Chronic exposure to nicotine alters endothelium-dependent arteriolar dilatation: effect of superoxide dismutase

Documento de consenso sobre tabaquismo y riesgo vascular

Consensus statement on smoking and vascular risk About 22% of the Spanish population are daily smokers. Men are more likely to smoke than women. In Spain, women between 15-25 years of age smoke as much or more than men. Every smoker should be assessed for: physical dependence on nicotine (Fagerström test), social and psychological dependence (Glover Nilsson test), level of motivation to quit (Richmond test), probability of therapy success (Henri-Mondor and Michael-Fiore tests), and stage of behavioral change development (Prochaska and DiClementi). Advice on smoking cessation is highly cost-effective and should always be provided. Smoking is an enhancer of cardiovascular risk because it acts as a pathogen agent in the development of arteriosclerosis and is associated with ischemic heart disease, stroke, and peripheral artery disease. Smoking increases the risk of chronic lung diseases (COPD) and is related to cancers of the lung, female genitalia, larynx, oropharynx, bladder, mouth, esophagus, liver and biliary tract, and stomach, among others. Combined oral contraceptives should be avoided in women smokers older than 35 years of age due to the risk of thromboembolism. In smoking cessation, the involvement of physicians, nurses, psychologists, etc. is important, and their multidisciplinary collaboration is needed. Effective pharmacological treatments for smoking cessation are available. Combined treatments are recommended when smoker's dependence is high. For individuals who are unable to quit smoking, a strategy based on tobacco damage management with a total switch to smokeless products could be a less dangerous alternative for their health than continuing to smoke.

Mitochondrial Dynamics in Pulmonary Hypertension

Mitochondria are essential organelles for energy production, calcium homeostasis, redox signaling, and other cellular responses involved in pulmonary vascular biology and disease processes. Mitochondrial homeostasis depends on a balance in mitochondrial fusion and fission (dynamics). Mitochondrial dynamics are regulated by a viable circadian clock. Hypoxia and nicotine exposure can cause dysfunctions in mitochondrial dynamics, increases in mitochondrial reactive oxygen species generation and calcium concentration, and decreases in ATP production. These mitochondrial changes contribute significantly to pulmonary vascular oxidative stress, inflammatory responses, contractile dysfunction, pathologic remodeling, and eventually pulmonary hypertension. In this review article, therefore, we primarily summarize recent advances in basic, translational, and clinical studies of circadian roles in mitochondrial metabolism in the pulmonary vasculature. This knowledge may not only be crucial to fully understanding the development of pulmonary hypertension, but also greatly help to create new therapeutic strategies for treating this devastating disease and other related pulmonary disorders.

Diabetes- versus smoking-related thrombo-inflammation in peripheral artery disease

Peripheral artery disease (PAD) is a major health problem with increased cardiovascular mortality, morbidity and disabling critical limb threatening ischemia (CLTI) and amputation. Diabetes mellitus (DM) and cigarette smoke are the main risk factors for the development of PAD. Although diabetes related PAD shows an accelerated course with worse outcome regarding complications, mortality and amputations compared with non-diabetic patients, current medical treatment does not make this distinction and includes standard antiplatelet and lipid lowering drugs for all patients with PAD. In this review we discuss the pathophysiologic mechanisms of PAD, with focus on differences in thrombo-inflammatory processes between diabetes-related and smoking-related PAD, and hypothesize on possible mechanisms for the progressive course of PAD in DM. Furthermore, we comment on current medical treatment and speculate on alternative medical drug options for patients with PAD and DM.

Smoking, alcohol and opioids effect on coronary microcirculation: an update overview

Smoking, heavy alcohol drinking and drug abuse are detrimental lifestyle factors leading to loss of million years of healthy life annually. One of the major health complications caused by these substances is the development of cardiovascular diseases (CVD), which accounts for a significant proportion of substance-induced death. Smoking and excessive alcohol consumption are related to the higher risk of acute myocardial infarction. Similarly, opioid addiction, as one of the most commonly used substances worldwide, is associated with cardiac events such as ischemia and myocardial infarction (MI). As supported by many studies, coronary artery disease (CAD) is considered as a major cause for substance-induced cardiac events. Nonetheless, over the last three decades, a growing body of evidence indicates that a significant proportion of substance-induced cardiac ischemia or MI cases, do not manifest any signs of CAD. In the absence of CAD, the coronary microvascular dysfunction is believed to be the main underlying reason for CVD. To date, comprehensive literature reviews have been published on the clinicopathology of CAD caused by smoking and opioids, as well as macrovascular pathological features of the alcoholic cardiomyopathy. However, to the best of our knowledge there is no review article about the impact of these substances on the coronary microvascular network. Therefore, the present review will focus on the current understanding of the pathophysiological alterations in the coronary microcirculation triggered by smoking, alcohol and opioids.

Redox Regulation of the Microcirculation

The microcirculation maintains tissue homeostasis through local regulation of blood flow and oxygen delivery. Perturbations in microvascular function are characteristic of several diseases and may be early indicators of pathological changes in the cardiovascular system and in parenchymal tissue function. These changes are often mediated by various reactive oxygen species and linked to disruptions in pathways such as vasodilation or angiogenesis. This overview compiles recent advances relating to redox regulation of the microcirculation by adopting both cellular and functional perspectives. Findings from a variety of vascular beds and models are integrated to describe common effects of different reactive species on microvascular function. Gaps in understanding and areas for further research are outlined. © 2020 American Physiological Society. Compr Physiol 10:229-260, 2020.

In times of tobacco-free nicotine consumption: The influence of nicotine on vascular calcification

BACKGROUND

Smoking remains the most important avoidable cause of global mortality. Even though the number of cigarette smokers declines in first world countries, the uses of alternative nicotine delivery products increase and may even surpass the sells of cigarettes. In this light, the explicit role of nicotine in the development of cardiovascular diseases should be elucidated.

OBJECTIVES

This narrative review attempts to connect current literature about possible effects of nicotine on the environment of the vasculature to the pathogenesis of vascular calcification, focusing on the tunica media of the vessel wall.

METHODS

For this review, papers found on Pubmed and Medline until December 2018 by searching for the keywords nicotine, vascular calcification, oxidative stress, osteoblastic transdifferentiation and matrix degradation were considered.

RESULTS

Nicotine creates an environment that probably facilitates and maybe even induces osteogenic transdifferentiation of VSMC by inflammation, endothelial dysfunction and reactive oxygen species. This process is believed to be a key event in calcification of the tunica media of the vessel wall. Furthermore, nicotine could lead to the formation of nucleation sites for hydroxyapatite by facilitating matrix vesicles and extracellular matrix degradation.

CONCLUSIONS

There is a growing body of evidence implicating that nicotine alone could impair vascular function and lead to vascular calcification. Further research is necessary to elucidate the explicit influence of nicotine on arteriosclerosis.

Protective Effect of Antenatal Antioxidant on Nicotine-Induced Heart Ischemia-Sensitive Phenotype in Rat Offspring

Fetal nicotine exposure increased risk of developing cardiovascular disease later in life. The present study tested the hypothesis that perinatal nicotine-induced programming of heart ischemia-sensitive phenotype is mediated by enhanced reactive oxygen species (ROS) in offspring. Nicotine was administered to pregnant rats via subcutaneous osmotic minipumps from day 4 of gestation to day 10 after birth, in the absence or presence of a ROS inhibitor, N-acetyl-cysteine (NAC) in drinking water. Experiments were conducted in 8 month old age male offspring. Isolated hearts were perfused in a Langendorff preparation. Perinatal nicotine treatment significantly increased ischemia and reperfusion-induced left ventricular injury, and decreased post-ischemic recovery of left ventricular function and coronary flow rate. In addition, nicotine enhanced cardiac ROS production and significantly attenuated protein kinase Cε (PKCε) protein abundance in the heart. Although nicotine had no effect on total cardiac glycogen synthase kinase-3β (GSK3β) protein expression, it significantly increased the phosphorylation of GSK3β at serine 9 residue in the heart. NAC inhibited nicotine-mediated increase in ROS production, recovered PKCε gene expression and abrogated increased phosphorylation of GSK3β. Of importance, NAC blocked perinatal nicotine-induced increase in ischemia and reperfusion injury in the heart. These findings provide novel evidence that increased oxidative stress plays a causal role in perinatal nicotine-induced developmental programming of ischemic sensitive phenotype in the heart, and suggest potential therapeutic targets of anti-oxidative stress in the treatment of ischemic heart disease.

