Effects of melatonin on the oxidant/antioxidant status and lung histopathology in rabbits exposed to cigarette smoke

OBJECTIVES AND BACKGROUND: To evaluate the effects of cigarette smoking on the histopathology and the oxidant/antioxidant status of the lungs and to test the potential antioxidant benefits of melatonin on these induced changes. METHODOLOGY: Rabbits were exposed to cigarette smoke in a glass chamber for 1 h daily for 1 month with or without intraperitoneal melatonin injection. A melatonin control group was given intraperitoneal melatonin only. A control group was exposed to clean air only. At the end of 1 month, animals were sacrificed and lung tissues were examined histopathologically. Blood levels of protein sulphydryls, carbonyls, prostaglandin F2alpha (PGF2alpha), malondialdehyde (MDA), glutathione peroxidase and superoxide dismutase (SOD) were measured. RESULTS: Intraparenchymal vascular congestion and thrombosis, intraparenchymal haemorrhage, respiratory epithelial proliferation, number of macrophages in the alveolar and bronchial lumen, alveolar destruction, emphysematous changes and bronchoalveolar haemorrhage scores were significantly increased in rabbits exposed to cigarette smoke compared with the control group. Protein sulphydryls and SOD levels were significantly decreased; carbonyls, PGF2alpha and MDA levels were significantly increased in the smoke exposed rabbits. Administration of melatonin to rabbits exposed to cigarette smoke caused a reduction in the bronchoalveolar haemorrhage score and blood carbonyls levels. Other parameters were unaffected by melatonin. CONCLUSION: Exposure to cigarette smoke causes severe histopathological changes and negatively affects the oxidant/antioxidant status in the lungs of rabbits. A low daily dose of melatonin has some protective effects on histopathological changes and oxidant/antioxidant status of the lungs in smoke exposed rabbits.     

Systemic effects of cigarette smoke exposure in the guinea pig

Chronic obstructive pulmonary disease is associated with systemic effects including reduced body weight, oxidative stress and altered circulating TNFalpha levels. The present study was aimed to investigate whether chronic exposure to cigarette smoke induces these systemic changes in a guinea pig model. Seven animals/group were exposed to the smoke of seven cigarettes/day, 5 days/week, during 2, 4 and 6 months (chronic exposure). Three animals/group were sacrificed immediately, 3 h or 24 h after exposure to seven cigarettes (acute exposure). Chronically smoke-exposed animals exhibited lower body weight gain, starting at 5th week, and goblet cell metaplasia in small bronchioles. At 6 months there was a trend for increased plasma and lung tissue TNFalpha levels. No changes, neither in skeletal muscle glutathione (GSH) nor in plasma lipid peroxidation, were observed at any time point after chronic exposure. However, skeletal muscle GSH decreased and plasma lipid peroxidation increased immediately after acute smoke exposure, equaling control levels thereafter. We conclude that cigarette smoke exposure in the guinea pig induces a transient and repeated oxidative effect, which might result in impaired systemic metabolism and consequent failure of smoke-exposed animals to gain weight. The effects of cigarette smoke on body weight antecede and appear to be independent from the alterations produced in small airways.     

Cigarette smoke impairs elastin resynthesis in lungs of hamsters with elastase-induced emphysema

The severity of pulmonary emphysema can be affected by exposure to cigarette smoke in several ways. Inactivation of alpha-1-antitrypsin and recruitment of leukocytes to lung airways shifts the protease-antiprotease balance towards increased elastolytic activity. The present study demonstrates an additional effect of cigarette smoke inhalation and retardation of the repair process and of the neosynthesis of cross-linked elastin. Hamsters with elastase-induced emphysema, exposed to cigarette smoke for 1 wk immediately after elastase administration, showed a 40% reduction of 14C-lysine incorporation into the elastin-specific cross-links, desmosine, and isodesmosine. Concomitantly, there was a decrease in the level of lung lysyl oxidase to that observed in uninjured control animals, in sharp contrast to the sevenfold increase in lysyl oxidase activity in hamsters with elastase-induced emphysema recovering under atmospheric conditions. These findings suggest that impairment of the production of lysyl oxidase and the resynthesis of cross-linked elastin by smoke inhalation exacerbates alveolar destruction.     

