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   

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.     

褪黑素对高氧致新生鼠慢性肺疾病肺组织氧化/抗氧化系统的影响

目的：探讨近年来发现的高效抗氧化剂褪黑素（MT）对高氧致新生鼠慢性肺疾病（CLD）肺组织氧化/抗氧化系统的影响。方法：采用高氧暴露（FiO2＝0.85）致新生鼠CLD模型,足月新生鼠共90只随机分为3组（每组30只）：空气对照组、高氧对照组、MT治疗组。空气对照组置于空气中,高氧对照组、MT治疗组（连同母鼠）置于玻璃氧箱中,维持FiO2为0.85;MT治疗组于生后0 d高氧暴露前30 min和生后每天给予MT 4 mg/kg腹腔注射直至实验结束。每组分别于实验后3,7,14 d随机选取10只处死,观察肺组织形态改变,分别测定肺组织中总抗氧化能力（T-AOC）、超氧化物歧化酶（SOD）、谷胱苷肽过氧化物酶（GSH-Px）活性、髓过氧化物酶（MPO）、过氧化氢酶（CAT）、NO水平（以NO2-/NO3-衡量）以及丙二醛（MDA）含量改变。结果：MT治疗组病理改变明显减轻。空气对照组、高氧对照组、MT治疗组T-AOC,SOD,GSH-Px及CAT活性随实验时间的延长均逐渐升高,但空气对照组、高氧对照组两组比较各项指标差异均无显著性（P>0.05）,MT治疗组各项指标在实验各时点与空气对照组、高氧对照组相比均明显升高（P<0.05）。高氧对照组NO2-/NO3-,MDA水平以及MPO含量在3,7,14 d均高于空气对照组（P<0.05或0.01）。MT治疗组NO2-/NO3-,MDA水平以及MPO含量则明显降低,与高氧对照组比较差异具有显著性（P<0.05）。结论：MT通过提高肺组织的抗氧化能力、抑制氧化应激反应,从而逆转了高氧致新生鼠CLD肺组织氧化/抗氧化系统失衡。［中国当代儿科杂志,2009,11（7）：581-584］     

MK-801对新生大鼠高氧性肺损伤的保护作用

目的观察谷氨酸(Glu)的NMDA受体拮抗剂MK-801对新生大鼠高氧性肺损伤的影响,探讨Glu在高氧性肺损伤中的可能作用。方法出生12h内的SD新生大鼠随机分为:空气对照组、空气 MK-801组、高氧对照组及高氧 MK-801组。观察持续高氧暴露7d后各组肺湿/干重比(W/D)、支气管肺泡灌洗液(BALF)中白细胞及中性粒细胞数、肺组织及BALF中一氧化氮(NO)含量的变化。结果MK-801可有效地抑制高氧所致新生大鼠肺W/D、BALF中白细胞和中性粒细胞、肺组织和BALF中NO含量的增高。结论MK-801可有效地减轻新生大鼠高氧性肺损伤,提示内源性Glu通过NMDA受体介导,促进NO的产生而加重肺损伤。     

Hyperoxia and tidal volume: Independent and combined effects on neonatal pulmonary inflammation

BACKGROUND: Hyperoxia and tidal volume mechanical ventilation are independent factors in the genesis of lung injury, but it remains unclear the extent to which each is responsible or contributes to this process in newborns. OBJECTIVES: To study the independent and combined effects of hyperoxia and tidal volume mechanical ventilation on the induction of lung inflammation in a newborn piglet model of ventilator-induced lung injury. METHODS: Following exposure to either ambient air or F(I)O2 = 1.0 for a period of 3 days, newborn piglets were randomized to receive mechanical ventilation with either high tidal volume (20 ml/kg) or low tidal volume (6 ml/kg) for 4 h while controlling for pH. RESULTS: Monocyte chemoattractant protein-1 level in the lungs of animals randomized to hyperoxia with high tidal volume ventilation was significantly elevated, compared to all other groups (p < 0.05). Myeloperoxidase assayed in lung homogenate was found to be significantly higher in nonventilated animals exposed to hyperoxia (p < 0.01). Only in animals previously exposed to hyperoxia did the addition of high tidal volume ventilation further increase the level of myeloperoxidase present (p < 0.05). Pulmonary vascular resistance was significantly elevated after 4 h of mechanical ventilation compared to 1 h (p < 0.001). CONCLUSIONS: We conclude that in neonatal piglets undergoing hyperoxic stress, superimposition of high tidal volume ventilation exacerbates the lung inflammation as assessed by lung monocyte chemoattractant protein-1 and level of myeloperoxidase.     

