E-Cigarette and Endothelial Function─A Critical Review of Preclinical Studies.

The traditional risk factors of hypercholesterolemia, hypertension, diabetes mellitus, and tobacco exposure identify a subset of patients at greater cardiovascular risk. A variety of clinical phenotypes, biochemical markers, and genetic polymorphisms have been proposed to explain the variance in risk not explained by the traditional factors. Notably, all of the traditional risk factors, as well as the great majority of new risk markers, are associated with endothelial vasodilator dysfunction. Because the end points (endothelial dysfunction leading to plaque formation, progression, and rupture) are the same, it follows that diverse risk factors ultimately share common pathways(s) of pathobiology. We and others have provided evidence for a ubiquitous mechanism of endothelial pathobiology shared by all risk factors and markers examined to date. This mechanism of endothelial derangement is mediated by an endogenous inhibitor of nitric oxide synthase (NOS), a molecule known as asymmetrical dimethylarginine (ADMA). Risk factors impair endothelial vasodilator function by causing the accumulation of ADMA. Furthermore, by blocking NO generation, ADMA initiates and promotes processes involved in atherogenesis, plaque progression. and plaque rupture. This review examines the burgeoning body of literature that supports ADMA as an “Uber marker,” a biochemical factor mediating the adverse vascular effects of many other risk factors and markers. Endothelial NOS converts the amino acid l-arginine into l-citrulline and NO. The importance of NO in vascular homeostasis has been discussed elsewhere.1 In addition to its vasodilator activity, NO inhibits key processes involved in vascular disease, including leukocyte adhesion, platelet aggregation, and vascular smooth muscle cell proliferation. In animal models, alterations in vascular NO synthesis profoundly influence the progression of atherosclerosis and restenosis.2–6 These experimental observations have gained greater significance with recent reports that impairment of the NOS pathway independently predicts cardiovascular events.7–11 Major causes of impairment of the NOS pathway are …

The initial description in 1980 by Furchgott and Zawadzki1 of endothelium-derived vasodilator factor has stimulated more than 2 decades of intense research to delineate the basic biology of the endothelium and its importance in the clinical setting.2 Endothelium-derived vasodilator factor has been identified as nitric oxide (NO).2 It is formed in endothelial cells from the amino acid l-arginine by endothelial isoform of NO synthase (eNOS), which is the product of the NOS3 gene.2,3 In addition to producing NO constitutively, the enzyme may be stimulated to increase NO synthesis by a variety of physiological agonists, shear stress, and pharmacological agents. Although discovered as a vasodilator, NO mediates many of the protective functions of the endothelium.4 It limits vascular recruitment of leukocytes by inhibiting the expression of proinflammatory cytokines, chemokines, and leukocyte adhesion molecules.2,4 It inhibits vascular smooth muscle proliferation and platelet adhesion and aggregation.2,4 NO also inhibits the production of tissue factor, a molecule that plays a critical role in the propensity of disrupted atherosclerotic plaques to cause intravascular thrombosis.5 In the setting of risk factors and experimental atherosclerosis, loss of the biological activity of endothelium-derived NO is accompanied by other alterations in endothelial phenotype that further increase the propensity for vasoconstriction, thrombosis, inflammation, and cellular proliferation in the vascular wall.6 Thus, endothelial dysfunction has the potential to contribute to key events in the course of human atherosclerosis. The experimental observations of Furchgott and others have stimulated translational research to elucidate the importance of endothelium-dependent vasodilation in human coronary atherosclerosis. Accordingly, Ludmer and colleagues7 administered the endothelium-dependent dilator acetylcholine into the coronary arteries of subjects undergoing cardiac catheterization. Acetylcholine induced dilation of normal epicardial coronary arteries but induced abnormal vasoconstriction, indicative of endothelial dysfunction, in patients with angiographic evidence of …

e-Cigarette Aerosol Reduces Left Ventricular Function in Adolescent Mice.

