12-MONTH INHALATION STUDY ON ROOM-AGED CIGARETTE SIDESTREAM SMOKE IN RATS

A 90-day OECD TG 413 rat inhalation study with systems toxicology endpoints demonstrates reduced exposure effects of the aerosol from the carbon heated tobacco product version 1.2 (CHTP1.2) compared with cigarette smoke. I. Inhalation exposure, clinical pathology and histopathology

Within the framework of a systems toxicology approach, the inhalation toxicity of aerosol from a novel tobacco-heating potentially modified risk tobacco product (MRTP), the carbon-heated tobacco product (CHTP) 1.2, was characterized and compared with that of mainstream smoke (CS) from the 3R4F reference cigarette in a 90-day nose-only rat inhalation study in general accordance with OECD TG 413. CHTP1.2 is a heat-not-burn product using a carbon heat source to produce an aerosol that contains nicotine and tobacco flavor. At equal or twice the nicotine concentration in the test atmospheres, inhalation of CHTP1.2 aerosol led to a significantly lower exposure to harmful constituents and induced less respiratory tract irritation, systemic, and pathological effects compared with CS. Nasal epithelial changes were less pronounced in the CHTP1.2- than in the CS-exposed groups and reverted in the nicotine concentration-matched group after a recovery period. Lung inflammation was minimal in the CHTP1.2-treated groups compared with the moderate extent seen in the 3R4F groups. Many other toxicological endpoints evaluated did not show CHTP1.2 aerosol exposure-related effects, and no effects not seen for 3R4F were observed. These observations were consistent with findings from previous studies in which rats were exposed to MRTP aerosols containing similar nicotine concentrations.

Comprehensive review of epidemiological and animal studies on the potential carcinogenic effects of nicotine per se

The effects of long-term use of nicotine per se on cancer risk, in the absence of tobacco extract or smoke, are not clearly understood. This review evaluates the strength of published scientific evidence, in both epidemiological and animal studies, for the potential carcinogenic effects of nicotine per se; that is to act as a complete carcinogen or as a modulator of carcinogenesis. For human studies, there appears to be inadequate evidence for an association between nicotine exposure and the presence of or lack of a carcinogenic effect due to the limited information available. In animal studies, limited evidence suggests an association between long-term nicotine exposure and a lack of a complete carcinogenic effect. Conclusive studies using current bioassay guidelines, however, are missing. In studies using chemical/physical carcinogens or transgenic models, there appears to be inadequate evidence for an association between nicotine exposure and the presence of or lack of a modulating (stimulating) effect on carcinogenesis. This is primarily due to the large number of conflicting studies. In contrast, a majority of studies provides sufficient evidence for an association between nicotine exposure and enhanced carcinogenesis of cancer cells inoculated in mice. This modulating effect was especially prominent in immunocompromized mice. Overall, taking the human and animal studies into consideration, there appears to be inadequate evidence to conclude that nicotine per se does or does not cause or modulate carcinogenesis in humans. This conclusion is in agreement with the recent US Surgeon General's 2014 report on the health consequences of nicotine exposure.

A 28-day rat inhalation study with an integrated molecular toxicology endpoint demonstrates reduced exposure effects for a prototypic modified risk tobacco product compared with conventional cigarettes

Towards a systems toxicology-based risk assessment, we investigated molecular perturbations accompanying histopathological changes in a 28-day rat inhalation study combining transcriptomics with classical histopathology. We demonstrated reduced biological activity of a prototypic modified risk tobacco product (pMRTP) compared with the reference research cigarette 3R4F. Rats were exposed to filtered air or to three concentrations of mainstream smoke (MS) from 3R4F, or to a high concentration of MS from a pMRTP. Histopathology revealed concentration-dependent changes in response to 3R4F that were irritative stress-related in nasal and bronchial epithelium, and inflammation-related in the lung parenchyma. For pMRTP, significant changes were seen in the nasal epithelium only. Transcriptomics data were obtained from nasal and bronchial epithelium and lung parenchyma. Concentration-dependent gene expression changes were observed following 3R4F exposure, with much smaller changes for pMRTP. A computational-modeling approach based on causal models of tissue-specific biological networks identified cell stress, inflammation, proliferation, and senescence as the most perturbed molecular mechanisms. These perturbations correlated with histopathological observations. Only weak perturbations were observed for pMRTP. In conclusion, a correlative evaluation of classical histopathology together with gene expression-based computational network models may facilitate a systems toxicology-based risk assessment, as shown for a pMRTP.

A comprehensive toxicological evaluation of three adhesives using experimental cigarettes

CONTEXT

Adhesives are used in several different manufacturing operations in the production of cigarettes. The use of new, "high-speed-manufacture" adhesives (e.g. vinyl acetate based) could affect the smoke chemistry and toxicology of cigarettes, compared with older "low-speed-manufacture" adhesives (e.g. starch based).

