Animals ; Animals, Newborn ; Hyperoxia ; physiopathology ; Lung ; drug effects ; pathology ; Oxygen ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Tretinoin ; pharmacology ; therapeutic use

OBJECTIVE: To study the expression and significance of ubiquitin-specific protease 7 (USP7) and the key factors of the Wnt signaling pathway in the lung tissue of preterm rats after hyperoxia exposure. METHODS: A total of 180 preterm neonatal Wistar rats were randomly divided into an air control group, an air intervention group, a hyperoxia control group, and a hyperoxia intervention group, with 45 rats in each group. Lung injury was induced by hyperoxia exposure in the hyperoxia groups. The preterm rats in the intervention groups were given intraperitoneal injection of the USP7 specific inhibitor P5091 (5 mg/kg) every day. The animals were sacrificed on days 3, 5, and 9 of the experiment to collect lung tissue specimens. Hematoxylin-eosin staining was used to observe the pathological changes of lung tissue. RT-PCR and Western blot were used to measure the mRNA and protein expression levels of USP7 and the key factors of the Wnt signaling pathway β-catenin and α-smooth muscle actin (α-SMA) in lung tissue. RESULTS: The air groups had normal morphology and structure of lung tissue; on days 3 and 5, the hyperoxia control group showed obvious alveolar compression and disordered structure, with obvious inflammatory cells, erythrocyte diapedesis, and interstitial edema. On day 9, the hyperoxia control group showed alveolar structural disorder and obvious thickening of the alveolar septa. Compared with the hyperoxia control group at the corresponding time points, the hyperoxia intervention group had significantly alleviated disordered structure, inflammatory cell infiltration, and bleeding in lung tissue. At each time point, the hyperoxia groups had a significantly lower radial alveolar count (RAC) than the corresponding air groups ( CONCLUSIONS Hyperoxia exposure can activate the Wnt/β-catenin signaling pathway, and USP7 may participate in hyperoxic lung injury through the Wnt/β-catenin signaling pathway. The USP7 specific inhibitor P5091 may accelerate the degradation of β-catenin by enhancing its ubiquitination, reduce lung epithelial-mesenchymal transition, and thus exert a certain protective effect against hyperoxic lung injury.
Animals ; Animals, Newborn ; Hyperoxia/physiopathology* ; Lung/physiopathology* ; Random Allocation ; Rats ; Rats, Wistar ; Thiophenes/pharmacology* ; Ubiquitin-Specific Peptidase 7/metabolism* ; Ubiquitin-Specific Proteases ; Wnt Signaling Pathway

OBJECTIVETo study the effect of oxygen at lethal levels (95%) on pulmonary development and lung injury in neonatal rats and establish rat models of bronchopulmonary dysplasia.

METHODSThree-day-old and adult SD rats were assigned to experimental or control groups and subjected to 95% O(2) exposure and room air for 7 days. Body weight and length of the rats were recorded, and histological study of the lung tissue and radical alveoli count (RAC) were carried out.

RESULTSThe mortality rate of the neonatal and adult rats was 12.5% and 35.2% in hyperoxia group, respectively. The newborn rats in hyperoxic group had lower body weight (18.02-/+0.68 vs 13.24-/+0.59 g) and length (8.83-/+0.25 vs 6.76-/+0.51 cm) than those in the control group (P<0.05), with also lower RAC (9.50-/+1.05 vs 13.00-/+1.79, P<0.05); RAC of the adult rats with hyperoxic exposure (12.67-/+2.25) was higher that of exposed neonatal rats, but not significantly different from that of the adult or neonatal rats in the control group (P>0.05). Structure configuration of the rats on the first 10 days of life resembled that of adulthood. The lung of hyperoxic neonatal rats showed thinner walls of alveoli, simple alveolar structure, fewer and larger alveoli, expanded and shrunk alveoli, while the lung of the adult rats displayed thicker septa, smaller space of alveoli, and cells in the space of the alveoli.

CONCLUSIONExposure of neonatal rats to 95% O(2) may result in mild pulmonary inflammation in addition to growth impediment and impaired lung development, which shares morphologic similarities to human bronchopulmonary dysplasia.

