Preserving fibre health: reducing oxidative stress throughout the life of the hair fibre.

Hair health is an important attribute to women globally--specifically attributes such as shine, healthy tips, frizz-free and strength. However, many women will claim to have at least moderate hair damage caused by habits and practices such as washing, combing and brushing, use of heated implements and regular use of chemical treatments. The objective of this work was to investigate two mechanisms of damage--hair colouring and UV exposure--where oxidative processes are involved. The role of copper in these oxidative processes was then investigated: its presence in hair and its consequent impact on hair damage via free radical formation. Finally, the role of chelants N,N'-ethylene diamine disuccinic acid (EDDS) and histidine in preventing free radical formation was investigated and shown to improve hair health.

Chronic, topical administration of 4-aminobiphenyl induces tissue-specific DNA adducts in mice.

While current human exposure to 4-aminobiphenyl (4-ABP) is mainly through inhalation, historically, occupational exposure occurred most often through the skin. 4-ABP targets the urinary bladder in humans, dogs, and rats and the liver and urinary bladder in mice. This study examines the time course of DNA adduct levels in mouse target tissues, liver and urinary bladder, and nontarget tissues, lung and skin, after repeated dermal exposure to subcarcinogenic doses of 4-ABP. It was found that, in female mice dermally treated with 50 nmol of 4-ABP twice weekly for 21 weeks, DNA adduct levels measured by 32P-postlabeling increased over time in target and nontarget tissues, but the greatest rate of accumulation occurred in urinary bladder. At 21 weeks liver, urinary bladder, and skin reached their highest median adduct levels of 55, 82, and 58, respectively. Median adduct levels in lung reached a maximum of 3.2 at 3 weeks of exposure. An adduct which had similar chromatographic properties to a standard previously identified as N-(deoxyguanosin-8-yl)-4-aminobiphenyl was the primary adduct detected in all tissues. There were significant correlations in adduct levels between liver and urinary bladder and liver and skin, but not between skin and urinary bladder. These data suggest that urinary bladder adducts are the result of hepatic and not dermal activation. However, adducts were detected at relatively high levels in skin but not in lung, suggesting that skin may have the metabolic capacity to activate 4-ABP when it is applied topically.

Chronic, topical exposure to benzo[a]pyrene induces relatively high steady-state levels of DNA adducts in target tissues and alters kinetics of adduct loss.

Carcinogen-DNA adduct measurements may become useful biomarkers of effective dose and/or early effect. However, validation of this biomarker is required at several levels to ensure that human exposure and response are accurately reflected. Important in this regard is an understanding of the relative biomarker levels in target and nontarget organs and the response of the biomarker under the chronic, low-dose conditions to which humans are exposed. We studied the differences between single and chronic topical application of benzo[a]pyrene (BAP) on the accumulation and removal of BAP-DNA adducts in skin, lung, and liver. Animals were treated with BAP at 10, 25, or 50 nMol topically once or twice per week for as long as 15 weeks. Animals were sacrificed either at 24, 48, or 72 hr after the last dose at 1 and 30 treatments, and after 24 hr for all other treatment groups. Adduct levels increased with increasing dose, but the slope of the dose-response was different in each organ. At low doses, accumulation was linear in skin and lung, but at high doses the adduct levels in the lung increased dramatically at the same time when the levels in the skin reached apparent steady state. In the liver adduct, levels were lower than in target tissues and apparent steady-state adduct levels were reached rapidly, the maxima being independent of dose, suggesting that activating metabolism was saturated in this organ. Removal of adducts from skin, the target organ, was more rapid following single treatment than with chronic exposure. This finding is consistent with earlier data, indicating that some areas of the genome are more resistant to repair. Thus, repeated exposure and repair cycles would be more likely to cause an increase in the proportion of carcinogen-DNA adducts in repair-resistant areas of the genome. These findings indicate that single-dose experiments may underestimate the potential for carcinogenicity for compounds that follow this pattern.

Biotransformation of benzo[a]pyrene and other polycyclic aromatic hydrocarbons and heterocyclic analogs by several green algae and other algal species under gold and white light.

