Augmentation of elastase-induced emphysema by cigarette smoke. Effects of reduced nicotine content

Electronic cigarettes: a task force report from the European Respiratory Society

There is a marked increase in the development and use of electronic nicotine delivery systems or electronic cigarettes (ECIGs). This statement covers electronic cigarettes (ECIGs), defined as "electrical devices that generate an aerosol from a liquid" and thus excludes devices that contain tobacco. Database searches identified published articles that were used to summarise the current knowledge on the epidemiology of ECIG use; their ingredients and accompanied health effects; second-hand exposure; use of ECIGs for smoking cessation; behavioural aspects of ECIGs and social impact; in vitro and animal studies; and user perspectives.ECIG aerosol contains potentially toxic chemicals. As compared to conventional cigarettes, these are fewer and generally in lower concentrations. Second-hand exposures to ECIG chemicals may represent a potential risk, especially to vulnerable populations. There is not enough scientific evidence to support ECIGs as an aid to smoking cessation due to a lack of controlled trials, including those that compare ECIGs with licenced stop-smoking treatments. So far, there are conflicting data that use of ECIGs results in a renormalisation of smoking behaviour or for the gateway hypothesis. Experiments in cell cultures and animal studies show that ECIGs can have multiple negative effects. The long-term effects of ECIG use are unknown, and there is therefore no evidence that ECIGs are safer than tobacco in the long term. Based on current knowledge, negative health effects cannot be ruled out.

Chronic electronic cigarette exposure in mice induces features of COPD in a nicotine-dependent manner

BACKGROUND

The use of electronic (e)-cigarettes is increasing rapidly, but their lung health effects are not established. Clinical studies examining the potential long-term impact of e-cigarette use on lung health will take decades. To address this gap in knowledge, this study investigated the effects of exposure to aerosolised nicotine-free and nicotine-containing e-cigarette fluid on mouse lungs and normal human airway epithelial cells.

METHODS

Mice were exposed to aerosolised phosphate-buffered saline, nicotine-free or nicotine-containing e-cigarette solution, 1-hour daily for 4 months. Normal human bronchial epithelial (NHBE) cells cultured at an air-liquid interface were exposed to e-cigarette vapours or nicotine solutions using a Vitrocell smoke exposure robot.

RESULTS

Inhalation of nicotine-containing e-cigarettes increased airway hyper-reactivity, distal airspace enlargement, mucin production, cytokine and protease expression. Exposure to nicotine-free e-cigarettes did not affect these lung parameters. NHBE cells exposed to nicotine-containing e-cigarette vapour showed impaired ciliary beat frequency, airway surface liquid volume, cystic fibrosis transmembrane regulator and ATP-stimulated K+ ion conductance and decreased expression of FOXJ1 and KCNMA1. Exposure of NHBE cells to nicotine for 5 days increased interleukin (IL)-6 and IL-8 secretion.

CONCLUSIONS

Exposure to inhaled nicotine-containing e-cigarette fluids triggered effects normally associated with the development of COPD including cytokine expression, airway hyper-reactivity and lung tissue destruction. These effects were nicotine-dependent both in the mouse lung and in human airway cells, suggesting that inhaled nicotine contributes to airway and lung disease in addition to its addictive properties. Thus, these findings highlight the potential dangers of nicotine inhalation during e-cigarette use.

[An inhalation chamber model for controlled studies of tobacco smoke toxicity in rodents]

INTRODUCTION

Smoking is a serious worldwide public health problem. Animal models act as a bridge between laboratory and human studies. The models applied are difficult to reproduce because of the use of different types of inhalation chambers and mainly because of the lack of continuous monitoring of smoke concentration.

OBJECTIVE

To develop an inhalation chamber for rats (with only the nose exposed) in which the amount of carbon monoxide (CO) can be maintained and monitored constantly.

MATERIAL AND METHODS

Male Wistar rats weighing 250g were exposed to 50ppm CO produced by the smoke from a filter-free cigarette. The animals were submitted to a single 2-h exposure and then sacrificed at 0, 4, 24 and 48h. The control group was left restrained inside the small perpendicular chambers, receiving only 5L/min of compressed air.

RESULTS

The model was able to increase HbCO levels immediately after the end of exposure (p<0.001), with a decrease being observed from 2h onwards when compared to the levels of the control group. Plasma cotinine increased immediately after exposure, and showed still detectable levels at 2 and 4h (p<0.05).

CONCLUSION

We conclude that the presented inhalation chamber system is able to maintain a controlled CO concentration in a model in which small animals are exposed to the inhalation of cigarette smoke, permitting well-controlled studies, as well as investigations involving other toxic gases and air pollutants.

The pathobiological mechanisms of emphysema models: what do they have in common?

Emphysema results from a multi-step, complex, process of lung destruction. This review aims at organizing the available information concerning the animal models of emphysema as to which step of the pathogenesis they address. The experimental models have been classified as to whether they are based on: (a) pharmacological, (b) environmental, or (c) genetic manipulations to induce emphysema and whether they are: (a) triggers or initiators of emphysema, (b) modifiers of lung predisposition to further damage by trigger factors, or (c) mediators of lung tissue destruction.

Animal models of cigarette smoke-induced COPD

OBJECTIVES

To review the animal models of COPD, and to compare these data to those found in humans.

RESULTS

Smoke-induced animal models can produce emphysema, although the lesions are not generally close mimics of human emphysema, as well as increases in mucous-secreting cells and vascular changes including pulmonary hypertension. There is considerable species-to-species variation in the degree and/or presence of these different abnormalities, so that care has to be used in selecting a species to study. Remarkably little information is available about the biochemical and molecular changes induced by cigarette smoke in animal models.

CONCLUSIONS

Great insights into the pathology of chronic obstructive lung disease have been made using various animal models.

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.