[Impact of chaperone-mediated autophagy on bilirubin-induced damage of mouse microglial cells]

OBJECTIVES

To investigate the effect of chaperone-mediated autophagy (CMA) on the damage of mouse microglial BV2 cells induce by unconjugated bilirubin (UCB).

METHODS

The BV2 cell experiments were divided into two parts. (1) For the CMA activation experiment: control group (treated with an equal volume of dimethyl sulfoxide), QX77 group (treated with 20 μmol/L QX77 for 24 hours), UCB group (treated with 40 μmol/L UCB for 24 hours), and UCB+QX77 group (treated with both 20 μmol/L QX77 and 40 μmol/L UCB for 24 hours). (2) For the cell transfection experiment: LAMP2A silencing control group (treated with an equal volume of dimethyl sulfoxide), LAMP2A silencing control+UCB group (treated with 40 μmol/L UCB for 24 hours), LAMP2A silencing group (treated with an equal volume of dimethyl sulfoxide), and LAMP2A silencing+UCB group (treated with 40 μmol/L UCB for 24 hours). The cell viability was assessed using the modified MTT method. The expression levels of p65, nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), and cysteinyl aspartate specific proteinase-1 (caspase-1) were detected by Western blot. The relative mRNA expression levels of the inflammatory cytokines interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) were determined by real-time quantitative polymerase chain reaction. Levels of IL-6 and TNF-α in the cell culture supernatant were measured using ELISA. The co-localization of heat shock cognate protein 70 with p65 and NLRP3 was detected by immunofluorescence.

RESULTS

Compared to the UCB group, the cell viability in the UCB+QX77 group increased, and the expression levels of inflammation-related proteins p65, NLRP3, and caspase-1, as well as the mRNA relative expression levels of IL-1β, IL-6, and TNF-α and levels of IL-6 and TNF-α decreased (P<0.05). Compared to the control group, there was co-localization of heat shock cognate protein 70 with p65 and NLRP3 in both the UCB and UCB+QX77 groups. After silencing the LAMP2A gene, compared to the LAMP2A silencing control+UCB group, the LAMP2A silencing+UCB group showed increased expression levels of inflammation-related proteins p65, NLRP3, and caspase-1, as well as increased mRNA relative expression levels of IL-1β, IL-6, and TNF-α and levels of IL-6 and TNF-α (P<0.05).

CONCLUSIONS

CMA is inhibited in UCB-induced BV2 cell damage, and activating CMA may reduce p65 and NLRP3 protein levels, suppress inflammatory responses, and counteract bilirubin neurotoxicity.

Vitamin D Status Modestly Regulates NOD-Like Receptor Family with a Pyrin Domain 3 Inflammasome and Interleukin Profiles among Arab Adults

Vitamin D (VD) deficiency has been associated with inflammation and dysregulation of the immune system. The NLRP3 inflammasome, a critical immune response component, plays a pivotal role in developing inflammatory diseases. VD hinders NLRP3 inflammasome activation and thus exerts anti-inflammatory effects. This study aimed to analyze the effect of VD deficiency on circulating levels of NLRP3 inflammasomes (NLRP3 and caspase-1) and associated interleukins (IL-1α, IL-1β, IL-18, IL-33 and IL-37) in Saudi adults. Methods: A total of 338 Saudi adults (128 males and 210 females) (mean age = 41.2 ± 9.1 years and mean BMI 31.2 ± 6.5 kg/m2) were included. Overnight-fasting serum samples were collected. Participants were stratified according to their VD status. Serum levels of NLRP3 inflammasomes and interleukins of interest were assessed using commercially available immuno-assays. Individuals with VD deficiency had significantly lower mean 25(OH)D levels than those with a normal VD status (29.3 nmol/L vs. 74.2 nmol/L, p < 0.001). The NLRP3 levels were higher in the VD-deficient group than their VD-sufficient counterparts (0.18 vs. 0.16, p = 0.01). Significant inverse associations were observed between NLRP3 levels with age (r = -0.20, p = 0.003) and BMI (r = -0.17, p = 0.01). Stepwise regression analysis identified insulin (β = 0.38, p = 0.005) and NLRP3 (β = -1.33, p = 0.03) as significant predictors of VD status, explaining 18.3% of the variance. The findings suggest that the VD status modestly regulates NLRP3 inflammasome and interleukin activities. This may provide novel insights into the pathogenesis and management of inflammatory disorders.

Discovery of Clinical Candidate NT-0796, a Brain-Penetrant and Highly Potent NLRP3 Inflammasome Inhibitor for Neuroinflammatory Disorders

The NLRP3 inflammasome is a component of the innate immune system involved in the production of proinflammatory cytokines. Neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis, have been shown to have a component driven by NLRP3 inflammasome activation. Diseases such as these with large unmet medical needs have resulted in an interest in inhibiting the NLRP3 inflammasome as a potential pharmacological treatment, but to date, no marketed drugs specifically targeting NLRP3 have been approved. Furthermore, the requirement for CNS-penetrant molecules adds additional complexity to the search for NLRP3 inflammasome inhibitors suitable for clinical investigation of neuroinflammatory disorders. We designed a series of ester-substituted carbamate compounds as selective NLRP3 inflammasome inhibitors, leading to NT-0796, an isopropyl ester that undergoes intracellular conversion to NDT-19795, the carboxylic acid active species. NT-0796 was shown to be a potent and selective NLRP3 inflammasome inhibitor with demonstrated in vivo brain penetration.

NLRP3 and cancer: Pathogenesis and therapeutic opportunities

More than a decade ago IL-1 blockade was suggested as an add-on therapy for the treatment of cancer. This proposal was based on the overall safety record of anti-IL-1 biologics and the anti-tumor properties of IL-1 blockade in animal models of cancer. Today, a new frontier in IL-1 activity regulation has developed with several orally active NLRP3 inhibitors currently in clinical trials, including cancer. Despite an increasing body of evidence suggesting a role of NLRP3 and IL-1-mediated inflammation driving cancer initiation, immunosuppression, growth, and metastasis, NLRP3 activation in cancer remains controversial. In this review, we discuss the recent advances in the understanding of NLRP3 activation in cancer. Further, we discuss the current opportunities for NLRP3 inhibition in cancer intervention with novel small molecules.

PM2.5 exposure aggravates acute liver injury by creating an inflammatory microenvironment through Kupffer cell

AIM

This work aimed to investigate the impact of PM2.5 exposure on acute liver injury METHODS: C57BL/6 mice were used to examine the hepatic histopathological changes in PM2.5-exposed mice, as well as in CCl4-mediated acute liver injury mice after long-term exposure to PM2.5. During in vitro experiments, Kupffer cells were detected for M1 polarization level after treating with PM2.5, and the activation level of NLRP3 inflammasomes were assessed.

RESULTS

According to our findings, PM2.5 can induce M1 polarization of Kupffer cells in the liver to create an inflammatory microenvironment. Long-term exposure to PM2.5 can aggravate acute liver injury in mice. Treatment with MCC950, an NLRP3 inhibitor, can inhibit the effect of PM2.5. As demonstrated by in vitro analysis, PM2.5 can promote M1 polarization of Kupffer cells.

CONCLUSION

As suggested by our results, long-term exposure to PM2.5 can create an inflammatory microenvironment to aggravate mouse acute liver injury. The effect is related to NLRP3-mediated M1 polarization in Kupffer cells.

NOD-like receptor protein 3 activation causes spontaneous inflammation and fibrosis that mimics human NASH

BACKGROUND AND AIMS

The NOD-like receptor protein 3 (NLRP3) inflammasome is a central contributor to human acute and chronic liver disease, yet the molecular and cellular mechanisms by which its activation precipitates injury remain incompletely understood. Here, we present single cell transcriptomic profiling of livers from a global transgenic tamoxifen-inducible constitutively activated Nlrp3A350V mutant mouse, and we investigate the changes in parenchymal and nonparenchymal liver cell gene expression that accompany inflammation and fibrosis.

APPROACH AND RESULTS

Our results demonstrate that NLRP3 activation causes chronic extramedullary myelopoiesis marked by myeloid progenitors that differentiate into proinflammatory neutrophils, monocytes, and monocyte-derived macrophages. We observed prominent neutrophil infiltrates with increased Ly6gHI and Ly6gINT cells exhibiting transcriptomic signatures of granulopoiesis typically found in the bone marrow. This was accompanied by a marked increase in Ly6cHI monocytes differentiating into monocyte-derived macrophages that express transcriptional programs similar to macrophages of NASH models. NLRP3 activation also down-regulated metabolic pathways in hepatocytes and shifted hepatic stellate cells toward an activated profibrotic state based on expression of collagen and extracellular matrix regulatory genes.

CONCLUSIONS

These results define the single cell transcriptomes underlying hepatic inflammation and fibrosis precipitated by NLRP3 activation. Clinically, our data support the notion that NLRP3-induced mechanisms should be explored as therapeutic target in NASH-like inflammation.

PM2.5 exposure inducing ATP alteration links with NLRP3 inflammasome activation

Fine particulate matter (PM_2.5) has been the primary air pollutant and the fourth leading risk factor for disease and death in the world. Exposure to PM_2.5 is related to activation of the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, but the mechanism of PM_2.5 affecting the NLRP3 inflammasome is still unclear. Previous studies have shown that PM_2.5 can cause alterations in adenosine triphosphate (ATP), and an increase in extracellular ATP and a decrease in intracellular ATP can trigger the activation process of the NLRP3 inflammasome. Therefore, we emphasize that ATP changes may be the central link and key mechanism of PM_2.5 exposure that activates the NLRP3 inflammasome. This review briefly elucidates and summarizes how PM_2.5 acts on ATP and subsequently further impacts the NLRP3 inflammasome. Investigation of ATP changes due to exposure to PM_2.5 may be essential to regulate NLRP3 inflammasome activation and treat inflammation-related diseases such as coronavirus disease 2019 (COVID-19).

