C/EBPbeta-mediated transcriptional regulation of bcl-xl gene expression in human breast epithelial cells in response to cigarette smoke condensate.

In earlier studies, we have shown that cigarette smoke condensate (CSC), a surrogate for cigarette smoke, is capable of transforming the spontaneously immortalized human breast epithelial cell line, MCF10A. These transformed cells displayed upregulation of the anti-apoptotic gene, bcl-xl. Upregulation of this gene may impede the apoptotic pathway and allow the accumulation of DNA damage that can lead to cell transformation and carcinogenesis. In the present study, we have determined the mechanism of CSC-mediated transcriptional upregulation of bcl-xl gene expression in MCF10A cells. We cloned the human bcl-xl promoter (pBcl-xLP) and identified putative transcription factor binding sites. Sequential deletion constructs that removed the putative cis-elements were constructed and transfected into MCF10A cells to determine the CSC-responsive cis-element(s) on the pBcl-xLP. Gel-shift, super-shift and chromatin immunoprecipitation analysis confirmed that CCAAT/enhancer-binding protein (C/EBPbeta) specifically bound to a C/EBP-binding site on the pBcl-xLP in vitro and in vivo. Additionally, overexpression of C/EBPbeta-LAP2 stimulated pBcl-xLP activity and Bcl-xL protein levels, which mimicked the conditions of CSC treatment. Our results indicate that C/EBPbeta regulates bcl-xl gene expression in MCF10A cells in response to CSC treatment; therefore, making it a potential target for chemotherapeutic intervention of cigarette smoke-induced breast carcinogenesis.

Cigarette smoke condensate-induced level of adenomatous polyposis coli blocks long-patch base excision repair in breast epithelial cells.

Our previous studies have shown that treatment with cigarette smoke condensate (CSC) transforms normal breast epithelial cell line, MCF-10A. In the present study, the mechanism of CSC-induced transformation of breast epithelial cells was examined. We first determined whether benzo[a]pyrene (B[a]P)- and CSC-induced levels of APC are capable of inhibiting long-patch base excision repair (LP-BER) since our earlier studies had shown that an interaction of APC with DNA polymerase beta (pol-beta) blocks strand-displacement synthesis. With the use of a novel in vivo LP-BER assay, it was demonstrated that increased and decreased APC levels in different breast cancer cell lines were associated with a decrease or increase in LP-BER activity, respectively. The effect of APC on LP-BER in malignant and pre-malignant breast epithelial cell lines was produced by either overexpression or knockdown of APC. Furthermore, it was shown that the decreased LP-BER in B[a]P- or CSC-treated pre-malignant breast epithelial cells is associated with an increased level of APC and decreased cell growth. Our results suggest that the decreased growth allows cells to repair the damaged DNA before mitosis, and failure to repair damaged DNA has the potential to transform pre-malignant breast epithelial cells.

Identification of kaempferol as an inhibitor of cigarette smoke-induced activation of the aryl hydrocarbon receptor and cell transformation.

The aryl hydrocarbon receptor (AHR) is a cytosolic receptor which upon activation by its agonists, translocates into the nucleus and forms a dimer with ARNT (aryl hydrocarbon nuclear translocator). The AHR/ARNT dimer regulates the expression of its target genes by binding to DNA recognition elements termed dioxin responsive elements (DREs). Many AHR agonists, like the polyaromatic hydrocarbons and polyhalogenated hydrocarbons are known human carcinogens. Human exposure to these compounds is common due to their presence in air pollution and cigarette smoke. Interestingly, many dietary constituents that have chemo preventative properties have been found to also act as antagonists of the AHR pathway. Thus, a chemopreventive approach that may be effective in decreasing the incidences of many human cancers may involve a dietary regimen that includes a number of these naturally occurring AHR antagonists. With this idea in mind, we have assayed the ability of 15 flavonoids to inhibit AHR activated reporter activity and selected kaempferol for further analysis. Kaempferol proved to be capable of inhibiting binding of agonist and agonist-induced formation of the AHR/ARNT DNA-binding complex and upregulation of the AHR target gene, CYP1A1. Using an in vitro paradigm of events that are thought to occur during cigarette-smoke-induced lung cancer, we found that kaempferol also inhibited the ability of cigarette smoke condensate to induce growth of immortalized lung epithelial (BEAS-2B) cells in soft agar. Taken together, these results illustrate the promise associated with the use of flavonoids, that inhibit both AHR signaling and the carcinogenic actions of AHR agonists, for chemopreventive purposes.

