Influenza A Virus Infection Activates NLRP3 Inflammasome through Trans-Golgi Network Dispersion

The NLRP3 inflammasome consists of NLRP3, ASC, and pro-caspase-1 and is an important arm of the innate immune response against influenza A virus (IAV) infection. Upon infection, the inflammasome is activated, resulting in the production of IL-1β and IL-18, which recruits other immune cells to the site of infection. It has been suggested that in the presence of stress molecules such as nigericin, the trans-Golgi network (TGN) disperses into small puncta-like structures where NLRP3 is recruited and activated. Here, we investigated whether IAV infection could lead to TGN dispersion, whether dispersed TGN (dTGN) is responsible for NLRP3 inflammasome activation, and which viral protein is involved in this process. We showed that the IAV causes dTGN formation, which serves as one of the mechanisms of NLRP3 inflammasome activation in response to IAV infection. Furthermore, we generated a series of mutant IAVs that carry mutations in the M2 protein. We demonstrated the M2 proton channel activity, specifically His37 and Trp41 are pivotal for the dispersion of TGN, NLRP3 conformational change, and IL-1β induction. The results revealed a novel mechanism behind the activation and regulation of the NLRP3 inflammasome in IAV infection.

Molecular investigation of candidate genes for pyroptosis-induced inflammation in diabetic retinopathy

BACKGROUND

Diabetic retinopathy is a diabetic microvascular complication. Pyroptosis, as a way of inflammatory death, plays an important role in the occurrence and development of diabetic retinopathy, but its underlying mechanism has not been fully elucidated. The purpose of this study is to identify the potential pyroptosis-related genes in diabetic retinopathy by bioinformatics analysis and validation in a diabetic retinopathy model and predict the microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) interacting with them. Subsequently, the competing endogenous RNA (ceRNA) regulatory network is structured to explore their potential molecular mechanism.

METHODS

We obtained mRNA expression profile dataset GSE60436 from the Gene Expression Omnibus (GEO) database and collected 51 pyroptosis-related genes from the PubMmed database. The differentially expressed pyroptosis-related genes were obtained by bioinformatics analysis with R software, and then eight key genes of interest were identified by correlation analysis, Gene Ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and protein-protein interaction (PPI) network analysis. Then, the expression levels of these key pyroptosis-related genes were validated with quantitative real-time polymerase chain reaction (qRT-PCR) in human retinal endothelial cells with high glucose incubation, which was used as an in vitro model of diabetic retinopathy. Western blot was performed to measure the protein levels of gasdermin D (GSDMD), dasdermin E (GSDME) and cleaved caspase-3 in the cells. Moreover, the aforementioned genes were further confirmed with the validation set. Finally, the ceRNA regulatory network was structured, and the miRNAs and lncRNAs which interacted with CASP3, TLR4, and GBP2 were predicted.

RESULTS

A total of 13 differentially expressed pyroptosis-related genes were screened from six proliferative diabetic retinopathy patients and three RNA samples from human retinas, including one downregulated gene and 12 upregulated genes. A correlation analysis showed that there was a correlation among these genes. Then, KEGG pathway and GO enrichment analyses were performed to explore the functional roles of these genes. The results showed that the mRNA of these genes was mainly related to inflammasome complex, interleukin-1 beta production, and NOD-like receptor signaling pathway. In addition, eight hub genes-CASP3, TLR4, NLRP3, GBP2, CASP1, CASP4, PYCARD, and GBP1-were identified by PPI network analysis using Cytoscape software. High glucose increased the protein level of GSDMD and GSDME, as critical effectors of pyroptosis, in retinal vascular endothelial cells. Verified by qRT-PCR, the expression of all these eight hub genes in the in vitro model of diabetic retinopathy was consistent with the results of the bioinformatics analysis of mRNA chip. Among them, CASP4, GBP1, CASP3, TLR4, and GBP2 were further validated in the GSE179568 dataset. Finally, 20 miRNAs were predicted to target three key genes-CASP3, GBP2, and TLR4, and 22 lncRNAs were predicted to potentially bind to these 20 miRNAs. Then, we constructed a key ceRNA network that is expected to mediate cellular pyroptosis in diabetic retinopathy.

CONCLUSION

Through the data analysis of the GEO database by R software and verification by qRT-PCR and validation set, we successfully identified potential pyroptosis-related genes involved in the occurrence of diabetic retinopathy. The key ceRNA regulatory network associated with these genes was structured. These findings might improve the understanding of molecular mechanisms underlying pyroptosis in diabetic retinopathy.

Environmental neurotoxicants and inflammasome activation in Parkinson's disease - A focus on the gut-brain axis

Inflammasomes are multi-protein complexes expressed in immune cells that function as intracellular sensors of environmental, metabolic and cellular stress. Inflammasome activation in the brain, has been shown to drive neuropathology and disease progression by multiple mechanisms, making it one of the most attractive therapeutic targets for disease modification in Parkinson's Disease (PD). Extensive inflammasome activation is evident in the brains of people with PD at the sites of dopaminergic degeneration and synuclein aggregation. While substantial progress has been made on validating inflammasome activation as a therapeutic target for PD, the mechanisms by which inflammasome activation is triggered and sustained over the disease course remain poorly understood. A growing body of evidence point to environmental and occupational chemical exposures as possible triggers of inflammasome activation in PD. The involvement of the gastrointestinal system and gut microbiota in PD pathophysiology is beginning to be elucidated, especially the profound link between gut dysbiosis and immune activation. While large cohort studies confirmed specific changes in the gut microbiota in PD patients compared to age-matched healthy controls, recent research suggest that synuclein pathology could be initiated in the gastrointestinal tract. In this review, we present a summarized perspective on current understanding on inflammasome activation and the gut-brain-axis link during PD pathophysiology. We discuss multiple environmental toxicants that are implicated as the etiological agents in causing idiopathic PD and their mechanistic underpinnings during neuroinflammatory events. We additionally present future directions that needs to address the research questions related to the gut-microbiome-brain mechanisms in PD.

Potential therapeutic role of pyroptosis mediated by the NLRP3 inflammasome in type 2 diabetes and its complications

As a new way of programmed cell death, pyroptosis plays a vital role in many diseases. In recent years, the relationship between pyroptosis and type 2 diabetes (T2D) has received increasing attention. Although the current treatment options for T2D are abundant, the occurrence and development of T2D appear to continue, and the poor prognosis and high mortality of patients with T2D remain a considerable burden in the global health system. Numerous studies have shown that pyroptosis mediated by the NLRP3 inflammasome can affect the progression of T2D and its complications; targeting the NLRP3 inflammasome has potential therapeutic effects. In this review, we described the molecular mechanism of pyroptosis more comprehensively, discussed the most updated progress of pyroptosis mediated by NLRP3 inflammasome in T2D and its complications, and listed some drugs and agents with potential anti-pyroptosis effects. Based on the available evidence, exploring more mechanisms of the NLRP3 inflammasome pathway may bring more options and benefits for preventing and treating T2D and drug development.

Fructose Induces Insulin Resistance of Gestational Diabetes Mellitus in Mice via the NLRP3 Inflammasome Pathway

BACKGROUND

Insulin resistance (IR), which is affected by dietary factors, is the main pathology underlying of gestational diabetes mellitus (GDM). Fructose (Fru), a sugar found in fruits, honey, and food sweeteners, has been reported to induce IR and inflammation. This study explored the effects and mechanisms of Fru on IR of GDM in pregnant and postpartum mice and their offspring.

METHODS

The 6-week-old female C57BL/6J mice were randomly divided into control (Chow) and fructose (Fru) groups, with the latter receiving 20% (w/v) Fru in drinking water from 2 weeks before pregnancy to the end of pregnancy. The effects of Fru on IR and inflammation were determined using serum parameters, glucose metabolism tests, immunohistochemistry, and western blotting.

RESULTS

Compared with the Chow group mice, pregnant mice treated with Fru exhibited greater gestational weight gain, higher fasting blood glucose and insulin concentrations, and a higher homeostasis model of assessment (HOMA) for IR index, but a lower HOMA for insulin sensitivity index. Treatment with Fru also increased the concentrations of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), IL-17, and C-reactive protein in sera and the expression of IL-6, TNF-α, IL-17, and IL-1β mRNA in liver tissues of pregnant mice. Both CD68 and IL-1β positive cell were increased in Fru-treated mice compared with in Chow mice. Fru treatment also promoted IR and inflammation in mice at 4 weeks after delivery and in offspring mice. Mechanistically, Fru promoted the nuclear translocation of nuclear factor-kappa B (NF-κB) p65 to activate the nucleotide-binding domain-like receptor protein 3 (NLRP3) inflammasome.

CONCLUSIONS

Exposure to Fru before and during pregnancy induced IR in pregnant mice, which continued at 4 weeks postpartum and affected the offspring. The effects of Fru may be associated with activation of the NF-κB-NLRP3 pathway.

