Nicotine and electronic cigarette (E-Cig) exposure decreases brain glucose utilization in ischemic stroke

Factors influencing brain recovery from stroke via possible epigenetic changes

Aim: To examine epigenetic changes leading to functional repair after damage to the central motor system.Data sources: A literature search was conducted using medical and health science electronic databases (PubMed, MEDLINE, Scopus) up to July 2023.Study selection: Data were summarized for type of intervention, study design, findings including human and animal studies.Data extraction: Data were extracted and double-checked independently for methodological quality. By means of the influence of environmental (calorie restriction or physical exercise) and other factors, epigenetic instructions were found to increase levels of BDNF and enhance synaptic neurotransmission, possibly leading to larger scale changes in structural and functional assets, which may end up to cognitive and motor repair after stroke.

The Hidden Dangers: E-Cigarettes, Heated Tobacco, and Their Impact on Oxidative Stress and Atherosclerosis-A Systematic Review and Narrative Synthesis of the Evidence

Electronic cigarettes and heated tobacco products have seen significant growth in sales and usage in recent years. Initially promoted as potentially less harmful alternatives to traditional tobacco, recent scientific evidence has raised serious concerns about the risks they pose, particularly in relation to atherosclerosis. While atherosclerosis has long been associated with conventional tobacco smoking, emerging research suggests that electronic cigarettes and heated tobacco may also contribute to the development of this condition and related cardiovascular complications. In a narrative review, we examined the potential effects of heated tobacco products and electronic cigarettes on oxidative stress and atherosclerosis. Several studies have shown that e-cigarettes and heated tobacco increase oxidative stress through the activation of enzymes such as NADPH oxidase. One of the primary effects of these products is their pro-thrombotic and pro-atherosclerotic impact on endothelial cells and platelets, which promotes inflammatory processes within the arteries. Furthermore, the chemicals found in electronic cigarette liquids may exacerbate inflammation and cause endothelial dysfunction. Furthermore, through a systematic review, we analyzed the effects of chronic exposure to electronic and heated tobacco cigarettes on endothelial function, as assessed by brachial flow-mediated dilation (FMD). Although electronic cigarettes and heated tobacco cigarettes are often perceived as safer alternatives to traditional smoking, they could still present risks to cardiovascular health. It is essential to raise public awareness about the potential dangers associated with these products and implement protective measures, particularly for young people.

Health outcomes of electronic cigarettes

ABSTRACT

The usage of electronic cigarettes (e-cigarettes) sparked an outbreak of unidentified vaping-related lung disease in the US during late 2019. With e-cigarettes becoming more and more popular, smokers have more options other than conventional cigarettes. Under these circumstances, a comprehensive evaluation of the general safety of new tobacco and tobacco-related products, represented by e-cigarettes, to human health is necessary. In this review, we summarize the current research on potential negative impacts of e-cigarette exposure on human health. In particular, studies detailing the relationship between e-cigarettes and the digestive system are summarized, with mechanisms mainly including hepatic metabolic dysfunction, impaired gut barrier, and worsened outcomes of inflammatory bowel disease (IBD). Although believed to be safer than traditional cigarettes, e-cigarettes exert adverse effects on systemic health and induce the development of multiple diseases including asthma, cardiovascular disease, and IBD. Moreover, nicotine-containing e-cigarettes have a negative impact on the childhood development and increase the risk of arterial stiffness compared to the non-nicotine e-cigarettes. However, non-nicotine e-cigarette components have detrimental effects including promoting liver damage and metabolic disorders.

Altered insular functional activity among electronic cigarettes users with nicotine dependence

Electronic cigarettes (e-cigs) use, especially among youngsters, has been on the rise in recent years. However, little is known about the long-term effects of the use of e-cigs on brain functional activity. We acquired the resting-state functional magnetic resonance imaging (rs-fMRI) data from 93 e-cigs users with nicotine dependence and 103 health controls (HC). The local synchronization was analyzed via the regional homogeneity (ReHo) method at voxel-wise level. The functional connectivity (FC) between the nucleus accumbens (NAcc), the ventral tegmental area (VTA), and the insula was calculated at ROI-wise level. The support vector machining classification model based on rs-fMRI measures was used to identify e-cigs users from HC. Compared with HC, nicotine-dependent e-cigs users showed increased ReHo in the right rolandic operculum and the right insula (p < 0.05, FDR corrected). At the ROI-wise level, abnormal FCs between the NAcc, the VTA, and the insula were found in e-cigs users compared to HC (p < 0.05, FDR corrected). Correlation analysis found a significant negative correlation between ReHo in the left NAcc and duration of e-cigs use (r = -0.273, p = 0.008, FDR corrected). The following support vector machine model based on significant results of rs-fMRI successfully differentiates chronic e-cigs users from HC with an accuracy of 73.47%, an AUC of 0.781, a sensitivity of 67.74%, and a specificity of 78.64%. Dysregulated spontaneous activity and FC of addiction-related regions were found in e-cigs users with nicotine dependence, which provides crucial insights into the prevention of its initial use and intervention for quitting e-cigs.

Comprehensive Management of Stroke: From Mechanisms to Therapeutic Approaches

Acute ischemic stroke (AIS) is a challenging disease, which needs urgent comprehensive management. Endovascular thrombectomy (EVT), alone or combined with iv thrombolysis, is currently the most effective therapy for patients with acute ischemic stroke (AIS). However, only a limited number of patients are eligible for this time-sensitive treatment. Even though there is still significant room for improvement in the management of this group of patients, up until now there have been no alternative therapies approved for use in clinical practice. However, there is still hope, as clinical research with novel emerging therapies is now generating promising results. These drugs happen to stop or palliate some of the underlying molecular mechanisms involved in cerebral ischemia and secondary brain damage. The aim of this review is to provide a deep understanding of these mechanisms and the pathogenesis of AIS. Later, we will discuss the potential therapies that have already demonstrated, in preclinical or clinical studies, to improve the outcomes of patients with AIS.

Comparison of Acute Effects of E-cigarettes With and Without Nicotine and Tobacco Cigarettes on Hemodynamic and Endothelial Parameters: A Systematic Review and Meta-analysis

INTRODUCTION

Smoke from traditional cigarettes and e-cigarette aerosols have distinct chemical compositions that may impact blood pressure (BP) and heart rate (HR) differently.

AIMS

This study compared the impact of nicotine-containing e-cigarettes (EC+) versus nicotine-free (EC-) on BP, HR and endothelial markers, and assessed if EC+ posed fewer risks than tobacco cigarettes (TC).

METHODS

Electronic databases were searched from inception until November 2023 for studies reporting changes in systolic and diastolic BP (SBP, DBP) and HR and endothelial parameters before and after the use of EC+, EC- and TC. Data were analyzed using weighted mean differences (WMDs) and 95% confidence intervals (CIs).

RESULTS

Fifteen studies (n = 752) were included in our meta-analysis. We demonstrate that EC+ significantly increased systolic BP (WMD = 3.41, 95% CI [0.1,6.73], p = 0.04], diastolic BP (WMD = 3.42, 95% CI [1.75, 5.09]; p < 0.01], and HR (WMD = 5.36 BPM, 95% CI [1.87, 8.85]; p < 0.01) compared to EC-. However, EC+ was observed to cause less detrimental effect on SBP (WMD = - 4.72 mmHg, 95% CI [- 6.58, - 2.86], p < 0.01), and HR (WMD = - 3.11 BPM, 95% CI [- 4.54, - 1.68]; p < 0.01) as compared to TC with no difference on DBP (WMD = - 1.14 mmHg, 95% CI [- 2.38, 0.1]; p = 0.07). EC+ also led to greater deterioration of endothelial parameters as compared to EC- but to a lesser degree as compared to TC.