Purinergic Signaling in the Regulation of Gout Flare and Resolution

Gout flares require monosodium urate (MSU) to activate the NLRP3 inflammasome and secrete sufficient IL-1β. However, MSU alone is not sufficient to cause a flare. This is supported by the evidence that most patients with hyperuricemia do not develop gout throughout their lives. Recent studies have shown that, besides MSU, various purine metabolites, including adenosine triphosphate, adenosine diphosphate, and adenosine bind to different purine receptors for regulating IL-1β secretion implicated in the pathogenesis of gout flares. Purine metabolites such as adenosine triphosphate mainly activate the NLRP3 inflammasome through P2X ion channel receptors, which stimulates IL-1β secretion and induces gout flares, while some purine metabolites such as adenosine diphosphate and adenosine mainly act on the G protein-coupled receptors exerting pro-inflammatory or anti-inflammatory effects to regulate the onset and resolution of a gout flare. Given that the purine signaling pathway exerts different regulatory effects on inflammation and that, during the inflammatory process of a gout flare, an altered expression of purine metabolites and their receptors was observed in response to the changes in the internal environment. Thus, the purine signaling pathway is involved in regulating gout flare and resolution. This study was conducted to review and elucidate the role of various purine metabolites and purinergic receptors during the process.

NLRP3 Inflammasome Mediates Neurodegeneration in Rats with Chronic Neuropathic Pain

ABSTRACT

Patients with chronic neuropathic pain (NP) have a significantly increased risk of central nervous degeneration. Trigeminal neuralgia (TN) is a typical NP, and this manifestation is more obvious. In addition to severe pain, patients with TN are often accompanied by cognitive dysfunction and have a higher risk of central nervous system degeneration, but the mechanism is not clear. The NOD-like receptor 3 (NLRP3) inflammasome assembles inside of microglia on activation, which plays an important role in neurodegeneration such as Alzheimer disease. MCC950 is a specific blocker of NLRP3 inflammasome, which can improve the performance of degenerative diseases. Although NLRP3 inflammasome assembles inside of microglia on activation has been shown to be essential for the development and progression of amyloid pathology, its whether it mediates the neurodegeneration caused by NP is currently unclear. By constructing a rat model of chronic TN, we found that as the course of the disease progresses, TN rats have obvious cognitive and memory deficit. In addition, Tau hyperphosphorylation and Aβ expression increase in the cortex and hippocampus of the brain. At the same time, we found that NLRP3 expression increased significantly in model rats. Interestingly, NLRP3 specific blocker MCC950 can alleviate the neurodegeneration of trigeminal neuralgia rats to a certain extent. It is suggested that our NLRP3 inflammasome plays an important role in the neurodegeneration of trigeminal neuralgia rats. And it is related to the activation of central nervous system inflammation.

FUNDC1 Regulates Autophagy by Inhibiting ROS-NLRP3 Signaling to Avoid Apoptosis in the Lung in a Lipopolysaccharide-Induced Mouse Model

ABSTRACT

The incidence and mortality of acute respiratory distress syndrome (ARDS) are high, but the relevant mechanism for this disorder remains unclear. Autophagy plays an important role in the development of ARDS. The mitochondrial outer membrane protein FUNDC1 is involved in hypoxia-mediated mitochondrial autophagy, which may contribute to ARDS development. This study explored whether FUNDC1 regulates autophagy by inhibiting ROS-NLRP3 signaling to avoid apoptosis in the lung in a lipopolysaccharide-induced mouse model. In this study, FUNDC1 knockout mice were constructed, and a lipopolysaccharide-induced mouse model was generated. HE staining of pathological sections from the lung, wet/dry lung measurements, myeloperoxidase concentration/neutrophil counts in BALF and survival time of mice were examined to determine the effect of modeling. The release of cytokines (TNF-α, IL-1β, IL-6, and IL-10) in response to LPS in the BALF and plasma was assessed using ELISA. The effects of oxidative stress (malondialdehyde, superoxide dismutase, catalase, glutathione peroxidase) in lung tissue in response to LPS were detected by biochemical analysis. Oxidative stress damage was validated by iNOS staining, and apoptosis was assessed by TUNEL staining after LPS. Finally, the expression of autophagy-associated proteins and inflammasome-associated proteins in lung tissue after LPS intervention was analyzed by western blot. We found that wild-type control, FUNDC1 knockout control, lipopolysaccharide-induced wild-type, and FUNDC1 knockout mouse models were used to investigate whether FUNDC1-mediated autophagy is involved in lung injury and its possible molecular mechanisms. Compared with the normal control group, lung tissue FUNDC1 and LC3 II increased and p62/SQSTM1 decreased after LPS intervention, and increased ROS levels led to a decrease in corresponding antioxidant enzymes along with an increased inflammatory response and apoptosis. Levels of autophagy in lipopolysaccharide-induced mice deficient in FUNDC1 were significantly decreased, but the expression of ROS and inflammatory factors in lung tissue was more severe than in lipopolysaccharide-induced wild-type mice, and the survival rate was significantly decreased. Western blot analysis showed that autophagy was significantly inhibited in the FUNDC1 KO+LPS group, and there was a significant increase in NLRP3, caspase-1, IL-1β, and ASC compared with the lipopolysaccharide-induced wild-type group. In summary, lipopolysaccharide-induced wild-type mice exhibit ROS-dependent activation of autophagy, and knocking out FUNDC1 promotes inflammasome activation and exacerbates lung injury.

How cytosolic compartments play safeguard functions against neuroinflammation and cell death in cerebral ischemia

Ischemic stroke is the second leading cause of mortality and disability globally. Neuronal damage following ischemic stroke is rapid and irreversible, and eventually results in neuronal death. In addition to activation of cell death signaling, neuroinflammation is also considered as another pathogenesis that can occur within hours after cerebral ischemia. Under physiological conditions, subcellular organelles play a substantial role in neuronal functionality and viability. However, their functions can be remarkably perturbed under neurological disorders, particularly cerebral ischemia. Therefore, their biochemical and structural response has a determining role in the sequel of neuronal cells and the progression of disease. However, their effects on cell death and neuroinflammation, as major underlying mechanisms of ischemic stroke, are still not understood. This review aims to provide a comprehensive overview of the contribution of each organelle on these pathological processes after ischemic stroke.

Danger-associated molecular pattern molecules take unexpectedly a central stage in Nlrp3 inflammasome-caspase-1-mediated trafficking of hematopoietic stem/progenitor cells

Like their homing after transplantation to bone marrow (BM), the mobilization of hematopoietic stem/progenitor cells (HSPCs) is still not fully understood, and several overlapping pathways are involved. Several years ago our group proposed that sterile inflammation in the BM microenvironment induced by pro-mobilizing agents is a driving force in this process. In favor of our proposal, both complement cascade (ComC)-deficient and Nlrp3 inflammasome-deficient mice are poor G-CSF and AMD3100 mobilizers. It is also known that the Nlrp3 inflammasome mediates its effects by activating caspase-1, which is responsible for proteolytic activation of interleukin-1β (IL-1β) and interleukin-18 (IL-18) and their release from cells along with several danger-associated molecular pattern molecules (DAMPs). We observed in the past that IL-1β and IL-18 independently promote mobilization of HSPCs. In the current work we demonstrated that caspase-1-KO mice are poor mobilizers, and, to our surprise, administration of IL-1β or IL-18, as in the case of Nlrp3-KO animals, does not correct this defect. Moreover, neither Caspase-1-KO nor Nlrp3-KO mice properly activated the ComC to execute the mobilization process. Interestingly, mobilization in these animals and activation of the ComC were both restored after injection of the DAMP cocktail eATP+HGMB1+S100A9, the components of which are normally released from cells in an Nlrp3 inflammasome-caspase-1-dependent manner. In addition, we report that caspase-1-deficient HSPCs show a decrease in migration in response to BM homing factors and engraft more poorly after transplantation. These results for the first time identify caspase-1 as an orchestrator of HSPC trafficking.

Effect of low oxygen concentration on activation of inflammation by Helicobacter pylori

The gastrointestinal tract of the human body is characterized by a highly unique oxygenation profile, where the oxygen concentration decreases toward the lower tract, not found in other organs. The epithelial cells lining the mucosa where Helicobacter pylori resides exist in a relatively low oxygen environment with a partial pressure of oxygen (pO2) below 58 mm Hg. However, the contribution of hypoxia to H. pylori-induced host immune responses remains elusive. In this study, we investigated the inflammasome activation induced by H. pylori under hypoxic, compared with normoxic, conditions. Our results indicated that the activation of caspase-1 and the subsequent secretion of IL-1β were significantly enhanced in infected macrophages under 1% oxygen, compared with those under a normal 20% oxygen concentration. The proliferation of H. pylori under aerobic conditions was 3-fold higher than under microaerophilic conditions, and the bacterial growth was more dependent on CO2 than on oxygen. Also, we observed that hypoxia-induced cytokine production as well as HIF-1α accumulation were both decreased when murine macrophages were treated with an HIF-1α inhibitor, KC7F2. Furthermore, hypoxia enhanced the phagocytosis of H. pylori in an HIF-1α-dependent manner. IL-1β production was also affected by the HIF-1α inhibitor in a mouse infection model, suggesting the important role of HIF-1α in the host defense system during infection with H. pylori. Our findings provide new insights into the intersection of low oxygen, H. pylori, and inflammation and disclosed how H. pylori under low oxygen tension can aggravate IL-1β secretion.

NLRP3 induces the autocrine secretion of IL-1β to promote epithelial-mesenchymal transition and metastasis in breast cancer

Tumor metastasis is a leading cause of mortality in patients with breast cancer (BC). As a predominant component of inflammasome, Nod-like receptor protein 3 (NLRP3) was found to be required for tumor progression, while the role of NLRP3 in BC metastasis remains largely undefined. In current study, we found that invasive BC had aberrant upregulation of NLRP3 expression, especially in the claudin-low subtype. And higher expression of NLRP3 predicted poor survival of BC patients. Further investigation suggested that NLRP3 promotes the migration and invasion, as well as the metastasis of BC cells. Moreover, we revealed that NLRP3 induces the autocrine secretion of IL-1β to promote epithelial-mesenchymal transition via a Caspase-1-dependent manner. Hence, this study suggested that upregulation of NLRP3 in BC induces the autocrine secretion of IL-1β and promotes EMT and metastasis of BC cells.

