Short-term secondhand smoke exposure decreases heart rate variability and increases arrhythmia susceptibility in mice

Preliminary study on the effect of first- and second-hand smoke of heat-not-burn tobacco products on urinary nicotine and cotinine levels and cardiovascular system

Heart rate variability (HRV) of 10 participants was assessed to evaluate the impact of exposure to first- and second-hand smoke from heat-not-burn (HnB) products and conventional cigarettes on cardiovascular health and the autonomic nervous system. The nicotine and cotinine concentrations in the urine of smokers and non-smokers exposed to this smoke were also measured. Nicotine levels in the urine of smokers exposed to HnB products and conventional cigarettes averaged 71.76 and 229.36 ng/ml, respectively. Short-term analyses of HRV in both time- and frequency-domain were performed. There were no significant differences in HRV indicators between both groups at baseline. However, decreases in SDNN, rMSSD, TINN, and pNN50 (%) were observed in smokers exposed to both first- and second-hand smoke from HnB products and conventional cigarettes. No significant trends were noted in non-smokers. The frequency-domain analysis revealed a decrease in low frequency components among smokers.

Chronic nicotine exposure is associated with electrophysiological and sympathetic remodeling in the intact rabbit heart

Nicotine is the primary addictive component of tobacco products. Through its actions on the heart and autonomic nervous system, nicotine exposure is associated with electrophysiological changes and increased arrhythmia susceptibility. To assess the underlying mechanisms, we treated rabbits with transdermal nicotine (NIC, 21 mg/day) or control (CT) patches for 28 days before performing dual optical mapping of transmembrane potential (RH237) and intracellular Ca2+ (Rhod-2 AM) in isolated hearts with intact sympathetic innervation. Sympathetic nerve stimulation (SNS) was performed at the first to third thoracic vertebrae, and β-adrenergic responsiveness was additionally evaluated following norepinephrine (NE) perfusion. Baseline ex vivo heart rate (HR) and SNS stimulation threshold were higher in NIC versus CT (P = 0.004 and P = 0.003, respectively). Action potential duration alternans emerged at longer pacing cycle lengths (PCL) in NIC versus CT at baseline (P = 0.002) and during SNS (P = 0.0003), with similar results obtained for Ca2+ transient alternans. SNS shortened the PCL at which alternans emerged in CT but not in NIC hearts. NIC-exposed hearts tended to have slower and reduced HR responses to NE perfusion, but ventricular responses to NE were comparable between groups. Although fibrosis was unaltered, NIC hearts had lower sympathetic nerve density (P = 0.03) but no difference in NE content versus CT. These results suggest both sympathetic hypoinnervation of the myocardium and regional differences in β-adrenergic responsiveness with NIC. This autonomic remodeling may contribute to the increased risk of arrhythmias associated with nicotine exposure, which may be further exacerbated with long-term use.NEW & NOTEWORTHY Here, we show that chronic nicotine exposure was associated with increased heart rate, increased susceptibility to alternans, and reduced sympathetic electrophysiological responses in the intact rabbit heart. We suggest that this was due to sympathetic hypoinnervation of the myocardium and diminished β-adrenergic responsiveness of the sinoatrial node following nicotine treatment. Though these differences did not result in increased arrhythmia propensity in our study, we hypothesize that prolonged nicotine exposure may exacerbate this proarrhythmic remodeling.

Assessing Causality Between Second-Hand Smoking and Potentially Associated Diseases in Multiple Systems: A Two-Sample Mendelian Randomization Study

INTRODUCTION

The global disease burden may be exacerbated by exposure to passive smoking (SHS), with the workplace being a primary location for such exposure. Numerous epidemiological studies have identified SHS as a risk factor for diseases affecting various systems, including cardiovascular, respiratory, immune, endocrine, and nervous systems. The conventional observational study has certain methodological constraints that can be circumvented through a Mendelian randomization (MR) study. Our MR study intends to investigate the causal link between workplace exposure to SHS and the potential associated diseases.

AIM AND METHODS

Summary statistics data involving European participants were sourced from three databases: the UK Biobank, the FinnGen study, and the European Bioinformatics Institute. Genetic variants linked with exposure to SHS in the workplace were identified as instrumental variables. The MR was carried out using inverse variance weighted (IVW), MR-Egger, and weighted median methods. Sensitivity tests were also undertaken within the MR to evaluate the validity of the causality.

RESULTS

According to the IVW model, genetically determined atrial fibrillation (AF) and stroke (p = 6.64E-04 and 5.68E-07, odds ratio = 2.030 and 2.494, 95% confidence interval = 1.350 to 3.051 and 1.743 to 3.569) were robustly associated with exposure to SHS in the workplace. Suggestive associations were found between workplace SHS and myocardial infarction (MI), asthma, and depression.

CONCLUSIONS

The MR study demonstrates that exposure to SHS in the workplace is a significant risk factor for AF and stroke in European individuals. Whether workplace exposure to SHS influences other diseases and the causality between them requires further exploration.

IMPLICATIONS

This study explored the causality between exposure to SHS in the workplace and potential associated diseases in multiple systems, including MI, AF, stroke, lung cancer, asthma, allergic disease, type 2 diabetes, and depression, using an MR study. The MR study can circumvent the methodological constraints of observational studies and establish a causal relationship. The two-sample MR analysis provides evidence supporting the causal association of frequent workplace SHS with AF and stroke. Individuals exposed to SHS in the workplace may also have a heightened risk of MI, asthma, and depression. However, whether SHS affects other diseases and the causality between them requires further investigation. To our knowledge, this is the first two-sample MR study to determine the causal relationship between SHS and potential diseases. Exposure to SHS in the workplace is a prevalent issue and may contribute to a global disease burden. The reduction of exposure following the introduction of smoke-free laws has led to a decrease in the admission rate for cardiac events and an improvement in health indicators. It is crucial to further advance smoke-free policies and their implementation.

Chronic nicotine exposure is associated with electrophysiological and sympathetic remodeling in the intact rabbit heart

Nicotine is the primary addictive component in tobacco products. Through its actions on the heart and autonomic nervous system, nicotine exposure is associated with electrophysiological changes and increased arrhythmia susceptibility. However, the underlying mechanisms are unclear. To address this, we treated rabbits with transdermal nicotine (NIC, 21 mg/day) or control (CT) patches for 28 days prior to performing dual optical mapping of transmembrane potential (RH237) and intracellular Ca 2+ (Rhod-2 AM) in isolated hearts with intact sympathetic innervation. Sympathetic nerve stimulation (SNS) was performed at the 1 st - 3 rd thoracic vertebrae, and β-adrenergic responsiveness was additionally evaluated as changes in heart rate (HR) following norepinephrine (NE) perfusion. Baseline ex vivo HR and SNS stimulation threshold were increased in NIC vs. CT ( P = 0.004 and P = 0.003 respectively). Action potential duration alternans emerged at longer pacing cycle lengths (PCL) in NIC vs. CT at baseline ( P = 0.002) and during SNS ( P = 0.0003), with similar results obtained for Ca 2+ transient alternans. SNS reduced the PCL at which alternans emerged in CT but not NIC hearts. NIC exposed hearts also tended to have slower and reduced HR responses to NE perfusion. While fibrosis was unaltered, NIC hearts had lower sympathetic nerve density ( P = 0.03) but no difference in NE content vs. CT. These results suggest both sympathetic hypo-innervation of the myocardium and diminished β-adrenergic responsiveness with NIC. This autonomic remodeling may underlie the increased risk of arrhythmias associated with nicotine exposure, which may be further exacerbated with continued long-term usage.

