Lhiaubet-Vallet V, Sarabia Z, Hernández D, Castell J V, Miranda M A
Departamento de Química, Instituto de Tecnología Química UPV-CSIC. Universidad Politécnica de Valencia, Camino de Vera s/n, E-46071 Valencia, Spain.
Toxicol In Vitro. 2003 Oct-Dec;17(5-6):651-6. doi: 10.1016/s0887-2333(03)00108-5.
The possible stereoselectivity in DNA-photosensitization by carprofen (a NSAID drug) and ofloxacin (a fluoroquinolone agent) was investigated. The different drug stereoisomers or racemic mixtures were UVA-irradiated and the relaxation of the supercoiled circular pBR322 quantified by electrophoresis. Formation of single strand breaks was compared for each group of compounds. Moreover a mechanistic study by means of repair enzymes: T4 endonuclease V (specific of cyclobutane pyrimidine dimers), E. coli endonuclease III (revealing oxidized pyrimidines) and E. coli Formamidopyrimidine-DNA glycosylase (revealing oxidized purines) provided further insights into a possible stereoselectivity of the different reaction pathways in drug photosensitized-DNA damage. Ofloxacin and levofloxacin (its S stereoisomer) were responsible of single strand breaks formation as well as oxidation of pyrimidine and purine bases. No pyrimidine dimers were observed. Racemic, R and S stereoisomers of carprofen were less efficient than ofloxacin in DNA single strand breaks formation and did not induce enzyme-sensitive sites. The photoproducts distribution of drug-photosensitized reactions of 2'-deoxyguanosine and thymidine were established by HPLC as fingerprints for assignment of the DNA-photosensitization mechanism. Both Type I and Type II mechanisms were assigned to nucleoside-photosensitization by ofloxacin and levofloxacin. In the case of carprofen, a weak nucleoside degradation was obtained. The data suggest that levofloxacin, the (S) stereoisomer, might be slightly more efficient than racemic ofloxacin. In the case of carprofen the (S) isomer appears to be somewhat less active than its (R) enantiomer. However, due to the small differences found, the possible stereoselectivity has to be confirmed by future studies.
研究了卡洛芬（一种非甾体抗炎药）和氧氟沙星（一种氟喹诺酮类药物）在DNA光致敏过程中可能存在的立体选择性。对不同的药物立体异构体或外消旋混合物进行UVA照射，并通过电泳对超螺旋环状pBR322的松弛情况进行定量。比较了每组化合物中单链断裂的形成情况。此外，通过修复酶进行的机理研究：T4内切核酸酶V（环丁烷嘧啶二聚体特异性酶）、大肠杆菌内切核酸酶III（揭示氧化的嘧啶）和大肠杆菌甲酰胺嘧啶-DNA糖基化酶（揭示氧化的嘌呤），进一步深入了解了药物光致敏-DNA损伤中不同反应途径可能存在 的立体选择性。氧氟沙星和左氧氟沙星（其S立体异构体）会导致单链断裂的形成以及嘧啶和嘌呤碱基的氧化。未观察到嘧啶二聚体。卡洛芬的外消旋体、R和S立体异构体在DNA单链断裂形成方面比氧氟沙星效率低，且不会诱导酶敏感位点。通过高效液相色谱法确定了2'-脱氧鸟苷和胸腺嘧啶的药物光致敏反应的光产物分布，作为DNA光致敏机制归属的指纹图谱。氧氟沙星和左氧氟沙星对核苷的光致敏作用既有I型机制也有II型机制。在卡洛芬的情况下，得到了较弱的核苷降解。数据表明，（S）立体异构体左氧氟沙星可能比外消旋体氧氟沙星略有效。在卡洛芬的情况下，（S）异构体似乎比其（R）对映体活性略低。然而，由于发现的差异较小，可能存在的立体选择性有待未来研究证实。
