Cardiac hypertrophy that affects hyperthyroidism occurs independently of the NLRP3 inflammasome.

Cardiac hypertrophy (CH) is an adaptive response to maintain cardiac function; however, persistent stress responses lead to contractile dysfunction and heart failure. Although inflammation is involved in these processes, the mechanisms that control cardiac inflammation and hypertrophy still need to be clarified. The NLRP3 inflammasome is a cytosolic multiprotein complex that mediates IL-1ß production. The priming step of NLRP3 is essential for increasing the expression of its components and occurs following NF-κB activation. Hyperthyroidism triggers CH, which can progress to maladaptive CH and even heart failure. We have shown in a previous study that thyroid hormone (TH)-induced CH is linked to the upregulation of S100A8, leading to NF-κB activation. Therefore, we aimed to investigate whether the NLRP3 inflammasome is involved in TH-induced CH and its potential role in CH pathophysiology. Hyperthyroidism was induced in NLRP3 knockout (NLRP3-KO), Caspase-1-KO and Wild Type (WT) male mice of the C57Bl/6J strain, aged 8-12 weeks, by triiodothyronine (7 µg/100 g BW, i.p.) administered daily for 14 days. Morphological and cardiac functional analysis besides molecular assays showed, for the first time, that TH-induced CH is accompanied by reduced NLRP3 expression in the heart and that it occurs independently of the NLRP3 inflammasome and caspase 1-related pathways. However, NLRP3 is important for the maintenance of basal cardiac function since NLRP3-KO mice had impaired diastolic function and reduced heart rate, ejection fraction, and fractional shortening compared with WT mice.

NAIP/NLRC4 inflammasome participates in macrophage responses to Trypanosoma cruzi by a mechanism that relies on cathepsin-dependent caspase-1 cleavage.

Inflammasomes are large protein complexes that, once activated, initiate inflammatory responses by activating the caspase-1 protease. They play pivotal roles in host defense against pathogens. The well-established role of NAIP/NLRC4 inflammasome in bacterial infections involves NAIP proteins functioning as sensors for their ligands. However, recent reports have indicated the involvement of NLRC4 in non-bacterial infections and sterile inflammation, even though the role of NAIP proteins and the exact molecular mechanisms underlying inflammasome activation in these contexts remain to be elucidated. In this study, we investigated the activation of the NAIP/NLRC4 inflammasome in response to Trypanosoma cruzi, the protozoan parasite responsible for causing Chagas disease. This parasite has been previously demonstrated to activate NLRP3 inflammasomes. Here we found that NAIP and NLRC4 proteins are also required for IL-1ß and Nitric Oxide (NO) release in response to T. cruzi infection, with their absence rendering macrophages permissive to parasite replication. Moreover, Nlrc4 -/- and Nlrp3 -/- macrophages presented similar impaired responses to T. cruzi, underscoring the non-redundant roles played by these inflammasomes during infection. Notably, it was the live trypomastigotes rather than soluble antigens or extracellular vesicles (EVs) secreted by them, that activated inflammasomes in a cathepsins-dependent manner. The inhibition of cathepsins effectively abrogated caspase-1 cleavage, IL-1ß and NO release, mirroring the phenotype observed in Nlrc4 -/-/Nlrp3 -/- double knockout macrophages. Collectively, our findings shed light on the pivotal role of the NAIP/NLRC4 inflammasome in macrophage responses to T. cruzi infection, providing new insights into its broader functions that extend beyond bacterial infections.

Necrotic Cell Death and Inflammasome NLRP3 Activity in Mycobacterium bovis-Infected Bovine Macrophages.