The effects of physical exercise on the cigarette smoke-induced pulmonary oxidative response

Studies have shown that the oxidative power of cigarettes is related to the pathogenesis of several pulmonary diseases and that regular physical exercise contributes significantly to reducing the deleterious effects of cigarettes. The objective of the present study was to investigate the therapeutic effects of physical exercise on histological and oxidative stress markers in animals exposed to cigarette smoke. Thirty-six male, eight-week-old C57BL-6 mice were divided into four groups (n = 9 for each group): control, exercise, cigarette smoke, and cigarette smoke plus exercise. The cigarette smoke (CS) groups were exposed to cigarette smoke 3 times/day (4 cigarettes/session) for 60 consecutive days. The exercise groups were submitted to swimming physical training 5 days/week for eight weeks. Forty-eight hours after the last exercise and cigarette exposure, the animals were sacrificed using cervical traction. The right lung was removed, processed, and stored for future analysis. In addition to the analysis of collagen content (hydroxyproline), oxidant production (anion superoxide), antioxidant enzyme activity (SOD and CAT), and lipid and protein oxidative damage (TBARS and Carbonylation), histological and morphological studies were performed. The results revealed that the animals exposed to cigarette smoke showed enlargement and destruction of the alveolar septum and increases in the numbers of macrophages and neutrophils, as well as in the amount of collagen. Our results also showed a decrease in the volume density of elastic fibers and an increase in the volume density of airspaces. However, physical exercise partially improved these markers. Additionally, physical exercise decreased oxidant production and increased the activity of the enzymatic antioxidant defense system, but did not reverse lipid and protein oxidative damage induced by cigarette smoke. These results suggest that physical training partially improves histological and oxidative stress parameters in the lungs of animals chronically exposed to cigarette smoke and that other therapies can contribute to potentiate these effects.     

Selective increase of antioxidant enzyme activity in the alveolar macrophages from cigarette smokers and smoke-exposed hamsters

Oxidants from cigarette smoke or those produced by phagocytes are implicated in the pathogenesis of emphysema. We reasoned that augmentation of antioxidant enzymes in cigarette smokers may be important in restricting direct and indirect oxidant damage to alveolar structures. Accordingly, we studied the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSHPx), in alveolar macrophages (AM) from cigarette smokers and from smoke-exposed hamsters. The activities of these antioxidant enzymes were compared with the activities found in AM from nonsmoking control subjects. The activities of SOD and CAT from AM of smokers and smoke-exposed hamsters were twice that found in control subjects (p less than 0.01), but there was no change in the activity of GSHPx. Using the hamster model, we found that filtration of smoke attenuated the increase in antioxidant activities, and that after smoking cessation, the increased activities had returned to those found with control subjects. An adaptive response was further suggested by prolonged survival of smoke-exposed hamsters in normobaric hyperoxia (O2 greater than 95%). Chronic smoke exposure in humans or hamsters causes increased SOD and CAT activities in AM. This augmented activity may serve as a mechanism to limit oxidant-mediated damage to alveolar structures.     

Cardiopulmonary effects of a brief exposure to cigarette smoke in the guinea pig

To investigate whether the acute inflammatory response produced by acute cigarette smoke exposure is associated with alterations in pulmonary and cardiovascular function, using a respirator we exposed 8 guinea pigs to 350 ml of cigarette smoke diluted in 2,000 ml room air for 10 min. Lung volumes, pressure volume curves and flow volume curves were performed. Measurements of pulmonary artery pressure, systemic pressure, heart rate and cardiac output were taken at baseline, immediately after the smoke exposure, and 1.5 h after smoke exposure. Aliquots of peripheral blood for total white cell count and differential count were obtained. After animal sacrifice, the right lung was lavaged and white cell count and differential count performed. We found that acute exposure to cigarette smoke produced a peripheral blood neutrophilia which rose progressively from a baseline of 36.3 +/- 8% to a maximum of 72.2 +/- 7.7% at 1.5 h after exposure. There was pulmonary neutrophilia with 24.6 +/- 6.3% neutrophils in the lavage fluid of the smoke-exposed animals compared to 8.4 +/- 4.3% in the control animals. Immediately after smoke exposure, there was acute airflow obstruction with a decrease in the peak flow and forced expiratory flow between 25-75% vital capacity. This was associated with airtrapping, as shown by a transient increase in residual volume. There was a slight decrease in systemic blood pressure in the smoke-exposed animals associated with a nonsignificant decrease in the heart rate, and the cardiac output remained stable.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in the glycosaminoglycans and glycoproteins in the tissues in rats exposed to cigarette smoke

