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Biomedical subjects

D R Bickers

Publications and source records attributed to D R Bickers.

At least 91 records · Page 5Linked to original sources
PubMed1987

Use of monoclonal antibodies to characterize the induction response of the cytochrome P-450-dependent mixed function oxidase system to nitrofluoranthenes.

In prior studies with neonatal rats we have suggested that nitrated polycyclic aromatic hydrocarbons (NPAH) are 3-methylcholanthrene (3-MC) type of inducers of cytochrome P-450. These observations have been extended by studying the effect of fluoranthene (FL) and its nitrated derivative, 3-nitrofluoranthene (3-NF) and a mixture of nitrated fluoranthenes (NFs) on the induction of hepatic and pulmonary monooxygenase activities in adult rats. We have characterized the effect of these compounds on hepatic cytochrome P-450 isozyme(s) using immunoblot analysis. The administration of 3-NF and NFs to rats resulted in highly significant induction (1.9- to 5.8-fold) of hepatic and pulmonary aryl hydrocarbon hydroxylase (AHH) and 7-ethoxyresorufin-O-deethylase (ERD) activities. FL was either ineffective or much less effective in inducing these enzyme activities. The enzyme induction response to these compounds occurred in the following order: NFs greater than 3-NF greater than FL. SDS-PAGE of hepatic microsomes prepared from FL-, 3-NF- and NFs-treated animals revealed a higher content of protein migrating in the P-450 region. Characterization of isozymes of P-450 was carried out by Western blot analysis with highly specific monoclonal antibodies (MAb) raised against 3-MC-specific P-450 (MAb 1-7-1) and phenobarbital-specific P-450 (MAb-2-66-3) isozymes. Hepatic microsomes prepared from 3-NF- and NFs-treated rats showed two distinct immunoprecipitin bands with MAb 1-7-1 whereas microsomes prepared from FL-treated animals showed a sharp band with MAb 2-66-3. MAb 1-7-1 significantly inhibited (approximately 80%) AHH activity induced by 3-NF and NFs. On the other hand FL-induced AHH activity was only moderately (approximately 30%) inhibited by MAb 1-7-1 whereas higher inhibition (approximately 60%) was observed with MAb 2-66-3. Analysis of BP metabolites by h.p.l.c. revealed enhanced production of metabolites by liver microsomes from 3-NF- and NFs-treated animals. The formation of BP 7,8-diol was 1.8- to 2.4-fold increased following treatment of animals with 3-NF and NFs respectively. Addition of MAb 1-7-1 to a microsomal mixture from 3-NF- and NFs-treated rats inhibited the formation of BP phenols (60-75%) and BP 7,8 diol (52-60%). These inhibitory effects were not observed with microsomes prepared from FL-treated rats. These studies suggest that NFs induce specific monooxygenases in liver and that they are inducers of P-450 isozymes c and d.

Animals↗
PubMed1987

Human hair follicle benzo[a]pyrene and benzo[a]pyrene 7,8-diol metabolism: effect of exposure to a coal tar-containing shampoo.

