The Role of NLRP3 Inflammasome in Lupus Nephritis

STAT3 inhibition ameliorates renal interstitial inflammation in MRL/lpr mice with diffuse proliferative lupus nephritis

BACKGROUND AND OBJECTIVES

Acute kidney injury (AKI) is one of the most common and severe clinical syndromes of diffuse proliferative lupus nephritis (DPLN), of which poor prognosis is indicated by aggravated renal function deterioration. However, the specific therapy and mechanisms of AKI in DPLN remain to be explored.

METHODS

The correlation between AKI and clinical pathological changes in DPLN patients was analyzed. Expression of STAT3 signaling was detected in MRL/lpr mice with DPLN using immunohistochemical staining and immunoblotting. Inhibition of STAT3 activation by combination therapy was assessed in MRL/lpr mice.

RESULTS

Correlation analysis revealed only the interstitial leukocytes were significantly related to AKI in endocapillary DPLN patients. MRL/lpr mice treated with vehicle, which can recapitulate renal damages of DPLN patients, showed upregulation of STAT3, pSTAT3 and caspase-1 in renal cortex. FLLL32 combined with methylprednisolone therapy significantly inhibited the STAT3 activation, improved acute kidney damage, reduced the interstitial infiltration of inflammatory cells and decreased the AKI incidence in MRL/lpr mice.

CONCLUSION

STAT3 activation may play an important role in the pathogenesis of DPLN and the development of AKI. Hence, STAT3 inhibition based on the combination of FLLL32 with methylprednisolone may represent a new strategy for treatment of DPLN with AKI.

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.

STAT1 aggravates kidney injury by NOD-like receptor (NLRP3) signaling in MRL-lpr mice

Systemic lupus erythematosus (SLE) is a persistent autoimmune disorder that can culminate in lupus nephritis (LN), an intricate renal complication. In pursuit of unraveling the intricate molecular underpinnings governing LN progression, we conducted bioinformatics analysis employing gene expression data sourced from the GSE32591 dataset. Our scrutiny revealed a panoply of differentially expressed genes (DEGs) within the glomerulus and tubulointerstitial compartments of LN patients. Enrichment analysis for DEGs engaged in diverse processes, encompassing virus defense, viral life cycle, cell adhesion molecules, and the NOD-like receptor signaling pathway. Notably, STAT1 emerged as an eminent central hub gene intrinsically tied to NOD-like receptor signaling. To explore the functional significance of STAT1 in the context of LN, MRL-lpr mice model was used to knockout STAT1. The results unveiled that STAT1 silencing yielded a migratory effect on kidney injury, concurrently curbing inflammatory markers. Meanwhile, knockout STAT1 also reduced NLRP3 expression and Cleaved caspase-1 expression. These findings offer tantalizing prospects for targeting STAT1 as a potential therapeutic conduit in the management of LN.

Gasdermin D deficiency aborts myeloid calcium influx to drive granulopoiesis in lupus nephritis

Gasdermin D (GSDMD) is emerging as an important player in autoimmune diseases, but its exact role in lupus nephritis (LN) remains controversial. Here, we identified markedly elevated GSDMD in human and mouse LN kidneys, predominantly in CD11b+ myeloid cells. Global or myeloid-conditional deletion of GSDMD was shown to exacerbate systemic autoimmunity and renal injury in lupus mice with both chronic graft-versus-host (cGVH) disease and nephrotoxic serum (NTS) nephritis. Interestingly, RNA sequencing and flow cytometry revealed that myeloid GSDMD deficiency enhanced granulopoiesis at the hematopoietic sites in LN mice, exhibiting remarkable enrichment of neutrophil-related genes, significant increases in total and immature neutrophils as well as granulocyte/macrophage progenitors (GMPs). GSDMD-deficient GMPs and all-trans-retinoic acid (ATRA)-stimulated human promyelocytes NB4 were further demonstrated to possess enhanced clonogenic and differentiation abilities compared with controls. Mechanistically, GSDMD knockdown promoted self-renewal and granulocyte differentiation by restricting calcium influx, contributing to granulopoiesis. Functionally, GSDMD deficiency led to increased pathogenic neutrophil extracellular traps (NETs) in lupus peripheral blood and bone marrow-derived neutrophils. Taken together, our data establish that GSDMD deletion accelerates LN development by promoting granulopoiesis in a calcium influx-regulated manner, unraveling its unrecognized critical role in LN pathogenesis.

