Abstract 606: Stimulation of Cardiomyocyte A- and B-Adrenoceptors Uniquely Regulates Exosome Generation and Mirna Content

Background and Purpose: Influence of adrenoceptor (AR) signaling for the regulation of exosomes secreted from cardiomyocytes is unknown and since catecholamines are increased in heart failure (HF), there is interest in uncovering whether α- or β-ARs can induce specific changes in circulating blood exosomes in HF. In this study, we have evaluated whether α- or β-AR stimulation of neonatal rat ventricle myocytes (NRVMs) can alter the number, size or microRNA (miR) content of secreted exosomes. Methods and Results: The number and size distribution of exosomes from NRVMs were evaluated by Nanosight NS300. Phenylephrine (PE, 10 uM for 3 days), an α-AR agonist, increased exosome number significantly of NRVM compared than vehicle (PBS) treatment group (Veh: 7.82X10 8 ± 5.06X10 7 and PE: 10.09X10 8 ± 15.0 X10 7 / 1X10 6 NRVMs, n=3) but Isoproterenol (ISO, 1uM), a β-AR agonist, did not. Both agonists had no effect on exosome size distribution. After purifying total RNA from secreted exosomes, we evaluated the expression level of 37 candidate miR’s, which were selected from previous microarray data. ISO treatment decreased 14 miR’s (miR-222, -106a, -292a, -181b, -210, -489, -214, -1947, -195, -17, -7b, -93, -532 and -19a) and PE increased 5 miR’s (miR-20a, -210, -17-1, -Let7a, and 146b). Importantly, PE or ISO regulated any identical miR’s. As a control for treatment effects, we found that PE and ISO elevated myocyte mRNA levels of ANP and BNP to similar degrees. Conclusions: Both α- and β-AR agonists are can stimulate cardiomyocyte hypertrophy to similar degrees, however they have distinct regulatory patterns for secreted exosomes. This includes the number produced and more importantly, miR content. These miR’s and exosomes found in circulating blood may be able to distinguish and be biomarkers for different modes of maladaptive cardiac hypertrophy and HF.