Prolonged exposure of rats to cigarette smoke resulted in significant alteration in the metabolism of glycosaminoglycans (GAG) and glycoproteins (GP). The concentration of many GAG fractions generally decreased in the aorta, liver and heart, but increased in the lungs. Concentration of chondroitin sulphates decreased in all the tissues. The activity of many enzymes concerned with the degradation of GAG (hyaluronidase, beta-glucuronidase and cathepsin-D) showed increase in these tissues. The concentration of the carbohydrate components (total hexose fucose and sialic acid) of aorta, heart and liver showed decrease in the rats exposed to cigarette smoke while there was increase in the lungs. The activity of many glycohydrolases generally showed increase in these tissues. Thus, exposure of rats to cigarette smoke for long periods produced changes in the aortic GAG and GP which are similar to those observed in atherosclerosis. On the other hand there was accumulation of many GAG in the lung tissue.     

Potentially Reduced Exposure Cigarettes Accelerate Atherosclerosis: Evidence for the Role of Nicotine

The tobacco industry markets potentially reduced exposure products (PREPs) as less harmful or addictive alternatives to conventional cigarettes. This study compared the effects of mainstream smoke from Quest, Eclipse, and 2R4F reference cigarettes on the development of atherosclerosis in apolipoprotein E-deficient (apoE −/−) mice. Mice were exposed to smoke from four cigarette types for 12 weeks beginning at age of 12 weeks, and in a separate study for 8 weeks, beginning at age of 8 weeks. In both studies, mice exposed to smoke from high-nicotine, high-tar Quest 1, and 2R4F cigarettes developed greater areas of lipid-rich aortic lesions than did non-smoking controls. Exposure to smoke from the lower-nicotine products, Eclipse, and Quest 3, was associated with smaller lesion areas, but animals exposed to smoke from all of the tested types of cigarette had larger lesions than did control animals not exposed to smoke. Urinary levels of isoprostane F2 alpha VI, increased proportionally to cigarette nicotine yield, whereas induction of pulmonary cytochrome P4501A1 was proportional to tar yield. Lesion area was associated with both nicotine and tar yields, although in multiple regression analysis only nicotine was a significant predictor of lesion area. Smoke exposure did not alter systolic blood pressure (SBP), heart rate (HR), blood cholesterol, or leukocyte count. Taken together, these observations suggest that smoking may accelerate atherosclerosis by increasing oxidative stress mediated at least in part via the actions of nicotine.     

The effect of acute airway inflammation on bronchial reactivity in guinea pigs

This study compared airways reactivity before and after an inflammatory response was induced in the airways by exposing them to cigarette smoke. Airways reactivity was measured to graded doses of histamine using a standard technique in 24 animals without drug pretreatment, in 17 pretreated with propranolol, in 17 pretreated with atropine, and in 18 pretreated with both atropine and propranolol. In each group, at least 5 animals not exposed to cigarette smoke served as controls, and the remaining animals were studied in groups of 4 or more at 30 min, 6, and 24 h after exposure to 100 puffs of whole cigarette smoke. The data show that airways reactivity was increased at 30 min but not at 6 and 24 h after exposure to cigarette smoke. Pretreatment with propranolol or the combination of propranolol and atropine prior to the histamine dose-response curve did not affect the increased response seen after cigarette smoke exposure, but pretreatment with atropine abolished it. Comparing this study with our previous histologic studies of the airways in similarly exposed animals, we conclude that the observed increase in airways reactivity occurs during the fluid exudative phase of the inflammatory response before the polymorphonuclear leukocytes migrate into the epithelium.     