This laboratory has shown that the metabolism of benzo[a]pyrene (BaP), a carcinogenic polycyclic aromatic hydrocarbon (PAH), by a freshwater green alga, Selenastrum capricornutum, under gold light proceeds through a dioxygenase pathway with subsequent conjugation and excretion. This study was undertaken to determine: (1) the effects of different light sources on the enzymatic or photochemical processes involved in the biotransformation of BaP over a dose range of 5-1200 mg/l; (2) the phototoxicity of carcinogenic PAHs and mutagenic quinones to a green alga; (3) the ability of other algal systems to metabolize BaP. Cultures were exposed to different doses of BaP for 2 days at 23 degrees C under gold, white or UV-A fluorescent light on a diurnal cycle of 16 h light, 8 h dark. Under gold light, metabolites of BaP produced by Selenastrum capricornutum were the dihydrodiols of which the 11,12-dihydrodiol was the major metabolite. Under white light, at low doses, the major metabolite was the 9,10-dihydrodiol. With increasing dose, the ratio of dihydrodiols to quinones decreased to less than two. With increasing light energy output, from gold to white to UV-A in the PAH absorbing region, BaP quinone production increased. Of other carcinogenic PAHs studied, only 7H-dibenz[c,g]carbazole was as phototoxic as BaP while 7,12-dimethylbenz[a]anthracene, dibenz[a,j]acridine and non-carcinogenic PAHs, anthracene and pyrene, were not phototoxic. The 3,6-quinone of BaP was found to be highly phototoxic while quinones that included menadione, danthron, phenanthrene-quinone and hydroquinone were not. The data suggest that the phototoxicity of BaP is due to photochemical production of quinones; the 3,6-quinone of BaP is phototoxic and is probably the result of the production of short lived cyclic reactive intermediates by the interaction of light with the quinone. Lastly, only the green algae, Selenastrum capricornutum, Scenedesmus acutus and Ankistrodesmus braunii almost completely metabolized BaP to dihydrodiols. The green alga Chlamydomonas reinhardtii, the yellow alga Ochromonas malhamensis, the blue green algae Anabaena flosaquae and euglenoid Euglena gracilis did not metabolize BaP to any extent. The data indicate that algae are important in their ability to degrade PAHs but the degradation is dependent on the dose of light energy emitted and absorbed, the dose of PAHs to which the algae are exposed, the phototoxicity of PAHs and their metabolite(s) and the species and strain of algae involved. All of these factors will be important in assessing the degradation and detoxification pathways of recalcitrant PAHs by algae.

32P-postlabelling analysis of dibenz[a,j]acridine-DNA adducts in mice: identification of proximate metabolites.

N-Heterocyclic polynuclear aromatics are widely-occurring environmental pollutants formed during the pyrolysis of nitrogen-containing organic chemicals. Dibenz[a,j]acridine (DBA), a member of this class, has been shown to be a skin carcinogen in mice. We undertook studies to determine the organ distribution of DBA-DNA adducts and to identify the DBA metabolites which lead to the formation of carcinogen-DNA adducts in vivo. DBA and its metabolites, trans-DBA-1,2-dihydrodiol (DBA-1,2-DHD) trans-DBA-3,4-dihydrodiol (DBA-3,4-DHD) and trans-DBA-5,6-dihydrodiol (DBA-5,6-DHD), were topically applied on mice. DNA was isolated using enzyme-solvent extraction methods, and analyzed for carcinogen-DNA adducts using 32P-postlabelling. In skin, DBA produced two distinct adducts (Adducts 1 and 2). The same two adducts were seen when DBA-3,4-DHD was applied. In addition, the total adduct level elicited by DBA-3,4-DHD was twice that of the parent compound. Two adducts (Adducts 3 and 4) were also seen in mouse skin when DBA-5,6-DHD was applied, but these differed chromatographically from adducts seen with DBA. However, when DBA-3,4-DHD was applied and analyzed using sensitive nuclease P1 32P-postlabelling, all four adducts could be detected. These results suggest that the major route of DBA activation to DNA-binding species in skin is through formation of DBA-3,4-DHD and subsequent metabolism of this compound to a bay-region diol-epoxide. However, we postulate that another activation pathway may proceed through a bis-dihydrodiol-epoxide.

Retardation of benzo[a]pyrene-induced epidermal tumor formation by the potent antioxidant 4b,5,9b,10-tetrahydroindeno[1,2-b]indole.

The ability of the potent antioxidant, 4b,5,9b,10-tetrahydroindeno[1,2-b]indole (THII), to inhibit tumor formation by topically-applied benzo[a]pyrene was evaluated using a complete carcinogenicity mouse skin bioassay. THII was administered by direct application to the skin, in the food or through the drinking water. In each case, THII increased the average time until the appearance of tumors by 4 weeks, and also decreased the total number of tumors compared with benzo[a]pyrene alone. These protective effects corresponded with the ability of THII to inhibit benzo[a]pyrene- or 12-O-tetradecanoylphorbol-13-acetate-induced epidermal ornithine decarboxylase activity, a biomarker of tissue proliferation in skin of the treated animals. This is the first report of an antioxidant administered in food or water inhibiting chemically induced skin carcinogenesis.

Influence of particle dose on the cytotoxicity of hamster and rat pulmonary alveolar macrophage in vitro.

