using SciFinder and Google Patents with the key word NLRP3 and NLRP3 inhibitors.

EXPERT OPINION

Although significant advances have been made in understanding the NLRP3 inflammasome, more studies are still needed to elucidate the molecular mechanisms underlying its roles in autoimmune diseases. A number of NLRP3 inhibitors have been patented, however, none of them have been approved for clinical use. Due to the complex nature of the NLRP3 inflammasome, novel screening assays along with target engagement methods could benefit the drug discovery and clinical translation. In addition, clinical trials on NLRP3 inhibitors are still in their early stages, and continuous investigations are needed to fully assess their safety and effectiveness.

Strategies of Targeting Inflammasome in the Treatment of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multiple organ dysfunction resulting from the production of multiple autoantibodies and adaptive immune system abnormalities involving T and B lymphocytes. In recent years, inflammasomes have been recognized as an important component of innate immunity and have attracted increasing attention because of their pathogenic role in SLE. In short, inflammasomes regulate the abnormal differentiation of immune cells, modulate pathogenic autoantibodies, and participate in organ damage. However, due to the clinical heterogeneity of SLE, the pathogenic roles of inflammasomes are variable, and thus, the efficacy of inflammasome-targeting therapies is uncertain. To provide a foundation for the development of such therapeutic strategies, in this paper, we review the role of different inflammasomes in the pathogenesis of SLE and their correlation with clinical phenotypes and propose some corresponding treatment strategies.

Insights into inflammasome regulation: cellular, molecular, and pathogenic control of inflammasome activation

Maintenance of immune homeostasis is an intricate process wherein inflammasomes play a pivotal role by contributing to innate and adaptive immune responses. Inflammasomes are ensembles of adaptor proteins that can trigger a signal following innate sensing of pathogens or non-pathogens eventuating in the inductions of IL-1β and IL-18. These inflammatory cytokines substantially influence the antigen-presenting cell's costimulatory functions and T helper cell differentiation, contributing to adaptive immunity. As acute and chronic disease conditions may accompany parallel tissue damage, we analyze the critical role of extracellular factors such as cytokines, amyloids, cholesterol crystals, etc., intracellular metabolites, and signaling molecules regulating inflammasome activation/inhibition. We develop an operative framework for inflammasome function and regulation by host cell factors and pathogens. While inflammasomes influence the innate and adaptive immune components' interplay modulating the anti-pathogen adaptive immune response, pathogens may target inflammasome inhibition as a survival strategy. As trapped between health and diseases, inflammasomes serve as promising therapeutic targets and their modus operandi serves as a scientific rationale for devising better therapeutic strategies.

Activation of NLRP3 Inflammasome in the Skin of Patients with Systemic and Cutaneous Lupus Erythematosus

NLRP3 inflammasome is suggested to contribute to the complex pathogenesis of systemic lupus erythematosus, but its role in cutaneous lupus erythematosus has not been addressed. This study investigated the expression of NLRP3 inflammasome components and levels of type I interferons in the skin of 20 patients with cutaneous lupus erythematosus. Expression of NLRP1/3, adaptor protein ASC (apoptosis-associated speck-like protein), caspase-1, interferon-α (IFN-α), myxovirus resistance protein (MxA), and interferon-induced proteins 1 and 2 (IFIT 1/2) in the skin was assessed using reverse transcription quantitative real-time PCR (RT-qPCR), western blotting and immunohistochemistry. Serum interferon-α protein levels from 12 patients were measured using digital enzyme-linked immunoassay (ELISA). Interleukin-1β expression was significantly upregulated in the lesional skin of patients with cutaneous lupus erythematosus compared with their uninvolved skin. However, NLRP1/3, ASC and caspase-1 were not significantly upregulated compared with the skin of control persons. IFN-α and IFN-induced proteins MxA and IFIT1/2 were strongly expressed in cutaneous lupus erythematosus skin. Variability in the expression of NLRP3 inflammasome components among patients suggests heterogeneity of pathological pathways in cutaneous lupus erythematosus.

