Cigarette smoke extract is a modulator of mitogenic action in vascular smooth muscle cells

An integral perspective of canonical cigarette and e-cigarette-related cardiovascular toxicity based on the adverse outcome pathway framework

BACKGROUND

Nowadays, cigarette smoking remains the leading cause of chronic disease and premature death, especially cardiovascular disease. As an emerging tobacco product, e-cigarettes have been advocated as alternatives to canonical cigarettes, and thus may be an aid to promote smoking cessation. However, recent studies indicated that e-cigarettes should not be completely harmless to the cardiovascular system.

AIM OF REVIEW

This review aimed to build up an integral perspective of cigarettes and e-cigarettes-related cardiovascular toxicity.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review adopted the adverse outcome pathway (AOP) framework as a pivotal tool and aimed to elucidate the association between the molecular initiating events (MIEs) induced by cigarette and e-cigarette exposure to the cardiovascular adverse outcome. Since the excessive generation of reactive oxygen species (ROS) has been widely approved to play a critical role in cigarette smoke-related CVD and may also be involved in e-cigarette-induced toxic effects, the ROS overproduction and subsequent oxidative stress are regarded as essential parts of this framework. As far as we know, this should be the first AOP framework focusing on cigarette and e-cigarette-related cardiovascular toxicity, and we hope our work to be a guide in exploring the biomarkers and novel therapies for cardiovascular injury.

Inhibition of FHL1 inhibits cigarette smoke extract-induced proliferation in pulmonary arterial smooth muscle cells

Cigarette smoke can induce pulmonary vascular remodeling, which involves pulmonary artery smooth muscle cell (PASMC) proliferation, resulting in pulmonary hypertension in chronic obstructive pulmonary disease. FHL1 is a member of the FHL subfamily, characterized by an N‑terminal half LIM domain, followed by four complete LIM domains, and has been suggested to be critical in cell proliferation. However, the effects of FHL1 on cigarette smoke‑induced PASMC proliferation and the precise molecular mechanism remain to be elucidated. The present study demonstrated that the protein expression of FHL1 correlated with cigarette smoke extract (CSE)‑induced PASMC proliferation. Knockdown of the expression of FHL1 using siRNA significantly suppressed cell proliferation and inhibited the cell cycle transition between the G1 and S phase by regulating the cyclin‑dependent kinase pathway at the basal level and following CSE stimulation. By contrast, overexpressing FHL1 using an adenovirus increased cell proliferation and promoted the cell cycle transition between the G1 and S phase. Furthermore, CSE significantly increased the protein expression of FHL1, however, exerted no effect on the mRNA expression levels. This alteration was due to the prolonged FHL1 half‑life, leading to the antagonizing of protein degradation. Collectively, these data suggested that FHL1 may be involved in excessive cell proliferation and may represent a potential therapeutic target for pulmonary hypertension.

Lowered plasma paraoxonase (PON)1 activity is a trait marker of major depression and PON1 Q192R gene polymorphism-smoking interactions differentially predict the odds of major depression and bipolar disorder

BACKGROUND

Major depression and bipolar disorder are accompanied by the activation of immune-inflammatory and Oxidative and Nitrosative Stress (O&NS) pathways and lowered levels of antioxidants. Paraoxonase (PON)1 (EC 3.1.8.1) is an antioxidant bound to High Density Lipoprotein (HDL). Polymorphisms in the PON1 Q192R coding sequence determine three functional genotypes, i.e. 192QQ, 192QR and 192RR.

AIMS

This study was carried out to delineate the associations of plasma PON1 activity and functional PON1 Q192R genotypes in major depression and bipolar disorder.

METHODS

PON1 status that is plasma PON1 abundance and three functional PON1 Q192R genotypes were assayed in 91 major depressed and 45 bipolar patients and compared to 199 normal controls.

RESULTS

Major depression, but not bipolar disorder, was accompanied by lowered PON1 activity. PON1 activity was decreased by smoking and a diagnosis by genotype interaction (i.e. lower PON1 in major depression with the QQ genotype). Logistic regression showed that smoking by QQ genotype significantly increased the odds of bipolar disorder and that major depression was predicted by plasma PON1 activity, serum HDL cholesterol and interactions between genotype×smoking.

