Comparison of the inhalation toxicity of kretek (clove cigarette) smoke with that of American cigarette smoke. II. Fourteen days,exposure

The comparative repeat dose toxicity of American cigarettes and kreteks (Indonesian cigarettes containing approximately 60% tobacco and 40% shredded clove buds) was assessed by exposure of groups of five male and five female rats to equivalent (approximately 2 mg/l in terms of total particulate matter) concentrations of smoke from each type of cigarette over 15 consecutive days. The smoke was delivered nose only using an HRC Rodent Smoking Machine (Mark IV). For each type of cigarette, three doses were used. These were achieved by regulating the daily total duration of exposure to smoke. The different doses used were 2x, 4x and 6x, 15-min exposures, presented daily over a period of approximately 6 h. Intergroup comparisons were made between American and kretek groups which received the same daily durations of smoke exposure. Higher doses of smoke resulted in reduced bodyweight gains and food consumption in male groups; the response of female groups was not as clear. At the highest dose, male rats exposed to kretek smoke gained significantly more weight by comparison with males exposed to American smoke. Higher doses of smoke tended to increase water consumption in both sexes of groups exposed to American smoke; kretek smoke produced no obvious effect. Smoke exposures produced the expected responses in certain haematological and blood biochemical parameters attributed to exposure to CO and the irritants present in cigarette smoke. Such responses were, however, confined largely to the groups exposed to American smoke. Macroscopic pathological findings attributed to smoke inhalation were confined to the lungs, and consisted of minimal to moderate discolouration and incomplete collapse of the lung. The latter finding occurred in 60% of males and 60% of females in the American high dose group and 20% of females in the kretek intermediate dose group. The weights of several organs appeared to have been affected by smoke exposures. Of these, only the increase in lung weight associated with exposure to American smoke was considered remarkable. In females exposed to American smoke, the group mean lung weights were significantly higher than the corresponding kretek group lung weights. In males, the difference was significant at the intermediate dose level only. The histopathological lesions seen in the lungs were typical of the lesions encountered in inhalation studies with tobacco smoke and included increased numbers, vacuolation and brown pigmentation of macrophages, acute alveolitis, bronchiolar epithelial hyperplasia and cuboidal ciliated cell metaplasia of alveolar duct; the two latter findings were present in some American high dose rats only. Occasional foci of alveolar haemorrhage were seen in odd rats but the incidence was not clearly dose related for either type of cigarette; the highest incidence, 30%, was seen in the high dose American group. At all dose levels, the lesions encountered were more severe with American smoke. No unique lesions were detected with kretek smoke.     

Characterization of biochemical,functional and structural changes in mice respiratory organs chronically exposed to cigarette smoke

Abstract

Female C57BL/6 mice were exposed to mainstream cigarette smoke at 600?μg WTPM/L, 4?h/day and 5 days/week for up to 52 weeks. At 26, 52 and 65 weeks (52 weeks of exposure plus 13 weeks of no exposure), lungs were assessed for inflammation, function, histopathology and morphometry. Structural changes were observed and accompanied by altered lung function at 26 and 52 weeks (e.g. increase of static compliance and hysteresis, and decrease of elastance). Lung morphometry quantified significant increase in airspace enlargement at 52 weeks. Chronic smoke exposure induced inflammation in respiratory organs, e.g. mixed inflammatory cell infiltrates, perivascular lymphocyte infiltrates and pigmented alveolar macrophages in the lungs. Minimal or mild alveolar emphysema was diagnosed in 70% by 26 weeks or 80% by 52 weeks. After 13 weeks of recovery, most biochemical, histopathological and morphometrical alterations were restored, while emphysema was observed to persist at 18% incidence by 65 weeks. In conclusion, the employed exposure conditions induced emphysematous changes in the lungs, accompanied by altered lung function and morphological/histopathological changes. Following the 13 weeks of no exposure, morphological changes persisted, although some functional/biochemical alterations regressed.     

