[Modulation of the activities and mRNA expression of cytochrome P450 isoenzymes in rat liver by Panax gingseng and coadministration with Veratrum nigrum].

OBJECTIVE: To study the modulatory effect of Panax gingseng and coadministration with Veratrum nigrum on the activity and mRNA expression of cytochrome P450 isoenzymes in rat liver. METHOD: Rat liver microsomal cytochrome P450, b5, aminopyrine N-demethylase(APND), p-nitrophenol-hydroxylase(pNPH)activities were quantitated by UV chromatography. The mRNA expression level of five CYP isoenzymes CYP1A1, CYP2B1/2, CYP2C11, CYP2E1 and CYP3A1 were detected by semi-quantitative reverse transcriptase-polymerase chain reaction(RT-PCR). RESULT: P. gingseng coadministrated with V. nigrum obviously decreased the P450 contents of liver microsomes, and the b5 contents. Both single and combined used inhibited the activities of aminopyrine N-demethylase. At the mRNA level, the expression of CYP2C11 markedly induced exposure to V. nigrum, but combinative groups decreased the expression of CYP2C11. The combination of P. gingseng and V. nigrum induced the expression of CYP1A1. P. gingseng has inhibitory effect on CYP2B1/2 and inductive effect used with V. nigrum. The combination of P. gingseng with V. nigrum also induced the expression of CYP3A1. CONCLUSION: P. gingseng used singly has some different modulation effects compared with combinative used, which may occur because of drug-drug interaction based on cytochrome P450. To elucidate the drug-drug interaction, it needs further analysis and metabolism research.

Inverse agonist activity of agouti and agouti-related protein.

Agouti and agouti-related protein (AgRP) are endogenous antagonists of the melanocortin receptors (MCxR). Previous data showed that recombinant full-length agouti and a synthetic fragment of AgRP, AgRP (83-132), are inverse agonists at the MC1R and MC4R, respectively. This study demonstrates the smaller analogs AgRP (87-120) and ASIP [90-132 (L89Y)], and short peptides Yc[CRFFNAFC]Y and Qc[CRFFRSAC]S are also MC4R inverse agonists. Furthermore, the relative affinity of the series of MC4R ligands for displacement of radiolabeled antagonist 125I-AgRP (86-132) versus radiolabeled agonist 125I-NDP-MSH did not correlate with ligand efficacy, which is more consistent with an induced-fit model than a simple two-state model of MC4R activation. These data shed new light on the determinants and mechanism of inverse agonism at the MC4R.

Food deprivation-induced expression of minoxidil sulfotransferase in the hypothalamus uncovered by microarray analysis.

We used oligonucleotide microarrays to analyze comprehensively hypothalamic gene expression changes that correlate with energy homeostasis. We compared the hypothalamic gene expression profiles of freely fed and 48-h fasted rats using 26,379 oligonucleotide probe sets. Expression of 96 genes was up-regulated and expression of 73 genes was down-regulated in a statistically significant manner with fasting. The gene encoding the enzyme minoxidil sulfotransferase, an enzyme that catalyzes the transfer of sulfonate groups to biogenic amines and other substrates, was foremost among a set of genes whose mRNAs were uniformly detectable and displaying the greatest transcriptional changes with fasting. Northern blot analysis indicated that minoxidil sulfotransferase mRNA is up-regulated in the fasted rat and mouse, ob/ob mouse, and fa/fa rat. Results of reverse transcription quantitative PCR indicated that minoxidil sulfotransferase mRNA is also up-regulated in the microdissected arcuate and paraventricular nuclei of the fasted rat. Several index genes known to be either up-regulated (neuropeptide Y) or down-regulated (amphetamine-regulated transcript and proopiomelanocortin) with fasting were also found to be present among our set of "differentially expressed" genes. This study identifies a novel gene induced by fasting and demonstrates the feasibility of using oligonucleotide microarrays for the study of complex neuronal processes.