CoASH and CoASSG levels in lungs of hyperoxic rats as potential biomarkers of intramitochondrial oxidant stresses

Coenzyme A (CoASH) is compartmentalized preferentially in the mitochondria, and CoASH and its mixed disulfide with glutathione (CoASSG) undergo thiol/disulfide exchange reactions with glutathione (GSH) and glutathione disulfide (GSSG) in vitro. We measured CoASH and CoASSG in freeze-clamped lung tissues from Fischer-344 and Sprague-Dawley rats maintained in room air or exposed to >95% O(2) for 48 h to test the hypothesis that oxidant stresses on lung thiol status would be observed in the CoASH/CoASSG redox couple, suggesting oxidant stress responses in the mitochondria. Lung tissue concentrations of CoASSG in the Fischer-344 rats declined from 0.89 +/- 0.15 to 0.51 +/- 0.13 nmol/g of lung after 48 h of hyperoxia. CoASH levels declined from 6.40 +/- 0.84 to 3.0 +/- 0.65 nmol/g of lung, and acetyl CoA levels also were lower in the lungs of animals exposed to hyperoxia. CoASH/CoASSG ratios were lower in animals exposed to hyperoxia, satisfying our previously defined criteria for an oxidant stress on this thiol/disulfide redox couple, but absolute CoASSG levels were not increased, as would be expected for oxidant stresses driven simply by increases in reactive oxygen species or other oxidants. Pulmonary edema was observed in the hyperoxic rats and accounted for some of the declines in CoASH concentrations, but CoASH contents per total lung also declined. Lung mitochondrial succinate dehydrogenase activities were not diminished in rats exposed to hyperoxia, indicating that the decreases in CoASH concentrations are not attributable to general destruction of lung mitochondria. Lung GSSG contents were greater in the hyperoxia animals, but GSH/GSSG ratios, which are dominated by extramitochondrial pools, did not decrease in these animals. The mechanisms responsible for, and the possible pathophysiologic consequences of, the decreases in lung CoASH concentrations are not evident from the data available at the present time, but the loss of more than half the tissue contents of CoASH is likely to generate additional metabolic effects that could have significant pathophysiologic consequences.     

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］     

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.     

The effect of hyperoxic exposure on antioxidant enzyme activities of alveolar type II cells in neonatal and adult rats.

Neonatal animals of several species are more tolerant of hyperoxic exposure than are adults, but the mechanisms of increased neonatal tolerance are unknown, as are the cell types, if any, that contribute to oxygen resistance. We studied the effect of in vivo exposure to 85% oxygen for 72 h on the activities of the antioxidant enzymes, glutathione peroxidase, catalase and superoxide dismutase (SOD), in alveolar type II cells and whole lung from adult and neonatal rats. Baseline antioxidant enzyme activities were generally lower in neonatal type II cells compared with adults. Baseline enzyme activities did not differ in neonatal type II cells and lung homogenates except for lower catalase activity in type II cells. Hyperoxic exposure resulted in 35-38% increases in antioxidant enzyme activities in neonatal whole lung. In neonatal type II cells, SOD activity increased by 170% after hyperoxia, whereas catalase and glutathione peroxidase were not significantly changed. In the adult whole lung, hyperoxic exposure resulted in increases in only glutathione peroxidase activity, whereas in adult type II cells there was a significant decrease in SOD activity after O2 exposure. Therefore, although baseline antioxidant enzyme activities were not higher in neonatal type II cells compared with whole lung, there were differences in the antioxidant enzyme responses of adult and neonatal type II cells to hyperoxia, particularly with respect to SOD. The ability of the neonatal type II cell to respond to hyperoxia with an early increase in SOD activity may contribute to the enhanced oxygen tolerance of the neonate.     

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.     

