Inhibition of the skin tumorigenicity of (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene by tannic acid, green tea polyphenols and quercetin in Sencar mice

The effect of pretreatment of skin of Sencar mice with topically applied tannic acid, quercetin and green tea polyphenols (GTP) on the skin tumor initiating activity of (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE-2) has been evaluated. The animals were pretreated with the plant phenols (tannic acid and quercetin (3000 nmol) or GTP 24 mg/mouse) for 7 days after which they received a single topical application of 200 nmol of BPDE-2 as the initiating agent. Beginning 7 days following initiation animals received twice weekly applications of 3.24 nmol of 12-O-tetradecanoyl phorbol-13-acetate (TPA). Tannic acid and GTP afforded significant protection against skin tumor induction. These inhibitory effects were verified both by prolongation of the latency period and subsequent development of tumors. Quercetin, on the other hand, afforded only moderate protection. Each phenolic compound was found to be highly effective in accelerating the disappearance of BPDE-2 from aqueous medium. Our results suggest that tannic acid and GTP have substantial potential for protecting against the skin tumorigenic response to BPDE-2 and the mechanism of inhibition may involve inactivation of the reactive carcinogenic moiety.

Alleviation of nickel-induced biochemical alterations by chelating agents

The effect of 1,4,8,11-tetraazacyclotetradecane (Cyclam), triethylenetetramine (TETA), reduced glutathione (GSH), ethylenediamine tetraacetic acid (EDTA), cyclohexanediamine tetraacetic acid (CDTA), diethylene triamine pentaacetic acid (DTPA), and hydroxyethylenediamine triacetic acid (HEDTA) on the alleviation of nickel-induced biochemical and trace-metal alterations in serum, liver, and kidney of nickel-treated rats was studied. The lipophilic chelating agents Cyclam and TETA exhibited a higher order of effectiveness in alleviating nickel-induced alterations compared to EDTA, CDTA, DTPA, and HEDTA, the hydrophilic chelating agents. The higher efficacy of lipophilic agents may be due to their ability to bind to nickel present in extracellular fluid as well as in intracellular fluid, while the hydrophilic agents may bind only to nickel present in extracellular fluid. Our data also suggest that the efficacy of Cyclam to ameliorate nickel-induced alterations is exceptionally high.

Metastatic extramammary Paget's disease: dramatic response to combined modality treatment

A case of extramammary Paget's disease is reported. The distinguishing features of the case are: (1) localization of the primary lesion to the scrotum, (2) development of metastases in the absence of a recognizable underlying carcinoma, and (3) response of the systemic disease to a combination of radiation therapy and chemotherapy. The histogenesis, clinical behavior, and treatment of extramammary Paget's disease are reviewed.

Differential role of reactive oxygen intermediates in photofrin-I- and photofrin-II-mediated photoenhancement of lipid peroxidation in epidermal microsomal membranes

Photoradiation therapy with porphyrins and light offers an alternative approach to the management of certain types of cancer. The mechanism of tissue destruction mediated by this modality is poorly understood. In this study, epidermal microsomes incubated in vitro with Photofrin-I (Pf-I) and Photofrin-II (Pf-II) followed by exposure to radiation (approximately 400 nm) resulted in increased (180%) NADPH-supported (enzymatic) as well as ADP/iron-supported (140%) (nonenzymatic) lipid peroxidative damage as measured by malondialdehyde formation. Lipid peroxidation by Pf-I and Pf-II was found to be differentially affected by quenchers of singlet oxygen (2,5-dimethylfuran, histidine, beta-carotene, ascorbic acid, and sodium azide), superoxide anion (superoxide dismutase), and the hydroxyl radical (sodium benzoate, mannitol, and ethanol). Catalase, a quencher of hydrogen peroxide, afforded significant protection only against Pf-II-enhanced lipid peroxidative damage while it had little effect against the Pf-I-mediated reaction. Deuterium oxide, which is known to increase the half-life of singlet oxygen, was found to enhance Pf-I-mediated lipid peroxidation but produced insignificant effects upon Pf-II-mediated photosensitization. Our results indicate that Pf-I and Pf-II, which are employed for the photodynamic therapy of malignant tumors, evoke membrane damage by generating different reactive oxygen species. The Pf-I-mediated photodestruction mainly involves a type II mechanism via singlet oxygen formation, whereas Pf-II-mediated photodestruction preferentially involves a type I mechanism by generating superoxide anions and hydroxyl radicals. Our data indicate that tumor necrosis evoked by porphyrins and light is likely due to the generation of reactive oxygen species.

