Nicotine and fibronectin expression in lung fibroblasts: implications for tobacco‐related lung tissue remodeling

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.

Environmental pollutants induce NLRP3 inflammasome activation and pyroptosis: Roles and mechanisms in various diseases

Environmental pollution is changing with economic development. Most environmental pollutants are characterized by stable chemical properties, strong migration, potential toxicity, and multiple exposure routes. Harmful substances are discharged excessively, and large quantities of unknown new compounds are emerging, being transmitted and amplifying in the food chain. The increasingly severe problems of environmental pollution have forced people to re-examine the relationship between environmental pollution and health. Pyroptosis and activation of the NLRP3 inflammasome are critical in maintaining the immune balance and regulating the inflammatory process. Numerous diseases caused by environmental pollutants are closely related to NLRP3 inflammasome activation and pyroptosis. We intend to systematically explain the steps and important events that are common in life but easily overlooked by which environmental pollutants activate the NLRP3 inflammasome and pyroptosis pathways. This comprehensive review also discusses the interaction network between environmental pollutants, the NLRP3 inflammasome, pyroptosis, and diseases. Thus, research progress on the impact of decreasing oxidative stress levels to inhibit the NLRP3 inflammasome and pyroptosis, thereby repairing homeostasis and reshaping health, is systematically examined. This review aims to deepen the understanding of the impact of environmental pollutants on life and health and provide a theoretical basis and potential programs for the development of corresponding treatment strategies.

Fibroblasts-Warriors at the Intersection of Wound Healing and Disrepair

Wound healing is triggered by inflammation elicited after tissue injury. Mesenchymal cells, specifically fibroblasts, accumulate in the injured tissues, where they engage in tissue repair through the expression and assembly of extracellular matrices that provide a scaffold for cell adhesion, the re-epithelialization of tissues, the production of soluble bioactive mediators that promote cellular recruitment and differentiation, and the regulation of immune responses. If appropriately deployed, these processes promote adaptive repair, resulting in the preservation of the tissue structure and function. Conversely, the dysregulation of these processes leads to maladaptive repair or disrepair, which causes tissue destruction and a loss of organ function. Thus, fibroblasts not only serve as structural cells that maintain tissue integrity, but are key effector cells in the process of wound healing. The review will discuss the general concepts about the origins and heterogeneity of this cell population and highlight the specific fibroblast functions disrupted in human disease. Finally, the review will explore the role of fibroblasts in tissue disrepair, with special attention to the lung, the role of aging, and how alterations in the fibroblast phenotype underpin disorders characterized by pulmonary fibrosis.

Preterm Birth, Developmental Smoke/Nicotine Exposure, and Life-Long Pulmonary Sequelae

This review delineates the main pulmonary issues related to preterm birth, perinatal tobacco/nicotine exposure, and its effects on offspring, focusing on respiratory health and its possible transmission to subsequent generations. We review the extent of the problem of preterm birth, prematurity-related pulmonary effects, and the associated increased risk of asthma later in life. We then review the impact of developmental tobacco/nicotine exposure on offspring asthma and the significance of transgenerational pulmonary effects following perinatal tobacco/nicotine exposure, possibly via its effects on germline epigenetics.

Harmful Impact of Tobacco Smoking and Alcohol Consumption on the Atrial Myocardium

Tobacco smoking and alcohol consumption are widespread exposures that are legal and socially accepted in many societies. Both have been widely recognized as important risk factors for diseases in all vital organ systems including cardiovascular diseases, and with clinical manifestations that are associated with atrial dysfunction, so-called atrial cardiomyopathy, especially atrial fibrillation and stroke. The pathogenesis of atrial cardiomyopathy, atrial fibrillation, and stroke in context with smoking and alcohol consumption is complex and multifactorial, involving pathophysiological mechanisms, environmental, and societal aspects. This narrative review summarizes the current literature regarding alterations in the atrial myocardium that is associated with smoking and alcohol.

The Human-Restricted Isoform of the α7 nAChR, CHRFAM7A: A Double-Edged Sword in Neurological and Inflammatory Disorders

CHRFAM7A is a relatively recent and exclusively human gene arising from the partial duplication of exons 5 to 10 of the α7 neuronal nicotinic acetylcholine receptor subunit (α7 nAChR) encoding gene, CHRNA7. CHRNA7 is related to several disorders that involve cognitive deficits, including neuropsychiatric, neurodegenerative, and inflammatory disorders. In extra-neuronal tissues, α7nAChR plays an important role in proliferation, differentiation, migration, adhesion, cell contact, apoptosis, angiogenesis, and tumor progression, as well as in the modulation of the inflammatory response through the “cholinergic anti-inflammatory pathway”. CHRFAM7A translates the dupα7 protein in a multitude of cell lines and heterologous systems, while maintaining processing and trafficking that are very similar to the full-length form. It does not form functional ion channel receptors alone. In the presence of CHRNA7 gene products, dupα7 can assemble and form heteromeric receptors that, in order to be functional, should include at least two α7 subunits to form the agonist binding site. When incorporated into the receptor, in vitro and in vivo data showed that dupα7 negatively modulated α7 activity, probably due to a reduction in the number of ACh binding sites. Very recent data in the literature report that the presence of the duplicated gene may be responsible for the translational gap in several human diseases. Here, we will review the studies that have been conducted on CHRFAM7A in different pathologies, with the intent of providing evidence regarding when and how the expression of this duplicated gene may be beneficial or detrimental in the pathogenesis, and eventually in the therapeutic response, to CHRNA7-related neurological and non-neurological diseases.

Screening and Identification of Hub Genes in the Corticosteroid Resistance Network in Human Airway Epithelial Cells via Microarray Analysis

Background and Objective: Corticosteroid resistance is a major barrier to chronic obstructive pulmonary disease (COPD), but the exact mechanism of corticosteroid resistance in COPD has been less well studied. Methods: The microarray dataset GSE11906, which includes genomic and clinical data on COPD, was downloaded from the Gene Expression Omnibus (GEO) database, and the differentially expressed genes (DEGs) were identified using R software. Gene set enrichment analysis (GSEA) and Kyoto Encyclopedia of Genes (KEGG) were utilized to enrich and analyze the gene cohort related to the response to steroid hormones, respectively. The Connectivity Map (CMap) database was used to screen corticosteroid resistance-related drugs that might exert a potential therapeutic effect. STRING was used to construct a protein-protein interaction (PPI) network of the gene cohort, and the CytoHubba plug-in of Cytoscape was used to screen the hub genes in the PPI network. The expression levels of hub genes in cigarette smoke extract (CSE)-stimulated bronchial epithelial cells were assayed by quantitative real-time PCR and western blotting. Results: Twenty-one genes were found to be correlated with the response to steroid hormones. In the CMap database, 32 small-molecule compounds that might exert a therapeutic effect on corticosteroid resistance in COPD were identified. Nine hub genes were extracted from the PPI network. The expression levels of the BMP4, FOS, FN1, EGFR, and SPP1 proteins were consistent with the microarray data obtained from molecular biology experiments. Scopoletin significantly restrained the increases in the levels of AKR1C3, ALDH3A1, FN1 and reversed the decreases of phosphorylated GR and HDAC2 caused by CSE exposure. Conclusion: The BMP4, FOS, FN1, EGFR, and SPP1 genes are closely correlated with CSE-induced glucocorticoid resistance in airway epithelial cells. Scopoletin may be a potential drug for the treatment of glucocorticoid resistance caused by CSE.