Importance of NLRP3 Inflammasome in Abdominal Aortic Aneurysms

Abdominal aortic aneurysm (AAA) is a chronic inflammatory degenerative aortic disease, which particularly affects older people. Nucleotide-binding oligomerization domain-like receptor family protein 3 (NLRP3) inflammasome is a multi-protein complex and mediates inflammatory responses by activating caspase 1 for processing premature interleukin (IL)-1β and IL-18. In this review, we first summarize the principle of NLRP3 inflammasome activation and the functionally distinct classes of small molecule NLRP3 inflammasome inhibitors. Next, we provide a comprehensive literature review on the expression of NLRP3 inflammasome effector mediators (IL-1β and IL-18) and components (caspase 1, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and NLRP3) in clinical and experimental AAAs. Finally, we discuss the influence of genetic deficiency or pharmacological inhibition of individual effector mediators and components of NLRP3 inflammasome on experimental AAAs. Accumulating clinical and experimental evidence suggests that NLRP3 inflammasome may be a promise therapeutic target for developing pharmacological strategies for clinical AAA management.

Contribution of the NLRP3/IL-1β axis to impaired vasodilation in sepsis through facilitation of eNOS proteolysis and the protective role of melatonin

Endothelial dysfunction is a typical characteristic of sepsis. Endothelial nitric oxide synthase (eNOS) is important for maintaining endothelial function. Our previous study reported that the NLRP3 inflammasome promoted endothelial dysfunction by enhancing inflammation. However, the effects of NLRP3 on eNOS require further investigation. Therefore, the present study aimed to investigate the role of NLRP3 on eNOS expression levels in cecal ligation and puncture-induced impaired endothelium-dependent vascular relaxation and to determine the protective effects of melatonin. eNOS expression levels were discovered to be downregulated in the mesenteric arteries of sepsis model mice. Inhibiting NLRP3 with 10 mg/ kg MCC950 or inhibiting IL-1β with 100 mg diacerein rescued the eNOS expression and improved endothelium-dependent vascular relaxation. In vitro, IL-1β stimulation downregulated eNOS expression levels in human aortic endothelial cells (HAECs) in a concentration- and time-dependent manner, while pretreatment with 1 µM of the proteasome inhibitor MG132 reversed this effect. In addition, treatment with 10 mg/kg MG132 also prevented the proteolysis of eNOS and improved endothelium-dependent vascular relaxation in vivo. Notably, treatment with 30 mg/kg melatonin downregulated NLRP3 expression levels and decreased IL-1β secretion, subsequently increasing the expression of eNOS and improving endothelium-dependent vascular relaxation. In conclusion, the findings of the present study indicated that the NLRP3/IL-1β axis may impair vasodilation by promoting the proteolysis of eNOS and melatonin may protect against sepsis-induced endothelial relaxation dysfunction by inhibiting the NLRP3/IL-1β axis, suggesting its pharmacological potential in sepsis.

Chronic stress promotes acute myeloid leukemia progression through HMGB1/NLRP3/IL-1β signaling pathway

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy with poor prognosis and overall survival. Clinical investigations show that chronic stress is commonly present in the course of AML and associated with adverse outcome. However, the underlying molecular mechanisms are elusive. In the present study, a chronic restraint stress mouse model was established to evaluate the effect of stress on AML. We found that mice under chronic stress exhibited significantly increased liver and spleen infiltration of leukemic cells and poorer overall survival. This was accompanied by elevated cellular NLR family pyrin domain containing 3 (NLRP3) and interleukin-1β (IL-1β) in the liver or bone marrow, and secreted IL-1β in the plasma, indicating the activation of inflammasomes under chronic restraint stress. High mobility group box 1 (HMGB1) expression was markedly increased in newly diagnosed AML patients, but reduced in complete remission AML patients. The expression level of HMGB1 was positively correlated with NLRP3 mRNA in AML patients. Knockdown of HMGB1 significantly decreased NLRP3 and IL-1β expression in AML cell lines, and secreted IL-1β in supernatant of AML cell culture, while HMGB1 stimulation caused contrary effects. These results implied that HMGB1 could be involved in the regulation of inflammasome activation in AML development. Mice model showed that chronic restraint stress-facilitated proliferation and infiltration of AML cells were largely abrogated by knocking down HMGB1. Knockdown of HMGB1 also ameliorated overall survival and remarkably neutralized NLRP3 and IL-1β expression under chronic restraint stress. These findings provide evidences that chronic stress promotes AML progression via HMGB1/NLRP3/IL-1β dependent mechanism, suggesting that HMGB1 is a potential therapeutic target for AML. KEY MESSAGES: • Chronic restraint stress promoted acute myeloid leukemia (AML) progression and mediated NLRP3 inflammasome activation in xenograft mice. • HMGB1 mediated NLRP3 inflammasome activation in AML cells. • Knockdown of HMGB1 inhibited AML progression under chronic stress in vivo.

Placental thromboinflammation impairs embryonic survival by reducing placental thrombomodulin expression

Excess platelet activation by extracellular vesicles (EVs) results in trophoblast inflammasome activation, interleukin 1β (IL-1β) activation, preeclampsia (PE), and partial embryonic lethality. Embryonic thrombomodulin (TM) deficiency, which causes embryonic lethality hallmarked by impaired trophoblast proliferation, has been linked with maternal platelet activation. We hypothesized that placental TM loss, platelet activation, and embryonic lethality are mechanistically linked to trophoblast inflammasome activation. Here, we uncover unidirectional interaction of placental inflammasome activation and reduced placental TM expression: although inflammasome inhibition did not rescue TM-null embryos from lethality, the inflammasome-dependent cytokine IL-1β reduced trophoblast TM expression and impaired pregnancy outcome. EVs, known to induce placental inflammasome activation, reduced trophoblast TM expression and proliferation. Trophoblast TM expression correlated negatively with IL-1β expression and positively with platelet numbers and trophoblast proliferation in human PE placentae, implying translational relevance. Soluble TM treatment or placental TM restoration ameliorated the EV-induced PE-like phenotype in mice, preventing placental thromboinflammation and embryonic death. The lethality of TM-null embryos is not a consequence of placental NLRP3 inflammasome activation. Conversely, EV-induced placental inflammasome activation reduces placental TM expression, promoting placental and embryonic demise. These data identify a new function of placental TM in PE and suggest that soluble TM limits thromboinflammatory pregnancy complications.

Aluminum Adjuvant Improves Survival Via NLRP3 Inflammasome and Myeloid Non-Granulocytic Cells in a Murine Model of Neonatal Sepsis

ABSTRACT

Neonatal sepsis leads to significant morbidity and mortality with the highest risk of death occurring in preterm (<37 weeks) and low birth weight (<2,500 g) infants. The neonatal immune system is developmentally immature with well-described defects in innate and adaptive immune responses. Immune adjuvants used to enhance the vaccine response have emerged as potential therapeutic options, stimulating non-specific immunity and preventing sepsis mortality. Aluminum salts ("alum") have been used as immune adjuvants for over a century, but their mechanism of action remains poorly understood. This study aims to identify potential mechanisms by which pretreatment with alum induces host protective immunity to polymicrobial sepsis in neonatal mice. Utilizing genetic and cell-depletion studies, we demonstrate here that the prophylactic administration of aluminum adjuvants in neonatal mice improves sepsis survival via activation of the nucleotide oligomerization domain-like receptor family, pyrin-domain-containing 3 inflammasome and dendritic cell activation. Furthermore, this beneficial effect is dependent on myeloid, non-granulocytic Gr1-positive cells, and MyD88-signaling pathway activation. These findings suggest a promising therapeutic role for aluminum-based vaccine adjuvants to prevent development of neonatal sepsis and improve mortality in this highly vulnerable population.

NLRP3 deficiency-induced hippocampal dysfunction and anxiety-like behavior in mice

Neuroinflammation has been classified as a trigger of behavioral alterations and cognitive impairments in many neurological conditions, including Alzheimer's disease, major depression, anxiety and others. Regardless of the cause of neuroinflammation, key molecules, which sense neuropathological conditions, are intracellular multiprotein signaling inflammasomes. Increasing evidence shows that the inflammatory response, mediated by activated nucleotide-binding oligomerization domain-, leucine-rich repeat- and pyrin domain-containing 3 (NLRP3) inflammasomes, is associated with the onset and progression of a wide range of diseases of the CNS. However, whether the NLRP3 inflammasome in the CNS is involved in the learning, development of anxiety and adult neurogenesis remains elusive. Therefore, the present study was designed to assess NLRP3 inflammasome contribution in anxiety and reveal its potential involvement in the experimental acquisition of fear responses and hippocampal neurogenesis. Behavioral, immunohistochemical and electrophysiological alterations were measured to evaluate role of neuroinflammation in the limbic system of mice. In this study, we describe interrelated neurophysiological mechanisms, which culminate in absence of NLRP3 inflammasome in young 4 months mice. These include the following: anxious behavior and deterioration in learning and memory of fear conditioning; impairment of adult neurogenesis; reduction and altered morphology of astrocytes in the brain; hyperexcitability in basolateral amygdala (BLA); impaired activation in axons of pyramidal cells of CA1 hippocampal zone in NLRP3 KO mice particularly via the Schaffer collateral pathway; and impaired synaptic transduction in pyramidal cells mediated by an embarrassment of neurotransmitter release from presynaptic site in CA3 hippocampal zone. The present study has demonstrated the novel findings that basal level of NLRP3 inflammasome in the brain of young mice is required for conditioning-induced plasticity in the ventral hippocampus and the basolateral amygdala. The deletion of NLRP3 impair synaptic transduction and caused anxiety-like behavior and labored fear learning, suggesting that low grade inflammation, mediated by NLRP3 expression, play a key role in memory consolidation.

