Cytochromes P450 decreased activity

Monshouwer M, Agnello D, Ghezzi P, Villa P. 2000. Decrease in brain cytochrome P450 enzyme activities during infection and inflammation of the central nervous system. Neu-roimmunomodulation 8 142-147. 

Buspirone is rapidly absorbed orally but undergoes extensive first-pass metabolism via hydroxylation and dealkylation reactions to form several active metabolites. The major metabolite is l-(2-pyrimidyl)-piperazine (1-PP), which has K2-adrenoceptor-blocking actions and which enters the central nervous system to reach higher levels than the parent drug. It is not known what role (if any) 1-PP plays in the central actions of buspirone. The elimination half-life of buspirone is 2-4 hours, and liver dysfunction may slow its clearance. Rifampin, an inducer of cytochrome P450, decreases the half-life of buspirone inhibitors of CYP3A4 (eg, erythromycin, ketoconazole, grapefruit juice, nefazodone) can markedly increase its plasma levels. 

Lampe JW, King IB, Li S, et al. Brassica vegetables increase and apiaceous vegetables decrease cytochrome P450 1A2 activity in humans changes in caffeine metabolite ratios in response to controlled vegetable diets. Carcinogenesis. 2000 21 1157-1162. 

Imidazole antimycotics, ketoconazole, clotrimazole, and miconazole are potent inhibitors of various cytochrome P450-isoenzymes that also affect the metabolism of retinoids. They were fust shown to inhibit the metabolism of RA in F9 embryonal carcinoma cells. When tested in vitm liarazole, a potent CYP-inhibitor, suppressed neoplastic transformation and upregulated gap junctional communication in murine and human fibroblasts, which appeared to be due to the presence of retinoids in the serum component of the cell culture medium. Furthermore, liarazole magnified the cancer chemopreventive activity of RA and (3-carotene in these experiments by inhibiting RA-catabolism as demonstrated by absence of a decrease in RA-levels in the culture medium in the presence of liarazole over 48 h, whereas without liarazole 99% of RA was catabolized. In vivo, treatment with liarazole and ketoconazole reduced the accelerated catabolism of retinoids and increased the mean plasma all-irans-RA-concentration in patients with acute promyelocytic leukemia and other cancels. 

Comparative study of LB films of cytochrome P450 wild type and recombinant revealed similar surface-active properties of the samples. CD spectra have shown that the secondary structure of these proteins is practically identical. Improved thermal stability is also similar for LB films built up from these proteins. Marked differences for LB films of wild type and recombinant protein were observed in surface density and the thickness of the deposited layer. These differences can be explained by improved purity of the recombinant sample. In fact, impurity can disturb layer formation, preventing closest packing and diminishing the surface density and the average monolayer thickness. Decreased purity of... 

Interferons reduce the activity of hepatic cytochrome P450 enzymes and decrease the clearance of drugs such as theophylline. Their effects may be additive with other drugs that have neurotoxic, hematotoxic or cardiotoxic activity. 

Chemomodulatory influence. Asafetida, administered orally to Sprague-Dawley rats at doses of 1.25% and 2.5% w/w in diet, produced an increase in the development and differentiation of ducts/ductules and lobules and a decrease in terminal end buds as compared to both normal and N-methyl-N-nitrosourea-treated control animals. Asafetida treatment significantly reduced the levels of cytochrome P450 and b5. There was an enhancement in the activities of glutathione-S-transferase, deoxythymi-dine-diaphorase, superoxide desmutase, catalase, and reduced glutathione " " . Central nervous (CNS) effects. Ethanol extract of the dried gum, administered orally to adults at a dose of 20 mL/person, was active "" . 

---