Effects of E-Cigarette Aerosols with Varying Levels of Nicotine on Biomarkers of Oxidative Stress and Inflammation in Mice

To provide insights into the cause of e-cigarette (e-cig) associated lung injury, we examined the effects of propylene glycol (PG) and glycerol (G), two common solvent carriers used to deliver nicotine/flavor, on markers of oxidative stress and inflammation in female B6C3F1 mice which had been used successfully in tobacco smoke (TS)-induced lung carcinogenesis. Mice exposed to air and TS were used as negative and positive controls, respectively. Using LC-MS/MS, we showed that PG/G alone, in the absence of nicotine, significantly increased the levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG or its tautomer 8-oxodG), a biomarker of DNA oxidative damage, in lung and plasma of mice; moreover, addition of nicotine (12 and 24 mg/mL) in e-cig liquid appears to suppress the levels of 8-oxodG. Exposure to e-cig aerosols or TS induced nonsignificant increases of plasma C-reactive protein (CRP), a biomarker of inflammation; nonetheless, the levels of fibronectin (FN), a biomarker of tissue injury, were significantly increased by e-cig aerosols or TS. Although preliminary, our data showed that exposure to e-cig aerosols induced a higher score of lung injury than did control air or TS exposure. Our results indicate that the B6C3F1 mouse model may be suitable for an in-depth examination of the impact of e-cig on lung injury associated with oxidative stress and inflammation and this study adds to the growing evidence that the use of e-cig can lead to lung damage.

α7 Nicotinic Acetylcholine Receptor Agonist PNU-282987 Ameliorates Cognitive Impairment Induced by Chronic Intermittent Hypoxia

PURPOSE

Cognitive impairment is an important complication of obstructive sleep apnea (OSA). Chronic intermittent hypoxia (CIH), the main pathophysiological characteristics of OSA, is closely related to cognitive dysfunction and may be mediated by alpha-7 nicotinic acetylcholine receptors (α7nAChR). This study investigated the effects and clarified the mechanisms of α7nAChR on the cognitive function of mice with CIH.

METHODS

Thirty CD-1 mice were randomly divided into room air (RA), CIH-2 weeks (CIH2W), and CIH-4 weeks (CIH4W) groups. Cognitive function was evaluated by novel object recognition (NOR) and Morris water maze (MWM) tests after exposure. Then, 104 CD-1 mice were exposed to CIH for 4 weeks and randomly divided into four groups: CIH4W (control), with dimethyl sulfoxide (DMSO) (sham), with α7nAChR-specific agonist PNU-282987 (PNU), and with α7nAChR-specific inhibitor methyllycaconitine and PNU-282987 (MLA+PNU). In addition to the evaluation of cognitive function, apoptotic bodies in the hippocampus were detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, changes in p-CREB and BDNF were detected by immunohistochemistry, while those of ERK1/2, CREB, PGC-1α, FNDC5, and BDNF were detected by Western blotting in the hippocampal tissues of the mice.

RESULTS

Compared to the CIH2W and RA groups, the CIH4W group showed cognitive dysfunction in the NOR and MWM tests. The changes in cognitive dysfunction were alleviated by PNU-282987; furthermore, MLA pretreatment offset the effect. In hippocampal tissues, TUNEL assays showed decreased apoptotic cells, immunohistochemical staining showed increased expressions of p-CREB and BDNF. The expression levels of p-ERK1/2/t-ERK1/2, p-CREB/t-CREB, PGC-1α, FNDC5, and BDNF were increased after PNU-282987 injection.

CONCLUSION

Four weeks of CIH caused cognitive dysfunction in mice. Activating α7nAChR might ameliorate this dysfunction by upregulating the ERK1/2/CREB signaling pathway; enhancing PGC-1α, FNDC5, and BDNF expression levels; and reducing cell apoptosis in the hippocampal tissue of mice.

Molecular alterations in oral cancer between tobacco chewers and smokers using serum proteomics

BACKGROUND

Tobacco exposure (through smoking or chewing) is one of the predominant risk factors associated with the development of oral squamous cell carcinoma (OSCC). Despite the growing number of patients diagnosed with OSCC, there are few circulating biomarkers for identifying individuals at a higher risk of developing the disease. Successful identification of candidate molecular markers for risk assessment could aid in the early detection of oral lesions and potentially be used for community screening of high-risk populations.

OBJECTIVE

Identification of differentially expressed proteins in the serum of oral cancer patients which can serve as biomarkers for the diagnosis of the onset of oral cancer among tobacco users.

METHODS

We employed a tandem mass tag (TMT)-based quantitative proteomics approach to study alterations in the serum proteomes of OSCC patients based on their tobacco exposure habits (chewing and smoking) compared to healthy individuals with no history of using any form of tobacco or any symptoms of the disease.

RESULTS

Mass spectrometry-based analysis resulted in the identification of distinct signatures in the serum of OSCC patients who either chewed or smoked tobacco. Pathway analysis revealed opposing effects of dysregulated proteins enriched in the complement-coagulation signaling cascades with a high expression of the Serpin family of proteins observed in OSCC patients who chewed tobacco compared to healthy individuals whereas these proteins showed decreased levels in OSCC patients who smoked. ELISA-based validation further confirmed our findings revealing higher expression of SERPINA6 and SERPINF1 across serum of OSCC patients who chewed tobacco compared to healthy individuals.

CONCLUSIONS

This study serves as a benchmark for the identification of serum-based protein markers that may aid in the identification of high-risk patients who either chew tobacco or smoke tobacco.

Nicotine Changes Airway Epithelial Phenotype and May Increase the SARS-COV-2 Infection Severity

(1) Background: Nicotine is implicated in the SARS-COV-2 infection through activation of the α7-nAChR and over-expression of ACE2. Our objective was to clarify the role of nicotine in SARS-CoV-2 infection exploring its molecular and cellular activity. (2) Methods: HBEpC or si-mRNA-α7-HBEpC were treated for 1 h, 48 h or continuously with 10-7 M nicotine, a concentration mimicking human exposure to a cigarette. Cell viability and proliferation were evaluated by trypan blue dye exclusion and cell counting, migration by cell migration assay, senescence by SA-β-Gal activity, and anchorage-independent growth by cloning in soft agar. Expression of Ki67, p53/phospho-p53, VEGF, EGFR/pEGFR, phospho-p38, intracellular Ca2+, ATP and EMT were evaluated by ELISA and/or Western blotting. (3) Results: nicotine induced through α7-nAChR (i) increase in cell viability, (ii) cell proliferation, (iii) Ki67 over-expression, (iv) phospho-p38 up-regulation, (v) EGFR/pEGFR over-expression, (vi) increase in basal Ca2+ concentration, (vii) reduction of ATP production, (viii) decreased level of p53/phospho-p53, (ix) delayed senescence, (x) VEGF increase, (xi) EMT and consequent (xii) enhanced migration, and (xiii) ability to grow independently of the substrate. (4) Conclusions: Based on our results and on evidence showing that nicotine potentiates viral infection, it is likely that nicotine is involved in SARS-CoV-2 infection and severity.

MicroRNA-98 reduces nerve growth factor expression in nicotine-induced airway remodeling

Evolving evidence suggests that nicotine may contribute to impaired asthma control by stimulating expression of nerve growth factor (NGF), a neurotrophin associated with airway remodeling and airway hyperresponsiveness. We explored the hypothesis that nicotine increases NGF by reducing lung fibroblast (LF) microRNA-98 (miR-98) and PPARγ levels, thus promoting airway remodeling. Levels of NGF, miR-98, PPARγ, fibronectin 1 (FN1), endothelin-1 (EDN1, herein referred to as ET-1), and collagen (COL1A1 and COL3A1) were measured in human LFs isolated from smoking donors, in mouse primary LFs exposed to nicotine (50 μg/ml), and in whole lung homogenates from mice chronically exposed to nicotine (100 μg/ml) in the drinking water. In selected studies, these pathways were manipulated in LFs with miR-98 inhibitor (anti-miR-98), miR-98 overexpression (miR-98 mimic), or the PPARγ agonist rosiglitazone. Compared with unexposed controls, nicotine increased NGF, FN1, ET-1, COL1A1, and COL3A1 expression in human and mouse LFs and mouse lung homogenates. In contrast, nicotine reduced miR-98 levels in LFs in vitro and in lung homogenates in vivo Treatment with anti-miR-98 alone was sufficient to recapitulate increases in NGF, FN1, and ET-1, whereas treatment with a miR-98 mimic significantly suppressed luciferase expression in cells transfected with a luciferase reporter linked to the putative seed sequence in the NGF 3'UTR and also abrogated nicotine-induced increases in NGF, FN1, and ET-1 in LFs. Similarly, rosiglitazone increased miR-98 and reversed nicotine-induced increases in NGF, FN1, and ET-1. Taken together, these findings demonstrate that nicotine-induced increases in NGF and other markers of airway remodeling are negatively regulated by miR-98.

