Naringenin ameliorates inflammation and cell proliferation in benzo(a)pyrene induced pulmonary carcinogenesis by modulating CYP1A1, NFκB and PCNA expression.

Lung cancer is the major cause of cancer-related mortality and is a growing economic burden worldwide. Chemoprevention has emerged as a very effective preventive measure against carcinogenesis and several bioactive compounds in diet have shown their cancer curative potential on lung cancer. Naringenin (NRG), a predominant flavanone found in citrus fruits has been reported to possess anti-oxidative, anti-inflammatory and anti-proliferative activity in a wide variety of cancer. The aim of the present study is to divulge the chemopreventive nature of NRG against benzo(a)pyrene (B[a]P) induced lung carcinogenesis in Swiss albino mice. Administration of B[a]P (50mg/kg, p.o.) to mice resulted in increased lipid peroxidation (LPO), proinflammatory cytokines (TNF-α, IL-6 and IL-1ß) with subsequent decrease in activities of tissue enzymic antioxidants (SOD, CAT, GPx, GR, GST) and non-enzymic antioxidants (GSH and Vit-C). Treatment with NRG (50mg/kg body weight) significantly counteracted all these alterations thereby showing potent anti-cancer effect in lung cancer. Moreover, assessment of protein expression by immunoblotting and mRNA expression by RT-PCR revealed that NRG treatment effectively negates B[a]P-induced upregulated expression of CYP1A1, PCNA and NF-κB. Further, the antiproliferative effect of NRG was confirmed by histopathological analysis and PCNA immunostaining in B[a]P induced mice which showed increased PCNA expression that was restored upon NRG administration. Overall, these findings substantiate the chemopreventive potential of NRG against chemically induced lung cancer in mice.

Human in Vivo Pharmacokinetics of [(14)C]Dibenzo[def,p]chrysene by Accelerator Mass Spectrometry Following Oral Microdosing.

Dibenzo(def,p)chrysene (DBC), (also known as dibenzo[a,l]pyrene), is a high molecular weight polycyclic aromatic hydrocarbon (PAH) found in the environment, including food, produced by the incomplete combustion of hydrocarbons. DBC, classified by IARC as a 2A probable human carcinogen, has a relative potency factor (RPF) in animal cancer models 30-fold higher than benzo[a]pyrene. No data are available describing the disposition of high molecular weight (>4 rings) PAHs in humans to compare to animal studies. Pharmacokinetics of DBC was determined in 3 female and 6 male human volunteers following oral microdosing (29 ng, 5 nCi) of [(14)C]-DBC. This study was made possible with highly sensitive accelerator mass spectrometry (AMS), capable of detecting [(14)C]-DBC equivalents in plasma and urine following a dose considered of de minimus risk to human health. Plasma and urine were collected over 72 h. The plasma Cmax was 68.8 ± 44.3 fg·mL(-1) with a Tmax of 2.25 ± 1.04 h. Elimination occurred in two distinct phases: a rapid (α)-phase, with a T1/2 of 5.8 ± 3.4 h and an apparent elimination rate constant (Kel) of 0.17 ± 0.12 fg·h(-1), followed by a slower (ß)-phase, with a T1/2 of 41.3 ± 29.8 h and an apparent Kel of 0.03 ± 0.02 fg·h(-1). In spite of the high degree of hydrophobicity (log Kow of 7.4), DBC was eliminated rapidly in humans, as are most PAHs in animals, compared to other hydrophobic persistent organic pollutants such as, DDT, PCBs and TCDD. Preliminary examination utilizing a new UHPLC-AMS interface, suggests the presence of polar metabolites in plasma as early as 45 min following dosing. This is the first in vivo data set describing pharmacokinetics in humans of a high molecular weight PAH and should be a valuable addition to risk assessment paradigms.

Nucleotide excision repair gene polymorphisms, meat intake and colon cancer risk.

