Lack Of Effect On Rat Lung Stress-Inducible Heat Shock Protein 70 After Acute Tobacco Smoke Inhalation

Abstract

few investigations have examined in vivo expression of heat shock proteins (HSPs) and stress proteins in the lung following environmental stress. Such proteins are thought to provide cellular protection against environmental trauma. This study describes the initial effects of tobacco smoke inhalation on stress-inducible HSP 70 level in the rat lung. Specifically, the expression and possible elevation of stress-inducible HSP 70 in the rat lung was examined 5 h following inhalation of tobacco smoke from one research cigarette (2R1/University of Kentucky). Male Sprague-Dawley rats were exposed nose-only to tobacco smoke (n = 6), while control rats were exposed to purified filtered air (n = 6). Samples of the peripheral lung from the right apical lobe were homogenized and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE), protein immunoblotting, chemiluminescence detection, and computerized optical densitometric scanning. The results revealed that stressinducible HSP 70 is present constitutively in the control rat lung at 30.83 ± 14.81 (SD) optical units and is elevated slightly at 35.33 ± 12.05 (SD) optical units but not significantly (p = .77) in lungs that inhaled tobacco smoke. A more complete time-course profile will determine whether stressinducible HSP 70 levels are elevated significantly following tobacco smoke inhalation. Changes in the levels of stress proteins that are elevated in damaged lung cells may be of utility for toxi-cological assessment following inhalation exposures to either tobacco smoke or other types of pulmonary toxicants in the atmosphere.     

Elevation of Stress-Inducible Heat Shock Protein 70 in the Rat Lung After Exposure to Ozone and Particle-Containing Atmospheres

Abstract

Heat shock proteins (HSPs) are elicited as part of a ubiquitous cellular defense mechanism following exposure to a variety of environmental assaults. Ozone (O₃) is a commonly encountered toxic air pollutant that is known to produce a variety of effects in the lung. However, the effects of O₃ exposure on lung HSP expression have not been reported. In this study, the expression and elevation of stress-inducible HSP 70 was examined in rat lungs (group sizes = 7) following inhalation exposure to either (a) 0.2 ppm O₃ or (b) a mixture of 0.2 ppm O₃, 350 ± 75 μg/m³ road dust particles with mass median aerodynamic diameter of 5 μm, 65 ± 14 μg/m³ ammonium sulfate (SO₄^?2), and 365 ± 35 μm/m³ ammonium nitrate (NO₃^?1). Exposures were episodic at 4 h/day, 4 consecutive days per week for 8 wk; control rats inhaled purified air (n = 4). Rats were euthanized at either 4 or 17 days after the last exposures, and samples of the peripheral lung from the right apical lobe were obtained for analysis of stress-inducible HSP 70 levels. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PACE) and subsequent protein immunoblotting revealed that stress-inducible HSP 70 was present constitutively in the control lungs. There were no differences in HSP 70 levels in the 4-day and 17-day sacrifice groups; therefore, the groups were pooled for statistical analysis. Statistical analysis by analysis of variance demonstrated that inhalation of atmospheres containing either O₃ or O₃ in combination with particles significantly elevated rat lung stress-inducible HSP 70 levels (p =.0007) over control animals that inhaled only purified air; a significant difference could be detected between O₃ inhalation and control air (p = .0003) and O₃ with the other particles versus the control animals (p =.0092). Furthermore, analysis of the two groups that inhaled either O₃ or O₃ in combination with other particles showed a significant difference (p =.0071). The data suggests that lung stress-inducible HSP 70 elevation after exposure to airborne pollutants may be important and that changes in HSP 70 levels may be an extremely sensitive indicator of early pulmonary stress and injury.     

