Although cigarette smoke has been epidemiologically associated with lung cancer in humans for many years, animal models of cigarette smoke-induced lung cancer have been lacking. This study demonstrated that life time whole body exposures of female B6C3F1 mice to mainstream cigarette smoke at 250 mg total particulate matter/m(3) for 6 h per day, 5 days a week induces marked increases in the incidence of focal alveolar hyperplasias, pulmonary adenomas, papillomas and adenocarcinomas. Cigarette smoke-exposed mice (n = 330) had a 10-fold increase in the incidence of hyperplastic lesions, and a 4.6-fold (adenomas and papillomas), 7.25-fold (adenocarcinomas) and 5-fold (metastatic pulmonary adenocarcinomas) increase in primary lung neoplasms compared with sham-exposed mice (n = 326). Activating point mutations in codon 12 of the K-ras gene were identified at a similar rate in tumors from sham-exposed mice (47%) and cigarette smoke-exposed mice (60%). The percentages of transversion and transition mutations were similar in both the groups. Hypermethylation of the death associated protein (DAP)-kinase and retinoic acid receptor (RAR)-beta gene promoters was detected in tumors from both sham- and cigarette smoke-exposed mice, with a tendency towards increased frequency of RAR-beta methylation in the tumors from the cigarette smoke-exposed mice. These results emphasize the importance of the activation of K-ras and silencing of DAP-kinase and RAR-beta in lung cancer development, and confirm the relevance of this mouse model for studying lung tumorigenesis.

No abstract

Cigarette smoke (CS) causes pulmonary emphysema in humans, but results of previous studies on CS-exposed laboratory animals have been equivocal and have not clearly demonstrated progression of the disease. In this study, morphometry and histopathology were used to assess emphysema in the lungs of B6C3F1 mice and Fischer-344 rats. The animals were exposed, whole-body, to CS at a concentration of 250 mg total particulate matter/m3 for 6 h/day, 5 days/week, for either 7 or 13 months. Morphometry included measurements of parenchymal air space enlargement (alveolar septa mean linear intercept [Lm], volume density of alveolar air space [VVair]), and tissue loss (volume density of alveolar septa [VVspt]). In addition, centriacinar intra-alveolar inflammatory cells were counted to assess species differences in the type of inflammatory response associated with CS exposure. In mice, many of the morphometric parameters indicating emphysema differed significantly between CS-exposed and control animals. In CS-exposed rats, only some of the parameters differed significantly from control values. The Lm in both CS-exposed mice and rats was increased at 7 and 13 months, indicating an enlargement of parenchymal air spaces, but the VVair was increased significantly only in CS-exposed mice. The VVspt was decreased at both time points in mice, but not in rats, indicating damage to the structural integrity of parenchyma. Morphologic evidence of tissue destruction in the mice included alveoli that were irregular in size and shape and alveoli with multiple foci of septal discontinuities and isolated septal fragments. Morphometric differences in the mice at 13 months were greater than at 7 months, suggesting a progression of the disease. Inflammatory lesions within the lungs of mice contained significantly more neutrophils than those lesions in rats. These results suggest that B6C3F1 mice are more susceptible than F344-rats to the induction of emphysema by this CS exposure regimen and that in mice the emphysema may be progressive. Furthermore, the type of inflammatory response may be a determining factor for species differences in susceptibility to emphysema induction by CS exposure.

No abstract

BackgroundThere are currently no licensed vaccines available for prevention of botulism in humans. The vaccination is not desirable due to expanding therapeutic indications of botulinum toxins. The only available specific treatment for botulism is antitoxin to remove circulating toxin, thus, preventing further neuronal damage. BAT® (Botulism Antitoxin Heptavalent (A, B, C, D, E, F, G)—(Equine)) has been developed and its therapeutic efficacy evaluated against botulinum neurotoxin serotype A (BoNT/A) in Rhesus macaques.Methods and findingsIn a post-exposure prophylaxis (PEP) study, animals were exposed to 4x LD50/kg of BoNT/A and administered intravenously with either BAT (1x or 0.1x scaled human dose), or placebo at 4 hours post-exposure. The animals were monitored for 14 days. For the therapeutic intervention studies, animals were exposed to a 1.7x LD50/kg of BoNT/A and treated intravenously with either placebo or BAT at a 1x scaled human dose at the onset of clinical signs. Animals were monitored on an hourly basis for 14 or 21 days. In the PEP study, all animals tolerated equine based antitoxin without any adverse clinical signs. A 100% survival was observed in groups treated with the BAT compared to 0% survival in those treated with the placebo (p<0.001, Fisher’s exact test). BAT antitoxin prevented the development of signs of neurotoxicity of botulinum toxin. In a therapeutic study, treatment with the BAT at scaled 1x human dose after the onset of clinical signs significantly enhanced survival compared to the placebo (46.6% vs. 0%, p<0.0001, Fisher’s exact test). Additionally, treatment with the BAT delayed the progression of signs (muscular weakness, respiratory distress, oral/nasal discharge) of toxin intoxication and reduced the severity of the disease.ConclusionsA single dose of BAT, when administered to symptomatic monkeys, resulted in a statistically significant survival benefit compared to the placebo. Additionally, BAT completely protected monkeys from the clinical signs of intoxication and subsequent death when administered as PEP treatment. These data in part supported the licensure of BAT under the Animal Rule in the United States by the Food and Drug Administration.