Animals ; Animals, Newborn ; Disease Models, Animal ; Female ; Hyperoxia ; complications ; physiopathology ; Lung ; physiopathology ; Lung Diseases ; etiology ; physiopathology ; Lung Injury ; Pregnancy ; Pulmonary Alveoli ; pathology ; physiopathology ; Random Allocation ; Rats ; Rats, Sprague-Dawley

OBJECTIVEOxygen toxicity is believed to play a critical role in the pathogenesis of bronchopulmonary dysplasia (BPD). U74389G, a potent 21-aminosteroid antioxidant, was applied to the 95% O(2) induced acute lung injury in newborn rat model. The present study aimed to investigate the mechanism of hyperoxic lung injury and the interaction of possible mediators, and to explore the effect of antioxidant intervention.

METHODSNewborn Sprague-Dawley rats were randomly divided into four groups: air-exposed control, air-exposed treated with U74389G, hyperoxia-exposed control, hyperoxia-exposed treated with U74389G. Hydroxyl radical formation (2,3-DHBA and 2,5-DHBA) was assessed by an aromatic hydroxylation assay using GC/MS with salicylate as the probe. The 8-isoprostane, a specific marker for in vivo lipid peroxidation, was quantitated by enzyme immunoassay. Pulmonary macrophage influx and nitrotyrosine formation were measured by means of immunohistochemistry. (3)H-TdR (autoradiography) incorporation was assessed as an index of active lung cell growth.

RESULTSExposure to 95% O(2) for 7 days induced significant lung injury and mortality. The contents of hydroxyl radical in the hyperoxia-exposed lungs were dramatically increased [(2,3-DHBA 49.2 +/- 3.5 pmol/mg), (2,5-DHBA 55.8 +/- 2.3 pmol/mg), P < 0.05) and were decreased by treatment with U74389G [(2,3-DHBA 37.9 +/- 2.4 pmol/mg), (2,5-DHBA 31.3 +/- 1.9 pmol/mg), P < 0.05). The level of 8-isoprostane in the lungs of 95% O(2)-exposed newborn rats was significantly raised (546.6 +/- 32.2 pg/mg, P < 0.05) and lowered down by U74389G (358.5 +/- 24.1 pg/mg, P < 0.05). This phenomenon was also observed in the air-exposed animals. Remarkable pulmonary macrophage infiltration was evident in hyperoxia-exposed newborn rats and was attenuated by U74389G treatment. Nitrotyrosine distributed in the lung parenchyma and epithelial cells of large airway of hyperoxia-exposed newborn rats. The extent of protein nitration was reduced by U74389G, but the oxygen induced morphological change was not significantly improved by U74389G treatment. Exposure to 95% O(2) induced lung growth arrest as shown by (3)H-TdR incorporation. U74389G partially preserved active lung cell growth in hyperoxia-exposed rats, but showed an inhibitory effect on normal lung cell growth.

CONCLUSIONThrough scavenging hydroxyl radical and lipid peroxides, U74389G could block pulmonary macrophage influx and partly avert alveolar development arrest in hyperoxia-exposed newborn rats. Antioxidant intervention holds promising in hyperoxic lung injury though cautions should be taken as possible interference on normal cell development.

Animals ; Animals, Newborn ; Antioxidants ; pharmacology ; therapeutic use ; Female ; Hydroxyl Radical ; metabolism ; Hyperoxia ; physiopathology ; Lung ; drug effects ; growth & development ; pathology ; Macrophages, Alveolar ; drug effects ; metabolism ; Pregnancy ; Pregnatrienes ; pharmacology ; therapeutic use ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Treatment Outcome

BACKGROUNDExposure of adult mice to more than 95% O2 produces a lethal injury by 72 hours. Nuclear factor kappa B (NF-κB) is a transcriptional factor that plays a key role in the modulation of cytokine networks during hyperoxia-induced acute lung injury (ALI). Osteopontin (OPN) is a phosphorylated glycoprotein produced principally by macrophages. Studies have reported that exogenous OPN can maintain the integrity of the cerebral microvascular basement membrane and reduce brain damage through inhibiting NF-κB activities in the brain after subarachnoid hemorrhage. However, it is not clear whether OPN can reduce lung injury during ALI by inhibiting transcriptional signal pathways of NF-κB and consequent inhibition of inflammatory cytokines. Thus we examined the effects and mechanisms of recombinant OPN (r-OPN) on ALI.

