Protective effect of 4-hydroxy-2, 2, 6, 6-tetramethylpiperidine on lung injury with intermittent hypoxia in premature rats / 中华实用儿科临床杂志

ABSTRACT

Objective:To investigate the effects of 4-hydroxy-2, 2, 6, 6-tetramethylpiperidine (Tempol) on the expressions of hypoxia inducible factor-1 α (HIF-1α)/vascular endothelial growth factor (VEGF) and lung development in premature neonatal rats under intermittent hypoxia (achieved by supplying a low concentration of oxygen).Methods:The intermittent hypoxia model was established.Caesarean section of rats was performed at 21 days of gestation when the fetal rats were estimated to be in labor.A total of 192 premature neonatal rats survived and were randomly divided into 6 groups according to random number table method: air control+ saline group, air control+ Tempol group, constant oxygen + saline group, constant oxygen + Tempol group, intermittent hypoxia + saline group, and intermittent hypoxia + Tempol group, 32 rats in each group.On the 7 th, 14 th and 21 st day of birth, the lung tissues of 8 neonatal preterm rats in each group were taken.Malondialdehyde (MDA) and total antioxidant capacity (TAOC) were detected by chemical analysis.The mRNA and protein levels of HIF-1α and VEGF were detected by real-time fluorescence quantitative PCR (qPCR) and immunohistochemistry, respectively.Another 8 neonatal rats in each group were taken for pulmonary function test on the 21 st day after birth. One- way ANOVA and SNK- q test were used for comparison among and between groups, respectively. Results:Compared with the constant oxygen + saline group, the intermittent hypoxia + saline group showed mild pulmonary septal thickening, increased MDA, decreased TAOC, elevated mRNA and protein expression levels of VEGF and HIF-1 α, and decreased lung function indexes.The differences were statistically significant (all P<0.05). Compared with the corresponding saline group, the intermittent hypoxia + Tempol group had decreased MDA and increased TAOC, and the differences were statistically significant at 14 d[MDA(3.09±0.45) nmol/(mg·pr) vs.4.02±0.30) nmol/(mg·pr), TAOC(3.13±0.31) U/(mg·pr) vs.(2.44±0.22) U/(mg·pr)]and 21 d[MDA(2.87±0.43) nmol/(mg·pr) vs.(4.47±0.56) nmol/(mg·pr), TAOC(3.47±0.35) U/(mg·pr) vs.(2.31±0.32) U/(mg·pr)] (all P<0.05). Compared with the corresponding saline group, the mRNA and protein expression of HIF-1 α and VEGF decreased in the intermittent hypoxia+ Tempol group, and the decrease in the mRNA expression of HIF-1 α was statistically significant at 14 d (2.11±0.60 vs.2.88±0.59) (all P<0.05). Lung function indexes, including tidal volume[(0.41 ± 0.01) mL vs.(0.36±0.02) mL], minute respiratory ventilation[(35.48 ± 2.95) mL vs.(30.62±2.27) mL], maximum expiratory flow[(2.19 ± 0.19) mL/s vs.(1.51±0.19) mL/s]and dynamic lung compliance[(2.65 ± 0.40) mL/cmH 2O vs.(1.83±0.34) mL/cmH 2O, 1 cmH 2O=0.098 kPa]increased (all P<0.05). Conclusions:Tempol can alleviate the lung injury induced by intermittent hypoxia under the intervention of a low concentration of oxygen to premature newborn rats and improve their lung function.