Metformin’s protection against blood-brain barrier disruption and neuronal dysfunction under oxygen-glucose deprivation and tobacco smoke and e-vape chemical exposure

Ischemic stroke occurs in 87% of all strokes and is the leading cause of disability in the United States. Smoking has been shown to increase brain edema after ischemic stroke and worsen long‐term clinical outcomes. Electronic nicotine delivery systems or e‐cigarettes (e‐Cigs) are gaining popularity over traditional tobacco smoke cigarettes, and have been reported influence stroke outcome. Previous work from our lab reported nicotine and e‐Cig exposure decreased glucose utilization in the brain in ischemic stroke models, further exacerbating the effects of ischemic injury. Myo‐inositol(MI), a major organic osmolyte that promotes cell membrane stability and various cellular functions, has been reported to reduce infarcted area and edema ratio in a diabetic ischemic mouse model. We also sought to understand the role of MI protection with regard to additional stroke comorbidities, such as e‐Cig or tobacco smoke exposure. In this study, we investigated the neuroprotective role of MI transporters during stroke and post‐stroke outcomes, especially related to the role of glial cells and post‐stroke reorganization. We hypothesize MI plays a role in increased recovery of motor function, after stroke, in animal groups exposed to tobacco smoke or e‐Cig vape. Primary astrocytes and primary neurons were used for in vitro studies and a middle cerebral artery occlusion (MCAO) mouse model for in vivo stroke studies. Immunocytochemistry (ICC) studies showed astrocytes express sodium dependent myo‐inositol transporter 1 (SMIT1) and sodium‐dependent glucose transporter 6 (SGLT6). Our data illustrated expression of both transporters increased in a time‐dependent manner during oxygen‐glucose deprivation (OGD), in tobacco smoke extract (TSE), and e‐Cig extract (ECE) treated cells. Further, this was confirmed by an increase of MI uptake in TSE treated astrocytes. Altered cell mitochondrial respiration levels were observed in astrocytes and neurons incubated for 24hr with TSE and ECE followed by OGD exposure using Seahorse XF Cell Mito Stress. Animal studies demonstrated post‐stroke administration of MI, reduced infarction size and edema ratios in tobacco smoke compared to non‐tobacco smoke animals. An improvement of motor function was also seen in selected behavioral tests. E‐cig exposed animals had a slight increase in infarction size compared to non‐e‐Cig animals. This preliminary data suggest myo‐inositol may have a neuroprotective role in ischemic stroke injury and could significantly improve stroke outcome in both tobacco smokers and e‐Cig users. Further investigation will include assessment of sex differences with regard to the neuroprotective mechanisms of MI in e‐Cig and tobacco smoke exposed animals.Support or Funding Information1R01DA0497375 and R01DA029121 to TJA and LC

