Differential expression of heat shock proteins and activation of mitogen-activated protein kinases in A549 alveolar epithelial cells exposed to cigarette smoke extract

HSP27-HSP40-HSP70-HSP90 pathway participated in molecular mechanism of selenium alleviating lead-caused oxidative damage and proteotoxicity in chicken Bursa of Fabricius

Lead (Pb), a toxic environmental pollutant, is hazardous to the health of humans and birds. Bursa of Fabricius (BF) is a unique organ of birds. Toxic substances can attack BF and induce proteotoxicity. Increased heat shock proteins (HSPs) can induce oxidative damage. Selenium (Se) can alleviate harmful substance-caused oxidative damage. This study aimed to investigate whether Pb can cause oxidative damage and proteotoxicity, as well as Se reverse Pb-caused chicken BF toxicity. A model of chickens treated with Se and Pb alone and in combination was established. BFs were collected on days 30, 60, and 90. H&E and qRT-PCR were performed to observe the microstructure and to detect HSP27, HSP40, HSP60, HSP70, and HSP90 mRNA levels, respectively, in BFs. Multivariate correlation analysis and principal component analysis were conducted to explore the correlation among the five HSPs. In our results, Pb caused BF damage and up-regulated the five HSPs at three time points, causing oxidative damage and proteotoxicity via HSP27-HSP40-HSP70-HSP90 pathway. Furthermore, Pb caused time-dependent stress on HSP27, HSP40, HSP60, and HSP70. In addition, Se relieved Pb-caused damage and up-regulation of HSPs. Taken together, we concluded that Se alleviated Pb-caused oxidative injury and proteotoxicity in chicken BFs via the HSP27-HSP40-HSP70-HSP90 pathway.

Exploring Mechanisms in COPD: Time for Biomarker Reappraisal?

Chronic obstructive pulmonary disease (COPD) is a widespread condition often overlooked in diagnosis [...].

The macrophage senescence hypothesis: the role of poor heat shock response in pulmonary inflammation and endothelial dysfunction following chronic exposure to air pollution

INTRODUCTION

Cardiovascular diseases (CVD) have been associated with high exposure to fine particulate air pollutants (PM_2.5). Alveolar macrophages are the first defense against inhaled particles. As soon as they phagocytize the particles, they reach an inflammatory phenotype, which affects the surrounding cells and associates with CVD. Not coincidentally, CVD are marked by a depleted heat shock response (HSR), defined by a deficit in inducing 70-kDa heat shock protein (HSP70) expression during stressful conditions. HSP70 is a powerful anti-inflammatory chaperone, whose reduced levels trigger a pro-inflammatory milieu, cellular senescence, and a senescence-associated secretory phenotype (SASP). However, whether macrophage senescence is the main mechanism by which PM_2.5 propagates low-grade inflammation remains unclear.

OBJECTIVE AND DESIGN

In this article, we review evidence supporting that chronic exposure to PM_2.5 depletes HSR and determines the ability to solve the initial stress.

RESULTS AND DISCUSSION

When exposed to PM_2.5, macrophages increase the production of reactive oxygen species, which activate nuclear factor-kappa B (NF-κB). NF-κB is naturally a pro-inflammatory factor that drives prostaglandin E2 (PGE2) synthesis and causes fever. PGE2 can be converted into prostaglandin A2, a powerful inducer of HSR. Therefore, when transiently activated, NF-κB can trigger the anti-inflammatory response through negative feedback, by inducing HSP70 expression. However, when chronically activated, NF-κB heads a set of pathways involved in mitochondrial dysfunction, endoplasmic reticulum stress, unfolded protein response, inflammasome activation, and apoptosis. During chronic exposure to PM_2.5, cells cannot properly express sirtuin-1 or activate heat shock factor-1 (HSF-1), which delays the resolution phase of inflammation. Since alveolar macrophages are the first immune defense against PM_2.5, we suppose that the pollutant impairs HSR and, consequently, induces cellular senescence. Accordingly, senescent macrophages change its secretory phenotype to a more inflammatory one, known as SASP. Finally, macrophages' SASP would propagate the systemic inflammation, leading to endothelial dysfunction and atherosclerosis.

