NF-kappaB inhibition is involved in tobacco smoke-induced apoptosis in the lungs of rats

The role of α7-nAChR-mediated PI3K/AKT pathway in lung cancer induced by nicotine

Nicotine enters the environment mainly through human activity, as well as natural sources. This review article examines the increasing evidence implicating nicotine in the initiation and progression of lung cancer. Moreover, it primarily focuses on elucidating the activation mechanism of phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB, also known as AKT) signaling pathway, regulated by α7 subtype nicotinic acetylcholine receptor (α7-nAChR), in relation to the proliferation, invasion, and metastasis of lung cancer cells induced by nicotine, as well as nicotine-mediated anti-apoptotic effects. This process involves PI3K/AKT phosphorylated-B-cell lymphoma-2 (Bcl-2) family proteins, PI3K/AKT/mammalian target of rapamycin (mTOR), PI3K/AKT/nuclear factor-κB (NF-κB), hepatocyte growth factor (HGF)/cellular-mesenchymal epithelial transition factor (c-Met)-induced PI3K/AKT and PI3K/AKT activated-hypoxia-inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) pathways. In addition, we also deliberated on the related challenges and upcoming prospects within this field. These lay the foundation for further study on nicotine, lung tumorigenesis, and PI3K/AKT related molecular mechanisms. This work has the potential to significantly contribute to the treatment and prognosis of gastric cancer in smokers. Besides, the crucial significance of PI3K/AKT signaling pathway in multiple molecular pathways also suggests that its target antagonists may inhibit the development and progression of lung cancer, providing a possible new perspective for solving the problem of nicotine-promoted lung cancer. The emerging knowledge about the carcinogenic mechanisms of nicotine action should be considered during the environmental assessment of tobacco and other nicotine-containing products.

Nicotinic receptors in airway disease

With continued smoking of tobacco products and expanded use of nicotine delivery devices worldwide, understanding the impact of smoking and vaping on respiratory health remains a major global unmet need. Although multiple studies have shown a strong association between smoking and asthma, there is a relative paucity of mechanistic understanding of how elements in cigarette smoke impact the airway. Recognizing that nicotine is a major component in both smoking and vaping products, it is critical to understand the mechanisms by which nicotine impacts airways and promotes lung diseases such as asthma. There is now increasing evidence that α7 nicotinic acetylcholine receptors (α7nAChRs) are critical players in nicotine effects on airways, but the mechanisms by which α7nAChR influences different airway cell types have not been widely explored. In this review, we highlight and integrate the current state of knowledge regarding nicotine and α7nAChR in the context of asthma and identify potential approaches to alleviate the impact of smoking and vaping on the lungs.

Animal models and mechanisms of tobacco smoke-induced chronic obstructive pulmonary disease (COPD)

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide, and its global health burden is increasing. COPD is characterized by emphysema, mucus hypersecretion, and persistent lung inflammation, and clinically by chronic airflow obstruction and symptoms of dyspnea, cough, and fatigue in patients. A cluster of pathologies including chronic bronchitis, emphysema, asthma, and cardiovascular disease in the form of hypertension and atherosclerosis variably coexist in COPD patients. Underlying causes for COPD include primarily tobacco use but may also be driven by exposure to air pollutants, biomass burning, and workplace related fumes and chemicals. While no single animal model might mimic all features of human COPD, a wide variety of published models have collectively helped to improve our understanding of disease processes involved in the genesis and persistence of COPD. In this review, the pathogenesis and associated risk factors of COPD are examined in different mammalian models of the disease. Each animal model included in this review is exclusively created by tobacco smoke (TS) exposure. As animal models continue to aid in defining the pathobiological mechanisms of and possible novel therapeutic interventions for COPD, the advantages and disadvantages of each animal model are discussed.

Cigarette Smoke-Induced Respiratory Response: Insights into Cellular Processes and Biomarkers

Cigarette smoke (CS) poses a significant risk factor for respiratory, vascular, and organ diseases owing to its high content of harmful chemicals and reactive oxygen species (ROS). These substances are known to induce oxidative stress, inflammation, apoptosis, and senescence due to their exposure to environmental pollutants and the presence of oxidative enzymes. The lung is particularly susceptible to oxidative stress. Persistent oxidative stress caused by chronic exposure to CS can lead to respiratory diseases such as chronic obstructive pulmonary disease (COPD), pulmonary fibrosis (PF), and lung cancer. Avoiding exposure to environmental pollutants, like cigarette smoke and air pollution, can help mitigate oxidative stress. A comprehensive understanding of oxidative stress and its impact on the lungs requires future research. This includes identifying strategies for preventing and treating lung diseases as well as investigating the underlying mechanisms behind oxidative stress. Thus, this review aims to investigate the cellular processes induced by CS, specifically inflammation, apoptosis, senescence, and their associated biomarkers. Furthermore, this review will delve into the alveolar response provoked by CS, emphasizing the roles of potential therapeutic target markers and strategies in inflammation and oxidative stress.

Beclin1 Haploinsufficiency accentuates second-hand smoke exposure -induced myocardial Remodeling and contractile dysfunction through a STING-mediated mechanism

Second-hand smoking evokes inflammation and cardiovascular diseases. Recent evidence has revealed a pivotal role for deranged autophagy in smoke exposure-induced cardiac anomalies. This study evaluated the impact of haploinsufficiency of the mTOR-independent autophagy protein Beclin1 on side-stream smoke exposure-induced cardiac anomalies and mechanism(s) involved. Adult WT and Beclin1 haploinsufficiency (Becn^+/-) mice were exposed to cigarette smoke for 1 h daily for 90 days. Echocardiographic, cardiomyocyte function, intracellular Ca²⁺, autophagy, mitophagy, apoptosis and inflammation were examined. DHE staining was employed to evaluate O₂^- level. Our data revealed that Beclin1 deficiency exacerbated smoke exposure-induced myocardial anomalies in geometry, fractional shortening, cardiomyocyte function, intracellular Ca²⁺ handling, TEM ultrastructure, and inflammation along with pronounced apoptosis and O₂^- production. Side-stream smoke provoked excessive autophagy/mitophagy, mtDNA release, and activation of innate immune response signals cyclic GMP-AMP synthase (cGAS) and its effector - stimulator of interferon genes (STING), the effect was abolished or unaffected by Becn haploinsufficiency. STING phosphorylation was overtly promoted by smoke exposure in Becn^+/- mice. Smoke exposure also suppressed phosphorylation of mTOR although it facilitated that of ULK1 in both groups. In vitro data revealed that inhibition of cGAS or STING failed to affect smoke extract-induced mitophagy although they abrogated smoke extract-induced cardiomyocyte dysfunction except cGAS inhibition in Becn^+/- mice. These data suggest that Beclin1 is integral in the maintenance of cardiac homeostasis under side-stream smoke exposure via a STING-mediated mechanism.