Simvastatin cardioprotection in cyclophosphamide-induced toxicity via the modulation of inflammasome/caspase1/interleukin1β pathway

Drug-induced cardiotoxicity is a serious adverse effect that occurs during the administration of chemotherapeutic agents such as cyclophosphamide (CYC). Therefore, there is a critical need to find cardioprotective agents to keep the heart healthy. The current study aimed to investigate the protective effect of simvastatin (SIM) against CYC-induced heart damage and evaluate different mechanisms involved in mediating this effect, including the inflammasome/caspase1/interleukin1β (IL1β) pathway and endothelial nitric oxide synthase (eNOS). 36 rats were randomly assigned to one of four groups: a control group that received only vehicles, a CYC group that received CYC (150 mg/kg/day) i.p. on the fourth and fifth days, a CYC+SIM group that received SIM (10 mg/kg/day) orally for 5 days and CYC (150 mg/kg/day) i.p. on the fourth and fifth days, and a CYC+SIM+ Nitro- ω-L-arginine (L-NNA) group that received L-NNA (25 mg/kg/day, SIM (10 mg/kg/day) orally for 5 days and CYC (150 mg/kg/day) i.p. on the 4th and 5th days. The CYC group revealed an obvious elevation in cardiac enzymes and heart weights with toxic histopathological changes. Moreover, there was an increase in malondialdehyde (MDA), tumor necrosis factor-alpha (TNFα) levels, and up-regulation of the NLRP3inflammasome/caspase1/IL1β pathway. In addition, total antioxidant capacity (TAC), eNOS, reduced glutathione (GSH), and superoxide dismutase (SOD) significantly decreased. CYC-induced cardiotoxicity was most properly reversed by SIM through its anti-oxidant, anti-inflammatory, and anti-apoptotic actions with the stimulation of eNOS. The co-administration of L-NNA diminished the protective effect of SIM, indicating the essential role of eNOS in mediating this effect. Therefore, SIM ameliorated CYC-induced cardiotoxicity.

Effects and mechanisms of SGLT2 inhibitors on the NLRP3 inflammasome, with a focus on atherosclerosis

Atherosclerosis is a lipid-driven chronic inflammatory disease that is widespread in the walls of large and medium-sized arteries. Its pathogenesis is not fully understood. The currently known pathogenesis includes activation of pro-inflammatory signaling pathways in the body, increased oxidative stress, and increased expression of cytokines/chemokines. In the innate immune response, inflammatory vesicles are an important component with the ability to promote the expression and maturation of inflammatory factors, release large amounts of inflammatory cytokines, trigger a cascade of inflammatory responses, and clear pathogens and damaged cells. Studies in the last few years have demonstrated that NLRP3 inflammatory vesicles play a crucial role in the development of atherosclerosis as well as its complications. Several studies have shown that NLRP3 binding to ligands promotes inflammasome formation, activates caspase-1, and ultimately promotes its maturation and the maturation and production of IL-1β and IL-18. IL-1β and IL-18 are considered to be the two most prominent inflammatory cytokines in the inflammasome that promote the development of atherosclerosis. SGLT2 inhibitors are novel hypoglycemic agents that also have significant antiatherosclerotic effects. However, their exact mechanism is not yet clear. This article is a review of the literature on the effects and mechanisms of SGLT2 inhibitors on the NLRP3 inflammasome, focusing on their role in antiatherosclerosis.

Periodontitis activates the NLRP3 inflammasome in serum and saliva

BACKGROUND

Nod-like receptor family pyrin domain-containing protein-3 (NLRP3) complex inflammasome has potentially been shown to play an important role in the development of periodontitis and diabetes. The objective of this study was to analyze the association between serum and salivary NLRP3 concentrations in patients with periodontitis and type-II diabetes mellitus (DM) and to evaluate whether this association was influenced by potential confounders.

METHODS

For the present study, a cohort of healthy controls (n = 32), and patients with periodontitis (n = 34), type-II DM (n = 33), and a combination of periodontitis + type-II DM (n = 34) were enrolled. Patients were characterized on the basis of their periodontal status and analyzed for demographic characteristics, serum mediators, and for serum and salivary concentrations of NLRP3. A uni- and multivariate model was established to analyze whether periodontitis, type-II DM, and CRP influenced serum and salivary NLRP3 concentrations.

RESULTS

In comparison to type-II DM patients and healthy controls, patients with periodontitis (serum, P = 0.003; saliva P = 0.012) and periodontitis + type-II DM (serum, P = 0.028; saliva, P = 0.003) had elevated serum and salivary NLRP3 concentrations. The multivariate regression model showed that periodontitis (P = 0.029) and HDL-cholesterol (P = 0.012) were significant predictors of serum NLRP3 concentrations whereas periodontitis (P = 0.036) and CRP (P = 0.012) were significant predictors of salivary NLRP3.

CONCLUSION

The results of the present study showed that periodontitis and periodontitis + type-II DM patients had higher serum and salivary NLRP3 concentrations in comparison to healthy controls and patients with type-II DM. Periodontitis was demonstrated to be a significant predictor of both serum and salivary NLRP3 concentrations.

The Influence of Mitochondrial-DNA-Driven Inflammation Pathways on Macrophage Polarization: A New Perspective for Targeted Immunometabolic Therapy in Cerebral Ischemia-Reperfusion Injury

Cerebral ischemia-reperfusion injury is related to inflammation driven by free mitochondrial DNA. At the same time, the pro-inflammatory activation of macrophages, that is, polarization in the M1 direction, aggravates the cycle of inflammatory damage. They promote each other and eventually transform macrophages/microglia into neurotoxic macrophages by improving macrophage glycolysis, transforming arginine metabolism, and controlling fatty acid synthesis. Therefore, we propose targeting the mtDNA-driven inflammatory response while controlling the metabolic state of macrophages in brain tissue to reduce the possibility of cerebral ischemia-reperfusion injury.

Acetoacetate is a trigger of NLRP3 inflammasome activation in bovine peripheral blood mononuclear cells

Repeat breeding, which is non-pregnancy following three or more breeding attempts, is a serious reproductive disorder in cattle. In the present study, metabolomic profiling was used to identify metabolites in the blood plasma of repeat breeder cows (RBCs) and non-RBCs. Metabolomic analysis showed that acetoacetate (AcAc), a ketone body, was detected in RBCs, but not in non-RBCs. In contrast, β-hydroxybutyrate (BHB) was at similar levels in both RBCs and non-RBCs. We hypothesized that an imbalance of AcAc and BHB induces abnormal inflammatory conditions, especially the NLRP3 inflammasome, which regulates sterile inflammation to control interleukin (IL)-1β secretion, and may be associated with repeat breeding in cattle. To investigate this hypothesis, blood samples were collected from both non-RBCs and RBCs on day 7 of the estrous cycle. The mRNA expression of IL1B in peripheral blood mononuclear cells (PBMCs) was observed to be higher in RBCs than in non-RBCs. To test the effects of AcAc and BHB on inflammatory responses, blood samples were collected from healthy cows and PBMCs were isolated. PBMCs were treated with AcAc and BHB to investigate the activation of the NLRP3 inflammasome (complex of NLRP3, ASC, and caspase-1) and IL-1β secretion. AcAc treatment resulted in higher protein and/or mRNA expression of NLRP3 and IL-1β in PBMCs. Moreover, AcAc increased the co-localization of NLRP3 and ASC and stimulated caspase-1 activation, indicating the formation of the platform of the NLRP3 inflammasome. Addition of specific NLRP3 inhibitor, MCC950, suppressed AcAc stimulation-induced IL-1β secretion. Contrary to the effects of AcAc, BHB treatment suppressed the activation of NLRP3 inflammasome and IL-1β secretion in response to AcAc and typical NLRP3 inflammasome triggers. These findings demonstrate that AcAc can potentially trigger NLRP3 inflammasome activation, resulting in IL-1β secretion, and that these inflammatory responses are suppressed by BHB in bovine PBMCs. In addition, the imbalance between AcAc and BHB with higher levels of IL-1β may be associated with repeat breeding in cattle.

The Chemokine Systems at the Crossroads of Inflammation and Energy Metabolism in the Development of Obesity

Obesity is characterized as a complex and multifactorial excess accretion of adipose tissue accompanied with alterations in the immune and metabolic responses. Although the chemokine systems have been documented to be involved in the control of tissue inflammation and metabolism, the dual role of chemokines and chemokine receptors in the pathogenesis of the inflammatory milieu and dysregulated energy metabolism in obesity remains elusive. The objective of this review is to present an update on the link between chemokines and obesity-related inflammation and metabolism dysregulation under the light of recent knowledge, which may present important therapeutic targets that could control obesity-associated immune and metabolic disorders and chronic complications in the near future. In addition, the cellular and molecular mechanisms of chemokines and chemokine receptors including the potential effect of post-translational modification of chemokines in the regulation of inflammation and energy metabolism will be discussed in this review.