METHODSNinety-six mice were randomly divided into phosphate buffered saline (PBS) and r-OPN groups. Mice were put in an oxygen chamber (>95% O2) and assessed for lung injury at 24, 48, and 72 hours. Expressions of NF-κB, matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9), and tissue inhibitors of MMP-2 and MMP-9 (TIMP-1, TIMP-2) mRNA in lungs were examined with RT-PCR. Expression and distribution of NF-κB protein in lungs were measured with immunohistochemistry.

RESULTSExposure to hyperoxia for 72 hours induced more severe lung injury in the PBS group compared with the r-OPN group. Expression of NF-κB mRNA in the PBS group exposed to hyperoxia for 48 and 72 hours was significantly higher than the r-OPN group (P < 0.05). With 72-hour exposure, expression of TIMP-1 mRNA in the r-OPN group was significantly higher than that of the PBS group (P < 0.05). Expression of TIMP-2 mRNA in the r-OPN group at 48 and 72 hours was significantly higher than those in the PBS group (P < 0.05). After 72-hour exposure, expression of NF-κB protein in airway epithelium in the PBS group was significantly higher than that in the r-OPN group (P < 0.05).

CONCLUSIONr-OPN can inhibit the release and activation of MMPs through inhibition of the expression of NF-κB and promotion of the expression of TIMPs, and alleviate hyperoxia-induced ALI.

Acute Lung Injury ; genetics ; metabolism ; Animals ; Hyperoxia ; metabolism ; physiopathology ; Matrix Metalloproteinase 2 ; genetics ; metabolism ; Matrix Metalloproteinase 9 ; genetics ; metabolism ; Mice ; NF-kappa B ; genetics ; metabolism ; Osteopontin ; genetics ; metabolism ; Tissue Inhibitor of Metalloproteinase-1 ; genetics ; metabolism ; Tissue Inhibitor of Metalloproteinase-2 ; genetics ; metabolism

BACKGROUNDExposure of adult mice to more than 95% O(2) produces a lethal injury by 72 hours. Nitric oxide synthase (NOS) is thought to contribute to the pathophysiology of murine hyperoxia-induced acute lung injury (ALI). Osteopontin (OPN) is a phosphorylated glycoprotein produced principally by macrophages. OPN inhibits inducible nitric oxide synthase (iNOS), which generates large amounts of nitric oxide production. However, the relationship between nitric oxide and endogenous OPN in lung tissue during hyperoxia-induced ALI has not yet been elucidated, thus we examined the role that OPN plays in the hyperoxia-induced lung injury and its relationships with NOS.

METHODSOne hundred and forty-four osteopontin knock-out (KO) mice and their matched wild type background control (WT) were exposed in sealed cages > 95% oxygen or room air for 24- 72 hours, and the severity of lung injury was assessed; expression of OPN, endothelial nitric oxide synthase (eNOS) and iNOS mRNA in lung tissues at 24, 48 and 72 hours of hyperoxia were studied by reverse transcription-polymerase chain reaction (RT-PCR); immunohistochemistry (IHC) was performed for the detection of iNOS, eNOS, and OPN protein in lung tissues.

RESULTSOPN KO mice developed more severe acute lung injury at 72 hours of hyperoxia. The wet/dry weight ratio increased to 6.85 +/- 0.66 in the KO mice at 72 hours of hyperoxia as compared to 5.31 +/- 0.92 in the WT group (P < 0.05). iNOS mRNA (48 hours: 1.04 +/- 0.08 vs. 0.63 +/- 0.09, P < 0.01; 72 hours: 0.89 +/- 0.08 vs. 0.72 +/- 0.09, P < 0.05) and eNOS mRNA (48 hours: 0.62 +/- 0.08 vs. 0.43 +/- 0.09, P < 0.05; 72 hours: 0.67 +/- 0.08 vs. 0.45 +/- 0.09, P < 0.05) expression was more significantly increased in OPN KO mice than their matched WT mice when exposed to hyperoxia. IHC study showed higher expression of iNOS (20.54 +/- 3.18 vs. 12.52 +/- 2.46, P < 0.05) and eNOS (19.83 +/- 5.64 vs. 9.45 +/- 3.82, P < 0.05) in lung tissues of OPN KO mice at 72 hours of hyperoxia.

CONCLUSIONOPN can protect against hyperoxia-induced lung injury by inhibiting NOS.