Silica and ferric oxide are common industrial exposures. Studies have indicated that all commonly occurring forms of crystalline silica can cause fibrotic lung disease. There is evidence to indicate that crystalline silica is carcinogenic in humans who have not developed silicosis, while amorphous silica is not carcinogenic in humans. An important biological response to particles deposited deep in the lung is their engulfment by pulmonary alveolar macrophages (AM). To assess the role of AM in silica-induced lung disease, particle size distribution and surface area of crystalline, gelled, precipitated, and fumed silica, ferric oxide, and aluminum oxide were characterized; the cytotoxicity of the particles to hamster and rat AM in vitro was measured at 0.0-0.5 mg/1 x 10(6) cells at 24 and 48 h using dye exclusion procedures. The count medium diameter for aluminum oxide, ferric oxide, and amorphous silica was equal to or less than 0.38 microns, while for crystalline silica the value was 0.83 microns. The surface areas for the amorphous silicas and the aluminum oxide ranged from 253 to 125 m2/g with gelled silica having the highest value; the values for crystalline silica and ferric oxide were 4.3 and 10.8 m2/g, respectively. Crystalline silica (1.6%) was detected in the fumed silica, while none was detected in precipitated or gelled silica. With gelled silica, based on the dose of the particle, the viability of the hamster AM decreased to 27% at 0.05 mg and to zero at 0.1 mg at 24 h. At doses of 0.05 and 0.1 mg of crystalline, precipitated, or fumed silica, the percent viability decreased significantly to 76-67% and 51-42%, respectively, and to zero at 0.5 mg. Macrophages viable at 24 h decreased further at 48 h compared with the control culture. The ferric oxide and the aluminum oxide showed minimal to no changes in viability. Similar results for the particles were obtained with rat AM. The results indicate that precipitated and fumed amorphous silica tested at equivalent doses are equally as toxic to AM lavaged from two species of rodents as crystalline silica; gelled silica is more toxic than crystalline. Ferric oxide and aluminum oxide are noncytotoxic in this system. The results of this study indicate that the dose as well as the surface area and surface characterization are important determinants in the cytotoxicity of hamster and rat AM to these particles.

Tissue distribution of DNA adducts of 7H-dibenzo[c,g]carbazole and its derivatives in mice following topical application.

7H-Dibenzo[c,g]carbazole (DBC) is a potent liver and skin carcinogen following topical administration. The objective was to determine the pattern of DBC-DNA adducts produced in both target and nontarget tissues when DBC and its metabolites were applied topically at carcinogenic doses. DBC phenolic derivatives 1-hydroxy-DBC, 2-hydroxy-DBC, 3-hydroxy-DBC, 4-hydroxy-DBC, 5-hydroxy-DBC, 6-hydroxy-DBC, 13-c-hydroxy-DBC, and N-methyl-DBC were applied dermally to Hsd:ICR (Br) mice. Tissues were harvested 24 h later, and DBC-DNA adduct levels were determined by 32P-postlabeling. The levels of DBC-DNA adducts were about 25 times greater in liver than in any other tissue. Total DBC-DNA adducts were seen in skin and lung at about equal levels, while adduct levels in kidney and other tissues were no more than one fourth that of lung and skin. Adduct 6 was the predominant adduct in liver, adducts 2 and 3 were formed preferentially in skin, and adduct 3 was formed preferentially in lung. 3-Hydroxy-DBC and 4-hydroxy-DBC produced higher levels of DNA adducts in skin, lung, and liver than did the parent compound or 2-hydroxy-DBC. DNA adducts were not seen in any tissue for the 1-, 5-, 6-, or 13-c-hydroxy compounds. In addition, hepatic DNA adducts were not seen when the nitrogen of DBC was methylated. In lung and skin, N-methyl-DBC induced DNA adducts at levels comparable to DBC, although the adduct profile in these tissues was different from that of DBC itself.(ABSTRACT TRUNCATED AT 250 WORDS)

32P-postlabeling analysis of dibenz[a,j]acridine DNA adducts in mice: preliminary determination of initial genotoxic metabolites and their effect on biomarker levels.

N-Heterocyclic aromatics (NHA) are widely occurring environmental pollutants formed during the pyrolysis of nitrogen-containing organic chemicals. NHA are found in significant amounts in tobacco condensates, synthetic fuels, gasoline engine exhaust, and effluents from the heating of coal. Dibenz[a,j]acridine (DBA) is an example of NHA. The potency of many carcinogenic compounds is related, at least in part, to the efficiency of their biological activation. We undertook studies to determine which initial metabolites of DBA lead to the formation of high levels of carcinogen-DNA adducts in vivo. DBA and its metabolites, trans-DBA-1,2-dihydrodiol (DBA-1,2-DHD), trans-DBA-3,4-dihydrodiol (DBA-3,4-DHD), and trans-DBA-5,6-dihydrodiol (DBA-5,6-DHD), were applied to the skin of mice. DNA was isolated using enzyme-solvent extraction method. DNA was 32P-postlabeled under conditions of limiting [32P]ATP. In skin, DBA produced two distinct adducts. The same two adducts were seen when DBA-3,4-DHD was applied. In addition the total adduct level elicited by DBA-3,4-DHD was higher than that of parent compound. Two adducts were seen when DBA-5,6DHD was applied, but these were very different from adducts seen with DBA. These results suggested that activation of DBA to DNA-binding compounds in skin includes initial formation of DBA-3,4-DHD. The data support development of biomarkers for the exposure and effect of this compound, and also suggest that specific metabolic susceptibility markers might be able to predict populations at increased risk.