一种新的香烟烟雾暴露装置的建立

目的建立一种新的香烟烟雾暴露装置,并构建COPD模型以检测该装置的有效性。方法 40只C57BL/6小鼠随机分为①对照组10只,饲养3个月;②模型组30只,分设3组,分别予以香烟烟雾暴露1、2、3个月。取支气管肺组织,HE染色后观察病理变化。结果随着烟雾暴露时间的延长,模型组小鼠的肺组织逐渐出现典型的COPD病理改变。结论该装置适用于大、小鼠COPD模型的构建。     

Comparison of the inhalation toxicity of kretek (clove cigarette) smoke with that of American cigarette smoke. I. One day exposure

The comparative acute toxicity of a branded American cigarette and kreteks (Indonesian cigarettes containing approximately 60% tobacco and 40% ground clove buds) was assessed by exposure of groups of ten male and ten female rats to three different but equivalent (in terms of total particulate matter) concentrations of smoke from each type of cigarette. The smoke was delivered nose only using an HRC Rodent Smoking Machine (Mark IV) within a single 1-h period, with a total delivery of 30 min smoke and a 15 min air-breathing period between the two smoke exposures. Comparison of the immediate response to smoke exposure was made by monitoring respiration during exposure and by observation of the animals immediately following exposure. At this level, the only differences observed were more severe signs of smoke intoxication in the American smoke exposed animals which, at least in part, was attributed to the higher concentrations of carbon monoxide (CO) to which these animals were exposed; CO concentrations in the American smoke atmospheres were 2–2.5 times higher than the corresponding kretek smoke atmospheres. Comparison of any delayed response was made by observation and measurement of body weight, food and water consumption for a sub-population maintained for 14 days following exposures. This comparison revealed no differences between the groups which could be attributed to the smoke exposures. Comparison of any lung changes induced were made at two intervals, 24h and 14 days following smoke exposures. These intervals were selected to provide information on any damage to the lung attributable to the smoke exposures and any subsequent development or repair. Lung changes were assessed by measurement of lung weights and by histopathological examination. Comparison of lung weights revealed no substantial differences between the groups which could be attributed to the smoke exposures. No qualitative histopathological differences were detected between the different types of cigarette either at 24 h or 14 days after exposure. However, a slight increase in the incidence and severity of focal alveolar haemorrhage was present in the high dose American group at 24 h compared with the high dose kretek group killed at the same time interval.     

Pathological alterations in Syrian golden hamster lungs after passive exposure to cigarette smoke

The effects of 2 types of research cigarettes, differing in their total smoke delivery and condensate, were examined as to their histopathological effects on Syrian golden hamster lungs. The animals were passively exposed to the total smoke of the cigarettes once a day, 5 days/week for 1 year. Experimental and control animals were killed one day after termination of exposure. Varying effects on the macrophages of pulmonary alveolar tissue were observed. Infiltration of lung tissue by “Brown cells” was a common pathological alteration. Qualitative and quantitative differences existed between the two cigarette groups with respect to the occurrence of such “Brown cell” clumps. The response of the lung tissue to smoke exposure would appear to be dependent upon the amount of mainstream total particulate matter (TPM), the amount of condensate, the time exposed and the number of cigarettes.     

Protective effects of N-acetylcysteine on peroxidative changes of the fetal rat lungs whose mothers were exposed to cigarette smoke

BACKGROUND: This experimental study investigated the protective effects of N-acetylcysteine (NAC) on peroxidative changes in fetal lungs in the offspring of rats exposed to cigarette smoke. METHODS: Thirty fetal rats used for analysis, were divided into three groups as follows: control group (n = 10), whose mothers were exposed to fresh air; group I (n =10), whose mothers were exposed to cigarette smoke; and group II (n =10), whose mothers were exposed to cigarette smoke and given 10 mg/kg per day NAC. In groups I and II, smoke exposure was started 4 weeks before the pregnancy, and continued to the 14th day of pregnancy, and in Group II, NAC was administered intraperitoneally for 14 days. The mothers and their fetuses were decapitated on the 14th day of pregnancy. Malondialdehyde (MDA) and glutathione (GSH) levels were determined in the lung tissues of fetuses to determine the oxidant-antioxidant balance. RESULTS: While tissue MDA levels in Group I were found significantly higher than the control group (129.7+/-65.4 versus 63.4 +/-15.4 nmol/100 mg protein, P <0.05), GSH levels were significantly lower (17.1+/-7.3 versus 45.4 + 8.1 nmol/mg protein, P <0.01). Furthermore, in Group II, MDA levels were significantly lower (56.9+/-20.6 versus 129.7+/-65.4 nmol/100 mg protein, P <0.05), and GSH levels were significantly higher (34.57+/-10.7 versus 17.1+/-7.3 nmol/mg protein, P <0.0001) when compared with Group I. No statistically significant difference was found in tissue MDA and GSH levels between Group II and the control group (P >0.05). CONCLUSIONS: These results suggest that smoke exposure during pregnancy causes oxidative damage in fetal lungs. This smoke-induced damage might be prevented by NAC.     

