Membrane microdomains regulate NLRP10- and NLRP12-dependent signalling in A549 cells challenged with cigarette smoke extract

Lipids in inflammasome activation and autoinflammatory disorders

Autoinflammatory diseases (AIDs) are a group of rare monogenetic disorders characterized by recurrent episodes of fever and systemic inflammation. A major pathologic hallmark of AIDs is excessive inflammasome assembly and activation, often the result of gain-of-function mutations in genes encoding core inflammasome components, including pyrin and cryopyrin. Recent advances in lipidomics have revealed that dysregulated metabolism of lipids such as cholesterol and fatty acids, especially in innate immune cells, exerts complex effects on inflammasome activation and the pathogenesis of AIDs. In this review, we summarize and discuss the impact of lipids and their metabolism on inflammasome activation and the disease pathogenesis of the most common AIDs, including familial Mediterranean fever, cryopyrin-associated periodic syndromes, and mevalonate kinase deficiency. We postulate that lipids hold diagnostic value in AIDs and that dietary and pharmacologic intervention studies could represent a promising approach to attenuate inflammasome activation and AID progression.

Rafting on the Evidence for Lipid Raft-like Domains as Hubs Triggering Environmental Toxicants' Cellular Effects

The plasma membrane lipid rafts are cholesterol- and sphingolipid-enriched domains that allow regularly distributed, sub-micro-sized structures englobing proteins to compartmentalize cellular processes. These membrane domains can be highly heterogeneous and dynamic, functioning as signal transduction platforms that amplify the local concentrations and signaling of individual components. Moreover, they participate in cell signaling routes that are known to be important targets of environmental toxicants affecting cell redox status and calcium homeostasis, immune regulation, and hormonal functions. In this work, the evidence that plasma membrane raft-like domains operate as hubs for toxicants' cellular actions is discussed, and suggestions for future research are provided. Several studies address the insertion of pesticides and other organic pollutants into membranes, their accumulation in lipid rafts, or lipid rafts' disruption by polychlorinated biphenyls (PCBs), benzo[a]pyrene (B[a]P), and even metals/metalloids. In hepatocytes, macrophages, or neurons, B[a]P, airborne particulate matter, and other toxicants caused rafts' protein and lipid remodeling, oxidative changes, or amyloidogenesis. Different studies investigated the role of the invaginated lipid rafts present in endothelial cells in mediating the vascular inflammatory effects of PCBs. Furthermore, in vitro and in vivo data strongly implicate raft-localized NADPH oxidases, the aryl hydrocarbon receptor, caveolin-1, and protein kinases in the toxic mechanisms of occupational and environmental chemicals.

Interplay between proteasome function and inflammatory responses in e-cig vapor condensate-challenged lung epithelial cells

Exposure to cigarettes and other nicotine-based products results in persistent inflammation in the lung. In recent years, electronic cigarettes (e-cigs) have become extremely popular among adults and youth alike. E-cigarette vapor-induced oxidative stress promotes protein breakdown, DNA damage and cell death, culminating in a variety of respiratory diseases. The proteasome, a multi-catalytic protease, superintends protein degradation within the cell. When cells are stimulated with inflammatory cytokines such as IFN-γ and TNF-α, the constitutive catalytic proteasome subunits are replaced by the inducible subunits-low-molecular mass polypeptide (LMP)2 (β1i), multi-catalytic endopeptidase complex-like (MECL)1 (β2i), and LMP7 (β5i), which are required for the production of certain MHC class I-restricted T-cell epitopes. In this study, we used human alveolar epithelial cells (A549) and exposed them to filtered air or (1%) tobacco-flavored (TF) electronic cigarette vapor condensate (ECVC) ± nicotine (6 mg/ml) (TF-ECVC ± N) for 24 h. We observed an increase in the levels of IFN-γ, TNF-α, and inducible proteasome subunits (LMP7/PSMB8, LMP2/PSMB9, MECL1/PSMB10), and a reduced expression of constitutive proteasome subunits (β1/PSMB6 and β2/PSMB7) in challenged A549 cells. Interestingly, knockdown of the inducible proteasome subunit LMP7 reversed ECVC-induced expression of NADPH oxidase and immunoproteasome subunits in A549 cells. In addition, pre-exposure to an LMP7 inhibitor (ONX-0914) abrogated the mRNA expression of several NOX subunits and rescued the excessive production/release of inflammatory cytokines/chemokines (IL-6, IL-8, CCL2, and CCL5) in ECVC-challenged cells. Our findings suggest an important role of LMP7 in regulating the expression of inflammatory mediators during ECVC exposure. Overall, our results provide evidence for proteasome-dependent ROS-mediated inflammation in ECVC-challenged cells.