CONCLUSION

EC+ shows greater impairment in hemodynamic and endothelial parameters than EC- but less than TC. Additional studies are needed to evaluate prolonged effects of EC use.

Electronic Cigarette Vape Exposure Exacerbates Post-Ischemic Outcomes in Female but Not in Male Rats

BACKGROUND

Nicotine-containing electronic cigarette (EC) vaping has become popular worldwide, and our understanding of the effects of vaping on stroke outcomes is elusive. Using a rat model of transient middle cerebral artery occlusion, the current exploratory study aims to evaluate the sex-dependent effects of EC exposure on brain energy metabolism and stroke outcomes.

METHODS

Adult Sprague-Dawley rats of both sexes were randomly assigned to air/EC vapor (5% nicotine Juul pods) exposure for 16 nights, followed by randomization into 3 cohorts. The first cohort underwent exposure to air/EC preceding randomization to transient middle cerebral artery occlusion (90 minutes) or sham surgery, followed by survival for 21 days. During the survival period, rats underwent sensorimotor and Morris water maze testing. Subsequently, brains were collected for histopathology. A second cohort was exposed to air/EC after which brains were collected for unbiased metabolomics analysis. The third cohort of animals was exposed to air/EC and received transient middle cerebral artery occlusion/sham surgery, and brain tissue was collected 24 hours later for biochemical analysis.

RESULTS

In females, EC significantly increased (P<0.05) infarct volumes by 94% as compared with air-exposed rats, 165±50 mm3 in EC-exposed rats, and 85±29 mm3 in air-exposed rats, respectively, while in males such a difference was not apparent. Morris water maze data showed significant deficits in spatial learning and working memory in the EC sham or transient middle cerebral artery occlusion groups compared with the respective air groups in rats of both sexes (P<0.05). Thirty-two metabolites of carbohydrate, glycolysis, tricarboxylic acid cycle, and lipid metabolism were significantly altered (P≤0.05) due to EC, 23 of which were specific for females. Steady-state protein levels of hexokinase significantly decreased (P<0.05) in EC-exposed females; however, these changes were not seen in males.

CONCLUSIONS

Even brief EC exposure over 2 weeks impacts brain energy metabolism, exacerbates infarction, and worsens poststroke cognitive deficits in working memory more in female than male rats.

The Role of Microglia in Sex- and Region-Specific Blood-Brain Barrier Integrity During Nicotine Withdrawal

Background

Smoking is the largest preventable cause of death and disease in the United States, with <5% of quit attempts being successful. Microglia activation and proinflammatory neuroimmune signaling in reward neurocircuitry are implicated in nicotine withdrawal symptomology. Microglia are integral regulators of blood-brain barrier (BBB) functionality as well; however, whether the effects of nicotine withdrawal on microglia function impact BBB integrity is unknown.

Methods

Mice were treated with chronic nicotine (12 mg/kg/day) and subjected to 48 hours nicotine withdrawal. Regional BBB permeability, together with messenger RNA and protein expression of tight junction proteins, were assessed. PLX5622 chow was used to deplete microglia to evaluate the role of microglia in regulating BBB integrity and nicotine withdrawal symptomology.

Results

Female mice had higher baseline BBB permeability in the prefrontal cortex and hippocampus than males. Nicotine withdrawal further exacerbated the BBB permeability selectively in the prefrontal cortex of females. These effects were concurrent with prefrontal cortex alterations in a subset of tight junction proteins with increased proinflammatory responses following nicotine withdrawal in females. Depletion of microglia via PLX5622 treatment prevented all these molecular effects and attenuated withdrawal-induced anxiety-like behavior in female mice.

Conclusions

These results are the first to show sex differences in regional BBB permeability during nicotine withdrawal. This represents a possible link to both the reduced smoking cessation success seen in women and women's increased risk for smoking-related neurovascular disorders. Furthermore, these findings open an avenue for sex-specific therapeutics that target microglia and BBB dysfunction during nicotine withdrawal in women.

A literature review addressing midwakh and e-cigarette use in the Gulf region

A notable decrease in conventional cigarette smoking has been witnessed on a global scale. However, this decrease has been accompanied by an equally striking global increase in the consumption of alternative tobacco products (ATPs), namely e-cigarettes and midwakh in the Arabian Gulf region. A literature review was used to outline the chemical composition of these two ATPs and review their impacts on health. The study was conducted using databases like PubMed, Google Scholar, MDPI, and WorldCat. The literature search included terms such as "e-cigarettes," "midwakh," "dokha," "heath impacts," "psychological effects," "social influences," and "cigarette smoking" with emphasis on literature from the Arabian Gulf region. Data shows that midwakh contains markedly high levels of tar, nicotine, and various compounds of notable effects on the human body. Similarly, it was found that e-cigarettes contain non-negligible amounts of nicotine and other chemical compounds that may not have been extensively investigated. Alarming reports of system-specific effects brought about by midwakh, and e-cigarette consumption, have been reported, although further research is needed to deduce the mechanism. We also discussed some of the social and psychological factors leading to their consumption within this population. Hence, this review raises questions around the safety of these two types of ATPs and encourages comprehensive studies globally and regionally.

Impact of in-utero electronic cigarette exposure on neonatal neuroinflammation, oxidative stress and mitochondrial function

Introduction: Despite the prevalence of the perception that electronic cigarettes (e-cig) are a safer alternative to tobacco smoke, growing concern about their potential toxic impact warrants adequate investigation focusing on special populations like maternal and pediatric groups. This study evaluated the consequences of maternal e-cig use on neonatal neuroinflammation, oxidative stress, and mitochondrial function in primary cultured neurons and postnatal day (PD) 7 and 90 brain. Methodology: Pregnant CD1 mice were exposed to e-cig vapor (2.4% nicotine) from gestational day 5 (E5) till PD7, and the primary neurons were isolated from pups at E16/17. Cellular total reactive oxygen species (ROS) and mitochondrial superoxide were measured in primary neurons using CM-H2DCFDA and Mitosox red, respectively. Mitochondrial function was assessed by Seahorse XF Cell Mitostress analysis. The level of pro-inflammatory cytokines was measured in primary neurons and PD7 and PD90 brains by RT-PCR and immunobead assay. Western blot analysis evaluated the expression of antioxidative markers (SOD-2, HO-1, NRF2, NQO1) and that of the proinflammatory modulator NF-κB. Results: Significantly higher level of total cellular ROS (p < 0.05) and mitochondrial superoxide (p < 0.01) was observed in prenatally e-cig-exposed primary neurons. We also observed significantly reduced antioxidative marker expression and increased proinflammatory modulator and cytokines expression in primary neurons and PD7 (p < 0.05) but not in PD90 postnatal brain. Conclusion: Our findings suggest that prenatal e-cig exposure induces postnatal neuroinflammation by promoting oxidative stress (OS), increasing cytokines' levels, and disrupting mitochondrial function. These damaging events can alter the fetal brain's immune functions, making such offspring more vulnerable to brain insults.

