NLRP3 inflammasome: Pathogenic role and potential therapeutic target for IgA nephropathy

A new era in the treatment of kidney diseases: NLRP3 inflammasome and cytokine-targeted therapies

The kidneys are crucial for filtering blood, managing overall body water, electrolyte, and acid-base balance, and regulating blood pressure. They remove metabolic waste products, toxins, and drugs. In addition, they limit inflammation by clearing cytokines and reduce immune cell activation by removing bacterial components. Dendritic cells (DCs) in the kidney maintain peripheral tolerance. About 85% of filtered water is reabsorbed by the proximal tubule, exposing distal nephron cells to high concentrations of low molecular weight antigens. These antigens are captured by DCs, helping to inactivate potentially autoreactive T cells and maintain tolerance to circulating antigens. In kidney failure, immune function is severely compromised due to the retention of toxins and cytokines, which activate immune cells and increase systemic inflammation. The kidneys are also vulnerable to immune-mediated diseases. Loss of immune homeostasis, characterized by over- or under-activity of the immune response, can adversely affect kidney function. With advances in immunology and cellular biology, biologic therapies targeting various pathways involved in the pathophysiology of kidney diseases are being developed. In this review, the immunologic aspects of kidney diseases and focus on cytokine-based therapies that may hold promise for the treatment of kidney diseases in the future will be presented.

Thiolutin, a novel NLRP3 inflammasome inhibitor, mitigates IgA nephropathy in mice

NLRP3 inflammasome plays a key role in IgA Nephropathy (IgAN) pathogenesis. Thiolutin (THL) is an NLRP3 inflammasome inhibitor with anti-inflammatory effects, but its role in IgAN is unclear. This study aimed to evaluate the protective efficacy of THL in IgAN mice, alongside assessing its inhibitory mechanisms. IgAN was induced by administration of bovine serum albumin combined with Staphylococcal Enterotoxin B in mice, followed by THL treatment. Kidney injury biomarkers, inflammatory cytokines, histological changes and the NLRP3 inflammasome pathway were assessed. The effect of THL on pyroptosis and action site on inflammasome was examined in J774A.1 cells, and co-immunoprecipitation was used to study specific protein interactions. In IgAN mice, THL treatment significantly reduced renal dysfunctional markers and histological injury without affecting hepatic function, accompanied by decreased serum IgA levels, renal IgA deposition and pro-inflammatory cytokine accumulation via regulating the mRNA and protein expression of key inflammasome components. It also attenuated pyroptosis and NLRP3 inflammasome activation instead of priming in macrophages, via disturbing the combination of NLRP3 with apoptosis-associated speck-like protein and NIMA-Related Kinase 7. THL has significant anti-inflammatory and renal protective effects in IgAN via inhibiting the NLRP3 inflammasome pathway. Its selective impact on the activation and assembly of the inflammasome, without affecting priming, highlights its potential as a targeted therapeutic agent in IgAN management.

C-reactive protein promotes diabetic kidney disease via Smad3-mediated NLRP3 inflammasome activation

Diabetic kidney disease (DKD) is the leading cause of end-stage kidney diseases resulting in enormous socio-economic burden. Accumulated evidence has indicated that C-reactive protein (CRP) exacerbates DKD by enhancing renal inflammation and fibrosis through TGF-β/Smad3 signaling. NLRP3 inflammasome is the key sensor contributing to renal inflammation. However, whether CRP enhances inflammation in DKD via NLRP3 inflammasome-related pathway remains unknown. In this study, we demonstrate that CRP promotes DKD via Smad3-mediated NLRP3 inflammasome activation as mice overexpressing human CRP gene exhibits accelerated renal inflammation in diabetic kidneys, which is associated with the activation of Smad3 and NLRP3 inflammasomes. In contrast, blockade of CPR signaling with a neutralizing anti-CD32 antibody attenuates CRP-induced activation of Smad3 and NLRP3 in vitro. Importantly, genetic deletion or pharmacological inhibition of Smad3 also mitigates CRP-induced activation of NLRP3 in diabetic kidneys or in high glucose-treated cells. Mechanistically, we reveal that Smad3 binds to the NLRP3 gene promoter, which is enhanced by CRP. Taken together, we conclude that CRP induces renal inflammation in DKD via a Smad3-NLRP3 inflammasome-dependent mechanism. Thus, targeting CRP or Smad3-NLRP3 pathways may be a new therapeutic potential for DKD.

Multi-modal investigation reveals pathogenic features of diverse DDX3X missense mutations

De novo mutations in the RNA binding protein DDX3X cause neurodevelopmental disorders including DDX3X syndrome and autism spectrum disorder. Amongst ~200 mutations identified to date, half are missense. While DDX3X loss of function is known to impair neural cell fate, how the landscape of missense mutations impacts neurodevelopment is almost entirely unknown. Here, we integrate transcriptomics, proteomics, and live imaging to demonstrate clinically diverse DDX3X missense mutations perturb neural development via distinct cellular and molecular mechanisms. Using mouse primary neural progenitors, we investigate four recurrently mutated DDX3X missense variants, spanning clinically severe (2) to mild (2). While clinically severe mutations impair neurogenesis, mild mutations have only a modest impact on cell fate. Moreover, expression of severe mutations leads to profound neuronal death. Using a proximity labeling screen in neural progenitors, we discover DDX3X missense variants have unique protein interactors. We observe notable overlap amongst severe mutations, suggesting common mechanisms underlying altered cell fate and survival. Transcriptomic analysis and subsequent cellular investigation highlights new pathways associated with DDX3X missense variants, including upregulated DNA Damage Response. Notably, clinically severe mutations exhibit excessive DNA damage in neurons, associated with increased cytoplasmic DNA:RNA hybrids and formation of stress granules. These findings highlight aberrant RNA metabolism and DNA damage in DDX3X-mediated neuronal cell death. In sum our findings reveal new mechanisms by which clinically distinct DDX3X missense mutations differentially impair neurodevelopment.

TLR4 Inhibitor TAK-242 Protected Henoch-Schonlein Purpura Nephritis in Rats by Regulating Inflammatory Response and Immune Competence via NF- κB/NLRP3 Signalling

This study aimed to explore the effect of toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB)/NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) signalling on Henoch-Schonlein purpura nephritis (HSPN). We established a HSPN rat model in a high-altitude hypoxic (HH) environment. Renal tissue lesions were observed by haematoxylin and Eosin (H&E) staining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL), CD20-postive B cells and CD68-postive macrophage cells were detected by immunohistochemistry, T-cell activation was detected by flow cytometry and toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB)/NOD-like receptor thermal protein domain associated protein 3 (NLRP3) signalling was detected by western blot. TAK-242 inhibited the expression of TLR4/NF-κB/NLRP3 signalling related-proteins, decreased the levels of 24 h urinary protein, serum creatinine, circular immune complex (CIC) and kidney immunoglobulin A (IgA), and improved renal histopathological damage in HH-HSPN rats. Furthermore, TAK-242 attenuated the infiltration of CD20 and CD68 into the kidney and increased the percentage of CD3+, CD4+ and CD4+/CD8+ cells in the blood of HH-HSPN rats. The study revealed that suppressing TLR4/NF-κB/NLRP3 signalling improved renal function and histopathological damage, and this improvement was related to inhibiting the inflammatory response and enhancing immune competence.