The Role of Inflammasomes in Glomerulonephritis

The inflammasome is an immune multiprotein complex that activates pro-caspase 1 in response to inflammation-inducing stimuli and it leads to IL-1β and IL-18 proinflammatory cytokine production. NLRP1 and NLRP3 inflammasomes are the best characterized and they have been related to several autoimmune diseases. It is well known that the kidney expresses inflammasome genes, which can influence the development of some glomerulonephritis, such as lupus nephritis, ANCA glomerulonephritis, IgA nephropathy and anti-GBM nephropathy. Polymorphisms of these genes have also been described to play a role in autoimmune and kidney diseases. In this review, we describe the main characteristics, activation mechanisms, regulation and functions of the different inflammasomes. Moreover, we discuss the latest findings about the role of the inflammasome in several glomerulonephritis from three different points of view: in vitro, animal and human studies.

AIM2 inflammasome contributes to aldosterone-induced renal injury via endoplasmic reticulum stress

Inflammatory response and renal fibrosis are the hallmarks of chronic kidney disease (CKD). However, the specific mechanism of aldosterone-induced renal injury in the progress of CKD requires elucidation. Emerging evidence has demonstrated that absent in melanoma 2 (AIM2)-mediated inflammasome activation and endoplasmic reticulum stress (ERS) play a pivotal role in the renal fibrosis. Here, we investigated whether overexpression or deficiency of AIM2 affects ERS and fibrosis in aldosterone-infused renal injury. Interestingly, we found that AIM2 was markedly expressed in the diseased proximal tubules from human and experimental CKD. Mechanically, overactivation of AIM2 aggravated aldosterone-induced ERS and fibrotic changes in vitro while knockdown of AIM2 blunted these effects in vivo and in vitro. By contrast, AIM2 deficiency ameliorated renal structure and function deterioration, decreased proteinuria levels and lowered systolic blood pressure in vivo; silencing of AIM2 blocked inflammasome-mediated signaling pathway, relieved ERS and fibrotic changes in vivo. Furthermore, mineralocorticoid receptor (MR) antagonist eplerenone and ERS inhibitor tauroursodeoxycholic acid (TUDCA) had nephroprotective effects on the basis of AIM2 overactivation in vitro, while they failed to produce a more remarkable renoprotective effect on the treatment of AIM2 silence in vitro. Notably, the combination of TUDCA with AIM2 knockdown significantly reduced proteinuria levels in vivo. Additionally, immunofluorescence assay identified that apoptosis-associated speck-like protein (ASC) recruitment and Gasdermin-D (GSDMD) cleavage respectively occurred in the glomeruli and tubules in vivo. These findings establish a crucial role for AIM2 inflammasome in aldosterone-induced renal injury, which may provide a novel therapeutic target for the pathogenesis of CKD.

Reviewing the importance of TLR-NLRP3-pyroptosis pathway and mechanism of experimental NLRP3 inflammasome inhibitors

Cells encounter continuous challenges due to tissue insult caused by endogenous and/or exogenous stimuli. Among the mechanisms set in place to counterbalance the tissue insult, innate immunity is always at the forefront. Cells of innate immunity efficiently recognize the 'danger signals' via a specialized set of membrane-bound receptors known as Toll-like receptors. Once this interaction is established, toll-like receptor passes on the responsibility to cytosolic NOD-like receptors through a cascade of signalling pathways. Subsequently, NOD-like receptors assemble to a specialized multiprotein intracellular complex, that is inflammasome. Inflammasome activates Caspase-1 and Gasdermin-D which initiate pyroptotic cell death in the affected tissue by two simultaneous mechanisms. Being a protease, caspase-1 cleaves and activates pro-inflammatory cytokines IL-1β and IL-18. On the other hand, Gasdermin-D causes proteolytic cleavage which forms a pore in the cell membrane. This review highlights the molecular events ranging from recognition of stimuli to pyroptosis. The review is also an attempt to discuss the mechanisms of the most specific experimental NLRP3 inhibitors.

The Role of NLRP3 Inflammasome in Lupus Nephritis

Lupus nephritis (LN) is the most frequent and severe of systemic lupus erythematosus (SLE) clinical manifestations and contributes to the increase of morbidity and mortality of patients due to chronic kidney disease. The NLRP3 (NLR pyrin domain containing 3) is a member of the NLR (NOD-like receptors), and its activation results in the production of pro-inflammatory cytokines, which can contribute to the pathogenesis of LN. In this review manuscript, we approach the relation between the NLRP3 inflammasome, SLE, and LN, highlighting the influence of genetic susceptibility of NLRP3 polymorphisms in the disease; the main functional studies using cellular and animal models of NLRP3 activation; and finally, some mechanisms of NLRP3 inhibition for the development of possible therapeutic drugs for LN.

