The protective effect of heat shock protein 70 (Hsp70) in atrial fibrillation in various cardiomyopathy conditions

Heat shock proteins (Hsp) protect myocardial cells from acute stress such as atrial fibrillation (AF) and also from the chronic stress. It is not understood that Hsp70 can prevent AF under cardiomyopathy (CM) conditions. Therefore, we hypothesized that Hsp70 might beneficially influence on the occurrence of AF in CM conditions. We purposed to investigate the correlation between Hsp70 and the AF inducibility in various CM conditions that are unclear. We constructed four different animal models using Sprague-Dawley rats: an ischemic CM group (n = 12), a non-ischemic dilated CM group (n = 12), a pressure-overload hypertrophic CM group (n = 12), and a sham group (CON, n = 12). After 4-6 weeks of intervention animals, AF was induced acutely prior to hemodynamic studies. Hemodynamic data using the Langendorff technique and histologic evaluation were conducted sequentially in all animal groups. Afterwards, levels of Hsp70 were measured from atrial tissues by real-time polymerase chain reaction study. The hemodynamic data and histologic studies proved that each animal model was suitable to this study protocol. All CM groups showed that Hsp70 was elevated significantly compared to the control groups (P < 0.005). Among these CM groups, the TAC group revealed lower Hsp70 levels and higher induction rates of atrial fibrillation than the other groups (P < 0.005). The level of Hsp70 was elevated in all the CM models and it was negatively correlated with AF induction rate in sham group. However, we could not find correlation between Hsp70 and AF among the CM models.