Cardiopulmonary Impact of Electronic Cigarettes and Vaping Products: A Scientific Statement From the American Heart Association

Vaping and electronic cigarette (e-cigarette) use have grown exponentially in the past decade, particularly among youth and young adults. Cigarette smoking is a risk factor for both cardiovascular and pulmonary disease. Because of their more limited ingredients and the absence of combustion, e-cigarettes and vaping products are often touted as safer alternative and potential tobacco-cessation products. The outbreak of e-cigarette or vaping product use-associated lung injury in the United States in 2019, which led to >2800 hospitalizations, highlighted the risks of e-cigarettes and vaping products. Currently, all e-cigarettes are regulated as tobacco products and thus do not undergo the premarket animal and human safety studies required of a drug product or medical device. Because youth prevalence of e-cigarette and vaping product use was as high as 27.5% in high school students in 2019 in the United States, it is critical to assess the short-term and long-term health effects of these products, as well as the development of interventional and public health efforts to reduce youth use. The objectives of this scientific statement are (1) to describe and discuss e-cigarettes and vaping products use patterns among youth and adults; (2) to identify harmful and potentially harmful constituents in vaping aerosols; (3) to critically assess the molecular, animal, and clinical evidence on the acute and chronic cardiovascular and pulmonary risks of e-cigarette and vaping products use; (4) to describe the current evidence of e-cigarettes and vaping products as potential tobacco-cessation products; and (5) to summarize current public health and regulatory efforts of e-cigarettes and vaping products. It is timely, therefore, to review the short-term and especially the long-term implications of e-cigarettes and vaping products on cardiopulmonary health. Early molecular and clinical evidence suggests various acute physiological effects from electronic nicotine delivery systems, particularly those containing nicotine. Additional clinical and animal-exposure model research is critically needed as the use of these products continues to grow.

The association between combustible/electronic cigarette use and stroke based on national health and nutrition examination survey

AIMS

This study aims to analyze the association between combustible/electronic cigarettes and the risk of stroke.

METHODS

We obtained data from the 2017-2018 National Health and Nutrition Examination Survey (NHANES). The stroke history and combustible/electronic cigarette use were acquired by questionnaires. Considering the sole or dual use of combustible cigarettes and electronic cigarettes (e-cigarettes), we divided all the individuals into four subgroups, including nonsmokers (reference group), sole combustible cigarette, sole e-cigarette, and dual use of both combustible cigarettes and e-cigarettes. We performed multivariable logistic regression to determine the association between cigarette use with the prevalence of stroke. We used odds ratios (ORs) with 95% confidence intervals (CIs) to show the effect size. Finally, we developed a prediction model to evaluate the risk of stroke for individuals with combustible or electronic cigarette use based on a random forest model.

RESULTS

We included a total of 4022 participants in the study. The median age was 55, and 48.3% of the participants were males. When we adjusted for age, gender, education attainment, race, total-to-HDL cholesterol (< 5.9 or ≥ 5.9), diabetes, hypertension, and alcohol consumption, the groups of sole e-cigarette use, sole combustible cigarette use, and dual use of combustible and electronic cigarettes were significantly associated with the prevalence of stroke with ORs (with 95%CI) of 2.07 (1.04-3.81), 2.36 (1.52-3.59), 2.34 (1.44-3.68), respectively. In the testing set, the AUC was 0.74 (95%CI = 0.65-0.84), sensitivity was 0.68, and specificity was 0.75.

CONCLUSION

Sole e-cigarettes and dual use of e-cigarettes with combustible cigarettes might increase the risk of stroke.

Maternal e-cigarette use can disrupt postnatal blood-brain barrier (BBB) integrity and deteriorates motor, learning and memory function: influence of sex and age

Electronic nicotine delivery systems (ENDS), also commonly known as electronic cigarettes (e-cigs) are considered in most cases as a safer alternative to tobacco smoking and therefore have become extremely popular among all age groups and sex. It is estimated that up to 15% of pregnant women are now using e-cigs in the US which keeps increasing at an alarming rate. Harmful effects of tobacco smoking during pregnancy are well documented for both pregnancy and postnatal health, however limited preclinical and clinical studies exist to evaluate the long-term effects of prenatal e-cig exposure on postnatal health. Therefore, the aim of our study is to evaluate the effect of maternal e-cig use on postnatal blood-brain barrier (BBB) integrity and behavioral outcomes of mice of varying age and sex. In this study, pregnant CD1 mice (E5) were exposed to e-Cig vapor (2.4% nicotine) until postnatal day (PD) 7. Weight of the offspring was measured at PD0, PD7, PD15, PD30, PD45, PD60 and PD90. The expression of structural elements of the BBB, tight junction proteins (ZO-1, claudin-5, occludin), astrocytes (GFAP), pericytes (PDGFRβ) and the basement membrane (laminin α1, laminin α4), neuron specific marker (NeuN), water channel protein (AQP4) and glucose transporter (GLUT1) were analyzed in both male and female offspring using western blot and immunofluorescence. Estrous cycle was recorded by vaginal cytology method. Long-term motor and cognitive functions were evaluated using open field test (OFT), novel object recognition test (NORT) and morris water maze test (MWMT) at adolescence (PD 40-45) and adult (PD 90-95) age. In our study, significantly reduced expression of tight junction proteins and astrocyte marker were observed in male and female offspring until PD 90 (P < 0.05). Additionally, prenatally e-cig exposed adolescent and adult offspring showed impaired locomotor, learning, and memory function compared to control offspring (P < 0.05). Our findings suggest that prenatal e-cig exposure induces long-term neurovascular changes of neonates by disrupting postnatal BBB integrity and worsening behavioral outcomes.

Human iPS-derived blood-brain barrier model exhibiting enhanced barrier properties empowered by engineered basement membrane

The basement membrane (BM) of the blood-brain barrier (BBB), a thin extracellular matrix (ECM) sheet underneath the brain microvascular endothelial cells (BMECs), plays crucial roles in regulating the unique physiological barrier function of the BBB, which represents a major obstacle for brain drug delivery. Owing to the difficulty in mimicking the unique biophysical and chemical features of BM in in vitro systems, current in vitro BBB models have suffered from poor physiological relevance. Here, we describe a highly ameliorated human BBB model accomplished by an ultra-thin ECM hydrogel-based engineered basement membrane (nEBM), which is supported by a sparse electrospun nanofiber scaffold that offers in vivo BM-like microenvironment to BMECs. BBB model reconstituted on a nEBM recapitulates the physical barrier function of the in vivo human BBB through ECM mechano-response to physiological relevant stiffness (∼500 kPa) and exhibits high efflux pump activity. These features of the proposed BBB model enable modelling of ischemic stroke, reproducing the dynamic changes of BBB, immune cell infiltration, and drug response. Therefore, the proposed BBB model represents a powerful tool for predicting the BBB permeation of drugs and developing therapeutic strategies for brain diseases.

Variation in Nicotine Metabolization According to Biological Factors and Type of Nicotine Consumer

This study aims to describe the nicotine metabolite ratio among tobacco smokers and electronic cigarette (e-cigarette) users and nonusers. We analyzed pooled data from a longitudinal and a cross-sectional study of the adult population from the city of Barcelona. The final sample included information on 166 smokers, 164 e-cigarettes users with nicotine, 41 e-cigarette users without nicotine, 95 dual users (users of both products), and 508 nonusers. We used log-linear models to control for the potential confounding effect of the daily number of cigarettes smoked. Salivary nicotine metabolic rate assessment included the rate of nicotine metabolism (cotinine/nicotine) and the nicotine metabolite ratio (trans-3′-hydroxycotinine/cotinine). Exclusive users of e-cigarette without nicotine have the lowest rate of nicotine metabolism (Geometric mean: 0.08, p-values < 0.001) while cigarette smokers have the highest (Geometric mean: 2.08, p-values < 0.001). Nonusers have lower nicotine metabolic rate than cigarette smokers (Geometric means: 0.23 vs. 0.18, p-value < 0.05). Younger individuals (18−44 years) have a higher rate of nicotine metabolism than older individuals (45−64 years and 65−89) (Geometric means: 0.53 vs. 0.42 and 0.31, respectively, p-values < 0.01) and individuals with lower body mass index (21−25 kg/m2) have a higher rate of nicotine metabolism than the rest (26−30 kg/m2 and 31−60 kg/m2) (Geometric means: 0.52 vs. 0.35 and 0.36, respectively-values < 0.01). Nicotine metabolic rates are useful biomarkers when reporting smoking status and biological differences between individuals.

