Microarray analysis of nicotine-induced changes in gene expression in endothelial cells

Differential Effects of Electronic Hookah Vaping and Traditional Combustible Hookah Smoking on Oxidation, Inflammation, and Arterial Stiffness

BACKGROUND

Traditional hookah smoking has grown quickly to become a global tobacco epidemic. More recently, electronic hookahs (e-hookahs)-vaped through traditional water pipes-were introduced as healthier alternatives to combustible hookah. With combustible tobacco smoking, oxidative stress, inflammation, and vascular stiffness are key components in the development and progression of atherosclerosis. The comparable effects of hookah are unknown.

RESEARCH QUESTION

What is the differential acute effect of e-hookah vaping vs combustible hookah smoking on oxidation, inflammation, and arterial stiffness?

STUDY DESIGN AND METHODS

In a randomized crossover design study, among a cohort of 17 healthy young adult chronic hookah smokers, we investigated the effect of e-hookah vaping and hookah smoking on measures of conduit arterial stiffness, including carotid-femoral pulse wave velocity (PWV), augmentation index-corrected for heart rate before and after a 30-min exposure session. We assessed a panel of circulating biomarkers indicative of inflammation and oxidants and measured plasma nicotine and exhaled carbon monoxide (CO) levels before and after the sessions.

RESULTS

e-Hookah vaping tended to lead to a larger acute increase in PWV than hookah smoking (mean ± SE: e-hookah, +0.74 ± 0.12 m/s; combustible hookah, +0.57 ± 0.14 m/s [P < .05 for both]), indicative of large artery stiffening. Compared with baseline, only e-hookah vaping induced an acute increase in augmentation index (e-hookah, +5.58 ± 1.54% [P = .004]; combustible hookah, +2.87 ± 2.12% [P = not significant]). These vascular changes were accompanied by elevation of the proinflammatory biomarkers high-sensitivity C-reactive protein, fibrinogen, and tumor necrosis factor α after vaping (all P < .05). No changes in biomarkers of inflammation and oxidants were observed after smoking. Compared with baseline, exhaled CO levels were higher after smoking than after vaping (+36.81 ± 6.70 parts per million vs -0.38 ± 0.22 parts per million; P < .001), whereas plasma nicotine concentrations were comparable (+6.14 ± 1.03 ng/mL vs +5.24 ± 0.96 ng/mL; P = .478).

INTERPRETATION

Although advertised to be "safe," flavored e-hookah vaping exerts injurious effects on the vasculature that are, at least in part, mediated by inflammation.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT03690427; URL: www.clinicaltrials.gov.

Nicotine exposure potentiates lung tumorigenesis by perturbing cellular surveillance

BACKGROUND

Nicotine is a major tobacco component and found at circulating concentrations in smokers' bloodstreams. Although considered a non-carcinogenic substance, nicotine rapidly defuses to tissues after being inhaled, inviting effects on cellular physiology, particularly in the lung. Widespread increased use of nicotine-based e-cigarettes, especially in younger adults, creates an urgent need for improved understanding of nicotine's potential to impact human health.

METHODS

Biological and biochemistry methods were used to interrogate the potential for nicotine to weaken the genetic integrity of murine and human-lung epithelial cells.

RESULTS

We demonstrate that nicotine potentiates the growth of the lung epithelial cells in a dose-response fashion. Nicotine elicits an acute increase in reactive oxygen species (ROS), which persists at moderately high levels throughout the duration of nicotine exposure. The aberrant increases in ROS appear to induce ER stress and UPR activation, as reflected by BIP upregulation and PERK phosphorylation. Furthermore, prolonged nicotine exposure interferes with p53 function triggered by sodium arsenite. Unless p53 is suppressed, persistent nicotine exposure does not induce colony formation by lung epithelial cells in soft agar.

CONCLUSION

The data suggest that nicotine treatment, by perturbing intracellular redox state and altering p53 function, can create a pro-tumorigenic environment in lung epithelium. The results suggest caution in using nicotine replacement therapies and e-cigarettes.

The role of alpha7 nicotinic acetylcholine receptors in inflammatory bowel disease: involvement of different cellular pathways

INTRODUCTION

Autonomic imbalance plays a pivotal role in the pathophysiology of inflammatory bowel diseases (IBD). The central nervous system (CNS) cooperates dynamically with the immune system to regulate inflammation through humoral and neural pathways. In particular, acetylcholine (Ach), the main neurotransmitter in the vagus nerve, decreases the production of pro-inflammatory cytokines through a mechanism dependent on the α7 nicotinic Ach receptors (α7nAChRs). Areas covered: Here, we review the evidence for involvement of the cholinergic anti-inflammatory pathway (CAP) in IBD. We also elaborate the role of α7nAChRs and subsequent cellular pathways in CAP. Finally, we review potential therapeutic implications of modulators of these receptors. Expert opinion: Alpha7nAChR modulators possess both cognitive improving and anti-inflammatory properties. Although, these agents demonstrated therapeutic benefits in experimental models, their efficacy has not always been translated in clinical trials. Thus, development of more specific α7nAChR ligands as well as more experimental studies and better controlled trials, especially in the field of IBD, are encouraged for a progress in this field.

Nicotine and oxidative stress induced exomic variations are concordant and overrepresented in cancer-associated genes

Although the connection between cancer and cigarette smoke is well established, nicotine is not characterized as a carcinogen. Here, we used exome sequencing to identify nicotine and oxidative stress-induced somatic mutations in normal human epithelial cells and its correlation with cancer. We identified over 6,400 SNVs, indels and microsatellites in each of the stress exposed cells relative to the control, of which, 2,159 were consistently observed at all nicotine doses. These included 429 nsSNVs including 158 novel and 79 cancer-associated. Over 80% of consistently nicotine induced variants overlap with variations detected in oxidative stressed cells, indicating that nicotine induced genomic alterations could be mediated through oxidative stress. Nicotine induced mutations were distributed across 1,585 genes, of which 49% were associated with cancer. MUC family genes were among the top mutated genes. Analysis of 591 lung carcinoma tumor exomes from The Cancer Genome Atlas (TCGA) revealed that 20% of non-small-cell lung cancer tumors in smokers have mutations in at least one of the MUC4, MUC6 or MUC12 genes in contrast to only 6% in non-smokers. These results indicate that nicotine induces genomic variations, promotes instability potentially mediated by oxidative stress, implicating nicotine in carcinogenesis, and establishes MUC genes as potential targets.

Characterizing the Genetic Basis for Nicotine Induced Cancer Development: A Transcriptome Sequencing Study

Nicotine is a known risk factor for cancer development and has been shown to alter gene expression in cells and tissue upon exposure. We used Illumina® Next Generation Sequencing (NGS) technology to gain unbiased biological insight into the transcriptome of normal epithelial cells (MCF-10A) to nicotine exposure. We generated expression data from 54,699 transcripts using triplicates of control and nicotine stressed cells. As a result, we identified 138 differentially expressed transcripts, including 39 uncharacterized genes. Additionally, 173 transcripts that are primarily associated with DNA replication, recombination, and repair showed evidence for alternative splicing. We discovered the greatest nicotine stress response by HPCAL4 (up-regulated by 4.71 fold) and NPAS3 (down-regulated by -2.73 fold); both are genes that have not been previously implicated in nicotine exposure but are linked to cancer. We also discovered significant down-regulation (-2.3 fold) and alternative splicing of NEAT1 (lncRNA) that may have an important, yet undiscovered regulatory role. Gene ontology analysis revealed nicotine exposure influenced genes involved in cellular and metabolic processes. This study reveals previously unknown consequences of nicotine stress on the transcriptome of normal breast epithelial cells and provides insight into the underlying biological influence of nicotine on normal cells, marking the foundation for future studies.