Early-life exposure to tobacco smoke alters airway signaling pathways and later mortality in D. melanogaster

Early life environmental influences such as exposure to cigarette smoke (CS) can disturb molecular processes of lung development and thereby increase the risk for later development of chronic respiratory diseases. Among the latter, asthma and chronic obstructive pulmonary disease (COPD) are the most common. The airway epithelium plays a key role in their disease pathophysiology but how CS exposure in early life influences airway developmental pathways and epithelial stress responses or survival is poorly understood. Using Drosophila melanogaster larvae as a model for early life, we demonstrate that CS enters the entire larval airway system, where it activates cyp18a1 which is homologues to human CYP1A1 to metabolize CS-derived polycyclic aromatic hydrocarbons and further induces heat shock protein 70. RNASeq studies of isolated airways showed that CS dysregulates pathways involved in oxidative stress response, innate immune response, xenobiotic and glutathione metabolic processes as well as developmental processes (BMP, FGF signaling) in both sexes, while other pathways were exclusive to females or males. Glutathione S-transferase genes were further validated by qPCR showing upregulation of gstD4, gstD5 and gstD8 in respiratory tracts of females, while gstD8 was downregulated and gstD5 unchanged in males. ROS levels were increased in airways after CS. Exposure to CS further resulted in higher larval mortality, lower larval-pupal transition, and hatching rates in males only as compared to air-exposed controls. Taken together, early life CS induces airway epithelial stress responses and dysregulates pathways involved in the fly's branching morphogenesis as well as in mammalian lung development. CS further affected fitness and development in a highly sex-specific manner.

Gene Expression Changes Induced by Exposure of RAW 264.7 Macrophages to Particulate Matter of Air Pollution: The Role of Endotoxins

Despite the variable chemical and physical characteristics of particulate air pollutants, inflammation and oxidative stress have been identified as common mechanisms for cell damage and negative health influences. These effects are produced by organic components, especially by endotoxins. This study analyzed the gene expression profile after exposure of RAW 264.7 cells to the standard particulate matter (PM) material, NIST1648a, and PM with a reduced organic matter content, LAp120, in comparison to the effects of lipopolysaccharide (LPS). The selected parameters of cell viability, cell cycle progression, and metabolic and inflammatory activity were also investigated. Both forms of PM negatively influenced the parameters of cell activity. These results were generally reflected in the gene expression profile. Only NIST1648a, excluding LAp120, contained endotoxins and showed small but statistically significant pro-inflammatory activity. However, the gene expression profiling revealed strong pro-inflammatory cell activation induced by NIST1648a that was close to the effects of LPS. Changes in gene expression triggered by LAp120 were relatively small. The observed differences in the effects of NIST1648a and LAp120 were related to the content of organic matter in which bacterial endotoxins play an important role. However, other organic compounds and their interactions with other PM components also appear to be of significant importance.

TRPV4 induces apoptosis via p38 MAPK in human lung cancer cells

Lung cancer is one of the most common cancers worldwide. TRPV4 belongs to the ‘transient receptor potential' (TRP) superfamily. It has been identified to profoundly affect a variety of physiological processes, including nociception, heat sensation, and inflammation. Unlike other TRP superfamily channels, its roles in cancers are unknown. Here, we elucidated the effects of TRPV4 and molecular mechanisms in human lung cancer cells. The levels of TRPV4 were detected in human lung cancer tissues and the paired paracarcinoma tissues by real-time PCR and western blotting analysis. The proliferation of human lung cancer cells was determined by MTT assay. Cell apoptosis was determined by FACS assay. The results demonstrated that low levels of TRPV4 were detected in clinical lung carcinoma specimens. Over-expression of TRPV4 induced cell death and inhibited cell proliferation and migration in A549 cells and H460 cells. Moreover, over-expression of TRPV4 enhanced the activation of p38 MAPK signal pathway. Inhibition of p38 MAPK abolished the effects of TRPV4 on cell proliferation, apoptosis, and migration in A549 cells. Collectively, our findings indicated that TRPV4 induced apoptosis via p38 MAPK in human lung cancer cells and suggested that TRPV4 was a potential target for therapy of human lung cancers.

