Oxidation–Reduction (Redox) Controls Fetal Hypoplastic Lung Growth

Abstract

Introduction. The persistent morbidity and mortality of congenital diaphragmatic hernia are largely due to associated pulmonary hypoplasia. We have shown previously that three antioxidants (vitamin C, glutathione, and vitamin E) could accelerate the growth of fetal hypoplastic lungs grown in culture. We hypothesize that this occurs via a reductant mechanism. Methods. Timed-pregnant rats were gavage-fed nitrofen (100 mg) on day 9.5 of gestation (term = day 22). Fetal lungs were harvested on day 13.5 and placed in organ culture containing serum-free BGJb medium with antibiotics. After randomization, the lung organ cultures were divided into a control group ( n = 31) and an experimental group that received the antioxidant N-acetylcysteine (NAC, 100 μM, n = 31). The fetal lung organ cultures were grown for 4 days at 37°C with 5% CO 2. Computer-assisted digital tracings of the airways were performed daily on live, unstained specimens, and lung bud count, perimeter, and area were measured. After 4 days, lungs were pooled, homogenized, and assayed for reduced and oxidized glutathione, normalized to protein, as an estimate of the tissue redox potential. Data were expressed as means ± SEM, and statistical comparisons were performed using Student's unpaired t test, with P < 0.05 considered significant. Results. Area, perimeter, lung bud count, and complexity (as measured by the perimeter/square root of area) were all significantly increased with NAC treatment from day 2 onward. Reduced glutathione levels were significantly increased following NAC administration (67.1 ± 5.8 versus 37.5 ± 4.2 μmol/mg, P = 0.0004). The ratio of reduced to oxidized glutathione was 2.23. Conclusions. N-Acetylcysteine stimulates nitrofen-induced hypoplastic fetal lung growth in organ culture and increases the ratio of reduced to oxidized glutathione. These data support the concept that oxidation–reduction (redox) may be an important control mechanism for fetal lung growth.