High prevalence of hypertension among smokers of conventional and e-cigarette: Using the nationally representative community dwelling survey

This study aimed to clarify the association between hypertension and conventional cigarette and electronic cigarette (e-cigarette) use, together or individually. A total of 275,762 participants were included, of which 120,766 were men and 154,996 were women. The data were drawn from the Korea Community Health Survey conducted in 2019. A multiple logistic regression model was used to examine the association between hypertension and types of smoking. Hypertension was defined as systolic blood pressure higher than 140 mmHg or diastolic blood pressure higher than 90 mmHg. Based on the types of smoking, participants were grouped as dual smokers of conventional and e-cigarettes, e-cigarette only smokers, conventional cigarette only smokers, past-smokers, and non-smokers. Compared to non-smokers, dual smokers presented the highest odds ratio for hypertension in the male [odds ratio (OR): 1.24, confidence interval (CI): 1.10 to 1.39] and female groups (OR: 1.44 CI: 0.96 to 2.15). According to the Cochran-Mantel-Haenszel test, the two-sided p-value of < 0.001 indicated an overall statistically significant association between types of smoking and hypertension. Use of both cigarette types was statistically significant in the male group, but only the use of conventional cigarettes and past smoking were statistically significant in the female group. Among smokers of the two cigarette types, those who were dual smokers of e-cigarettes and conventional cigarettes were the most likely to have the highest prevalence of hypertension.

Short-term exposure to JUUL electronic cigarettes can worsen ischemic stroke outcome

BACKGROUND

The short and long-term health effects of JUUL electronic cigarette (e-Cig) are largely unknown and warrant extensive research. We hypothesized that JUUL exposure could cause cerebrovascular toxicities impacting the progression and outcome of ischemic stroke comparable to tobacco smoke (TS) exposure.

METHODS

We exposed male C57 mice to TS/JUUL vapor for 14 days. LCMS/MS was used to measure brain and plasma nicotine and cotinine level. Transient middle cerebral artery occlusion (tMCAO) followed by reperfusion was used to mimic ischemic stroke. Plasma levels of IL-6 and thrombomodulin were assessed by enzyme-linked immunosorbent assay. At the same time, western blotting was used to study blood-brain barrier (BBB) tight junction (TJ) proteins expression and key inflammatory and oxidative stress markers.

RESULTS

tMCAO upregulated IL-6 and decreased plasma thrombomodulin levels. Post-ischemic brain injury following tMCAO was significantly worsened by JUUL/TS pre-exposure. TJ proteins expression was also downregulated by JUUL/TS pre-exposure after tMCAO. Like TS, exposure to JUUL downregulated the expression of the antioxidant Nrf2. ICAM-1 was upregulated in mice subjected to tMCAO following pre-exposure to TS or JUUL, with a greater effect of TS than JUUL.

CONCLUSIONS

These results suggest that JUUL exposure could negatively impact the cerebrovascular system, although to a lesser extent than TS exposure.

Time course of changes in inflammatory and oxidative biomarkers in lung tissue of mice induced by exposure to electronic cigarette aerosol

Significance

Electronic cigarettes (e-cigarettes) have become a popular way to smoke all over the world. Chronic exposure to e-cigarette aerosol may influence lung health. This study uses an animal model to explore the time course of the effect of exposure to e-cigarette aerosols on the lung.

Methods

Lung samples were collected after exposure of Balb/c mice to e-cigarette aerosols for 1 h/day (6 times/week) for 1, 2 and 4 weeks and compared to sham-exposed controls. Examined biomarkers including inflammatory cells, tumor necrosis factor α (TNFα), interleukin-6 (IL-6), interleukin-10 (IL-10), reduced glutathione (GSH), oxidized glutathione (GSSG), glutathione peroxidase (GPx), catalase, superoxide dismutase (SOD), and Thiobarbituric acid reactive substances (TBARS).

Results

Exposure of animals to e-cigarette aerosols induced significant increases (P < 0.05) in total inflammatory cells, eosinophils, macrophages and TNFα in the lung tissue after 1, 2 and 4 weeks of exposure. Furthermore, level of IL-10 significantly decreased, whereas levels of neutrophils and basophils significantly increased (P < 0.05) after 1 week of exposure. Exposure of animals to e-cigarette aerosol also induced significant decreases (P < 0.05) in the GSH/GSSG ratio, and GPx levels after 2 and 4 weeks of exposures. The activity of catalase was also reduced (P < 0.05) after 4 weeks of exposure. Level of TBARS showed a trend of elevation with time and it reached a significant elevation after 4 weeks (P < 0.01).

Conclusion

Current results indicate that inhalation of unflavored e-cigarette aerosol might be associated with inflammation in lung tissue that worsen as the duration of exposure increases. Further experiments including more time points, histopathology and pulmonary physiology experiments are needed to confirm the current results.

Brain Energy Metabolism in Ischemic Stroke: Effects of Smoking and Diabetes

Proper regulation of energy metabolism in the brain is crucial for maintaining brain activity in physiological and different pathophysiological conditions. Ischemic stroke has a complex pathophysiology which includes perturbations in the brain energy metabolism processes which can contribute to worsening of brain injury and stroke outcome. Smoking and diabetes are common risk factors and comorbid conditions for ischemic stroke which have also been associated with disruptions in brain energy metabolism. Simultaneous presence of these conditions may further alter energy metabolism in the brain leading to a poor clinical prognosis after an ischemic stroke event. In this review, we discuss the possible effects of smoking and/or diabetes on brain glucose utilization and mitochondrial energy metabolism which, when present concurrently, may exacerbate energy metabolism in the ischemic brain. More research is needed to investigate brain glucose utilization and mitochondrial oxidative metabolism in ischemic stroke in the presence of smoking and/or diabetes, which would provide further insights on the pathophysiology of these comorbid conditions and facilitate the development of therapeutic interventions.

Potential role of astrocyte angiotensin converting enzyme 2 in the neural transmission of COVID-19 and a neuroinflammatory state induced by smoking and vaping

BACKGROUND

Knowledge of the entry receptors responsible for SARS-CoV-2 is key to understand the neural transmission and pathogenesis of COVID-19 characterized by a neuroinflammatory scenario. Understanding the brain distribution of angiotensin converting enzyme 2 (ACE2), the primary entry receptor for SARS-CoV-2, remains mixed. Smoking has been shown as a risk factor for COVID-19 severity and it is not clear how smoking exacerbates the neural pathogenesis in smokers.

METHODS

Immunohistochemistry, real-time PCR and western blot assays were used to systemically examine the spatial-, cell type- and isoform-specific expression of ACE2 in mouse brain and primary cultured brain cells. Experimental smoking exposure was conducted to evaluate the effect of smoking on brain expression.

RESULTS

We observed ubiquitous expression of ACE2 but uneven brain distribution, with high expression in the cerebral microvasculature, medulla oblongata, hypothalamus, subventricular zones, and meninges around medulla oblongata and hypothalamus. Co-staining with cell type-specific markers demonstrates ACE2 is primarily expressed in astrocytes around the microvasculature, medulla oblongata, hypothalamus, ventricular and subventricular zones of cerebral ventricles, and subependymal zones in rhinoceles and rostral migratory streams, radial glial cells in the lateral ventricular zones, tanycytes in the third ventricle, epithelial cells and stroma in the cerebral choroid plexus, as well as cerebral pericytes, but rarely detected in neurons and cerebral endothelial cells. ACE2 expression in astrocytes is further confirmed in primary cultured cells. Furthermore, isoform-specific analysis shows astrocyte ACE2 has the peptidase domain responsible for SARS-CoV-2 entry, indicating astrocytes are indeed vulnerable to SARS-CoV-2 infection. Finally, our data show experimental tobacco smoking and electronic nicotine vaping exposure increase proinflammatory and/or immunomodulatory cytokine IL-1a, IL-6 and IL-5 without significantly affecting ACE2 expression in the brain, suggesting smoking may pre-condition a neuroinflammatory state in the brain.

