Inhaled nitric oxide attenuates hyperoxic lung injury in lambs

Cytochrome P450 (CYP) inhibition with cimetidine reduces hyperoxic lung injury in young lambs. Nitric oxide (NO), also a CYP inhibitor, has been shown to either aggravate or protect against oxidant stress depending on experimental context. The objective of this study was to determine whether NO, like cimetidine, would protect young lambs against hyperoxic lung injury, and whether its effect was associated with CYP inhibition. Three groups of lambs were studied: 1) room air exposure, 2) >95% O2, and 3) >95% O2 plus inhaled NO. After 72 h, hyperoxia alone resulted in a significant increase in arterial P(CO2) and number of polymorphonuclear leukocytes in bronchoalveolar lavage (BAL), and a significant decrease in arterial/alveolar O2 tension (a/A). The addition of inhaled NO significantly decreased the hypercarbia and BAL polymorphonuclear cellular response associated with hyperoxia but had no beneficial effect on a/A ratio. There were no significant differences in F2-isoprostanes or isofurans (markers of lipid peroxidation) measured in BAL or lung tissue among study groups. No intergroup differences were detected in BAL epoxyeicosatrienoic acid levels (index of CYP activity). The results of this study indicate that hypercarbia and inflammation accompanying hyperoxic lung injury in young lambs can be attenuated by inhaled NO. However, this study provides no direct evidence that NO is inhibiting CYP-mediated oxidant lung injury.     

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.     

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.     

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.     

The effect of inhaled nitric oxide and oxygen on the hydroxylation of salicylate in rat lungs

Inhaled nitric oxide (iNO) is used as a selective pulmonary vasodilator, and often under conditions when a high fraction of inspired oxygen is indicated. However, little is known about the potential toxicity of iNO therapy with or without concomitant oxygen therapy. NO can combine with superoxide (O2-) to form peroxynitrite (ONOO-), which can in turn decompose to form hydroxyl radical (OH.). Both OH. and ONOO- are involved in various forms of lung injury. To begin evaluation of the effect of iNO under either normoxic or hyperoxic conditions on OH. and/or ONOO- formation, rats were exposed for 58 h to either 21% O2, 21% O2 + 10 parts per million (ppm) NO, 21% O2 + 100 ppm NO, 50% O2, 90% O2, 90% O2 + 10 ppm NO, or 90% O2 + 100 ppm NO. We used a salicylate hydroxylation assay to detect the effects of these exposures on lung OH. and/or ONOO- formation measured as the appearance of 2,3-dihydroxybenzoic acid (2,3-DHBA). Exposure to 90% O2 and 90% O2 + 100 ppm NO resulted in significantly (p < 0.05) greater lung wet weight (1.99 +/- 0.14 g and 3.14 +/- 0.30 g, respectively) compared with 21% O2 (1.23 +/- 0.01 g). Exposure to 21% O2 + 100 ppm NO led to 2.5 times the control (21% O2 alone) 2,3 DHBA formation (p < 0.05) and exposure to 90% O2 led to 2.4 times the control 2,3-DHBA formation (p < 0.05). However, with exposure to both 90% O2 and 100 ppm NO, the 2,3-DHBA formation was no greater than the control condition (21% O2). Thus, these results indicate that, individually, both the hyperoxia and the 100 ppm NO led to greater salicylate hydroxylation, but that the combination of hyperoxia and 100 ppm NO led to less salicylate hydroxylation than either did individually. The production of OH. and/or ONOO- in the lung during iNO therapy may depend on the ratio of NO to O2.     