Redox States of Protein Cysteines in Pathways of Protein Turnover and Cytoskeleton Dynamics Are Changed with Aging and Reversed by Slc7a11 Restoration in Mouse Lung Fibroblasts

Slc7a11 is the key component of system X_c⁻, an antiporter that imports cystine (CySS) and exports glutamate. It plays an important role in cellular defense against oxidative stress because cysteine (Cys), reduced from CySS, is used for and limits the synthesis of glutathione (GSH). We have shown that downregulation of Slc7a11 is responsible for oxidation of extracellular Cys/CySS redox potential in lung fibroblasts from old mice. However, how age-related change of Slc7a11 expression affects the intracellular redox environment of mouse lung fibroblasts remains unexplored. The purpose of this study is to evaluate the effects of aging on the redox states of intracellular proteins and to examine whether Slc7a11 contributes to the age-dependent effects. Iodoacetyl Tandem Mass Tags were used to differentially label reduced and oxidized forms of Cys residues in primary lung fibroblasts from young and old mice, as well as old fibroblasts transfected with Slc7a11. The ratio of oxidized/reduced forms (i.e., redox state) of a Cys residue was determined via multiplexed tandem mass spectrometry. Redox states of 151 proteins were different in old fibroblasts compared to young fibroblasts. Slc7a11 overexpression restored redox states of 104 (69%) of these proteins. Ingenuity Pathway Analysis (IPA) showed that age-dependent Slc7a11-responsive proteins were involved in pathways of protein translation initiation, ubiquitin-proteasome-mediated degradation, and integrin-cytoskeleton-associated signaling. Gene ontology analysis showed cell adhesion, protein translation, and organization of actin cytoskeleton were among the top enriched terms for biological process. Protein-protein interaction network demonstrated the interactions between components of the three enriched pathways predicted by IPA. Follow-up experiments confirmed that proteasome activity was lower in old cells than in young cells and that upregulation of Slc7a11 expression by sulforaphane restored this activity. This study finds that aging results in changes of redox states of proteins involved in protein turnover and cytoskeleton dynamics, and that upregulating Slc7a11 can partially restore the redox states of these proteins.

COX-2-derived prostaglandins as mediators of the deleterious effects of nicotine in chronic kidney disease

Tobacco smoking has been identified as a risk factor in the progression of chronic kidney disease (CKD). In previous studies, we showed that nicotine induces cyclooxygenase (COX)-2 expression in vivo and in vitro and that the administration of nicotine in vivo worsens the severity of renal injury in a model of subtotal renal ablation. In the present study, we tested the role of COX-2-derived prostaglandins on the deleterious effects of nicotine in CKD. Sham and 5/6 nephrectomy (5/6Nx) rats received tap water or nicotine (100 μg/mL) in the drinking water for 12 wk. Additional groups also systemically received the COX-2 inhibitor NS-398 (1.5 mg·kg^-1·day^-1 via osmotic minipump). The administration of nicotine worsened renal injury and proteinuria in 5/6Nx rats and increased proteinuria in sham rats. 5/6Nx rats had increased cortical production of the prostaglandins PGE₂, PGI₂, PGD₂, and PGF_2α and of thromboxane A₂. In these rats, nicotine reduced the production of all prostaglandins examined except thromboxane A₂. Treatment with the COX-2 inhibitor NS-398 resulted in complete inhibition of all prostaglandins studied and ameliorated renal injury and proteinuria in 5/6Nx rats on nicotine but not in 5/6 Nx rats on tap water. Nicotine also reduced the expression of megalin in all groups examined, and this was partially prevented by COX-2 inhibition. In the present study, we showed that in CKD, nicotine worsens renal injury at least in part by producing an imbalance in the production of prostaglandins. This imbalance in the production of prostaglandins likely plays a role in the deleterious effects of smoking on the progression of CKD.

Nicotine instigates podocyte injury via NLRP3 inflammasomes activation

Background/Aims: Recent studies have shown that nicotine induces podocyte damage. However, it remains unknown how nicotine induces podocyte injury. The present study tested whether nicotine induces NLRP3 inflammasomes activation and thereby contributes to podocyte injury.

Results: Nicotine treatment significantly increased the colocalization of NLRP3 with Asc, caspase-1 activity, IL-β production, cell permeability in podocytes compared to control cells. Pretreatment with caspase-1 inhibitor, WEHD significantly abolished the nicotine-induced colocalization of NLRP3 with Asc, caspase-1 activity, IL-1β production and cell permeability in podocytes. Immunofluorescence analysis showed that nicotine treatment significantly decreased the podocin and nephrin expression compared to control cells. However, prior treatment with WEHD attenuated the nicotine-induced podocin and nephrin reduction. In addition, we found that nicotine treatment significantly increased the O₂^.- production compared to control cells. However, prior treatment with WEHD did not alter the nicotine-induced O₂^.- production. Furthermore, prior treatment with ROS scavenger, NAC significantly attenuated the nicotine-induced caspase-1 activity, IL-1β production, podocin and nephrin reduction in podocytes.

Conclusions: Nicotine-induced the NLRP3 inflammasome activation in podocytes and thereby results in podocyte injury.

Methods: Inflammasome formation and immunofluorescence expressions were quantified by confocal microscopy. Caspase-1 activity, IL-1β production and O₂^.- production were measured by ELISA and ESR.

The impact of perinatal nicotine exposure on fetal lung development and subsequent respiratory morbidity

Maternal smoking during pregnancy remains as a significant public health crisis as it did decades ago. Although its prevalence is decreasing in high-income countries, it has worsened globally, along with a concerning emergence of electronic-cigarette usage within the last two decades. Extensive epidemiologic and experimental evidence exists from both human and animal studies, demonstrating the detrimental long-term pulmonary outcomes in the offspring of mothers who smoke during pregnancy. Even secondhand and thirdhand smoke exposure to the developing lung might be as or even more harmful than firsthand smoke exposure. Furthermore, these effects are not limited only to the exposed progeny, but can also be transmitted transgenerationally. There is compelling evidence to support that the majority of the effects of perinatal smoke exposure on the developing lung, including the transgenerational transmission of asthma, is mediated by nicotine. Nicotine exposure induces cell-specific molecular changes in lungs, which offers a unique opportunity to prevent, halt, and/or reverse the resultant damage through targeted molecular interventions. Experimentally, the proposed interventions, such as administration of peroxisome proliferator-activated receptor gamma (PPARγ) agonists can not only block but also potentially reverse the perinatal nicotine exposure-induced respiratory morbidity in the exposed offspring. However, the development of a safe and effective intervention is still many years away. In the meantime, electropuncture at specific acupoints appears to be emerging as a more practical and safe physiologic approach to block the harmful pulmonary consequences of perinatal nicotine exposure.

