Cigarette smoke inhibits the NLRP3 inflammasome and leads to caspase-1 activation via the TLR4-TRIF-caspase-8 axis in human macrophages

Repeated intratracheal instillation of whole-cigarette smoke condensate to assess lung damage in a rat model

Cigarette smoke induces an inflammatory response in the lungs by recruiting inflammatory cells, leading to lung diseases such as lung cancer, chronic obstructive pulmonary disease, and pulmonary fibrosis. Existing inhalation exposure methods for assessing the adverse effects of cigarette smoke require expensive equipment and are labor-intensive. Therefore, we attempted to develop a novel method to assess these adverse effects using intratracheal instillation (ITI) of whole cigarette smoke condensate (WCSC). The WCSC (0, 5, 10, or 20 mg/mL) was administered by ITI once daily for 6 or 12 days using an automatic video instillator. Repeated WCSC ITI increased the lung weight, and monocyte chemoattractant protein-1 (MCP-1), neutrophil, and lymphocyte levels within bronchoalveolar lavage fluid compared to the control. In the histopathological analysis of the lung tissue, a mild inflammatory response was observed in the 6 and 12 days 20 mg/mL WCSC exposure groups. The genome-wide RNA-seq expression patterns revealed that inflammatory and immune response-related genes, such as the chemokine signaling pathway, Th1/Th2 cell differentiation, and cytokine-cytokine receptor interaction, were employed following WCSC exposure. In addition, MCP-1 was time-dependent and increased in the 10 mg/mL exposure group compared to the control group. These results suggested that the WCSC might induce the potential pulmonary inflammatory response. Furthermore, we proposed that ITI may be a rapid and effective method of evaluating the adverse effects of WCSC within a short exposure period (less than 2 weeks), and it can be used to evaluate cigarette inhalation toxicity studies as an alternative method.

Exploring the role of genetic variations in NAFLD: implications for disease pathogenesis and precision medicine approaches

Non-alcoholic fatty liver disease (NAFLD) is one of the leading causes of chronic liver diseases, affecting more than one-quarter of people worldwide. Hepatic steatosis can progress to more severe forms of NAFLD, including NASH and cirrhosis. It also may develop secondary diseases such as diabetes and cardiovascular disease. Genetic and environmental factors regulate NAFLD incidence and progression, making it a complex disease. The contribution of various environmental risk factors, such as type 2 diabetes, obesity, hyperlipidemia, diet, and sedentary lifestyle, to the exacerbation of liver injury is highly understood. Nevertheless, the underlying mechanisms of genetic variations in the NAFLD occurrence or its deterioration still need to be clarified. Hence, understanding the genetic susceptibility to NAFLD is essential for controlling the course of the disease. The current review discusses genetics' role in the pathological pathways of NAFLD, including lipid and glucose metabolism, insulin resistance, cellular stresses, and immune responses. Additionally, it explains the role of the genetic components in the induction and progression of NAFLD in lean individuals. Finally, it highlights the utility of genetic knowledge in precision medicine for the early diagnosis and treatment of NAFLD patients.

Polygalasaponin F ameliorates middle cerebral artery occlusion-induced focal ischemia / reperfusion injury in rats through inhibiting TXNIP/NLRP3 signaling pathway

BACKGROUND

Polygalasaponin F (PGSF), an oleanane triterpenoid saponin extracted from Polygala japonica, has been demonstrated with neuroprotective effect. However, the therapeutic effects and mechanisms of PGSF on focal ischemia remain unknown; METHODS: In this study, male Sprague Dawley (SD) rats aged 6-8 weeks were initially selected to establish a rat model of middle cerebral artery occlusion (MCAO) to evaluate the therapeutic effect of PGSF intervention and to investigate the impact of PGSF on the thioredoxin-interacting protein/NOD-, LRR-, and pyrin domain-containing protein 3 (TXNIP/NLRP3) inflammatory pathway. Secondly, brain neuron cells were isolated, and the cells received oxygen-glucose deprivation/reoxygenation (OGD/R) culture to establish the cell injury model in vitro. The mechanism of PGSF on the TXNIP/NLRP3 pathway was further validated; RESULTS: Our results showed that PGSF treatment reduced neurological scores, brain tissue water content and infarct volume and ameliorated the pathological changes in cerebral cortex in MCAO-induced focal ischemia rats. The TNF-α, IL-1β and IL-6 levels decreased in MCAO-induced focal ischemia rats after PGSF treatment. Moreover, PGSF down-regulated the protein expressions of TXNIP, NLRP3, ASC, cleaved caspase-1, IL-1β, and IL-18 in MCAO-induced focal ischemia rats. Meanwhile, PGSF treatment inhibited apoptosis, and reduced the levels of ROS, inflammatory cytokine and TXNIP/NLRP3 pathway-related proteins (TXNIP, NLRP3, ASC, cleaved caspase-1, IL-1β, and IL-18) in OGD/R-induced neuronal injury cells. Finally, PGSF treatment also disrupted the interaction between NLRP3 and TXNIP in vitro; CONCLUSIONS: Our study demonstrated the therapeutic effects of PGSF on MCAO-induced focal ischemia rats. Moreover, the neuroprotective mechanism of PGSF on focal ischemia was associated with the inhibition of TXNIP/NLRP3 signaling pathway.

The transcriptomic landscape of canonical activation of NLRP3 inflammasome from bone marrow-derived macrophages

The NLRP3 inflammasome has gained significant attention due to its participation in diverse cellular processes. Nevertheless, the detailed framework of the canonical NLRP3 inflammasome assembly still remains unrevealed. This study aims to elucidate the transcriptomic landscape of the various stages involved in the canonical activation of the NLRP3 inflammasome in BMDMs by integrating RNA-seq, bioinformatics, and molecular dynamics analyses. The model for the canonical activation of the NLRP3 inflammasome was confirmed through morphological observations, functional assessments (ELISA and LDH), and protein detection (western blot). Subsequently, cells were subjected to RNA sequencing following three groups: control, priming (LPS 500 ng/ml, 4 h), and activation (LPS 500 ng/ml, 4 h; ATP 5 mM, 1 h). A total of 9116 differentially expressed genes (DEGs) were identified, which exerted regulatory effects on various pathways, including cell metabolism, ion fluxes, post-translational modifications, and organelles. Subsequently, six hub genes (Sirt3, Stat3, Syk, Trpm2, Tspo, and Txnip) were identified via integrating literature review and database screening. Finally, the three-dimensional structures of these six hub proteins were obtained using the MD-optimized RoseTTAFold and Gromacs simulations (at least 200 ns). In summary, our research offers novel insights into the transcriptomic-level understanding of the assembly of the canonical NLRP3 inflammasome.