Mycobacterium bovis is a facultative intracellular bacterium that produces cellular necrosis in granulomatous lesions in bovines. Although M. bovis-induced inflammation actively participates in granuloma development, its role in necrotic cell death and in bovine macrophages has not been fully explored. In this study, we evaluate the effect of M. bovis AN5 and its culture filtrate protein extract (CFPE) on inflammasome activation in bovine macrophages and its consequences on cell death. Our results show that both stimuli induce necrotic cell death starting 4 h after incubation. CFPE treatment and M. bovis infection also induce the maturation of IL-1ß (>3000 pg/mL), oligomerization of ASC (apoptosis-associated speck-like protein containing CARD), and activation of caspase-1, following the canonical activation pathway of the NLRP3 inflammasome. Inhibiting the oligomerization of NLRP3 and caspase-1 decreases necrosis among the infected or CFPE-stimulated macrophages. Furthermore, histological lymph node sections of bovines naturally infected with M. bovis contained cleaved gasdermin D, mainly in macrophages and giant cells within the granulomas. Finally, the induction of cell death (apoptosis and pyroptosis) decreased the intracellular bacteria count in the infected bovine macrophages, suggesting that cell death helps to control the intracellular growth of the mycobacteria. Our results indicate that M. bovis induces pyroptosis-like cell death that is partially related to the NLRP3 inflammasome activation and that the cell death process could control bacterial growth.

NLRP3 Inflammasome Involved with Viral Replication in Cytopathic NADL BVDV Infection and IFI16 Inflammasome Connected with IL-1ß Release in Non-Cytopathic NY-1 BVDV Infection in Bovine Macrophages.

Inflammasomes are multiprotein complexes that play a role in the processing of proinflammatory cytokines such as interleukin 1 beta (IL-1ß). The secretion of IL-1ß in bovine macrophages infected with the bovine viral diarrhea virus (BVDV) cytopathic strain NADL (NADLcp-BVDV) is caspase 1-dependent. In the present study, we found that in macrophages infected with NADL, the NLRP3 inflammasome participated in the maturation of IL-1ß as the level decreased from 4629.3 pg/mL to 897.0 pg/mL after treatment with cytokine release inhibitory drug 3 (CRID3). Furthermore, NLRP3 activation has implications regarding viral replication, as there was a decrease in the viral titer until 1 log of a supernatant of macrophages that were inhibited with CRID3 remained. In the case of the non-cytopathic BVDV strain NY-1 (NY-1 ncpBVDV), IL-1ß secretion is not affected by NLRP3, but could be related to the IFI16 inflammasome; we found a colocalization of IFI16 with ASC using confocal microscopy in infected macrophages with the NY-1 ncp-BVDV biotype. To relate IFI16 activation to IL-1ß release, we used ODN TTAGGG (A151), a competitive inhibitor of IFI16; the results show a decrease in its level from 248 pg/mL to 128.3 pg/mL. Additionally, we evaluated the caspase 1 activation downstream of IFI16 and found a decrease in the IL-1ß from 252.9 pg/mL to 63.5 pg/mL when caspase 1 was inhibited with Y-VAD. Our results provide an improved understanding of the mechanisms involved in the viral replication, inflammation and pathogenesis of bovine viral diarrhea.

Inflammasome Coordinates Senescent Chronic Wound Induced by Thalassophryne nattereri Venom.

Thalassophryne nattereri toadfish (niquim) envenomation, common in the hands and feet of bathers and fishermen in the north and northeast regions of Brazil, is characterized by local symptoms such as immediate edema and intense pain. These symptoms progress to necrosis that lasts for an extended period of time, with delayed healing. Wound healing is a complex process characterized by the interdependent role of keratinocytes, fibroblasts, and endothelial and innate cells such as neutrophils and macrophages. Macrophages and neutrophils are actively recruited to clear debris during the inflammatory phase of wound repair, promoting the production of pro-inflammatory mediators, and in the late stage, macrophages promote tissue repair. Our hypothesis is that injury caused by T. nattereri venom (VTn) leads to senescent wounds. In this study, we provide valuable information about the mechanism(s) behind the dysregulated inflammation in wound healing induced by VTn. We demonstrate in mouse paws injected with the venom the installation of γH2AX/p16Ink4a-dependent senescence with persistent neutrophilic inflammation in the proliferation and remodeling phases. VTn induced an imbalance of M1/M2 macrophages by maintaining a high number of TNF-α-producing M1 macrophages in the wound but without the ability to eliminate the persistent neutrophils. Chronic neutrophilic inflammation and senescence were mediated by cytokines such as IL-1α and IL-1ß in a caspase-1- and caspase-11-dependent manner. In addition, previous blocking with anti-IL-1α and anti-IL-ß neutralizing antibodies and caspase-1 (Ac YVAD-CMK) and caspase-11 (Wedelolactone) inhibitors was essential to control the pro-inflammatory activity of M1 macrophages induced by VTn injection, skewing towards an anti-inflammatory state, and was sufficient to block neutrophil recruitment and senescence.