Objective: Cigarette smoking is a life-threatening habit that has rapidly spread in every socioeconomic part of the public worldwide. There exist mechanisms of nicotine delivery available to use in the hope of halting cigarette smoking, and the electronic cigarette (EC) is one of the common methods used for tobacco smoking replacement. This study aimed to investigate experimentally the oxidative effects of tobacco smoke and EC smoke which contain nicotine. Method: We constructed smoke circuit rooms for exposing the rats to EC or tobacco smoke. Three groups were created, the control group (N = 8); the electronic cigarette group (N = 8), exposure to electronic cigarette smoke for 2 h per day; and the tobacco group (N = 8), exposure to traditional cigarette smoke for 2 h per day. After the first and second week of exposure, blood samples were obtained, and serum oxidative stress index (OSI), paraoxonase 1 (PON1) activity, and prolidase levels were evaluated. Results: Higher values of OSI and prolidase levels were detected in the first week of EC or tobacco smoke exposure in both study groups (p < 0.001) when compared with the control group, and partial decrements were observed in the second week. By contrast, elevated PON1 levels were observed in the second week after EC or tobacco smoke exposure. The highest OSI levels were observed in the tobacco smoke group (p < 0.001). The lowest values of PON1 levels were detected in the first week of the electronic cigarette smoke group, and this decremental value was statistically different than normal, the second week of the electronic cigarette smoke group, the first week of the traditional cigarette smoke exposure group, and the second week of the traditional cigarette smoke exposure group values (p < 0.000). Conclusion: Our results indicate that EC smoke induced oxidative stress. Therefore, ECs are potentially risky for human health and can lead to important health problems.

Usefulness of Brachial Artery Flow-Mediated Dilation to Predict Long-Term Cardiovascular Events in Subjects Without Heart Disease

This in vitro study compared the effects of conventional and electronic cigarettes on the aesthetics (color stability and translucency) of two types of composite resins: micro and nano-hybrid. Methods: A total of 120 specimens from two different composite materials Filtek Z250 XT (Nano-hybrid, 3M) and Filtek Z250 (Micro-hybrid, 3M) were divided into four groups (n = 30); shade A2 was used. The samples were exposed to conventional and electronic cigarette smoke via a custom made chamber device. The color values and measurements were recorded using a spectrophotometer before and after the exposure. The color and translucency were evaluated using the three-dimensional CIE Lab. Results: There was a significant change in the color (ΔE) and the translucency parameter (TP) in all of the specimens exposed to electronic cigarettes and conventional cigarettes. The results showed that the highest ΔE mean is for the nano-hybrid composite exposed to conventional cigarettes with 1.74 ΔE while the same material is 0.64 under the electronic cigarettes and the difference is significant with (p &lt; 0.05). The micro-hybrid composite data showed less changes in color under both exposures with 0.85 ΔE mean under the conventional cigarette smoke and 0.48 under the electronic cigarette smoke with (p &lt; 0.004). Conclusions: The conventional cigarette smoke has more effect on the color stability of the composite resins than electronic cigarettes. From a clinical point of view, the effect of smoke exposure on the tested specimens’ color, for the time duration to which the specimens were exposed, were moderate (ΔE &lt; 2). The micro-hybrid composites showed better color stability as compared to the nano-hybrid composites.

Molecular Impact of Electronic Cigarette Aerosol Exposure in Human Bronchial Epithelium.

The aim of this study was to examine the association of conventional cigarette smoking and electronic cigarette vaping with periodontal disease in South Korean adults. For this study, data from 13,551 participants, a subset derived from the Korean National Health and Nutrition Examination Survey conducted between 2013 and 2015, were examined. Participants were divided into four categories: electronic cigarettes vapers, conventional cigarettes smokers, ex-users, and non-users. Periodontal status was measured by the Community Periodontal Index. Multiple logistic regression analysis was performed to examine the association of periodontal disease with smoking and vaping individually. Out of 187 men and 35women who vape electronic cigarette, 67 (35.8%) men and 10 (28.6%) women had periodontal diseases. Out of 1,957 men and 363women who smoke conventional cigarettes, 861 (44.0%) men and 121 (35.3%) women had periodontal diseases. Periodontal disease was more prevalent in each vapers and smokers than non-users in men (electronic cigarettes: odds ratio [OR]=2.34, 95% confidence interval [CI]=1.52 to 3.59, conventional cigarettes: OR=2.17, 95% CI=1.76 to 2.68). Furthermore, both vaping and smoking had significant relation to dental caries, toothache, and dental damages. Electronic and conventional cigarette use was each significantly associated with increased periodontal disease rates. After adjusting for demographic, socioeconomic, and health-related characteristics, both vaping and smoking each had significant association with periodontal diseases. Therefore, this study suggests that vaping may not be a safe alternative to smoking. Cessation of both types of cigarettes is necessary for maintaining oral health.