GPR40 agonist inhibits NLRP3 inflammasome activation via modulation of nuclear factor-κB and sarco/endoplasmic reticulum Ca2+-ATPase

The NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome is a multi-protein intracellular complex that activates proinflammatory cytokines, including interleukin (IL)-1β and IL-18. Inflammasome activation is related to metabolic inflammation, such as the progression of non-alcoholic steatohepatitis. Fasiglifam (TAK875), a selective G-protein coupled receptor 40 (GPR40) agonist with high affinity, significantly improves glucose-dependent insulin secretion and weight gain without hypoglycemia. Interestingly, we found that two GPR40 agonists, TAK875 and AMG1638, suppressed activation of the NLRP3 inflammasome in bone marrow-derived macrophages (BMDMs). TAK875 inhibited inflammasome activation by blocking formation of apoptosis-associated speck-like protein containing a CARD (ASC), an inflammasome component. TAK875 also suppressed NLRP3 inflammasome-induced pyroptosis of BMDMs. Moreover, nuclear factor-kappa B (NF-κB)-dependent priming of the NLRP3 inflammasome was partially inhibited by TAK875 and AMG1638. The intracellular Ca²⁺ increase caused by ATP, nigericin (pore-forming toxin), or endoplasmic reticulum stress activates the NLRP3 inflammasome. Pre-exposure of BMDMs to TAK875 suppressed the ATP-induced intracellular Ca²⁺ increase, which was reversed by thapsigargin, a sarco/endoplasmic reticulum Ca²⁺-ATPase inhibitor. Oral administration of mice with TAK875 suppressed the increase in serum IL-1β in mice treated with lipopolysaccharide/D-galactosamine in vivo. These findings indicate that the free fatty acid-sensing GPR40 plays a key role in the NLRP3 inflammasome pathway.

MiR-17-5p Inhibits TXNIP/NLRP3 Inflammasome Pathway and Suppresses Pancreatic β-Cell Pyroptosis in Diabetic Mice

Objective: Diabetes mellitus is a chronic progressive inflammatory metabolic disease with pancreatic β-cells dysfunction. The present study aimed to investigate whether miR-17-5p plays a protective effect on pancreatic β-cells function in diabetes mellitus (DM) mice and dissect the underlying mechanism.

Methods: C57BL/6J mice were randomly divided into control, DM, DM + Lentivirus negative control (LV-NC), and DM + Lenti-OE™ miR-17-5p (LV-miR-17-5) groups. DM was established by feeding a high-fat diet and intraperitoneal injection with streptozotocin (STZ) in mice. Blood glucose and glucose tolerance in circulation were measured. Meanwhile, the activation of nod-like receptor protein 3 (NLRP3) inflammasome, pancreas pyroptosis, and the expression of miR-17-5p and thioredoxin-interacting protein (TXNIP) were detected in the pancreas of DM mice. Pancreatic β-cell line INS-1 subjected to different concentrations of glucose was used in in vitro experiments.

Results: Compared with control mice, glucose tolerance deficit, elevated blood glucose level, and decreased pancreatic islet size, were presented in DM mice, which was associated with a downregulation of miR-17-5p. Importantly, exogenous miR-17-5p alleviated pancreas injury, and consequently improved glucose tolerance and decreased blood glucose in DM mice. In vitro experiments showed that high glucose decreased miR-17-5p expression and impaired insulin secretion in INS-1 cells. Mechanistically, miR-17-5p inhibited the expression of TXNIP and NLRP3 inflammasome activation, and thus decreased pancreatic β-cell pyroptosis.

Conclusion: Our results demonstrated that miR-17-5p improves glucose tolerance, and pancreatic β-cell function and inhibits TXNIP/NLRP3 inflammasome pathway-related pyroptosis in DM mice.

NLRP3 Inflammasome in Diabetic Cardiomyopathy and Exercise Intervention

Diabetic cardiomyopathy (DCM), as a common complication of diabetes, is characterized by chronic low-grade inflammation. The NLRP3 inflammasome is a key sensor mediating innate immune and inflammatory responses. However, the mechanisms initiating and promoting NLRP3 inflammasome activation in DCM is largely unexplored. The aim of the present review is to describe the link between NLRP3 inflammasome and DCM, and to provide evidence highlighting the importance of exercise training in DCM intervention. Collectively, this evidence suggests that DCM is an inflammatory disease aggravated by NLRP3 inflammasome-mediated release of IL-1β and IL-18. In addition, chronic exercise intervention is an effective preventive and therapeutic method to alleviate DCM via modulating the NLRP3 inflammasome.

Activation of NLRP3 Inflammasome by Palmitic Acid in Human Sebocytes

Background

Sebocytes are the main cells involved in the pathogenesis of acne by producing lipids and inflammatory cytokines. Although palmitic acid (PA) has been suggested to induce an inflammatory reaction, its effect on sebocytes remains to be elucidated.

Objective

In the present study, we investigated whether PA promotes inflammasome-mediated inflammation of sebocytes both in vivo and in vitro.

Methods

We intradermally injected PA into the mice ears. And, we treated cultured human sebocytes with PA. Inflammasome-mediated inflammation was verified by immunohistochemistry, Western blot and ELISA.

Results

PA-treated mice developed an inflammatory response associated with increased interleukin (IL)-1β expression in the sebaceous glands. When PA was added to cultured human sebocytes, caspase-1 activation and IL-1β secretion were significantly enhanced. In addition, NLRP3 knockdown attenuated IL-1β production by sebocytes stimulated with PA. PA-mediated inflammasome activation required reactive oxygen species.

Conclusion

These findings indicate that PA activates the NLRP3 inflammasome before induction of an inflammatory response in sebocytes. Thus, PA may play a role in the inflammation of acne.

Urolithin A suppresses glucolipotoxicity-induced ER stress and TXNIP/NLRP3/IL-1β inflammation signal in pancreatic β cells by regulating AMPK and autophagy

BACKGROUND

Pancreatic inflammation plays a key role in diabetes pathogenesis and progression. Urolithin A (UA), an intestinal flora metabolite of pomegranate, has anti-diabetic, anti-inflammatory and kidney protection effects among others. However, its effects on pancreatic inflammation and the potential mechanisms have not been clearly established.

PURPOSE

This study aimed at investigating the molecular mechanisms of UA anti-pancreatic inflammation under a diabetic environment.

METHODS

Diabetes induction in male C57BL/6 mice was achieved by a high fat diet and intraperitoneal streptozotocin injections. Then, diabetic mice were orally administered with UA for 8 weeks. In vitro, endoplasmic reticulum stress and MIN6 pancreatic β cell inflammation were induced using 25 mM glucose and 0.5 mM palmitic acid. The effects of UA were evaluated by immunohistochemistry, Western blot, and enzyme linked immunosorbent assays. Finally, the underlying mechanisms were elucidated using an autophagy inhibitor (chloroquine, CQ) and an AMPK inhibitor (dorsomorphin dihydrochloride).

RESULTS

UA significantly inhibited IL-1β secretion and TXNIP/NLRP3 expression in the pancreas of diabetic mice and in MIN6 pancreatic cells. UA downregulated the ER stress protein, p-PERK, and promoted AMPK phosphorylation. UA activated autophagy to inhibit TXNIP/NLRP3 IL-1β inflammatory signal, an effect that was reversed by CQ. Dorsomorphin 2HCL, reversed the autophagy-activation and anti-inflammatory effects of UA. Verapamil, clinically applied as an antiarrhythmic drug, is a TXNIP inhibitor for prevention of beta cell loss and diabetes development, but limited by its cardiac toxicity. In this study, verapamil (as positive control) inhibited NLRP3 /IL-1β signaling in MIN6 cells. Inhibitory effects of UA on TXNIP and IL-1β were weaker than those of verapamil (both at 50 μM, p < 0.05, p < 0.01). Conversely, inhibitory effects of UA on p62 were stronger, relative to those of verapamil (p < 0.05), and there were no differences in AMPK activation and LC3 enhancement effects between UA and verapamil.

CONCLUSION

UA is a potential anti-pancreatic inflammation agent that activates AMPK and autophagy to inhibit endoplasmic reticulum stress associated TXNIP/NLRP3/IL-1β signal pathway.