LPS Triggers Acute Neuroinflammation and Parkinsonism Involving NLRP3 Inflammasome Pathway and Mitochondrial CI Dysfunction in the Rat.

Whether neuroinflammation leads to dopaminergic nigrostriatal system neurodegeneration is controversial. We addressed this issue by inducing acute neuroinflammation in the substantia nigra (SN) with a single local administration (5 µg/2 µL saline solution) of lipopolysaccharide (LPS). Neuroinflammatory variables were assessed from 48 h to 30 days after the injury by immunostaining for activated microglia (Iba-1 +), neurotoxic A1 astrocytes (C3 + and GFAP +), and active caspase-1. We also evaluated NLRP3 activation and Il-1ß levels by western blot and mitochondrial complex I (CI) activity. Fever and sickness behavior was assessed for 24 h, and motor behavior deficits were followed up until day 30. On this day, we evaluated the cellular senescence marker ß-galactosidase (ß-Gal) in the SN and tyrosine hydroxylase (TH) in the SN and striatum. After LPS injection, Iba-1 (+), C3 (+), and S100A10 (+) cells were maximally present at 48 h and reached basal levels on day 30. NLRP3 activation occurred at 24 h and was followed by a rise of active caspase-1 (+), Il-1ß, and decreased mitochondrial CI activity until 48 h. A significant loss of nigral TH (+) cells and striatal terminals was associated with motor deficits on day 30. The remaining TH (+) cells were ß-Gal (+), suggesting senescent dopaminergic neurons. All the histopathological changes also appeared on the contralateral side. Our results show that unilaterally LPS-induced neuroinflammation can cause bilateral neurodegeneration of the nigrostriatal dopaminergic system and are relevant for understanding Parkinson's disease (PD) neuropathology.

Inflammasome coordinates senescent chronic wound induced by Thalassophryne nattereri venom

Thalassophryne nattereri toadfish (niquim) envenomation, common in the hands and feet of bathers and fishermen in the north and northeast regions of Brazil, is characterized by local symptoms such as immediate edema and intense pain. These symptoms progress to necrosis that lasts for an extended period of time, with delayed healing. Wound healing is a complex process characterized by the interdependent role of keratinocytes, fibroblasts, and endothelial and innate cells such as neutrophils and macrophages. Macrophages and neutrophils are actively recruited to clear debris during the inflammatory phase of wound repair, promoting the production of pro-inflammatory mediators, and in the late stage, macrophages promote tissue repair. Our hypothesis is that injury caused by T. nattereri venom (VTn) leads to senescent wounds. In this study, we provide valuable information about the mechanism(s) behind the dysregulated inflammation in wound healing induced by VTn. We demonstrate in mouse paws injected with the venom the installation of γH2AX/p16Ink4a-dependent senescence with persistent neutrophilic inflammation in the proliferation and remodeling phases. VTn induced an imbalance of M1/M2 macrophages by maintaining a high number of TNF-α-producing M1 macrophages in the wound but without the ability to eliminate the persistent neutrophils. Chronic neutrophilic inflammation and senescence were mediated by cytokines such as IL-1α and IL-1β in a caspase-1- and caspase-11-dependent manner. In addition, previous blocking with anti-IL-1α and anti-IL-β neutralizing antibodies and caspase-1 (Ac YVAD-CMK) and caspase-11 (Wedelolactone) inhibitors was essential to control the pro-inflammatory activity of M1 macrophages induced by VTn injection, skewing towards an anti-inflammatory state, and was sufficient to block neutrophil recruitment and senescence.

