Significant correlation between endothelial nitric oxide synthase (eNOS) expression and alveolar repair in elastase-induced rat pulmonary emphysema

Angiogenic factors, such as endothelial nitric oxide synthase (eNOS), are thought to play an important role in the repair of pulmonary emphysema (PE); yet, the correlation of the factors involved has not been investigated. We conducted this study to clarify the positive correlation between eNOS expression and alveolar repair in PE recovery. We used elastase to induce PE in rats, which were divided into Groups A (Control), B (G-CSF), C (PE) and D (PE + G-CSF). G-CSF was injected for 12 days, 4 weeks after which the alveolar walls, arterioles, and angiogenic factors including eNOS were examined histopathologically and by western blotting. In comparing Groups A, B, C, and D, the alveolar density was 2.4 +/- A 0.2, 2.4 +/- A 0.1, 1.8 +/- A 0.1, 2.5 +/- A 0.1 per 100 mu m(2), respectively (C vs. others; p < 0.00001) and the number of arterioles was 4.5 +/- A 1.0, 5.6 +/- A 0.6, 3.2 +/- A 0.5, 5.5 +/- A 0.7/mm(2), respectively (C vs. others; p < 0.05). Immunohistochemical staining (IHC) revealed different eNOS expression in Group D versus Group C (p < 0.0001) and western blotting revealed different eNOS, VEGF, and FLT-1 expression in Group D versus Group C (p < 0.01, p < 0.05, p < 0.001), reflecting the contribution of angiogenesis to PE repair. eNOS showed a significantly positive correlation to alveolar density and arteriole repair. Alveolar repair was correlated positively with eNOS expression by vascular regeneration in elastase-induced rat PE.