Recruitment of pro-IL-1α to mitochondrial cardiolipin, via shared LC3 binding domain, inhibits mitophagy and drives maximal NLRP3 activation

The balance between NLRP3 inflammasome activation and mitophagy is essential for homeostasis and cellular health, but this relationship remains poorly understood. Here we found that interleukin-1α (IL-1α)-deficient macrophages have reduced caspase-1 activity and diminished IL-1β release, concurrent with reduced mitochondrial damage, suggesting a role for IL-1α in regulating this balance. LPS priming of macrophages induced pro-IL-1α translocation to mitochondria, where it directly interacted with mitochondrial cardiolipin (CL). Computational modeling revealed a likely CL binding motif in pro-IL-1α, similar to that found in LC3b. Thus, binding of pro-IL-1α to CL in activated macrophages may interrupt CL-LC3b-dependent mitophagy, leading to enhanced Nlrp3 inflammasome activation and more robust IL-1β production. Mutation of pro-IL-1α residues predicted to be involved in CL binding resulted in reduced pro-IL-1α-CL interaction, a reduction in NLRP3 inflammasome activity, and increased mitophagy. These data identify a function for pro-IL-1α in regulating mitophagy and the potency of NLRP3 inflammasome activation.

Tomentosin inhibit cerebral ischemia/reperfusion induced inflammatory response via TLR4/ NLRP3 signalling pathway - in vivo and in vitro studies

Stoke is a global threat, leading to 50 % of deaths worldwide and it causes permanent disability to about 5 million individuals globally each year. In this study, we assessed the potency of tomentosin to inhibit the neuroinflammation in in vivo and in vitro models. The Sprague Dawley rats were pretreated with 25 mg/kg bodyweight (b.wt) and 50 mg/kg b.wt of tomentosin for seven days followed by induction of cerebral ischemic reperfusion. The brain edema and cerebral infractions were analyzed. The levels of antioxidants and the interleukins were measured by standard methods. The NLRP3 signaling proteins expression was evaluated using qPCR analysis. In vitro studies were performed in SH-SY5Y-cells pretreated with tomentosin and subjected to OGD-R treatment. Our results depicts tomentosin scavenges the free radicals, enhances antioxidant system, inhibits the NLRP3 signaling. In vitro results substantiates with in vivo results. To conclude, our in vivo and in vitro results confirm tomentosin may be potent alternative for existing antistroke drugs.

Metabolic competition between host and pathogen dictates inflammasome responses to fungal infection

The NLRP3 inflammasome has emerged as a central immune regulator that senses virulence factors expressed by microbial pathogens for triggering inflammation. Inflammation can be harmful and therefore this response must be tightly controlled. The mechanisms by which immune cells, such as macrophages, discriminate benign from pathogenic microbes to control the NLRP3 inflammasome remain poorly defined. Here we used live cell imaging coupled with a compendium of diverse clinical isolates to define how macrophages respond and activate NLRP3 when faced with the human yeast commensal and pathogen Candida albicans. We show that metabolic competition by C. albicans, rather than virulence traits such as hyphal formation, activates NLRP3 in macrophages. Inflammasome activation is triggered by glucose starvation in macrophages, which occurs when fungal load increases sufficiently to outcompete macrophages for glucose. Consistently, reducing Candida’s ability to compete for glucose and increasing glucose availability for macrophages tames inflammatory responses. We define the mechanistic requirements for glucose starvation-dependent inflammasome activation by Candida and show that it leads to inflammatory cytokine production, but it does not trigger pyroptotic macrophage death. Pyroptosis occurs only with some Candida isolates and only under specific experimental conditions, whereas inflammasome activation by glucose starvation is broadly relevant. In conclusion, macrophages use their metabolic status, specifically glucose metabolism, to sense fungal metabolic activity and activate NLRP3 when microbial load increases. Therefore, a major consequence of Candida-induced glucose starvation in macrophages is activation of inflammatory responses, with implications for understanding how metabolism modulates inflammation in fungal infections.

Activation of the immune regulator NLRP3 inflammasome by microbial pathogens has been shown to play both protective and destructive roles in infection, underscoring the importance of tight control over NLRP3-driven inflammation to ensure host health. A key microbe recognised by NLRP3 is the human yeast commensal and pathogen Candida albicans, which is responsible for mucosal and invasive infections. We demonstrate that innate immune cells sense their metabolic status to trigger NLRP3 activation only when microbial numbers have reached dangerous levels. This regulation is a consequence of metabolic competition between C. albicans and macrophages for an essential nutrient–glucose. The NLRP3 inflammasome is activated when increased fungal load in the infection microenvironment drives down glucose levels, thereby causing glucose starvation in macrophages. Restoring glucose homeostasis in macrophages reduced NLRP3 activation and production of the proinflammatory cytokine IL-1β, suggesting that metabolism regulates NLRP3 inflammasome activity in fungal infections.

A Spotlight on the Underlying Activation Mechanisms of the NLRP3 Inflammasome and its Role in Atherosclerosis: A Review

The world's number one cause of death is cardiovascular diseases. The pathogenesis of different disease entities in the cardiovascular disease spectrum is complicated and multifactorial. Inflammation in these complicated etiologies serves as a key position and is a significant cause of atherosclerosis, which contributes to the underlying pathology. Therefore, therapeutic targeting of inflammatory pathways in patients with cardiovascular diseases such as atherosclerosis enhances cardiovascular results. Inflammasomes are intracellular protein complexes engaged in atherosclerosis pathogenesis and activated by multiple danger signals. Emerging proof has revealed that Nod-like receptor protein 3 (NLRP3) inflammasome, which regulates caspase-1 activation and later pro-interleukin processing, triggers inflammatory reactions in the vascular wall and leads to atherosclerotic plaque formation. Inflammasome-mediated signaling interference could decrease inflammation and mitigate illness severity. In this section, we provide an overview of the present literature on the underlying mechanisms leading to the activation of NLRP3 inflammasome and the role of NLRP3 inflammasome in the progression of atherogenesis and highlight the possibility of therapeutic interventions due to mechanisms involved in the of inhibition of NLRP3 activation.

NLRP3 inflammasome-dependent pyroptosis and apoptosis in hippocampus neurons mediates depressive-like behavior in diabetic mice

A relatively large number of diabetic patients risk complications of clinical depression that lead to poorer quality of life, however the precise mechanisms for diabetes-associated depression are not fully understood. Links between hyperglycemia-induced oxidative stress and NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome activation have been reported in the pathogenesis of diabetes. The present study aimed to elucidate the contribution of NLRP3-mediated apoptotic/pyroptotic neuronal cell death to diabetes-associated depression. We found that depressive-like behavior in streptozotocin (STZ)-induced diabetic mice was associated with hippocampal NLRP3 inflammasome activation. Hyperglycemia increased reactive oxygen species (ROS) production, thus leading to NLRP3 inflammasome activation in hippocampal neurons. It was found that STZ treatment induced apoptotic and pyroptotic cell death in the hippocampus as evidenced by increases of cleaved caspase 3 positive hippocampal neurons, TUNEL-positive cells, protein levels of p53, Bax, Puma, and the cleaved GSDMD N-terminal fragment, all of which were decreased in NLRP3 deficient mice. Using murine hippocampal neuronal cell line HT22, we found that high glucose induced apoptotic and pyroptotic cell death in a NLRP3 inflammasome-dependent manner in vitro. In addition, NLRP3 deficiency alleviated depressive-like behavior in STZ-induced diabetic mice. Our results suggest that hyperglycemia results in apoptosis and pyroptosis of hippocampal neuron cells in a NLRP3-dependent manner, which was associated with the depressive phenotypes evoked by STZ-induced diabetes. The study identifies a novel function of NLRP3 activation in high glucose-induced neuronal cell death, which sheds further light on the pathogenesis and new therapeutic targets of diabetes-associated depression.

The Roles of the NLRP3 Inflammasome in Neurodegenerative and Metabolic Diseases and in Relevant Advanced Therapeutic Interventions

Inflammasomes are intracellular multiprotein complexes in the cytoplasm that regulate inflammation activation in the innate immune system in response to pathogens and to host self-derived molecules. Recent advances greatly improved our understanding of the activation of nucleotide-binding oligomerization domain-like receptor (NLR) family pyrin domain containing 3 (NLRP3) inflammasomes at the molecular level. The NLRP3 belongs to the subfamily of NLRP which activates caspase 1, thus causing the production of proinflammatory cytokines (interleukin 1β and interleukin 18) and pyroptosis. This inflammasome is involved in multiple neurodegenerative and metabolic disorders including Alzheimer's disease, multiple sclerosis, type 2 diabetes mellitus, and gout. Therefore, therapeutic targeting to the NLRP3 inflammasome complex is a promising way to treat these diseases. Recent research advances paved the way toward drug research and development using a variety of machine learning-based and artificial intelligence-based approaches. These state-of-the-art approaches will lead to the discovery of better drugs after the training of such a system.

Pyroptosis in Osteoblasts: A Novel Hypothesis Underlying the Pathogenesis of Osteoporosis

Osteoporosis has become a worldwide disease characterized by a reduction in bone mineral density and the alteration of bone architecture leading to an increased risk of fragility fractures. And an increasing number of studies have indicated that osteoblasts undergo a large number of programmed death events by many different causes in osteoporosis and release NLRP3 and interleukin (e.g., inflammatory factors), which play pivotal roles in contributing to excessive differentiation of osteoclasts and result in exaggerated bone resorption. NLRP3 is activated during pyroptosis and processes the precursors of IL-1β and IL-18 into mature forms, which are released into the extracellular milieu accompanied by cell rupture. All of these compounds are the classical factors of pyroptosis. The cellular effects of pyroptosis are commonly observed in osteoporosis. Although many previous studies have focused on the pathogenesis of these inflammatory factors in osteoporosis, pyroptosis has not been previously evaluated. In this review, pyroptosis is proposed as a novel hypothesis of osteoporosis pathogenesis for the first time, thus providing a new direction for the treatment of osteoporosis in the future.