Age-dependent oxidation of extracellular cysteine/cystine redox state (Eh(Cys/CySS)) in mouse lung fibroblasts is mediated by a decline in Slc7a11 expression

Aging is associated with progressive oxidation of the extracellular environment. The redox state of human plasma, defined by the concentrations of cysteine (Cys) and cystine (CySS), becomes more oxidized as we age. Recently, we showed that fibroblasts isolated from the lungs of young and old mice retain this differential phenotype; old cells produce and maintain a more oxidizing extracellular redox potential (E_h(Cys/CySS)) than young cells. Microarray analysis identified down-regulation of Slc7a11, the light subunit of the CySS/glutamate transporter, as a potential mediator of age-related oxidation in these cells. The purpose of the present study was to investigate the mechanistic link between Slc7a11 expression and extracellular E_h(Cys/CySS). Sulforaphane treatment or overexpression of Slc7a11 was used to increase Slc7a11 in lung fibroblasts from old mice, and sulfasalazine treatment or siRNA-mediated knock down was used to decrease Slc7a11 in young fibroblasts. Slc7a11 mRNA levels were measured by real-time PCR, Slc7a11 activity was determined by measuring the rate of glutamate release, Cys, CySS, glutathione (GSH) and its disulfide (GSSG) were measured by HPLC, and E_h(Cys/CySS) was calculated from the Nernst equation. The results showed that both E_h(Cys/CySS) and E_h(GSH/GSSG) were more oxidized in the conditioned media of old cells than in young cells. Up-regulation of Slc7a11 via overexpression or sulforaphane treatment restored extracellular E_h(Cys/CySS) in cultures of old cells, whereas down-regulation reproduced the oxidizing E_h(Cys/CySS) in young cells. Only sulforaphane treatment was able to increase total GSH and restore E_h(GSH/GSSG), whereas overexpression, knock down and sulfasalazine had no effect on these parameters. In addition, inhibition of GSH synthesis with buthionine sulfoximine had no effect on the ability of cells to restore their extracellular redox potential in response to an oxidative challenge. In conclusion, our study reveals Slc7a11 is the key regulator of age-dependent changes in extracellular E_h(Cys/CySS) in primary mouse lung fibroblasts, and its effects are not dependent on GSH synthesis.

Lung carcinogenesis and fibrosis taken together: just coincidence?

PURPOSE OF REVIEW

The pathogenesis of lung cancer and pulmonary fibrotic disorders partially overlaps. This review focuses on the common features of the two disease categories, aimed at advancing our translational understanding of their pathobiology and at fostering the development of new therapies.

RECENT FINDINGS

Both malignant and collagen-producing lung cells display enhanced cellular proliferation, increased resistance to apoptosis, a propensity for invading and distorting the lung parenchyma, as well as stemness potential. These characteristics are reinforced by the tissue microenvironment and inflammation seems to play an important adjuvant role in both types of disorders.

SUMMARY

Unraveling the thread of the common and distinct characteristics of lung fibrosis and cancer might contribute to a more comprehensive approach of the pathobiology of both diseases and to a pathfinder for novel and personalized therapeutic strategies.

Epigenetic regulation of EC-SOD expression in aging lung fibroblasts: Role of histone acetylation

Lung disorders characterized by fibroproliferation and excessive deposition of extracellular matrices occur in late adulthood, and their pathological manifestations become more prominent with aging. The exact mechanisms linking aging and fibroproliferative disorders are unknown, but increased oxidative stress resulting in the accumulation of damaged proteins, DNA, and lipids is considered a major factor. In the lung, and especially in the pulmonary fibroblasts, the extracellular superoxide dismutase (EC-SOD) is a major antioxidant enzyme that has been implicated in pulmonary fibrosing disorders, among others. Here, we investigate the regulation of EC-SOD in pulmonary lung fibroblasts derived from young (up to 3 month) and old (24 month) C57BL6 mice. We found that old fibroblasts have marginally elevated levels of reactive oxidant species (ROS), which coincides with attenuated expression a number of antioxidant enzymes including EC-SOD. Exposure of old fibroblasts to the DNA methyltransferase inhibitor 5-aza-dC did not restore expression of EC-SOD. On the other hand, repression of EC-SOD expression was associated with deacetylation of lysine 9 on histone H3 and lysines 5, 8, 12 and 16 on histone H4 located at the gene promoter. Interestingly, the repressive tri-methylation of lysine 27 on histone H3 was elevated in old compared to young fibroblasts. In addition, exposure of old lung fibroblasts to HDAC class 1 and class 2 inhibitors restored EC-SOD expression to the level observed in young fibroblasts. While the exact mechanism of age-dependent downregulation of EC-SOD is yet to be defined, our studies indicate a potential role of epigenetic mechanisms including histone deacetylation in this process.

The instructive extracellular matrix of the lung: basic composition and alterations in chronic lung disease

The pulmonary extracellular matrix (ECM) determines the tissue architecture of the lung, and provides mechanical stability and elastic recoil, which are essential for physiological lung function. Biochemical and biomechanical signals initiated by the ECM direct cellular function and differentiation, and thus play a decisive role in lung development, tissue remodelling processes and maintenance of adult homeostasis. Recent proteomic studies have demonstrated that at least 150 different ECM proteins, glycosaminoglycans and modifying enzymes are expressed in the lung, and these assemble into intricate composite biomaterials. These highly insoluble assemblies of interacting ECM proteins and their glycan modifications can act as a solid phase-binding interface for hundreds of secreted proteins, which creates an information-rich signalling template for cell function and differentiation. Dynamic changes within the ECM that occur upon injury or with ageing are associated with several chronic lung diseases. In this review, we summarise the available data about the structure and function of the pulmonary ECM, and highlight changes that occur in idiopathic pulmonary fibrosis (IPF), pulmonary arterial hypertension (PAH), chronic obstructive pulmonary disease (COPD), asthma and lung cancer. We discuss potential mechanisms of ECM remodelling and modification, which we believe are relevant for future diagnosis and treatment of chronic lung disease.

Nicotine stimulates collagen type I expression in lung via α7 nicotinic acetylcholine receptors

Background

Tobacco-related chronic lung diseases are characterized by alterations in lung architecture leading to decreased lung function. Knowledge of the exact mechanisms involved in tobacco-induced tissue remodeling and inflammation remains incomplete. We hypothesize that nicotine stimulates the expression of extracellular matrix proteins, leading to relative changes in lung matrix composition, which may affect immune cells entering the lung after injury.

Methods

Pulmonary fibroblasts from wildtype and α7 nicotinic acetylcholine receptor knockout (α7KO) mice were exposed to nicotine and examined for collagen type 1 mRNA and protein expression. Testing the potential role on immune cell function, pulmonary fibroblasts were retained in culture for 120 h. The fibroblasts were eliminated by osmotic lysis and the remaining matrix-coated dishes were washed thoroughly. U937 cells were incubated on the matrix-coated dishes for 24 h followed by evaluation of IL-1β gene expression. Wildtype or α7KO C57BL/6 mice (female, 8–12 weeks) were fed normal diet and exposed to nicotine in their drinking water (100 μg/ml) for 8-12weeks. Lungs were processed for mRNA, protein, and histology. Statistical significance was determined at p ≤ .05 by two-tailed test or 2-way ANOVA with Bonferroni posttest.

Results

We found that nicotine stimulated collagen type I mRNA and protein expression in a dose-dependent manner and up to 72 h in primary lung fibroblasts. The stimulatory effect of nicotine was inhibited in α7KO primary lung fibroblasts. Testing the potential role of these events on immune cell function, U937 monocytic cells were cultured atop matrices derived from nicotine-treated lung fibroblasts. These cells expressed more IL-1β than those cultured atop matrices derived from untreated fibroblasts, and antibodies against the α2β1 collagen integrin receptor inhibited the effect. Nicotine also stimulated fibroblast proliferation via MEK-1/ERK, unveiling a potentially amplifying pathway. In vivo, nicotine increased collagen type I expression was detected in wildtype, but not in α7KO mice. Wildtype mice showed increased collagen staining in lung, primarily around the airways.

Conclusions

These observations suggest that nicotine stimulates fibroblast proliferation and their expression of collagen type I through α7 nAChRs, thereby altering the relative composition of the lung matrix without impacting the overall lung architecture; this may influence inflammatory responses after injury.