NEW & NOTEWORTHY

Here we show that chronic nicotine exposure was associated with increased heart rate, lower threshold for alternans and reduced sympathetic electrophysiological responses in the intact rabbit heart. We suggest that this was due to the sympathetic hypo-innervation of the myocardium and diminished β- adrenergic responsiveness observed following nicotine treatment. Though these differences did not result in increased arrhythmia propensity in our study, we hypothesize that prolonged nicotine exposure may exacerbate this pro-arrhythmic remodeling.

Effects of chronic secondhand smoke exposure on cardiovascular regulation and the role of soluble epoxide hydrolase in mice

Background: Secondhand smoke (SHS) is a significant risk factor for cardiovascular morbidity and mortality with an estimated 80% of SHS-related deaths attributed to cardiovascular causes. Public health measures and smoking bans have been successful both in reducing SHS exposure and improving cardiovascular outcomes in non-smokers. Soluble epoxide hydrolase (sEH) inhibitors have been shown to attenuate tobacco exposure-induced lung inflammatory responses, making them a promising target for mitigating SHS exposure-induced cardiovascular outcomes. Objectives: The objectives of this study were to determine 1) effects of environmentally relevant SHS exposure on cardiac autonomic function and blood pressure (BP) regulation and 2) whether prophylactic administration of an sEH inhibitor (TPPU) can reduce the adverse cardiovascular effects of SHS exposure. Methods: Male C57BL/6J mice (11 weeks old) implanted with BP/electrocardiogram (ECG) telemetry devices were exposed to filtered air or 3 mg/m3 of SHS (6 hr/d, 5 d/wk) for 12 weeks, followed by 4 weeks of recovery in filtered air. Some mice received TPPU in drinking water (15 mg/L) throughout SHS exposure. BP, heart rate (HR), HR variability (HRV), baroreflex sensitivity (BRS), and BP variability were determined monthly. Results: SHS exposure significantly decreased 1) short-term HRV by ∼20% (p < 0.05) within 4 weeks; 2) overall HRV with maximum effect at 12 weeks (-15%, p < 0.05); 3) pulse pressure (-8%, p < 0.05) as early as week 4; and 4) BRS with maximum effect at 12 weeks (-11%, p < 0.05). Four weeks of recovery following 12 weeks of SHS ameliorated all SHS-induced cardiovascular detriments. Importantly, mice exposed to TPPU in drinking water during SHS-related exposure were protected from SHS cardiovascular consequences. Discussion: The data suggest that 1) environmental relevant SHS exposure significantly alters cardiac autonomic function and BP regulation; 2) cardiovascular consequences from SHS can be reversed by discontinuing SHS exposure; and 3) inhibiting sEH can prevent SHS-induced cardiovascular consequences.

Cardiac Rhythms and Variation in Hibernating Arctic Ground Squirrels

AbstractThe dramatic decrease in heart rate (HR) during entrance into hibernation is not a mere response to the lowering of core body temperature (Tb) but a highly regulated fall, as the decrease in HR precedes the drop in Tb. This regulated fall in HR is thought to be mediated by increased cardiac parasympathetic activity. Conversely, the sympathetic nervous system is thought to drive the increase of HR during arousal. Despite this general understanding, we lack temporal information on cardiac parasympathetic regulation throughout a complete hibernation bout. The goal of this study was to fill this gap in knowledge by using Arctic ground squirrels implanted with electrocardiogram/temperature telemetry transmitters. Short-term HR variability (root mean square of successive differences [RMSSD]), an indirect measure of cardiac parasympathetic regulation, was calculated in 11 Arctic ground squirrels. RMSSD, normalized as RMSSD/RR interval (RRI), increased fourfold during early entrance (from 0.2 ± 0.1 to 0.8 ± 0.2 , P < 0.05 ). RMSSD/RRI peaked after HR dropped by over 90% and Tb fell by 70%. Late entrance was delineated by a decline in RMSSD/RRI while Tb continued to decrease. During arousal, HR started to increase 2 h before Tb, with a concurrent decrease in RMSSD/RRI to a new minimum. As Tb increased to a maximum during interbout arousal, HR declined, and RMSSD/RRI increased. These data suggest that activation of the parasympathetic nervous system initiates and regulates the HR decrease during entrance into hibernation and that withdrawal of parasympathetic activation initiates arousal. We conclude that cardiac parasympathetic regulation persists throughout all phases of a hibernation bout-a feature of the autonomic nervous system's regulation of hibernation that was not appreciated previously.

Guidelines for assessment of cardiac electrophysiology and arrhythmias in small animals

Cardiac arrhythmias are a major cause of morbidity and mortality worldwide. Although recent advances in cell-based models, including human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM), are contributing to our understanding of electrophysiology and arrhythmia mechanisms, preclinical animal studies of cardiovascular disease remain a mainstay. Over the past several decades, animal models of cardiovascular disease have advanced our understanding of pathological remodeling, arrhythmia mechanisms, and drug effects and have led to major improvements in pacing and defibrillation therapies. There exist a variety of methodological approaches for the assessment of cardiac electrophysiology and a plethora of parameters may be assessed with each approach. This guidelines article will provide an overview of the strengths and limitations of several common techniques used to assess electrophysiology and arrhythmia mechanisms at the whole animal, whole heart, and tissue level with a focus on small animal models. We also define key electrophysiological parameters that should be assessed, along with their physiological underpinnings, and the best methods with which to assess these parameters.

Secondhand tobacco smoke exposure, urine cotinine, and risk of incident atrial fibrillation: The multi-ethnic study of atherosclerosis

BACKGROUND

Secondhand tobacco smoke (SHS) exposure may reduce heart rate variability and lead to atrial fibrillation (AF); however prior study findings have not been confirmed using objective measures for both SHS and AF events.

METHODS

We prospectively examined the association between SHS exposure and incident AF in 5731 participants, ages of 45-84 years and free of known AF and other cardiovascular diseases (CVD) at baseline (2000-2002), who were followed through 2015 in the Multi-Ethnic Study of Atherosclerosis (MESA). SHS weekly exposure time was identified by self-report. Urine cotinine was collected in a cohort subset of 3237 current non-smoking cohort participants. AF events were identified using Medicare claims, hospital records, and 12‑lead electrocardiographic findings. A multivariable Cox proportional hazards regression analysis was used with simultaneous adjustment for demographic factors, educational level, health insurance status, active smoking status, tobacco pack-years, traditional CVD risk factors, depressive symptoms and medications.

RESULTS

During a median follow-up of 14.0 years, 856 and 452 AF events were identified in the overall and the cohort subset, respectively. No association of SHS exposure time or urine cotinine with incident AF was observed. However, a higher AF risk with greater urine cotinine (8.53-442.0 ng/mL) compared with lower urine cotinine (≤7.07 ng/mL) was observed in never smokers [hazard ratios (HR) and 95% confidence intervals: 1.60 (1.16, 2.19)], but not in former smokers [HR: 0.88 (0.63, 1.23)] (p-value for multiplicative interaction: 0.009 and for additive interaction: 0.017, respectively).