PURPOSE: Much of the DNA damage from colon cancer-related carcinogens, including heterocyclic amines (HCA) and polycyclic aromatic hydrocarbons (PAH) from red meat cooked at high temperature, are repaired by the nucleotide excision repair (NER) pathway. Thus, we examined whether NER non-synonymous single nucleotide polymorphisms (nsSNPs) modified the association between red meat intake and colon cancer risk. METHODS: The study consists of 244 African-American and 311 white colon cancer cases and population-based controls (331 African Americans and 544 whites) recruited from 33 counties in North Carolina from 1996 to 2000. Information collected by food frequency questionnaire on meat intake and preparation methods were used to estimate HCA and benzo(a)pyrene (BaP, a PAH) intake. We tested 7 nsSNPs in 5 NER genes: XPC A499V and K939Q, XPD D312N and K751Q, XPF R415Q, XPG D1104H, and RAD23B A249V. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated using unconditional logistic regression. RESULTS: Among African Americans, we observed a statistically significant positive association between colon cancer risk and XPC 499 AV+VV genotype (OR=1.7, 95% CI: 1.1, 2.7, AA as referent), and an inverse association with XPC 939 QQ (OR=0.3, 95%CI: 0.2, 0.8, KK as referent). These associations were not observed among whites. For both races combined, there was interaction between the XPC 939 genotype, well-done red meat intake and colon cancer risk (OR=1.5, 95% CI=1.0, 2.2 for high well-done red meat and KK genotype as compared to low well-done red meat and KK genotype, pinteraction=0.05). CONCLUSIONS: Our data suggest that NER nsSNPs are associated with colon cancer risk and may modify the association between well-done red meat intake and colon cancer risk.

Early changes in proteome levels upon acute deltamethrin exposure in mammalian skin system associated with its neoplastic transformation potential.

Deltamethrin, a pyrethroid insecticide, used extensively for pest control has been reported to cause adverse health effects including carcinogenic/toxic effects in animals but the underlying mechanism remains elusive. In the present study, we investigated the effect of deltamethrin after short exposure on early protein expression changes involved in neoplastic transformation in mouse skin, validated the results in human keratinocyte HaCaT cells and thereby explore the possible underlying mechanism. Deltamethrin (4 mg/kg b.wt) and benzo[a]pyrene (B[a]P, 0.05 mg/kg b.wt) were topically applied on Swiss albino mice, respectively. The comparative protein expression profiles with vehicle control were generated by 2-dimensional gel electrophoresis (2-DE) and mass spectrometry. 2-DE maps of deltamethrin and B[a]P treated mouse skin showed 20 and 24 significant (2 fold change, p < 0.05) differentially expressed protein spots, against vehicle controls. However, comparison between them showed relatively similar expression level of 20 spots. Among them, 5 proteins (carbonic anhydrase III, peroxiredoxin-2, calcyclin, superoxide dismutase [Cu-Zn], ubiquitin) are of particular significance as these are involved in cancer-related key processes. Deregulation of these was confirmed at protein and mRNA levels by immunoblotting and RT-PCR in mouse skin and HaCaT cells. Therefore, we conclude that these preliminarily identified proteins might be responsible for the neoplastic transformation of mouse skin epidermal cells and HaCaT cells by deltamethrin. This study proposes complementary mechanism where inhibition of proteasome activator protein (PA200) is responsible for accumulation of ubiquitinated-calcyclin, regulates deltamethrin-induced neoplastic changes in mouse skin and HaCaT cells.

Dibenzo[def,p]chrysene (DBC) suppresses antibody formation in spleen cells following oral exposures of mice.

Dibenzo[def,p]chrysene (DBC) is a potent environmental carcinogen in rodents, fish, and human cells examined in culture. There are numerous similarities between the patterns of cytochrome P-450 (P450) activation of DBC and its covalent binding to DNA and proteins with another polycyclic aromatic hydrocarbon (PAH), 7,12-dimethylbenz[a]anthracene (DMBA). Our lab has previously shown that DMBA produces immunosuppression in rodents and human cell systems. Therefore, the purpose of these studies was to examine the immunotoxicity of DBC in a rodent model that was found to be sensitive to the immunosuppressive effects of DMBA. Data showed that DBC had similar potency to DMBA in producing suppression of a T-dependent antibody response (TDAR) and altered spleen cell subsets in a similar manner as DMBA when DMBA was given by gavage for 5 d in corn oil to mice at doses of 1-100 mg/kg total cumulative doses. T-cell-independent antigen (TNP-Ficoll) responses were quantitatively less sensitive to DBC suppression. It was also found that as with DMBA, DBC produced a persistent immunosuppression, which lasted for at least 4 wk following dosing with a novel pill method for self-administration of DBC. In conclusion, DBC appears to possess many of the same characteristics of DMBA in terms of its immunotoxicity.

