Cytotoxicity and plasmid DNA cleavage of three vanadyl(IV) complexes with oxodiacetate derivatives ligands on a human osteosarcoma cell line in culture

LEÓN I.E , ; BUTENKO N; BARAN E; CAVACO I; ETCHEVERRY SB

Simposio; International Symposium on Metal Complexes (ISMEC 2012); 2012

Strong chelating ligands are important in aqueous media because they offer the opportunity of trapping different metal species [1]. This process becomes particularly significant in living systems, where different metals are acquired, transported and stored mostly by low-molecular weight compounds involving multidentate oxygen donors from carboxylate, hydroxamate and catecholate ligands [1, 2]. Among the family of multidentate oxygen donor species, oda= oxodiacetate, O(CH2COO-)2, stands as a versatile complexing agent. Oda holds an OOO donor set and can complex metal ions by forming chelate rings. On the other hand, vanadium is a transition element broadly distributed in nature in trace amounts [3, 4]. Concerning animals and human beings, vanadium compounds, once absorbed, are retained mainly in bones [3, 5]. Besides, it has been reported that vanadium derivatives are potentially useful drugs from a pharmacological point of view. In fact, they display potential therapeutic applications as insulin mimics, [6] antineoplastic drugs [7-9] and osteogenic effects have also been reported [10, 11]. In particular, we are very interested in the antitumoral actions of alternative non-platinum compounds such as vanadium derivatives to provide a broad source of compounds worthy to be tested for alternative cancer treatments in a near future. Some vanadium compounds have shown deleterious effects on tumoral cell proliferation and differentiation as well as on cellular morphology [12, 13]. This antitumoral action seems to be mediated through different mechanisms such as the generation of oxidative stress [14] as well as their interaction with DNA [8] which support at least in part the antiproliferative effects of vanadium compounds. In this work we report the biological effects of three interesting complexes of vanadyl(IV) cation with oda VO(oda)(H20)2, oda and ophen = o-phenanthroline [VO(oda)(ophen)]1.5H2O, and oda and 2,2´-bipyridine [VO(oda)(bipy)].2H2O, on the tumoral osteoblastic cell line; MG-63 (osteosarcoma derived from human bone). The effects on cell proliferation (crystal violet bioassay), cytotoxicity investigation through the determination of the effects on mitochondrial activity (MTT bioassay) and lysosomal activity (neutral red uptake) as well as on cell morphology (Giemsa staining and light microscopy), were investigated. Besides, we studied the mechanisms involved in the cyto- and genotoxicity (oxidative stress and DNA cleavage). [VO(oda)(ophen)]1.5H2O caused an inhibitory effect on cell proliferation in the range of 50-100 µM with a stronger effect than [VO(oda)(bipy)].2H2O and VO(oda)(H20)2 (ca 40%, 70%, 80% of survival, respectively). Moreover they altered the lysosomal and mitochondria metabolisms with similar results to those of the proliferation assay (p< 0.001). Morphological studies showed important transformations and a decrease in the number of cells in a dose response manner. Besides, [VO(oda)(ophen)]1.5H2O and VO(oda)(H20)2 interacted with plasmidic DNA (pA1) causing single and double strand cleavage with a stronger effect by [VO(oda)(ophen)]1.5H2O than VO(oda)(H20)2. Currently, the cleavage effect of [VO(oda)(bipy)].2H2O is under investigation. Besides, [VO(oda)(ophen)]1.5H2O increased the level of Reactive Oxigen Species (ROS) over 300% the basal unlike the low level observed in VO(oda)(H20)2 and [VO(oda)(bipy)]. 2H2O (p