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Thomas R Sutter

Publications and source records attributed to Thomas R Sutter.

5 recordsLinked to original sources
PubMed2003

Effects of dietary soy and estrous cycle on adrenal cytochrome p450 1B1 expression and DMBA metabolism in adrenal glands and livers in female Sprague-Dawley rats.

Cytochrome p450 1B1 (CYP1B1) has been shown to be important in the bioactivation of 7,12-dimethylbenz[a]anthracene (DMBA) to an adrenal toxin in rats. We investigated the effects of diet and stage of estrous cycle on CYP1B1 expression in rat adrenal glands and on DMBA metabolism by rat adrenal and hepatic microsomes. Female Sprague-Dawley (SD) rats were placed on either standard soy-containing NIH-31 rat chow or soy- and alfalfa-free 5K96 diet from postnatal day (PND) 21 until sacrifice at PND50+/-5. Stage of estrous at sacrifice was assessed by vaginal cytology and confirmed by histological examination of the vagina. Dietary soy at the level present in NIH-31 diet did not affect serum estrogen and progesterone levels. Immunohistochemical analysis confirmed that CYP1B1 was exclusively expressed in the zona fasciculata and zona reticularis in adrenal cortex, which are the regions vulnerable to DMBA-induced adrenal necrosis. Adrenal CYP1B1 protein expression, 3H-DMBA depletion, and formation of DMBA-3,4-, and -8,9-dihydrodiols by adrenal microsomes were greater in animals fed 5K96 diet, and the stage of the estrous cycle affected these parameters only in the soy-free 5K96 diet. In hepatic microsomes, the formation of DMBA-3,4-dihydrodiol, 7-hydroxy- and 12-hydroxy-DMBA were lower in animals fed NIH-31 diet than in those fed 5K96 diet. Thus, dietary soy and the estrous cycle appear to regulate adrenal CYP1B1 expression and DMBA metabolism by both adrenal and hepatic microsomes. The use of different basal diets containing variable levels of soy components may affect certain toxicity assessments.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2003

Evaluation of the cancer chemopreventive potency of dithiolethione analogs of oltipraz.

Oltipraz and related dithiolethiones constitute an important class of chemopreventive agents that enhance the expression of carcinogen detoxication and antioxidant genes. Dose-response studies were undertaken to characterize the cancer chemopreventive activities of several dithiolethiones that are at least as active as oltipraz as inducers. Inhibition of formation of pre-neoplastic lesions and formation of DNA adducts in livers of rats exposed to aflatoxin B1 (AFB1) was monitored. In the tumorigenesis experiment, the dithiolethiones were orally gavaged 3 days/week for 3 successive weeks and at four doses ranging from 0.03 to 0.3 mmol/kg body wt. AFB1 was gavaged beginning 1 week after the start of the dithiolethiones and for two successive weeks. The burden of AFB1-induced putative pre-neoplastic lesions (glutathione S-transferase-placental isoform positive foci) was quantified by light microscopy. Reduction in AFB-DNA adduct burden was assessed 24 h following the first dose of AFB1. Both the parent 1,2-dithiole-3-thione (D3T) and its 5-tert-butyl derivative were more potent inhibitors than oltipraz against these endpoints, while two of the seven tested analogs were slightly less inhibitory. D3T, the most potent dithiolethione of this series, was examined by microarray analysis for induction of hepatic genes at an intermediate chemopreventive dose (0.1 mmol/kg). Transcript levels of eight genes, including two known to detoxify aflatoxin, namely, glutathione S-transferase A5 (GSTA5) and AFB1 aldehyde reductase (AFAR) were elevated. Western analysis indicated that induction of hepatic GSTA5 and AFAR were directly related to the dose of D3T. At the highest dose of D3T (0.3 mmol/kg), protein levels of GSTA5 and AFAR were induced by 7- and 27-fold, respectively. While efficacy in humans has yet to be tested, D3T is clearly more potent than oltipraz and serves as a useful molecular probe for determining the key events associated with protection by this class of agents.

Aflatoxin B1↗
PubMed2003

Single amino acid mutations, but not common polymorphisms, decrease the activity of CYP1B1 against (-)benzo[a]pyrene-7R-trans-7,8-dihydrodiol.

Genetic differences that underlie inter-individual variation in the metabolism of common carcinogens are important potential sources of cancer susceptibility. Cytochrome P450 1B1 (CYP1B1), a central enzyme in the activation of the ubiquitous environmental carcinogen benzo[a]pyrene (B[a]P), has several genetic variants. This study investigated six rare mutations and four common polymorphisms for their effects on B[a]P metabolism. Five missense mutations associated with congenital glaucoma (Gly61Glu, Gly365Trp, Asp374Asn, Pro437Leu and Arg469Tryp) dramatically decreased the capacity of CYP1B1 to convert (-)benzo[a]pyrene-7R-trans-7,8-dihyrodiol (B[a]P-7,8-diol) to (+/-)benzo[a]pyrene-r-7,t-8-dihydrodiol-9,10-epoxides. These five mutations resulted in enzymes with 3-12% of normal activity when assayed in vitro using an Saccharomyces cerevisiae microsomal expression system. A 10 bp deletion mutation produced no detectable protein or activity. In contrast, proteins containing all possible combinations of four common single nucleotide polymorphisms (Arg48Gly, Ala199Ser, Val432Leu, Asn453Ser) had modest effects on B[a]P-7,8-diol metabolism. Michaelis-Menten analysis suggested that two alleles, Arg48, Ala119, Val432, Ser453 (RAVS) and Arg48, Ala119, Leu432, Ser453 (RALS), have KM values 2-fold lower than Arg48, Ala119, Val432, Ser453 (RAVN): 1.4+/-0.3 and 1.3+/-0.4 microM, respectively, compared with 2.8+/-0.8 microM (P<0.05). However, these differences could not be confirmed with direct measurements of rate at low substrate concentration. There were no significant differences for either of two other kinetic parameters, kcat or kcat/KM. Allele frequency analysis in three populations reveals the Ser453 variant is rare among those of Asian (<1%) and African ancestry (<4%), and more common in individuals of European ancestry (16%). Haplotypes containing the Ser453 variant were uncommon; only RALS was detectable in our small populations. The RALS allele occurred between 0.5% in Asians and 15% in Europeans. Our study demonstrates that rare, disease-associated mutations in CYP1B1 significantly decrease the enzyme's metabolism of B[a]P-7,8-diol; however, our results do not identify any major differences in this metabolism due to four common single amino acid polymorphisms.

Aryl Hydrocarbon Hydroxylases↗
PubMed2002

Multiple comparisons model-based clustering and ternary pattern tree numerical display of gene response to treatment: procedure and application to the preclinical evaluation of chemopreventive agents.

Microarray technology has greatly aided the identification of genes that are expressed differentially. Statistical analysis of such data by multiple comparisons procedures has been slow to develop, in part, because methods to cluster the results of such comparisons in biologically meaningful ways have not been available. We isolated and analyzed, by Northern blot and GeneChip, replicate liver RNA samples (n = 4/group) from rats fed with control diet or diet containing one of three chemopreventive compounds, selected because their pharmacological activities, including RNA expression response, are relatively well understood. We report on a classification tree, based on the results of nonparametric multiple comparisons, which results in the bipolar hierarchical clustering of genes in relation to their response to treatment. In addition to identifying treatment-responsive genes, application of this procedure to our test study identified the known pharmacological relationships among the treatment groups without supervision. Also, small treatment-specific subsets of genes were identified that may be indicative of additional pharmacophores present in the test compounds.

Animals↗