Peroxidase-mediated reaction of the carcinogenic non-aminoazo dye 1-phenylazo-2-hydroxynaphthalene with transfer ribonucleic acid

Abstract

Horseradish peroxidase in the presence of hydrogen peroxide has the ability to mediate the activation of carcinogenic 1-phenylazo-2-hydroxynaphthalene (Sudan I) to DNA- and transfer RNA (tRNA)-bound products in vitro. tRNA is more accessible for modification by the activated carcinogen studied. tRNA modified by activated Sudan I becomes colored and has an absorption maximum of approximately 480 nm. Binding of metabolite(s) to tRNA is inhibited by ascorbate, glutathione, Mg2+ ions and nitrosobenzene. The mechanism of these protections was shown to be different for the different agents. tRNA modified by activated Sudan I exhibits a significantly increased acceptance for L-methionine. Enzymatic hydrolysis of modified tRNA with subsequent separation of nucleosides by HPLC suggests that the covalent modification of tRNA originating from the formation of more than one adduct with the nucleosides in tRNA is the predominant interaction of the activated Sudan I with tRNA.

Oxidation of the carcinogenic non-aminoazo dye 1-phenylazo-2-hydroxy-naphthalene (Sudan I) by cytochromes P450 and peroxidases: a comparative study

“…It should be noted that the Sudan I metabolites formed by peroxidase ( Figure 3 ) are much less likely to be formed physiologically than in the in vitro system (Semanská et al ., 2008 ), because many nucleophilic molecules are present in cells to scavenge the Sudan I reactive species. Indeed, during Sudan I oxidation by peroxidase in the presence of nuclephiles such as DNA, tRNA polydeoxynucleotides, polynucleotides and or proteins, the formation of adducts runs parallel to a decrease in generation of Sudan I metabolites (Stiborová et al ., 1990a ; b ; 1991 ; 1999b ; and Stiborova et al ., unpublished data). Hence, formation of adducts of Sudan I reactive species with these nucleophilic compounds seems to be the preferred reaction under physiological conditions.…”

“…It is a clastogenic compound, inducing micronuclei in the bone marrow of rats (Westmoreland and Gatehouse, 1991 ). There is also evidence that this compound exhibits genotoxic effects, after its metabolic activation by hepatic cytochrome P450 (CYP) and peroxidase enzymes in vitro , and in the rat liver and urinary bladder in vivo (Stiborová et al ., 1988b ; c ; 1990a ; b ; 1992 ; 1993 ; 1995a ; b ; 1999a ; b ; 2002 ; 2006 ; Dixit et al ., 2008 ; Zhang et al ., 2008b ,), and in a human hepatoma cell line, HepG2 (An et al ., 2007 ; Zhang et al ., 2008b ).…”

“…But relatively high levels of peroxidases are expressed in this tissue (Wise et al ., 1984 ). We have found that in addition to microsomal CYP enzymes, Sudan I and its C-hydroxylated metabolites are also oxidized by peroxidases such as a model plant peroxidase from horseradish as well as the mammalian enzyme, prostaglandin H synthase (cyclooxygenase), as a consequence DNA, RNA and protein adducts are formed (Stiborová et al ., 1988c ; 1990a ; b ; 1991 ; 1992 ; 1993 ; 1995a ; 1999b ) ( Figure 2 ). In bladder, therefore, peroxidase-catalyzed activation of Sudan I has been suggested, similar to other carcinogens such as carcinogenic aromatic amines (Wise et al ., 1984 ; Yamazoe et al ., 1985 ; Eling et al ., 1990 ; Chen et al, 1996 ).…”

“…In bladder, therefore, peroxidase-catalyzed activation of Sudan I has been suggested, similar to other carcinogens such as carcinogenic aromatic amines (Wise et al ., 1984 ; Yamazoe et al ., 1985 ; Eling et al ., 1990 ; Chen et al, 1996 ). We have suggested a CYP- or peroxidase-mediated activation of Sudan I or a combination of both mechanisms as an explanation for the organ specificity of this carcinogen for liver and urinary bladder in animals (Stiborová et al ., 1988b ; 1990a ; b ; 1992 ; 1995b ; 2002 ; 2005 ; Martínek and Stiborová, 2002 ). Indeed, the 8-(phenylazo)guanine DNA adduct generated from the BDI, the product of CYP activation, was found in the liver of rats treated with Sudan I (Stiborová et al ., 2006 ) ( Figure 3 ), whereas the physico-chemical properties of DNA adducts found in the urinary bladder are identical to those formed by the peroxidase-mediated Sudan I activation that contain the whole molecule of Sudan I (Stiborová et al ., 1999a ).…”

“…In the meantime, we have confirmed this for the two major metabolites (Semanská et al ., 2008 ), one is a Sudan I dimer ( Figure 4 A) generated by a Sudan I one electron oxidation, while the other is the product of secondary, enzyme independent reactions of this Sudan I dimer, spiro-bezoxadiazine derivative of Sudan I (Semanská et al ., 2008 ) ( Figure 4 B). Plant horseradish peroxidase (HRP) was found in these studies to be an acceptable model for Sudan I oxidation by mammalian enzymes such as non-specific urinary bladder peroxidases and/or cyclooxygenases (Stiborová et al ., 1990a ; b ; 1996 ; 2000 ; 2002 ; 2006 ). Even though mammalian and plant peroxidases are structurally different proteins, the oxidation mechanisms are similar due to analogous arrangements of their active sites (Wise et al ., 1984 ; Yamazoe et al ., 1985 ; Eling et al ., 1990 ; Stiborová et al ., 1991 , 2000 ; Chen et al, 1996 ).…”