Inflammasome-Independent Role for NLRP3 in Controlling Innate Antihelminth Immunity and Tissue Repair in the Lung

Alternatively activated macrophages are essential effector cells during type 2 immunity and tissue repair following helminth infections. We previously showed that Ym1, an alternative activation marker, can drive innate IL-1R-dependent neutrophil recruitment during infection with the lung-migrating nematode, Nippostrongylus brasiliensis, suggesting a potential role for the inflammasome in the IL-1-mediated innate response to infection. Although inflammasome proteins such as NLRP3 have important proinflammatory functions in macrophages, their role during type 2 responses and repair are less defined. We therefore infected Nlrp3 -/- mice with N. brasiliensis Unexpectedly, compared with wild-type (WT) mice, infected Nlrp3 -/- mice had increased neutrophilia and eosinophilia, correlating with enhanced worm killing but at the expense of increased tissue damage and delayed lung repair. Transcriptional profiling showed that infected Nlrp3 -/- mice exhibited elevated type 2 gene expression compared with WT mice. Notably, inflammasome activation was not evident early postinfection with N. brasiliensis, and in contrast to Nlrp3 -/- mice, antihelminth responses were unaffected in caspase-1/11-deficient or WT mice treated with the NLRP3-specific inhibitor MCC950. Together these data suggest that NLRP3 has a role in constraining lung neutrophilia, helminth killing, and type 2 immune responses in an inflammasome-independent manner.

Hippo Signaling Controls NLR Family Pyrin Domain Containing 3 Activation and Governs Immunoregulation of Mesenchymal Stem Cells in Mouse Liver Injury

The Hippo pathway, an evolutionarily conserved protein kinase cascade, tightly regulates cell growth and survival. Activation of yes-associated protein (YAP), a downstream effector of the Hippo pathway, has been shown to modulate tissue inflammation. However, it remains unknown as to whether and how the Hippo-YAP signaling may control NLR family pyrin domain containing 3 (NLRP3) activation in mesenchymal stem cell (MSC)-mediated immune regulation during liver inflammation. In a mouse model of ischemia/reperfusion (IR)-induced liver sterile inflammatory injury, we found that adoptive transfer of MSCs reduced hepatocellular damage, shifted macrophage polarization from M1 to M2 phenotype, and diminished inflammatory mediators. MSC treatment reduced mammalian Ste20-like kinase 1/2 and large tumor suppressor 1 phosphorylation but augmented YAP and β-catenin expression with increased prostaglandin E2 production in ischemic livers. However, disruption of myeloid YAP or β-catenin in MSC-transferred mice exacerbated IR-triggered liver inflammation, enhanced NLRP3/caspase-1 activity, and reduced M2 macrophage phenotype. Using MSC/macrophage coculture system, we found that MSCs increased macrophage YAP and β-catenin nuclear translocation. Importantly, YAP and β-catenin colocalize in the nucleus while YAP interacts with β-catenin and regulates its target gene X-box binding protein 1 (XBP1), leading to reduced NLRP3/caspase-1 activity after coculture. Moreover, macrophage YAP or β-catenin deficiency augmented XBP1/NLRP3 while XBP1 deletion diminished NLRP3/caspase-1 activity. Increasing NLRP3 expression reduced M2 macrophage arginase1 but augmented M1 macrophage inducible nitric oxide synthase expression accompanied by increased interleukin-1β release. Conclusion: MSCs promote macrophage Hippo pathway, which in turn controls NLRP3 activation through a direct interaction between YAP and β-catenin and regulates XBP1-mediated NLRP3 activation, leading to reprograming macrophage polarization toward an anti-inflammatory M2 phenotype. Moreover, YAP functions as a transcriptional coactivator of β-catenin in MSC-mediated immune regulation. Our findings suggest a therapeutic target in MSC-mediated immunotherapy of liver sterile inflammatory injury.

Pharmacological Inhibitors of the NLRP3 Inflammasome

Inflammasomes play a crucial role in innate immunity by serving as signaling platforms which deal with a plethora of pathogenic products and cellular products associated with stress and damage. By far, the best studied and most characterized inflammasome is NLRP3 inflammasome, which consists of NLRP3 (nucleotide-binding domain leucine-rich repeat (NLR) and pyrin domain containing receptor 3), ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain), and procaspase-1. Activation of NLRP3 inflammasome is mediated by highly diverse stimuli. Upon activation, NLRP3 protein recruits the adapter ASC protein, which recruits the procaspase-1 resulting in its cleavage and activation, inducing the maturation, and secretion of inflammatory cytokines and pyroptosis. However, aberrant activation of the NLRP3 inflammasome is implicated in various diseases including diabetes, atherosclerosis, metabolic syndrome, cardiovascular, and neurodegenerative diseases; raising a tremendous clinical interest in exploring the potential inhibitors of NLRP3 inflammasome. Recent investigations have disclosed various inhibitors of the NLRP3 inflammasome pathway which were validated through in vitro studies and in vivo experiments in animal models of NLRP3-associated disorders. Some of these inhibitors directly target the NLRP3 protein whereas some are aimed at other components and products of the inflammasome. Direct targeting of NLRP3 protein can be a better choice because it can prevent off target immunosuppressive effects, thus restrain tissue destruction. This paper will review the various pharmacological inhibitors of the NLRP3 inflammasome and will also discuss their mechanism of action.

Inflammasome and α-synuclein in Parkinson's disease: A cross-sectional study

BACKGROUND

Alpha-synuclein and inflammatory pathology are evident in Parkinson's disease (PD) but, their link to disease pathogenesis needs further elucidation.

OBJECTIVES

To explore α-synuclein-mediated inflammation in the serum of PD patients and its link with disease severity.

METHODS

Serum levels of IL-1β, NLRP3, total and phosphorylated α-synuclein were compared.

RESULTS

IL-1β, NLRP3 levels were significantly increased in PD. We also observed a linear correlation of NLRP3 with α-synuclein. Phosphorylated α-synuclein levels were significantly elevated in later stages of PD.

CONCLUSIONS

The α-synuclein-NLRP3 mediated inflammation may underline the pathophysiology of PD and might serve as a novel therapeutic target in PD.

Fine particulate matter-induced cardiovascular injury is associated with NLRP3 inflammasome activation in Apo E-/- mice

Epidemiological evidences have indicated that fine particulate matter (PM_2.5) is associated with the increased risk of cardiovascular morbidity and mortality. Although several mechanisms linking PM_2.5 and inflammatory responses have been widely implicated, the detailed mechanisms involving the occurrence of inflammation in PM_2.5-induced adverse effects are lacking. This study aims to investigate whether PM_2.5 exposure-induced cardiovascular injury is associated with NLRP3 inflammasome activation in apolipoprotein E^-/- (Apo E^-/-) mice. Thirty-two Apo E^-/- mice were randomly divided into four groups. The mice were fed with normal chow (NC) or high-fat chow (HFC) for 10 weeks, respectively. From week 11, the mice were exposed to concentrated PM_2.5 (PM) or filter air (FA) using Shanghai Meteorological and Environmental Animal Exposure System for 16 weeks. The cardiac function and myocardial injury were evaluated by echocardiography and histopathological examination. Meanwhile, the expression of NLRP3-related signaling pathway in myocardium was detected. Compared with the FA mice, the PM mice showed the underlying cardiac dysfunction and injury in both NC and HFC groups. Mononuclear macrophages (CD11c⁺) were significant higher in bone marrow of the PM mice than that in the FA mice, whilst CD206⁺ macrophages were lower. Accordingly, PM_2.5 exposure induced the increase of circulating inflammatory cytokine TNF-α and decrease of anti-inflammatory cytokine IL-10. PM_2.5 exposure was also associated with the activation of NLRP3 inflammasome, which characterized by elevated protein expression of NLRP3, ASC, caspase-1, IL-1β and IL-18 in myocardium. All these results demonstrated PM_2.5-related cardiac injury is mediated by macrophages polarization and NLRP3 inflammasome activation.

The Immunomodulatory Properties of 2-Hydroxyethyl Methacrylate are Mediated by the NLRP3 Inflammasome

PURPOSE

The methacrylate monomer 2-hydroxyethyl methacrylate (HEMA), commonly used in dentistry, has multiple effects on the immune system. This study examined whether HEMA affects the immune system by inducing formation of the NLRP3 inflammasome.

MATERIALS AND METHODS

Human peripheral blood mononuclear cells (PBMCs) and the human monocyte cell line THP1 were cultured with or without 1000 μM HEMA. To block NLRP3 inflammasome activation, 130 mM KCl was also added to some of the cultures. For the in vivo studies, two different experimental setups were used. In the first experimental setup, mice were injected subcutaneously at the base of the tail with 20 μmol HEMA with or without 100 mM KCl. After 3 weeks, the animals were given an identical booster injection. Two weeks after the last injection, the mice were sacrificed and splenectomized. In the second experimental setup, HEMA (20 μmol), with or without 100 mM KCl, was injected subcutaneously into the tails of BALB/c mice. The mice were given two similar injections at 3-week intervals to allow evaluation of the local inflammation induced by HEMA. After the last inoculation, the injection site was examined daily for 4 days, after which the mice were sacrificed.

RESULTS

Cultures of PBMCs and THP1 cells exposed to HEMA in vitro produced more IL-1ß and IL-18 than did control cells. Increased extracellular concentration of KCl inhibited the secretion of IL-1ß. HEMA exposure did not induce cytokine production in variants of the THP1 cell line unable to form the NLRP3 inflammasome. For the first experimental setup, the level of unstimulated basic splenocyte proliferation in vitro was significantly higher in cultures from mice exposed in vivo to HEMA only than in cultures from mice injected with HEMA plus KCl. In the second experimental setup of the in vivo studies, the HEMA-treated mice developed more pronounced inflammation at the site of injection compared to the group of mice given HEMA plus KCl.