Bone biomechanical property deterioration due to tobacco smoke exposure.

Tobacco smoking has been implicated in the development of osteoporosis and early onset of menopause in women smokers. We measured various biomechanical properties of femurs and tibiae obtained from smoke-exposed and control mice to determine cigarette smoke influences on bone mass, structure, and strength. Growing female C57BL mice were exposed to sidestream cigarette smoke in a whole-body exposure chamber, set at 30 +/- 2 mg smoke particulates/m3 for 4 hours/day and 5 days/week for 12 consecutive weeks. Elevated levels of urinary cotinine and pulmonary ethoxyresorufin deethylase activity in smoke-exposed mice confirmed their effective exposure to cigarette smoke. There were no differences in body weight and physical size (length, medial-lateral and anterior-posterior widths, midshaft cortical area and thickness) of femurs and tibiae between smoke-exposed and control mice. The femoral mid-shaft yield load, stiffness, yield stress, and modulus were, respectively 8%, 13%, 10%, and 14% lower (P < 0.05) in smoke-exposed compared to control mice. The ultimate load and stress in mid-shaft femurs showed decreasing trends (P < 0.1) in smoke-exposed mice. In the femoral neck, the ultimate load and stiffness were 9% and 12% lower (P < 0.05) in smoke-exposed mice, respectively. Further, the ash-to-dry bone weight ratio was smaller ( approximately 6%, P < 0.05), and micro-computed tomographic scanning of distal femoral bone volume/total volume (%) and trabecular thickness showed decreasing trends in smoke-exposed mice compared to the control group. We conclude that exposure to tobacco smoke deteriorates some of the biomechanical properties of bone in growing female mice.

Effect of cigarette smoke exposure on the modulation of 8-oxo-2'-deoxyguanosine in rat lungs as analyzed by 32P-postlabeling and HPLC-ECD.

Cigarette smoke contains several oxidants and free radicals. In the present study, we examined the formation of 8-oxo-2'-deoxyguanosine (8-oxodG) in the lungs of female Sprague-Dawley rats exposed to side-stream cigarette smoke for 6 h a day, 7 days a week for 1, 2, 4 and 12 weeks in a whole body-exposure system. The samples were analyzed for 8-oxodG by 32P-postlabeling-TLC enrichment and HPLC-ECD techniques to confirm and compare results. Animals were sacrificed 15 h after the cessation of smoke exposure and lung DNA was isolated by phenol/Sevag extractions in the presence of the free radical traps, 8-hydroxyquinoline (6.8 mM) and N-t-butyl-alpha-phenyl nitrone (500 microM) to minimize artifactual formation of 8-oxodG during sample work up. Analysis of lung DNA by 32P-postlabeling-TLC showed 8-oxodG levels (mean +/- SE) of 1.45+/-0.24, 2.68+/-0.65, 2.23+/-0.28 and 2.93+/-0.54 per 106 nucleotides after 1, 2, 4 and 12 weeks of smoke exposure. The respective values in sham-treated rats were 2.76+/-0.19, 3.69+/-0.20, 1.44+/-0.43 and 2.84+/-0.45 per 106 nucleotides, suggesting no significant effect of smoke exposure on tissue levels of 8-oxodG. HPLC-ECD procedure yielded slightly higher values for 8-oxodG in all groups, however, again significant differences between sham and smoke-exposed groups were not detected. It is concluded that the chronic exposure to side-stream cigarette smoke does not enhance the formation of 8-oxodG in rat lungs.