CONCLUSION

Objectively measured greater SHS exposure expressed by urine cotinine might be associated with 1.6-fold higher risk of incident AF in never smokers.

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

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

Differences in Stroke or Systemic Thromboembolism Readmission Risk After Hospitalization for Atrial Fibrillation and Atrial Flutter

Background

Although atrial fibrillation (AF) and atrial flutter (AFL) are different arrhythmias, they are assumed to confer the same risk of stroke and systemic thromboembolism (STE) despite a lack of available evidence. In this study, we investigated the difference in the risk of stroke or STE after AF and AFL hospitalizations.

Methodology

The National Readmission Database (NRD) 2018 was used to identify AF and AFL patients using appropriate International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) codes and were followed until the end of the calendar year to identify stroke or STE readmissions. Survival estimates were calculated, and a Cox proportional hazards model was used to calculate the adjusted hazards ratio (aHR) and compare the risk of stroke or STE readmissions between AF and AFL groups.

Results

A total of 215,810 AF and 15,292 AFL patients were identified. AFL patients were more likely to be younger (66 vs. 70 years), male (68% vs. 47%), and had higher prevalence of obesity (25% vs. 22%), obstructive sleep apnea (14% vs. 12%), diabetes mellitus (31% vs. 26%), and alcohol use (6.9% vs. 5.5%) (all p < 0.01). After adjusting for potential patient and hospital-level characteristics, there was a statistically significant decrease in one-year stroke or STE readmission risk in AFL patients compared to AF patients (aHR 0.79 (0.66-0.95); p = 0.01).

Conclusions

AFL patients are commonly younger males with a higher burden of medical comorbidity. There is a decrease in the one-year risk of stroke or STE events in AFL patients compared to AF. The predictors of stroke and STE are similar in both AFL and AF groups. Further studies with longer follow-up and anticoagulation data are needed to verify the results.

Secondhand Smoke Decreased Excitability and Altered Action Potential Characteristics of Cardiac Vagal Neurons in Mice

Background: Secondhand smoke (SHS), a major indoor pollutant, is a significant risk factor for cardiovascular morbidity and mortality including arrhythmias and sudden cardiac death. Exposure to SHS can produce autonomic imbalance, as evidenced by reduced heart rate variability (HRV)—a clinical metric of cardiac vagal regulation. Currently, the mechanisms through which SHS changes the vagal preganglionic neuronal inputs to the heart to produce this remains unknown.

Objectives: To characterize the effect of SHS on both the excitability and action potential (AP) characteristics of anatomically identified cardiac vagal neurons (CVNs) in the nucleus ambiguus and examine whether SHS alters small conductance calcium-activated potassium (SK) channel activity of these CVNs.

Methods: Adult male mice were exposed to four weeks of filtered air or SHS (3 mg/m³) 6 h/day, 5 day/week. Using patch-clamp recordings on identified CVNs in brainstem slices, we determined neuronal excitability and AP characteristics with depolarizing step- and ramp-current injections.

Results: Four weeks of SHS exposure reduced spiking responses to depolarizing current injections and increased AP voltage threshold in CVNs. Perfusion with apamin (20 nM) magnified these SHS-induced effects, suggesting reduced SK channel activity may serve to minimize the SHS-induced decreases in CVNs excitability. Medium afterhyperpolarization (a measurement of SK channel activity) was smaller in the SHS group, further supporting a lower SK channel activity. AP amplitude, rise rate, fast afterhyperpolarization amplitude (a measurement of voltage-gated channel activity), and decay rate were higher in the SHS group at membrane voltages more positive to 0 mV, suggesting altered inactivation properties of voltage-dependent channels underlying APs.

Discussion: SHS exposure reduced neuronal excitability of CVNs with compensatory attenuation of SK channel activity and altered AP characteristics. Neuroplasticity of CVNs could blunt regulatory cardiac vagal signaling and contribute to the cardiovascular consequences associated with SHS exposure, including reduced HRV.

Measures of repolarization variability predict ventricular arrhythmogenesis in heptanol-treated Langendorff-perfused mouse hearts

BACKGROUND

Time-domain and non-linear methods can be used to quantify beat-to-beat repolarization variability but whether measures of repolarization variability can predict ventricular arrhythmogenesis in mice have never been explored.

METHODS

Left ventricular monophasic action potentials (MAPs) were recorded during constant right ventricular 8 ​Hz pacing in Langendorff-perfused mouse hearts, in the presence or absence of the gap junction and sodium channel inhibitor heptanol (0.1, 0.5, 1 or 2 ​mM).

RESULTS

Under control conditions, mean action potential duration (APD) was 39.4 ​± ​8.1 ​ms. Standard deviation (SD) of APDs was 0.3 ​± ​0.2 ​ms, coefficient of variation was 0.9 ​± ​0.8% and the root mean square (RMS) of successive differences in APDs was 0.15 ​± ​0.14 ​ms. Poincaré plots of APDn+1 against APDn revealed ellipsoid morphologies with a SD along the line-of-identity (SD2) to SD perpendicular to the line-of-identity (SD1) ratio of 4.6 ​± ​2.1. Approximate and sample entropy were 0.61 ​± ​0.12 and 0.76 ​± ​0.26, respectively. Detrended fluctuation analysis revealed short- and long-term fluctuation slopes of 1.49 ​± ​0.27 and 0.81 ​± ​0.36, respectively. Heptanol at 2 ​mM induced ventricular tachycardia in five out of six hearts. None of the above parameters were altered by heptanol during which reproducible electrical activity was observed (KW-ANOVA, P ​> ​0.05). Contrastingly, SD2/SD1 decreased to 2.03 ​± ​0.41, approximate and sample entropy increased to 0.82 ​± ​0.12 and 1.45 ​± ​0.34, and short-term fluctuation slope decreased to 0.82 ​± ​0.19 during the 20-s period preceding spontaneous ventricular tachy-arrhythmias (n ​= ​6, KW-ANOVA, P ​< ​0.05).

CONCLUSION

Measures of repolarization variability, such as SD2/SD1, entropy, and fluctuation slope are altered preceding the occurrence of ventricular arrhythmogenesis in mouse hearts. Changes in these variables may allow detection of impending arrhythmias for early intervention.

Is second hand smoking associated with atrial fibrillation risk among women in Israel? A case-control study

BACKGROUND

The first complete ban on indoor smoking in all public spaces (including bars and restaurants) occurred in 1994 in Israel, because of clear scientific evidence that SHS (Second Hand Smoking) is dangerous to non-smokers. Despite the smoking-ban law warning about the dangers of smoking, SHS remains in houses. The role of cigarette smoking on cardiac arrhythmia is less clearly defined and secondhand smoke (SHS) impact on the risk of atrial fibrillation (AF) remains unknown. The aim of this study was to evaluate the relationship between SHS and AF risk in Israeli women.

