Soldevila Sonia, Consuelo Cuquerella M, Lhiaubet-Vallet Virginie, Edge Ruth, Bosca Francisco
Instituto Universitario Mixto de Tecnologia Quimica (UPV-CSIC), Universitat Politecnica de Valencia, 46022 Valencia, Spain.
Dalton Cumbrian Facility, The University of Manchester, Cumbria CA24 3HA, UK.
Free Radic Biol Med. 2014 Feb;67:417-25. doi: 10.1016/j.freeradbiomed.2013.11.027. Epub 2013 Dec 4.
The mechanism responsible for the remarkable photomutagenicity of fluoroquinolone (FQ) antibiotics remains unknown. For this reason, it was considered worthwhile to study in detail the interactions between DNA and a dihalogenated FQ such as lomefloxacin (LFX; one of the most photomutagenic FQs) and its N-acetyl derivative ALFX. Studies of photosensitized DNA damage by (A)LFX, such as formation of DNA single-strand breaks (SSBs), together with pulse radiolysis, laser flash photolysis, and absorption and fluorescence measurements, have shown the important effects of the cationic character of the piperazinyl ring on the affinity of this type of drug for DNA. Hence, the formation of SSBs was detected for LFX, whereas ALFX and ciprofloxacin (a monofluorated FQ) needed a considerably larger dose of light to produce some damage. In this context, it was determined that the association constant (Ka) for the binding of LFX to DNA is ca. 2×10(3)M(-1), whereas in the case of ALFX it is only ca. 0.5×10(3)M(-1). This important difference is attributed to an association between the cationic peripheral ring of LFX and the phosphate moieties of DNA and justifies the DNA SSB results. The analysis of the transient species detected and the photomixtures has allowed us to establish the intermolecular processes involved in the photolysis of FQ in the presence of DNA and 2'-deoxyguanosine (dGuo). Interestingly, although a covalent binding of the dihalogenated FQ to dGuo occurs, the photodegradation of FQ…DNA complexes did not reveal any significant covalent attachment. Another remarkable outcome of this study was that (A)LFX radical anions, intermediates required for the onset of DNA damage, were detected by pulse radiolysis but not by laser flash photolysis.
氟喹诺酮（FQ）类抗生素具有显著的光致突变性，但其作用机制尚不清楚。因此，详细研究DNA与二卤代FQ（如洛美沙星，LFX，是光致突变性最强的FQ之一）及其N - 乙酰衍生物ALFX之间的相互作用被认为是有价值的。对（A）LFX介导的光敏DNA损伤的研究，如DNA单链断裂（SSB）的形成，结合脉冲辐解、激光闪光光解以及吸收和荧光测量，表明哌嗪环的阳离子特性对这类药物与DNA的亲和力有重要影响。因此，检测到LFX可形成SSB，而ALFX和环丙沙星（单氟代FQ）需要相当大剂量的光才能产生一些损伤。在此背景下，确定LFX与DNA结合的缔合常数（Ka）约为2×10³M⁻¹，而ALFX的缔合常数仅约为0.5×10³M⁻¹。这一重要差异归因于LFX的阳离子外周环与DNA的磷酸基团之间的缔合，这也解释了DNA SSB的结果。对检测到的瞬态物种和光混合物的分析使我们能够确定在DNA和2'-脱氧鸟苷（dGuo）存在下FQ光解过程中涉及的分子间过程。有趣的是，尽管二卤代FQ与dGuo发生了共价结合，但FQ…DNA复合物的光降解并未显示出任何显著的共价附着。这项研究的另一个显著结果是，通过脉冲辐解检测到了（A）LFX自由基阴离子（DNA损伤起始所需的中间体），但激光闪光光解未检测到。