Jinmaitong Alleviates Diabetic Neuropathic Pain Through Modulation of NLRP3 Inflammasome and Gasdermin D in Dorsal Root Ganglia of Diabetic Rats

Jinmaitong (JMT) is a compound prescription of traditional Chinese medicine that has been used to treat diabetic neuropathic pain (DNP) for many years. Here, we investigated the effects of JMT on the activation of NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome and pyroptosis in Dorsal root ganglia (DRG) of diabetic rats. Streptozotocin (STZ)-induced diabetic rats were gavaged with JMT (0.88 g/kg/d) or alpha-lipoic acid (ALA, positive control, 0.48 mmol/kg/d) for 12 weeks. Distilled water was administered as a vehicle control to both diabetic and non-affected control rats. Blood glucose levels and body weights were measured. Behavioral changes were tested with mechanical withdrawal threshold (MWT) and tail-flick latency (TFL) tests. Morphological injury associated with DRG was observed with hematoxylin and eosin (H&E) and Nissl’s staining. mRNA and protein levels of NLRP3 inflammasome components (NLRP3, ASC, caspase-1), downstream IL-1β and gasdermin D (GSDMD) were evaluated by immunohistochemistry, quantitative real time-PCR and western blot. The results showed that JMT had no effect on blood glucose levels and body weights, but significantly improved MWT and TFL behavior in diabetic rats, and attenuated morphological damage in the DRG tissues. Importantly, JMT decreased the mRNA and protein levels of components of NLRP3 inflammasome, including NLRP3, ASC and caspase-1. JMT also down-regulated the expression of IL-1β and GSDMD in the DRG of DNP rats. In addition, ALA treatment did not perform better than JMT. In conclusion, JMT effectively relieved DNP by decreasing NLRP3 inflammasome activation and pyroptosis, providing new evidence supporting JMT as an alternative treatment for DNP.

Evaluation of protein kinase D auto-phosphorylation as biomarker for NLRP3 inflammasome activation

BACKGROUND

The NLRP3 inflammasome is a critical component of sterile inflammation, which is involved in many diseases. However, there is currently no known proximal biomarker for measuring NLRP3 activation in pathological conditions. Protein kinase D (PKD) has emerged as an important NLRP3 kinase that catalyzes the release of a phosphorylated NLRP3 species that is competent for inflammasome complex assembly.

METHODS

To explore the potential for PKD activation to serve as a selective biomarker of the NLRP3 pathway, we tested various stimulatory conditions in THP-1 and U937 cell lines, probing the inflammasome space beyond NLRP3. We analyzed the correlation between PKD activation (monitored by its auto-phosphorylation) and functional inflammasome readouts.

RESULTS

PKD activation/auto-phosphorylation always preceded cleavage of caspase-1 and gasdermin D, and treatment with the PKD inhibitor CRT0066101 could block NLRP3 inflammasome assembly and interleukin-1β production. Conversely, blocking NLRP3 either genetically or using the MCC950 inhibitor prevented PKD auto-phosphorylation, indicating a bidirectional functional crosstalk between NLRP3 and PKD. Further assessments of the pyrin and NLRC4 pathways, however, revealed that PKD auto-phosphorylation can be triggered by a broad range of stimuli unrelated to NLRP3 inflammasome assembly.

CONCLUSION

Although PKD and NLRP3 become functionally interconnected during NLRP3 activation, the promiscuous reactivity of PKD challenges its potential use for tracing the NLRP3 inflammasome pathway.

Glycogen synthesis and beyond, a comprehensive review of GSK3 as a key regulator of metabolic pathways and a therapeutic target for treating metabolic diseases

Glycogen synthase kinase‐3 (GSK3) is a highly evolutionarily conserved serine/threonine protein kinase first identified as an enzyme that regulates glycogen synthase (GS) in response to insulin stimulation, which involves GSK3 regulation of glucose metabolism and energy homeostasis. Both isoforms of GSK3, GSK3α, and GSK3β, have been implicated in many biological and pathophysiological processes. The various functions of GSK3 are indicated by its widespread distribution in multiple cell types and tissues. The studies of GSK3 activity using animal models and the observed effects of GSK3‐specific inhibitors provide more insights into the roles of GSK3 in regulating energy metabolism and homeostasis. The cross‐talk between GSK3 and some important energy regulators and sensors and the regulation of GSK3 in mitochondrial activity and component function further highlight the molecular mechanisms in which GSK3 is involved to regulate the metabolic activity, beyond its classical regulatory effect on GS. In this review, we summarize the specific roles of GSK3 in energy metabolism regulation in tissues that are tightly associated with energy metabolism and the functions of GSK3 in the development of metabolic disorders. We also address the impacts of GSK3 on the regulation of mitochondrial function, activity and associated metabolic regulation. The application of GSK3 inhibitors in clinical tests will be highlighted too. Interactions between GSK3 and important energy regulators and GSK3‐mediated responses to different stresses that are related to metabolism are described to provide a brief overview of previously less‐appreciated biological functions of GSK3 in energy metabolism and associated diseases through its regulation of GS and other functions.

Bisdemethoxycurcumin attenuates lipopolysaccharide-induced intestinal damage through improving barrier integrity, suppressing inflammation, and modulating gut microbiota in broilers

Bisdemethoxycurcumin has good antioxidant and anti-inflammatory effects and has been widely used as food and feed supplements in the form of curcuminoids. However, the beneficial effect of individual bisdemethoxycurcumin on preventing lipopolysaccharide (LPS)-induced inflamed intestinal damage is unclear. The present study aimed to investigate whether dietary bisdemethoxycurcumin supplementation could attenuate LPS-induced intestinal damage and alteration of cecal microbiota in broiler chickens. In total, 320 one-day-old male Arbor Acres broiler chickens with a similar weight were randomly divided into four treatments. The treatments were designed as a 2 × 2 factorial arrangement: basal diet (CON); 150 mg/kg bisdemethoxycurcumin diet (BUR); LPS challenge + basal diet (LPS); LPS challenge + 150 mg/kg bisdemethoxycurcumin diet (L-BUR). Results showed that dietary bisdemethoxycurcumin supplementation attenuated the LPS-induced decrease of average daily feed intake. LPS challenge compromised the intestinal morphology and disrupted the intestinal tight junction barrier. Dietary bisdemethoxycurcumin supplementation significantly increased villus length:crypt depth ratio and upregulated the mRNA expression of intestinal tight junction proteins. Moreover, a remarkably reduced mRNA expression of inflammatory mediators was observed following bisdemethoxycurcumin supplementation. The cecal microbiota analysis showed that bisdemethoxycurcumin supplementation increased the relative abundance of the genus Faecalibacterium while decreased the relative abundance of the genera Bacteroides and Subdoligranulum. In conclusion, dietary bisdemethoxycurcumin supplementation could counteract LPS-induced inflamed intestinal damage in broiler chickens by improving intestinal morphology, maintaining intestinal tight junction, downregulating pro-inflammatory mediators, and restoring cecal microbiota.

A Novel Cascade Nanoreactor Integrating Two-Dimensional Pd-Ru Nanozyme, Uricase and Red Blood Cell Membrane for Highly Efficient Hyperuricemia Treatment

Nanozyme-based cascade reaction has emerged as an effective strategy for disease treatment because of its high efficiency and low side effects. Herein, a new and highly active two-dimensional Pd-Ru nanozyme is prepared and then integrated with uricase and red blood cell (RBC) membrane to fabricate a tandem nanoreactor, Pd-Ru/Uricase@RBC, for hyperuricemia treatment. The designed Pd-Ru/Uricase@RBC nanoreactor displayed not only good stability against extreme pH, temperature and proteolytic degradation, but also long circulation half-life and excellent safety. The nanoreactor can effectively degrade UA by uricase to allantoin and H₂ O₂ and remove H₂ O₂ by using Pd-Ru nanosheets (NSs) with the catalase (CAT)-like activity. More importantly, the finally produced O₂ from H₂ O₂ decomposition can in turn facilitate the catalytic oxidation of UA, as the degradation of UA is an O₂ consumption process. By integrating the high-efficiency enzymatic activity, long circulation capability, and good biocompatibility, the designed Pd-Ru/Uricase@RBC can effectively and safely treat hyperuricemia without side effects. The study affords a new alternative for the exploration of clinical treatment of hyperuricemia.

β-hydroxybutyrate suppresses NLRP3 inflammasome-mediated placental inflammation and lipopolysaccharide-induced fetal absorption

The immune system contributes to the regulation of pregnancy, and the disruption of well-controlled immune functions leads to pregnancy complications. Recently, the nucleotide-binding oligomerization domain, leucine-rich repeat-, and pyrin domain-containing 3 (NLRP3) inflammasome mechanisms [(a protein complex of NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and caspase-1)] have been reported to play roles in controlling placental inflammation involved in pregnancy pathologies. The ketone body β-hydroxybutyrate (BHB) can suppress NLRP3 inflammasome activation and improve various inflammatory diseases. Therefore, we hypothesized that BHB could suppress activation of the NLRP3 inflammasome in the placenta, resulting in the improvement of pregnancy complications. In human placental tissue culture, treatment with BHB suppressed the secretion levels of inflammatory cytokines, such as interleukin (IL)-1β, IL-6, and IL-8, but did not affect the mRNA expression levels of NLRP3 inflammasome-associated factors. Treatment with BHB reduced IL-1β secretion and the amount of mature IL-1β protein induced by lipopolysaccharide (LPS) stimulation in the placenta. In human trophoblast cells, BHB reduced ASC and activated-caspase-1 expression, resulting in the inhibition of IL-1β secretion. To investigate the effect of BHB during pregnancy, we used an animal model of LPS (100 μg/kg intraperitoneally [i.p.] on gestational day 14)-induced pregnancy complications. Administration of BHB (100 mg/kg i.p.) clearly suppressed the absorption rate and IL-1β production in the placenta induced by LPS in pregnant mice. Moreover, LPS-induced pregnancy abnormalities were improved in NLRP3-deficient mice. These findings suggest that BHB play a role in reducing placental inflammation and pregnancy complications via inhibition of NLRP3 inflammasome activation.

