Olga Mazuryk

Interaction of apo-transferrin with anticancer ruthenium complexes NAMI-A and its reduced form.

NAMI-A i.e. (ImH)[trans-RuCl(4)(DMSO)(Im)] (where Im is imidazole) is a ruthenium(III) complex with promising antimetastatic activity, which has been classified for II phase clinical trial. In this study, its binding properties toward apo-transferrin (apo-Tf) with regard to its hydrolytic and redox behavior are systematically investigated by the use of fluorescence spectroscopy. The reaction of NAMI-A and its reduced form with apo-Tf is proceeded by formation of aqua derivatives and the presence of at least one labile aqua ligand is sufficient to form adducts. It is found that presence of bicarbonate is not necessary for interaction of studied ruthenium complexes with apo-Tf. The calculated association constants for both NAMI-A and its reduced form are very similar with the values of 1.28 × 10(4)M(-1) and 1.36 × 10(4)M(-1) at 37 °C, respectively however, the reduced derivatives reach the equilibrium ca. 8-10 times slower. The percentage of ruthenium content in protein fractions separated from protein-unbounded ruthenium by using FPLC (fast protein liquid chromatography) method is rather high and depends on redox state of the complex, for most samples is found higher for reduced species.

Nitroimidazole derivatives of polypyridyl ruthenium complexes: Towards understanding their anticancer activity and mode of action

ABSTRACT The mechanism of cell death induced by the ruthenium polypyridyl complexes comprising two 4,7‐diphenyl‐1,10‐phenanthroline ligands as well as one unmodified 2,2′‐bipyridyl or modified with 2‐nitroimidazole moiety attached by shorter (–C3H6–) or longer (–C6H12–) linker was investigated. Cytotoxicity and proliferation assays revealed that the studied Ru polypyridyl complexes are more toxic against human pancreas carcinoma PANC‐1 cell line than normal human keratinocytes HaCaT with IC50 of 3–5 &mgr;M. The Ru complexes despite accumulation in mitochondria do not lead to mitochondrial disfunction, though decreasing of mitochondrial Ca2 + causes mitochondria membrane hyperpolarization. The Ru polypyridyl conjugates induce some phenotypical characteristic of apoptosis, such as condensation of chromatin or phosphatidylserine translocation, however no caspase or calpain activation in the studied cell lines was observed, indicating that detected cell death does not occur via mitochondria‐ or ER‐activated pathways. Caspase‐independent cell death is caused by enormous ROS formation, mainly hydrogen peroxide and peroxyl radicals as well as by intracellular Ca2 + homeostasis disruption. Accumulation of the Ru compounds inhibits the completion of DNA synthesis, arresting cells in S‐phase of cell cycle. Graphical abstract Figure. No Caption available.