CONCLUSIONS

The present study demonstrates a spatial- and cell type-specific expression of ACE2 in the brain, which might help to understand the acute and lasting post-infection neuropsychological manifestations in COVID-19 patients. Our data highlights a potential role of astrocyte ACE2 in the neural transmission and pathogenesis of COVID-19. This also suggests a pre-conditioned neuroinflammatory and immunocompromised scenario might attribute to exacerbated COVID-19 severity in the smokers.

Effect Comparison of E-Cigarette and Traditional Smoking and Association with Stroke-A Cross-Sectional Study of NHANES

Introduction: Tobacco use is one of the most significant risk factors for stroke. Besides traditional cigarettes and combustible products, the use of e-cigarettes and electronic nicotine delivery products has been widespread among young adults in the recent era. Furthermore, the trend of vaping has increased over the last decade. However, the relationship between e-cigarettes and stroke is largely unknown. The aim of this study was to evaluate the prevalence and identify the relationship between e-cigarette smoking and stroke. Methods: A cross-sectional study was performed using the NHANES database of the US population. Adults with a history of smoking were considered in our study and divided into three groups, e-cigarette users, traditional, and dual smokers. The Chi-squared test, Wilcoxon rank-sum test, and multivariable logistic regression analysis were used to identify the prevalence and association of e-cigarette consumption and stroke. Results: Out of a total of 266,058 respondents from 2015 to 2018, we found 79,825 respondents who smoked e-cigarettes (9.72%) or traditional (29.37%) or dual smoking (60.91%). Stroke prevalence among e-cigarette smokers was 1.57%. Stroke was more prevalent among traditional smokers than among e-cigarette smokers. (6.75% vs. 1.09%; p < 0.0001) E-cigarette smokers had early onset of stroke in comparison with traditional smokers. (median age: 48 vs. 59 years; p < 0.0001). Among females with stroke, the prevalence of e-cigarette use was higher in comparison with traditional smoking (36.36% vs. 33.91%; p < 0.0001). Among the stroke population, the prevalence of e-cigarette use was higher among Mexican-Americans (21.21% vs. 6.02%) and other Hispanics (24.24% vs. 7.70%) compared with traditional smoking (p < 0.0001). The regression analysis found higher odds of stroke history among e-cigarette users than traditional smokers [aOR: 1.15; 95% CI: 1.15−1.16)]. Conclusion: Though stroke was more prevalent in traditional smokers, the incidence of stroke was early-in-onset and was strongly associated with e-cigarette use compared to traditional smokers. We have also identified vascular effects of e-cigarettes components as possible triggers for the stroke.

Exosomal miR-4466 from nicotine-activated neutrophils promotes tumor cell stemness and metabolism in lung cancer metastasis

Smoking is associated with lung cancer and has a profound impact on tumor immunity. Nicotine, the addictive and non-carcinogenic smoke component, influences various brain cells and the immune system. However, how long-term use of nicotine affects brain metastases is poorly understood. We, therefore, examined the mechanism by which nicotine promotes lung cancer brain metastasis. In this study, we conducted a retrospective analysis of 810 lung cancer patients with smoking history and assessed brain metastasis. We found that current smoker's lung cancer patients have significantly higher brain metastatic incidence compared to the never smokers. We also found that chronic nicotine exposure recruited STAT3-activated N2-neutrophils within the brain pre-metastatic niche and secreted exosomal miR-4466 which promoted stemness and metabolic switching via SKI/SOX2/CPT1A axis in the tumor cells in the brain thereby enabling metastasis. Importantly, exosomal miR-4466 levels were found to be elevated in serum/urine of cancer-free subjects with a smoking history and promote tumor growth in vivo, suggesting that exosomal miR-4466 may serve as a promising prognostic biomarker for predicting increased risk of metastatic disease among smoker(s). Our findings suggest a novel pro-metastatic role of nicotine-induced N2-neutrophils in the progression of brain metastasis. We also demonstrated that inhibiting nicotine-induced STAT3-mediated neutrophil polarization effectively abrogated brain metastasis in vivo. Our results revealed a novel mechanistic insight on how chronic nicotine exposure contributes to worse clinical outcome of metastatic lung cancer and implicated the risk of using nicotine gateway for smoking cessation in cancer patients.

Biological determinants impact the neurovascular toxicity of nicotine and tobacco smoke: A pharmacokinetic and pharmacodynamics perspective

Accumulating evidence suggests that the detrimental effect of nicotine and tobacco smoke on the central nervous system (CNS) is caused by the neurotoxic role of nicotine on blood-brain barrier (BBB) permeability, nicotinic acetylcholine receptor expression, and the dopaminergic system. The ultimate consequence of these nicotine associated neurotoxicities can lead to cerebrovascular dysfunction, altered behavioral outcomes (hyperactivity and cognitive dysfunction) as well as future drug abuse and addiction. The severity of these detrimental effects can be associated with several biological determinants. Sex and age are two important biological determinants which can affect the pharmacokinetics and pharmacodynamics of several systemically available substances, including nicotine. With regard to sex, the availability of gonadal hormone is impacted by the pregnancy status and menstrual cycle resulting in altered metabolism rate of nicotine. Additionally, the observed lower smoking cessation rate in females compared to males is a consequence of differential effects of sex on pharmacokinetics and pharmacodynamics of nicotine. Similarly, age-dependent alterations in the pharmacokinetics and pharmacodynamics of nicotine have also been observed. One such example is related to severe vulnerability of adolescence towards addiction and long-term behavioral changes which may continue through adulthood. Considering the possible neurotoxic effects of nicotine on the central nervous system and the deterministic role of sex as well as age on these neurotoxic effects of smoking, it has become important to consider sex and age to study nicotine induced neurotoxicity and development of treatment strategies for combating possible harmful effects of nicotine. In the future, understanding the role of sex and age on the neurotoxic actions of nicotine can facilitate the individualization and optimization of treatment(s) to mitigate nicotine induced neurotoxicity as well as smoking cessation therapy. Unfortunately, however, no such comprehensive study is available which has considered both the sex- and age-dependent neurotoxicity of nicotine, as of today. Hence, the overreaching goal of this review article is to analyze and summarize the impact of sex and age on pharmacokinetics and pharmacodynamics of nicotine and possible neurotoxic consequences associated with nicotine in order to emphasize the importance of including these biological factors for such studies.

Exposure to e-cigarette aerosol over two months induces accumulation of neurotoxic metals and alteration of essential metals in mouse brain

Despite a recent increase in e-cigarette use, the adverse human health effects of exposure to e-cigarette aerosol, especially on the central nervous system (CNS), remain unclear. Multiple neurotoxic metals have been identified in e-cigarette aerosol. However, it is unknown whether those metals accumulate in the CNS at biologically meaningful levels. To answer this question, two groups of mice were whole-body exposed twice a day, 5 days a week, for two months, to either a dose of e-cigarette aerosol equivalent to human secondhand exposure, or a 5-fold higher dose. After the last exposure, the olfactory bulb, anterior and posterior frontal cortex, striatum, ventral midbrain, cerebellum, brainstem, remaining brain tissue and spinal cord were collected for metal quantification by inductively coupled plasma mass spectrometry and compared to tissues from unexposed control mice. The two-month exposure caused significant accumulation of several neurotoxic metals in various brain areas - for some metals even at the low exposure dose. The most striking increases were measured in the striatum. For several metals, including Cr, Cu, Fe, Mn, and Pb, similar accumulations are known to be neurotoxic in mice. Decreases in some essential metals were observed across the CNS. Our findings suggest that chronic exposure to e-cigarette aerosol could lead to CNS neurotoxic metal deposition and endogenous metal dyshomeostasis, including potential neurotoxicity. We conclude that e-cigarette-mediated metal neurotoxicity may pose long-term neurotoxic and neurodegenerative risks for e-cigarette users and bystanders.