DISCUSSION

The results suggest that lowered plasma PON1 activity is a trait marker of major depression and that PONQ192R gene-environment (smoking) interactions differentially predict the odds of depression and bipolar disorder.

LIMITATIONS

Association studies are prone to a risk of false positive findings and replication is essential.

CONCLUSIONS

The findings suggest that there are differential PON1 Q192R functional genotype×environment interactions in major depression and bipolar disorder. The effects of lowered PON1 activity may contribute to increased O&NS and immune-inflammatory burden in depression. PON1 status may contribute to the comorbidity between depression and other immune- and O&NS-related disorders, e.g. cardiovascular disorder.

Etanercept attenuates short-term cigarette-smoke-exposure-induced pulmonary arterial remodelling in rats by suppressing the activation of TNF-a/NF-kB signal and the activities of MMP-2 and MMP-9

The pathogenesis of cigarette-smoke-exposure-induced pulmonary vasculature impairment is unclear. Cigarette-smoke-exposure-induced the accumulation of tumour necrosis factor-alpha (TNF-α) and upregulates the expression and activities of matrix metalloproteinases (MMPs) involved in smoke-induced vascular remodelling, which are important processes in the pathogenesis of vasculature impairment. The TNF-α antagonist Etanercept is an anti-inflammatory drug with a potential role in regulating MMP expression. To determine the effect of Etanercept on short-term smoke-induced pulmonary arteriole impairment and investigate its possible mechanism, male Sprague-Dawley rats were exposed to cigarette-smoke daily for two weeks in both the absence and presence of Etanercept. Cigarette-smoke-exposure-induced elevation of mean pulmonary artery pressures and medial hypertrophy of pulmonary arterioles were partially reduced by Etanercept. Up-regulation of the expression and activities of MMP-2 and MMP-9, induced by cigarette-smoke, were also suppressed significantly by Etanercept. Furthermore, Etanercept treatment significantly attenuated cigarette-smoke-induced TNFα accumulation and activation of nuclear factor NF-kB signal. These results suggest that Etanercept have the protective effects in cigarette-smoke-induced pulmonary vascular remodelling, with the attenuation of the up-regulated expression and activities of MMP-2 and MMP-9 and activation of TNF-α/NF-kB signal pathway probably being involved as part of its mechanism. Our study might provide insight into the development of new interventions for vasculature impairment.

CCN2 promotes cigarette smoke-induced proliferation of rat pulmonary artery smooth muscle cells through upregulating cyclin D1 expression

Cigarette smoke has been demonstrated to induce pulmonary vascular remodeling, which is characterized by medial thickening of the pulmonary arteries mainly resulting from the abnormal proliferation of pulmonary artery smooth muscle cells (PASMCs). However, the molecular mechanism underlying this process is still unclear. In the present study, we investigated whether CCN2 regulated rat PASMCs (rPASMCs) proliferation induced by cigarette smoke extract (CSE) and nicotine by upregulating cyclin D1 in vitro. CCN2 siRNA or cyclin D1 siRNA were transfected to rPASMCs which were then exposed to CSE and nicotine. Both mRNA and protein expressions of CCN2 were significantly increased in rPASMCs treated with 2% CSE or 1 µM nicotine, which markedly promoted the proliferation of rPASMCs. CCN2 siRNA inhibited the proliferation of rPASMCs induced by CSE or nicotine. Furthermore, CCN2 siRNA markedly suppressed the mRNA and protein expressions of cyclin D1 in rPASMCs and led to cell cycle arrest in G0/G1 phase resulting in reduced rPASMCs proliferation. These findings suggest that CCN2 contributes to the CSE and nicotine-induced proliferation of rPASMCs at least in part by upregulating cyclin D1 expression.

