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D R Bickers

Publications and source records attributed to D R Bickers.

At least 19 recordsLinked to original sources
PubMed1992

Glutathione S-transferase-dependent conjugation of leukotriene A4-methyl ester to leukotriene C4-methyl ester in mammalian skin.

The glutathione S-transferase (GST)-dependent conjugation of reduced glutathione (GSH) with leukotriene A4 (LTA4)-methyl ester in rodent and human skin was investigated. Incubation of [3H]LTA4-methyl ester (1 nmole, approximately 200,000 dpm) with cytosol prepared from rat, mouse and human skin or with affinity purified GST from rat skin cytosol in the presence of GSH resulted in the formation of LTC4-methyl ester. Maximum enzyme activity was observed in rat skin followed by mouse and human skin. With heat-denatured cytosol or in the absence of GSH, the product formation was negligible. GST purified from rat skin cytosol by GSH-agarose affinity chromatography exhibited a several-fold increase in the specific activity of enzyme with 1-chloro-2,4-dinitrobenzene (55-fold), ethacrynic acid (67-fold) and LTA4-methyl ester (12-fold) as substrates. Western blot analysis of the affinity purified GST indicated a predominant expression of the Pi class of GST isozyme followed by Mu and Alpha classes of isozymes. The formation of LTC4-methyl ester was established by its radioactivity profile on high pressure liquid chromatography and absorption spectroscopy. These results suggest that, in addition to xenobiotic metabolism, cutaneous GSTs may also be capable of metabolizing physiological substrates such as LTA4.

Animals↗
PubMed1992

Immunogenetic influences on the initiation stage of the cutaneous chemical carcinogenesis pathway.

While it is generally agreed that environmental exposure to solar radiation and to certain classes of chemicals are the major causes of nonmelanoma skin cancer, it is also believed that genetic polymorphisms regulating immunological responses are important determinants of individual susceptibility to skin cancer. However, little is known about their interactions with the chemical carcinogenesis pathway prior to the actual development of tumors. This issue was examined by comparing susceptibility to skin cancer in C3H/HeN and C3H/HeJ mice, two strains that differ only at the lipopolysaccharide genetic locus, which serves as a regulator of a number of immunological activities. When subjected to a two-stage cutaneous tumorigenesis protocol, C3H/HeJ mice, which have a mutation at the lipopolysaccharide genetic locus that renders them deficient in their capacity to produce cytokines and to activate macrophages, developed nearly three times as many tumors as did C3H/HeN mice, which do not have this mutation. Epidermal DNA binding of 7,12-[3H]dimethylbenz(alpha)anthracene, an index of tumor initiation, was also significantly greater in C3H/HeJ than in C3H/HeN mice. Immunological activities regulated by the lipopolysaccharide genetic locus thus confer resistance to DMBA-induced cutaneous tumorigenesis in mice and are associated with changes that occur early in the tumorigenesis pathway, prior to the development of tumors.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1992

Photodynamic effects of chloroaluminum phthalocyanine tetrasulfonate are mediated by singlet oxygen: in vivo and in vitro studies utilizing hepatic microsomes as a model membrane source.

Chloroaluminum phthalocyanine tetrasulfonate (AlPcTS) is a promising photosensitizer for the photodynamic therapy (PDT) of cancer. In this study, we investigated the in vivo and in vitro photodestruction of hepatic microsomal membranes by AlPcTS and studied the role of reactive oxygen species in this process. Irradiation of hepatic microsomes prepared from AlPcTS-pretreated SENCAR mice to approximately 675 nm light resulted in rapid destruction of cytochrome P450 and associated monooxygenase activities, and enhancement of lipid peroxidation in a light-dose-dependent manner. The specificity of AlPcTS and light dependency on photodestruction of microsomal membranes was confirmed by Western blot analysis. Similar results were obtained when AlPcTS was added in vitro to a suspension of hepatic microsomes prepared from control animals followed by irradiation to approximately 675 nm light. Among the quenchers of singlet oxygen, superoxide anion, hydrogen peroxide, and hydroxyl radical, only the quenchers of singlet oxygen such as sodium azide, histidine, and 2,5-dimethyl furan afforded substantial protection in a dose-dependent manner against AlPcTS-mediated photodestruction of cytochrome P450 and associated monooxygenase activities, and photoenhancement of lipid peroxidation under both in vivo and in vitro conditions. These results suggest that lipid-rich microsomal membranes may be the potential targets of cell injury by AlPcTS-based PDT and that this process is mediated by singlet oxygen.

Animals↗
PubMed1992

Purification and molecular characterization of beta-naphthoflavone-inducible cytochrome P-450 from rat epidermis.

