Abstract 456: Role of Signal Transducer and Activator of Transcription protein (STAT)-1 in the Angiotensin II-induced Cardiovascular Damage
Background: Inflammation participates importantly in hypertensive organ damage. Angiotensin II (Ang II) plays a crucial role in hypertension and induces inflammation. An essential mediator of inflammation is the transcription factor STAT1 which is activated by interferon but also by Ang II. We hypothesized that activation of STAT1 during Ang II infusion upregulates chemokines, enhances chemotaxis and consequently results in heart fibrosis and vessel dysfunction independent on blood pressure and hypertrophy
Methods: C57BL/6, C57BL/6 receiving candesartan (5mg/kg) and STAT1-/- mice received infusion of Ang II 1.5 μg/g/day or placebo for 4 weeks (n=9/group). Blood pressure was measured using tail cuff pletysmography. Expression of chemokines Cxcl10, Cxcl9 and MCP-1 as well as Nos2 were investigated. Small mesenteric arteries (SMA) were mounted in a wire myograph to assess their function. Cardiac hypertrophy and inflammation (CD45 staining) and fibrosis (hydroxyproline assay) were determined.
Results: Ang II caused expression of IFNg in C57BL/6 and STAT1-/- in vitro and in vivo. Blood pressure and cardiac hypertrophy did not differ between angiotensin treated C57BL/6 and STAT1-/- mice. Ang II increased in C57BL/6 expression of STAT1 dependent genes of chemokines and Nos2 (Cxcl10: 4.8-fold, Cxcl9: 3.4-fold, MCP-1: 6.6-fold, Nos2: 2.6-fold; all P<0.05) whereas this remained abolished in STAT1-/- mice. Ang II lead in STAT1-/- mice as compared to C57BL/6 to decreased cardiac CD45 number/view (C57BL/6-AngII: 27±4 STAT1-/--AngII: 11±5; P<0.05) and reduced cardiac fibrosis (hydroxyproline assay: C57BL/6-AngII: 80.6±11.8μmol/l versus STAT1-/- -AngII: 55.0±8.4μmol/l; P<0.05). Mesenteric arteries of STAT1-/- mice were fully protected against angiotensin induced endothelial dysfunction. Candesartan (AT1 receptor antagonist) inhibited action of Ang II in C57BL/6 and reduced but not reversed expression of chemokines in the heart.
Conclusions: Lack of STAT1 revealed protection against Ang II-induced cardiac fibrosis and endothelial dysfunction. We suggest that STAT1-induced chemokine activation induces chemotaxis into hypertensive target organs and modifies cardiac fibrosis and vascular dysfunction in a blood pressure-independent manner.
Author Disclosures: S. Chmielewski: None. C. Aoqui: None. H. Bluijssen: None. M. Baumann: None.
- © 2014 by American Heart Association, Inc.