Transplacental carcinogenesis with dibenzo[def,p]chrysene (DBC): timing of maternal exposures determines target tissue response in offspring.

Dibenzo[def,p]chrysene (DBC) is a transplacental carcinogen in mice (15mg/kg; gestation day (GD) 17). To mimic residual exposure throughout pregnancy, dams received four smaller doses of DBC (3.75mg/kg) on GD 5, 9, 13 and 17. This regimen alleviated the previously established carcinogenic responses in the thymus, lung, and liver. However, there was a marked increase in ovarian tumors (females) and hyperplastic testes (males). [(14)C]-DBC (GD 17) dosing revealed transplacental distribution to fetal tissues at 10-fold lower concentrations than in paired maternal tissue and residual [(14)C] 3weeks post-dose. This study highlights the importance of developmental stage in susceptibility to environmental carcinogens.

Preliminary physiologically based pharmacokinetic models for benzo[a]pyrene and dibenzo[def,p]chrysene in rodents.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants generated as byproducts of natural and anthropogenic combustion processes. Despite significant public health concern, physiologically based pharmacokinetic (PBPK) modeling efforts for PAHs have so far been limited to naphthalene, plus simpler PK models for pyrene, nitropyrene, and benzo[a]pyrene (B[a]P). The dearth of published models is due in part to the high lipophilicity, low volatility, and myriad metabolic pathways for PAHs, all of which present analytical and experimental challenges. Our research efforts have focused upon experimental approaches and initial development of PBPK models for the prototypic PAH, B[a]P, and the more potent, albeit less studied transplacental carcinogen, dibenzo[def,p]chrysene (DBC). For both compounds, model compartments included arterial and venous blood, flow limited lung, liver, richly perfused and poorly perfused tissues, diffusion limited fat, and a two compartment theoretical gut (for oral exposures). Hepatic and pulmonary metabolism was described for both compounds, as were fractional binding in blood and fecal clearance. Partition coefficients for parent PAH along with their diol and tetraol metabolites were estimated using published algorithms and verified experimentally for the hydroxylated metabolites. The preliminary PBPK models were able to describe many, but not all, of the available data sets, comprising multiple routes of exposure (oral, intravenous) and nominal doses spanning several orders of magnitude.

Human cancer-associated mutations in the Aα subunit of protein phosphatase 2A increase lung cancer incidence in Aα knock-in and knockout mice.

Strong evidence has indicated that protein phosphatase 2A (PP2A) is a tumor suppressor, but a mouse model for testing the tumor suppressor activity was missing. The most abundant forms of trimeric PP2A holoenzyme consist of the scaffolding Aα subunit, one of several regulatory B subunits, and the catalytic Cα subunit. Aα mutations were discovered in a variety of human carcinomas. All carcinoma-associated mutant Aα subunits are defective in binding the B or B and C subunits. Here we describe two knock-in mice expressing cancer-associated Aα point mutants defective in binding B' subunits, one knockout mouse expressing truncated Aα defective in B and C subunit binding, and a floxed mouse for generating conditional Aα knockouts. We found that the cancer-associated Aα mutations increased the incidence of cancer by 50 to 60% in lungs of FVB mice treated with benzopyrene, demonstrating that PP2A acts as a tumor suppressor. We show that the effect of Aα mutation on cancer incidence is dependent on the tumor suppressor p53. The finding that the Aα mutation E64D, which was detected in a human lung carcinoma, increases the lung cancer incidence in mice suggests that this mutation also played a role in the development of the carcinoma in which it was discovered.

Early genotoxic effects in gill cells and haemocytes of Dreissena polymorpha exposed to cadmium, B[a]P and a combination of B[a]P and Cd.