AIP1 Regulates Ocular Angiogenesis Via NLRP12-ASC-Caspase-8 Inflammasome-Mediated Endothelial Pyroptosis

Pathological ocular angiogenesis is a significant cause of irreversible vision loss and blindness worldwide. Currently, most studies have focused on the angiogenesis factors in ocular vascular diseases, and very few endogenous anti-angiogenic compounds have been found. Moreover, although inflammation is closely related to the predominant processes involved in angiogenesis, the mechanisms by which inflammation regulates pathological ocular angiogenesis remain obscure. In this study, a vascular endothelial cells (VECs)-specific anti-angiogenic factor is identified, apoptosis signal-regulating kinase 1(ASK1)-interacting protein-1 (AIP1) as a key pathogenic regulator in a typical ocular angiogenesis model, oxygen-induced retinopathy (OIR), using single-cell RNA sequencing. It is demonstrated that AIP1 inhibited pathological angiogenesis by preventing a particular inflammatory death pathway, namely pyroptosis, in retinal VECs. The assembly of a noncanonical inflammasome is further uncovered, the NLRP12-ASC-caspase-8 inflammasome, which is promoted by decreased AIP1 in OIR. This inflammasome elicited gasdermin D (GSDMD)-dependent endothelial pyroptosis, which in turn promoted the release of vascular endothelial growth factor (VEGF) and interleukin (IL)-1β. Suppression of NLRP12-CASP8-GSDMD axis and AIP1 upregulation reduced VEGF signaling, limiting new vessel formation. These findings reveal a previously uncharacterized inflammatory angiogenic process involving VECs pyroptosis-inducing retinal neovascularization, paving the way for promising therapeutic avenues targeting angiogenesis via AIP1 or pyroptosis.

Therapy Targeted to the NLRP3 Inflammasome in Chronic Kidney Disease

Background

The NLRP3 inflammasome is a cytoplasmic polymeric protein complex composed of the cytoplasmic sensor NLRP3, the apoptosis-related spot-like protein ASC, and the inflammatory protease caspase-1. NLRP3 activates and releases IL-1β through classical pathways, and IL-18 mediates inflammation and activates gasdermin-D protein to induce cellular pyroptosis. Numerous studies have also emphasized the non-classical pathway activated by the NLRP3 inflammasome in chronic kidney disease (CKD) and the inflammasome-independent function of NLRP3.

Summary

The NLRP3-targeting inflammasome and its associated pathways have thus been widely studied in models of CKD treatment, but no drug that targets NLRP3 has thus far been approved for the treatment of CKD.

Key Messages

We herein reviewed the current interventional methods for targeting the NLRP3 inflammasome in various CKD models, analyzed their underlying mechanisms of action, classified and compared them, and discussed the advantages and follow-up directions of various interventional methods. This review therefore provides novel ideas and a reference for the development of targeted NLRP3-inflammasome therapy in CKD.

Ferroptosis-Related Genes in IgA Nephropathy: Screening for Potential Targets of the Mechanism

Aims: Exploring key genes and potential molecular pathways of ferroptosis in immunoglobulin A nephropathy (IgAN). Methods: The IgAN datasets and ferroptosis-related genes (FRGs) were obtained in the Gene Expression Omnibus (GEO) and FerrDb database. Differentially expressed genes (DEGs) were identified using R software and intersected with FRGs to obtain differentially expressed FRGs (DE-FRGs). After that, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis (PEA) and Gene Ontology (GO) functional annotation were performed on DE-FRGs. In the Search Tool for the Retrieval of Interacting Genes (STRING) website, we construct a protein-protein interaction (PPI) network. The PPI network was further investigated with screening hub genes with Cytoscape software. The core genes were then subjected to gene set enrichment analysis (GSEA). Finally, the samples were analyzed for immune infiltration in R, and the correlation between hub genes and immune cells was analyzed. Results: A total of 347 DEGs were identified. CD44, CDO1, CYBB, IL1B, RRM2, AKR1C1, activated transcription factor-3 (ATF3), CDKN1A, GDF15, JUN, MGST1, MIOX, MT1G, NR4A1, PDK4, TNFAIP3, and ZFP36 were determined as DE-FRGs. JUN, IL1B, and ATF3 were then screened as hub genes. GSEA and immune infiltration analysis revealed that the hub genes were closely associated with immune inflammatory responses such as NOD-like receptor signaling, IL-17 signaling, and TNF signaling. Conclusions: Our results show that JUN and ATF3 are possibly critical genes in the process of IgAN ferroptosis and may be related with immune cell infiltration.

Renal macrophages and NLRP3 inflammasomes in kidney diseases and therapeutics

Macrophages are exceptionally diversified cell types and perform unique features and functions when exposed to different stimuli within the specific microenvironment of various kidney diseases. In instances of kidney tissue necrosis or infection, specific patterns associated with damage or pathogens prompt the development of pro-inflammatory macrophages (M1). These M1 macrophages contribute to exacerbating tissue damage, inflammation, and eventual fibrosis. Conversely, anti-inflammatory macrophages (M2) arise in the same circumstances, contributing to kidney repair and regeneration processes. Impaired tissue repair causes fibrosis, and hence macrophages play a protective and pathogenic role. In response to harmful stimuli within the body, inflammasomes, complex assemblies of multiple proteins, assume a pivotal function in innate immunity. The initiation of inflammasomes triggers the activation of caspase 1, which in turn facilitates the maturation of cytokines, inflammation, and cell death. Macrophages in the kidneys possess the complete elements of the NLRP3 inflammasome, including NLRP3, ASC, and pro-caspase-1. When the NLRP3 inflammasomes are activated, it triggers the activation of caspase-1, resulting in the release of mature proinflammatory cytokines (IL)-1β and IL-18 and cleavage of Gasdermin D (GSDMD). This activation process therefore then induces pyroptosis, leading to renal inflammation, cell death, and renal dysfunction. The NLRP3-ASC-caspase-1-IL-1β-IL-18 pathway has been identified as a factor in the development of the pathophysiology of numerous kidney diseases. In this review, we explore current progress in understanding macrophage behavior concerning inflammation, injury, and fibrosis in kidneys. Emphasizing the pivotal role of activated macrophages in both the advancement and recovery phases of renal diseases, the article delves into potential strategies to modify macrophage functionality and it also discusses emerging approaches to selectively target NLRP3 inflammasomes and their signaling components within the kidney, aiming to facilitate the healing process in kidney diseases.

The role of inflammasomes in human diseases and their potential as therapeutic targets

Inflammasomes are large protein complexes that play a major role in sensing inflammatory signals and triggering the innate immune response. Each inflammasome complex has three major components: an upstream sensor molecule that is connected to a downstream effector protein such as caspase-1 through the adapter protein ASC. Inflammasome formation typically occurs in response to infectious agents or cellular damage. The active inflammasome then triggers caspase-1 activation, followed by the secretion of pro-inflammatory cytokines and pyroptotic cell death. Aberrant inflammasome activation and activity contribute to the development of diabetes, cancer, and several cardiovascular and neurodegenerative disorders. As a result, recent research has increasingly focused on investigating the mechanisms that regulate inflammasome assembly and activation, as well as the potential of targeting inflammasomes to treat various diseases. Multiple clinical trials are currently underway to evaluate the therapeutic potential of several distinct inflammasome-targeting therapies. Therefore, understanding how different inflammasomes contribute to disease pathology may have significant implications for developing novel therapeutic strategies. In this article, we provide a summary of the biological and pathological roles of inflammasomes in health and disease. We also highlight key evidence that suggests targeting inflammasomes could be a novel strategy for developing new disease-modifying therapies that may be effective in several conditions.