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.

Therapeutic potential of MCC950, a specific inhibitor of NLRP3 inflammasome in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder with a pathogenesis that remains incompletely understood, resulting in limited treatment options. MCC950, a highly specific NLRP3 inflammasome inhibitor, effectively suppresses the activation of NLRP3, thus reducing the production of caspase-1, the pro-inflammatory cytokines IL-1β and IL-18. This review highlights the pivotal role of NLRP3 inflammasome activation pathways in the pathogenesis of SLE and discusses the potential therapeutic application of MCC950 in SLE. Notably, it comprehensively elucidates the mechanism of MCC950 targeting the NLRP3 pathway in SLE treatment, outlining its potential role in regulating autophagy and necroptosis. The insights gained contribute to a deeper understanding of the value of MCC950 in SLE therapy, serving as a robust foundation for further research and potential clinical applications.

Roles of the Caspase-11 Non-Canonical Inflammasome in Rheumatic Diseases

Inflammasomes are intracellular multiprotein complexes that activate inflammatory signaling pathways. Inflammasomes comprise two major classes: canonical inflammasomes, which were discovered first and are activated in response to a variety of pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs), and non-canonical inflammasomes, which were discovered recently and are only activated in response to intracellular lipopolysaccharide (LPS). Although a larger number of studies have successfully demonstrated that canonical inflammasomes, particularly the NLRP3 inflammasome, play roles in various rheumatic diseases, including rheumatoid arthritis (RA), infectious arthritis (IR), gouty arthritis (GA), osteoarthritis (OA), systemic lupus erythematosus (SLE), psoriatic arthritis (PA), ankylosing spondylitis (AS), and Sjögren's syndrome (SjS), the regulatory roles of non-canonical inflammasomes, such as mouse caspase-11 and human caspase-4 non-canonical inflammasomes, in these diseases are still largely unknown. Interestingly, an increasing number of studies have reported possible roles for non-canonical inflammasomes in the pathogenesis of various mouse models of rheumatic disease. This review comprehensively summarizes and discusses recent emerging studies demonstrating the regulatory roles of non-canonical inflammasomes, particularly focusing on the caspase-11 non-canonical inflammasome, in the pathogenesis and progression of various types of rheumatic diseases and provides new insights into strategies for developing potential therapeutics to prevent and treat rheumatic diseases as well as associated diseases by targeting non-canonical inflammasomes.

Identification of pattern recognition receptor genes in peripheral blood mononuclear cells and monocytes as biomarkers for the diagnosis of lupus nephritis

BACKGROUND

The study aimed to investigate the diagnostic value of lupus-related pattern recognition receptors (PRRs) genes in peripheral blood mononuclear cells (PBMCs) and monocytes (MONs) for lupus nephritis (LN).

METHODS

PBMCs were isolated from a cohort with 37 LN patients and 39 healthy controls (HCs), and MONs were derived from another cohort with 70 LN patients and 66 HCs. Q-PCR was used to measure the mRNA levels of CGAS, IFNB1, AIM2, IL1Β, NLRC4, NLRP3, NLRP12 and ZBP1 in the PBMCs and MONs. The Mann-Whitney U test was used to compare the data in LN patients and HCs. Eleven GEO datasets of SLE/LN were used to perform differentially expressed genes (DEGs) analysis to these PRR genes. Receiver operating characteristic (ROC) curve analysis was employed to assess the performance of individual genes or the disease prediction model established by combining multiple genes in LN diagnosis. Spearman correlation method was done to analyze the correlation between these PRRs and other clinical characteristics.

RESULTS

The mRNA levels of five genes (AIM2, NLRC4, IL1B, NLRP12 and ZBP1) in PBMCs, and seven genes (CGAS, IFNB1, AIM2, IL1B, NLRP3, NLRP12 and ZBP1) in MONs of LN patients were significantly higher than those of HCs (P < 0.05). DEGs analysis based on the GEO datasets showed that ZBP1, AIM2 and IL1B were significantly increased in several datasets. The ROC curve analysis indicated that the area under curve (AUC) of the LN prediction models derived from PBMCs or MONs were 0.82 or 0.91 respectively. In addition, the expression levels of these PRRs were correlated with other clinical features in LN patients, including Anti-Sm, ESR, serum Cr, and C3.