Arrhythmogenic Risk Assessment Following Four-Week Pretreatment With Nicotine and Black Tea in Rat

BACKGROUND

There is the controversy concerning the main component of tobacco, which is responsible for its arrhythmogenesis. In addition, there is the lack of adequate information about the influence of combination of black tea and nicotine on heart rhythm.

OBJECTIVES

This study aimed to examine whether pretreatment with black tea and nicotine could modulate the susceptibility to lethal ventricular arrhythmias.

MATERIALS AND METHODS

Animals were randomized to control, black tea, nicotine, and black tea plus nicotine groups. Test groups were treated with black tea brewed (orally) and nicotine (2 mg/kg, subcutaneous), alone and in combination for four weeks. On day 29, aconitine was infused intravenously for induction of cardiac arrhythmia.

RESULTS

In comparison with the control group, each of tea and nicotine significantly decreased the duration of the ventricular tachycardia (VT) plus ventricular fibrillation (VF) and the score of arrhythmia severity (P < 0.05 and P < 0.01, respectively,). The latency for the first VT event was significantly longer in the all test groups, but VF latency was significant only in tea and nicotine groups compared with control group (P < 0.05 and P < 0.01, respectively).Threshold dose of aconitine for inducing VT and VF increased in all test groups, but only VT showed a significant difference in comparison to the control group (P < 0.001).

CONCLUSIONS

The findings suggest that sub-chronic consumption of nicotine or black tea alone with appropriate doses could potentially be antiarrhythmic and its combination regimen does not increase the risk of fatal ventricular arrhythmias during four-week consumption period in rats.

Antenatal Antioxidant Prevents Nicotine-Mediated Hypertensive Response in Rat Adult Offspring

Previous studies have demonstrated that perinatal nicotine exposure increased blood pressure (BP) in adult offspring. However, the underlying mechanisms were unclear. The present study tested the hypothesis that perinatal nicotine-induced programming of hypertensive response is mediated by enhanced reactive oxygen species (ROS) in the vasculature. Nicotine was administered to pregnant rats via subcutaneous osmotic mini-pumps from Day 4 of gestation to Day 10 after birth, in the absence or presence of the ROS inhibitor N-acetyl-cysteine (NAC) in the drinking water. Experiments were conducted in 8-mo-old male offspring. Perinatal nicotine treatment resulted in a significant increase in arterial ROS production in offspring, which was abrogated by NAC. Angiotensin II (Ang II)-induced BP responses were significantly higher in nicotine-treated group than in saline-treated control group, and NAC treatment blocked the nicotine-induced increase in BP response. Consistent with that, the nicotine treatment significantly increased both Ang II-induced and phorbol [12, 13]-dibutyrate (PDBu, a Prkc activator)-induced arterial contractions in adult offspring, which were blocked by NAC treatment. In addition, perinatal nicotine treatment significantly attenuated acetylcholine-induced arterial relaxation in offspring, which was also inhibited by NAC treatment. Results demonstrate that inhibition of ROS blocks the nicotine-induced increase in arterial reactivity and BP response to vasoconstrictors in adult offspring, suggesting a key role for increased oxidative stress in nicotine-induced developmental programming of hypertensive phenotype in male offspring.

Endothelial disruptive proinflammatory effects of nicotine and e-cigarette vapor exposures

The increased use of inhaled nicotine via e-cigarettes has unknown risks to lung health. Having previously shown that cigarette smoke (CS) extract disrupts the lung microvasculature barrier function by endothelial cell activation and cytoskeletal rearrangement, we investigated the contribution of nicotine in CS or e-cigarettes (e-Cig) to lung endothelial injury. Primary lung microvascular endothelial cells were exposed to nicotine, e-Cig solution, or condensed e-Cig vapor (1-20 mM nicotine) or to nicotine-free CS extract or e-Cig solutions. Compared with nicotine-containing extract, nicotine free-CS extract (10-20%) caused significantly less endothelial permeability as measured with electric cell-substrate impedance sensing. Nicotine exposures triggered dose-dependent loss of endothelial barrier in cultured cell monolayers and rapidly increased lung inflammation and oxidative stress in mice. The endothelial barrier disruptive effects were associated with increased intracellular ceramides, p38 MAPK activation, and myosin light chain (MLC) phosphorylation, and was critically mediated by Rho-activated kinase via inhibition of MLC-phosphatase unit MYPT1. Although nicotine at sufficient concentrations to cause endothelial barrier loss did not trigger cell necrosis, it markedly inhibited cell proliferation. Augmentation of sphingosine-1-phosphate (S1P) signaling via S1P1 improved both endothelial cell proliferation and barrier function during nicotine exposures. Nicotine-independent effects of e-Cig solutions were noted, which may be attributable to acrolein, detected along with propylene glycol, glycerol, and nicotine by NMR, mass spectrometry, and gas chromatography, in both e-Cig solutions and vapor. These results suggest that soluble components of e-Cig, including nicotine, cause dose-dependent loss of lung endothelial barrier function, which is associated with oxidative stress and brisk inflammation.

Pathophysiological Mechanisms of Tobacco-Related CVD

Cigarette smoking is a leading preventable risk factor for the development and progression of cardiovascular diseases (CVDs). Epidemiologic studies conclusively prove that both active smoking and secondhand smoke contribute significantly to morbidity and mortality related to CVD. Cigarette smoke is a mixture of several toxic chemicals, of which nicotine, carbon monoxide, and oxidant chemicals are most commonly implicated in the pathogenesis of cardiovascular disease. Tobacco causes endothelial dysfunction, inflammation, insulin resistance, alteration of lipid profile, hemodynamic alterations, and a hypercoagulable state. All of these act synergistically as pathobiologic mechanisms of atherothrombosis in tobacco users.

Haemodynamic responses to tobacco smoke inhalation in male adolescents in Lusaka, Zambia

Background

Tobacco smoke causes changes in the levels of catecholamines in the blood. This leads to an increase in blood pressure and heart rate. This is due to nicotine which has also been noted to cause a decrease in vasodilatory activities leading to an increase in both the blood pressure and heart rate.

Aim

To determine the acute effects of tobacco smoke on haemodynamics in black male adolescents in Lusaka, Zambia.

Study design

This was an observational study done at the University of Zambia School of Medicine Cardiovascular Research Laboratory in the month of December, 2014.

Methodology

Twenty-two (22) black, male-adolescent (age range 19-25 years), active-smokers, consented to participate in the study. The Diasys Ambulatory Blood Pressure Monitoring system (Novacor, France) was used to obtain the Systolic and Diastolic blood pressures (SBP and DBP) and the heart rate. These were obtained 15 minutes before smoking at 5 minute intervals and averaged to obtain the baseline, during the 15 minutes of smoking and on immediate cessation of smoking and thereafter every 15 minutes up to an hour after smoking.

Results

There was a significant rise in SBP (mmHg) during smoking (127.9 ± 13.80 mmHg) from baseline values (113.5 ± 13.15 mmHg) (P = .00). It took 30 minutes for the SBP to return to baseline after cessation of smoking. DBP (mmHg) also increased from baseline (79.5 ± 8.79 mmHg) to 85.6 ± 10.92 mmHg during smoking (P = .01). It returned to baseline values immediately after cessation of smoking. The heart rate (bpm) was also noted to significantly increase during smoking (95.2 ± 16.72 bpm) from the values noted before smoking (74.3 ± 13.75 bpm) (P = .05). The mean value for heart rate returned to baseline value by the 15^th minute of recovery.

Conclusion

The present study demonstrates that smoking may be the cause for the acute increases in SBP, DBP and heart rate in smokers. The smoking caused significant increases in all the haemodynamic indices considered in this study within 15 minutes. Both SBP and DBP increase are indices for stroke and coronary heart disease respectively. The effect of increased SBP was noted to last for 30 minutes while DBP returned to baseline immediately after smoking. A significant increase in heart rate was also noted in the study.