An association between electronic nicotine delivery systems use and a history of stroke using the 2016 behavioral risk factor surveillance system

ABSTRACT

Electronic nicotine delivery systems (ENDS) are growing in use and many of the health implications with these devices remain unknown. This study aims to assess, using a survey representative of the USA general population, if an association exists between a history of ENDS use and a history of stroke.This cross-sectional study was a secondary data analysis using the 2016 behavioral risk factor surveillance system survey. The main exposure variable of the study was a self-reported history of ENDS use. The main outcome was a self-reported history of stroke. Covariates included sex, race, traditional cigarette use, smokeless tobacco use, chronic kidney disease, diabetes, myocardial infarction, and coronary artery disease. Unadjusted and adjusted logistic regression analyses were done. Adjusted odds ratios (AOR) and their corresponding 95% confidence intervals (CI) were calculated.Of the 486,303 total behavioral risk factor surveillance system survey participants, 465,594 met the inclusion criteria for this study of ENDS use and stroke. This study shows that current ENDS use was positively associated with a history of stroke. AOR of some daily ENDS use with stroke was 1.28 (95% CI: 1.02-1.61) and AOR of current daily ENDS use with stroke was 1.62 (95% CI: 1.18-2.31). The majority (55.9%) of current daily ENDS users reported former traditional cigarette smoking. Female sex, non-white ethnicity, elderly age, chronic kidney disease, coronary artery disease, diabetes, and traditional cigarette use characteristics were all also associated with increased odds of reporting a stroke.This study found a statistically significant and positive association between ENDS use and a history of stroke. Further research is warranted to investigate the reproducibility and temporality of this association. Nevertheless, this study contributes to the growing body of knowledge about the potential cardiovascular concerns related to ENDS use and the need for large cohort studies.

Predicting molecular mechanisms, pathways, and health outcomes induced by Juul e-cigarette aerosol chemicals using the Comparative Toxicogenomics Database

•

Vaping chemicals of Juul aerosols were analyzed using CTD.

•

CTD can be used to predict disease associations of Juul aerosol chemicals.

•

Predictive pathways that relate vaping aerosols to diseases are described.

There is a critical need to understand the health risks associated with vaping e-cigarettes, which has reached epidemic levels among teens. Juul is currently the most popular type of e-cigarette on the market. Using the Comparative Toxicogenomics Database (CTD; http://ctdbase.org), a public resource that integrates chemical, gene, phenotype and disease data, we aimed to analyze the potential molecular mechanisms of eight chemicals detected in the aerosols generated by heating Juul e-cigarette pods: nicotine, acetaldehyde, formaldehyde, free radicals, crotonaldehyde, acetone, pyruvaldehyde, and particulate matter. Curated content in CTD, including chemical-gene, chemical-phenotype, and chemical-disease interactions, as well as associated phenotypes and pathway enrichment, were analyzed to help identify potential molecular mechanisms and diseases associated with vaping. Nicotine shows the most direct disease associations of these chemicals, followed by particulate matter and formaldehyde. Together, these chemicals show a direct marker or mechanistic relationship with 400 unique diseases in CTD, particularly in the categories of cardiovascular diseases, nervous system diseases, respiratory tract diseases, cancers, and mental disorders. We chose three respiratory tract diseases to investigate further, and found that in addition to cellular processes of apoptosis and cell proliferation, prioritized phenotypes underlying Juul-associated respiratory tract disease outcomes include response to oxidative stress, inflammatory response, and several cell signaling pathways (p38MAPK, NIK/NFkappaB, calcium-mediated).

The effect of electronic cigarettes exposure on learning and memory functions: behavioral and molecular analysis

Objective: Electronic cigarettes (ECIGs) are battery-powered devices that emit vaporized solutions for the user to inhale. ECIGs are marketed as a less harmful alternative to combustible cigarettes. The current study examined the effects of ECIG aerosol exposure on learning and memory, expression of brain derived neurotrophic factor (BDNF), and the activity of antioxidant enzymes in the hippocampus.Methods: Male Wistar rats were exposed to ECIG aerosol, by a whole-body exposure system, 1 h/day for 1 week, 4 weeks, and 12 weeks. Spatial learning and memory were tested using the Radial Arm Water Maze (RAWM). Hippocampal BDNF protein level, and oxidative stress biomarkers (GPx, SOD, GSH, GSSG, GSH/GSSG ratio) were also assessed.Results: ECIG aerosol exposure for 4 and 12 weeks impaired both short- and long- term memory and induced reductions in the hippocampus BDNF, SOD and GPx activities, and GSH/GSSG ratio (p < 0.05). No changes in any examined biomarkers were observed after 1-week exposure to ECIG aerosol (p > 0.05).Conclusions: ECIG aerosol exposure impaired functional memory and elicited changes in brain chemistry that are consistent with reduced function and oxidative stress.

Comparative assessment of in vitro BBB tight junction integrity following exposure to cigarette smoke and e-cigarette vapor: a quantitative evaluation of the protective effects of metformin using small-molecular-weight paracellular markers

Background

The blood–brain barrier (BBB) plays a critical role in protecting the central nervous system (CNS) from blood-borne agents and potentially harmful xenobiotics. Our group’s previous data has shown that tobacco smoke (TS) and electronic cigarettes (EC) affect the BBB integrity, increase stroke incidence, and are considered a risk factor for multiple CNS disorders. Metformin was also found to abrogate the adverse effects of TS and EC.

Methods

We used sucrose and mannitol as paracellular markers to quantitatively assess TS and EC’s impact on the BBB in-vitro. Specifically, we used a quantitative platform to determine the harmful effects of smoking on the BBB and study the protective effect of metformin. Using a transwell system and iPSCs-derived BMECs, we assessed TS and EC’s effect on sucrose and mannitol permeability with and without metformin pre-treatment at different time points. Concurrently, using immunofluorescence (IF) and Western blot (WB) techniques, we evaluated the expression and distribution of tight junction proteins, including ZO-1, occludin, and claudin-5.

Results

Our data showed that TS and EC negatively affect sucrose and mannitol permeability starting after 6 h and up to 24 h. The loss of barrier integrity was associated with a reduction of TEER values. While the overall expression level of ZO-1 and occludin was not significantly downregulated, the distribution of ZO-1 was altered, and discontinuation patterns were evident through IF imaging. In contrast to occludin, claudin-5 expression was significantly decreased by TS and EC, as demonstrated by WB and IF data.

Conclusion

In agreement with previous studies, our data showed the metformin could counteract the negative impact of TS and EC on BBB integrity, thus suggesting the possibility of repurposing this drug to afford cerebrovascular protection.

Repurposing metformin to treat age-related neurodegenerative disorders and ischemic stroke

Aging is a risk factor for major central nervous system (CNS) disorders. More specifically, aging can be inked to neurodegenerative diseases (NDs) because of its deteriorating impact on neurovascular unit (NVU). Metformin, a first line FDA-approved anti-diabetic drug, has gained increasing interest among researchers for its role in improving aging-related neurodegenerative disorders. Additionally, numerous studies have illustrated metformin's role in ischemic stroke, a cerebrovascular disorder in which the NVU becomes dysfunctional which can lead to permanent life-threatening disabilities. Considering metformin's beneficial preclinical actions on various disorders, and the drug's role in alleviating severity of these conditions through involvement in commonly characterized cellular pathways, we discuss the potential of metformin as a suitable drug candidate for repurposing in CNS disorders.

