Biomedical subjects

Matthew J Zaya

Publications and source records attributed to Matthew J Zaya.

4 recordsLinked to original sources

PubMed2006

Epirubicin glucuronidation and UGT2B7 developmental expression.

The usefulness of epirubicin in the treatment of adult and childhood malignant diseases is related in part to the potential reduction in cardiac toxicity compared with that of other anthracyclines given at equivalent doses. An important pathway for epirubicin detoxification is UGT2B7-dependent glucuronidation. This study was implemented to provide a preclinical evaluation of the metabolism of epirubicin with respect to age-related changes in epirubicin glucuronidation in pediatric liver microsomes. Rates of epirubicin glucuronidation and levels of UGT2B7 were determined for liver microsomes from four pediatric age categories (n = 32) and one adult age category (n = 8). Both sets of data showed an increase in UGT2B7 activity and content with increasing age. Epirubicin glucuronidation activity in the adult group was statistically higher compared with all pediatric age groups (p < or = 0.01). UGT2B7 expression also was statistically higher in adults compared with children below 11 years of age, with evidence of significant differences in protein levels among the pediatric age categories. A positive correlation (r = 0.68) between UGT2B7 levels and postnatal age was observed, suggesting a progressive increase in UGT2B7 protein expression with increasing age. However, allometric scaling using the (3/4) power rule suggested no difference in activity between any of the pediatric age categories and the adult, although only a single neonatal sample was included in the analysis. In summary, these in vitro data show differences in epirubicin glucuronidation and UGT2B7 content within pediatric age groups and support the use of epirubicin in pediatric patients at least 6 months of age.

Adolescent↗

PubMed2003

Developmental expression of the major human hepatic CYP3A enzymes.

The human cytochrome P4503A forms show expression patterns subject to developmental influence. CYP3A7 and CYP3A4 are generally classified as the major fetal and adult liver forms, respectively. However, characterization of CYP3A4, -3A5, and -3A7 developmental expression has historically been confounded by the lack of CYP3A isoform-specific antibodies or marker enzyme activities. Therefore, the objective of this study was to characterize the developmental expression of hepatic CYP3A forms from early gestation to 18 years of age using up to 212 fetal and pediatric liver samples. Based on immunoquantitation, CYP3A5 protein expression was found to be highly variable, generally independent of age, and more frequently observed for African-American individuals. For differentiation of CYP3A4 and -3A7 levels, dehydroepiandrosterone metabolite patterns for expressed CYP3A forms were characterized and used for simultaneous quantitation of protein levels within liver microsome samples. The major metabolite formed by CYP3A4, 7beta-hydroxy-dehydroepiandrosterone, was identified based on cochromatography and mass spectra matching with the authentic standard. Kinetic analysis showed a 34-fold greater intrinsic clearance of 7beta-hydroxy-dehydroepiandrosterone by CYP3A4 versus -3A7, whereas CYP3A7 showed the highest 16alpha-hydroxy-dehydroepiandrosterone intrinsic clearance. Metabolite profiles for the expressed enzymes were fit to a multiple response model and CYP3A4 and -3A7 levels in fetal and pediatric liver microsome samples were calculated. Fetal liver microsomes showed extremely high CYP3A7 levels (311-158 pmol/mg protein) and significant expression through 6 months postnatal age. Low CYP3A4 expression was noted for fetal liver (< or =10 pmol/mg), with mean levels increasing with postnatal age.

Aryl Hydrocarbon Hydroxylases↗

PubMed2003

Identification of phenylisoxazolines as novel and viable antibacterial agents active against Gram-positive pathogens.

A new and promising group of antibacterial agents, collectively known as the oxazolidinones and exemplified by linezolid (PNU-100766, marketed as Zyvox), have recently emerged as important new therapeutic agents for the treatment of infections caused by Gram-positive bacteria. Because of their significance, extensive synthetic investigations into the structure-activity relationships of the oxazolidinones have been conducted at Pharmacia. One facet of this research effort has focused on the identification of bioisosteric replacements for the usual oxazolidinone A-ring. In this paper we describe studies leading to the identification of antibacterial agents incorporating a novel isoxazoline A-ring surrogate. In a gratifying result, the initial isoxazoline analogue prepared was found to exhibit in vitro antibacterial activity approaching that of the corresponding oxazolidinone progenitor. The synthesis and antibacterial activity profile of a preliminary series of isoxazoline analogues incorporating either a C-C or N-C linkage between their B- and C-rings will be presented. Many of the analogues exhibited interesting levels of antibacterial activity. The piperazine derivative 54 displayed especially promising in vitro activity and in vivo efficacy comparable to the activity and efficacy of linezolid.

Animals↗

PubMed2003

Expression and characterization of functional dog flavin-containing monooxygenase 1.

A full-length dog (beagle) flavin-containing monooxygenase 1 (FMO1) cDNA (dFMO1) was obtained from liver by reverse transcription-polymerase chain reaction. The amino acid sequence of dFMO1 was 89% homologous to human FMO1. Using a baculovirus expression system in Sf-9 insect cells, dFMO1 was expressed to protein levels of 0.4 nmol/mg, as determined by immunoquantitation. The flavin content of the expressed enzyme was consistent with immunodetectable dFMO1 protein levels. Expressed dFMO1 catalyzed NADPH-dependent methyl p-tolyl sulfide oxidation, with K(m) and V(max) values of 98.6 microM and 63.8 nmol of S-oxide formed/min/mg of protein, respectively. By comparison, human FMO1 showed similar values of 87.1 microM (K(m)) and 51.0 nmol/min/mg (V(max)). Activity for dFMO1 showed characteristic pH dependence, with a 4.5-fold increase in S-oxidase activity as the incubation pH increased from 7.6 to 9.0. Human FMO1 also showed an increase in reaction rate with pH but a somewhat lower optimum of 8.0 to 8.4. dFMO1 also catalyzed imipramine N-oxidation, with a K(m) of 4.7 microM and a V(max) of 82.1 nmol/min/mg of protein. This enzyme displayed other characteristics of FMO enzymes, with rapid depletion of enzyme activity upon heating in the absence of NADPH. Protein levels of 74 pmol of dFMO1/mg of microsomal protein were determined for a pooled liver microsome sample, suggesting that this enzyme is a major canine hepatic monooxygenase. In conclusion, the expression and characterization of catalytically active dFMO1 will allow the role of this enzyme in the metabolism of xenobiotics to be determined.

Animals↗