Immunopathogenesis and therapeutic potential of macrophage influx in diffuse parenchymal lung diseases

INTRODUCTION

The diffuse parenchymal lung diseases (DPLD)/interstitial lung diseases (ILD) are progressive lung disorders with usually unclear etiology, poor long-term survival and no effective treatment. Their pathogenesis is characterized by alveolar epithelial cell injury, inflammation, epithelial-mesenchymal transition, and parenchymal fibrosis. Macrophages play diverse roles in their development, both in the acute phase and in tissue repair.

AREAS COVERED

In this review, we summarize the current state of knowledge regarding the role of macrophages and their phenotypes in the immunopathogenesis of DPLDs; CVD-ILD, UIP, NSIP, DIP, RB-ILD, AIP, HP, Sarcoidosis, etc. Our goal is to update the understanding of the immune mechanisms underlying the initiation and progression of fibrosis in DPLDs. This will help in identification of biomarkers and in developing novel therapeutic strategies for DPLDs. A thorough literature search of the published studies in PubMed (from 1975 to 2020) was done.

EXPERT OPINION

The macrophage associated inflammatory markers needs to be explored for their potential as biomarkers of disease activity and progression. Pharmacological targeting of macrophage activation may reduce the risk of macrophage activation syndrome (MAS) and help improving the survival and prognosis of these patients.

Knockout of macrophage migration inhibitory factor accentuates side-stream smoke exposure-induced myocardial contractile dysfunction through dysregulated mitophagy

Second hand smoke exposure increases the prevalence of chronic diseases partly attributed to inflammatory responses. Macrophage migration inhibitory factor (MIF), a proinflammatory cytokine, is involved in the pathogenesis of multiple diseases although its role in second hand smoke exposure-induced cardiac anomalies remains elusive. This study evaluated the impact of MIF knockout on side-stream smoke exposure-induced cardiac pathology and underlying mechanisms. Adult WT and MIF knockout (MIFKO) mice were placed in a chamber exposed to cigarette smoke for 1 h daily for 60 consecutive days. Echocardiographic, cardiomyocyte function and intracellular Ca²⁺ handling were evaluated. Autophagy, mitophagy and apoptosis were examined using western blot. DHE staining was used to evaluate superoxide anion (O₂^-) generation. Masson trichrome staining was employed to assess interstitial fibrosis. Our data revealed that MIF knockout accentuated side-stream smoke-induced cardiac anomalies in fractional shortening, cardiomyocyte function, intracellular Ca²⁺ homeostasis, myocardial ultrastructure and mitochondrial content along with overt apoptosis and O₂^- generation. In addition, unfavorable effects of side-stream smoke were accompanied by excessive formation of autophagolysosome and elevated TFEB, the effect of which was exacerbated by MIF knockout. Recombinant MIF rescued smoke extract-induced myopathic anomalies through promoting AMPK activation, mitophagy and lysosomal function. Taken together, our data suggest that MIF serves as a protective factor against side-stream smoke exposure-induced myopathic changes through facilitating mitophagy and autophagolysosome formation.

In-Depth Characterization of the Effects of Cigarette Smoke Exposure on the Acute Trauma Response and Hemorrhage in Mice

INTRODUCTION

Hemorrhagic shock accounts for a large amount of trauma-related mortality. The severity of trauma can be further aggravated by an additional blunt chest trauma (TxT), which independently contributes to mortality upon the development of an acute lung injury (ALI). Besides, cigarette smoke (CS) exposure before TxT enhanced posttraumatic inflammation, thereby aggravating ALI. We therefore aimed to characterize the impact of an acute and/or chronic lung injury on organ dysfunction in a murine model of traumatic hemorrhagic shock (HS).

METHODS

After 3 weeks of CS exposure, anesthetized mice underwent HS with/without TxT. Hemorrhagic shock was implemented for 1 h followed by retransfusion of shed blood and intensive care therapy for 4 h including lung-protective mechanical ventilation, fluid resuscitation, and noradrenaline titrated to maintain mean arterial pressure ≥50 mmHg. Lung mechanics and gas exchange were assessed together with systemic hemodynamics, metabolism, and acid-base status. Postmortem blood and tissue samples were analyzed for cytokine and chemokine levels, protein expression, mitochondrial respiration, and histological changes.

RESULTS

CS exposure and HS alone coincided with increased inflammation, decreased whole blood sulfide concentrations, and decreased diaphragmatic mitochondrial respiration. CS-exposed mice, which were subjected to TxT and subsequent HS, showed hemodynamic instability, acute kidney injury, and high mortality.

CONCLUSIONS

Chronic CS exposure per se had the strongest impact on inflammatory responses. The degree of inflammation was similar upon an additional TxT, however, mice presented with organ dysfunction and increased mortality rates. Hence, in mice the degree of inflammation may be dissociated from the severity of organ dysfunction or injury.

Cigarette Smoking-Mediated Macrophage Reprogramming: Mechanistic Insights and Therapeutic Implications

Macrophages, the mature form of the monocytes, play a significant role in tissue homeostasis and immunity. In response to environmental cues, they can undergo classical or alternative activation, polarizing into specialized functional subsets. A common hallmark of the pathologic environment is represented by cigarette smoking. Although the contribution of cigarette smoke to various cellular processes has been extensively studied, its roles in macrophage polarization have been conflicting. This review discusses the molecular and functional differences of cigarette smoke-exposed macrophages that exist between pro-inflammatory and anti-inflammatory states. We also highlight the most recent advances in therapeutic potential of targeting signaling molecules associated with smoking to modulate macrophage plasticity and polarized activation.

