Proton NMR studies are reported on the complementary d(C1-C2-A3-C4-T5-A6-oxo-G7-T8-C9-A10-C11-C12).d(G13-G14-T15- G16-A17-A18-T19- A20-G21-T22-G23-G24) dodecanucleotide duplex (designated 8-oxo-7H-dG.dA 12-mer), which contains a centrally located 7-hydro-8-oxodeoxyguanosine (8-oxo-7H-dG) residue, a group commonly found in DNA that has been exposed to ionizing radiation or oxidizing free radicals. From the NMR spectra it can be deduced that this moiety exists as two tautomers, or gives rise to two DNA conformations, that are in equilibrium and that exchange slowly. The present study focuses on the major component of the equilibrium that originates in the 6,8-dioxo tautomer of 8-oxo-7H-dG. We have assigned the exchangeable NH1, NH7, and NH2-2 base protons located on the Watson-Crick and Hoogsteen edges of 8-oxo-7H-dG7 in the 8-oxo-7H-dG.dA 12-mer duplex, using an analysis of one- and two-dimensional nuclear Overhauser enhancement (NOE) data in H2O solution. The observed NOEs derived from the NH7 proton of 8-oxo-7H-dG7 to the H2 and NH2-6 protons of dA18 establish an 8-oxo-7H-dG7(syn).dA 18(anti) alignment at the lesion site in the 8-oxo-7H-dG.dA 12-mer duplex in solution. This alignment, which places the 8-oxo group in the minor groove, was further characterized by an analysis of the NOESY spectrum of the 8-oxo-7H-dG.dA 12-mer duplex in D2O solution. We were able to detect a set of intra- and interstrand NOEs between protons (exchangeable and nonexchangeable) on adjacent residues in the d(A6-oxo-G7-T8).d(A17-A18-T19) trinucleotide segment centered about the lesion site that establishes stacking of the oxo-dG7(syn).dA(anti) pair between stable Watson-Crick dA6.dT19 and dT8.dA17 base pairs with minimal perturbation of the helix. Thus, both strands of the 8-oxo-7H-dG.dA 12-mer duplex adopt right-handed conformations at and adjacent to the lesion site, the unmodified bases adopt anti glycosidic torsion angles, and the bases are stacked into the helix. The energy-minimized conformation of the central d(A6-oxo-G7-T8).d(A17-A18-T19) segment requires that the 8-oxo-7H-dG7(syn).dA18(anti) alignment be stabilized by two hydrogen bonds from NH7 and O6 of 8-oxo-7H-dG7(syn) to N1 and NH2-6 of dA18(anti), respectively, at the lesion site.(ABSTRACT TRUNCATED AT 400 WORDS)

NMR structural studies of the ionizing radiation adduct 7-hydro-8-oxodeoxyguanosine (8-oxo-7H-dG) opposite deoxyadenosine in a DNA duplex. 8-Oxo-7H-dG(syn).cntdot.dA(anti) alignment at lesion site

Therapeutic Potential and Strategies for Inhibiting Tumor Necrosis Factor-α

Substrate specificity and reaction mechanism of murine 8-oxoguanine-DNA glycosylase.

Series of 1,2-diarylimidazoles has been synthesized and found to contain highly potent and selective inhibitors of the human COX-2 enzyme. The paper describes a short synthesis of the target 1,2-diarylimidazoles starting with aryl nitriles. Different portions of the diarylimidazole (I) were modified to establish SAR. Systematic variations of the substituents in the aryl ring B have yielded very potent (IC50 = 10−100 nm) and selective (1000−12500) inhibitors of the COX-2 enzyme. The study on the influence of substituents in the imidazole ring established that a CF3 group at position 4 gives the optimum oral activity. A number of the diarylimidazoles showed excellent inhibition in the adjuvant induced arthritis model (e.g., ED50 = 0.02 mpk for 22 and 34). The diarylimidazoles are also potent inhibitors of carrageenan-induced edema (ED50 = 9−30 mpk) and hyperalgesia (ED50 = 11−40 mpk). Several orally active diarylimidazoles show no GI toxicity in the rat and mouse up to 200 mpk.