CONCLUSION

Our study suggests that these lupus-related PRRs might be served as potential biomarkers of LN.

Gbp3 is associated with the progression of lupus nephritis by regulating cell proliferation, inflammation and pyroptosis

Lupus nephritis (LN) is a major cause death in patients with systemic lupus erythematosus. We aimed to find the differentially expressed genes (DEGs) in LN and confirm the regulatory mechanism on LN. The mouse model of LN was constructed by subcutaneous injection of pristane. RNA-seq screened 392 up-regulated and 447 down-regulated DEGs in LN mouse model, and KEGG analysis found that the top 20 DEGs were enriched in arachidonic acid metabolism, tryptophan metabolism, etc. The hub genes, Kynu, Spidr, Gbp3, Cbr1, Cyp4b1, and Cndp2 were identified, in which Gbp3 was selected for following study. Afterwards, the function of Gbp3 on the proliferation, inflammation, and pyroptosis of LN was verified by CCK-8, ELISA, and WB in vitro. The results demonstrated that si-Gbp3 promoted cell proliferation and inhibited the levels of inflammatory factors (IL-1β, TNF-α and IL-8) and pyroptosis-related proteins (GSDMD, Caspase-1 and NLRP3) in a cell model of LN. In constrast, Gbp3 overexpression played an opposite role. In summary, Gbp3 promoted the progression of LN via inhibiting cell proliferation and facilitating inflammation and pyroptosis.

Mitochondrial-derived peptides in cardiovascular disease: Novel insights and therapeutic opportunities

BACKGROUND

Mitochondria-derived peptides (MDPs) represent a recently discovered family of peptides encoded by short open reading frames (ORFs) found within mitochondrial genes. This group includes notable members including humanin (HN), mitochondrial ORF of the 12S rDNA type-c (MOTS-c), and small humanin-like peptides 1-6 (SHLP1-6). MDPs assume pivotal roles in the regulation of diverse cellular processes, encompassing apoptosis, inflammation, and oxidative stress, which are all essential for sustaining cellular viability and normal physiological functions. Their emerging significance extends beyond this, prompting a deeper exploration into their multifaceted roles and potential applications.

AIM OF REVIEW

This review aims to comprehensively explore the biogenesis, various types, and diverse functions of MDPs. It seeks to elucidate the central roles and underlying mechanisms by which MDPs participate in the onset and development of cardiovascular diseases (CVDs), bridging the connections between cell apoptosis, inflammation, and oxidative stress. Furthermore, the review highlights recent advancements in clinical research related to the utilization of MDPs in CVD diagnosis and treatment.

KEY SCIENTIFIC CONCEPTS OF REVIEW

MDPs levels are diminished with aging and in the presence of CVDs, rendering them potential new indicators for the diagnosis of CVDs. Also, MDPs may represent a novel and promising strategy for CVD therapy. In this review, we delve into the biogenesis, various types, and diverse functions of MDPs. We aim to shed light on the pivotal roles and the underlying mechanisms through which MDPs contribute to the onset and advancement of CVDs connecting cell apoptosis, inflammation, and oxidative stress. We also provide insights into the current advancements in clinical research related to the utilization of MDPs in the treatment of CVDs. This review may provide valuable information with MDPs for CVD diagnosis and treatment.