Tandem mass tags labeled quantitative proteomics to study the effect of tobacco smoke exposure on the rat lung

BACKGROUND

The causal link between tobacco smoke exposure (TSE) and numerous severe respiratory system diseases (RSD), including chronic bronchitis, chronic obstructive pulmonary disease, and lung cancer, is well established. However, the pathogenesis of TSE-induced RSD remains incompletely understood. This research aims to detect the pathogenetic mechanisms and potential therapeutic targets of TSE-induced RSD.

METHODS

This study employed TSE model which rats were exposed to a concentration of 60% tobacco smoke in a toxicant exposure system for four weeks. Tandem mass tags (TMT) labeled quantitative proteomics combined with off-line high pH reversed-phase fractionation, and nano-liquid chromatography-mass spectrometry method (off-line high pH RPF-nano-LC-MS/MS) were adopted to detect differentially expressed proteins (DEPs) in the lung tissues of the TSE model rats and to compare them with those in control. The accuracy of the results was verified by western blot.

RESULTS

Compared with the control group, 33 proteins in the TSE model group's lung tissues showed significant differential expression. Analysis based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways indicated that, several biological pathways, such as the steroid biosynthesis pathway, were involved and played significant roles in the pathogenesis of the experimental group's TSE.

CONCLUSIONS

These findings make a crucial contribution to the search for a comprehensive understanding of TSE-induced RSD's pathogenesis, and furthermore provide guidance for the diagnosis and treatment of TSE-induced RSD.

PM2.5 obtained from urban areas in Beijing induces apoptosis by activating nuclear factor-kappa B

BACKGROUND

Particulate matter (PM), which has adverse effects on citizen health, is a major air pollutant in Beijing city. PM_2.5 is an indicator of PM in urban areas and can cause serious damage to human health. Many epidemiological studies have shown that nuclear factor-kappa B (NF-κB) is involved in PM_2.5-induced cell injury, but the exact mechanisms are not well understood.

METHODS

The cytotoxic effects of PM_2.5 at 25-1600 μg/ml for 24 h were determined by MTT assay in Chinese hamster ovary cells (CHO) cells. Flow cytometry was used to determine the apoptosis rate induced by PM_2.5. The destabilized enhanced green fluorescent protein (d2EGFP) green fluorescent protein reporter system was used to determine the NF-κB activity induced by PM_2.5. The expression of pro-apoptotic Bcl-2-associated death promoter (BAD) proteins induced by PM_2.5 was determined by western blotting to explore the relationship between PM_2.5 and the NF-κB signaling pathway and to determine the toxicological mechanisms of PM_2.5.

RESULTS

PM_2.5 collected in Beijing urban districts induces cytotoxic effects in CHO cells according to MTT assay with 72.28% cell viability rates even at 200 μg/ml PM_2.5 and flow cytometry assays with 26.97% apoptosis rates at 200 μg/ml PM_2.5. PM_2.5 increases the activation levels of NF-κB, which have maintained for 24 h. 200 μg/ml PM_2.5 cause activation of NF-κB after exposure for 4 h, the activation peak appears after 13.5 h with a peak value of 25.41%. The average percentage of NF-κB activation in whole 24 h is up to 12.9% by 200 μg/ml PM_2.5. In addition, PM_2.5 decreases the expression level of the pro-apoptotic protein BAD in a concentration-dependent manner.

CONCLUSIONS

PM_2.5 induces NF-κB activation, which persists for 24 h. The expression of pro-apoptotic protein BAD decreased with increased concentrations of PM_2.5. These findings suggest that PM_2.5 plays a major role in apoptosis by activating the NF-κB signaling pathway and reducing BAD protein expression.

Sex and strain-based inflammatory response to repeated tobacco smoke exposure in spontaneously hypertensive and Wistar Kyoto rats

CONTEXT

Approximately four million people die every year from chronic obstructive pulmonary disease (COPD), with more than 80% of the cases attributed to smoking.

OBJECT

The purpose of this study was to examine the rat strain and sex-related differences and the extended tobacco smoke exposure to induce lung injury and inflammation with the goal of finding a suitable rodent model to study COPD.

METHODS

Male and female spontaneously hypertensive (SH) and male Wistar Kyoto (WKY) rats were exposed to filtered air (FA) or to tobacco smoke (TS: 90 mg/m3 particulate concentration) for 6 h/day, three days/week for 4 or 12 weeks.

RESULTS

Male SH rats demonstrated an enhanced, persistent inflammatory response compared to female SH and male WKY rats with extended TS exposure. Following four weeks of TS exposure, male SH rats had significantly increased total leukocytes and macrophage numbers, levels of TNF-alpha and elevated lactate dehydrogenase activity in bronchoalveolar lavage fluid compared with female SH, male WKY rats and corresponding controls. After 12 weeks of TS exposure, male SH rats continued to show significant increase in inflammatory cells and TNF-alpha, as well as IL-6 mRNA lung expression. In addition, the alveolar airspace of male SH rats exposed to TS was significantly enlarged compared to their FA controls, female SH and WKY rats.

CONCLUSION

The male SH rat demonstrates greater cellular, inflammatory and structural changes highly reminiscent of COPD compared to female SH and male WKY rats, suggesting that the male SH rat is an optimal rodent model to study COPD.

Temporal and Spatial Expression of Transforming Growth Factor-β after Airway Remodeling to Tobacco Smoke in Rats

Airway remodeling is strongly correlated with the progression of chronic obstructive pulmonary disease (COPD). In this study, our goal was to characterize progressive structural changes in site-specific airways, along with the temporal and spatial expression of transforming growth factor (TGF)-β in the lungs of male spontaneously hypertensive rats exposed to tobacco smoke (TS). Our studies demonstrated that TS-induced changes of the airways is dependent on airway generation and exposure duration for proximal, midlevel, and distal airways. Stratified squamous epithelial cell metaplasia was evident in the most proximal airways after 4 and 12 weeks but with minimal levels of TGF-β-positive epithelial cells after only 4 weeks of exposure. In contrast, epithelial cells in midlevel and distal airways were strongly TGF-β positive at both 4 and 12 weeks of TS exposure. Airway smooth muscle volume increased significantly at 4 and 12 weeks in midlevel airways. Immunohistochemistry of TGF-β was also found to be significantly increased at 4 and 12 weeks in lymphoid tissues and alveolar macrophages. ELISA of whole-lung homogenate demonstrated that TGF-β2 was increased after 4 and 12 weeks of TS exposure, whereas TGF-β1 was decreased at 12 weeks of TS exposure. Airway levels of messenger RNA for TGF-β2, as well as platelet-derived growth factor-A, granulocyte-macrophage colony-stimulating factor, and vascular endothelial growth factor-α, growth factors regulated by TGF-β, were significantly decreased in animals after 12 weeks of TS exposure. Our data indicate that TS increases TGF-β in epithelial and inflammatory cells in connection with airway remodeling, although the specific role of each TGF-β isoform remains to be defined in TS-induced airway injury and disease.