Advances in the Relationship Between Pyroptosis and Diabetic Neuropathy

Pyroptosis is a novel programmed cell death process that promotes the release of interleukin-1β (IL-1β) and interleukin-18 (IL-18) by activating inflammasomes and gasdermin D (GSDMD), leading to cell swelling and rupture. Pyroptosis is involved in the regulation of the occurrence and development of cardiovascular and cerebrovascular diseases, tumors, and nerve injury. Diabetes is a metabolic disorder characterized by long-term hyperglycemia, insulin resistance, and chronic inflammation. The people have paid more and more attention to the relationship between pyroptosis, diabetes, and its complications, especially its important regulatory significance in diabetic neurological diseases, such as diabetic encephalopathy (DE) and diabetic peripheral neuropathy (DPN). This article will give an in-depth overview of the relationship between pyroptosis, diabetes, and its related neuropathy, and discuss the regulatory pathway and significance of pyroptosis in diabetes-associated neuropathy.

Inherited Autoinflammatory Syndromes

Autoinflammation describes a collection of diverse diseases caused by indiscriminate activation of the immune system in an antigen-independent manner. The rapid advancement of genetic diagnostics has allowed for the identification of a wide array of monogenic causes of autoinflammation. While the clinical picture of these syndromes is diverse, it is possible to thematically group many of these diseases under broad categories that provide insight into the mechanisms of disease and therapeutic possibilities. This review covers archetypical examples of inherited autoinflammatory diseases in five major categories: inflammasomopathy, interferonopathy, unfolded protein/cellular stress response, relopathy, and uncategorized. This framework can suggest where future work is needed to identify other genetic causes of autoinflammation, what types of diagnostics need to be developed to care for this patient population, and which options might be considered for novel therapeutic targeting. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Tyrosine phosphorylation of NLRP3 by the Src family kinase Lyn suppresses the activity of the NLRP3 inflammasome

[Figure: see text].

Astaxanthin attenuates contrast-induced acute kidney injury in rats via ROS/NLRP3 inflammasome

OBJECTIVE

To explore the protective effect and mechanism of astaxanthin on the kidney of rats with contrast-induced acute kidney injury.

METHODS

Forty SD rats were randomly divided into five groups: Control group (CON); Astaxanthin control group (AST); Contrast media group (CM); Astaxanthin pre-treatment group (AST + CM); N-acetylcysteine pre-treatment group (NAC + CM), each group with eight rats. The rats were killed 72 h after the modeling, the blood supernatant and kidneys were collected, and then the serum creatinine and blood urea nitrogen levels were measured; HE staining was used to observe the pathological changes in kidney tissue; TUNEL was used to detect apoptosis level in renal tubular epithelial cells; frozen section was used to observe the expression of ROS in renal tissue by reactive oxygen staining; the expression of NLRP3, ASC, caspase-1, IL-1β, IL-18 were detected by immunohistochemistry and western blot.

RESULTS

The CI-AKI rat model was induced by iohexol. Then the elevated level of ROS activated the inflammatory response mediated by NLRP3 inflammasome (NLRP3, ASC, caspase-1). Subsequently, the increase in renal tubular epithelial cell apoptosis caused the destruction of the pathological structure of the kidney and finally led to renal impairment. While after the pretreatment of astaxanthin, the level of ROS was decreased. The activation level of NLRP3 inflammasome and its mediated inflammatory response were alleviated significantly. Eventually, the level of renal tubular epithelial cell apoptosis and renal damage were significantly mitigated.

CONCLUSION

Astaxanthin can protect the kidney in CI-AKI by inhibiting the activation of NLRP3 inflammasome-IL-1β/IL-18 through inhibition of the production of ROS.

NLRP3 inflammasome is involved in ambient PM2.5-related metabolic disorders in diabetic model mice but not in wild-type mice

AIMS

To explore the role of nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome in ambient fine particulate matter (PM_2.5)-related metabolic disorders.

METHODS

In this study, the C57BL/6 and db/db mice were exposed to concentrated PM_2.5 or filtered air (FA) using Shanghai Meteorological and Environmental Animal Exposure System (Shanghai-METAS) for 12 weeks. Indices of lipid metabolism, glucose metabolism, insulin sensitivity, and protein expression of NLRP3 inflammasome in visceral adipose tissue (VAT) were measured, respectively.

RESULTS

The results showed that PM_2.5 exposure increased circulatory insulin, triglycerides (TG), and total cholesterol (TC), and decreased high-density lipoprotein (HDL) in both C57BL/6 and db/db mice. The levels of NLRP3-related circulatory inflammatory cytokines including both interleukin (IL)-18 and IL-1β in serum were increased in the PM_2.5-exposed mice and accompanied by the elevation in fasting blood glucose and insulin. The results also showed that exposure to PM_2.5 promoted the activation of NLRP3, pro-caspase-1, caspase-1, and apoptosis-associated speck-like protein containing CARD (ASC), simultaneously accompanied by the increase of IL-18 and IL-1β expression in VAT, but the statistically significant difference only found in the db/db mice, not in C57BL/6 mice.

CONCLUSION

The activation of NLRP3 inflammasome might be not the main mechanism of PM_2.5-related metabolic disorders in wide type mice but it partly mediated the exacerbation of metabolic disorders in diabetic model mice.

Targeting NLRP3 Inflammasome in the Treatment Of Diabetes and Diabetic Complications: Role of Natural Compounds from Herbal Medicine

Diabetes, a common metabolic disease with various complications, is becoming a serious global health pandemic. So far there are many approaches in the management of diabetes; however, it still remains irreversible due to its complicated pathogenesis. Recent studies have revealed that nucleotide-binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome plays a vital role in the progression of diabetes and many of its complications, making it a promising therapeutic target in pharmaceutical design. Natural derived herbal medicine, known for its utilization of natural products such as herbs or its bioactive ingredients, is shown to be able to ameliorate hyperglycemia-associated symptoms and to postpone the progression of diabetic complications due to its anti-inflammatory and anti-oxidative properties. In this review, we summarized the role of NLRP3 inflammasome in diabetes and several diabetic complications, as well as 31 active compounds that exert therapeutic effect on diabetic complications via inhibiting NLRP3 inflammasome. Improving our understanding of these promising candidates from natural compounds in herbal medicine targeting NLRP3 inflammasome inspires us the relationship between inflammation and metabolic disorders, and also sheds light on searching potential agents or therapies in the treatment of diabetes and diabetic complications.

Abortive HIV-1 RNA induces pro-IL-1β maturation via protein kinase PKR and inflammasome activation in humans

The proinflammatory cytokine IL-1β mediates high levels of immune activation observed during acute and chronic human immunodeficiency virus 1 (HIV-1) infection. Little is known about the mechanisms that drive IL-1β activation during HIV-1 infection. Here, we have identified a crucial role for abortive HIV-1 RNAs in inducing IL-1β in humans. Abortive HIV-1 RNAs were sensed by protein kinase RNA-activated (PKR), which triggered activation of the canonical NLRP3 inflammasome and caspase-1, leading to pro-IL-1β processing and secretion. PKR activated the inflammasome via ROS generation and MAP kinases ERK1/2, JNK, and p38. Inhibition of PKR during HIV-1 infection blocked IL-1β production. As abortive HIV-1 RNAs are produced during productive infection and latency, our data strongly suggest that targeting PKR signaling might attenuate immune activation during acute and chronic HIV-1 infection.

Priming of NLRP3 inflammasome activation by Msn kinase MINK1 in macrophages

The nucleotide-binding domain, leucine-rich-repeat containing family, pyrin domain-containing 3 (NLRP3) inflammasome is essential in inflammation and inflammatory disorders. Phosphorylation at various sites on NLRP3 differentially regulates inflammasome activation. The Ser725 phosphorylation site on NLRP3 is depicted in multiple inflammasome activation scenarios, but the importance and regulation of this site has not been clarified. The present study revealed that the phosphorylation of Ser725 was an essential step for the priming of the NLRP3 inflammasome in macrophages. We also showed that Ser725 was directly phosphorylated by misshapen (Msn)/NIK-related kinase 1 (MINK1), depending on the direct interaction between MINK1 and the NLRP3 LRR domain. MINK1 deficiency reduced NLRP3 activation and suppressed inflammatory responses in mouse models of acute sepsis and peritonitis. Reactive oxygen species (ROS) upregulated the kinase activity of MINK1 and subsequently promoted inflammasome priming via NLRP3 Ser725 phosphorylation. Eliminating ROS suppressed NLRP3 activation and reduced sepsis and peritonitis symptoms in a MINK1-dependent manner. Altogether, our study reveals a direct regulation of the NLRP3 inflammasome by Msn family kinase MINK1 and suggests that modulation of MINK1 activity is a potential intervention strategy for inflammasome-related diseases.