SIRT1 slows the progression of lupus nephritis by regulating the NLRP3 inflammasome through ROS/TRPM2/Ca2+ channel

Systemic lupus erythematosus (SLE) is a chronic multisystem inflammatory disease associated with autoantibody formation. Lupus nephritis (LN) is one of the most severe organ manifestations of SLE. The inflammatory response is a key factor in kidney injury, and the NLRP3 inflammasome is frequently associated with the pathogenesis of LN. Sirtuin 1 (SIRT1), a nicotinamide adenine dinucleotide (NAD +)-dependent histone deacetylase, is a promising therapeutic target for preventing renal injury. However, the mechanism of SIRT1 in LN remains unclear. Here, we aimed to investigate the mechanism by which SIRT inhibits the NLRP3 inflammasome to slow the progression of LN. We detected the expression of SIRT1 and the infiltration of macrophages in MRL/lpr mice; the results showed that the expression of SIRT1 was decreased, and the symptoms of lupus nephritis were relieved after the use of resveratrol, which upregulated SIRT1. In vitro studies showed that after lipopolysaccharide (LPS) stimulation, SIRT1 expression decreased, and the NLRP3 inflammasome was activated. Upregulation of SIRT1 inhibits NLRP3 inflammasome activation and assembly by interfering with two signalling pathways. First, SIRT1 affects NF-κB expression, transcription, and inflammatory cytokine expression. Second, SIRT1 modulates calcium influx induced by transient receptor potential channel M2 (TRPM2), which could be partly due to the inhibition of reactive oxygen species (ROS) production. Our findings suggest that upregulated SIRT1 inhibits the NLRP3 inflammasome to slow the progression of lupus nephritis by regulating NF-κB and ROS/TRPM2/Ca2+ channels. This study reveals a new anti-inflammatory mechanism of SIRT1, suggesting that SIRT1 may be a potential therapeutic target for the prevention of LN.

Modulation of the immunity and inflammation by autophagy

Autophagy, a highly conserved cellular self-degradation pathway, has emerged with novel roles in the realms of immunity and inflammation. Genome-wide association studies have unveiled a correlation between genetic variations in autophagy-related genes and heightened susceptibility to autoimmune and inflammatory diseases. Subsequently, substantial progress has been made in unraveling the intricate involvement of autophagy in immunity and inflammation through functional studies. The autophagy pathway plays a crucial role in both innate and adaptive immunity, encompassing various key functions such as pathogen clearance, antigen processing and presentation, cytokine production, and lymphocyte differentiation and survival. Recent research has identified novel approaches in which the autophagy pathway and its associated proteins modulate the immune response, including noncanonical autophagy. This review provides an overview of the latest advancements in understanding the regulation of immunity and inflammation through autophagy. It summarizes the genetic associations between variants in autophagy-related genes and a range of autoimmune and inflammatory diseases, while also examining studies utilizing transgenic animal models to uncover the in vivo functions of autophagy. Furthermore, the review delves into the mechanisms by which autophagy dysregulation contributes to the development of three common autoimmune and inflammatory diseases and highlights the potential for autophagy-targeted therapies.

Identification of Shared Immune Cells and Immune-Related Co-Disease Genes in Chronic Heart Failure and Systemic Lupus Erythematosus Based on Transcriptome Sequencing

Purpose

The purpose was to identify shared immune cells and co-disease genes in chronic heart failure (HF) and systemic lupus erythematosus (SLE), as well as explore the potential mechanisms of action between HF and SLE.

Methods

A collection of peripheral blood mononuclear cells (PBMCs) from ten patients with HF and SLE and ten normal controls (NC) was used for transcriptome sequencing. Differentially expressed genes (DEGs) analysis, enrichment analysis, immune infiltration analysis, weighted gene co-expression network analysis (WGCNA), protein-protein interaction (PPI) analysis, and machine learning were applied for the screening of shared immune cells and co-disease genes in HF and SLE. Gene expression analysis and correlation analysis were used to explore the potential mechanisms of co-disease genes and immune cells in HF and SLE.

Results

In this study, it was found that two immune cells, T cells CD4 naïve and Monocytes, displayed similar expression patterns in HF and SLE at the same time. By taking intersection of the above immune cell-associated genes with the DEGs common to both HF and SLE, four immune-associated co-disease genes, CCR7, RNASE2, RNASE3 and CXCL10, were finally identified. CCR7, as one of the four key genes, was significantly down-regulated in HF and SLE, while the rest three key genes were all significantly up-regulated in both diseases.

Conclusion

T cells CD4 naïve and Monocytes were first revealed as possible shared immune cells of HF and SLE, and CCR7, RNASE2, RNASE3 and CXCL10 were identified as possible key genes common to HF and SLE as well as potential biomarkers or therapeutic targets for HF and SLE.