Chronic Nose-only Inhalation Study in Rats,comparing Room-aged Sidestream Cigarette Smoke and Diesel Engine Exhaust

Nose-only exposure of male and female Wistar rats to a surrogate for environmental tobacco smoke, termed room-aged sidestream smoke (RASS), to diesel engine exhaust (DEE), or to filtered, fresh air (sham) was performed 6 hours/day, 7 days/week for 2 years, followed by a 6-month post-exposure period. The particulate concentrations were 3 and 10 mg/m³. Markers of inflammation in bronchoalveolar lavage showed that DEE (but not RASS) produced a dose-related and persistent inflammatory response. Lung weights were increased markedly in the DEE (but not RASS) groups and did not decrease during the 6-month post-exposure period. Bulky lung DNA adducts increased in the RASS groups, but not in the DEE groups. Cell proliferation in the lungs was unaffected by either experimental treatment. Histopathological responses in the RASS groups were minimal and almost completely reversible; lung tumors were similar in number to those seen in the sham-exposed groups. Rats exposed to DEE showed a panoply of dose-related histopathological responses: largely irreversible and in some cases progressive. Malignant and multiple tumors were seen only in the DEE groups; after 30 months, the tumor incidence (predominantly bronchiolo-alveolar adenomas) was 2% in the sham-exposed groups, 5%in the high RASS groups, and 46% in the high DEE groups (sexes combined). Our results suggest that in rats exposed to DEE, but not to RASS, the following series of events occurs: particle deposition in lungs → lung “overload” → pulmonary inflammation → tumorigenesis, without a significant modifying role of cell proliferation or DNA adduct formation.     

Gene Expression Profiling in Lung Tissues from Mice Exposed to Cigarette Smoke,Lipopolysaccharide, or Smoke Plus Lipopolysaccharide by Inhalation

The purpose of this study was to investigate whether coexposure to lipopolysacchride (LPS) will heighten the inflammatory response and other pulmonary lesions in mice exposed to cigarette smoke, and thus to evaluate the potential use of this LPS-compromised mouse model as a model for chronic obstructive pulmonary disease (COPD) investigation. AKR/J male mice were exposed to HEPA-filtered air (sham control group), cigarette smoke (smoke group), LPS (LPS group), or smoke plus LPS (smoke–LPS group) by nose-only inhalation. Lungs were collected at the end of the 3-wk exposure and processed for microarray analysis. Clustering and network analysis showed decreased heat-shock response and chaperone activity, increased immune and inflammatory response, and increased mitosis in all three exposed groups. Two networks/function modules were exclusively found in the smoke–LPS group, that is, the downregulated muscle development/muscle contraction process and the upregulated reactive oxygen species production process. Notably, the number of genes and function modules/networks associated with inflammation was reduced in the smoke–LPS group compared to the LPS group. The most upregulated gene in the smoke group, MMP12, is a matrix metalloproteinase that preferentially degrades elastin and has been implicated in COPD development. NOXO1, which was upregulated in all three treatment groups, positively regulates the expression of a subunit of NADPH oxidase (NOX1), a major source of reactive oxygen species, and may play an important role in the pathogenesis of COPD. Serum amyloid A1, which is an acute-phase systemic inflammation marker and can be induced by LPS exposure, was significantly upregulated in the LPS and smoke–LPS groups. MARCO, a scavenger receptor expressed in macrophages that may play a significant role in LPS-induced inflammatory response, was upregulated in the LPS group and the smoke–LPS group, but not in the smoke group. In conclusion, gene expression profiling identified genes and function modules that may be related to COPD pathogenesis and may be useful as biomarkers to monitor COPD progression. In addition, an LPS-compromised mouse model showed potential as a useful tool for studying cigarette smoke-associated COPD.     

Effect of Chronic Cigarette Smoke Exposure on Lung Clearance of Tracer Particles Inhaled by Rats

Cigarette smoking can influence the pulmonary disposition ofother inhaled materials in humans and laboratory animals. Thisstudy was undertaken to investigate the influence of cigarettesmoke exposures of rats on the pulmonary clearance of inhaled,relatively insoluble radioactive tracer particles. Following13 weeks of whole-body exposure to air or mainstream cigarettesmoke for 6 hr/day, 5 days/week at concentrations of 0, 100,or 250 mg total particulate matter (TPM)/m³, rats were acutelyexposed pernasally to ⁸⁵Sr-labeled fused aluminosilicate (⁸⁵Sr-FAP)tracer particles, then air or smoke exposures were resumed.A separate group of rats was exposed to the ⁸⁵Sr-FAP then seriallyeuthanized through 6 months after exposure to confirm the relativeinsolubility of the tracer particles. We observed decreasedtracer particle clearance from the lungs that was smoke concentration-dependent.By 180 days after exposure to the tracer aerosol, about 14,20, and 40% of the initial activity of tracer was present incontrol, 100 mg TPM/m³, and 250 mg TPM/m³ groups, respectively.Body weight gains were less in smoke-exposed rats than in controls.Smoke exposure produced lung lesions which included increasednumbers of pigmented alveolar macrophages distributed throughoutthe parenchyma and focal collections of enlarged alveolar macrophageswith concomitant alveolar epithelial hyperplasia and neutro-philicalveolitis. The severity of the lesions increased with smokeexposure duration and concentration to include interstitialaggregates of pigmented macrophages and interstitial fibrosis.Our data confirm previous findings that exposure to cigarettesmoke decreases the ability of the lungs to clear inhaled materials.We further demonstrate an exposure-concentration related magnitudeof effect, suggesting that the cigarette smoke-exposed rat constitutesa useful model for studies of the effects of cigarette smokeon the disposition of inhaled particles.     

