BONGIOVANNI guillermina Azucena
congresos y reuniones científicas
Kinetic analysis of early arsenite-induced cytotoxicity involving pro-carcinogenetic pathways
SORIA, EA; BONGIOVANNI, GUILLERMINA A.; EYNARD, ALDO R
Congreso; Biennial UICC World Cancer Congress 2008 (UICC).; 2008
UICC (INTERNATIONAL UNION AGAINST CANCER).
Background: Arsenic is a naturally occurring element widely present in the environment, with drinking water accounting for the majority of chronic human arsenic exposures worldwide. An epidemiological link with an elevated risk of different carcinoma types has been found in countries with high levels of arsenic in the drinking water, such as Argentina and Taiwan (IARC Working Group, 2004). The mechanisms of this tumour-promoting activity are still not fully understood. However, oxidative stress is being increasingly recognized for its involvement in arsenic toxicity and carcinogenicity (Valko et al., 2006). Some stress markers arise during a cytotoxic response, and have thus been implicated in the carcinogenic progress, when arsenic exposure becomes prolonged (Arya et al., 2007). With respect to this, these events may be counteracted early on (Bongiovanni et al., 2007), in order to prevent cellular neoplastic transformation taking place, showing that transformed cells may respond differentially to cytoprotection (Soria et al., 2007). Objectives: To develop a cellular model to study the time course of the toxicological response to arsenite. Methods: CHO-K1 cells were treated with FBS-completed DMEM, containing 200 µM sodium arsenite for 0-8 h. The following parameters were evaluated: hydroperoxide formation (HP, colorimetric assay), c-jun N-terminal kinase activation (JNK, Western blot), actin microfilament organization (MF, immunocytochemistry), cellular viability (CV, vital staining), and apoptosis (annexin-V/PI cytofluorescence). The data were analyzed by ANOVA, followed by the Tukey test (p<0.05). Results (respect to controls): During the first two hours, the aqueous and lipid HPs increased by 2.054 and 1.573 times, respectively. Subsequently (after 2-4 h), cells responded by reorganizing the MF (perinuclear pattern with fibres) and activating the JNK (by 2 fold), with both co-localizing. Cell death started after 4 hours with an apoptotic phenotype, which progressed with cell detachment (6-8 h CV: 60.15% and 52.92%, respectively). Conclusions: The arsenite-induced cytotoxicity involved oxidative stress, followed by early cellular responses including MF changes and JNK activation. When exposure was prolonged, apoptosis was triggered. Since these modifications have been recognized as possible pro-carcinogenetic events (Arya et al., 2007), this model allows the study of early arsenic-related pro-carcinogenetic events and the assessment of nutritional chemopreventive approaches.