Drug Metabolism Letters - Volume 1, Issue 2, 2007

The present study demonstrates that exogenous ONOO- can result in rapid declines in intracellular free magnesium ions ([Mg2+]i) concomitant with rapid rises in intracellular free calcium ions ([Ca2+]i) and, subsequently, trigger apoptosis but not necrosis in rat aortic SMCs; high [Mg2+] significantly attenuates ONOO--induced apoptosis. ONOO-- induced apoptosis in vascular SMCs appears to involve activation of Ca2+-Mg2+-dependent endonucleases and caspase-3. Mg deficiency itself could not induce apoptosis in these SMCs, but it could significantly enhance ONOO-- induced apoptosis.

Cryopreserved human hepatocytes in suspension were used to estimate in vivo hepatic clearances for six different drugs. In vitro intrinsic clearances were measured on the basis of substrate depletion. The number of different hepatocyte donors required for a reasonable estimate of in vivo hepatic clearance-within twice or 1 / 2 of the actual value—was determined. Depending upon the desired level of confidence, anywhere from 9-20 donors are required by this method.

The metabolism of (-)-deprenyl (N-methyl,N-propargylamphetamine) and N-methyl,N-propargylphenylethylamine (MPPE), monoamine oxidase inhibitors with neuroprotective properties, was studied using human liver microsomes and cDNA-expressed cytochrome P450 (CYP) enzymes. The metabolic pathways of MPPE parallel those of (-)- deprenyl, but some marked differences were observed, particularly with regard to the contributions of CYP2B6 and CYP2D6.

Glucuronidation of 5'-DFCR, a metabolite of capecitabine, was confirmed in experimental models from rats whereas 5'-DFCR glucuronide was detected neither in bile or liver from mice nor in livermicrosomes from human. Metabolic interactions at the level of the glucuronidation pathway between CAP and other drugs are unlikely in patients.

Fresh hepatocytes have been the choice for interspecies comparative drug metabolism studies. Cryopreserved hepatocytes represent a readily available alternative when combined with acceptance limits based on the metabolic turnover of 7-ethoxycoumarin. Results for the ten NCEs examined show that the metabolites formed were strongly correlated in fresh and cryopreserved hepatocytes.

The equilibrium of the creation and scavenging of free radicals is mandatory in the spermatozoa to fertilize and initiate a full-term pregnancy. The glutathione (GSH) enzymatic system studies have discovered its relationship with oxidative stress in the ejaculate and new strategies to regulate its activity in the semen could be developed. Intracellular sperm GSH system components are altered in infertile men, and these alterations seem to be linked to sperm morphology. We have been able to correlate embryo morphology on 8 cell embryos with the sperm expression of GPx family members; this relationship appears quite promising for discovery of molecular causes of male infertility. Oxidative stress imbalance potentially leads to damage of the structure of plasma membrane. The freezing and subsequent thawing of sperm is a physically stressful process carried out during routine procedures in assisted reproduction, which results in a highly variable and unpredictable reduction of motile sperm. Subsequently, oxidative status can positively or negatively affect the motility, viability, and fertilizing capacity of thawed sperm. A reserve of glutathione, together with GPx expression, is necessary to eliminate free radicals using GSH or GPx-4 like structural protein and seems to be essential for a good post thaw recovery.

The use of rat half-life data to predict human half-lives for drugs and other xenobiotics has previously been shown to be of value. Since transgenic and knockout mice are increasingly used in early stages of preclinical drug development, we wondered whether the estimation of half-life values in mice might be used in the same way that has been recommended for rats. A dataset of mouse and human half-life values was assembled for 88 drugs. Three different regression models were then applied to the prediction of human half-life values from mouse values. The results showed that none of the models was superior to any other, and that all models, including the simplest linear regression model, could predict a human half-life value from a mouse half-life value such that there would be an 80% chance that the predicted value would be within three-fold (i.e. between 0.33 times and 3 times) of the actual human value.

Nanogels of cholesterol-bearing pullulan modified with amino-groups (CHPNH2) were utilized as a career to introduce quantum dots (QDs) into periodontal ligament (PDL) cells. Nanogel-QD effectively labeled PDL cells over 3 weeks. These results indicate that CHPNH2nanogels have a potential as a research tool in the studies of intracellular delivery system.

Different functional alleles for each subtype of cytochrome P450 (CYPs), thiopurine S-methyltransferase (TPMT), glutathione S-transferase (GST) and sulfotransferase (SULT) enzymes, have been identified. In this review, the genetic polymorphisms of drug-metabolizing enzymes in the Japanese population and their effects on metabolic activity are described in detail.

The home-made resin salve from Norway spruce is traditionally and widely used in folk medicine to heal various skin infections and wounds in Northern Finland. We have performed laboratory studies to solve the mechanism of resin salve. The resin salve exhibited a bacteriostatic effect against all tested Gram-positive bacteria important in human medicine including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococcus (VRE), but was not effective against Gram-negative bacteria. An exception among the Gram-negative bacteria was Proteus vulgaris against which resin salve was effective. High amounts of lipophilic extractives, like resin acids were dissolved into water from the resin salve. Also, a large proportion of lignans and cinnamic acid were found in the water extract.

A stable cell line was developed to assess activation of rat pregnane X receptor (rPXR) by xenobiotics. Characterization revealed that the greatest response occurred with dexamethasone (6-10 fold increase) while rifampicin failed to transactivate rPXR. Rodent PXR transactivation assays can be used to understand species differences in enzyme induction.

The disposition of vorinostat, an anticancer agent, was investigated in rats and dogs. Vorinostat possessed high serum clearance, a short elimination half-life and low oral bioavailability in both species. The renal route played an important role in the elimination of drug-related material and vorinostat was eliminated primarily by metabolic biotransformation.

A single nucleotide polymorphism in the dog CYP1A2 gene causes these animals to be CYP1A2 deficient (i.e., lack functional CYP1A2 enzyme activity). Genotyping a colony of 79 dogs revealed 77% wild-type, 19% heterozygous, and 4% homozygous mutant animals. These genetic frequencies are significantly different from those previously reported and illustrate that different sources and populations of dogs can have dramatically different frequencies of this polymorphism.