High-dose inhaled nitric oxide and hyperoxia increases lung collagen accumulation in piglets

Nitric oxide (NO), a pro-oxidant gas, is used with hyperoxia (O(2)) to treat neonatal pulmonary hypertension and recently bronchopulmonary dysplasia, but great concerns remain regarding NO's potential toxicity. Based on reports that exposure to oxidant gases results in pulmonary extracellular matrix injury associated with elevated lavage fluid levels of extracellular matrix components, we hypothesized that inhaled NO with or without hyperoxia will have the same effect. We measured alveolar septal width, lung collagen content, lavage fluid hydroxyproline, hyaluronan and laminin levels in neonatal piglets after 5 days' exposure to room air (RA), RA + 50 ppm NO (RA + NO), O(2) (FiO(2) > 0.96) or O(2) + NO. Matrix metalloproteinase (MMP) activity and MMP-2 mRNA were also measured. In recovery experiments, we measured lung collagen content in piglets exposed to RA + NO or O(2) + NO and then allowed to recover for 3 days. The results show that lung collagen increased 4-fold in the RA + NO piglets, the O(2) and O(2) + NO groups had only a 2-fold elevation relative to RA controls. Unlike the RA + NO piglets, the O(2) and O(2) + NO groups had more than 20-fold elevation in lung lavage fluid hydroxyproline compared to the RA group. O(2) and O(2) + NO also had increased lung MMP activity, extravascular water, and lavage fluid proteins. MMP-2 mRNA levels were unchanged. After 3 days' recovery in room air, the RA + NO groups' lung collagen had declined from 4-fold to 2-fold above the RA group values. The O(2) + NO group did not decline. Alveolar septal width increased significantly only in the O(2) and O(2) + NO groups. We conclude that 5 days' exposure to NO does not result in pulmonary matrix degradation but instead significantly increases lung collagen content. This effect appears potentially reversible. In contrast, hyperoxia exposure with or without NO results in pulmonary matrix degradation and increased lung collagen content. The observation that NO increased lung collagen content represents a new finding and suggests NO could potentially induce pulmonary fibrosis.     

Monocyte chemoattractant protein-1 and its receptor CCR-2 in piglet lungs exposed to inhaled nitric oxide and hyperoxia.

Monocyte chemoattractant protein-1 (MCP-1), acting through its C-C chemokine receptor 2 (CCR-2), has important roles in inflammation, angiogenesis, and wound repair. The individual and combined effects of inhaled nitric oxide (NO) and hyperoxia on lung MCP-1 and CCR-2 in relation to lung leukocyte dynamics are unknown. Because MCP-1 gene is up-regulated by oxidants, we hypothesized that inhaled NO with hyperoxia will increase MCP-1 production and CCR-2 expression more than either gas alone. We randomly assigned young piglets to breathe room air (RA), RA+50 ppm NO (RA+NO), O(2), or O(2)+NO for 1 or 5 d before sacrifice. Lungs were lavaged and tissues preserved for hybridization studies, Western blotting, histology, and immunohistochemistry. The results show that lung MCP-1 production and alveolar macrophage count were significantly elevated in the 5-d O(2) and O(2)+NO groups relative to the RA group (p < or = 0.05). In contrast, lung CCR-2 abundance was diminished in the O(2) group (p 相似文献   

Responses of pulmonary platelet-derived growth factor peptides and receptors to hyperoxia and nitric oxide in piglet lungs

The peptides platelet-derived growth factor-A (PDGF-A) and especially -B have important roles in lung development. The effect of hyperoxic exposure with and without inhaled nitric oxide (iNO) on lung expression of PDGF and its receptors is unknown. We hypothesized that hyperoxia exposure would suppress mRNA expression and protein production of these ligands and their receptors. The addition of iNO to hyperoxia may further aggravate the effects of hyperoxia. Thirteen-day-old piglets were randomized to breathe 1) room air (RA); 2) 0.96 fraction of inspired oxygen (O2), or 3) 0.96 fraction of inspired oxygen plus 50 ppm of NO (O2+NO), for 5 d. Lungs were preserved for mRNA, Western immunoblot, and immunohistochemical analyses for PDGF-A and -B and their receptors PDGFR-alpha and -beta. PDGF-B mRNA expression was greater than that of PDGF-A or PDGFR-alpha and -beta in RA piglet lungs (p<0.05). Hyperoxia with or without iNO reduced lung PDGF-B mRNA and protein expression relative to the RA group lungs (p<0.01). PDGF-B immunostain intensity was significantly increased in the alveolar macrophages, which were present in greater numbers in the hyperoxia-exposed piglet lungs, with or without NO (p<0.01). PDGFR-beta immunostaining was significantly increased in airway epithelial cells in O2- and O2+NO-exposed piglets. PDGF-A and PDGFR-alpha immunostain intensity and distribution pattern were unchanged relative to the RA group. Sublethal hyperoxia decreases PDGF-B mRNA and protein expression but not PDGF-A or their receptors in piglet lungs. iNO neither aggravates nor ameliorates this effect.     