The aim of this study was to assess the genotoxic potential of environmentally relevant concentrations of Cd on the zebra mussel, an important freshwater sentinel organism, and to determine the stability of DNA damage in gill cells and haemocytes. The oxidative DNA damage and the co-genotoxicity of Cd in combination with B[a]P were investigated. We measured DNA damage in haemocytes and gill cells of zebra mussels exposed for 11 days to a constant concentration of Cd (10µg/L), B[a]P (10µg/L) or the two combined chemicals (10µg/L+1µg/L). Enzymatic dissociation of gills with dispase gave the lower percentage DNA in tail, compared with collagenase/dispase or collagenase. Bioaccumulation of cadmium in the soft tissues of mussels exposed to CdCl(2) or CdCl(2)+B[a]P increased in a time-dependent manner indicating that both exposures were effective. Cd (10µg/L) is genotoxic only during the first 3 days of exposure in gill cells, while in haemocytes the genotoxicity of Cd was observed later. B[a]P (10µg/L) induced an early increase of DNA damage in gill cells (after 10h and 1 day), while in both gill cells and haemocytes, B[a]P caused a marked increase of DNA damage after 3 days of exposure. The Cd+B[a]P mixture decreased the DNA-damaging effect of Cd and B[a]P in both cell types. Cd induced an increase of DNA damage in Fpg-treated slides, indicating that Cd contributed to oxidative DNA damage. Cadmium induced a cytogenetic effect in gill cells, assessed by the number of micronuclei, throughout the duration of the exposure, while B[a]P did not induce any cytogenetic effect. B[a]P, Cd and Cd+B[a]P induced a transient increase in the number of bi-nucleated cells. Our data clearly show that gills are more sensitive to Cd and B[a]P, which makes them more suitable for future bio-monitoring studies.

3-Hydroxybenzo(a)pyrene as a biomarker of dermal exposure to benzo(a)pyrene.

The aim of this study was to determine the percutaneous absorption flux of BaP (20 microg/cm(2) in ethanol) and the usefulness of urinary 3-OHBaP as a bio-indicator of dermal exposure to BaP. The percutaneous absorbed dose and absorption flux were estimated by comparison with intravenous administration of BaP (0.01 and 0.05 mg/kg in Cremophor) as reference way. A percutaneous absorption flux of 0.37 microg/cm(2)/h was determined by killing groups of rats, following exposure time of 4.5 and 24 h. [(14)C] skin content was 3.1 microg/cm(2), after 24 h exposure to BaP. Total urinary 3-OHBaP accounted for 0.4% of the real absorbed dose, which was fourfold higher than the percentage of an intravenous dose excreted as 3-OHBaP. This finding reveals that percutaneous absorption of BaP, based on the ratio of urinary excretion of 3-OHBaP following percutaneous exposure compared to percutaneous absorption following intravenous administration of BaP, is overestimated in the rat. In vitro, BaP was intensively metabolised by rat skin. Unchanged BaP and 3-OHBaP in receptor fluid accounted for 50 and 30% of the total radioactivity. This percutaneous first past effect of BaP in rats could, in part, explain the higher urinary excretion ratio of 3-OHBaP compared to the value based on intravenous administration of BaP. Conversely, BaP was largely lower metabolised as 3-OHBaP during percutaneous absorption by humans, so BaP absorption flux should be overestimated to a lesser extent in humans than in rats.

Mutations induced by benzo[a]pyrene and dibenzo[a,l]pyrene in lacI transgenic B6C3F1 mouse lung result from stable DNA adducts.

Dibenzo[a,l]pyrene (DB[a,l]P) and benzo[a]pyrene (B[a]P) are carcinogenic polycyclic aromatic hydrocarbons (PAHs) that are each capable of forming a variety of covalent adducts with DNA. Some of the DNA adducts formed by these PAHs have been demonstrated to spontaneously depurinate, producing apurinic (AP) sites. The significance of the formation of AP sites as a key event in the production of mutations and tumours by PAHs has been a subject of ongoing investigations. Because cells have efficient and accurate mechanisms for repairing background levels of AP sites, the contribution of PAH-induced AP site mutagenesis is expected to be maximal in conditions where those induced AP sites are produced in significant excess of the endogenous AP sites. In this study, we investigated the effect of two dosing regimens on the mutagenicity of DB[a,l]P and B[a]P in vivo using the Big Blue(R) transgenic mouse system. We compared administration of a single highly tumorigenic dose of each PAH with a fractionated delivery of the same total dose administered over 5 days, with the expectation that PAH-induced AP sites would be produced at a greater margin above background levels in animals receiving the high single dose than in the animals receiving the fractionated doses. Treatment with DB[a,l]P yielded a 2.5-fold (single dose) to 3-fold (fractionated dose) increase in mutant frequencies relative to controls. Both single-dose and fractionated dose treatment regimens with B[a]P produced about a 15-fold increase in mutant frequencies compared to controls. The mutations induced by B[a]P and DB[a,l]P correlated with the stable covalent DNA adducts produced by each. These mutation results are consistent with the previously identified stable covalent DNA adducts being the promutagenic lesions produced by these two PAHs and do not support a major role for depurinating adducts, contributing to PAH-induced mutagenesis in mouse lung in vivo.