Assay systems for the evaluation of carcinogen interaction with human tissues are essential for assessing cancer risk. Hair follicles are a readily available source of human epithelial tissue and offer an excellent system with which to study carcinogen metabolism in human populations. In this study freshly plucked human hair follicles were employed to measure the metabolism of benzo[a]pyrene (BP), benzo[a]pyrene-7,8-diol (BP 7,8-diol), and the enzyme-mediated binding of [3H]-BP to DNA. The effect of human exposure to a crude coal tar (CCT)-containing shampoo, a preparation rich in polycyclic aromatic hydrocarbons (PAHs), on these parameters was also evaluated. Twelve healthy volunteers were studied before and after shampooing their hair daily for 4 days with the CCT-containing shampoo. Wide interindividual variation was observed in basal cytochrome P-450-dependent aryl hydrocarbon hydroxylase (AHH) activity which ranged from 0.6-17.6 fmol water-soluble BP metabolites/h/hair follicle (mean +/- SE of 32 individuals was 9.7 +/- 0.9). After use of the shampoo for 4 days AHH activity increased in 10 of the 12 volunteers (50-148%) and enhancement of enzyme-mediated binding of BP to DNA was detected in most subjects. Hair follicles were shown to convert BP to several metabolic species including BP 7,8-diol, a major precursor of the ultimate carcinogenic metabolite of BP. Benzo[a]pyrene-7,8-diol itself was also metabolized by the human hair follicles in this system. Clotrimazole, a known inhibitor of the metabolism of BP as well as the carcinogenicity of the hydrocarbon in rodent skin, was found to inhibit AHH and the in vitro metabolism of BP and BP 7,8-diol in human hair follicles. Oral administration of a similar antifungal imidazole, ketoconazole at a dose of 200 mg daily for 5 days, to healthy volunteers also resulted in greater than 90% inhibition of hair follicle AHH activity. These studies indicate that hair follicles represent an accessible tissue suitable for assessing the extent of PAH carcinogen metabolism in human subjects. Furthermore, enzyme activity critical to cancer induction by PAHs was shown to be inducible following the use of a CCT-containing shampoo. This carcinogen-activating enzyme system was substantially inhibited by imidazole compounds, suggesting that they may prove effective as anticarcinogens in human populations.

Aryl Hydrocarbon Hydroxylases↗
PubMed1986

Carcinogen metabolism in human skin grafted onto athymic nude mice: a model system for the study of human skin carcinogenesis.

Human skin grafted onto athymic nude mice maintains its major histological features and may provide a useful system with which to assess the carcinogen interaction with human skin. Significant differences were observed in basal levels of cytochrome P-450 and cytochrome P-448-dependent monooxygenase activities between human grafted and nude mouse epidermis. Topical application of crude coal tar (CCT) to human skin transplanted onto nude mice resulted in 3.9 & 3.5; 3.2 & 2.9 and 1.1 & 1.2 fold increases in mouse and human epidermal aryl hydrocarbon hydroxylase (AHH), ethoxyresorufin deethylase (ERD) and ethoxycoumarin deethylase (ECD) activities, respectively. CCT applied topically to mouse skin resulted in 27.8 & 6.4; 12.8 & 3.3 and 1.7 & 2.6 fold increases in mouse and human epidermal AHH, ERD and ECD activities, respectively. Topical application of coal tar either onto human transplanted skin or to mouse skin also resulted in substantial induction of hepatic and pulmonary AHH and ERD activities. These studies indicate that human skin grafted onto nude mice preserves its metabolic capacity and offers a useful model system with which to assess the effects of polycyclic aromatic hydrocarbons and CCT on cutaneous xenobiotic metabolism in the human population.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1986

Comparative effects of topically applied nitrated arenes and their nonnitrated parent arenes on cutaneous and hepatic drug and carcinogen metabolism in neonatal rats.

The effect of a single topical application of several nitroarenes (1-nitropyrene, nitropyrenes mixture, nitrobenzo(ghi)perylene mixture, 3-nitrofluoranthene, nitrofluoranthene mixture, and nitroperylene mixture) and their corresponding parent arenes to neonatal rats on hepatic and cutaneous drug and carcinogen metabolism was studied. Topical application of each nitroarene (10 mg/kg) resulted in significant induction of aryl hydrocarbon hydroxylase (AHH), 7-ethoxyresorufin O-deethylase (ERD), and 7-ethoxycoumarin O-deethylase (ECD) activities in both skin (1.5- to 14.6-fold) and liver (1.3- to 41.9-fold). The induction of these enzymes by each of the nitroarenes was significant when compared to control or to their corresponding parent arenes. Among the nitroarenes studied, 1-nitropyrene was the least effective in inducing enzyme activities. The inducibility in both skin and liver by different nitroarenes tested was in the following order: nitrofluoranthenes mixture greater than 3-nitrofluoranthene greater than nitroperylenes mixture greater than nitrobenzo(ghi)perylenes mixture greater than nitropyrenes mixture greater than 1-nitropyrene. The nitrofluoranthenes mixture and the nitroperylenes mixture were almost as effective as 3-methylcholanthrene (3-MC). Parent arenes were either ineffective or significantly less effective than nitrated arenes in inducing hepatic and/or cutaneous monooxygenase activities. Hepatic and/or cutaneous benzphetamine N-demethylase (BPD), NADPH cytochrome c reductase, NADH ferricyanide reductase activities, and the levels of cytochrome P-450 and cytochrome b5, remained unchanged following treatment with either topically applied nitroarenes or arenes. However, a shift of approximately 1 nm to the blue region in the absorption maximum of hepatic cytochrome P-450 was observed in animals treated with nitroarenes. This shift was not evident in the case of 1-nitropyrene. Analysis of benzo(a)pyrene metabolites by high-pressure liquid chromatography revealed a significant enhancement in the production of metabolites by nitroarene-treated rat skin and liver microsomes. Our studies suggest that nitroarenes are inducers of hepatic and cutaneous monooxygenases in neonatal rats after topical administration and that they resemble the 3-MC type of inducers in this regard.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1986