Decipher the Immunopathological Mechanisms and Set Up Potential Therapeutic Strategies for Patients with Lupus Nephritis

Lupus nephritis (LN) is one of the most severe complications in patients with systemic lupus erythematosus (SLE). Traditionally, LN is regarded as an immune complex (IC) deposition disease led by dsDNA-anti-dsDNA-complement interactions in the subendothelial and/or subepithelial basement membrane of glomeruli to cause inflammation. The activated complements in the IC act as chemoattractants to chemically attract both innate and adaptive immune cells to the kidney tissues, causing inflammatory reactions. However, recent investigations have unveiled that not only the infiltrating immune-related cells, but resident kidney cells, including glomerular mesangial cells, podocytes, macrophage-like cells, tubular epithelial cells and endothelial cells, may also actively participate in the inflammatory and immunological reactions in the kidney. Furthermore, the adaptive immune cells that are infiltrated are genetically restricted to autoimmune predilection. The autoantibodies commonly found in SLE, including anti-dsDNA, are cross-reacting with not only a broad spectrum of chromatin substances, but also extracellular matrix components, including α-actinin, annexin II, laminin, collagen III and IV, and heparan sulfate proteoglycan. Besides, the glycosylation on the Fab portion of IgG anti-dsDNA antibodies can also affect the pathogenic properties of the autoantibodies in that α-2,6-sialylation alleviates, whereas fucosylation aggravates their nephritogenic activity. Some of the coexisting autoantibodies, including anti-cardiolipin, anti-C1q, anti-ribosomal P autoantibodies, may also enhance the pathogenic role of anti-dsDNA antibodies. In clinical practice, the identification of useful biomarkers for diagnosing, monitoring, and following up on LN is quite important for its treatments. The development of a more specific therapeutic strategy to target the pathogenic factors of LN is also critical. We will discuss these issues in detail in the present article.

The Interplay between Immune and Metabolic Pathways in Kidney Disease

Kidney disease is a significant health problem worldwide, affecting an estimated 10% of the global population. Kidney disease encompasses a diverse group of disorders that vary in their underlying pathophysiology, clinical presentation, and outcomes. These disorders include acute kidney injury (AKI), chronic kidney disease (CKD), glomerulonephritis, nephrotic syndrome, polycystic kidney disease, diabetic kidney disease, and many others. Despite their distinct etiologies, these disorders share a common feature of immune system dysregulation and metabolic disturbances. The immune system and metabolic pathways are intimately connected and interact to modulate the pathogenesis of kidney diseases. The dysregulation of immune responses in kidney diseases includes a complex interplay between various immune cell types, including resident and infiltrating immune cells, cytokines, chemokines, and complement factors. These immune factors can trigger and perpetuate kidney inflammation, causing renal tissue injury and progressive fibrosis. In addition, metabolic pathways play critical roles in the pathogenesis of kidney diseases, including glucose and lipid metabolism, oxidative stress, mitochondrial dysfunction, and altered nutrient sensing. Dysregulation of these metabolic pathways contributes to the progression of kidney disease by inducing renal tubular injury, apoptosis, and fibrosis. Recent studies have provided insights into the intricate interplay between immune and metabolic pathways in kidney diseases, revealing novel therapeutic targets for the prevention and treatment of kidney diseases. Potential therapeutic strategies include modulating immune responses through targeting key immune factors or inhibiting pro-inflammatory signaling pathways, improving mitochondrial function, and targeting nutrient-sensing pathways, such as mTOR, AMPK, and SIRT1. This review highlights the importance of the interplay between immune and metabolic pathways in kidney diseases and the potential therapeutic implications of targeting these pathways.