Innate immunity receptors in depression and suicide: upregulated NOD-like receptors containing pyrin (NLRPs) and hyperactive inflammasomes in the postmortem brains of people who were depressed and died by suicide

BACKGROUND

Abnormalities of inflammation have been implicated in the pathophysiology of depression and suicide, based on observations of increased levels of proinflammatory cytokines in the serum of people who were depressed and died by suicide. More recently, abnormalities in cytokines and innate immunity receptors such as toll-like receptors have also been observed in the postmortem brains of people who were depressed and died by suicide. In addition to toll-like receptors, another subfamily of innate immunity receptors known as NOD-like receptors containing pyrin (NLRPs) are the most widely present NOD-like receptors in the central nervous system. NLRPs also form inflammasomes that play an important role in brain function. We studied the role of NLRPs in depression and suicide.

METHODS

We determined the protein and mRNA expression of NLRP1, NLRP3 and NLRP6 and the components of their inflammasomes (i.e., adaptor molecule apoptosis-associated speck-like protein [ASC], caspase1, caspase3, interleukin [IL]-1β and IL-18) postmortem in the prefrontal cortex of people who were depressed and died by suicide, and in healthy controls. We determined mRNA levels using quantitative polymerase chain reaction, and we determined protein expression using Western blot immunolabelling.

RESULTS

We found that the protein and mRNA expression levels of NLRP1, NLRP3, NLRP6, caspase3 and ASC were significantly increased in people who were depressed and died by suicide compared to healthy controls.

LIMITATIONS

Some people who were depressed and died by suicide were taking antidepressant medication at the time of their death.

CONCLUSION

Similar to toll-like receptors, NLRP and its inflammasomes were upregulated in people who were depressed and died by suicide compared to healthy controls. Innate immunity receptors in general - and NLRPs and inflammasomes in particular - may play an important role in the pathophysiology of depression and suicide.

Out of Control: The Role of the Ubiquitin Proteasome System in Skeletal Muscle during Inflammation

The majority of critically ill intensive care unit (ICU) patients with severe sepsis develop ICU-acquired weakness (ICUAW) characterized by loss of muscle mass, reduction in myofiber size and decreased muscle strength leading to persisting physical impairment. This phenotype results from a dysregulated protein homeostasis with increased protein degradation and decreased protein synthesis, eventually causing a decrease in muscle structural proteins. The ubiquitin proteasome system (UPS) is the predominant protein-degrading system in muscle that is activated during diverse muscle atrophy conditions, e.g., inflammation. The specificity of UPS-mediated protein degradation is assured by E3 ubiquitin ligases, such as atrogin-1 and MuRF1, which target structural and contractile proteins, proteins involved in energy metabolism and transcription factors for UPS-dependent degradation. Although the regulation of activity and function of E3 ubiquitin ligases in inflammation-induced muscle atrophy is well perceived, the contribution of the proteasome to muscle atrophy during inflammation is still elusive. During inflammation, a shift from standard- to immunoproteasome was described; however, to which extent this contributes to muscle wasting and whether this changes targeting of specific muscular proteins is not well described. This review summarizes the function of the main proinflammatory cytokines and acute phase response proteins and their signaling pathways in inflammation-induced muscle atrophy with a focus on UPS-mediated protein degradation in muscle during sepsis. The regulation and target-specificity of the main E3 ubiquitin ligases in muscle atrophy and their mode of action on myofibrillar proteins will be reported. The function of the standard- and immunoproteasome in inflammation-induced muscle atrophy will be described and the effects of proteasome-inhibitors as treatment strategies will be discussed.

Adipocyte factor CTRP6 inhibits homocysteine-induced proliferation, migration, and dedifferentiation of vascular smooth muscle cells through PPARγ/NLRP3

NLRP3 and PPARγ play important roles in the development of atherosclerosis (AS). Studies have shown that PPARγ regulates the expression of NLRP3 in vascular diseases. In addition, the adipocyte factor CTRP6 can improve the activation of PPARγ in vascular diseases. However, the regulatory relationship between CTRP6, PPARγ, and NLRP3 in AS and its underlying mechanism have not been reported. Since proliferation, migration, and dedifferentiation of vascular smooth muscle cells (VSMCs) are key events in AS, in this study, we induced proliferation, migration, and dedifferentiation of VSCMs through homocysteine (HCY) to detect the specific effects of CTRP6, PPARγ, and NLRP3. Subsequently, CTRP6 was overexpressed and the PPARγ inhibitor GW9662 and agonist rosiglitazone were administered to HCY-induced VSCMs to investigate the mechanisms. The results show that the expression of CTRP6 decreased in HCY-induced VSMCs. In addition, CTRP6 overexpression inhibited the proliferation and migration of HCY-induced VSMCs, as well as cell cycle acceleration and dedifferentiation. Overexpression of CTRP6 increased HCY-induced PPARγ expression and inhibited NLRP3 expression. The addition of GW9662 and rosiglitazone further demonstrated that overexpression of CTRP6 inhibited HCY-induced VSMC proliferation, migration, and dedifferentiation through PPARγ/NLRP3 signaling. In conclusion, CTRP6 inhibited HCY-induced proliferation, migration, and dedifferentiation of VSMCs through PPARγ/NLRP3.

Protection of Retinal Function by Nucleoside Reverse Transcriptase Inhibitors Following Retinal Ischemia/Reperfusion Injury

Purpose: Retinal ischemia/reperfusion (I/R) injury is a common cause of visual impairment and blindness for which there remain limited treatment options. Nucleoside reverse transcriptase inhibitors (NRTIs), such as zidovudine (AZT), have been shown to block the NLRP3 inflammasome and prevent retinal degeneration in a mouse model of age-related macular degeneration. The NLRP3 inflammasome has also been shown to be triggered in I/R injury. Therefore, we studied the neuroprotective effects of AZT using a pressure-induced retinal ischemia mouse model. Methods: C57BL/6J mice were randomly assigned to 1 of 2 treatment groups: vehicle-treated retinal I/R injury (n = 6) or AZT-treated retinal I/R injury (n = 6). Vehicle (1% dimethyl sulfoxide [DMSO] in phosphate-buffered saline [PBS]) or AZT 50 mg/kg in 1% DMSO in PBS were injected intraperitoneally twice daily for 5 days. On day 2 of treatment, retinal ischemia was induced by transient elevation of intraocular pressure for 45 min. Scotopic electroretinography (ERG) was used to quantify retinal function before and 1 week after retinal ischemic insult. Retinal morphology was examined 1 week after ischemic insult. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assays and caspase 1 immunostaining was performed 24 h after retinal I/R injury. Results: Following I/R injury, ERG a- and b-wave amplitudes were significantly reduced in the vehicle-treated mice. AZT treatment significantly attenuated I/R-induced loss of retinal function as compared with vehicle-treated mice. Additionally, AZT-treated mice experienced significantly less inner retinal thinning as compared with vehicle-treated mice. TUNEL-positive cells were prevalent in the vehicle-treated I/R injury mouse retinas compared with the AZT-treated I/R injury mouse retinas. More caspase-1 immunoreactivity was detected in ganglion cell layer and inner nuclear layer (INL) in vehicle-treated I/R injury group than in AZT-treated I/R injury group. Conclusion: AZT treatment resulted in relative preservation of retinal structure and function following ischemic insult as compared with controls. This suggests AZT may have therapeutic value in the management of retinal ischemic diseases.

Preventive and Prebiotic Effect of α-Galacto-Oligosaccharide against Dextran Sodium Sulfate-Induced Colitis and Gut Microbiota Dysbiosis in Mice

β-Galacto-oligosaccharide (β-GOS) showed great potential in ulcerative colitis (UC) adjuvant therapy. Herein, the preventive and prebiotic effect of enzymatic-synthesized α-linked galacto-oligosaccharide (α-GOS) was investigated in dextran sodium sulfate-induced colitis and gut microbiota dysbiosis mice. Compared with β-GOS, the α-GOS supplement was more effective in improving preventive efficacy, promoting colonic epithelial barrier integrity, and alleviating inflammation cytokines. Moreover, the activation of the NOD-like receptor (NLR) family member NLRP3 inflammasome-mediated inflammation was significantly inhibited by both α-GOS and β-GOS. Gut microbiota analysis showed that α-GOS treatment reshaped the dysfunctional gut microbiota. The subsequent Spearman's correlation coefficient analysis indicated that these gut microbiota changes were significantly correlated with the inflammatory parameters. These results suggested that the enzymatic-synthesized α-GOS is a promising therapeutic agent in UC prevention and adjuvant treatment by maintaining intestinal homeostasis.