Cigarette smoke extract induced rat pulmonary artery smooth muscle cells proliferation via PKCα-mediated cyclin D1 expression

Cigarette smoke could induce pulmonary smooth muscle cells (PASMCs) proliferation. Although our previous study had implied the involvement of protein kinase Cα (PKCα), the molecular mechanism underlying PKCα pathway in this process is still unknown. In this study, rat PASMCs were stimulated by cigarette smoke extract (CSE) or PMA (a special activator to PKCα). Two percent CSE and PMA significantly enhanced cyclin D1 expression and cells proliferation. But cyclin D1-specific siRNA successfully inhibited DNA synthesis in CSE-treated or PMA-treated cells. On the other hand, PKCα-specific siRNA significantly suppressed cyclin D1 expression in CSE-treated cells. Moreover, PKCα-specific siRNA resulted in a cell-cycle arrest in G0/G1 and decreased cells number significantly. We conclude that CSE induced rat PASMCs proliferation at least partly via PKCα-mediated cyclin D1 expression.

Knockdown of connective tissue growth factor by plasmid-based short hairpin RNA prevented pulmonary vascular remodeling in cigarette smoke-exposed rats

Cigarette smoking may contribute to pulmonary hypertension in chronic obstructive pulmonary disease by resulting in pulmonary vascular remodeling that involves pulmonary artery smooth muscle cell proliferation. Connective tissue growth factor (CTGF) is a cysteine-rich peptide implicated in several biological processes such as cell proliferation, survival, and migration. This study investigated the potential role of CTGF in pulmonary vascular remodeling. We constructed a plasmid-based short hairpin RNA (shRNA) to knock down the expression of CTGF in primary cultured rat pulmonary artery smooth muscle cells (rPASMCs) and in rat lung vessels. Rat PASMCs were challenged with cigarette smoke extract (CSE). Rats were exposed to cigarette smoke for 3 months in the absence or in the presence of plasmid-based short hairpin RNA against CTGF which was administrated by tail vein injection. CTGFshRNA significantly prevented CTGF and cyclin D1 expression, arrested cell cycle at G0/G1 phase and suppressed cell proliferation in rPASMCs exposed to CSE. CTGFshRNA administration ameliorated pulmonary vascular remodeling, inhibited cigarette smoke-induced CTGF elevation and reversed the cyclin D1 increase in pulmonary vessels in rats. Collectively, our data demonstrated that plasmid-based shRNA against CTGF attenuated pulmonary vascular remodeling in cigarette smoke-exposed rats.

Effect of cigarette smoke components on vascular smooth muscle cell migration toward platelet-derived growth factor BB

Cigarette smoking is one of the factors causing accumulation of vascular smooth muscle cells (VSMCs) in atherosclerotic plaques. Changes in cell migration toward platelet-derived growth factor BB were investigated using a Boyden chamber after 48-h preincubation of GBaSM-4 VSMCs with nicotine or nicotine-free cigarette smoke extract (CSE). A nicotine concentration of 0.1 µM maximally promoted cell migration; 0.1% CSE also promoted cell migration, while high CSE concentrations damaged GBaSM-4 cells. Fetal bovine serum (FBS) long-depletion induced decrease in migration of GBaSM-4 cells. Our results suggest that nicotine and some CSE components can induce GBaSM-4 cell migration.

Plasmid-based short hairpin RNA against cyclin D1 attenuated pulmonary vascular remodeling in smoking rats

Accumulating evidence indicated that smoking might directly induce pulmonary vascular remodeling at the initial stage of chronic obstructive pulmonary disease (COPD). However, the molecular mechanism underlying this process remains poorly understood. To investigate the role of cyclin D1 in pulmonary vascular remodeling, we constructed a plasmid-based short hairpin RNA (shRNA) to knock down the expression of cyclin D1 in smoking rats. Specific shRNA against cyclin D1 significantly prevented the cyclin D1 expression and the cell proliferation in rat pulmonary artery smooth muscle cells (rPASMCs). Furthermore, the plasmid-based shRNA successfully decreased the cyclin D1 protein in intra-pulmonary arteries of smoking rats and subsequently decreased the wall thickness of pulmonary vessels and the percentage of muscularized vessels. We conclude that the plasmid-based shRNA against cyclin D1 gene attenuated pulmonary vascular remodeling in smoking rats. Cyclin D1 might play a critical role in cigarette smoke-induced pulmonary vascular remodeling via regulating rPASMCs proliferation.