Aortic remodelling in chronic nicotine-administered rat

Vascular remodelling is an adaptive mechanism, which counteracts pressure changes in blood circulation. Nicotine content in cigarette increases the risk of hypertension. The exact relationship between nicotine and vascular remodelling still remain unknown. Current study was aimed to determine the effect of clinically relevant dosage of nicotine (equivalent to light smoker) on aortic reactivity, oxidative stress markers and histomorphological changes. Twelve age-matched male Sprague-Dawley rats were randomly divided into two groups, i.e.: normal saline as control or 0.6 mg/kg nicotine for 28 days (i.p., n=6 per group). On day-29, the rats were sacrificed and the thoracic aorta was dissected immediately for further studies. Mean arterial pressure (MAP) and pulse pressure (PP) of nicotine-treated vs. control were significantly increased (p<0.05). Nicotine-treated group showed significant (p<0.05) increase tunica media thickness, and decrease in lumen diameter, suggesting vascular remodelling which lead to prior hypertension state. The phenylephrine (PE)-induced contractile response in nicotine group was significantly higher than control group (ED50=1.44×10(5) M vs. 4.9×10(6) M) (p<0.05~0.001). However, nicotine-treated rat showed significantly lower endothelium-dependent relaxation response to acetylcholine (ACh) than in control group (ED50=6.17×10(7) M vs. 2.82×10(7) M) (p<0.05), indicating loss of primary vascular function. Malondialdehyde (MDA), a lipid peroxidation marker was significantly higher in nicotine group. Superoxide dismutase (SOD) enzymatic activity and glutathione (GSH) were all reduced in nicotine group (p<0.05) vs. control, suggesting nicotine induces oxidative imbalance. In short, chronic nicotine administration impaired aortic reactivity, probably via redox imbalance and vascular remodelling mechanism.

Antenatal nicotine induces heightened oxidative stress and vascular dysfunction in rat offspring

BACKGROUND AND PURPOSE

Antenatal nicotine exposure causes aberrant vascular reactivity and increased blood pressure in adult male rat offspring in a sex-dependent manner. The present study tested the hypothesis that maternal nicotine administration increases the production of reactive oxygen species resulting in the vascular hypertensive reactivity in male offspring.

EXPERIMENTAL APPROACH

Nicotine was administered to pregnant rats via subcutaneous osmotic minipumps throughout the gestation. The vascular oxidative damage and dysfunction were determined in 5-month-old male offspring. Contraction studies were performed on isolated aortas and their expression of NADPH oxidase (Nox2)/gp91 and nox4 determined by Western blot analysis. In addition, oxidative damage in the vessel wall was determined by measuring malondialdehyde concentrations, vascular superoxide production and SOD activity.

KEY RESULTS

Antenatal nicotine significantly increased angiotensin II-induced arterial contractions in the offspring. The exaggerated vascular contractions were inhibited by both apocynin (a Nox inhibitor) and tempol (a SOD mimetic) in a concentration-dependent manner. In addition, ACh-induced relaxations were impaired in aortas isolated from the nicotine-treated offspring, which were restored by both apocynin and tempol in a concentration-dependent manner. The nicotine treatment significantly decreased the superoxide dismutase activity and increased malondialdehyde, superoxide and nitrotyrosine protein levels in the vascular wall. Consistently, antenatal nicotine exposure significantly enhanced the protein expression of NADPH oxidase Nox2/gp91, but not Nox4 in the aorta.

CONCLUSIONS AND IMPLICATIONS

The present findings suggest that antenatal nicotine exposure results in the programming of heightened oxidative stress and vascular hypertensive reactivity via a Nox2-dependent mechanism, leading to an increased risk of hypertension in adult offspring.

Chronic administration of nicotine-free cigarette smoke extract impaired endothelium-dependent vascular relaxation in rats via increased vascular oxidative stress

Cigarette smoking has been implicated in the initiation and progression of cardiovascular disorders and atherosclerosis. Here, we examined the effects of nicotine-free cigarette smoke extract (CSE) on the regulation of cardiovascular function. Rats were subcutaneously administered PBS or nicotine-free CSE at 0.05 to 1.5 mL/day per rat for 4 weeks. Blood pressure, cardiac function, and vascular responsiveness were measured at 4 weeks after administration. Furthermore, acute effects of nicotine-free CSE were also studied in the aorta isolated from normal rats. Blood pressure and left ventricular systolic pressure (LVSP) were significantly increased in the nicotine-free CSE-administered rats, but heart rate, dP/dt(max), and dP/dt(min) were not affected. Endothelium-dependent relaxation by acetylcholine (ACh) in the nicotine-free CSE-treated rats was significantly attenuated compared to PBS-treated rats, but endothelium-independent relaxation by sodium nitroprusside (SNP) did not differ. Pretreatment with superoxide dismutase restored the attenuated ACh-induced relaxation. Contractions by phenylephrine, angiotensin II, and KCl did not differ between two groups. In vitro acute nicotine-free CSE treatment did not alter the response to ACh or SNP. These results suggest that chronic nicotine-free CSE administration impairs endothelial function by increased production of superoxide derived from the vascular wall components other than smooth muscles and induces slight hypertension accompanied with LVSP elevation.

Nitric oxide-mediated blood flow regulation as affected by smoking and nicotine

Cigarette smoking is a major risk factor for atherosclerosis, cerebral and coronary vascular diseases, hypertension, and diabetes mellitus. Chronic smoking impairs endothelial function by decreasing the formation of nitric oxide and increasing the degradation of nitric oxide via generation of oxygen free radicals. Nitric oxide liberated from efferent nitrergic nerves is also involved in vasodilatation, increased regional blood flow, and hypotension that are impaired through nitric oxide sequestering by smoking-induced factors. Influence of smoking on nitric oxide-induced blood flow regulation is not necessarily the same in all organs and tissues. However, human studies are limited mainly to the forearm blood flow measurement that assesses endothelial function under basal and stimulated conditions and also determination of penile tumescence and erection in response to endothelial and neuronal nitric oxide. Therefore, information about blood flow regulation in other organs, such as the brain and placenta, has been provided mainly from studies on experimental animals. Nicotine, a major constituent of cigarette smoke, acutely dilates cerebral arteries and arterioles through nitric oxide liberated from nitrergic neurons, but chronically interferes with endothelial function in various vasculatures, both being noted in studies on experimental animals. Cigarette smoke constituents other than nicotine also have some vascular actions. Not only active but also passive smoking is undoubtedly harmful for both the smokers themselves and their neighbors, who should bear in mind that they can face serious diseases in the future, which may result in lengthy hospitalization, and a shortened lifespan.

The acute effects of smokeless tobacco on central aortic blood pressure and wave reflection characteristics

The main objectives of this study were to examine the acute effect of a single dose of smokeless tobacco (ST) on central aortic blood pressure and wave reflection characteristics. Fifteen apparently healthy male subjects (aged 30.6 ± 6.2 y) were given a 2.5 g oral dose of ST after baseline measurements were recorded. Pulse wave analysis using radial artery applanation tonometry was performed in triplicate at baseline (0 min) and at 10-min intervals during (10, 20 and 30 min) and after (40, 50 and 60 min) ST use. An acute dose of ST was associated with a significant increase in heart rate (HR), central aortic systolic and diastolic blood pressure, peripheral brachial systolic and diastolic blood pressure, and aortic augmentation index normalized to a fixed heart rate of 75 bpm (AIx@75). Furthermore, ejection duration and round trip travel time of the reflected pressure wave (Δt(p)) were significantly decreased as a result of one time ST use. As a result of changes in aortic pressure wave reflection characteristics, there was a significant increase in wasted left ventricular pressure energy (LVE(w)) and the tension-time index (TTI) as a result of ST use. In conclusion, one time use of ST elicits significant transient increases in HR, central aortic pressures, AIx@75, the TTI and LVE(w). Chronic users subjected to decades of elevated central pressures and left ventricular work may have an increased cardiovascular risk as central aortic pressures are even more strongly related to cardiovascular outcomes than peripheral blood pressures.