Role of NLRP3 Inflammasome in Lupus Nephritis and Therapeutic Targeting by Phytochemicals

Systemic lupus erythematosus (SLE) is a multisystem autoimmune inflammatory condition that affects multiple organs and provokes extensive and severe clinical manifestations. Lupus nephritis (LN) is one of the main clinical manifestations of SLE. It refers to the deposition of immune complexes in the glomeruli, which cause kidney inflammation. Although LN seriously affects prognosis and represents a key factor of disability and death in SLE patients, its mechanism remains unclear. The NACHT, leucine-rich repeat (LRR), and pyrin (PYD) domains-containing protein 3 (NLRP3) inflammasome regulates IL-1β and IL-18 secretion and gasdermin D-mediated pyroptosis and plays a key role in innate immunity. There is increasing evidence that aberrant activation of the NLRP3 inflammasome and downstream inflammatory pathways play an important part in the pathogenesis of multiple autoimmune diseases, including LN. This review summarizes research progress on the elucidation of NLRP3 activation, regulation, and recent clinical trials and experimental studies implicating the NLRP3 inflammasome in the pathophysiology of LN. Current treatments fail to provide durable remission and provoke several sides effects, mainly due to their broad immunosuppressive effects. Therefore, the identification of a safe and effective therapeutic approach for LN is of great significance. Phytochemicals are found in many herbs, fruits, and vegetables and are secondary metabolites of plants. Evidence suggests that phytochemicals have broad biological activities and have good prospects in a variety of diseases, including LN. Therefore, this review reports on current research evaluating phytochemicals for targeting NLRP3 inflammasome pathways in LN therapy.

Variability of the rs333 in Polish patients with lupus erythematosus

Introduction

Lupus erythematosus (LE) is an autoimmune disease with a strong influence of genetic and environmental factors. C-C motif chemokine receptor 5 (CCR5) gene expression may affect the development and intensity of LE.

Aim

To evaluate the possible association between the 32bp deletion in rs333 locus located within the CCR5 gene and the development of LE or the occurrence of various clinical symptoms in the course of the disease.

Material and methods

One hundred and twenty patients with LE (77 with systemic lupus erythematosus (SLE) and 43 with discoid lupus erythematosus (DLE)) and 100 healthy controls from the Polish population were genotyped for deletion in rs333.

Results

32 bp deletion in the rs333 was significantly more frequent among healthy individuals than DLE patients. Moreover, heterozygotes and homozygotes with deletion in rs333 were significantly more frequent within the control group than the group of patients with discoid lupus erythematosus. In contrast, any statistically significant differences in allele or genotype frequencies between healthy persons and SLE patients were observed. Furthermore, nucleotide sequence variability of rs333 was not associated with certain clinical symptoms of LE patients.

Conclusions

Deletion in the rs333 might be a protective factor for DLE, but not SLE in the Polish population. Nevertheless further studies performed on larger populations are needed to confirm these observations.

Association of NLRP3 rs35829419 and rs10754558 Polymorphisms With Risks of Autoimmune Diseases: A Systematic Review and Meta-Analysis

The existing knowledge about the association between NLRP3 rs35829419/rs10754558 polymorphisms and susceptibility to autoimmune diseases (AIDs) remains controversial. Herein, a meta-analysis was performed to evaluate such association. We searched databases for relevant studies published in English up to February 2021. Stata14 was used to assess the odds ratio (OR). As for NLRP3 rs35829419, no significant association to overall AIDs was found in three genetic models [A vs. C: OR (95%CI) = 0.89 (0.69-1.14); AC vs. CC: 1.00 (0.77-1.30); AA/AC vs. CC: 0.93 (0.71-1.20)]. However, subgroup analysis by disease type showed that NLRP3 rs35829419 A allele may have a significant protective effect on rheumatoid arthritis (RA) susceptibility [A vs. C: 0.74 (0.57-0.96)]. NLRP3 rs10754558 polymorphism contributes to significantly reduce the risk of AIDs in the allelic model [G vs. C: 0.78 (0.71-0.87)], homozygote co-dominant model [GG vs. CC: 0.63 (0.51-0.77)], heterozygote co-dominant model [GC vs. CC: 0.78 (0.66-0.91)], dominant model [GG/GC vs. CC: 0.73 (0.63-0.84)], and recessive model [GG vs. GC/CC: 0.73 (0.62-0.88)]. In the subgroup analysis by ethnicity, association was observed between the NLRP3 rs10754558 G allele and AIDs in Latin Americans, but not in European, Arabian, or Asian populations. Stratification by disease type showed a significant association of the NLRP3 rs10754558 G allele with type 1 diabetes (T1D), RA, and systemic lupus erythematosus (SLE), but not with celiac disease (CD), multiple sclerosis (MS), or myasthenia gravis (MG). This meta-analysis suggests that the NLRP3 rs10754558, but not rs35829419, polymorphism is associated with susceptibility to AIDs, especially in Latin American individuals.