This study was designed to characterize epidermal cytochrome P-450 (P-450) induced by skin application of beta-naphthoflavone (beta-NF). Topical application of beta-NF (40 mg/kg) to rats resulted in a 2.6-times increase in epidermal P-450 content and a 3--14-times increase in epidermal monooxygenase activities. The purified epidermal P-450 showed a major band at 54 kDa on SDS-PAGE, which comigrated with hepatic P-4501A1 and cross-reacted with monoclonal and polyclonal antibodies specific to P-4501A1. The specific content of purified epidermal P-450 was 1.53 nmol/mg protein, representing 42-times purification. HPLC analysis of the purified epidermal P-450 showed similar elution profile and retention time as that of hepatic P-4501A1. The purified preparation efficiently catalyzed-benzo(a)pyrene hydroxylation when reconstituted with purified NADPH--P-450 reductase and phospholipid. Peptide fingerprint analysis of the purified epidermal P-450 and hepatic P-4501A1 showed similar monoclonal antibody 1-7-1 reacting epitopes. Partial N-terminal amino acid sequence analysis of purified epidermal P-450 showed complete homology with the known sequence of P-4501A1. Similarly, HPLC analysis of tryptic digest of purified epidermal P-450 and hepatic P-4501A1 showed identical peptide peaks with comparable retention times. N-terminal amino acid sequence analysis of three randomly selected tryptic peptides showed complete homology with the known sequence of P-4501A1. These results indicate that rat epidermal P-450 induced by beta-NF is similar to hepatic P-4501A1.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1992

Photodynamic therapy of chemically- and ultraviolet B radiation-induced murine skin papillomas by chloroaluminum phthalocyanine tetrasulfonate.

Photodynamic therapy (PDT) of cancer combines irradiation of tumors with visible light following selective uptake of the photosensitizer by the tumor cells. PhotofrinR-II (Pf-II) is the only photosensitizer which is in clinical use in PDT, whereas chloroaluminum phthalocyanine tetrasulfonate (AlPcTS) has also shown promise in preclinical studies. In most such studies, the effectiveness of the photosensitizers has been assessed in implanted tumor model systems rather than in model systems where tumors are allowed to grow in their own connective tissue matrix. In this study the pharmacokinetics, tumor ablation capability and cutaneous photosensitization response of AlPcTS have been assessed in mice bearing chemically- and ultraviolet B radiation (UVB)-induced benign skin papillomas. When tumor-bearing animals were injected intraperitoneally with AlPcTS (5 mg/kg body wt), maximum tumor:normal skin ratio of 2.4 was observed at 48 h, at which time the mice were irradiated within the absorption spectrum of the photosensitizer. In tumor ablation studies with SENCAR mice bearing chemically-induced skin tumors, AlPcTS resulted in greater than 80% ablation in tumor volume at 20 days post-irradiation. In cutaneous photosensitization response, AlPcTS produced only transient effects (no effect after 24 h) in SENCAR mice. Pharmacokinetics data, tumor ablation effects and cutaneous photosensitization response of AlPcTS were comparable in SKH-1 hairless mice bearing UVB-induced skin tumors. Our data indicate that AlPcTS produces significant photodynamic effects towards the ablation of murine skin tumors, and that it does not produce prolonged cutaneous photosensitivity.

Animals↗
PubMed1991

Antimutagenic and antitumorigenic activities of nordihydroguaiaretic acid.

Nordihydroguaiaretic acid (NDGA), which occurs in the resinous exudates of many plants is used as an antioxidant in fats and oils. In this study we show that NDGA inhibited the mutagenicity of methyl methanesulfonate, benzo[a]pyrene (BP), 2-aminofluorene, and aflatoxin B1 in Salmonella typhimurium strain TA100 or TA98 in the absence and presence of rat hepatic microsomal activation system. The addition of NDGA during and after nitrosation of methylurea (MU) resulted in a dose-dependent inhibition of mutagenicity induced by nitrosation products of MU. In a two-stage skin tumorigenesis protocol using 7,12-dimethylbenz[a]anthracene (DMBA) as the initiating agent followed by twice weekly applications of 12-O-tetradecanoylphorbol-13-acetate (TPA) as tumor promoter, pretreatment of animals with NDGA prior to DMBA application, afforded significant protection against skin tumorigenicity in female SENCAR mice. In additional studies, skin application of NDGA also inhibited the binding of topically applied [3H]BP and [3H]DMBA to epidermal DNA. When assessed in the anti-tumor promotion protocol, pretreatment of animals with NDGA before each application of TPA in DMBA-initiated mouse skin, resulted in 72% decrease in the total number of tumors when compared to non-NDGA pretreated animals. The possible mechanism(s) of the antimutagenic and anti-tumorigenic activities may be due to the multiple effects of NDGA as inhibitor of the carcinogen metabolism and DNA-adduct formation, scavenger of carcinogen free radicals, and as inhibitor of TPA-induced ornithine decarboxylase activity.

