Formation of Hepatic DNA Adducts by Methyleugenol in Mouse Models: Drastic Decrease by Sult1a1 Knockout and Strong Increase by Transgenic Human SULT1A1/2

Carcinogenesis. 2014 Apr;35(4):935-41. doi: 10.1093/carcin/bgt408. Epub 2013 Dec 6.

Abstract

Methyleugenol--a natural constituent of herbs and spices--is hepatocarcinogenic in rodent models. It can form DNA adducts after side-chain hydroxylation and sulfation. We previously demonstrated that human sulfotransferases (SULTs) 1A1 and 1A2 as well as mouse Sult1a1, expressed in Salmonella target strains, are able to activate 1'-hydroxymethyleugenol (1'-OH-ME) and 3'-hydroxymethylisoeugenol (3'-OH-MIE) to mutagens. Now we investigated the role of these enzymes in the formation of hepatic DNA adducts by methyleugenol in the mouse in vivo. We used FVB/N mice [wild-type (wt)] and genetically modified strains in this background: Sult1a1 knockout (ko), transgenic for human SULT1A1/2 (tg) and the combination of both modifications (ko-tg). Methyleugenol (50mg/kg body mass) formed 23, 735, 3770 and 4500 N (2)-(trans-methylisoeugenol-3'-yl)-2'-deoxyguanosine adducts per 10(8) 2'-deoxyribonucleosides (dN) in ko, wt, ko-tg and tg mice, respectively. The corresponding values for an equimolar dose of 1'-OH-ME were 12, 1490, 12 400 and 13 300 per 10(8) dN. Similar relative levels were observed for the minor adduct, N (6)-(trans-methylisoeugenol-3'-yl)-2'-deoxyadenosine. Thus, the adduct formation by both compounds was nearly completely dependent on the presence of SULT1A enzymes, with human SULT1A1/2 producing stronger effects than mouse Sult1a1. Moreover, a dose of 0.05 mg/kg methyleugenol (one-fourth of the estimated average daily exposure of humans) was sufficient to form detectable adducts in humanized (ko-tg) mice. Although 3'-OH-MIE was equally mutagenic to 1'-OH-ME in Salmonella strains expressing human SULT1A1 or 1A2, it only formed 0.14% of hepatic adducts in ko-tg mice compared with an equimolar dose of 1'-OH-ME, suggesting an important role of detoxifying pathways for this isomer in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arylsulfotransferase / genetics*
  • Base Sequence
  • DNA Adducts*
  • DNA Primers
  • Dose-Response Relationship, Drug
  • Eugenol / analogs & derivatives*
  • Eugenol / metabolism
  • Eugenol / pharmacology
  • Female
  • Humans
  • Limit of Detection
  • Liver / drug effects*
  • Liver / enzymology
  • Liver / metabolism
  • Male
  • Mice
  • Mice, Knockout
  • Mice, Transgenic
  • Polymerase Chain Reaction

Substances

  • DNA Adducts
  • DNA Primers
  • methyleugenol
  • Eugenol
  • Arylsulfotransferase
  • SULT1A1 protein, human
  • SULT1A2 protein, human
  • Sult1a1 protein, mouse