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

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

Caspase-8 activation by cigarette smoke induces pro-inflammatory cell death of human macrophages exposed to lipopolysaccharide

Cigarette smoking impairs the lung innate immune response making smokers more susceptible to infections and severe symptoms. Dysregulation of cell death is emerging as a key player in chronic inflammatory conditions. We have recently reported that short exposure of human monocyte-derived macrophages (hMDMs) to cigarette smoke extract (CSE) altered the TLR4-dependent response to lipopolysaccharide (LPS). CSE caused inhibition of the MyD88-dependent inflammatory response and activation of TRIF/caspase-8/caspase-1 pathway leading to Gasdermin D (GSDMD) cleavage and increased cell permeability. Herein, we tested the hypothesis that activation of caspase-8 by CSE increased pro-inflammatory cell death of LPS-stimulated macrophages. To this purpose, we measured apoptotic and pyroptotic markers as well as the expression/release of pro-inflammatory mediators in hMDMs exposed to LPS and CSE, alone or in combination, for 6 and 24 h. We show that LPS/CSE-treated hMDMs, but not cells treated with CSE or LPS alone, underwent lytic cell death (LDH release) and displayed apoptotic features (activation of caspase-8 and -3/7, nuclear condensation, and mitochondrial membrane depolarization). Moreover, the negative regulator of caspase-8, coded by CFLAR gene, was downregulated by CSE. Activation of caspase-3 led to Gasdermin E (GSDME) cleavage. Notably, lytic cell death caused the release of the damage-associated molecular patterns (DAMPs) heat shock protein-60 (HSP60) and S100A8/A9. This was accompanied by an impaired inflammatory response resulting in inhibited and delayed release of IL6 and TNF. Of note, increased cleaved caspase-3, higher levels of GSDME and altered expression of cell death-associated genes were found in alveolar macrophages of smoker subjects compared to non-smoking controls. Overall, our findings show that CSE sensitizes human macrophages to cell death by promoting pyroptotic and apoptotic pathways upon encountering LPS. We propose that while the delayed inflammatory response may result in ineffective defenses against infections, the observed cell death associated with DAMP release may contribute to establish chronic inflammation. CS exposure sensitizes human macrophages to pro-inflammatory cell death. Upon exposure to LPS, CS inhibits the TLR4/MyD88 inflammatory response, downregulating the pro-inflammatory genes TNF and IL6 and the anti-apoptotic gene CFLAR, known to counteract caspase-8 activity. CS enhances caspase-8 activation through TLR4/TRIF, with a partial involvement of RIPK1, resulting on the activation of caspase-1/GSDMD axis leading to increased cell permeability and DAMP release through gasdermin pores [19]. At later timepoints caspase-3 becomes strongly activated by caspase-8 triggering apoptotic events which are associated with mitochondrial membrane depolarization, gasdermin E cleavage and secondary necrosis with consequent massive DAMP release.

Multiple TLRs elicit alternative NLRP3 inflammasome activation in primary human monocytes independent of RIPK1 kinase activity

The canonical NOD-like receptor family pyrin domain containing 3 (NLRP3) pathway involves a priming step to induce pro-IL-1β followed by a secondary signal such as K+ efflux to activate inflammasome formation. This then leads to the maturation of IL-1β and the formation of gasdermin D (GSDMD) pores that initiate pyroptosis and mediate IL-1β release. In contrast, primary human monocytes also engage an alternative pathway in response to toll-like receptor (TLR) 4 activation, without the need for a secondary signal. Data from a monocyte-like cell line suggest that the alternative pathway functions via the TLR adaptor protein TIR-domain-containing adapter-inducing interferon-β (TRIF), receptor-interacting protein kinase 1 (RIPK1), FAS-associated death domain (FADD) and caspase-8 upstream of NLRP3 activation, but in the absence of K+ efflux or pyroptosis. Usage of the alternative pathway by other members of the TLR family that induce IL-1β but do not signal through TRIF, has yet to be explored in primary human monocytes. Furthermore, the mechanism by which IL-1β is released from monocytes remains unclear. Therefore, this study investigated if the alternative NLRP3 inflammasome pathway is initiated following activation of TLRs other than TLR4, and if GSDMD was necessary for the release of IL-1β. Monocytes were stimulated with ligands that activate TLR1/2, TLR2/6, TLR4 and TLR7 and/or TLR8 (using a dual ligand). Similar to TLR4, all of the TLRs investigated induced IL-1β release in a NLRP3 and caspase-1 dependent manner, indicating that TRIF may not be an essential upstream component of the alternative pathway. Furthermore, inhibition of RIPK1 kinase activity had no effect on IL-1β release. Although IL-1β was released independently of K+ efflux and pyroptosis, it was significantly reduced by an inhibitor of GSDMD. Therefore, it is feasible that low level GSDMD pore formation may facilitate the release of IL-1β from the cell, but not be present in sufficient quantities to initiate pyroptosis. Together these data suggest that the alternative pathway operates independently of RIPK1 kinase activity, downstream of diverse TLRs including TLR4 in primary human monocytes and supports the potential for IL-1β release via GSDMD pores alongside other unconventional secretory pathways.

The Activation of M1 Macrophages is Associated with the JNK-m6A-p38 Axis in Chronic Obstructive Pulmonary Disease

Background

Excessive activation of M1 macrophages affects the chronic inflammatory response of the airways and leads to the development of chronic obstructive pulmonary disease (COPD). Therefore, it needs to be closely monitored and investigated. MAPK signaling pathway is involved in the activation of M1 macrophages, and N6-methyladenosine (m6A) is involved in the pathogenesis of COPD. However, it is unknown whether activation of the MAPK signaling pathway is mediated by m6A in M1 macrophages in COPD.

Methods

The GEO data were analyzed using bioinformatics techniques to assess the differences between COPD and healthy individuals in the levels of M1 macrophages, their secreted cytokines, and m6A regulators. The MAPK signaling pathway was significantly enriched in the list of differentially regulated genes between COPD and healthy individuals. We further analyzed the correlation between M1 macrophages, m6A, and the MAPK signaling pathway. Next, blood samples from COPD and healthy individuals were collected and analyzed by using flow cytometry, ELISA, and RT-PCR. Western blotting was performed using CSE-induced THP-1 cells. COPD and healthy mice were used for Me-RIP sequencing and flow cytometry experiments. Validation of the results of the above bioinformatics analysis by molecular biology experiments and sequencing techniques.

Results

We found that GEO data and blood specimens from COPD patients showed increased M1 macrophages, higher levels of IL-6 and TNF-α, and higher mRNA expression of key mediators of the MAPK signaling pathway (p38, ERK, and JNK). Western blotting showed increased expression of p38, ERK, and JNK in the CSE group. In contrast, the expression of m6A regulators was low. Also, M1 macrophages in COPD mice were hyperactivated and had reduced m6A modifications of p38, ERK, and JNK compared with control.

Conclusion

m6A may be involved in M1 macrophage hyperactivation by regulating the MAPK signaling pathway, thereby influencing the development of COPD.

Reframing the link between metabolism and NLRP3 inflammasome: therapeutic opportunities

Inflammasomes are multiprotein signaling platforms in the cytosol that senses exogenous and endogenous danger signals and respond with the maturation and secretion of IL-1β and IL-18 and pyroptosis to induce inflammation and protect the host. The inflammasome best studied is the Nucleotide-binding oligomerization domain, leucine-rich repeat-containing family pyrin domain containing 3 (NLRP3) inflammasome. It is activated in a two-step process: the priming and the activation, leading to sensor NLRP3 oligomerization and recruitment of both adaptor ASC and executioner pro-caspase 1, which is activated by cleavage. Moreover, NLRP3 inflammasome activation is regulated by posttranslational modifications, including ubiquitination/deubiquitination, phosphorylation/dephosphorylation, acetylation/deacetylation, SUMOylation and nitrosylation, and interaction with NLPR3 protein binding partners. Moreover, the connection between it and metabolism is receiving increasing attention in this field. In this review, we present the structure, functions, activation, and regulation of NLRP3, with special emphasis on regulation by mitochondrial dysfunction-mtROS production and metabolic signals, i.e., metabolites as well as enzymes. By understanding the regulation of NLRP3 inflammasome activation, specific inhibitors can be rationally designed for the treatment and prevention of various immune- or metabolic-based diseases. Lastly, we review current NLRP3 inflammasome inhibitors and their mechanism of action.

