Antioxidants protect against increased risk of atherosclerosis induced by exposure to cigarette smoke: Histological and biochemical study

Background and objectivesThis study aimed to assess the dose-dependent effect of antioxidants in protection against cardiovascular changes induced by exposure to cigarette smoke.Design and settingThis was an experimental study, conducted at King Fahd Medical Research Center, King Abdulaziz University.Materials and methodsThis study was carried out on 57 male albino rats divided into nine groups. Rats of experimental groups were exposed to cigarette smoke from a total of 100 cigarettes per week for four weeks in a specially designed chamber. The antioxidants used (vitamin C, E, and B-carotene) were administrated at low (9, 7.2, and 0.27 mg/day) and high doses (18, 14.4, and 0.54 mg/day), respectively, through gastric feeding tubes. The lipid profile was estimated, and the carotids and heart were removed, weighed, and then processed, and the carotid intima-media thickness was measured. Statistical analysis was performed using the Statistical Package for Social Sciences.ResultsThe lipid profile was significantly improved in all groups treated with low or high doses of antioxidants after or during the exposure to cigarette smoke. Improvement was marked in the group treated with a high dose of antioxidants.The histological changes, as well as the intima-medial thickness of the carotid artery induced by exposure to cigarette smoke, have been improved by treatment with antioxidants (at either low or high doses), either after or during exposure to cigarette smoke. Improvement was marked in the group treated with a low dose of antioxidant. Treatment with antioxidants could not improve degenerated cardiac muscle fibers, while they could reduce the thickness of the branches of the coronary vessels.ConclusionThese results indicated that antioxidants ameliorated the cigarette smoke contribution to atherosclerosis, but they could not completely reverse the changes induced by cigarette smoke. Simultaneous intake of antioxidants could ameliorate the cigarette-smoke-induced changes apart from those of the heart.     

Antioxidant action of propolis on mouse lungs exposed to short-term cigarette smoke

Propolis is a natural product with antioxidant properties. In this study, we tested the efficacy of propolis against acute lung inflammation (ALI) caused by cigarette smoke (CS). C57BL6 male mice were exposed to CS and treated with propolis (200 mg/kg orally, CS+P) or only with propolis (P). A Control group treated with propolis was sham-smoked (Control+P). We collected the lungs for histological and biochemical analyses. We observed an increase in alveolar macrophages and neutrophils in the CS group compared with the Control+P. These counts reduced in the CS+P group compared to the CS group. The treatment with propolis normalized all biochemical parameters in the CS+P group compared with the CS group, including nitrite, myeloperoxidase level, antioxidant enzyme activities (superoxide dismutase, catalase and glutathione peroxidase), reduced glutathione/oxidized glutathione ratio and malondialdehyde. Additionally, TNF-α expression reduced in the CS+P group when compared with the CS group. These data imply a potential antioxidant and anti-inflammatory role for propolis with regard to ALI caused by CS in mice.     

Hydroperoxide and cigarette smoke induced effects on lung mechanics and glutathione status in rat isolated perfused and ventilated lungs

The effects of t-butylhydroperoxide (TBH) and cigarette smoke on lung mechanics (CDYN and RL) and glutathione status (GSH) were studied using an isolated perfused and ventilated rat lung preparation. TBH (200, 400, 1000 microM) infused via the pulmonary circulation caused a dose-related bronchoconstriction. The lung GSH-levels were also significantly reduced. Pretreatment of rats with diethylmaleate (DEM) potentiated the TBH elicited bronchoconstriction. DEM (1 mM) infused into the pulmonary circulation caused an almost complete depletion of GSH-content but no effects on lung mechanics were seen. Indomethacin (2.8 and 28 microM) infusion attenuated TBH (400 microM) induced bronchoconstriction. These findings suggest that the TBH induced bronchoconstriction is at least partly mediated via arachidonic acid metabolites. When TBH was administered intratracheally, weak and not dose-related bronchoconstriction was observed even though doses higher than those given intravascularly were used. However, the GSH-content of the lungs was markedly decreased. Cigarette smoke caused weak if any effects on lung mechanics but significantly decreased lung GSH-content.     