Involvement of B-cell CLL/lymphoma 2 promoter methylation in cigarette smoke extract-induced emphysema

Abnormal apoptotic events play an important role in the pathogenesis of emphysema. The B-cell CLL/lymphoma 2 (Bcl-2) family proteins are essential and critical regulators of apoptosis. We determined whether the anti-apoptotic Bcl-2 play a role in the cigarette smoke extract (CSE)-induced emphysema. Furthermore, given the involvement of epigenetics in chronic obstructive pulmonary disease, we hypothesized that the deregulation of Bcl-2 might be caused by gene methylation. The emphysema in BALB/C mice was established by intraperitoneally injection of CSE. 5-aza-2'-deoxycytidine (AZA; a demethylation reagent) and phosphate-buffered saline were also administered intraperitoneally as CSE. TUNEL assay was used to assess apoptotic index of pulmonary cells. The methylation status of CpG dinucleotides within the Bcl-2 promoter was observed in all groups by bisulfite sequencing PCR. Pulmonary expression of Bcl-2, Bax, and cytochrome C were measured after four weeks of treatment. The apoptotic index of pulmonary cells in CSE injection group was much higher than control ((25.88 ± 7.55)% vs (6.28 ± 2.96)%). Compared to control mice, decreased expression of Bcl-2 and high methylation of Bcl-2 promoter was observed in CSE injected mice (0.88 ± 0.08 vs 0.49 ± 0.11, (3.82 ± 1.34)% vs (35.68 ± 5.99)%, P < 0.01).CSE treatment induced lung cell apoptosis and decreased lung function. AZA treatment increased Bcl-2 expression with Bcl-2 promoter demethylation. AZA also alleviated the lung cell apoptosis and function failure caused by CSE treatment. The decreased expression of anti-apoptotic Bcl-2 might account for the increased apoptosis in CSE induced-emphysema. Apparently, epigenetic alternation played a role in this deregulation of Bcl-2 expression, and it might support the involvement of epigenetic events in the pathogenesis of emphysema.

Deficiency in adiponectin exaggerates cigarette smoking exposure-induced cardiac contractile dysfunction: Role of autophagy

Second hand smoke is an independent risk factor for cardiovascular disease. Adiponectin (APN), an adipose-derived adipokine, has been shown to offer cardioprotective effect through an AMPK-dependent manner. This study was designed to evaluate the impact of adiponectin deficiency on second hand smoke-induced cardiac pathology and underlying mechanisms using a mouse model of side-stream smoke exposure. Adult wild-type (WT) and adiponectin knockout (APNKO) mice were placed in a chamber exposed to cigarette smoke for 1 hour daily for 40 days. Echocardiographic, cardiomyocyte function, and intracellular Ca2+ handling were evaluated. Autophagy and apoptosis were examined using western blot. 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA) staining was used to evaluate reactive oxygen species (ROS) generation. Masson trichrome staining was employed to measure interstitial fibrosis. Our data revealed that adiponectin deficiency provoked smoke exposure-induced cardiomyopathy (compromised fractional shortening, disrupted cardiomyocyte function and intracellular Ca2+ homeostasis, apoptosis and ROS generation). In addition, these detrimental effects of side-stream smoke were accompanied by defective autophagolysosome formation, the effect of which was exacerbated by adiponectin deficiency. Blocking autophagolysosome formation using bafilomycin A1 (BafA1) negated the cardioprotective effect of rapamycin against smoke extract. Induction of autophagy using rapamycin and AMPKα activation using AICAR rescued against smoke extract-induced myopathic anomalies in APNKO mice. Our data suggest that adiponectin serves as an indispensable cardioprotective factor against side-stream smoke exposure-induced myopathic changes possibly through facilitating autophagolysosome formation.

Combined effects of fine particulate matter and lipopolysaccharide on apoptotic responses in NR8383 macrophages

Alveolar macrophages (AM) are the predominant lung cells responsible for both ingestion and clearance of inhaled particulate matter (PM). The aims of this study were (1) to examine effects of fine PM on rat NR8383 cell line apoptosis, and (2) to determine whether NR8383 cell functions are further affected when exposed to fine PM in the presence of inflammation induced by lipopolysaccharide (LPS). Standard Reference Material 2786 (SRM 2786) for fine PM was used to measure the following parameters: cytotoxicity, apoptotic rate, Bax/Bcl-2 expression, nitric oxide (NO) production, and reactive oxygen species (ROS) generation in NR8383 cells. Data showed that SRM 2786 alone induced damage and apoptosis in NR8383 cells in a concentration-dependent manner as demonstrated by significant decrease in expression of Bcl-2 and increase in expression of Bax, suggesting fine PM might trigger apoptosis involving a mitochondria-mediated apoptotic pathway. In addition, there was elevated production of free radicals, such as NO and ROS, suggesting oxidative stress plays a role in the observed apoptotic responses. Further, LPS pretreatment enhanced apoptosis of NR8383 cells induced by SRM 2786. Consequently, data indicate that SRM 2786 triggered cell apoptosis in NR8383 cells, probably by mechanisms involving oxidative stress, as evidenced by elevated NO and ROS levels, while the degree of apoptosis was further aggravated by inflammation.

Cigarette smoking promotes inflammation in patients with COPD by affecting the polarization and survival of Th/Tregs through up-regulation of muscarinic receptor 3 and 5 expression

Background

CD4⁺ T cells in the lung are involved in the pathogenesis of chronic obstructive pulmonary disease (COPD), although CD4⁺ T cell subsets and the direct effect of smoking on these cells, especially the expression of MRs, have not been comprehensively examined.