Modulation of pulmonary cytochrome P4501A1 expression by hyperoxia and inhaled nitric oxide in the newborn rat: implications for lung injury

Inhaled nitric oxide (iNO), with supplemental oxygen, is used in the treatment of hypoxic respiratory failure of the newborn. In this study, we tested the hypothesis that exposure of newborn rats to iNO, hyperoxia, or iNO + hyperoxia would modulate the expression of pulmonary cytochrome P450 (CYP)1A1 in relation to acute lung injury. Newborn Fischer 344 rats were maintained in room air, or exposed to iNO, hyperoxia (>95%), or iNO (20 or 40 ppm) + hyperoxia for up to 168 h, and lung injury parameters and CYP1A1 expression were studied. Animals given iNO (40 ppm) + hyperoxia were more susceptible to lung injury than those exposed to hyperoxia or iNO alone. On the other hand, animals exposed to iNO (20 ppm) + hyperoxia did not elicit lung damage. Pulmonary CYP1A1 protein and mRNA expression were induced by hyperoxia, iNO (20 or 40 ppm), or iNO (20 ppm) + hyperoxia for up to 168 h, compared with air-breathing controls. In animals given iNO (40 ppm) + hyperoxia, pulmonary CYP1A1 was enhanced at 48 h, followed by down-regulation at later time points. Immunohistochemistry experiments showed localization of CYP1A1 in the pulmonary epithelial and endothelial cells. In conclusion, because previous studies have shown beneficial effects of CYP1A1 induction in hyperoxic lung injury, our current observations showing maintenance of pulmonary CYP1A1 induction by iNO (20 ppm) + hyperoxia through the 168-h period support the hypothesis that this phenomenon may contribute to the protective effects of iNO against hyperoxic injury.     

粘着斑激酶在早产大鼠高氧肺损伤肺组织中的表达变化和意义

目的探讨粘着斑激酶(FAK)与高氧肺损伤发生、发展的关系。方法剖宫术取出孕21 d大鼠作为早产鼠,分别置早产鼠于85％高氧环境下3、7和14 d,各组均以空气组早产鼠为对照,留取肺组织标本,采用免疫组织化学法和Western blot技术对高氧组和空气组肺组织FAK多肽表达进行定位、定量检测,采用RT-PCR方法对FAK mRNA表达水平进行半定量分析。结果 FAK mRNA和蛋白在空气组早产大鼠肺组织均有较高水平表达,高氧暴露3、7和14 d后,FAK mRNA和蛋白表达水平均呈不同程度的下降,尤以高氧14 d最明显。结论高氧抑制FAK表达是导致正常肺泡化过程受阻以及不成熟肺组织损伤后异常修复的重要因素,其机制可能与其抑制肺泡上皮细胞增殖、分化,以及毛细血管形成有关。     

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   

肺表面活性物质和吸入一氧化氮治疗家兔胎粪吸入性肺损伤

目的　观察在应用肺表面活性物质 (Surf)和吸入一氧化氮 (NO)预防性治疗家兔胎粪吸入性急性肺损伤 (ALI)并机械通气时的疗效。方法　将 3 3只成年家兔随机分为 5组进行治疗 :即对照组 (C ,n =8)、NO组 (n =6)、Surf组 (n =7)、NO +Surf组 (SNO ,n =6)、正常组 (N ,n =6)。前四组用胎粪生理盐水混悬液滴入气道内经机械通气造成ALI并随机分四组治疗 ;N组气道内滴入生理盐水替代 ;NO组连续吸入NO 1× 10 - 6 、10× 10 - 6 、2 0× 10 - 6 、40× 10 - 6 各 1h ,间隔停用 3 0min ;Surf组气道内滴入猪肺Surf10 0mg/kg ;SNO组联合NO吸入及Surf组治疗 ,各组均治疗 6h ,同时测定血气、肺呼吸力学判断疗效。化学发光法检测吸入气NO浓度。结果　在C组胎粪滴入 3 0min后动脉血氧合 (PaO2 /FiO2 )及呼吸顺应性 (DynamicCompliance ,Cdyn)显著变差 ,治疗后血氧合、Cdyn在SNO组显著改善 ,Surf和NO组略有改善。在湿化器前持续接入NO可在供气管道“Y”近端测得较为稳定的吸入NO浓度 ,受呼出气的影响最小 ,( 10～ 2 0 )× 10 - 6 NO吸入有较好的效果。结论　Surf联合NO治疗在有效预防ALI上优于单独应用Surf或NO。从呼吸机供气管路持续接入NO测定到稳定NO浓度与接入气和监测部位有关     

