Abstract 12745: Interleukin-4 Promotes Procollagen Type-I Alpha 1 Gene Expression via Activator Protein 1 Activation in Cardiac Fibroblasts
Interleukin-4 (IL-4) activates the signal transducer and activator of transcription 6 signaling pathway, resulting in the upregulation of procollagen genes and promotion of collagen production in cardiac fibroblasts (CFs). In addition, transcription factors may participate in the transcriptional activation of collagen genes. We hypothesize that IL-4 activates activator protein 1 (AP-1) via c-Jun phosphorylation, promoting transcriptional activation of the procollagen type-I alpha 1 (Col1α1) gene and collagen type-I expression in CFs. Primary mouse CFs were used. Western blot analyses revealed that IL-4 (10 ng/ml) increased phosphorylation of c-Jun, a subunit of AP-1. Additionally, our experiments utilizing electrophoretic mobility shift assay (EMSA) revealed a significant increase in DNA binding activity for AP-1 in IL-4-treated CFs compared to control cells (1.00±0.07 to 2.14±0.38 fold change versus control, p<0.05). Here we aimed to determine whether IL-4-activated AP-1 participates in transcriptional activation of the Col1α1 gene leading to increased collagen type-I expression in CFs. To that end, we blocked AP-1 with shRNA lentiviral particles specific for c-Jun in CFs, detected Col1α1 mRNA by qRT-PCR, and measured collagen type-I by Western blot. We found that IL-4 significantly induced Col1α1 mRNA expression after incubation with control shRNA-transduced cells for 6 hours (1.01±0.01 to 1.52±0.07 fold change versus control, p<0.005), and it increased collagen type-I expression after 24 hours of incubation (1.00±0.01 to 1.95±0.12 fold change versus control, p<0.005). In contrast, IL-4 did not increase mRNA levels of Col1α1 (1.09±0.02 to 0.98±0.03, p>0.05) and the collagen type-I (0.95±0.05 to 1.01±0.10, p>0.05) in c-Jun shRNA-transfected cells. Our data demonstrate that IL-4-activated AP-1, an ubiquitous transcription factor containing phosphorylated c-Jun, enhanced Col1α1 gene expression and collagen type-I expression in CFs. Data generated from this study provides a novel molecular basis for potential treatment of cardiac fibrosis by targeting IL-4-induced signaling in CFs.
Author Disclosures: H. Peng: None. M. Wu: None. E. Peterson: None. N. Rhaleb: None.
- © 2016 by American Heart Association, Inc.