Puerarin protects renal ischemia-reperfusion injury in rats through NLRP3/Caspase-1/GSDMD pathway

Purpose: To observe the effect of puerarin on renal ischemia-reperfusion (I/R) injury in rats, and to explore its mechanism based on NLRP3/Caspase-1/GSDMD pathway. Methods: Twenty-one Sprague-Dawley rats were divided into three groups: sham-operated group (sham), model group (RIRI), and puerarin treatment group (RIRI + Pue). The model of acute renal I/R injury was established by cutting the right kidney and clamping the left renal pedicle for 45 min. Results: Renal function parameters were statistically significant in group comparisons. The renal tissue structure of rats in sham group was basically normal. Pathological changes were observed in the RIRI group. The renal pathological damage score and apoptosis rate in the RIRI group were higher than those in the sham group, and significantly lower in the RIRI + Pue group than in the RIRI group. Indicators of oxidative stress-superoxide dismutase, malondialdehyde, and glutathione peroxidase-were statistically significant in group comparisons. Compared with the sham group, the relative expressions of NLRP3, Caspase-1 and GSDMD proteins in the RIRI group were increased. Compared with the RIRI group, the RIRI + Pue group had significant reductions. Conclusions: Puerarin can inhibit the activation of NLRP3/Caspase-1/GSDMD pathway, inhibit inflammatory response and pyroptosis, and enhance the antioxidant capacity of kidney, thereby protecting renal I/R injury in rats.

AIM2 inflammasome activation may mediate high mobility group box 1 release in murine allergic rhinitis / Ativação do inflamassoma AIM2 pode mediar a liberação da proteína do grupo Box-1 de alta mobilidade no modelo murino de rinite alérgica

Abstract Introduction: High mobility group box 1 protein participates in the pathogenesis of allergic rhinitis. Activation of the inflammasome can mediate the release of high mobility group box 1. The role of the absent in melanoma 2 inflammasome in allergic rhinitis remains unclear. Objective: This study aimed to investigate the function of absent in melanoma 2 inflammasome in murine allergic rhinitis and the interaction between high mobility group box 1 and the absent in melanoma 2 inflammasome. Methods: A murine allergic rhinitis model was established using twenty Balb/c mice. Expression of the components of the absent in melanoma 2 inflammasome: absent in melanoma 2, apoptosis-associated speck-like protein containing a CARD (Asc), caspase-1 p20, and additional nod-like receptor family pyrin domain containing 3 (Nlrp3) were detected by western blotting during allergic rhinitis. Alterations of absent in melanoma 2, caspase-1, and high mobility group box 1 after ovalbumin challenge were demonstrated by immunohistochemistry. TdT-mediated dUTP Nick end labeling, TUNEL assay, and cleavage of caspase-3 and PARP-1 were used for the observation of pyroptosis. Results: Eosinophilia and goblet cell infiltration were observed in the nasal mucosa of mice in the allergic rhinitis group. Absent in melanoma 2, Asc, and caspase-1 p20 increased after ovalbumin exposure while Nlrp3 did not. High mobility group box 1 was released in the nasal mucosa of allergic rhinitis mice. TUNEL-positive cells increased in the epithelium and laminae propria, whereas cleavage of caspase-3 and PARP-1 was not observed. Conclusions: The absent in melanoma 2 inflammasome was activated and pyroptosis may occur in the nasal mucosa after ovalbumin treatment. These may contribute to the translocation of high mobility group box 1 and the development of allergic rhinitis.

