Biomedical subjects

Caroline Fradette

Publications and source records attributed to Caroline Fradette.

7 recordsLinked to original sources

PubMed2005

The 21-aminosteroid U74389G prevents the down-regulation and decrease in activity of CYP1A1, 1A2 and 3A6 induced by an inflammatory reaction.

In vivo, the 21-aminosteroid U74389G prevents the decrease in cytochrome P450 (P450) activity produced by a turpentine-induced inflammatory reaction (TIIR). To investigate the underlying mechanism of action, four groups of rabbits were used, controls receiving or not U74389G, and rabbits with the inflammatory reaction receiving or not U74389G. Hepatocytes were isolated 48h later and incubated for 4 and 24h with the serum of the rabbits. In vivo, the TIIR diminished CYP1A1/2 and 3A6 expression, and enhanced hepatic malondialdehyde (MDA) and nitric oxide (NO*) concentrations (p<0.05). U74389G prevented the increase in MDA, as well as the decrease in CYP1A1/2 amounts and activity, but increased CYP3A6 expression by 40% (p<0.05). In vitro, compared with serum from control rabbits (S(CONT)), incubation of serum from rabbits with TIIR (S(TIIR)) for 4 and 24h with hepatocytes from rabbits with TIIR (H(TIIR)) reduced CYP1A2 and CYP3A6 activity (p<0.05) and increased the formation of NO* and MDA. In rabbits with TIIR pretreated with U74389G, the S(TIIR+U) failed to reduce CYP1A2 activity or to increase MDA, although increased NO* and further reduced CYP3A6 activity. On the other hand, in hepatocytes harvested from rabbits with TIIR pretreated with U74389G, S(TIIR) did not decrease CYP1A2 activity and did not enhance MDA, but still increased NO*. In vitro, the reduction of CYP1A2 and CYP3A6 activity by S(TIIR) is not associated to NF-kappaB activation. In conclusion, U74389G prevents CYP1A1/2 down-regulation and decrease in activity by a double mechanism: hindering the release of serum mediators and by averting intracellular events, effect possibly associated with its antioxidant activity. On the other hand, U74389G up-regulates CYP3A6 but inhibits its catalytic activity.

Animals↗

PubMed2005

Modulation of CYP1A2 and CYP3A6 catalytic activities by serum from rabbits with a turpentine-induced inflammatory reaction and interleukin 6.

Inflammatory reactions reduce the activity of cytochrome P450 isoforms. The aim of the study was to determine the mechanisms underlying the decrease in CYP1A2 and CYP3A6 catalytic activities produced by serum from rabbits with a turpentine-induced inflammatory reaction (S(TIIR)) and interleukin 6 (IL-6). S(TIIR) and IL-6 were incubated with cultured primary hepatocytes from control rabbits (H(CONT)), and from rabbits with a turpentine-induced inflammatory reaction (H(TIIR)) in the absence or presence of pyrrolidine dithiocarbamate (PDTC), an antioxidant and inhibitor of nuclear factor kappaB transcription; 2'-amino-3'-methoxyflavone (PD98059), an inhibitor of extracellular signal-related kinase (Erk1/2); 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole (SB203580), an inhibitor of p38MAPK; Nomega-nitro-L-arginine methyl ester, an inhibitor of nitric-oxide synthase 2 (NOS2); the combination of PDTC, PD98059, and SB203580; and genistein, an inhibitor of Janus-associated protein tyrosine kinase (JAK). After 4 and 24 h of incubation of H(CONT) with S(TIIR) and IL-6, CYP1A2 activity was reduced without changes in expression; the reduction in activity was partially prevented by the inhibition of JAK, Erk1/2, and NOS2. In H(CONT), S(TIIR) and IL-6 did not affect CYP3A6 activity; however, PDTC reduced CYP3A6 activity by 40 and 80% after 4 and 24 h of incubation. In H(TIIR), S(TIIR) and IL-6 reduced both CYP1A2 and CYP3A6 activities; this decrease is partially prevented by inhibitors of protein tyrosine kinases, Erk1/2, and NOS2. In H(TIIR), SB203580 increased CYP3A6 activity in a dose-dependent manner without changes in protein expression. These results show that the signal transduction pathways mediating the decrease in CYP1A2 and 3A6 activity, produced by S(TIIR) and IL-6, involve JAK, Erk1/2, and NOS2.