Nicotine-induced respiratory effects of cigarette smoke in dogs

We report that nicotine is responsible for both a blood-borne stimulation of the respiratory center and a direct effect on intrathoracic airway tone in dogs. We introduced cigarette smoke into the lungs of donor dogs and injected arterial blood obtained from them into the circulation of recipient dogs to show that a blood-borne material increased breathing and airway smooth muscle tone. Smoke from cigarettes containing 2.64 mg of nicotine was effective; that from cigarettes containing 0.42 mg of nicotine was not. Nicotine, in doses comparable to the amounts absorbed from smoke, also increased breathing and tracheal smooth muscle tension when injected into the vertebral circulation of recipient dogs. Finally, blockade of nicotine receptors in the central nervous system and in the airway parasympathetic ganglia inhibited the effects of inhaled cigarette smoke and intravenous nicotine on the respiratory center and on bronchomotor tone. We conclude that nicotine absorbed from cigarette smoke is the main cause of cigarette smoke-induced bronchoconstriction. It caused central respiratory stimulation, resulting in increased breathing and airway smooth muscle tension, and had a direct effect on airway parasympathetic ganglia as well.     

The effect of cigarette smoke on the metabolism of arachidonic acid in isolated hamster lungs

The effects of cigarette smoke on the metabolism of exogenous arachidonic acid (AA) were investigated in isolated hamster lungs. Arachidonate was injected into the pulmonary circulation and the metabolites were analysed from the nonrecirculating perfusion effluent by thin layer chromatography. After the pulmonary injection of 66 nmol of ¹⁴C-AA about 20 % of the injected radioactivity appreated in the perfusion effluent mostly as metabolites in six minutes. When isolated lungs were ventilated with cigarette smoke during the perfusion, the amounts of PGF_2α, PGE₂ and two unidentified metabolite groups increased in the lung effluent. In two other experimental series hamsters were exposed to cigarette smoke before the lung perfusion either once for 30 min or during one hour daily for ten consecutive days. Neither pre-exposures caused any changes in the amounts of arachidonate metabolites in the lung effluent.     

The antioxidant and anti-inflammatory properties of lycopene in mice lungs exposed to cigarette smoke

Lycopene is a carotenoid with known antioxidant and anti-inflammatory properties. We aimed to evaluate the in vitro and in vivo effects of lycopene on reducing the redox imbalance and inflammation induced by cigarette smoke (CS). For the in vitro study, J774A.1 (macrophages) cells were incubated in the presence of 0.5, 1.0, 2.0, 4.0, 8.0, 10.0 and 25 μM of lycopene for 3, 6 and 24 h or in the presence of 0.1%, 0.25%, 0.5%, 0.625%, 1.25%, 2.25%, 5% and 10% cigarette smoke extract (CSE) for 3, 6 and 24 h to assess cell viability and measurement of intracellular reactive oxygen species (ROS). For the in vivo study, 40 mice were divided into 5 groups: a control exposed to ambient air (CG), a vehicle-control group that received 200 μl of sunflower oil by orogastric gavage, a group exposed to CS and two groups administered lycopene (diluted in sunflower oil) at doses of either 25 or 50 mg/kg/day prior to exposure to CS (LY25+CS and LY50+CS). The total treatment time lasted 5 days. A cell viability decrease was observed at 10- and 25-μM concentrations of lycopene in 3, 6 and 24 h compared with CG. There was an increase of ROS production in 24 h in CS compared with CG. Lycopene concentrations of 1 μM and 2 μM were able to reduce the production of ROS in 24 h compared with CS. In the bronchoalveolar lavage fluid, the total number of leukocytes increased in the CS group compared with the control groups (CG). Administration with lycopene at the highest dose suppressed this CS-induced increase in leukocytes. Lipid peroxidation and DNA damage increased in the CS group compared with that in the controls, and this increase was suppressed by lycopene at the highest dose. In contrast, superoxide dismutase activity decreased in the CS group compared with that in the controls. Catalase activity also increased in the CS group compared with that in both control groups, and this increase was suppressed in LY25+CS and LY50+CS. There was an increase in the levels of tumor necrosis factor-α, interferon-γ and interleukin-10 after exposure to CS, and these effects were suppressed by both doses of lycopene. These data elucidate the role of lycopene as an antioxidant and anti-inflammatory agent in these two models of short-term exposure to CS.     

