Abstract 138: Identification of a Novel Small Molecule Activator of ATF6 that Confers Protection Against Ischemia/reperfusion Injury in the Heart

Abstract

Rationale: Reactive oxygen species generated during myocardial ischemia/reperfusion (I/R) potentiate myocyte death and cardiac dysfunction. Recently, our lab published a newly described role for the adaptive ER stress sensor and transcription factor, ATF6, as a novel inducer of an adaptive antioxidant gene family. These results highlight the need for the development of small molecule drug candidates that preferentially activate endogenous ATF6 to promote the adaptive effects of ER stress and ameliorate myocardial I/R damage. To this end we used of a cell-based high throughput-screen to identify a novel small molecular activator of endogenous ATF6, herein called compound 147, and tested its efficacy in cardiac myocytes and in the heart. Objective/Methods: The ability of compound 147 to activate endogenous ATF6, as measured by nuclear localization of ATF6 and ATF6-specific target gene induction was examined in cultured neonatal rat ventricular myocytes (NRVM). The effects of compound 147 on the viability of NRVM treated with H2O2 to generate ROS, or simulated I/R were assessed. Finally, the effects of compound 147 in the mouse heart were examined in vivo by administering the compound to mice and, 24h later, determining the effects of simulated I/R on cardiac myocytes isolated from the mice, or determining the effects of ex vivo I/R on hearts isolated from compound 147-treated mice. Results: Compared to a control compound, treatment of NRVM with compound 147 specifically and acutely activated ATF6 and primed cells to mount an adaptive response when treated with H2O2 or subjected to simulated I/R. Treatment of both neonatal and adult ventricular myocytes with compound 147 increased survival in cells subjected to simulated I/R. Compared to control, the cardiac myocytes and hearts from mice treated with compound 147 exhibited increased viability and functional recovery in response to I/R, respectively. Conclusions: Compound 147 specifically activates ATF6 in cardiac myocytes and confers cardioprotection during I/R, in vitro and in vivo . Thus, compound 147 represents a potential first- in-class small molecule drug candidate that enhances myocardial recovery from I/R damage, specifically by activating the endogenous adaptive ATF6 gene program in the heart.