Abstract 11950: S100A1 Protein Delivery Reverses Abnormal Hemodynamics in Isolated Perfused Lung From Knockout Mice with Pulmonary Hypertension
Background: Knockout mice (KO) deficient in S100A1, an endothelial cell (EC) protein with intra and extra-cellular activity, develop pulmonary arterial hypertension (PAH) with reduced endothelial nitric oxide synthase (eNOS) activity, impaired production of NO, and increased EC apoptosis. To explore therapeutic potential in PAH, the impact of exogenous S100A1 protein delivery on hemodynamics in isolated perfused lungs and signalling in cultured pulmonary ECs was examined in KO and wild-type (WT) mice.
Methods and Results: In vivo, KO exhibited elevation in right ventricular systolic pressure (28.41±3.6 vs.14.9±2.41 mmHg in WT, p< 0.05, n=5), with no change in left ventricular (LV) hemodynamics including LV end-diastolic pressure volume relationship (0.35±0.15 vs.0.33±0.05 mmHg/µl vs.WT, n=8). KO perfused lungs exhibited augmented basal pulmonary vascular resistance (R0) and responses to 1µg/ml Angiotensin II (0.15±0.03 and 0.23±0.06 vs.0.09±0.01 and 0.12±0.01 mmHg*ml-1*kg-1* min-1 in WT respectively, n=5). Acetylcholine-induced dose-dependent reduction in PA pressures (PAP) was absent in KO (10.27±0.08 at 10-9 M and 10.38±1.38 at 10-6 M vs. 8.2±0.18 at 10-9 M and 6.2±0.08 mmHg at 10-6 M in WT, respectively, p<0.05, n=5). Pre-treatment of KO lungs with 1µM recombinant S100A1 for 30 min blunted acute (2min) AII-induced increases in PAP and R0 (Δ PAP: 0.96±0.39 vs. 2.88±0.86 mmHg in saline controls; Δ R0: 0.039±0.02vs. 0.23±0.10 mmHg*ml-1*kg-1*min-1 in saline controls, n=6), resembling WT lung responses. The effect of S100A1 in KO persisted for 60 min post AII. Phosphorylation of eNOS at residue Ser1177, Akt, and Erk1/2 were increased in pulmonary ECs by exogenous S100A1 (100nM, 30 min) in KO and to a greater extent in WT (2.19- fold, 1.98- fold, and 1.93-fold, respectively, p<0.05, n=4), responses attenuated by pre-incubation with blocking antibodies for the cell surface receptor for advanced glycation end-products (RAGE, 166µg/ml).
Conclusion: Exogenous S100A1 reduces PAP and R0 in isolated lungs in a S100A1 KO with PAH. Moreover, S100A1 induces stimulatory eNOS phosphorylation in both WT and KO ECs by a RAGE-dependent mechanism. Thus, S100A1 is a potential novel therapeutic agent for treatment of PAH, amenable to further testing in vivo.
- © 2011 by American Heart Association, Inc.