UHPLC-MS/HRMS method for the quantitation of pyrithione metabolites in human urine.

Pyrithione glucuronide (PTG) and 2-thiopyridine glucuronide (ThPG) have been reported to be the major urinary metabolites in multiple animal species following administration of zinc pyrithione (ZnPT). However, the formation of these metabolites has never been confirmed in humans. A simple and rugged ultra-high-performance liquid chromatography high resolution mass spectrometry (UHPLC-MS/HRMS) method was developed and validated for the quantification of PTG and ThPG to investigate human metabolism of pyrithione following topical application of ZnPT as a shampoo. A UHPLC-MS/HRMS method was required due to the matrix interferences that were observed with the typical industry standard HPLC/tandem mass spectrometry (LC-MS/MS) methodology based on nominal mass triple quadrupole (QQQ) platform approach. Using UPLC-MS/HRMS, both PTG and ThPG were identified in human urine following topical application of ZnPT. The presence of these human urinary metabolites of pyrithione are consistent with findings from earlier studies in multiple animal species and suggest the metabolism of pyrithione is similar amongst those mammalian species studied.

Intrinsic relative potency of a series of pyrrolizidine alkaloids characterized by rate and extent of metabolism.

1,2-Unsaturated pyrrolizidine alkaloids (PAs) are sometimes present in foods or herbal supplements/medicines as impurities and pose potential concerns for liver genotoxicity/carcinogenicity. PAs display a strong structure toxicity relationship, however, current regulatory approaches to risk assessment take the precautionary approach of assuming all PAs display the same potency as the most toxic congeners lasiocarpine (LAS) and riddelliine (RID). Here we explore the relative potencies of a series of structurally diverse PAs by measuring DNA adduct formation in vitro in a rat sandwich culture hepatocyte (SCH) cell system. The adducts generated are consistent with those identified in vivo as biomarkers of PA exposure and potential liver-tumor formation. DNA reactive PAs require metabolic activation to form intermediates that bind DNA, therefore, adduct formation is a direct reflection of reactive metabolite formation. Since the area under the concentration versus time curve (AUC) for the depletion of parent PA from the extracellular media is a measure of PA exposure, the ratio of adducts/AUC provides a measure of hepatocyte exposure to DNA-binding metabolites corresponding to an intrinsic potency for DNA adduct formation. Intrinsic potencies relative to potencies for LAS compare well with existing relative potency data further affirming that PA toxicity varies considerably with chemical structure.

Comparing Surfactant Penetration into Human Skin and Resulting Skin Dryness Using In Vivo and Ex Vivo Methods.

Numerous tests have been developed to estimate a surfactant's mildness in rinse-off formulations. In this study, mixed surfactant systems were examined for their impact on surfactant penetration into the skin and skin hydration using in vivo and ex vivo methods. A forearm controlled application test (FCAT) was conducted, and skin hydration was evaluated using corneometry and visual dryness grading. Tape strip and cup scrub extractions were completed within the FCAT to examine the penetration of five individual surfactants into the skin in vivo. The ratio of surfactant mass extracted by five pooled tape strips to surfactant mass extracted by cup scrubs was found to be in the range of 40-59%. Furthermore, cup scrub collection and analysis was less time-consuming and less expensive to conduct than tape stripping. Thus, we recommend cup scrub extraction as a suitable substitute for tape stripping in future surfactant skin penetration analyses. In vivo results were compared with ex vivo 14C-sodium dodecyl sulfate (14C-SDS) penetration into human cadaver skin from the same surfactant systems. In vivo measurements conducted in the FCAT, including corneometer reading, visual dryness score, and individual surfactant (sodium laureth (1) ether sulfate and cocamidopropyl betaine) extracted from the skin, were found to correlate well with 14C-SDS penetration into the skin ex vivo for anion-based surfactant systems. Thus, 14C-SDS skin penetration may be a useful preclinical test for skin dryness induced by rinse-off products containing anionic surfactants.

Effects of season stratum corneum barrier function and skin biomarkers.

The skin on the lower legs of 25 female subjects was evaluated first in the winter, and then again in the summer of the same subjects. Barrier function was determined by measuring transepidermal water loss (TEWL), and skin hydration and dryness were evaluated by electrical measurements (Corneometer ® CM825) and visual grading. Stratum corneum (SC) was sampled using 10 sequential D-Squame sampling discs and analyzed for 2-pyrrolidone-5-carboxylic acid (PCA), keratin-1,10,11, interleukin 1α (IL-1α), interleukin 1 receptor antagonist (IL-1ra), selected ceramides, cholesterol, cholesterol sulfate, and selected free fatty acids. TEWL as well as the visual dryness grades were significantly lower in the summer while hydration was higher. PCA was significantly higher in the summer as were the keratins. The ratio IL-1ra:IL-1α, an indicator of skin inflammation, was significantly lower in the summer. The amount of protein removed by the tape strips was also significantly lower in summer indicating better SC cohesion. Among the SC lipids measured, total ceramides, individual ceramides, total fatty acids, and cholesterol were higher in summer compared to winter. Stearic acid and cholesterol sulfate were not significantly different between winter and summer.

The Y2 receptor mediates increases in collateral-dependent blood flow in a model of peripheral arterial insufficiency.

We have utilized a rat model of peripheral artery disease (PAD) to examine whether the known angiogenic activity of the Y(2) receptor would translate into a meaningful increase in collateral blood flow. The maximal increase in collateral blood flow capacity of approximately 60% (p<0.001) was obtained with a 10microg/kgday (IA infusion, 14 days) of either PYY or PYY(3-36) and did not differ from that obtained with a maximally angiogenic dose of VEGF(165). Pharmacodynamic modeling based upon single dose pharmacokinetic plasma profiles of both agonists suggests that E(max) is reached when the Y(2) receptor is occupied by >or=50%. Furthermore, for PYY(3-36), occupancy of the Y(2) receptor is sufficient to promote a significant benefit in collateral blood flow.