Animals ; Hyperoxia ; genetics ; physiopathology ; Immunohistochemistry ; Lung ; metabolism ; Lung Injury ; etiology ; genetics ; metabolism ; Mice ; Mice, Knockout ; Nitric Oxide Synthase ; genetics ; metabolism ; Nitric Oxide Synthase Type II ; genetics ; Nitric Oxide Synthase Type III ; genetics ; Osteopontin ; genetics ; physiology ; Reverse Transcriptase Polymerase Chain Reaction

OBJECTIVETo investigate the effect of γ-secretase inhibitor (N-[N-(3,5-difluorophenacetyl)-l -alanyl]-S-phenylglycine t-butyl ester, DAPT) on hyperoxia-induced brain white matter injury in mice.

MWTHODSThree-day-old C57BL/10J mouse pups were divided into air control (C) group, control+DAPT (10 mg/kg, injected intraperitoneally) group, hyperoxia group (exposed to 80% oxygen for 48 h), and hyperoxia+DAPT group. The brain and body weights of the mice were measured at postnatal days 3, 5, 12, and 28. Real-time PCR was used to detect Notch intracellular domain (NICD) mRNA expression in the brain after modeling, and the expressions of NG2 and myelin basic protein (MBP) were detected by double-labeled immunofluorescence assay to verify the oligdendrocycle type at postnatal day 12. The mice in each group were bred until postnatal day 28 for Morris water maze test.

RESULTSThe brain and body weights were significantly decreased in mice in hyperoxia group compared to the control mice, but increased significantly after DAPT treatment (P<0.05). Real-time PCR showed that a 48-hour hyperoxia exposure significantly increased NICD mRNA expression in the brain (P<0.05), which was decreased by co-treatment by DAPT (P<0.05). Hyperoxia also resulted in enhanced NG2 expression and lowered MBP expression in the brain (P<0.05). Compared with the control mice, the mice exposed to hyperoxia showed prolonged escape latency (P<0.05) and spent less time in the target quadrant with a lowered number of passing through the virtual platform (P<0.05). All these parameters were significantly improved by co-treatment with DAPT.

CONCLUSIONSpecific inhibition of Notch signaling pathway activation in the brain by the γ-secretase inhibitor DAPT can ameliorate white matter injury and learning and memory impairment in newborn mice with hyperoxia exposure.

Amyloid Precursor Protein Secretases ; antagonists & inhibitors ; Animals ; Body Weight ; Brain ; metabolism ; pathology ; Dipeptides ; pharmacology ; Hyperoxia ; physiopathology ; Mice ; Mice, Inbred C57BL ; Mice, Inbred Strains ; Organ Size ; Receptors, Notch ; metabolism ; Signal Transduction ; White Matter ; pathology

OBJECTIVETo investigate characteristics of pulmonary stem cells labeled with bromodeoxyuridine (Brdu) and telomerase reverse transcriptase (TERT) in lung tissue, as well as the effects of proliferation and differentiation of the stem cells on lung development and repair of pulmonary injury.

METHODSA model of hyperoxia in neonatal rats was made by exposing the rats to 95% O2 for 7 d. Before sacrificing the rats, Brdu was injected through peritoneum, and immune staining positive cells were analyzed after the rats were sacrificed. TERT positive cells were stained by an immunohistochemical method. At the same time, the double staining for surfactant protein C (SPC) and Brdu or SPC and TERT were performed. Lung histologic study was done on HE stained tissue slices.