Novel insights into NOD-like receptors in renal diseases

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

In vitro study of the role of FOXO transcription factors in regulating cigarette smoke extract-induced autophagy

Cigarette smoking is the chief etiological factor for chronic obstructive pulmonary disease (COPD). Oxidative stress induced by cigarette smoke (CS) causes protein degradation, DNA damage, and cell death, thereby resulting in acute lung injury (ALI). In this regard, autophagy plays a critical role in regulating inflammatory responses by maintaining protein and organelle homeostasis and cellular viability. Expression of autophagy-related proteins (ARPs) is regulated by the fork head box class O (FOXO) transcription factors. In the current study, we examined the role of FOXO family proteins-FOXO1 and FOXO3a-in regulating CS extract (CSE)-induced autophagy. Using human lung adenocarcinoma cells with type II alveolar epithelial characteristics (A549), we observed CSE-mediated downregulation of FOXO3a. In contrast, there was a pronounced increase in the expression of FOXO1 at both the transcriptional and translational levels in the CSE-challenged cells compared with controls. Interestingly, knockdown of FOXO3a heightened the CSE-mediated increase in expression of cytokines/chemokines (IL-6, IL-8, and MCP-1), ARPs, and the FOXO1 transcription factor. Moreover, FOXO1 knockdown rescued CSE-mediated upregulation of ARPs in A549 cells. In addition, using the ROS inhibitor N-acetyl-L-cysteine (NAC), we observed abrogated mRNA expression of several ARPs and production of inflammatory cytokines/chemokines (IL-6, IL-8, MCP-1, and CCL-5) in the CSE-challenged cells suggesting an important role of ROS in regulating CSE-induced autophagy. Chromatin immunoprecipitation of FOXO1 and FOXO3a demonstrated increased binding of the former to promoter regions of autophagy genes- BECLIN1, ATG5, ATG12, ATG16, and LC3 in CSE challenged cells. These findings suggest the role of FOXO1 in regulating the expression of these genes during CSE exposure. Overall, our findings provide evidence for FOXO3a-dependent FOXO1-mediated regulation of autophagy in the CSE-challenged cells. Graphical abstract.

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.

E-cig vapor condensate alters proteome and lipid profiles of membrane rafts: impact on inflammatory responses in A549 cells

Electronic cigarettes (e-cigs) are battery-operated heating devices that aerosolize e-liquid, typically containing nicotine and several other chemicals, which is then inhaled by a user. Over the past decade, e-cigs have gained immense popularity among both smokers and non-smokers. One reason for this is that they are advertised as a safe alternative to conventional cigarettes. However, the recent reports of e-cig use associated lung injury have ignited a considerable debate about the relative harm and benefits of e-cigs. The number of reports about e-cig-induced inflammation and pulmonary health is increasing as researchers seek to better understand the effects of vaping on human health. In line with this, we investigated the molecular events responsible for the e-cig vapor condensate (ECVC)-mediated inflammation in human lung adenocarcinoma type II epithelial cells (A549). In an attempt to limit the variables caused by longer ingredient lists of flavored e-cigs, tobacco-flavored ECVC (TF-ECVC±nicotine) was employed for this study. Interestingly, we observed significant upregulation of cytokines and chemokines (IL-6, IL-8, and MCP-1) in A549 cells following a 48 h TF-ECVC challenge. Furthermore, there was a significant increase in the expression of pattern recognition receptors TLR-4 and NOD-1, lipid raft-associated protein caveolin-1, and transcription factor NF-кB in TF-ECVC with and/or without nicotine-challenged lung epithelial cells. Our results further demonstrate the harboring of TLR-4 and NOD-1 in the caveolae of TF-ECVC-challenged A549 cells. Proteomic and lipidomic analyses of lipid raft fractions from control and challenged cells revealed a distinct protein and lipid profile in TF-ECVC (w/wo nicotine)-exposed A549 cells. Interestingly, the inflammatory effects of TF-ECVC (w/wo nicotine) were inhibited following the caveolin-1 knockdown, thus demonstrating a critical role of caveolae raft-mediated signaling in eliciting inflammatory responses upon TF-ECVC challenge. Graphical Abstract Graphical Abstract.