Animals↗

PubMed2005

The utility of the population approach applied to bioequivalence in patients: comparison of 2 formulations of cyclosporine.

Mixed-effect modeling was used to compare the population pharmacokinetics of 2 formulations of cyclosporine in patients. An open-label, multicenter, conversion study in stable, 6-month post-renal allograft recipients was conducted to compare the safety and pharmacokinetics of oral Pliva Cyclosporine Soft Gelatin Capsules (USP Modified) with Neoral (cyclosporine soft gelatin capsules, USP Modified) in stable post-renal transplant patients. Blood samples were collected predose and for 12 hours postdose on days 1, 14, 15, 28, and 29. Whole-blood samples were analyzed for cyclosporine using high-performance liquid chromatography and mass spectroscopy. Estimates of pharmacokinetic parameters were generated using noncompartmental and population compartmental pharmacokinetic analysis. Moreover, the effects of demographic factors on the pharmacokinetics of cyclosporine were evaluated using the nonlinear mixed-effects modeling program NONMEM. The rate and extent of bioavailability of cyclosporine did not differ between Pliva Cyclosporine Soft Gelatin Capsules and Neoral. In the final model, gender and actual body weight significantly affected the central and peripheral volumes of distribution. In addition, the pharmacokinetics of cyclosporine was defined robustly in this patient population using population pharmacokinetic approaches. Results indicate that the Pliva Cyclosporine Soft Gelatin Capsules and Neoral are bioequivalent when administered to renal transplant patients. Pliva Cyclosporine Soft Gelatin Capsules can then be substituted for Neoral in stabilized patients without anticipating dose adjustments.

Adult↗

PubMed2004

Signal transduction pathways implicated in the decrease in CYP1A1, 1A2 and 3A6 activity produced by serum from rabbits and humans with an inflammatory reaction.

Incubation of serum from rabbits with a turpentine-induced inflammatory reaction and from humans with an upper respiratory viral infection with hepatocytes from rabbits with a turpentine-induced inflammatory reaction for 4h reduces total cytochrome P450 content and activity of cytochrome P450 isoforms CYP1A1/1A2 and 3A6 without affecting the expression of these proteins. To document the signal transduction pathways implicated in the decrease in CYP1A1/1A2 and 3A6 activity, hepatocytes from rabbits with a turpentine-induced inflammatory reaction were incubated with serum from rabbits with a turpentine-induced inflammatory reaction, serum from individuals with a viral infection and interleukin-6 for 4h in presence of inhibitors of protein kinases. The sera-induced decrease in CYP1A1/1A2 and 3A6 activity was partially prevented by the inhibition of Janus-associated protein tyrosine kinase, double-stranded RNA-dependent protein kinase, protein kinase C, and p42/44 mitogen-activated protein kinase. The serum from rabbits with a turpentine-induced inflammatory reaction increased the phosphorylation of Erk1/2, effect prevented by PD98059 but not by bis-indolylmaleimide, a specific inhibitor of protein kinase C. The results demonstrated that the decrease in total cytochrome P450 content and in CYP1A1/1A2 and 3A6 activity by sera and interleukin-6 involves the activation of protein tyrosine kinases, p42/44 mitogen-activated protein kinase and protein kinase C. Indirect evidence supported that nitric oxide is implicated in the decrease in activity of these enzymes.

Animals↗

PubMed2004

5-Hydroxytryptamine is biotransformed by CYP2C9, 2C19 and 2B6 to hydroxylamine, which is converted into nitric oxide.

There is circumstantial evidence suggesting that 5-hydroxytryptamine (5-HT) could be biotransformed by enzymatic systems other than monoamino oxidase A, and that the isoforms of cytochrome P450 may be a source of nitric oxide. This study aimed to assess whether cytochrome P450 contributes to 5-HT biotransformation, and to provide evidence that 5-HT metabolism generates nitric oxide. Addition of 5-HT to cultured hepatocytes yielded 5-hydroxyindol acetic acid, a formation modulated by cytochrome P450 enzyme inducers and inhibitors. Recombinant human CYP2B6, 2C9 and 2C19 biotransformed 5-HT in 5-hydroxyindol acetic acid, but not CYP1A2, 2D6 or 3A4. Cultured hepatocytes with 5-HT generated nitric oxide, the amount of which was altered by cytochrome P450 enzyme inducers and inhibitors. In the presence of CYP2B6, 2C9 and 2C19, 5-HT relaxed precontracted isolated aortic rings, with or without endothelium, an effect prevented by the addition of methylene blue and an inhibitor of catalase, but not by myoglobin. In the absence of catalase, hydroxylamine was always assayed as a byproduct of 5-HT metabolism. In conclusion, CYP2B6, 2C9 and 2C19 biotransform 5-HT, yielding hydroxylamine, which is converted to nitric oxide in the presence of catalase. British Journal of Pharmacology (2004) 141, 407-414. doi:10.1038/sj.bjp.0705632

