Maryse Jaouen

Inhibitory metabolite complex formation of methylenedioxymethamphetamine with rat and human cytochrome P450. Particular involvement of CYP 2D.

Methylenedioxymethamphetamine (MDMA or ecstasy) is a common recreational drug used at rave parties. Unfortunately, MDMA may have neurological effects and in some cases causes hepatotoxicity. MDMA binds to cytochrome P450 in rat and human hepatic microsomal preparations. Upon metabolic transformation of either the methylenedioxy or the methylamino function, it forms an inhibitory P450-metabolite complex. This inhibitory complex is formed predominantly with the P450 2D isozymes. This complex formation may account for the clinical toxicity observed upon ingestion of MDMA, particularly with other compounds normally metabolized by P450 2D6.

Chaperone-assisted expression, purification, and characterization of recombinant nitrile hydratase NI1 from Comamonas testosteroni.

Nitrile hydratases (NHases) are industrially important iron- and cobalt-containing enzymes that are used in the large-scale synthesis of acrylamide. Heterologous expression of NHases has been complicated by the fact that other proteins (activators or metallochaperones) appear to be required to produce NHases in their catalytically active form. We report a novel heterologous system for the expression of catalytically active iron-containing NI1 NHase in Escherichia coli, involving coexpression with the E. coli GroES and GroEL chaperones. The purified recombinant enzyme was found to be highly similar to the enzyme purified from Comamonas testosteroni according to its spectroscopic features, catalytic properties with various substrates, and post-translational modifications. In addition, we report a rapid and convenient spectrophotometric method to monitor the activity of NI1 NHase during purification.

Recognition and oxidative metabolism of cyclodipeptides by hepatic cytochrome P450.

Possible recognition of peptide derivatives by hepatic cytochrome P450 3A has been suggested by binding and metabolism of numerous pseudopeptidic compounds such as ergot derivatives and cyclosporin. Natural linear or cyclic dipeptides containing hydrophobic amino acids produced by microorganisms and present in mammals are able to interact with the P450 active site through either iron-amine interactions (Type II) or hydrophobic Type I interactions. P450 3A from dexamethasone-treated rats or yeast-expressed P450 human 3A4 are the most potent in such interactions, which are particularly strong with peptides containing a histidyl residue. Some cyclodipeptides are rapidly transformed by rat cytochrome P450 3A to mono- or dihydroxylated metabolites, with turnovers around 3 nmoles min(-1) P450(-1). Linear peptides are poorly transformed in these conditions. This metabolism of cyclodipeptides occurs in 8 species including man. Such interactions and metabolism have only minor consequences in terms of P450 3A binding and metabolism of classical P450 3A substrates. These data reinforce the concept that, in addition to their effect on the regulation of P450 neosynthesis, naturally occurring endogenous peptides are also substrates of P450 3A. The physiological activities of these peptides may be modulated by their metabolism.

Microsomal lipid peroxidation and oxy-radicals formation are induced by insoluble iron-containing minerals

Lipid peroxidation, measured by malondialdehyde formation is induced in rat liver microsomes by insoluble iron-containing minerals (pyrite, magnetite, nemalite and an iron ore, minette de Lorraine) which are generally found either in iron mines or as contaminants of asbestos fibers. In spin-trapping studies using DMPO as a spin trap those minerals are also found to catalyze the oxidation of formate to carboxylate radicals by oxygen, via the formation of hydroxyl radicals. The two processes are mainly due to the presence of redox active iron at the surface of the solid particles and thus are greatly inhibited by desferrioxamine, a strong iron chelator. However, these reactions are not correlated.

VITAMIN E DERIVATIVES AS NEW POTENT INHIBITORS OF MICROSOMAL LIPID PEROXIDATION

Several synthetic Vitamin E derivatives are strong inhibitors of lipid peroxidation induced in rat liver microsomes either chemically by ferrous ions and ascorbate or enzymatically by NADPH and carbon tetrachloride. The relative activities of these inhibitors are consistent with their intrinsic antioxidant properties, as peroxyl radicals scavengers. Among them, a 3,4-dihydro-6-hydroxy-2H-1-naphtopyran with IC50 around 0.08 microM is one of the most potent yet known inhibitor of lipid peroxidation.

Réactions des dérivés de l'iode(III) avec les ferroporphyrines et le cytochrome P-450: Formation de complexes σ-aryles du fer(III) et de N-aryl-porphyrines du fer(II) à partir de sels de diaryliodonium

Abstract Diaryliodonium salts ArAr′I + X − , such as diphenyliodonium chloride or iodide ( a and 4b ), p -chlorophenyl(2-thienyl)iodonium chloride ( 5 ) and bis(2-thienyl)iodonium chloride ( 6 ), oxidize Fe II (TPP) (TPP = tetraphenylporphyrin) to give the corresponding ferric porphyrin complex. In the presence of an excess of reducing agent (iron powder), compounds 4 and 5 react with Fe(TPP) to give the σ-aryl complexes, Fe III (TPP)(Ar) (with Ar  C 6 H 5 and p -ClC 6 H 4 , respectively). Using of an excess of 4a or 4b , gave in addition the Fe II (N-C 6 H 5 -TPP)(Cl or I) complexes. Reaction of compounds 4 , 5 and 6 with the hepatic cytochromes P-450 in the presence of NADPH or sodium dithionite, also gave σ-aryl ferric complexes characterized by a Sorek peak around 480 nm.

In vivo effects of immunostimulating lipopeptides on mouse liver microsomal cytochromes P-450 and on paracetamol-induced toxicity.

Immunomodulating lipopeptides lauroyl-L-Ala-γ-D-Glu-LL-A2pmNH2-Gly (RP 44.102) and lauroyl-L-Ala-γ-D-Glu-LL-A2pmNH2 (RP 56.142) were found to protect mice against the hepatotoxicity of paracetamol, which is due to cytochrome P-450 dependent formation of toxic metabolites and radicals. In fact they decreased the amount of hepatic microsomal cytochrome P-450, and the level of CCl4-induced lipid peroxidation. In contrast lauroyl-L-Ala-γ-D-Glu-DD-A2pmNH2 (RP 53.204), which only differs by the configuration of the two chiral carbons of A2pm (diaminopimelic acid) and is not an immunomodulating agent, failed to protect against poisoning by paracetamol and had no effect on the level of hepatic cytochrome P-450 or the microsomal CCl4-induced lipid peroxidation. This provides a clear connection between the immunostimulating properties of a compound and its effects on xenobiotic biotransformations.

Drug interactions with macrolide antibiotics: specificity of pseudo-suicide inhibition and induction of cytochrome P-450.

Macrolide antibiotics like Erythromycin and Tri-acetyl oleandomycin (TAO) are metabolized to nitrosoderivatives which cause inactivation of Cytochrome P-450 by forming stable complex with the Iron of the hemoporphyrin. Several derivatives of erythromycin having lost their cladinose moiety are stronger inducer of liver cytochrome P-450 itself. The major form of cytochrome P-450 induced by all these macrolides in rat liver electrophoretically and immunologically indistinguishable from the major form induced by pregnenolone 16 alpha carbonitrile (PCN). This form is particularly able to metabolize macrolide and to lead to the corresponding 456 nm absorbing cytochrome P-450 complexes in vivo and in vitro.