BackgroundThe potential mechanisms of microRNA-1 (miR-1) in the electrical remodeling of atrial fibrillation remain unclear. The purpose of this study was to evaluate the effects of miR-1 on the atrial effective refractory period (AERP) in a right atrial tachypacing model and to elucidate the potential mechanisms.Methods and ResultsQRT-PCR and western blot were used to detect the expression of the miR-1, KCNE1, and KCNB2 genes after 1-week of right atrial tachypacing in New Zealand white rabbits. The AERP was measured using a programmable multichannel stimulator, and atrial fibrillation was induced by burst stimulation in vivo. The slowly activating delayed rectifier potassium current (IKs) and AERP in atrial cells were measured by whole cell patch clamp in vitro. Right atrial tachypacing upregulated miR-1 expression and downregulated KCNE1 and KCNB2 in this study, while the AERP was decreased and the atrial IKs increased. The downregulation of KCNE1 and KCNB2 levels was greater when miR-1 was further upregulated through in vivo lentiviral infection. Electrophysiological tests indicated a shorter AERP, a great increase in the IKs and a higher atrial fibrillation inducibility. In addition, similar results were found when the levels of KCNE1 and KCNB2 were downregulated by small interfering RNA while keeping miR-1 level unaltered. Conversely, knockdown of miR-1 by anti-miR-1 inhibitor oligonucleotides alleviated the downregulation of KCNE1 and KCNB2, the shortening of AERP, and the increase in the IKs. KCNE1 and KCNB2 as the target genes for miR-1 were confirmed by luciferase activity assay.ConclusionsThese results indicate that miR-1 accelerates right atrial tachypacing-induced AERP shortening by targeting potassium channel genes, which further suggests that miR-1 plays an important role in the electrical remodeling of atrial fibrillation and exhibits significant clinical relevance as a potential therapeutic target for atrial fibrillation.

BackgroundA critical mechanism in atrial fibrillation (AF) is cardiac autonomic nerve remodeling (ANR). MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the post-transcriptional level. Numerous miRNAs are involved in diseases of the nervous and cardiovascular systems.ObjectiveWe aimed to assess the underlying role of miRNAs in regulating cardiac ANR in AF by right atrial tachypacing (A-TP) in canines.Methods and ResultsFollowing 4-week A-TP, the superior left ganglionated plexuses (SLGPs), which are embedded in the fat pads of the left atrium, were subjected to miRNA expression profiling to screen preferentially expressed miRNAs. Sixteen miRNAs showed significantly differential expression between the control and A-TP groups, including miR-206, miR-203, miR-224 and miR-137. In particular, we focused on miR-206, which was elevated ~10-fold in A-TP dogs. Forced expression of miR-206 through lentiviral infection based on A-TP in vivo significantly shortened the atrial effective refractory period (AERP) (81 ± 7 vs. 98 ± 7 ms, P < 0.05). Immunohistochemical analysis showed that the regeneration of nerves increased more than 2-fold by miR-206 overexpression (P < 0.01). The expression of superoxide dismutase 1 (SOD1) was repressed by miR-206 overexpression by Western blot and luciferase assay, indicative of SOD1 as a direct target of miR-206. Overexpression of miR-206 increased reactive oxygen species (ROS) levels in vitro and in vivo, whereas miR-206 silencing attenuated irradiation- or A-TP-induced ROS. Knockdown of SOD1 effectively abolished ROS reduction caused by miR-206 silencing.ConclusionsOur results found the differential expression of miRNAs in response to ANR in AF and elucidated the important role of miR-206 by targeting SOD1. The study illustrated the novel molecular mechanism of ANR and indicated a potential therapeutic target for AF.

The combination use of clopidogrel and certain types of PPIs (omeprazole, lansoprazole, esomeprazole, pantoprazole) increases the risk of MACE in patients with coronary artery disease. Only in the RMs of CYP2C19, PPIs were associated with significantly increased MACE in patients coadministered with clopidogrel.