Resumo Introdução: A proteína do grupo Box-1 de alta mobilidade participa da patogênese da rinite alérgica. A ativação do inflamassoma pode mediar a liberação de proteína do grupo Box-1 de alta mobilidade. O papel do inflamassoma ausente no melanoma 2 na rinite alérgica permanece incerto. Objetivo: Investigar a função do inflamassoma ausente no melanoma 2 em um modelo murino de rinite alérgica e a interação entre a proteína do grupo Box-1 de alta mobilidade e o inflamassoma ausente no melanoma 2. Método: Um modelo murino de rinite alérgica foi estabelecido com 20 camundongos Balb/c. A expressão dos componentes do inflamassoma ausente no melanoma 2, da proteína speck-like associada à apoptose com CARD (Asc), da caspase-1 p20 e do domínio de pirina da família NLR adicional com 3 (Nlrp3) foi detectada por western blotting durante a rinite alérgica. Alterações de inflamassoma ausente no melanoma 2, na caspase-1 e na proteína do grupo Box-1 de alta mobilidade após o teste de provocação com ovalbumina foram demonstradas por imuno-histoquímica. O ensaio dUTP Nick-End Labeling mediado por TdT, TUNEL e clivagem de caspase-3 e PARP-1 foram usados para a observação de piroptose. Resultados: Eosinofilia e infiltração de células caliciformes foram observadas na mucosa nasal de camundongos do grupo rinite alérgica. Inflamassoma ausente no melanoma 2, Asc e caspase-1 p20 aumentou após a exposição à ovalbumina, enquanto Nlrp3 não aumentou. A proteína do grupo Box-1 de alta mobilidade foi liberada na mucosa nasal de camundongos com rinite alérgica. As células TUNEL-positivas aumentaram no epitélio e na lâmina própria, enquanto a clivagem da caspase-3 e a PARP-1 não foram observadas. Conclusão: O inflamassoma ausente no melanoma 2 foi ativado e pode ocorrer piroptose na mucosa nasal após o tratamento com ovalbumina. Esses fatores podem contribuir para a translocação de proteína do grupo Box-1 de alta mobilidade e o desenvolvimento de rinite alérgica.

Caspase-1 and Cathepsin B Inhibitors from Marine Invertebrates, Aiming at a Reduction in Neuroinflammation.

Neuroinflammation is a condition associated with several types of dementia, such as Alzheimer's disease (AD), mainly caused by an inflammatory response to amyloid peptides that induce microglial activation, with subsequent cytokine release. Neuronal caspase-1 from inflammasome and cathepsin B are key enzymes mediating neuroinflammation in AD, therefore, revealing new molecules to modulate these enzymes may be an interesting approach to treat neurodegenerative diseases. In this study, we searched for new caspase-1 and cathepsin B inhibitors from five species of Brazilian marine invertebrates (four cnidarians and one echinoderm). The results show that the extract of the box jellyfish Chiropsalmus quadrumanus inhibits caspase-1. This extract was fractionated, and the products monitored for their inhibitory activity, until the obtention of a pure molecule, which was identified as trigonelline by mass spectrometry. Moreover, four extracts inhibit cathepsin B, and Exaiptasia diaphana was selected for subsequent fractionation and characterization, resulting in the identification of betaine as being responsible for the inhibitory action. Both molecules are already found in marine organisms, however, this is the first study showing a potent inhibitory effect on caspase-1 and cathepsin B activities. Therefore, these new prototypes can be considered for the enzyme inhibition and subsequent control of the neuroinflammation.

Inflammasome activation and assembly in Huntington's disease.

Huntington's disease (HD) is a rare neurodegenerative disease characterized by motor, cognitive, and psychiatric symptoms. Inflammasomes are multiprotein complexes capable of sensing pathogen-associated and damage-associated molecular patterns, triggering innate immune pathways. Activation of inflammasomes results in a pro-inflammatory cascade involving, among other molecules, caspases and interleukins. NLRP3 (nucleotide-binding domain, leucine-rich-repeat containing family, pyrin domain-containing 3) is the most studied inflammasome complex, and its activation results in caspase-1 mediated cleavage of the pro-interleukins IL-1ß and IL-18 into their mature forms, also inducing a gasdermin D mediated form of pro-inflammatory cell death, i.e. pyroptosis. Accumulating evidence has implicated NLRP3 inflammasome complex in neurodegenerative diseases. The evidence in HD is still scant and mostly derived from pre-clinical studies. This review aims to present the available evidence on NLRP3 inflammasome activation in HD and to discuss whether targeting this innate immune system complex might be a promising therapeutic strategy to alleviate its symptoms.

Enhanced Activity of NLRP3 Inflammasome in the Lung of Patients with Anti-Synthetase Syndrome.