Differential cell-specific cytotoxic responses of oral cavity cells to tobacco preparations

To examine the effects of standardized (reference) tobacco preparations on human oral cavity cells, two oral squamous cell carcinoma cell lines (101A, 101B) and normal human gingival epithelial cells (HGEC) were treated with cigarette smoke total particulate matter (TPM), smokeless tobacco extracted with complete artificial saliva (ST/CAS), or whole-smoke conditioned media (WS-CM). EC-50 values, as determined by sulforhodamine B assays, varied among the cell types and agents. When normalized to nicotine content, cytotoxicity for WS-CM and TPM was higher compared to that observed with ST/CAS. Nicotine alone had no or only minimal cytotoxicity for all cell types in the applied range. Activation of pro-apoptotic caspase-3 was examined in all cell types at their respective EC-50 doses for the three agents. TPM, but not ST/CAS or WS-CM significantly activated caspase-3 in all three cell types. Fluorescence-activated cell sorting (FACS) for expression of the early apoptosis marker Annexin V and for nuclear staining by 7-aminoactinomycin (7-AAD) revealed different extents of apoptosis versus non-apoptotic cell death for the three agents. These data characterize differential responses of normal and malignant oral cells after exposure to TPM, ST/CAS, or WS-CM. They assist in understanding differential effects of combustible versus non-combustible tobacco products, and in identifying novel biomarkers for tobacco smoke exposure and effect in the oral cavity.

Molecular characterization of peripheral arterial disease in proximal extremity arteries

PURPOSE

Although risk factors for atherosclerosis in peripheral arterial disease (PAD) are well defined, the underlying mechanisms are poorly understood and no medication exists for causal therapy. Molecular pathways that could be targeted have not been identified so far. To address this issue, we compared the molecular profiles of healthy versus PAD proximal femoral arteries.

METHODS

Gene expression profiles from proximal femoral arteries of patients with PAD (Fontaine stage IIb-IV; n = 20) and femoral arteries from healthy controls (CO) (n = 3) were compared by microarray technology. We evaluated all samples by histopathology and performed microdissection on the CO tissue before molecular analysis. We analyzed genes regarding their cellular localization, molecular function, and risk factors such as hypercholesterolemia, smoking, and diabetes. We used a selected panel of genes for polymerase chain reaction validation of microarray results and compared the data with previously published studies.

RESULTS

Most genes overexpressed in PAD versus CO were located in the cytoplasm, membrane, and nucleus. Functionally, they had binding activity to nucleotides, cytoskeletal proteins, and transcription factors. They were mainly involved in immune regulation (e.g., interleukin-8, chemokine ligand 18, and allograft-inflammatory factor-1) (P < 0.01). Down-regulated genes in PAD versus CO were located in the extracellular region. They had transporter and G-protein receptor activity. They were associated with signaling, cell growth, and tissue formation (e.g., myosin VB, marker for differentiated aortic smooth muscle, myosin 11) (P < 0.01). Polymerase chain reaction successfully validated the expression of the differences among 10 selected genes (e.g., chemokine ligand 18, common leukocyte antigen, killer cell lectin-like receptor subfamily B, member 1, and interleukin-8).

CONCLUSIONS

Genes enrolled in immune regulation and inflammatory response were identified as key players in PAD. Various membrane-bound molecules with binding activity are hereunder. Identification of such molecules may elucidate relevant players that act as candidates for therapeutic targets or prognostic markers in the future.

Chronic nicotine exposure attenuates proangiogenic activity on human umbilical vein endothelial cells

The pathogenic mechanism of nicotine, a major product of smoking, on vascular endothelial cells is not well defined yet. The purpose of this study was to determine whether chronic exposure to nicotine alters angiogenic activity in human umbilical vein endothelial cells and to identify a potential role for endothelial nitric oxide synthase (eNOS) expression. Our study demonstrated that acute nicotine treatment enhanced nitric oxide release, eNOS activation, and proangiogenic activity. However, chronic nicotine exposure impaired proangiogenic function (decreased cell migration and tubular structure formation) in human umbilical vein endothelial cells compared with acute exposure, but sustained the antiapoptotic effect. These findings seem to be related to eNOS gene expression and nitric oxide production, which may be involved in the pathophysiology of chronic nicotine addicts.

Combined effects of smoking, anti-EBNA antibodies, and HLA-DRB1*1501 on multiple sclerosis risk

OBJECTIVE

To examine the interplay between smoking, serum antibody titers to the Epstein-Barr virus nuclear antigens (anti-EBNA), and HLA-DR15 on multiple sclerosis (MS) risk.

METHODS

Individual and pooled analyses were conducted among 442 cases and 865 controls from 3 MS case-control studies-a nested case-control study in the Nurses' Health Study/Nurses' Health Study II, the Tasmanian MS Study, and a Swedish MS Study. Conditional logistic regression models were used to calculate odds ratios (ORs) and 95% CIs for the association between smoking, anti-EBNA titers, HLA-DR15, and MS risk. Study estimates were pooled using inverse variance weights to determine a combined effect and p value.

RESULTS

Among MS cases, anti-EBNA titers were significantly higher in ever smokers compared to never smokers. The increased risk of MS associated with high anti-EBNA Ab titers was stronger among ever smokers (OR = 3.9, 95% CI = 2.7-5.7) compared to never smokers (OR = 1.8, 95% CI = 1.4-2.3; p for interaction = 0.001). The increased risk of MS associated with a history of smoking was no longer evident after adjustment for anti-EBNA Ab titers. No modification or confounding by HLA-DR15 was observed. The increased risk of MS associated with ever smoking was only observed among those who had high anti-EBNA titers (OR = 1.7, 95% CI = 1.1-2.6).

CONCLUSIONS

Smoking appears to enhance the association between high anti-EBNA titer and increased multiple sclerosis (MS) risk. The association between HLA-DR15 and MS risk is independent of smoking. Further work is necessary to elucidate possible biologic mechanisms to explain this finding.

Overexpression of activated nuclear factor-kappa B in aorta of patients with coronary atherosclerosis

BACKGROUND

Inflammation is an established risk factor for atherosclerosis. In an inflammatory state, nuclear factor-kappa B (NF-kappaB) is frequently activated as a key transcription activator for the downstream responses.

HYPOTHESIS

The aim of this study was to investigate the changes of NF-kappaB in the aorta of patients with coronary atherosclerosis and its association with atherosclerotic risk factors.

METHODS

From 2004 to 2005, we collected a small piece of ascending aorta in the bypass procedure from patients (n = 31) undergoing coronary artery bypass graft (CABG) surgery. The expression of NF-kappaB was determined by immunohistochemistry, and its transcriptional activity was evaluated by electrophoretic mobility shift assay. Celiac aortic tissues from 4 subjects without known atherosclerosis through the kidney donation program were taken as control.

RESULTS

NF-kappaB was detectable in aortas from CABG patients with the transcriptional activities significantly increased. The relative level of aortic NF-kappaB expression was elevated in patients who were smokers or with hypertension. Spearman correlation revealed that aortic NF-kappaB expression had significant correlation with coronary severity scores (Gensini score, r = 0.608, P < .05). The NF-kappaB expression was positively correlated with the levels of blood glucose, low-density lipoprotein cholesterol, lipoprotein(a), total cholesterol, and non-high-density lipoprotein cholesterol (P < .05); but negatively correlated with high-density lipoprotein cholesterol (P < .05).

CONCLUSIONS

Our study demonstrates a highly activated NF-kappaB in aortas from patients with coronary atherosclerosis, which may reflect overall arterial overinflammatory status. The findings of hyperactive NF-kappaB in aortas may provide a diagnostic parameter for the inflammation that is associated with and may cause atherosclerosis.