Cigarette smoking: Effects on P selectin expression and subsequent inflammatory responses in ethanol-induced gastric mucosal damage

Abstract Experimental evidence has shown that cigarette smoking potentiates ulcer formation and delays ulcer healing. The exact mechanisms are still not completely defined. We investigated the effects of cigarette smoking on P selectin expression and its actions on neutrophil infiltration and nitric oxide formation in ethanol-induced gastric mucosal damage. In the present study, rats were exposed to cigarette smoke for three 1 h periods. Cigarette smoke exposure significantly up-regulated P selectin expression in the gastric mucosa. Cigarette smoke exposure following ethanol challenge substantially potentiated the mucosal damage, which was accompanied with an increase in myeloperoxidase and inducible nitric oxide synthase activities. Anti-neutrophil serum completely abolished these changes, whereas aminoguanidine produced similar effects without affecting myeloperoxidase activity. Taken together, cigarette smoke exposure can up-regulate P selectin expression, which facilitates neutrophil rolling, margination and infiltration when challenged with ethanol. These actions activate inducible nitric oxide synthase activity, which may contribute to the potentiating effect of cigarette smoking on ethanol-induced gastric ulceration in rats.     

Albuminuria and Diabetic Retinopathy in Type 2 Diabetes Mellitus Sankara Nethralaya Diabetic Retinopathy Epidemiology And Molecular Genetic Study (SN-DREAMS,report 12)

Background

The purpose of this study was to evaluate the effects of cigarette smoke exposure before pregnancy on diabetic rats and their offspring development.

Methods

Diabetes was induced by streptozotocin and cigarette smoke exposure was conducted by mainstream smoke generated by a mechanical smoking device and delivered into a chamber. Diabetic female Wistar rats were randomly distributed in four experimental groups (n minimum = 13/group): nondiabetic (ND) and diabetic rats exposed to filtered air (D), diabetic rats exposed to cigarette smoke prior to and into the pregnancy period (DS) and diabetic rats exposed to cigarette smoke prior to pregnancy period (DSPP). At day 21 of pregnancy, rats were killed for maternal biochemical determination and reproductive outcomes.

Results

The association of diabetes and cigarette smoke in DSPP group caused altered glycemia at term, reduced number of implantation and live fetuses, decreased litter and maternal weight, increased pre and postimplantation loss rates, reduced triglyceride and VLDL-c concentrations, increased levels of thiol groups and MDA. Besides, these dams presented increased SOD and GSH-Px activities. However, the increased antioxidant status was not sufficient to prevent the lipid peroxidation observed in these animals.

Conclusion

Despite the benefits stemming from smoking interruption during the pregnancy of diabetic rats, such improvement was insufficient to avoid metabolic alterations and provide an adequate intrauterine environment for embryofetal development. Therefore, these results suggest that it is necessary to cease smoking extensive time before planning pregnancy, since stopping smoking only when pregnancy is detected may not contribute effectively to fully adequate embryofetal development.     

Effects of cigarette smoking and dietary lipids on rat lipoprotein metabolism

The effects of cigarette smoke inhalation on rat lipoprotein metabolism have been examined. Rats were subjected to cigarette smoke exposure over a 3-week period (two 1-h sessions/day) using a Bat-Mason inhalation machine. Rats exposed to cigarette smoke showed a decrease in total serum triglyceride and an increase in very low density lipoprotein cholesterol (VLDL-C). Administration of cigarette smoke to rats fed a saturated fat and cholesterol enriched diet also led to an increase in VLDL-C and a decrease in total serum triglycerides compared to controls. In addition, cigarette smoke exposure to animals fed the lipid enriched diet caused a decrease in high density lipoprotein cholesterol (HDL-C). Pair-feeding experiments indicated that the increase in VLDL-C and the decrease in HDL-C could not be solely attributed to the reduction in food intake and the small decrease in growth rate observed following cigarette smoke exposure. The changes observed in VLDL-C and HDL-C are at least qualitatively similar to the changes seen in human smokers compared to non-smokers.     