Anti-synthetase syndrome (ASSD) is an autoimmune disorder characterized by inflammatory interstitial lung disease (ILD). The main objective of this work was to quantify the concentrations of cytokines and molecules associated with inflammasome activation in bronchoalveolar lavage (BAL) of patients with ASSD and a comparison group of systemic sclerosis (SSc) patients. Cytokines and lactate dehydrogenase (LDH) were determined using the concentrated BAL protein. The activity of caspase-1 and concentration of NLRP3 with the protein purified from the cell pellet in each group of patients. We found higher caspase-1 levels in ASSD vs. SSc, 1.25 RFU vs. 0.75 RFU p = 0.003, and LDH levels at 0.15 OD vs. 0.09 OD p < 0.001. A significant difference was observed in molecules associated with inflammasome activation, IL-18: 1.42 pg/mL vs. 0.87 pg/mL p = 0.02 and IFN-γ: 0.9 pg/mL vs. 0.86 pg/mL, p = 0.01. A positive correlation was found between caspase-1 and LDH in the patients with ASSD Rho 0.58 (p = 0.008) but not in the SSc group. In patients with ASSD, greater caspase-1 and higher LDH activity were observed in BAL, suggesting cell death due to pyroptosis and activation of the inflammasome pathway.

AIM2 inflammasome activation may mediate high mobility group box 1 release in murine allergic rhinitis.

INTRODUCTION: High mobility group box 1 protein participates in the pathogenesis of allergic rhinitis. Activation of the inflammasome can mediate the release of high mobility group box 1. The role of the absent in melanoma 2 inflammasome in allergic rhinitis remains unclear. OBJECTIVE: This study aimed to investigate the function of absent in melanoma 2 inflammasome in murine allergic rhinitis and the interaction between high mobility group box 1 and the absent in melanoma 2 inflammasome. METHODS: A murine allergic rhinitis model was established using twenty Balb/c mice. Expression of the components of the absent in melanoma 2 inflammasome: absent in melanoma 2, apoptosis-associated speck-like protein containing a CARD (Asc), caspase-1 p20, and additional nod-like receptor family pyrin domain containing 3 (Nlrp3) were detected by western blotting during allergic rhinitis. Alterations of absent in melanoma 2, caspase-1, and high mobility group box 1 after ovalbumin challenge were demonstrated by immunohistochemistry. TdT-mediated dUTP Nick end labeling, TUNEL assay, and cleavage of caspase-3 and PARP-1 were used for the observation of pyroptosis. RESULTS: Eosinophilia and goblet cell infiltration were observed in the nasal mucosa of mice in the allergic rhinitis group. Absent in melanoma 2, Asc, and caspase-1 p20 increased after ovalbumin exposure while Nlrp3 did not. High mobility group box 1 was released in the nasal mucosa of allergic rhinitis mice. TUNEL-positive cells increased in the epithelium and laminae propria, whereas cleavage of caspase-3 and PARP-1 was not observed. CONCLUSIONS: The absent in melanoma 2 inflammasome was activated and pyroptosis may occur in the nasal mucosa after ovalbumin treatment. These may contribute to the translocation of high mobility group box 1 and the development of allergic rhinitis.

Caspase-1 and cathepsin B inhibitors from marine invertebrates, aiming at a reduction in neuroinflammation

Neuroinflammation is a condition associated with several types of dementia, such as Alzheimer’s disease (AD), mainly caused by an inflammatory response to amyloid peptides that induce microglial activation, with subsequent cytokine release. Neuronal caspase-1 from inflammasome and cathepsin B are key enzymes mediating neuroinflammation in AD, therefore, revealing new molecules to modulate these enzymes may be an interesting approach to treat eurodegenerative diseases. In this study, we searched for new caspase-1 and cathepsin B inhibitors from five species of Brazilian marine invertebrates (four cnidarians and one echinoderm). The results show that the extract of the box jellyfish Chiropsalmus quadrumanus inhibits caspase-1. This extract was fractionated, and the products monitored for their inhibitory activity, until the obtention of a pure molecule, which was identified as trigonelline by mass spectrometry. Moreover, four extracts inhibit cathepsin B, and Exaiptasia diaphana was selected for subsequent fractionation and characterization, resulting in the identification of betaine as being responsible for the inhibitory action. Both molecules are already found in marine organisms, however, this is the first study showing a potent inhibitory effect on caspase-1 and cathepsin B activities. Therefore, these new prototypes can be considered for the enzyme inhibition and subsequent control of the neuroinflammation.

