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Biomedical subjects

D R Bickers

Publications and source records attributed to D R Bickers.

At least 145 records · Page 8Linked to original sources
PubMed1982

Uroporphyrin I stimulation of collagen biosynthesis in human skin fibroblasts. A unique dark effect of porphyrin.

Porphyria cutanea tarda and erythropoietic porphyria are disorders of heme synthesis that originate in the liver and bone marrow, respectively. Each is characterized by increased accumulation of uroporphyrin, I, by cutaneous photosensitivity, and in some patients by indurated plaques and scarring that resemble scleroderma. These scleroderma-like lesions occur in light-exposed and light-protected body areas. In these studies we evaluated the role of uroporphyrin I and of light in evoking the scleroderma-like cutaneous changes. Normal human skin fibroblasts were exposed to uroporphyrin I and to 400 nm radiation and the effect of these agents on collagen accumulation by the cells was determined. Radioactive tracer studies showed that uroporphyrin I caused a specific increase in the accumulation of newly synthesized collagen by fibroblast monolayer cultures, as verified by [(3)H]hydroxyproline and collagenase digestion assays. Collagen accumulation was stimulated 1.5- to 2.7-fold by uroporphyrin I, whereas noncollagenous protein accumulation was unchanged. The increased collagen accumulation was time and uroporphyrin I-concentration-dependent, and occurred both in the presence or absence of ultraviolet light exposure. Further studies demonstrated that the increased accumulation was not the result of decreased rates of collagen degradation nor was it due to changes in cell population growth parameters (generation times and saturation densities). No changes in morphology of the treated cells occurred. These studies indicate that porphyrins possess previously undemonstrated biological effects that are independent of their photosensitizing properties. This novel dark effect of uroporphyrin I may account for the sclerodermatous lesions seen in the skin of patients with porphyria cutanea tarda and erythropoietic porphyria.

Cells, Cultured↗
PubMed1982

Environmental and drug factors in hepatic porphyria.

Numerous drugs and environmental chemicals are capable of influencing the clinical expression of human hepatic porphyria primarily by interfering with the orderly regulation of heme synthesis in the liver. Some agents trigger the disease in otherwise normal individuals whereas others exacerbate an underlying genetic abnormality leading to disease expression. In both instances careful avoidance of exposure to these drugs and chemicals can largely prevent the development of manifest disease. The mechanisms whereby these agents impair the normal regulation of hepatic heme synthesis have been carefully studied in recent years and have provided valuable new insights into this form of drug-induced hepatotoxicity.

5-Aminolevulinate Synthetase↗
PubMed1982

Studies on microsomal cytochrome P-450, monooxygenases and epoxide hydrolase in cultured keratinocytes and intact epidermis from BALB/C mice.

Studies of drug and carcinogen metabolism in cultured keratinocytes and in intact epidermis from the skin of BALB/C mice were performed. The cultured cells were shown to retain 33 to 40% of corresponding intact epidermal aryl hydrocarbon hydroxylase (AHH), 7-ethoxycoumarin-O-de-ethylase (7-ED) and epoxide hydrolase activities. In vitro treatment of the cells or in vivo application to the skin of animals with the polycyclic aromatic hydrocarbons benz(a)anthracene (BA) or benzo(a)pyrene resulted in significant induction of AHH and 7-ED activities. The responsiveness of AHH was greater than that of 7-ED in both preparations. BA (4 x 10(-4) M) induced AHH and 7-ED at least 12- and 4-fold, respectively, in either the keratinocytes or intact epidermis, whereas epoxide hydrolase activity was not altered in either preparation. All of these enzyme activities were predominantly located in the microsomal fraction of the keratinocytes and the epidermis. Keratinocyte AHH had a pH optimum at 7.4. The apparent Km for benzo(a)pyrene as substrate in control and BA-induced cells was 10 and 6 microM, respectively, whereas Vmax was 15-fold greater in the carcinogen-treated cells. CO-difference spectra demonstrated the presence of the heme-protein cytochrome P-450 in microsomes prepared from keratinocytes and intact epidermis; absorption maximum was between 451 to 453 nm. The metabolic activity of keratinocytes was further demonstrated in the Ames mutagen assay. A supernatant (9000 x g) prepared from keratinocytes pretreated with BA enhanced the mutagenesis of 2-aminoanthracene in the TA98 strain of Salmonella typhimurium. These studies indicate that cultured keratinocytes provide a useful experimental model system for the study of epidermal drug and carcinogen metabolism.

Animals↗
PubMed1981

Photoallergic contact dermatitis to musk ambrette. Histopathologic features of photobiologic reactions observed in a persistent light reactor.

Studies concerning a patient with contact photosensitivity to musk ambrette, a commonly used fragrance, are reported. The patient had a persistent light reaction. The patient's history, clinical appearance, and phototest and photopatch test results are described. The observed patterns of these were identical to those previously noted in patients who had persistent light reactions after exposure to other photosensitizers such as the halogenated salicylanilides. The histopathologic findings in the phototest and photopatch test sites were those of an acute spongiotic dermatitis. No abnormal change was seen with ultraviolet A radiation exposure alone.