OBJECTIVE

This study was conducted to determine whether the inclusion of different levels of three adhesives (ethylene vinyl acetate, polyvinyl acetate and starch) in experimental cigarettes results in different smoke chemistry and toxicological responses in in vitro and in vivo assays.

MATERIALS AND METHODS

A battery of tests (analytical chemistry, in vitro and in vivo assays) was used to compare the chemistry and toxicology of smoke from experimental cigarettes made with different combinations of the three adhesives. Varying levels of the different side-seam adhesives, as well as the transfer of adhesives from packaging materials, were tested.

RESULTS

There were differences in some mainstream cigarette smoke constituents as a function of the level of adhesive added to experimental cigarettes and between the tested adhesives. None of these differences translated into statistically significant differences in the in vitro or in vivo assays.

CONCLUSION

The use of newer "high-speed-manufacture" vinyl acetate-based adhesives in cigarettes does not produce toxicological profiles that prevent the adhesives from replacing the older "low-speed-manufacture" adhesives (such as starch).

Inhalation studies for the safety assessment of nanomaterials: status quo and the way forward

While technical and medical potential offered by nanotechnologies increase, the safety assessment of engineered nanomaterials (NMs) needs to follow this pace. Inhalation is a major route of occupational and environmental exposure, and is most relevant for most of the respective safety assessment studies. Control and generation of aerosol from the test materials for this route of administration are technically demanding, and not surprisingly, there are relatively few NMs tested in toxicokinetic, short-term, and subchronic inhalation studies. These studies were in part adapted to the peculiarities of inhaled NMs, but few were also conducted according to organization for economic co-operation and development (OECD) test guidelines. Inhalation studies on the potential to develop chronic diseases, or studies to check the potential analogy to cardiovascular diseases associated with adverse health effects from ambient air pollution, are largely missing. On the way forward, appropriate inhalation studies need to be performed on a number of NMs to assess their hazards and to provide a sound database for correlation and validation of alternative in vitro methods. Moreover, these studies can potentially aid in the grouping of different NMs based on their biokinetics or biological effects. For carcinogenic and cardiovascular effects, research studies are needed to verify-or disprove-the relevance and the mechanisms by which NMs contribute to these effects.

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

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/m(3). 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.

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.

Concentrations of the carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in sidestream cigarette smoke increase after release into indoor air: results from unpublished tobacco industry research

Research has shown that the toxicity of sidestream cigarette smoke, the primary constituent of secondhand smoke, increases over time. To find potential mechanisms that would explain the increase in sidestream smoke toxicity over time, we analyzed unpublished research reports from Philip Morris Co. using the internal tobacco industry documents now available at the University of California San Francisco Legacy Tobacco Documents Library and other Web sites. Unpublished research from Philip Morris Tobacco Company shows that 4-(methylnitrosamino)-I-(3-pyridyl)-1-butanone (NNK), a highly carcinogenic tobacco-specific nitrosamine, can form in sidestream cigarette smoke after it has been released into ambient air. In experiments done between 1983 and 1997, Philip Morris scientists measured the concentration of NNK in sidestream smoke in a sealed stainless steel test chamber at initial particle concentrations of 24 mg/m(3) over the course of 6 to 18 h. They repeatedly showed that airborne NNK concentrations in sidestream cigarette smoke can increase by 50% to 200% per hour during the first 6 h after cigarettes are extinguished. Two experiments done in a real office showed that NNK concentrations increase for the first 2 h after cigarettes are extinguished. If NNK formation also occurs in the lower smoke concentrations observed in real smoking environments, these results suggest that nitrosation of nicotine and/or nicotine breakdown products in aging secondhand smoke is a significant contributor to nitrosamine exposure in humans.

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.

CC16 as a marker of lung epithelial hyperpermeability in an acute model of rats exposed to mainstream cigarette smoke

The Clara cell secretory protein (CC16), which is produced along the tracheal-bronchial tree, has been shown to be a sensitive marker for the detection of lung hyperpermeability. Cigarette smoke inhalation has been associated with increased lung epithelial permeability. In this study we investigated the changes in CC16 in serum and bronchoalveolar lavage fluid (BALF) from female Sprague Dawley rats after a single exposure (2 x 1 h) to diluted mainstream cigarette smoke (MS) from the Reference Cigarette 2R4F. Rats were nose-only exposed to MS at concentrations of 0 (sham exposure), 250, 500, 750, 1000 or 1250 microg total particulate matter per liter. At 2, 4, 15 and 24h after exposure, serum and BALF-samples were collected. CC16 was determined in BALF and serum. Albumin in BALF, another marker for lung permeability was also determined. A trend towards a lower CC16 recovery was observed in BALF from smoke-exposed rats. The CC16 concentration in serum showed a marked (up to five-fold) concentration- and time-dependent increase after MS exposure. The increase of CC16 in serum was most prominent at the early timepoints, i.e. 2 and 4 h after exposure, and a return to baseline concentrations was obvious at 24 h after exposure. The effect of MS exposure on the amount of albumin in BALF was limited (up to 60% increase). This study clearly showed that CC16 is a good marker for the assessment of the increased permeability of the lung/blood barrier after MS-exposure.