Methods

First, circulating CD4⁺ T cell subsets in healthy nonsmokers, patients with SCOPD and patients with AECOPD were evaluated by flow cytometry. Then, differentiation experiments were carried out using RT-PCR, and Ki-67/Annexin V antibodies were used to measure proliferation and apoptosis. We also explored the impact of CSE on the differentiation and survival of CD4⁺Th/Tregs and examined the expression of MRs in healthy nonsmokers and patients with SCOPD.

Results

We found the percentages of circulating Th1 and Th17 cells were increased in patients with AECOPD, while the percentage of Th2 cells was decreased in patients with SCOPD. The percentages of Th10 cells were decreased in both patients with SCOPD and patients with AECOPD, while the percentages of Tregs were increased. In addition, the percentages of CD4⁺α-7⁺ T cells were decreased in patients with SCOPD and patients with AECOPD. However, only the decrease observed in patients with AECOPD was significant. In vitro studies also revealed MR expression affected the polarization of T cells, with different CD4⁺ T cell subtypes acquiring different MR expression profiles. The addition of CSE facilitated CD4⁺ T cell polarization towards pro-inflammatory subsets (Th1 and Th17) and affected the survival of CD4⁺ T cells and Treg cells by up-regulating the expression of MR3 and 5, resulting in an imbalance of CD4⁺ T cell subsets.

Conclusions

Our findings suggest an imbalance of circulating CD4⁺ T cell subsets is involved in COPD pathogenesis in smokers. Cigarette smoking may contribute to this imbalance by affecting the polarization and survival of Th/Tregs through the up-regulation of MR3 and MR5.

Simvastatin inhibits smoke-induced airway epithelial injury: implications for COPD therapy

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death. The statin drugs may have therapeutic potential in respiratory diseases such as COPD, but whether they prevent bronchial epithelial injury is unknown. We hypothesised that simvastatin attenuates acute tobacco smoke-induced neutrophilic lung inflammation and airway epithelial injury. Spontaneously hypertensive rats were given simvastatin (20 mg·kg(-1) i.p.) daily for either 7 days prior to tobacco smoke exposure and during 3 days of smoke exposure, or only during tobacco smoke exposure. Pretreatment with simvastatin prior to and continued throughout smoke exposure reduced the total influx of leukocytes, neutrophils and macrophages into the lung and airways. Simvastatin attenuated tobacco smoke-induced cellular infiltration into lung parenchymal and airway subepithelial and interstitial spaces. 1 week of simvastatin pretreatment almost completely prevented smoke-induced denudation of the airway epithelial layer, while simvastatin given only concurrently with the smoke exposure had no effect. Simvastatin may be a novel adjunctive therapy for smoke-induced lung diseases, such as COPD. Given the need for statin pretreatment there may be a critical process of conditioning that is necessary for statins' anti-inflammatory effects. Future work is needed to elucidate the mechanisms of this statin protective effect.

Cigarette smoke induced airway inflammation is independent of NF-κB signalling

RATIONALE

COPD is an inflammatory lung disease largely associated with exposure to cigarette smoke (CS). The mechanism by which CS leads to the pathogenesis of COPD is currently unclear; it is known however that many of the inflammatory mediators present in the COPD lung can be produced via the actions of the transcription factor Nuclear Factor-kappaB (NF-κB) and its upstream signalling kinase, Inhibitor of κB kinase-2 (IKK-2). Therefore the NF-κB/IKK-2 signalling pathway may represent a therapeutic target to attenuate the inflammation associated with COPD.

AIM

To use a range of assays, genetically modified animals and pharmacological tools to determine the role of NF-κB in CS-induced airway inflammation.

METHODS

NF-κB pathway activation was measured in pre-clinical models of CS-induced airway inflammation and in human lung tissue from COPD patients. This data was complemented by employing mice missing a functional NF-κB pathway in specific cell types (epithelial and myeloid cells) and with systemic inhibitors of IKK-2.

RESULTS

We showed in an airway inflammation model known to be NF-κB-dependent that the NF-κB pathway activity assays and modulators were functional in the mouse lung. Then, using the same methods, we demonstrated that the NF-κB pathway appears not to play an important role in the inflammation observed after exposure to CS. Furthermore, assaying human lung tissue revealed that in the clinical samples there was also no increase in NF-κB pathway activation in the COPD lung, suggesting that our pre-clinical data is translational to human disease.

CONCLUSIONS

In this study we present compelling evidence that the IKK-2/NF-κB signalling pathway does not play a prominent role in the inflammatory response to CS exposure and that this pathway may not be important in COPD pathogenesis.

Characteristic comparison of three rat models induced by cigarette smoke or combined with LPS: to establish a suitable model for study of airway mucus hypersecretion in chronic obstructive pulmonary disease

There is a need of in vivo COPD models for mucus hypersecretion study. The current study compared three rat models induced by cigarette smoke (CS) exposure alone or combined with pre- or post-treatment with lipopolysaccharide (LPS). Forty rats were randomly divided into the four following groups: control group, LPS + CS group (CS exposure for 4-wk combined with LPS pretreatment), CS group (CS exposure for 6-wk), CS + LPS group (CS exposure for 6-wk combined with LPS post-treatment). The results showed that both CS and CS + LPS groups had more severe pro-inflammatory cytokines secretion, inflammatory cells infiltration, and emphysema as compared to that in LPS + CS group animals. From the PAS staining sections, we found a remarkable hyperplasia of goblet-cell in epitheliums of trachea, bronchi, and bronchiole of all of three modeling groups, especially in CS and CS + LPS groups. From the western-blotting results, there were significant increase in the activities of NF-κB, AP-1, EGFR, TLR4, and MAPKs in all of three modeling groups, while HDAC2 activity was remarkably repressed in CS group only. Moreover, the expression and secretion of MUC5AC were exhibited significant increase in all of three modeling groups, which correlated well with the total transcription activity integration of NF-κB, AP-1, and HDAC2 (r = 0.946, p < 0.01). These results indicated that MUC5AC hypersecretion is consistent with activation of EGFR-AP-1/NF-κB and TLR4-AP-1/NF-κB signaling pathways, as well as repression of HDAC2 activity. Based on these results, we speculated that the 6-wk CS exposure rat model is a reliable COPD rat model, while the 6-wk CS exposure combined with LPS post-treatment rat model is a suitable COPD exacerbation model for mucus hypersecretion study.