METHODS

This was a population-based case-control study consisting of never-smoking women aged 30-80 from Israel: 102 cases (diagnosed) of AF and 109 population- based controls. All participants were interviewed using a socio-demographic questionnaire that also related to past and current exposure to SHS.

RESULTS

SHS was associated with AF risk with adjusted odds ratio (OR) of 3.81 (95% confidence interval, CI 2.02-7.18). Higher exposure to SHS was associated with higher risk of AF compared to never-exposed women. Those exposed to SHS during one, two, or three life-periods (childhood, adolescence or adulthood) had an OR of 1.71 (95% CI 0.76-3.86), 2.87 (95% CI 1.25-6.56), and 9.14 (95% CI 4.09-20.44), respectively. Moreover, exposure to one pack/day increased the risk of AF by 2.89 times compared to 'never exposed' (95% CI 2.05-4.09).

CONCLUSIONS

SHS exposure in women who never smoked is associated with increased risk for AF.

The Use of Percent Change in RR Interval for Data Exclusion in Analyzing 24-h Time Domain Heart Rate Variability in Rodents

While epidemiological data support the link between reduced heart rate variability (HRV) and a multitude of pathologies, the mechanisms underlying changes in HRV and disease progression are poorly understood. Even though we have numerous rodent models of disease for mechanistic studies, not being able to reliably measure HRV in conscious, freely moving rodents has hindered our ability to extrapolate the role of HRV in the progression from normal physiology to pathology. The sheer number of heart beats per day (>800,000 in mice) makes data exclusion both time consuming and daunting. We sought to evaluate an RR interval exclusion method based on percent (%) change of adjacent RR intervals. Two approaches were evaluated: % change from “either” and “both” adjacent RR intervals. The data exclusion method based on standard deviation (SD) was also evaluated for comparison. Receiver operating characteristic (ROC) curves were generated to determine the performance of each method. Results showed that exclusion based on % change from “either” adjacent RR intervals was the most accurate method in identifying normal and abnormal RR intervals, with an overall accuracy of 0.92–0.99. As the exclusion value increased (% change or SD), the sensitivity (correctly including normal RR intervals) increased exponentially while the specificity (correctly rejecting abnormal RR intervals) decreased linearly. Compared to the SD method, the “either” approach had a steeper rise in sensitivity and a more gradual decrease in specificity. The intersection of sensitivity and specificity where the exclusion criterion had the same accuracy in identifying normal and abnormal RR intervals was 10–20% change for the “either” approach and ∼ 1 SD for the SD-based exclusion method. Graphically (tachogram and Lorenz plot), 20% change from either adjacent RR interval resembled the data after manual exclusion. Finally, overall (SDNN) and short-term (rMSSD) indices of HRV generated using 20% change from “either” adjacent RR intervals as the exclusion criterion were closer to the manual exclusion method with lower subject-to-subject variability than those generated using the 2 SD exclusion criterion. Thus, 20% change from “either” adjacent RR intervals is a good criterion for data exclusion for reliable 24-h time domain HRV analysis in rodents.

Cardiovascular injury induced by tobacco products: assessment of risk factors and biomarkers of harm. A Tobacco Centers of Regulatory Science compilation

Although substantial evidence shows that smoking is positively and robustly associated with cardiovascular disease (CVD), the CVD risk associated with the use of new and emerging tobacco products, such as electronic cigarettes, hookah, and heat-not-burn products, remains unclear. This uncertainty stems from lack of knowledge on how the use of these products affects cardiovascular health. Cardiovascular injury associated with the use of new tobacco products could be evaluated by measuring changes in biomarkers of cardiovascular harm that are sensitive to the use of combustible cigarettes. Such cardiovascular injury could be indexed at several levels. Preclinical changes contributing to the pathogenesis of disease could be monitored by measuring changes in systemic inflammation and oxidative stress, organ-specific dysfunctions could be gauged by measuring endothelial function (flow-mediated dilation), platelet aggregation, and arterial stiffness, and organ-specific injury could be evaluated by measuring endothelial microparticles and platelet-leukocyte aggregates. Classical risk factors, such as blood pressure, circulating lipoproteins, and insulin resistance, provide robust estimates of risk, and subclinical disease progression could be followed by measuring coronary artery Ca2+ and carotid intima-media thickness. Given that several of these biomarkers are well-established predictors of major cardiovascular events, the association of these biomarkers with the use of new and emerging tobacco products could be indicative of both individual and population-level CVD risk associated with the use of these products. Differential effects of tobacco products (conventional vs. new and emerging products) on different indexes of cardiovascular injury could also provide insights into mechanisms by which they induce cardiovascular harm.

Exposure to Secondhand Smoke and Arrhythmogenic Cardiac Alternans in a Mouse Model

BACKGROUND

Epidemiological evidence suggests that a majority of deaths attributed to secondhand smoke (SHS) exposure are cardiovascular related. However, to our knowledge, the impact of SHS on cardiac electrophysiology, [Formula: see text] handling, and arrhythmia risk has not been studied.

OBJECTIVES

The purpose of this study was to investigate the impact of an environmentally relevant concentration of SHS on cardiac electrophysiology and indicators of arrhythmia.

METHODS

Male C57BL/6 mice were exposed to SHS [total suspended particles (THS): [Formula: see text], nicotine: [Formula: see text], carbon monoxide: [Formula: see text], or filtered air (FA) for 4, 8, or 12 wk ([Formula: see text]]. Hearts were excised and Langendorff perfused for dual optical mapping with voltage- and [Formula: see text]-sensitive dyes.

RESULTS

At slow pacing rates, SHS exposure did not alter baseline electrophysiological parameters. With increasing pacing frequency, action potential duration (APD), and intracellular [Formula: see text] alternans magnitude progressively increased in all groups. At 4 and 8 wk, there were no statistical differences in APD or [Formula: see text] alternans magnitude between SHS and FA groups. At 12 wk, both APD and [Formula: see text] alternans magnitude were significantly increased in the SHS compared to FA group ([Formula: see text]). SHS exposure did not impact the time constant of [Formula: see text] transient decay ([Formula: see text]) at any exposure time point. At 12 wk exposure, the recovery of [Formula: see text] transient amplitude with premature stimuli was slightly (but nonsignificantly) delayed in SHS compared to FA hearts, suggesting that [Formula: see text] release via ryanodine receptors may be impaired.

CONCLUSIONS

In male mice, chronic exposure to SHS at levels relevant to social situations in humans increased their susceptibility to cardiac alternans, a known precursor to ventricular arrhythmia. https://doi.org/10.1289/EHP3664.

The effects of waterpipe tobacco smoking on health outcomes: an updated systematic review and meta-analysis

Background and aims

A systematic review conducted in 2008 found significant associations between waterpipe tobacco smoking and lung cancer, respiratory disease, periodontal disease and low birthweight. Since then, a number of relevant studies have been published. The objective of this study was to update the systematic review on the effects of waterpipe tobacco smoking on health outcomes.

Methods

In May 2015 we electronically searched the following databases with no date restrictions: MEDLINE, EMBASE and the ISI Web of Science using a detailed search strategy with no language restrictions. We also screened the references' lists of the included studies. We included cohort, case-control and cross-sectional studies, and excluded case reports, conference abstracts, editorials and reviews. We excluded studies not conducted in humans, assessing physiological outcomes, not distinguishing waterpipe tobacco smoking from other forms of smoking or not reporting association measures. We assessed risk of bias for each included study and conducted meta-analyses for each of the outcomes of interest.