Identification of oxidation products of solanesol produced during air sampling for tobacco smoke by electrospray mass spectrometry and HPLC

Solanesol, a 45-carbon, trisesquiterpenoid alcohol found in tobacco leaves and tobacco smoke, has been used as a quantitative marker for tobacco smoke for years. However, solanesol appears to be unreliable as a quantitative marker for tobacco smoke during environmental air sampling because it can be degraded substantially when present as a component of tobacco smoke and by as much as 100% when present as pure solanesol on fortified filters during air sampling. Since there is strong evidence that ozone is the agent responsible for the degradation, solanesol appears to be unreliable as a quantitative marker during indoor air sampling when indoor levels of ozone are greater than about 15 ppb. The degree of loss of pure solanesol is directly proportional to the concentration of ozone and the length of the sampling period and depends on the type of 37 mm membrane filter used for air sampling (PTFE or quartz fiber). While the degree of loss of solanesol is inversely proportional to the relative humidity of the air at a sampling rate of 1.7 L min(-1), the degree of loss is virtually independent of relative humidity at a lower sampling rate; i.e., 0.25 L min(-1). A curve of loss of solanesol on a filter versus concentration of ozone from an ozone generator is virtually identical to a curve segment based on atmospheric ozone under the same conditions of air sampling. Oxidation of solanesol by ozone to approximately 25 to 60% completion produces at least three series of products for a total of at least 26 compounds: (1) isoprenoid acetones, (2)omega-hydroxyisoprenoid acetaldehydes, and (3) isoprenoid oxoaldehydes. All products in each series were tentatively identified as their derivatives with 2-(p-aminophenyl)ethanol (APE) by electrospray mass spectrometry (ES-MS). Ten ozonation products were detected as their 2,4-dinitrophenylhydrazine derivatives by HPLC at 360 nm: 4-oxopentanal and nine isoprenoid acetones (acetone, 6-methyl-5-hepten-2-one, geranylacetone, farnesylacetone, tetraprenylacetone, geranylfarnesylacetone, farnesylfarnesylacetone, farnesylgeranylgeranylacetone and bombiprenone.

Frequency and nature of spontaneous age-related eye lesions observed in a 2-year inhalation toxicity study in rats

A group of 160 Wistar rats (both sexes) from a larger chronic inhalation toxicity study was monitored at baseline and after 1 and 2 years with a photo-slitlamp microscope and a direct ophthalmoscope to record spontaneous age-related eye lesions and treatment-related eye lesions over a period of 24 months. A second group from the same study was monitored at the start and after 5 months of a 6-month posttreatment period immediately following the inhalation period. Rats were nose-only exposed for 6 h/day, 7 days/week, for 2 years to low (3 microg/l) or high (10 microg/l) total particulate matter concentrations of room-aged cigarette sidestream smoke (RASS) or diesel engine exhaust (DEE). Control animals were exposed to filtered fresh air. All ophthalmological examinations were performed in mydriasis, and relevant observations were documented on color slide film. At baseline, all animals with eye lesions were excluded from the study. After 1 year, only minor lesions were found: retrolental opacities (14%) and a few cases of corneal dryness with reddish lid margins. After 2 years, 23% of the animals had unilateral or bilateral retrolental opacities, but the most frequent eye lesions were posterior subcapsular cataracts (PSC, 32%). Water clefts and spokes were found in 11% of the lenses and mature cataracts in 6%. All other eye lesions observed were much less frequent. There were a few cases of glaucoma, corneal dryness and stromal neovascularization. The frequency and type of lesion in animals monitored from the start of the posttreatment period was comparable to what was seen after 2 years. Toward the end of this period the frequency of mature cataracts went up to 9% and that of (secondary) glaucomas to 5%. None of the eye lesions observed showed any association in frequency or severity of expression to the treatment, either RASS or DEE, or to the sex of the animals. In comparison to the (limited) literature data available, far fewer corneal lesions were found in this study, but PSCs and mature cataracts were more frequent. Strain differences may influence these parameters. This study provided valuable information on the nature and frequency of spontaneous age-related eye lesions (0-56%, depending on the tissue) in long-term toxicity studies in Wistar rats.

Hemoglobin adducts in rats chronically exposed to room-aged cigarette sidestream smoke and diesel engine exhaust

Under controlled conditions with exaggerated concentrations of environmental aerosols, the biologically effective dose markers suggested in the literature as being specific for ETS (i.e., HPB Hb adducts for TSNA exposure) and DEE (i.e., l-aminopyrene Hb adducts for l-nitropyrene exposure) did not respond. A slight but dose-dependent increase in 4-ABP Hb adduct levels was seen in RASS-exposed rats.