Abstract 1993: Histone Deacetylase -1 Induces Autophagy in Post-natal Ventricular Myocytes
Autophagy is a cellular process that involves macromolecular break-down of proteins and cellular organelles during nutrient deprivation or metabolic stress. Recently, autophagy has been detected in a number of cardiac pathologies however, the underlying mechanisms remain cryptic. Epigenetic changes by histone modifying deacetylases influence chromatin structure and gene transcription. In this report we provide new compelling evidence that the class I histone deacetylase HDAC1 sensitizes ventricular myocytes to autophagy induced by TNFa by a mechanism that disrupts NF-kB signaling. Cells treated with TNFa (100uM) displayed a 5.0 fold increase in NF-kB gene transcription (p<0.001) with no apparent change in viability compared to vehicle treated. However, in the presence of HDAC1, a significant increase in autophagosomes were observed in ventricular myocytes as evidenced by an increase in GFP-LC3 punctate staining and increased conversion of LC3I to LC3II. This coincided with a marked reduction in NF-kB activity and basal cell survival in cells treated with TNFa. Interestingly, HDAC1 mediated repression of NF-kB gene transcription and autophagy was associated with changes in Atg 5 and Atg 12 and abrogated by inhibition of HDAC 1 by trichostatin A (TSA, 50mM) or by deacetylase defective mutations of HDAC1 (H141A). To assess whether HDAC1 mediated repression of NF-kB transcription and autophagy induction was related to alterations in the DNA binding or transactivation capacity of NF-kB, we tested the impact of HDAC1 on heterologous fusion constructs comprised of the Gal4 DNA binding domain fused in frame to the transactivation domain of p65 NF-kB subunit. Wild type but not the deacetylase defective mutation of HDAC1 suppressed NF-kB gene transcription driven by Gal4 heterologous promoter. Furthermore, IKKb-mediated activation of NF-kB suppressed GFP-LC3 staining induced by TNFa. To our knowledge the data provide first direct evidence that autophagy induced by TNFa involves the deacetylase activity of HDAC1 and is operationally linked to NF-kB activation.