Gene regulation of alpha4beta2 nicotinic receptors: microarray analysis of nicotine-induced receptor up-regulation and anti-inflammatory effects

alpha4beta2 Nicotinic acetylcholine receptors play an important role in the reward pathways for nicotine. We investigated whether receptor up-regulation of alpha4beta2 nicotinic acetylcholine receptors involves expression changes for non-receptor genes. In a microarray analysis, 10 muM nicotine altered expression of 41 genes at 0.25, 1, 8 and 24 h in halpha4beta2 SH-EP1 cells. The maximum number of gene changes occurred at 8 h, around the initial increase in (3)[H]-cytisine binding. Quantitative RT-PCR corroborated gene induction of endoplasmic reticulum proteins CRELD2, PDIA6, and HERPUD1, and suppression of the pro-inflammatory cytokines IL-1beta and IL-6. Nicotine suppresses IL-1beta and IL-6 expression at least in part by inhibiting NFkappaB activation. Antagonists dihydro-beta-erythroidine and mecamylamine blocked these nicotine-induced changes showing that receptor activation is required. Antagonists alone or in combination with nicotine suppressed CRELD2 message while increasing alpha4beta2 binding. Additionally, small interfering RNA knockdown of CRELD2 increased basal alpha4beta2 receptor expression, and antagonists decreased CRELD2 expression even in the absence of alpha4beta2 receptors. These data suggest that endoplasmic reticulum proteins such as CRELD2 can regulate alpha4beta2 expression, and may explain antagonist actions in nicotine-induced receptor up-regulation. Further, the unexpected finding that nicotine suppresses inflammatory cytokines suggests that nicotinic alpha4beta2 receptor activation promotes anti-inflammatory effects similar to alpha7 receptor activation.

Significant association of ANKK1 and detection of a functional polymorphism with nicotine dependence in an African-American sample

The dopaminergic system in the brain plays a critical role in nicotine addiction. Genetic variants in the dopaminergic system, including those in dopamine receptor genes, represent plausible candidates for the genetic study of nicotine dependence (ND). We investigated various polymorphisms in the dopamine D(2) receptor gene (DRD2) and its neighboring ankyrin repeats and kinase domain containing 1 gene (ANKK1) to determine whether they were associated with ND. We examined 16 single nucleotide polymorphisms (SNPs) at DRD2 and 7 SNPs at ANKK1 in our Mid-South Tobacco Family cohort, which consisted of 2037 participants representing two distinct American populations. Several SNPs (rs7131056, rs4274224, rs4648318, and rs6278) in DRD2, along with the Taq IA polymorphism (rs1800497) in ANKK1, revealed initial significant associations with ND in European Americans, but not after correction for multiple testing, indicating a weak association of DRD2 with ND. In contrast, associations for ANKK1 with ND in the African-American and pooled samples, specifically for SNP rs2734849, remained significant after correction. With a non-synonymous G to A transition, rs2734849 produces an amino-acid change (arginine to histidine) in C-terminal ankyrin repeat domain of ANKK1. Using the luciferase reporter assay, we further demonstrated that the variant alters expression level of NF-kappaB-regulated genes. Since DRD2 expression is regulated by transcription factor NF-kappaB, we suspect that rs2734849 may indirectly affect dopamine D(2) receptor density. We conclude that ANKK1 is associated with ND and polymorphism rs2734849 in ANKK1 represents a functional causative variant for ND in African-American smokers.

Alcohol and nicotine consumption exacerbates choroidal neovascularization by modulating the regulation of complement system

The objective of the present study was to investigate the effect of alcohol and nicotine consumption on the pathogenesis of choroidal neovascularization (CNV) in rats after laser-photocoagulation. Confocal microscopic analysis demonstrated an increase in CNV complex size in rats fed with alcohol (2.3-fold), nicotine (1.9-fold), and the combination of alcohol and nicotine (2.7-fold) compared with the control groups. Immunohistochemical analysis revealed that alcohol and nicotine consumption increased MAC deposition and VEGF expression in laser spots. Expression of CD59 by RT-PCR and Western blot was drastically reduced in the animals that were fed with alcohol, nicotine and alcohol and nicotine compared to those fed with water alone and this was associated with exacerbation of CNV.

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

Apoptosis is a vital mechanism for the regulation of cell turnover and plays a critical role in tissue homeostasis and development of many disease processes. Previous studies have demonstrated the apoptotic effect of tobacco smoke; however, the molecular mechanisms by which tobacco smoke triggers apoptosis remain unclear. In the present study we investigated the effects of tobacco smoke on the induction of apoptosis in the lungs of rats and modulation of nuclear factor-kappa B (NF-kappaB) in this process. Exposure of rats to 80 mg/m(3) tobacco smoke significantly induced apoptosis in the lungs. Tobacco smoke resulted in inhibition of NF-kappaB activity, noted by suppression of inhibitor of kappaB (IkappaB) kinase (IKK), accumulation of IkappaBalpha, decrease of NF-kappaB DNA binding activity, and downregulation of NF-kappaB-dependent anti-apoptotic proteins, including Bcl-2, Bcl-xl, and inhibitors of apoptosis. Initiator caspases for the death receptor pathway (caspase 8) and the mitochondrial pathway (caspase 9) as well as effector caspase 3 were activated following tobacco smoke exposure. Tobacco smoke exposure did not alter the levels of p53 and Bax proteins. These findings suggest the role of NF-kappaB pathway in tobacco smoke-induced apoptosis.

Emerging role of MAP kinase pathways as therapeutic targets in COPD

Studies examining the cellular mechanisms of inflammation and protease production in the lung tissue and airways of COPD patients have shed light on the important role of kinase-based signaling cascades. These pathways can be activated by environmental stimuli such as tobacco smoke, and by endogenous signals such as cytokines, growth factors, and inflammation-derived oxidants. The three most widely characterized cascades are those directed by the classical mitogen activated protein (MAP) kinase (ERK1/2), stress activated protein kinase/c-Jun N-terminal protein kinase, and p38 enzymes. These phosphorylation cascades transmit and amplify extracellular, receptor-mediated signals through the cytoplasm of the cell to activate nuclear transcription factors which bind and induce expression of target genes. The result is tight control of diverse cellular events, and rapid responses to external stimuli. However, recent research suggests that constitutive or aberrant activation of MAP kinases contributes to several COPD-associated phenotypes, including mucus overproduction and secretion, inflammation, cytokine expression, apoptosis, T cell activation, matrix metalloproteinase production, and fibrosis. This review explores the biological functions of the MAP kinase pathways in the pathogenesis of COPD, their activation by cigarette smoke, and discusses the potential role of MAP kinase inhibitors in COPD therapy.

Nicotine and apoptosis

Cigarette smoking is associated with a plethora of different diseases. Nicotine is the addictive component of cigarette but also acts onto cells of the non-neuronal system, including immune effector cells. Although nicotine itself is usually not referred to as a carcinogen, there is ongoing debate whether nicotine functions as a 'tumor enhancer.' By binding to nicotinic acetylcholine receptors, nicotine deregulates essential biological processes like angiogenesis, apoptosis, and cell-mediated immunity. Apoptosis plays critical roles in a wide variety of physiologic processes during fetal development and in adult tissue and is also a fundamental aspect of the biology of malignant diseases. This review provides an overlook how nicotine influences apoptotic processes and is thus directly involved in the etiology of pathological conditions like cancer and obstructive diseases.

Neuroproteomics and its applications in research on nicotine and other drugs of abuse

The rapidly growing field of neuroproteomics is able to track changes in protein expression and protein modifications underlying various physiological conditions, including the neural diseases related to drug addiction. Thus, it presents great promise in characterizing protein function, biochemical pathways, and networks to understand the mechanisms underlying drug dependence. In this article, we first provide an overview of proteomics technologies and bioinformatics tools available to analyze proteomics data. Then we summarize the recent applications of proteomics to profile the protein expression pattern in animal or human brain tissues after the administration of nicotine, alcohol, amphetamine, butorphanol, cocaine, and morphine. By comparing the protein expression profiles in response to chronic nicotine exposure with those appearing in response to treatment with other drugs of abuse, we identified three biological processes that appears to be regulated by multiple drugs of abuse: energy metabolism, oxidative stress response, and protein degradation and modification. Such similarity indicates that despite the obvious differences among their chemical properties and the receptors with which they interact, different substances of abuse may cause some similar changes in cellular activities and biological processes in neurons.