Inhibition of immunological function mediated DNA damage of alveolar macrophages caused by cigarette smoke in mice

Exposure to cigarette smoke impairs the pulmonary immune system, including alveolar macrophage function, although the mechanisms by which this occurs are not fully elucidated. This study investigates the effect of cigarette smoke exposure on the antigen-presenting activity of alveolar macrophages, which is required for antigen-specific response to T cells. C57BL/6 mice were exposed to cigarette smoke for 10 days using a Hamburg II smoking machine, and alveolar macrophages were obtained by bronchoalveolar lavage. The antigen-presenting activity of alveolar macrophages was significantly inhibited in mice exposed to cigarette smoke compared with mice not exposed to cigarette smoke. Major histocompatibility complex class II cell surface molecule–positive cells, B7-1 molecule–positive cells, and interleukin-1β messenger RNA gene expression in alveolar macrophages were significantly decreased in mice exposed to cigarette smoke compared with mice not exposed to cigarette smoke. In contrast, DNA damage and generation of superoxide and hydrogen peroxide in alveolar macrophages were significantly increased by cigarette smoke exposure. These results suggest that inhibition of the antigen-presenting activity of alveolar macrophages may result from decreased expression of major histocompatibility complex class II and B7-1 molecules and interleukin-1β messenger RNA gene expression following cigarette smoke exposure. Furthermore, inhibition of antigen presentation in alveolar macrophage may result from DNA damage induced by excessive amounts of reactive oxygen species being generated by alveolar macrophages following cigarette smoke exposure. These findings suggest that cigarette smoke impairs the immunological function of alveolar macrophages and, as a result, increases the risk for pulmonary infection.     

Influences of cigarette smoke inhalation on pharmacokinetics of cimetidine in rats.

The influences of cigarette smoke inhalation on the pharmacokinetics of cimetidine administered orally and parenterally were investigated in rats using a smoking machine. The animals were exposed to two kinds of cigarette smoke, low- or high-nicotine.tar, inhaled for 10 min immediately after oral (50 mg/kg), intraperitoneal (25 mg/kg) or intravenous (10 mg/kg) administration of cimetidine. The plasma level after cimetidine was administered orally was lower in the absorption phase in the two cigarette smoke inhaling groups than in the non-smoking control group, and was particularly marked in the high-nicotine.tar cigarette smoke inhaling group. In contrast, no significant difference was found in cimetidine plasma level between the cigarette smoke inhaling groups and the non-smoking control group when administered intraperitoneally or intravenously. These results suggest that cigarette smoke inhalation may cause a suppression or a delay in cimetidine absorption from the gastrointestinal tract, and that the degree of influence is dependent upon the content of nicotine.tar in the cigarette smoke.     

Cigarette smoke exposure does not prevent cadmium-induced alterations in rat lungs.

Cigarette smoke has been demonstrated to suppress the biosynthesis of connective tissue in the lung. To further characterize this suppressant effect, we studied the ability of cigarette smoke to prevent or ameliorate cadmium-induced alterations in rat lungs in vivo. The effects of beta-aminopropionitrile (beta APN), an agent that inhibits the cross-linking of elastin, also were studied. Eighty-eight young female Long-Evans rats were randomly divided into seven groups as follows: control, cigarette smoke, sham smoke, beta APN, cadmium, cadmium + cigarette smoke, and cadmium + beta APN. Each animal in the cigarette smoke group was exposed to mainstream smoke generated from University of Kentucky 2R1 reference cigarettes (10 puffs daily for 12 wk). Sham-treated animals received room air in place of cigarette smoke. beta APN (0.5 g/kg) was injected intraperitoneally twice weekly. In cadmium-treated groups, each rat received intermittently three intratracheal instillations of cadmium chloride (0.15 mumol/kg) over a 5-d period. For the cadmium + cigarette smoke group, smoke exposure began 3 d after the first cadmium instillation and was continued for 12 wk. The beta APN administration began 5 d before cadmium instillation and also was continued for 12 wk. After these treatments, pulmonary function and lung morphometry were examined. Neither cigarette smoke, sham smoke, nor beta APN produced significant changes in lung function or morphometry. Cadmium caused significant decreases in total lung capacity, dynamic and static compliance, and carbon monoxide diffusing capacity, as well as significant increases in lung weight and alveolar wall thickness. In addition, the quasistatic deflation pressure-volume curve showed a rightward shift whereas the mean linear intercept of the alveoli did not change significantly. Efforts to prevent or ameliorate the changes through exposure to cigarette smoke or administration of beta APN were unsuccessful. It is concluded that interventions designed to inhibit the biosynthesis of lung connective tissue do not perforce inhibit the development of cadmium-induced pulmonary changes in the rat.     