Independent and combined effects of prolonged inhaled nitric oxide and oxygen on lung inflammation in newborn piglets

Clinical use of nitric oxide (NO) is usually in conjunction with high oxygen concentrations, the effects of which may include lung neutrophil accumulation, apoptosis and upregulation of antioxidant enzyme activity. To define the effects of NO on neutrophils from young piglets and its relationship to lung neutrophil dynamics during hyperoxia we exposed thirty piglets to room air (RA), RA+NO (50 ppm NO), O2 (FiO2> or =0.96) or O2+NO for 5 days. Ten additional animals breathed RA+NO or O2+NO, then recovered in RA for 3 days before sacrifice. Neutrophil CD18 and intracellular oxidant production were measured by flow cytometry. Lung apoptosis were assessed by TUNEL assay. Lung myeloperoxidase, SOD and catalase were measured biochemically. When compared to RA group, there was significant reduction in neutrophil CD18 and intracellular oxidant production in the RA+NO group, but lung MPO was unchanged. The O2 and O2+NO groups did not differ in CD18 expression or in intracellular oxidant production, but had significant increase in lung myeloperoxidase compared to the RA group. Apoptosis increased significantly only in the O2+NO group. The O2 group showed significantly increased lung SOD and catalase activity compared to the RA group, whereas the RA+NO and O2+NO groups did not. We conclude that inhaled NO at 50 ppm decreases neutrophil CD18 expression as well as intracellular oxidant production. However, this effect does not impact lung neutrophil accumulation during concurrent hyperoxia. The combination of NO and O2 exposure produces an increase in lung apoptosis. Finally, NO may prevent upregulation of SOD and catalase activity during hyperoxia, potentially increasing injury.     

高氧、维甲酸对早产鼠肺组织基质金属蛋白酶-2、-9 及特异性组织抑制物-1、-2表达的影响

目的探讨基质金属原蛋白-2(MMP-2)、MMP-9、基质金属蛋白酶特异性组织抑制物-1(TIMP-1)和TIMP-2在高氧肺损伤中的作用及维甲酸(RA)的保护作用机制。方法建立高氧(FiO285%)暴露早产SD大鼠肺损伤模型,应用RT-PCR法检测MMP-2、MMP-9、TIMP-1和TIMP-2mRNA表达,采用明胶酶谱检测MMP-2和MMP-9酶原及活酶表达,采用Western blot技术检测TIMP-1和TIMP-2蛋白表达。结果与空气组比较,高氧暴露4、7、14d,MMP-2、MMP-9和TIMP-1 mRNA的表达均显著升高(P均<0.01),MMP-2活酶、MMP-9酶原及活酶和TIMP-1蛋白的表达明显上调(P<0.05);RA对空气暴露下它们的表达均无明显影响(P均>0.05),但不同程度下调高氧暴露后MMP-2、MMP-9、TIMP-1mRNA的表达和MMP-2活酶、MMP-9酶原及活酶的表达,进一步提高TIMP-1蛋白表达;高氧、RA对TIMP-2 mRNA和蛋白的表达均无明显影响(P均>0.05)。结论高氧暴露明显改变MMPs/TIMPs的表达,在肺泡形成关键时期,MMPs/TIMPs之间平衡关系的破坏是造成肺发育受阻和纤维化的重要因素;通过协调MMPs/TIMPs之间的表达,改善肺泡结构,降低肺纤维化程度,从而逆转高氧所致肺损伤,是RA发挥保护作用的重要机制之一。     

