ABSTRACT
Objective To investigate the role of endoplasmic reticulum stress (ERS) pathway involving protein kinase R-like ER kinase (PERK)-activating transcription factor 4 (ATF4)-CCAAT/enhancer binding protein homologous protein (CHOP) in apoptosis in lungs of rats with bronchopulmonary dysplasis (BPD).Methods Forty eight premature SD rats were divided into BPD group and control group according to random number table.Rats in BPD group were continually exposed to O2 with volumetric concentration factor of 850 mL/L,while rats in control group were exposed to air.Lung tissues in each group were obtained in 7,14 and 21 days respectively.The apoptosis in lung cells was evaluated by terminal dexynucleotifyl transferase-mediated dUTP nick end labeling (TUNEL) assay.The mRNA levels of glucose regulated protein 78 (GRP78),PERK,ATF4 and CHOP were detected by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR).The protein levels of GRP78,phosphorylated PERK (pho-PERK),ATF4 and CHOP were detected by using Western blot.Results Compared with control group,the lung cells of the rats in BPD group developed more serious apoptosis.Furthermore,the apoptosis index (AI) in lung cells of the rats increased rapidly with the hyperoxia exposure time.This had been statistically verified by comparison with the control group at different timing(7 d:15.50 ± 0.58 vs 1.25 ± 0.50,14 d:27.75 ± 1.71 vs 3.25 ± 0.96,21 d:50.50 ±3.70 vs 4.00 ± 1.15 ;t =57.00,20.58,25.16,all P ＜0.01).The mRNA levels of GRP78,PERK,ATF4 and CHOP in BPD group increased significantly compared to the control group [GRP78:7 d (33.88 ± 3.73) vs (11.65 ± 1.00),14 d (54.50 ±2.18)vs(12.84 ± 1.41),21 d (95.34 ± 7.61)vs(12.43 ±0.59) ;PERK:7 d (5.23 ±0.92)vs (1.45 ±0.46),14 d (7.60 ± 1.56)vs(2.18 ±0.97),21 d (16.55 ±0.50)vs(2.90 ± 1.18) ;ATF4:7 d (23.04 ± 2.45)vs(12.56 ±2.81),14 d (28.66 ±2.66)vs(15.18 ±2.92),21 d (36.63 ±2.99)vs(15.14 ±2.09) ;CHOP:7 d (2.21 ±0.19)vs(0.81 ±0.02),14 d (4.19 ±0.17)vs(0.90 ±0.08),21 d (6.08 ±0.38)vs(0.88 ±0.10) ;all P ＜ 0.05].The protein levels of GRP78,pho-PERK,ATF4 and CHOP in BPD group increased significantly as well [GRP78:7 d (1.33 ±0.03)vs(0.85 ±0.04),14 d (1.31 ±0.02)vs(0.92 ±0.01),21 d (1.82 ±0.28)vs(0.87 ± 0.01);pho-PERK:7 d (0.68±0.02)vs(0.54±0.01),14 d (1.04±0.01)vs(0.65±0.01),21 d (1.29± 0.02)vs(0.73 ±0.01) ;ATF4:7 d (1.26 ±0.01) vs(0.83 ±0.01),14 d (1.39 ±0.02) vs (0.87 ±0.02),21 d (1.67 ±0.02)vs(0.94 ±0.02) ;CHOP:7 d (1.37 ±0.01)vs(0.47 ±0.06),14 d (1.50 ±0.04)vs(0.74 ±0.05),21 d (1.61 ± 0.03) vs (0.55 ± 0.02) ; all P ＜ 0.05].Positive correlation was demonstrated between the expression levels of CHOP protein and AI,PERK,ATF4 in the BPD group (r =0.87,0,92,0.93 respectively,all P ＜ 0.05).Conclusion PERK-ATF4-CHOP mediated ERS may participate in and contribute to the apoptosis mechanism in lungs of rats with BPD.
ABSTRACT
Objective To explore the protective effect of Red Sage Root on bronchopulmonary dysplasis(BPD) induced by hyperoxia in newborn rats.Methods On the 2nd postnatal day,SD newborn rats were randomly assigned to 4 groups:air and NS group(group Ⅰ),air and Red Sage Root group(group Ⅱ),hyperoxia and NS group(group Ⅲ),hyperoxia and Red Sage Root group(group Ⅳ).The rats in group Ⅲ and group Ⅳ were exposed to hyperoxia(the level of oxygen was 900-960 mL/L).The rats in group Ⅱ and group Ⅳ were injected with Red Sage Root intraperitoneally(10 mg/kg)daily.On 14 days after birth,6 rats in each group were killed.Lung histologic changes,radical alveolar counts(RAC)were monitored.Thiobarbituric acid method,nitrite method,2-nitroben zoic acid method were used to determine the concentration of malony ldialdengde(MDA),superoxidedismutase(SOD),glutathione peroxidase(GSH-Px) were monitored.Results 1.Group Ⅲ and group Ⅳ showed the inhibition of lung development and the evident lung fibrosis.In contrast to group Ⅰ and group Ⅱ,RAC in group Ⅲ and group Ⅳ decreased dramatically(Pa