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.     

Expression of C-Reactive Protein and Heat-Shock Protein-70 in the Lung Epithelial Cell Line A549, in Response to PM10 Exposure

Increased levels of C-reactive protein (CRP) and heat-shock protein-70 (Hsp70) in plasma are known to be associated with an increased risk of cardiovascular disease. In this study we have investigated the effects of environmental air pollution particles (PM10) and ultrafine carbon black (ufCB) on the expression of CRP and Hsp70 in the lung epithelial cell line, A549. After treatment with PM10 or ufCB the cells were found to have increased expression of CRP and Hsp70 localized in both the cell cytoplasm and nucleus. Analysis of the cell supernatants revealed that CRP and Hsp70 were present, suggesting secretion of both proteins in response to the particulate treatment. To investigate if the expression of CRP and Hsp70 was the result of free radical production, cells were treated with ufCB in the presence of antioxidants (NAL and Trolox). This revealed that antioxidants reduced the amount of CRP and Hsp70 secreted from the cells. These findings suggest that CRP and Hsp70 may be secreted from the lung epithelium as a result of oxidative stress and have important effects on the inflammatory response associated with inhalation of particulate matter.     

Immunohistochemical Evaluation of Oxidative Stress in Murine Lungs After Cigarette Smoke Exposure

Cigarette smoking generates an oxidative stress in the lung, which may contribute to the pathogenesis of chronic obstructive pulmonary disease. We performed an immunohistochemical study to evaluate oxidative stress in the lung after acute cigarette smoke (CS) exposure in mice. Paraffin-embedded lung tissue sections were prepared from mice exposed and unexposed to CS for 1 h. The sections were immunostained with antibodies against 8-hydroxy-2'-deoxyguanosine (8-OHdG), an oxidative DNA adduct, and 4-hydroxy-2-nonenal (4-HNE), a lipid peroxidation product. The bronchiolar and alveolar epithelium of mice unexposed to CS exhibited weak signals for 8-OHdG and 4-HNE, whereas by 1 h after CS exposure the signals in the bronchiolar epithelial cells and the alveolar epithelial cells, particularly type II cells, had increased dramatically. The increases in both were associated with increased 8-OHdG levels in bronchoalveolar lavage fluid as determined by enzyme-linked immunoassay. These results suggest that acute CS exposure imposes oxidative stress predominantly on bronchiolar epithelial and alveolar type II cells, confirming that cigarette smoking causes oxidative damage to the respiratory epithelium.     

Comparison of Fresh and Room-Aged Cigarette Sidestream Smoke in a Subchronic Inhalation Study on Rats

Two experimental types of cigarette sidestream smoke (SS) werecompared in a subchronic inhalation study on rats. Fresh SS(FSS) was generated continuously from the reference cigarette2R1. Room-aged SS (RASS) was generated by aging FSS for 1.5h in a room with noninert surfaces with materials typicallyfound in residences or offices. Male Sprague-Dawley rats werehead-only exposed to three dose levels of each SS type and tofiltered, conditioned fresh air (sham-exposure) for 6 h/day,7 days/week, for 90 days. Room-aging resulted in decreased concentrationsof various SS components, e.g., total participate matter (TPM)and nicotine, while other components, such as carbon monoxide(CO), were not affected. The CO concentrations were 6, 13, and28 ppm for both SS types. TPM concentrations were between 0.6and 8.7 (µg/liter and thus up to 100-fold above the maximumof average concentrations of respiratory suspended particlesreported for environmental tobacco smoke. Slight reserve cellhyperplasia in the anterior part of the nose as well as hyperplasticand metaplastic epithelial changes in the larynx were the onlyobserved dose-dependent findings. The metabolism of benzo(a)-pyrene-asa proxy for polycyclic aromatic hydrocarbon metabolism-was inducedin the nasal respiratory epithelium and in the lungs while noeffect was seen in the nasal olfactory epithelium. The lowest-observedeffect level was 6 ppm CO or 0.6 µg TPM/liter. Most ofthe effects seen were less expressed in RASS- than in FSS-exposedrats when compared on the basis of the CO concentrations. Whencompared on the basis of TPM, these effects were equally pronouncedfor both SS types, suggesting a major role of particulate matter-associatedcompounds. All findings reverted to sham control levels followinga 42-day postinhalation period.     

