Apoptosis induced by in vivo Interferon-a2b (IFN) treatment in preneoplastic rat livers: Foxo3a and wnt/b-catenin pathway participation

PARODY J P; ALVAREZ M L; CEBALLOS M P; FRANCÉS D E; CARNOVALE C E; CARRILLO M C

Barcelona

Congreso; 47th annual meeting of the European Association for the Study of the Liver (EASL).; 2012

Background: Previously we have demonstrated that in vivo IFN treatment in our rat liver preneoplastic model attenuates the aberrant activated wnt/beta-catenin pathway. Furthermore, we observed a reduction of altered hepatic foci (AHF) by an apoptotic process mediated by reactive oxygen species (ROS) and TGF-beta1. FoxO3a is a transcription factor whose subcellular localization is regulated by Akt and JNK phosphorylation. Nuclear FoxO3a promotes the transcription of genes implicated in apoptosis and cell cycle arrest. Since FoxO3a also interacts with beta-catenin, we decided to analyze the participation of this transcription factor in the events mentioned before.Methods: Wistar rats were subjected to a two-phase model of hepatocarcinogenesis (IP). A group of IP rats was treated with IFN (IP+IFN). Another group of IP rats was treated with IFN and ascorbic acid (IP+IFN+ASC). AHF detection was assessed by confocal immunofluorescence. Activation of Akt and JNK kinases, FoxO3a phosphorylated by Akt and nuclear localization of FoxO3a were evaluated by immunoblotting with specific antibodies. A co-immunoprecipitation assay was performed to analyze beta-catenin/TCF and beta-catenin/FoxO3a interaction. Finally, expression of FoxO3a target gene was evaluated by semiquantitative RT-PCR.Results: p-Akt and p-(Ser253)-FoxO3a levels were significantly decreased in IP+IFN (Akt: -82%*; p-FoxO3a: -68%*) and IP+IFN+ASC (Akt: -92%*; p-FoxO3a: -79%*) groups compared with IP. Total Akt levels were unchanged in all groups. Conversely, p-JNK levels were significantly increased (+390%*) in IP+IFN group compared with IP. In nuclear fraction, FoxO3a levels were significantly increased (+210%*) in IP+IFN group compared with IP. By co-immunoprecipitation assay we found higher beta-catenin/TCF association in IP and IP+IFN+ASC groups; and higher beta-catenin/FoxO3a association in IP+IFN group. Expression of p130 gene was significantly upregulated (+110%*) in IP+IFN group. *p<0.05.Conclusion: Our data suggest that in vivo IFN treatment negatively regulates Akt activation by a mechanism not mediated by ROS. Moreover, IFN-induced ROS promotes JNK activation and FoxO3a nuclear localization where promotes transcription of genes related with apoptosis and cell cycle arrest. Finally, ROS stimulates beta-catenin/FoxO3a association instead of beta-catenin/TCF association, enhancing FoxO3a activity and leading to an attenuation of the TCF transcriptional activity. As a consequence, apoptosis pathway is activated favoring the elimination of preneoplastic cells.