Abstract 12229: MicroRNA Regulation of JAK-STAT System in the Atrial Fibrillation-Related Fibrotic Response
Introduction: MicroRNAs (miRNAs) are involved in cardiac remodeling, but their role in atrial fibrillation (AF) is poorly understood. JAK-STAT signalling is activated by the pro-fibrotic mediator PDGF, but its contribution to AF substrate formation is unknown. Here, we investigated miRNA regulation of the JAK-STAT system in in the heart failure (HF) induced AF fibrotic substrate.
Methods: HF was induced in dogs by ventricular tachypacing (VTP, 240 bpm) for 2 weeks. Fibroblasts (FBs) isolated from the left atrium (LA) and left ventricle (LV) of control (CTL) dogs were treated with PDGF-AB. PDGF, JAK2, STAT3 and miRNA expression was assessed by qPCR. JAK2, STAT3 and collagen-I (COL-1) proteins were quantified by Western Blot. miRNA targets were validated by luciferase reporter assay. miRNA mimic or antisense oligonucleotides (AMOs) were used for miRNA manipulation in FBs.
Results: HF dogs developed AF susceptibility and LA-selective fibrosis beginning at 1 wk VTP. PDGF and JAK2 mRNA, along with phosphorylated (activated) JAK2 protein, were increased in HF atria (by 1.4-2.9* fold, *p<0.05). miR-30a and miR-133a were predicted bioinformatically to target JAK2, and were downregulated by 51%-52%** and 48%-71%** (**p<0.01) in HF LA FBs at 1-2 wk VTP. PDGF-AB increased the expression of JAK2 and STAT3 mRNA (by 1.4-1.5* fold) and COL-1 protein (by 2*** fold, ***p<0.001) in canine LA FBs, while reducing the expression of miR-30a and miR-133a (by ~50%-80% ***). Smaller changes were seen in LV FBs with PDGF-stimulation. Luciferase assay confirmed miR-30a and miR-133a targeting of JAK2. Overexpression of miR-133a downregulated JAK2 mRNA (by 30%***) and protein (by 50%, p=0.05) in LA FBs. This effect was abolished by co-transfection of miR-133a and AMO-133a. The upregulation of JAK2 and COL-1 expression induced by PDGF-AB stimulation was reversed by miR-133a overexpression in LA FBs (reduced by 49%* and 53%*** versus PDGF stimulation alone).
Conclusions: PDGF-induced disinhibition of JAK2 expression by downregulation of miR-30a and miR-133a may contribute to AF-associated fibrotic responses. MicroRNA targeting of the JAK-STAT system regulates LA FB function, appears to be involved in HF-induced LA fibrosis and is a potential therapeutic target for AF prevention.
Author Disclosures: Y. Chen: None. S. Surinkaew: None. J. Xiao: None. C.T. Wu: None. H. Huang: None. Y. Sun: None. D. Dobrev: None. S. Nattel: None.
- © 2015 by American Heart Association, Inc.