GLUTATHIONE ADDITION TO PARENTERAL NUTRITION PREVENTS PULMONARY OXIDATIVE STRESS AND HYPO-ALVEOLARIZATION IN NEWBORN GUINEA PIG

Abstract

Abstract BACKGROUND Parenteral nutrition (PN) is contaminated by peroxides, which induce oxidative stress (oxidized redox potential) and hypoalveolarization in lungs of newborn animals. In human premature newborns, PN is associated to an oxidized redox potential and to a greater prevalence of bronchopulmonary dysplasia (BPD). Peroxides are detoxified by glutathione that is deficient in preterm infants. Hypothesis: Improving glutathione level in premature infants prevents BPD development caused by oxidative stress. OBJECTIVES Assess dose-response effect of glutathione added in PN on alveolarization index and pulmonary redox potential of glutathione (specific oxidative stress marker for peroxides) in newborn guinea pigs. DESIGN/METHODS At day 3 of life, through a jugular catheter, guinea pigs (N=55) received PN (dextrose, amino acids, lipids, vitamins, electrolytes) enriched in glutathione (0, 50, 120, 165, 270, 370, 650 μg GSSG/kg/d). GSSG was used rather than GSH because it has a better stability in PN and similar efficiency in vivo. A control group (no manipulation, fed by mouth) served as reference. After 4 days, lungs were taken for determination of GSH, GSSG, redox potential (capillary electrophoresis) and alveolarization index (AI) (number of intercepts between a 1 mm line and histological structures); higher is AI, higher is the number of alveoli. Data (mean±sem) from animals on PN were compared by ANOVA, p<0.05. RESULTS There was no difference in the alveolarization index between groups receiving doses ranging from 0 to 120 μg/kg/d (25.9 ± 0.6 intercepts/mm) and between those with doses ranging between 165 and 650 μg/kg/d (30.5 ± 0.6 intercepts/mm). However, the difference between the lowest (0–120 μg/kg/d) and the highest doses (165–650 μg/kg/d) was highly significant (p<0.001). The control AI value was 29.4 ± 1.2 intercepts/mm. Increasing GSSG in PN has allowed a significant (r2=0.47; p<0.001) reduction of redox potential, from oxidized status of -205 ± 2 in PN without GSSG to -215 ± 2 mV with the highest dose (650 μg/kg/d); control = -222 ± 3 mV. GSSG in PN was also associated with a decreasing GSSG values (r2=0.49; p<0.001), from 0.84 ± 0.10 in PN without GSSG to 0.38 ± 0.06 nmol/mg prot with the highest dose (650 μg/kg/d); control = 0.35 ± 0.07 nmol/mg prot. There was no effect on GSH (mean value of 29 ± 1 nmol/mg prot). CONCLUSION Addition of glutathione into PN prevents pulmonary oxidative stress. The dose-response curve suggests a specific minimal dose of GSSG to maintain the alveolar integrity. Lower doses were inefficient whereas higher doses are unnecessary, as the index of alveolarization reached a plateau with a mean value similar to that one observed in the control group. This pre-clinical study brings basic data that will serve for the clinical phase I-II study that we are starting soon.