Melatonin Treatment in Kidney Diseases

Melatonin is a neurohormone that is mainly secreted by the pineal gland. It coordinates the work of the superior biological clock and consequently affects many processes in the human body. Disorders of the waking and sleeping period result in nervous system imbalance and generate metabolic and endocrine derangements. The purpose of this review is to provide information regarding the potential benefits of melatonin use, particularly in kidney diseases. The impact on the cardiovascular system, diabetes, and homeostasis causes melatonin to be indirectly connected to kidney function and quality of life in people with chronic kidney disease. Moreover, there are numerous reports showing that melatonin plays a role as an antioxidant, free radical scavenger, and cytoprotective agent. This means that the supplementation of melatonin can be helpful in almost every type of kidney injury because inflammation, apoptosis, and oxidative stress occur, regardless of the mechanism. The administration of melatonin has a renoprotective effect and inhibits the progression of complications connected to renal failure. It is very important that exogenous melatonin supplementation is well tolerated and that the number of side effects caused by this type of treatment is low.

Honokiol suppresses the aberrant interactions between renal resident macrophages and tubular epithelial cells in lupus nephritis through the NLRP3/IL-33/ST2 axis

Lupus nephritis (LN) is a type of immune-complex nephritis caused by systemic lupus erythematosus and is a major contributor to mortality and morbidity. Honokiol (HNK) has been found to have a therapeutic effect on LN, but its action mechanism remains unclear. In this study, we first demonstrated that HNK attenuates kidney injury in MRL/lpr mice. Results from RNA sequencing combined with ingenuity pathway analysis suggested that HNK plays an anti-LN role through inhibition of the NLRP3 inflammasome and IL33. GEO chip data, single-cell data, and clinical samples from LN patients demonstrated that the pyroptosis and IL-33/ST2 pathways are abnormally activated during the stage of LN. In vivo, similar to the results of the AAV-mediated NLRP3 shRNA MRL/lpr model, HNK downregulated serum and renal IL-33 levels, and suppressed NLRP3 inflammasome and the IL-33/ST2 axis in the kidney. In vitro, co-culturing NLRP3-overexpressing or IL-33 knocked-down rat renal macrophages with NRK-52E cells confirmed that NLRP3 activation in resident macrophages directly upregulates IL-33, which in turn mediates the IL-33/ST2/NF-κB pathway to promote the inflammatory response of renal tubular epithelial cells. Furthermore, a molecular docking model and surface plasmon resonance analysis were utilized to demonstrate a direct interaction between HNK and NLRP3. In conclusion, this study provides a novel anti-LN treatment strategy in which HNK plays a preventive and therapeutic role against LN by suppressing the abnormal crosstalk between renal resident macrophages and renal tubular epithelial cells by inhibiting the activation of the NLRP3/IL-33/ST2 axis.

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.

Renal NLRP3 Inflammasome activation is associated with disease activity in lupus nephritis

The current study was initiated to comprehensively evaluate renal NLRP3 inflammasome pathway activation in lupus nephritis (LN) patients and their clinicopathological significances based on a Chinese LN cohort. We found that the expressions of NLRP3, ASC, caspase-1, IL-1β and IL-18 were all significantly higher in the kidneys of LN patients and were predominantly expressed in glomerular mesangial cells, podocytes, renal tubular epithelial cells and macrophages. The expressions of NLRP3, ASC, caspase-1 and IL-1β were positively correlated to SLEDAI scores and several renal pathological activity indices, while the expression of NLRP3 was negatively associated with chronicity scores. Moreover, the foot process width was positively correlated with glomerular caspase-1 levels, and several podocyte injury markers were decreased significantly in LN patients with higher caspase-1 expression compared with those with lower expression. Our findings indicated that renal NLRP3 inflammasome was activated in LN patients and correlated with disease activity, which needs further explorations.

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.

The Role of NLRP3 Inflammasome in IgA Nephropathy

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerular disease worldwide today. The NLRP3 inflammasome is a polyprotein complex and an important participant in inflammation. Accumulating studies have shown that the NLRP3 inflammasome participates in a variety of kidney diseases, including IgAN. This review focuses on the role of the NLRP3 inflammasome in IgAN and summarizes multiple involved pathways, which may provide novel treatments for IgAN treatment.