Animals↗
PubMed1991

Involvement of singlet oxygen in chloroaluminum phthalocyanine tetrasulfonate-mediated photoenhancement of lipid peroxidation in rat epidermal microsomes.

In recent studies chloroaluminum phthalocyanine tetrasulfonate (AlPCTS) has been shown to be an effective photosensitizer for the tumor necrosis in a modality known as photodynamic therapy, but the mechanism of photodynamic effect of AlPCTS is poorly understood. In this study, in vitro incubation of rat epidermal microsomes with AlPCTS followed by exposure to red light (approximately 675 nm) resulted in an increase in ADP/iron-supported lipid peroxidation, a measure of membrane damage. This photodestructive effect was found to be dependent on both the duration of light exposure and the dose of AlPCTS. Studies employing various quenchers of reactive oxygen species revealed that scavengers of singlet oxygen (histidine, 2,5-dimethylfuran, beta-carotene and sodium azide) afforded substantial protection (up to 90%) of photoenhancement whereas the scavengers of hydrogen peroxide (catalase), superoxide anion (superoxide dismutase), and hydroxyl radical (sodium benzoate, mannitol and ethanol) were ineffective in this regard. Our data indicate that AlPCTS-mediated photodestruction mainly involves a type II reaction via singlet oxygen formation and suggest that the latter could play a significant role in the tumor necrosis evoked by AlPCTS and light.

Animals↗
PubMed1991

All-trans retinoic acid protects against conversion of chemically induced and ultraviolet B radiation-induced skin papillomas to carcinomas.

It is becoming increasingly clear that cutaneous carcinogenesis in murine skin is a stepwise process comprising of initiation, promotion and progression. Most of the papillomas induced by an initiation-promotion protocol regress, while a few of them progress to malignant carcinomas. Progression of benign tumors into malignant cancer is critical since the latter lesions are capable of metastatic spread and eventual death. Inhibitors of the conversion process are therefore likely to be useful as cancer chemopreventive agents. All-trans retinoic acid (RA) is a known regulator of cellular proliferation and differentiation, and a known inhibitor of tumor promotion in murine skin. In this study we assessed the effect of topical application of RA on conversion of benign skin papillomas to malignant carcinomas. Papillomas were induced in SENCAR mice by topical application of 7,12-dimethylbenz[a]anthracene (DMBA) as tumor initiator followed by 12-O-tetradecanoylphorbol-13-acetate (TPA) as tumor promoter. In SKH-1 hairless mice papillomas were induced by thrice weekly exposure to ultraviolet B (UVB) radiation. At 18 (DMBA/TPA group) and 25 (UVB group) weeks papilloma yield stabilized and no new tumors developed. Beginning at the 20th week (DMBA/TPA group) and at the 27th week (UVB group), malignant conversion was achieved by twice weekly topical application of TPA or free radical-generating compounds benzoyl peroxide (BPO), 2,2-azobis(2-amidinopropane) (ABP) and tert-butyl peroxybenzoate (BPB). Application of RA (10 micrograms/animal) 1 h prior to skin application of TPA, BPO, ABP or BPB afforded significant protection (up to 70%) only against malignant conversion mediated by free radical-generating compounds in both chemically induced and UVB-induced benign skin papillomas. On the other hand, preapplication of RA was less effective in the suppression of spontaneous malignant conversion in vehicle-treated animals. These results suggest that, in addition to their anti-tumor promoting effects, retinoids may also act as anti-carcinogens by inhibiting the process of malignant conversion induced by free radical-generating compounds.

Animals↗
PubMed1991

Inhibition of mutagenicity in Salmonella typhimurium and skin tumor initiating and tumor promoting activities in SENCAR mice by glycyrrhetinic acid: comparison of 18 alpha- and 18 beta-stereoisomers.