Research Progress of Pyroptosis in Renal Diseases

Kidney diseases, particularly Acute Kidney Injury (AKI) and Chronic Kidney Disease (CKD), are identified as global public health issues affecting millions of individuals. In addition, the frequency of renal diseases in the population has increased dramatically and rapidly in recent years. Renal disorders have become a significant public health burden. The pathophysiology of renal diseases is significantly connected with renal cell death, including apoptosis, necrosis, necroptosis, ferroptosis, pyroptosis, and autophagy, as is now recognized. Unlike other forms of cell death, pyroptosis is a unique planned cell death (PCD). Scientists have proven that pyroptosis is crucial in developing various disorders, and this phenomenon is gaining increasing attention. It is considered a novel method of inflammatory cell death. Intriguingly, inflammation is among the most significant pathological characteristics of renal disease. This study investigates the effects of pyroptosis on Acute Kidney Injury (AKI), Chronic Kidney Disease (CKD), Diabetic Nephropathy (DN), Immunoglobulin A (IgA) Nephropathy, and Lupus Nephritis (LN) to identify novel therapeutic targets for kidney diseases.

Autoinflammatory diseases and the kidney

The kidney represents an important target of systemic inflammation. Its involvement in monogenic and multifactorial autoinflammatory diseases (AIDs) vary from peculiar and relatively frequent manifestations to some rare but severe features that may end up requiring transplantation. The pathogenetic background is also very heterogeneous ranging from amyloidosis to non-amyloid related damage rooted in inflammasome activation. Kidney involvement in monogenic and polygenic AIDs may present as renal amyloidosis, IgA nephropathy, and more rarely as various forms of glomerulonephritis (GN), namely segmental glomerulosclerosis, collapsing glomerulopathy, fibrillar, or membranoproliferative GN. Vascular disorders such as thrombosis or renal aneurysms and pseudoaneurysms may be encountered in patients with Behcet's disease. Patients with AIDs should be routinely assessed for renal involvement. Screening with urinalysis, serum creatinine, 24-h urinary protein, microhematuria, and imaging studies should be carried out for early diagnosis. Awareness of drug-induced nephrotoxicity, drug-drug interactions as well as addressing the issue of proper renal adjustment of drug doses deserve a special mention and should always be considered when dealing with patients affected by AIDs. Finally, we will explore the role of IL-1 inhibitors in AIDs patients with renal involvement. Targeting IL-1 may indeed have the potential to successfully manage kidney disease and improve long-term prognosis of AIDs patients.

Effects and mechanisms of Chinese herbal medicine on IgA nephropathy

BACKGROUND

Immunoglobulin A nephropathy (IgAN), is the main cause of end-stage renal disease, that causes serious physical and psychological burden to patients worldwide. Some traditional treatment measures, such as blocking the renin-angiotensin-aldosterone system, controlling blood pressure, and following a low-protein diet, may not achieve satisfactory results. Therefore, more effective and safe therapies for IgAN are urgently needed.

PURPOSE

The aim of this review is to summarize the clinical efficacy of Chinese herbal medicines (CHMs) and their active ingredients in the treatment and management of IgAN based on the results of clinical trials, systematic reviews, and meta-analyses, to fully understand the advantages and perspectives of CHMs in the treatment of IgAN.

STUDY DESIGN AND METHODS

For this review, the following electronic databases were consulted: PubMed, ResearchGate, Science Direct, Web of Science, Chinese National Knowledge Infrastructure and Wanfang Data, "IgA nephropathy," "traditional Chinese medicine," "Chinese herbal medicine," "herb," "mechanism," "Meta-analysis," "systematic review," "RCT" and their combinations were the keywords to search the relevant literature. Data were collected from 1990 to 2022.

RESULTS

This review found that the active ingredients of CHMs commonly act on multiple signaling pathways in the clinical treatment of IgAN, mainly with antioxidant, anti-inflammatory and anti-fibrosis effects, and regulation of autophagy.

CONCLUSION

Compared with the single-target therapy of modern medicine, CHMs can regulate the corresponding pathways from the aspects of anti-inflammation, anti-oxidation, anti-fibrosis and autophagy to play a multi-target treatment of IgAN through syndrome differentiation and treatment, which has good clinical efficacy and can be used as the first choice or alternative therapy for IgAN treatment. This review provides evidence and research direction for a comprehensive clinical understanding of the protective effect of Chinese herbal medicine on IgAN.

Role of cuproptosis in understanding diseases

Cell death is involved in a wide range of physiological and pathological processes. Recently, the term "cuproptosis" was coined to describe a novel type of cell death. This type of cell death, characterized by copper accumulation and proteotoxic stress, is a copper-dependent manner of death. Despite the progress achieved toward a better understanding of cuproptosis, mechanisms and related signaling pathways in physiology and pathology across various diseases remain to be proved. This mini review summarizes current research on cuproptosis and diseases, providing insights into prospective clinical therapies via targeting cuproptosis.

DNA-damaged podocyte-CD8 T cell crosstalk exacerbates kidney injury by altering DNA methylation

Recent epigenome-wide studies suggest an association between blood DNA methylation and kidney function. However, the pathological importance remains unclear. Here, we show that the homing endonuclease I-PpoI-induced DNA double-strand breaks in kidney glomerular podocytes cause proteinuria, glomerulosclerosis, and tubulointerstitial fibrosis with DNA methylation changes in blood cells as well as in podocytes. Single-cell RNA-sequencing analysis reveals an increase in cytotoxic CD8+ T cells with the activating/costimulatory receptor NKG2D in the kidneys, which exhibit a memory precursor effector cell phenotype, and the CD44high memory CD8+ T cells are also increased in the peripheral circulation. NKG2D blockade attenuates the renal phenotype caused by podocyte DNA damage. Blood methylome shows increased DNA methylation in binding sites for STAT1, a transcription factor contributing to CD8+ T cell homeostasis. Collectively, podocyte DNA damage alters the blood methylome, leading to changes in CD8+ T cells, which contribute to sustained renal injury in chronic kidney disease.

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.

Identification of key cuproptosis-related genes and their targets in patients with IgAN

BACKGROUND

IgA nephropathy (IgAN) is one of the most common forms of chronic glomerulonephritis, but the aetiology and pathogenesis remain unclear. Cuproptosis is a newly identified form of cell death that plays an important role in many diseases. Researchers have not clearly determined whether the expression of cuproptosis-related genes (CRGs) is involved in the pathogenesis of IgAN.

METHODS

The GSE93798, GSE50469 and GSE37460 datasets containing microarray data from patients with IgAN (63) and healthy controls (31) were downloaded from the GEO database. Immune cells and immune-related functions were analysed in patients with IgAN and controls, and genes were identified that may be related to cuproptosis. A logistic regression model was established according to the results, and then GO and KEGG enrichment analyses were performed. Finally, possible drugs were selected using the DSigDB database.

RESULTS

The subjects in the different groups showed significantly different fractions of immune cells and immune-related functions, and 11 genes related to cuproptosis may be involved in these processes. Based on these 11 genes, the ROC curve was plotted, and the AUC value was calculated (0.898, 95% CI: 0.839-0.958). The result revealed good predictability. Then, genes with P < 0.05 (lipoyltransferase 1, LIPT1) were selected to plot an ROC curve, and the AUC value was calculated (0.729, 95% CI: 0.636-0.821). Enrichment analyses showed that the TCA cycle and multiple metabolic pathways may also be involved in the occurrence of IgAN. Finally, 293 potential drugs that may be used to treat IgAN were identified based on these genes.

CONCLUSION

In this study, we identified some novel CRGs that may be involved in IgAN, among which LIPT1 was significantly differentially expressed. It may predict the risk of IgAN and provides a possible target for the treatment of IgAN. Further experimental studies are needed to explore how these CRGs mediate the occurrence and development of IgAN.