Sidestream cigarette smoke accelerates atherogenesis in apolipoprotein E-/- mice.

Epidemiological studies have strongly implicated active and passive smoking with increased risk of cardiovascular diseases. The present study was performed to determine if exposure to sidestream cigarette smoke (SSCS), a surrogate of environmental tobacco smoke, promotes atherogenesis in a mouse model of human atherosclerosis. Female ApoE-deficient mice, maintained on a Western diet, were exposed to SSCS in a whole-body exposure chamber for a total of 6 h each day, 5 days a week for 7, 10 and 14 weeks. Animals exposed to filtered ambient air served as controls. Elevated concentrations of blood carboxyhemoglobin and pulmonary CYP1A1 ascertained effective exposure of animals to SSCS. There were no consistent changes in serum concentrations of cholesterol between control and SSCS-exposed mice. Morphometric assessment of grossly discernible lesions covering the intimal area of aorta showed remarkable increases in SSCS-exposed mice at all three exposure durations studied. Increases in the lesion area defined by en face measurements were accompanied by parallel increases in the levels of esterified and unesterified cholesterol in the aortic tissues of SSCS mice. These results clearly demonstrate promotion of atherosclerotic lesion development by tobacco smoke in an atherosclerosis-susceptible mouse model.

Inhibition of cigarette smoke-related DNA adducts in rat tissues by indole-3-carbinol.

Indole-3-carbinol (I3C) found in various cruciferous vegetables has been shown to exert anti-carcinogenic activity in several target organs. In this study, we have investigated the effects of I3C on cigarette smoke-related lipophilic DNA adduct formation, potentially a key step in chemical carcinogenesis. Female Sprague-Dawley rats were exposed to sidestream cigarette smoke in a whole-body exposure chamber for 6 h per day, 7 days a week for 4 weeks. Control animals received only vehicle while the intervention groups received I3C (1. 36 or 3.40 mmol/kg, b.wt.) daily by gavage starting from 1 week prior to smoke initiation until the end of the experiment. Analysis of tissue DNA by nuclease P1-mediated 32P-postlabeling showed one major and several minor smoke-related adducts in lung, trachea, heart and bladder. The high dose of I3C significantly inhibited the major adducts in lung (#5) and trachea (#3) by 55% each; minor adducts were slightly inhibited (20-40%). The low dose of I3C showed lesser degree of inhibition (30-40%) in both lung and trachea; however, it was found statistically significant in lung only. The major smoke-related adduct in bladder (#2) was strongly inhibited (>65%) by high dose of I3C approaching adduct levels achieved in sham-exposed rats. A small but statistically significant decrease in the smoke-related DNA adduct (#5) in heart tissue was also observed by intervention with high dose I3C. Low levels (30-50 adducts/10(10) nucleotides) of I3C-derived DNA adducts were also found in all the tissues examined although their significance remains unknown. These data show significant inhibition of cigarette smoke-related DNA adducts by I3C, particularly in the lung, trachea, and bladder.

Perinatal sidestream cigarette smoke exposure and the developing pulmonary surfactant system in rats.