Nicotine and hippocampus-dependent learning: implications for addiction

Addiction is a complex disorder because many factors contribute to the development and maintenance of addiction. One factor is learning. For example, drug-context associations that develop during drug use could facilitate drug craving upon re-exposure to contexts previously associated with drugs. Additionally, deficits in cognitive processes associated with withdrawal could precipitate relapse in attempts to ameliorate those deficits. Because addiction and learning involve common neural areas and cell signaling cascades, addiction-related changes in processes underlying plasticity may contribute to addiction. This article examines similarities between addiction and learning at the behavioral, neural, and cellular levels, with emphasis on the neural substrates underlying the effects of acute nicotine, chronic nicotine, and withdrawal from chronic nicotine on hippocampus-dependent contextual learning.

Smoking habit and load influence age at diagnosis and disease extent in ulcerative colitis

INTRODUCTION

Cigarette smoking affects susceptibility to ulcerative colitis (UC), but its effects on age at diagnosis, disease extent, and need for surgery are less well defined. We examined these parameters in a detailed retrospective analysis of a large cohort of well-characterized UC patients.

METHODS

499 UC patients (254 male, median age 34.3 yr) were studied. Data were collected on smoking habits, smoking load (pack-years), age at recruitment, age at diagnosis, surgery, and disease extent. Colonoscopic and histological data at both diagnosis and follow-up (median follow-up time 4.6 yr) were available on 349 patients.

RESULTS

Ex-smokers were older at diagnosis than current or nonsmokers, (46.5 yr vs 31.1 or 29.4 yr, respectively, P < 0.001). Before diagnosis, ex-smokers had a higher smoking load than current smokers (13.0 vs 6.94 pack-years, P < 0.001). A Cox model for age at diagnosis, with smoking as a time-dependent covariate, showed that at any age, ex-smokers were significantly more likely to develop UC than current smokers (hazard ratio 1.8, 95% CI 1.41-2.44, P < 0.001). For current smokers at latest colonoscopy, those with extensive disease were the lightest smokers (median 0.320 pack-years), whereas those with healthy colons were the heaviest smokers (median 9.18 pack-years, P= 0.006). At 5 yr, regression of extensive disease was more frequent in current than ex-smokers or nonsmokers (30% current smokers vs 8% nonsmokers and 5% ex-smokers, chi(2)= 30.4, P < 0.001) but these differences were not maintained over a longer time period.

CONCLUSIONS

Smoking habit influences the age at diagnosis and changes in disease extent in UC. Mechanisms are likely to be complex and require further investigation.

ERK 1/2 signaling pathway is involved in nicotine-mediated neuroprotection in spinal cord neurons

Evidence indicates that agonists of neuronal nicotinic receptors (nAChRs), including nicotine, can induce neuroprotective and anti-apoptotic effects in the CNS. To study these mechanisms, the present study focused on nicotine-mediated modulation of the extracellular regulated kinase 1 and 2 (ERK1/2) pathway in cultured spinal cord neurons. Exposure to nicotine (0.1-10 microM) for as short as 1 min markedly upregulated levels of phosphorylated ERK1/2 (pERK1/2) and increased total ERK1/2 activity. Inhibition studies with mecamylamine and alpha-bungarotoxin revealed that these effects were mediated by the alpha7 nicotinic receptor. In addition, pre-exposure to U0126, a specific inhibitor of the ERK1/2 signaling, prevented nicotine-mediated anti-apoptotic effects. To indicate if treatment with nicotine also can activate ERK1/2 in vivo, a moderate spinal cord injury (SCI) was induced in rats using a weight-drop device and nicotine was injected 2 h post-trauma. Consistent with in vitro data, nicotine increased levels of pERK1/2 in this animal model of spinal cord trauma. Results of the present study indicate that the ERK1/2 pathway is involved in anti-apoptotic effects of nicotine in spinal cord neurons and may be involved in therapeutic effects of nicotine in spinal cord trauma.

Ventral Tegmental Transcriptome Response to Intermittent Nicotine Treatment and Withdrawal in BALB/cJ, C57BL/6ByJ, and Quasi-Congenic RQI Mice

The aim of this study was to identify neurochemical pathways and candidate genes involved in adaptation to nicotine treatment and withdrawal. Locomotor sensitization was assessed in a nicotine challenge test after exposure to intermittent nicotine treatment and withdrawal. About 24 h after the challenge test the ventral tegmentum of the mesencephaion was dissected and processed using oligonucleotide microarrays with 22,690 probe sets (Affymetrix 430A 2.0). Quasi-congenic RQI, and donor BALB/cJ mice developed significant locomotor sensitization, while sensitization was not significant in the background partner, C57BL/6By. Comparing saline treated controls of C57BL/6ByJ and BALB/cJ by a rigorous statistical microarray analysis method we identified 238 differentially expressed transcripts. Quasi-congenic strains B6.Cb4i5-alpha4/Vad and B6.Ib5i7-beta25A/Vad significantly differed from the background strain in 11 and 11 transcripts, respectively. Identification of several cis- and trans-regulated genes indicates that further work with quasi-congenic strains can quickly lead to mapping of Quantitative Trait Loci for nicotine susceptibility because donor chromosome regions have been mapped in quasi-congenic strains. Nicotine treatment significantly altered the abundance of 41, 29, 54, and 14 ventral tegmental transcripts in strains C57BL/6ByJ, BALB/cJ, B6.Cb4i5-alpha4/Vad, and B6.Ib5i7-beta25A/Vad, respectively. Although transcript sets overlapped to some extent, each strain showed a distinct profile of nicotine sensitive genes, indicating genetic effects on nicotine-induced gene expression. Nicotine-responsive genes were related to processes including regulation of signal transduction, intracellular protein transport, proteasomal ubiquitin-dependent protein catabolism, and neuropeptide signaling pathway. Our results suggest that while there are common regulatory mechanisms across inbred strains, even relatively small differences in genetic constitution can significantly affect transcriptome response to nicotine.

Nicotine inhibits the production of proinflammatory mediators in human monocytes by suppression of I-kappaB phosphorylation and nuclear factor-kappaB transcriptional activity through nicotinic acetylcholine receptor alpha7

Macrophages/monocytes and the proinflammatory mediators, such as tumour necrosis factor (TNF)-alpha, prostaglandin E(2) (PGE(2)), macrophage inflammatory protein (MIP)-1alpha and MIP-1alpha, play a critical role in the progression of immunological disorders including rheumatoid arthritis, Behçet's disease and Crohn's disease. In addition, the nicotinic acetylcholine receptor-alpha7 (alpha7nAChR) subunit is an essential regulator of inflammation. In this study, we evaluated the expression of the alpha7nAChR subunit on human peripheral monocytes and the effect of nicotine on the production of these proinflammatory mediators by activated monocytes. Fluorescein isothiocyanate (FITC)-labelled alpha-bungarotoxin demonstrated the cell surface expression of the alpha7nAchR subunit. Pretreatment with low-dose nicotine caused inhibition of TNF-alpha, PGE(2), MIP-1alpha and MIP-1alpha production, and mRNA expression of TNF-alpha, MIP-1alpha and MIP-1alpha and COX-2 in lipopolysaccharide (LPS)-activated monocytes. These suppressive effects of nicotine were caused at the transcriptional level and were mediated through alpha7nAChR. Nicotine suppressed the phosphorylation of I-kappaB, and then inhibited the transcriptional activity of nuclear factor-kappaB. These immunosuppressive effects of nicotine may contribute to the regulation of some immune diseases.