CONCLUSION

HEMA affects the immune system by inducing formation of the NLRP3 inflammasome.

Amygdalin attenuates acute liver injury induced by D-galactosamine and lipopolysaccharide by regulating the NLRP3, NF-κB and Nrf2/NQO1 signalling pathways

Acute liver injury (ALI) is a life-threatening syndrome accompanied by overwhelming inflammation. Amygdalin (AGD) has been reported to possess various biological activities, particularly anti-inflammatory activity. The current study was designed to assess the protective effects and underlying mechanisms of AGD against ALI induced by d-galactosamine (GalN) and lipopolysaccharide (LPS) in mice. The results indicated that AGD treatment effectively reduced the lethality, ameliorated the histopathological liver changes, reduced the malondialdehyde (MDA) and myeloperoxidase (MPO) levels, and decreased the alanine transaminase (ALT) and aspartate aminotransferase (AST) levels resulting from LPS/GalN challenge. Moreover, AGD significantly inhibited LPS/GalN-induced inflammatory responses in mice with ALI by reducing not only the secretion of tumour necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 but also the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Additionally, our results demonstrated that the inhibitory effect of AGD was due to the suppressed activation of nuclear factor-kappa B (NF-κB) and nucleotide-binding domain (NOD-)like receptor protein 3 (NLRP3) inflammasome activity. Furthermore, AGD treatment substantially increased nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation and enhanced NAD (P) H: quinoneoxidoreductase 1 protein expression, which was reversed by a Nrf2 inhibitor, in HepG2 cells. In summary, our investigations suggested that the ability of AGD to ameliorate LPS/GalN-induced ALI may involve the inhibition of the NLRP3 inflammasome and NF-κB signalling pathways and the upregulation of the Nrf2/NQO1 signalling pathway.

Regulation of epithelial injury and bile duct obstruction by NLRP3, IL-1R1 in experimental biliary atresia

BACKGROUND & AIMS

Biliary atresia (BA) results from a neonatal inflammatory and fibrosing obstruction of bile ducts of unknown etiology. Although the innate immune system has been linked to the virally induced mechanism of disease, the role of inflammasome-mediated epithelial injury remains largely undefined. Here, we hypothesized that disruption of the inflammasome suppresses the neonatal proinflammatory response and prevents experimental BA.

METHODS

We determined the expression of key inflammasome-related genes in livers from infants at diagnosis of BA and in extrahepatic bile ducts (EHBDs) of neonatal mice after infection with rotavirus (RRV) immediately after birth. Then, we determined the impact of the wholesale inactivation of the genes encoding IL-1R1 (Il1r1^-/-), NLRP3 (Nlrp3^-/-) or caspase-1 (Casp1^-/-) on epithelial injury and bile duct obstruction.

RESULTS

IL1R1, NLRP3 and CASP1 mRNA increased significantly in human livers at the time of diagnosis, and in EHBDs of RRV-infected mice. In Il1r1^-/- mice, the epithelial injury of EHBDs induced by RRV was suppressed, with dendritic cells unable to activate natural killer cells. A similar protection was observed in Nlrp3^-/- mice, with decreased injury and inflammation of livers and EHBDs. Long-term survival was also improved. In contrast, the inactivation of the Casp1 gene had no impact on tissue injury, and all mice died. Tissue analyses in Il1r1^-/- and Nlrp3^-/- mice showed decreased populations of dendritic cells and natural killer cells and suppressed expression of type-1 cytokines and chemokines.

CONCLUSIONS

Genes of the inflammasome are overexpressed at diagnosis of BA in humans and in the BA mouse model. In the experimental model, the targeted loss of IL-1R1 or NLRP3, but not of caspase-1, protected neonatal mice against RRV-induced bile duct obstruction.

LAY SUMMARY

Biliary atresia is a severe inflammatory and obstructive disease of bile ducts occurring in infancy. Although the cause is unknown, activation of the innate and adaptive immune systems injures the bile duct epithelium. In this study we found that patients' livers had increased expression of inflammasome genes. Using mice engineered to inactivate individual inflammasome genes, the epithelial injury and bile duct obstruction were prevented by the loss of Il1r1 or Nlrp3, with a decreased activation of natural killer cells and expression of cytokines and chemokines. In contrast, the loss of Casp1 did not change the disease phenotype. Combined, the findings point to a differential role of inflammasome gene products in the pathogenic mechanisms of biliary atresia.

Chemical disruption of the pyroptotic pore-forming protein gasdermin D inhibits inflammatory cell death and sepsis

Dysregulation of inflammatory cell death is a key driver of many inflammatory diseases. Pyroptosis, a highly inflammatory form of cell death, uses intracellularly generated pores to disrupt electrolyte homeostasis and execute cell death. Gasdermin D, the pore-forming effector protein of pyroptosis, coordinates membrane lysis and the release of highly inflammatory molecules, such as interleukin-1β, which potentiate the overactivation of the innate immune response. However, to date, there is no pharmacologic mechanism to disrupt pyroptosis. Here, we identify necrosulfonamide as a direct chemical inhibitor of gasdermin D, the pyroptotic pore-forming protein, which binds directly to gasdermin D to inhibit pyroptosis. Pharmacologic inhibition of pyroptotic cell death by necrosulfonamide is efficacious in sepsis models and suggests that gasdermin D inhibitors may be efficacious clinically in inflammatory diseases.

The role of NLRP3 inflammasome in stroke and central poststroke pain

BACKGROUND

NLRP3 inflammasome plays a prominent role in the pathogenesis and progression of many diseases, such as type 2 diabetes mellitus, obesity, atherosclerosis, and Alzheimer's disease. However, little knowledge is known about the role of NLRP3 inflammasome in central post-stroke pain (CPSP).

METHODS

We selected relevant studies by searching PubMed, Embase, and Medline from inception through February, 2018. We systematically reviewed available publications according to the terms "NLRP3 inflammasome" and "stroke" or "central post-stroke pain" in the title/abstract field.

RESULTS

We reviewed the articles and put forward two possible ways for NLRP3 inflammasome in CPSP. One way is that NLRP3 activation causes cerebral cortex injure, decreasing descending projection fiber to thalamus. Such condition may let GABAergic releases reduce, making the ventral basal (VB) neurons excitability increased. Finally, CPSP occur. Another way is that NLRP3 inflammasome leads to thalamic lesion and strengthens inflammatory response of microglia at the same time. Persistent inflammation causes GABAergic alteration in thalamus reticular neurons (TRN) to restrain VB interneurons functions, contributing to CPSP.

CONCLUSIONS

These possible mechanisms will help become knowledgeable about the occurrence CPSP and provide potential therapy for CPSP.

Physical activity protects NLRP3 inflammasome-associated coronary vascular dysfunction in obese mice

Activation of the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome mediates the release of pro-inflammatory cytokine interleukin (IL)-1β and thereby plays a pivotal role in the inflammatory response in vascular pathology. An active lifestyle has beneficial effects on inflammation-associated vascular dysfunction in obesity. However, it remains unclear how physical activity regulates NLRP3 inflammasome-mediated vascular dysfunction in obesity. Therefore, we explored the protective effect of physical activity on NLRP3 inflammasome-associated vascular dysfunction in mouse hearts, and the potential underlying mechanisms. C57BL/6J male mice were randomly divided into four groups: (1) control low-fat diet (LF-SED), (2) LF diet with free access to a voluntary running wheel (LF-RUN), (3) high-fat diet (HF-SED; 45% of calories from fat), and (4) HF-RUN. We examined NLRP3 inflammasome-related signaling pathways, nitric oxide (NO) signaling, and oxidative stress in coronary arterioles to test effects of HFD and physical activity. Voluntary running reduced NLRP3 inflammasome and its downstream effects, caspase-1 and IL-1β in coronary arteriole endothelium of obese mice in immunofluorescence staining. HF-RUN attenuated HFD-dependent endothelial NO synthase (eNOS) reduction and thus increased NO production compared to HF-SED. HFD elevated intracellular superoxide production in coronary arterioles while voluntary running ameliorated oxidative stress. Our findings provide the first evidence that voluntary running attenuates endothelial NLRP3 inflammasome activation in coronary arterioles of HFD feeding mice. Results further suggest that voluntary running improves obesity-induced vascular dysfunction by preserved NO bioavailability via restored expression of eNOS and reduced oxidative stress.

Deactivation of the NLRP3 inflammasome in infiltrating macrophages by duodenal-jejunal bypass surgery mediates improvement of beta cell function in type 2 diabetes

OBJECTIVE

Bariatric surgery could improve pancreatic beta cell function, thereby leading to the remission of the type 2 diabetes mellitus (T2DM). However, the specific mechanism underlying this phenomenon is yet to be revealed. The aim of this study is to test the hypothesis that Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome in infiltrating macrophages plays an important role in the modulation of beta cell function after duodenal-jejunal bypass (DJB) surgery.

METHODS

DJB and sham surgery were performed in diabetic Sprague-Dawley (SD) rats induced by high-fat diet (HFD) and streptozotocin (STZ). Body weight, food intake, and glucose tolerance test (GTT) were measured at indicated time points. Apoptosis of the beta cells was measured by Terminal deoxynucleotidyl transferase mediated dUTP Nick End Labeling (TUNEL) assay. We also assessed the macrophage content and NLRP3 expression in the rat model. Furthermore, macrophage reconstitution was performed after DJB surgery. Beta cell function and NLRP3 inflammasome pathway were re-evaluated in wild-type macrophage reconstitution group and NLRP3-knockdown macrophage reconstitution group.

