Abstract 190: HSP27 is Sufficient and Required for Prevention of Tachycardia Induced Remodeling in a Cell Model for Tachypacing

Abstract

We previously found evidence that heat shock protein (HSP) induction protects against the promotion of atrial fibrillation (AF) by atrial tachypacing-remodeling in dogs. In this study, we evaluated the effect of HSP induction in a tachypaced atrial cell-line (HL-1) model of tachycardia-remodeling. Methods: The effects of tachypacing HL-1 myocytes (3 Hz, 0 – 4 hrs) on Ca 2+ transients (CaT) and cell shortening (CS), were studied with and without HSP-inducing pre-treatments like mild heat shock (HS), or the non-toxic inducer geranylgeranylacetone (GGA), transient transfection of human HSP70, HSP27, a phosphorylation deficient mutant HSP27-AAA or the phospho-mimicking mutant HSP27-DDD. Knockdown of HSP27 was performed with short-hairpin forming siRNA. Results: In HL-1 myocytes, tachypacing significantly and progressively reduced CaT and CS after 4 hours (Fig A ). HSP induction by HS or GGA protected HL-1 myocytes against suppression of CaT and CS by 4 hours of tachypacing. Protective effects were also seen upon transfection with HSP27 and a phosphorylation-mimicking HSP27 mutant, but not by HSP70 or a non-phosphorylatable HSP27-mutant construct (Fig B ). Knockdown of HSP27 with shRNA prevented GGA-mediated protection (Fig C ). Conclusions: Our findings indicate that HSP27 induction protects against AF-promoting remodeling, that the protective effect requires HSP27 phosphorylation, and HSP27 is sufficient for protection. These findings advance our understanding of the biochemical determinants of the protective effects of HSP induction against atrial tachycardia remodeling.