Comparative 13-Week Inhalation Study of Cigarette Smoke from Cigarettes Containing Cast Sheet Tobacco

A subchronic, nose-only inhalation study was conducted to compare the effects of mainstream smoke from a reference cigarette containing conventional reconstituted tobacco sheet at 30% of the finished blend to mainstream smoke from cigarettes containing 10% or 15% cast sheet (a specific type of reconstituted tobacco sheet) substituted for part of the conventional reconstituted tobacco. Male and female Sprague-Dawley rats were exposed for 1 h/day, 5 d/wk, for 13 wk to mainstream smoke at 0, 0.06, 0.20, or 0.80 mg wet total particulate matter per liter of air. Clinical signs, body and organ weights, clinical chemistry, hematology, carboxyhemoglobin (COHb), serum nicotine, plethysmography, gross pathology, and histopathology were determined. Exposure to cigarette smoke induced a number of changes in respiratory physiology, histopathology, and serum nicotine and COHb levels when compared to sham animals. When corresponding dose groups of reference and cast sheet mainstream smokes were compared, no biological differences were noted. At the end of the exposure period, subsets of rats from each group were maintained without smoke exposures for an additional 13 wk (recovery period). At the end of the recovery period, there were no statistically significant differences in histopathological findings observed between the reference and either cast sheet cigarette. Substitution of 10% or 15% cast sheet tobacco for conventional reconstituted tobacco sheet does not alter the inhalation toxicology of the mainstream smoke when compared to mainstream smoke from a reference cigarette containing conventional reconstituted tobacco sheet.     

Feasibility of Using a Near-Infrared Device for the Determination of Nicotine in Cigarette Smoke Presented to Animals in Inhalation Studies

Abstract

Summary: Nicotine in smoke presented to animals in inhalation studies is currently determined by placing glass-fiber pads (“Cambridge“ pads) in unoccupied animal ports in the smoking machine and pulling a fixed volume of smoke through the pad. The nicotine is extracted from the pad and quantified using gas chromatography (GC). A near-infrared (NIR) instrument was used to develop an alternative technique, which provides estimates of nicotine concentrations on Cambridge pads in only 1–2 min. For given cigarette types, the NIR data are highly correlated with the GC data. This new method results in considerable time-saving during inhalation studies with cigarette smoke.     

Reduced Toxicological Activity of Cigarette Smoke by the Addition of Ammonia Magnesium Phosphate to the Paper of an Electrically Heated Cigarette: Subchronic Inhalation Toxicology

Cigarette smoke is a complex chemical mixture that causes a variety of diseases, such as lung cancer. With the electrically heated cigarette smoking system (EHCSS), temperatures are applied to the tobacco below those found in conventional cigarettes, resulting in less combustion, reduced yields of some smoke constituents, and decreased activity in some standard toxicological tests. The first generation of electrically heated cigarettes (EHC) also resulted in increased formaldehyde yields; therefore, a second generation of EHC was developed with ammonium magnesium phosphate (AMP) in the cigarette paper in part to address this increase. The toxicological activity of mainstream smoke from these two generations of EHC and of a conventional reference cigarette was investigated in two studies in rats: a standard 90-day inhalation toxicity study and a 35-day inhalation study focusing on lung inflammation. Many of the typical smoke exposure-related changes were found to be less pronounced after exposure to smoke from the second-generation EHC with AMP than to smoke from the first-generation EHC or the conventional reference cigarette, when compared on a particulate matter or nicotine basis. Differences between the EHC without AMP and the conventional reference cigarette were not as prominent. Overall, AMP incorporated in the EHC cigarette paper reduced the inhalation toxicity of the EHCSS more than expected based on the observed reduction in aldehyde yields.     