Exercise training restores impaired dilator responses of cerebral arterioles during chronic exposure to nicotine

Our goal was to determine whether exercise training (ExT) alleviates impaired nitric oxide synthase (NOS)-dependent dilation of pial arterioles during chronic exposure to nicotine. We measured dilation of cerebral (pial) arterioles in sedentary and exercised control and nicotine-treated (2 mg·kg(-1)·day(-1) for 4 wk via an osmotic minipump) rats to an endothelial NOS (eNOS)-dependent (ADP), a neuronal NOS (nNOS)-dependent [N-methyl-D-aspartic acid (NMDA)], and a NOS-independent (nitroglycerin) agonist. In addition, we harvested brain tissue from sedentary and exercised control and nicotine-treated rats to measure the production of superoxide anion and measured superoxide dismutase-1 (SOD-1) protein in cerebral microvessels using Western blot. We found that eNOS-and nNOS-dependent, but not NOS-independent, vasodilation was impaired in nicotine-treated compared with control rats. In addition, the production of superoxide anion (lucigenin chemiluminescence) was increased, and SOD-1 protein decreased, in rats treated with nicotine compared with control rats. Further, although ExT did not significantly affect eNOS- or nNOS-dependent vasodilation in control rats, ExT restored impaired eNOS- and nNOS-dependent responses in nicotine-treated rats. In addition, the increase in superoxide anion production observed in nicotine-treated rats was reduced by ExT, and SOD-1 protein was increased in nicotine-treated rats by ExT. We suggest that ExT restores impaired NOS-dependent dilation of pial arterioles during chronic exposure to nicotine by a mechanism related to the formation of superoxide anion.

Melatonin reverses urinary system and aorta damage in the rat due to chronic nicotine administration

We have evaluated the changes in contractile activity and oxidant damage of corpus cavernosum, urinary bladder, kidney and aorta after chronic nicotine administration in rats. The effects of melatonin on these parameters were investigated also. Male Wistar albino rats were injected intraperitoneally with nicotine hydrogen bitartrate (0.6 mg kg−1 daily for 21 days) or saline. Melatonin (10 mg kg−1, i.p.) was administered either alone or with nicotine injections. Corpus cavernosum, bladder and aorta were used for contractility studies, or stored with kidneys for the measurement of malondialdehyde and glutathione levels. Corpus cavernosum, bladder, and aorta samples were examined histologically and the extent of microscopic tissue damage was scored. In the nicotine-treated group, the contraction of corpus cavernosum, bladder and aorta samples and the relaxation of corporeal and aorta tissues decreased significantly compared with controls. However, melatonin treatment restored these responses. In the nicotine-treated group, there was a significant increase in the malondialdehyde levels of the corporeal tissue, bladder, kidney and aorta, with marked reductions in glutathione levels compared with controls. Melatonin treatment reversed these effects also. Melatonin administration to nicotine-treated animals caused a marked reduction in the microscopic damage of the tissues compared with those of the untreated group. In this study, nicotine-induced dysfunction of the corpus cavernosum, bladder and aorta of rats was reversed by melatonin treatment. Moreover, melatonin, as an antioxidant, abolished elevation in lipid peroxidation products, and reduction in the endogenous antioxidant glutathione, and protected the tissues from severe damage due to nicotine exposure.

Evidence for the involvement of matrix metalloproteinases in the cardiovascular effects produced by nicotine

Nicotine plays a role in smoking-associated cardiovascular diseases, and may upregulate matrix metalloproteinase (MMP)-2 and MMP-9. We examined whether nicotine induces the release of MMP-2 and MMP-9 by rat smooth muscle cells (SMC), and whether doxycycline (non-selective MMP inhibitor) inhibits the vascular effects produced by nicotine. SMC were incubated with nicotine 0, 50, and 150 nM for 48 h. MMP-2 and MMP-9 levels in the cell supernatants were determined by gelatin zymography. The acute changes in mean arterial pressure caused by nicotine 2 micromol/kg (or saline) were assessed in rats pretreated with doxycycline (or saline). We also examined whether doxcycline (30 mg/Kg, i.p., daily) modifies the effects of nicotine (10mg/kg/day; 4 weeks) on the endothelium-dependent relaxations of rat aortic rings. Aortic MMP-2 levels were assessed by gelatin zymography. Aortic gelatinolytic activity was assessed using a gelatinolytic activity kit. MMP-2 and MMP-9 levels increased in the supernatant of SMC cells incubated with nicotine 150 nM (P<0.05) but not with 50 nM. Nicotine (2 micromol/kg) produced lower increases in the mean arterial pressure in rats pretreated with doxycycline than those found in rats pretreated with saline (26+/-4 vs. 37+/-4 mm Hg, respectively; P<0.05). Nicotine impaired of the endothelium-dependent responses to acetylcholine, and treatment with doxycycline increased the potency (pD2) by approximately 25% (P<0.05). While we found no significant differences in aortic MMP-2 levels, nicotine significantly increased gelatinolytic activity (P<0.05). These findings suggest that nicotine produces cardiovascular effects involving MMPs. It is possible that MMPs inhibition may counteract the effects produced by nicotine.

Effects of exogenous selenium on nicotine-induced oxidative stress in rats

The effect of two different doses of selenium [1 and 50 microg selenium/100 g body weight (wt)] on nicotine-induced oxidative damage in liver was investigated in experimental rats. Male albino rats were maintained for 60 days as follows: (1) control group (normal diet), (2) nicotine group (0.6 mg/kg body wt)/day, (3) high-dose selenium (50 microg/100 g body wt)/day, (4) high-dose selenium (50 microg/100 g body wt) + nicotine (0.6 mg/kg body wt)/day, (5) low-dose selenium (1 microg/100 g body wt)/day, and (6) low-dose selenium (1 microg/100 g body wt) + nicotine (0.6 mg/kg body wt)/day. Nicotine administration caused a decrease in the activity of antioxidant enzymes, an increase in the concentration of lipid peroxidation products and protein carbonyls and an increase in the activity of nitric oxide synthase compared to the control group. Coadministration of nicotine and selenium reduced the concentration of lipid peroxidation products and increased the activity of antioxidant enzymes compared to the nicotine group. Selenium also enhanced the metabolism of nicotine. The antioxidant effect was more significant in the group administered a low dose of selenium.

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

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

Vascular responses to manual PC6 acupuncture in nonsmokers and smokers assessed by the second derivative of the finger photoplethysmogram waveform

BACKGROUND

Smoking is reported to increase arterial stiffness. Indices obtained from the second derivative of digital volume pulse (SDDVP) waveform have been proposed to characterize vascular aging and arterial rigidity. PC6 (Neiguan) is a traditional acupoint in each forearm that has been shown to modify cardiovascular functioning.

OBJECTIVE

To investigate the acute effects of manual needling with PC6 on SDDVP indices in healthy chronic smoker and nonsmoker subjects.

SUBJECTS AND METHODS

Aging index (AI) was defined as (b - c - d - e)/a, B:A was calculated as the ratio of the absolute value for the height of the b wave (B) to that of the a wave (A), and D:A was calculated as the ratio of the absolute value for the height of the d wave (D) to that of the a wave (A). These indices derived of the wave components of SDDVP of healthy nonsmokers (n=40; 28.3+/-3.0 years old) vs. chronic smokers (n=30; 29.9+/-2.9 years old) were compared. The digital volume pulse (DVP) was obtained by measuring infrared light transmission through the finger. Of each subject, a DVP registration 20 minutes long was obtained. PC6 was stimulated unilaterally by manual needling for 5 minutes (1-6 minutes). SDDVP indices were compared in each subject in pre- vs. post-acupuncture periods (30 seconds vs. 18 minutes, respectively).

RESULTS

At baseline, we found significant difference in B:A between nonsmokers and smokers. Comparing pre- vs. post-acupuncture periods, B:A and D:A did not show significant differences among nonsmokers, but B:A improved significantly in smokers and AI improved significantly in both nonsmokers and smokers.

CONCLUSION

These findings suggest that manual needling with PC6 could revert some of the deleterious effects on vascular functioning produced by chronic cigarette smoking.