Nicotine causes age-dependent changes in gene expression in the adolescent female rat brain

Humans often start smoking during adolescence. Recent results suggest that rodents may also be particularly vulnerable to nicotine dependence during adolescence. We examined the effect of chronic nicotine exposure on gene expression profiles during adolescence in female rats, who were dosed with nicotine (and control animals were dosed with saline) via subcutaneously implanted osmotic minipumps. Brain samples were collected at four ages: before puberty (postnatal day 25), at about the time of puberty in females (postnatal day 35), and after puberty (postnatal days 45 and 55). The expression of 7931 genes in three brain areas was measured using DNA microarrays. Quantitative RT-PCR was also employed to confirm the expression patterns of selected genes. We used a novel clustering technique (principal cluster analysis) to classify 162 nicotine-regulated genes into five clusters, of which only one (cluster A) showed similar patterns of gene expression across all three brain areas (ventral striatum, prefrontal cortex, and hippocampus). Three clusters of genes (A, B, and C) showed dramatic peaks in their nicotine responses at the same age (p35). The other two clusters (D1 and D2) showed smaller peaks and/or valleys in their nicotine responses at p35 and p45. Thus, the age of maximal gene expression response to nicotine in female rats corresponds approximately to the age of maximal behavioral response and the age of puberty.

Receptor-mediated tobacco toxicity: cooperation of the Ras/Raf-1/MEK1/ERK and JAK-2/STAT-3 pathways downstream of alpha7 nicotinic receptor in oral keratinocytes

The use of tobacco products is associated with an increased incidence of periodontal disease, poor response to periodontal therapy, and a high risk for developing head and neck cancer. Nicotine and tobacco-derived nitrosamines have been shown to exhibit their pathobiologic effects due in part to activation of the nicotinic acetylcholine (ACh) receptors (nAChRs), mainly alpha7 nAChR, expressed by oral keratinocytes (KCs). This study was designed to gain mechanistic insight into alpha7-mediated morbidity of tobacco products in the oral cavity. We investigated the signaling pathways downstream of alpha7 nAChR in monolayers of oral KCs exposed for 24 h to aged and diluted sidestream cigarette smoke (ADSS) or an equivalent concentration of pure nicotine. By both real-time polymerase chain reaction (PCR) and In-cell Western, the KCs stimulated with ADSS or nicotine showed multifold increases of STAT-3. These effects could be completely blocked or significantly (P<0.05) diminished if the cells were pretreated with the alpha7 antagonist alpha-bungarotoxin (alphaBTX) or transfected with anti-alpha7 small interfering RNA (siRNA-alpha7). The use of pathway inhibitors revealed that signaling through the Ras/Raf-1/MEK1/ERK steps mediated alpha7-dependent up-regulation of STAT-3. Targeted mutation of the alpha7 gene prevented ERK1/2 activation by nicotine. Using the gel mobility shift assay, we demonstrated that an increased protein binding activity of STAT-3 caused by ADSS or pure nicotine was mediated by janus-activated kinase (JAK)-2. Activation of JAK-2/STAT-3 pathway could be prevented by alphaBTX or siRNA-alpha7. Thus, nuclear transactivation of STAT-3 in KCs exposed to tobacco products is mediated via intracellular signaling downstream from alpha7, which proceeds via two complementary pathways. The Ras/Raf-1/MEK1/ERK cascade culminates in up-regulated expression of the gene encoding STAT-3, whereas recruitment and activation of tyrosine kinase JAK-2 phosphorylates it. Elucidation of this novel mechanism of nicotine-dependent nuclear transactivation of STAT-3 identifies oral alpha7 nAChR as a promising molecular target to prevent, reverse, or retard tobacco-related periodontal disease and progression of head and neck cancer by receptor inhibitors.

Nicotine induces the fragile histidine triad methylation in human esophageal squamous epithelial cells

The fragile histidine triad (FHIT) gene has been proposed to have an important role in very early carcinogenesis. Methylation of the FHIT gene is associated with transcriptional inactivation in esophageal squamous cell carcinoma, and FHIT inactivation has been linked to smoking-related carcinogenesis. In this study, we confirmed methylation of the FHIT gene in human esophageal squamous epithelial cells (HEECs) and examined whether nicotine induced alteration of FHIT. Methylation status in the promoter region of the FHIT gene and p16(INK4A) gene was determined by methylation-specific PCR in HEECs exposed to nicotine under various conditions. Methylation status of the FHIT gene was confirmed by DNA-sequencing analysis. Protein expression of Fhit and the DNA methyltransferases (DNMTs) DNMT1 and DNMT3a were assessed by immunoblot analysis. In the absence of nicotine, methylation of the FHIT gene and attenuation of Fhit protein were not detected in HEECs. Nicotine induced the methylation of FHIT gene and attenuated Fhit protein in association with increased expression of DNMT3a. Reexpression of Fhit protein in HEECs was found after cessation of moderate- to long-term exposure to nicotine. Our results show that nicotine induces methylation of the FHIT gene followed by loss of Fhit protein expression in HEECs. Continuous smoking may thus increase the risk of esophageal cancer.

Proteins differentially expressed in response to nicotine in five rat brain regions: identification using a 2-DE/MS-based proteomics approach

To determine protein expression patterns within the central nervous system (CNS) in response to nicotine, 2-DE/MS was performed on samples from five brain regions of rats that had received nicotine bitartrate by osmotic minipump infusion at a dose of 3.15 mg/kg/day for 7 days. After spot matching and statistical analysis, 41 spots in the amygdala, 49 in the nucleus accumbens (NA), 46 in the prefrontal cortex (PFC), 36 in the striatum, and 28 in the ventral tegmental area (VTA) showed significant differences in the nicotine-treated compared with control samples. Using MALDI-TOF MS peptide fingerprinting, 14 proteins in the amygdala, 11 in the NA, 19 in the PFC, 13 in the striatum, and 19 in the VTA were identified. Several proteins (e.g. dynamin 1, laminin receptors, aldolase A, enolase 1 alpha, Hsc70-ps1, and N-ethylmaleimide-sensitive fusion protein) were differentially expressed in multiple brain regions. By gene ontology analysis, these differentially expressed proteins were grouped into biological process categories, such as energy metabolism, synaptic function, and oxidative stress metabolism. These data, in combination with microarray analysis of mRNA transcripts, have the potential to identify the CNS gene products that show coordinated changes in expression at both the RNA and protein levels in response to nicotine.

Phosphodiesterase 4D polymorphisms and the risk of cerebral infarction in a biracial population: the Stroke Prevention in Young Women Study

An association between polymorphisms within the phosphodiesterase 4D gene (PDE4D) and ischemic stroke was initially reported in older adults from Iceland and has been supported by studies in several other primarily elderly populations. In the present study, we examined the association between PDE4D polymorphisms and early-onset ischemic stroke in a biracial female population. A systematic search for polymorphisms in the highly evolutionary conserved regions of PDE4D was performed on 48 African-American and 48 Caucasian participants. Novel and known polymorphisms were then prioritized and genotyped in the entire study population of 224 cases of first ischemic stroke among women aged 15-49 and 211 age- and ethnicity-balanced control subjects. Forty novel and previously reported polymorphisms with a minor allele frequency greater than 0.05 were determined, with 23 polymorphisms selected for analysis in the full case-control sample. Single nucleotide polymorphism (SNP), linkage disequilibrium and haplotype analyses were performed. SNP rs918592, found in an intron near the 5' end of the gene, was significantly associated with stroke (age- and race-adjusted odds ratio (OR=1.5, P=0.007), with four other SNPs showing significant, albeit less strong, associations. The magnitude of association was similar across African-Americans and Caucasians and across multiple stroke subtypes (e.g. atherosclerotic, lacunar and non-lacunar of undetermined etiology). The association of rs918592 with stroke was confined exclusively to current smokers (OR=3.2, P=0.00014), with no association observed among never-smokers (OR=0.9, P=0.75) or former smokers (OR=1.2, P=0.66), demonstrating a gene-environment interaction (P=0.03). A strong dose-response relationship was also seen among current smokers. No specific risk haplotypes were identified.