Differential Regulation of the Extracellular Cysteine/Cystine Redox State (EhCySS) by Lung Fibroblasts from Young and Old Mice

Aging is associated with progressive oxidation of plasma cysteine (Cys)/cystine (CySS) redox state, expressed as E_hCySS. Cultured cells condition their media to reproduce physiological E_hCySS, but it is unknown whether aged cells produce a more oxidized extracellular environment reflective of that seen in vivo. In the current study, we isolated primary lung fibroblasts from young and old female mice and measured the media E_hCySS before and after challenge with Cys or CySS. We also measured expression of genes related to redox regulation and fibroblast function. These studies revealed that old fibroblasts produced a more oxidizing extracellular E_hCySS than young fibroblasts and that old fibroblasts had a decreased capacity to recover from an oxidative challenge due to a slower rate of reduction of CySS to Cys. These defects were associated with 10-fold lower expression of the Slc7a11 subunit of the xCT cystine-glutamate transporter. Extracellular superoxide dismutase (Sod3) was the only antioxidant or thiol-disulfide regulating enzyme among 36 examined that was downregulated in old fibroblasts by more than 2-fold, but there were numerous changes in extracellular matrix components. Thus, aging fibroblasts not only contribute to remodeling of the extracellular matrix but also have a profound effect on the extracellular redox environment.

"Scar-cinoma": viewing the fibrotic lung mesenchymal cell in the context of cancer biology

Lung cancer and pulmonary fibrosis are common, yet distinct, pathological processes that represent urgent unmet medical needs. Striking clinical and mechanistic parallels exist between these distinct disease entities. The goal of this article is to examine lung fibrosis from the perspective of cancer-associated phenotypic hallmarks, to discuss areas of mechanistic overlap and distinction, and to highlight profibrotic mechanisms that contribute to carcinogenesis. Ultimately, we speculate that such comparisons might identify opportunities to leverage our current understanding of the pathobiology of each disease process in order to advance novel therapeutic approaches for both. We anticipate that such "outside the box" concepts could be translated to a more precise and individualised approach to fibrotic diseases of the lung.

Alterations in Cholinergic Pathways and Therapeutic Strategies Targeting Cholinergic System after Traumatic Brain Injury

Traumatic brain injury (TBI) results in varying degrees of disability in a significant number of persons annually. The mechanisms of cognitive dysfunction after TBI have been explored in both animal models and human clinical studies for decades. Dopaminergic, serotonergic, and noradrenergic dysfunction has been described in many previous reports. In addition, cholinergic dysfunction has also been a familiar topic among TBI researchers for many years. Although pharmacological agents that modulate cholinergic neurotransmission have been used with varying degrees of success in previous studies, improving their function and maximizing cognitive recovery is an ongoing process. In this article, we review the previous findings on the biological mechanism of cholinergic dysfunction after TBI. In addition, we describe studies that use both older agents and newly developed agents as candidates for targeting cholinergic neurotransmission in future studies.

Perinatal nicotine exposure suppresses PPARγ epigenetically in lung alveolar interstitial fibroblasts

Due to the active inhibition of the adipogenic programming, the default destiny of the developing lung mesenchyme is to acquire a myogenic phenotype. We have previously shown that perinatal nicotine exposure, by down-regulating PPARγ expression, accentuates this property, culminating in myogenic pulmonary phenotype, though the underlying mechanisms remained incompletely understood. We hypothesized that nicotine-induced PPARγ down-regulation is mediated by PPARγ promoter methylation, controlled by DNA methyltransferase 1 (DNMT1) and methyl CpG binding protein 2 (MeCP2), two known key regulators of DNA methylation. Using cultured alveolar interstitial fibroblasts and an in vivo perinatal nicotine exposure rat model, we found that PPARγ promoter methylation is strongly correlated with inhibition of PPARγ expression in the presence of nicotine. Methylation inhibitor 5-aza-2'-deoxycytidine restored the nicotine-induced down-regulation of PPARγ expression and the activation of its downstream myogenic marker fibronectin. With nicotine exposure, a specific region of PPARγ promoter was significantly enriched with antibodies against chromatin repressive markers H3K9me3 and H3K27me3, dose-dependently. Similar data were observed with antibodies against DNA methylation regulatory factors DNMT1 and MeCP2. The knock down of DNMT1 and MeCP2 abolished nicotine-mediated increases in DNMT1 and MeCP2 protein levels, and PPARγ promoter methylation, restoring nicotine-induced down regulation of PPARγ and upregulation of the myogenic protein, fibronectin. The nicotine-induced alterations in DNA methylation modulators DNMT1 and MeCP2, PPARγ promoter methylation, and its down-stream targets, were also validated in perinatally nicotine exposed rat lung tissue. These data provide novel mechanistic insights into nicotine-induced epigenetic silencing of PPARγ that could be exploited to design novel targeted molecular interventions against the smoke exposed lung injury in general and perinatal nicotine exposure induced lung damage in particular.

Duplicated copy of CHRNA7 increases risk and worsens prognosis of COPD and lung cancer

Recent genome-wide association studies implicated that the nicotinic acetylcholine receptors (nAChRs) are common susceptible genes of two contextual diseases: chronic obstructive pulmonary disease (COPD) and lung cancer. We aimed to test whether the copy number variations (CNVs) in nAChRs have hereditary contributions to development of the two diseases. In two, two-stage, case-control studies of southern and eastern Chinese, a common CNV-3956 that duplicates the cholinergic receptor, nicotinic, α7 (CHRNA7) gene was genotyped in a total of 7880 subjects and its biological phenotype was assessed. The ≥4-copy of CNV-3956 increased COPD risk (≥4-copy vs 2/3-copy: OR=1.44, 95% CI=1.23-1.68) and caused poor lung function, and it similarly augmented risk (OR=1.49, 95% CI=1.29-1.73) and worsened prognosis (hazard ratio (HR)=1.25, 95% CI=1.07-1.45) of lung cancer. The ≥4-copy was estimated to account for 1.56% of COPD heritability and 1.87% of lung cancer heritability, respectively. Phenotypic analysis further showed that the ≥4-copy of CNV-3956 improved CHRNA7 expression in vivo and increased the carriers' smoking amount. The CNV-3956 of CHRNA7 contributed to increased risks and poor prognoses of both COPD and lung cancer, and this may be a genetic biomarker of the two diseases.

Nicotine stimulates nerve growth factor in lung fibroblasts through an NFκB-dependent mechanism

RATIONALE

Airway hyperresponsiveness (AHR) is classically found in asthma, and persistent AHR is associated with poor asthma control. Although airway smooth muscle (ASM) cells play a critical pathophysiologic role in AHR, the paracrine contributions of surrounding cells such as fibroblasts to the contractile phenotype of ASM cells have not been examined fully. This study addresses the hypothesis that nicotine promotes a contractile ASM cell phenotype by stimulating fibroblasts to increase nerve growth factor (NGF) secretion into the environment.

METHODS

Primary lung fibroblasts isolated from wild type and α7 nicotinic acetylcholine receptor (α7 nAChR) deficient mice were treated with nicotine (50 µg/ml) in vitro for 72 hours. NGF levels were measured in culture media and in bronchoalveolar lavage (BAL) fluid from asthmatic, smoking and non-smoking subjects by ELISA. The role of the NFκB pathway in nicotine-induced NGF expression was investigated by measuring NFκB nuclear translocation, transcriptional activity, chromatin immunoprecipitation assays, and si-p65 NFκB knockdown. The ability of nicotine to stimulate a fibroblast-mediated, contractile ASM cell phenotype was confirmed by examining expression of contractile proteins in ASM cells cultured with fibroblast-conditioned media or BAL fluid.

RESULTS

NGF levels were elevated in the bronchoalveolar lavage fluid of nicotine-exposed mice, current smokers, and asthmatic children. Nicotine increased NGF secretion in lung fibroblasts in vitro in a dose-dependent manner and stimulated NFκB nuclear translocation, p65 binding to the NGF promoter, and NFκB transcriptional activity. These responses were attenuated in α7 nAChR deficient fibroblasts and in wild type fibroblasts following NFκB inhibition. Nicotine-treated, fibroblast-conditioned media increased expression of contractile proteins in ASM cells.

