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Mitochondrial dysfunction, caspase activation and caspase-dependent DNA fragmentation are involved in cell damage in many tissues. However, differentiated cardiomyocytes repress the expression of the canonical apoptotic pathway and their death during ischemia is caspase-independent. The atypical BH3-only protein Bnip3 is involved in the process leading to caspase-independent DNA fragmentation in cardiomyocytes. However, the pathway by which DNA degradation ensues following Bnip3 activation is not resolved. To identify the mechanism involved, we analyzed the interdependence of Bnip3, Nix and EndoG in mitochondrial damage and DNA fragmentation during experimental ischemia in neonatal rat ventricular cardiomyocytes. Our results show that the expression of EndoG and Bnip3 increases in the heart throughout development, while the caspase-dependent machinery is silenced. TUNEL-positive DNA damage, which depends on caspase activity in other cells, is caspase-independent in ischemic cardiomyocytes and ischemia-induced DNA high and low molecular weight fragmentation is blocked by repressing EndoG expression. Ischemia-induced EndoG translocation and DNA degradation are prevented by silencing the expression of Bnip3, but not Nix, or by overexpressing Bcl-xL. These data establish a link between Bnip3 and EndoG-dependent, TUNEL-positive, DNA fragmentation in ischemic cardiomyocytes in the absence of caspases, defining an alternative cell death pathway in postmitotic cells. ; The work was supported by the Ministry of Science and Innovation of Spain (SAF2005-02197 and SAF2008-02271) to DS and Programa de Suport a Grups de Recerca de Catalunya from the Government of Catalonia (AGAUR) (SGR2005-00628) and Ciberned from the Spanish Government to JXC, Instituto de Salud Carlos III -Ministerio de Sanidad y Consumo (FIS) (PI04/2537 and PS09/00140) to ML. JZ was recipient of a pre-doctoral fellowship (FPI program) from the Ministry of Education and Science of Spain and JY is recipient of a fellowship from the Universitat de Lleida. URLs: Ministry of Science and Innovation of Spain: http://www.micinn.es; AGAUR: http://www10.gencat.cat/agaur_web/AppJava/catala/index.jsp; Ministry of Education: http://www.educacion.es/portada.html; Instituto de Salud Carlos III: http://www.isciii.es/htdocs/index.jsp. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Glioblastoma multiforme is resistant to conventional anti-tumoral treatments due to its infiltrative nature and capability of relapse; therefore, research efforts focus on characterizing gliomagenesis and identifying molecular targets useful on therapy. New therapeutic strategies are being tested in patients, such as Histone deacetylase inhibitors (HDACi) either alone or in combination with other therapies. Here two HDACi included in clinical trials have been tested, suberanilohydroxamic acid (SAHA) and valproic acid (VPA), to characterize their effects on glioma cell growth in vitro and to determine the molecular changes that promote cancer cell death. We found that both HDACi reduce glioma cell viability, proliferation and clonogenicity. They have multiple effects, such as inducing the production of reactive oxygen species (ROS) and activating the mitochondrial apoptotic pathway, nevertheless cell death is not prevented by the pan-caspase inhibitor Q-VD-OPh. Importantly, we found that HDACi alter cell cycle progression by decreasing the expression of G2 checkpoint kinases Wee1 and checkpoint kinase 1 (Chk1). In addition, HDACi reduce the expression of proteins involved in DNA repair (Rad51), mitotic spindle formation (TPX2) and chromosome segregation (Survivin) in glioma cells and in human glioblastoma multiforme primary cultures. Therefore, HDACi treatment causes glioma cell entry into mitosis before DNA damage could be repaired and to the formation of an aberrant mitotic spindle that results in glioma cell death through mitotic catastrophe-induced apoptosis. ; This work was supported by the Spanish Ministry of Health grant ISCIII and the European Fund for Regional Development (FEDER) PS09/00140 to ML, ISCIII-PI080790 to JH and Programa de Suport a Grups de Recerca from the Government of Catalonia (AGAUR) (2009-SGR-346) to ML, DS and JXC.

The endonuclease G gene (Endog), which codes for a mitochondrial nuclease, was identified as a determinant of cardiac hypertrophy. How ENDOG controls cardiomyocyte growth is still unknown. Thus, we aimed at finding the link between ENDOG activity and cardiomyocyte growth. Endog deficiency induced reactive oxygen species (ROS) accumulation and abnormal growth in neonatal rodent cardiomyocytes, altering the AKT-GSK3β and Class-II histone deacethylases (HDAC) signal transduction pathways. These effects were blocked by ROS scavengers. Lack of ENDOG reduced mitochondrial DNA (mtDNA) replication independently of ROS accumulation. Because mtDNA encodes several subunits of the mitochondrial electron transport chain, whose activity is an important source of cellular ROS, we investigated whether Endog deficiency compromised the expression and activity of the respiratory chain complexes but found no changes in these parameters nor in ATP content. MtDNA also codes for humanin, a micropeptide with possible metabolic functions. Nanomolar concentrations of synthetic humanin restored normal ROS levels and cell size in Endog-deficient cardiomyocytes. These results support the involvement of redox signaling in the control of cardiomyocyte growth by ENDOG and suggest a pathway relating mtDNA content to the regulation of cell growth probably involving humanin, which prevents reactive oxygen radicals accumulation and hypertrophy induced by Endog deficiency. ; This work was supported by Grant SAF2013–44942R from the Ministerio de Economía y Competitividad (MINECO) to DS, Grant 20153810 from Fundació La Marató de TV3 to DS, Program "Redes Temáticas de Investigación Cooperativa en Salud" (RETICS) Grants RD12/0042/0035, RD12/0042/0056 and RD12/0042/0021, Red de Investigación Cardiovascular (RIC) from the Instituto de Salud Carlos-III (ISCIII) to DS, DG-D and JV, Grant 2009SGR-346 from the Agència de Gestió d'Ajuts Universitaris i de Recerca (AGAUR) from the Government of Catalonia to DS. AB is supported by Fundació La Marató de TV3 and GB is supported by a predoctoral contract from the Universitat de Lleida.