降钙素基因相关肽调控细胞外信号调节激酶减轻高体积分数氧对胎鼠肺泡Ⅱ型上皮细胞的损伤作用

目的 探讨降钙素基因相关肽(CGRP)对高体积分数氧(高氧)暴露下胎鼠肺泡Ⅱ型上皮细胞( AECⅡ)氧化损伤的影响,及其作用是否由细胞外信号调节激酶(ERK)所介导.方法 原代分离培养孕21 d胎鼠AECⅡ,培养12 h待细胞贴壁后分为6组:空气组、空气CGRP组、空气CGRP拮抗剂组、高氧组、高氧CGRP组、高氧CGRP拮抗剂组.空气组和高氧组分别在氧体积分数为210 mL·L-1的空气或850 mL·L-1的氧气中培养18 h.CGRP组和CGRP拮抗剂组分别在空气或高氧暴露前加入CGRP或同时加入CGRP和其受体拮抗剂CGRPS-37,终浓度分别为10-8 mol·L-1和10-7 mol·L-1.用免疫比浊法测定培养液LDH、AKP和丙二醛(MDA)水平,流式细胞术测定细胞内活性氧(RoS)水平,荧光显微镜检测胞质表面活性蛋白C(SP-C)的表达情况,Western blot检测磷酸化ERK1,2(p-ERK1/2)的表达水平.结果 高氧组MDA、LDH、AKP、ROS及p-ERK1/2水平均明显高于空气组[(2.29±0.10) μmol ·L-1 vs (1.06 ±0.14)μmol·L-1,( 58.79±5.01)U·L-1 vs(25.92±3.68)U·L-1,(24.63±2.92)U·L-1 vs (10.34±1.78)U·L-1,47.74±3.35 vs 25.96±5.04,1.21±0.06 vs 0.45±0.05,Pa＜0.01],而细胞内SP-C表达则明显低于空气组(22.75±3.31 vs 43.50±4.42);与高氧组及高氧CGRP拮抗剂组比较,高氧CGRP组MDA、LDH、ROS及AKP水平显著降低,而p-ERK1/2及SP-C的表达水平则明显增高(Pa＜0.01).空气组、空气CGRP组、空气CGRP拮抗剂组组间MDA、LDH、ROS、AKP及SP-C表达水平比较差异均无统计学意义;空气CGRP组p-ERK1/2表达水平明显高于空气组及空气CGRP拮抗剂组(Pa＜0.01).结论 CGRP可减轻高氧对AECⅡ的氧化损伤,其作用机制可能是通过ERK的活化来介导.     

Matrigel胶对高氧损伤早产鼠肺泡Ⅱ型细胞黏着斑激酶表达变化及其对肺泡Ⅱ型细胞增殖和凋亡的影响

目的 探讨人工重组基底膜Matrigel胶对高氧暴露下早产鼠Ⅱ型肺泡上皮细胞(Alveolar Epithelial CellⅡ,AECⅡ)黏着斑激酶(focal adhesion kinase,FAK)表达变化及其对AECⅡ增殖、凋亡的影响.方法 原代培养早产鼠AECⅡ,建立高氧细胞模型,采用免疫印迹分析Matrigel胶对AECⅡFAK蛋白、磷酸化FAK( FAK- Tyr397)蛋白、FAK mRNA表达的影响,以了解Matrigel胶对FAK活性的调节作用;并进一步用细胞核增殖抗原(proliferating cell nuclear antigen,PCNA)免疫细胞化学法和原位缺口末端标记(TUNEL)法分别检测FAK抑制和激活状态下AECⅡ增殖和凋亡状况.结果 接种于Matrigel胶后,AECⅡFAK蛋白、FAK-Tyr397蛋白及FAK mRNA表达水平均明显增加;与空气对照组比较,高氧暴露12h时,AECⅡPCNA表达强度明显下降(0.1498±0.009 vs 0.0953±0.006,P＜0.05),TUNEL标记细胞明显增多(1.232 ±0.6 Vs 13.40±3.2,P＜0.01);接种于Matrigel胶后AECⅡ凋亡指数差异无统计学意义,而PCNA表达强度明显增强(0.1498±0.009 Vs 0.1921±0.008,P＜0.01).与高氧组比较,高氧+Matrigel组AECⅡPCNA表达明显增高(0.0953±0.006 Vs0.1125±0.012,P＜0.05),凋亡指数明显下降(13.40±3.2 Vs 7.641±1.6,P＜0.05).结论 高浓度氧抑制AECⅡ增殖、诱导其凋亡,并抑制AECⅡFAK的表达;Matrigel胶具有抑制AECⅡ凋亡、促进AECⅡ增殖作用,对高氧暴露下AECⅡ具有保护作用,且与其促进FAK表达和活化有关.     

