Chemoprevention of human actinic keratoses by topical DL-alpha-tocopherol.

Prior research shows that topical application of free, nonfatty acid-conjugated vitamin E (DL-alpha-tocopherol) prevents skin cancer in mice, as well as immunosuppression induced by UVB radiation. This study investigated the chemopreventive potential of DL-alpha-tocopherol in humans through monitoring surrogate end point biomarkers in sun-damaged skin. Contralateral arms of healthy human volunteers with actinic keratoses (AK) were randomly assigned to receive either 12.5% DL-alpha-tocopherol or placebo in a crème base for 6 months. Changes in number of AKs, levels of p53 protein expression, proliferating cell nuclear antigen, and polyamines were assessed along with skin and systemic vitamin E levels. Following treatment, plasma concentration levels of DL-alpha-tocopherol were unchanged, but skin levels were highly elevated (P < 0.001). Levels of p53 and proliferating cell nuclear antigen did not change significantly, whereas number of AKs declined insignificantly in both placebo and treatment arms. Regression models showed significant decreases in putrescine, spermidine, spermine, and total polyamine concentrations following treatment. Topically applied DL-alpha-tocopherol was substantially absorbed in skin, but the 6-month application did not significantly reduce numbers of preexisting AKs on moderately to severely sun-damaged forearms. Increases in polyamine synthesis are expected during tumor initiation and promotion; conversely, the significant reductions in polyamine levels resulting from the topical DL-alpha-tocopherol application are consistent with reductions in tumorigenesis potential. Topical tocopherol did not normalize established sun-induced lesions, but DL-alpha-tocopherol-induced reductions in polyamine metabolism are consistent with the inhibition of skin squamous cell carcinogenesis as seen in previous human trials and animal models.

Dichlorido(4,5-diaza-fluoren-9-one-κN,N')palladium(II).

The structure of the title compound, [PdCl(2)(C(11)H(6)N(2)O)], shows a nearly square-planar geometry for the Pd(II) atom within a Cl(2)N(2) donor set.

Effects of repeated green tea catechin administration on human cytochrome P450 activity.

PURPOSE: Preclinical studies suggested that green tea or green tea catechins can modulate the activities of drug-metabolizing enzymes. We conducted this clinical study to determine the effect of repeated green tea catechin administration on human cytochrome P450 (CYP) enzyme activities. METHODS: Forty-two healthy volunteers underwent a 4-week washout period by refraining from tea or tea-related products. At the end of the washout period, study participants received a cocktail of CYP metabolic probe drugs, including caffeine, dextromethorphan, losartan, and buspirone for assessing the activity of CYP1A2, CYP2D6, CYP2C9, and CYP3A4, respectively. Blood and urine samples before and 8 h after probe drug administration were collected to determine parent drug and metabolite concentrations for measurements of baseline CYP enzyme activities. Following the baseline evaluation, study participants underwent 4 weeks of green tea catechin intervention at a dose that contains 800 mg epigallocatechin gallate (EGCG) daily. The green tea catechin product was taken on an empty stomach to optimize the p.o. bioavailability of EGCG. The EGCG dose given in this study exceeded the amounts provided by average green tea consumption. Upon completion of the green tea catechin intervention, the postintervention CYP enzyme activities were evaluated as described above. RESULTS: There are large between-subject variations in CYP enzyme activities in healthy individuals. Four weeks of green tea catechin intervention did not alter the phenotypic indices of CYP1A2, CYP12D6, and CYP12C9, but resulted in a 20% increase (P = 0.01) in the area under the plasma buspirone concentration-time profile, suggesting a small reduction in CYP3A4 activity. CONCLUSIONS: We conclude that repeated green tea catechin administration is not likely to result in clinically significant effects on the disposition of drugs metabolized by CYP enzymes.

Reproducibility and expression of skin biomarkers in sun-damaged skin and actinic keratoses.