Toxoplasma gondii profilin induces NLRP3 activation and IL-1β production/secretion in THP-1 cells

Toxoplasma gondii is a highly prevalent protozoan that infects a broad spectrum of warm-blooded animals. Profilin is a critical protein that plays a role in the movement and invasion of T. gondii. In the current study, we assessed how profilin stimulates inflammasomes and how it induces transcription and secretion of IL-1β. For this purpose, we assessed the level of TLR 2, 4, 5, and 9 expressions in a THP-1 cell line treated with profilin from T. gondii (TgP). In addition, we analyzed the expression levels of various inflammasomes, as well as IL-1β, and IL-18 in THP-1 cells treated with the NLRP3 inhibitor MCC950. TgP significantly increased the expression of TLR5 but the expression of TLR2, 4, and 9 was not significantly increased. In addition, TgP did not significantly increase the level of inflammasomes after 5 h. Treatment with MCC950 significantly reduced NLRP3 and IL-1β on both transcription and protein levels. Although the transcription level of NLRP3 was reduced 5 h after treatment with TgP, western blot analysis showed an increase in NLRP3. The western blot and ELISA analysis also showed that TgP increased both pro- and mature IL-1β. In summary, our study showed that NLRP3 most probably plays a pivotal role in the expression and production levels of IL-1β during the interaction between TgP and macrophages.

Tyndallized Bacteria Preferentially Induce Human Macrophage M1 Polarization: An Effect Useful to Balance Allergic Immune Responses and to Control Infections

Macrophage polarization is a dynamic process through which macrophages acquire specific features whose extremes are represented by M1 and M2 polarization. Interleukin (IL)-6, IL-1β, IL-12 and IL-8 belong to M1 macrophages while transforming growth factor-beta (TGF-β belongs to M2 cytokines. M2 polarization prevalence is observed in allergic diseases. Tyndallization is a thermal process able to inactivate microorganisms and to allow their use for chronic respiratory disease treatment via immune response modulation. The present study explores the effects of a blend of tyndallized bacteria (TB) on macrophage polarization. THP-1-derived macrophages were exposed to different concentrations of TB (106, 5 × 106, 107, 5 × 107, 108 CFU/mL) and then cell viability and TB phagocytosis, and IL-8, IL-1β, IL-6, IL-12 and TGF-β1 gene expression and release were assessed. TB were tolerated, phagocyted and able to increase IL-8, IL-1β and IL-6 gene expression and release IL-12 gene expression, as well as decrease TGF-β1 gene expression and release. The effects on IL-8, IL-6 and TGF-β1 release were confirmed in human monocyte-derived macrophages (hMDMs) exposed to TB. In conclusion, TB promote M1 polarization, and this mechanism might have valuable potential in controlling allergic diseases and infections, possibly preventing disease exacerbations.

Platelet-Rich stroma from Crohn's disease patients for treatment of perianal fistula shows a higher myeloid cell profile compared to non-IBD controls

BACKGROUND

New cell-based therapies are under investigation to improve perianal fistulizing Crohn's disease (pCD) healing. Autologous stromal vascular fraction combined with platelet-rich plasma (referred to as platelet-rich stroma [PRS]) is a new adipose-derived stromal therapy. The effect of Crohn's disease (CD) on adipose tissue, and adipose-derived therapies, is largely unknown. We characterized the cellular composition of subcutaneous lipoaspirate and PRS of pCD patients and non-Inflammatory Bowel Disease (IBD) controls.

METHODS

Consecutive pCD patients (≥18 years) and non-IBD controls, who underwent liposuction for the purpose of autologous PRS therapy, were included (October 2020 and March 2021). Mechanically fractionated lipoaspirate and the combined PRS product were analyzed for cell surface marker expression using fluorescence-activated cell sorting analysis.

RESULTS

Twenty-three patients (37.8 [IQR 30.7-45.0] years; 9 [39.1 %] male; 11CD patients) were included. Similar total number of cells were found in CD and non-IBD lipoaspirate (CD 8.23 ± 1.62*10⁵ cells/mL versus non-IBD 12.20 ± 3.39*10⁵). Presence of stromal cells, endothelial like cells, immune cells, T-cells, myeloid cells and M2/M1 macrophage ratio were similar in CD and non-IBD lipoaspirate. In PRS samples, more cells/mL were seen in CD patients (P = 0.030). Myeloid cells were more abundant in CD PRS samples (P = 0.007), and appeared to have a higher regulatory M2/M1 ratio. Interdonor variation was observed between lipoaspirate and PRS samples.

CONCLUSIONS

The composition of CD and non-IBD lipoaspirate were found to be similar and interdonor variation was observed. However, PRS from CD patients showed more myeloid cells with a regulatory phenotype. Crohn's disease does not appear to alter the immunological composition of adipose-derived products.

The NLRP3 Genetic Variant (rs10754555) Reduces the Risk of Adverse Outcome in Middle-Aged Patients with Chronic Coronary Syndrome

Background

Inflammation is central in development of cardiovascular disease (CVD). Aberrant function of the Nod-Like Receptor Protein 3 (NLRP3) inflammasome, a central mediator in the proinflammatory response, has been associated with atherosclerosis. The influence of genetic determinants on this inflammatory pathway and its downstream effects is less known. We aimed to investigate the frequency of a single NLRP3 gene variant according to clinical outcome in CVD and its influence on NLRP3-related markers.

Methods

In this observational study, we included 1001 patients with chronic coronary syndrome. Blood samples were drawn at inclusion, including whole-blood and PAXgene tubes for DNA and RNA isolation, respectively. Allelic discrimination of the NLRP3 single nucleotide polymorphism rs10754555 was performed; and gene expression of NLRP3, Toll-Like Receptor 4, Interleukin- (IL-) 1β, and IL-18 was relatively quantified, both methods by RT-PCR. Circulating IL-6, high-sensitivity (hs) C-reactive protein, IL-18, and IL-12 were measured by enzyme-like immunosorbent assays. Clinical endpoints during 2 years (n = 106) were a composite of unstable angina pectoris, myocardial infarction, nonhemorrhagic stroke, and death.

Results

Minor allele frequency of the NLRP3 variant was 0.36. In all, no association of the NLRP3 variant with clinical subgroups or outcome was found, neither any significant influence on the genes' mRNA expression or circulating protein. However, in subjects < 56 years (25 percentile), the variant G-allele is associated with significant lower risk of suffering a composite event (OR = 0.43 (95% CI 0.19, 0.97), p = 0.043, adjusted). In the same age group, the NLRP3 gene was accordingly downregulated in G-allele carriers vs. noncarriers, and circulating IL12 was significantly reduced (p < 0.05, both). In subjects > 56 years, no significant effect of the variant was observed.

Conclusion

The age-related reduced risk of composite endpoint in rs10754555 G-allele carriers accompanied by diminished NLRP3 mRNA expression is hypothesis generating and needs to be further explored. The study is registered at http://www.clinicaltrials.gov, with identification number NCT00222261.