Inhaled nitric oxide enhances distal lung growth after exposure to hyperoxia in neonatal rats

Exposure of newborn rats to hyperoxia impairs alveolarization and vessel growth, causing abnormal lung structure that persists during infancy. Recent studies have shown that impaired angiogenesis due to inhibition of vascular endothelial growth factor (VEGF) signaling decreases alveolar and vessel growth in the developing lung, and that nitric oxide (NO) mediates VEGF-dependent angiogenesis. The purpose of this study was to determine whether hyperoxia causes sustained reduction of lung VEGF, VEGF receptor, or endothelial NO synthase (eNOS) expression during recovery, and whether inhaled NO improves lung structure in infant rats after neonatal exposure to hyperoxia. Newborn rat pups were randomized to hyperoxia [fraction of inspired oxygen (Fio(2)), 1.00] or room air exposure for 6 d, and then placed in room air with or without inhaled NO (10 ppm) for 2 wk. Rats were then killed for studies, which included measurements of body weight, lung weight, right ventricular hypertrophy (RVH), morphometric analysis of alveolarization (by mean linear intercept (MLI), radial alveolar counts (RAC), and vascular volume (Vv), and immunostaining and Western blot analysis. In comparison with controls, neonatal hyperoxia reduced body weight, increased MLI, and reduced RAC in infant rats. Lung VEGF, VEGFR-2, and eNOS protein expression were reduced after hyperoxia. Inhaled NO treatment after hyperoxia increased body weight and improved distal lung growth, as demonstrated by increased RAC and Vv and decreased MLI. We conclude that neonatal hyperoxia reduced lung VEGF expression, which persisted during recovery in room air, and that inhaled NO restored distal lung growth in infant rats after neonatal hyperoxia.     

Effects of pulmonary oxygen injury on airway content of surfactant-associated protein A

The use of therapeutic hyperoxia has greatly improved the survival of infants born prematurely. However, high concentrations of oxygen cause pulmonary injury, leading to decreased pulmonary compliance and decreased oxygen diffusion. This injury can result in chronic pulmonary insufficiency. It has been hypothesized that the adverse effects of hyperoxia are mediated, in part, through changes in the pulmonary surfactant system. We investigated the effects of hyperoxia on surfactant-associated protein A (SP-A), the abundant surfactant-specific glycoprotein. Adult male rats were exposed to 85% oxygen for 72 h. Total lung volume and pulmonary compliance were measured, and alveolar surfactant material recovered by lavage. Hyperoxia decreased total lung capacity, and altered inflation and deflation hysteresis patterns. Disaturated phosphatidylcholine and SP-A content were significantly increased in alveolar surfactant material isolated from oxygen-treated rats. SP-A content was also significantly increased in lung tissue from oxygen-treated rats. The SP-A in the lavage of oxygen-treated rats appeared to be intact protein as no proteolytic fragments were detected and the SP-A migrated identically to that recovered from room air animals when analyzed by two-dimensional isoelectric focusing. We conclude that the decreased pulmonary compliance associated with pulmonary oxygen injury is not due to quantitative decreases in two major surfactant components, disaturated phosphatidylcholine and SP-A.     