The molecular pathogenesis of triptolide-induced hepatotoxicity

Triptolide (TP) is the major pharmacologically active ingredient and toxic component of Tripterygium wilfordii Hook. f. However, its clinical potential is limited by a narrow therapeutic window and multiple organ toxicity, especially hepatotoxicity. Furthermore, TP-induced hepatotoxicity shows significant inter-individual variability. Over the past few decades, research has been devoted to the study of TP-induced hepatotoxicity and its mechanism. In this review, we summarized the mechanism of TP-induced hepatotoxicity. Studies have demonstrated that TP-induced hepatotoxicity is associated with CYP450s, P-glycoprotein (P-gp), oxidative stress, excessive autophagy, apoptosis, metabolic disorders, immunity, and the gut microbiota. These new findings provide a comprehensive understanding of TP-induced hepatotoxicity and detoxification.

Antibiotic pretreatment promotes orally-administered triptolide absorption and aggravates hepatotoxicity and intestinal injury in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Triptolide (TP) exhibits extensive pharmacological activity, but its hepatotoxicity and intestinal injury are significant and limit its clinical use.

AIM OF THE STUDY

To investigate the effect of gut microbiota disturbance after antibiotic pretreatment on TP-induced hepatotoxicity, intestinal injury and their mechanism.

MATERIALS AND METHODS

We compared the characteristics of TP-induced hepatotoxicity and intestinal injury in mice with or without antibiotic pretreatment. The levels of cytokines in the serum, immunohistochemistry, and the pharmacokinetics of TP were determined.

RESULT

Antibiotic pretreatment aggravates TP-induced hepatotoxicity and ileum/colon injury. TP induces hepatotoxicity in a dose-dependent manner after antibiotic pretreatment. Serum IL-1β and IL-6 levels were increased in mice given oral TP after antibiotic pretreatment. TP can increase the expression of NLRP3 inflammasome in hepatocytes, and Oral TP after antibiotic pretreatment can significantly enhance its expression, but NLRP3 inflammasome no significant change in colon and ileum. The pharmacokinetic characteristics of TP are altered significantly by antibiotic pretreatment, as shown by a 145.87% increase in C_max, a 155.11% increase in AUC_0-t, a 155.1% increase in relative bioavailability, and a 15.44% delay in MRT. Moreover, TP causes hepatotoxicity in a time-dependent manner.

CONCLUSIONS

Antibiotic pretreatment aggravates triptolide-induced hepatotoxicity and intestinal injury through elevated inflammatory response and promoted triptolide absorption.

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.

Novel insights into NOD-like receptors in renal diseases

Nucleotide-binding oligomerization domain-like receptors (NLRs), including NLRAs, NLRBs (also known as NAIPs), NLRCs, and NLRPs, are a major subfamily of pattern recognition receptors (PRRs). Owing to a recent surge in research, NLRs have gained considerable attention due to their involvement in mediating the innate immune response and perpetuating inflammatory pathways, which is a central phenomenon in the pathogenesis of multiple diseases, including renal diseases. NLRs are expressed in different renal tissues during pathological conditions, which suggest that these receptors play roles in acute kidney injury, obstructive nephropathy, diabetic nephropathy, IgA nephropathy, lupus nephritis, crystal nephropathy, uric acid nephropathy, and renal cell carcinoma, among others. This review summarises recent progress on the functions of NLRs and their mechanisms in the pathophysiological processes of different types of renal diseases to help us better understand the role of NLRs in the kidney and provide a theoretical basis for NLR-targeted therapy for renal diseases.

Involvement of Inflammasome Components in Kidney Disease

Inflammasomes are multiprotein complexes with an important role in the innate immune response. Canonical activation of inflammasomes results in caspase-1 activation and maturation of cytokines interleukin-1β and -18. These cytokines can elicit their effects through receptor activation, both locally within a certain tissue and systemically. Animal models of kidney diseases have shown inflammasome involvement in inflammation, pyroptosis and fibrosis. In particular, the inflammasome component nucleotide-binding domain-like receptor family pyrin domain containing 3 (NLRP3) and related canonical mechanisms have been investigated. However, it has become increasingly clear that other inflammasome components are also of importance in kidney disease. Moreover, it is becoming obvious that the range of molecular interaction partners of inflammasome components in kidney diseases is wide. This review provides insights into these current areas of research, with special emphasis on the interaction of inflammasome components and redox signalling, endoplasmic reticulum stress, and mitochondrial function. We present our findings separately for acute kidney injury and chronic kidney disease. As we strictly divided the results into preclinical and clinical data, this review enables comparison of results from those complementary research specialities. However, it also reveals that knowledge gaps exist, especially in clinical acute kidney injury inflammasome research. Furthermore, patient comorbidities and treatments seem important drivers of inflammasome component alterations in human kidney disease.

TRIM40 inhibits IgA1-induced proliferation of glomerular mesangial cells by inactivating NLRP3 inflammasome through ubiquitination

IgA nephropathy, as the most common type of glomerulonephritis, causes chronic renal disease and progresses into kidney failure. Aberrant IgA deposition in the glomerular mesangium induces NLRP3 inflammasome activation for massive local inflammation, and is recognized as the primary pathogenesis in IgA nephropathy. Tripartite motif (TRIM)-containing proteins are E3 ubiquitin ligases that possess crucial regulatory functions in innate immunity, but their functional roles in IgA nephropathy are still unclear. Here, we aimed to identify TRIM-containing proteins that regulate IgA nephropathy and their underlying mechanisms. An in vitro IgA1-induction model was established in glomerular mesangial cells (GMCs) and showed that IgA1 could promote GMC proliferation by activating NLRP3 inflammasome. TRIM40, which was downregulated by IgA1 and interacted with NLRP3, was recognized as a promising candidate. In addition, TRIM40 could suppress IgA1-induced GMC proliferation by inhibiting the activation of NLRP3 inflammasome. Based on coimmunoprecipitation and ubiquitination assays, we confirmed that TRIM40 could mediate the ubiquitination of NLRP3, which explained its regulatory effects on NLRP3 inflammasome and GMC proliferation. More importantly, a dominant-negative mutant of TRIM40 lacking the RING domain (ΔRING) did not affect NLRP3 ubiquitination, and had no effects on IgA1-induced GMC proliferation or NLRP3 inflammasome activation. This study revealed the biological functions of TRIM40 in IgA nephropathy, facilitating its application as therapeutic target for IgA nephropathy and other NLRP3 inflammasome-relevant diseases.

LncRNA CRNDE Exacerbates IgA Nephropathy Progression by Promoting NLRP3 Inflammasome Activation in Macrophages

BACKGROUND

Activation of NLRP3 inflammasome in macrophages contributes greatly to IgA nephropathy (IgAN) progression. This study intended to investigate the underlying mechanism of NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation in the development of IgAN.

METHODS

We examined the expression levels of colorectal neoplasia differentially expressed (CRNDE), NLRP3 inflammasome-related proteins in peripheral blood mononuclear cells (PBMCs) and J774A.1 cells and detected inflammatory cytokine levels in the serum of IgAN patients and cell supernatants of in vitro IgAN model. RNA pull-down and RNA immunoprecipitation (RIP) experiments were conducted to evaluate the interaction between CRNDE and NLRP3. Then, the ubiquitin level of NLRP3 and its binding ability to TRIM family member 31 (TRIM31) were determined.