1. Epidemiological studies have strongly implicated passive smoking with increased incidence of various respiratory diseases in children. Our earlier studies have shown that chronic exposure to tobacco smoke significantly changes the composition and the surface activity of the pulmonary surfactant in adult rats. The aim of the present study was to determine if perinatal exposure to sidestream cigarette smoke influences the composition and function of pulmonary surfactant system in developing rat pups. 2. Pregnant Sprague Dawley rats were exposed to sidestream cigarette smoke in a whole body exposure chamber for a total of 6 h each day and the pups born to these dams were further exposed to sidestream smoke for 2 h/day during postnatal period. Exposure of animals to smoke was ascertained by measuring their plasma cotinine. Surfactant analysis was performed on bronchoalveolar lavage fluids (BALF) collected from pups on postnatal day 1, 3, 7, 14, 21 and 35. The phospholipid (PL) content, percentage disaturated phosphatidylcholine (DSPC) and surfactant proteins (SP-A and SP-B) in BALF surfactant preparations from sham and smoke-exposed pups were compared. 3. Significant differences between the two groups were observed at two exposure points: a reduced level of SP-A on day 1, and, a higher level of SP-A and PLs on day 21, in smoke-exposed pups. Surface activity analysis of the surfactant films by pulsating bubble surfactometer did not show any significant differences between the sham and smoke-exposed groups at any exposure point. 4. The results indicate that perinatal exposure to sidestream smoke is capable of producing biochemical changes in the composition of pulmonary surfactant at different stages of development but these changes do not influence surface tension reducing properties of the surfactant.

Enhancement of pre-existing DNA adducts in rodents exposed to cigarette smoke.

Exposure to tobacco smoke has been implicated in the increased incidence of cancer and cardiovascular diseases. This report describes various experimental studies in animals that were carried out to determine the ability of cigarette smoke to form DNA adducts and to define chromatographic nature of the major adducts. Tissues from rodents exposed to mainstream or sidestream cigarette smoke in nose-only and whole-body exposure systems, respectively, for different durations were analyzed for DNA adducts by 32P-postlabeling assay. The results showed essentially similar qualitative patterns in various respiratory (lung, trachea, larynx) and non-respiratory (heart, bladder) tissues of smoke-exposed rats. However, adduct pattern in the nasal mucosa was different. The mean total DNA adducts in various tissues expressed as per 1010 nucleotides exhibited the following order: heart (700)>lung (420)>trachea (170)>larynx (150)>bladder (50). Some qualitatively identical adducts were routinely detected in tissues from sham-treated rats but at greatly reduced levels (5- to 25-fold). The levels of lung DNA adducts increased with the duration of exposure up to 23 weeks and returned to control levels 19 weeks after the cessation of exposure. Species-related differences in adduct magnitude and patterns were observed among rats, mice and guinea pigs; mouse being the most sensitive to DNA damage and guinea pig the least sensitive. Whole-body exposure of rats to sidestream cigarette smoke also enhanced the pre-existing DNA adducts by several fold in different tissues. Selective chromatography, and extractability in butanol suggested lipophilic nature of smoke-associated DNA adducts, which were, however, recovered significantly better in nuclease P1 than butanol enrichment procedure. The major smoke-associated adducts were chromatographically different from any of the reference adducts of polycyclic aromatic hydrocarbons (PAHs) co-chromatographed with the smoke DNA samples. Because PAH-DNA adducts are recovered with equal efficiency by the two enrichment procedures, the above observations suggested that smoke-associated adducts are not related to typical PAHs, like benzo[a]pyrene. It is concluded that cigarette smoke increased the levels of pre-existing endogenous DNA adducts (the so-called I-compounds) in animal models and that these adducts are unrelated to those formed by typical PAHs.

Manganese superoxide dismutase protects mitochondrial complex I against adriamycin-induced cardiomyopathy in transgenic mice.

Adriamycin (ADR) is a potent anticancer drug that causes severe cardiomyopathy. We have previously demonstrated that ADR-induced ultrastructural mitochondrial injury in the heart was attenuated in manganese superoxide dismutase (MnSOD) transgenic mice. To further investigate the biochemical mechanisms by which MnSOD protected mitochondria against ADR-induced damage, cardiac mitochondrial function and activities were evaluated. The results showed that ADR caused significant decrease in state 3 respiration and respiratory control ratio using both complex I and II substrates in nontransgenic mice. In transgenic mice, state 3 respiration for complex I substrates remained unaffected by ADR, but was reduced for complex II substrate. Complex I activity was significantly decreased in nontransgenic, but not in transgenic mice after ADR treatment, suggesting that mitochondrial complex I is sensitive to inactivation by superoxide radicals. The activities of complex II and mitochondrial creatine kinase were decreased by ADR in both nontransgenic and transgenic mice. These results support our previous observations on the protective role of MnSOD on the ultrastructural damage of the heart after ADR treatment and extend the understanding of its mechanisms in mitochondria.