Comparative metabolism of 7H-dibenzo[c,g]carbazole and dibenz[a,j]acridine by mouse and rat liver microsomes.

The comparative metabolism of the carcinogenic pollutants 7H-dibenzo[c,g]-carbazole (DBC) and dibenz[a,j]acridine (DBA) was investigated in vitro using 3-methylcholanthrene (3MC) induced Sprague-Dawley rat and Hsd:ICR(Br) mouse liver microsomal preparations with benzo[a]pyrene (BaP) as the positive control. Metabolites were isolated and separated by HPLC and identified by spectroscopic and co-chromatographic techniques using synthetic standards. The major metabolites of DBC were the phenols: the 5-OH-DBC, 3-OH-DBC, and 2-OH-DBC. Traces of 1-OH-DBC were also found yet no dihydrodiols were identified. The major metabolites of DBA were the 3,4-diol-DBA and 5,6-diol-DBA, 1,2-diol-DBA, DBA-5,6-oxide and 4-OH-DBA. Treatment of both mice and rats with 3MC resulted in significant (P less than or equal to 0.05) increases relative to control in the microsomal metabolism of DBA to dihydrodiol and phenol metabolites, similar to that observed for BaP. 3MC-induced rat liver microsomes significantly (P less than or equal to 0.05) increased DBC metabolism relative to control microsomes whereas DBC metabolism was not increased with 3MC-induced mouse liver microsomes. These data indicate that different enzymatic pathways are involved in the metabolic activation of DBC in the Hsd:ICR(Br) mouse and Sprague-Dawley rat.

Conjugation of benzo[a]pyrene metabolites by freshwater green alga Selenastrum capricornutum.

Benzo[a]pyrene (BaP) undergoes metabolic transformation in mammals via oxidative, hydrolytic, and conjugative processes; however, little is known concerning BaP conjugation in freshwater algae. It has been shown in this laboratory that BaP is metabolized by Selenastrum capricornutum via a dioxygenase pathway. This study describes the conjugation of BaP metabolites by a green alga, Selenastrum capricornutum. Cultures were exposed to 1160 micrograms/l [14C]BaP for 4 days at 23 degrees C under gold fluorescent lights on a diurnal cycle of 16 h light, 8 h dark. Of the total metabolites in the algal culture, 89% were present in media. BaP and non-conjugated metabolites were separated from conjugated metabolites by chromatography on neutral alumina columns using solvents of increasing polarity. Seventy-one percent of the BaP metabolites were conjugates of which 12.2%, 12.0% and 12.4% were sulfate ester and alpha- and beta-glucose conjugates, respectively. Conjugates that coeluted with sulfate esters were hydrolyzed with arylsulfatase, alpha- or beta-glucosidase; high performance liquid chromatography (HPLC) analysis indicated that the major product of each enzymatic hydrolysis was the 4,5-dihydrodiol (87.2, 69 and 53%, respectively). Eighty-six percent of the conjugates were acid labile following incubation for 2 h in 4 N HCl at 37 degrees C. To our knowledge this is the first demonstration of the metabolism of a polynuclear aromatic hydrocarbon by a freshwater green alga through a dioxygenase pathway and subsequent conjugation and excretion.

The metabolism of dibenz[a,j]acridine in the isolated perfused lung.

The metabolism of the carcinogenic N-heterocyclic aromatic, dibenz[a,j]-acridine (DB[a,j]A), was investigated in an isolated perfused rabbit lung preparation. The rate of metabolism of DB[a,j]A was less than the rate of metabolism of 7H-dibenzo[c,g]carbazole (DB[c,g]C) in the untreated and corn oil-pretreated animals. A significantly increased rate of metabolism was observed for DB[a,j]A in benzo[a]pyrene(B[a]P)-pretreated animals. This resulted in marked increases in conjugation and distribution of conjugates and total metabolites in blood and lung. Two major metabolites characterized spectroscopically were assigned as the 3,4-dihydrodiol and a phenol of DB[a,j]A. The results indicate that in the lung DB[a,j]A is metabolized in a manner similar to that of B[a]P.