Results

We identified 50 eligible studies. We found that waterpipe tobacco smoking was significantly associated with: respiratory diseases [COPD; odds ratio (OR) = 3.18, 95% confidence interval CI = 1.25, 8.08; bronchitis OR = 2.37, 95% CI = 1.49, 3.77; passive waterpipe smoking and wheeze OR) = 1.97, 95% CI = 1.28, 3.04]; oral cancer OR = 4.17, 95% CI = 2.53, 6.89; lung cancer OR = 2.12, 95% CI = 1.32, 3.42; low birthweight (OR = 2.39, 95% CI = 1.32, 4.32); metabolic syndrome (OR 1.63-1.95, 95% CI = 1.25, 2.45); cardiovascular disease (OR = 1.67, 95% CI = 1.25, 2.24); and mental health (OR 1.30-2.4, 95% CI = 1.20, 2.80). Waterpipe tobacco smoking was not significantly associated with: oesophageal cancer (OR = 4.14, 95% CI = 0.93, 18.46); worse quality of life scores [standardized mean difference (SMD) = -0.16, 95% CI = -0.66, 0.34]; gastric carcinoma (OR = 2.16, 95% CI = 0.72, 6.47); bladder cancer (OR = 1.25, 95% CI = 0.99, 1.57); prostate cancer (OR = 7.00, 95% CI = 0.90, 56.90); hepatitis C infection (OR = 0.98, 95%0.80, 1.21); periodontal disease (OR = 3.00, 5.00); gastro-oesophageal reflux disease (OR = 1.25, 95% CI = 1.01, 1.56); nasopharyngeal carcinoma (OR = 0.49, 95% CI = 0.20, 1.23); bladder cancer (OR = 1.25, 95% CI = 0.99, 1.57); infertility (OR = 2.50, 95% CI = 1.00, 6.30); and mortality (OR = 1.15, 95% CI = 0.93, 1.43).

Conclusions

There is accumulating evidence about the association of waterpipe tobacco smoking with a growing number of health outcomes.

Cardiovascular effects of linalyl acetate in acute nicotine exposure

Backgroud

Smoking is a risk factor for cardiovascular diseases as well as pulmonary dysfunction. In particular, adolescent smoking has been reported to have a higher latent risk for cardiovascular disease. Despite the risk to and vulnerability of adolescents to smoking, the mechanisms underlying the effects of acute nicotine exposure on adolescents remain unknown. This study therefore evaluated the mechanism underlying the effects of linalyl acetate on cardiovascular changes in adolescent rats with acute nicotine exposure.

Methods

Parameters analyzed included heart rate (HR), systolic blood pressure, lactate dehydrogenase (LDH) activity, vascular contractility, and nitric oxide levels.

Results

Compared with nicotine alone, those treated with nicotine plus 10 mg/kg (p = 0.036) and 100 mg/kg (p = 0.023) linalyl acetate showed significant reductions in HR. Moreover, the addition of 1 mg/kg (p = 0.011), 10 mg/kg (p = 0.010), and 100 mg/kg (p = 0.011) linalyl acetate to nicotine resulted in significantly lower LDH activity. Nicotine also showed a slight relaxation effect, followed by a sustained recontraction phase, whereas nicotine plus linalyl acetate or nifedipine showed a constant relaxation effect on contraction of mouse aorta (p < 0.001). Furthermore, nicotine-induced increases in nitrite levels were decreased by treatment with linalyl acetate (p < 0.001).

Conclusions

Taken together, our findings suggest that linalyl acetate treatment resulted in recovery of cell damage and cardiovascular changes caused by acute nicotine-induced cardiovascular disruption. Our evaluation of the influence of acute nicotine provides potential insights into the effects of environmental tobacco smoke and suggests linalyl acetate as an available mitigating agent.

Environmental Tobacco Smoke and Atrial Fibrillation: The REasons for Geographic And Racial Differences in Stroke (REGARDS) Study

OBJECTIVE

This study examines the association between environmental tobacco smoke (ETS) exposure and atrial fibrillation (AF).

METHODS

We examined the cross-sectional association between ETS exposure and AF in 12,021 participants (mean age: 65 ± 9.9 years; 60% women; 40% blacks) from the REasons for Geographic And Racial Differences in Stroke study who self-identified as never smokers between 2003 and 2007.

RESULTS

A total of 2503 (21%) participants reported ETS exposure. In a multivariate logistic regression model adjusted for sociodemographics and potential confounders, ETS exposure was significantly associated with AF (odds ratio = 1.27, 95% confidence interval = 1.08, 1.50).

CONCLUSIONS

Our findings suggest that the harmful effects of ETS exposure extend to sustained arrhythmias such as AF.

Ambient and household air pollution: complex triggers of disease

Concentrations of outdoor air pollution are on the rise, particularly due to rapid urbanization worldwide. Alternatively, poor ventilation, cigarette smoke, and other toxic chemicals contribute to rising concentrations of indoor air pollution. The World Health Organization recently reported that deaths attributable to indoor and outdoor air pollutant exposure are more than double what was originally documented. Epidemiological, clinical, and animal data have demonstrated a clear connection between rising concentrations of air pollution (both indoor and outdoor) and a host of adverse health effects. During the past five years, animal, clinical, and epidemiological studies have explored the adverse health effects associated with exposure to both indoor and outdoor air pollutants throughout the various stages of life. This review provides a summary of the detrimental effects of air pollution through examination of current animal, clinical, and epidemiological studies and exposure during three different periods: maternal (in utero), early life, and adulthood. Additionally, we recommend future lines of research while suggesting conceivable strategies to curb exposure to indoor and outdoor air pollutants.

Lifetime cumulative exposure to waterpipe smoking is associated with coronary artery disease

OBJECTIVE

Globally, waterpipe (WP) smoking is becoming a more prevalent form of tobacco consumption. Whilst research so far has demonstrated a significant link between WP use and a number of health outcomes, little is known of its association with heart disease. We examine in this study the association of WP smoking with angiographically confirmed coronary artery disease (CAD).

METHODS

A total of 1210 patients, aged 40 years and over and free from smoking-associated illnesses or history of cardiovascular procedures, admitted for coronary angiography at four major hospitals in Lebanon, were included. The extent of CAD was summarized in two ways, firstly as diseased (≥ 50% and ≥ 70% occlusion in at least one main coronary artery) versus non-diseased (entirely normal coronaries), and secondly, as CAD cumulative score based on Duke CAD Prognostic Index. A score of WP-years, capturing intensity and lifetime duration of exposure, was estimated for each individual.

RESULTS

Lifetime exposure exceeding 40 WP-years was associated with a threefold significant increase in the odds of having severe stenosis (≥ 70%) compared to non-smokers (OR = 2.94, 95% CI 1.04-8.33) as well as with the CAD Index (β = 7.835, p-value = 0.027), net of the effect of socio-demographic characteristics, health behaviors and co-morbidity. A dose-response relationship between WP-years and percent stenosis was also established. WP smoking status (never, past and current) did not associate with CAD.