Inhibition of cigarette smoke-related lipophilic DNA adducts in rat tissues by dietary oltipraz.

The present study investigated the effects of dietary oltipraz on cigarette smoke-related lipophilic DNA adduct formation. Female Sprague-Dawley rats were exposed daily to sidestream cigarette smoke in a whole-body exposure chamber 6 h/day for 4 consecutive weeks. One group of rats was maintained on control diet while another group received the same diet supplemented with either a low (167 p.p.m.) or high (500 p.p.m.) dose of oltipraz, starting 1 week prior to initiation of smoke exposure until the end of the experiment. Analysis of lipophilic DNA adducts by the nuclease P1-mediated 32P-post-labeling showed up to five smoke-related adducts. Adduct no. 5 predominated in both the lung and the heart while adduct nos 3 and 2 predominated in the trachea and bladder, respectively. Quantitative analysis revealed that the total adduct level was the highest in lungs (270+/-68 adducts/10(10) nucleotides), followed by trachea (196+/-48 adducts/10(10) nucleotides), heart (141+/-22 adducts/10(10) nucleotides) and bladder (85+/-16 adducts/10(10) nucleotides). High dose oltipraz treatment reduced the adduct levels in lungs and bladder by >60%, while the reduction in lungs in the low-dose group was approximately 35%. In trachea, the effect of low and high dietary oltipraz on smoke DNA adduction was equivocal, while smoke-related DNA adducts in the heart were minimally inhibited by high-dose oltipraz. In a repeat experiment that employed a 3-fold lower dose of cigarette smoke, oltipraz (500 p.p.m.) was found to inhibit the formation of DNA adducts in rat lungs and trachea by 80 and 65%, respectively. These data clearly demonstrate a high efficacy of oltipraz in inhibiting the formation of cigarette smoke-induced DNA adducts in the target tissues.

Amiodarone-induced pulmonary toxicity in Fischer rats: release of tumor necrosis factor alpha and transforming growth factor beta by pulmonary alveolar macrophages.

Amiodarone is an antiarrhythmic drug with numerous side effects, the most serious being the development of pulmonary toxicity. We have previously reported that a single intratracheal instillation of amiodarone to Fischer 344 rats results in pulmonary fibrosis within 6 wk of treatment. Presently, the mechanism of amiodarone-induced pulmonary toxicity is unknown. Cytokines that stimulate fibroblast proliferation and/or collagen production may play a role in amiodarone-induced pulmonary toxicity. To investigate this possibility, female rats were given a single intratracheal instillation of amiodarone (6.25 mg/kg), its metabolite desethylamiodarone (5 mg/kg), or vehicle (sterile water). At 1, 2, 3, or 6 wk after treatment the lungs were lavaged and the recovered cells were counted and identified. The alveolar macrophages were isolated by attachment to plastic petri dishes, cultured overnight, and the spent media collected for tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta) analyses. Desethylamiodarone treatment resulted in a neutrophilic alveolitis, but the levels of TNF-alpha and TGF-beta were not significantly different from control animals. In contrast, amiodarone treatment resulted in a lymphocytic alveolitis and significantly higher amounts of TNF-alpha were observed at 3 and 6 wk after treatment. A trend toward higher levels of TGF-beta was also noted in the amiodarone-treated group at wk 1-3 but the values were not significantly different from those of controls. In conclusion, the release of TNF-alpha may play a role in the development of amiodarone-induced pulmonary toxicity.

Alteration of pulmonary surfactant proteins in rats chronically exposed to cigarette smoke.

