Direct effects of airborne PM2.5 exposure on macrophage polarizations

BackgroundExposure of atmospheric particulate matter with an aerodynamic diameter less than 2.5 μm (PM_2.5) is epidemiologically associated with illnesses. Potential effects of air pollutants on innate immunity have raised concerns. As the first defense line, macrophages are able to induce inflammatory response. However, whether PM_2.5 exposure affects macrophage polarizations remains unclear.MethodsWe used freshly isolated macrophages as a model system to demonstrate effects of PM_2.5 on macrophage polarizations. The expressions of cytokines and key molecular markers were detected by real-time PCR, and flow cytometry. The specific inhibitors and gene deletion technologies were used to address the molecular mechanisms.ResultsPM_2.5 increased the expression of pro-inflammatory cytokines granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor alpha (TNFα). PM_2.5 also enhanced the lipopolysaccharide (LPS)-induced M1 polarization even though there was no evidence in the change of cell viability. However, PM_2.5 significantly decreased the number of mitochondria in a dose dependent manner. Pre-treatment with NAC, a scavenger of reactive oxygen species (ROS), prevented the increase of ROS and rescued the PM_2.5-impacted M1 but not M2 response. However, mTOR deletion partially rescued the effects of PM_2.5 to reduce M2 polarization.ConclusionsPM_2.5 exposure significantly enhanced inflammatory M1 polarization through ROS pathway, whereas PM_2.5 exposure inhibited anti-inflammatory M2 polarization through mTOR-dependent pathway.General significanceThe present studies suggested that short-term exposure of PM_2.5 acts on the balance of inflammatory M1 and anti-inflammatory M2 macrophage polarizations, which may be involved in air pollution-induced immune disorders and diseases. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.     

Effect of Vitamin E and Omega-3 Fatty Acids on Protecting Ambient PM2.5-Induced Inflammatory Response and Oxidative Stress in Vascular Endothelial Cells

Although the mechanisms linking cardiopulmonary diseases to ambient fine particles (PM_2.5) are still unclear, inflammation and oxidative stress play important roles in PM_2.5-induced injury. It is well known that inflammation and oxidative stress could be restricted by vitamin E (Ve) or omega-3 fatty acids (Ω-3 FA) consumption. This study investigated the effects of Ve and Ω-3 FA on PM_2.5-induced inflammation and oxidative stress in vascular endothelial cells. The underlying mechanisms linking PM_2.5 to vascular endothelial injury were also explored. Human umbilical vein endothelial cells (HUVECs) were treated with 50 μg/mL PM_2.5 in the presence or absence of different concentrations of Ve and Ω-3 FA. The inflammatory cytokines and oxidative stress markers were determined. The results showed that Ve induced a significant decrease in PM_2.5-induced inflammation and oxidative stress. Malondialdehyde (MDA) in supernatant and reactive oxygen species (ROS) in cytoplasm decreased by Ve, while the superoxide dismutase (SOD) activity elevated. The inflammatory cytokines interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α) also reduced by Ve. Moreover, Ω-3 FA played the same role on decreasing the inflammation and oxidative stress. IL-6 and TNF-α expressions were significantly lower in combined Ve with Ω-3 FA than treatment with Ve or Ω-3 FA alone. The Ve and Ω-3 FA intervention might abolish the PM_2.5-induced oxidative stress and inflammation in vascular endothelial cells. There might be an additive effect of these two nutrients in mediating the PM_2.5-induced injury in vascular endothelial cells. The results suggested that inflammation and oxidative stress might be parts of the mechanisms linking PM_2.5 to vascular endothelial injury.     

