Abstract 148: Sterol Regulatory Element-Binding Protein-1 Is Involved in the Development of Angiotensin II-Induced Cardiac Fibrosis
Sterol Regulatory Element Binding Protein (SREBP)-1 is a transcription factor for triglyceride synthesis. SREBP-1 is shown to contribute to the organ damages such as pancreatic beta cell, liver, and kidney; however, it is unclear whether SREBP-1 also contributes to the cardiac pathogenesis. We made cardiac dysfunction and fibrosis model by 2-week infusion of angiotensin II (A-II, 1.44 mg/kg BW/day). Mice were divided into followings (n=5∼6 in each group): wild with vehicle (WC), wild with A-II (WA), SREBP-1 knockout mice (SREBP-KO) with vehicle (SC), and SREBP-KO with A-II (SA). WA clearly demonstrated cardiac dysfunction and severe perivascular fibrosis compared to WC; however, these findings were not observed in SA compared to SC. We analyzed gene expression by DNA microarray using the software DAVID and quantitative RT-PCR to find gene clusters mostly illustrative for these phenotypes. Gene expression of extracellular matrix (Col1a, 3a, periostin) was increased in WA. Highly scored annotations in WA were chemokines (CCL5, CXCL10) and their receptors (CCR5, CXCR3), and Th2 cytokines (IL-13 and TGFb), suggesting that chronic inflammatory and repairing responses occurred. These changes were normalized in SA compared to SC. Expression of NOX4, a component of NADPH oxidase, was significantly increased in WA and SA compared to each control in a similar extent, suggesting that the Ang II-induced oxidative stress to the heart did not differ. To elucidate why the cardiac fibrosis differed between WA and SA, we analyzed the expression of transcription factors. Nrf2, a transcription factor for detoxification and anti-oxidant gene against to reactive oxygen species (ROS), was significantly decreased in WA compared to WC; however, it did not differ between in SA and SC. Furthermore, expression of the Nrf2-inducible genes HO-1 and NQO1, antioxidant genes, was significantly decreased in WA compared to WC; meanwhile, there were no differences between in SA and SC. [Conclusion] SREBP-1 may positively contribute to the A-II-induced cardiac fibrosis via the involvement of chronic inflammatory responses, which is induced partly by the reduction of antioxidant activity.
- © 2012 by American Heart Association, Inc.