Use of a soluble epoxide hydrolase inhibitor in smoke-induced chronic obstructive pulmonary disease

Tobacco smoke-induced chronic obstructive pulmonary disease (COPD) is a prolonged inflammatory condition of the lungs characterized by progressive and largely irreversible airflow limitation attributable to a number of pathologic mechanisms, including bronchitis, bronchiolitis, emphysema, mucus plugging, pulmonary hypertension, and small-airway obstruction. Soluble epoxide hydrolase inhibitors (sEHIs) demonstrated anti-inflammatory properties in a rat model after acute exposure to tobacco smoke. We compared the efficacy of sEHI t-TUCB (trans-4-{4-[3-(4-trifluoromethoxy-phenyl)-ureido]-cyclohexyloxy}-benzoic acid) and the phosphodiesterase-4 (PDE4) inhibitor Rolipram (Biomol International, Enzo Life Sciences, Farmingdale, NY) to reduce lung injury and inflammation after subacute exposure to tobacco smoke over a period of 4 weeks. Pulmonary physiology, bronchoalveolar lavage, cytokine production, and histopathology were analyzed to determine the efficacy of sEHI and Rolipram to ameliorate tobacco smoke-induced inflammation and injury in the spontaneously hypertensive rat. Both t-TUCB and Rolipram inhibited neutrophil elevation in bronchoalveolar lavage. sEHI t-TUCB suppressed IFN-γ, while improving lung function by reducing tobacco smoke-induced total respiratory resistance and tissue damping (small-airway and peripheral tissue resistance). Increases in tobacco smoke-induced alveolar airspace size were attenuated by t-TUCB. Rolipram inhibited the production of airway mucus. Both t-TUCB and Rolipram inhibited vascular remodeling-related growth factor. These findings suggest that sEHI t-TUCB has therapeutic potential for treating COPD by improving lung function and attenuating the lung inflammation and emphysematous changes caused by tobacco smoke. To the best of our knowledge, this is the first report to demonstrate that sEHI exerts significant protective effects after repeated, subacute tobacco smoke-induced lung injury in a rat model of COPD.

Leukocytes are recruited through the bronchial circulation to the lung in a spontaneously hypertensive rat model of COPD

Chronic obstructive pulmonary disease (COPD) kills approximately 2.8 million people each year, and more than 80% of COPD cases can be attributed to smoking. Leukocytes recruited to the lung contribute to COPD pathology by releasing reactive oxygen metabolites and proteolytic enzymes. In this work, we investigated where leukocytes enter the lung in the early stages of COPD in order to better understand their effect as a contributor to the development of COPD. We simultaneously evaluated the parenchyma and airways for neutrophil accumulation, as well as increases in the adhesion molecules and chemokines that cause leukocyte recruitment in the early stages of tobacco smoke induced lung disease. We found neutrophil accumulation and increased expression of adhesion molecules and chemokines in the bronchial blood vessels that correlated with the accumulation of leukocytes recovered from the lung. The expression of adhesion molecules and chemokines in other vascular beds did not correlate with leukocytes recovered in bronchoalveolar lavage fluid (BALF). These data strongly suggest leukocytes are recruited in large measure through the bronchial circulation in response to tobacco smoke. Our findings have important implications for understanding the etiology of COPD and suggest that pharmaceuticals designed to reduce leukocyte recruitment through the bronchial circulation may be a potential therapy to treat COPD.

Hydrogen inhalation reduced epithelial apoptosis in ventilator-induced lung injury via a mechanism involving nuclear factor-kappa B activation

We recently demonstrated the inhalation of hydrogen gas, a novel medical therapeutic gas, ameliorates ventilator-induced lung injury (VILI); however, the molecular mechanisms by which hydrogen ameliorates VILI remain unclear. Therefore, we investigated whether inhaled hydrogen gas modulates the nuclear factor-kappa B (NFκB) signaling pathway. VILI was generated in male C57BL6 mice by performing a tracheostomy and placing the mice on a mechanical ventilator (tidal volume of 30 ml/kg or 10 ml/kg without positive end-expiratory pressure). The ventilator delivered either 2% nitrogen or 2% hydrogen in balanced air. NFκB activation, as indicated by NFκB DNA binding, was detected by electrophoretic mobility shift assays and enzyme-linked immunosorbent assay. Hydrogen gas inhalation increased NFκB DNA binding after 1h of ventilation and decreased NFκB DNA binding after 2h of ventilation, as compared with controls. The early activation of NFκB during hydrogen treatment was correlated with elevated levels of the antiapoptotic protein Bcl-2 and decreased levels of Bax. Hydrogen inhalation increased oxygen tension, decreased lung edema, and decreased the expression of proinflammatory mediators. Chemical inhibition of early NFκB activation using SN50 reversed these protective effects. NFκB activation and an associated increase in the expression of Bcl-2 may contribute, in part, to the cytoprotective effects of hydrogen against apoptotic and inflammatory signaling pathway activation during VILI.

Effect of passive smoking on blood lymphocyte apoptosis in children

BACKGROUND

Passive smoking is a well-known risk factor for both recurrent respiratory infections and disturbed lipid profile. Whether passive smoking problems are related to altered lymphocyte survival and its relation to altered lipid profile are the points of concern in this work.

MATERIALS AND METHODS

Urinary cotinine and creatinine levels as well as lipid profile and flow cytometric assessment of apoptosis of peripheral blood lymphocytes (PBL) were assessed in 26 children with history of indoor exposure to cigarette smokers in comparison with 14 matched children with no such history.

RESULTS

Lipid profile showed significantly higher mean levels of triglycerides, cholesterol and low-density lipoprotein (LDL) and significantly lower mean levels of high-density lipoprotein (HDL) in passive smoking children compared to nonpassive-smoking ones. Furthermore, cotinine parameters were positively correlated with triglycerides and LDL and negatively correlated with HDL. Early apoptosis of PBL was significantly higher in exposed vs nonexposed ones.