Surfactant proteins (SP) play an important role in enhancing the surface properties of pulmonary surfactant and participate in host-defense mechanism(s) of the lung. Although it is known that cigarette smoking alters both pulmonary surfactant lipid composition and function, its effect on SPs is unknown. The present study was carried out to determine if chronic exposure to cigarette smoke alters pulmonary SPs, namely, SP-A and SP-B, in a rat model. Sprague-Dawley rats were exposed to cigarette smoke in a nose-only exposure system twice a day, every day for 70 weeks. At termination, bronchoalveolar lavage (BAL) fluid and the lung tissues were collected from room control, sham-treated (SH), and smoke-exposed (SM) animals for analyses. The total protein levels in the BAL fluid of SM rats tended to be higher but were not statistically different from those of the SH group. However, the albumin content of BAL fluid in SM rats, measured by quantitative immunoblotting, was significantly higher than in control groups. Compared to control groups, SP-A and SP-B levels in the BAL fluid of SM rats were significantly reduced by 25 and 50%, respectively, when expressed as units per microgram of BAL fluid protein. However, when calculated as total BAL fluid SP recovered per rat, only the SP-B levels of SM rats were significantly different from the control groups. Further analysis by ELISA confirmed the reduced levels of SP-B in SM rats. In contrast to BAL fluid, the lung tissue levels of SP and their respective mRNAs were not significantly different between the control and smoke-exposed groups. These results show a selective reduction in SP-B content on the bronchoalveolar surface following chronic exposure to cigarette smoke and suggest an inhibitory effect of cigarette smoke on surfactant secretory processes and/or a localized destruction of SPs on the bronchoalveolar surface.

Amiodarone-induced pulmonary fibrosis in Fischer 344 rats.

Amiodarone is a potent antiarrhythmic agent with a number of side-effects, the most serious being the development of pulmonary toxicity. The purpose of the study was to determine if a single intratracheal instillation of amiodarone would induce pulmonary fibrosis and associated functional changes in rats. Female Fischer 344 rats were given a single intratracheal instillation of 200 microliters containing 1.25 mg amiodarone (n = 9) while the control group received an equivalent volume of sterile water (n = 8). After 6 weeks, pulmonary function tests, lung hydroxyproline measurements and lung histology were performed. The amiodarone-treated animals showed a significant reduction in the coefficient of diffusion (kCO) and a significant increase in lung hydroxyproline levels as compared to the control group. The treated group had abnormal histology including areas of septal thickening with cellular infiltration of the interstitial and alveolar spaces, whereas the control group had normal histology. These observations suggest that the intratracheal instillation route of amiodarone treatment produces a fibrotic response in rats that can be measured physiologically, biochemically and histologically. This model may aid in the elucidation of the mechanism of amiodarone-induced pulmonary toxicity (AIPT)./ABS.

Biochemical and biophysical characterization of pulmonary surfactant in rats exposed chronically to cigarette smoke.

The pulmonary surfactant plays an important role in the gas exchange functions of the lungs. Although previous studies suggest that cigarette smoking alters the pulmonary surfactant system in human smokers, the nature of such changes is poorly understood. The aim of the present study was to determine if biochemical and biophysical properties of pulmonary surfactant are affected in rats following chronic exposure to cigarette smoke. Female Sprague-Dawley rats were exposed daily to smoke from the University of Kentucky high tar/high nicotine reference cigarettes, twice a day, for 60 weeks in a nose-only exposure system. Blood carboxyhemoglobin, plasma cotinine, and pulmonary aryl hydrocarbon hydroxylase activity measurements showed that animals effectively inhaled smoke during exposures. At termination, the bronchoalveolar lavage fluids (BALF) and the lung tissues were collected for biochemical and biophysical analyses of surfactant. The total phospholipid content of the BALF and the lung tissues from room control (RC), sham-treated (SH), and smoke-exposed (SM) animals were the same among the different groups. However, disaturated phosphatidylcholine (DSPC) levels in the BALF were significantly decreased in SM rats compared to RC or SH groups. In contrast, the lung tissue DSPC content in SM rats was not significantly different from that of control groups. Phospholipid profile analysis of the BALF also did not reveal any significant differences among other major constituents of surfactant from control and SM animals. The organic extracts of BALF obtained from different animal groups were assessed for surface activity using a Wilhelmy balance. The results showed an increase in surface compressibility and a reduction in respreadability index in SM group.(ABSTRACT TRUNCATED AT 250 WORDS)

Sidestream cigarette smoke exposure and airway reactivity during early life.