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

Passive smoking exposure is a topic of great concern for public health because of its well-known adverse effects on human health (International Agency for Research on Cancer 2004). Two news articles on this topic were published in the February 2011 issue of Environmental Health Perspectives (Burton 2011; Lubick 2011). Lubick (2011) discussed the global health burden of secondhand smoke, and Burton (2011) emphasized a new and alarming consequence of smoking in indoor environments—“thirdhand smoke”—a term first coined in 2006 (Szabo 2006). Secondhand smoke is defined as “the combination of smoke emitted from the burning end of a cigarette or other tobacco products and smoke exhaled by the smoker” (World Health Organization 2007). Thus, secondhand smoke exposure consists of an unintentional inhalation of smoke that occurs close to people smoking and/or in indoor environments where tobacco was recently used. Thirdhand smoke is a complex phenomenon resulting from residual tobacco smoke pollutants that adhere to the clothing and hair of smokers and to surfaces, furnishings, and dust in indoor environments. These pollutants persist long after the clearing of secondhand smoke. They are reemitted into the gas phase or react with oxidants or other compounds present in the environment to form secondary contaminants, some of which are carcinogenic or otherwise toxic for human health (Matt et al. 2011). Thus, thirdhand smoke exposure consists of unintentional intake (mainly through inhalation but also via ingestion and dermal routes) of tobacco smoke and other related chemicals that occurs in the absence of concurrent smoking. Exposure can even take place long after smoking has ceased, through close contact with smokers and in indoor environments in which tobacco is regularly smoked. Lubick (2011) considers secondhand smoke synonymous with passive smoking, as do the majority of the authors publishing on this topic. However, in light of new evidence about thirdhand smoke (Matt et al. 2011), it is no longer appropriate to use the term “secondhand smoke” as a synonym for passive smoking or environmental tobacco smoke, because it represents a pars pro toto. In other words, using the term “secondhand smoke” mistakes one part of the problem for the whole. Instead, we propose that “passive smoking” or “environmental tobacco smoke” be used as a more inclusive term to describe any tobacco smoke exposure outside of active smoking. This question of terminology is of particular concern for researchers evaluating passive smoking exposure in indoor settings, especially in domestic environments. Since numerous countries have introduced smoking bans in enclosed public places, domestic environments have become the main sources of passive smoking exposure (World Health Organization 2007). We believe researchers should determine the independent contributions of secondhand and thirdhand smoke when they assess the magnitude of pollutant intake due to passive smoking exposure.

E-cigarettes for tobacco cessation: Not the solution.

Testing of a hypothesis for osmotic opening of the blood-brain barrier.

Tobacco Control Policy and Electronic Cigarettes

Blood-brain barrier (BBB) disruption is a common pathological feature of many neurological disorders including stroke and brain trauma, therefore is an important therapeutic target for treatment of these diseases. Basic fibroblast growth factor (bFGF) as a member of FGF superfamily plays critical roles in angiogenesis, neurogenesis, and neuron survival. We recently showed that recombinant bFGF protects against BBB disruption in traumatic brain injury in mice. In this study, we further investigated the mechanisms of recombinant bFGF in BBB protection by measuring the permeability of cultured endothelial cell monolayer induced by oxygen-glucose deprivation and reoxygenation (OGD/R). We found that recombinant bFGF significantly decreased OGD/R-induced permeability of primary human brain microvascular endothelial cell (HBMEC) monolayer and preserved OGD/R-induced decreases of trans-endothelial electrical resistance (TEER). Western blot and immunocytochemistry showed that bFGF significantly rescued OGD/R-induced downregulation of junction proteins ZO-1, occludin, and VE-cadherin. We further show that the BBB protective effect of bFGF is via FGF receptor 1 (FGFR1) activation as FGFR1 inhibitor can block this protection effect. Moreover, we revealed that the BBB protection effect of bFGF is at least partially through rescuing the OGD/R-induced downregulation of sphingosine-1-phosphate receptor 1 (S1PR1) protein, as S1PR1 inhibitor or SIPR1 small interfering RNA blocked the BBB protective effect of bFGF, whereas S1PR1 agonist alone has comparable BBB protection effect of bFGF. These findings will improve our understanding of the protective effect and mechanisms of bFGF on BBB and propose bFGF as a potential therapeutic agent against BBB damage in neurological disorders.

BackgroundThe 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.MethodsWe 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.ResultsOur 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.ConclusionIn 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.