OBJECTIVES: To explore p53 and proliferating cell nuclear antigen (PCNA) expression and polyamine content as biomarkers in skin cancer chemoprevention trials, we evaluated their expression in early stages of UV-induced squamous cell tumorigenesis. METHODS: Biopsies were collected from three groups: 78 subjects with sun damage on forearms, 33 with actinic keratosis (AK) on forearms, and 32 with previous squamous cell carcinoma. Participants with sun damage were randomized to sunscreen or no sunscreen. RESULTS: We found significant differences in p53 and polyamines in forearms from the sun-damaged group (11.5 +/- 1.2% for p53, 65.5 +/- 1.9 nmol/g for putrescine, and 187.7 +/- 3.3 nmol/g for spermidine) compared with the group with sun damage plus AK (20.9 +/- 2.3% for p53, P = 0.0001; 81.7 +/- 3.9 nmol/g for putrescine, P = 0.0001; 209.4 +/- 8.2 nmol/g for spermidine, P < 0.06). PCNA was not different. When lesion histology was considered, there was a stepwise significant increase in p53 in biopsies without characteristics of AK compared with early AK (P = 0.02) and AK (P = 0.0006) and a similar pattern for PCNA with the only significant difference between early AK and AK. There was a stepwise increase in putrescine and spermidine in normal, sun-damaged forearm, forearm from subjects with AK, and the AK lesion itself (P < 0.0001). No significant differences in p53 or polyamines were seen in 3-month biopsies or, as a result of sunscreen use, although PCNA in the sun-damaged group not using sunscreen decreased significantly. CONCLUSIONS: p53 expression and polyamines in skin were elevated in early stages of skin tumorigenesis and were not affected by sunscreen, adding validity to their use as biomarkers in skin cancer chemoprevention trials.

Quantification of a cytochrome P450 3A4 substrate, buspirone, in human plasma by liquid chromatography-tandem mass spectrometry.

A sensitive HPLC-tandem mass spectrometry method was developed for determination of buspirone levels in human plasma. After solid phase extraction and reversed phase HPLC separation, detection of buspirone and the internal standard (prazosin) was performed using eletrospray ionization and selected reaction monitoring in the positive ion mode. Linear calibration curves were established over a concentration range of 0.025-2.5 ng/ml when 0.5 ml aliquots of plasma were used. Satisfactory results of within-day precision (RSD of 1.9-7.7%) and accuracy (% difference of 0.5-6.6%) and between-day precision (RSD of 3.7-11.1%) and accuracy (% difference of 2.2-6.8%) were obtained. The assay has been successfully applied to the analysis of buspirone levels in more than 500 human plasma samples collected from a drug interaction study.

Circulating endogenous retinoic acid concentrations among participants enrolled in a randomized placebo-controlled clinical trial of retinyl palmitate.

Retinoids have been studied extensively for their chemopreventive properties. The biological activity of retinoids is acquired through their conversion to retinoic acid (RA). Characterization of endogenous circulating RA concentrations after supplementation with vitamin A over longer time periods has not been done previously. Our investigation was conducted to determine whether vitamin A (retinyl palmitate) supplementation significantly increases circulating RA concentrations of all-trans-, 9-cis-, and 13-cis-RA. Using plasma samples from 41 participants enrolled in a randomized clinical trial of placebo, 25,000, 50,000, or 75,000 IU supplemental retinyl palmitate daily, high-performance liquid chromatography analyses were conducted for concentrations of three RA isomers. Seven plasma samples were analyzed for each participant over a 16-month period. Based on an intention-to-treat analysis, results obtained using linear mixed models showed that supplementation with retinyl palmitate statistically significantly increased concentrations of all three RA isomers from baseline levels. This study suggests that supplementation with retinyl palmitate is an effective means to increase circulating all-trans, 9-cis-, and 13-cis-RA concentrations among humans.

Expression and regulation of glutathione S-transferase P1-1 in cultured human epidermal cells.

Six families of glutathione S-transferases (GSTs), which play an important role in cellular detoxification, are identified in human cells. We report that human keratinocytes and melanocytes express significant levels of GST activity, for which GSTP1-1 is mainly responsible. But, in contrast to previous reports that GSTP1-1 level increases in skin tumor tissues, GSTP1-1 expression does not increase in transformed keratinocytes and melanocytes in culture. Although the human GSTP1 gene carries in its 5'-flanking region multiple copies of the antioxidant response element (ARE), no increase in GSTP1-1 expression was observed after treatment of human keratinocytes (HaCaT) with ARE-mediated inducers. ARE is a cis-acting DNA element and stimulates the transcription of many genes. While studies suggest that an NF-kappaB binding site in the promoter region might suppress the ARE function, such a mechanism does not appear to exist in HaCaT cells. Moreover, although ras has been shown to stimulate the expression of human GSTP1-1, the effect of c-Ha-ras on GSTP1-1 expression in HaCaT cells appears limited.