Capsaicin induces CYP3A4 expression via pregnane X receptor and CCAAT/enhancer-binding protein ß activation.

SCOPE: Capsaicin (8-methyl-N-vanillyl-6-nonenamide) is the principal pungent ingredient in hot red and chili peppers. Many studies have focused on the anticarcinogenic or chemopreventive activities of capsaicin. However, the influence of capsaicin on CYP3A4, its involvement in drug metabolism, and the underlying mechanisms remain unclear. METHODS AND RESULTS: Here, we examined the effect of capsaicin on CYP3A4 expression and the metabolism of CYP3A1 substrate, nifedipine in male Sprague-Dawley rats. Capsaicin induced the enzymatic activity and expression of CYP3A4 in HepG2 cells. Treatment with a human pregnane X receptor (hPXR) inhibitor reduced the inductive effects of capsaicin on CYP3A4 expression. Capsaicin also induced the activation of CCAAT/enhancer-binding protein ß (C/EBPß). Moreover, capsaicin increased the activation of the transient receptor potential vanilloid type-1 receptor downstream signaling components Ca²âº/calmodulin-dependent protein kinase and Akt. Capsaicin elevated the level of CYP3A1 in rat liver and significantly increased the biotransformation of nifedipine to dehydronifedipine. CONCLUSION: From these data, we conclude that capsaicin induces CYP3A4 expression in vitro and in vivo. This induction was achieved by the activation of hPXR and C/EBPß. Our results suggest that capsaicin might induce CYP3A4 expression; thus, exposure to capsaicin may increase the metabolism of CYP3A4 substrate and potentially cause food-drug interactions.

Simultaneous determination of zolazepam and tiletamine in dog plasma by liquid chromatography coupled to a tandem mass spectrometry.

A mixture of tiletamine, a dissociative anesthetic, and zolazepam, a minor tranquilizer, has been widely used as an anesthetic or an immobilizing agent in a variety of animal species. However, interestingly, their pharmacokinetic behaviors have been published only in polar bears and pigs. In this study, we introduce a sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for determining the two drugs in dog plasma. After simple protein precipitation with acetonitrile including midazolam (internal standard), the analytes were chromatographed on a reversed-phase column with a mobile phase of 10 m m ammonium acetate aqueous solution and acetonitrile (1:4, v/v). The accuracy and precision of the assay were in accordance with FDA regulations for the validation of bioanalytical methods. This method was used to measure the concentrations of zolazepam and tiletamine in plasma after a single intramuscular 10 mg dose of each in beagle dogs.

Biotransformation of geniposide by human intestinal microflora on cytotoxicity against HepG2 cells.

Intestinal microflora (IM) is able to produce toxic and carcinogenic metabolites and induce more potent cytotoxicity against cells than non-metabolites. This study was performed to investigate the cytotoxic responses of geniposide (GS) and its metabolite and to determine the role of metabolism by IM in GS-induced cytotoxicity. Genipin (GP), a GS metabolite, increased cytotoxic effects in cells, but GS did not. Following GS incubation with IM for metabolic activation, increased cytotoxicity was detected compared to GS. Western blot analysis revealed that the activated GS inhibited Bcl-2 expression with a subsequent increase in Bax expression. Likewise, GS activation by IM stimulated caspase-3 and the production of reactive oxygen species (ROS). In addition, activated GS-induced apoptosis was confirmed by apoptosis and ROS assays; N-acetyl-l-cysteine (NAC) suppressed ROS production and apoptotic cell death. Activated GS induced sustained JNK phosphorylation. Moreover, activated GS-induced cell death was reversed by SP600125. Taken together, these findings suggest that human IM is able to metabolize GS into GP, and the related biological activities induce apoptosis through ROS/JNK signaling.

Simultaneous determination of glimepiride and its metabolites in human plasma by liquid chromatography coupled to a tandem mass spectrometry.

Glimepiride, a second-generation sulfonylurea, is a glucose-lowering agent widely used to treat diabetes mellitus. It is converted into metabolite M1 by CYP2C9, and M1 is then transformed into the carboxyl derivative M2 by cytosolic enzymes. In this study, we introduce a sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for determining glimepiride, M1, and M2 in human plasma. After simple protein precipitation with acetonitrile, the analytes were chromatographed on a reversed-phase CN column with a mobile phase of 10 mM ammonium acetate aqueous solution and acetonitrile (1:1, v/v). The accuracy and precision of the assay were in accordance with FDA regulations for the validation of bioanalytical methods. This method was used to measure the concentrations of glimepiride, M1, and M2 in plasma after a single oral 2-mg dose of glimepiride in volunteers.

Analysis of enantiomers of sibutramine and its metabolites in rat plasma by liquid chromatography-mass spectrometry using a chiral stationary-phase column.

Sibutramine, a monoamine reuptake inhibitor, is used as a racemate, for the treatment of obesity. It is converted in vivo mainly to two desmethyl active metabolites, mono-desmethylsibutramine (MDS) and di-desmethylsibutramine (DDS). In the present study, we introduced a rapid and simple chromatographic method for separating the R(+)- and S(-)-isomers of sibutramine, MDS, and DDS, respectively. The stereoisomers of the three compounds were extracted from rat plasma using diethyl ether and n-hexane under alkaline conditions. After evaporating the organic layer, the residue was reconstituted in the mobile phase (10 mM ammonium acetate buffer adjusted to pH 4.03 with acetic acid:acetonitrile, 94:6, v/v). The enantiomers in the extract were separated on a Chiral-AGP stationary-phase column and were quantified in a tandem mass spectrometry. The accuracy and precision of the assay were in accordance with FDA regulations for the validation of bioanalytical methods. This method was used to measure the concentrations of the enantiomers of sibutramine, MDS, and DDS in plasma after a single oral dose of 10 mg/kg racemic sibutramine in rats.