Skin tumor initiating activity of therapeutic crude coal tar as compared to other polycyclic aromatic hydrocarbons in SENCAR mice.

Crude coal tar (CCT), a complex mixture rich in polycyclic aromatic hydrocarbons (PAHs) including carcinogens such as benzo[a]pyrene (BP), is widely used therapeutically in dermatological practice, particularly in combination with ultraviolet radiation in the treatment of chronic dermatoses such as psoriasis. In this study we analyzed the tumor initiating activity of therapeutic CCT preparation (USP) in a two-stage model system (initiation and promotion) in SENCAR mice. The tumorigenicity of CCT was compared with other conventionally studied carcinogenic PAHs; 7,12-dimethylbenz[a]anthracene (DMBA), 3-methylcholanthrene (MCA), benzo[a]pyrene 7,8-diol (BP-7,8-diol) and benzo[a]pyrene (BP). A single topical application of an initiating dose of CCT (20 microliter), DMBA (39 nmol), MCA (746 nmol), BP-7,8-diol (352 nmol) or BP (396 nmol) was followed by twice weekly application of 12-O-tetradecanoylphorbol-13-acetate (TPA) (3.24 nmol). The first tumor appearance in the CCT treated group was at 6 weeks on test as compared with DMBA and MCA (3 weeks) and BP-7,8-diol and BP (4-5 weeks). In a total of 20 animals after 8 weeks on test the DMBA, MCA, BP-7,8-diol, BP and CCT groups of mice showed 457, 176, 106, 76 and 46 tumors, respectively. After 11 weeks 100% of the mice in each experimental group had developed tumors and the number of tumors/mouse was 24.3, 15.0 9.8, 6.6 and 3.3 in the DMBA, MCA, BP-7,8-diol, BP and CCT groups, respectively. These studies provide first evidence that a single topical application of a therapeutic preparation of CCT possesses skin tumor initiating activity.

Administration, Topical↗
PubMed1986

Benzo(a)pyrene diol epoxide-I-DNA adduct formation in the epidermis and lung of SENCAR mice following topical application of crude coal tar.

The levels of benzo[a]pyrene diol epoxide-I-deoxyguanosine (BPDE-I-dG) adduct formation in epidermis and lung of SENCAR mice following the topical application of benzo[a]pyrene (BP) alone, crude coal tar (CCT) alone, and the two combined were determined in an enzyme linked immunosorbent (ELISA) assay using monoclonal antibodies. Topical application of two doses of BP (20 micrograms) at 72-h intervals, with sacrifice 24 h later resulted in the formation of 197 fmol and 205 fmol BPDE-I-dG adducts per mg DNA in epidermis and lung, respectively. Topical application of 0.5 ml CCT alone resulted in the formation of 278 fmol and 410 fmol BPDE-I-dG adducts per mg DNA in epidermis and lung, respectively. Simultaneous topical application of 20 micrograms BP and CCT (0.1-0.5 ml) resulted in substantially lower BPDE-I-dG adducts in the epidermis as well as in the lung. Our results suggest that CCT may contain inhibitors of carcinogen-DNA adduct formation and that topical application of CCT produces greater effects on DNA-adduct formation in lung than in epidermis. Thus the cancer-causing potency of the polycyclic aromatic hydrocarbons (PAHs) in CCT may be reduced by other anticarcinogenic constituents present in CCT and systemic absorption of carcinogenic PAHs in CCT applied to skin might have tumorigenic effects in other tissues.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1986

Effect of continued ultraviolet B phototherapy on the duration of remission of psoriasis: a randomized study.