Licorice has been used as medicine and as sweetening agent in food products. The major water-soluble constituent of licorice is glycyrrhizin (GL), an oleanane triterpenoide, which is known to be partly hydrolyzed by glucuronidase to its aglycone glycyrrhetinic acid (GA) which exists in 18 alpha (alpha-GA) and 18 beta (beta-GA) stereoisomeric forms. In this study alpha-GA and beta-GA were found to inhibit the mutagenicity of benzo[a]pyrene (B[a]P), 2-aminofluorene and aflatoxin B1 in Salmonella typhimurium TA98 and TA100. beta-GA was more effective than alpha-GA as an antimutagen. In the two-stage skin tumorigenesis protocol using 7,12-dimethylbenz[a]anthracene (DMBA) as the tumor initiating agent followed by twice weekly applications of 12-O-tetradecanoylphorbol-13-acetate as tumor promoter, pretreatment of SENCAR mice with alpha-GA or beta-GA resulted in significant protection against tumor initiation as well as tumor promotion. As an anti-tumor initiating agent, beta-GA was found to be more effective than alpha-GA. Similarly, topical application of beta-GA was found to be more effective than alpha-GA in inhibiting the binding of both [3H]B[a]P and [3H]DMBA to epidermal DNA. However, as an anti-tumor promoter, alpha-GA and beta-GA showed comparable effects. Our results suggest that both alpha-GA and beta-GA possess substantial anti-skin tumor initiating and anti-skin tumor promoting activities.

Animals↗
PubMed1991

Protection against ultraviolet B radiation-induced photocarcinogenesis in hairless mice by green tea polyphenols.

Our recent studies have shown that polyphenols present in green tea (GTP) possess significant antigenotoxic activity and afford protection against polycyclic aromatic hydrocarbon-induced skin tumor initiation in mice. In this study we assessed the effect of oral feeding and topical application of GTP on ultraviolet B (UVB) radiation-induced skin carcinogenesis in female SKH-1 hairless mice. Chronic oral feeding of GTP (0.1%, w/v) in drinking water resulted in significantly (P less than 0.01) lower tumor yield (percent of animals with tumors and number of tumors per mouse) and extended TDT50 (P less than 0.05), as compared to animals receiving normal drinking water. Topical application of GTP before UVB irradiation also afforded protection against photocarcinogenesis; however, the protective response was lower than that observed by oral feeding of GTP in drinking water. These results, in conjunction with our prior publications, suggest that consumption of green tea may reduce the risk of some forms of human cancer induced by both physical and chemical environmental carcinogens.

Animals↗
PubMed1991

Photodynamic therapy of murine skin tumors using Photofrin-II.

Photodynamic therapy (PDT) is a new experimental cancer therapy in which a photosensitizing chemical that selectively localizes within tumors is given to a tumor-bearing individual and the tumor is then irradiated by wavelengths within the visible spectrum of the photosensitizer. The only photosensitizer currently approved for human clinical trials is Photofrin-II (Pf-II). In most preclinical studies, the effectiveness of Pf-II has been assessed in implanted tumor models rather than in systems in which tumors are grown in their own connective tissue matrix. In this study, the pharmacokinetics, tumor ablation capability and cutaneous photosensitizing capacity of Pf-II were assessed in mice bearing chemically induced or ultraviolet B radiation (UVB)-induced benign skin neoplasms. Intraperitoneal administration of Pf-II (5 mg/kg body weight) to tumor-bearing animals showed maximum tumor: normal skin ratio of the photosensitizer at 72 h. When SENCAR mice bearing chemically induced tumors were irradiated with visible light corresponding to the absorption spectrum of the photosensitizer, up to 89% ablation in tumor volume at 20 d post-irradiation was observed. Animals treated with Pf-II and exposed to visible light showed significant cutaneous photosensitization for at least 6 d after-irradiation. Treatment of SKH-1 hairless mice bearing UVB-induced cutaneous neoplasms with Pf-II exhibited similar pharmacokinetics, skin tumor ablation effects and cutaneous photosensitivity. Our data indicate that Pf-II has significant activity towards the ablation of murine skin benign tumors grown in their own tissue matrix, suggesting that such a murine skin tumor model system could be valuable in evaluating the photodynamic effects of newly developed photosensitizers.

Animals↗
PubMed1990

Evidence for the involvement of singlet oxygen in the photodestruction by chloroaluminum phthalocyanine tetrasulfonate.

In recent years, choloroaluminum phthalocyanine tetrasulfonate (A1PCTS) has been shown to be a promising photosensitizer for the photodynamic therapy (PDT) of cancer. Although its mechanism of photodynamic action is not well defined, A1PCTS is going to be under clinical trials of PDT. In this study, in vitro addition of A1PCTS to a suspension of rat epidermal microsomes followed by irradiation with red light (approximately 675 nm) resulted in significant destruction of cytochrome P-450 and associated monooxygenase activities. The photodestructive effect was dependent on both the dose of A1PCTS and the duration of light exposure. Studies using various quenchers of reactive oxygen species showed that only scavengers of singlet oxygen such as histidine, 2,5-dimethylfuran, beta-carotene and sodium azide afforded substantial protection against photodestruction. Our data indicate the direct involvement of singlet oxygen in the A1PCTS-mediated photodestructive process.