Benzo[a]pyrene-3,6-dione inhibited VEGF expression through inducing HIF-1alpha degradation.

Vascular endothelial growth factor (VEGF) is a potent angiogenesis inducer for tumor growth and angiogenesis. Benzo[a]pyrene (BaP) belongs to polycyclic aromatic hydrocarbons (PAHs) and is known to cause carcinogenesis. But the effects of BaP and its metabolites on VEGF and HIF-1 expression remain to be elucidated. In this study, we found benzo[a]pyrene-3,6-dione (BPQ), but not BaP and benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE) inhibited VEGF expression in a dose-dependent manner. BPQ inhibited VEGF transcriptional activation through hypoxia-inducible factor 1 (HIF-1) binding site. BPQ specifically decreased HIF-1alpha, but not HIF-1beta subunit expression in A549 cells. We found that BPQ did not inhibit HIF-1alpha mRNA level, but inhibited its protein expression in a proteasome-dependent manner. To further clarify the mechanism of BPQ in regulating HIF-1alpha stability, we found that BPQ inhibited HIF-1alpha protein expression by the increase of the proteasome-dependent degradation, and by the disruption of HIF-1alpha and Hsp90 association.

Dibenzo[A,L]pyrene-induced genotoxic and carcinogenic responses are dramatically suppressed in aryl hydrocarbon receptor-deficient mice.

Dibenzo[a,l]pyrene (DB[a,l]P), a notorious air pollutant, is the most powerful carcinogenic polycyclic aromatic hydrocarbon (PAH) ever tested. Although the carcinogenicity of PAH may be primarily mediated by the aryl hydrocarbon receptor (AhR), the in vivo role of AhR in skin carcinogenesis remains to be defined. In this context, we investigated the genotoxic and carcinogenic responses of the AhR-deficient mouse skin to DB[a,l]P. A single painting resulted in a striking epidermal hyperplasia in AhR+/+ mice but not in AhR-/- mice. Bromodeoxyuridine-labeling index and accumulation of p53 protein in epidermal cells of AhR+/+ mice were 8- and 33-fold higher than those of AhR-/- mice, respectively. 32P-Postlabeling assay for DB[a,l]P-DNA adducts displayed a 2-fold increase in the AhR+/+ mouse skin. After DB[a,l]P exposure, AhR-/- mice arranged a nearly 60% reduction in the induction of epidermal cytochrome P450 (CYP)1A1, but CYP1B1 was constitutively expressed in both genotypes of mice, irrespective of DB[a,l]P treatment. As compared with AhR+/+ mice, AhR-/- mice had both significantly lower incidence (100% vs. 33%) and multiplicity (2.7 vs. 0.46) of skin tumors by the complete carcinogenesis study. These observations indicate that a reduced tumor yield in AhR-/- mice may be secondary to reduction of inducible CYP1A1 activation and subsequent DNA adduction. It is evident from our continuous work that although AhR is likely to play a central role in epidermal proliferation and possibly neoplastic transformation, the relative importance of AhR for carcinogenesis may be different among PAH examined.

Effect of single neonatal treatment with the soy bean phytosteroid, genistein on the sexual behavior of adult rats.

Hormonal imprinting develops during the perinatal critical period, when the target hormone meets the yet unmatured receptor. As a consequence of imprinting the receptor accomplishes its maturation reaching the binding capacity characteristic to adults. In this period in the presence of foreign molecules similar to the target hormone faulty imprinting may occur with life-long consequences. Soy bean contains phytosteroids which can mimic estrogen effects. In the present experiments single genistein (20 microg) or combined genistein + benzpyrene (20 microg) treatments were done neonatally and the sexual behavior of male and female adult animals was studied. Genistein significantly increased the lordosis quotient of females, which was compensated by neonatal benzpyrene treatment. Genistein also enhanced the sexual activity of males, and this was significantly not reduced by parallel benzpyrene treatment. The results show that neonatal genistein exposure can imprint sexual activity for life and the presence of a second imprinter can modify genistein's behavioral effect.