The effects of passive inhalation of cigarette smoke on exercise performance

The purpose of this investigation was to evaluate the effect of passive smoke inhalation on submaximal and maximal exercise performance. Eight female subjects ran on a motor driven treadmill for 20 min at 70% VO2max followed by an incremental change in grade until maximal work capacity was obtained. Each subject completed the exercise trial with and without the presence of residual cigarette smoke. Compared to the smokeless trials, the passive inhalation of smoke significantly reduced maximal oxygen uptake by 0.25 l X min-1 and time to exhaustion by 2.1 min. The presence of sidestream smoke also elevated maximal R value (1.01 vs 0.93), maximal blood lactate (6.8 vs 5.5 mM), and ratings of perceived exertion (17.4 vs 16.5 units). Passive inhalation of smoke during submaximal exercise significantly elevated the CO2 output (1.68 vs 1.58 l X min-1), R values (0.91 vs 0.86), heart rate (178 vs 172 bts X min-1) and rating of perceived exertion (13.8 vs 11.8 units). These findings suggest that passive inhalation of sidestream smoke adversely affects exercise performance.     

The acute effects of cigarette smoke exposure on experimental skin flaps

Random vascular patterned caudally based McFarlane-type skin flaps were elevated in groups of Fischer 344 rats. Groups of rats were then acutely exposed on an intermittent basis to smoke generated from well-characterized research filter cigarettes. Previously developed smoke inhalation exposure protocols were employed using a Maddox-ORNL inhalation exposure system. Rats that continued smoke exposure following surgery showed a significantly greater mean percent area of flap necrosis compared with sham-exposed groups or control groups not exposed. The possible pathogenesis of this observation as well as considerations and correlations with chronic human smokers are discussed. Increased risks of flap necrosis by smoking in the perioperative period are suggested by this study.     

Acute effects of cigarette smoke inhalation on peripheral airways in dogs

We studied the acute effects of the inhalation of cigarette smoke on the central and peripheral airways of 35 open-chested and tracheotomized dogs by the direct measurement of central (Rc) and peripheral (Rp) airway resistances. Rc was calculated by dividing the pressure difference between a tracheal catheter and a retrograde catheter by mouth flow, and Rp was obtained by dividing the pressure difference between the retrograde catheter and a pleural capsule by mouth flow. The pleural capsule was attached to the pleural surface for alveolar pressure measurement. Rc and Rp were measured by the 2-Hz forced oscillation method. With lung inhalation of the smoke of two-thirds of one cigarette in vagi intact dogs, Rp increased to 239% of the control value and Rc increased to 112%. After bilateral vagotomy, Rp increased to 143% and Rc increased to 104%. Propranolol did not influence the results. Hexamethonium and atropine both blocked these responses when vagi were intact. When the upper trachea, larynx, and nasopharynx, which were completely blocked by vagotomy, were exposed to the smoke of two-thirds of a cigarette, Rp increased to 155% and Rc increased to 144%. We thus conclude that cigarette smoke causes a major increase in Rp, mainly via the vagal reflex and partially via the stimulation of parasympathetic ganglia (probably nicotine), and a minor increase in Rc via vagal reflex.     

Mitosis-arresting effects of cigarette smoke condensate on human lymphoid cell lines

Whole-smoke condensates from the University of Kentucky reference cigarettes induced partial mitotic arrest in 4 human lymphoid cell lines. Treatment of cells for 3 h with 100 and 200 μg of cigarette-smoke condensate/ml of culture medium increased the frequency of metaphases and decreased the proportion of anaphases in the treated cell populations. Cytoskeletal studies using antitubulin immunofluorescence techniques and transmission electron microscopic studies demonstrated that in early stages of mitosis the formation of aster and the separation of centrosomes in condensate-treated cells were comparable to those of untreated control cells, but the poleward migration of centrosomes was inhibited. Arrested metaphases revealed two centrosomes surrounded by aggregated chromosomes in the center of each cell but the structure of the centrioles, microtubules and the kinetochores appeared normal. The results demonstrate the presence of antimitotic compounds in the tobacco-smoke condensate.     

