Dataset Information

Molecular dosimetry of N2-hydroxymethyl-dG DNA adducts in rats exposed to formaldehyde.

ABSTRACT: In this study, both endogenous and exogenous N(2)-hydroxymethyl-dG adducts in nasal DNA of rats exposed to 0.7, 2, 5.8, 9.1, or 15.2 ppm [(13)CD(2)] formaldehyde for 6 h were quantified by a highly sensitive nano-UPLC-MS/MS method. Our data clearly demonstrated that exogenous formaldehyde DNA adducts form in a highly nonlinear fashion, with a 21.7-fold increase in exposure causing a 286-fold increase in exogenous adducts. The ratio of exogenous/endogenous DNA adducts demonstrated that endogenous DNA adducts dominated at low exposures, comprising more than 99%. In contrast, exogenous adducts were not detectable in the bone marrow of rats exposed to 15.2 ppm [(13)CD(2)] formaldehyde.

SUBMITTER: Lu K

PROVIDER: S-EPMC3128468 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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Molecular dosimetry of N2-hydroxymethyl-dG DNA adducts in rats exposed to formaldehyde.

Lu Kun K Moeller Benjamin B Doyle-Eisele Melanie M McDonald Jacob J Swenberg James A JA

Chemical research in toxicology 20101214 2

In this study, both endogenous and exogenous N(2)-hydroxymethyl-dG adducts in nasal DNA of rats exposed to 0.7, 2, 5.8, 9.1, or 15.2 ppm [(13)CD(2)] formaldehyde for 6 h were quantified by a highly sensitive nano-UPLC-MS/MS method. Our data clearly demonstrated that exogenous formaldehyde DNA adducts form in a highly nonlinear fashion, with a 21.7-fold increase in exposure causing a 286-fold increase in exogenous adducts. The ratio of exogenous/endogenous DNA adducts demonstrated that endogenous ...[more]

PMID: 21155545

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Project description:Michael addition of trans-4-hydroxynonenal (HNE) to deoxyguanosine yields diastereomeric 1,N(2)-dG adducts in DNA. When placed opposite dC in the 5'-CpG-3' sequence, the (6S,8R,11S) diastereomer forms a N(2)-dG:N(2)-dG interstrand cross-link [Wang, H.; Kozekov, I. D.; Harris, T. M.; Rizzo, C. J. J. Am. Chem. Soc.2003, 125, 5687-5700]. We refined its structure in 5'-d(G(1)C(2)T(3)A(4)G(5)C(6)X(7)A(8)G(9)T(10)C(11)C(12))-3'·5'-d(G(13)G(14)A(15)C(16)T(17)C(18)Y(19)C(20)T(21)A(22)G(23)C(24))-3' [X(7) is the dG adjacent to the C6 carbon of the cross-link or the α-carbon of the (6S,8R,11S) 1,N(2)-dG adduct, and Y(19) is the dG adjacent to the C8 carbon of the cross-link or the γ-carbon of the HNE-derived (6S,8R,11S) 1,N(2)-dG adduct; the cross-link is in the 5'-CpG-3' sequence]. Introduction of (13)C at the C8 carbon of the cross-link revealed one (13)C8→H8 correlation, indicating that the cross-link existed predominantly as a carbinolamine linkage. The H8 proton exhibited NOEs to Y(19) H1', C(20) H1', and C(20) H4', orienting it toward the complementary strand, consistent with the (6S,8R,11S) configuration. An NOE was also observed between the HNE H11 proton and Y(19) H1', orienting the former toward the complementary strand. Imine and pyrimidopurinone linkages were excluded by observation of the Y(19)N(2)H and X(7) N1H protons, respectively. A strong H8→H11 NOE and no (3)J((13)C→H) coupling for the (13)C8-O-C11-H11 eliminated the tetrahydrofuran species derived from the (6S,8R,11S) 1,N(2)-dG adduct. The (6S,8R,11S) carbinolamine linkage and the HNE side chain were located in the minor groove. The X(7)N(2) and Y(19)N(2) atoms were in the gauche conformation with respect to the linkage, maintaining Watson-Crick hydrogen bonds at the cross-linked base pairs. A solvated molecular dynamics simulation indicated that the anti conformation of the hydroxyl group with respect to C6 of the tether minimized steric interaction and predicted hydrogen bonds involving O8H with C(20)O(2) of the 5'-neighbor base pair G(5)·C(20) and O11H with C(18)O(2) of X(7)·C(18). These may, in part, explain the stability of this cross-link and the stereochemical preference for the (6S,8R,11S) configuration.