The determination of hydrogen peroxide generated from cigarette smoke with an ultrasensitive and highly selective chemiluminescence method

Monitoring hydrogen peroxide (H(2)O(2)) in aqueous cigarette smoke condensate (CSC) is helpful for interpreting the relationship between cigarette smoke and oxidative stress, inflammation and disease. It is also significative for elucidating the pathogenic effects of CSC. In this paper, a novel flow-injection chemiluminescence (FI-CL) method was well established for determination of H(2)O(2) in the complex sample CSC which did not need pretreatment. The sensitive and selective method is based on the CL reaction of luminol with low concentration (10(-7) molL(-1)) and H(2)O(2) at low concentration level (<10(-8) molL(-1)) in an alkaline medium catalyzed by a complex K(5)[Cu(HIO(6))(2)] (DPC), which has proved no interference of other metal ions or horseradish peroxidase (HRP). The proposed method had been used to determine trace amount of H(2)O(2) with a limit of detection (3sigma) of 4.1 x 10(-11) molL(-1), which enables minimal amount of sample for analysis. A satisfactory result has been gained for the determination of H(2)O(2) in CSC sample by use of the proposed method. The concentration of H(2)O(2) in two reference cigarette (84 cm, Longfeng) smoke condensate have been determined at 4-6 micromolL(-1) level.

High-throughput spectrophotometric assay of reactive oxygen species in serum

The derivatives of reactive oxygen metabolites (D-ROM) test has been developed to determine the amount of oxygen-centered free radicals in a blood sample as a marker of oxidative stress. This study aims to improve the D-ROM test and develop an automated assay system by use of a clinical chemistry analyzer. Five microliters of serum was added to 1 well of a 96-well microtiter plate for a total 240microl of reaction solution containing alkylamine and metals. This was followed by automatic mixing, incubation and measurement of reactive oxygen species (ROS) levels as a color development at 505nm using a spectrophotometer with catalytic capability for transition metals. This assay system was used to measure serum levels of ROS in cigarette smokers and never-smokers, by way of example. The levels of serum ROS determined by this system correlate with the amounts of free radicals and peroxides, which reacted with various molecules in the body and formed stable metabolites. This test can use frozen sera as well as fresh ones. The inter- and intra-deviation of this system was within 5% and showed consistent linearity in the range between 4 and 500mg/l of hydrogen peroxides. Serum ROS levels among smokers increased with the number of cigarettes smoked per day (36.5% increment per pack per day; P<0.0001). This assay system will be a simple, inexpensive, and reliable tool for assessing oxidative stress in human populations. Our preliminary results on cigarette smoking imply that this assay system has potential for application in various epidemiological and clinical settings.

Early atherosclerotic lesions in infancy: role of parental cigarette smoking

Cigarette smoking is associated with an increased incidence of atherosclerotic diseases. The aim of this study was to examine the progression of the pre atherosclerotic lesions previously observed by us in coronary arteries of fetuses of smoker mothers and in infants with smoker parents. We examined the coronary arteries of 34 infants, aged 1-36 months, and the histological and biological [c-fos, proliferating cell nuclear antigen (PCNA), and apoptosis] features of the early atherosclerotic lesions. In 17 infants (50%), at least one parent smoked, generally more than five cigarettes a day. In 18 cases (53%), we observed variable thickening of the coronary walls from pre-atherosclerotic lesions to juvenile atherosclerotic plaques, related to parental smoking habit. This morphological progression of the lesions was accompanied by a sequence of biological changes in the smooth muscle cells of the tunica media. We suggest that the oxidants present in the gas phase of the parental cigarette smoke pass through the endothelium and induce at first the c-fos gene activation and subsequently the PCNA positivity, that is, a proliferative process.