DDAH1 plays dual roles in PM2.5 induced cell death in A549 cells

BackgroundDimethylarginine dimethylaminohydrolase 1 (DDAH1) is an enzyme that can degrade asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase (NOS) inhibitor. Emerging evidence suggests that alterations in the ADMA–DDAH1 pathway are involved in environmental pollution induced airway inflammation. However, the role of DDAH1 in protection against cytotoxicity of ambient airborne particulate matter is unclear.MethodsWe examined the influence of DDAH1 expression on oxidative stress and cell apoptosis in human type II alveolar epithelial A549 cells exposed to PM_2.5 (particulate matter with an aerodynamic diameter less than 2.5 μM).ResultsWe found that PM_2.5 exposure for 48 h significantly decreased DDAH1 expression. However, knockdown of DDAH1 prior to PM_2.5 exposure actually attenuated the cytotoxicity of PM_2.5. Cytoprotection in DDAH1 deficient cells was due to increased reactive oxygen species, activation of PI3K–AKT and mitogen-activated protein kinase (MAPK) pathways, subsequent activation of nuclear factor erythroid-2-related factor 2 (Nrf2) and this caused a subsequent reduction in PM_2.5 induced oxidative stress relative to control. DDAH1 depletion also repressed the induction of inducible NOS (iNOS) in PM_2.5-exposed cells and knockdown of iNOS protected cells against PM_2.5 induced cell death. Interestingly, overexpression of DDAH1 also exerted a protective effect against the cytotoxicity of PM_2.5 and this was associated with a reduction in oxidative stress and upregulation of the anti-apoptotic protein Bcl-2.ConclusionsOur data indicate that DDAH1 plays dual roles in protection against cytotoxicity of PM_2.5 exposure, apparently by limiting PM_2.5 induced oxidative stress.General significanceOur findings reveal new insights into the role(s) of the DDAH1/ADMA in pulmonary protection against airborne pollutants. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.     

Neuroprotective effects of aucubin on hydrogen peroxide-induced toxicity in human neuroblastoma SH-SY5Y cells via the Nrf2/HO-1 pathway

BackgroundWhen redox balance is lost in the brain, oxidative stress can cause serious damage that leads to neuronal loss, in congruence with neurodegenerative diseases. Aucubin (AU) is an iridoid glycoside and that is one of the active constituents of Eucommia ulmoides, has many pharmacological effects such as anti-inflammation, anti-liver fibrosis, and anti-atherosclerosis.PurposeThe present study aimed to evaluate the inhibitory effects of AU on cell oxidative stress against hydrogen peroxide (H₂O₂)-induced injury in SH-SY5Y cells in vitro.MethodsSH-SY5Y cells were simultaneously treated with AU and H₂O₂ for 24 h. Cell viability was measured by CCK-8. Additionally, mitochondrial membrane depolarization, reactive oxygen species (ROS) generation, and cell apoptosis were measured by flow cytometry.ResultsThe results showed that AU can significantly increase the H₂O₂-induced cell viability and the mitochondrial membrane potential, decrease the ROS generation, malondialdehyde (MDA), and increase glutathione (GSH) contents and the superoxide dismutase (SOD) activity. We also found that H₂O₂ stimulated the production of nitric oxide (NO), which could be reduced by treatment with AU through inhibiting the inducible nitric oxide synthase (iNOS) protein expression. In H₂O₂-induced SH-SY5Y cells, the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) content and cell apoptosis were significantly reduced by AU treatment through nuclear factor E2-related factor 2/hemo oxygenase-1 (Nrf2/HO-1) activation, inhibiting the expression of p-NF-κB/NF-κB and down-regulating MAPK and Bcl-2/Bax pathways.ConclusionThese results indicate that AU can reduce inflammation and oxidative stress through the NF-κB, Nrf2/HO-1, and MAPK pathways.     