Project description:Acrolein reacts with dG to form hydroxylated 1,N(2)-propanodeoxyguanosine (OH-PdG) adducts. Most abundant are the epimeric 3-(2-deoxy-beta-D-erythro-pentofuranosyl)-5,6,7,8-tetrahydro-8-hydroxypyrimido[1,2a] purin-10(3H)-ones, commonly referred to as the gamma-OH-PdG adducts. When placed complementary to deoxycytosine in duplex DNA, these undergo rearrangement to the N(2)-(3-oxopropyl)-dG aldehyde. The latter forms diastereomeric interstrand N(2)-dG:N(2)-dG cross-links in the 5'-CpG-3' sequence. Here we report the structure of the stereochemically favored (R)-gamma-hydroxytrimethylene N(2)-dG:N(2)-dG interstrand DNA cross-link in 5'-d(G(1)C(2)T(3)A(4)G(5)C(6)X(7)A(8)G(9)T(10)C(11)C(12))-3' x 5'-d(G(13)G(14)A(15)C(16)T(17)C(18)Y(19)C(20)T(21)A(22)G(23)C(24))-3' (X(7) is the dG linked to the alpha-carbon of the carbinolamine linkage, and Y(19) is the dG linked to the gamma-carbon of the carbinolamine linkage; the cross-link is in the 5'-CpG-3' sequence). The structure was characterized using isotope-edited (15)N nuclear Overhauser enhancement spectroscopy heteronuclear single quantum correlation (NOESY-HSQC) NMR, in which the exocyclic amines at X(7) or Y(19) were (15)N-labeled. Analyses of NOE intensities involving Y(19) N(2)H indicated that the (R)-gamma-hydroxytrimethylene linkage was the major cross-link species, constituting 80-90% of the cross-link. The X(7) and Y(19) imino resonances were observed at 65 degrees C. Additionally, for the 5'-neighbor base pair G(5) x C(20), the G(5) imino resonance remained sharp at 55 degrees C but broadened at 65 degrees C. In contrast, for the 3'-neighbor A(8) x T(17) base pair, the T(17) imino resonance was severely broadened at 55 degrees C. Structural refinement using NOE distance restraints obtained from isotope-edited (15)N NOESY-HSQC data indicated that the (R)-gamma-hydroxytrimethylene linkage maintained the C(6) x Y(19) and X(7) x C(18) base pairs with minimal structural perturbations. The (R)-gamma-hydroxytrimethylene linkage was located in the minor groove. The X(7) N(2) and Y(19) N(2) atoms were in the gauche conformation with respect to the linkage, which maintained Watson-Crick hydrogen bonding of the cross-linked base pairs. The anti conformation of the hydroxyl group with respect to C(alpha) of the tether minimized steric interaction and, more importantly, allowed the formation of a hydrogen bond between the hydroxyl group and C(20) O(2) located in the 5'-neighboring base pair G(5) x C(20). The formation of this hydrogen bond may, in part, explain the thermal stability of this carbinolamine interstrand cross-link and the stereochemical preference for the (R) configuration of the cross-link.

Dataset Information

Molecular dosimetry of N2-hydroxymethyl-dG DNA adducts in rats exposed to formaldehyde.

Publications

Molecular dosimetry of N2-hydroxymethyl-dG DNA adducts in rats exposed to formaldehyde.

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