RESULTS

DJB surgery group rats displayed rapid and sustained improvement in glucose tolerance. Decreased apoptosis and improved secretion function of the beta cells were observed in DJB surgery group. NLRP3 inflammasome pathway in infiltrating macrophages was also suppressed after DJB surgery. Moreover, diabetic remission acquired by DJB sustained in NLRP3-knockdown macrophage reconstitution group, while extinguished in group reconstituted with wild-type macrophage.

CONCLUSIONS

NLRP3 inflammasome deactivation in infiltrating macrophages is involved in marked beta cell function improvement after DJB surgery.

Inflammasome biology, molecular pathology and therapeutic implications

Inflammasomes are intracellular multiprotein signaling complexes, mainly present in myeloid cells. They commonly assemble around a cytoplasmic receptor of the nucleotide-binding leucine-rich repeat containing receptor (NLR) family, although other cytoplasmic receptors like pyrin have been shown to form inflammasomes. The nucleation of the multiprotein scaffolding platform occurs upon detection of a microbial, a danger or a homeostasis pattern by the receptor that will, most commonly, associate with the adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD) through homotypic domain interactions resulting in recruitment of procaspase-1. This will lead to the autoproteolytic activation of caspase-1, which regulates the secretion of proinflammatory IL1β and IL18 cytokines and pyroptosis, a caspase-1-mediated form of cell death. Pyroptosis occurs through cleavage of Gasdermin D, a membrane pore forming protein. Recently, non-canonical inflammasomes have been described, which directly sense intracellular pathogens through caspase-4 and -5 in humans, leading to pyroptosis. Inflammasomes are important in host defense; however, a deregulated activity is associated with a number of inflammatory, immune and metabolic disorders. Furthermore, mutations in inflammasome receptor coding genes are causal for an increasing number of rare autoinflammatory diseases. Biotherapies targeting the products of inflammasome activation as well as molecules that directly or indirectly inhibit inflammasome nucleation and activation are promising therapeutic areas. This review discusses recent advances in inflammasome biology, the molecular pathology of several inflammasomes, and current therapeutic approaches in autoinflammatory diseases and in selected common multifactorial inflammasome-mediated disorders.

The use of gold nanorods as a new vaccine platform against schistosomiasis

Schistosomiasis is an important parasitic disease affecting >207 million people in 76 countries around the world and causing approximately 250,000 deaths per year. At present, the main strategy adopted for the control of schistosomiasis is the use of safe chemotherapy, such as praziquantel. However, the high rates of reinfection after treatment restrict the use of this treatment approach and assume the need for other forms of control such as vaccination. Sm29 is a protein that is localized in the Schistosoma mansoni tegument of adult worms and schistosomula and is considered a powerful vaccine candidate. Because of the chemical, physical and immunological characteristics of nanoparticles, nanocarriers have received increasing attention. In the field of nanotechnology, gold nanorods are considered potential vaccine carriers. In this study, we bound S. mansoni rSm29 protein to gold nanorods either directly or by cysteamine functionalization. When the worm burden was evaluated, the AuNRs-NH₂-rSm29 group of immunized mice showed the best protection level (34%). Following AuNRs-NH₂-rSm29 immunization, we observed a Th1 immunological response in mice with higher production of IFN-γ, mainly by CD4⁺ and CD8⁺ T cells. Furthermore, AuNRs-NH₂-rSm29 could activate dendritic cells in vitro, enhancing MHCII and MHCI expression and the production of IL-1β in a NLRP3-, ASC- and Caspase-1-dependent manner. In summary, our findings support the use of nanorods as an immunization strategy in vaccine development against infectious diseases.

NLRP3 inflammasome driven liver injury and fibrosis: Roles of IL-17 and TNF in mice

The NLRP3 inflammasome, a caspase-1 activation platform, plays a key role in the modulation of liver inflammation and fibrosis. Here, we tested the hypothesis that interleukin 17 (IL-17) and tumor necrosis factor (TNF) are key cytokines involved in amplifying and perpetuating the liver damage and fibrosis resulting from NLRP3 activation. To address this hypothesis, gain-of-function Nlrp3A350V knock-in mice were bred onto il17a and Tnf knockout backgrounds allowing for constitutive Nlrp3 activation in myeloid derived cells in mice deficient in IL-17 or TNF. Livers of Nlrp3A350V knock-in mice exhibited severe liver inflammatory changes characterized by infiltration with neutrophils, increased expression of chemokine (C-X-C motif) ligand (CXCL) 1 and CXCL2 chemokines, activated inflammatory macrophages, and elevated levels of IL-17 and TNF. Mutants with ablation of il17a signal showed fewer neutrophils when compared to intact Nlrp3A350V mutants, but still significant inflammatory changes when compared to the nonmutant il17a knockout littermates. The severe inflammatory changes associated with mutant Nlrp3 were almost completely rescued by Tnf knockout in association with a marked decrease in circulating IL-1β levels. Intact Nlrp3A350V mutants showed changes in liver fibrosis, as evidenced by morphometric quantitation of Sirius Red staining and increased mRNA levels of profibrotic genes, including connective tissue growth factor and tissue inhibitor of matrix metalloproteinase 1. Il17a lacking mutants exhibited amelioration of the aforementioned fibrosis, whereas Tnf-deficient mutants showed no signs of fibrosis when compared to littermate controls. Conclusion: Our study uncovers key roles for TNF and, to a lesser extent, IL-17 as mediators of liver inflammation and fibrosis induced by constitutive NLRP3 inflammasome activation in myeloid-derived cells. These findings may lead to therapeutic strategies aimed at halting the progression of liver injury and fibrogenesis in various liver pathogeneses driven by NLRP3 activation. (Hepatology 2018;67:736-749).

Zearalenone (ZEA)-induced intestinal inflammation is mediated by the NLRP3 inflammasome

To ascertain whether zearalenone (ZEA) could induce intestinal inflammation and investigate its possible mechanism, we investigated inflammatory cytokine release and the activation of the NLRP3 inflammasome after ZEA treatment both in vitro or in vivo. First, intestinal porcine enterocyte cell line (IPEC-J2) cells and mouse peritoneal macrophages were treated with ZEA to detect NLRP3 inflammasome activation, and the role of reactive oxygen species (ROS) in ZEA-induced inflammation was investigated. Then, Balb/c mice were fed a gavage of ZEA, and the disease activity indices (DAIs) and histological analysis were used to assess intestinal inflammation. Our study showed that the mRNA expression of NLRP3 inflammasome, pro-interleukin-1β (pro-IL-1β), and pro-interleukin-18 (pro-IL-18) was up-regulated 0.5- to 1-fold and that the release of IL-1β and IL-18 increased from 48 pg mL^-1 to 55 pg mL^-1 and 110 pg mL^-1 to 145 pg mL^-1, respectively. However, ROS inhibitor N-acetyl-l-cysteine (NAC) reduced IL-1β and IL-18 release to 45 pg mL^-1 and 108 pg mL^-1. Moreover, the same phenomenon was observed in intestinal tissues of ZEA-treated mice. In addition, clinical parameters of treated mice showed stools became loose and contained mucous. In addition, the presence of gross blood stool was found in the last 2 d. Histological analysis showed obvious inflammatory cell infiltration and tissue damage in the colon. These findings uncovered a possible mechanism of intestinal mucosal innate immunity in response to mycotoxin ZEA that ZEA could activate the ROS-mediated NLRP3 inflammasome and, in turn, contribute to the caspase-1-dependent activation of the inflammatory cytokines IL-1β and IL-18.

Suppression of inflammatory and infection responses in lung macrophages by eucalyptus oil and its constituent 1,8-cineole: Role of pattern recognition receptors TREM-1 and NLRP3, the MAP kinase regulator MKP-1, and NFκB

Eucalyptus oil (EO) used in traditional medicine continues to prove useful for aroma therapy in respiratory ailments; however, there is a paucity of information on its mechanism of action and active components. In this direction, we investigated EO and its dominant constituent 1,8–cineole (eucalyptol) using the murine lung alveolar macrophage (AM) cell line MH-S. In an LPS-induced AM inflammation model, pre-treatment with EO significantly reduced (P ≤0.01or 0.05) the pro-inflammatory mediators TNF-α, IL-1 (α and β), and NO, albeit at a variable rate and extent; 1,8-cineole diminished IL-1 and IL-6. In a mycobacterial-infection AM model, EO pre-treatment or post-treatment significantly enhanced (P ≤0.01) the phagocytic activity and pathogen clearance. 1,8-cineole also significantly enhanced the pathogen clearance though the phagocytic activity was not significantly altered. EO or 1,8-cineole pre-treatment attenuated LPS-induced inflammatory signaling pathways at various levels accompanied by diminished inflammatory response. Among the pattern recognition receptors (PRRs) involved in LPS signaling, the TREM pathway surface receptor (TREM-1) was significantly downregulated. Importantly, the pre-treatments significantly downregulated (P ≤0.01) the intracellular PRR receptor NLRP3 of the inflammasome, which is consistent with the decrease in IL-1β secretion. Of the shared downstream signaling cascade for these PRR pathways, there was significant attenuation of phosphorylation of the transcription factor NF-κB and p38 (but increased phosphorylation of the other two MAP kinases, ERK1/2 and JNK1/2). 1,8-cineole showed a similar general trend except for an opposite effect on NF-κB and JNK1/2. In this context, either pre-treatment caused a significant downregulation of MKP-1 phosphatase, a negative regulator of MAPKs. Collectively, our results demonstrate that the anti-inflammatory activity of EO and 1,8-cineole is modulated via selective downregulation of the PRR pathways, including PRR receptors (TREM-1 and NLRP3) and common downstream signaling cascade partners (NF-κB, MAPKs, MKP-1). To our knowledge, this is the first report on the modulatory role of TREM-1 and NLRP3 inflammasome pathways and the MAPK negative regulator MKP-1 in context of the anti-inflammatory potential of EO and its constituent 1,8-cineole.