Airborne fine particulate matter induces multiple cell death pathways in human lung epithelial cells

Our group was the first one reporting that autophagy could be triggered by airborne fine particulate matter (PM) with a mean diameter of less than 2.5 μm (PM_2.5) in human lung epithelial A549 cells, which could potentially lead to cell death. In the present study, we further explored the potential interactions between autophagy and apoptosis because it was well documented that PM_2.5 could induce apoptosis in A549 cells. Much to our surprise, we found that PM_2.5-exposure caused oxidative stress, resulting in activation of multiple cell death pathways in A549 cells, that is, the tumor necrosis factor-alpha (TNF-α)-induced pathway as evidenced by TNF-α secretion and activation of caspase-8 and -3, the intrinsic apoptosis pathway as evidenced by increased expression of pro-apoptotic protein Bax, decreased expression of anti-apoptotic protein Bcl-2, disruption of mitochondrial membrane potential, and activation of caspase-9 and -3, and autophagy as evidenced by an increased number of double-membrane vesicles, accompanied by increases of conversion and punctuation of microtubule-associated proteins light chain 3 (LC3) and expression of Beclin 1. It appears that reactive oxygen species (ROS) function as signaling molecules for all the three pathways because pretreatment with N-acetylcysteine, a scavenger of ROS, almost completely abolished TNF-α secretion and significantly reduced the number of apoptotic and autophagic cells. In another aspect, inhibiting autophagy with 3-methyladenine, a specific autophagy inhibitor, enhanced PM_2.5-induced apoptosis and cytotoxicity. Intriguingly, neutralization of TNF-α with an anti-TNF-α special antibody not only abolished activation of caspase-8, but also drastically reduced LC3-II conversion. Thus, the present study has provided novel insights into the mechanism of cytotoxicity and even pathogenesis of diseases associated with PM_2.5 exposure.     

Prolonged cigarette smoke exposure alters mitochondrial structure and function in airway epithelial cells

Background

Cigarette smoking is the major risk factor for COPD, leading to chronic airway inflammation. We hypothesized that cigarette smoke induces structural and functional changes of airway epithelial mitochondria, with important implications for lung inflammation and COPD pathogenesis.

Methods

We studied changes in mitochondrial morphology and in expression of markers for mitochondrial capacity, damage/biogenesis and fission/fusion in the human bronchial epithelial cell line BEAS-2B upon 6-months from ex-smoking COPD GOLD stage IV patients to age-matched smoking and never-smoking controls.

Results

We observed that long-term CSE exposure induces robust changes in mitochondrial structure, including fragmentation, branching and quantity of cristae. The majority of these changes were persistent upon CSE depletion. Furthermore, long-term CSE exposure significantly increased the expression of specific fission/fusion markers (Fis1, Mfn1, Mfn2, Drp1 and Opa1), oxidative phosphorylation (OXPHOS) proteins (Complex II, III and V), and oxidative stress (Mn-SOD) markers. These changes were accompanied by increased levels of the pro-inflammatory mediators IL-6, IL-8, and IL-1β. Importantly, COPD primary bronchial epithelial cells (PBECs) displayed similar changes in mitochondrial morphology as observed in long-term CSE-exposure BEAS-2B cells. Moreover, expression of specific OXPHOS proteins was higher in PBECs from COPD patients than control smokers, as was the expression of mitochondrial stress marker PINK1.

Conclusion

The observed mitochondrial changes in COPD epithelium are potentially the consequence of long-term exposure to cigarette smoke, leading to impaired mitochondrial function and may play a role in the pathogenesis of COPD.     

PM2.5 exposure-induced autophagy is mediated by lncRNA loc146880 which also promotes the migration and invasion of lung cancer cells

BackgroundEvidence shows that individuals who are under long-term exposure to environmental PM_2.5 are at increased risk of lung cancer. Various laboratory experiments also suggest several mechanistic links between PM_2.5 exposure and lung carcinogenesis. However, a long non-coding RNA (lncRNA) mediated pathogenic change after PM_2.5 exposure and its potential roles in tumorigenesis and disease progression have not been reported.MethodsCytotoxicity induced by PM_2.5 was assessed by using scanning electron microscopy and transmission electron microscopy. ROS generation, autophagy, and metastasis induced by PM_2.5 were detected by using comprehensive approaches. Expression of lncRNA-loc146880 and lc3b (autophagy marker) in A549 cells, lung tissue and serum were determined by RT-PCR and Western blotting.ResultsPM_2.5 could be internalized into lung cancer cells, resulting in marked increases in ROS levels and autophagy. ROS may be responsible for increased expression of loc146880 which further up-regulates autophagy. Both loc146880 and autophagy could promote lung tumor cell migration, invasion and EMT. In addition, a positive correlation was observed between loc146880 expression and lc3b levels in tumor tissues and serum of lung cancer patients.ConclusionTaken together, our data suggest that PM_2.5 exposure induces ROS, which activates loc146880 expression. The lncRNA, in turn, up-regulates autophagy and promotes the malignant behaviors of lung cancer cells.General significanceThe results show the toxicological effects of PM_2.5 in lung tumor progression and metastasis.     