Nicotine: a pro-angiogenic factor

Angiogenesis, the formation of new blood vessels from pre-existing ones, is regulated by the balance between angiogenic activating and inhibiting factors. Recent evidence indicates that nicotine, an alkaloid compound, presents pro-angiogenic effects in certain concentrations. Nicotine-induced angiogenesis results from the stimulation of non-neuronal nicotinic acetylcholinergic receptors (particularly alpha 7-NAChR subtype) and involves growth factor secretion and activation of intracellular signalling pathways. Although nicotine is a constituent of tobacco smoke, its contribution towards pathophysiology of several tobacco-associated pathologies is controversial. Nowadays, nicotine is used in tobacco smoke cessation programs, but, again, its use is still a matter of discordance regarding cardiovascular morbidity. Nevertheless, given the established effects of nicotine-induced angiogenesis, this alkaloid might be of therapeutic value in situations of inefficient angiogenesis, such as peripheral vascular impairment and tissue ischemia. Conversely, blockade of nicotine pathway can be helpful in complications exhibiting excessive angiogenesis, namely in diabetic retinopathy and nephropathy or neoplasia. Knowing that nicotine is involved in many angiogenic-associated disorders with a high prevalence in the western world, and that this alkaloid widely used in smoke cessation programs, elucidation of the action of nicotine on the vascularization process is of utmost importance. The current paper provides an overview of the effects of nicotine in angiogenesis.

Nitric oxide synthase-dependent responses of the basilar artery during acute infusion of nicotine

INTRODUCTION

Our goals were to determine whether acute exposure to nicotine alters nitric oxide synthase (NOS)-dependent responses of the basilar artery and to identify a potential role for activation of NAD(P)H oxidase in nicotine-induced impairment in NOS-dependent responses of the basilar artery.

METHODS

We measured in vivo diameter of the basilar artery in response to NOS-dependent (acetylcholine) and NOS-independent (nitroglycerin) agonists before and during an acute infusion of nicotine (2 microg/kg/min intravenously for 30 min followed by a maintenance dose of 0.35 microg/kg/min). In addition, we measured superoxide anion production (lucigenin chemiluminescence) by the basilar artery in response to nicotine in the absence or presence of apocynin.

RESULTS

We found that NOS-dependent, but not NOS-independent, vasodilation was impaired during infusion of nicotine. In addition, treatment of the basilar artery with apocynin (100 microM, 30 min prior to infusion of nicotine) prevented nicotine-induced impairment in NOS-dependent vasodilation. Further, the production of superoxide anion was increased in the basilar artery by nicotine, and this increase could be inhibited by apocynin.

DISCUSSION

Our findings suggest that acute exposure to nicotine impairs NOS-dependent dilation of the basilar artery by a mechanism that appears to be related to the release of superoxide anion. A possible source of superoxide may be via the activation of NAD(P)H oxidase.

Smoking and smoking cessation -- the relationship between cardiovascular disease and lipoprotein metabolism: a review

Cigarette smoking is generally accepted as the most preventable cause of death in the United States today. Individuals who smoke experience a wide range of physiologic side effects that increase the risk of cardiovascular disease (CVD), including insulin resistance, elevated catecholamine levels which contribute to an elevated heart rate and blood pressure, and hypercholesterolemia. The link between hypercholesterolemia and cardiovascular disease has been extensively researched and is undeniable. What is more, this link is strengthened in smokers as cigarette smoking is known to increase total cholesterol (TC), triglycerides (TG), and low-density lipoprotein (LDL), while acting to decrease the cardio-protective high-density lipoprotein (HDL). Alterations in the enzymes that control lipid transport may be a key underlying mechanism contributing to these health destroying effects. This review examines the current literature related to: (1) smoking, lipoproteins, and lipid-related enzymes; (2) the impact of nicotine, carbon monoxide and free radicals on physiologic parameters related to health; and (3) metabolic issues involving smoking cessation and nicotine replacement therapy.

Cigarette smoking decreases neurotrophin-3 expression in rat hippocampus after transient forebrain ischemia

Stroke is a common cause of death and severe disability among adults in developed countries. Cigarette smoking adversely affects human health in many ways and is considered to be a risk factor for a stroke. However, the mechanism that determines the relative importance of neurotrophins in this process remains unclear. To study the effect of chronic cigarette smoking on ischemic stroke, in situ hybridization and immunohistochemistry were employed to detect the mRNA and protein expression of neurotrophin-3 (NT-3), respectively, which is thought to play a critical role in protection against neuronal death in brain ischemia. Rats, with or without chronic cigarette smoking, were subjected to 20 min of transient forebrain ischemia. Distribution and quantification of mRNA and protein of NT-3 in the whole hippocampus and the cell death in the hippocampal CA1-CA3 regions were determined in these rats. Experimental results show that chronic cigarette smoking produces a significantly delay and persistent down-regulation of ischemia-induced NT-3 mRNA and protein changes at 6-24h post-ischemia, and seemingly increases neuron death 7 days after reperfusion. These experimental results indicate that by influencing NT-3 expression, directly or indirectly, chronic cigarette smoking has a potentially harmful effect when acute brain ischemia attacks.

Regulation of nicotine-induced apoptosis of pulmonary artery endothelial cells by treatment of N-acetylcysteine and vitamin E

This study investigated the frequency of apoptosis in rat pulmonary artery endothelial cells after intraperitoneal nicotine injection, examining the roles of the inflammatory markers myeloperoxidase (MPO), tumour necrosis factor alpha (TNF-alpha), and vascular endothelial growth factor (VEGF) in nicotine-induced vascular damage and the protective effects of two known antioxidant agents, N-acetylcysteine (NAC) and vitamin E. Female Wistar rats were divided into four groups, each composed of nine rats: negative control group, positive control group, NAC-treated group (500 mg/kg), and vitamin E-treated group (500 mg/kg). Nicotine was intraperitoneally injected at a dosage of 0.6 mg/kg for 21 days. Following nicotine injection, the antioxidants were administered orally; treatment was continued until the rats were killed. Lung tissue samples were stained with hematoxylin-eosin (H&E) for histopathological assessments. Apoptosis level in endothelial cells was determined by using TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling) method. Staining of cytoplasmic TNF-alpha and VEGF in endothelial cells, and perivascular MPO activity were evaluated by immunohistochemistry. The treatments with NAC and vitamin E significantly reduced the rate of nicotine-induced endothelial cell apoptosis. NAC and vitamin E significantly reduced the increases in the local production of TNF-alpha and VEGF, and perivascular MPO activity. This findings suggest that NAC can be as effective as vitamin E in protecting against nicotine-induced endothelial cell apoptosis.

Effects of smoking cessation, acute re-exposure and nicotine replacement in smokers on AIR inhaled insulin pharmacokinetics and glucodynamics

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

* Only one other study (Becker et al.) has reported on the influence of smoking cessation and smoking resumption on inhaled insulin pharmacokinetics and glucodynamics, concluding that the rapid changes associated with smoking resumption carry the risk for hypoglycaemia and thus should not be used by active smokers.

WHAT THIS STUDY ADDS

* This is the first euglycaemic clamp study on the impact of smoking cessation, acute smoking re-exposure and nicotine replacement on AIR((R)) inhaled insulin pharmacokinetics and glucodynamics. * We demonstrate clinically and statistically significant shifts in glucodynamic response to acute re-exposure to a single cigarette, leading us to conclude that active smokers should be advised against inhaled insulin therapy until smoking abstinence is stable. * Additionally, these results are also the first to demonstrate an apparent independent effect of nicotine replacement therapy on insulin exposure and glucodynamic response.

AIMS

To explore the effects of smoking cessation and acute smoking re-exposure on the pharmacokinetic (PK) and glucodynamic (GD) profiles of AIR inhaled insulin (AIR Insulin) with or without nicotine replacement therapy (NRT).

METHODS

Nondiabetic smokers (n = 24) with normal pulmonary function completed a two-phase (four-period), open-label, randomized euglycaemic clamp study. During the initial study phase, subjects underwent glucose clamps following AIR Insulin dosing, shortly after smoking, 8-12 h after smoking, or following subcutaneous insulin lispro shortly after smoking. AIR Insulin PK and GD were again assessed during and after a 4-week smoking-cessation period with or without NRT. In the last study period, subjects smoked one cigarette shortly before final AIR Insulin dosing and glucose clamp, to study the effect of acute smoking re-exposure on inhaled insulin PK and GD.