Diabetic Nephropathy: Pathogenesis to Cure

Diabetic nephropathy (DN) is a leading cause of end-stage renal disorder (ESRD). It is defined as the increase in urinary albumin excretion (UAE) when no other renal disease is present. DN is categorized into microalbuminuria and macroalbuminuria. Factors like high blood pressure, high blood sugar levels, genetics, oxidative stress, hemodynamic and metabolic changes affect DN. Hyperglycemia causes renal damage through activating protein kinase C (PKC), producing advanced end glycation products (AGEs) and reactive oxygen species (ROS). Growth factors, chemokines, cell adhesion molecules, inflammatory cytokines are found to be elevated in the renal tissues of the diabetic patient. Many different and new diagnostic methods and treatment options are available due to the increase in research efforts and progression in medical science. However, until now, no permanent cure is available. This article aims to explore the mechanism, diagnosis, and therapeutic strategies in current use for increasing the understanding of DN.

Mast Cell Cytokines in Acute and Chronic Gingival Tissue Inflammation: Role of IL-33 and IL-37

Much evidence suggests autoimmunity in the etiopathogenesis of periodontal disease. In fact, in periodontitis, there is antibody production against collagen, DNA, and IgG, as well as increased IgA expression, T cell dysfunction, high expression of class II MHC molecules on the surface of gingival epithelial cells in inflamed tissues, activation of NK cells, and the generation of antibodies against the azurophil granules of polymorphonuclear leukocytes. In general, direct activation of autoreactive immune cells and production of TNF can activate neutrophils to release pro-inflammatory enzymes with tissue damage in the gingiva. Gingival inflammation and, in the most serious cases, periodontitis, are mainly due to the dysbiosis of the commensal oral microbiota that triggers the immune system. This inflammatory pathological state can affect the periodontal ligament, bone, and the entire gingival tissue. Oral tolerance can be abrogated by some cytokines produced by epithelial cells and activated immune cells, including mast cells (MCs). Periodontal cells and inflammatory-immune cells, including mast cells (MCs), produce cytokines and chemokines, mediating local inflammation of the gingival, along with destruction of the periodontal ligament and alveolar bone. Immune-cell activation and recruitment can be induced by inflammatory cytokines, such as IL-1, TNF, IL-33, and bacterial products, including lipopolysaccharide (LPS). IL-1 and IL-33 are pleiotropic cytokines from members of the IL-1 family, which mediate inflammation of MCs and contribute to many key features of periodontitis and other inflammatory disorders. IL-33 activates several immune cells, including lymphocytes, Th2 cells, and MCs in both innate and acquired immunological diseases. The classic therapies for periodontitis include non-surgical periodontal treatment, surgery, antibiotics, anti-inflammatory drugs, and surgery, which have been only partially effective. Recently, a natural cytokine, IL-37, a member of the IL-1 family and a suppressor of IL-1b, has received considerable attention for the treatment of inflammatory diseases. In this article, we report that IL-37 may be an important and effective therapeutic cytokine that may inhibit periodontal inflammation. The purpose of this paper is to study the relationship between MCs, IL-1, IL-33, and IL-37 inhibition in acute and chronic inflamed gingival tissue.

CD36 aggravates podocyte injury by activating NLRP3 inflammasome and inhibiting autophagy in lupus nephritis

A major cause of proteinuria in lupus nephritis (LN) is podocyte injury, and determining potential therapeutic targets to prevent podocyte injury is important from a clinical perspective in the treatment of LN. CD36 is involved in podocyte injury in several glomerulopathies and was reported to be a vital candidate gene in LN. Here, we determined the role of CD36 in the podocyte injury of LN and the underlying mechanisms. We observed that CD36 and NLRP3 (NLR family pyrin domain containing 3) were upregulated in the podocytes of lupus nephritis patients and MRL/lpr mice with renal impairment. In vitro, CD36, NLRP3 inflammasome, and autophagy were elevated accompanied with increased podocyte injury stimulated by IgG extracted from lupus nephritis patients compared that from healthy donors. Knocking out CD36 with the CRISPR/cas9 system decreased the NLRP3 inflammasome levels, increased the autophagy levels and alleviated podocyte injury. By enhancing autophagy, NLRP3 inflammasome was decreased and podocyte injury was alleviated. These results demonstrated that, in lupus nephritis, CD36 promoted podocyte injury by activating NLRP3 inflammasome and inhibiting autophagy by enhancing which could decrease NLRP3 inflammasome and alleviate podocyte injury.

