Chronic Atrial Fibrillation Increases MicroRNA-21 in Human Atrial Myocytes Decreasing L-Type Calcium Current

Abstract

Background— Atrial fibrillation is characterized by progressive atrial structural and electrical changes (atrial remodeling) that favor arrhythmia recurrence and maintenance. Reduction of L-type Ca 2+ current ( I Ca,L ) density is a hallmark of the electrical remodeling. Alterations in atrial microRNAs could contribute to the protein changes underlying atrial fibrillation–induced atrial electrical remodeling. This study was undertaken to compare miR-21 levels in isolated myocytes from atrial appendages obtained from patients in sinus rhythm and with chronic atrial fibrillation (CAF) and to determine whether L-type Ca 2+ channel subunits are targets for miR-21. Methods and Results— Quantitative polymerase chain reaction analysis showed that miR-21 was expressed in human atrial myocytes from patients in sinus rhythm and that its expression was significantly greater in CAF myocytes. There was an inverse correlation between miR-21 and the mRNA of the α1c subunit of the calcium channel (CACNA1C) expression and I Ca,L density. Computational analyses predicted that CACNA1C and the mRNA of the β2 subunit of the calcium channel (CACNB2) could be potential targets for miR-21. Luciferase reporter assays demonstrated that miR-21 produced a concentration-dependent decrease in the luciferase activity in Chinese Hamster Ovary cells transfected with CACNA1C and CACNB2 3′ untranslated region regions. miR-21 transfection in HL-1 cells produced changes in I Ca,L properties qualitatively similar to those produced by CAF (ie, a marked reduction of I Ca,L density and shift of the inactivation curves to more depolarized potentials). Conclusions— Our results demonstrated that CAF increases miR-21 expression in enzymatically isolated human atrial myocytes. Moreover, it decreases I Ca,L density by downregulating Ca 2+ channel subunits expression. These results suggested that this microRNA could participate in the CAF-induced I Ca,L downregulation and in the action potential duration shortening that maintains the arrhythmia.

Tbx20 controls the expression of the KCNH2 gene and of hERG channels

“…Therefore, Tbx20 effects on the L-type Ca 2+ current (I CaL ) were tested in both HL-1 cells and hiPSC-CMs. In HL-1 cells, I CaL was measured using Ba 2+ as a charge carrier (I Ba ) (15,18). Fig.…”

“…HL-1 and Chinese hamster ovary cells were transiently transfected by using Lipofectamine 2000 and FuGENE X-tremeGENE, respectively, and cultured as described (15,17,18,30).…”

“…Currents were recorded using the whole-cell patch-clamp technique (15,17,18,30). Series resistance was compensated manually using the compensation unit of the Axopatch amplifier; ≥80% compensation was achieved.…”

Atrial Fibrillation-Mediated Upregulation of miR-30d Regulates Myocardial Electrical Remodeling of the G-Protein-Gated K⁺ Channel, <i>I</i>_K.ACh

“…[19][20][21][22] Although the molecular mechanisms underlying post-transcriptional ion channel remodeling in AF cardiomyocytes remain unresolved, recent studies have pointed out several miRNAs as key regulators of the Ca 2+ current (ICa) and IK1 in AF cardiomyocytes. 13, 14 To date, a pair of miRNAs with an AF history of 6 months or longer, whose age ranged from 60 to 79 years. Accordingly, to the best of our knowledge, miR-30d was identified for the first time as one of the most abundantly expressed and significantly upregulated miRNA by this comprehensive analysis of miRNA expression profiles in the human atrium with persistent AF.…”

A New Insight into the Molecular Mechanism of Atrial Fibrillation: The Role of MicroRNAs

“…This finding suggests that there is more than one site of action of miR-21. miR-150 prevents fibrosis, and its expression is significantly reduced in patients with chronic atrial fibrillation [5,6]. …”