1,2-Diarylimidazoles as Potent, Cyclooxygenase-2 Selective, and Orally Active Antiinflammatory Agents

Reaction of nitric oxide with superoxide anion produces the highly reactive species peroxynitrite (ONOO−). This compound has been shown to be a strong oxidant of lipids and proteins. However, no data are available on its effect on DNA, with the exception of the induction of strand breaks. We report the result of studies on the reactions of peroxynitrite with the adenine and guanine moieties of nucleosides and isolated DNA. The samples were analyzed for 8-oxo-7,8-dihydro-2′-deoxyguano-sine (8-oxo-dGuo), 2,2-diamino-4–[(2-deoxy-β-D-erythro-pentofuranosyl)amino]-5–(2H)-oxazolone (oxazolone) and 8-oxo-7,8-dihydro-2′-deoxyadenosine (8-oxo-dAdo). The effects of peroxynitrite treatment were compared with those of ionizing radiation in aerated aqueous solution, chosen as a source of hydroxyl radicals. At the nucleoside level, both oxidizing conditions led to the formation of oxazolone and 8-oxo-dAdo. In addition, evidence was provided for the formation of the 4R* and 4S* diastereoisomers of 4-hydroxy-8-oxo-4,8-di...

Peroxynitrite Mediated Oxidation of Purine Bases of Nucleosides and Isolated DNA

A variety of 8-substituted guanosine and 2'-deoxyguanosine derivatives were synthesized and tested as inducers of the differentiation of Friend murine erythroleukemia cells in culture. The most active agents in the guanosine series were 8-substituted-N(CH3)2, -NHCH3, -NH2, -OH, and -SO2CH3, which caused 68, 42, 34, 33, and 30% of erythroleukemia cells to attain benzidine positivity, a functional measure of maturation, at concentrations of 5, 1, 0.4, 5, and 5 mM, respectively. The 8-OH derivative of the 2'-deoxyguanosine series produced comparable activity, causing 62% benzidine-positive cells at a level of 0.2 mM. These findings indicate that 8-substituted analogues of guanosine and 2'-deoxyguanosine have the potential to terminate leukemia cell proliferation through conversion to end-stage differentiated cells.

8-Substituted guanosine and 2'-deoxyguanosine derivatives as potential inducers of the differentiation of Friend erythroleukemia cells.

Several antimetabolites have been demonstrated to have the capacity to initiate differentiation in vitro of a variety of leukemic cell lines. To explore the structural requirements for this activity, a series of purine and 8-substituted purine arabinofuranosyl and ribofuranosyl nucleoside derivatives were synthesized and tested as inducers of the differentiation of Friend murine erythroleukemia cells. 9-(beta-D-Arabinofuranosyl)hypoxanthine and 6-(hydroxyamino)-9-(beta-D-arabinofuranosyl)purine were effective inducers of maturation, producing 82% and 74% benzidine-positive cells, a measure of the number of cells synthesizing hemoglobin. 6-Mercapto-9-(beta-D-ribofuranosyl)purine and 6-(methylmercapto)-9-(beta-D-ribofuranosyl)purine and their corresponding beta-D-arabinofuranosyl derivatives were also effective initiators of maturation, causing approximately 50% of the cell population to assume a differentiated phenotype.

Purine and 8-substituted purine arabinofuranosyl and ribofuranosyl nucleoside derivatives as potential inducers of the differentiation of the Friend erythroleukemia.

8-substituted guanosine and 2′-deoxyguanosine derivatives as potential inducers of the differentiation of friend erythroleukemia cells

Purine and 8‐Substituted Purine Arabinofuranosyl and Ribofuranosyl N ucleoside Derivatives as Potential Inducers of the Differentiation of the Friend Erythroleukemia.

Jia Chong Cheng

Papers

8-Substituted guanosine and 2'-deoxyguanosine derivatives as potential inducers of the differentiation of Friend erythroleukemia cells.

Purine and 8-substituted purine arabinofuranosyl and ribofuranosyl nucleoside derivatives as potential inducers of the differentiation of the Friend erythroleukemia.

8-substituted guanosine and 2′-deoxyguanosine derivatives as potential inducers of the differentiation of friend erythroleukemia cells

Purine and 8‐Substituted Purine Arabinofuranosyl and Ribofuranosyl N ucleoside Derivatives as Potential Inducers of the Differentiation of the Friend Erythroleukemia.