Due to the growing popularity of electronic cigarettes (ECs) and heated tobacco products (HTPs) as alternatives to conventional cigarettes (CCs), there is an increasing need to monitor the emissions of these new devices. ECs generate significant concentrations of second-hand aerosol (ECSHA), which is visible in dense clouds and can be smelled. Particulate matter (PM) is an important component of CC, HTP and EC aerosols, and Optical Particle Counters (OPCs) enable its real-time measurement, which is expressed either as the number of particles or as mass. This study specifically addresses the limitations associated with EC mass measurement using OPC technology and identifies the strict necessity of the measurement of a corresponding density (k factor) not only for each specific PM source but also for the desired PM size. Therefore, a standard measurement requires the simultaneous operation of the OPC equipment and a certified reference instrument. Four different OPCs were used. Crucially, this study also proves that this setup may be inapplicable because the extreme volatility of EC-generated aerosols makes it impractical to gauge the correct EC k factor.

Electronic cigarette (e-cig) aerosol encounters all constituents in users' mouths, including soft and hard tissues and dental implants. Deposition of the e-cig aerosols on dental implants can lead to implant failure (peri-implantitis). This study aims to evaluate the effect of e-cig vaping on the interactions of normal and diabetic human fibroblasts with dental implant materials. Human gingival and diabetic skin fibroblasts were cultured on titanium (Ti-6Al-4V and Ti-6Al-4V-nitride) dental implant disks and exposed for 10 min, twice a day, to e-cig aerosol containing 12 mg/ml of nicotine. Twenty-four hours post-exposure, we evaluated the effects of the e-aerosol on fibroblast adhesion, growth, migration, collagen contractility, and cell apoptosis/necrosis. The e-cig aerosol significantly decreased adhesion (p < 0.01). This effect was observed in both normal gingival and diabetic skin fibroblasts. There was also a significant (p < 0.01) decrease in cell viability/proliferation of gingival and diabetic skin fibroblasts on dental implant materials following exposure to e-cig aerosol. The cell migration assay demonstrated that e-cig aerosol delayed wound healing after monolayer cell damage. Collagen contraction assay demonstrated that e-cig aerosol decreased the contractile capacity of gingival and diabetic skin fibroblasts. The adverse effect of e-cig aerosol on human fibroblasts involves the apoptotic/necrotic pathway, as the apoptotic cell rate increased from 0.75% in the control to 5.25% in gingival fibroblasts exposed to e-cig aerosol. A similar observation was made with diabetic skin fibroblasts. This study demonstrated, for the first time, possible adverse effects of e-cig aerosol on the interactions between gingival and diabetic skin fibroblasts and dental implants. This study suggests that e-cigs may pose a potential risk to oral health. Clinicians providing dental care to patients with dental implants should consider special care when patients vape. Also, e-cig users should consider an accurate mouth hygiene plan to prevent periodontal disease.

