OBJECTIVETo study the effect of recombinant human erythropoietin (rhEPO) on apoptosis following hyperoxic lung injury in neonatal rats.

METHODSNinety-six neonatal Sprague-Dawley rats were randomly divided into four groups: air-exposed control, air-exposed rhEPO-treated, hyperoxia-exposed placebo (95% oxygen), and hyperoxia-exposed rhEPO-treated. rhEPO (800 U/kg) was administered 2, 4, and 6 days after air or hyperoxia exposure. The rats were sacrificed 3, 7 and 14 days after air or hyperoxia exposure for the assessment of lung histological changes by hematoxylin and eosin staining (n=8 each time point). p-JNK levels were measured by Western blot. Lung cell apoptosis was evaluated by TUNEL assay.

RESULTSCompared with the air-exposed control group, inflammatory cell infiltration was found at 3 days and increased obviously at 7 days, and widening of the alveolar septa was observed, the number of alveoli decreased and normal alveolarization disappeared at 14 days after hyperoxia exposure in the hyperoxia-exposed placebo group. rhEPO treatment alleviated significantly the hyeroxia-induced alterations in lung pathology. P-JNK protein levels and the number of apoptosis cells decreased significantly in the hyperoxia-exposed rhEPO-treated compared with those in the hyperoxia-exposed placebo group.

CONCLUSIONSrhEPO may reduce apoptosis and thus provide a protective effect against hyperoxic lung injury in neonatal rats. JNK signal pathway may be involved in the protective mechanism.

Animals ; Animals, Newborn ; Apoptosis ; drug effects ; Bronchopulmonary Dysplasia ; drug therapy ; Erythropoietin ; pharmacology ; Female ; Humans ; Hyperoxia ; pathology ; Infant, Newborn ; JNK Mitogen-Activated Protein Kinases ; metabolism ; Lung ; pathology ; Male ; Rats ; Rats, Sprague-Dawley ; Recombinant Proteins

Fetal lung development normally occurs in a hypoxic environment. Hypoxia-inducible factor (HIF)-1alpha is robustly induced under hypoxia and transactivates many genes that are essential for fetal development. Most preterm infants are prematurely exposed to hyperoxia, which can halt hypoxia-driven lung maturation. We were to investigate whether the HIF-1alpha inducer, deferoxamine (DFX) can improve alveolarization in a rat model of bronchopulmonary dysplasia (BPD). A rat model of BPD was produced by intra-amniotic lipopolysaccharide (LPS) administration and postnatal hyperoxia (85% for 7 days), and DFX (150 mg/kg/d) or vehicle was administered to rat pups intraperitoneally for 14 days. On day 14, the rat pups were sacrificed and their lungs were removed and examined. A parallel in vitro study was performed with a human small airway epithelial cell line to test whether DFX induces the expression of HIF-1alpha and its target genes. Alveolarization and pulmonary vascular development were impaired in rats with BPD. However, DFX significantly ameliorated these effects. Immunohistochemical analysis showed that HIF-1alpha was significantly upregulated in the lungs of BPD rats treated with DFX. DFX was also found to induce HIF-1alpha in human small airway epithelial cells and to promote the expression of HIF-1alpha target genes. Our data suggest that DFX induces and activates HIF-1alpha, thereby improving alveolarization and vascular distribution in the lungs of rats with BPD.
Animals ; Bronchopulmonary Dysplasia/*drug therapy/*metabolism/pathology ; Deferoxamine/*administration & dosage ; Female ; Hypoxia-Inducible Factor 1, alpha Subunit/*metabolism ; Male ; Pulmonary Alveoli/drug effects/*growth & development/metabolism/pathology ; Pulmonary Veins/drug effects/*growth & development/pathology ; Rats ; Rats, Sprague-Dawley ; Treatment Outcome ; Up-Regulation/drug effects

OBJECTIVEIn addition to regulating blood pressure, angiotensin II is involved in lung fibrogenesis. This study aimed to explore the effect of losartan, an angiotensin II type 1 receptor antagonist, on lung fibrosis in neonatal rats with hyperoxia-induced chronic lung disease (CLD) and its possible mechanisms.

METHODSNeonatal Wistar rats were randomly divided into four groups within 24 hrs after birth: room air exposure, hyperoxia exposure (85%-90% O2), hyperoxia exposure + losartan, and hyperoxia exposure + placebo. Losartan (5 mg/kg/d) or placebo was administered beginning on the 6th day after birth. After 7, 14 and 21 days of exposure, 8 rats in each group were sacrificed. Lung histological changes were evaluated by hematoxylin-eosin staining. Levels of hydroxyproline (HYP), superoxide dismutase (SOD) and malondialdehyde (MDA) in lung tissues were determined by spectroscopy.

RESULTSHyperoxia exposure resulted in decreased alveolar septation, enlarged terminal air space, increased collagen deposition, pulmonary hemorrhage, and pulmonary consolidation. In the hyperoxia exposure + losartan group, the alveolar septum became thinner and lung fibrosis was alleviated, but the alveolar space was not obviously deflated and the number of secondary septum was not increased. Hyperoxia exposure increased significantly the HYP contents in lung tissues 14 and 21 days after exposure. Addition of losartan to the hyperoxia exposure resulted in decreased HYP contents (471.46 +/- 30.63 mu g/kg vs 545.15 +/- 34.90 mu g/kg for hypoxia alone; P < 0.01) after 21 days of exposure. SOD activity increased 7 days after hyperoxia exposure and then decreased to levels similar to the air exposure group. MDA levels increased to a peak at 7 days and remained at higher levels through 21 days of exposure when compared with the air exposure group (P < 0.01). Losartan treatment significantly increased SOD activities (82.94 +/- 4.62 U/mg protein vs 67.78 +/-8.02 U/mg protein; P < 0.01) and decreased MDA levels (30.54 +/- 5.89 nmol/mg protein vs 48.75 +/- 8.09 nmol/mg protein, P < 0.01) compared with the hyperoxia exposure group 21 days after exposure.

CONCLUSIONSLosartan attenuated lung fibrosis in neonatal rats with hyperoxia-induced CLD, possibly through an increase of antioxidase enzyme activity and reduction of lipid peroxidation.

Angiotensin II Type 1 Receptor Blockers ; therapeutic use ; Animals ; Animals, Newborn ; Bronchopulmonary Dysplasia ; drug therapy ; metabolism ; pathology ; Humans ; Hydroxyproline ; analysis ; Hyperoxia ; complications ; Infant, Newborn ; Losartan ; therapeutic use ; Lung ; pathology ; Malondialdehyde ; analysis ; Pulmonary Fibrosis ; drug therapy ; pathology ; Rats ; Rats, Wistar ; Superoxide Dismutase ; metabolism