Effect of a single treatment (imprinting) with genistein or combined treatment with genistein+benzpyrene on the binding capacity of glucocorticoid and estrogen receptors of adult rats.

Hormonal imprinting takes place perinatally at the first encounter between the hormone and its target receptor. This is needed for the normal finishment of the maturation of the receptor-signal transduction system. In excess of foreign molecules, which can also bind to the receptor, faulty imprinting develops with life-long consequences. Genistein, a soybean phytosteroid (isoflavone), has estrogen-like effects and can be bound by steroid receptors. In the present experiments, single neonatal treatment (imprinting) with 20 microg of genistein, or combined treatment with 20 microg of genistein+20 microg of benzpyrene was done and liver and thymus glucocorticoid receptors of adult male and female rats and uterine estrogen receptors were studied. There was no difference in the binding capacity of uterine estrogen receptors. Genistein treatment alone caused a significant reduction of liver glucocorticoid receptor density in males; however, there were no other significant alterations. After combined genistein+benzpyrene treatment, more.than half of the thymus and liver glucocorticoid receptor values significantly changed. The results call attention to the imprinting-modifying effect of a second (environmental) imprinter.

Experimental hepatic tumorigenicity by environmental hydrocarbon dibenzo[a,l]pyrene.

There is an evident need of low-cost vertebrates to be used in experimental carcinogenesis. Medaka (Oryzias latipes) provide a useful vertebrate model system for investigating tissue tropism of carcinogens and the action mechanisms of environmental contaminants posing a potential risk to human health. Juvenile medaka 2 months of age fed diets containing 100 ppm (dry weight basis) dibenzo[a,l]pyrene (DBP) for 28 days responded with hepatic neoplasia predominately of hepatocellular origin. When sampled 9 months following the termination of carcinogen exposure, medaka showed 26% incidence of neoplasia and 25% hepatic neoplasia, compared with 8% total neoplasia and 0% hepatic neoplasia in control fish. The predominant spontaneous neoplasms in this group of medaka were ovarian germ cell tumors. Hepatic neoplasia occurred at a higher incidence in female DBP-treated medaka than in males (11/29 vs 5/36). Nonneoplastic lesions observed in the livers of DBP-exposed fish included spongiosis hepatis, globular hyaline eosinophilic cytoplasmic inclusions in hepatocytes, foci of hepatocellular degeneration, extensive cytomegaly, and karyomegaly of hepatocytes. No activating exon I mutations in the one ras protooncogene examined were detected among six liver neoplasms. These results indicate that medaka are sensitive to the tumorigenic effects of the environmental carcinogen DBP, administered by dietary exposure.

Inflammatory response of mouse skin exposed to the very potent carcinogen dibenzo[a,l]pyrene: a model for tumor promotion.

The potent carcinogenicity of dibenzo[a,l]pyrene in mouse skin is associated with an inflammation unique among polycyclic aromatic hydrocarbons and expressed as erythema. The time course of erythema and the associated histological events in the skin of female SENCAR mice were determined after a single application of 6.25-200 nmol dibenzo[a,l]pyrene or selected metabolites. Dibenzo[a,l]pyrene and dibenzo[a,l]pyrene-11,12-dihydrodiol, precursor to the bay-region diol epoxide, induced an erythema first present 5-6 days after treatment. Dibenzo[a,l]pyrene-8,9-dihydrodiol and other dibenzo[a, l]pyrene metabolites, however, did not induce erythema. These findings suggest a central role for the bay-region diol epoxide in the induction of the observed inflammation. The intensity and duration of erythema were dose-dependent, whereas the delayed appearance of erythema was constant and dose-independent. These results suggest induction of an immune hypersensitivity by dibenzo[a, l]pyrene and its 11,12-dihydrodiol. Histological changes in the skin were consistent with a contact hypersensitivity reaction and included, in association with erythema, epidermal hyperplasia and the presence of mononuclear leukocytes in the dermis. Animals were tested for dibenzo[a,l]pyrene-induced contact hypersensitivity. Female SENCAR mice were treated with a single dermal application of dibenzo[a,l]pyrene or 7,12-dimethylbenz[a]anthracene. Five days later, the animals were challenged with a single application of dibenzo[a,l]pyrene or 7,12-dimethylbenz[a]anthracene to the ear pinna. Ear swelling exhibited features of a contact hypersensitivity reaction, including (1) delayed appearance after challenge, (2) noninducibility in animals not previously exposed to chemical sensitizer, and (3) chemical specificity. The results suggest that dibenzo[a,l]pyrene induces, via its bay-region diol epoxide, a contact hypersensitivity reaction that may promote tumor development and thereby enhance carcinogenic potency.