Tobacco cigarette smoke (TCS) was previously demonstrated to affect the innate and adaptive immune responses as a consequence of oxidant generation which play a pivotal role in neutrophilic airway inflammation. Aim of this paper was to investigate whether electronic cigarette smoke (ECS) generates reactive oxygen species (ROS) similarly to cigarette smoke. By means of a house made apparatus, ECS and TCS were collected in fetal bovine serum (FBS) which was used to grow immune cells isolated from rats. As index of oxidative products nitrite, superoxide, and thiobarbituric acid-reactive substances (TBARS) were determined in the medium before and after cell growth. The results showed that: i) ECS caused a remarkable increase of nitrites and TBARS although in lesser extension than TCS; ii) the spleen and lymph node cells grown in ECS and TCS-exposed medium were able to reduce TBARS but not nitrites present in the medium; iii) PBMC in TCS-exposed medium were able to reduce nitrites and TBARS more efficiently than spleen and lymph node cells, but released more superoxide anion; iv) TCS and ECS not influence the PBMC and spleen T cell subtype populations (CD4+, CD8+). As ECS nicotine-free gave the same results of unexposed medium, we can support the hypothesis that the increase of ROS in ECS exposed medium was prevalently due to nicotine.

Free radicals and other oxygen- or nitrogen-derived reactive species formed during cellular metabolism and respiration, like superoxide (O2·−), hydrogen peroxide (H2O2), and nitric oxide (NO), are important second messengers and fundamental mediators in biological processes, redox signaling, and cellular growth. However, over the past 2 decades it has become clear that reactive oxygen species (ROS) in particular are also important participants in a number of pathological processes, including cardiovascular and kidney diseases. In fact, increased production of ROS has been proposed as a common pathomechanism by which cardiovascular risk factors affect the vessel wall to induce and amplify vessel and organ injury. See page 943 Several possible enzymatic sources of ROS have been identified in blood vessels and other tissues, such as nicotineamide adenine dinucleotide (phosphate) oxidase (NAD(P)H oxidase), xanthine oxidase (XO), and uncoupled nitric oxide synthase. NAD(P)H oxidase has long been considered one of the most important sources of ROS in the vessel wall. One of its most potent stimulants is angiotensin II. In turn, NAD(P)H oxidase mediates several downstream effects of angiotensin II like inflammation, endothelial dysfunction, collagen deposition, and vascular hypertrophy. Nevertheless, an important role in the pathogenesis of cardiovascular disease has also been ascribed to XO. This …

Background: E-cigarettes (ECs), also known as electronic nicotine delivery systems (ENDS) are battery-operated devices that deliver nicotine through inhaled aerosols. The health risks associated with EC use are unclear, but ECs have been promoted as a safer alternative to tobacco smoking and a smoking cessation aid. Currently, more than 13% of American high school students and 10% adults report using ECs. EC aerosols contain unique constituents (e.g. silicate beads, tin and flavorants), as well as other toxicants also present in tobacco smoke, including carcinogens and reactive oxygen species (ROS). The potential of EC aerosols to induce DNA damage has not been fully characterized. Aims: (1) To examine the effects of EC aerosol exposure in the levels of cellular reactive oxygen species (ROS); and (2) To evaluate the potential of EC aerosols to cause oxidative DNA damage. Methods: EC aerosols and mainstream smoke extracts were generated from distinct brands of ECs containing diverse nicotine concentrations and a reference combustible cigarette, in controlled conditions using a modified smoking apparatus. Human normal epithelial and oral cancer cell lines were exposed up to 2 weeks to diverse doses of EC aerosol extracts equivalent to 1 to 100 EC puffs. Levels of ROS were evaluated using the 2’,7’ -dichlorofluorescin diacetate (DCFDA) cellular ROS detection assay kit (Abcam). Overall DNA damage was quantified using two distinct assays q-PADDA and Comet assay. 8-Oxoguanine, one of the most common DNA lesions resulting from ROS, was quantified using a commercially available ELISA kit. Data were analyzed by Student’s t-test. Results: Exposure to EC aerosols caused a significant increase in ROS levels. Exposure to EC extracts induce significant DNA damage measurable by q-PADDA and Comet assay. Overall, EC aerosol extracts induced significantly less DNA damage than mainstream smoke extracts. Yet, a significant increase in 8-oxoguanine lesions was observed after acute and long-term exposure to EC extracts compared to the control. Conclusion: Both short- and long-term exposure to EC aerosols can increase cellular ROS levels and cause significant DNA damage. Moreover, EC aerosols cause oxidative DNA lesions which are highly mutagenic, and can lead to tumor initiation and progression. Our study emphasizes the urgent need to further investigate the potential short- and long-term health effects of EC aerosols. Grant support: This work was supported by the Oklahoma Tobacco Research Center (LQ). Dr. Queimado holds a Presbyterian Health Foundation Endowed Chair in Otorhinolaryngology. Citation Format: Vengatesh Ganapathy, Jimmy Manyanga, Dehra McGuire, Daniel Brobst, Theodore Wagener, David Rubenstein, Ilangovan Ramachandran, Lurdes Queimado. Electronic cigarette aerosols increase cellular reactive oxygen species and induce significant oxidative DNA damage [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 502. doi:10.1158/1538-7445.AM2017-502