In situ evidence for the involvement of superoxide anions in cutaneous porphyrin photosensitization

Dihematoporphyrin ether, also known as Photofrin-II (Pf-II) is currently used in the diagnosis and management of a variety of epithelial neoplasms, in a modality known as photodynamic therapy (PDT). A major drawback of these porphyrins for PDT is their ability to evoke prolonged cutaneous photosensitization. The mechanism of tumor ablation and cutaneous photosensitization by these photosensitizers is thought to relate to the generation of one or more reactive oxygen species such as superoxide anion, singlet oxygen and hydroxyl radical. However, the role of these oxygen species has not been established unequivocally. In this study, the mechanism of Pf-II-mediated cutaneous photosensitization was examined using murine ear swelling as a marker. The mice treated with Pf-II and light demonstrated two-fold enhancement of ear swelling whereas animals treated with the SOD mimic, beta-carotene and dimethyl sulfoxide (DMSO) had considerably less ear swelling (p less than 0.01). The observed protective effect was dependent on the dose of each quencher and followed the pattern SOD mimic DMSO beta-carotene. The histopathologic alterations caused by Pf-II photosensitization were significantly alleviated by pretreatment with SOD mimic whereas beta-carotene and (DMSO) were less effective. Inhibitors of superoxide dismutase (sodium diethyldithiocarbamate) and catalase (hydroxyl amine and 3, amino 1,2,4-triazole) augmented Pf-II-mediated cutaneous photosensitization. These data provide the first in vivo evidence for the involvement of superoxide anion in cutaneous porphyrin photosensitization.

Evidence for the involvement of hydroxyl radicals in nickel mediated enhancement of lipid peroxidation: implications for nickel carcinogenesis

The administration of nickel to rats resulted in enhanced hepatic lipid peroxidation, levels of glutathione and iron with a concomitant decrease in glutathione peroxidase activity. These effects were dose dependent. Enhanced lipid peroxidation was found to be inhibited by the exogenous addition of ethylenediamine tetraacetic acid (EDTA), benzoate and ethanol while catalase and superoxide dismutase were ineffective in this regard. Our data strongly suggest the involvement of hydroxyl radicals in the nickel mediated enhancement of lipid peroxidation which may have their implications in the carcinogenicity of nickel compounds.

Role of glutathione metabolizing enzymes in nickel mediated induction of hepatic glutathione

The administration of nickel to rats resulted in a dose-dependent increase in the level of hepatic glutathione and in the activities of glutathione reductase and glutathione-S-transferase with a concomitant decrease in the activities of glutathione peroxidase and gamma-glutamyl transpeptidase. The increase in hepatic glutathione may be due to the decrease in the activities of glutathione utilizing enzymes and increase in the activity of glutathione reductase leading to the increased turnover of glutathione.

Evaluation of chelating drugs on the toxicity, excretion, and distribution of nickel in poisoned rats

The effects of various doses of two macrocyclic drugs, namely, 1,4,8,11-tetraazacyclotetradecane (Cyclam) and 5,7,7',12,14,14'-hexamethyl-1,4,8,11-tetraazacyclotetradecane++ + (Cyclam s), on the toxicity, distribution, and excretion of nickel were evaluated in nickel-poisoned rats and compared with the linear counterpart triethylenetetraamine (TETA) and a tripeptide, glutathione (GSH). Cyclam and Cyclam s revealed a higher order of efficacy against the lethal response of nickel even at a lower dose. These drugs significantly enhanced the urinary and biliary excretion of nickel and restored the altered levels of trace metals (viz., Cu, Zn, Fe, Mn) compared to TETA and GSH. The efficacy of these drugs in vivo may be related to their ability to transport nickel across an artificial lipid membrane, a phenomenon was not exhibited by TETA or GSH.

Cytochrome P-450 dependent metabolism of testosterone in rat skin

The incubation of microsomes of whole skin, dermis and epidermis with 14C testosterone in the presence of NADPH resulted in the formation of 6 beta-, 7 alpha- and 16 alpha-testosterone. Maximum enzyme activity occurred in epidermal microsomes followed by dermis and whole skin. Epidermal testosterone hydroxylase activity required NADPH and oxygen and was found to be inhibited by SKF 525A and metyrapone. Our data strongly suggest that testosterone is metabolized by the cytochrome P-450 dependent monooxygenase in skin and provides the first evidence for an endogenous substrate for cytochrome P-450 in this tissue. The formation of several hydroxylated products further suggests the existence of multiple isozymes of cytochrome P-450 in rat skin. These studies provide additional evidence that target tissues may modulate their hormone levels by enzyme pathways that are locally regulated.

Evaluation of LD50 of some polyaminocarboxylic acids used as chelating drugs in metal intoxication

The LD50 of the following metal-binding chelating drugs, EDTA, diethylenetriaminepentaacetic acid (DTPA), hydroxyethylenediaminetriacetic acid (HEDTA), cyclohexanediaminotetraacetic acid (CDTA) and triethylenetetraminehexaacetic acid (TTHA) was evaluated in terms of mortality in rats after intraperitoneal administration and was found to be in the order: CDTA greater than EDTA greater than DTPA greater than TTHA greater than HEDTA. A possible correlation between the toxicity and molecular structure of the compounds is discussed.