The inflammasomes: crosstalk between innate immunity and hematology

BACKGROUND

The inflammasome is a cytosolic multi-protein complex responsible for the proteolytic maturation of pro-inflammatory cytokines IL-1ß and IL-18 and of gasdermin-D, which mediates membrane pore formation and the cytokines release, or eventually a lytic cell death known as pyroptosis. Inflammation has long been accepted as a key component of hematologic conditions, either oncological or benign diseases.

OBJECTIVES

This study aims to review the current knowledge about the contribution of inflammasome in hematologic diseases. We attempted to depict the participation of specific inflammasome receptors, and the possible cell-specific consequence of complex activation, as well as the use of anti-inflammasome therapies.

METHODS

We performed a keyword-based search in public databases (Pubmed.gov, ClinicalTrials.gov.).

CONCLUSION

Different blood cells variably express inflammasome components. Considering the immunosuppression associated with both the disease and the treatment of some hematologic diseases, and a microenvironment that allows neoplastic cell proliferation, inflammasomes could be a link between innate immunity and disease progression, as well as an interesting therapeutic target.

Cigarette smoke promotes inflammasome-independent activation of caspase-1 and -4 leading to gasdermin D cleavage in human macrophages

Mechanisms and consequences of gasdermin D (GSDMD) activation in cigarette smoke (CS)-associated inflammation and lung disease are unknown. GSDMD is a downstream effector of caspase-1, -8, and -4. Upon cleavage, GSDMD generates pores into cell membranes. Different degrees of GSDMD activation are associated with a range of physiological outputs ranging from cell hyperactivation to pyroptosis. We have previously reported that in human monocyte-derived macrophages CS extract (CSE) inhibits the NLRP3 inflammasome and shifts the response to lipopolysaccharide (LPS) towards the TLR4-TRIF axis leading to activation of caspase-8, which, in turn, activates caspase-1. In the present work, we investigated whether other ASC-dependent inflammasomes could be involved in caspase activation by CSE and whether caspase activation led to GSDMD cleavage and other downstream effects. Presented results demonstrate that CSE promoted ASC-independent activation of caspase-1 leading to GSDMD cleavage and increased cell permeability, in the absence of cell death. GSDMD cleavage was strongly enhanced upon stimulation with LPS+CSE, suggesting a synergistic effect between the two stimuli. Noteworthy, CSE promoted LPS internalization leading to caspase-4 activation, thus contributing to increased GSDMD cleavage. Caspase-dependent GSDMD cleavage was associated with mitochondrial superoxide generation. Increased cleaved GSDMD was found in lung macrophages of smokers compared to ex-smokers and non-smoking controls. Our findings revealed that ASC-independent activation of caspase-1, -4, and -8 and GSDMD cleavage upon exposure to CS may contribute to macrophage dysfunction and feed the chronic inflammation observed in the smokers' lung.

Cigarette smoke-induced gasdermin D activation in bronchoalveolar macrophages and bronchial epithelial cells dependently on NLRP3

Chronic pulmonary inflammation and chronic obstructive pulmonary disease (COPD) are major health issues largely due to air pollution and cigarette smoke (CS) exposure. The role of the innate receptor NLRP3 (nucleotide-binding domain and leucine-rich repeat containing protein 3) orchestrating inflammation through formation of an inflammasome complex in CS-induced inflammation or COPD remains controversial. Using acute and subchronic CS exposure models, we found that Nlrp3-deficient mice or wild-type mice treated with the NLRP3 inhibitor MCC950 presented an important reduction of inflammatory cells recruited into the bronchoalveolar space and of pulmonary inflammation with decreased chemokines and cytokines production, in particular IL-1β demonstrating the key role of NLRP3. Furthermore, mice deficient for Caspase-1/Caspase-11 presented also decreased inflammation parameters, suggesting a role for the NLRP3 inflammasome. Importantly we showed that acute CS-exposure promotes NLRP3-dependent cleavage of gasdermin D in macrophages present in the bronchoalveolar space and in bronchial airway epithelial cells. Finally, Gsdmd-deficiency reduced acute CS-induced lung and bronchoalveolar space inflammation and IL-1β secretion. Thus, we demonstrated in our model that NLRP3 and gasdermin D are key players in CS-induced pulmonary inflammation and IL-1β release potentially through gasdermin D forming-pore and/or pyroptoctic cell death.

Role of Caspase Family in Intervertebral Disc Degeneration and Its Therapeutic Prospects

Intervertebral disc degeneration (IVDD) is a common musculoskeletal degenerative disease worldwide, of which the main clinical manifestation is low back pain (LBP); approximately, 80% of people suffer from it in their lifetime. Currently, the pathogenesis of IVDD is unclear, and modern treatments can only alleviate its symptoms but cannot inhibit or reverse its progression. However, in recent years, targeted therapy has led to new therapeutic strategies. Cysteine-containing aspartate proteolytic enzymes (caspases) are a family of proteases present in the cytoplasm. They are evolutionarily conserved and are involved in cell growth, differentiation, and apoptotic death of eukaryotic cells. In recent years, it has been confirmed to be involved in the pathogenesis of various diseases, mainly by regulating cell apoptosis and inflammatory response. With continuous research on the pathogenesis and pathological process of IVDD, an increasing number of studies have shown that caspases are closely related to the IVDD process, especially in the intervertebral disc (IVD) cell apoptosis and inflammatory response. Therefore, herein we study the role of caspases in IVDD with respect to the structure of caspases and the related signaling pathways involved. This would help explore the strategy of regulating the activity of the caspases involved and develop caspase inhibitors to prevent and treat IVDD. The aim of this review was to identify the caspases involved in IVDD which could be potential targets for the treatment of IVDD.

Polyphenols, flavonoids and inflammasomes: the role of cigarette smoke in COPD

COPD is predicted to become the third leading cause of morbidity and mortality worldwide by 2030. Cigarette smoking (active or passive) is one of its chief causes, with about 20% of cigarette smokers developing COPD from cigarette smoke (CS)-induced irreversible damage and sustained inflammation of the airway epithelium. Inflammasome activation leads to the cleavage of pro-interleukin (IL)-1β and pro-IL-18, along with the release of pro-inflammatory cytokines via gasdermin D N-terminal fragment membrane pores, which further triggers acute phase pro-inflammatory responses and concurrent pyroptosis. There is currently intense interest in the role of nucleotide-binding oligomerisation domain-like receptor family, pyrin domain containing protein-3 inflammasomes in chronic inflammatory lung diseases such as COPD and their potential for therapeutic targeting. Phytochemicals including polyphenols and flavonoids have phyto-medicinal benefits in CS-COPD. Here, we review published articles from the last decade regarding the known associations between inflammasome-mediated responses and ameliorations in pre-clinical manifestations of CS-COPD via polyphenol and flavonoid treatment, with a focus on the underlying mechanistic insights. This article will potentially assist the development of drugs for the prevention and therapy of COPD, particularly in cigarette smokers.

