temporal and gefitinib-sensitive regulation of cardiac cytokine expression via chronic beta-adrenergic receptor stimulation.pdf

Chronic stimulation<br>of -adrenergic receptors (AR) can promote survival signaling<br>via transactivation of epidermal growth factor receptor (EGFR)<br>but ultimately alters cardiac structure and contractility over time, in<br>part via enhanced cytokine signaling. We hypothesized that chronic<br>catecholamine signaling will have a temporal impact on cardiac<br>transcript expression in vivo, in particular cytokines, and that EGFR<br>transactivation plays a role in this process. C57BL/6 mice underwent<br>infusion with vehicle or isoproterenol (Iso)  gefitinib (Gef) for 1 or<br>2 wk. Cardiac contractility decreased following 2 wk of Iso treatment,<br>while cardiac hypertrophy, fibrosis, and apoptosis were enhanced at<br>both timepoints. Inclusion of Gef preserved contractility, blocked<br>Iso-induced apoptosis, and prevented hypertrophy at the 2-wk timepoint,<br>but caused fibrosis on its own. RNAseq analysis revealed<br>hundreds of cardiac transcripts altered by Iso at each timepoint with<br>subsequent RT-quantitative PCR validation confirming distinct temporal<br>patterns of transcript regulation, including those involved in<br>cardiac remodeling and survival signaling, as well as numerous<br>cytokines. Although Gef infusion alone did not significantly alter<br>cytokine expression, it abrogated the Iso-mediated changes in a<br>majority of the AR-sensitive cytokines, including CCL2 and TNF-.<br>Additionally, the impact of AR-dependent EGFR transactivation on<br>the acute regulation of cytokine transcript expression was assessed in<br>isolated cardiomyocytes and in cardiac fibroblasts, where the majority<br>of Iso-dependent, and EGFR-sensitive, changes in cytokines occurred.<br>Overall, coincident with changes in cardiac structure and contractility,<br>AR stimulation dynamically alters cardiac transcript expression over<br>time, including numerous cytokines that are regulated via EGFRdependent<br>signaling.