Mitogen-activated protein kinase pathway was significantly activated in human bronchial epithelial cells by nicotine

Nicotine is potentially associated with the onset of chronic obstructive pulmonary disease (COPD) and lung cancer. To gain insights into the molecular mechanism underlying such nicotine-induced conditions, microarray- bioinformatics analysis was carried out in the present study to explore the gene expression profiles in human bronchial epithelial cells (HBECs) treated with 5 microM nicotine for 4, 8, and 10 h. Of 1,800 assessed genes overall, 260 (14.4%) were upregulated and 17 (0.9%) down regulated significantly. Gene ontology analysis demonstrated that most of the differentially expressed genes belonged to the category of molecular function, especially to the subcategories of enzyme activity. The integration of obtained information with bioinformatics tools in DAVID and KEGG databases indicated that the greatest number of overexpressed genes was involved in mitogen-activated protein kinase (MAPK) pathway. Membrane array analysis subsequently suggested that both extracellular signal-regulated kinase (ERK) 1/2 and c-Jun-NH(2)-terminal kinase (JNK) signalings but not p38 MAPK signaling were activated in response to nicotine. Pretreatment of HBECs with specific inhibitors against ERK 1/2 and JNK but not p38 could significantly inhibit nicotine-induced interleukin- 8 production. These results suggest that MAPK pathway may mediate the effect of nicotine through ERK 1/2 and JNK but not p38 in HBECs treated with nicotine.

Gene expression is differentially regulated by neurotransmitters in embryonic neuronal cortical culture

Neurotransmitters and their receptors have been involved in both proper brain development and neurodevelopmental disorders. The role that nicotinic receptors play in immature cortical neurons was initially investigated by gene profiling using Affymetrix DNA arrays. Both short (15 min) and prolonged (18 h) treatments with nicotine did not induce modification in gene expression, whereas a significant down-regulation of c-fos protein levels was observed after 18 h treatment. Conversely, a brief treatment with the glutamatergic agonist NMDA triggered up-regulation of immediate early genes and transcription factors, which remained unaffected by pre-treatment for 18 h with nicotine. Calcium imaging studies revealed that NMDA activated a sustained increase in intracellular calcium concentration in the majority of neurons, whereas nicotine evoked only a transient calcium increase in a smaller percentage of neurons, suggesting that the calcium signalling response was correlated with activation of gene expression. Nicotine effects on immature cortical neurons perhaps do not require gene regulation but may be still acting on signalling pathways.

Environmental tobacco smoke suppresses nuclear factor-kappaB signaling to increase apoptosis in infant monkey lungs

RATIONALE

Exposure to environmental tobacco smoke in early life has adverse effects on lung development. Apoptosis plays an essential role in development; however, the molecular mechanisms of pulmonary apoptosis induced by environmental tobacco smoke is unknown.

OBJECTIVES

To investigate the mechanistic role of nuclear factor (NF)-kappaB, a critical cell survival pathway, in the developing lungs exposed to environmental tobacco smoke.

METHODS

Timed-pregnant rhesus monkeys and their offspring were exposed to filtered air or to aged and diluted sidestream cigarette smoke as a surrogate to environmental tobacco smoke (a total suspended particulate concentration of 0.99 mg/m(3) for 6 h/d, 5 d/wk) from 45-50 d gestational age to 72-77 d postnatal age (n = 4/group).

MEASUREMENTS AND MAIN RESULTS

NF-kappaB-DNA binding activity, regulated anti-apoptotic genes, and apoptosis were measured in lung tissues. Exposure to environmental tobacco smoke significantly suppressed NF-kappaB activation pathway and activity. Environmental tobacco smoke further down-regulated NF-kappaB-dependent anti-apoptotic genes and induced activation of caspases, cleavage of cellular death substrates (poly(ADP)-ribose polymerase and caspase-activated DNase) and an increase in the rate of apoptosis in the lung parenchyma. No significant alterations were observed for activator protein 1, p53 or Akt activity.

CONCLUSIONS

Our results indicate that exposure to low levels of environmental tobacco smoke during a critical window of maturation in the neonatal nonhuman primate may compromise lung development with potential implications for future lung growth and function. These findings support our hypothesis that NF-kappaB plays a key role in the regulation of the apoptotic process.

Nicotine-induced sensitization in mice: changes in locomotor activity and mesencephalic gene expression

It is believed that drug-induced behavioral sensitization is an important process in the development of substance dependence. In order to explore mechanisms of sensitization, a mouse model of nicotine-induced locomotor sensitization was established, and effects of the sensitization process on mesencepahlic gene expression were examined. A schedule, which included 3 weeks of intermittent nicotine exposure (0.5 mg/kg, s.c.) and 3 weeks of withdrawal, resulted in locomotor sensitization. Effects of sensitization on mesencephalic expression of approximately 14,000 genes were assessed using oligonucleotide microarrays. Signal intensity differences in samples obtained from repeated nicotine- and saline-exposed animals were analyzed with z-test after False Discovery Rate (FDR) multiple test correction. Genes related to GABA-A receptors and protein phosphatases were among 68 genes showing significantly different expression levels between the saline and the nicotine groups. We hypothesize that some of the gene expression changes in the mesencephalon are involved in pathways leading to nicotine-induced sensitization. Down-regulation of GABA-A receptors induced by repeated nicotine exposure may facilitate dopaminergic neuronal transmission and may contribute to increased locomotor activity.

Differential modulation of gene expression in the NMDA postsynaptic density of schizophrenic and control smokers

Nicotine is known to induce the release of multiple neurotransmitters, including glutamate and dopamine, through activation of nicotinic receptors. Gene expression in the N-methyl-d-aspartate postsynaptic density (NMDA-PSD), as well as other functional groups, was compared in postmortem hippocampus of schizophrenic and nonmentally ill smokers and nonsmokers utilizing a microarray and quantitative RT-PCR approach. The expression of 277 genes was significantly changed between all smokers and nonsmokers. Specific gene groups, most notably genes expressed in the NMDA-PSD, were prevalent among these transcripts. Analysis of the interaction between smoking and schizophrenia identified several genes in the NMDA-PSD that were differentially affected by smoking in patients. The present findings suggest that smoking may differentially modulate glutamatergic function in schizophrenic patients and control subjects. The biological mechanisms underlying chronic tobacco use are likely to differ substantially between these two groups.

Nicotine induces proinflammatory responses in macrophages and the aorta leading to acceleration of atherosclerosis in low-density lipoprotein receptor(-/-) mice

OBJECTIVE

We investigated the molecular mechanism of nicotine-accelerated atherosclerosis in a hyperlipidemic low-density lipoprotein receptor(-/-) mouse model.

METHODS AND RESULTS

Low-density lipoprotein receptor(-/-) mice received time-release nicotine or placebo pellets for 90 days. Aortic lesion size was 2.5 times larger in nicotine-treated than in placebo-treated mice (P<0.001). A mild increase in lipids was seen in treated mice. We quantified 18 different serum cytokines and found a significant increase of tumor necrosis factor alpha, interleukin 1beta, and keratinocyte-derived chemokine in nicotine-treated mice. Among 107 nuclear factor kappaB (NF-kappaB) target genes screened from the aorta, we found that nicotine treatment upregulated only 4 atherogenic genes including vascular adhesion molecule 1 and cyclooxygenase 2 on day 60 and platelet-derived growth factor B and platelet 12-lipoxygenase on day 90. At the cellular level, nicotine induced tumor necrosis factor alpha and inducible nitric oxide synthase expression in RAW264.7 cells via the nicotinic acetylcholine receptors. Induction was confirmed in peritoneal macrophages isolated from nicotine-treated mice. Finally, we showed that preconditioned medium from nicotine-treated RAW264.7 cells activated NF-kappaB in human smooth muscle cells and vascular endothelial cells as evidenced by nuclear localization and electromobility shift assay.

CONCLUSIONS

Chronic nicotine exposure augments atherosclerosis by enhancing the production of proinflammatory cytokines by macrophages, which, in turn, activate atherogenic NF-kappaB target genes in the aortic lesions.