Constitutive Activation of Epidermal Growth Factor Receptor Promotes Tumorigenesis of Cr(VI)-transformed Cells through Decreased Reactive Oxygen Species and Apoptosis Resistance Development

Hexavalent chromium (Cr(VI)) compounds are well-established lung carcinogens. Epidermal growth factor receptor (EGFR) is a tyrosine kinase transmembrane receptor that regulates cell survival, tumor invasion, and angiogenesis. Our results show that chronic exposure of human bronchial epithelial (BEAS-2B) cells to Cr(VI) is able to cause malignant cell transformation. These transformed cells exhibit apoptosis resistance with reduced poly ADP-ribose polymerase cleavage (C-PARP) and Bax expression and enhanced expressions of Bcl-2 and Bcl-xL. These transformed cells also exhibit reduced capacity of reactive oxygen species (ROS) generation along with elevated expression of antioxidant manganese superoxide dismutase 2 (SOD2). The expression of this antioxidant was also elevated in lung tumor tissue from a worker exposed to Cr(VI) for 19 years. EGFR was activated in Cr(VI)-transformed BEAS-2B cells, lung tissue from animals exposed to Cr(VI) particles, and human lung tumor tissue. Further study indicates that constitutive activation of EGFR in Cr(VI)-transformed cells was due to increased binding to its ligand amphiregulin (AREG). Inhibition of EGFR or AREG increased Bax expression and reduced Bcl-2 expression, resulting in reduced apoptosis resistance. Furthermore, inhibition of AREG or EGFR restored capacity of ROS generation and decreased SOD2 expression. PI3K/AKT was activated, which depended on EGFR in Cr(VI)-transformed BEAS-2B cells. Inhibition of PI3K/AKT increased ROS generation and reduced SOD2 expression, resulting in reduced apoptosis resistance with commitment increase in Bax expression and reduction of Bcl-2 expression. Xenograft mouse tumor study further demonstrates the essential role of EGFR in tumorigenesis of Cr(VI)-transformed cells. In summary, the present study suggests that ligand-dependent constitutive activation of EGFR causes reduced ROS generation and increased antioxidant expression, leading to development of apoptosis resistance, contributing to Cr(VI)-induced tumorigenesis.     

Mitochondrial Complex III-generated Oxidants Activate ASK1 and JNK to Induce Alveolar Epithelial Cell Death following Exposure to Particulate Matter Air Pollution

