Both mainstream and side stream cigarette smoke have been shown to cause heightened platelet activation, adhesion aggregation, and inflammation.Based on the possible clinical implications of altered platelet exposure, the potential effects of e-cigarette extracts on platelet function have also been investigated.Platelet activation and aggregation were increased following exposure to e-liquid aerosol extracts. Platelet adhesion potential for fibrinogen and von Willebrand factor were also increased, indicating that e-cigarette extracts had a pro-thrombotic effect. In this study, the effects were caused by the non-nicotine constituents of e-cigarettes, while other studies have shown increased platelet aggregation and/or activation after exposure to e-cigarette vapor with nicotine.One such study found shortened thrombosis occlusion and bleeding times in mice.Increases in serum p-selectin were also detected, but these findings were contradicted by another study which reported decreased serum p-select in levels. These conflicting data may be due to variability in devices and/or exposure conditions. Recently,cannabis grow table endothelial and platelet-derived microparticles have been used as biomarkers of endothelial dysfunction and thrombosis, respectively. These particles, which are <1 mm in diameter, are formed as a consequence of cell blebbing during cellular stress and apoptosis. Microparticles play a role in arterial occlusion aided by p-selectin expression on activated platelets.
Elevation of platelet microparticles in combustible smokers has been reported elsewhere,and has recently been shown to occur following acute clinical exposure to e-cigarettes.Combined, these data suggest one potential mechanism whereby e-cigarettes use could lead to myocardial infarction and stroke.Consistent with the known sympathomimetic effects of nicotine, e-cigarette aerosol exposure in humans acutely increases heart rate and blood pressure.Moheimani et al. Measured heart rate variability in participants who were habitual e-cigarettes users or healthy non-users. The high-frequency component of heart rate variability, an indicator of vagal activity, was decreased in e-cigarette users, while the low-frequency component and low-frequency to high-frequency ratio, reflecting cardiac sympathovagal balance, were increased by e-cigarettes use, consistent with an increase in sympathetic activity. In another study by the same group,healthy subjects who were not current tobacco smokers or e-cigarette users were exposed to e-cigarette aerosols with nicotine and showed a shift in heart rate variability, suggesting an increase in sympathetic tone. Moreover, those exposed to only the non-nicotine components of e-cigarette aerosols did not show an acute sympathomimetic effect. The authors concluded that nicotine was needed to produce an increase in sympathetic activity. In contrast, D’Ruiz et al., found that 5 days of e-cigarettes use did not cause higher blood pressure or heart rate.Other studies have found acute effects of e-cigarette use on heart rate, both with and without nicotine. Hence, the effects of e-cigarettes on hemodynamics has been variable, and might be partially dependent on how much nicotine is delivered.
Importantly, this could contribute to a sympathomimetic increase left ventricular hypertrophy, adverse LV remodeling, and potential rhythm disturbances.While the effects of e-cigarette use on vascular pathology, sympathetic induction, and platelet abnormalities are relatively well established,there is currently little to no evidence linking e-cigarette use to heart disease.While there are no reports of cardiac dysfunction as a result of e-cigarette exposure in humans, chronic increases in arterial stiffness and blood pressure could potentially cause adverse cardiac remodeling. Unfortunately, these data are unavailable due to the novelty of e-cigarette devices and will likely emerge over time. However, animal models and in vitro studies can be used as a proxy, and these studies have found limited evidence of cardiac dysfunction as a result of e-cigarette exposure. One study in apolipo protein-E knockout mice found that just 12 weeks of chronic e-cigarette exposure resulted in reduced ejection fraction and alterations in cardiomyocyte structure typical of cardiomyopathy.However, this study included a small number of mice , and this result could not be replicated by another group after as long as 6 months of exposure using the same mouse model and a larger sample size .While changes in ejection fraction have not been noted in exposed, otherwise healthy mice, one study noted significant collagen deposition in cardiac tissue as a result of e-cigarette exposure, with a 2.75-fold increase in cardiac collagen after 6 months of chronic e-cigarette exposure.A study of cultured rat cardiomyoblast cells found that several e-liquids were cytotoxic at high concentrations, but that e-liquids were less cytotoxic than tobacco smoke extract.Although the half-maximal inhibitory concentration of these extracts was 3-fold lower than cigarette smoke condensate, these observations indicated that e-cigarettes extracts were cytotoxic to cardiac myoblasts, and that the toxicity may have been related to the production process and/or the presence of different flavors.In chronic smokers, pulmonary disease generally occurs following decades of smoking.