CONCLUSIONS

Cumulative exposure to WP smoking is significantly associated with severe CAD. There is a need to monitor WP use among cardiac patients and include this information in their medical charts in the same manner cigarettes smoking is documented. This is likely to increase awareness of the hazards of WP smoking and prompt physicians to target WP tobacco control by providing advice to their patients on WP smoking cessation.

The effect of workplace smoking bans on heart rate variability and pulse wave velocity of non-smoking hospitality workers

OBJECTIVES

To investigate the effect of a change in second-hand smoke (SHS) exposure on heart rate variability (HRV) and pulse wave velocity (PWV), this study utilized a quasi-experimental setting when a smoking ban was introduced.

METHODS

HRV, a quantitative marker of autonomic activity of the nervous system, and PWV, a marker of arterial stiffness, were measured in 55 non-smoking hospitality workers before and 3-12 months after a smoking ban and compared to a control group that did not experience an exposure change. SHS exposure was determined with a nicotine-specific badge and expressed as inhaled cigarette equivalents per day (CE/d).

RESULTS

PWV and HRV parameters significantly changed in a dose-dependent manner in the intervention group as compared to the control group. A one CE/d decrease was associated with a 2.3% (95% CI 0.2-4.4; p = 0.031) higher root mean square of successive differences (RMSSD), a 5.7% (95% CI 0.9-10.2; p = 0.02) higher high-frequency component and a 0.72% (95% CI 0.40-1.05; p < 0.001) lower PWV.

CONCLUSIONS

PWV and HRV significantly improved after introducing smoke-free workplaces indicating a decreased cardiovascular risk.

Effects of cigarette smoke on Holter ECG recordings in patients with arterial hypertension. Part 1: Time domain parameters of heart rate variability

This report was intended to evaluate the effect of cigarette smoke on heart rate variability (HRV) in patients with arterial hypertension (AH). 223 individuals were qalified to the studies. The following groups of patients not suffering from other disease which may affect HRV were delineated: 1 - patients with AH (n=145); 2 - patients without AH (n=48). In group 1 the following patient groups were studied: A - active smokers (n=42), B - non-smokers exposed to cigarette smoke (n=30), C - non-smokers not exposed to tobacco smoke (n=34), D - former smokers (n=26). A time domain HRV analysis was carried out. Group 1 versus group 2 manifested significantly lower mean values of most parameters in the HRV time domain analysis. Subgroups A, B and D versus subgroup C also exhibited significantly lower mean values of most parameters in the HRV time domain analysis. Active cigarette smoking and passive exposure to tobacco smoke represented independent risk factors for a decreased HRV.

CONCLUSIONS

Active and passive exposure to cigarette smoke decreases HRV in hypertensive patients.

Circadian clock function is disrupted by environmental tobacco/cigarette smoke, leading to lung inflammation and injury via a SIRT1-BMAL1 pathway

Patients with obstructive lung diseases display abnormal circadian rhythms in lung function. We determined the mechanism whereby environmental tobacco/cigarette smoke (CS) modulates expression of the core clock gene BMAL1, through Sirtuin1 (SIRT1) deacetylase during lung inflammatory and injurious responses. Adult C57BL6/J and various mice mutant for SIRT1 and BMAL1 were exposed to both chronic (6 mo) and acute (3 and 10 d) CS, and we measured the rhythmic expression of clock genes, circadian rhythms of locomotor activity, lung function, and inflammatory and emphysematous responses in the lungs. CS exposure (100-300 mg/m(3) particulates) altered clock gene expression and reduced locomotor activity by disrupting the central and peripheral clocks and increased lung inflammation, causing emphysema in mice. BMAL1 was acetylated and degraded in the lungs of mice exposed to CS and in patients with chronic obstructive pulmonary disease (COPD), compared with lungs of the nonsmoking controls, linking it mechanistically to CS-induced reduction of SIRT1. Targeted deletion of Bmal1 in lung epithelium augmented inflammation in response to CS, which was not attenuated by the selective SIRT1 activator SRT1720 (EC50=0.16 μM) in these mice. Thus, the circadian clock, specifically the enhancer BMAL1 in epithelium, plays a pivotal role, mediated by SIRT1-dependent BMAL1, in the regulation of CS-induced lung inflammatory and injurious responses.

Exposure to secondhand smoke promotes sympathetic activity and cardiac muscle cachexia

Recent trials demonstrated that a single brief exposure to secondhand smoke (SHS) generates acute adverse health effects. We evaluated the acute (immediately after exposure) and short-term (0.5, 1, 2, 3 and 4 h after exposure) effects of SHS on cardiac autonomic control and myocardial integrity. Nineteen adult healthy never-smokers underwent a 1 h exposure to SHS at bar/restaurant levels and a 1 h control exposure. Heart rate variability (HRV), serum cotinine, and six cardiac protein markers were assessed before, during, and up to four hours following each exposure. SHS reduced the standard deviation of normal-to-normal intervals and increased cotinine levels, creatine kinase (CK)-MB, and myoglobin (p < 0.05). We conclude that acute exposure to SHS suppresses HRV and augments CK-MB and myoglobin. The SHS-induced elevations in CK-MB and myoglobin may reflect a generalized lytic state, especially of the cardiac muscle, which is apparent for at least 2 h following the SHS exposure.

Second-hand tobacco smoke and cardiovascular disease risk: an epidemiological review

In this review, we have sought to examine the epidemiological, basic science, and public health data regarding the association between second-hand smoke (SHS) exposure and the development of coronary heart disease (CHD). SHS increases the risk of CHD by 25-30% according to multiple cohort, case-control, and meta-analytical studies. Physiologic and basic science research suggest that the mechanisms by which SHS affects the cardiovascular system are multiple and include increased thrombogenesis and low-density lipoprotein oxidation, decreased exercise tolerance, dysfunctional flow-mediated vasodilatation, and activation of inflammatory pathways with concomitant oxidative damage and impaired vascular repair. As a result, chronic exposure promotes atherogenesis and the development of cardiovascular disease, increasing the risk of having an acute coronary syndrome (ACS). With the implementation of statewide and nationwide public smoke-free legislation across the United States and Europe, respectively, over the last 10-15 years, there has been a significant and reciprocal decline in the incidence of emergency admissions for ACS by an average 17% despite persistent attempts on the part of the tobacco industry to diminish the correlation between SHS exposure and CHD. These findings underscore the importance of the effects of smoking legislation on community health.

Acute toxicant exposure and cardiac autonomic dysfunction from smoking a single narghile waterpipe with tobacco and with a "healthy" tobacco-free alternative

Tobacco smoking using a waterpipe (narghile, hookah, shisha) has become a global epidemic. Unlike cigarette smoking, little is known about the health effects of waterpipe use. One acute effect of cigarette smoke inhalation is dysfunction in autonomic regulation of the cardiac cycle, as indicated by reduction in heart rate variability (HRV). Reduced HRV is implicated in adverse cardiovascular health outcomes, and is associated with inhalation exposure-induced oxidative stress. Using a 32 participant cross-over study design, we investigated toxicant exposure and effects of waterpipe smoking on heart rate variability when, under controlled conditions, participants smoked a tobacco-based and a tobacco-free waterpipe product promoted as an alternative for "health-conscious" users. Outcome measures included HRV, exhaled breath carbon monoxide (CO), plasma nicotine, and puff topography, which were measured at times prior to, during, and after smoking. We found that waterpipe use acutely decreased HRV (p<0.01 for all measures), independent of product smoked. Plasma nicotine, blood pressure, and heart rate increased only with the tobacco-based product (p<0.01), while CO increased with both products (p<0.01). More smoke was inhaled during tobacco-free product use, potentially reflecting attempted regulation of nicotine intake. The data thus indicate that waterpipe smoking acutely compromises cardiac autonomic function, and does so through exposure to smoke constituents other than nicotine.