Fourteen-Day Inhalation Study in Rats, Using Aged and Diluted Sidestream Smoke from a Reference Cigarette: I. Inhalation Toxicology and Histopathology

Sprague-Dawley rats were exposed 6 hr per day for 14 consecutivedays to aged and diluted sidestream smoke (ADSS), used as asurrogate for Environmental Tobacco Smoke (ETS), at concentrationsof 0.1 (typical), 1 (extreme), or 10 (exaggerated) mg of particulatesper cubic meter. Animals were exposed nose-only, inside whole-bodychambers, to ADSS from the 1R4F reference cigarette. End-pointsincluded histopathology, CO-ox-imetry plasma nicotine and cotinine,clinical pathology, and organ and body weights. The only pathologicalresponse observed was slight to mild epithelial hyperplasiaand inflammation in the most rostral part of the nasal cavity,in the high-exposure group only. No effects were noted at mediumor low exposures. The minimal changes noted were reversible,using a subgroup of animals kept without further treatment foran additional 14 days. Overall, the end-points used in the studydemonstrated that there was no detectable biological activityof ADSS at typical or even 10-fold ETS concentrations and thatthe activity was only minimal at very exaggerated concentrations(particle concentrations 100 times higher than typical real-worldconcentrations).     

雾化吸入和腹腔注射依达拉奉对烟雾吸入性损伤肺模型大鼠保护作用的比较研究

目的:比较雾化吸入和腹腔注射依达拉奉对烟雾吸入性肺损伤模型大鼠急性肺损伤的保护作用。方法:将30只雄性SD大鼠按照随机数字表法分为正常对照组(A组)、致伤空白组(B组)、致伤腹腔注射治疗组(C组)和致伤低、高剂量雾化吸入治疗组(D、E组),每组6只。B~E组大鼠均被置于含松木屑的烟雾发生器中复制烟雾吸入性肺损伤模型;A组大鼠除不放松木屑外,其余操作同上。造模后30 min,C组大鼠腹腔注射依达拉奉18 mg/kg(每间隔70 min重复1次,共4次);D、E组大鼠雾化吸入依达拉奉9、18 mg/kg(雾化吸入10 min,每间隔60 min重复1次,共4次);A、B组大鼠不作任何处理。末次给药后6 h,进行大鼠动脉血气分析,并计算大鼠肺湿干比(W/D)和肺组织含水率;采用双抗体夹心酶联免疫吸附测定(ELISA)法检测其血清中肿瘤坏死因子α(TNF-α)、白细胞介素6(IL-6)、IL-10含量;采用ELISA等方法检测其肺组织中丙二醛(MDA)、髓过氧化物酶(MPO)、超氧化物歧化酶(SOD)、胱天蛋白酶3(Caspase-3)含量;采用苏木精-伊红染色法观察其肺组织病理改变;采用TUNEL法检测其肺组织细胞凋亡率。结果:A组大鼠肺组织未见异常;B组大鼠肺组织中可见出血及水肿,肺泡结构难以辨认,并可见炎症细胞和红细胞浸润;C~E组大鼠肺组织上述症状均有不同程度改善。与A组比较,其余组大鼠动脉氧分后和吸入氧浓度比值(PaO2/FiO2)以及肺组织SOD含量均显著降低(P<0.05);肺含水率、W/D,血清TNF-α、IL-6、IL-10含量以及肺组织MDA、MPO、Caspase-3含量和细胞凋亡率均显著升高(P<0.05)。与B组比较,各给药组大鼠动脉PaO2/FiO2以及血清IL-10含量均显著升高(P<0.05);肺含水率、W/D,血清TNF-α、IL-6含量以及肺组织MDA、MPO、Caspase-3含量和细胞凋亡率均显著降低,且呈剂量依赖性(P<0.05)。结论:依达拉奉对烟雾吸入性肺损伤模型大鼠具有一定的保护作用,可剂量依赖性地减少炎症介质和(或)细胞因子的产生及释放、减轻过氧化损伤并抑制细胞凋亡,且雾化吸入较腹腔注射的效果更明显。     

