Abstract 17982: Krìppel-Like Transcription Factor- 2 Preserves Endothelial Function and Protects Against Pulmonary Hypertension
RATIONALE: Pulmonary Hypertension (PH) is associated with ongoing endothelial cell (EC) dysfunction. Shear-responsive Krüppel-like Transcription Factor- 2 (KLF2) is thought to maintain EC homeostasis and to enhance NO bioavailability by inducing eNOS transcription and decreasing caveolin-1 expression. Thus, we hypothesized that KLF2 expression would be reduced in experimental PH, and KLF2 overexpression would prevent pulmonary arterial (PA) remodeling and preserve EC function in chronic hypoxia (CH)-induced PH.
METHODS: Lung KLF2 mRNA levels were measured at 1, 3, 7, or 21 days in the CH (10% O2) rat model of PH. Selective gene transfer of KLF2 or empty plasmid to lung ECs was achieved by intravenous injection of jetPEI™ with plasmid DNA (150µg) at day 3 of CH. At 21 days of CH, right ventricular systolic pressure (RVSP), RV hypertrophy, and medial area in PAs with external diameters of <30µm and 30-50µm were assessed. Ex vivo lung functional analyses were performed and eNOS expression was assessed 24 hrs after shKLF2 delivery.
RESULTS: KLF2 mRNA expression was reduced at 3 days of CH (0.3±0.1;P<0.05; normalized to sham), returning to control levels at 7 and 21 days. Compared with control transfection, KLF2 gene therapy reduced RVSP (69.5 ± 6.5 vs. 46.5 ± 2.6 mmHg; P<0.01; n=11-13) and RV/LV+S weight ratios (0.35 ± 0.02 vs. 0.28 ± 0.01, n=11-13; P<0.05), associated with a 1.3 fold increase in lung eNOS expression (P=0.04), but no change in PA medial area at day 21. Moreover, KLF2 knockdown resulted in increased RVSP in normoxic rats, matched with reduced eNOS expression to 0.60 ± 0.08 fold and a blunted vasodilator response to ACh (-4.68 ± 0.99 vs. -7.17 ± 0.80 ⋔mmHg; P<0.01; n=6), while SNP-induced dilation was unchanged (n=4) compared to transfected controls (RS).
CONCLUSIONS: These results suggest that KLF2 is protective in the CH model of PH. The mechanism of protection involved maintenance of eNOS expression and endothelial dilatory function, rather than vascular remodeling.
- © 2011 by American Heart Association, Inc.