We established a guinea pig model to investigate effects of in utero and neonatal exposure to sidestream cigarette smoke (SSCS) on bronchial reactivity during early life. Animals were divided into four groups: 1) room air/room air, 2) sham/sham, 3) SSCS/room air, and 4) SSCS/SSCS. Pregnant and neonatal animals of group 1 breathed room air and those of group 2 were sham treated. Pregnant animals of both groups 3 and 4 as well as neonates of group 4 were exposed to SSCS. SSCS exposure was limited to between days 28 and 55 of pregnancy and days 8 and 24 of the neonatal period. Bronchial response to acetylcholine (ACh) and substance P (SP) were determined in very young animals at 25 days of age. Maximal expiratory flow was used as an index of airway dimension. SP, but not ACh, induced a significantly larger decrease in peak maximal expiratory flow in group 4, indicating an important role of neonatal SSCS exposure in augmenting bronchial response to SP. To further investigate the role of tachykinins in cigarette smoke-induced changes in bronchial reactivity, four additional groups (the same as above) of neonates were pretreated with capsaicin to deplete tachykinins. In the SSCS/SSCS group, SP-induced airway hyperreactivity was abolished by capsaicin pretreatment. Furthermore, in all four groups, capsaicin pretreatment abolished the bronchial response to SP but not the response to ACh. In additional very young animals, acute SSCS caused a nonsignificant increase in bronchial response to SP. These results indicate that chronic neonatal SSCS exposure induces bronchial hyperreactivity to SP; this hyperreactivity is abolished by capsaicin pretreatment.

Low ignition propensity cigarettes: smoke analysis for carcinogens and testing for mutagenic activity of the smoke particulate matter.

In 1990, more than 20% of the almost 5200 deaths from fires in the United States occurred in fires from cigarettes. This fact led to the investigation of cigarettes with low ignition propensity. 32 experimental cigarettes differing in tobacco, cigarette circumference and in cigarette paper were tested for ignition propensity. This communication reports the results of comparative analyses of smoke from two low-propensity experimental cigarettes, A and B, which differed only in the porosity and treatment of the paper, and of the smoke from a reference cigarette C and from two leading US commercial cigarettes D and E. Model cigarette A delivered higher smoke yields of total particulate matter (TPM), nicotine, CO and benzo[a]pyrene than the other four cigarettes, but had lower smoke yields of the carcinogenic, volatile, and tobacco-specific N-nitrosamines than cigarettes C, D and E. The TPM of cigarette A was less active as a frameshift mutagen in tests with Salmonella strain TA98 than was the TPM of cigarettes C, D and E. TPM of cigarette A was also less active as a frameshift mutagen in tester strain TA1538 than was the TPM of reference cigarette C. However, when the mutagenic potencies of the particulate matters were compared on a cigarette-to-cigarette basis, there were no significant differences between the TPM of the individual cigarettes. Replacing the conventional cigarette filter with a perforated filter may significantly reduce the smoke yield of cigarette A. If this can be achieved without changing the ignition propensity, detailed chemical-analytical analyses and in vitro and in vivo assays for toxicity, ciliatoxicity, mutagenic activity and carcinogenicity need to be obtained for the smoke of such a prototype cigarette.

Protective role of manganese superoxide dismutase against cigarette smoke-induced cytotoxicity.