Presence of a mutation in PSEN1 or PSEN2 gene is associated with an impaired brain endothelial cell phenotype in vitro

Background

Alzheimer’s disease (AD) is the most common form of neurodegenerative disease. It is an irreversible condition marked by irreversible cognitive loss, commonly attributed to the loss of hippocampal neurons due to the formation of senile plaques and neurofibrillary tangles. Although the sporadic form is the most prevalent, the presence of familial form (involving several genes such as APP, PSEN1, and PSEN2) of the disease is commonly used as a model for understanding the pathophysiology of the disease. The aim of this study is to investigate the effect of a mutation on PSEN1 and PSEN2 genes on the BBB function using induced pluripotent stem cells (iPSCs).

Methods

iPSC lines from patients suffering from a familial form of Alzheimer’s disease and harboring mutations in PSEN1 or PSEN2 were used in this study and compared to a control iPSC line. Cells were differentiated into brain microvascular endothelial cells (BMECs) following established differentiation protocols. Barrier function was assessed by measuring TEER and fluorescein permeability, drug transporter activity was assessed by uptake assay, glucose uptake and metabolism assessed by cell flux analyzer, mitochondrial potential by JC-1, and lysosomal acidification by acridine orange.

Results

iPSC-derived BMECs from the FAD patient presenting a mutation in the PSEN1 gene showed impaired barrier function compared to the FAD patient harboring a mutation in PSEN2 and to the control group. Such impaired barrier function correlated with poor tight junction complexes and reduced drug efflux pump activity. In addition, both PSEN1 and PSEN2-BMECs displayed reduced bioenergetics, lysosomal acidification, autophagy, while showing an increase in radical oxygen species (ROS) production. Finally, PSEN1- and PSEN2-BMECs showed an elevated secretion of Aβ1–40 peptides compared to control-BMECs.

Conclusions

Our study reports that iPSC-derived BMECs obtained from FAD patients showed impaired barrier properties and BMEC metabolism. In particular, mutation in the PSEN1 gene was associated with a more detrimental phenotype than mutation in PSEN2, as noted by a reduced barrier function, reduced drug efflux pump activity, and diminished glucose metabolism. Therefore, assessing the contribution of genetic mutations associated with Alzheimer’s disease will allow us to better understand the contribution of the BBB in dementia, but also other neurodegenerative diseases.

Effects of Electronic Nicotine Delivery Systems and Cigarettes on Systemic Circulation and Blood-Brain Barrier: Implications for Cognitive Decline

Electronic nicotine delivery systems (often known as e-cigarettes) are a novel tobacco product with growing popularity, particularly among younger demographics. The implications for public health are twofold, as these products may represent a novel source of tobacco-associated disease but may also provide a harm reduction strategy for current tobacco users. There is increasing recognition that e-cigarettes impact vascular function across multiple organ systems. Herein, we provide a comparison of evidence regarding the role of e-cigarettes versus combustible tobacco in vascular disease and implications for blood-brain barrier dysfunction and cognitive decline. Multiple non-nicotinic components of tobacco smoke have been identified in e-cigarette aerosol, and their involvement in vascular disease is discussed. In addition, nicotine and nicotinic signaling may modulate peripheral immune and endothelial cell populations in a highly context-dependent manner. Direct preclinical evidence for electronic nicotine delivery system-associated neurovascular impairment is provided, and a model is proposed in which non-nicotinic elements exert a proinflammatory effect that is functionally antagonized by the presence of nicotine.

The Role of Smoking and Nicotine in the Transmission and Pathogenesis of COVID-19

Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 virus, is turning out to be one of the most devastating global pandemics in the history of humankind. There is a shortage of effective therapeutic strategies or preventative vaccines for this disease to date. A rigorous investigation is needed for identifying and developing more effective therapeutic strategies for COVID-19. Angiotensin-converting enzyme 2 (ACE2), a crucial factor in COVID-19 pathogenesis, has been identified as a potential target for COVID-19 treatment. Smoking and vaping are potential risk factors for COVID-19 that are also shown to upregulate ACE2 expression. In this review, we have discussed the pathobiology of COVID-19 in the lungs and brain and the role of ACE2 in the transmission and pathobiology of this disease. Furthermore, we have shown possible interactions between nicotine/smoking and ACE2 in the lungs and brain, which could aggravate the transmission and pathobiology of COVID-19, resulting in a poor disease outcome. SIGNIFICANCE STATEMENT: This review addresses the present global pandemic of coronavirus disease 2019 (COVID-19) with respect to its pathobiology in the lungs and brain. It focuses on the potential negative impact of tobacco and nicotine exposure on the outcomes of this disease by interaction with the angiotensin-converting enzyme 2 receptor. It adds to the time-sensitive and critically important growing knowledge about the risk factors, transmission, pathobiology, and prognosis of COVID-19.

Validation of a nicotine vapor self-administration model in rats with relevance to electronic cigarette use

The debate about electronic cigarettes is dividing healthcare professionals, policymakers, manufacturers, and communities. A key limitation in our understanding of the cause and consequences of vaping is the lack of animal models of nicotine vapor self-administration. Here, we developed a novel model of voluntary electronic cigarette use in rats using operant behavior. We found that rats voluntarily exposed themselves to nicotine vapor to the point of reaching blood nicotine levels that are similar to humans. The level of responding on the active (nicotine) lever was similar to the inactive (air) lever and lower than the active lever that was associated with vehicle (polypropylene glycol/glycerol) vapor, suggesting low positive reinforcing effects and low nicotine vapor discrimination. Lever pressing behavior with nicotine vapor was pharmacologically prevented by the α4β2 nicotinic acetylcholine receptor partial agonist and α7 receptor full agonist varenicline in rats that self-administered nicotine but not vehicle vapor. Moreover, 3 weeks of daily (1 h) nicotine vapor self-administration produced addiction-like behaviors, including somatic signs of withdrawal, allodynia, anxiety-like behavior, and relapse-like behavior after 3 weeks of abstinence. Finally, 3 weeks of daily (1 h) nicotine vapor self-administration produced cardiopulmonary abnormalities and changes in α4, α3, and β2 nicotinic acetylcholine receptor subunit mRNA levels in the nucleus accumbens and medial prefrontal cortex. These findings validate a novel animal model of nicotine vapor self-administration in rodents with relevance to electronic cigarette use in humans and highlight the potential addictive properties and harmful effects of chronic nicotine vapor self-administration.

Neurotoxicity of e-cigarettes

It appears that electronic cigarettes (EC) are a less harmful alternative to conventional cigarette (CC) smoking, as they generate substantially lower levels of harmful carcinogens and other toxic compounds. Thus, switching from CC to EC may be beneficial for smokers. However, recent accounts of EC- or vaping-associated lung injury (EVALI) has raised concerns regarding their adverse health effects. Additionally, the increasing popularity of EC among vulnerable populations, such as adolescents and pregnant women, calls for further EC safety evaluation. In this state-of-the-art review, we provide an update on recent findings regarding the neurological effects induced by EC exposure. Moreover, we discuss possible neurotoxic effects of nicotine and numerous other chemicals which are inherent both to e-liquids and EC aerosols. We conclude that in recognizing pertinent issues associated with EC usage, both government and scientific researchers must address this public health issue with utmost urgency.

Risk of Stroke With E-Cigarette and Combustible Cigarette Use in Young Adults

INTRODUCTION

Rising trends in stroke incidence and hospitalizations because of combustible cigarette smoking have been noted among younger adults. However, the association between e-cigarette use and stroke in this population remains largely unknown. This study examines the association between e-cigarette use with or without a history of previous or concurrent combustible cigarette use and stroke among young adults.