Analysis of the human locus coeruleus in perinatal and infant sudden unexplained deaths. Possible role of the cigarette smoking in the development of this nucleus

We investigated the immunohistochemical expression of the tyrosine hydroxylase (TH) enzyme and the morphometric parameters of the human locus coeruleus (LC) in the brainstems of 32 subjects aged from 17 gestational weeks to 12 postnatal month, died of unknown (sudden unexplained perinatal and infant deaths) and known causes. The goals of this study were: (1) to obtain basic information about the structure and physiology of the LC during the first phases of human nervous system development; (2) to evaluate whether there is altered expression of TH and/or structural alterations of the LC in cases of sudden perinatal and infant death; and (3) to verify if morphological and/or physiological abnormalities of the LC could be related to maternal cigarette smoking. Morphometric analysis showed homogeneous data in cases of sudden perinatal and infant death and in age-matched controls who had died of known aetiology. However, immunohistochemistry demonstrated in a wide subset of sudden and unexplained deaths a negativity or low positivity of TH. High distribution of TH protein were instead detectable in the LC neurons of foetuses aged 17-18 gestational weeks who had died of known causes. Therefore, we postulate the functional importance of the LC in the early phases of central nervous system development. Besides, the observation of a significant correlation between sudden unexplained death, negativity of TH staining and maternal smoking, prompted us to suppose a close relation between smoking in utero and a decrease of the noradrenergic activity of the LC, leading to sudden death in the last part of pregnancy and in the first year of life.

Genetic influence on cigarette-induced cardiovascular disease

Cigarette smoking as an addictive habit has accompanied human beings for more than 4 centuries. It is also one of the most potent and prevalent environmental health risks human beings are exposed to, and it is responsible for more than 1000 deaths each day in the United States. With recent research progress, it becomes clear that cigarette smoking can cause almost all major diseases prevalent today, such as cancer or heart disease. These detrimental effects are not only present in active smokers who choose the risk, but also to innocent bystanders, as passive smokers, who are exposed to cigarettes not-by-choice. While the cigarette-induced harm to human health is indiscriminate and severe, the degree of damage also varies from individual to individual. This intersubject variability in cigarette-induced pathologies is partly mediated by genetic variants of genes that may participate in detoxification process, eg, cytochrome P450 (CYP), cellular susceptibility to toxins, such as p53, or disease development. Through population studies, we have learned that certain CYP1A1 variants, such as Mspl polymorphism, may render the carriers more susceptible to cigarette-induced lung cancer or severe coronary atherosclerosis. The endothelial nitric oxide synthase intron 4 rare allele homozygotes are more likely to have myocardial infarction if they also smoke. In vitro experimental approach has further demonstrated that cigarettes may specifically regulate these genes in genotype-dependent fashion. While we still know little about genetic basis and molecular pathways for cigarette-induced pathological changes, understanding these mechanisms will be of great value in designing strategies to further reduce smoking in targeted populations, and to implement more effective measures in prevention and treatment of cigarette-induced diseases.

Effect of cigarette smoke extract on neonatal porcine vascular smooth muscle cells

RATIONALE

Cigarette smoke exposure in the perinatal period increases the risk of various prenatal and postnatal complications, including sudden infant death syndrome (SIDS) and persistent pulmonary hypertension of the newborn (PPHN). We investigated the cellular effects of cigarette smoke extract (CSE) in the developing vasculature.

METHODS

Vascular smooth muscle cells (VSMC) were isolated from neonatal porcine carotid arteries, splenic arteries, and main and resistance pulmonary arteries. Effects of CSE on VSMC proliferation, viability, apoptosis, and media nitrates and nitrites were evaluated. The effects of known constituents of CSE (nicotine, benzopyrene, acrolein, acetaldehyde), aged CSE, CSE with added hemoglobin, devolatilized CSE, CSE with added dithiothreitol (DTT), and reduced glutathione (GSH) on cell proliferation and viability were assessed.

RESULTS

CSE caused a dose- and time-dependent decrease in neonatal VSMC numbers isolated from all four sites, mainly as a result of increased cell necrosis and not apoptosis. Nitrates and nitrites were below the threshold of detection. Nicotine and benzopyrene did not affect cell counts, while acrolein and acetaldehyde decreased cell counts in a dose-dependent manner. Addition of hemoglobin, devolatilization, and the addition of DTT or GSH slightly decreased CSE inhibition.

CONCLUSIONS

CSE causes necrosis of neonatal VSMC, and this toxicity is mediated mainly by volatile components such as acrolein and acetaldehyde, possibly in association with nitric oxide and carbon monoxide.