维甲酸下调结缔组织生长因子表达减轻新生大鼠高氧肺损伤的研究

目的：探讨维甲酸（RA）对高氧肺损伤保护作用的机制。方法：90 只Sprague Dawley新生鼠随机平分为空气组、高氧组和高氧+RA 组。高氧组、高氧+RA 组置于 85% 氧浓度的氧箱中,高氧+RA 组每日腹腔注射RA 500 μg/kg。分别于实验第 4天、7天、14天行开胸术取新生鼠肺组织,苏木精-伊红染色光镜下行辐射状肺泡计数,逆转录聚合酶链反应（RT-PCR）、免疫组化检测肺组织结缔组织生长因子（CTGF）表达。结果：与空气组相比,高氧组和高氧+RA 组肺组织随氧暴露时间延长,出现炎性细胞浸润,肺泡结构紊乱,肺泡数量减少,肺间隔增厚,其中高氧+RA 组病理改变明显轻于高氧组;在第7天和第14天,高氧组和高氧+RA组肺组织 CTGF 的 mRNA 和蛋白表达比空气组增加（P＜0.05）;且高氧+RA组中 CTGF 的 mRNA 和蛋白表达在第 14 d 比高氧组减少（P＜0.05）。结论：高氧暴露下新生鼠肺组织 CTGF 表达增加,RA 保护高氧肺损伤可能是通过下调 CTGF 表达。     

Relation between serum insulinlike growth factor-1, insulinlike growth factor binding protein-2, and insulinlike growth factor binding protein-3 and nutritional intake in premature infants with bronchopulmonary dysplasia.

BACKGROUND: The usefulness of serum insulinlike growth factor (IGF)-system-peptide measurement to assess the adequacy of nutritional intake in premature infants with chronic lung disease bronchopulmonary dysplasia (BPD) was assessed. METHODS: Twenty-nine premature infants had serial measurements taken of their serum IGF-1, insulinlike growth factor binding protein (IGFBP)-2, and IGFBP-3 concentrations between 2 and 6 weeks of age. Regression analyses were used to examine the relation between nutritional parameters and IGF-1, IGFBP-2, and IGFBP-3 concentrations in premature infants with and without BPD. RESULTS: The group of infants with BPD (n = 12) did not differ from infants without BPD (n = 17) in gestational age or weight at entry, but gained less weight during the study period. In infants without BPD, IGF-1 correlated positively with protein intake (r = 0.50) and caloric intake (r = 0.41) over the 3 days before sample collection and with weight change over the previous week (r = 0.46). In contrast, infants with BPD showed a significant correlation between IGF-1 and weight change (r = 0.54) only. There was a significant negative correlation between IGFBP-2 and protein intake in infants without BPD (r = -0.50) and in infants with BPD (r = -0.41). Negative correlations between IGFBP-2 and both weight change (r = -0.64) and caloric intake (r = -0.43) over the previous week were found only in the group of infants without BPD. IGFBP-3 correlated positively with weight changes and protein intake in both groups but correlated with caloric intake only in the group without BPD. Multiple regression analyses were used to determine significant independent variables associated with IGF-1, IGFBP-2, and IGFBP-3. In infants without BPD, significant independent predictors of IGFBP-2 were 7-day weight change and 2-day protein intake; 3-day caloric intake was the only significant independent predictor for IGFBP-3. For infants with BPD, 3-day weight gain was the only independent variable associated with serum IGF-1. Protein intake in the week before sample collection was an independent predictor of IGFBP-2 and 3-day weight change and 2-day protein intake were independent predictors of IGFBP-3. CONCLUSIONS: These results confirm that changes in serum IGF-1, IGFBP-2, and IGFBP-3 reflect the nutritional status of premature infants and demonstrate that the relation between these proteins and nutritional intake differs in premature infants with and without BPD. Refinement of these observations by future studies may permit a more accurate determination of the protein and caloric intake sufficient for growth and repair after injury in premature infants with lung disease.     