We have previously reported that airborne particulate matter air pollution (PM) activates the intrinsic apoptotic pathway in alveolar epithelial cells through a pathway that requires the mitochondrial generation of reactive oxygen species (ROS) and the activation of p53. We sought to examine the source of mitochondrial oxidant production and the molecular links between ROS generation and the activation of p53 in response to PM exposure. Using a mitochondrially targeted ratiometric sensor (Ro-GFP) in cells lacking mitochondrial DNA (ρ⁰ cells) and cells stably expressing a small hairpin RNA directed against the Rieske iron-sulfur protein, we show that site III of the mitochondrial electron transport chain is primarily responsible for fine PM (PM_2.5)-induced oxidant production. In alveolar epithelial cells, the overexpression of SOD1 prevented the PM_2.5-induced ROS generation from the mitochondria and prevented cell death. Infection of mice with an adenovirus encoding SOD1 prevented the PM_2.5-induced death of alveolar epithelial cells and the associated increase in alveolar-capillary permeability. Treatment with PM_2.5 resulted in the ROS-mediated activation of the oxidant-sensitive kinase ASK1 and its downstream kinase JNK. Murine embryonic fibroblasts from ASK1 knock-out mice, alveolar epithelial cells transfected with dominant negative constructs against ASK1, and pharmacologic inhibition of JNK with SP600125 (25 μm) prevented the PM_2.5-induced phosphorylation of p53 and cell death. We conclude that particulate matter air pollution induces the generation of ROS primarily from site III of the mitochondrial electron transport chain and that these ROS activate the intrinsic apoptotic pathway through ASK1, JNK, and p53.Epidemiologic studies have consistently demonstrated a strong link between the daily levels of particulate matter air pollution <2.5 μm in diameter (PM_2.5)³ and PM <10 μmin diameter (PM₁₀) and cardiopulmonary morbidity and mortality (1–3). In humans, exposure to PM₁₀ has been associated with an increase in mortality from ischemic cardiovascular events including stroke and myocardial infarction, an acceleration in the age-related decline in lung function in normal adults, impairment in normal lung development in children, exacerbations of asthma in children and adults, accelerated atherosclerosis in women, increased rates of lung cancer, and the development of myocardial ischemia in men with stable coronary artery disease (4–10). The intracellular generation of reactive oxygen species (ROS) has emerged as a common mechanism by which particulates might initiate signaling pathways that end in these diverse pathologic conditions (11). We have reported that the PM-induced generation of ROS requires a functional electron transport chain, suggesting that PM might induce the inadvertent transfer of electrons from one or more sites in the electron transport chain to molecular oxygen (12).One of the mechanisms by which exposure to PM can contribute to alveolar epithelial dysfunction, lung injury and inflammation, and lung cancer is by activating the intrinsic apoptotic pathway to induce cell death (11, 12). We have reported that this process requires the activation of p53; however, the molecular events linking the generation of ROS by the mitochondrial electron transport chain with the activation of p53 are not known (12). In this paper, we show that exposure of alveolar epithelial cells to PM_2.5 induces the generation of ROS from site III of the mitochondrial electron transport chain. These mitochondrially derived oxidants activate the mitogen-activated signaling kinase kinase kinase (MAPKKK) apoptosis signaling kinase 1 (ASK1), which activates the c-Jun N-terminal kinase (JNK) signaling pathway. The activation of JNK is required for the phosphorylation of p53 and the subsequent cell death. Inhibition of mitochondrial oxidant production in mouse lungs prevents PM_2.5-induced cell death and the associated PM_2.5-induced increase in the permeability of the alveolar-capillary barrier.     

The Moraxella catarrhalis-induced pro-inflammatory immune response is enhanced by the activation of the epidermal growth factor receptor in human pulmonary epithelial cells

Background

Chronic lower airway inflammation is considered to be a major cause of pathogenesis and disease progression in chronic obstructive pulmonary disease (COPD). Moraxella catarrhalis is a COPD-associated pathogen causing exacerbations and bacterial colonization in the lower airways of patients, which may contribute to chronic inflammation. Increasing evidence suggests that the epidermal growth factor receptor (EGFR) modulates inflammatory processes in the human airways. The goal of this study was to investigate the role of EGFR in the M. catarrhalis-induced pro-inflammatory immune response in airway epithelial cells.

Methods

The effects of inhibition and gene silencing of EGFR on M. catarrhalis-dependent pro-inflammatory cytokine expression in human primary bronchial epithelial cells (NHBEs), as well as the pulmonary epithelial cell lines BEAS-2B and A549 were analyzed. We also assessed the involvement of EGFR-dependent ERK and NF-κB signaling pathways.

Results

The M. catarrhalis-induced pro-inflammatory immune response depends, at least in part, on the phosphorylation and activation of the EGF receptor. Interaction of M. catarrhalis with EGFR increases the secretion of pro-inflammatory cytokines, which is mediated via ERK and NF-κB activation.