Free-radical-induced oxidative damage has been implicated as an important mechanism responsible for the toxicity of both active and passive smoking. Cigarette smoke contains short- and long-lived radicals and can stimulate cellular production of highly reactive oxygen species. One of the antioxidant enzymes that is protective against reactive oxygen-induced damage is manganese superoxide dismutase (MnSOD), which is located in the mitochondria of mammalian cells. The present study was conducted to examine the role of oxidative damage in cigarette smoke toxicity. A mouse fibroblast cell line (C3H10T1/2) and its MnSOD-transfected, enzymatically active clone, R2 cells, which possessed about five-fold greater MnSOD activity, were used to test the cytotoxicity of condensates from mainstream (MS-CSC) and sidestream (SS-CSC) cigarette smoke. Growth and respiration studies of the two test cell lines showed that the R2 cells grew to a higher cell density and exhibited greater oxygen uptake than the parent cells under normal growth conditions. Both smoke condensates were cytotoxic to test cells, but SS-CSC exhibited slightly greater toxicity, and R2 cells were significantly less susceptible to SS-CSC toxicity than the parent cells. SS-CSC caused a slightly greater inhibition of respiratory activity in parent cells than in R2 cells. These results suggest a significant contribution of oxidative damage in SS-CSC cytotoxicity.

Mainstream and sidestream cigarette smoke-induced DNA adducts in C7Bl and DBA mice.

Exposure to environmental tobacco smoke (ETS), which is largely composed of the sidestream cigarette smoke, has been implicated in increased incidence of cancer among nonsmokers. The present study was conducted to compare the potential of mainstream and sidestream cigarette smoke to induce DNA adducts in mice. Groups of female C57Bl and DBA mice were exposed twice daily for 65-70 weeks to mainstream or sidestream smoke from the University of Kentucky reference cigarettes (2R1) in a nose-only exposure system. Animals received a total particulate matter dose of about 16 and 6 mg/kg body weight/exposure and exhibited blood carboxyhemoglobin levels of about 16 and 34%, for mainstream and sidestream smoke-exposed groups, respectively. Pulmonary aryl hydrocarbon hydroxylase (AHH) activity was induced by about 2- to 3-fold in both mainstream and sidestream groups of C57Bl and in mainstream smoke-exposed group of DBA mice, but not in sidestream smoke-exposed DBA mice. An analysis of total DNA adduct levels by the 32P-postlabeling assay showed a significant (12- to 25-fold) increase in the magnitude of preexisting lung DNA adducts in both mainstream and sidestream smoke-exposed C57Bl and DBA mice. Smoke exposures did not affect the total preexisting DNA adducts in liver of either strain. It is concluded that both mainstream and sidestream smoke are capable of enhancing preexisting DNA adducts in the lungs of chronically smoke-exposed mice.

Reproductive organ blood flow measured using radioactive microspheres in diestrous and estrous mice.

Blood flow is a primary mechanism controlling reproductive organ functions. In the present study, radioactive microsphere techniques were adapted to measure ovarian, uterine, and vaginal blood flow levels in C57BL mice. Anesthetized animals were tracheostomized and the left carotid artery was cannulated. The heart was exposed and 113Sn-labeled spheres (15 microns size, 2 microCi, 0.1 ml) were injected via the left ventricle. Reference sample was obtained by carotid artery blood "free flowing" into a tared microfuge tube for 1 min. The animal was killed, and selected tissues were excised for weighing and radioactivity measurement to determine flow. Absence of differences in flow levels (ml.min-1.g-1) to paired nonreproductive organs (adrenals and kidneys) validated the procedure. Blood flow levels were significantly higher in the ovaries, but not in the uterus and vagina of estrous mice vs. diestrous mice. Comparison of left vs. right ovaries suggested consistent blood flow distribution during diestrus. Ovarian blood flow level is enhanced during estrus and, in addition, is highly nonuniform regarding right-left flow distribution. Nonuniform ovarian blood flow distribution in estrous mice leads us to speculate that alternating right-left (i.e. nonuniform) ovulation predominates during each murine estrous cycle.