Thirdhand smoke: a new dimension to the effects of cigarette smoke on the developing lung

The underlying mechanisms and effector molecules involved in mediating in utero smoke exposure-induced effects on the developing lung are only beginning to be understood. However, the effects of a newly discovered category of smoke, i.e., thirdhand smoke (THS), on the developing lung are completely unknown. We hypothesized that, in addition to nicotine, other components of THS would also affect lung development adversely. Fetal rat lung explants were exposed to nicotine, 1-(N-methyl-N-nitrosamino)-1-(3-pyridinyl)-4-butanal (NNA), or 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), the two main tobacco-specific N-nitrosamine constituents of THS, for 24 h. We then determined key markers for alveolar paracrine signaling [epithelial differentiation markers surfactant phospholipid and protein synthesis; mesenchymal differentiation markers peroxisome proliferator-activated receptor γ (PPAR-γ), fibronectin and calponin], the BCL-2-to-Bax ratio (BCL-2/Bax), a marker of apoptosis and the involvement of nicotinic acetylcholine receptors (nAChR)-α3 and -α7 in mediating NNA's and NNK's effects on the developing lung. Similar to the effects of nicotine, exposure of the developing lung to either NNK or NNA resulted in disrupted homeostatic signaling, indicated by the downregulation of PPAR-γ, upregulation of fibronectin and calponin protein levels, decreased BCL-2/Bax, and the accompanying compensatory stimulation of surfactant phospholipid and protein synthesis. Furthermore, nAChR-α3 and -α7 had differential complex roles in mediating these effects. NNK and NNA exposure resulted in breakdown of alveolar epithelial-mesenchymal cross-talk, reflecting lipofibroblast-to-myofibroblast transdifferentiation, suggesting THS constituents as possible novel contributors to in utero smoke exposure-induced pulmonary damage. These data are particularly relevant for designing specific therapeutic strategies, and for formulating public health policies to minimize THS exposure.     

Cytogenetic effects of cigarette smoke condensates in vitro and in vivo

Summary Various cigarette smoke condensates (CSC) were analyzed with respect to the induction of sister-chromatid exchanges (SCE) in human lymphocytes in vitro. CSC from a reference cigarette, from three different tobaccos of the reference cigarette, and from a British cigarette induced similar SCE frequencies. CSC from the reference cigarette did not induce SCE in Chinese hamster bone marrow cells in vivo.     

Stimulation of rapidly adapting receptors in canine lungs by a single breath of cigarette smoke

Inhalation of smoke generated from high-nicotine cigarettes frequently evoked an immediate augmented inspiration in conscious dogs (J. Appl. Physiol. 54: 562-570, 1983); this reflex response was believed to result from a stimulation of rapidly adapting receptors in the lungs. To test this hypothesis, we recorded the vagal afferent activity arising from the rapidly adapting receptors in the lungs and delivered 120 ml of high- and low-nicotine cigarette smoke separately in a single ventilatory cycle in 20 anesthetized open-chest and artificially ventilated dogs. These receptors were stimulated on the first breath of delivery of smoke generated by high-nicotine cigarettes; activity increased from a base line of 0.9 +/- 0.2 to a peak of 9.9 +/- 1.2 (SE) impulses/breath (n = 58). After three to six breaths when the receptors' discharge returned toward base-line activity, a delayed increase of activity emerged (peak activity = 3.4 +/- 0.6 impulses/breath, n = 58) in 32 of the 58 receptors studied and lasted for three to seven breaths. By contrast, only a mild stimulatory effect of low-nicotine cigarette smoke was found, either immediately or after a delay, in 15 of the 54 receptors studied. We conclude that rapidly adapting receptors are stimulated by a single breath of cigarette smoke and that nicotine is the primary stimulant agent.     