RESULTS

Compared with the preceding active smoking phase, the administration of AIR Insulin in nondiabetic subjects undergoing a 4-week period of smoking abstinence resulted in a decrease in PK and GD of approximately 25% (P = 0.008 for both), an effect which was greater in subjects using NRT. Following rechallenge with a single cigarette (without NRT), GD response to AIR Insulin increased significantly (P = 0.006) towards precessation levels, relative to smoking abstinence. In subjects using NRT, however, the increase in GD was less pronounced.

CONCLUSION

Smoking, smoking cessation and acute re-exposure with a single cigarette are associated with clinically significant alterations in AIR Insulin pharmacokinetics and glucodynamics. AIR Insulin should not be used by smokers or those at risk for recidivism.

Acute infusion of nicotine impairs nNOS-dependent reactivity of cerebral arterioles via an increase in oxidative stress

Our goals were to determine whether acute exposure to nicotine alters neuronal nitric oxide synthase (nNOS)-dependent reactivity of cerebral arterioles and to identify a potential role for oxidative stress in nicotine-induced impairment in nNOS-dependent responses of cerebral arterioles. We measured in vivo diameter of cerebral arterioles to nNOS-dependent (N-methyl-d-aspartate and kainate) and -independent (nitroglycerin) agonists before and during acute treatment with nicotine. We found that nNOS-dependent, but not -independent, vasodilatation was impaired during treatment with nicotine. In addition, treatment of the cerebral microcirculation with tempol (1 h before infusion of nicotine) prevented nicotine-induced impairment in nNOS-dependent vasodilatation. Furthermore, the production of superoxide anion (lucigenin chemiluminescence) was increased in parietal cortex tissue of rats by treatment with nicotine, and this increase in superoxide anion production could be inhibited by tempol. Our findings suggest that acute exposure to nicotine impairs nNOS-dependent dilatation of cerebral arterioles by a mechanism that appears to be related to the formation of superoxide anion.

Cigarette smoking as a risk factor for atherosclerosis and renal disease: novel pathogenic insights

Cigarette smoking is the major cause of preventable morbidity and mortality in the United States. It is a major risk factor for atherosclerotic vascular disease and recently was identified as an important risk factor in the progression of chronic kidney disease. Several compounds in cigarette smoke, including nicotine and reactive aldehydes (eg, acrolein), have been implicated as mediators of endothelial dysfunction and atherosclerosis in smokers. In addition, studies have demonstrated that nicotine induces endothelial dysfunction in humans and accelerates atherosclerosis in animals. Large clinical trials have suggested that cigarette smoking is a risk factor for progression of chronic kidney disease in diabetics and nondiabetics, and in polycystic kidney disease, lupus nephritis, and IgA nephropathy. Recent studies suggest that nicotine has powerful mitogenic effects and induces extracellular matrix production in human mesangial cells via reactive oxygen species generation. These effects of nicotine may play a major role in the pathogenic mechanisms that mediate the deleterious effects of smoking in renal disease.

Nicotine-induced activation of AMP-activated protein kinase inhibits fatty acid synthase in 3T3L1 adipocytes: a role for oxidant stress

Recent studies suggest that the AMP-activated protein kinase (AMPK) acts as a major energy sensor and regulator in adipose tissues. The objective of this study was to investigate the role of AMPK in nicotine-induced lipogenesis and lipolysis in 3T3L1 adipocytes. Exposure of 3T3L1 adipocytes to smoking-related concentrations of nicotine increased lipolysis and inhibited fatty acid synthase (FAS) activity in a time- and dose-dependent manner. The effects of nicotine on FAS activity were accompanied by phosphorylation of both AMPK (Thr(172)) and acetyl-CoA carboxylase (ACC; Ser(79)). Nicotine-induced AMPK phosphorylation appeared to be mediated by reactive oxygen species based on the finding that nicotine significantly increased superoxide anions and 3-nitrotyrosine-positive proteins, exogenous peroxynitrite (ONOO(-)) mimicked the effects of nicotine on AMPK, and N-acetylcysteine (NAC) abolished nicotine-enhanced AMPK phosphorylation. Inhibition of AMPK using either pharmacologic (insulin, compound C) or genetic means (overexpression of dominant negative AMPK; AMPK-DN) abolished FAS inhibition induced by nicotine or ONOO(-). Conversely, activation of AMPK by pharmacologic (nicotine, ONOO(-), metformin, and AICAR) or genetic (overexpression of constitutively active AMPK) means inhibited FAS activity. Notably, AMPK activation increased threonine phosphorylation of FAS, and this effect was blocked by adenovirus encoding dominant negative AMPK. Finally, AMPK-dependent FAS phosphorylation was confirmed by (32)P incorporation into FAS in adipocytes. Taken together, our results strongly suggest that nicotine, via ONOO(-) activates AMPK, resulting in enhanced threonine phosphorylation and consequent inhibition of FAS.

Direct effects of nicotine on contractility of the uterine artery in pregnancy

Recent studies indicate that smoking/nicotine increases maternal blood pressure and decrease in uterine blood flow in pregnancy. However, the mechanisms are not fully understood. The present study was designed to test the hypothesis that nicotine exposure decreases endothelium-dependent relaxation and increases vascular contractility of the uterine artery in pregnancy. Uterine arteries were isolated from near-term ( approximately 140 days gestation) pregnant ewes. Arteries were subjected to acute (20 min) or chronic (48 h) nicotine treatment, and agonist-induced contractions and relaxations were measured in tissue bath. Endothelial eNOS was detected by immunohistochemistry in situ in arteries and by Western blotting in isolated endothelial cells. Chronic nicotine treatment produced a concentration-dependent increase in alpha(1)-adrenoceptor agonist phenylephrine-induced contractions. In contrast, the acute treatment showed no effect. Inhibition of eNOS with N(G)-nitro-L-arginine (L-NNA) significantly increased phenylephrine-induced contractions, which was abolished in uterine arteries after chronic nicotine treatment. In the presence of L-NNA, there was no significant difference in phenylephrine-induced contractions between control and nicotine-treated vessels. Chronic, but not acute, nicotine treatment significantly attenuated the calcium ionophore A23187-induced relaxations. Unlike A23187, the endothelium-independent relaxation mediated by sodium nitroprusside was not affected by nicotine. Endothelial eNOS protein levels and the phosphorylation levels of eNOS(Ser1179) were significantly decreased in nicotine-treated uterine arteries. The results suggest that nicotine impairs uterine vascular function in pregnancy, which may lead to an increased vascular resistance and a decrease in uterine blood flow.

Function of Kv1.5 channels and genetic variations of KCNA5 in patients with idiopathic pulmonary arterial hypertension

The pore-forming alpha-subunit, Kv1.5, forms functional voltage-gated K(+) (Kv) channels in human pulmonary artery smooth muscle cells (PASMC) and plays an important role in regulating membrane potential, vascular tone, and PASMC proliferation and apoptosis. Inhibited Kv channel expression and function have been implicated in PASMC from patients with idiopathic pulmonary arterial hypertension (IPAH). Here, we report that overexpression of the Kv1.5 channel gene (KCNA5) in human PASMC and other cell lines produced a 15-pS single channel current and a large whole cell current that was sensitive to 4-aminopyridine. Extracellular application of nicotine, bepridil, correolide, and endothelin-1 (ET-1) all significantly and reversibly reduced the Kv1.5 currents, while nicotine and bepridil also accelerated the inactivation kinetics of the currents. Furthermore, we sequenced KCNA5 from IPAH patients and identified 17 single-nucleotide polymorphisms (SNPs); 7 are novel SNPs. There are 12 SNPs in the upstream 5' region, 2 of which may alter transcription factor binding sites in the promoter, 2 nonsynonymous SNPs in the coding region, 2 SNPs in the 3'-untranslated region, and 1 SNP in the 3'-flanking region. Two SNPs may correlate with the nitric oxide-mediated decrease in pulmonary arterial pressure. Allele frequency of two other SNPs in patients with a history of fenfluramine and phentermine use was significantly different from patients who have never taken the anorexigens. These results suggest that 1) Kv1.5 channels are modulated by various agonists (e.g., nicotine and ET-1); 2) novel SNPs in KCNA5 are present in IPAH patients; and 3) SNPs in the promoter and translated regions of KCNA5 may underlie the altered expression and/or function of Kv1.5 channels in PASMC from IPAH patients.

