The scurfy mutant mouse strain suffers from a fatal lymphoproliferative disease leading to early death within 3–4 wk of age. A frame-shift mutation of the forkhead box transcription factor Foxp3 has been identified as the molecular cause of this multiorgan autoimmune disease. Foxp3 is a central control element in the development and function of regulatory T cells (T reg cells), which are necessary for the maintenance of self-tolerance. However, it is unclear whether dysfunction or a lack of T reg cells is etiologically involved in scurfy pathogenesis and its human correlate, the IPEX syndrome. We describe the generation of bacterial artificial chromosome–transgenic mice termed “depletion of regulatory T cell” (DEREG) mice expressing a diphtheria toxin (DT) receptor–enhanced green fluorescent protein fusion protein under the control of the foxp3 gene locus, allowing selective and efficient depletion of Foxp3+ T reg cells by DT injection. Ablation of Foxp3+ T reg cells in newborn DEREG mice led to the development of scurfy-like symptoms with splenomegaly, lymphadenopathy, insulitis, and severe skin inflammation. Thus, these data provide experimental evidence that the absence of Foxp3+ T reg cells is indeed sufficient to induce a scurfy-like phenotype. Furthermore, DEREG mice will allow a more precise definition of the function of Foxp3+ T reg cells in immune reactions in vivo.

As the popularity of natural health product (NHP) use increases, unfortunately, so does the frequency of cases reporting suspected adverse interactions. Adverse reactions associated with concomitant NHP-therapeutic use may result from competing interactions at the level of the key xenobiotic-biotransforming phase I enzyme cytochrome P450 3A4 (CYP3A4) or the membrane-bound ATP-dependent protein pump P-glycoprotein (P-gp). In this study, selected NHPs of interest to the HIV+ community were assessed for their ability to affect these two important mechanisms of drug disposition. Briefly, commercial-source teas and powdered extracts in capsule formulations were examined for their ability to inhibit CYP3A4-mediated metabolism of the coadministered reference substrate dibenzyl-fluorescein, and their ability to stimulate P-gp ATPase activity. Among the herbal capsules, it was found that aqueous extracts of two different goldenseal (Hydrastis canadensis L.) products were the most inhibitory of CYP3A4-mediated metabolism among all NHPs tested (IC 50 : 3.03 and 3.23 mg/mL). Goldenseal and milk thistle [Silybum marianum (L.) Gaertn.] teas were found to stimulate P-gp ATPase to a greater degree than the reference positive control verapamil (20 µM). As well, 70% ethanol extracts of one goldenseal product (designated NRP 121) and aqueous extracts of another (designated NRP 17) had the highest relative P-gp ATPase activity overall. Milk thistle and goldenseal products were further analyzed * Dedicated to Professor John Thor Arnason of the University of Ottawa, Department of Biology, on the occasion of his sixtieth birthday.

-Purpose.

Natural health products containing Echinacea have been used by many patient populations and although there are reports of adverse effects with products containing Echinacea, few clearly characterized the nature of the product with respect to constituent content, the nature of the products and the mechanism underlying the interaction. The objective of this study was to examine blended and single-entity Echinacea products containing ground plant material or extracts in commercial capsules, herbal teas, tablets, tinctures and soft gel liquid-filled capsule formulations in an attempt to correlate biomarker constituent content and effects on cellular and subcellular parameters of interest. HPLC analysis indicated significant variability in the major biomarker constituent content in extracts from these Echinacea products. These extracts were also examined for their potential to affect cytochrome P450 CYP1A1/2, 2C9*1, 2C9*2, 2C19, 2D6, 3A4, 3A5, 3A7, and flavin-containing monooxygenase 3 (FMO3); CYP3A5-mediated metabolism, and expression of CYP3A4 and ABCB1. The extracts of some products were also examined for their effect cellular processes such as cell proliferation, nitric oxide formation as a marker of immunostimulatory capacity, and lactate dehydrogenase release as a marker for cell toxicity. The present study indicated that key Echinacea constituents varied widely within and between the products tested and that these levels did not correlate with the ability of these products to markedly affect the cellular processes studied.

No abstract

In this study, we used an in vitro Caco-2 cell monolayer model to evaluate aqueous extracts of commercial-source goldenseal (Hydrastis canadensis) and milk thistle (Silybum marianum) capsule formulations, their marker phytochemicals (berberine and silibinin, respectively), as well as dillapiol, vinblastine, and the HIV protease inhibitor saquinavir for their ability to modulate CYP3A4 and ABCB1 expression after short-term exposure (48 h). Both upregulation and downregulation of CYP3A4 expression was observed with extracts of varying concentrations of the two natural health products (NHPs). CYP3A4 was highly responsive in our system, showing a strong dose-dependent modulation by the CYP3A4 inhibitor dillapiol (upregulation) and the milk thistle flavonolignan silibinin (downregulation). ABCB1 was largely unresponsive in this cellular model and appears to be of little value as a biomarker under our experimental conditions. Therefore, the modulation of CYP3A4 gene expression can serve as an important marker for the in vitro assessment of NHP-drug interactions.