高氧对新生大鼠肺caspase-3和p53基因表达及肺细胞凋亡的影响

目的探讨高氧对新生大鼠肺caspase3和p53基因表达及肺细胞凋亡的影响。方法采用SpraqueDawley新生大鼠95%氧气暴露建立高氧肺损伤模型。应用RTPCR技术检测肺组织caspase3mRNA和p53mRNA水平,凝胶电泳条带用成像系统照相分析结果。计算目的基因PCR产物条带与内参照βactin条带光密度值的比值,作为p53基因的相对表达量,结果以x±s标记,而caspase3mRNA表达量则以阳性表达或阴性表达为标记。应用脱氧核糖核酸转移酶介导的细胞凋亡标记技术(TUNEL)原位检测细胞凋亡。光镜下随机计算5个视野中500个肺细胞中的阳性细胞数,结果以x±s标记。结果新生大鼠暴露于95%氧浓度环境中24h后肺组织中p53mRNA表达中度增加(q=3.2305,P>0.05),48h后表达显著增加,与空气对照组相比差异有统计学意义(q=7.2941,P<0.05)。新生鼠高氧处理72h、96h后,肺组织p53mRNA表达又恢复到正常水平。在各空气对照组和各高氧处理组中个别新生鼠肺的caspase3mRNA有微量表达,绝大多数新生鼠肺的caspase3mRNA没有表达,差异无统计学意义。95%氧暴露7天的新生鼠肺细胞凋亡水平明显高于空气暴露组新生鼠肺细胞凋亡水平,两者比较差异有极显著的统计学意义(F=100,P<0.001)。结论在高浓度供氧下,肺组织通过暂时上调p53基因的表达,介导细胞周期停滞,阻止G0/G1期细胞进入S期,抑制细胞分裂、增殖,同时p53促进细胞凋亡,从而导致肺生长发育受阻和肺损伤。新生鼠暴露于95%氧环境中,肺组织caspase3基因基本上不表达,因此推测高氧肺细胞凋亡可能存在不经过caspase3的凋亡途径。     

Endostatin and vascular endothelial cell growth factor (VEGF) in piglet lungs: effect of inhaled nitric oxide and hyperoxia

Pulmonary hyperoxic injury manifests as widespread alveolar-epithelial and microvascular endothelial cell necrosis, resolution of which requires angiogenesis. We investigated the hypothesis that inhaled nitric oxide (iNO) and hyperoxia each decreases lung vascular endothelial growth factor (VEGF) expression but increases endostatin and that concurrent administration of both gases will show a greater effect. Piglets were randomized to breathe for 5 d room air (RA); RA + NO (RA + 50 ppm NO), O(2) (hyperoxia, F(I)O(2) >0.96), O(2) + NO, or O(2) + NO + REC (O(2) + NO plus recovery in 50% O(2) for 72 h. After the piglets were killed, we measured lung capillary leak, VEGF mRNA, VEGF, and endostatin protein in homogenates, plasma, and lavage. VEGF mRNA decreased significantly with O(2) and O(2) + NO compared with breathing RA (p < or = 0.05). VEGF protein declined in the experimental groups with a significant reduction in the recovery group compared with the RA group (p < or = 0.05). Similar but more dramatic, endostatin declined in all groups relative to the RA group (p < 0.001). Lavage fluid VEGF protein and lung capillary leak rose significantly with O(2) and O(2) + NO compared with RA, but endostatin was unchanged. At 72 h of recovery from hyperoxia, VEGF mRNA and lavage fluid VEGF but not lung VEGF protein had normalized. Hyperoxia and iNO suppresses lung endostatin expression, but iNO unlike hyperoxia alone does not alter lung VEGF production. Hyperoxia paradoxically raises lavageable VEGF levels. This latter effect and that on VEGF mRNA level but not protein is abrogated by recovery in reduced F(I)O(2) for 72 h.     

Bone metabolism and circulating IGF-I and IGFBPs in dexamethasone-treated preterm infants