This review compiles current investigations into the role of polyphenols/flavonoids in the alleviation of cigarette smoke-induced inflammasome; notably it provides a promising hit for rectifying the treatment of COPD.https://bit.ly/36OcUO9

E-cigarette exposure with or without heating the e-liquid induces differential remodeling in the lungs and right heart of mice

Various cardiopulmonary pathologies associated with electronic cigarette (EC) vaping have been reported. This study investigated the differential adverse effects of heating-associated by-products versus the intact components of EC aerosol to the lungs and heart of mice. We further dissected the roles of caspase recruitment domain-containing protein 9 (CARD9)-associated innate immune response and NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome in EC exposure-induced cardiopulmonary injury. C57BL/6 wild type (WT), CARD9^-/-, and NLRP3^-/- mice were exposed to EC aerosol 3 h/day, 5 days/week for 6 month with or without heating the e-liquid with exposure to ambient air as the control. In WT mice, EC exposure with heating (EwH) significantly increased right ventricle (RV) free wall thickness at systole and diastole. However, EC exposure without heating (EwoH) caused a significant decrease in the wall thickness at systole. RV fractional shortening was also markedly reduced following EwH in WT and NLRP3^-/- mice. Further, EwH activated NF-κB and p38 MAPK inflammatory signaling in the lungs, but not in the RV, in a CARD9- and NLRP3-dependent manner. Levels of circulatory inflammatory mediators were also elevated following EwH, indicating systemic inflammation. Moreover, EwoH activated TGF-β1/SMAD2/3/α-SMA fibrosis signaling in the lungs but not the RV of WT mice. In conclusion, EC aerosol exposure following EwH or EwoH induced differential cardiopulmonary remodeling and CARD9 innate immune and NLRP3 inflammasome contributed to the adverse effects.

Cigarette smoke extract mediates cell premature senescence in chronic obstructive pulmonary disease patients by up-regulating USP7 to activate p300-p53/p21 pathway

OBJECTIVES

Tobacco hazard is one of the most severe public health issues in the world. It is believed that smoking is the most important factor leading to chronic obstructive pulmonary disease (COPD). Endothelial progenitor cells (EPCs) originate from the bone marrow and can effectively repair vascular endothelial damage and improve vascular endothelial function. Current studies suggest that EPCs senescence and EPCs depletion exist in smoking-related COPD, but the molecular mechanism remains unclear.

METHODS

Co-immunoprecipitation was used to detect the interaction between USP7 and p300. EPCs from smoking COPD patients were isolated, and the expressions of USP7 and p300 were detected by RT-PCR and Western Blot. Different concentrations of cigarette smoke extract (CSE) and USP7 or p300 inhibitors were used to treat EPCs, then the expression of p53, p53 target genes and aging-related genes were detected. Cell Counting Kit - 8 (CCK8) was used to detect cell proliferation, flow cytometry was used to detect cell cycle distribution, β-galactosidase (β-gal) staining and Lamp1 immunofluorescence was used to detect the proportion of aging cells. COPD mouse models were used to confirm the molecular mechanism.

RESULTS

USP7 and p300 interacted with each other, and USP7 affected the protein stability of p300 by regulating the ubiquitination of p300. There existed high expressions of USP7 and p300 proteins in EPCs of smoking COPD patients and COPD mouse model. CSE promoted the high expressions of USP7 and p300 in EPCs. Further studies showed that CSE mediated the USP7/p300-dependent high expression of p53 and activated the expression of p53 target genes especially p21. Activation of p53 - p21 pathway finally inhibited cell activity, led to cell cycle arrest and premature senescence of EPCs.

CONCLUSION

CSE mediated up-regulation of USP7 and p300 activated p53 - p21 pathway was a molecular mechanism that might lead to COPD.

Inflammasome involvement in CS-induced damage in HaCaT keratinocytes

Cigarette smoke (CS) alters cutaneous biological processes such as redox homeostasis and inflammation response that might be involved in promoting skin inflammatory conditions. Exposure to CS has also been linked to a destabilization of the NLRP3 inflammasome in pollution target tissues such as the lung epithelium, resulting in a more vulnerable immunological response to several exogenous and endogenous stimuli related to oxidative stress. Thus, CS has an adverse effect on host defense, increasing the susceptibility to develop lung infections and pathologies. In the skin, another direct target of pollution, inflammasome disorders have been linked to an increasing number of diseases such as melanoma, psoriasis, vitiligo, atopic dermatitis, and acne, all conditions that have been connected directly or indirectly to pollution exposure. The inflammasome machinery is an important innate immune sensor in human keratinocytes. However, the role of CS in the NLRP1 and NLRP3 inflammasome in the cutaneous barrier has still not been investigated. In the present study, we were able to determine in keratinocytes exposed to CS an increased oxidative damage evaluated by 4-HNE protein adduct and carbonyl formation. Of note is that, while CS inhibited NLRP3 activation, it was able to activate NLRP1, leading to an increased secretion of the proinflammatory cytokines IL-1β and IL-18. This study highlights the importance of the inflammasome machinery in CS that more in general, in pollution, affects cutaneous tissues and the important cross-talk between different members of the NLRP inflammasome family.

High Mobility Group Box 1: Biological Functions and Relevance in Oxidative Stress Related Chronic Diseases

In the early 1970s, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and named high-mobility group (HMG) proteins. High-mobility group box 1 (HMGB1) is the most studied HMG protein that detects and coordinates cellular stress response. The biological function of HMGB1 depends on its subcellular localization and expression. It plays a critical role in the nucleus and cytoplasm as DNA chaperone, chromosome gatekeeper, autophagy maintainer, and protector from apoptotic cell death. HMGB1 also functions as an extracellular alarmin acting as a damage-associated molecular pattern molecule (DAMP). Recent findings describe HMGB1 as a sophisticated signal of danger, with a pleiotropic function, which is useful as a clinical biomarker for several disorders. HMGB1 has emerged as a mediator in acute and chronic inflammation. Furthermore, HMGB1 targeting can induce beneficial effects on oxidative stress related diseases. This review focus on HMGB1 redox status, localization, mechanisms of release, binding with receptors, and its activities in different oxidative stress-related chronic diseases. Since a growing number of reports show the key role of HMGB1 in socially relevant pathological conditions, to our knowledge, for the first time, here we analyze the scientific literature, evaluating the number of publications focusing on HMGB1 in humans and animal models, per year, from 2006 to 2021 and the number of records published, yearly, per disease and category (studies on humans and animal models).

Interactions between NLRP3 inflammasome and glycolysis in macrophages: New insights into chronic inflammation pathogenesis

NLRP3 inflammasome activation in macrophages fuels sterile inflammation, which has been tied with metabolic reprogramming characterized by high glycolysis and low oxidative phosphorylation. The key enzymes in glycolysis and glycolysis‐related products can regulate and activate NLRP3 inflammasome. In turn, NLRP3 inflammasome is considered to affect glycolysis, as well. However, the exact mechanism remains ambiguous. On the basis of these findings, the focus of this review is mainly on the developments in our understanding of interaction between NLRP3 inflammasome activation and glycolysis in macrophages, and small molecule compounds that influence the activation of NLRP3 inflammasomes by regulating glycolysis in macrophages. The application of this interaction in the treatment of diseases is also discussed. This paper may yield valuable clues for development of novel therapeutic agent for NLRP3 inflammasome‐related diseases.