Caspase-1 has a critical role in blood-brain barrier injury and its inhibition contributes to multifaceted repair

Background

Excessive inflammation might activate and injure the blood-brain barrier (BBB), a common feature of many central nervous system (CNS) disorders. We previously developed an in vitro BBB injury model in which the organophosphate paraoxon (PX) affects the BBB endothelium by attenuating junctional protein expression leading to weakened barrier integrity. The objective of this study was to investigate the inflammatory cellular response at the BBB to elucidate critical pathways that might lead to effective treatment in CNS pathologies in which the BBB is compromised. We hypothesized that caspase-1, a core component of the inflammasome complex, might have important role in BBB function since accumulating evidence indicates its involvement in brain inflammation and pathophysiology.

Methods

An in vitro human BBB model was employed to investigate BBB functions related to inflammation, primarily adhesion and transmigration of peripheral blood mononuclear cells (PBMCs). Caspase-1 pathway was studied by measurements of its activation state and its role in PBMCs adhesion, transmigration, and BBB permeability were investigated using the specific caspase-1 inhibitor, VX-765. Expression level of adhesion and junctional molecules and the secretion of pro-inflammatory cytokines were measured in vitro and in vivo at the BBB endothelium after exposure to PX. The potential repair effect of blocking caspase-1 and downstream molecules was evaluated by immunocytochemistry, ELISA, and Nanostring technology.

Results

PX affected the BBB in vitro by elevating the expression of the adhesion molecules E-selectin and ICAM-1 leading to increased adhesion of PBMCs to endothelial monolayer, followed by elevated transendothelial-migration which was ICAM-1 and LFA-1 dependent. Blocking caspase-8 and 9 rescued the viability of the endothelial cells but not the elevated transmigration of PBMCs. Inhibition of caspase-1, on the other hand, robustly restored all of barrier insults tested including PBMCs adhesion and transmigration, permeability, and VE-cadherin protein levels. The in vitro inflammatory response induced by PX and the role of caspase-1 in BBB injury were corroborated in vivo in isolated blood vessels from hippocampi of mice exposed to PX and treated with VX-765.

Conclusions

These results shed light on the important role of caspase-1 in BBB insult in general and specifically in the inflamed endothelium, and suggest therapeutic potential for various CNS disorders, by targeting caspase-1 in the injured BBB.

Estimation of Hub Genes and Infiltrating Immune Cells in Non-Smoking Females with Lung Adenocarcinoma by Integrated Bioinformatic Analysis

BACKGROUND In recent years, the morbidity and mortality rates of lung adenocarcinoma in non-smoking females have been increasing dramatically. Although much research has been done with some progress, the molecular mechanism remains unclear. In this study we aimed to estimate hub genes and infiltrating immune cells in non-smoking females with lung adenocarcinoma. MATERIAL AND METHODS Firstly, we obtained differentially expressed genes (DEGs) by GEO2R analysis based on 3 independent mRNA microarray datasets of GSE10072, GSE31547, and GSE32863. The DAVID database was utilized for functional enrichment analysis of DEGs. Moreover, we identified hub genes with prognostic value by STRING, Cytoscape, and Kaplan Meier plotter. Subsequently, these genes were further analyzed by Gene Expression Profiling Interactive Analysis, Oncomine, Tumor Immune Estimation Resource, and Human Protein Atlas. Finally, the immune infiltration analysis was performed by CIBERSORT and The Cancer Genome Atlas with R packages. RESULTS We found 315 DEGs enriching in the extracellular matrix organization, cell adhesion, integrin binding, angiogenesis, and hypoxic response. And among these DEGs, we identified 10 hub genes (SPP1, ENG, ATF3, TOP2A, COL1A1, PAICS, CAV1, CAT, TGFBR2, and ANGPT1) of significant prognostic value. Simultaneously, we illustrated the distribution and differential expressions of 22 immune cell subtypes. and dendritic cells resting and macrophages M1 were identified with prognostic significance. CONCLUSIONS The results indicated that 10 hub genes and 2 immune cell subtypes might be promising biomarkers for lung adenocarcinoma in non-smoking females. This finding needs to be further evaluated.