Ginsenoside Rg3 attenuates cisplatin-induced kidney injury through inhibition of apoptosis and autophagy-inhibited NLRP3

The NOD-like receptor family pyrin domain-containing (NLRP3) inflammasomes is centrally implicated in cisplatin (CP)-induced kidney injury. Autophagy is critical for inhibiting production of NLRP3 protein that effectively reduces the inflammatory response. Ginsenoside Rg3 (SY), an active component extracted from ginseng, is reported to protect against CP-induced nephrotoxicity. However, the mechanisms underlying renoprotection by SY have not been established to date. Our results indicate that SY attenuated CP-induced apoptosis and damage in vivo and in vitro, as evidenced by increased cell viability, decreased the proportion of late apoptotic cells, elevated mitochondrial membrane potential, and ameliorated histopathological damage of the kidney. SY ameliorated CP-induced human renal tubular (HK-2) cells and kidney injury through upregulation of LC3II/I and beclin-1, inhibition of p62, NLRP3, ASC, caspase-1, and interleukin-1β. However, blockade of autophagy by 3-methyladenine reversed the suppression of SY on NLRP3 inflammasome activation and the protection of SY on HK-2 cells. Our collective results support the utility of SY as a therapeutic agent that effectively protects against CP-induced kidney injury by activating the autophagy-mediated NLRP3 inhibition pathway.

Chloride sensing by WNK1 regulates NLRP3 inflammasome activation and pyroptosis

The NLRP3 inflammasome mediates the production of proinflammatory cytokines and initiates inflammatory cell death. Although NLRP3 is essential for innate immunity, aberrant NLRP3 inflammasome activation contributes to a wide variety of inflammatory diseases. Understanding the pathways that control NLRP3 activation will help develop strategies to treat these diseases. Here we identify WNK1 as a negative regulator of the NLRP3 inflammasome. Macrophages deficient in WNK1 protein or kinase activity have increased NLRP3 activation and pyroptosis compared with control macrophages. Mice with conditional knockout of WNK1 in macrophages have increased IL-1β production in response to NLRP3 stimulation compared with control mice. Mechanistically, WNK1 tempers NLRP3 activation by balancing intracellular Cl- and K+ concentrations during NLRP3 activation. Collectively, this work shows that the WNK1 pathway has a critical function in suppressing NLRP3 activation and suggests that pharmacological inhibition of this pathway to treat hypertension might have negative clinical implications.

Peripheral CB1R as a modulator of metabolic inflammation

Obesity is associated with chronic inflammation in insulin-sensitive tissues, including liver and adipose tissue, and causes hormonal/metabolic complications, such as insulin resistance. There is growing evidence that peripheral cannabinoid-type 1 receptor (CB1R) is a crucial participant in obesity-induced pro-inflammatory responses in insulin-target tissues, and its selective targeting could be a novel therapeutic strategy to break the link between insulin resistance and metabolic inflammation. In this review, we introduce the role of peripheral CB1R in metabolic inflammation and as a mediator of hormonal/metabolic complications that underlie metabolic syndrome, including fatty liver, insulin resistance, and dyslipidemia. We also discuss the therapeutic potential of second- and third-generation peripherally restricted CB1R antagonists for treating obesity-induced metabolic inflammation without eliciting central CB1R-mediated neurobehavioral effects, predictive of neuropsychiatric side effects, in humans.

Thiol-based redox-active proteins as cardioprotective therapeutic agents in cardiovascular diseases

Thiol-based redox compounds, namely thioredoxins (Trxs), glutaredoxins (Grxs) and peroxiredoxins (Prxs), stand as a pivotal group of proteins involved in antioxidant processes and redox signaling. Glutaredoxins (Grxs) are considered as one of the major families of proteins involved in redox regulation by removal of S-glutathionylation and thereby reactivation of other enzymes with thiol-dependent activity. Grxs are also coupled to Trxs and Prxs recycling and thereby indirectly contribute to reactive oxygen species (ROS) detoxification. Peroxiredoxins (Prxs) are a ubiquitous family of peroxidases, which play an essential role in the detoxification of hydrogen peroxide, aliphatic and aromatic hydroperoxides, and peroxynitrite. The Trxs, Grxs and Prxs systems, which reversibly induce thiol modifications, regulate redox signaling involved in various biological events in the cardiovascular system. This review focuses on the current knowledge of the role of Trxs, Grxs and Prxs on cardiovascular pathologies and especially in cardiac hypertrophy, ischemia/reperfusion (I/R) injury and heart failure as well as in the presence of cardiovascular risk factors, such as hypertension, hyperlipidemia, hyperglycemia and metabolic syndrome. Further studies on the roles of thiol-dependent redox systems in the cardiovascular system will support the development of novel protective and therapeutic strategies against cardiovascular diseases.

The Nlrp3 inflammasome - the evolving story of its positive and negative effects on hematopoiesis

PURPOSE OF REVIEW

Hematopoiesis is co-regulated by innate immunity, which is an ancient evolutionary defense mechanism also involved in the development and regeneration of damaged tissues. This review seeks to shed more light on the workings of the Nlrp3 inflammasome, which is an intracellular innate immunity pattern recognition receptor and sensor of changes in the hematopoietic microenvironment, and focus on its role in hematopoieisis.

RECENT FINDINGS

Hematopoietic stem progenitor cells (HSPCs) are exposed to several external mediators of innate immunity. Moreover, since hemato/lymphopoietic cells develop from a common stem cell, their behavior and fate are coregulated by intracellular innate immunity pathways. Therefore, the Nlrp3 inflammasome is functional both in immune cells and in HSPCs and affects hematopoiesis in either a positive or negative way, depending on its activity level. Specifically, while a physiological level of activation regulates the trafficking of HSPCs and most likely maintains their pool in the bone marrow, hyperactivation may lead to irreversible cell damage by pyroptosis and HSPC senescence and contribute to the origination of myelodysplasia and hematopoietic malignancies.

SUMMARY

Modulation of the level of Nrp3 inflammasome activation will enable improvements in HSPC mobilization, homing, and engraftment strategies. It may also control pathological activation of this protein complex during HSPC senescence, graft-versus-host disease, the induction of cytokine storms, and the development of hematopoietic malignancies.

TIM-3 restrains anti-tumour immunity by regulating inflammasome activation

T cell immunoglobulin and mucin-containing molecule 3 (TIM-3), first identified as a molecule expressed on interferon-γ producing T cells1, is emerging as an important immune-checkpoint molecule, with therapeutic blockade of TIM-3 being investigated in multiple human malignancies. Expression of TIM-3 on CD8+ T cells in the tumour microenvironment is considered a cardinal sign of T cell dysfunction; however, TIM-3 is also expressed on several other types of immune cell, confounding interpretation of results following blockade using anti-TIM-3 monoclonal antibodies. Here, using conditional knockouts of TIM-3 together with single-cell RNA sequencing, we demonstrate the singular importance of TIM-3 on dendritic cells (DCs), whereby loss of TIM-3 on DCs-but not on CD4+ or CD8+ T cells-promotes strong anti-tumour immunity. Loss of TIM-3 prevented DCs from expressing a regulatory program and facilitated the maintenance of CD8+ effector and stem-like T cells. Conditional deletion of TIM-3 in DCs led to increased accumulation of reactive oxygen species resulting in NLRP3 inflammasome activation. Inhibition of inflammasome activation, or downstream effector cytokines interleukin-1β (IL-1β) and IL-18, completely abrogated the protective anti-tumour immunity observed with TIM-3 deletion in DCs. Together, our findings reveal an important role for TIM-3 in regulating DC function and underscore the potential of TIM-3 blockade in promoting anti-tumour immunity by regulating inflammasome activation.

The Role of Interleukin-1β in Destruction of Transplanted Islets

Islet transplantation is a promising β-cell replacement therapy for type 1 diabetes, which can reduce glucose lability and hypoglycemic episodes compared with standard insulin therapy. Despite the tremendous progress made in this field, challenges remain in terms of long-term successful transplant outcomes. The insulin independence rate remains low after islet transplantation from one donor pancreas. It has been reported that the islet-related inflammatory response is the main cause of early islet damage and graft loss after transplantation. The production of interleukin-1β (IL-1β) has considered to be one of the primary harmful inflammatory events during pancreatic procurement, islet isolation, and islet transplantation. Evidence suggests that the innate immune response is upregulated through the activity of Toll-like receptors and The NACHT Domain-Leucine-Rich Repeat and PYD-containing Protein 3 inflammasome, which are the starting points for a series of signaling events that drive excessive IL-1β production in islet transplantation. In this review, we show recent contributions to the advancement of knowledge of IL-1β in islet transplantation and discuss several strategies targeting IL-1β for improving islet engraftment.