Sodium Tanshinone IIA Sulfonate Attenuates Cigarette Smoke Extract-Induced Mitochondrial Dysfunction, Oxidative Stress, and Apoptosis in Alveolar Epithelial Cells by Enhancing SIRT1 Pathway

Emphysema is one of the most important phenotypes for chronic obstructive pulmonary disease (COPD). Apoptosis in alveolar epithelial cells (AECs) causes the emphysematous alterations in the smokers and patients with COPD. Sirtuin 1 (SIRT1) is able to attenuate mitochondrial dysfunction, oxidative stress, and to modulate apoptosis. It has been shown that sodium tanshinone IIA sulfonate (STS), a water-soluble derivative of tanshinone IIA, protects against cigarette smoke (CS)-induced emphysema/COPD in mice. However, the mechanisms underlying these findings remain unclear. Here, we investigate whether and how STS attenuates AEC apoptosis via a SIRT1-dependent mechanism. We found that STS treatment decreased CS extract (CSE)-induced apoptosis in human alveolar epithelial A549 cells. STS reduced oxidative stress, improved mitochondrial function and mitochondrial membrane potential (ΔΨm), and restored mitochondrial dynamics-related protein expression. Moreover, STS promoted mitophagy, and increased oxidative phosphorylation protein levels (complexes I-IV) in CSE-stimulated A549 cells. The protective effects of STS were associated with SIRT1 upregulation, because SIRT1 inhibition by EX 527 significantly attenuated or abolished the ability of STS to reverse the CSE-induced mitochondrial damage, oxidative stress, and apoptosis in A549 cells. In conclusion, STS ameliorates CSE-induced AEC apoptosis by improving mitochondrial function and reducing oxidative stress via enhancing SIRT1 pathway. These findings provide novel mechanisms underlying the protection of STS against CS-induced COPD.

Smoking induces sex-specific changes in the small airway proteome

Introduction

Cigarette smoke triggers many cellular and signaling responses in the lung and the resulting inflammation plays a central role in smoke-related lung diseases, such as COPD. We explored the effects of smoking on the small airway proteome in samples obtained by collection of exhaled particles with the aim to identify specific proteins dysregulated by smoking.

Methods

Exhaled particles were obtained from 38 current smokers, 47 former smokers and 22 healthy controls with the PExA method. 120 ng of sample was collected from individual subjects and analyzed with the SOMAscan proteomics platform. General linear model-based statistics were performed.

Results

Two hundred and three proteins were detected in at least half of 107 total samples. Active smoking exerted a significant impact on the protein composition of respiratory tract lining fluid (RTLF), with 81 proteins altered in current smokers compared to never smokers (p < 0.05, q < 0.124). Among the proteins most clearly discriminating between current and never smokers were sRAGE, FSTL3, SPOCK2 and protein S, all of them being less abundant in current smokers. Analysis stratified for sex unveiled sex differences with more pronounced proteomic alterations due to active smoking in females than males. Proteins whose abundance was altered by active smoking in women were to a larger extent related to the complement system. The small airway protein profile of former smokers appeared to be more similar to that observed in never smokers.

Conclusions

The study shows that smoking has a strong impact on protein expression in the small airways, and that smoking affects men and women differently, suggesting PExA sampling combined with high sensitivity protein analysis offers a promising platform for early detection of COPD and identification of novel COPD drug targets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01825-6.

