Heart‐Brain Communication by Extracellular Vesicles Contributes to the Sympatho‐Excitation in Chronic Heart Failure by Targeting Nrf2/ARE Signaling

Abstract

In previous studies we showed that cardiac derived miRNA-enriched EVs contribute to the dysregulation of Nrf2/antioxidant enzyme signaling in the myocardium via intercellular cross-talk. We also showed that Nrf2 signaling was reduced in sympatho-regulatory areas of the brain in rats with chronic heart failure (CHF). However, it is unclear if cardiac-derived EVs circulate to the central nervous system to evoke sympatho-excitation by disrupting central redox homeostasis. To investigate the underlining mechanisms by which the heart communicates with the brain in CHF, we employed the rat myocardial infarction (MI)-induced CHF model to isolate and characterize EVs derived from the myocardium in the circulation and in brain tissue using differential ultracentrifugation, transmission electron microscope (TEM), NanoSight light scattering, western blotting and qRT-PCR. EVs from rats with CHF were microinjected into the rostral ventrolateral medulla (RVLM) of normal rats in order to determine if the pathophysiological phenotype (sympatho-excitation) could be transferred from CHF-EVs to normal animals by determining plasma norepinephrine (NE) concentration and recording renal sympathetic nerve activity (RSNA). In vitro EV-labeling, IVIS imaging system and cardiac-specific membrane GFP+ transgenic mice were used to track the brain distribution of cardiac-derived EVs. The data demonstrate that Nrf2 dysregulation in the RVLM of CHF rats is associated with an up-regulation of Nrf2-targeting miRNAs, which are highly enriched in cardiac-derived and circulating EVs from CHF rats. Importantly, Nrf2-targeting miRNAs and cardiac-specific miRNAs were also abundant in brain-derived EVs, suggesting brain distribution of cardiac-derived EVs. Moreover, circulating EVs labelled with PKH26 red fluorescent dye and systemically administrated were also observed to distribute predominately in the brain and to be taken up by neurons in the RVLM. Brain sections from cardiac-specific membrane GFP+ transgenic mice further support inter-organ communication. Circulating EVs derived from CHF rats injected into the RVLM of normal rats evoked an increase in RSNA and plasma NE concentration compared to circulating EVs from Sham rats. These phenotypic changes could be attributed to CHF-EV-mediated Nrf2 down-regualtion and subsequent oxidative stress increase in the RVLM which was restored by CHF-EV transfections with antagomirs inhibiting Nrf2-targeting miRNAs (See Figure). Taken together, this study shows that post MI cardiac miRNA-enriched EVs mediate the Heart-Brain crosstalk in the oxidative regulation of sympathetic outflow through targeting the Nrf2/Antioxidant signaling pathway. These data suggest a new endocrine signaling pathway regulating sympathetic outflow in CHF that can be exploited for novel therapeutics.