The effect of resveratrol in tracheal tissue of rats exposed to cigarette smoke

Objective: The aim of this study was to evaluate the effect of resveratrol on the tracheal tissue of rats exposed to cigarette smoke.

Materials and methods: 40 adult Wistar albino rats were divided into four groups for an experiment of 6 weeks. Animals in group 1 were controls (n?=?10). Rats in group 2 were exposed to cigarette smoke only, and rats in group 3 received daily intraperitoneal injections of resveratrol (10?mg/kg/d). Animals in group 4 were exposed to both cigarette smoke and intraperitoneal injections of resveratrol. Rats of all groups were sacrificed using cervical dislocation. The tracheas were removed and embedded in paraffin blocks. Sections of 4–5 μm thickness were prepared from the blocks. These sections were stained with hematoxylin and eosin, periodic acid–Schiff, and Alcian blue and viewed with a Leica DFC 280 light microscope.

Results: Tracheal sections showed that, in group 2 (cigarette smoke group), there was desquamation of epithelial cells into the tracheal lumen, loss of cilia in the epithelial layer, an increase of goblet cells, activation of serous glands at the submucosa, and cell infiltration. In group 4 (cigarette smoke + resveratrol group), all these findings also existed but only a few sections were affected. It was observed that cigarette smoking caused morphological changes such as epithelial degeneration in the upper airway. These morphological changes were correlated with the amount of toxic substances in the cigarette smoke.

Conclusion: We found that resveratrol had a preventive role in the histopathological changes caused by cigarette smoking in the rat trachea.     

Quantitative Histology and Cytochrome P-450 Immunocytochemistry of the Lung Parenchyma Following 6 Months of Exposure of Strain A/J Mice to Cigarette Sidestream Smoke

Abstract

Male strain A/J mice were exposed for 6 h/day, 5 days/wk to aged and diluted cigarette sidestream smoke (ADSS) at a chamber concentration of 4 mg/m³ of total suspended particulate matter (TSP). After 6 mo, the lungs were examined for altered expression of cytochrome P-450 isozymes and for differences in total alveolar tissue volume or surface area, as well as changes in the numbers of epithelial type II cells and alveolar macrophages. Morphologic measurements showed no statistically significant differences for the air, alveolar tissue, or capillary volumes of the lungs or changes in the total number of epithelial type II cells or alveolar macrophages. In contrast, cytochrome P-4501A1 was elevated in the lungs of ADSS-exposed animals and localized in capillary endothelial cells. CYP2B1 was present in airway epithelial cells as well as in epithelial cells throughout the lung parenchyma, but its distribution was not changed by ADSS exposure. Isozyme CYP2E1 was also found in airway epithelial cells, but not in the lung parenchyma, with no differences noted between ADSS exposed animals and controls. CYP2F2 was found in the bronchiolar Clara cells and in type II cells located within the alveolar parenchyma, but was also unchanged. It is concluded that chronic exposure to cigarette ADSS at 4 mg/m³ of TSP produces no changes in alveolar macrophages or epithelial type II cells in mouse lung but increases the expression of cytochrome P4501A1.     

Influences of exposure to cigarette smoke on concentration of nicorandil in plasma of rats.