Prenatal cigarette smoke decreases lung cAMP and increases airway hyperresponsiveness

Epidemiologic studies suggest that in utero exposure to tobacco smoke, primarily through maternal smoking, increases the risk for asthma in children; however, the mechanism of this phenomenon is not clear. Cyclic adenosine monophosphate relaxes airway smooth muscles in the lung and acts as an antiasthmatic. In this study, we examined the effects of in utero cigarette smoke exposure of Balb/c mice on airway responsiveness, as determined by Penh measurements. Animals exposed prenatally but not postnatally to cigarette smoke exhibited increased airway hyperresponsiveness after a single intratracheal injection of Aspergillus fumigatus extract. The increased airway hyperresponsiveness was not associated with increased leukocyte migration or mucous production in the lung but was causally related to decreased lung cyclic adenosine monophosphate levels, increased phosphodiesterase-4 enzymatic activity, and phosphodiesterase-4D (PDE4D) isoform-specific messenger ribonucleic acid expression in the lung. Exposure of adult mice to cigarette smoke did not significantly alter airway responsiveness, cyclic adenosine monophosphate levels, or the phosphodiesterase activity. These results suggest that prenatal exposure to cigarette smoke affects lung airway reactivity by modulating the lung cyclic adenosine monophosphate levels through changes in phosphodiesterase-4D activity, and these effects are independent of significant mucous production or leukocyte recruitment into the lung.     

Dissociation of chronic vascular cell proliferation and vascular contractility after chronic cigarette smoke exposure.

In guinea pigs, chronic cigarette smoke exposure produces physiological and structural alterations in the pulmonary vasculature via unknown mechanisms. This study aimed to determine whether chronic cigarette smoke exposure can induce altered pulmonary vascular reactivity, and whether chronic smoke exposure would be associated with a continued increase in vascular cell deoxyribonucleic acid (DNA) synthesis, indicative of cell proliferation. Guinea-pigs were therefore exposed to two regimens of smoke. In the first experiment, animals were exposed once to the smoke of seven cigarettes, and sacrificed 24 h post-smoke, while in the second experiment, the guinea-pigs were exposed for 5 days each week for 4 months. Control animals were exposed to air. Lung explant preparations and computer linked image photography were utilized to determine vascular reactivity, and DNA synthesis was assessed using the 5-bromo-2'-deoxyuridine technique. Neither acute nor chronic smoke exposure affected vascular reactivity, although the older animals had lesser reactivity. In the chronically smoked animals, evidence was found of ongoing vascular DNA synthesis, and evidence of structural alterations with increased muscularization of the arterioles (34.7+/-7.6% of arterioles in control versus 62.7+/-5.5% after smoke exposure). Despite evidence of continued deoxyribonucleic acid synthesis in the peribronchiolar vessels, the alterations of vascular physiology previously found in this model cannot be ascribed to increased reactivity at this site. Instead, the chronic deoxyribonucleic acid synthesis in the arterioles adjacent to the alveolar ducts, culminating in an increased number of fully muscularized vessels, would suggest this compartment as the most probable source.     

Increased airway responsiveness and decreased alveolar attachment points following in utero smoke exposure in the guinea pig

Maternal smoking during pregnancy has been shown to result in abnormalities in lung function in newborn infants, including reduced expiratory flow and increased airway responsiveness to inhaled agonists. The mechanisms by which this occurs remain unclear. Using a guinea pig model of in utero smoke exposure, we measured airway responsiveness and lung morphology in a group of neonatal guinea pigs 21 d after delivery. Pregnant guinea pigs were exposed to cigarette smoke from Day 28 to term (Day 68 of gestation). After delivery newborn animals did not receive any smoke exposure. Airway wall thickness, smooth muscle area, and the number of points where the alveoli attached to the airway adventitia were measured. Airway responsiveness was increased (p < 0.05) and the mean distance between alveolar attachment points was increased (mean 0.052 +/- SE 0.001 mm versus 0.046 +/- 0.001, p = 0.001) in animals exposed to cigarette smoke in utero compared with nonexposed animals. Although not statistically significant, both the inner and outer airway wall and the smooth muscle area were greater in exposed animals compared with nonexposed animals. The increased mean distance between alveolar attachments in the smoke-exposed group was the result of a reduction in the number of attachments and an increase in the outer airway wall perimeter. These findings suggest that the increased airway responsiveness observed in postnatal animals, subsequent to in utero cigarette smoke exposure, may be the result of decreased alveolar attachment points to the airways and changes in airway dimensions.     