However, the adverse effects on lung function, coupled with earlier onset biochemical and/or structural changes in lung function, are present long before COPD or other chronic respiratory disease is detected. For example, adverse effects of conventional cigarette smoking on respiratory health including wheezing, coughing, and resultant decreased lung function have been found in adolescents.Spirometry is typically used to determine the FEV1. However, FEV1 measurements can be noisy and FEV1 over forced vital capacity is also used for COPD diagnosis. FEV1 has been measured immediately after vaping and some researchers reported airflow obstruction,cannabis drying trays while others do not.In healthy subjects who vaped regularly for at least 6 months, a decrease in FEV1 was not apparent.However, there were also no differences in FEV1 in the healthy smokers’ cohort during this time period and longer studies are usually required to show accelerated loss of lung function.In contrast, a reduced FEV1 and FEV1/FVC ratio was reported in vapers elsewhere.Tobacco smokers who switched to e-cigarettes had little or only moderate improvement in lung function.In small scale studies of smokers and non-smokers without pre-existing lung disease, e-cigarette use was not associated with acute changes in FEV1. While important diagnostically, spirometry does not always correlate well with early disease manifestations in COPD such as small airway/alveolar damage.Thus, these measurements may not be a sensitive index of the early effects of vaping and should be interpreted with caution. Although our current knowledge comes from studies with small sample sizes, evidence is growing that asthma and other respiratory disorders can be induced and/or exacerbated by ecigarette use, albeit less so than seen with combustible cigarettes.In a study on e-cigarette use and chronic bronchitis, the risk of disease symptoms was increased approximately by 2-fold in current and past e-cigarette users compared with non-vapers/non-smokers, and the risk was also increased with the frequency of vaping.Moreover, studies in adolescents found a positive association between e-cigarette use and asthma risk that was independent of smoking tobacco or marijuana.Decreased fractional exhaled nitric oxide concentration is a biomarker of airway inflammation that has been used to study vapers. In a study with 30 participants, as little as 5 min of vaping caused a significant reduction in FeNO.In contrast, another study showed a significant increase in FeNO levels in subjects who vaped for 2 h.In a longitudinal study, vaping was found to be an independent risk factor for respiratory disease.Similarly, in a retrospective analysis of two cross-sectional cohorts , switching from combustible cigarettes to e-cigarettes did not improve lung function, and was associated with an increased incidence of COPD.These discrepancies suggest that depending on the length or the frequency of e-cigarette consumption, NO levels can change in either direction, indicating a need for more research. A summary of the potential pulmonary biomarkers of exposure/harm following vaping are shown in Table 2 and are discussed in more detail below.In a series of cross-sectional studies, samples were obtained from different regions of vapers’ lungs and subjected to both “omics”-style and targeted approaches. These studies may show changes at the molecular/biochemical levels before gross structural and/or physiological changes can be detected. Nasal biopsies from e-cigarette users showed greater reductions in immune-related gene expression than those from tobacco smokers, indicating e-cigarette induced immunosuppression.