RESULTS

Compared with the control group, the expressions of CRNDE and NLRP3 inflammasome-related proteins in PBMCs and J774A.1 cells and levels of IL-1β, TNF-α and IL-12 in serum of IgAN patients and cell supernatants of IgA-IC-induced J774A.1 cells were all increased. CRNDE silencing down-regulated NLRP3 inflammasome-related proteins and the levels of IL-1β, TNF-α and IL-12 in cell supernatants, while NLRP3 overexpression reversed these effects. Additionally, CRNDE could interact with NLRP3 and promote NLRP3 expression. Furthermore, inhibition of CRNDE reduced NLRP3 protein level and promoted TRIM31-mediated NLRP3 ubiquitination and degradation.

CONCLUSION

CRNDE exacerbates IgA nephropathy progression through restraining ubiquitination and degradation of NLRP3 and facilitating NLRP3 inflammasome activation in macrophages.

An Update on Targeted Treatment of IgA Nephropathy: An Autoimmune Perspective

Immunoglobulin (Ig) A nephropathy (IgAN) is the commonest form of primary glomerulonephritis worldwide and is, considered a significant cause of end-stage renal disease in young adults. The precise pathogenesis of IgAN is unclear. The clinical and pathological features vary significantly between individuals and races, which makes treating IgAN difficult. Currently, the therapeutic strategies in IgAN are still optimal blood pressure control and proteinuria remission to improve the renal function in most cases. Immunosuppressive drugs such as corticosteroids can be considered in patients with persistent proteinuria and a high risk of renal function decline; however, they include a high toxicity profile. Therefore, the safety and selectivity of medications are critical concerns in the treatment of IgAN. Various pharmacological therapeutic targets have emerged based on the evolving understanding of the autoimmune pathogenesis of IgAN, which involves the immune response, mucosal immunity, renal inflammation, complement activation, and autophagy; treatments based on these mechanisms have been explored in preclinical and clinical studies. This review summarizes the progress concerning targeted therapeutic strategies and the relevant autoimmune pathogenesis in IgAN.

Cf-02, a novel benzamide-linked small molecule, blunts NF-κB activation and NLRP3 inflammasome assembly and improves acute onset of accelerated and severe lupus nephritis in mice

In the present study, acute onset of severe lupus nephritis was successfully treated in mice using a new, benzamide-linked, small molecule that targets immune modulation and the NLRP3 inflammasome. Specifically, 6-(2,4-difluorophenyl)-3-(3-(trifluoromethyl)phenyl)-2H-benzo[e][1,3]oxazine-2,4(3H)-dione (Cf-02) (a) reduced serum levels of IgG anti-dsDNA, IL-1β, IL-6, and TNF-α, (b) inhibited activation of dendritic cells and differentially regulated T cell functions, and (c) suppressed the NF-κB/NLRP3 inflammasome axis, targeting priming and activating signals of the inflammasome. Moreover, treatment with Cf-02 significantly inhibited secretion of IL-1β in lipopolysaccharide-stimulated macrophages, but this effect was abolished by autophagy induction. These results recommend Cf-02 as a promising drug candidate for the serious renal conditions associated with systemic lupus erythematosus. Future investigations should examine whether Cf-02 may also be therapeutic in other types of chronic kidney disease involving NLRP3 inflammasome-driven signaling.

Downregulation of miR‑214-3p attenuates mesangial hypercellularity by targeting PTEN‑mediated JNK/c-Jun signaling in IgA nephropathy

Mesangial cell (MC) proliferation and matrix expansion are basic pathological characteristics of IgA nephropathy (IgAN). However, the stepwise mechanism of MC proliferation and the exact set of related signaling molecules remain largely unclear. In this study, we found a significant upregulation of miR-214-3p in the renal cortex of IgAN mice by miRNA sequencing. In situ hybridization analysis showed that miR-214-3p expression was obviously elevated in MCs in the renal cortex in IgAN. Functionally, knockdown of miR-214-3p alleviated mesangial hypercellularity and renal lesions in IgAN mice. In vitro, the inhibition of miR-214-3p suppressed MC proliferation and arrested G1-S cell cycle pSrogression in IgAN. Mechanistically, a luciferase reporter assay verified PTEN as a direct target of miR-214-3p. Downregulation of miR-214-3p increased PTEN expression and reduced p-JNK and p-c-Jun levels, thereby inhibiting MC proliferation and ameliorating renal lesions in IgAN. Moreover, these changes could be attenuated by co-transfection with PTEN siRNA. Collectively, these results illustrated that miR-214-3p accelerated MC proliferation in IgAN by directly targeting PTEN to modulate JNK/c-Jun signaling. Therefore, miR-214-3p may represent a novel therapeutic target for IgAN.

Pyroptosis: A New Frontier in Kidney Diseases

Pyroptosis is a pattern of programmed cell death that significantly differs from apoptosis and autophagy in terms of cell morphology and function. The process of pyroptosis is characterized predominantly by the formation of gasdermin protein family-mediated membrane perforation, cell collapse, and the release of inflammatory factors, including IL-1β and IL-18. In recent years, with the rise of pyroptosis research, scholars have devoted time to study the mechanism of pyroptosis in kidney-related diseases. Pyroptosis is probably involved in kidney diseases through two pathways: the caspase-1-mediated canonical pathway and the caspase-4/5/11-mediated noncanonical pathway. In addition, some scholars have identified targets for the treatment of kidney-related diseases from the viewpoint of pyroptosis and developed corresponding medicines, which may become a recommendation for prognosis, targeted treatment, and clinical diagnosis of kidney diseases. This paper focuses on the up-to-date advances in the field of pyroptosis, especially on the key pathogenic role of pyroptosis in the development and progression of kidney diseases. It presents a more in-depth understanding of the pathogenesis of kidney diseases and introduces novel therapeutic targets for the prevention and clinical treatment of kidney diseases.

LCC18, a benzamide-linked small molecule, ameliorates IgA nephropathy in mice

IgA nephropathy (IgAN), an immune complex-mediated process and the most common primary glomerulonephritis, can progress to end-stage renal disease in up to 40% of patients. Accordingly, a therapeutic strategy targeting a specific molecular pathway is urgently warranted. Aided by structure characterisation and target identification, we predicted that a novel ring-fused 6-(2,4-difluorophenyl)-3-(3-(trifluoromethyl)phenyl)-2H-benzo[e][1,3]oxazine-2,4(3H)-dione (LCC18) targets the NLRP3 inflammasome, which participates in IgAN pathogenesis. We further developed biomarkers for the disease. We used two complementary IgAN models in C57BL/6 mice, involving TEPC-15 hybridoma-derived IgA, and in gddY mice. Moreover, we created specific cell models to validate therapeutic effects of LCC18 on IgAN and to explain its underlying mechanisms. IgAN mice benefited significantly from treatment with LCC18, showing dramatically improved renal function, including greatly reduced proteinuria and renal pathology. Mechanistic studies showed that the mode of action specifically involved: (1) blocking of the MAPKs/COX-2 axis-mediated priming of the NLRP3 inflammasome; (2) inhibition of ASC oligomerisation and NLRP3 inflammasome assembly by inhibiting NLRP3 binding to PKR, NEK7 and ASC; and (3) activation of autophagy. LCC18 exerts therapeutic effects on murine IgAN by differentially regulating NLRP3 inflammasome activation and autophagy induction, suggesting this new compound as a promising drug candidate to treat IgAN. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

A Synthetic Small Molecule F240B Decreases NLRP3 Inflammasome Activation by Autophagy Induction