苦杏仁甙对高氧暴露早产鼠肺泡Ⅱ型细胞的保护作用

目的 探讨苦杏仁甙对体外高氧暴露早产鼠肺泡Ⅱ型细胞(type 2 alveolar epithelial cell,AECⅡ)的保护作用机制。方法 原代培养早产鼠AECⅡ,建立高氧细胞模型,采用MTT比色法、流式细胞术、免疫印迹(Western blot)、逆转录聚合酶链反应(RT-PCR)等方法,观察苦杏仁甙对高氧暴露早产鼠AECⅡ增殖及表面活性物质蛋白(surfactant associated protein,SP)mRNA表达的影响。结果 高氧暴露导致早产鼠AECⅡ增殖抑制,AECⅡ SPs mRNA表达降低。MTT试验显示,苦杏仁甙50～200μmol／L时呈剂量依赖方式促进早产鼠AECⅡ细胞增殖,200μmol／L浓度时,其作用最强,400μmol／L浓度时反而呈抑制作用。200μmol／L苦杏仁甙可显著促进体外高氧暴露AECⅡ增殖,提高其SP mRNA表达水平。结论 高氧暴露导致早产鼠AECⅡ增殖抑制及SP mRNA表达降低,200μmol／L苦杏仁甙对体外高氧暴露的早产鼠AECⅡ有一定保护作用。     

Lipid peroxidation in newborn rabbits: effects of oxygen, lipid emulsion, and vitamin E

The extent of in vivo lipid peroxidation and the in vivo antioxidant effects of alpha-tocopherol and alpha-tocopheryl acetate were studied in newborn rabbits exposed to one of two oxidant stresses: hyperoxia (FIO2 greater than 0.9) or parenteral lipid emulsion infusion. Lipid peroxidation was monitored by measurement of expired ethane and pentane, tissue thiobarbituric acid (TBA) reactants, and tissue lipid peroxides. Seventy-two h of hyperoxia did not increase any of the parameters of lipid peroxidation although mortality was higher in oxygen exposed animals. alpha-Tocopherol (100 mg/kg, intravenous) lowered expired hydrocarbons and tissue TBA reactants, but raised liver lipid peroxides in both air and hyperoxia exposed pups. Infusion of soybean oil emulsion increased production of ethane and pentane, liver TBA reactants, and lung lipid peroxides. Both alpha-tocopherol and alpha-tocopheryl acetate prevented the soybean oil emulsion induced increase in volatile hydrocarbons. alpha-Tocopherol (100 mg/kg, intravenous) administration also prevented the increase in liver TBA reactants and lung lipid peroxides. In identically treated animals, alpha-tocopheryl acetate administration decreased liver TBA reactants but had no effect on lung lipid peroxides. We conclude that alpha-tocopherol reduces lipid peroxidation in newborn rabbits including animals exposed to hyperoxia or infused with lipid emulsions. alpha-Tocopheryl acetate results in lower tissue alpha-tocopherol concentrations and is less effective as an antioxidant in lipid emulsion infused rabbits.     