Phototherapy using sunburn spectrum ultraviolet radiation (UVB) is now a frequently utilized treatment for psoriasis that is extensive or has not responded to topical preparations. Four university centers performed a prospective randomized clinical trial to compare remission times of patients with psoriasis who continued UVB phototherapy after initial clearing with this therapy and patients whose UVB phototherapy was discontinued within 3 weeks of clearing. As assessed by life table methods, the time to flare after initial clearing for patients on UVB maintenance therapy was significantly longer than for patients who discontinued UVB within 3 weeks after initial clearing. Our data suggest that continuing UVB phototherapy after initial clearing contributes to the duration of disease control and is justified for many patients.

Actuarial Analysis↗
PubMed1986

Photoradiation diagnosis and therapy. Dermatologic and photobiologic aspects.

Photoradiation with photosensitizing porphyrins offers a potentially useful approach to the diagnosis and treatment of certain human cancers. The mechanism of porphyrin photosensitivity as studied in cultured cells or in the skin has been studied thoroughly. Possible targets that have been identified include membranous cellular organelles, DNA, and the plasma membrane. Mediators of the reaction include reactive oxygen species, particularly singlet oxygen, that may elicit lipid peroxidation and the activation of complement. Further research is needed to identify photosensitizers with greater selectivity for malignant cells and to develop even better sources of radiant energy.

Animals↗
PubMed1986

Cutaneous porphyrin photosensitization: murine ear swelling as a marker of the acute response.

Acute cutaneous photosensitivity is a major manifestation of certain forms of human porphyria and also occurs in patients treated with hematoporphyrin derivative (HpD) photoradiation for the diagnosis and treatment of malignant tumors. In this study a quantitative animal model useful for in vivo studies of acute porphyrin photosensitization in cutaneous tissue was developed. C3H mice injected with HpD and irradiated 6 h later with 405 nm energy developed a 40-90% increase in ear thickness which was present immediately after irradiation and persisted for at least 24 h. No ear swelling occurred in animals receiving 405 nm radiation alone or HpD alone. Histologically, this photosensitivity reaction was manifest as edema, vascular dilatation, and mast cell degranulation immediately after irradiation followed by an influx of polymorphonuclear leukocytes and epidermal necrosis 24 h later. Tissue injury evoked by HpD and light was accompanied by extravasation of intravenously administered 125I-labeled albumin in the irradiated ears, indicating that photosensitization was accompanied by transudation of serum into the site of tissue injury. An in vivo correlation of this approach was verified by detection of measurable increase in ear thickness in irradiated mice rendered porphyric by the ingestion of a griseofulvin-containing diet. The mouse ear swelling model offers a useful system with which to study acute porphyrin photosensitization in the skin, and may lead to important new insights into the pathogenesis and prevention of this form of phototoxicity.

Animals↗
PubMed1986

Clotrimazole, an inhibitor of benzo[a]pyrene metabolism and its subsequent glucuronidation, sulfation, and macromolecular binding in BALB/c mouse cultured keratinocytes.