Lithium intoxication induced pyroptosis via ROS/NF-κB/NLRP3 inflammasome regulatory networks in kidney of mice

Humans and animals may be exposed to increasing contaminant lithium (Li) concentrations in the environment with the use and disposal of Li-containing products. Meanwhile, Li plays a key role in the treatment of human mental disorders, while the excessive accumulation of Li salts in the body can cause renal damage and nephrotic syndrome. In this study, the mechanism of renal inflammatory reaction induced by Li excessive intake was studied by establishing mice models in vitro and in vivo. The results of histopathology staining and TdT-mediated dUTP nick-end labeling assay showed that high Li condition (Lithium carbonate, 20 mg/kg/twice a day, i.e., for 30 consecutive days) caused inflammatory damage and apoptosis in kidney tissue cells. Western blot, qPCR, and immunohistochemical analysis were used to further study. In the vivo experiments, we found that Li reduced antioxidant enzyme capacity (glutathione peroxidase, total superoxide dismutase, total antioxidant capacity, and catalase) and induced the production of reactive oxygen species (ROS). Moreover, excessive Li activated nuclear factor kappa-B (NF-κB) signaling pathway and nucleotide-binding oligomerization domain-like receptors domains-containing protein 3 (NLRP3) inflammasome, resulting in activation of inflammatory factors tumor necrosis factor-α and IL-1β in the kidney of mice. In the vitro study, ROS as an upstream signal phosphorylated IκBα and NF-κB, up-regulated the NLRP3 inflammasome, increased caspase3, 6, 7, and 9 to exaggerate inflammation response, finally inducing pyroptosis in renal cells.

Recent Advances in Understanding Nrf2 Agonism and Its Potential Clinical Application to Metabolic and Inflammatory Diseases

Oxidative stress is a major component of cell damage and cell fat, and as such, it occupies a central position in the pathogenesis of metabolic disease. Nuclear factor-erythroid-derived 2-related factor 2 (Nrf2), a key transcription factor that coordinates expression of genes encoding antioxidant and detoxifying enzymes, is regulated primarily by Kelch-like ECH-associated protein 1 (Keap1). However, involvement of the Keap1–Nrf2 pathway in tissue and organism homeostasis goes far beyond protection from cellular stress. In this review, we focus on evidence for Nrf2 pathway dysfunction during development of several metabolic/inflammatory disorders, including diabetes and diabetic complications, obesity, inflammatory bowel disease, and autoimmune diseases. We also review the beneficial role of current molecular Nrf2 agonists and summarize their use in ongoing clinical trials. We conclude that Nrf2 is a promising target for regulation of numerous diseases associated with oxidative stress and inflammation. However, more studies are needed to explore the role of Nrf2 in the pathogenesis of metabolic/inflammatory diseases and to review safety implications before therapeutic use in clinical practice.

The Roles of NOD-like Receptors in Innate Immunity in Otitis Media

Acute otitis media (AOM) can persist or lead to various complications in individuals in which the innate immune system is impaired. In this context, impaired expression of nucleotide-binding oligomerization domain (NOD)-like receptor (NLR), an intracellular pathogen-recognition receptor (PRR), is involved in the etiology of OM in humans and animals, affecting its development, severity, chronicity, recurrence, and associated complications. To assess this relationship, we reviewed literature reports relating NLR expression patterns with the pathophysiology and clinical features of OM in the larger context of impaired innate immunity. We summarized the results of published studies on the expression of NLRs in animals and humans in acute otitis media (AOM), otitis media with effusion (OME), chronic otitis media (COM) with cholesteatoma, and COM without cholesteatoma. NLRs were expressed mainly in association with bacterial infection in AOM, OME, COM with cholesteatoma, and COM without cholesteatoma. In addition, expression of NLRs was affected by the presence or absence of bacteria, fluid characteristics, disease recurrence, tissue type, and repeated surgery. Various factors of the innate immune system are involved in the pathogenesis of OM in the middle ear. NLRs are expressed in AOM, OME, COM with cholesteatoma, and COM without cholesteatoma. Impaired NLR expression induced the development, chronicity and recurrence of OM and exacerbated associated complications, indicating that NLRs have important roles in the pathogenesis of OM.