HSP60 regulates the cigarette smoke-induced activation of TLR4-NF-κB-MyD88 signalling pathway and NLRP3 inflammasome

Chronic obstructive pulmonary disease (COPD) is characterized by increased cellular stress and inflammation. Heat shock protein 60 (HSP60) is a highly conserved stress protein that acts as a cellular "danger" signal for immune reactions. In this study, we investigated the role of HSP60 in COPD and explored the underlying mechanisms. Expression levels of HSP60 in patients with acute exacerbation of COPD (AECOPD), stable COPD, and healthy people were detected by Western blotting and enzyme-linked immunosorbent assay (ELISA). Moreover, the effect and molecular mechanism of HSP60 in COPD were studied in cigarette smoke (CS)-treated C57BL/6 mice and macrophages. The results showed significant upregulation of HSP60 expression in the peripheral blood mononuclear cells (PBMCs) and sera of patients with AECOPD compared to those with stable COPD or healthy people. CS induced the expression of HSP60 in the COPD mouse model, accelerated the activation of toll-like receptor 4 (TLR4) and NLR family pyrin domain containing 3 (NLRP3) signalling pathways, promoted the increase of inflammatory cells in alveolar lavage fluid and serum inflammatory factors, and induced destruction of lung tissue structure. Furthermore, HSP60 knockdown affected TLR4 and MyD88 expression, IκBα degradation, and nuclear localization of NF-κB and NLRP3 inflammasome activity. Our study revealed that CS stimulates the expression of HSP60, activating the TLR4-MyD88-NF-κB signalling pathway and the NLRP3 inflammasome.

NLRP3 inflammasome activation in COVID-19: an interlink between risk factors and disease severity

NLRP3 inflammasome is a critical immune component that plays a crucial role in mounting innate immune responses. The deleterious effects of inflammasome activation have been correlated with the COVID-19 disease severity. In the presence of several underlying disorders, the immune components of our bodies are dysregulated, creating conditions that could adversely affect us other than providing a required level of protection. In this review, we focused on the occurrence of NLRP3 inflammasome activation in response to SARS-COV-2 infection, dysregulation of NLRP3 activation events in the presence of several comorbidities, the contribution of activated NLRP3 inflammasome to the severity of COVID-19, and available therapeutics for the treatment of such NLRP3 inflammasome related diseases based on current knowledge. The primed state of immunity in individuals with comorbidities (risk factors) could accelerate many deaths and severe COVID-19 cases via activation of NLRP3 inflammasome and the release of downstream inflammatory molecules. Therefore, a detailed understanding of the host-pathogen interaction is needed to clarify the pathophysiology and select a potential therapeutic approach.

Spotlight on NLRP3 Inflammasome: Role in Pathogenesis and Therapies of Atherosclerosis

Inflammation is an intricate biological response of body tissues to detrimental stimuli. Cardiovascular disease (CVD) is the leading cause of death worldwide, and inflammation is well documented to play a role in the development of CVD, especially atherosclerosis (AS). Emerging evidence suggests that activation of the NOD-like receptor (NLR) family and the pyridine-containing domain 3 (NLRP3) inflammasome is instrumental in inflammation and may result in AS. The NLRP3 inflammasome acts as a molecular platform that triggers the activation of caspase-1 and the cleavage of pro-interleukin (IL)-1β, pro-IL-18, and gasdermin D (GSDMD). The cleaved GSDMD forms pores in the cell membrane and initiates pyroptosis, inducing cell death and the discharge of intracellular pro-inflammatory factors. Hence, the NLRP3 inflammasome is a promising target for anti-inflammatory therapy against AS. In this review, we systematically summarized the current understanding of the activation mechanism of NLRP3 inflammasome, and the pathological changes in AS involving NLRP3. We also discussed potential therapeutic strategies targeting NLRP3 inflammasome to combat AS.

Cigarette smoke upregulates Notch-1 signaling pathway and promotes lung adenocarcinoma progression

Notch-1 pathway plays an important role in lung carcinoma, stem cell regulation, cellular communication, growth and differentiation. Cigarette smoke is involved in the regulation of Notch signaling. However, current data regarding the impact of cigarette smoke on the Notch pathway in lung cancer progression are limited. The present study aimed to explore whether cigarette smoke exposure altered Notch-1 pathway in ex-vivo (surgical samples of lung parenchyma from non-smoker and smoker patients with lung adenocarcinoma) and in vitro (adenocarcinoma A549 cell line) approaches. The expression of Notch-1, Jagged-1 and CD133 in surgical samples was evaluated by immunohistochemistry. A549 were exposed to cigarette smoke extracts (2.5% and 5% CSE for 6, 24 and 48 h) and the expression of Notch-1, Jagged-1 and Hes-1 was evaluated by Real-Time PCR and Western Blot (nuclear fractions). Expression and localization of Notch-1, Hes-1, CD133 and ABCG2 were assessed by immunofluorescence. The expression of survivin and Ki-67 was assessed by flow cytometry following CSE exposure and inhibition of Notch-1 signaling. Smokers lung parenchyma exhibited higher expression of Notch-1. CSE exposure increased Notch-1 and Hes-1 gene and nuclear protein expression in A549. Immunofluorescence confirmed higher expression of nuclear Hes-1 in CSE-stimulated A549 cells. CSE increased both survivin and Ki-67 expression and this effect was reverted by inhibition of the Notch-1 pathway. In conclusion, these data show that cigarette smoke may promote adenocarcinoma progression by activating the Notch-1 pathway thus supporting its role as hallmark of lung cancer progression and as a new target for lung cancer treatment.

Cigarette smoke extracts induce apoptosis in Raw264.7 cells via endoplasmic reticulum stress and the intracellular Ca2+/P38/STAT1 pathway

Cigarette smoke (CS) exposure is a risk factor for chronic obstructive pulmonary disease (COPD). CS exposure impairs the ability of killing pathogens in macrophages, which might be due to the abnormal apoptosis induced by CS. This study explored the effects and mechanisms of cigarette smoke extract (CSE) on the apoptosis of macrophages in vitro. Raw264.7 cells were treated with CSE at different concentrations, and viability and apoptosis of cells was accessed. The protein expression was detected by western blot. The intracellular Ca²⁺ level was evaluated by Fluo-4 AM probe assay. CSE induced the apoptosis and increased the expression of cleaved caspase 3, which were attenuated by a caspase inhibitor. CSE increased the expression of CHOP, BiP and P-eif2α, and the inhibitor of endoplasmic reticulum stress (ERS) decreased the apoptosis induced by CSE. Phosphorylation levels of P38, JNK and ERK1/2 were increased following incubation with CSE. Only P38 inhibitor significantly reduced apoptosis induced by CSE, while ERK1/2 inhibitor promoted apoptosis. Phosphorylation of STAT1 at Ser727 was activated by CSE and attenuated by the P38 inhibitor. Finally, CSE increased the level of intracellular Ca²⁺, and calcium chelator partly attenuated the apoptosis and phosphorylation of P38 and STAT1 induced by CSE. CSE induced a caspase 3-dependent apoptosis in Raw264.7 cells via ERS and intracellular Ca²⁺/P38/STAT1 pathway.

Host Immune-Metabolic Adaptations Upon Mycobacterial Infections and Associated Co-Morbidities

Mycobacterial diseases are a major public health challenge. Their causative agents include, in order of impact, members of the Mycobacterium tuberculosis complex (causing tuberculosis), Mycobacterium leprae (causing leprosy), and non-tuberculous mycobacterial pathogens including Mycobacterium ulcerans. Macrophages are mycobacterial targets and they play an essential role in the host immune response to mycobacteria. This review aims to provide a comprehensive understanding of the immune-metabolic adaptations of the macrophage to mycobacterial infections. This metabolic rewiring involves changes in glycolysis and oxidative metabolism, as well as in the use of fatty acids and that of metals such as iron, zinc and copper. The macrophage metabolic adaptations result in changes in intracellular metabolites, which can post-translationally modify proteins including histones, with potential for shaping the epigenetic landscape. This review will also cover how critical tuberculosis co-morbidities such as smoking, diabetes and HIV infection shape host metabolic responses and impact disease outcome. Finally, we will explore how the immune-metabolic knowledge gained in the last decades can be harnessed towards the design of novel diagnostic and therapeutic tools, as well as vaccines.