Research on secondhand electronic cigarette (ECIG) aerosol exposure using aerosol monitors has demonstrated that ECIG use can generate high concentrations of particulate matter (PM) and impact indoor air quality. However, quantifying indoor air PM concentrations using real-time optical monitors with on-site calibration specifically for different PM exposures has not been established. Therefore, the ECIG aerosol filter correction factors were calculated for different PM sizes (PM1, PM2.5, and PM10) and different aerosol optical monitors, the MiniWRAS, pDR, and SidePak. ECIG aerosol generation was achieved using five ECIGs representing three ECIG types, disposable, pod-mod, and box mod. The aerosol size distribution by mass was measured for the five ECIGs during PM generation. Compared to the discrete filter measurements, the MiniWRAS performed the best when the concentrations were low, followed by the pDR and SidePak. The average PM concentrations and correction factor ranges for the different ECIGs were 323-1,775 μg/m3 and 0.64-6.01 for the MiniWRAS, 1,388-13,365 μg/m3 and 0.41-0.80 for the pDR, and 4,632-55,339 μg/m3 and 0.13-0.20 for the SidePak, respectively. The mass median diameter ranged from 0.41 and 0.62 μm, and most particles generated from the ECIGs were smaller than 1 μm. This study demonstrates that aerosol size distribution varies between ECIGs. Likewise, the correction factors developed for the real-time aerosol monitors are specific to the ECIG used. Thus, these data can help improve ECIG aerosol exposure measurement accuracy.

During the past decade, numerous experimental and clinical studies have demonstrated that many common conditions predisposing to atherosclerosis, such as hypercholesterolemia, hypertension, diabetes, and smoking, are associated with a reduced vascular availability of nitric oxide (NO•). Nitric oxide not only produces vasodilation but also has potent antiatherogenic properties. These properties include inhibition of platelet aggregation, prevention of smooth muscle cell proliferation, reduction of lipid peroxidation, and inhibition of adhesion molecule expression. Thus, the loss of NO• observed in these various conditions not only alters vascular tone but also may explain in part why these conditions are risk factors for atherosclerosis. See p 2673 Given this apparent link between loss of nitric oxide and atherosclerosis, several groups have been interested in the concept that endothelium-dependent vasodilation, a surrogate for NO• bioavailability, may predict cardiovascular events. Indeed, Suwaidi et al1 followed 157 patients with mildly diseased coronary arteries for an average of 28 months and observed cardiac events only in the patients with the lowest tertile of coronary vasodilation to acetylcholine. Similarly, in a study of 147 patients, Schachinger et al2 used 3 different stimuli for endothelial release of NO: acetylcholine, cold pressor testing, and increased blood flow. The authors showed that responses to each of these stimuli were independent predictors of cardiovascular events during a follow-up period of ≈8 years. Perticone et al3 also demonstrated that endothelial dysfunction in the forearm circulation predicts cardiovascular events in hypertensive subjects. There have been several explanations for why the various risk factors impair endothelial function. One that has received substantial attention is increased production of reactive oxygen species within the vessel.4 In particular, superoxide (O2•-) reacts rapidly with NO•, resulting in the formation of the peroxynitrite anion and loss of NO• …