The effect of the antifungal imidazole compound, clotrimazole, on the metabolism of benzo[a]pyrene (BP) was studied in cultured keratinocytes prepared from BALB/c mouse epidermis. Varying concentrations of clotrimazole added to the cultured keratinocytes resulted in a dose-dependent inhibition of the activities of the microsomal cytochrome P-450-dependent monooxygenases aryl hydrocarbon hydroxylase and 7-ethoxycoumarin O-deethylase. The major organic solvent-soluble metabolites of BP identified in the cultured cells were trans-7,8-dihydro-7,8-dihydroxybenzo[a]pyrene (BP-7,8-diol), 9-hydroxybenzo[a]pyrene (9-OH-BP), and 3-hydroxybenzo[a]pyrene (3-OH-BP), although small amounts of trans-4,5-dihydro-4,5-dihydroxybenzo[a]pyrene, BP-quinones, and trans-9,10-dihydroxybenzo[a]pyrene were also present. The major organic solvent-extractable metabolites of BP found in the extracellular culture medium were primarily the diols with smaller quantities of phenols and quinones. The major water-soluble metabolites of BP present both intracellularly and extracellularly were glucuronide conjugates of 3-OH-BP, 9-OH-BP, and benzo[a]pyrene-3,6-dione and to a lesser extent sulfate conjugates (primarily of the BP-7,8-diol). Clotrimazole inhibited the generation of organic solvent-soluble and water-soluble conjugates in a dose-dependent manner. The in vitro metabolism of BP by microsomes prepared from control and benz[a]anthracene (BA)-induced cultured keratinocytes was also inhibited by clotrimazole with greater inhibitory effect on BA-induced keratinocytes especially with respect to the formation of diols and quinones. The enzyme-mediated covalent binding of BP to mouse keratinocyte DNA and protein was also substantially diminished by clotrimazole in a dose-dependent fashion. These results indicate that clotrimazole, a widely used drug for the management of a variety of superficial dermatophyte infections of the skin, is a potent inhibitor of cytochrome P-450-dependent transformation of polycyclic aromatic hydrocarbons in cultured murine keratinocytes. This system offers a convenient approach for studies as inhibitors of carcinogen metabolism in the epidermis.

Animals↗
PubMed1986

Additive effects of ultraviolet B and crude coal tar on cutaneous carcinogen metabolism: possible relevance to the tumorigenicity of the Goeckerman regimen.

The effect of cutaneous exposure to ultraviolet B (UVB) radiation alone, to crude coal tar (CCT) alone, and to the combination of UVB and CCT on the inducibility of the microsomal cytochrome P-450-dependent carcinogen-metabolizing enzyme aryl hydrocarbon hydroxylase (AHH) and other monooxygenases such as 7-ethoxyresorufin O-deethylase (ERD) and 7-ethoxycoumarin O-deethylase (ECD) activities in the skin of neonatal rats was studied. Exposure of the animals to UVB (400-1600 mJ/cm2) alone resulted in a dose-dependent increase in cutaneous enzyme activities. At a UVB dose of 1200 mJ/cm2 increases in AHH, ECD, and ERD were 194%, 115%, and 244%, respectively. A single topical application of CCT (10 ml/kg) 24 h before sacrifice resulted in significant induction of AHH (350%), ECD (921%), and ERD (796%) activities. Treatment of animals with the same dose of CCT followed by UVB exposure resulted in additive and/or synergistic effects on AHH (858%), ECD (1229%), and ERD (1166%) activities in the skin. In contrast, exposure of animals to UVB prior to CCT application had effects no different from those of CCT alone. Epoxide hydrolase and glutathione S-transferase activities in skin from all experimental groups were not different from those of controls. High-pressure liquid chromatographic analysis of the metabolism of benzo[a]pyrene (BP) by cutaneous microsomes prepared from animals treated with UVB alone, CCT alone, and the combination of UVB and CCT revealed increased formation of all the metabolites in each experimental group. The largest increase in metabolite formation occurred in animals receiving CCT followed by UVB exposure. The inducibility of trans-7,8-diol formation by UVB alone and CCT alone was 203% and 435%, respectively, whereas with CCT followed by UVB it was 1065%. The differential responses in AHH activity were found to parallel the capacity of skin microsomal enzymes to enhance the binding of [3H]-BP to DNA. These studies indicate that the sequence of exposure to the components of the Goeckerman regimen in rodents greatly influences metabolic activity in skin. When applied in the same sequence employed in the Goeckerman regimen (CCT followed by UVB exposure) the additive effect upon catalytic activity essential for cancer initiation suggests a possible mechanism for the enhancement of human skin cancer in individuals exposed to this therapeutic regimen.

Animals↗
PubMed1986

Pharmacological modification of epidermal detoxification systems.