Roles of Inflammasome in Cigarette Smoke-Related Diseases and Physiopathological Disorders: Mechanisms and Therapeutic Opportunities

Cigarette smoke damages a wide range of immunological functions, including innate and adaptive immune responses. Emerging literature demonstrates that inflammasome constitutes an essential component in innate immune response. In this review, we focus on the cumulative mechanisms of inflammasome in cigarette smoke-related diseases and physiopathological disorders, and summarize potential therapeutic opportunities targeting inflammasome. This review suggests that inflammasomes (NLRP3, NLRP6, NLRP12 and AIM2) are involved in the pathogenesis of several cigarette smoke-related diseases (including COPD, ALI, atherosclerosis, kidney injury, bladder dysfunction, and oral leukoplakia) and physiopathological disorders (macrophage dysfunction, endothelial barrier dysfunction, podocyte injury, and ubiquitin-mediated proteasomal processing). MyD88/NF-κB, HMGB1, production of ROS, endoplasmic reticulum stress and mitochondrial dysfunction, and Ca²⁺ influx are potentially involved in cigarette smoke induced-inflammasome activation. Strategies targeting ROS/NLRP3 inflammasome axis are most widely investigated and show potential therapeutic effects.

Cigarette Smoke Stimulates SARS-CoV-2 Internalization by Activating AhR and Increasing ACE2 Expression in Human Gingival Epithelial Cells

A large body of evidence shows the harmful effects of cigarette smoke to oral and systemic health. More recently, a link between smoking and susceptibility to coronavirus disease 2019 (COVID-19) was proposed. COVID-19 is due to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which uses the receptor ACE2 and the protease TMPRSS2 for entry into host cells, thereby infecting cells of the respiratory tract and the oral cavity. Here, we examined the effects of cigarette smoke on the expression of SARS-CoV-2 receptors and infection in human gingival epithelial cells (GECs). We found that cigarette smoke condensates (CSC) upregulated ACE2 and TMPRSS2 expression in GECs, and that CSC activated aryl hydrocarbon receptor (AhR) signaling in the oral cells. ACE2 was known to mediate SARS-CoV-2 internalization, and we demonstrate that CSC treatment potentiated the internalization of SARS-CoV-2 pseudovirus in GECs in an AhR-dependent manner. AhR depletion using small interference RNA decreased SARS-CoV-2 pseudovirus internalization in CSC-treated GECs compared with control GECs. Our study reveals that cigarette smoke upregulates SARS-CoV-2 receptor expression and infection in oral cells. Understanding the mechanisms involved in SARS-CoV-2 infection in cells of the oral cavity may suggest therapeutic interventions for preventing viral infection and transmission.

Inflammasome Activation in Pollution-Induced Skin Conditions

SUMMARY

Exposure to air pollutants has been now associated with detrimental effects on a variety of organs, including the heart, lungs, GI tract, and brain. However, recently it has become clear that pollutant exposure can also promote the development/exacerbation of a variety of skin conditions, including premature aging, psoriasis, acne, and atopic dermatitis. Although the molecular mechanisms by which pollutant exposure results in these cutaneous pathological manifestations, it has been noticed that an inflammatory status is a common denominator of all those skin conditions. For this reason, recently, the activation of a cytosolic multiprotein complex involved in inflammatory responses (the inflammasome) that could promote the maturation of proinflammatory cytokines interleukin-1β and interleukin-18 has been hypothesized to play a key role in pollution-induced skin damage. In this review, we summarize and propose the cutaneous inflammasome as a novel target of pollutant exposure and the eventual usage of inflammasome inhibitor as new technologies to counteract pollution-induced skin damage. Possibly, the ability to inhibit the inflammasome activation could prevent cutaneous inflammaging and ameliorate the health and appearance of the skin.

An Emerging Syndemic of Smoking and Cardiopulmonary Diseases in People Living with HIV in Africa

Background: African countries have the highest number of people living with HIV (PWH). The continent is home to 12% of the global population, but accounts for 71% of PWH globally. Antiretroviral therapy has played an important role in the reduction of the morbidity and mortality rates for HIV, which necessitates increased surveillance of the threats from pernicious risks to which PWH who live longer remain exposed. This includes cardiopulmonary comorbidities, which pose significant public health and economic challenges. A significant contributor to the cardiopulmonary comorbidities is tobacco smoking. Indeed, globally, PWH have a 2–4-fold higher utilization of tobacco compared to the general population, leading to endothelial dysfunction and atherogenesis that result in cardiopulmonary diseases, such as chronic obstructive pulmonary disease and coronary artery disease. In the context of PWH, we discuss (1) the current trends in cigarette smoking and (2) the lack of geographically relevant data on the cardiopulmonary conditions associated with smoking; we then review (3) the current evidence on chronic inflammation induced by smoking and the potential pathways for cardiopulmonary disease and (4) the multifactorial nature of the syndemic of smoking, HIV, and cardiopulmonary diseases. This commentary calls for a major, multi-setting cohort study using a syndemics framework to assess cardiopulmonary disease outcomes among PWH who smoke. Conclusion: We call for a parallel program of implementation research to promote the adoption of evidence-based interventions, which could improve health outcomes for PWH with cardiopulmonary diseases and address the health inequities experienced by PWH in African countries.

COVID-19 and Smoking: What Evidence Needs Our Attention?

The current COVID-19 pandemic has caused severe morbidity and mortality worldwide. Although relevant studies show that the smoking rate of COVID-19 patients is relatively low, the current smoking status of people with COVID-19 cannot be accurately measured for reasons. Thus, it is difficult to assess the relationship between smoking and COVID-19. Smoking can increase the risk of severe COVID-19 symptoms and aggravate the condition of patients with COVID-19. Nicotine upregulates the expression of ACE2, which can also increase susceptibility to COVID-19, aggravatiing the disease. Although nicotine has certain anti-inflammatory effects, there is no evidence that it is related to COVID-19 treatment; therefore, smoking cannot be considered a preventative measure. Furthermore, smokers gathering and sharing tobacco may promote the spread of viruses. Despite the COVID-19 epidemic, the findings suggested that COVID-19 has not encouraged smokers to quit. Additionally, there is evidence that isolation at home has contributed to increased smoking behavior and increased quantities. Therefore, it is recommended that governments increase smoking cessation messaging as part of public health measures to contain the COVID-19 pandemic. This review analyzes the existing research on smoking's impact on COVID-19 so that governments and medical institutions can develop evidence-based smoking-related prevention and control measures for COVID-19.

Cigarette smoke extract induces pyroptosis in human bronchial epithelial cells through the ROS/NLRP3/caspase-1 pathway

AIMS

Pyroptosis and inflammation are involved in the development of chronic obstructive pulmonary disease (COPD). However, the cigarette smoke-mediated mechanism of COPD remains unclear. In this study, we aimed to investigate the role of nucleotide-binding domain-like receptor protein-3 (NLRP3) inflammasome-mediated pyroptosis in the death of human bronchial epithelial (HBE) cells after cigarette smoke extract (CSE) exposure.