CONCLUSION

Nicotine stimulates NGF release by lung fibroblasts through α7 nAChR and NFκB dependent pathways. These novel findings suggest that the nicotine-α7 nAChR-NFκB- NGF axis may provide novel therapeutic targets to attenuate tobacco smoke-induced AHR.

The electronic cigarette: a knight in shining armour or a Trojan horse?

Electronic cigarettes have caused a sharp debate in the public health community, with some promoting them as a means of harm reduction for tobacco users and some taking a strong stand against them because of fear of renormalising smoking behaviour and interrupting tobacco control progress. People with mental health problems smoke at high rates and e-cigarettes seem a potentially attractive method of cessation in this population, and their use should be studied carefully.

Exposure to biomass smoke extract enhances fibronectin release from fibroblasts

COPD induced following biomass smoke exposure has been reported to be associated with a more fibrotic phenotype than cigarette smoke induced COPD. This study aimed to investigate if biomass smoke induced extracellular matrix (ECM) protein production from primary human lung fibroblasts in vitro. Primary human lung fibroblasts (n = 5–10) were stimulated in vitro for up to 72 hours with increasing concentrations of biomass smoke extract (BME) or cigarette smoke extract (CSE) prior to being assessed for deposition of ECM proteins, cytokine release, and activation of intracellular signalling molecules. Deposition of the ECM proteins perlecan and fibronectin was upregulated by both CSE (p<0.05) and BME (p<0.05). The release of the neutrophilic chemokine IL-8 was also enhanced by BME. ERK1/2 phosphorylation was significantly upregulated by BME (p<0.05). Chemical inhibition of ERK signalling molecules partially attenuated these effects (p<0.05). Stimulation with endotoxin had no effect. This study demonstrated that BME had similar effects to CSE in vitro and had the capacity to directly induce fibrosis by upregulating production of ECM proteins. The mechanisms by which both biomass and cigarette smoke exposure cause lung damage may be similar.

Nicotine exposure during differentiation causes inhibition of N-myc expression

Background

The ability of chemicals to disrupt neonatal development can be studied using embryonic stem cells (ESC). One such chemical is nicotine. Prenatal nicotine exposure is known to affect postnatal lung function, although the mechanisms by which it has this effect are not clear. Since fibroblasts are a critical component of the developing lung, providing structure and secreting paracrine factors that are essential to epithelialization, this study focuses on the differentiation of ESC into fibroblasts using a directed differentiation protocol.

Methods

Fibroblasts obtained from non-human primate ESC (nhpESC) differentiation were analyzed by immunohistochemistry, immunostaining, Affymetrix gene expression array, qPCR, and immunoblotting.

Results

Results of these analyses demonstrated that although nhpESCs differentiate into fibroblasts in the presence of nicotine and appear normal by some measures, including H&E and SMA staining, they have an altered gene expression profile. Network analysis of expression changes demonstrated an over-representation of cell-cycle related genes with downregulation of N-myc as a central regulator in the pathway. Further investigation demonstrated that cells differentiated in the presence of nicotine had decreased N-myc mRNA and protein expression and longer doubling times, a biological effect consistent with downregulation of N-myc.

Conclusions

This study is the first to use primate ESC to demonstrate that nicotine can affect cellular differentiation from pluripotency into fibroblasts, and in particular, mediate N-myc expression in differentiating ESCs. Given the crucial role of fibroblasts throughout the body, this has important implications for the effect of cigarette smoke exposure on human development not only in the lung, but in organogenesis in general.

The EDA-containing cellular fibronectin induces epithelial-mesenchymal transition in lung cancer cells through integrin α9β1-mediated activation of PI3-K/AKT and Erk1/2

Cellular fibronectin (cFN) is one of the main components of tissue extracellular matrices and is involved in multiple physiologic and pathologic processes such as embryogenesis, wound healing, inflammation and tumor progression. The function of fibronectin in regulating normal cell adhesion and migration is well documented, but its function in cancer progression is only partially unraveled. We have reported previously that fibronectin stimulates the proliferation and survival of non-small lung carcinoma cells through upregulation of pro-oncogenic signals related to cyclooxygenase-2/phosphatidylinositol-3-kinase/protein kinase B (COX-2/PI3-K/AKT)/mammalian target of rapamycin triggered by activation of the integrin α5β1. Here, we extend these studies by showing that fibronectin promotes epithelial-mesenchymal transition (EMT) in lung cancer cells. We found that cFN, but not plasma fibronectin or type 1 collagen, induces lung carcinoma cell scattering in vitro, promotes cell migration and invasion of Matrigel and stimulates the expression of the mesenchymal marker α-smooth muscle actin while decreasing the expression of the epithelial marker E-cadherin through PI3-K and Erk pathways. Interestingly, the extra domain A (EDA) within cFN was found to be crucial for this process, as confirmed by testing cells overexpressing EDA or cells exposed to EDA-containing matrices. We found that the integrin α9, but not α5, mediated cFN-induced EMT as silencing integrin α9 neutralized cFN-induced EMT. Overall, our findings show that the EDA domain within cFN induces EMT in lung carcinoma cells through integrin α9-mediated activation of PI3-K and Erk.

Nicotine signaling and progression of chronic kidney disease in smokers

The deleterious health effects of cigarette smoking are far reaching, and it remains the most important modifiable risk factor for improving overall morbidity and mortality. In addition to being a risk factor for cancer, cardiovascular disease and lung disease, there is strong evidence, both from human and animal studies, demonstrating a role for cigarette smoking in the progression of chronic kidney disease (CKD). Clinical studies have shown a strong correlation between cigarette smoking and worsening CKD in patients with diabetes, hypertension, polycystic kidney disease, and post kidney transplant. Nicotine, in addition to its role in the addictive properties of cigarette smoking, has other biological effects via activation of non-neuronal nicotinic acetylcholine receptors (nAChRs). Several nAChR subunits are expressed in the normal kidney and blockade of the α7-nAChR subunit ameliorates the effects of nicotine in animal models of CKD. Nicotine increases the severity of renal injury in animal models including acute kidney injury, diabetes, acute nephritis and subtotal nephrectomy. The renal effects of nicotine are also linked to increased generation of reactive oxygen species and activation of pro-fibrotic pathways. In humans, nicotine induces transitory increases in blood pressure accompanied by reductions in glomerular filtration rate and effective renal plasma flow. In summary, clinical and experimental evidence indicate that nicotine is at least in part responsible for the deleterious effects of cigarette smoking in the progression of CKD. The mechanisms involved are the subject of active investigation and may result in novel strategies to ameliorate the effects of cigarette smoking in CKD.

Nicotinic acetylcholine receptors are sensors for ethanol in lung fibroblasts

BACKGROUND

Chronic ethanol (EtOH) abuse in humans is known to independently increase the incidence of and mortality due to acute lung injury in at-risk individuals. However, the mechanisms by which EtOH affects lung cells remain incompletely elucidated. In earlier work, we reported that EtOH increased the expression in lung fibroblasts of fibronectin, a matrix glycoprotein implicated in lung injury and repair. This effect was blocked by α-bungarotoxin, a neurotoxin that binds certain nicotinic acetylcholine receptors (nAChRs) thereby implicating nAChRs in this process. Here, we examine the identity of these receptors.

METHODS

Mouse lung fibroblasts were stimulated with EtOH (60 mM) or acetylcholine (100 to 500 μM) and evaluated for the expression of fibronectin and nAChRs. Inhibitors to nAChRs or the antioxidant N-acetyl cysteine (NAC) were used to assess changes in fibronectin expression. Animals exposed to EtOH for up to 6 weeks were used to evaluate the expression of nAChRs in vivo.