Role and mechanisms of autophagy in lung metabolism and repair

Mammalian lungs are metabolically active organs that frequently encounter environmental insults. Stress responses elicit protective autophagy in epithelial barrier cells and the supportive niche. Autophagy promotes the recycling of damaged intracellular organelles, denatured proteins, and other biological macromolecules for reuse as components required for lung cell survival. Autophagy, usually induced by metabolic defects, regulates cellular metabolism. Autophagy is a major adaptive response that protects cells and organisms from injury. Endogenous region-specific stem/progenitor cell populations are found in lung tissue, which are responsible for epithelial repair after lung damage. Additionally, glucose and fatty acid metabolism is altered in lung stem/progenitor cells in response to injury-related lung fibrosis. Autophagy deregulation has been observed to be involved in the development and progression of other respiratory diseases. This review explores the role and mechanisms of autophagy in regulating lung metabolism and epithelial repair.

miR-4456/CCL3/CCR5 Pathway in the Pathogenesis of Tight Junction Impairment in Chronic Obstructive Pulmonary Disease

Background: Cigarette smoke exposure (CSE) is a major cause of chronic obstructive pulmonary disease (COPD). The smoke disrupts cell-cell adhesion by inducing epithelial barrier damage to the tight junction (TJ) proteins. Even though the inflammatory mechanism of chemokine (C-C motif) ligand 3 (CCL3) in COPD has gained increasing attention in the research community, however, the underlying signaling pathway, remains unknown.

Objectives: To identify the relationship of CCL3 in the pathogenesis of tight junction impairment in COPD and the pathway through which CSE causes damage to TJ in COPD via CCL3, both in vivo and in vitro.

Methods: We screened the inflammatory factors in the peripheral blood mononuclear cells (PBMCs) from healthy controls and patients at each GOLD 1-4 stage of chronic obstructive pulmonary disease. RT-PCR, western blot, and ELISA were used to detect the levels of CCL3, ZO-1, and occludin after Cigarette smoke exposure. Immunofluorescence was applied to examine the impairment of the TJs in 16-HBE and A549 cells. The reverse assay was used to detect the effect of a CCR5 antagonist (DAPTA) in COPD. In the CSE-induced COPD mouse model, H&E staining and lung function tests were used to evaluate the pathological and physical states in each group. Immunofluorescence was used to assess the impairment of TJs in each group. ELISA and RT-PCR were used to examine the mRNA or protein expression of CCL3 or miR-4456 in each group.

Results: The in vivo and in vitro results showed that CCL3 expression was increased in COPD compared with healthy controls. CCL3 caused significant injury to TJs through its C-C chemokine receptor type 5 (CCR5), while miR-4456 could suppress the effect of CCL3 on TJs by binding to the 3′-UTR of CCL3.

Conclusion: miR-4456/CCL3/CCR5 pathway may be a potential target pathway for the treatment of COPD.

Cigarette smoke and extracellular Hsp70 induce secretion of ATP and differential activation of NLRP3 inflammasome in monocytic and bronchial epithelial cells

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is an inflammatory disease mainly caused by smoking. Cigarette smoke damages airway epithelium and activates lung macrophages, causing inflammatory responses. It was suggested that nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome might have an important role in COPD development. Study aimed to explore whether cigarette smoke extract (CSE), extracellular heat shock protein 70 (eHsp70) or their combinations induce adenosine triphosphate (ATP) release and NLRP3 inflammasome activation.

METHODS

We detected NLRP3 and interleukin (IL)-1β mRNA expression, extracellular IL-1β and ATP concentrations as well as lactate dehydrogenase (LDH) activity. We used bronchial epithelial (NCI-H292, 16HBE and NHBE) and monocytic cells (monocyte-derived macrophages (MDMs) and THP-1) as representative of local airway and systemic compartments that could be affected in COPD.

RESULTS

CSE and eHsp70 increased NLRP3 and IL-1β mRNA expression as well as IL-1β and ATP secretion in all cells compared to untreated cells. Lytic cell death was observed in cell lines, especially those of bronchial epithelium origin, but not in primary cells (NHBE, MDMs). Regarding LDH activity, eHsp70 did not modulate CSE effects, except in NCI-H292 cell line. However, eHsp70 significantly affected CSE-provoked NLRP3 inflammasome activation by causing mostly antagonistic effects in airway epithelial cells and synergistic effects in MDMs.