MAIN METHODS

The protein level of NLRP3 in lung tissue was measured after cigarette smoke exposure in vivo. In vitro, HBE cells were treated with CSE. Subsequently, the activity of caspase-1, lactate dehydrogenase (LDH) release, release of interleukin (IL)-1β and NLRP3 expression levels were measured. The involvement of reactive oxygen species (ROS) was also explored.

KEY FINDINGS

After exposure to CSE, increased release of LDH, the transcriptional and translational upregulation of NLRP3, the caspase-1 activity levels, and enhanced IL-1β and IL-18 release were observed in 16HBE cells. In addition, NLRP3 was required to activate the caspase-1. Our results suggested that pre-stimulated of 16HBE with a caspase-1 inhibitor, or using NLRP3 siRNA to silence NLRP3 expression, also caused the decrease of IL-1β release and pyroptosis.

SIGNIFICANCES

CSE induced inflammation and contributed to pyroptosis through the ROS/NLRP3/caspase-1 pathway in 16HBE cells. The NLRP3 inflammasome participates in CSE-induced HBE cell damage and pyroptosis, which could provide new insights into COPD.

Cigarette smoke extract reduces FOXO3a promoting tumor progression and cell migration in lung cancer

Lung cancer is the leading cause of cancer death worldwide, and the carcinogens in tobacco smoke play a role in its progression and metastasis. The related molecular events are largely unknown. FOXO3a is a transcription factor considered a tumor suppressor. Its inhibition leads to cell transformation, tumor progression and metastasis. The aim of this study was to investigate, in different types of lung cancer cell lines (A549, COLO 699 N, SK-MES-1), the effects of cigarette smoke on mitochondrial status and cell metabolism and on key pathways involved in tumor progression and cell migration, looking at the role of FOXO3a in these mechanisms. The different lung cancer cells were exposed to cigarette smoke extract (CSE) and TGF-β1. Reactive oxygen species (ROS), mitochondrial superoxide, intracellular ATP, extracellular lactate, FOXO3a, p21, survivin, epithelial-to-mesenchymal transition (EMT) markers (E-cadherin, SNAIL1), MMP-9 and cellular migration were assessed by flow-cytometry, fluorimetry, western blot analysis, Real-Time PCR and scratch test. Our results showed that exposure to CSE: (i) increased ROS, mitochondrial superoxide, lactate release while reducing intracellular ATP; (ii) decreased FOXO3a and increased survivin and p21 in the cytoplasm; (iii) decreased E-cadherin, increased SNAIL1 and MMP-9 and promoted cell migration like TGF-β1 did. These effects could be partly explained by downregulation of FOXO3a, as demonstrated by silencing experiments. These data suggest that cigarette smoke induces oxidative stress and mitochondrial damage leading to metabolic reprogramming associated with increased glycolytic flux. This is accompanied with a downregulation of FOXO3a contributing to EMT processes and cell migration therefore promoting tumor progression.

Etidronate down-regulates Toll-like receptor 2 ligand-induced chemokine production by inhibiting MyD88 expression and NF-κB activation

OBJECTIVE

Pretreatment of J774.1 cells with etidronate, a non-nitrogen-containing bisphosphonate (non-NBP) used as an antibone resorptive drug, was previously reported to inhibit Toll-like receptor (TLR) 2 agonist-induced proinflammatory cytokine production. The present study aimed to examine the effects of etidronate on chemokine production by human monocytic U937 cells incubated with Pam₃Cys-Ser-(Lys)₄ (Pam₃CSK₄, a TLR2 ligand) and lipid A (a TLR4 ligand).

METHODS

U937 cells were pretreated with or without etidronate, and then incubated with or without Pam₃CSK₄ or lipid A. Levels of secreted human interleukin (IL)-8 and monocyte chemoattractant protein-1 (MCP-1) in culture supernatants and activation of nuclear factor-κB (NF-κB) p65 were measured by enzyme-linked immunosorbent assay (ELISA). Cytotoxicity was determined by measuring lactate dehydrogenase (LDH) activity in supernatants. Expression of intracellular adhesion molecule (ICAM)-1 and MyD88 was analyzed by flow cytometry and Western blot analysis, respectively.

RESULTS

Etidronate down-regulated IL-8 and MCP-1 production and NF-κB p65 activation induced by Pam₃CSK_4, but not lipid A, in U937 cells. Etidronate also inhibited MyD88 expression in U937 cells incubated with Pam₃CSK₄.

CONCLUSION

Etidronate down-regulates IL-8 and MCP-1 production in U937 cells by inhibiting both the expression of MyD88 and activation of NF-κB p65 in the TLR2, but not TLR4, pathway.

Lipopolysaccharide upregulates miR-132/212 in Hirschsprung-associated enterocolitis, facilitating pyroptosis by activating NLRP3 inflammasome via targeting Sirtuin 1 (SIRT1)

Hirschsprung disease (HSCR) is a congenital disorder attributed to the failure of the neural crest derivatives migrating and/or differentiating along the hindgut. The most frequent complication in Hirschsprung disease patients is Hirschsprung-associated enterocolitis (HAEC). However, its pathogenesis has not been fully understood. This study investigated miRNAs influenced by Lipopolysaccharide (LPS) in postoperative HAEC patients, their effect on enterocolitis and the underlying mechanism. MiR-132 and miR-212 were up-regulated in HAEC dilated tissues and LPS-treated mice enteritis samples. LPS-stimulated HT29 cells showed a high expression of miR-132 and miR-212. QRT-PCR analysis, western blotting, luciferase reporter assay, and flow cytometric analysis were carried out in vitro, showing that miR-132 and miR-212 could directly inhibit Sirtuin 1 (SIRT1) expression. Consequently, SIRT1 deficiency in LPS-stimulated HT29 cell line and LPS-treated mice activated NLRP3 inflammasome and Caspase-1-mediated pyroptosis. Furthermore, the above inflammation activation was reversed by miR-132/212 inhibitor or SIRT1 overexpression plasmid transfection.In conclusion, LPS upregulated miR-132 and miR-212 expression in HAEC, suppressing SIRT1 and facilitating NLRP3 inflammasome activation, which induced pyroptosis. Our findings illustrated the role of LPS/miR-132/-212/SIRT1/NLRP3 regulatory network in the occurrence and progression of HAEC and proposed a new molecular pathway for LPS-mediated cell pyroptosis.

Cellular Models and Assays to Study NLRP3 Inflammasome Biology

The NLRP3 inflammasome is a multi-protein complex that initiates innate immunity responses when exposed to a wide range of stimuli, including pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs). Inflammasome activation leads to the release of the pro-inflammatory cytokines interleukin (IL)-1β and IL-18 and to pyroptotic cell death. Over-activation of NLRP3 inflammasome has been associated with several chronic inflammatory diseases. A deep knowledge of NLRP3 inflammasome biology is required to better exploit its potential as therapeutic target and for the development of new selective drugs. To this purpose, in the past few years, several tools have been developed for the biological characterization of the multimeric inflammasome complex, the identification of the upstream signaling cascade leading to inflammasome activation, and the downstream effects triggered by NLRP3 activation. In this review, we will report cellular models and cellular, biochemical, and biophysical assays that are currently available for studying inflammasome biology. A special focus will be on those models/assays that have been used to identify NLRP3 inhibitors and their mechanism of action.