Nadia Panera, Daniela Gnani, Emanuela Piermarini, Stefania Petrini, Enrico Bertini, Valerio Nobili, Anna Pastore, Fiorella Piemonte, Anna Alisi

Cardiac hypertrophy occurs in response to different stimuli and is mainly characterized by an enlargement of cardiomyocyte size. During hypertrophy, cardiomyocytes undergo not only radical changes of the cellular architecture but also activation of signaling cascades that counteract the atrophy genes. Experimental studies highlighted that chronic low concentrations of H2O2, induce a hypertrophic phenotype, while higher levels of H2O2 promote apoptosis. In this study, we explored the early and long-term hypertrophic effects of high concentrations of H2O2 on H9c2 rat cardiomyocytes. We found that 2-h stimulation with 200μM H2O2 caused an early dramatic reduction of cell viability, accompanied, 5-days later, by increased cell size and up-regulation of atrial natriuretic peptide transcription. This hypertrophic phenotype is associated to increased Akt phosphorylation and a consequent reduction of the FOXO3a and atrogin-1 gene expression. Moreover, we observed that H2O2 caused the overexpression of miR-212/miR-132 cluster concomitantly to a down-regulation of PTEN transcript without changes in its protein expression. Noteworthy, we found that the treatment of cardiomyocytes with H2O2 further led to an increase of oxidized glutathione and glutathionylation of proteins, including PTEN. In conclusion, our results permit to reconstruct the molecular cascade triggering the cardiomyocyte hypertrophy upon high concentrations of H2O2.