CONCLUSION

We demonstrated that both CSE and eHsp70 induce ATP secretion and differential activation of NLRP3 inflammasome in bronchial epithelial and monocytic cells. We suggest that these mechanisms might be involved in pathophysiology of COPD by contributing to the propagation of inflammation.

Effects of transport stress on pathological injury and main heat shock protein expression in the respiratory system of goats

The aim of the present study was to investigate the pathological injury and the expression of heat shock proteins in the caprine lung, trachea and bronchus under transport stress. 12 healthy male goats were selected and randomly divided into three groups. The control group (non-transported group), 2 hr transport-treated group and 6 hr transport-treated group. Morphological changes as well as the expression of heat shock proteins (HSPs, mainly HSP27, HSP70 and HSP90) in three parts of the respiratory tract were examined. Our results showed swollen mucosa and congestive blood vessels in mucous layer and submucosa, inflammatory cell infiltration as well as degeneration and necrosis of mucosal epithelial cells in trachea and bronchus of the transport-treated groups. The epithelial cells were degenerated, and the exfoliated cells and debris could be seen in the alveolar cavity. The results of immunohistochemistry showed that HSP27 and HSP70 were strongly expressed in tracheal and bronchial epithelium, glandular epithelium, vascular endothelium and bronchiole epithelium. And the amount of positive inflammatory cells was increased in transport-treated groups. Western blot results indicated that the expression of all three proteins had no obvious difference among the three groups in bronchi (p > .05). In trachea, there was no significant difference in the expression of heat shock proteins among the three groups except that the expression of HSP70 which was obviously higher in the two transported groups than the control group (p < .05). The expression level of HSP70 in the 2 hr transport-treated group was significantly higher than the 6 hr group (p < .05) and control groups (p < .05). However, there was no significant difference in the expression level of HSP27 and HSP90 in three groups (p > .05). In conclusion, our data showed that transport stress could damage the caprine respiratory system.

Cigarette smoke and glutathione: Focus on in vitro cell models

Cigarette smoke (CS) is one of the most important preventable risk factors for the development of respiratory diseases, cardiovascular diseases, stroke, and various types of cancer. Due to its high intracellular concentration and central role in maintaining the cellular redox state, glutathione (GSH) is one of the key players in several enzymatic and non-enzymatic reactions necessary for protecting cells against CS-induced oxidative stress. A plethora of in vitro cell models have been used over the years to assess the effects of CS on intracellular GSH and its disulphide forms, i.e. glutathione disulphide (GSSG) and S-glutathionylated proteins. In this review, we described the effects of cell exposure to CS on cellular GSH and formation of its oxidized forms and adducts (GSH-conjugates). We also discussed the limitations and relevance of in vitro cell models of exposure to CS and critically assessed the congruence between smokers and in vitro cell models. What emerges clearly is that results obtained in vitro should be interpreted with extreme caution, bearing in mind the limitations of the specific cell model used. Despite this, in vitro cell models remain important tools in the assessment of CS-induced oxidative damage.

Effects of extracellular Hsp70 and cigarette smoke on differentiated THP-1 cells and human monocyte-derived macrophages