β-Glucan protects against chronic nicotine-induced oxidative damage in rat kidney and bladder

In this study, we investigated the protective effect of β-glucan against nicotine induced oxidative damage in urinary bladder and kidney tissues. Wistar albino rats were injected i.p. with nicotine hydrogen bitartarate (0.6mg/kg daily for 21 days) or saline. β-Glucan (50mg/kg, p.o.) was administered alone or with nicotine injections for 21 days. After decapitation, the urinary bladder and kidney tissues were taken for the measurement of malondialdehyde (MDA) and glutathione (GSH) levels, and myeloperoxidase (MPO) activity. Tissue samples were also examined histologically. In serum samples MDA, GSH, BUN, creatinine, TNF-α levels and LDH activity were analyzed. Chronic nicotine administration caused a significant decrease in GSH levels and increases in MDA levels and MPO activity in kidney and bladder tissues, suggesting oxidative organ damage, which was also histologically verified. Furthermore, β-glucan restored the reduced GSH levels, while it significantly decreased MDA levels and MPO activity. Renal function tests, LDH and TNF-α levels, which were increased significantly due to nicotine administration, were decreased with β-glucan treatment. The present data suggest that β-glucan supplementation effectively counteracts the chronic nicotine toxicity and attenuates oxidative damage of bladder and kidney tissues possibly by its antioxidant effects.

Involvement of DDAH/ADMA/NOS pathway in nicotine-induced endothelial dysfunction

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase (NOS) inhibitor, is a key contributor for endothelial dysfunction. Decrease in activity of dimethylarginine dimethylaminohydrolase (DDAH), a major hydrolase of ADMA, causes accumulation of ADMA under cardiovascular abnormalities. The study was to determine whether nicotine-induced endothelial dysfunction is related to modulating DDAH/ADMA/NOS pathway. Four-week oral nicotine treatment (5 mg/kg/day) significantly increased the plasma level of ADMA and decreased aortic DDAH expression as well as impaired endothelial function in Sprague-Dawley rats. Similarly, the medium levels of both ADMA and lactate dehydrogenase were markedly elevated in umbilical vein endothelial cells (HUVECs) treated with nicotine (10 microM) for 48 h. Nicotine-induced endothelial damages were markedly attenuated by L-arginine or overexpression of DDAH-II. Nicotine greatly downregulated both mRNA and protein levels of DDAH-II, and decreased DDAH activity in HUVECs. HUVECs express alpha7 nicotinic acetylcholine receptor (alpha7 nAChR), whose antagonists could block these effects of nicotine mentioned above. Intracellular Ca2+ chelator did not affect nicotine-induced decrease in DDAH-II mRNA level. In conclusion, nicotine modulates DDAH/ADMA/NOS pathway of endothelial cell via activation of alpha7 nAChR, which may be involved in endothelial dysfunction associated to smoking.

The Protective Effect of Captopril on Nicotine-Induced Endothelial Dysfunction in Rat

This study was designed to examine the in vivo and in vitro effects of captopril, an angiotensin-converting enzyme inhibitor, on nicotine-induced endothelial dysfunction in rats. Endothelial dysfunction was induced by exposing isolated rat mesenteric arteries to nicotine (0.01, 0.1, or 1 mM) for 24 hr using an organ culture system, or by treating rats with nicotine (2 mg/kg/day, intraperitoneally) for 4 weeks. The protective effects of captopril were tested by exposing isolated mesenteric arteries to captopril (0.01, 0.03, or 0.1 mM) + nicotine (0.1 mM) for 24 hr, or by treating rats with captopril (3 mg/kg/day, intravenously) + nicotine (2 mg/kg/day, intraperitoneally) for 4 weeks. Exposure of the isolated mesenteric arteries to nicotine induced a significant concentration -dependent inhibition of endothelium-dependent relaxation. Co-culture of segments of mesenteric artery with captopril (0.03 or 0.1 mM) attenuated the nicotine-induced impairment of vasorelaxation in a dose-dependent manner. Administration of nicotine to rats for 4 weeks significantly impaired endothelium-dependent relaxation compared with control rats. This impairment was accompanied by a reduction in nitrite/nitrate, nitric oxide (NO) synthase (NOS), and superoxide dismutase (SOD) activities in the serum and aorta. Chronic captopril treatment not only improved the impairment of endothelium-dependent relaxation, but also prevented the reduction of nitrite/nitrate contents and of NOS and SOD activities in the serum and aorta. However, there were no significant differences in serum angiotensin-converting enzyme activity among the three groups. These results indicate that captopril can be used to attenuate nicotine-induced endothelial dysfunction, an effect that may be related not only to antioxidation, but also to enhancing NO production by preventing the decrease in NOS.

Evidence for the role of nitric oxide in antiapoptotic and genotoxic effect of nicotine on human gingival fibroblasts

Resistance to apoptosis is essential for cancer survival and plays a critical role in carcinogenesis. Growing evidence suggests that nicotine can act as a tumor promoter, impairing apoptotic process in certain types of human cancer cell lines. Our previous study revealed in human gingival fibroblasts (HGFs) a concomitant antiapoptotic and genotoxic effect of nicotine, manifested by the attenuation of staurosporine (STP)-induced apoptosis and the increase of micronucleus frequency. The present report provides evidence that nitric oxide (NO) is critically involved in these actions. In vitro treatment with sodium nitroprusside as NO donor showed that NO produced similar effects as those observed with nicotine: it caused DNA damage and partially prevented apoptosis induced by staurosporine. Exposure of HGFs to nicotine, at concentrations similar to those found in the blood of habitual smokers, leads to the production of NO associated with the induction of inducible nitric oxide synthase (iNOS) expression. Experiments using an inhibitor of iNOS, N-monomethyl-L-arginine (NMA), together with nicotine confirmed the involvement of NO in the drug action, abrogating completely cell death and a good part of the genotoxicity. Finally, we show by different approaches that the inhibition of cell death by nicotine through NO release is related to modulation of caspase-1 activation.

Nicotine effect on cardiovascular system and ion channels

Smoking is a leading cause of cardiovascular disease, hypertension, myocardial infarction, and stroke. Nicotine is one of the components of cigarette smoke. Nicotine effects on the cardiovascular system reflect the activity of the nicotine receptors centrally and on peripheral autonomic ganglia. It has been found that cigarette smoke extract-induced contraction of porcine coronary arteries is related to superoxide anion-mediated degradation of nitric oxide. Treatment of rabbit aortas with an oxygen free radicals scavenger attenuated cigarette smoke impairment of arterial relaxation. Treatment of smokers with vitamin C, an antioxidant, improved impaired endothelium-dependent reactivity of large peripheral arteries. Thus it appears that chronic smoking and acute exposure to cigarette smoke extract may alter endothelium-dependent reactivity via the production of oxygen derived free radicals. This review discusses the effects of nicotine on resistance arterioles, compliance arteries, smooth muscle cells, and ion channels in the cardiovascular system. We discuss studies performed on humans, nicotine-exposed animals, and cell cultures yielding varying and inconsistent results that may be due to differences in experimental design, species, and the dose of exposure. Nicotine exposure appears to induce a combination of free radical production, vascular wall adhesion, and a reduction of fibrinolytic activity in the plasma.

Nicotine inhibits large conductance Ca(2+)-activated K(+) channels and the NO/-cGMP signaling pathway in cultured human endothelial cells

OBJECTIVE

The effects of nicotine on endothelium-dependent vasorelaxation mediated by nitric oxide (NO) are controversial. Since endothelial NO synthesis has been shown to depend on the activity of large conductance Ca(2 + )-activated K(+) channels (BK(Ca)), the present study investigated whether nicotine alters BK(Ca) single channel activity induced by the K(+) channel opener NS1619, and to examine a possible interaction with the endothelial NO generation.

DESIGN

The patch-clamp technique was used to examine the BK(Ca) activity. NO production was measured indirectly using a [(3)H]-cGMP-radioimmunoassay. All experiments were performed using cultured endothelial cells derived from human umbilical cord veins.