Effects of chronic exposure to cigarette smoke on amine levels and turnover in various hypothalamic catecholamine nerve terminal systems and on the secretion of pituitary hormones in the male rat

Male rats were exposed to the smoke from 2 cigarettes every morning for a total-period of 9 days. The next day they were decapitated immediately after the exposure to the smoke from 4 cigarettes (Kentucky reference IR-1 type) burned at 30-min intervals. Control animals were exposed to air alone or to nicotine-free cigarette smoke (Cambridge glass fibre filters). In contrast to chronic exposure to filtered smoke, exposure to unfiltered smoke resulted in a 10% increase in catecholamine (CA) levels (quantitative histofluorimetry) within the lateral palisade zone, the posterior periventricular hypothalamic nucleus and within the dorsomedial hypothalamic nucleus. There was also an increase in amine turnover (tyrosine hydroxylase inhibition by alpha-methyl-dl-p-tyrosine methylester; alpha MT) in the dopamine (DA) systems of the medial and lateral palisade zones and in the periventricular noradrenaline (NA) hypothalamic systems. Chronic exposure to unfiltered cigarette smoke resulted in reductions of prolactin, LH and FSH levels (radioimmunoassay). Following alpha MT treatment chronic exposure to unfiltered cigarette smoke still led to reduced prolactin serum levels. In addition an increased vasopressin serum concentration was found. The effects of chronic exposure to cigarette smoke on neuroendocrine function and on hypothalamic CA systems are suggested to be mediated via nicotine. Combined with the results from a previous study the present results indicate that tolerance does not develop with regard to the inhibitory effects of exposure to cigarette smoke on prolactin, LH and FSH secretions. The same is true for the stimulatory effects on the tubero-infundibular DA neurons and the periventricular NA systems. But chronic exposure to cigarette smoke seemed to induce tolerance with regard to its stimulatory effects on subependymal, dorsomedial and paraventricular hypothalamic NA systems and on corticosterone release.     

Chronic cigarette smoke exposure enhances brain-derived neurotrophic factor expression in rats with traumatic brain injury

The involvement of brain-derived neurotrophic factor (BDNF) in regulating neuronal survival during neuron differentiation, growth, and maturation, and during the regeneration of injured nerve cells, has already been documented. In experimental Parkinson’s disease, chronic exposure to cigarette smoke increased BDNF levels and survival of dopaminergic neurons. BDNF is also elevated in traumatic brain injury (TBI), where it is potentially involved in post-injury repair and regeneration. The aim of this study was to investigate the effects of chronic exposure to cigarette smoke on BDNF expression and apoptosis in rats with TBI. Three groups of rats were compared: rats with TBI after chronic exposure to cigarette smoke, rats with TBI and no exposure to cigarette smoke, and sham-operated rats. BDNF mRNA expression in the hippocampus increased from 2 to 24 h after TBI, and chronic exposure to cigarette smoke upregulated TBI-induced BDNF mRNA elevation at 0, 2, 4, 12, and 24 h after head injury. The BDNF protein levels generally corresponded to the mRNA levels in the hippocampal region. Compared to the TBI group without smoke exposure, chronic cigarette smoke exposure in rats inhibited the decrease of the Bcl-2/Bax ratio and reduced P53 expression and apoptosis 24 h after TBI. In addition, neuronal damage in the parietal and cingulate cortex 7 days after TBI was less extensive in rats exposed to cigarette smoke. In conclusion, although chronic exposure to cigarette smoke is a risk factor for myocardial and pulmonary disease, cigarette smoke exposure increases BDNF expression after TBI and thereby can play a neuroprotective role.     