Disruption of blood-brain barrier (BBB), formed mainly by human brain microvascular endothelial cells (HBMECs), constitutes the major cause of mortality following ischaemic stroke. This study investigates whether OECs (outgrowth endothelial cells) can restore BBB integrity and function following ischaemic damage and how inhibition of NOX2, a main source of vascular oxidative stress, affects the characteristics of BBB established with OECs and HBMECs in ischaemic settings. In vitro models of human BBB were constructed by co-culture of pericytes and astrocytes with either OECs or HBMECs before exposure to oxygen-glucose deprivation (OGD) alone or followed by reperfusion (OGD + R) in the absence or presence of NOX2 inhibitor, gp91ds-tat. The function and integrity of BBB were assessed by measurements of paracellular flux of sodium fluorescein (NaF) and transendothelial electrical resistance (TEER), respectively. Treatment with OECs during OGD + R effectively restored BBB integrity and function. Compared to HBMECs, OECs possessed lower NADPH oxidase activity, superoxide anion levels and had greater total antioxidant capacity during OGD and OGD + R. Inhibition of NADPH oxidase during OGD and OGD + R restored the integrity and function of BBB established by HBMECs. This was evidenced by reductions in NADPH oxidase activity and superoxide anion levels. In contrast, treatment with gp91ds-tat aggravated ischaemic injury-induced BBB damage constructed by OECs. In conclusion, OECs are more resistant to ischaemic conditions and can effectively repair cerebral barrier following ischaemic damage. Suppression of oxidative stress through specific targeting of NOX2 requires close attention while using OECs as therapeutics.

Background:Early initiation of tobacco use among adolescents is a significant public health concern. While there is extensive research on overall tobacco use, much of it focuses on initiation in late adolescence, uses cross-sectional designs, and lacks specific exploration of electronic versus conventional cigarette use. This study aims to investigate social determinants influencing the early initiation of electronic and conventional cigarette use among U.S. adolescents.Methods:We utilized data from the Adolescent Brain Cognitive Development (ABCD) study, which follows a cohort of tobacco-naïve children from age nine through age 16. The social determinants examined included household income, parental education, financial difficulties, racial/ethnic minority status, family structure, neighborhood income, and gender minority status. Structural equation models were employed to assess associations between these determinants and early initiation of electronic and conventional cigarette use.Results:Male gender was associated with a higher likelihood of conventional cigarette use, while the risk of early initiation of electronic cigarette use was similar across genders. White adolescents were at a higher risk of conventional cigarette use; however, the risk for electronic cigarette use was comparable across White and non-White groups. Financial difficulties were linked to an increased likelihood of early initiation of conventional cigarette use but not electronic cigarette use. Higher household income was associated with a reduced risk of initiating conventional cigarettes but did not significantly impact electronic cigarette use. Adolescents from married families were less likely to initiate electronic cigarette use. No significant effects were found for parental education or neighborhood income on the initiation of either type of cigarette use. Age did not significantly affect the initiation of either cigarette type, and gender minority status was marginally associated with early initiation of conventional cigarette use.Conclusions:The social patterning of electronic cigarette use differs from that of conventional cigarette use, suggesting that distinct tobacco products do not pose a uniform risk across all adolescents. This study underscores the importance of tailored prevention efforts that address the unique challenges associated with early initiation of electronic and conventional cigarette use among adolescents. The differential risk factors identified suggest targeted prevention strategies for conventional cigarette use, focusing on financial difficulties, household income, and gender-specific interventions. In contrast, prevention efforts for electronic cigarette use may require broader, more inclusive approaches that address all adolescents, regardless of their background. Comprehensive universal screening for electronic cigarette use and targeted screening for conventional cigarette use among adolescents are recommended.