Particulate phase cigarette smoke increases MnSOD, NQO1, and CINC-1 in rat lungs

Loss of antioxidant/oxidant homeostasis perpetuates inflammation in the lungs and may contribute to the development of COPD and lung cancer. Cigarette smoke (CS) is a primary source of airway oxidative stress and recruits inflammatory cells into smokers' lungs. However, whether these consequences are attributable to a specific or the collective fraction of CS is unknown. We investigated whether the particulate or the gas phase of CS would alter expression of the antioxidant enzymes MnSOD and NQO1 or CINC-1. Sprague Dawley rats were exposed to sham (n = 10) or the particulate phase (PP; n = 10) or gas phase (n = 10) of a Kentucky reference cigarette (1R4F) for 2 h/d for 28 d, after which animals were sacrificed and the lower left lobe of the lung was removed. Immunoblots for SOD and NQO1 revealed that lungs exposed to PP had higher MnSOD/actin and NQO1/actin ratios than either sham-or gas phase-treated animals. In contrast, CuZnSOD remained unchanged. In PP-exposed animals, CINC-1 was 3-fold higher than in sham-exposed animals. The increases in MnSOD and NQO1 protein were associated with increases in total SOD, NQO1, and MPO activities. These data provide evidence that the PP of CS alters oxidant/antioxidant homeostasis in the lungs and participates in the pathogenesis of CS-induced lung diseases such as COPD and cancer.     

Acute effects of cigarette smoke on breathing in rats: vagal and nonvagal mechanisms

The acute ventilatory response to inhalation of cigarette smoke was studied in anesthetized Sprague-Dawley rats. Cigarette smoke (6 ml, 50%) generated by a machine was inhaled spontaneously via a tracheal cannula. Within the first two breaths of smoke inhalation, a slowing of respiration resulting from a prolonged expiratory duration (173 +/- 6% of the base line; n = 32) was elicited in 88% of the rats studied. This initial inhibitory effect on breathing was not affected either by an increase (410%) in the nicotine content of the cigarette smoke or by pretreatment with hexamethonium (33 mg/kg iv). However, bilateral vagotomy completely eliminated the initial ventilatory inhibition. Cooling both vagi to 5.1 degrees C blocked the reflex apneic response to lung inflation, but it did not abolish the inhibitory effect of smoke. After the initial response, a rapid shallow breathing pattern developed and reached its peak 5-12 breaths after inhalation of high-nicotine cigarette smoke; this delayed response could not be prevented by vagotomy and was undetectable after inhalation of low-nicotine smoke. We conclude that the initial inhibitory effect of smoke on breathing is mediated by vagal bronchopulmonary C-fiber afferents, which are stimulated by smoke constituents other than nicotine, whereas the delayed tachypneic response to smoke is caused by the absorbed nicotine.     

Metals in cigarette smoke

Metals are vital for a huge number of physiological processes in the human body, but can also destroy health when the concentration is not within the physiologically favourable range. Cigarette smoking interferes with the carefully controlled metal homeostasis of the human body. This review focuses on the consequences of metal delivery to the human body by cigarette smoking and discusses the body's responses. The metal content of tobacco plants, smoke, the circulation, and various organs is discussed. Finally, we link individual cigarette smoke contained metals to the genesis of human diseases.     

The metabolism of arachidonic acid in isolated rat lungs is not changed during cigarette smoke ventilation

Cigarette smoke ventilation of isolated perfused rat lungs partially inhibited the pulmonary vascular pressor response to arachidonic acid. The amounts of metabolites of exogenous arachidonic acid in the perfusion effluent remained unchanged during smoke ventilation. The antiaggregatory effect of the effluent during pulmonary infusion of AA was not decreased by smoke ventilation. The cause of the previously reported increased platelet aggregation after smoking remains unclear.     

Cilomilast counteracts the effects of cigarette smoke in airway epithelial cells

Cigarette smoke extracts (CSE) alter TLR4 expression and activation in bronchial epithelial cells. Cilomilast, a phosphodiesterase-4 inhibitor, inhibits cigarette smoke-induced neutrophilia.This study was aimed to explore whether cilomilast, in a human bronchial epithelial cell line (16-HBE), counteracted CSE effects. In particular, TLR4 expression, IP-10 and IL-8 release, lymphocyte and neutrophil chemotactic activity and ERK and IkBa phosphorylation in CSE and LPS-stimulated 16-HBE were assessed.CSE increased TLR4 expression, reduced IP-10 release and lymphocyte chemotactic activity and increased IL-8 release and neutrophil chemotactic activity. Cilomilast reduced TLR4 expression, IL-8 release and neutrophil chemotactic activity as well as it increased IP-10 release and lymphocyte chemotactic activity. All these cilomilast mediated effects were associated with a reduced ERK1/2 and with an increased IkBa phosphorylation.In conclusion, the present study provides compelling evidences that cilomilast may be considered a possible valid therapeutic option in controlling inflammatory processes present in smokers.