Conjugated polyenes are a class of widely occurring natural products with various biological functions. We previously identified 4-hydroxy auxarconjugatin B (4-HAB) as anti‐inflammatory agent with an IC₅₀ of ~20 µM. In this study, we synthesized a new anti‐inflammatory 4-HAB analogue, F240B, which has an IC₅₀ of less than 1 µM. F240B dose-dependently induced autophagy by increasing autophagic flux, LC3 speck formation and acidic vesicular organelle formation. F240B inhibited NACHT, LRR and PYD domain-containing protein 3 (NLRP3) inflammasome activation through autophagy induction. In a mechanistic study, F240B inhibited interleukin (IL)-1β (IL-1β) precursor expression, promoted degradation of NLRP3 and IL-1β, and reduced mitochondrial membrane integrity loss in an autophagy-dependent manner. Additionally, F240B inhibited apoptosis-associated speck-like protein containing a CARD (ASC) oligomerization and speck formation without affecting the interaction between NLRP3 and ASC or NIMA-related kinase 7 (NEK7) and double-stranded RNA-dependent kinase (PKR). Furthermore, F240B exerted in vivo anti-inflammatory activity by reducing the intraperitoneal influx of neutrophils and the levels of IL-1β, active caspase-1, IL-6 and monocyte chemoattractant protein-1 (MCP-1) in lavage fluids in a mouse model of uric acid crystal-induced peritonitis. In conclusion, F240B attenuated the NLRP3 inflammasome through autophagy induction and can be developed as an anti-inflammatory agent in the future.

Pinocembrin relieves lipopolysaccharide and bleomycin induced lung inflammation via inhibiting TLR4-NF-κB-NLRP3 inflammasome signaling pathway

Inflammation is a defense response of the body to stimuli. Lung injury caused by external stimuli can stimulate inflammatory cells to accumulate at the site of injury and secrete cytokines. Pinocembrin is a flavonoid with anti-inflammatory effects. Based on previous studies, we further explored the anti-inflammatory mechanisms of pinocembrin in vitro and in vivo. In vitro studies indicated that pinocembrin inhibited lipopolysaccharide (LPS)-stimulated inflammatory response in macrophages. In vivo studies also showed that pinocembrin could reduce LPS and bleomycin (BLM) induced lung inflammatory response in mice. Further mechanistic studies indicated that pinocembrin could regulate the TLR4-NF-κB signaling pathway and suppressed the activation and assembly of NLRP3 inflammasomes. In summary, pinocembrin could relieve pulmonary inflammatory response induced by LPS and BLM mainly via inhibiting TLR4-NF-κB-NLRP3 inflammasome axis. These results contribute to the understanding of the anti-inflammatory mechanisms of pinocembrin and serve as reference for future research on pinocembrin.

Tris DBA ameliorates IgA nephropathy by blunting the activating signal of NLRP3 inflammasome through SIRT1- and SIRT3-mediated autophagy induction

Tris (dibenzylideneacetone) dipalladium (Tris DBA), a small-molecule palladium complex, can inhibit cell growth and proliferation in pancreatic cancer, lymphocytic leukaemia and multiple myeloma. Given that this compound is particularly active against B-cell malignancies, we have been suggested that it can alleviate immune complexes (ICs)-mediated conditions, especially IgA nephropathy (IgAN). The therapeutic effects of Tris DBA on glomerular cell proliferation and renal inflammation and mechanism of action were examined in a mouse model of IgAN. Treatment of IgAN mice with Tris DBA resulted in markedly improved renal function, albuminuria and renal pathology, including glomerular cell proliferation, neutrophil infiltration, sclerosis and periglomerular inflammation in the renal interstitium, together with (Clin J Am Soc Nephrol. 2011, 6, 1301-1307) reduced mitochondrial ROS generation; (Am J Physiol-Renal Physiol. 2011. 301, F1218-F1230) differentially regulated autophagy and NLRP3 inflammasome; (Clin J Am Soc Nephrol. 2012, 7, 427-436) inhibited phosphorylation of JNK, ERK and p38 MAPK signalling pathways, and priming signal of the NLRP3 inflammasome; and (Free Radic Biol Med. 2013, 61, 285-297) blunted NLRP3 inflammasome activation through SIRT1- and SIRT3-mediated autophagy induction, in renal tissues or cultured macrophages. In conclusion, Tris DBA effectively ameliorated the mouse IgAN model and targeted signalling pathways downstream of ICs-mediated interaction, which is a novel immunomodulatory strategy. Further development of Tris DBA as a therapeutic candidate for IgAN is warranted.

Compound K inhibits priming and mitochondria-associated activating signals of NLRP3 inflammasome in renal tubulointerstitial lesions

BACKGROUND

Renal tubulointerstitial lesions (TILs), a key pathological hallmark for chronic kidney disease to progress to end-stage renal disease, feature renal tubular atrophy, interstitial mononuclear leukocyte infiltration and fibrosis in the kidney. Our study tested the renoprotective and therapeutic effects of compound K (CK), as described in our US patent (US7932057B2), on renal TILs using a mouse unilateral ureteral obstruction (UUO) model.

METHODS

Renal pathology was performed and renal draining lymph nodes were subjected to flow cytometry analysis. Mechanism-based experiments included the analysis of mitochondrial dysfunction, a model of tubular epithelial cells (TECs) under mechanically induced constant pressure (MICP) and tandem mass tags (TMT)-based proteomics analysis.

RESULTS

Administration of CK ameliorated renal TILs by reducing urine levels of proinflammatory cytokines, and preventing mononuclear leukocyte infiltration and fibrosis in the kidney. The beneficial effects clearly correlated with its inhibition of: (i) NF-κB-associated priming and the mitochondria-associated activating signals of the NLRP3 inflammasome; (ii) STAT3 signalling, which in part prevents NLRP3 inflammasome activation; and (iii) the TGF-β-dependent Smad2/Smad3 fibrotic pathway, in renal tissues, renal TECs under MICP and/or activated macrophages, the latter as a major inflammatory player contributing to renal TILs. Meanwhile, TMT-based proteomics analysis revealed downregulated renal NLRP3 inflammasome activation-associated signalling pathways in CK-treated UUO mice.

CONCLUSIONS

The present study, for the first time, presents the potent renoprotective and therapeutic effects of CK on renal TILs by targeting the NLRP3 inflammasome and STAT3 signalling.

Zhen-Wu-Tang Protects IgA Nephropathy in Rats by Regulating Exosomes to Inhibit NF-κB/NLRP3 Pathway

Immunoglobulin A nephropathy (IgAN) is one of the most frequent kinds of primary glomerulonephritis characterized by IgA immune complexes deposition and glomerular proliferation. Zhen-wu-tang (ZWT), a well-known traditional Chinese formula has been reported to ameliorate various kidney diseases. However, its pharmacological mechanism remains unclear. Exosomes have been described in diverse renal diseases by mediating cellular communication but rarely in the IgAN. The purpose of the present study is to explore whether the underlying mechanisms of the effect of ZWT on IgAN is correlated to exosomes. Our results demonstrated that in human renal tubular epithelial cells (HK-2) stimulated by lipopolysaccharide, exosomes are obviously released after ZWT-containing serum treatment especially with 10% ZWT. In addition, once released, HK-2-derived exosomes were uptaked by human mesangial cells (HMC), which impeded the activation of NF-κB/NLRP3 signaling pathway to exert anti-inflammatory effects in a lipopolysaccharide induced proliferation model. Moreover, IgAN rat model was established by bovine serum albumin, CCL₄ mixed solution and LPS. We found that 10% ZWT could significantly promote the release of exosomes from HK-2 and inhibit HMC proliferation to improve inflammation. Thus HK-2-derived exosomes treated with 10% ZWT (ZWT-EXO) were administered to the rats by tail vein injection. Our results showed that ZWT-EXO decreased the levels of 24 h proteinuria, urinary erythrocyte, IgA deposition in glomerulus and renal pathological injury which ameliorated the kidney damage. In addition, ZWT was able to dramatically promote secretion of exosomes in renal tissues while blocked NF-κB nuclear translocation as well as activation of NLRP3 inflammasome, leading to the inhibition of IL-1β and caspase-1. In conclusion, our study reveal that ZWT has protective effects on IgAN by regulating exosomes secretion to inhibit the activation of NF-κB/NLRP3 pathway, thereby attenuating the renal dysfunction. These findings may provide a new therapeutic target for the treatment of IgAN.