Hydrogen sulfide inhibits cigarette smoke-induced inflammation and injury in alveolar epithelial cells by suppressing PHD2/HIF-1α/MAPK signaling pathway

Chronic obstructive pulmonary fibrosis (COPD) is a chronic and fatal lung disease with few treatment options. Sodium hydrosulfide (NaHS), a donor of hydrogen sulfide (H2S), was found to alleviate cigarette smoke (CS)-induced emphysema in mice, however, the underlying mechanisms have not yet been clarified. In this study, we investigated its effects on COPD in a CS-induced mouse model in vivo and in cigarette smoke extract (CSE)-stimulated alveolar epithelial A549 cells in vitro. The results showed that NaHS not only relieved emphysema, but also improved pulmonary function in CS-exposed mice. NaHS significantly increased the expressions of tight junction proteins (i.e., ZO-1, Occludin and claudin-1), and reduced apoptosis and secretion of pro-inflammatory cytokines (i.e., TNF-α, IL-6 and IL-1β) in CS-exposed mouse lungs and CSE-incubated A549 cells, indicating H2S inhibits CS-induced inflammation, injury and apoptosis in alveolar epithelial cells. NaHS also upregulated prolyl hydroxylase (PHD)2, and suppressed hypoxia-inducible factor (HIF)-1α expression in vivo and in vitro, suggesting H2S inhibits CS-induced activation of PHD2/HIF-1α axis. Moreover, NaHS inhibited CS-induced phosphorylation of ERK, JNK and p38 MAPK in vivo and in vitro, and treatment with their inhibitors reversed CSE-induced ZO-1 expression and inflammation in A549 cells. These results suggest that NaHS may prevent emphysema via the suppression of PHD2/HIF-1α/MAPK signaling pathway, and subsequently inhibition of inflammation, epithelial cell injury and apoptosis, and may be a novel strategy for the treatment of COPD.

NLRP10 ablation protects against ischemia/reperfusion-associated brain injury by suppression of neuroinflammation

Ischemic stroke leads to neuronal cell death and induces a cascade of inflammatory signals that results in secondary brain damage. Although constant efforts to develop therapeutic strategies and to reveal the molecular mechanism resulting in the physiopathology of this disease, much still remains unclear. Membrane-bound Toll-like receptors (TLRs) and cytosolic nucleotide binding oligomerization domain (NOD)-like receptors (NLRs) are two major families of pattern recognition receptors that initiate pro-inflammatory signaling pathways. In the present study, we explored the role of NLRP10 in regulating inflammatory responses in acute ischemic stroke using the wild type (WT) and NLRP10 knockout (KO) mice by inducing middle cerebral artery occlusion/reperfusion (MCAO) injuries. The study first showed that NLRP10 was over-expressed in the ischemic penumbra of WT mice. Then, the brain infarct volume was significantly decreased, and the moving activity was improved post-MCAO in mice with NLRP10 knockout. Apoptosis was also alleviated by NLRP10-knockout, as evidenced by the decreased number of TUNEL-staining cells. Further, NLRP10 deficiency attenuated the activation of glia cells in hippocampus of mice with MCAO operation. NLRP10 inhibition ameliorated the levels of inflammatory factors in peripheral blood serum and hippocampus of mice after stroke. The activation of toll-like receptor (TLR)-4/nuclear factor-κB (NF-κB) signaling pathways was markedly suppressed by NLRP10 ablation in mice after MCAO treatment. Importantly, inflammasome, including NLRP12, ASC and Caspase-1, induced by MCAO in hippocampus of mice was clearly impeded by the loss of NLRP10. The results above were mainly verified in LPS-incubated astrocytes in the absence of NLRP10. Correspondingly, in LPS-treated astrocytes, NLRP10 knockout-reduced inflammation via impairing TLR-4/NF-κB and NLRP12/ASC/Caspase-1 pathways was evidently restored by over-expressing NLRP10. Therefore, the results above indicated an essential role of NLRP10 in regulating ischemic stroke, presenting NLRP10 as a promising target to protect human against stroke.

Caveolae, caveolin-1 and lung diseases of aging

INTRODUCTION

Flask-shaped plasma membrane (PM) invaginations called caveolae and their constitutive caveolin and cavin proteins regulate cellular function via plasma membrane and intracellular signal transduction pathways. Caveolae are present in a variety of cells in the lung including airway smooth muscle (ASM) where they interact with other proteins, receptors, and ion channels and thereby have the potential to affect both normal and disease processes such as inflammation, contractility, and fibrosis. Given their involvement in cell signaling, caveolae may play important roles in mediating and modulating aging processes, and contribute to lung diseases of aging. Areas covered: This review provides a broad overview of the current state of knowledge regarding caveolae and their constituent proteins in lung diseases in the elderly and identifies potential mechanisms that can be targeted for future therapies. Expert Commentary: Caveolin-1 may play a protective role in lung disease. What is less clear is whether altered caveolin-1 with aging is a natural process, or a biomarker of disease progression in the elderly.