RESULTS

First, in EtOH-treated fibroblasts, we observed increased expression of α4 and α9 nAChR subunits. Second, we found that acetylcholine, a natural ligand for nAChRs, mimicked the effects of EtOH. Dihydro-β-erythroidin hydrobromide, a competitive inhibitor of α4 nAChR, blocked the increase in fibronectin expression and cell proliferation. Furthermore, EtOH-induced fibronectin expression was inhibited in cells silenced for α4 nAChR. However, EtOH-treated cells showed increased α-bungarotoxin binding suggesting that α4 nAChR mediates the effects of EtOH via a ligand-independent pathway. Knowing there are several important cysteine residues near the ligand-binding site of α4 nAChRs, we tested the antioxidant NAC and found that it too blocked the induction of fibronectin expression by EtOH. Also, fibroblasts exposed to oxidant stress showed increased fibronectin expression that was blocked with α-bungarotoxin. Finally, we showed increased expression of α4 nAChRs in the lung tissue of mice and rats exposed to EtOH suggesting a role for these receptors in vivo.

CONCLUSIONS

Altogether, our observations suggest that α4 nAChRs serve as sensors for EtOH-induced oxidant stress in lung fibroblasts, thereby revealing a new mechanism by which EtOH may affect lung cells and tissue remodeling and pointing to nAChRs as potential targets for intervention.

Perinatal nicotine exposure induces asthma in second generation offspring

BACKGROUND

By altering specific developmental signaling pathways that are necessary for fetal lung development, perinatal nicotine exposure affects lung growth and differentiation, resulting in the offsprings' predisposition to childhood asthma; peroxisome proliferator-activated receptor gamma (PPARγ) agonists can inhibit this effect. However, whether the perinatal nicotine-induced asthma risk is restricted to nicotine-exposed offspring only; whether it can be transmitted to the next generation; and whether PPARγ agonists would have any effect on this process are not known.

METHODS

Time-mated Sprague Dawley rat dams received either placebo or nicotine (1 mg/kg, s.c.), once daily from day 6 of gestation to postnatal day (PND) 21. Following delivery, at PND21, generation 1 (F1) pups were either subjected to pulmonary function tests, or killed to obtain their lungs, tracheas, and gonads to determine the relevant protein markers (mesenchymal contractile proteins), global DNA methylation, histone 3 and 4 acetylation, and for tracheal tension studies. Some F1 animals were used as breeders to generate F2 pups, but without any exposure to nicotine in the F1 pregnancy. At PND21, F2 pups underwent studies similar to those performed on F1 pups.

RESULTS

Consistent with the asthma phenotype, nicotine affected lung function in both male and female F1 and F2 offspring (maximal 250% increase in total respiratory system resistance, and 84% maximal decrease in dynamic compliance following methacholine challenge; P < 0.01, nicotine versus control; P < 0.05, males versus females; and P > 0.05, F1 versus F2), but only affected tracheal constriction in males (51% maximal increase in tracheal constriction following acetylcholine challenge, P < 0.01, nicotine versus control; P < 0.0001, males versus females; P > 0.05, F1 versus F2); nicotine also increased the contractile protein content of whole lung (180% increase in fibronectin protein levels, P < 0.01, nicotine versus control, and P < 0.05, males versus females) and isolated lung fibroblasts (for example, 45% increase in fibronectin protein levels, P < 0.05, nicotine versus control), along with decreased PPARγ expression (30% decrease, P < 0.05, nicotine versus control), but only affected contractile proteins in the male trachea (P < 0.05, nicotine versus control, and P < 0.0001, males versus females). All of the nicotine-induced changes in the lung and gonad DNA methylation and histone 3 and 4 acetylation were normalized by the PPARγ agonist rosiglitazone except for the histone 4 acetylation in the lung.

CONCLUSIONS

Germline epigenetic marks imposed by exposure to nicotine during pregnancy can become permanently programmed and transferred through the germline to subsequent generations, a ground-breaking finding that shifts the current asthma paradigm, opening up many new avenues to explore.

Nicotine, cigarette smoking and cardiac arrhythmia: an overview

Tobacco smoke is the single most important modifiable risk factor for coronary diseases and the leading preventable cause of death in the US. While the effect of cigarette smoking on the progression of atherosclerotic diseases is established and well studied, the role of cigarette smoking on cardiac arrhythmia is less clearly defined. In fact the pathophysiological mechanism of cigarette smoking-induced cardiac arrhythmia is very likely a complex one where the pro-fibrotic effect of nicotine on myocardial tissue with consequent increased susceptibility to catecholamine might play a role. Moreover, other constituents of cigarette smoking, such as carbon monoxide and oxidative stress, are likely to contribute to the generation of arrhythmias. Finally, cigarette smoking may induce coronary artery disease and chronic obstructive pulmonary disease, which also might cause arrhythmia independently. The objective of this paper is to summarize the published studies relating to cardiac arrhythmia induced by cigarette smoking, and to identify a pathophysiological mechanism by which cigarette smoking might induce cardiac arrhythmia.

Beneficial effects of omega-3 fatty acids in the proteome of high-density lipoprotein proteome

Background

Omega-3 poly-unsaturated fatty acids (ω-3 PUFAs) have demonstrated to be beneficial in the prevention of cardiovascular disease, however, the mechanisms by which they perform their cardiovascular protection have not been clarified. Intriguingly, some of these protective effects have also been linked to HDL. The hypothesis of this study was that ω-3 PUFAs could modify the protein cargo of HDL particle in a triglyceride non-dependent mode. The objective of the study was to compare the proteome of HDL before and after ω-3 PUFAs supplemented diet.

Methods

A comparative proteomic analysis in 6 smoker subjects HDL before and after a 5 weeks ω-3 PUFAs enriched diet has been performed.

Results

Among the altered proteins, clusterin, paraoxonase, and apoAI were found to increase, while fibronectin, α-1-antitrypsin, complement C1r subcomponent and complement factor H decreased after diet supplementation with ω-3 PUFAs. Immunodetection assays confirmed these results. The up-regulated proteins are related to anti-oxidant, anti-inflammatory and anti-atherosclerotic properties of HDL, while the down-regulated proteins are related to regulation of complement activation and acute phase response.

Conclusions

Despite the low number of subjects included in the study, our findings demonstrate that ω-3 PUFAs supplementation modifies lipoprotein containing apoAI (LpAI) proteome and suggest that these protein changes improve the functionality of the particle.

In utero nicotine exposure promotes M2 activation in neonatal mouse alveolar macrophages

BACKGROUND

Maternal smoking in utero has been associated with adverse health outcomes including lower respiratory tract infections in infants and children, but the mechanisms underlying these associations continue to be investigated. We hypothesized that nicotine plays a significant role in mediating the effects of maternal tobacco smoke on the function of the neonatal alveolar macrophage (AM), the resident immune cell in the neonatal lung.

METHODS

Primary AMs were isolated at postnatal day 7 from a murine model of in utero nicotine exposure. The murine AM cell line MH-S was used for additional in vitro studies.

RESULTS

In utero nicotine increased interleukin-13 and transforming growth factor-β1 (TGFβ1) in the neonatal lung. Nicotine-exposed AMs demonstrated increased TGFβ1 and increased markers of alternative activation with diminished phagocytic function. However, AMs from mice deficient in the α7 nicotinic acetylcholine receptor (α7 nAChR) had less TGFβ1, reduced alternative activation, and improved phagocytic functioning despite similar in utero nicotine exposure.

CONCLUSION

In utero nicotine exposure, mediated in part via the α7 nAChR, may increase the risk of lower respiratory tract infections in neonates by changing the resting state of AM toward alternative activation. These findings have important implications for immune responses in the nicotine-exposed neonatal lung.