AIM: To characterize the ontogeny of circulating IGF-I, the IGF binding proteins (IGFBPs) and biochemical markers of bone turnover in dexamethasone (DEX)-treated preterm infants with chronic lung disease. METHODS: Plasma and urine samples from 17 infants were obtained prior to DEX, after 9-12 days of DEX and 10 days after the completion of DEX to assess plasma IGF-I, IGFBPs, osteocalcin and urinary N-telopeptide. Nutrient intakes and growth were monitored from birth until term corrected age at which time body composition was evaluated by dual energy X-ray absorptiometry. RESULTS: Although nutrient intakes did not differ during or after DEX, weight gain (115 vs. 174 g/week) and length gain (0.7 vs. 1.0 cm/week) were higher after DEX treatment. Plasma IGF-I, IGFBP-3 and osteocalcin increased over time. N-telopeptide was the only biochemical parameter which appeared to be suppressed during DEX (1342 nM bone collagen equivalents/mM creatinine vs. 2486 (pre-DEX) and 2292 (post-DEX)). At term corrected age, bone mineral content was lower in dexamethasone-treated infants compared to preterm and term reference infants. CONCLUSION: Changes in circulating IGFBP-2 and IGFBP-3 paralleled the changes reported in non-steroid-treated infants; however, it remains uncertain whether the natural rise in IGF-I was suppressed by DEX treatment. Assessment of these circulating components provided limited insight into the mechanisms by which DEX alters growth and bone turnover.     

Up-regulation of connective tissue growth factor in hyperoxia-induced lung fibrosis

Pulmonary oxygen toxicity plays an important role in the lung injury process that leads to the development of bronchopulmonary dysplasia. Connective tissue growth factor (CTGF) is a fibroblast mitogen and promoter of collagen deposition. We investigated the effects of postnatal hyperoxia on lung collagen and CTGF expression in rats. Rat pups were exposed to 7 d of >95% O2 and a further 3 wk of 60% O2. CTGF mRNA and protein expression increased after hyperoxia treatment, and the values were significantly higher in hyperoxia-exposed rats on postnatal d 7 and 14. Lung collagen levels increased as rats aged, and the values were comparable between room air-exposed and hyperoxia-exposed rats on postnatal d 7 and 14 and were significantly higher in hyperoxia-exposed rats on postnatal d 21 and 28. Increases in CTGF mRNA and protein expressions preceded the onset of increased lung collagen. These data demonstrate that CTGF is up-regulated at time points preceding the fibrotic phase of the lung injury adding credence to the hypothesis that CTGF seems to be involved in the pathogenesis of hyperoxia-induced lung fibrosis and an anti-CTGF strategy might attenuate hyperoxia-induced lung fibrosis.     

新生大鼠高氧肺损伤血管内皮生长因子蛋白及其mRNA表达变化研究

目的：血管内皮生长因子（VEGF）参与肺的发育和损伤修复,VEGF具有促进肺泡和肺血管增殖以及预防新生儿支气管肺发育不良（BPD）的作用。该研究的目的是探讨新生大鼠高氧肺损伤后肺组织VEGF蛋白及VEGF mRNA表达的变化。方法：新生Sprague-Dawley大鼠48只随机分为高氧实验组和空气对照组,高氧实验组吸入95%以上高氧建立高氧肺损伤模型。分别采用免疫组化法和逆转录多聚酶链式反应（RT-PCR）检测新生大鼠3 d,7 d,14 d肺组织VEGF蛋白及VEGF mRNA表达变化。结果：空气对照组新生大鼠生后随着肺发育,肺组织中VEGF蛋白及VEGF mRNA表达逐渐增加。高氧实验组新生鼠吸入高氧3 d,肺VEGF蛋白表达出现降低,在7 d,14 d明显降低与对照组比较差异有显著性（VEGF 蛋白:12.67±3.82 vs 7.79±5.23; 15.10±8.91 vs 5.85±3.37, 均P<0.01）;高氧实验组VEGF mRNA表达在3 d,7 d,14 d均明显低于对照组（VEGF mRNA: 1.19±0.63 vs 0.78±0.22, 1.52±0.47 vs 0.53±0.18, 1.89±0.81 vs 0.48±0.12, 均P<0.01）。结论：VEGF能促进新生大鼠肺发育,VEGF蛋白及VEGF mRNA表达与新生大鼠肺发育有密切关系。高氧可抑制VEGF蛋白及VEGF mRNA在新生大鼠肺内的表达,VEGF在新生鼠肺发育和高氧肺损伤发病机制中起重要作用。     

Differential response of the epithelium and interstitium in developing human fetal lung explants to hyperoxia

