Abstract 13694: Hsf1 Attenuates Pressure Overload Induced-cardiac Fibrosis via Inhibiting Smad3 Phosphorylation and Nuclear Translocation

Abstract

Introduction: Heat shock transcription factor 1 (HSF1) is an intrinsic cardioprotective factor against cardiac hypertrophy. However, little is known about the role of HSF1 in cardiac fibrosis. Here we hypothesize that HSF1 reverses pressure overload induced-cardiac fibrosis via inhibiting Smad3 phosphorylation and nuclear translocation. Methods: Human tissue samples were collected from the left ventricles of dilated cardiomyopathy patients undergoing heart transplant and normal heart donors for control and were interrogated via western blot and realtime-PCR. A HSF1 transgenic (TG) mouse was generated. Transverse aortic constriction (TAC) was performed with wild type (WT) mice as control and cardiac structure and function were measured by echocardiography and pathological test. Cardiomyocytes (CMs) isolated from neonatal mice were imposed with mechanical stretch (MS) in vitro. Results: HSF1 phosphorylation at Ser230 was significantly decreased in failing hearts (55% vs normal hearts) characterized with significant cardiac fibrosis manifested with increased expression of collagen III and connective tissue growth factor (CTGF) . WT mice and TG mice were subjected to TAC. After 4 weeks of TAC, WT mice developed a remarkable maladaptive hypertrophy and cardiac fibrosis in comparison to WT mice. TG mice exhibited a smaller LV end-diastolic diameter (LVEDD), higher ejection fraction (EF), decreased LV weight/tibial length (LW/TL) and CMs cross sectional area (CSA), less interstitial and perivascular fibrosis, as well as preserved expression of collagen III and CTGF compared to WT mice. TG mouse hearts also showed reduced phosphorylation and nuclear translocation of Smad3 than WT mice. MS was found to significantly inhibit HSF1 phosphorylation, but promoted the Smad3 phosphorylation and nuclear translocation in CMs. Co-Immunoprecipitation showed that HSF1 directly binds Smad3 in CMs in vitro, which was decrease by MS or treatment with KNK437 (HSF1 inhibitor). TG mice demonstrate more of HSF1 and Smad3 binding and less phosphorylation and nuclear translocation of Smad3 compared to WT mice after TAC. Conclusion: HSF1 attenuates pressure overload induced-cardiac fibrosis by inhibiting Smad3 phosphorylation and nuclear translocation.