Human atrial ion channel and transporter subunit gene-expression remodeling associated with valvular heart disease and atrial fibrillation

Background - Valvular heart disease (VHD), which often leads to atrial fibrillation (AF), and AF both cause ion-channel remodeling. We evaluated the ion-channel gene expression profile of VHD patients, in permanent AF (AF-VHD) or in sinus rhythm (SR-VHD), in comparison with patients without AF or VHD, respectively. Methods and Results - We used microarrays containing probes for human ion-channel and Ca2+-regulator genes to quantify mRNA expression in atrial tissues from 7 SR-VHD patients and 11 AF-VHD patients relative to 11 control patients in SR without structural heart disease (SR-CAD). From the data set, we selected for detailed analysis 59 transcripts expressed in the human heart. SR-VHD patients differentially expressed 24/59 ion-channel and Ca2+-regulator transcripts. There was significant overlap between VHD groups, with 66% of genes altered in SR-VHD patients being similarly modified in AF-VHD. Statistical differences between the AF- and SR-VHD groups identified the specific molecular portrait of AF, which involved 12 genes that were further confirmed by real-time reverse transcription-polymerase chain reaction. For example, phospholamban, the beta-subunit MinK (KCNE1) and MIRP2 (KCNE3), and the 2-pore potassium channel TWIK-1 were upregulated in AF- VHD compared with SR-VHD, whereas the T-type calcium-channel Cav3.1 and the transient-outward potassium channel Kv4.3 were downregulated. Two-way hierarchical clustering separated SR-VHD from AF- VHD patients. AF- related changes in L-type Ca2+-current and inward-rectifier current were confirmed at protein and functional levels. Finally, for 13 selected genes, SR restoration reversed ion-channel remodeling. Conclusions - VHD extensively remodels cardiac ion-channel and transporter expression, and AF alters ion-channel expression in VHD patients.