Nicotine exposure and the progression of chronic kidney disease: role of the α7-nicotinic acetylcholine receptor

Clinical studies have established the role of cigarette smoking as a risk factor in the progression of chronic kidney disease (CKD). We have shown that nicotine promotes mesangial cell proliferation and hypertrophy via nonneuronal nicotinic acetylcholine receptors (nAChRs). The α7-nAChR is one of the most important subunits of the nAChRs. These studies were designed to test the hypothesis that nicotine worsens renal injury in rats with 5/6 nephrectomy (5/6Nx) and that the α7-nAChR subunit is required for these effects. We studied five different groups: Sham, 5/6Nx, 5/6Nx + nicotine (Nic; 100 μg/ml dry wt), 5/6Nx + Nic + α7-nAChR blocker methyllicaconitine (MLA; 3 mg·kg(-1)·day(-1) sq), and Sham + Nic. Blood pressure was measured by the tail-cuff method, and urine was collected for proteinuria. After 12 wk, the rats were euthanized and kidneys were collected. We observed expression of the α7-nAChR in the proximal and distal tubules. The administration of nicotine induced a small increase in blood pressure and resulted in cotinine levels similar to those found in the plasma of smokers. In 5/6Nx rats, the administration of nicotine significantly increased urinary protein excretion (onefold), worsened the glomerular injury score and increased fibronectin (∼ 50%), NADPH oxidase 4 (NOX4; ∼100%), and transforming growth factor-β expression (∼200%). The administration of nicotine to sham rats increased total proteinuria but not albuminuria, suggesting direct effects on tubular protein reabsorption. These effects were prevented by MLA, demonstrating a critical role for the α7-nAChR as a mediator of the effects of nicotine in the progression of CKD.

Cholinergic regulation of airway inflammation and remodelling

Acetylcholine is the predominant parasympathetic neurotransmitter in the airways that regulates bronchoconstriction and mucus secretion. Recent findings suggest that acetylcholine regulates additional functions in the airways, including inflammation and remodelling during inflammatory airway diseases. Moreover, it has become apparent that acetylcholine is synthesized by nonneuronal cells and tissues, including inflammatory cells and structural cells. In this paper, we will discuss the regulatory role of acetylcholine in inflammation and remodelling in which we will focus on the role of the airway smooth muscle cell as a target cell for acetylcholine that modulates inflammation and remodelling during respiratory diseases such as asthma and COPD.

Matrix proteins from smoke-exposed fibroblasts are pro-proliferative

Airway remodeling decreases lung function in chronic obstructive pulmonary disease (COPD). Extracellular matrix (ECM) deposition is increased in remodeled airways and drives cellular processes of proliferation, migration, and inflammation. We investigated the role of cigarette smoke in altering the ECM deposited from human lung fibroblasts. Lung fibroblasts isolated from patients with COPD or other lung disease were exposed to cigarette smoke extract (CSE) and 5 ng/ml transforming growth factor-β1 for 72 hours; in some experiments, inhibitors of signaling molecules were added. Deposition of perlecan, fibronectin, and elastin were measured by ELISA, as was release of IL-8 and IL-13. Unstimulated fibroblast cells were reseeded onto deposited matrix and assessed for proliferation and cytokine release. CSE (5%) increased deposition of fibronectin and perlecan from only COPD fibroblasts. Fibronectin and perlecan deposition was attenuated by addition of the NF-κB inhibitor, BMS-345541, and the signal transduction and activator of transcription-1/3 inhibitor, pyridone 6, respectively. CSE (5%) increased IL-8 release from COPD fibroblasts more than non-COPD fibroblasts. This increase was attenuated by BMS-345541. Matrix deposited after 5% CSE stimulation increased proliferation of fibroblasts, but did not alter cytokine release. ECM produced from COPD fibroblasts after CSE exposure has proproliferative effects. Thus, the ECM in patients with COPD may create an environment that promotes airway remodeling.

Nicotine: specific role in angiogenesis, proliferation and apoptosis

Nowadays, tobacco smoking is the cause of ~5-6 million deaths per year, counting 31% and 6% of all cancer deaths (affecting 18 different organs) in middle-aged men and women, respectively. Nicotine is the addictive component of tobacco acting on neuronal nicotinic receptors (nAChR). Functional nAChR, are also present on endothelial, haematological and epithelial cells. Although nicotine itself is regularly not referred to as a carcinogen, there is an ongoing debate whether nicotine functions as a 'tumour promoter'. Nicotine, with its specific binding to nAChR, deregulates essential biological processes like regulation of cell proliferation, apoptosis, migration, invasion, angiogenesis, inflammation and cell-mediated immunity in a wide variety of cells including foetal (regulation of development), embryonic and adult stem cells, adult tissues as well as cancer cells. Nicotine seems involved in fundamental aspects of the biology of malignant diseases, as well as of neurodegeneration. Investigating the biological effects of nicotine may provide new tools for therapeutic interventions and for the understanding of neurodegenerative diseases and tumour biology.

Peroxisome proliferator-activated receptors in lung cancer

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily. Their discovery in the 1990s provided insights into the cellular mechanisms involved in the control of energy homeostasis; the regulation of cell differentiation, proliferation, and apoptosis; and the modulation of important biological and pathological processes related to inflammation, among others. Since then, PPARs have become an exciting therapeutic target for several diseases. PPARs are expressed by many tumors including lung carcinoma cells, and their function has been linked to the process of carcinogenesis in lung. Consequently, intense research is being conducted in this area with the hope of discovering new PPAR-related therapeutic targets for the treatment of lung cancer. This review summarizes the research being conducted in this area and focuses on the mechanisms by which PPARs are believed to affect lung tumor cell biology.

Activated PPARgamma Targets Surface and Intracellular Signals That Inhibit the Proliferation of Lung Carcinoma Cells

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily. Their discovery in the 1990s provided insights into the cellular mechanisms involved in the control of energy homeostasis, the regulation of cell differentiation, proliferation, and apoptosis, and the modulation of important biological and pathological processes related to inflammation and cancer biology, among others. Since then, PPARs have become an exciting target for the development of therapies directed at many disorders including cancer. PPARs are expressed in many tumors including lung cancer, and their function has been linked to the process of carcinogenesis. Consequently, intense research is being conducted in this area with the hope of discovering new PPAR-related therapeutic targets for the treatment of lung cancer. This review summarizes the research being conducted in this area, and focuses on the mechanisms by which a member of this family (PPARγ) is believed to affect lung tumor cell biology.

Angiotensin II increases periostin expression via Ras/p38 MAPK/CREB and ERK1/2/TGF-β1 pathways in cardiac fibroblasts

AIMS

Angiotensin II (AngII) is involved in extracellular matrix (ECM) accumulation contributing to heart failure. Periostin, a 90 kDa ECM protein, is a key regulator of cardiac fibrosis, and its expression is significantly higher in failing hearts. We determined the modulatory effect of AngII on periostin level and explored the possible signal transduction mechanism.

METHODS AND RESULTS

AngII (400 ng/kg/min) or normal saline was infused subcutaneously for 28 days into rats; AngII antagonism was with losartan (10 mg/kg/day orally). AngII infusion induced cardiac fibrosis and increased periostin expression, which was attenuated by losartan. In cultured adult rat cardiac fibroblasts, AngII promoted the mRNA and protein expression of periostin. AngII provoked activation of cAMP response element-binding protein (CREB), and CREB small interfering RNA (siRNA) suppressed AngII-induced periostin expression. Inhibition of p38 mitogen-activated protein kinase (p38 MAPK) with SB202190 attenuated AngII-induced CREB activation and periostin expression. Transfection with Ras guanyl-releasing protein 1 siRNA or RasN17 dominant-negative plasmid prevented AngII-induced p38 MAPK phosphorylation and periostin expression. Transforming growth factor (TGF)-β1 antibody decreased the stimulatory effect of AngII on periostin expression. The extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor PD98059 attenuated AngII-induced TGF-β1 expression, Smad2/3 nuclear accumulation, and periostin expression.

CONCLUSION

The activation of the Ras/p38 MAPK/CREB pathway is required for AngII-induced periostin expression. ERK1/2 also participates in AngII-induced periostin expression by regulating TGF-β1/Smad signalling.