Potentials and pitfalls of DNA array analysis of the endothelial stress response

Endothelial cells respond to inflammatory stimuli with complex genetic alterations that determine the immune response and the outcome of the inflammatory process. An additional layer of complexity is added by the different phenotypes and functional heterogeneity of endothelial cells in the various tissues. To understand these complex gene response patterns and the regulatory pathways involved, many investigators increasingly use DNA microarray analysis. There are, however, many potential pitfalls in the use of microarrays that can result in false data and erroneous conclusions. This review surveys the principles of DNA microarray technology and its applications in endothelial cell research. We also attempt to outline some of the caveats and standard criteria that have to be considered in order to realize the full potential of microarrays in inflammation research.

Microarray analysis identifies an aberrant expression of apoptosis and DNA damage-regulatory genes in multiple sclerosis

To clarify the molecular mechanisms underlying multiple sclerosis (MS)-promoting autoimmune process, we have investigated a comprehensive gene expression profile of T cell and non-T cell fractions of peripheral blood mononuclear cells (PBMC) isolated from 72 MS patients and 22 age- and sex-matched healthy control (CN) subjects by using a cDNA microarray. Among 1258 genes examined, 173 genes in T cells and 50 genes in non-T cells were expressed differentially between MS and CN groups. Downregulated genes greatly outnumbered upregulated genes in MS. More than 80% of the top 30 most significant genes were categorized into apoptosis signaling-related genes of both proapoptotic and antiapoptotic classes. They included upregulation in MS of orphan nuclear receptor Nurr1 (NR4A2), receptor-interacting serine/threonine kinase 2 (RIPK2), and silencer of death domains (SODD), and downregulation in MS of TNF-related apoptosis-inducing ligand (TRAIL), B-cell CLL/lymphoma 2 (BCL2), and death-associated protein 6 (DAXX). Furthermore, a set of the genes involved in DNA repair, replication, and chromatin remodeling was downregulated in MS. These results suggest that MS lymphocytes show a complex pattern of gene regulation that represents a counterbalance between promoting and preventing apoptosis and DNA damage of lymphocytes.

Using in vitro models for expression profiling studies on ethanol and drugs of abuse

The use of expression profiling with microarrays offers great potential for studying the mechanisms of action of drugs of abuse. Studies with the intact nervous system seem likely to be most relevant to understanding the mechanisms of drug abuse-related behaviours. However, the use of expression profiling with in vitro culture models offers significant advantages for identifying details of cellular signalling actions and toxicity for drugs of abuse. This study discusses general issues of the use of microarrays and cell culture models for studies on drugs of abuse. Specific results from existing studies are also discussed, providing clear examples of relevance for in vitro studies on ethanol, nicotine, opiates, cannabinoids and hallucinogens such as LSD. In addition to providing details on signalling mechanisms relevant to the neurobiology of drugs of abuse, microarray studies on a variety of cell culture systems have also provided important information on mechanisms of cellular/organ toxicity with drugs of abuse. Efforts to integrate genomic studies on drugs of abuse with both in vivo and in vitro models offer the potential for novel mechanistic rigor and physiological relevance.

Tobacco smoke dysregulates endothelial vasoregulatory transcripts in vivo

We hypothesized that human smoking and its deleterious effects on endothelial function can be modeled by exposure of mice to tobacco smoke, and further that these changes would be reflected in gene regulation in vascular endothelium. We used for these studies a mouse strain that expresses green fluorescent protein under the control of an endothelial-specific promoter, Tie-2. Mice were exposed to sidestream smoke from reference cigarettes at 34 mg total suspended particulates/m3. After exposure for 5 days/wk for 1 and 6 wk, aortas were pooled from treatment and control groups. Endothelial cells were rapidly isolated by collagenase treatment followed by fluorescent activated cell sorting to yield populations of >95% purity. RNA isolated from >500 endothelial cells was amplified and analyzed on deeply representative long oligo microarrays. Transcripts dysregulated by >2.5-fold were confirmed by real-time PCR and selected proteins by immunofluorescent localization. In the endothelial cells, the observed more than threefold upregulation of complement factor H (Cfh), calcitonin receptor-like (Calcr1), and soluble epoxide hydrolase (Epxh2) may play a role in hypertensive responses of the vasculature to smoking. We have identified gene regulation in vivo in vascular endothelium that potentially underlies hypertensive responses to tobacco smoke.

Expression profiling of cardiovascular disease

Cardiovascular disease is the most important cause of morbidity and mortality in developed countries, causing twice as many deaths as cancer in the USA. The major cardiovascular diseases, including coronary artery disease (CAD), myocardial infarction (MI), congestive heart failure (CHF) and common congenital heart disease (CHD), are caused by multiple genetic and environmental factors, as well as the interactions between them. The underlying molecular pathogenic mechanisms for these disorders are still largely unknown, but gene expression may play a central role in the development and progression of cardiovascular disease. Microarrays are high-throughput genomic tools that allow the comparison of global expression changes in thousands of genes between normal and diseased cells/tissues. Microarrays have recently been applied to CAD/MI, CHF and CHD to profile changes in gene expression patterns in diseased and non-diseased patients. This same technology has also been used to characterise endothelial cells, vascular smooth muscle cells and inflammatory cells, with or without various treatments that mimic disease processes involved in CAD/MI. These studies have led to the identification of unique subsets of genes associated with specific diseases and disease processes. Ongoing microarray studies in the field will provide insights into the molecular mechanism of cardiovascular disease and may generate new diagnostic and therapeutic markers.

Time-dependent changes in transcriptional profiles within five rat brain regions in response to nicotine treatment

Many years of behavioral and neurobiology studies have demonstrated broad physiological and pharmacological effects of nicotine on the central nervous system (CNS). However, the gene expression profiles associated with these effects are largely unknown. In this study, we characterized gene expression profiles in the prefrontal cortex, striatum, hypothalamus, amygdala and ventral tegmental area of the rat brain in response to subacute and chronic systemic nicotine administration using a pathway-focused microarray developed in this laboratory that contains 638 sequence-verified genes representing broad, yet targeted, biological functions. By comparing the regional effects of nicotine treatment on gene expression levels, we derived the expression profiles of targeted genes and gene families responding to the new environment created by nicotine throughout the complex connections of the CNS. While the expression of many genes was modulated by nicotine in several regions, only a few were co-modulated in multiple brain regions, suggesting region-specific transcriptional responses. Cluster analysis of significantly altered genes within each brain region over the course of nicotine treatment indicated the genes could be grouped into clusters. Subsequent ANOVA analysis demonstrated these clusters within each brain region to be significantly different at most time points. The clusters were comprised of broad functional groups, such as signaling, neurotransmission and protein modifications, demonstrating unique expression patterns within each region. Using a systematic approach to compare the different regional responses to nicotine administration will eventually provide a better understanding of how the different brain regions responding to this drug.

Nicotine increases in vivo blood–brain barrier permeability and alters cerebral microvascular tight junction protein distribution

The blood-brain barrier (BBB) is critical to the health of the central nervous system. The BBB is formed primarily by the presence of tight junctions (TJ) between cerebral microvessel endothelial cells. In light of the known effects of nicotine on endothelial cell biology, the specific effects of nicotine on the in vivo BBB were examined. Using in situ brain perfusion, it was found that continuous administration of nicotine (4.5 mg free base x kg(-1) x day(-1)) for 1 and 7 days led to increased permeability of the BBB to [14C]-sucrose without significant changes in its initial volume of distribution. The expression and distribution of the TJ-associated proteins actin, occludin, claudin-1, -3, and -5, and ZO-1 and -2 were analyzed by Western blot and immunofluorescence microscopy. Though no changes in total protein expression were observed, nicotine treatment was associated with altered cellular distribution of ZO-1 and diminished junctional immunoreactivity of claudin-3. It is proposed that nicotine leads to changes in BBB permeability via the modulation of TJ proteins.