RESULTS

The BK(Ca) opener NS1619 (10 micromol/l) significantly increased the BK(Ca) open-state probability (NPo) from 0.011+/-0.007 (control) to 0.052+/-0.019. Co-perfusion with nicotine (1 micromol/l) significantly decreased NS1619 induced NPo (n = 14, p < 0.05). Intracellular cGMP levels were significantly increased, if cells were stimulated with NS1619 (+ 225%; n = 10, p < 0.05), which was blocked by Nicotine (1 micromol/l).

CONCLUSIONS

The results of the present study demonstrate that BK(Ca) activation by NS1619 plays an important role in the regulation of the NO-/cGMP-signaling-pathway. Endothelial dysfunction caused by nicotine may be connected with a decrease in BK(Ca)-activity.

Inhibition of NADPH oxidase improves impaired reactivity of pial arterioles during chronic exposure to nicotine

Our goals were to determine whether chronic exposure to nicotine alters nitric oxide synthase (NOS)-dependent reactivity of cerebral (pial) arterioles and to identify a potential role for NADPH oxidase in impaired NOS-dependent responses during chronic exposure to nicotine. We measured in vivo diameter of pial arterioles to NOS-dependent (acetylcholine and ADP) and -independent (nitroglycerin) agonists in saline-treated rats and rats chronically treated with nicotine (2 mg.kg(-1).day(-1) for 2 wk via an osmotic minipump). We found that NOS-dependent, but not -independent, vasodilatation was impaired in nicotine-treated compared with saline-treated rats. In addition, the production of superoxide anion (lucigenin chemiluminescence) was increased in rats treated with nicotine compared with saline-treated rats. Furthermore, using Western blot analysis, we found that chronic exposure to nicotine increased p47phox protein in the parietal cortex. Finally, we found that apocynin (40 mg.kg(-1).day(-1)) in the drinking water to inhibit NADPH oxidase alleviated impaired NOS-dependent cerebral vasodilatation in nicotine treated rats but did not alter NOS-dependent responses in saline treated rats and did not alter NOS-independent reactivity in saline- or nicotine-treated rats. These findings suggest that chronic exposure to nicotine impairs NOS-dependent dilatation of pial arterioles by a mechanism that appears to be related to the formation of superoxide anion via activation of NADPH oxidase.

Mediation of the Effect of Nicotine on Kir6.1 Channels by Superoxide Anion Production

KATP channels are a complex of regulatory sulfonylurea receptor subunits and the pore-forming inward rectifiers such as Kir6.1. Using the whole-cell patch-clamp technique, we investigated the interaction of nicotine with the Kir6.1 subunit as well as the underlying mechanism. Stable expression of Kir6.1 in HEK-293 cells yielded a detectable inward rectifier KATP current. This inward current was significantly inhibited by PNU-37883A and by a specific anti-Kir6.1 antibody. Nicotine at 30 and 100 microM increased Kir6.1 currents by 42 +/- 11.8% and 26.2 +/- 14.6%, respectively (n = 4-6, P < 0.05). In contrast, nicotine at 1-3 mM inhibited Kir6.1 currents (P < 0.05). Nicotine at 100 microM increased the production of superoxide anion (O2) by 20.3 +/- 5.7%, whereas at 1 mM it significantly decreased the production of O2 by 37.7 +/- 4.3%. Coapplication of hypoxanthine (HX) and xanthine oxidase (XO) to the transfected HEK-293 cells resulted in a significant and reproducible increase in Kir6.1 currents (P < 0.05). The stimulatory effect of HX/XO on Kir6.1 current was abolished by tempol, a scavenger of O2. Tempol also abolished the stimulatory effect of 30 muM nicotine on Kir6.1 currents. In conclusion, nicotine stimulates Kir6.1 channel at least in part through the production of O2.

Taurine treatment protects against chronic nicotine-induced oxidative changes

Experiments have shown that chronic nicotine administration caused oxidative damage in various organs by increasing lipid peroxidation products and decreasing the activity of endogenous antioxidants. The aim of this study was to investigate the effects of taurine treatment on nicotine-induced oxidative changes in rat thoracic aorta and heart and to explore the possible mechanisms of action. Male Wistar albino rats (200-250 g) were injected with nicotine hydrogen bitartrate (0.6 mg/kg; i.p.) or saline for 21 days. Taurine was administered (50 mg/kg; i.p.) alone or along with nicotine injections. After decapitation, the thoracic aorta and heart tissues were excised. The aorta was used for in vitro contractility studies or stored along with the heart samples for the measurement of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen content. Tissue samples were also examined histologically. Serum samples were stored for the measurement of MDA, GSH and lactate dehydrogenase (LDH) activity. Chronic nicotine treatment impaired both the contraction and relaxation responses of the aortic rings to phenylephrine and acetylcholine, respectively. It increased lipid peroxidation, MPO levels and tissue collagen content of both aorta and heart samples. Taurine supplementation to nicotine-treated animals reversed the contractile dysfunction and restored the endogenous GSH levels and decreased high lipid peroxidation and MPO activities in both tissues. These data suggest that taurine supplementation effectively attenuates the oxidative damage because of chronic nicotine administration possibly by its antioxidant effects.

Iminium metabolite mechanism for nicotine toxicity and addiction: Oxidative stress and electron transfer

The mechanism of nicotine toxicity is not completely delineated. Considerable evidence points to involvement of oxidative stress (OS), reactive oxygen species, lipid peroxidation, DNA damage, and beneficial effect of antioxidants. Previously, a suggestion was advanced for participation of iminium metabolites which might operate, via electron transfer (ET) with redox cycling, to produce radical entities. The conjugated iminium functionality is one of the less well-known ET types. The cationic metabolites arise from several routes, including oxidation of nicotine itself, and protonation of myosmine which originates from nornicotine via demethylation of nicotine. Reduction potentials, which are in the range amenable to ET in vivo, lend credence to the theoretical framework. An alternate metabolic route entails hydrolysis of nicotine iminium to an open-chain ketoamine that, in turn, undergoes nitrosation to form a toxic nitrosamine. Subsequently, the nitrosamine serves as a DNA alkylator which can also generate conjugated iminiums by attack on certain nitrogens of DNA bases. During the past 14 years, the hypothesis has enjoyed substantial support. Increasing evidence points to a role for OS in toxicity by nicotine entailing major body organs, including the lung, cardiovascular system, central nervous system, liver, kidney, testes, ovary, pancreas, and esophagus. The mechanism of addiction is also addressed based on interaction of iminiums with normal electron transport chains or electrical phenomena in the brain. The process might occur with or without participation of reactive oxygen species. Evidence indicates that free radicals are widely involved in cell signaling entailing redox processes in the categories of ion transport, neuromodulation, and transcription. Low levels of radicals appear to participate since high concentrations are associated with toxicity. Various possibilities for future work based on the hypothetical approach are addressed, including some that may have practical utility in relation to health improvement, toxicity, and addiction. Insight should be gained from computational studies on the energetics of electron uptake by metabolic iminiums, and on stability of the resultant delocalized radicals. Additional large-scale investigations of antioxidant effects are needed in order to resolve prior conflicting reports. Other proposals are based on interference with metabolism to iminiums and nitrosamines, and destruction of harmful metabolites. Since the iminium entities are proposed to play crucial, adverse roles, it would be worthwhile to explore them with regard to receptors, physiological activities, possible generation of reactive oxygen species, and effect of antioxidants.

The pathophysiology of cigarette smoking and cardiovascular disease: an update

Cigarette smoking (CS) continues to be a major health hazard, and it contributes significantly to cardiovascular morbidity and mortality. Cigarette smoking impacts all phases of atherosclerosis from endothelial dysfunction to acute clinical events, the latter being largely thrombotic. Both active and passive (environmental) cigarette smoke exposure predispose to cardiovascular events. Whether there is a distinct direct dose-dependent correlation between cigarette smoke exposure and risk is debatable, as some recent experimental clinical studies have shown a non-linear relation to cigarette smoke exposure. The exact toxic components of cigarette smoke and the mechanisms involved in CS-related cardiovascular dysfunction are largely unknown, but CS increases inflammation, thrombosis, and oxidation of low-density lipoprotein cholesterol. Recent experimental and clinical data support the hypothesis that cigarette smoke exposure increases oxidative stress as a potential mechanism for initiating cardiovascular dysfunction.