Macrophage polarization in innate immune responses contributing to pathogenesis of chronic kidney disease

Chronic kidney disease (CKD) is characterized by inflammation, injury and fibrosis. Dysregulated innate immune responses mediated by macrophages play critical roles in progressive renal injury. The differentiation and polarization of macrophages into pro-inflammatory 'M1' and anti-inflammatory 'M2' states represent the two extreme maturation programs of macrophages during tissue injury. However, the effects of macrophage polarization on the pathogenesis of CKD are not fully understood. In this review, we discuss the innate immune mechanisms underlying macrophage polarization and the role of macrophage polarization in the initiation, progression, resolution and recurrence of CKD. Macrophage activation and polarization are initiated through recognition of conserved endogenous and exogenous molecular motifs by pattern recognition receptors, chiefly, Toll-like receptors (TLRs), which are located on the cell surface and in endosomes, and NLR inflammasomes, which are positioned in the cytosol. Recent data suggest that genetic variants of the innate immune molecule apolipoprotein L1 (APOL1) that are associated with increased CKD prevalence in people of African descent, mediate an atypical M1 macrophage polarization. Manipulation of macrophage polarization may offer novel strategies to address dysregulated immunometabolism and may provide a complementary approach along with current podocentric treatment for glomerular diseases.

IgA Nephropathy Benefits from Compound K Treatment by Inhibiting NF-κB/NLRP3 Inflammasome and Enhancing Autophagy and SIRT1

IgA nephropathy (IgAN), the most common primary glomerular disorder, has a relatively poor prognosis yet lacks a pathogenesis-based treatment. Compound K (CK) is a major absorbable intestinal bacterial metabolite of ginsenosides, which are bioactive components of ginseng. The present study revealed promising therapeutic effects of CK in two complementary IgAN models: a passively induced one developed by repeated injections of IgA immune complexes and a spontaneously occurring model of spontaneous grouped ddY mice. The potential mechanism for CK includes 1) inhibiting the activation of NLRP3 inflammasome in renal tissues, macrophages and bone marrow-derived dendritic cells, 2) enhancing the induction of autophagy through increased SIRT1 expression, and 3) eliciting autophagy-mediated NLRP3 inflammasome inhibition. The results support CK as a drug candidate for IgAN.

Critical Role for the NLRP3 Inflammasome in Mediating IL-1β Production in Shigella sonnei-Infected Macrophages

Shigella is one of the leading bacterial causes of diarrhea worldwide, affecting more than 165 million people annually. Among the serotypes of Shigella, Shigella sonnei is physiologically unique and endemic in human immunodeficiency virus-infected men who have sex with men. The NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome, a protein complex composed of NLRP3, apoptosis-associated speck-like protein, and caspase-1, recognizes, and responds to pathogen infection and diverse sterile host-derived or environmental danger signals to induce IL-1β and IL-18 production. Although the Shigella flexneri-mediated activation of the NLRP3 inflammasome has been reported, the effect of S. sonnei on NLRP3 inflammasome activation remains unclear. We found that S. sonnei induced IL-1β production through NLRP3-dependent pathways in lipopolysaccharide-primed macrophages. A mechanistic study revealed that S. sonnei induced IL-1β production through P₂X₇ receptor-mediated potassium efflux, reactive oxygen species generation, lysosomal acidification, and mitochondrial damage. In addition, the phagocytosis of viable S. sonnei was important for IL-1β production. Furthermore, we demonstrated that NLRP3 negatively regulated phagocytosis and the bactericidal activity of macrophages against S. sonnei. These findings provide mechanistic insight into the activation of the NLRP3 inflammasome by S. sonnei in macrophages.

Inflammasome activation in podocytes: a new mechanism of glomerular diseases

INTRODUCTION

Inflammasome is a multi-protein complex which is an important constituent of innate immunity. It mainly consists of three parts, apoptosis-associated speck-like protein containing caspase recruitment domain (ASC), caspase protease, and a NOD-like receptor (NLR) family protein (such as NLRP1) or an HIN200 family protein (such as AIM2). Inflammasome is widely studied in many autoimmune diseases and chronic inflammatory reactions, such as familial periodic autoinflammatory response, type 2 diabetes, Alzheimer's disease, and atherosclerosis. Activation of inflammasome in the kidney has been widely reported in glomerular and tubular-interstitial diseases. Podocytes play a critical role in maintaining the normal structure and function of glomerular filtration barrier. Recently, it has been demonstrated that podocytes, as a group of renal residential cells, can express all necessary components of NLRP3 inflammasome, which is activated and contribute to inflammatory response in the local kidney.

METHODS

Literature review was conducted to further summarize current evidence of podocyte NLRP3 inflammasome activation and related molecular mechanisms under different disease conditions.

RESULTS

Podocytes are a key component of the glomerular filtration barrier, and the loss of podocyte regeneration is a major limiting factor in the recovery of proteinuria. Through a more comprehensive study of inflammasome in podocytes, it will provide new targets and possibilities for the treatment of kidney diseases.

Inherited Autoinflammatory Disease with Immunodeficiency Combined with IgA Nephropathy

The etiology of unexplained periodic fever is often complex, and hereditary factors play an important role. This article describes a 26-year-old chinese women with intermittent fever for 9 years, with 10-year history of IgA nephropathy. Her fever is relieved during pregnancy, but after a baby is born, fever reappears, accompanied by headache, gasping after activity, chest pain, abdominal pain, blood in the stool, ataxia, intermittent back erythema, skin biopsy suggests amyloidosis, the autoinflammatory PLCG2 associated antibody deficiency and immune dysregulation was diagnosed by genetic testing. The fever was gradually relieved after treatment with rilonacept.

Expression of miRNA-223 and NLRP3 gene in IgA patients and intervention of traditional Chinese medicine

Objective

The purpose of this study was to investigate the expression of miRNA-223 and NLRP3 in IgA patients and the intervention of traditional Chinese medicine (TCM), so as to realize the basic pathological changes of IgA patients, the expression of miRNA-223 and NLRP3 in IgA patients and the changes of patients' body indexes before and after the treatment of TCM.

Methods

Firstly, according to the clinical data, patients with IgA nephropathy were divided into different groups according to their pathological changes. After that, the chemical sections and staining steps of the immune kidney were carried out. Immunohistochemical pv-9000 two-step method was used to stain it. By this method, miRNA-223 and NLRP3 genes in kidney were determined. After that, the image analysis method was used for semi quantitative experiment. Finally, the intervention of TCM was used to study the changes of indicators before and after treatment.

Results

miRNA-223 and NLRP3 genes could be found mainly in the cytoplasm of renal tubular epithelial cells and the interstitium of monocyte in renal tissue, and there were significant differences between miRNA-223 and NLRP3 genes in the expression levels of proteinuria alone, hematuria albuminuria alone and hematuria alone. There was a positive correlation between miRNA-223 and NLRP3 expression and 24-hour urinary protein in IgA nephropathy. In addition, it also had positive correlation with MCP-1 and IL-18.