Conclusion

The interaction between M. catarrhalis and EGFR increases airway inflammation caused by this pathogen. Our data suggest that the inhibition of EGFR signaling in COPD could be an interesting target for reducing M. catarrhalis-induced airway inflammation.     

Oxidative stress mediates chemical hypoxia-induced injury and inflammation by activating NF-κb-COX-2 pathway in HaCaT cells

Hypoxia of skin is an important physiopathological process in many diseases, such as pressure ulcer, diabetic ulcer, and varicose ulcer. Although cellular injury and inflammation have been involved in hypoxia-induced dermatic injury, the underlying mechanisms remain largely unknown. This study was conducted to investigate the effects of cobalt chloride (CoCl₂), a hypoxia-mimicking agent, on human skin keratinocytes (HaCaT cells) and to explore the possible molecular mechanisms. Exposure of HaCaT cells to CoCl₂ reduced cell viability and caused overproduction of reactive oxygen species (ROS) and oversecretion of interleukin-6 (IL-6) and interleukin-8 (IL-8). Importantly, CoCl₂ exposure elicited overexpression of cyclooxygenase-2 (COX-2) and phosphorylation of nuclear factor-kappa B (NF-κB) p65 subunit. Inhibition of COX-2 by NS-398, a selective inhibitor of COX-2, significantly repressed the cytotoxicity, as well as secretion of IL-6 and IL-8 induced by CoCl₂. Inhibition of NF-κB by PDTC (a selective inhibitor of NF-κB) or genetic silencing of p65 by RNAi (Si-p65), attenuated not only the cytotoxicity and secretion of IL-6 and IL-8, but also overexpression of COX-2 in CoCl₂-treated HaCaT cells. Neutralizing anti-IL-6 or anti-IL-8 antibody statistically alleviated CoCl₂-induced cytotoxicity in HaCaT cells. N-acetyl-L-cysteine (NAC), a well characterized ROS scavenger, obviously suppressed CoCl₂-induced cytotoxicity in HaCaT cells, as well as secretion of IL-6 and IL-8. Additionally, NAC also repressed overexpression of COX-2 and phosphorylation of NF- B κ p65 subunit induced by CoCl₂ in HaCaT cells. In conclusion, our results demonstrated that oxidative stress mediates chemical hypoxia-induced injury and inflammatory response through activation of NF-κB-COX-2 pathway in HaCaT cells.     

Reactive oxygen species (ROS) reduce the expression of BRAK/CXCL14 in human head and neck squamous cell carcinoma cells

Abstract

The present study investigated the effects of oxidative stress induced by reactive oxygen species (ROS), such as hydrogen peroxide (H₂O₂) and hydroxyl radical (HO^?), on the expression of both BRAK , which is also known as non-ELR motif angiostatic CXC chemokine ligand 14 (CXCL14), in head and neck squamous cell carcinoma (HNSCC) cells. When HNSCC cells were cultured in the presence of ROS, the expression of BRAK was significantly decreased whereas that of IL-8 was increased. Interestingly, the effects on the expression of both genes in HNSCC cells were much greater with HO^? than with H₂O₂. The effects of ROS on both BRAK and IL-8 expression were attenuated by pre-treatment with N-acetyl-L-cysteine (NAC), epidermal growth factor receptor (EGFR), and mitogen-activated protein kinase (MAPK) inhibitors. These results indicate that oxidative stress induced by H₂O₂ or HO^? stimulates angiogenesis and tumuor progression by altering the gene expression of BRAK and IL-8 via the EGFR/MEK/ERK pathway in human HNSCC cells.     