Hyperoxia is closely linked with the development of chronic lung disease of prematurity (CLD), but the exact mechanisms whereby hyperoxia alters the lung architecture in the developing lung remain largely unknown. We developed a fetal human lung organ culture model to investigate (a) the morphologic changes induced by hyperoxia and (b) whether hyperoxia resulted in differential cellular responses in the epithelium and interstitium. The effects of hyperoxia on lung morphometry were analyzed using computer-assisted image analysis. The lung architecture remained largely unchanged in normoxia lasting as long as 4 d. In contrast, hyperoxic culture of pseudoglandular fetal lungs resulted in significant dilatation of airways, thinning of the epithelium, and regression of the interstitium including the pulmonary vasculature. Although there were no significant differences in Ki67 between normoxic and hyperoxic lungs, activated caspase-3 was significantly increased in interstitial cells, but not epithelial cells, under hyperoxic conditions. These changes show that exposure of pseudoglandular lungs to hyperoxia modulates the lung architecture to resemble saccular lungs.     

高氧对发育中人胎儿肺组织分化的影响及地塞米松作用的研究

目的：高氧可能通过改变未成熟肺组织正常结构发育而导致肺功能异常。该研究通过观察高氧时体外培养胎儿肺组织结构和细胞分化的变化特点及地塞米松对这些肺组织的作用,旨在了解高氧对胎儿肺组织发育的影响。方法：用培养人假腺体期胎儿肺组织模型分别于高氧(95%O2,5%CO2)及正常氧(21%O2,5%CO2)中培养72 h,两组又分为地塞米松组(10-6M)及无地塞米松组。收获的肺组织以细胞角蛋白(pancytokeratin)确定上皮细胞,K i-67作为增生性细胞标记物。形态学结果用计算机辅助图像分析系统处理,分别计算出平均气道厚度,气道占组织比例(%),平均气道面积及细胞增生指数。结果：正常氧培养72 h,肺结构无明显改变,而高氧组气道明显扩张。高氧组与正常氧组比较,气道面积6 662μm2vs 2 728μm2;气道厚度7.8μm vs 8.1μm;气道所占比例35.2%vs 23.4%,差异有显著性(均P<0.05)。高氧并用地塞米松组气道面积(3 174μm2)及气道所占比例(23.9%)与高氧组比较,均明显降低,P<0.05;气道厚度无明显变化。高氧组上皮增生指数(21.8%)明显高于正常氧组(5.1%)及并用地塞米松组(7.4%),P<0.05。结论：高氧促进假腺体期胎儿肺组织分化为类似囊状期样结构,这种变化与气道上皮细胞异常增生有关;地塞米松具有抑制高氧对胎儿肺组织的损伤作用。     

85%高浓度氧长期暴露诱发早产大鼠肺损伤(英文)

目的：探讨长期高浓度氧(85％)暴露对早产新生大鼠肺组织的损伤作用。方法：早产SD大鼠生后第2天被随机分为Ⅰ空气组、Ⅱ高氧组(置85％O2中)。分别于暴露3,7,14 d后,检测支气管肺泡灌洗液(BALF)中总蛋白(TP)、丙二醛(MDA)、羟脯氨酸(HYP)含量和细胞总数及分类,肺组织湿重/干重(W/D),肺组织胶原含量;于暴露3,7,14,21 d后,行肺组织病理学检查和辐射状肺泡计数(RAC)。结果：3 d时Ⅱ组仅MDA含量增加(P<0.05);7,14 d时,Ⅱ组BALF中MDA,TP,HYP含量、细胞总数、细胞分类中性粒细胞所占比例及肺W/D均明显增加(P<0.05或<0.01)。两组肺胶原含量差异无显著性(P>0.05)。除3 d外,Ⅱ组肺组织病理学检查可见不同程度的肺泡炎改变和肺发育滞后。7 d时Ⅱ组RAC值较Ⅰ组明显减少[(5.9±0.9)vs(7.1±0.9)](P<0.05);14,21 d时RAC值Ⅱ组较Ⅰ组[(7.0±0.8)vs(9.9±0.6);(7.3±0.9)vs(10.5±0.8)]减少更明显(P<0.01)。结论：85％O2长期暴露,可引起早产新生大鼠亚急性炎症性肺损伤和肺发育受抑。     

VEGF attenuates hyperoxic injury through decreased apoptosis in explanted rat embryonic lung