Another study found increased platelet-activating factor receptor expression in e-cigarette users’ nasal epithelia.Importantly, Streptococcus pneumoniae adhere to PAFR, and e-cigarette vapor increased pneumococcal adhesion to airway cells in vitro, independently of nicotine, suggesting increased virulence.Together, these studies are suggestive of dampened immunity in the upper airways from those who vape. Reidel et al. induced sputum from healthy non-smokers, vapers, and cigarette smokers and performed proteomics. Interestingly, they found more changes in sputum protein in vapers compared to that of smokers, relative to non-smokers.Ghosh et al. performed bronchial brush biopsies on nonsmokers, smokers, and vapers and also found a significant number of unique proteins were independently elevated in vapers airways.Elevated levels of aldehyde-detoxifying enzymes, including aldehyde dehydrogenase 3A1, metabolic isozyme, glutathione S-transferase, and an antioxidant, thioredoxin were found.These enzymes play an important role in detoxifying e-cigarette toxicants as well as by maintaining the redox homeostasis in cells. Tsai et al. found that inflammasome complex proteins, caspase-1 and apoptosis-associated specklike protein containing caspase activation and recruitment domain, which promotes cellular pyroptosis, were elevated in the BAL fluid of e-cigarette users.The anti-inflammatory club cell protein 16 was significantly elevated in serum of vapers after 25 puffs of the aerosol, suggesting an acute response to epithelial dysfunction/injury in the lungs.These data suggest that the lung responds to the increased toxic burden from vaping by upregulating metabolic processes.Using proteomics, Reidel et al. found evidence of increased proteases in vapers’ sputum. These data were suggestive of increased neutrophil lysis. Ghosh et al. subsequently measured protease levels and activity in vaper’s bronchoalveolar lavage fluid and found protease levels were equally upregulated at the protein level and by activity in both vapers and smokers.Furthermore, a subset of vaper/never-smokers also had increased lung protease levels. Consistent with these observations, both neutrophils and alveolar macrophages were stimulated by nicotine to secrete these proteases. In contrast, PG/VG did not stimulate protease secretion. Taken together, these data indicate that a number of molecular markers that are associated with pulmonary disease are upregulated in vapers’ airways. Despite not controlling for either e-cigarette device type or e-liquid brand, the human omics studies and targeted studies found remarkably consistent results.These data suggest that many of the changes in gene/protein expression were driven by exposure to nicotine, PG/VG, and/or their metabolites. However, with control for e-cigarette type and flavor type, more changes may have been found. Importantly, the human and murine findings reinforce the need for standardized protocols to fully understand the lung effects of e-cigarette constituents and aerosols. Use of different e-cigarette solutions of varying humectant composition, nicotine concentrations, flavorings, and temperature settings for the generation of aerosols complicates the difficulty in interpretation of findings.Mucus clearance is a key component of the lung’s innate defense system, and reductions in mucus clearance lead to airway obstruction, inflammation, and chronic infection, as seen in cystic fibrosis and COPD.E-cigarette vapor containing nicotine led to significant mucociliary dysfunction in sheep.Given the impact that mucus clearance has on lung function, these findings are important and need to be addressed further in humans. The ability of e-cigarette aerosols to induce inflammatory responses in animals has been varied. Lerner et al. demonstrated significantly increased MCP-1 and IL-6 cytokine levels in BAL fluid after exposure of C57BL/6 mice for 3 days to side-stream aerosols of Blu e-cigarettes.However, another group showed reduced IL-6 levels after a 2-week exposure of mice to NJOY aerosols.Additional studies, using different exposures, e-cigarettes, and mouse strains, have added to the uncertainty. Many mouse exposure studies have supported the hypothesis that exposure to e-cigarette aerosols induces an inflammatory response in the lung,while others found that exposure to e-cigarette aerosols induced little or no inflammation or oxidative stress.These outcomes suggest that pulmonary inflammation may depend on the time of exposure, the e-cigarette brand used, the operation of the device, and possibly the strain of mice tested. Several murine studies suggest that innate defense is impaired in e-cigarette-exposed mice. Reduced clearance of S. pneumonia and influenza virus A suggests that e-cigarettes may have the potential to dampen immune responses to infection.BALF from the mice exposed to NJOY e-cigarette aerosol for 2- weeks prior to challenge with S. pneumonia had significantly greater bacterial growth compared to the unexposed counterparts.These data suggest exposure to e-cigarette aerosols may cause both inflammation and immunosuppression. Animal studies also have shown e-cigarette aerosol exposure induces changes in lung structure.