Animals↗

PubMed2003

Hypoxia-inducible factor-1 and activator protein-1 modulate the upregulation of CYP3A6 induced by hypoxia.

1. Moderate hypoxia in vivo and serum from rabbits subjected to moderate hypoxia (SHYPO) in vitro reduce CYP1A1 and 1A2 p450 isoforms and upregulate CYP3A6. The aim of this project was to investigate the signal transduction pathways implicated in the upregulation of CYP3A6 expression by hypoxia. 2. Hypoxia in vivo and SHYPO in vitro increased the expression of hypoxia-inducible factor-1alpha (HIF-1alpha) and c-jun, as well as CYP3A6. By electrophoresis mobility shift assay, it was shown that HIF-1 and activator protein-1 (AP-1) bind to CYP3A6 oligonucleotide probe after exposure to hypoxia in vivo and SHYPO in vitro. The effects of hypoxia in vivo or SHYPO in vitro were reproduced by CoCl2 and lead acetate, activators of HIF-1 and AP-1, respectively. 2. PD98059, a p42/44 MAPK inhibitor, prevented the increase of CYP3A6 and c-jun, but did not impede the increase of HIF-1alpha and binding to CYP3A6 oligonucleotide probe. Genistein, an inhibitor of protein tyrosine kinases (PTKs), prevented the increase in HIF-1alpha, c-jun and CYP3A6, as well as HIF-1 and AP-1 binding to CYP3A6 oligonucleotide probe. Moreover, hypoxia in vivo induced constitutive androstane receptor (CAR) as well as CAR binding to the CYP3A6 oligonucleotide probe, but not the pregnane X receptor. 4. In conclusion, hypoxia in vivo and SHYPO induce the expression of CYP3A6. The in vitro induction of CYP3A6 by SHYPO is PTK- and p42/44 MAPK-dependent. The present data support the hypothesis that HIF-1 and AP-1 are part of the signalling pathway leading to CYP3A6 induction by hypoxia.

Animals↗

PubMed2002

Hypoxia-induced down-regulation of CYP1A1/1A2 and up-regulation of CYP3A6 involves serum mediators.

1. Acute moderate hypoxia modifies the catalytic activity and expression of certain isoenzymes of hepatic cytochrome P450 (P450). The aim of this study was to document whether hypoxia affects hepatic P450 directly or through the release of serum mediators. 2. Rabbits were subjected to a FiO(2) of 8% for 48 h, sacrificed, and serum and hepatocytes were isolated; hepatocytes from control and rabbits with hypoxia were incubated with serum from control and hypoxic rabbits for 4 and 24 h, and total P450 content, CYP1A1, 1A2 and 3A6 activities and expressions were assessed. Sera were fractionated by size exclusion chromatography and fractions tested for their ability to modify activity and amount of P450, and serum mediators were identified through neutralization experiments. 3. Total serum and fractions with proteins of 15-23 and 65-94 kDa of M(r) reduced P450 content and expression of CYP1A1, 1A2 and 3A6, as well as CYP1A1, 1A2 and 3A6 mRNA. Total serum and the fraction with 32-44 kDa proteins increased CYP3A6 activity and protein and mRNA. The serum mediators implicated in the decrease in activity and expression of CYP1A1, 1A2 and 3A6 were interferon-gamma (IFN-gamma), interleukin-1beta (IL-1beta) and IL-2. Erythropoietin (Epo) was partly responsible for the increase in P450 content and CYP3A6 expression. 4. In conclusion, acute moderate hypoxia diminishes the activity and expression of CYP1A1, 1A2 and CYP1A1, 1A2 mRNA, and increases CYP3A6 protein, activity and CYP3A6 mRNA. Several mechanisms contribute to these changes in P450, among them the release of cytokines acting as serum mediators.

Animals↗