In Silico Drug Repurposing for Anti-Inflammatory Therapy: Virtual Search for Dual Inhibitors of Caspase-1 and TNF-Alpha.

Inflammation involves a complex biological response of the body tissues to damaging stimuli. When dysregulated, inflammation led by biomolecular mediators such as caspase-1 and tumor necrosis factor-alpha (TNF-alpha) can play a detrimental role in the progression of different medical conditions such as cancer, neurological disorders, autoimmune diseases, and cytokine storms caused by viral infections such as COVID-19. Computational approaches can accelerate the search for dual-target drugs able to simultaneously inhibit the aforementioned proteins, enabling the discovery of wide-spectrum anti-inflammatory agents. This work reports the first multicondition model based on quantitative structure-activity relationships and a multilayer perceptron neural network (mtc-QSAR-MLP) for the virtual screening of agency-regulated chemicals as versatile anti-inflammatory therapeutics. The mtc-QSAR-MLP model displayed accuracy higher than 88%, and was interpreted from a physicochemical and structural point of view. When using the mtc-QSAR-MLP model as a virtual screening tool, we could identify several agency-regulated chemicals as dual inhibitors of caspase-1 and TNF-alpha, and the experimental information later retrieved from the scientific literature converged with our computational results. This study supports the capabilities of our mtc-QSAR-MLP model in anti-inflammatory therapy with direct applications to current health issues such as the COVID-19 pandemic.

Activation of the NLRP3 Inflammasome Increases the IL-1ß Level and Decreases GLUT4 Translocation in Skeletal Muscle during Insulin Resistance.

Low-grade chronic inflammation plays a pivotal role in the pathogenesis of insulin resistance (IR), and skeletal muscle has a central role in this condition. NLRP3 inflammasome activation pathways promote low-grade chronic inflammation in several tissues. However, a direct link between IR and NLRP3 inflammasome activation in skeletal muscle has not been reported. Here, we evaluated the NLRP3 inflammasome components and their role in GLUT4 translocation impairment in skeletal muscle during IR. Male C57BL/6J mice were fed with a normal control diet (NCD) or high-fat diet (HFD) for 8 weeks. The protein levels of NLRP3, ASC, caspase-1, gasdermin-D (GSDMD), and interleukin (IL)-1ß were measured in both homogenized and isolated fibers from the flexor digitorum brevis (FDB) or soleus muscle. GLUT4 translocation was determined through GLUT4myc-eGFP electroporation of the FBD muscle. Our results, obtained using immunofluorescence, showed that adult skeletal muscle expresses the inflammasome components. In the FDB and soleus muscles, homogenates from HFD-fed mice, we found increased protein levels of NLRP3 and ASC, higher activation of caspase-1, and elevated IL-1ß in its mature form, compared to NCD-fed mice. Moreover, GSDMD, a protein that mediates IL-1ß secretion, was found to be increased in HFD-fed-mice muscles. Interestingly, MCC950, a specific pharmacological NLRP3 inflammasome inhibitor, promoted GLUT4 translocation in fibers isolated from the FDB muscle of NCD- and HFD-fed mice. In conclusion, we found increased NLRP3 inflammasome components in adult skeletal muscle of obese insulin-resistant animals, which might contribute to the low-grade chronic metabolic inflammation of skeletal muscle and IR development.

Differences in pyroptosis of recent thymic emigrants CD4+ T Lymphocytes in ART-treated HIV-positive patients are influenced by sex.

Pyroptosis cell death in recent thymus emigrants (RTE) CD4+ T lymphocytes plays an important role on HIV-1 infection as a cause of CD4+ T cell depletion, being influenced by several factors, among them, the sex. Thus, the aim of this study was evaluated pyroptosis levels in RTE CD4+ T lymphocytes of individuals under antiretroviral therapy (ART) stratified by sex. Thirty-seven ART-treated HIV-positive patients (22 females and 15 males) and 12 (seven females and five males) clinically health subjects were recruited. Analysis by flow-cytometry of RTE CD4+ cells (CD4+ CD31+ /fluorescent-labeled inhibitors of caspases-Caspase-1+) were performed. Clinical and sociodemographic aspects were also evaluated from medical records. We observed statistically higher levels of pyroptosis RTE CD4+ T cells in male individuals (69.3%) compared with female group (39.1%) (P = 0.0356). Pre- and post-treatment CD4+ T cell counts were also higher in women than men (P = 0.004 and P = 0.012, respectively). Our data provides important evidence of the sex as a potential predictor of immunological reconstitution in ART-treated individuals.