CONCLUSIONS

Passive smoking in children could be a risk factor for enhanced lymphocytic apoptosis. It is possible that altered lipid profile may play a role in the increased risk. The impact of this lymphocytic derangement on increased frequency of infections is noticeable.

Lung injury after cigarette smoking is particle related

The specific component responsible and the mechanistic pathway for increased human morbidity and mortality after cigarette smoking are yet to be delineated. We propose that 1) injury and disease following cigarette smoking are associated with exposure to and retention of particles produced during smoking and 2) the biological effects of particles associated with cigarette smoking share a single mechanism of injury with all particles. Smoking one cigarette exposes the human respiratory tract to between 15,000 and 40,000 μg particulate matter; this is a carbonaceous product of an incomplete combustion. There are numerous human exposures to other particles, and these vary widely in composition, absolute magnitude, and size of the particle. Individuals exposed to all these particles share a common clinical presentation with a loss of pulmonary function, increased bronchial hyperresponsiveness, pathologic changes of emphysema and fibrosis, and comorbidities, including cardiovascular disease, cerebrovascular disease, peripheral vascular disease, and cancers. Mechanistically, all particle exposures produce an oxidative stress, which is associated with a series of reactions, including an activation of kinase cascades and transcription factors, release of inflammatory mediators, and apoptosis. If disease associated with cigarette smoking is recognized to be particle related, then certain aspects of the clinical presentation can be predicted; this would include worsening of pulmonary function and progression of pathological changes and comorbidity (eg, emphysema and carcinogenesis) after smoking cessation since the particle is retained in the lung and the exposure continues.

Inhibition by cigarette smoke of nuclear factor-κB-dependent response to bacteria in the airway

Although individuals exposed to cigarette smoke are more susceptible to respiratory infection, the effects of cigarette smoke on pulmonary defense are incompletely understood. Based on the observation that interactions between bacteria and host cells result in the expression of critical defense genes regulated by NF-κB, we hypothesized that cigarette smoke alters NF-κB function. In this study, primary human tracheobronchial epithelial cells were treated with cigarette smoke extract (CSE) and exposed to Haemophilus influenzae, and the effects of CSE on bacteria-induced signaling and gene expression were assessed. CSE inhibited high concentrations of induced NF-κB activation and the consequent expression of defense genes that occurred in airway epithelial cells in response to H. influenzae. This decreased activation of NF-κB was not attributable to cell loss or cytotoxicity. Glutathione augmentation of epithelial cells decreased the effects of CSE on NF-κB-dependent responses, as well as the effects on the inhibitor of κB and the inhibitor of κB kinase, which are upstream NF-κB regulators, suggesting the involvement of reactive oxygen species. The relevance of these findings for lung infection was confirmed using a mouse model of H. influenzae airway infection, in which decreased NF-κB pathway activation, keratinocyte chemoattractant (KC) chemokine expression, and neutrophil recruitment occurred in animals exposed to cigarette smoke. The results indicate that although cigarette smoke can cause inflammation in the lung, exposure to smoke inhibits the robust pulmonary defense response to H. influenzae, thereby providing one explanation for the increased susceptibility to respiratory bacterial infection in individuals exposed to cigarette smoke.

A further review of inhalation studies with cigarette smoke and lung cancer in experimental animals, including transgenic mice

CONTEXT

The lack of an effective animal model for pulmonary carcinogenesis in smokers is a continuing problem for researchers trying to design Potentially Reduced Risk Products for those smokers who are either unwilling or unable to quit smoking. The major failing of inhalation assays with cigarette smoke in laboratory animals is that these assays produce only small percentages of animals with pulmonary tumors (e.g. adenomas, with the occasional adenocarcinoma), as opposed to the highly invasive carcinomas (e.g. small cell and squamous cell) seen in smokers.

OBJECTIVE

To update previous reviews on animal models, and to add different types of transgenic (Tg) mice to the review.

METHODS

Reviews were made of articles retrieved from PubMed and elsewhere.

RESULTS

The addition of Tg mice to the arsenal of tests used for the evaluation of the carcinogenic potential of cigarettes did not result in any better understanding of the inability of such testing to reflect the epidemiological evidence for lung cancer in smokers.

CONCLUSION

As in previous reviews on the subject, the best assay providing support for the epidemiology data is still the 5-month whole-body exposure of male A/J mice to a combination of mainstream/sidestream smoke, followed by a 4-month recovery.

The preventative role of curcumin on the lung inflammatory response induced by cardiopulmonary bypass in rats

BACKGROUND

Acute lung injury is a frequent complication after cardiopulmonary bypass (CPB). Recent studies have reported that NF-κB plays an important role in the pathogenesis of post-CPB pulmonary dysfunction. Several signaling pathways, including the TLR4 pathway, induce NF-κB leading to an inflammatory response. We designed this study to determine whether or not curcumin inhibits TLR4 and MyD88 protein levels and ameliorates lung inflammatory injury in a rat CPB model.

MATERIALS AND METHODS

Sprague-Dawley rats were randomly divided into the following five groups (n = 12): sham; control (CPB); vehicle; low-dose curcumin (L-Cur); and high-dose curcumin (H-Cur). The percutaneous beating heart CPB model of rat was established. Animals were pretreated with a single intraperitoneal injection of vehicle, L-Cur (50 mg/kg), or H-Cur (200 mg/kg) 2 h prior to CPB. Blood were sampled at various time points, then lung tissues and bronchoalveolar lavage fluid were harvested 24 h after CPB.

RESULTS

CPB induced a marked increase in the concentrations of interleukin-8, tumor necrosis factor-α, and matrix metalloproteinase-9 in plasma, bronchoalveolar lavage fluid, and lung tissues (P < 0.05 versus sham group), whereas curcumin pretreatment reduced these inflammatory markers. Curcumin had effective inhibitory effects on the expression of TLR4, MyD88, and NF-κB in lung tissues 24 h post-CPB (P < 0.05 versus vehicle group). Administration of curcumin remarkably decreased the lung injury score (L-Cur versus vehicle group, P = 0.024; H-Cur versus vehicle group, P = 0.013).

CONCLUSIONS

Curcumin may be an alternative therapy for protecting CPB-induced lung injury by suppressing the expression of inflammatory cytokines. This anti-inflammatory effect of curcumin is partly related to the inhibition of TLR4, MyD88, and NF-κB.