Ambient oxygen concentration and vascular endothelial growth factor (VEGF)-A are vital in lung development. Since hypoxia stimulates VEGF-A production and hyperoxia reduces it, we hypothesized that VEGF-A down-regulation by exposure of airways to hyperoxia may result in abnormal lung development. An established model of in vitro rat lung development was used to examine the effects of hyperoxia on embryonic lung morphogenesis and VEGF-A expression. Under physiologic conditions, lung explant growth and branching is similar to that seen in vivo. However, in hyperoxia (50% O2) the number of terminal buds and branch length was significantly reduced after 4 d of culture. This effect correlated with a significant increase in cellular apoptosis and decrease in proliferation compared with culture under physiologic conditions. mRNA for Vegf164 and Vegf188 was reduced during hyperoxia and addition of VEGF165, but not VEGF121, to explants grown in 50% O2 resulted in partial reversal of the decrease in lung branching, correlating with a decrease in cell apoptosis. Thus, hyperoxia suppresses VEGF-A expression and inhibits airway growth and branching. The ability of exogenous VEGF165 to partially reverse apoptotic effects suggests this may be a potential approach for the prevention of hyperoxic injury.     

基质金属蛋白酶及其组织抑制剂在高氧性肺损伤中的变化

目的 探讨基质金属蛋白酶(MMPs)及其组织抑制剂(TIMPs)在高氧性肺损伤中表达及意义。方法 幼年Wistar大鼠32只,随机分为空气组和高氧组,并于高氧暴露3、7、14 d后用免疫组织化学方法(SABC)观察MMP-2、MMP-9、TIMP-1、TIMP-2在肺组织中的分布,用逆转录聚合酶链反应(RT-PCR)观察MMP-2、MMP-9、TIMP-1、TIMP-2 mRNA在肺组织中表达,此外对支气管肺泡灌洗液(BALF)中的蛋白含量、肺通透系数、肺湿／干重比(W／D)及肺组织病理学改变也进行对比分析。结果 高氧组3 d时肺组织出现水肿、出血、炎性细胞浸润,7 d时进一步加重,14 d时间质细胞增生,肺间隔明显增宽,出现肺纤维化倾向。W／D值、肺通透系数和BALF蛋白含量在3、7、14 d均明显高于空气组(P均<0.05)。免疫组化法示MMP-2、MMP-9、TIMP-1、TIMP-2在正常肺泡上皮细胞、支气管上皮细胞呈弱阳性表达,高氧组3 d时肺泡上皮细胞、支气管上皮细胞、巨噬细胞、肺泡间质细胞均呈强阳性表达,7、14 d表达更广泛。与空气组相比,高氧3 d时MMP-2、MMP-9 mRNA表达水平明显增加,7 d时最显著,14 d开始下降(P均<0.05),而TIMP-1、TIMP-2 mRNA表达却持续增加,14 d时仍无明显下降(P均<0.05)。高氧暴露后MMP-2／TIMP-2、MMP-9／TIMP-1比值亦增加,其中7 d时最为显著,14 d开始下降。结     

Altered expressions of fibroblast growth factor receptors and alveolarization in neonatal mice exposed to 85% oxygen

In the present study, we tested the hypothesis that exposure of newborn mice to sublethal hyperoxia would alter lung development and expressions of fibroblast growth factor receptors (FGFRs)-3 and FGFR-4. Newborn FVB mice were exposed to 85% O2 or maintained in room air for up to 14 d. No animal mortality was observed, and body weight gains were not affected by hyperoxia. At postnatal d 7 and 14 (P7, P14), lungs of mice exposed to 85% O2 showed fewer alveolar secondary crests and larger alveoli or terminal air spaces than did mice in room air. In pups kept in room air, lung levels of FGFR-3 and FGFR-4 mRNA were greater at P3 than at P1, but similar increases were not observed in hyperoxic mice. Immunoreactivity of FGFR-3 and FGFR-4 was lower in lungs of hyperoxic mice than in controls at P14. In pups kept in room air, lung fibroblast growth factor (FGF)-7 mRNA levels were greater at P14 than at P1, but similar changes were not observed in hyperoxic mice. The temporally and spatially specific alterations in the expressions of FGFR-3, FGFR-4, and FGF-7 in the mice exposed to hyperoxia may contribute to aberrant lung development.