Hemoglobin adducts of furfuryl alcohol in genetically modified mouse models: Role of endogenous sulfotransferases 1a1 and 1d1 and transgenic human sulfotransferases 1A1/1A2.

Furfuryl alcohol (FFA) is a heat-induced food contaminant. Conversion by sulfotransferases (SULT) yields 2-sulfoxymethylfuran, which is prone to react with DNA and proteins. In order to monitor the internal FFA exposure we developed a technique for the mass spectrometric quantification of the adduct N-((furan-2-yl)methyl)-valine (FFA-Val) after cleavage from the N-termini of hemoglobin. In the current study the method was applied to investigate the influence of different SULT forms on the adduct formation in wild-type mice and three genetically modified mouse models treated with FFA. Two lines were devoid of endogenous Sult1a1 or Sult1d1, while another mouse line carried a transgene of human SULT1A1/1A2 in the Sult1a1/1d1 double knockout background. The Sult1d1 knockout did not influence adduct formation, whereas the lack of Sult1a1 reduced mean FFA-Val levels by 80% and 58% in male and female mice, respectively, in comparison to FFA-treated wild-type mice. The levels of FFA-Val in the humanized mice were elevated by factors of 2.7 (males) and 2.2 (females) as compared to the wild-type, indicating that SULT1A1/1A2 play a central role for FFA bioactivation also in humans. The excellent correlation between adduct levels in hepatic DNA and hemoglobin (r2 = 0.97) indicated that 2-sulfoxymethylfuran of hepatic origin is sufficiently stable to enter circulation and pass the cellular membrane of erythrocytes. This is a prerequisite for the application of FFA-Val as a biomarker of internal FFA exposure.

Determination of sulfotransferase forms involved in the metabolic activation of the genotoxicant 1-hydroxymethylpyrene using bacterially expressed enzymes and genetically modified mouse models.

1-Methylpyrene, a carcinogenic polycyclic aromatic hydrocarbon, forms benzylic DNA adducts, in particular N2-(1-methylpyrenyl)-2'-deoxyguanosine, in mice and rats. It is bioactivated via 1-hydroxymethylpyrene (1-HMP) to electrophilic 1-sulfooxymethylpyrene (1-SMP). In this study, we explored the role of individual mouse sulfotransferase (SULT) forms in this activation. First, we showed that all nine mouse SULTs tested were able to activate 1-HMP to a mutagen in the his- Salmonella typhimurium reversion test. Some activation was even observed with Sult2a3 and Sult5a1, orphan forms for which no substrates were identified hitherto. Subsequently, we used cytosolic preparations from tissues of four mouse lines (wild-type, Sult1a1-, Sult1d1-, and transgenic for human SULT1A1/2) for the activation of 1-HMP in the mutagenicity assay. The most prominent impacts of the genetic SULT status were 96% decrease in hepatic activation by Sult1a1 knockout, 99% decrease in renal activation by Sult1d1 knockout, and 100-fold increase in pulmonary activation by transgenic human SULT1A1/2. Finally, we treated the various mouse lines with 1-HMP (19.3 mg/kg, intraperitoneally), and then determined 1-SMP levels in plasma and DNA adducts in tissues. Transgenic human SULT1A1/2 strongly enhanced 1-SMP plasma levels and DNA adduct formation in the liver, lung, heart, and kidney but not in the colon. Sult1a1 and Sult1d1 knockout reduced plasma 1-SMP levels as well as DNA adduct formation in some tissues (strongest effects: 97% decrease in 1-SMP and 89% decrease in hepatic adducts in Sult1a1- mice). The adduct levels detected in various tissues did not accurately reflect the activation capacity of these tissues determined in vitro, probably due to the distribution of the reactive metabolite 1-SMP via the circulation. In conclusion, we demonstrated that many mouse SULT forms are able to activate 1-HMP. In vivo, we verified a prominent role of Sult1a1 in hepatic and renal adduct formation and a smaller but unambiguous role of Sult1d1, and demonstrated the strong impact of transgenic human SULT1A1/2.

Reversibility of cellular and organ pathology in enzyme replacement trials in animal models of lysosomal storage diseases.

UNLABELLED: Enzyme replacement therapy (ERT) has now become a feasible treatment option for several lysosomal storage diseases (LSDs). Although the rationale behind this approach is straightforward, there are many factors that may influence the efficacy of treatment. The reversibility of cellular and organ pathology depends on several factors including the particular organ targeted, the dose and biodistribution of enzyme, the accessibility of the target cell to the infused enzyme, the abundance of receptors for mannose-6-phosphate and other ligands in the target tissue and the activity of endocytosis. In addition, each lysosomal enzyme is unique and its ability to reverse pathology must be individually determined according to source, glycosylation and phosphorylation status. The extent to which cellular pathology may be corrected depends upon the delivery of sufficient enzyme to the diseased tissues. CONCLUSION: Studies in animal models have identified numerous factors that influence the therapeutic efficacy of ERT. This would suggest that in patients affected by LSDs rigorous evaluation of each therapeutic preparation will be needed.

Aryl sulfotransferase IV deficiency in rat liver carcinogenesis initiated with diethylnitrosamine and promoted with N-2-fluorenylacetamide or its C-9-oxidized metabolites.

Down regulation of aryl sulfotransferase IV (AST IV) in promotion/progression of liver carcinogenesis by N-2-fluorenylacetamide (2-FAA) has been established. This study examined whether the C-9 oxidized metabolites of 2-FAA, which have recently been shown to promote diethylnitrosamine (DEN)-initiated liver carcinogenesis in male Sprague-Dawley rats, effect the above change. Hence, in DEN-initiated rats, the effects of promoting regimens of 9-OH-2-FAA or 9-oxo-2-FAA, 15 oral doses at 50 and 100 mumol/kg of body weight, were compared to those of 2-FAA at 50 mumol/kg of body weight and of the vehicle on the activity of N-hydroxy(OH)-2-FAA sulfotransferase (ST), an isozyme of AST IV and AST IV expression and distribution. Relative to the vehicle, treatment with the fluorenyl compounds led to decreased levels in hepatic N-OH-2-FAA ST activity and development of hepatic nodules and tumors which had still lower levels of the ST activity than the respective remnant livers. At approximately 8 months after treatment with the C-9-oxidized compounds at doses twice that of 2-FAA, the extents of decreases in the hepatic N-OH-2-FAA ST activity and cytosolic AST IV protein in tumors were comparable to those with 2-FAA. Immunocytochemical analysis showed close association of AST IV deficiency with neoplastic liver lesions. In comparison to N-OH-2-FAA, 9-OH-2-FAA had only low and 9-oxo-2-FAA lacked sulfate acceptor activity in the presence of male rat liver cytosol or AST IV. At 3.3-fold greater concentration than N-OH-2-FAA, 9-oxo-2-FAA inhibited (27%) the sulfate acceptor activity of N-OH-2-FAA in the presence of AST IV, which suggested interference by 9-oxo-2-FAA at the active site. Although the C-9-oxidized compounds do not appear to be substrates for N-OH-2-FAA ST, their ability to cause a decrease in N-OH-2-FAA ST activity and protein similar to that of 2-FAA supports their role in hepatocarcinogenesis. Whereas 9-OH-2-FAA had a 3.9-fold greater sulfate acceptor activity in the presence of female than male rat liver cytosol and inhibited dehydroepiandrosterone ST activity of female rat liver, N-OH-2-FAA and 9-oxo-2-FAA inhibited estrone ST activity of male rat liver, suggesting that the C-9-oxidized compounds as well as N-OH-2-FAA are substrates for STs other than AST IV.