Nicotine, cigarette smoking and cardiac arrhythmia: an overview

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

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

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

Effects of active and passive tobacco cigarette smoking on heart rate variability

Given the widespread incidence of smoking as well as its deleterious health effects, it is crucial to examine practical and cost effective prognostic markers assessing its health impact. Heart rate variability (HRV) is a straightforward and cost effective technique to foresee health problems of cardiovascular nature and may be used to predict in advance smoking-induced health effects. In this review we evaluate the existing biological evidence regarding the effects of smoking on HRV and their associated cardiovascular consequences. In addition, we summarize fundamental information on the various HRV indicators and their diagnostic significance in relation to heart failure. An in depth analysis of the various HRV indices characterizing changes in the activation of the autonomic nervous system is provided together with a critical evaluation of all evidence published to date on the influence of chronic and acute active and passive smoking on HRV. Overall, the vast majority of published evidence suggests that acute and chronic active and passive smoking generate marked disruptions in the normal autonomic nervous system functioning characterized by increased sympathetic drive and reduced HRV and parasympathetic modulation. The proposed mechanisms that may generate this smoke-induced HRV reduction as well as its clinical implications are thoroughly evaluated.

Resveratrol preserves cardiac function, but does not prevent endothelial dysfunction or pulmonary inflammation after environmental tobacco smoke exposure

The mechanisms by which environmental tobacco smoke (ETS) causes adverse cardiovascular effects remain unclear. Resveratrol is a natural polyphenol from red wine which may be beneficial to the cardiovascular system. Therefore, the ability of daily oral resveratrol (5mg/kg) to prevent adverse effects of a 14-day ETS exposure (1 h/day) on endothelial function (flow-mediated dilation), left ventricular function (echocardiography) and blood pressure (oscillometry) was assessed in juvenile male pigs (n=4 pigs/group). After a 14-day exposure to ETS, flow-mediated dilation was impaired while plasma nitrotyrosine was increased compared to sham-exposed pigs indicating impaired endothelial function. In ETS-exposed pigs, plasma C-reactive protein levels, lung cytochrome P4501A1 activity, bronchoalveolar lavage fluid total white blood cell count and leukocyte elastase activity were all significantly increased compared to sham-exposed pigs. Resveratrol treatment failed to prevent most ETS-mediated effects examined, but did increase left ventricular end-diastolic volume and ejection fraction in the presence of ETS exposure. In summary, ETS exposure impaired endothelial function and increased oxidative stress which was associated with pulmonary and systemic inflammation, but resveratrol failed to protect against these changes. More importantly, resveratrol exerted a positive effect on left ventricular function which may help explain the French paradox.

Environmental tobacco smoke furthers progression of diabetic nephropathy

Clinical studies suggest that smoking is a risk factor in the progression of chronic kidney disease, including diabetic nephropathy. The mechanisms involved are not completely understood. We have previously demonstrated that nicotine, one of the compounds present in large amounts in tobacco, promotes mesangial cell proliferation and fibronectin production. In this study, we hypothesized that exposure to environmental tobacco smoke (ETS) promotes the progression of diabetic nephropathy by increasing the expression of profibrotic cytokines such as transforming growth factor-beta (TGF-β) and the extracellular matrix proteins fibronectin and collagen IV. Six-week-old diabetic (db/db) mice were divided into 2 groups. The experimental group (n = 12) was exposed to ETS at a concentration of 30 mg/m for 6 hr/d, 5 d/wk for 8 weeks. The control group (n = 8) was exposed to room air. Urine was collected before euthanasia for albumin (enzyme-linked immunosorbent assay) and creatinine measurements (mass spectrometry). After euthanasia, the kidneys were harvested for morphometric analysis and Western blot analysis. Serum was saved for cotinine measurements by enzyme-linked immunosorbent assay. ETS exposure resulted in serum levels of cotinine similar to those found in human smokers. ETS exposure for 8 weeks induced significant mesangial expansion (approximately 50% increase) that was accompanied by concomitant increases in TGF-β and fibronectin expression (approximately 20%). However, ETS did not modify results in significant changes in urinary albumin excretion. These studies demonstrate that ETS exposure worsens the progression of diabetic nephropathy by increasing the amount of mesangial expansion and that these effects are likely mediated by increased expression of profibrotic cytokines such as TGF-β.

Using blood pressure telemetry to assess acute changes in arterial stiffness in rats after nitric oxide synthase inhibition or environmental tobacco smoke exposure

Although environmental tobacco smoke (ETS) exposure has been reported to acutely increase arterial stiffness in humans, understanding of the underlying mechanisms is unclear and few studies have measured these effects in experimental animals. One potential mechanism for the increased arterial stiffness is reduced nitric oxide (NO) bioactivity as a result of oxidative stress. Thus, the objective of this study was to determine whether acute changes in arterial stiffness could be detected using arterial pulse wave dP/dt in blood pressure telemetry implanted rats and to investigate the role of NO in regulating dP/dt. Intravenous injection of acetylcholine (0.91 ng/kg) decreased and norepinephrine (0.02 mg/kg) increased dP/dt compared to saline vehicle (0.5 mL/kg). Injection of the NO synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME; 30 mg/kg) decreased plasma nitrate/nitrite (NOx), but transiently increased dP/dt. ETS at low and high doses had no effect on dP/dt, but increased plasma NOx levels at high ETS exposure and increased plasma nitrotyrosine levels in both ETS groups. In conclusion, acute changes in NO production via acetylcholine or L-NAME alter the arterial pulse wave dP/dt consistently with the predicted changes in arterial stiffness. Although acute ETS appears to biologically inactivate NO, a concomitant increase in NO production at high ETS exposure may explain why dP/dt was not acutely altered by ETS in the current study.