Aged↗
PubMed1981

Treatment of the porphyrias: mechanisms of action.

The porphyrias are diseases that result from inherited or acquired abnormalities of porphyrin-heme synthesis in the liver and the bone marrow. Only the hepatic porphyrias are known to be aggravated by exposure to a variety of exogenous drugs and chemicals. Simple avoidance of these agents will reduce the risk of developing hepatic porphyria and may lead to clinical improvement in patients with active disease. Some types of therapy of the hepatic porphyrias are effective because of their ability to modulate the activity of delta-aminolevulinic acid synthetase, the rate-limiting enzyme for heme synthesis. Most of the porphyrias are associated with cutaneous photosensitivity, the treatment of which centers about either reducing the excessive production of porphyrins or of inhibiting the photobiological response to these photosensitizing chemicals in the skin.

5-Aminolevulinate Synthetase↗
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↗
PubMed1978

Hydroa vacciniforme.

Two patients with hydroa vacciniforme, a rare photodermatosis of unknown etiology, demonstrated distinctive scarring and vesiculobullous skin lesions on light-exposed body areas. Results of blood and urine porphyrin studies were normal, and no systemic abnormalities were noted. A small bullous lesion was produced in normal skin in case 1 with 15 times the minimal erythema dose of ultraviolet energy. The conditions of both patients improved while they were taking beta carotene orally.

Carotenoids↗
PubMed1977

Studies in porphyria. VI. Biosynthesis of porphyrins in mammalian skin and in the skin of porphyric patients.

Porphyrin biosynthesis in mammalian skin and in skin obtained from patients with selected types of porphyria has been studied. Cutaneous porphyrinogenesis required the precursor delta-aminolevulinic acid (ALA) which, when added to murine, rat, and human skin in vitro, was rapidly converted to porphyrins. Total porphyrin content was quantitated by fluorescence assay, and spectral studies indicated that more than 80% of the porphyrin produced was protoporphyrin. The majority of skin porphyrinogenesis occurrred in epidermis or in epidermal derivatives such as hair roots. Known inducers of hepatic delta-aminolevulinic acid synthetase (ALAS), the rate-limiting enzyme for heme biosynthesis, were not inducers when added to skin in vitro. Skin from patients with acute intermittent porphyria demonstrated a 43% decrease in cutaneous porphyrin production as compared to unaffected normals. This is consistent with the known deficiency of uroporphyrinogen synthetase that has been previously demonstrated in the liver and red blood cells of these patients. Porphyrinogenesis in skin of patients with porphyria cutanea tarda was not different from controls. These studies demonstrate that skin has the enzymatic capacity to synthesize porphyrins from added ALA and that cutaneous porphyrinogenesis from ALA is deficient in patients with acute intermittent porphyria.

Allylisopropylacetamide↗
PubMed1977

Induction of a deficiency of steroid delta 4-5 alpha-reductase activity in liver by a porphyrinogenic drug.

The hepatic enzymes that catalyze drug oxidations and the reductive metabolism of steroid hormones to 5alpha-derivatives are localized in membranes of the endoplasmic reticulum. Phenobarbital, which exacerbates acute intermittent porphyria in man, induces drug-oxidizing enzymes in liver. Additionally, patients in whome the primary gene defect (uroporphyrinogen-I-synthetase deficiency) of acute intermittent porphyria has become clinically expressed have low levels of hepatic steroid delta4-5alpha-reductase activity. This 5alpha-reductase deficiency in acute intermittent porphyria leads to the disproportionate generation of 5beta-steroid metabolites from precursor hormones; such steroid metabolites have significant porphyria-inducing action experimentally. In this study the effects of phenobarbital on drug oxidation and steroid 5alpha-reduction in man were examined to determine if this drug could produce changes in steroid 5alpha-reductase activity which mimicked those seen in patients with acute intermittent porphyria. Metabolic studies with [14C]-testosterone and 11beta-[3H]hydroxyandrostenedione were carried out in five normal volunteers. In all five subjects phenobarbital administration (2 mg/kg/per day for 21 days) enhanced plasma removal of the test drugs antipyrine and phenylbutazone as expected; but in four subjects phenobarbital also substantially depressed 5alpha-metabolite formation from [14C]testosterone and resulted in a pattern of hormone biotransformation characterized by a high ratio of 5beta/5alpha-metabolite formation. Studies with 11beta-[3H]hydroxy-androstenedione in three subjects confirmed that phenobarbital produced this high 5beta/5alpha ratio of steroid metabolism by depressing 5alpha-reductase activity for steroid hormones in liver. The high ratio of 5beta/5alpha-metabolites formed in normals after drug treatment mimicks the high 5beta/5alpha-steroid metabolite ratio formed from endogenous hormones in acute intermittent porphyria. The proximate mechanism by which phenobarbital induces reciprocal changes in activities of the microsomal enzymes which catalyze drug oxidations and steroid 5alpha-reductions is not known. This action of phenobarbital raises the possibility, however, that certain drugs which provoke exacerbations of human porphyria may do so, in part, by producing deleterious shifts in the patterns of endogenous steroid hormone metabolism.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