Deposition of Cigarette Smoke Particles in the Rat

The fractional deposition of cigarette smoke particles in therespiratory tracts of rats was studied. Male and female ratswere conditioned in nose-only exposure tubes 25 min/day for2 days, exposed to cigarette smoke at mass concentrations of95 or 341 mg/m³ 25 min/day for 3 days, and then exposed to smokeat mass concentrations of 212 and 657 mg/m³, 25 min/day for5 days. Mainstream cigarette smoke was generated by a modifiedWalton smoking machine from two 1R3 research cigarettes burnedsequentially for each exposure. Deposition studies were conductedby placing the rats in plethysmograph tubes to allow respiratoryminute volume measurements during exposure, then exposing themto [¹⁴C] cigarette smoke at mass concentrations of 202 or 624mg/m³ for 25 min, using the same smoking machine. Size distribution,real-time concentration, and ¹⁴C activity of the smoke particleswere determined using a multijet Mercer impactor, a real-timeaerosol monitor, and filter samples, respectively. Immediatelyafter the exposure, the rats were terminated to determine thedistribution of the ¹⁴C. Individual lung lobes, trachea andlobar bronchi, head, larynx, kidneys, liver, gastrointestinal(GI) tract, blood, and depelted carcass of each rat were analyzedfor ¹⁴C content. Results showed that the GI tract contained16–31% of the total activity, indicating significant clearancefrom the large airways and nose to the GI tract during the exposureand during the 10–15 min between the cessation of theexposure and the removal ofthe organs. Total deposition of theinhaled ¹⁴C activity was 20.1 ? 1.6% for both exposure concentrations.The intrapulmonary deposition fractions (lung lobes plus airwaysbelow the lobar bronchi) were 12.4 ? 0.9 and 15.9 ? 1.4% forconcentrations of 202 and 624 mg/m³ respectively, suggestinga slight enhancement in upper airway deposition for animalsexposed to the higher smoke concentration.     

Lung Function Changes in Sprague-Dawley Rats After Prolonged Inhalation Exposure to Silver Nanoparticles

The antimicrobial activity of silver nanoparticles has resulted in their widespread use in many consumer products. However, despite the continuing increase in the population exposed to silver nanoparticles, the effects of prolonged exposure to silver nanoparticles have not been thoroughly determined. Accordingly, this study attempted to investigate the inflammatory responses and pulmonary function changes in rats during 90 days of inhalation exposure to silver nanoparticles. The rats were exposed to silver nanoparticles (18 nm diameter) at concentrations of 0.7 × 10⁶ particles/cm³ (low dose), 1.4 × 10⁶ particles /cm³ (middle dose), and 2.9 × 10⁶ particles /cm³ (high dose) for 6 h/day in an inhalation chamber for 90 days. The lung function was measured every week after the daily exposure, and the animals sacrificed after the 90-day exposure period. Cellular differential counts and inflammatory measurements, such as albumin, lactate dehydrogenase (LDH), and total protein, were also monitored in the acellular bronchoalveolar lavage (BAL) fluid of the rats exposed to the silver nanoparticles for 90 days. Among the lung function test measurements, the tidal volume and minute volume showed a statistically significant decrease during the 90 days of silver nanoparticle exposure. Although no statistically significant differences were found in the cellular differential counts, the inflammation measurements increased in the high-dose female rats. Meanwhile, histopathological examinations indicated dose-dependent increases in lesions related to silver nanoparticle exposure, such as infiltrate mixed cell and chronic alveolar inflammation, including thickened alveolar walls and small granulomatous lesions. Therefore, when taken together, the decreases in the tidal volume and minute volume and other inflammatory responses after prolonged exposure to silver nanoparticles would seem to indicate that nanosized particle inhalation exposure can induce lung function changes, along with inflammation, at much lower mass dose concentrations when compared to submicrometer particles.     