洛沙坦对高氧致慢性肺疾病新生大鼠肺纤维化的影响

目的：血管紧张素II除了调节血压,还参与肺纤维化的发生。研究血管紧张素II 1型受体拮抗剂洛沙坦对高氧致慢性肺疾病（CLD）新生大鼠肺组织的影响,探讨洛沙坦在抗纤维化的作用及可能的机制。方法：将Waistar新生大鼠生后24 h内随机分为：空气组、高氧组、高氧+注射用水组、高氧+ 洛沙坦组,高氧组氧浓度为85%~90%,高氧+注射用水组、高氧+洛沙坦组在生后6 d每天用注射用水或洛沙坦(5 mg/kg)灌胃至实验结束,于7,14,21 d处死。观察病理组织学改变;生化检测肺组织超氧化物歧化酶活性(SOD)、丙二醛(MDA)和羟脯氨酸(HYP)的含量。结果：高氧暴露后大鼠肺泡数目减少,终末气腔扩张,次级隔数目减少,肺泡间隔显著增厚,甚至出现肺出血和肺实变。洛沙坦干预后肺泡间隔变薄,但肺泡腔没有明显缩小,且肺泡次级隔仍较少。高氧后14和21 d新生大鼠肺组织HYP含量较同期空气组显著增加(P<0.01),洛沙坦治疗2周后肺组织HYP含量较高氧组明显下降 (471.46±30.63 μg/kg vs 545.15±34.90 μg/kg, P<0.01); 高氧组在高氧暴露7 d时,SOD活力呈代偿性增加,之后逐渐下降至空气组水平;MDA水平在高氧暴露后显著增加,但随日龄增加呈下降趋势。洛沙坦治疗能增加高氧肺组织SOD的活力, 21 d时差异有显著性(82.94±4.62 U/mg protein vs 67.78±8.02 U/mg protein, P<0.01),同时降低MDA的水平(30.54±5.89 nmol/mg protein vs 48.75±8.09 nmol/mg protein, P<0.01)。结论：洛沙坦治疗能减轻高氧诱导新生鼠CLD肺纤维化的程度,该过程可能与肺组织抗氧化酶活性增加以及膜脂质过氧化减轻密切相关。［中国当代儿科杂志,2007,9（6）：591-594］     

Failure of premature rabbits to increase antioxidant enzymes during hyperoxic exposure: increased susceptibility to pulmonary oxygen toxicity compared with term rabbits

Although the prematurely born are known to have decreased baseline levels of protective antioxidant enzymes (Frank L, Sosenko IRS: J Pediatr 110:9 and 106, 1987), the ability to augment the baseline values during high O2 exposure is the key factor determining O2 tolerance versus O2 susceptibility. We have compared the pulmonary antioxidant enzyme responses of prematurely delivered rabbits (gestational d 29 of 32) and full-term rabbits to 48-72 h of hyperoxic exposure. We found that although full-term newborns exposed to greater than 90% O2 consistently showed elevated superoxide dismutase, catalase, glutathione peroxidase, and glucose-6-phosphate dehydrogenase activities, the premature animals repeatedly failed to respond to hyperoxia with increased antioxidant enzyme activity levels. Consistent with the comparative antioxidant enzyme responses were the evidences of O2 toxicity in the two age groups. The prematurely born rabbits had significantly increased lung lavage protein content, lung conjugated diene levels, and more severe light microscopic lung pathology compared with the full-term animals during equal O2 exposure time. This first reported comparison of prematurely born versus full-term animal responses to hyperoxia might help to explain the clinical observation that the very prematurely born infant is excessively prone to the development of O2-induced lung injury and the progressive development of bronchopulmonary dysplasia.     

Surfactant composition and function in a primate model of infant chronic lung disease: effects of inhaled nitric oxide

Bronchopulmonary dysplasia, or chronic lung disease (CLD), of premature infants involves injury from hyperoxia and mechanical ventilation to an immature lung. We examined surfactant and nitric oxide (NO), which are developmentally deficient in premature infants, in the baboon model of developing CLD. Fetuses were delivered at 125 d gestation and were managed for 14 d with ventilation and oxygen prn without (controls) or with inhaled NO at 5 ppm. Compared with term infants, premature control infants had reduced maximal lung volume, decreased tissue content of surfactant proteins SP-A, -B, and -C, abnormal lavage surfactant as assessed by pulsating bubble surfactometer, and a low concentration of SP-B/phospholipid. NO treatment significantly increased maximal lung volume and tissue SP-A and SP-C, reduced recovery of lavage surfactant by 33%, decreased the total protein:phospholipid ratio of surfactant by 50%, and had no effect on phospholipid composition or SP content except for SP-C (50%). In both treatment groups, levels of SP-B and SP-C in surfactant were negatively correlated with STmin, with a 5-fold greater SP efficiency for NO versus control animals. By contrast, lung volume and compliance were not correlated with surfactant function. We conclude that surfactant is often dysfunctional in developing CLD secondary to SP-B deficiency. NO treatment improves the apparent ability of hydrophobic SP to promote low surface tension, perhaps secondary to less protein inactivation of surfactant, and improves lung volume by a process unrelated to surfactant function.