[NLRP3 inflammasome induces pyroptosis in lung tissues of radiation-induced lung injury in mice]

Objective To establish a radiation-induced lung injury model and investigate the role of caspase-1-dependent programmed cell death (pyroptosis) in the pathogenesis of radiation pneumonitis. Methods BALB/c mice were sacrificed after receiving 5-day 15 Gy X-ray irradiation at chest cavity. The pathological changes of pulmonary tissues were observed by HE staining. The apoptosis of lung tissues cells after irradiation was detected by TUNEL assay. The expressions of γ-H2AX, ki67, NLR family pyrin domain containing 3 (NLRP3), caspase-1, apoptosis-associated speck-like protein containing a CARD (ASC/TMS-1) were detected by Western blot analysis. Real-time quantitative PCR was used to check mRNA levels of interleukin-6 (IL-6), IL-8, tumor necrosis factor α (TNF-α), monocyte chemoattractant protein 1 (MCP-1), NLRP3, caspase-1, IL-1β and IL-18. Immunohistochemical staining was used to determine the expressions of NLRP3, caspase-1 and TMS1 in lung tissues. The activity of caspase-1 was evaluated by caspase-1 assay kit, and the serum levels of IL-1β and IL-18 were detected by ELISA. Results After irradiation, the capillaries of the alveolar wall of the mice were dilated and congested, inflammatory cells infiltrated, the alveolar wall thickened. Positive rate of lung tissue cells was raised in TUNEL staining. The expressions of γ-H2AX and ki67 were elevated, indicating that DNA damage and cell proliferation activity decreased in lung tissues. The mRNA levels of IL-6, IL-8, TNF-α and MCP-1 in lung cells increased; the serum levels of IL-1β and IL-18 increased; the expressions of IL-1β, IL-18, NLRP3, caspase-1 and ASC/TMS-1 in lung tissues were enhanced; and caspase-1 activity increased. Conclusion After irradiation, the pyroptosis caused by the activation of NLRP3 inflammatory body occurred in the lung tissue of mice.

Current role of the NLRP3 inflammasome on obesity and insulin resistance: A systematic review

NLRP3 inflammasome activation seems to be a culprit behind the chronic inflammation characteristic of obesity and insulin resistance (IR). Nutrient excess generates danger-associated molecules that activate NLRP3 inflammasome-caspase 1, leading to maturation of IL-1β and IL-18, which are proinflammatory cytokines released by immune cells infiltrating the adipose tissue (AT) from obese subjects. Although several studies have reported an association of the NLRP3 inflammasome with obesity and/or IR; contradictory results were also reported by other studies. Therefore, we conducted a systematic review to summarize results of studies that evaluated the association of the NLRP3 with obesity and IR. Nineteen studies were included in the review. These studies focused on NLRP3 expression/polymorphism analyses in AT. Overall, human studies indicate that obesity and IR are associated with increased NLRP3 expression in AT. Studies in obese mice corroborate this association. Moreover, high fat diet (HFD) increases Nlrp3 expression in murine AT while calorie-restricted diet decreases its expression. Hence, Nlrp3 blockade in mice protects against HFD-induced obesity and IR. NLRP3 rs10754558 polymorphism is associated with risk for T2DM in Chinese Han populations. In conclusion, available studies strongly points for an association between NLRP3 inflammasome and obesity/IR.

The NLRP3 inflammasome contributes to sarcopenia and lower muscle glycolytic potential in old mice

The mechanisms underpinning decreased skeletal muscle strength and slowing of movement during aging are ill-defined. "Inflammaging," increased inflammation with advancing age, may contribute to aspects of sarcopenia, but little is known about the participatory immune components. We discovered that aging was associated with increased caspase-1 activity in mouse skeletal muscle. We hypothesized that the caspase-1-containing NLRP3 inflammasome contributes to sarcopenia in mice. Male C57BL/6J wild-type (WT) and NLRP3^-/- mice were aged to 10 (adult) and 24 mo (old). NLRP3^-/- mice were protected from decreased muscle mass (relative to body mass) and decreased size of type IIB and IIA myofibers, which occurred between 10 and 24 mo of age in WT mice. Old NLRP3^-/- mice also had increased relative muscle strength and endurance and were protected from age-related increases in the number of myopathic fibers. We found no evidence of age-related or NLRP3-dependent changes in markers of systemic inflammation. Increased caspase-1 activity was associated with GAPDH proteolysis and reduced GAPDH enzymatic activity in skeletal muscles from old WT mice. Aging did not alter caspase-1 activity, GAPDH proteolysis, or GAPDH activity in skeletal muscles of NLRP3^-/- mice. Our results show that the NLRP3 inflammasome participates in age-related loss of muscle glycolytic potential. Deletion of NLRP3 mitigates both the decline in glycolytic myofiber size and the reduced activity of glycolytic enzymes in muscle during aging. We propose that the etiology of sarcopenia involves direct communication between immune responses and metabolic flux in skeletal muscle.

N-methyl-D-aspartic acid receptor 1 (NMDAR1) aggravates secondary inflammatory damage induced by hemin-NLRP3 pathway after intracerebral hemorrhage

OBJECTIVE

Inflammation plays a critical role in secondary brain damage after intracerebral hemorrhage (ICH). However, the mechanisms of inflammatory injury following ICH are still unclear, particularly the involvement of NLRP3 inflammasome, which are crucial to sterile inflammatory responses. In this study, we aim to test the hypothesis that NLRP3 signaling pathway takes a vital position in ICH-induced secondary inflammatory damage and detect the role of N-methyl-D-aspartic acid receptor 1 (NMDAR1) in this progress.

METHODS

ICH was induced in mice by microinjection of hemin into the striatum. The protein levels of NMDAR1, NMDAR1 phosphorylation, NLRP3 and IL-1b were measured by Western blot. The binding of NMDAR1 to NLRP3 was detected by immunoprecipitation.

RESULTS

The expression of NMDAR1, NMDAR1 phosphorylation, NLRP3 and IL-1b were rapidly increased after ICH. Hemin treatment enhanced NMDAR1 expression and NMDAR1 phosphorylation, as well in cultured microglial cells treated by hemin. Hemin up regulated NLRP3 and IL-1b level, which was reversed by MK801 (NMDAR antagonist) in vitro. Hemin also promoted the binding of NMDAR1 to NLRP3.

CONCLUSION

Our findings suggest that NMDAR1 plays a pivotal role in hemin-induced NLRP3-mediated inflammatory damage through synergistic activation.

Trichomonas vaginalis induces IL-1β production in a human prostate epithelial cell line by activating the NLRP3 inflammasome via reactive oxygen species and potassium ion efflux

BACKGROUND

Trichomonas vaginalis is a sexually transmitted protozoan parasite that causes vaginitis in women, and urethritis and prostatitis in men. IL-1β is synthesized as immature pro-IL-1β, which is cleaved by activated caspase-1. Caspase-1 is, in turn, activated by a multi-protein complex known as an inflammasome. In this study, we investigated the inflammatory response of a prostate epithelial cell line (RWPE-1) to T. vaginalis and, specifically, the capacity of T. vaginalis to activate the NLRP3 inflammasome.

METHODS

RWPE-1 cells were stimulated by live T. vaginalis, and subsequent expression of pro-IL-1β, IL-1β, NLRP3, ASC and caspase-1 was determined by real-time PCR and Western blotting. IL-1β and caspase-1 production was also measured by ELISA. To evaluate the effects of NLRP3 and caspase-1 on IL-1β production, the activated RWPE-1 cells were transfected with small interfering RNAs to silence the NLRP3 and caspase-1 genes. Activation of the NLRP3 inflammasome was observed by fluorescence microscopy. Intracellular reactive oxygen species (ROS) were evaluated by spectrofluorometry.

RESULTS

When RWPE-1 cells were stimulated with live T. vaginalis, the mRNA and protein expression of IL-1β, NLRP3, ASC, and caspase-1 increased. Moreover, silencing of NLRP3 and caspase-1 attenuated T. vaginalis-induced IL-1β secretion. The NADPH oxidase inhibitor DPI and high extracellular potassium ion suppressed the production of IL-1β, caspase-1, and the expression of NLRP3 and ASC proteins. The specific NF-κB inhibitor, Bay 11-7082, inhibited IL-1β production, and also inhibited the production of caspase-1, ASC and NLRP3 proteins.

CONCLUSIONS

T. vaginalis induces the formation of the NLRP3 inflammasome in human prostate epithelial cells via ROS and potassium ion efflux, and this results in IL-1β production. This is the first evidence for activation of the NLRP3 inflammasome in the inflammatory response by prostate epithelial cells infected with T. vaginalis. Prostate 76:885-896, 2016. © 2016 Wiley Periodicals, Inc.

Uric acid regulates hepatic steatosis and insulin resistance through the NLRP3 inflammasome-dependent mechanism

BACKGROUND & AIMS

Hyperuricemia significantly increases risk of non-alcoholic fatty liver disease (NAFLD) and insulin resistance. However, the mechanisms responsible for this association are as yet unclear. This study aimed to investigate the effects and underlying mechanisms of uric acid on development of NAFLD and insulin resistance.

METHODS

We initially analyzed the impact of uric acid on the development of hepatic steatosis and insulin resistance in mice and in two cell models, HepG2 and L02. Subsequently, we studied the role of the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome in uric acid-induced fat accumulation and insulin signaling impairment.

RESULTS

We found that uric acid directly induces hepatocyte fat accumulation, insulin resistance, and insulin signaling impairment both in vivo and in vitro. We also found that uric acid-induced NLRP3 inflammasome activation, whereas lowering uric acid by allopurinol inhibited NLRP3 inflammasome activation in a high fat diet mouse model of NAFLD. Moreover, knocking down NLRP3 expression significantly attenuated uric acid-induced fat accumulation both in HepG2 cells and L02 cells. Knocking down NLRP3 expression also rescued uric acid-induced insulin signaling impairment in both cell types.

CONCLUSIONS

Uric acid regulates hepatic steatosis and insulin resistance through the NLRP3 inflammasome. Uric acid may be a new therapeutic target for NAFLD and insulin resistance.