Mechanisms Involved in A/J Mouse Lung Tumorigenesis Induced by Inhalation of an Environmental Tobacco Smoke Surrogate

Abstract

Lung tumors have been reproducibly induced in A/J mice exposed to a surrogate for experimental environmental tobacco smoke (ETSS) in a 5-mo inhalation period followed by 4 mo without further exposure. In order to increase our mechanistic understanding of this model, male mice were whole-body exposed for 6 h/d, 5 d/wk to ETSS with a particulate matter concentration of 100 mg/m³. Food restriction regimens were included to model or exceed the ETSS-related impairment of body weight development. Half of the mice were pretreated with a single ip injection of urethane to study the effect of the above treatments on lung tumor development induced by this substance. At 5 mo, the tumor response was statistically the same for all groups of non-pretreated mice; however, the expected urethane-induced lung tumorigenesis was significantly inhibited by approximately 25% by ETSS and food restriction. This inhibition was accompanied by a threefold increase in blood corticosterone as a common stress marker for both ETSS and food restriction. At 9 mo, in mice not pretreated, the lung tumor incidence and multiplicity were significantly increased by twofold in the ETSS group; in the urethane-treated groups, the same high tumor multiplicity was reached regardless of previous treatment. The predominant tumor type in all groups was bronchiolo-alveolar adenoma. There was no induction of a specific K-ras mutation pattern by ETSS exposure. These data suggest a stress-induced inhibition of lung tumorigenesis in this model, explaining the need for the posttreatment period.     

A Review of the Influence of Particle Size,Puff Volume,and Inhalation Pattern on the Deposition of Cigarette Smoke Particles in the Respiratory Tract

Ventilation of the cigarette was designed to allow dilution of the cigarette smoke and thereby reduce the dose delivered to the smoker. Following the toxicological principle of dose response, a lower concentration of cigarette smoke should be associated with a lower toxicological response. However, there have been many studies reporting on the phenomenon of compensation whereby the smoker increases puff volume and/or frequency in order to obtain higher volumes of smoke This article reviews studies of the particle size of cigarette smoke and examines, based on available literature, the associated differences in the tobacco smoke and smoking behavior and their relationship to deposition patterns in the lung. The data available indicate that particle size of the cigarette smoke does not significantly change as a function of cigarette type or smoking behavior. The cigarette smoke particle size is in the same range as the minimum deposition particle size in the lung. While varying concentrations of particles are taken into the mouth, the subsequent inhalation pattern has been reported as remaining constant and also does not appear to change significantly under different smoking types and conditions. The dynamics of what happens to the smoke in the short time it is retained in the mouth have not been studied, and this perhaps should be the subject of future investigations. The current data therefore suggest that the particle deposition pattern of the smoke within the lung would not change significantly if compensation occurs.     

Numerical Simulation of the Effects of Dilution Level,Depth of Inhalation,and Smoke Composition on Nicotine Vapor Deposition During Cigarette Smoking

A numerical model of an aerosol containing vaporizable nicotine depositing to the walls of a tube was developed and applied to simulate the vapor deposition of nicotine in a denuder tube and under conditions approximating those in the respiratory tract during mainstream cigarette smoke inhalation. The numerical model was validated by comparison to data for denuder tube collection of nicotine from the smoke of three types of cigarette differing in smoke acidity and nicotine volatility. Simulations predict that the absorption of water by aerosol particles inhibits nicotine vapor deposition to tube walls, and that increased temperature, decreased tube diameter, and increased dilution enhance nicotine vapor deposition rate. The combined effect of changing these four parameters to approximate the transition from conducting to gas exchange regions of the respiratory tract was a significant net increase in predicted nicotine vapor deposition rate. Comparisons of nicotine deposition rates between conditions in the conducting airways and those in the gas exchange region were informative with regard to reported nicotine retention measurements during human smoking. Reports that vaporizable nicotine can penetrate past the conducting airways, that nicotine can be retained at near 100% efficiency from mainstream smoke, and that cigarettes with differing acidity and nicotine volatility have similar nicotine uptake rates are all shown to be consistent with the results of the model simulations.     

盐酸氨溴索雾化吸入治疗70例慢性阻塞性肺疾病患者的临床价值研究

目的:分析盐酸氨溴索雾化吸入治疗慢性阻塞性肺疾病患者的临床价值。方法:选择2013年1月~2015年1月某站收治的慢性阻塞性肺疾病患者70例作为研究对象,按照随机分组方式,分成对照与观察两组,对照组给予常规对症治疗,观察组在此前提上加入盐酸氨溴索雾化吸入治疗,比对两组治疗效果。结果:治疗之后,观察组总治疗有效率达97.15%,与对照组相比具有统计学意义(P<0.05)。结论:将盐酸氨溴索雾化吸入治疗用于慢性阻塞性肺疾病,可有效提升临床疗效。