METHODS

Pooled data (2016-2017) were analyzed from the Behavior Risk Factor Surveillance System, a nationally representative, cross-sectional telephone survey, in 2019. The sample size was 161,529 participants aged 18-44 years. The association between e-cigarette use and stroke was examined using logistic regression adjusting for patient demographics, relevant comorbidities without or with history, and concurrent use of combustible cigarette use.

RESULTS

Current dual use of e-cigarettes and combustible cigarettes was associated with 2.91 times higher odds of stroke versus nonsmokers (AOR=2.91, 95% CI=1.62, 5.25) and 1.83 times higher odds versus current sole combustible cigarette users (AOR=1.83, 95% CI=1.06, 3.17). Compared with nonsmokers, current sole e-cigarette users did not show significantly different odds of stroke (AOR=0.69, 95% CI=0.34, 1.42). However, odds of stroke were lower for sole e-cigarette users versus current sole combustible cigarette users (AOR=0.43, 95% CI=0.20, 0.93).

CONCLUSIONS

Sole e-cigarette use is not associated with greater odds of stroke in young adults. However, if young adults have former or current combustible cigarette use, odds of stroke are significantly increased even compared with current sole combustible cigarette use. Switching from combustible cigarettes to e-cigarettes does not confer stroke benefits.

Prenatal electronic cigarette exposure decreases brain glucose utilization and worsens outcome in offspring hypoxic-ischemic brain injury

It has been shown that prenatal nicotine and tobacco smoke exposure can cause different neurobehavioral disorders in the offspring. We hypothesize that prenatal exposure to nicotine-containing electronic cigarette (e-Cig) vapor can predispose newborn to enhanced sensitivity to hypoxic-ischemic (HI) brain injury and impaired motor and cognitive functions. In this study, pregnant CD1 mice were exposed to e-Cig vapor (2.4% nicotine). Primary cortical neurons isolated from e-Cig exposed fetus were exposed to oxygen-glucose deprivation followed by reoxygenation (OGD/R) to mimic HI brain injury. Cell viability and glucose utilization were analyzed in these neurons. HI brain injury was induced in 8-9-day-old pups. Short-term brain injury was evaluated by triphenyltetrazolium chloride staining. Long-term motor and cognitive functions were evaluated by open field, novel object recognition, Morris water maze, and foot fault tests. Western blotting and immunofluorescence were done to characterize glucose transporters in offspring brain. We found that e-Cig exposed neurons demonstrated decreased cell viability and glucose utilization in OGD/R. Prenatally e-Cig exposed pups also had increased brain injury and edema 24 hr after HI brain injury. Further, in utero e-Cig exposed offspring with HI brain injury displayed impaired memory, learning, and motor coordination at adolescence. Additionally, the expression of glucose transporters decreased in e-Cig exposed offspring brain after HI brain injury. These results indicate that reduced glucose utilization can contribute to prenatal e-Cig exposure induced worsened HI brain injury in offspring. This study is instrumental in elucidating the possible deleterious effects of e-Cig use in the general population.

Nicotinic Receptors Underlying Nicotine Dependence: Evidence from Transgenic Mouse Models

Nicotine underlies the reinforcing properties of tobacco cigarettes and e-cigarettes. After inhalation and absorption, nicotine binds to various nicotinic acetylcholine receptor (nAChR) subtypes localized on the pre- and postsynaptic membranes of cells, which subsequently leads to the modulation of cellular function and neurotransmitter signaling. In this chapter, we begin by briefly reviewing the current understanding of nicotine's actions on nAChRs and highlight considerations regarding nAChR subtype localization and pharmacodynamics. Thereafter, we discuss the seminal discoveries derived from genetically modified mouse models, which have greatly contributed to our understanding of nicotine's effects on the reward-related mesolimbic pathway and the aversion-related habenulo-interpeduncular pathway. Thereafter, emerging areas of research focusing on modulation of nAChR expression and/or function are considered. Taken together, these discoveries have provided a foundational understanding of various genetic, neurobiological, and behavioral factors underlying the motivation to use nicotine and related dependence processes, which are thereby advancing drug discovery efforts to promote long-term abstinence.

Modeling drug exposure in rodents using e-cigarettes and other electronic nicotine delivery systems

Smoking tobacco products is the leading cause of preventable death worldwide. Coordinated efforts have successfully reduced tobacco cigarette smoking in the United States; however, electronic cigarettes (e-cigarette) and other electronic nicotine delivery systems (ENDS) recently have replaced traditional cigarettes for many users. While the clinical risks associated with long-term ENDS use remain unclear, advancements in preclinical rodent models will enhance our understanding of their overall health effects. This review examines the peripheral and central effects of ENDS-mediated exposure to nicotine and other drugs of abuse in rodents and evaluates current techniques for implementing ENDS in preclinical research.

The cardiovascular effects of electronic cigarettes: A systematic review of experimental studies

BACKGROUND

Smoking is responsible for substantial cardiovascular morbidity and mortality. Electronic cigarettes have been advocated as a means to reduce this disease burden; by reducing exposure to harmful substances in smokers who are unable to quit. Concerns have been raised however, about cardiovascular effects of their use, with inhalants containing carbonyls and fine particulate matter. We systematically reviewed experimental studies of in vitro, animal, and human cardiovascular effects associated with electronic cigarette use.

METHODS

A literature search was conducted using Ovid MEDLINE & Embase databases, identifying experimental studies investigating cardiovascular effects of electronic cigarette use. Subsequently, Cochrane Risk of Bias tools were used to assess study quality. Any differences in outcomes by conflict of interest and risk of bias status were sought.

RESULTS

38 studies were included, investigating animals (n=6), humans (n=24) and human cardiovascular cells in vitro (n=8). 74.3% of studies found potentially harmful effects. Increased sympathetic nerve activity was observed in human studies, whilst platelet haemostatic processes, reactive oxygen species production and endothelial dysfunction were reported across all study types. Studies with conflicts of interest or median-high risk of bias were less likely to identify potentially harmful effects (p=0.0007, p=0.04 respectively).

DISCUSSION

Most studies suggest potential for cardiovascular harm from electronic cigarette use, through mechanisms that increase risk of thrombosis and atherosclerosis. Notably, studies with conflicts of interest are significantly less likely to identify concerning cardiovascular effects. Included studies examine healthy, adult participants, limiting generalisation to potential high-risk groups including individuals with established cardiovascular disease or young, non-smokers.

Neurovascular unit transport responses to ischemia and common coexisting conditions: smoking and diabetes

Transporters at the neurovascular unit (NVU) are vital for the regulation of normal brain physiology via ion, water, and nutrients movement. In ischemic stroke, the reduction of cerebral blood flow causes several complex pathophysiological changes in the brain, one of which includes alterations of the NVU transporters, which can exacerbate stroke outcome by increased brain edema (by altering ion, water, and glutamate transporters), altered energy metabolism (by altering glucose transporters), and enhanced drug toxicity (by altering efflux transporters). Smoking and diabetes are common risk factors as well as coexisting conditions in ischemic stroke that are also reported to change the expression and function of NVU transporters. Coexistence of these conditions could cause an additive effect in terms of the alterations of brain transporters that might lead to worsened ischemic stroke prognosis and recovery. In this review, we have discussed the effects of ischemic stroke, smoking, and diabetes on some essential NVU transporters and how the simultaneous presence of these conditions can affect the clinical outcome after an ischemic episode. Further scientific investigations are required to elucidate changes in NVU transport in cerebral ischemia, which can lead to better, personalized therapeutic interventions tailor-made for these comorbid conditions.