Influences of acute exposure to cigarette smoke on plasma concentrations of nicorandil administered orally and parenterally were investigated in rats by HPLC. The animals were exposed to tobacco smoke of two kinds of cigarettes using a smoking machine (i.e., the cigarette smoke contained either low or high nicotine and tar). The plasma concentration of nicorandil administered orally at a dose of 10 mg/kg had a lower absorption phase in two cigarette smoke-exposed groups, particularly in the high nicotine and tar-containing cigarette smoke-exposed group, compared with the nonsmoking control group. The AUC and MRT values in a high nicotine and tar-containing cigarette smoke-exposed group were lower and higher, respectively, than in the nonsmoking control group. However, there was no marked difference in nicorandil plasma concentrations between the cigarette smoke-exposed group and the nonsmoking control group when nicorandil was administered ip or iv at a dose of 5 mg/kg. These results suggest that cigarette smoke exposure causes the suppression or delay of absorption of nicorandil from the gastrointestinal tract.     

Oral exposure to cadmium and mercury alone and in combination causes damage to the lung tissue of Sprague-Dawley rats

Environmental presence and human exposure to heavy metals in air and cigarette smoke has led to a worldwide increase in respiratory disease. The effects of oral exposure to heavy metals in liver and kidney structure and function have been widely investigated and the respiratory system as a target is often overlooked. The aim of the study was to investigate the possible structural changes in the lung tissue of Sprague-Dawley rats after oral exposure for 28 days to cadmium (Cd) and mercury (Hg), alone and in combination at 1000 times the World Health Organization’s limit for each metal in drinking water. Following exposure, the general morphology of the bronchiole and lungs as well as collagen and elastin distribution was evaluated using histological techniques and transmission electron microscopy. In the lungs, structural changes to the alveoli included collapsed alveolar spaces, presence of inflammatory cells and thickening of the alveolar walls. In addition, exposure to Cd and Hg caused degeneration of the alveolar structures resulting in confluent alveoli. Changes in bronchiole morphology included an increase in smooth muscle mass with luminal epithelium degeneration, detachment and aggregation. Prominent bronchiole-associated lymphoid tissue was present in the group exposed to Cd and Hg. Ultrastructural examination confirmed the presence of fibrosis where in the Cd exposed group, collagen fibrils arrangement was dense, while in the Hg exposed group, additional prominent elastin was present. This study identified the lungs as target of heavy metals toxicity following oral exposure resulting in cellular damage, inflammation and fibrosis and increased risk of respiratory disease where Hg showed the greatest fibrotic effect, which was further, aggravated in combination with Cd.     

Effects of cigarette smoke on the metabolism of vasoactive hormones in rat isolated lungs.

1. The effects of exposure of rats to cigarette smoke have been studied on the metabolism of vasoactive hormones in isolated lungs from these animals. 2. Rats were exposed for 1 h per day to cigarette smoke for 1 day or for 10 days. 3. Angiotensin I conversion was increased after 1 day's exposure but after 10 days' exposure conversion returned to normal. 4. Inactivation of prostaglandin E2 was decreased after 1 day's exposure. After 10 days' exposure there was a further decrease which could not be attributed to smoke alone. 5. The inactivation of 5-hydroxytryptamine and bradykinin remained unchanged after both short and longer exposures to smoke. 6. The metabolic activity of the lung towards some vasoactive hormones in the pulmonary circulation is affected by exposure of the animal to cigarette smoke and such changes may be relevant to the initiation of cardiovascular changes consequent upon cigarette smoking.     

Effect of Cigarette Smoke Exposure on Biomarkers of Lung Injury in the Rat

Abstract

Rats exposed to tobacco cigarette smoke (CS) via inhalation from a high-tar cigarette for 4 h/day over a 14-day period showed measurable changes in specific biochemical and immunological markers of lung injury when compared to control rats exposed to clean dry air. We found epithelial cell layer thickening and increased lung permeability as measured by histopathological examination, and increased levels in hexose and protein exudation present in bronchoalveolar lavage fluid. Exposure to CS also caused a significant reduction in immunoglobulin A (lgA) levels (p < .001), which persisted after postexposure recovery. In addition, alveolar macrophages from rats exposed to CS were unresponsive to lipopolysaccharide stimulation in vitro as shown by reduced expression of cytokine interleukin 1β mRNA compared to air controls. These results suggest that high-tar cigarette smoke can induce disfunctional changes in immune systems. However, as no reproducible smoke-induced changes were seen using medium-tar cigarettes, we have to conclude that the rat may not be the most sensitive species in which to evaluate the mode of action of cigarette smoke on the lung.     