Extracellular Hsp70 (eHsp70) can act as pro-inflammatory mediator and is elevated in blood of chronic obstructive pulmonary disease (COPD) patients. Most of those patients are smokers, and it was suggested previously that cigarette smoke might induce Hsp70 secretion from the circulating cells. Therefore, we aimed to explore inflammation-associated effects of cigarette smoke extract (CSE) and its combinations with eHsp70 in monocyte-derived macrophages (MDMs) and THP-1 cell line, used as systemic component models of COPD. We hypothesized that eHsp70 induces inflammation, but that it can also modulate cigarette smoke extract (CSE)-stimulated inflammatory responses. We assessed IL-8 secretion, TLR2, TLR4 and Hsp70 expressions, MAPKs and NF-κB activation, and cytotoxicity after treating the cells with CSE (2.5 and 5%) and its combinations with low-endotoxin recombinant human (rh) Hsp70, used to mimic eHsp70 effects. CSE induced IL-8 secretion from both cell types, but its combinations with rhHsp70 increased IL-8 release compared to CSE alone only from MDMs. In THP-1, combinations of rhHsp70 with 2.5% CSE induced TLR2 and TLR4 mRNA, while 5% CSE decreased TLR2 expression. In MDMs, CSE alone attenuated TLR2, while rhHsp70 increased TLR2 and lowered TLR4 gene expression. Hsp70 mRNA expression was suppressed in THP-1 with rhHsp70 and CSE; however, the same treatments increased its level in MDMs. CSE had cytotoxic effect only on MDMs, but cytotoxicity was reduced in co-treatments with rhHsp70, which also triggered apoptosis. CSE and rhHsp70 activated p38 and JNK, while ERK was activated only by rhHsp70 in MDMs. In THP-1, 2.5% CSE activated ERK, and 5% CSE activated p38. Inhibition of NF-κB and JNK in MDMs, and ERK and JNK in THP-1 cells, attenuated IL-8 release after rhHsp70 treatment. In conclusion, rhHsp70 provoked pro-inflammatory effects and could also modulate inflammatory response to CSE on protein and gene expression levels in THP-1 cells and MDMs, which suggests that eHsp70 might be implicated in systemic inflammation induced by cigarette smoke.

Modeling cellular metabolomic effects of oxidative stress impacts from hydrogen peroxide and cigarette smoke on human lung epithelial cells

The respiratory system is continuously exposed to variety of biological and chemical irritants that contain reactive oxygen species, and these are well known to cause oxidative stress responses in lung epithelial cells. There is a clinical need to identify biomarkers of oxidative stress which could potentially support early indicators of disease and health management. To identify volatile biomarkers of oxidative stress, we analyzed the headspace above human bronchial epithelial cell cultures (HBE1) before and after hydrogen peroxide (H₂O₂) and cigarette smoke extract (CSE) exposure. Using stir bar and headspace sorptive extraction-gas chromatography-mass spectrometry, we searched for volatile organic compounds (VOC) of these oxidative measures. In the H₂O₂ cell peroxidation experiments, four different H₂O₂ concentrations (0.1, 0.5, 10, 50 mM) were applied to the HBE1 cells, and VOCs were collected every 12 h over the time course of 48 h. In the CSE cell peroxidation experiments, four different smoke extract concentrations (0%, 10%, 30%, 60%) were applied to the cells, and VOCs were collected every 12 h over the time course of 48 h. We used partial-least squares (PLS) analysis to identify putative compounds from the mass spectrometry results that highly correlated with the known applied oxidative stress. We observed chemical emissions from the cells that related to both the intensity of the oxidative stress and followed distinct time courses. Additionally, some of these chemicals are aldehydes, which are thought to be non-invasive indicators of oxidative stress in exhaled human breath. Together, these results illustrate a powerful in situ cell culture model of oxidative stress that can be used to explore the putative biological genesis of exhaled breath biomarkers that are often observed in human clinical studies.

Cigarette Smoke-Induced Oxidative Stress and Autophagy in Human Alveolar Epithelial Cell Line (A549 Cells)

Chronic exposure to cigarette smoke (CS) causes structural and functional changes in the respiratory tract. It is a major risk factor for cardiovascular and systemic pulmonary diseases. The aim of this study was to investigate the effect of acute CS exposure (2 h) on oxidative stress, heat shock protein 70 (HSP70) expression, autophagy (LC3 expression), and oxidative stress (DCF fluorescence) in human alveolar epithelial cell line A549. Cell culture medium was conditioned with CS using commercial cigarettes, and A549 cells were grown in modified media for 2 h. In some experiments, A549 cells were pretreated with 100 μM of L-buthionine-sulfoximine (BSO) for 24 h to induce glutathione (GSH) depletion. In the cells grown in CS-conditioned medium, GSH was depleted by more than 30%, and reactive oxygen species were increased. Moreover, there was a considerable overexpression of HSP70 and a substantial accumulation of LC3. Similar changes were found when the cells were pretreated with BSO. We conclude that the short-term exposure of epithelial cells to CS increases oxidative stress that entails enhanced autophagy activity.