Conclusion

This study could provide some direction and guidance for clinical diagnosis and treatment of IgA nephropathy.

Role of Inflammasomes in Kidney Diseases via Both Canonical and Non-canonical Pathways

Inflammasomes, multiprotein complex induced by harmful factors in the body, play a crucial role in innate immunity. Activation of inflammasomes lead to the activation of casepase-1 and then the secretion of inflammatory cytokines, including IL-1β and IL-18, subsequently leading to a type of cell death called pyroptosis. There are two types of signaling pathways involved in the process of inflammasome activation: the canonical and the non-canonical signaling pathway. The canonical signaling pathway is mainly dependent on casepase-1; the non-canonical signal pathway, which was recently discovered, is mainly dependent on caspase-11, but is also meditated by caspase-4, caspase-5, and caspase-8. Kidney inflammation is basically associated with inflammatory factor exudation and inflammatory cell infiltration. Several studies have showed that inflammasomes are closely related to kidney diseases, especially the NOD-, LRR- and pyrin domain-containing 3 (NLRP3) inflammasome, which play a role in regulating kidney inflammation and fibrosis. In this review, we focus on the relationship between inflammasomes and kidney diseases, especially the role of the NLRP3 inflammasome in different kinds of kidney disease via both canonical and non-canonical signal pathways.

IL-20 in Acute Kidney Injury: Role in Pathogenesis and Potential as a Therapeutic Target

Acute kidney injury (AKI) causes over 1 million deaths worldwide every year. AKI is now recognized as a major risk factor in the development and progression of chronic kidney disease (CKD). Diabetes is the main cause of CKD as well. Renal fibrosis and inflammation are hallmarks in kidney diseases. Various cytokines contribute to the progression of renal diseases; thus, many drugs that specifically block cytokine function are designed for disease amelioration. Numerous studies showed IL-20 functions as a pro-inflammatory mediator to regulate cytokine expression in several inflammation-mediated diseases. In this review, we will outline the effects of pro-inflammatory cytokines in the pathogenesis of AKI and CKD. We also discuss the role of IL-20 in kidney diseases and provide a potential therapeutic approach of IL-20 blockade for treating renal diseases.

The Role of Inflammasome-Dependent and Inflammasome-Independent NLRP3 in the Kidney

Cytoplasmic nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) forms an inflammasome with apoptosis-associated speck-like protein containing a CARD (ASC) and pro-caspase-1, which is followed by the cleavage of pro-caspase-1 to active caspase-1 and ultimately the activation of IL-1β and IL-18 and induction of pyroptosis in immune cells. NLRP3 activation in kidney diseases aggravates inflammation and subsequent fibrosis, and this effect is abrogated by genetic or pharmacologic deletion of NLRP3. Inflammasome-dependent NLRP3 mediates the progression of kidney diseases by escalating the inflammatory response in immune cells and the cross-talk between immune cells and renal nonimmune cells. However, recent studies have suggested that NLRP3 has several inflammasome-independent functions in the kidney. Inflammasome-independent NLRP3 regulates apoptosis in tubular epithelial cells by interacting with mitochondria and mediating mitochondrial reactive oxygen species production and mitophagy. This review will summarize the mechanisms by which NLRP3 functions in the kidney in both inflammasome-dependent and inflammasome-independent ways and the role of NLRP3 and NLRP3 inhibitors in kidney diseases.

Accelerated and Severe Lupus Nephritis Benefits From M1, an Active Metabolite of Ginsenoside, by Regulating NLRP3 Inflammasome and T Cell Functions in Mice

Chinese herbal medicines used in combination have long-term been shown to be mild remedies with “integrated effects.” However, our study provides the first demonstration that M1, an active metabolite of ginsenoside, exerted its dramatic therapeutic effects on accelerated and severe lupus nephritis (ASLN) mice, featuring acute renal function impairment, heavy proteinuria, high serum levels of anti-dsDNA, and high-grade, diffuse proliferative renal lesions. In the present study, NZB/WF1 mice were given injections of lipopolysaccharide to induce the ASLN model. M1 (30 mg/kg) was then administered to the mice by gavage daily, and the mice were sacrificed on week 3 and week 5 after the induction of disease. To identify the potential mechanism of action for the pure compound, levels of NLRP3 inflammasome activation in bone marrow-derived dendritic cells (BMDCs), podocytes and macrophages, and antigen-specific T cell activation in BMDCs were determined in addition to mechanistic experiments in vivo. Treatment with M1 dramatically improved renal function, albuminuria and renal lesions and reduced serum levels of anti-dsDNA in the ASLN mice. These beneficial effects with M1 treatment involved the following cellular and molecular mechanistic events: [1] inhibition of NLRP3 inflammasome associated with autophagy induction, [2] modulation of T help cell activation, and [3] induction of regulatory T cell differentiation. M1 improved the ASLN mice by blunting NLRP3 inflammasome activation and differentially regulating T cell functions, and the results support M1 as a new therapeutic candidate for LN patients with a status of abrupt transformation of lower-grade (mesangial) to higher-grade (diffuse proliferative) nephritis.

Interleukin-18 binding protein attenuates renal injury of adriamycin-induced mouse nephropathy

Nephrotic syndrome is one of the most common kidney diseases in children, most of which were caused by minimal change disease, which could be typically reversible with the use of corticosteroid therapy in steroid-sensitive nephrotic syndrome. At the same time, there still exist some side effects caused by drugs and steroid-resistant nephrotic syndrome. It's urgent to investigate more accurate treatment to improve the situation. In this study, we chose mice model by adriamycin to observe the effect of IL-18BP intervention. It was shown that (1) weak general conditions appeared after adriamycin administration; (2) Proteinuria showed up after adriamycin-administration and then decreased with IL-18 binding protein intervention; (3) the level of triglyceride, cholesterol, IL-18, IFN-γ, and TNF-α in the IL-18 binding protein intervening group were significantly lower than those in the adriamycin-minimal change disease MCD group (all P < 0.01), and the levels of serum total protein, albumin, and IL-4 were significantly higher than those in the adriamycin-minimal change disease MCD group (P < 0.05, P < 0.01, P < 0.05); (4) ultramicrostructural examination demonstrated wide fusion of foot processes of glomerular epithelial cells in adriamycin-minimal change disease MCD mice, while only focal fusion occurred in IL-18 binding protein intervening mice. In conclusion, IL-18BP repaired the proteinurine, histopathological injury of kidney, and the induction of serum cytokines in mice models of minimal change disease induced by adriamycin.

Roles of Inflammasomes in Inflammatory Kidney Diseases

The immune system has a central role in eliminating detrimental factors, by frequently launching inflammatory responses towards pathogen infection and inner danger signal outbreak. Acute and chronic inflammatory responses are critical determinants for consequences of kidney diseases, in which inflammasomes were inevitably involved. Inflammasomes are closely linked to many kidney diseases such as acute kidney injury and chronic kidney diseases. Inflammasomes are macromolecules consisting of multiple proteins, and their formation initiates the cleavage of procaspase-1, resulting in the activation of gasdermin D as well as the maturation and release of interleukin-1β and IL-18, leading to pyroptosis. Here, we discuss the mechanism in which inflammasomes occur, as well as their roles in inflammatory kidney diseases, in order to shed light for discovering new therapeutical targets for the prevention and treatment of inflammatory kidney diseases and consequent end-stage renal disease.