Particulate matter inhalation exacerbates cardiopulmonary injury in a rat model of isoproterenol-induced cardiomyopathy

Ambient particulate matter (PM) exposure is linked to cardiovascular events and death, especially among individuals with heart disease. A model of toxic cardiomyopathy was developed in Spontaneously Hypertensive Heart Failure (SHHF) rats to explore potential mechanisms. Rats were infused with isoproterenol (ISO; 2.5 mg/kg/day subcutaneous [sc]), a beta-adrenergic agonist, for 28 days and subsequently exposed to PM by inhalation. ISO induced tachycardia and hypotension throughout treatment followed by postinfusion decrements in heart rate, contractility, and blood pressures (systolic, diastolic, pulse), and fibrotic cardiomyopathy. Changes in heart rate and heart rate variability (HRV) 17 days after ISO cessation indicated parasympathetic dominance with concomitantly altered ventilation. Rats were subsequently exposed to filtered air or Harvard Particle 12 (HP12) (12 mg/m(3))--a metal-rich oil combustion-derived PM--at 18 and 19 days (4 h/day) after ISO infusion via nose-only inhalation to determine if cardio-impaired rats were more responsive to the effects of PM exposure. Inhalation of PM among ISO-pretreated rats significantly increased pulmonary lactate dehydrogenase, serum high-density lipoprotein (HDL) cholesterol, and heart-to-body mass ratio. PM exposure increased the number of ISO-pretreated rats that experienced bradyarrhythmic events, which occurred concomitantly with acute alterations of HRV. PM, however, did not significantly affect mean HRV in the ISO- or saline-pretreated groups. In summary, subchronic ISO treatment elicited some pathophysiologic and histopathological features of heart failure, including cardiomyopathy. The enhanced sensitivity to PM exposure in SHHF rats with ISO-accelerated cardiomyopathy suggests that this model may be useful for elucidating the mechanisms by which PM exposure exacerbates heart disease.

Telemetric analysis to detect febrile responses in mice following vaccination with a live-attenuated virus vaccine

Non-human primates (NHP) are considered to be the most appropriate model for predicting how humans will respond to many infectious diseases. Due to ethical and monetary concerns associated with the use of NHP, rodent models that are as predictive of responses likely to be seen in human vaccine recipients are warranted. Using implanted telemetry devices, body temperature and activity were monitored in inbred and outbred mouse strains following administration of the live-attenuated vaccine for Venezuelan equine encephalitis virus (VEEV), V3526. Following analysis of individual mouse data, only outbred mouse strains showed changes in diurnal temperature and activity profiles following vaccination. Similar changes were observed following VEEV challenge of vaccinated outbred mice. From these studies, we conclude, outbred mouse strains implanted with telemeters are a sensitive model for predicting responses in humans following vaccination.

Central neuroplasticity and decreased heart rate variability after particulate matter exposure in mice

BACKGROUND

Epidemiologic studies show that exposure to fine particulate matter [aerodynamic diameter < or = 2.5 microm (PM(2.5))] increases the total daily cardiovascular mortality. Impaired cardiac autonomic function, which manifests as reduced heart rate variability (HRV), may be one of the underlying causes. However, the cellular mechanism(s) by which PM(2.5) exposure induces decreased HRV is not known.

OBJECTIVES

We tested the hypothesis that exposure to PM(2.5) impairs HRV by decreasing the excitability of the cardiac vagal neurons in the nucleus ambiguus. We also determined the effect of iron on PM-exposure-induced decrease in HRV.

METHODS

We measured 24-hr HRV in time domains from electrocardiogram telemetry recordings obtained in conscious, freely moving mice after 3 days of exposure to PM(2.5) in the form of soot only or iron-soot. In parallel studies, we determined the intrinsic properties of identified cardiac vagal neurons, retrogradely labeled with a fluorescent dye applied to the sinoatrial node.

RESULTS

Soot-only exposure decreased short-term HRV (root mean square of successive difference). With the addition of iron, all HRV parameters were significantly reduced. In nonexposed mice, vagal blockade significantly reduced all HRV parameters, suggesting that HRV is, in part, under vagal regulation in mice. Iron-soot exposure had no significant effect on resting membrane potential but decreased spiking responses of the identified cardiac vagal neurons to depolarizations (p < 0.05). The decreased spiking response was accompanied with a higher minimal depolarizing current required to evoke spikes and a lower peak discharge frequency.

CONCLUSIONS

The data suggest that PM-induced neuroplasticity of cardiac vagal neurons may be one mechanism contributing to the cardiovascular consequences associated with PM(2.5) exposure seen in humans.

Role of smoking in the recurrence of atrial arrhythmias after cardioversion

We aimed to determine whether smoking status affects the recurrence of atrial fibrillation or atrial flutter in patients after cardioversion. The clinical data of patients undergoing cardioversion for atrial flutter from January 1, 2000 to December 31, 2005 were prospectively collected. Arrhythmia recurrences were detected by retrospective review of comprehensive medical records and were determined using electrocardiography. The smoking history was prospectively collected through a standardized clinical form and subsequently categorized as lifetime nonsmoker, exsmoker, or current smoker. Univariate and multivariate associations with end points for clinical and lifestyle variables were assessed with Cox proportional hazards models. Women who were current smokers at cardioversion had a greater risk of atrial arrhythmia recurrence than did nonsmokers (hazard ratio 1.71, 95% confidence interval 1.10 to 2.67, p = 0.02). The increased risk of arrhythmia recurrence in female smokers was not seen in male smokers. Compared to lifetime nonsmokers, the mortality hazard ratio among men was 1.18 (95% confidence interval 0.88 to 1.58; p = 0.28) in exsmokers and 1.93 (95% confidence interval 1.20 to 3.11; p = 0.007) in current smokers. The risk of death after cardioversion was not increased in women. In conclusion, smoking is an independent predictor of atrial arrhythmia recurrence after cardioversion in women; however, an increased mortality risk, but not arrhythmia recurrence risk, was seen in men.

Variables influencing heart rate

In both physiologic and pathological conditions, instantaneous heart rate value is the result of a rather complex interplay. It constantly varies under the influence of a number of factors: nonmodifiable and modifiable ones. Pharmacologic blockade with beta-adrenergic antagonists and/or with parasympathetic antagonists such as atropine have permitted the identification of the mechanisms of autonomic nervous regulation of heart rate in a variety of physiologic and pathological conditions. The analysis of heart rate and blood pressure variability has yielded additional information on the autonomic control of the circulation, which has proven to have diagnostic and prognostic implications in a number of clinically relevant conditions such as hypertension, acute myocardial infarction, heart failure, and predisposition to sudden cardiac death. This article will summarize, based on available epidemiologic and clinical studies, the key variables influencing heart rate and heart rate variability in view of the known association between heart rate and cardiovascular disease.

Is nicotine a key player or spectator in the induction and progression of cardiovascular disorders?

Cigarette smoking is common in societies worldwide and a growing body of evidence suggests that chronic cigarette smoking may affect the structure and function of cardiovascular system. The chronic exposure to high levels of nicotine, a major component of cigarette smoking, has been observed to play a pathogenic role in the induction and progression of cardiovascular disorders including cardiomyopathy and peripheral vascular disease. Nicotine alters the function of vascular endothelium, initiates the adhesion cascade and stimulates the vascular inflammatory events to induce atherosclerosis and hypertension. Moreover, nicotine has been noted to induce direct coronary spasm and ischemia, which develop coronary artery disease and myocardial infarction. In addition, nicotine stimulates the excessive release of impulses from sinoatrial node that may account for the induction of cardiac arrhythmia. The present review critically discussed the possible detrimental role of chronic nicotine exposure in cardiac and vascular endothelial dysfunction. Moreover, the signaling mechanisms involved in the pathogenesis of nicotine exposure-induced cardiovascular dysfunction have been discussed. In addition, the pharmacological interventions to ameliorate chronic nicotine exposure-induced cardiovascular abnormalities have been delineated.