Caracterización de los mecanismos que median la muerte celular inducida por diferentes tipos de acetogeninas de annonacaeas en líneas tumorales humanas

Resumo

There is an ongoing and unmet need for new anti¿neoplastic drugs to combat cancer as we face the reality that certain types of cells are resistant to current chemotherapeutic treatments (Shyng¿Shiou et al. 2002). Acetogenins (ACGs) are a group of secondary metabolites isolated from species of the Annonaceae exhibiting a broad range of biological properties, including cytotoxic, antitumoral, antiparasitic and antimicrobial (Bermejo et al. 2005). Mechanism of action studies have demonstrated that ACGs are among the most potent known inhibitors of the mitochondrial Complex I (NADH:ubiquinone oxidoreductase). Despite substantial work exploring the cytotoxic activity of these compounds on tumor cell lines, the correlations between their inhibitory potential with respect to the mitochondrial Complex I and cytotoxicity have not been readily apparent (Royo et al. 2003; Tormo et al. 2005). ACGs have also been described as inducers of apoptosis, although the mechanisms and factors that modulate their efficacy against cancer cells are yet unknown. In the present studies, we have used rotenone, a classical inhibitor of Complex I, as a model compound. Irreversible binding and inactivation of Complex I of the mitochondrial electron transport chain results in inhibition of oxidative phosphorylation and reduced energy metabolism (Isenberg et al. 1999). Furthermore, said inhibition has been shown to increase ROS formation, reduce ¿¿m and produce a characteristic nuclear morphology typically associated with apoptosis. We describe herein the in vitro cytotoxic activity of 18 ACGs on six tumoral and two normal cell lines. Based on binding characteristics to Complex I and antiproliferative potency, four of these compounds (cherimolin¿1, motrilin, laherradurin and rolliniastatin¿1) were selected to study their effects on the apoptotic cascade in direct comparison with rotenone. We observed that ACGs were potent inducers of apoptosis in HepG2 cells, although they do not do so all in the same time frame; we show for example that rolliniastin¿1 induces cell death after only one hour of incubation whereas the effects by laherradurin are not apparent until 24 hours of treatment. In addition, to further scope out the therapeutic potential of this class of compounds, we have evaluated a first measure of biological safety of ACGs by detailing their behavior on three cardiac ion channels (hERG, Nav1.5, Cav1.2). Our results show that these compounds are able to compete with ligands of these channels, but their effect on their functionality is very limited.