Aluminum↗
PubMed1990

Inhibition of benzoyl peroxide-mediated tumor promotion in 7,12-dimethylbenz(a)anthracene-initiated skin of Sencar mice by antioxidants nordihydroguaiaretic acid and diallyl sulfide.

Benzoyl peroxide (BPO), a free radical generating compound, is widely used in topical medications prescribed for acne vulgaris and in cosmetic products. It has been shown to possess tumor-promoting activity in murine skin initiated with chemical carcinogens such as 7,12-dimethylbenz(a)anthracene (DMBA). In the present study we assessed the effect of the antioxidants nordihydroguaiaretic acid (NDGA) and diallyl sulfide (DAS) against BPO-mediated tumor promotion in murine skin. Pretreatment of Sencar mice with NDGA and DAS prior to skin application of BPO resulted in a time- and dose-dependent inhibition of epidermal ODC induction caused by BPO. Tumor initiation was achieved by a single topical application of DMBA (10 micrograms/animal) to Sencar mice. Ten days later tumor promotion was begun by twice-weekly topical application of BPO (20 mg/animal). The anticarcinogenic effects of NDGA (25 mumol/mouse) and DAS (20 mumol/mouse) were evaluated by administering these agents topically 60 min prior to each BPO application. After 26 weeks on test, the number of benign papillomas/mouse were 0.10 +/- 0.07 and 2.15 +/- 0.30 in the NDGA and DAS pretreated group of animals as compared to 4.40 +/- 1.14 in animals receiving BPO alone. After 51 weeks on test, the number of squamous cell carcinomas/mouse were 0.00 +/- 0.00, 0.35 +/- 0.10 in the NDGA and DAS pretreated group of animals as compared to 0.65 +/- 0.12 in animals receiving BPO alone. From these data we suggest that the antioxidants NDGA and DAS can abrogate the tumor-promoting effects of BPO in murine skin and that NDGA is substantially more effective than DAS in this regard.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1990

[Principles of photobiology and photochemistry].

The relationship between light exposure and UV induced skin diseases is presented. The basic law is: "No photobiology--no photochemistry". Photoaging, phototoxic and photoallergic reactions, porphyria, UV-carcinogenesis, and alterations of immune functions are discussed.

Humans↗
PubMed1978

Human skin aryl hydrocarbon hydroxylase. Induction by coal tar.

Coal tar products, which are widely used in treating dermatologic disease, contain numerous polycyclic aromatic hydrocarbons, including 3,4-benzo[a]pyrene (BP). BP is among the most potent environmental chemical carcinogens and is known to evoke tumors in the skin of experimental animals and perhaps also of man. In this study the effect of cutaneous application of coal tar solution (U. S. Pharmacopeia) on aryl hydrocarbon hydroxylase (AHH) activity in the skin of patients usually treated with this drug was investigated. AHH, a cytochrome P-450 dependent carcinogen-metabolizing enzyme appears to play an important role in the activation of polycyclic hydrocarbons into reactive moieties that can bind to DNA and that may directly induce cancer. Application of coal tar solution to human skin caused a two to five-fold induction of cutaneous AHH in nine subjects. In further studies, the incubation of human skin with coal tar solution in vitro also caused variable induction of cutaneous AHH. Maximum responses in both systems occurred after 24 h and enzyme activity in vitro was time- and tissue- and substrate-concentration dependent. Studies in experimental animals showed that topical application of coal tar solution caused induction of AHH in skin and, after percutaneous absorption, in liver as well. Assay of several defined constituents of coal tar for AHH induction showed that BP was the most potent inducer of AHH tested. These studies indicate that topical application of coal tar solution in doses ordinarily used in treating dermatologic disease causes induction of AHH in human skin and suggest that such induced enzymatic activity could relate to carcinogenic responses to this agent in skin or, after percutaneous absorption, in other tissues as well.

Animals↗
PubMed1978

Porphyria cutanea tarda. A rare cutaneous manifestation of hepatic tumors.

Porphyria cutanea tarda (PCT), the most common form of porphyria, may be one of the rare cutaneous manifestations of hepatic tumors, benign, malignant, or metastatic. The liver damage associated with PCT may predispose to the development of hepatocellular carcinoma. Our experience and a review of the literature suggest that in patients with PCT in whom the usual precipitating factors are absent, or in patients with PCT of long duration and an unexplained exacerbation, liver scan is indicated to rule out the presence of a hepatic tumor.

Adenoma↗