CASP8 polymorphisms contribute to cancer susceptibility: evidence from a meta-analysis of 23 publications with 55 individual studies

Several potentially functional polymorphisms of CASP8 encoding an apoptotic enzyme, caspase 8, have been implicated in cancer risk, but individually published studies showed inconclusive results. We performed a meta-analysis of 23 publications with a total of 55 174 cancer cases and 59 336 controls from 55 individual studies. We summarized the data on the associations between three studied CASP8 polymorphisms (G>C D302H, -652 6N del and Ex14-271A>T) and cancer risk and performed subgroup analysis by ethnicity, cancer type, study design and etiology. We found that D302H CC and CG variant genotypes were associated with significantly reduced overall risk of cancers using conservative random genetic models [homozygote comparison: odds ratios (OR) = 0.79; 95% confidence interval (CI): 0.69-0.92; dominant comparison: OR = 0.93, 95% CI: 0.89-0.98; recessive comparison: OR = 0.81, 95% CI: 0.71-0.93). In further stratified analyses, the reduced cancer risk remained for subgroups of Caucasians, breast or estrogen-related cancers, and hospital- or population-based studies, except for an elevated risk for brain tumors. Similarly, the -652 6N del polymorphism was also associated with significantly reduced overall risk of cancers (homozygote comparison: OR = 0.84, 95% CI: 0.75-0.94; dominant comparison: OR = 0.88, 95% CI: 0.81-0.96; recessive comparison: OR = 0.90, 95% CI: 0.82-0.99) and all subgroups analyzed. However, the Ex14-271A>T polymorphism did not appear to have an effect on cancer risk. These results suggest that CASP8 D302H and -652 6N del polymorphisms are potential biomarkers for cancer risk.

Effects of cigarette smoke on the activation of oxidative stress-related transcription factors in female A/J mouse lung

Cigarette smoke contains a high concentration of free radicals and induces oxidative stress in the lung and other tissues. Several transcription factors are known to be activated by oxidative stress, including nuclear factor-kappaB (NF-kappaB), activator protein-1 (AP-1), and hypoxia-inducible factor (HIF). Studies were therefore undertaken to examine whether cigarette smoke could activate these transcription factors, as well as other transcription factors that may be important in lung carcinogenesis. Female A/J mice were exposed to cigarette smoke for 2, 5, 10, 15, 20, 42, or 56 d (6 hr/d, 5 d/wk). Cigarette smoke did not increase NF-kappaB activation at any of these times, but NF-kappaB DNA binding activity was lower after 15 d and 56 d of smoke exposure. The DNA binding activity of AP-1 was lower after 10 d and 56 d but was not changed after 42 d of smoke exposure. The DNA binding activity of HIF was quantitatively increased after 42 d of smoke exposure but decreased after 56 d. Whether the activation of other transcription factors in the lung could be altered after exposure to cigarette smoke was subsequently examined. The DNA binding activities of FoxF2, myc-CF1, RORE, and p53 were examined after 10 d of smoke exposure. The DNA binding activities of FoxF2 and p53 were quantitatively increased, but those of myc-CF1 and RORE were unaffected. These studies show that cigarette smoke exposure leads to quantitative increases in DNA binding activities of FoxF2 and p53, while the activations of NF-kappaB, AP-1, and HIF are largely unaffected or reduced.

Characterisation of the proximal airway squamous metaplasia induced by chronic tobacco smoke exposure in spontaneously hypertensive rats

Background

Continuous exposure to tobacco smoke (TS) is a key cause of chronic obstructive pulmonary disease (COPD), a complex multifactorial disease that is difficult to model in rodents. The spontaneously hypertensive (SH) rat exhibits several COPD-associated co-morbidities such as hypertension and increased coagulation. We have investigated whether SH rats are a more appropriate animal paradigm of COPD.

Methods

SH rats were exposed to TS for 6 hours/day, 3 days/week for 14 weeks, and the lung tissues examined by immunohistochemistry.

Results

TS induced a CK13-positive squamous metaplasia in proximal airways, which also stained for Ki67 and p63. We hypothesise that this lesion arises by basal cell proliferation, which differentiates to a squamous cell phenotype. Differences in staining profiles for the functional markers CC10 and surfactant D, but not phospho-p38, indicated loss of ability to function appropriately as secretory cells. Within the parenchyma, there were also differences in the staining profiles for CC10 and surfactant D, indicating a possible attempt to compensate for losses in proximal airways. In human COPD sections, areas of CK13-positive squamous metaplasia showed sporadic p63 staining, suggesting that unlike the rat, this is not a basal cell-driven lesion.

Conclusion

This study demonstrates that although proximal airway metaplasia in rat and human are both CK13+ and therefore squamous, they potentially arise by different mechanisms.

Distinct pathophysiologic pathways induced by in vitro infection and cigarette smoke in normal human fetal membranes

OBJECTIVE

The purpose of this study was to document distinct pathways that are initiated by lipopolysaccharide and cigarette smoke stimulation of normal term fetal membranes.

STUDY DESIGN

Fetal membranes from nonsmoking women at term, not in labor, from cesarean deliveries were placed in an organ explant system and stimulated with cigarette smoke extracts (CSEs), lipopolysaccharide, or lipopolysaccharide + CSE. Media were assayed for an interleukin (IL)-1beta, -1 receptor antagonist, -6, -8, -10, tumor necrosis factor alpha, soluble tumor necrosis factor receptors 1 and 2, and matrix metalloproteinases 1, 2, 3, 8, 9, and 12. Tissue homogenates were assayed for apoptotic markers (p53, caspase 3 activity, and cleaved poly [ADP-ribose] polymerase-1).

RESULTS

Lipopolysaccharide stimulation resulted in higher cytokine and matrix metalloproteinase concentrations, whereas it was lower after CSE and CSE + lipopolysaccharide stimulations, compared with control specimens. Apoptotic factors were several folds higher after CSE or CSE + lipopolysaccharide stimulation, compared with control specimens or lipopolysaccharide stimulations.

CONCLUSION

Cigarette smoke showed immunoinhibitory properties that potentially were mediated by apoptosis and lipopolysaccharide-induced proinflammatory response. This study demonstrated 2 independent pathophysiologic pathways that may alter pregnancy outcome.