Three functional variants in the NLRP3 gene are associated with susceptibility and clinical characteristics of systemic lupus erythematosus

OBJECTIVE

Nod-like receptor pyrin domain containing 3 (NLRP3) gene encodes an intracellular receptor whose dysregulation in systemic lupus erythematosus (SLE) has been reported in multiple studies. Activation of NLRP3 inflammasome leads to the induction of inflammatory response via cleaving and producing of specific cytokines. In the present study, we assessed the possible association between three functional polymorphisms in this gene and SLE risk in the Iranian population. These variants include two gain of function (rs4612666 and rs10754558) and one loss of function (rs6672995) which are correlated with modulation of expression of NLRP3.

METHODS

A case-control study involving 110 SLE patients and 116 control subjects was undertaken to estimate the frequency of rs4612666, rs10754558, and rs6672995 genotypes using real-time PCR high resolution melting method (HRM).

RESULTS

Our findings revealed significant associations between GG genotype and G allele of rs10754558 with increased risk of SLE (OR _{for GG genotype}= 2.82; 95%CI [1.45-5.46]/OR _{for G allele}= 1.97; 95%CI [1.36-2.87]). Although, no significant associations were recognized between allele and genotype frequencies of rs4612666 and rs6672995 polymorphisms with SLE risk (P > 0.05). Also, our analysis revealed that the C allele in rs4612666 and G allele in rs10754558 was correlated with the severity of disease activity (P < 0.001). Moreover, these common variants were associated with lower age of onset and some clinical symptoms in the patient group, such as skin manifestation, neurological symptom and, renal involvement (P < 0.05).

CONCLUSION

This study demonstrates a substantial association between NLRP3 polymorphisms with increased risk, clinical symptoms, and the severity of disease activity of SLE.

Cannabinoids as Key Regulators of Inflammasome Signaling: A Current Perspective

Inflammasomes are cytoplasmic inflammatory signaling protein complexes that detect microbial materials, sterile inflammatory insults, and certain host-derived elements. Inflammasomes, once activated, promote caspase-1–mediated maturation and secretion of pro-inflammatory cytokines, interleukin (IL)-1β and IL-18, leading to pyroptosis. Current advances in inflammasome research support their involvement in the development of chronic inflammatory disorders in contrast to their role in regulating innate immunity. Cannabis (marijuana) is a natural product obtained from the Cannabis sativa plant, and pharmacologically active ingredients of the plant are referred to as cannabinoids. Cannabinoids and cannabis extracts have recently emerged as promising novel drugs for chronic medical conditions. Growing evidence indicates the potent anti-inflammatory potential of cannabinoids, especially Δ⁹-tetrahydrocannabinol (Δ⁹-THC), cannabidiol (CBD), and synthetic cannabinoids; however, the mechanisms remain unclear. Several attempts have been made to decipher the role of cannabinoids in modulating inflammasome signaling in the etiology of chronic inflammatory diseases. In this review, we discuss recently published evidence on the effect of cannabinoids on inflammasome signaling. We also discuss the contribution of various cannabinoids in human diseases concerning inflammasome regulation. Lastly, in the milieu of coronavirus disease-2019 (COVID-19) pandemic, we confer available evidence linking inflammasome activation to the pathophysiology of COVID-19 suggesting overall, the importance of cannabinoids as possible drugs to target inflammasome activation in or to support the treatment of a variety of human disorders including COVID-19.

Is there an Inflammation Role for MYD88 in Rheumatoid Arthritis?