Uterus estrogen receptors' binding capacity is reduced in rat if exposed by benzpyrene neonatally.

During the critical period of receptor maturation within the first 5 days after birth female rats were treated with benzpyrene three times and their uterus estrogen receptor characteristic were examined in adulthood. Estrogen receptor density decreased significantly. There was no alteration in receptor affinity. Present experiment draws attention to the disadvantageous effect of aromatic hydrocarbons coming from the polluted air on steroid receptor development.

The co-carcinogen benzo[e]pyrene increases the binding of a low dose of the carcinogen benzo[a]pyrene to DNA in Sencar mouse epidermis.

The mechanism of the co-carcinogenic activity of benzo[e]pyrene (BeP) was investigated by determining the effects of BeP on the binding of the carcinogen benzo[a]pyrene (BaP) to DNA in Sencar mouse epidermis. The dose of BaP used was 20 nmol/mouse, a dose which is not carcinogenic in a single application but is carcinogenic after multiple treatments such as those in the BaP-BeP co-carcinogenesis experiments described by Van Duuren and Goldschmidt (J. Natl. Cancer Inst., 56, 1237, 1976). After 3 h of exposure to [3H]BaP and BeP at BaP:BeP dose ratios of 1:3 and 1:10, [3H]BaP-DNA adducts in both BeP-treated groups were lower than in an acetone-BaP control group. After 12 and 24 h of exposure, the BaP-BeP (1:10) group contained 19% and 33% higher [3H]BaP-DNA adduct levels than the control. In the BaP-BeP (1:3) group, the amount of [3H]BaP-DNA adduct levels was higher than the control after 12 h. BeP co-treatment with either [3H]BaP-7,8-dihydrodiol or anti-[3H]BaPDE had no effect on the amount of BaPDE-DNA adducts present. These results demonstrate that the co-carcinogen BeP increases the amount of a low dose of BaP that binds to mouse epidermal DNA and indicate that the increase in BaP-DNA adducts results from increased metabolism of BaP to the proximate carcinogen BaP-7,8-dihydrodiol.

Analysis of human exposure to benzo(a)pyrene via inhalation and food ingestion in the Total Human Environmental Exposure Study (THEES).

The Total Human Environmental Exposure Study (THEES) focuses on benzo(a)pyrene (BaP) as an example of a combustion-generated polycyclic aromatic hydrocarbon (PAH) compound. Primary pathways for environmental exposures to BaP are inhalation and ingestion. This program of field studies was conducted in Phillipsburg, New Jersey, a small, industrial city in the Delaware River valley. The study protocols included direct monitoring of BaP exposures via inhalation and ingestion pathways during three separate periods, each lasting 14 days. BaP concentrations in air were sampled at outdoor and in-home locations, with personal air sampling added during the latter two phases. Cooked food samples from each household were acquired, using a constant portion "second plate" of each meal prepared at home. Ambient levels were 4-10 times higher during the cold months compared with the late summer study period. Space heating and regional aerosol were major contributors to community levels of BaP in the air during the wintertime. Penetration of outdoor air, cooking activities, combustion appliances, and cigarette smoke were important sources of indoor air exposures. Cooking activities, besides releasing BaP-enriched particles indoors, produced food imbued with BaP and added substantially to exposure via the ingestion route. Among the study subjects, the range and magnitude of dietary exposures (2 to 500 ng/d) were much greater than for inhalation (10 to 50 ng/d). Nevertheless, there were ample individual cases where inhalation of BaP was the predominant exposure route. Indoor air BaP levels were closely correlated with ambient levels in most of the homes. For some individuals, measured personal air BaP exposures were adequately predicted by time-weighting of microenvironmental (i.e., outdoor and in-home) concentrations. However, enormously high exposures for ingestion or inhalation were detected only by direct observation, not from microenvironmental data.