Abstract 14466: S100KO Mice Develop Pulmonary Hypertension Associated With Endothelial Cell Dysfunction, Apoptosis and Reduced Nitric Oxide Production.
Background: Knockout mice deficient in S100A1 (KO), a Ca 2+-binding protein present in endothelial cells (EC), develop systemic hypertension with impaired production of nitric oxide (NO). We demonstrated that S100A1 is expressed in pulmonary EC. As endothelial dysfunction contributes to clinical and experimental pulmonary arterial hypertension (PAH), we investigated the potential role of S100A1 in PAH by examining pulmonary vascular physiology in KO, and associated signalling pathways in pulmonary EC.
Methods and Results: At baseline, S100A1 deficient mice exhibited a significant elevation in right ventricular systolic pressure (28.41±3.6 vs.14.9±2.41 mmHg in wild-type (WT), p< 0.05, n=5). Real-time imaging of fluorescent NO-sensitive dye DAF-FM in capillaries of isolated lung revealed reduced basal NO level in KO vs. WT and blunted dose-responsiveness to acetylcholine (ACh,10−4 M increased fluorescence 1.43±0.31-fold versus 3.91±0.43-fold, respectively, p<0.05, n=5). By contrast, NO-donor (SNAP, 1mmol/L) resulted in comparable fluorescence increase in WT and KO vessels (4.77±0.65 vs. 4.17±0.42-fold, n=5). Precontracted (1 μg angiotensin II) isolated perfused lungs of KO had no endothelium-dependent vasorelaxation to ACh (10−6 M, increase in pulmonary artery pressure of 18±10% in KO vs. decrease by 16±2% in WT, p<0.05, n=5). Phosphorylation of endothelial nitric oxide synthase (eNOS) at stimulatory residue, Ser1177, Akt, and Erk1/2 was increased in pulmonary EC by exogenous S100A1 treatment (100 ng/ml 5, 30 min) more in WT versus KO (2.19- fold, 1.98- fold, and 1.93-fold, respectively, all p<0.05, n=4). Incubation with PI3 kinase (LY-294002) and Erk1/2 (PD-98059) inhibitors blocked eNOS phosphorylation, indicating dual Akt and Erk1/2-dependence. TNF-α (20ng/ml) induction of EC apoptosis assessed by flow cytometry was 25.4 % greater in KO versus WT, a difference blocked by S100A1 treatment.
Conclusions: Our data demonstrate that absence of S100A1 results in PAH by disruption of its normal capacity to enhance pulmonary EC survival, and regulation of eNOS activity and NO levels via Akt/Erk1/2 pathways. The ability of exogenous S100A1 to positively modulate these targets make it an attractive therapeutic target in the treatment of PAH.
- © 2010 by American Heart Association, Inc.