Topical calcitriol application promotes diabetic corneal wound healing and reinnervation through inhibiting NLRP3 inflammasome activation

Vitamin D (VD) deficiency delays corneal wound healing in those with diabetes, which cannot be rescued with supplemental diet. Here, we employed topical calcitriol application to evaluate its efficiency in corneal wound healing and reinnervation in diabetic mice. Type 1 diabetic mice were topically administrated calcitriol, or subconjunctivally injected with NLRP3 antagonist MCC950 or IL-1β blocking antibody after epithelial debridement. Serum VD levels, corneal epithelial defect, corneal sensation and nerve density, NLRP3 inflammasome activation, neutrophil infiltration, macrophage phenotypes, and gene expressions were examined. Compared with those of normal mice, diabetic mice showed reduced serum VD levels. Topical calcitriol application promoted corneal wound healing and nerve regeneration, as well as sensation recovery in diabetic mice. Moreover, calcitriol ameliorated neutrophil infiltration and promoted the M1-to-M2 macrophage transition, accompanied by suppressed overactivation of the NLRP3 inflammasome. Treatment with NLRP3 antagonist or IL-1β blockage demonstrated similar improvements as those of topical calcitriol application. Additionally, calcitriol administration upregulated desmosomal and hemidesmosomal gene expression in the diabetic cornea. In conclusion, topical calcitriol application promotes corneal wound healing and reinnervation during diabetes, which may be related to the suppression of the overactivation of NLRP3 inflammasome.

Redox-dependent and independent effects of thioredoxin interacting protein

Thioredoxin interacting protein (TXNIP) is an important physiological inhibitor of the thioredoxin (TXN) redox system in cells. Regulation of TXNIP expression and/or activity not only plays an important role in redox regulation but also exerts redox-independent physiological effects that exhibit direct pathophysiological consequences including elevated inflammatory response, aberrant glucose metabolism, cellular senescence and apoptosis, cellular immunity, and tumorigenesis. This review provides a brief overview of the current knowledge concerning the redox-dependent and independent roles of TXNIP and its relevance to various disease states. The implications for the therapeutic targeting of TXNIP will also be discussed.

Gasdermin D in peripheral nerves: the pyroptotic microenvironment inhibits nerve regeneration

Wallerian degeneration (WD) involves the recruitment of macrophages for debris clearance and nerve regeneration, and the cause of the foamy macrophages that are frequently observed in peripheral transection injuries is unknown. Recent studies indicated that these foamy cells are generated by gasdermin D (GSDMD) via membrane perforation. However, whether these foamy cells are pyroptotic macrophages and whether their cell death elicits immunogenicity in peripheral nerve regeneration (PNR) remain unknown. Therefore, we used GSDMD-deficient mice and mice with deficiencies in other canonical inflammasomes to establish a C57BL/6 J mouse model of sciatic nerve transection and microanastomosis (SNTM) and evaluate the role of GSDMD-executed pyroptosis in PNR. In our study, the GSDMD^−/− mice with SNTM showed a significantly diminished number of foamy cells, better axon regeneration, and a favorable functional recovery, whereas irregular axons or gaps in the fibers were found in the wild-type (WT) mice with SNTM. Furthermore, GSDMD activation in the SNTM model was dependent on the NLRP3 inflammasome and caspase-1 activation, and GSDMD-executed pyroptosis resulted in a proinflammatory environment that polarized monocytes/macrophages toward the M1 (detrimental) but not the M2 (beneficial) phenotype. In contrast, depletion of GSDMD reversed the proinflammatory microenvironment and facilitated M2 polarization. Our results suggested that inhibition of GSDMD may be a potential treatment option to promote PNR.

Interplay Between Reactive Oxygen/Reactive Nitrogen Species and Metabolism in Vascular Biology and Disease

Reactive oxygen species (ROS; e.g., superoxide [O₂^•-] and hydrogen peroxide [H₂O₂]) and reactive nitrogen species (RNS; e.g., nitric oxide [NO^•]) at the physiological level function as signaling molecules that mediate many biological responses, including cell proliferation, migration, differentiation, and gene expression. By contrast, excess ROS/RNS, a consequence of dysregulated redox homeostasis, is a hallmark of cardiovascular disease. Accumulating evidence suggests that both ROS and RNS regulate various metabolic pathways and enzymes. Recent studies indicate that cells have mechanisms that fine-tune ROS/RNS levels by tight regulation of metabolic pathways, such as glycolysis and oxidative phosphorylation. The ROS/RNS-mediated inhibition of glycolytic pathways promotes metabolic reprogramming away from glycolytic flux toward the oxidative pentose phosphate pathway to generate nicotinamide adenine dinucleotide phosphate (NADPH) for antioxidant defense. This review summarizes our current knowledge of the mechanisms by which ROS/RNS regulate metabolic enzymes and cellular metabolism and how cellular metabolism influences redox homeostasis and the pathogenesis of disease. A full understanding of these mechanisms will be important for the development of new therapeutic strategies to treat diseases associated with dysregulated redox homeostasis and metabolism. Antioxid. Redox Signal. 34, 1319-1354.

Roles of NLRP3 inflammasome in intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) is one of the leading causes of low back pain and one of the most common health problems in the world. The nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing-3 (NLRP3) inflammasome, as a pattern recognition receptor, has been shown to be associated with the pathological processes of many diseases in recent years. With the exploration of the mechanism of IVDD, recent studies have shown that activation of the NLRP3 inflammasome is associated with intervertebral disc (IVD) inflammation, pyroptosis, extracellular matrix degradation and apoptosis of IVD cells. In this review, we summarize the structural characteristics of NLRP3 inflammasome and the activation signalling mechanisms. We also describe the role of the NLRP3 inflammasome in the pathological process of IVDD and the application of the targeting the NLRP3 inflammasome in IVDD treatment.

Verapamil inhibits early acute liver failure through suppressing the NLRP3 inflammasome pathway

Acute liver failure (ALF) is a rare disease characterized by the sudden onset of serious hepatic injury, as manifested by a profound liver dysfunction and hepatic encephalopathy in patients without prior liver disease. In this paper, we aim to investigate whether verapamil, an antagonist of TXNIP, inhibits early ALF through suppressing the NLRP3 inflammasome pathway. Firstly, an ALF mouse model was induced by lipopolysaccharide (LPS)/D-galactosamine (GalN) treatment. The optimal concentration of verapamil in treating early ALF mice was determined followed by investigation on its mechanism in LPS/GalN-induced liver injury. Western blot analysis and co-immunoprecipitation were performed to determine the activation of the TXNIP/NLRP3 inflammasome pathway. Subsequently, overexpression of NLRP3 in mouse liver was induced by transfection with AAV-NRLP3 in vivo and in vitro to identity whether verapamil inhibited early ALF through suppressing the activation of NLRP3 inflammasome. We found that ALF was induced by LPS/GalN in mice but was alleviated by verapamil through a mechanism that correlated with suppression of the NLRP3 inflammasome pathway. Oxidative stress and inflammatory response were induced by intraperitoneal injection of LPS/GalN, but alleviated with injection of verapamil. Overexpression of NLRP3 via AAV in mouse liver in vivo and in vitro reduced the therapeutic effect of verapamil on LPS/GalN-induced ALF. Taken together, the TXNIP antagonist verapamil could inhibit activation of the NLRP3 inflammasome, inflammatory responses and oxidative stress to alleviate LPS/GalN-induced ALF.

Subacute toxicity of mesoporous silica nanoparticles to the intestinal tract and the underlying mechanism

The biological safety of mesoporous silica nanoparticles (MSNs) has gradually attracted attention. However, few studies of their toxicity to the intestine and mechanism are available. In this study, their primary structures were characterized, and their subacute toxicity to mice was investigated. After 2 weeks of intragastric administration of MSNs, they significantly enhanced serum ALP, ALT, AST and TNF-α levels and caused infiltration of inflammatory cells in the spleen and intestines. MSNs induced intestinal oxidative stress and colonic epithelial cell apoptosis in mice. Intestinal epithelial cells exhibited mitochondrial ridge rupture and membrane potential decrease after MSN treatment. Additionally, MSNs increased ROS and NLRP3 levels and inhibited expression of the autophagy proteins LC3-II and Beclin1. MSNs significantly changed the intestinal flora diversity in mice, especially for harmful bacteria, leading to intestinal microecology imbalance. Meanwhile, MSNs influenced the expression of metabolites, which were involved in a range of metabolic pathways, including pyrimidine metabolism, central carbon metabolism in cancer, protein digestion and absorption, mineral absorption, ABC transport and purine metabolism. These results indicated that the subacute toxicity of mesoporous silicon was mainly caused by intestinal damage. Thus, our research provides additional evidence about the safe dosage of MSNs in the clinical and food industries.