RESULTS(1) The lung with hyperoxic injury had thinner walls of alveoli, simple alveolar structure, fewer and larger alveoli, expanded and shrunken alveoli, and there were many fell-off alveolar epithelial cells in the alveolar cavities as well. (2) The cells positively stained with Brdu located in septa, mucosa and submucosa of various bronchi, scattering in epithelium of bronchi, and the number of positive cells was low, having a large nucleus. The TERT-positive cells were apparent in the septa and alveolar walls of peripheral lung tissue, characterized by uneven distribution in the lung lobes, the number of positive cells was less than that of Brdu-positive cells [integral of expression (1.61 +/- 0.83) vs. (0.62 +/- 0.55), P < 0.05]. The number of Brdu- and TERT-positive cells had no significant difference in hyperoxic rats compared to that in controls [integral of expression (1.43 +/- 0.85) vs. (1.61 +/- 0.83); (0.62 +/- 0.55) vs. (0.83 +/- 0.84), P > 0.05]. (3) After double staining, a few positive cells were found in double-stained tissues with SPC and Brdu or TERT. (4) The cells positively stained with SPC antibody had different size. The percentage of positive cells was not significantly different between the hyperoxia group (80.3%) and control group (78.6%). The Brdu positive staining located in nucleus of cells that had larger size than the cells not stained, round nucleus with intense staining (seldom, pole-shaped) and the number of such cells was less than that of the SPC positive cells. The percentage of positive cells was not significantly different between the hyperoxia group (28.5%) and control group (21.4%). (5) The TERT staining located in nucleus of cell that had smaller size than the cells not stained, various nuclear shape, including round intensively stained, round slightly stained, pole-shaped and divided shape. The percentage of positive cells was not significantly different between the hyperoxia group (2.3%) and control group (1.5%).

CONCLUSIONS(1) Brdu and TERT, as markers of stem cells having different capability of differentiation, possess special characteristics, respectively. The cells with Brdu could be transit amplifying cell (TAC) which retains characteristics of stem cells originated from differentiated stem cells, while, the cells stained with TERT especially reflects the characteristics of stem cells. (2) The proliferation and differentiation of pulmonary stem cells during hypoxic lung injury are limited and may be related with arrest of alveolization.

Alveolar Epithelial Cells ; pathology ; Animals ; Animals, Newborn ; Biomarkers ; metabolism ; Bromodeoxyuridine ; metabolism ; Cell Differentiation ; Cell Proliferation ; Disease Models, Animal ; Female ; Hyperoxia ; complications ; Immunohistochemistry ; Lung ; cytology ; metabolism ; pathology ; Lung Injury ; etiology ; metabolism ; pathology ; physiopathology ; Male ; Peptides ; metabolism ; Rats ; Rats, Sprague-Dawley ; Stem Cells ; metabolism ; pathology ; Telomerase ; metabolism

Hyperoxic ventilation induces detrimental effects on the respiratory system, and ambient oxygen may be harmful unless compensated by physiological anti-oxidants, such as vitamin C. Here we investigate the changes in electrolyte transport of airway epithelium in mice exposed to normobaric hyperoxia and in gulonolacton oxidase knock-out (gulo[-/-]) mice without vitamin C (Vit-C) supplementation. Short-circuit current (Isc) of tracheal epithelium was measured using Ussing chamber technique. After confirming amiloride-sensitive Na+ absorption (DeltaIsc,amil), cAMP-dependent Cl- secretion (DeltaIsc,forsk) was induced by forskolin. To evaluate Ca2+-dependent Cl- secretion, ATP was applied to the luminal side (DeltaIsc,ATP). In mice exposed to 98% PO2 for 36 hr, DeltaIsc,forsk decreased, DeltaIsc,amil and DeltaIsc,ATP was not affected. In gulo(-/-) mice, both DeltaIsc,forsk and DeltaIsc,ATP decreased from three weeks after Vit-C deprivation, while both were unchanged with Vit-C supplementation. At the fourth week, tissue resistance and all electrolyte transport activities were decreased. An immunofluorescence study showed that the expression of cystic fibrosis conductance regulator (CFTR) was decreased in gulo(-/-) mice, whereas the expression of KCNQ1 K+ channel was preserved. Taken together, the CFTR-mediated Cl- secretion of airway epithelium is susceptible to oxidative stress, which suggests that supplementation of the antioxidant might be beneficial for the maintenance of airway surface liquid.
Animals ; Ascorbic Acid Deficiency/*metabolism ; Biological Transport/drug effects ; Chlorides/*metabolism ; Cystic Fibrosis Transmembrane Conductance Regulator/antagonists & inhibitors/drug ; Forskolin/pharmacology ; Hyperbaric Oxygenation ; Hyperoxia/*physiopathology ; Ion Transport/drug effects ; Mice ; Mice, Inbred C57BL ; Mice, Inbred ICR ; Mice, Knockout/metabolism ; Mice, Transgenic ; Microscopy, Fluorescence ; Oxidative Stress ; Oxygen/adverse effects/pharmacology ; Potassium Channels/metabolism ; Respiratory Mucosa/drug effects/*metabolism/secretion ; Sodium ; Sugar Acids/metabolism