Evidence for inflammasome activation in the brain of mucopolysaccharidosis type II mice.

Hunter syndrome or mucopolysaccharidosis type II (MPS II) is an X-linked recessive disease caused by the deficiency of iduronate 2-sulfatase (IDS), leading to storage of undegraded heparan and dermatan sulfate. Patients with the severe form present neurological abnormalities, but the mechanisms of such alterations are unknown. Here, we hypothesized that the undegraded substances found in this disease could be recognized as damage-associated molecular patterns (DAMPS), leading to activation of the inflammasome. Brains from 2 and 5 months normal and MPS II mice were studied. We observed an increase in cathepsin B activity in the brain tissue and leakage of this enzyme from the lysosome to the cytoplasm in a MPS II neuronal cell line, which is a known activator of the inflammasome. Furthermore, Caspase-1 activity and IL-1-beta levels were elevated at 5 months, confirming that this pathway is indeed altered. Our results suggest that undegraded GAG activate the inflammasome pathway in MPS II and future studies could focus on blocking such pathway to better understand the role of this process to the pathogenesis of MPS II.

NLRC4 biology in immunity and inflammation.

Inflammasomes are cytosolic multiprotein complexes that sense microbial infections or host cell damage, triggering cytokine production and a proinflammatory form of cell death, called pyroptosis. Whereas pyroptosis and cytokine production may often promote host resistance to infections, uncontrolled inflammasome activation leads to autoinflammatory diseases in humans. Among the multiple inflammasomes described, the neuronal apoptosis inhibitory protein/nucleotide-binding domain leucine-rich repeat-containing protein family caspase activation and recruitment domain-containing protein 4 (NLRC4) inflammasome emerged as a critical component for the restriction of bacterial infections. Accordingly, our understanding of this inflammasome advanced remarkably over the last 10 yr, expanding our knowledge about ligand-receptor interaction; cryo-EM structure; and downstream effectors and substrates, such as gasdermin-D, caspase-1, caspase-8, and caspase-7. In this review, we discuss recent advances on the biology of the NLRC4 inflammasome, in terms of structure and activation mechanisms, importance in bacterial and nonbacterial diseases, and the identification of NLRC4 gain-of-function mutations leading to NLRC4-associated autoinflammatory diseases in humans.

Dengue Virus Serotype 2 and Its Non-Structural Proteins 2A and 2B Activate NLRP3 Inflammasome.

Dengue is the most prevalent and rapidly transmitted mosquito-borne viral disease of humans. One of the fundamental innate immune responses to viral infections includes the processing and release of pro-inflammatory cytokines such as interleukin (IL-1ß and IL-18) through the activation of inflammasome. Dengue virus stimulates the Nod-like receptor (NLRP3-specific inflammasome), however, the specific mechanism(s) by which dengue virus activates the NLRP3 inflammasome is unknown. In this study, we investigated the activation of the NLRP3 inflammasome in endothelial cells (HMEC-1) following dengue virus infection. Our results showed that dengue infection as well as the NS2A and NS2B protein expression increase the NLRP3 inflammasome activation, and further apoptosis-associated speck-like protein containing caspase recruitment domain (ASC) oligomerization, and IL-1ß secretion through caspase-1 activation. Specifically, we have demonstrated that NS2A and NS2B, two proteins of dengue virus that behave as putative viroporins, were sufficient to stimulate the NLRP3 inflammasome complex in lipopolysaccharide (LPS)-primed endothelial cells. In summary, our observations provide insight into the dengue-induced inflammatory response mechanism and highlight the importance of DENV-2 NS2A and NS2B proteins in activation of the NLRP3 inflammasome during dengue virus infection.