Investigation of the Use of Antioxidants to Diminish the Adverse Effects of Postnatal Glucocorticoid Treatment on Mortality and Cardiac Development

BACKGROUND: In premature infants, glucocorticoids ameliorate chronic lung disease, but have adverse effects on growth and the cardiovascular system. Glucocorticoid excess promotes free radical overproduction and vascular dysfunction. OBJECTIVES: We hypothesized that the adverse effects of postnatal glucocorticoid therapy are secondary to oxidative stress and that antioxidant treatment would diminish unwanted effects. METHODS: Male rat pups received a clinically relevant course of dexamethasone (Dex), or Dex with vitamins C and E (DexCE), on postnatal days 1-6 (P1-6). Controls received saline (Ctrl) or saline with vitamins (CtrlCE). RESULTS: At P21, Dex reduced survival (Ctrl: 96 vs. Dex: 70%) and promoted asymmetric growth restriction (ponderal index, Ctrl: 6.3 +/- 0.1 g . mm(-3) x 10(-5) vs. Dex: 7.4 +/- 0.2 g . mm(-3) x 10(-5)), both p < 0.05. Dex increased cardiac oxidative stress (protein expression: 4-HNE +20%, Hsp90 -42% and eNOS -54%), induced left ventricle (LV) wall thinning (LV wall volume: Ctrl: 47.2 +/- 1.2 mm(3) vs. Dex: 38.9 +/- 1.7 mm(3)) and decreased the ratio of the aortic lumen:total vessel area (Ctrl: 0.74 +/- 0.01 vs. Dex: 0.66 +/- 0.02), all p < 0.05. DexCE restored towards control values survival, growth symmetry the aortic lumen:total vessel area, and increased the cardiac expression of Hsp90 relative to Dex. In addition, relative to controls, the decrease in the cardiac expression of eNOS was no longer significant in DexCE animals (-20.3 +/- 14.4%, p > 0.05). However, DexCE did not prevent growth retardation, cardiac 4-HNE upregulation (DexCE: +29%) or LV thinning (DexCE: 40.1 +/- 1.1 mm(3)). Treatment of neonates with vitamins alone affected somatic growth and promoted thinner LV walls (CtrlCE: 39.9 +/- 0.5 mm(3), p < 0.05). CONCLUSIONS: Combined glucocorticoid and antioxidant therapy in premature infants may be safer than glucocorticoids alone in the treatment of chronic lung disease. However, antioxidant therapy in healthy offspring is not recommended.