Rheumatoid arthritis (RA) is an autoimmune and inflammatory disease with strong genetic influence, especially upon immune response components. Several cytokines from the toll-like receptors activation pathway display recognized role for RA establishment. However, few studies have verified the role of key mediators such as MYD88 gene and its genetic variants. In the present study, we aim to evaluate the rs6853 functional single-nucleotide variation (SNV) role in RA etiopathogenesis, clinical severity status, and its impact in MYD88 mRNA levels and IL-lβ protein levels. For the association study, a total of 423 RA patients and 346 health individuals, enrolled as control, from Northeast and Southeast Brazil were genotyped using specific Taqman probe. For the gene expression assays, we performed a MYD88 rs6853 genotype-guided monocyte cell culture divided into non-stimulated and lypopolysaccharides (LPS)-stimulated cells from healthy individuals. MYD88 gene expression was measured using primer specifics while IL-1β levels were evaluated by ELISA. We observed that A allele and AA genotype were associated to an increased risk to RA development (OR = 1.60; 95% CI 1.24-2.08; p = 0.0004/OR = 2.83; 95% CI 1.25-6.41; p = 0.0152). The AA genotype exhibited lower MYD88 mRNA levels than GG genotype in non-stimulated monocyte cell culture (FC - 3.83; p = 0.003). Additionally, we verified an increase of IL-1β levels when AA genotype non-stimulated monocytes were compared to AA genotype LPS-stimulates (p = 0.021). In summary, MYD88 rs6853 polymorphism associated to RA development in our Brazilian cohort and showed influence upon MYD88 mRNA levels' expression and IL-lβ production.

Blockade of anti-dsDNA ameliorates systemic lupus erythematosus in MRL/Faslpr mice through ameliorating inflammation via the PKCδ-NLRC4 axis

Anti-double-stranded DNA (anti-dsDNA) is closely associated with the inflammatory burden in the brain after ischemic stroke. Here, we studied the inflammatory cascade and investigated the mechanisms behind the pro-inflammatory role of dsDNA in systemic lupus erythematosus (SLE). The serum levels of interleukin-1beta (IL-1β) and IL-6 in SLE patients and the corresponding controls were evaluated using ELISA, and the expression level of caspase-1 was evaluated using quantitative real-time polymerase chain reaction (qRT-PCR). We found that the serum levels of IL-1β and IL-6 were increased in the SLE patients. The expression of caspase-1 was upregulated and positively correlated with the levels of pro-inflammatory factors. The level of anti-dsDNA was also elevated and positively correlated with the results for the mean fluorescence intensity (MFI) of caspase-1. Additionally, we evaluated the functions of PRKCD encoding protein kinase c delta (PKCδ) and NLRC4, in vivo, in MRL/Faslpr mice. We found that renal injury was aggravated, and the levels of pro-inflammatory factors were increased in the MRL/Faslpr mice. We also found that increased levels of NLRC4 in the mice exacerbated renal injury and increased the levels of pro-inflammatory factors, whereas inhibition of PKCδ had the opposite results. These findings provide unique perspectives on pathogenesis of SLE and indicate that inhibition of anti-dsDNA could attenuate renal inflammatory burden, representing a promising therapeutic opportunity for SLE.

Role of the NLRP3 inflammasome in autoimmune diseases

NOD-like receptor family pyrin domain containing 3 (NLRP3) is an intracellular receptor that senses foreign pathogens and endogenous danger signals. It assembles with apoptosis-associated speck-like protein containing a CARD (ASC) and caspase-1 to form a multimeric protein called the NLRP3 inflammasome. Among its various functions, the NLRP3 inflammasome can induce the release of the pro-inflammatory cytokines interleukin (IL)-1β and IL-18 while also promoting gasdermin D (GSDMD)-mediated pyroptosis. Previous studies have established a vital role for the NLRP3 inflammasome in innate and adaptive immune system as well as its contribution to several autoimmune diseases including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjögren's syndrome (SS), systemic sclerosis (SSc), and ankylosing spondylitis (AS). In this review, we briefly introduce the biological features of the NLRP3 inflammasome and present the mechanisms underlying its activation and regulation. We also summarize recent studies that have reported on the roles of NLRP3 inflammasome in the immune system and several autoimmune diseases, with a focus on therapeutic and clinical applications.