The role of complement in cigarette smoke-induced chemotactic activity of lung fluids

To help explain increased recruitment of leukocytes to smokers' lungs, we examined the possibility that the smoke-induced chemotactic activity in lung fluids may be partly complement-dependent. Acute inhalation exposure of rats to smoke from 2R1 Kentucky Reference cigarettes caused an increase in the leukocyte chemotactic activity of their lung secretions (collected by bronchoalveolar lavage 1 h after exposure). Prior depletion of circulating complement, by intravenous administration of purified cobra venom factor 24 h beforehand, prevented the smoke-induced rise in lavage fluid chemotactic activity. Crossed immunoelectrophoretic analysis of lavage C3 from smoke-exposed animals demonstrated a modified form of the molecule with increased electrophoretic (anodal) mobility. When 2 strains of mice, C5-deficient DBA/2 and C5-sufficient BALB/c, were acutely exposed to cigarette smoke, only the C5-sufficient animals (BALB/c) had increased neutrophil chemotactic activity in their lung fluids 1 h after exposure. These results show that the increased chemotactic activity in lung fluids of laboratory animals immediately after acute cigarette smoke exposure is complement-dependent.     

A rat model to determine the biomedical consequences of concurrent ethanol ingestion and cigarette smoke exposure

BACKGROUND: Although scientists have used animal models for years to study the effects of ethanol (EtOH) ingestion on humans, the compounding effect of cigarette smoking has been virtually ignored. Because 80 to 95% of human alcoholics smoke, it is imperative to consider the added effects of smoking when trying to determine the consequences of excessive alcohol ingestion. We therefore have developed a rat model for studying the separate and combined results of smoking and drinking on human health. METHODS: Male Sprague-Dawley rats were exposed daily for 12 weeks in whole-body chambers to cigarette smoke (smoke-exposed) or room air (sham-exposed). During the final 5 weeks of exposure, the rats were fed liquid diets that contained 0, 16, 26, or 36% EtOH calories. Smoke exposure was quantified by measurement of carboxyhemoglobin, nicotine, and cotinine levels. Body weights, food consumption, blood EtOH concentrations, and various assessments of liver damage and function also were followed. RESULTS: Smoke exposure in this rat model approximates that of a moderate to heavy human smoker. Smoke-exposed rats weighed significantly less and ate less food than sham-exposed controls, but both groups ingested equivalent amounts of EtOH for their body weights and had comparable blood EtOH levels. Liver aspartate and alanine aminotransferase levels remained normal. There was an EtOH-induced decrease in asialoglycoprotein receptor binding, but it was not exacerbated by smoke exposure. Alterations in blood cholesterol levels reflected what has been reported for humans, rising with increasing EtOH ingestion and decreasing with smoke exposure. CONCLUSION: Our rat model is relevant to what transpires in the vast majority of alcoholics. Both ethanol ingestion and smoke exposure can be manipulated to mimic light to moderate to heavy levels, making it appropriate for studying the separate and combined biomedical consequences of alcohol abuse and cigarette smoking.     

Long Term Cigarette Smoke Exposure Does Not Increase Airway Responsiveness in Rats

To ascertain whether chronic cigarette smoke exposure induces increased airway responsiveness, we performed methacholine response tests in Sprague-Dawley rats by calculating pulmonary resistance after nebulization of saline followed by an increasing concentration of methacholine. We also calculated the concentration of methacholine which doubled the baseline resistance (R200). Tests were performed at baseline and after 2, 4, 8, and 12 months of exposure to the smoke of seven cigarettes per day, 5 days each week; control animals were exposed to room air. At the completion of the study, there were 13 rats in the smoke-exposed group and 7 rats remaining in the control group. Airway morphology was assessed using a point counting technique. We found that (1) chronic exposure to cigarette smoke did not alter either the baseline resistance or the R200; (2) the saline baseline resistance decreased over time in the control animals; and (3) at the 12-month time point, smokers with increased baseline airway resistance had greater amounts of airway smooth muscle compared with the smoke-exposed animals without increased resistance. We conclude that in this animal model, long term exposure to cigarette smoke did not alter the response to methacholine but did increase airway smooth muscle and baseline resistance in some but not all animals. Accepted for publication: 4 December 1997