The imbalance between the synthesis of reactive oxygen species and their elimination by antioxidant defense systems results in macromolecular damage and disruption of cellular redox signaling, affecting cardiac structure and function, thus contributing to contractile dysfunction, myocardial hypertrophy, and fibrosis in chronic heart failure [chronic heart failure (CHF)]. The Kelch-like ECH-associated protein 1-nuclear factor erythroid 2-related factor 2 (Nrf2) pathway is an important antioxidant defense mechanism and is closely associated with oxidative stressmediated cardiac remodeling in CHF. In the present study, we investigated the regulation of myocardial Nrf2 in the postmyocardial infarction (post-MI) state. Six weeks post-MI, Nrf2 protein was downregulated in the heart, resulting in a decrease of Nrf2-targeted antioxidant enzymes, whereas paradoxically the transcription of Nrf2 was increased, suggesting that translational inhibition of Nrf2 may contribute to the dysregulation in CHF. We therefore hypothesized that microRNAs may be involved in the translational repression of Nrf2 mRNA in the setting of CHF. Using quantitative real-time PCR analysis, we found that three microRNAs, including microRNA-27a, microRNA-28-3p, and microRNA-34a, were highly expressed in the left ventricle of infarcted hearts compared with other organs. Furthermore, in vitro analysis revealed that cultured cardiac myocytes and fibroblasts expressed these three microRNAs in response to TNF-α stimulation. These microRNAs were preferentially incorporated into exosomes and secreted into the extracellular space in which microRNA- enriched exosomes mediated intercellular communication and Nrf2 dysregulation. Taken together, these results suggest that increased local microRNAs induced by MI may contribute to oxidative stress by the inhibition of Nrf2 translation in CHF. NEW & NOTEWORTHY The results of this work provide a novel mechanism mediated by microRNA-enriched exosomes, contributing to the nuclear factor erythroid 2-related factor 2 dysregulation and subsequent oxidative stress. Importantly, these new findings will provide a promising strategy to improve the therapeutic efficacy through targeting nuclear factor erythroid 2-related factor 2-related microRNAs in the chronic heart failure state, which show potentially clinical applications.
|Journal||American Journal of Physiology - Heart and Circulatory Physiology|
|State||Published - May 2018|
Bibliographical noteFunding Information:
This work was supported by National Heart, Lung, and Blood Institute Grant P01-HL-62222 (to I. H. Zucker).
using ImageJ software [National Institutes of Health (NIH), Bethesda, MD]. The percentage of scar area to the whole LV was used to quantify infarct size. All animal experiments were approved by the Institutional Animal Care and Use Committee of the University of Nebraska Medical Center and were carried out under the guidelines of the NIH Guide for the Care and Use of Laboratory Animals.
© 2018 the American Physiological Society.
- Exosomal microRNAs
- Myocardial infarction
- Nuclear factor erythroid 2-related factor 2 dysregulation
- Oxidative stress
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)