Targeting miR-423-5p Reverses Exercise Training–Induced HCN4 Channel Remodeling and Sinus Bradycardia

• Published in: Circulation research Vol. 121; no. 9; pp. 1058 - 1068
• Main Authors: D’Souza, Alicia, Pearman, Charles M., Wang, Yanwen, Nakao, Shu, Logantha, Sunil Jit R.J., Cox, Charlotte, Bennett, Hayley, Zhang, Yu, Johnsen, Anne Berit, Linscheid, Nora, Poulsen, Pi Camilla, Elliott, Jonathan, Coulson, Jessica, McPhee, Jamie, Robertson, Abigail, da Costa Martins, Paula A., Kitmitto, Ashraf, Wisløff, Ulrik, Cartwright, Elizabeth J., Monfredi, Oliver, Lundby, Alicia, Dobrzynski, Halina, Oceandy, Delvac, Morris, Gwilym M., Boyett, Mark R.
• Format: Journal Article
• Language: English
• Published: United States American Heart Association, Inc 13.10.2017; Lippincott Williams & Wilkins Ovid Technologies; Lippincott Williams & Wilkins
• Subjects: Adolescent; Adult; Animal models; Animals; Bradycardia; Bradycardia - genetics; Bradycardia - metabolism; Bradycardia - physiopathology; Cardiac arrhythmia; Computer applications; Exercise - physiology; Fitness training programs; Gene Knockdown Techniques - methods; Gene Targeting - methods; Heart rate; Humans; Hyperpolarization; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels - genetics; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels - metabolism; Ion channels (cyclic nucleotide-gated); Male; Mice; Mice, Inbred C57BL; MicroRNAs - genetics; MicroRNAs - metabolism; miRNA; Molecular Medicine; Muscle Proteins - genetics; Muscle Proteins - metabolism; Nkx2.5 protein; Physical Conditioning, Animal - methods; Physical Conditioning, Animal - physiology; Physical training; Polymerase chain reaction; Potassium Channels - genetics; Potassium Channels - metabolism; Reverse transcription; Sinoatrial Node - metabolism; Sinoatrial Node - physiopathology; Sinus; Sinuses; Young Adult; sinoatrial node; ion channel remodeling; athletes; micro-RNAs; sinus bradycardia; exercise training
• DOI: 10.1161/CIRCRESAHA.117.311607
• ISSN: 0009-7330; 1524-4571

RATIONALE:Downregulation of the pacemaking ion channel, HCN4 (hyperpolarization-activated cyclic nucleotide gated channel 4), and the corresponding ionic current, If, underlies exercise training–induced sinus bradycardia in rodents. If this occurs in humans, it could explain the increased incidence of bradyarrhythmias in veteran athletes, and it will be important to understand the underlying processes. OBJECTIVE:To test the role of HCN4 in the training-induced bradycardia in human athletes and investigate the role of microRNAs (miRs) in the repression of HCN4. METHODS AND RESULTS:As in rodents, the intrinsic heart rate was significantly lower in human athletes than in nonathletes, and in all subjects, the rate-lowering effect of the HCN selective blocker, ivabradine, was significantly correlated with the intrinsic heart rate, consistent with HCN repression in athletes. Next-generation sequencing and quantitative real-time reverse transcription polymerase chain reaction showed remodeling of miRs in the sinus node of swim-trained mice. Computational predictions highlighted a prominent role for miR-423-5p. Interaction between miR-423-5p and HCN4 was confirmed by a dose-dependent reduction in HCN4 3′-untranslated region luciferase reporter activity on cotransfection with precursor miR-423-5p (abolished by mutation of predicted recognition elements). Knockdown of miR-423-5p with anti-miR-423-5p reversed training-induced bradycardia via rescue of HCN4 and If. Further experiments showed that in the sinus node of swim-trained mice, upregulation of miR-423-5p (intronic miR) and its host gene, NSRP1, is driven by an upregulation of the transcription factor Nkx2.5. CONCLUSIONS:HCN remodeling likely occurs in human athletes, as well as in rodent models. miR-423-5p contributes to training-induced bradycardia by targeting HCN4. This work presents the first evidence of miR control of HCN4 and heart rate. miR-423-5p could be a therapeutic target for pathological sinus node dysfunction in veteran athletes.