Synergistic control of keratinocyte adhesion through muscarinic and nicotinic acetylcholine receptor subtypes

The biological mechanisms involved in initiating, coordinating, and ultimately terminating cell-cell adhesion in the stratified epithelium are not well understood at present. This study was designed to elucidate the roles of the muscarinic M3, the nicotinic alpha3, and the mixed muscarinic-nicotinic alpha9 acetylcholine receptors in physiologic control of keratinocyte adhesion. Both muscarinic and nicotinic antagonists caused keratinocyte detachment and reversibly increased the permeability of keratinocyte monolayers, indicative of the involvement of both muscarinic and nicotinic pathways in the cholinergic control of keratinocyte adhesion. Since phosphorylation of adhesion proteins plays an important role in rapid assembly and disassembly of intercellular junctions, we measured muscarinic and nicotinic effects on phosphorylation of keratinocyte adhesion molecules. The phosphorylation levels of E-cadherin, beta-catenin, and gamma-catenin increased following pharmacological blockage of muscarinic receptors. Long-term blocking of alpha3, alpha9, and M3 receptor signaling pathways with antisense oligonucleotides resulted in cell-cell detachment and changes in the expression levels of E-cadherin, beta-catenin, and gamma-catenin in cultured human keratinocytes. Simultaneous inhibition of several receptor subtypes with a mixture of antisense oligonucleotides produced intensified abnormalities with cell adhesion. Moreover, altered cell-cell adhesion was found in the stratified epithelium of alpha3, alpha9, and M3 receptor knockout mice. Keratinocytes from these mice exhibited abnormal expression of adhesion molecules at both the protein and the mRNA levels. Thus, our data indicate that the alpha3, alpha9, and M3 acetylcholine receptors play key roles in regulating in a synergistic mode keratinocyte adhesion, most probably by modulating cadherin and catenin levels and activities. These findings may aid in the development of novel methods useful for the treatment of skin adhesion diseases and tumor metastasis.

Candidate genes for nicotine dependence via linkage, epistasis, and bioinformatics

Many smoking-related phenotypes are substantially heritable. One genome scan of nicotine dependence (ND) has been published and several others are in progress and should be completed in the next 5 years. The goal of this hypothesis-generating study was two-fold. First, we present further analyses of our genome scan data for ND published by Straub et al. [1999: Mol Psychiatry 4:129-144] (PMID: 10208445). Second, we used the method described by Cox et al. [1999: Nat Genet 21:213-215] (PMID: 9988276) to search for epistatic loci across the markers used in the genome scan. The overall results of the genome scan nearly reached the rigorous Lander and Kruglyak [1995: Nat Genet 11:241-247] criteria for "significant" linkage with the best findings on chromosomes 10 and 2. We then looked for correspondence between genes located in the 10 regions implicated in affected sibling pair (ASP) and epistatic linkage analyses with a list of genes suggested by microarray studies of experimental nicotine exposure and candidate genes from the literature. We found correspondence between linkage and microarray/candidate gene studies for genes involved with the mitogen-activated protein kinase (MAPK) signaling system, nuclear factor kappa B (NFKB) complex, neuropeptide Y (NPY) neurotransmission, a nicotinic receptor subunit (CHRNA2), the vesicular monoamine transporter (SLC18A2), genes in pathways implicated in human anxiety (HTR7, TDO2, and the endozepine-related protein precursor, DKFZP434A2417), and the micro 1-opioid receptor (OPRM1). Although the hypotheses resulting from these linkage and bioinformatic analyses are plausible and intriguing, their ultimate worth depends on replication in additional linkage samples and in future experimental studies.

Clinical applications of DNA microarray analysis

Microarray technology provides a revolutionary macro-genetic and bioinformatic-rich platform for understanding human diseases. DNA microarrays facilitate the study of complex diseases, enabling several observations simultaneously that can become foundations for newer hypotheses-shifting us towards a non-reductionist approach to biological phenomenon. This appears of particular value for scientific and clinical dissection of tumor pathologies. Despite the tremendous potential presented by microarray technology for the investigation of disease, concrete insights and advances that translate to the clinical setting are only recently beginning to be tapped. Here, we discuss specific examples of how microarray technology is being integrated into our ever-evolving approach to clinical disease. We focus on molecular strategies for (a) disease classification, (b) disease outcome, and (c) disease mechanisms.

Modulation of CREB expression and phosphorylation in the rat nucleus accumbens during nicotine exposure and withdrawal

The nucleus accumbens region of the brain has been shown to play a role in reward and reinforcing mechanisms of drugs of abuse. To understand the molecular mechanisms of nicotine addiction, the present investigation examined the effects of acute and chronic nicotine treatment and its withdrawal on cAMP-responsive element binding (CREB) protein expression and phosphorylation (serine-133) in nucleus accumbens (NAc) structures of rats. it was found that acute treatment (1 and 18 hr of withdrawal) with nicotine had no effects on total creb and phosphorylated CREB (p-CREB) protein levels in shell or core structures of rat NAc. On the other hand, 18-hr withdrawal after chronic nicotine exposure produced significant reductions in the total CREB and p-CREB protein levels in the shell but not in core structures of nac. interestingly, nicotine withdrawal (1 hr) after chronic exposure maintained normal levels of total CREB and p-CREB protein levels in the shell and core structures of NAc. These results suggest the possibility that decreased CREB activity in the shell of NAc may be associated with abnormal reward mechanisms during nicotine withdrawal after chronic exposure.

Influence of smoking on predictors of vascular disease

Beyond the already well-established strong causative relationship with cancer, smoking increases the risk for vascular disease. Smoking may act directly or adversely influence risk factors contributing to the development of vascular disease. Smoking causes endothelial dysfunction, dyslipidemia (decreased high-density lipoprotein cholesterol levels, hypertriglyceridemia and increased oxidation of low-density lipoprotein cholesterol) and platelet activation leading to a prothrombotic state. Smoking increases emerging risk factors (eg, fibrinogen, homocysteine, and high-sensitivity C-reactive protein) and increases insulin resistance and the risk of developing type 2 diabetes mellitus. The beneficial effects of statins and antioxidants (eg, vitamins C and E, beta-carotene) are counteracted by smoking. Smoking-induced alterations in growth factors, adhesion molecules, and even in genes can accelerate the progression of atherosclerosis. The aim of this review is to consider the adverse consequences of smoking on the factors predisposing to vascular disease and to emphasize the beneficial effects of smoking cessation.

Microarray analysis of peroxisome proliferator-activated receptor-gamma induced changes in gene expression in macrophages

We used a combination of expression microarray and Northern blot analyses to identify target genes for peroxisome proliferator-activated receptor (PPAR) gamma in RAW264.7 macrophages. PPARgamma natural ligand 15-deoxy-Delta(12,14) prostaglandin and synthetic ligands ciglitazone and rosiglitazone increased the expression of scavenger receptor CD36 and ATP-binding cassette transporter A1, as well as adipophilin (a lipid droplet coating protein involved in intracellular lipid storage and transport), calpain (a protease implicated in ABCA1 protein degradation), and ADAM8 (a disintegrin and metalloprotease protein involved in cell adhesion). These findings are relevant to understanding the effect of PPARgamma activation on gene expression and cognate pathways in macrophages.

Identification of endothelial cell genes by combined database mining and microarray analysis

Vascular endothelial cells maintain the interface between the systemic circulation and soft tissues and mediate critical processes such as inflammation in a vascular bed-selective fashion. To expand our understanding of the genetic pathways that underlie these specific functions, we have focused on the identification of novel genes that are differentially expressed in all endothelial cells, as well as restricted groups of this cell type. Virtual subtraction was conducted employing gene expression data deposited in public databases and 384 genes identified. These genes were spotted on custom microarrays, along with 288 genes identified through subtraction cloning from TGF-beta-stimulated endothelial cells. Arrays were evaluated with RNA samples representing endothelial cells cultured from four vascular sources and five non-endothelial cell types. These studies identified 64 pan-endothelial markers that were differentially expressed with at least a threefold difference (range 3- to 55-fold). In addition, differences in gene expression profiles among endothelial cells from different vascular beds were identified. Validation of these findings was performed by RNA blot expression studies, and a number of the novel genes were shown to be expressed under angiogenic conditions in the developing mouse embryo. The combined tools of database mining and transcriptional profiling thus provide expanded knowledge of endothelial cell gene expression and endothelial cell biology.