Models of emphysema produced by exposing animals to cigarette smoke (CS) have potential for use in testing treatments of this disease. To better characterize development of emphysema in an animal model, male and female mice of the B6C3F1 and A/J strains were exposed to CS at 250 mg total particulate material (TPM)/m3 for 15 weeks. Emphysema was evident in both strains of mice to differing degrees of severity. The CS-induced increase in the mean linear intercept (normalized to BW) of A/J mice was 51% greater than the control value, while CS-exposed B6C3F1 had an increase of 38% in this morphometric measurement of alveolar air space enlargement. In separate experiments, female B6C3F1 mice and male A/J mice were exposed to CS for 32 weeks and 15 weeks, respectively, and were then used to test the efficacy of all trans-retinoic acid (ATRA) treatments to ameliorate emphysema lesions. Following CS exposure, the B6C3F1 mice were treated once daily for 14 days in a 3-week period by nose-only inhalation exposure to aerosols of 180 or 1,800 mg-minutes ATRA/m3. The A/J mice were treated once daily, 4 days/week, for three weeks by either intraperitoneal injection of ATRA (0.5 or 2.5 mg/kg) or inhalation exposure to ATRA (3,600 or 18,000 mg-minutes/m3). Neither the injections nor inhalation exposures of ATRA in either strain of mouse caused reversal of the emphysema. In summary, CS-induced emphysema was more severe in A/J mice than in B6C3F1 mice. Treatment with ATRA did not reverse emphysema in either strain of CS-exposed mice.

There is increasing interest in diesel fuels derived from plant oils or animal fats ("biodiesel"), but little information on the toxicity of biodiesel emissions other than bacterial mutagenicity. F344 rats were exposed by inhalation 6 h/day, 5 days/wk for 13 wk to 1 of 3 dilutions of emissions from a diesel engine burning 100% soybean oil-derived fuel, or to clean air as controls. Whole emissions were diluted to nominal NO(x) concentrations of 5, 25, or 50 ppm, corresponding to approximately 0.04, 0.2, and 0.5 mg particles/m(3), respectively. Biologically significant, exposure-related effects were limited to the lung, were greater in females than in males, and were observed primarily at the highest exposure level. There was a dose-related increase in the numbers of alveolar macrophages and the numbers of particles in the macrophages, as expected from repeated exposure, but no neutrophil response even at the highest exposure level. The macrophage response was reduced 28 days after cessation of the exposure. Among the high-level females, the group mean lung weight/body weight ratio was increased, and minimal, multifocal bronchiolar metaplasia of alveolar ducts was observed in 4 of 30 rats. Lung weights were not significantly increased, and metaplasia of the alveolar ducts was not observed in males. An increase in particle-laden macrophages was the only exposure-related finding in lungs at the intermediate and low levels, with fewer macrophages and fewer particles per macrophage at the low level. Alveolar histiocytosis was observed in a few rats in both exposed and control groups. There were statistically significant, but minor and not consistently exposure-related, differences in body weight, nonpulmonary organ weights, serum chemistry, and glial fibrillary acidic protein in the brain. There were no significant exposure-related effects on survival, clinical signs, feed consumption, ocular toxicity, hematology, neurohistology, micronuclei in bone marrow, sister chromatid exchanges in peripheral blood lymphocytes, fertility, reproductive toxicity, or teratology. This study demonstrated modest adverse effects at the highest exposure level, and none other than the expected physiological macrophage response to repeated particle exposure at the intermediate level.

No abstract