To assess the acute effects of nicotine-containing electronic cigarettes versus tobacco smoking on vascular and respiratory function and circulating microparticles, particularly platelet microparticles (PMPs, biomarker of haemostasis/thrombosis) and endothelial microparticles (EMPs, biomarker of endothelial function). Heart rate (HR), blood pressure, reactive hyperaemia index (RHI, microvascular reactivity), augmentation index (arterial stiffness) and respiratory function were assessed in 20 smokers immediately before and after electronic cigarettes use and tobacco smoking. The number of microparticles was determined by flow cytometry using counting beads as a reference. Labelling with Annexin-V was used to detect the total microparticle fraction. EMPs were characterized as CD31+CD42- and PMPs as CD31+CD42+. HR increased after electronic cigarettes use and tobacco smoking (P < 0.001), whereas blood pressure remained unchanged (P > 0.05). RHI (P = 0.006), augmentation index (P = 0.010) but not augmentation index standardized to HR 75 bpm (P > 0.05) increased with electronic cigarettes use but not with tobacco smoking. Following tobacco smoking, there was a significant increase in total microparticles (P < 0.001), EMPs (P < 0.001) and PMPs (P < 0.001). In contrast, electronic cigarettes were only associated with an increase in PMPs (P < 0.001), with no significant changes in the total microparticle fraction or EMPs (all P > 0.05). Peak expiratory flow significantly decreased following electronic cigarettes use (P = 0.019). Our results demonstrate that acute exposure to tobacco smoking as well as electronic cigarettes influences vascular and respiratory function. Where tobacco smoking significantly increased microparticle formation, indicative of possible endothelial injury, electronic cigarettes use induced vasoreactivity and decreased peak expiratory flow. These findings suggest that both electronic cigarettes and tobacco smoking negatively impact vascular function.

Position Statement on Tobacco Exposures in Children and Families

Interleukin (IL)-25, a member of the IL-17 family of cytokines, is expressed in the brains of normal mice. However, the cellular source of IL-25 and its function in the brain remain to be elucidated. Here, we show that IL-25 plays an important role in preventing infiltration of the inflammatory cells into the central nervous system. Brain capillary endothelial cells (BCECs) express IL-25. However, it is down-regulated by inflammatory cytokines, including tumor necrosis factor (TNF)-alpha, IL-17, interferon-gamma, IL-1beta, and IL-6 in vitro, and is also reduced in active multiple sclerosis (MS) lesions and in the inflamed spinal cord of experimental autoimmune encephalomyelitis, an animal model of MS. Furthermore, IL-25 restores the reduced expression of tight junction proteins, occludin, junction adhesion molecule, and claudin-5, induced by TNF-alpha in BCECs and consequently repairs TNF-alpha-induced blood-brain barrier (BBB) permeability. IL-25 induces protein kinase Cepsilon (PKCepsilon) phosphorylation, and up-regulation of claudin-5 is suppressed by PKCepsilon inhibitor peptide in the IL-25-stimulated BCECs. These results suggest that IL-25 is produced by BCECs and protects against inflammatory cytokine-induced excessive BBB collapse through a PKCepsilon-dependent pathway. These novel functions of IL-25 in maintaining BBB integrity may help us understand the pathophysiology of inflammatory brain diseases such as MS.

Neutrophils block permeability increases induced by oxygen glucose deprivation in a culture model of the human blood–brain barrier

ObjectivesThe present study evaluated the association of electronic cigarette (EC) exposure with serum uric acid (UA) level and hyperuricemia (HUA) using a nationally representative sample of South Korea.MethodsThis study included 10,692 participants (9,905, 609, and 178, never, ever, and current EC users, respectively). Urinary cotinine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) levels were used to determine conventional smoking exposure among EC users. The association between EC use and UA level was evaluated by linear regression analysis. Multivariable logistic regression analysis was used to assess the association between EC and HUA. Subgroup analysis confined to cotinine-verified active smokers was performed to address the association between the dual use of EC and combustible cigarettes and serum UA levels.ResultsThe serum UA level was highest among current EC users, followed by ever and never EC users. The prevalence of HUA was 26.2%, 19.3%, and 10.8% in current, ever, and never EC users, respectively. Although EC exposure was positively associated with HUA in a dose-dependent manner only in men (Ptrend = 0.04), a similar tendency was also observed in women with marginal significance (Ptrend = 0.102). The positive association of HUA with EC exposure was more apparent among dual users (odds ratio [OR] = 1.96, 95% confidence interval [CI]: 1.29–2.99) than among those who only smoked combustible cigarettes.ConclusionsEC exposure was associated with higher serum UA level and higher OR of HUA. The positive association between EC exposure and HUA was more prominent in dual users who concurrently consumed EC and combustible cigarettes.