Perilla frutescens Leaf Extract Inhibits Mite Major Allergen Der p 2-induced Gene Expression of Pro-Allergic and Pro-Inflammatory Cytokines in Human Bronchial Epithelial Cell BEAS-2B

Perilla frutescens has been used in traditional medicine for respiratory diseases due to its anti-bacterial and anti-inflammatory activity. This study aimed to investigate effects of Perilla frutescens leaf extract (PFE) on expression of pro-allergic and pro-inflammatory cytokines in airway epithelial cells exposed to mite major allergen Der p 2 (DP2) and the underlying mechanisms. Our results showed that PFE up to 100 µg/mL had no cytotoxic effect on human bronchial epithelial cell BEAS-2B. Further investigations revealed that PFE dose-dependently diminished mRNA expression of pro-allergic cytokine IL-4, IL-5, IL-13 and GM-CSF, as well as pro-inflammatory cytokine IL-6, IL-8 and MCP-1 in BEAS-2B cells treated with DP2. In parallel to mRNA, the DP-2-elevated levels of the tested cytokines were decreased. Further investigation showed that DP2-indued phosphorylation of p38 MAPK (P38) and JNK, but not Erk1/2, was also suppressed by PFE. In addition, PFE elevated cytosolic IκBα level and decreased nuclear NF-κB level in DP2-stimulated BEAS-2B cells. Taken together, these findings revealed that PFE significantly diminished both mRNA expression and protein levels of pro-allergic and pro-inflammatory cytokines in response to DP2 through inhibition of P38/JNK and NK-κB activation. These findings suggest that PFE should be beneficial to alleviate both allergic and inflammatory responses on airway epithelium in response to aeroallergens.     

Association of EGF Receptor and NLRs signaling with Cardiac Inflammation and Fibrosis in Mice Exposed to Fine Particulate Matter

?Ambient fine particulate matter (PM_2.5) could induce cardiovascular diseases (CVD), but the mechanism remains unknown. To investigate the roles of epidermal growth factor receptor (EGFR) and NOD‐like receptors (NLRs) in PM_2.5‐induced cardiac injury, we set up a BALB/c mice model of PM_2.5‐induced cardiac inflammation and fibrosis with intratracheal instillation of PM_2.5 suspension (4.0 mg/kg b.w.) for 5 consecutive days (once per day). After exposure, we found that mRNA levels of CXCL1, interleukin (IL)‐6, and IL‐18 were elevated, but interestingly, mRNA level of NLRP12 was significant decreased in heart tissue from PM_2.5‐induced mice compared with those of saline‐treated mice using real‐time PCR. Protein levels of phospho‐EGFR (Tyr1068), phospho‐Akt (Thr308), NLRP3, NF‐κB‐p52/p100, and NF‐κB‐p65 in heart tissue of PM_2.5‐exposed mice were all significantly increased using immunohistochemistry or Western blotting. Therefore, PM_2.5 exposure could induce cardiac inflammatory injury in mice, which may be involved with EGFR/Akt signaling, NLRP3, and NLRP12.     

The presence of serotonin in cigarette smoke – a possible mechanistic link to 5-HT-induced airway inflammation

We previously reported the involvement of serotonin (5-HT) metabolism in cigarette smoke-induced oxidative stress in rat lung in vivo. Here, we report cigarette smoke as a source of serotonin (5-HT) to the airways and aim at investigating the effects of 5-HT on oxidative stress and inflammation in human bronchial epithelial cells (BEAS-2B). A 5-HT analog was identified to be present in aqueous phase cigarette smoke using the LC-MS/MS approach, which was later confirmed by a 5-HT enzyme-linked immune assay (EIA). Furthermore, exposure to 5-HT caused a time-dependent elevation of intracellular ROS level, which was blocked in the presence of apocynin (a NOX inhibitor). In support, the immunoblot analysis indicated that there was an increase in the expression of NOX2 time-dependently. 5-HT-induced elevation of IL-8 at both mRNA and protein levels was observed, which was inhibited by TEMPOL (a free radical scavenger), and inhibitors for p38 MAPK (SB203580) and ERK (U0126), in line with the time-dependent phosphorylation of p38 MAPK and ERK. In conclusion, our findings suggest that 5-HT presented in bronchial epithelium of smokers may be involved in cigarette smoke-induced oxidative stress and inflammation via activation of p38 MAPK and ERK pathway after the formation of free radicals.