Numerous herbal extracts are capable of activating PXR, as shown in in vitro cell based reporter gene assays. In some cases, for example H. perforatum, G. biloba, Ivacaftor S. chinensis, and tian xian, the fold boost in reporter action is much like that obtained for rifampicin, that's a known agonist of human PXR.
In other cases, Ivacaftor reporter activity data were corroborated by results showing coactivator recruitment, ligand binding to the receptor, and induction of PXR target gene expression not only in cultured human and mouse hepatocytes but also hepatocytes isolated from PXR knockout mice and transgenic mice expressing human PXR. Whether any of the herbal extracts are capable of activating PXR in vivo in humans is still largely not known, except for H. perforatum, which has been shown to increase the clearance of drugs that are metabolized by CYP3A4. CAR is expressed predominantly in liver and also in small intestines. Similar to PXR, CAR regulates the expression of a wide array of genes involved in biotransformation and transport of endogenous substances, naturally occurring compounds, drugs, and other xenochemicals.
In addition, CAR has also been shown to regulate the repression of enzymes involved in gluconeogenesis, such as phosphoenoylpyuvate carboxykinase 1, and beta oxidation enzymes, such as carnitine palmitoyltransferase 1. Overall, CAR regulates a broad array of genes of fundamental importance, such as bioactivation, detoxication, and NSCLC transport JNJ 1661010 of drugs, other xenochemicals, and endogenous substance. Therefore, alteration in CAR function may impact not only pharmacokinetics, efcacy, and toxicity of drugs but also endocrine homeostasis, energy metabolism, and cell proliferation/tumorigenesis. In contrast to PXR, CAR is constitutively active. In the basal state, CAR is localized in the cytoplasm in a complex with HSP90 and CCRP.
Upon binding to an agonist, CAR is dissociated from HSP90 and CCRP, and the ligand bound CAR translocates to the nucleus, where it forms a heterodimer with RXR and recruits coactivators and dissociates corepressors. The CAR?RXR?coac tivator complex binds to DNA response elements in CAR target genes, resulting in increased gene transcription. Ivacaftor SRC 1, transcription factor Sp1, and signal cointegrator 2 are examples of coactivators of CAR, whereas NCoR is an example of a corepressor of CAR. Interestingly, CAR activation may also occur without direct binding of the ligand to CAR, and this is exemplied by the activation of CAR by phenobarbital and various other compounds. The reader is referred to recent reviews on the mechanistic details of direct and indirect activation of CAR and the interplay between CAR and other nuclear receptors.
This drug is an agonist of mouse CAR, but it is not an agonist of human CAR. In fact, meclizine is an inverse agonist of human CAR.
Wednesday, February 27, 2013
Ivacaftor JNJ 1661010 Builders Unite!
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