Effect of cigarette smoking on theophylline pharmacokinetics in rats.

The effect of acute cigarette smoke inhalation on the plasma levels of theophylline administered orally and parenterally to rats has been studied. The animals were exposed to smoke containing low- or high-nicotine/tar concentration for 10 min immediately after oral, intraperitoneal (i.p.) or intravenous (i.v.) administration of theophylline. The plasma levels of theophylline when administered orally (20 mg kg-1) were lower in the two cigarette smoke-inhaling groups than in the non-smoking restrained control group, with the lowest values in the high-nicotine/tar group. The plasma levels (8 and 12 h after administration) in the high-nicotine/tar group when theophylline was administered i.p. (10 mg kg-1), were also slightly lower than in the non-smoking restrained control group but this was not significant. When theophylline was administered i.v. (5 mg kg-1), there was no difference between the high-nicotine/tar group and the non-smoking restrained control group. These data indicate that cigarette smoke inhalation causes suppression or delay of theophylline absorption from the gastrointestinal tract.     

The effects of caffeic acid phenethyl ester on tissue damage in lung after hindlimb ischemia-reperfusion.

AIM: The aim of this study was to investigate the effects of caffeic acid phenethyl ester (CAPE) on the lungs as a remote organ after performing hindlimb ischemia-reperfusion (I/R) and by assessing biochemical and histopathological analysis. METHODS: The animals were divided into three groups: control, I/R, and I/R with CAPE. I/R period for 8 h was performed on the right hindlimb of all the anesthesied rats in I/R and CAPE with I/R group. In the CAPE with I/R group, the animals received CAPE 10 microM by intraperitoneal injection 1h before the reperfusion. The animals in the control and I/R groups received a similar volume of saline solution by means of intraperitoneal injection. At the end of the reperfusion period, a midsternotomy was performed. Blood, bronchoalveolar lavage (BAL) and lung tissue were obtained, and were used for biochemical and histopathological examination. RESULTS: The tissue and serum malondyaldehyde levels were significantly lower in the control (P=0.0001 and 0.001, respectively) and in the CAPE with I/R groups (P=0.0001 and 0.003, respectively) compared to the I/R group. Tissue Na(+)-K(+) ATPase activity in the CAPE with I/R group was significantly higher than in the I/R group (P=0.0001). Reduced activity was found in the I/R group compared to the control group (P=0.0001). Myeloperoxidase activity (P=0.001) and protein concentration (P=0.034) in BAL were significantly reduced in CAPE-treated animals when compared with the I/R group. A decreased activity and protein concentration were found in the control group compared to the I/R group (P=0.0001 and 0.024, respectively). The lungs of the I/R group displayed intense peribronchial and perivascular leukocytic infiltration in histopathological examination compared to the CAPE with I/R group (P<0.05). CONCLUSION: CAPE seems to be effective in protecting remote organ injury caused by increased oxidative stress and neutrophil accumulation that results from an I/R injury.     

Sequential changes in the structure of the rat respiratory system during and after exposure to cigarette smoke

The effect of twice daily exposure to diluted cigarette smoke on the structure of the respiratory system was examined in rats exposed for up to 84 days. Changes in respiratory tract structure were also determined in animals which were exposed for 42 days and then left untreated for an equal length of time. Daily food consumption and growth rate were reduced in sham-smoked and in smoke-exposed rats compared with cage controls. When both these treatments were stopped, food consumption and growth rate increased. Goblet cell hyperplasia of tracheal and bronchial epithelia, increased numbers of alveolar macrophages, squamous metaplasia, and hyperplasia of the larynx were seen in rats after 2 weeks of exposure to smoke. Except for tracheal goblet cell hyperplasia, within 14 to 42 days of exposure commencing all these changes showed a maximal observed response which was subsequently maintained as exposures continued up to 84 days. Tracheal goblet cell hyperplasia and alveolar metaplasia increased progressively during this extended exposure period. When exposure to smoke was discontinued after 42 days, larynx, trachea, and bronchus all reverted to normal at varying rates. The incidence, but not the severity, of the alveolar metaplasia induced during the smoke-exposure period continued to increase when animals were not being exposed to smoke.     