The skin is a major interface between the body and the environment and possesses membrane-bound cytochrome P-450-dependent enzyme activity that is capable of both detoxifying endogenous and exogenous substrates and enhancing the toxic effects of selected substances. The use of chemical inhibitors of enzyme activation by P-450-dependent enzymes represents one possible approach to controlling toxic responses in target tissue such as the skin. Our data indicate that certain polyphenols and imidazoles are potent inhibitors of epidermal carcinogen metabolism, and of the DNA binding and the carcinogenicity of PAHs such as BP. The use of such agents may offer a novel approach to the prevention of environmentally induced cancer.

Animals↗
PubMed1986

Iron therapy for hepatic dysfunction in erythropoietic protoporphyria.

Erythropoietic protoporphyria, caused by an inherited deficiency of ferrochelatase, results in increased free protoporphyrin concentrations in erythrocytes and plasma. Cutaneous photosensitivity is the primary clinical manifestation, but in some patients, protoporphyrin accumulation in the liver may lead to fatal hepatic failure. No treatment exists for this lethal complication. We report the case of a patient with erythropoietic protoporphyria and abnormal results of liver function tests in whom oral iron therapy led to a substantial decrease in free erythrocyte and stool protoporphyrin levels with return of liver function to normal. Iron therapy should be considered for preventing potentially fatal hepatic failure in patients with erythropoietic protoporphyria.

Administration, Oral↗
PubMed1986

Inhibition of 3-methylcholanthrene-induced skin tumorigenicity in BALB/c mice by chronic oral feeding of trace amounts of ellagic acid in drinking water.

Chronic p.o. feeding of small amounts of ellagic acid, a naturally occurring dietary plant phenol, to BALB/c mice in drinking water afforded significant protection against skin tumorigenesis induced by 3-methylcholanthrene, a polycyclic aromatic hydrocarbon carcinogen. A significant increase in the latent period for the development of skin tumors by 3-methylcholanthrene was observed in the ellagic acid-fed group of mice (9 wk on test) as compared to the control group of animals (6 wk on test). The observed protection against tumor induction in the ellagic acid-fed group of animals may be due to the inhibition of the metabolic activation of the polycyclic aromatic hydrocarbon since epidermal aryl hydrocarbon hydroxylase activity was found to be significantly inhibited. Our results suggest that dietary supplementation with small amounts of ellagic acid may prove useful in reducing the risk of skin carcinogenesis induced by environmental chemicals.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1986

Porphyria. Basic science aspects.

The porphyrias are a heterogeneous group of clinical disorders that share a common etiologic background in that each manifests a major metabolic defect in the synthesis of heme. The porphyrias represent an important category of human disease, perhaps as much for what they can teach us about how metabolic abnormalities are translated into clinical manifestations as they are as diseases per se. In this discussion an effort is made to describe, in some detail, the metabolic steps involved in the synthesis of heme and to correlate known abnormalities in this sequence of reactions that are associated with human porphyria.

5-Aminolevulinate Synthetase↗
PubMed1985

Topically applied nitropyrenes are potent inducers of cutaneous and hepatic monooxygenases.

The inducibility of skin and liver microsomal cytochrome P-450 dependent aryl hydrocarbon hydroxylase and other monooxygenases by a mixture of nitropyrenes was assessed and compared with the parent non-nitrated compound, pyrene. A single topical application of nitropyrenes to neonatal rats resulted in highly significant induction of aryl hydrocarbon hydroxylase, ethoxycoumarin O-de-ethylase, and ethoxyresorufin O-de-ethylase activities in skin and liver after 24 hours. Inducibility of the skin and liver enzymes was 3.9-5.7 fold and 1.8-10.3 fold respectively. On the other hand, aminopyrine N-demethylase, benzphetamine N-demethylase and epoxide hydrolase activities in the liver were unaffected by topically applied nitropyrenes. Furthermore, treatment with nitropyrenes produced a 1 nm shift to the blue region in the wavelength maximum of hepatic microsomal cytochrome P-450. Topically applied pyrene produced only marginal or no effects on cutaneous and hepatic enzyme activities. Our results suggest that nitration of pyrene, a relatively ineffective enzyme inducer, produces nitropyrenes which are potent inducers of hepatic and cutaneous monooxygenases and they resemble 3-methylcholanthrene in this inducing effect.

7-Alkoxycoumarin O-Dealkylase↗