小剂量红霉素对香烟烟雾诱导肺气肿中缺氧诱导因子-1α的抑制作用及其机制

目的探索小剂量红霉素对慢性阻塞性肺疾病(Chronic obstructive pulmonary disease,COPD)的抗炎作用及其潜在机制。方法将实验大鼠(雄性Wistar大鼠)随机分为3组,每组8只:正常对照组(C组),香烟烟雾模型组(CS组),红霉素+香烟烟雾模型组(ERY+CS组)。通过香烟烟雾诱导制备大鼠肺气肿模型,同时通过灌胃给予大鼠小剂量红霉素治疗。对比三组肺病理组织形态学改变,肺功能,肺泡灌洗液(BALF)中炎症介质(TNF-α及IL-8)表达以及肺组织缺氧诱导因子-1α(HIF-1α)的表达。结果与C组相比,CS组肺平均内衬间隔(MLI)及平均肺泡数(MAN)均明显增加(P<0.05);与CS组相比,ERY+CS组MLI及MAN均明显好转(P<0.05)。与C组相比,CS组大鼠BALF中炎症介质TNF-α及IL-8表达均明显增高(P<0.01)。经红霉素干预后,ERY+CS组TNF-α及IL-8表达有所降低(P<0.01);香烟烟雾暴露后,CS组大鼠肺功能呈现明显的阻塞性通气功能障碍,FEV0.3及FEV0.3/FVC均降低(P<0.01)。经红霉素干预治疗后,ERY+CS组大鼠肺功能明显改善(P<0.01);免疫组化及Western blot结果表明,香烟烟雾诱导后,CS组大鼠肺气肿组织HIF-α蛋白表达均明显增高(P<0.01);红霉素干预后,ERY+CS组香烟烟雾诱导的HIF-α增高较前降低(P<0.05)。结论小剂量红霉素可通过调控抑制肺部HIF-1α的表达,从而发挥对香烟烟雾诱导的肺气肿的保护性作用,进而改善患者的肺部炎症反应,改善肺功能。     

Glutathione metabolism and utilization of external thiols by cigarette smoke-challenged, isolated rat and rabbit lungs

The purpose of the present investigation was to understand the acute effects of cigarette smoke on glutathione (GSH) metabolism and on utilization of external thiols by cigarette smoke-exposed, perfused rat and rabbit lungs. Most of the experiments were carried out using freshly drawn cigarette smoke. However, cigarette smoke condensate was used in some perfusions for the comparison of the effects between the types of exposures on utilization of external thiols. Cigarette smoke decreased GSH levels significantly (50%) without any increase in glutathione disulfide (GSSG) in both rabbit and rat lungs. In smoke-exposed rabbit lungs, protein thiol groups (protein-SH) decreased significantly (17%) without a significant change in protein-GSH mixed disulfides. However, in the rat lungs, cigarette smoke did not decrease protein-SH and protein-GSH mixed disulfides, indicating species variation in the effect of cigarette smoke. Cigarette smoke inhibited selenium-dependent and -independent GSH peroxidase activities in the rat lung (33%), but not in the rabbit lung. GSH S-transferase and GSSG reductase activities were not altered in cigarette smoke-challenged rabbit and rat lungs. gamma-Glutamylcysteine synthetase and glucose-6-phosphate dehydrogenase activities were significantly lower in smoke-exposed rat lungs as against control lungs, indicating that rat lung enzymes were more susceptible to the effects of cigarette smoke when compared to those of rabbits. N-Acetylcysteine, but not GSH, added to the perfusate significantly protected rabbit lung from smoke-induced GSH depletion. Smoke condensate added to the perfusate also caused GSH depletion in rabbit lung, and GSH or N-acetylcysteine added to the perfusion medium protected the lung indicating that GSH in the media directly interacts with condensate in the media before coming in contact with cellular GSH. These results indicate that acute smoke inhalation decreases pulmonary GSH and that the decreased GSH was not related to disulfide formation. Inhibited GSH synthesis in rat lung could account for the loss of GSH in part after exposure to cigarette smoke. The alternative pathway of GSH utilization could be conjugation with electrophilic smoke components. Thiols, like N-acetylcysteine, were protective against cigarette smoke-induced damage to the rabbit lung. The mechanism could be either by the increased GSH synthesis or by the direct delivery of sulfhydryls from N-acetylcysteine.