Angiotensin II receptor blockade inhibits pneumocyte apoptosis in experimental meconium aspiration

Lung tissue inflammation and apoptosis are implicated in the pathogenesis of meconium aspiration-induced lung injury in the newborn, but the mechanisms of these reactions are still poorly known. We investigated the time-dependent leukocyte influx and appearance of apoptosis, as well as the contribution of angiotensin (ANG) II receptor action on these processes in the meconium-induced lung injury. Experimental meconium aspiration was induced by intratracheal instillation of human meconium in 18 rats, and eight rats were further pretreated with an unspecific ANG II receptor inhibitor saralasin. Rats were ventilated with 60% oxygen for 1, 3, or 5 h, and the lungs were then studied histologically for tissue injury and with DNA nick-end labeling and electron microscopy for apoptotic cell death. Lung tissue myeloperoxidase activity and expression of angiotensinogen mRNA and endothelial monocyte-activating polypeptide (EMAP) II protein were also analyzed. The meconium-instilled lungs showed increasing neutrophil migration and histologic injury after the first hour, whereas the number of epithelial apoptotic cells was elevated from the control level throughout the study. Myeloperoxidase activity was high, and the angiotensinogen mRNA and EMAP II protein was up-regulated at 5 h after the meconium insult. Pretreatment with saralasin significantly prevented the increase in lung tissue myeloperoxidase activity, EMAP II, and lung epithelial apoptosis. The results suggest that pulmonary meconium insult rapidly results in epithelial apoptosis, before significant neutrophil sequestration into the lungs. Apoptotic cell death is further connected with ANG II receptor action in the meconium-contaminated lung tissue.     

Melatonin protects against oxidative damage in a neonatal rat model of bronchopulmonary dysplasia

Background  Oxidative stress plays an important role in the pathogenesis of bronchopulmonary dysplasia (BPD). Melatonin (MT) has direct and indirect free radical detoxifying activity. The present study was to investigate whether treatment with MT would attenuate hyperoxia-induced lung injury and the effect of MT on imbalance of oxidants/antioxidants in the lung of neonatal rats. Methods  BPD was induced by exposure to hyperoxia in neonatal rats (n=90). The rats were divided randomly into three groups (n=30 each): air-exposed control group, hyperoxia-exposed group, and hyperoxia-exposed MT-treated group. Lung specimens were obtained respectively on day 3, day 7, and day 14 after exposure (n=10 each). Activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT), and levels of myeloperoxidase (MPO), nitrite/nitrate, and malondialdehyde (MDA) were assayed. Histopathologic changes were observed in the tissues stained with hematoxylin and eosin and Masson’s trichrome stain. Results  Increased levels of MPO, nitrite/nitrate, and MDA in the hyperoxia-exposed rats were significantly reduced by MT (P<0.05). Activities of GSH-Px, SOD, and CAT which did not change after exposure to hyperoxia were increased by MT (P<0.05). Furthermore, BPD associated histopathological alterations such as reduced total number of alveoli and interstitial fibrosis were obviously abated in the MT-treated group. Conclusions  MT can reverse oxidants/antioxidants imbalance in damaged lung tissue and thus exert a beneficial effect on hyperoxia-induced lung disease in neonatal rats. With regard to humans, there may be a protective effect of MT on BPD.     

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.     

吸入一氧化氮对早产猪未成熟肺的作用

目的：研究早产猪在机械通气下吸入一氧化氮(NO)对未成熟肺的呼吸功能、核转录因子(NFκB)表达的影响,以研究出生早期吸入NO是否对不成熟肺产生不良反应,并判断应用肺表面活性物质(PS)及NO的肺保护作用效果及其调节炎症反应的作用和机制。方法：选择101～103d孕龄(89%足月孕期)母猪,行剖宫产获得32头早产猪(平均出生体重870g),气管插管后行间歇正压机械通气,随机分成4组(每组n=8)治疗:单纯机械通气(C组);吸入NO(NO组);加用肺表面活性物质(PS组);NO和PS联合应用(SNO组)。另选同窝自主呼吸组(N组)用于比较NFκB水平、肺湿干重比及肺组织病理学。机械通气各组分别测肺功能,血气分析,计算氧合指数(OI)和通气指数(VI)。机械通气6h后处死动物。结果：治疗6h肺顺应性(Cdyn)和气道阻力(Raw)在各组间无统计学差异,OI在SNO组显著低于C组2.3±1.9vs9.5±7.5(P<0.05),VI在NO和SNO组低于C组和PS组(P<0.05或P<0.01)。NO组及N组NFκB活性最低,与C组相比差异有显著性,P<0.05。NO吸入过程中监测NO2水平均<1ppm。所有动物高铁血红蛋白(MetHb)浓度均<4%。NO和SNO组肺组织湿干重比显著低于C组6.88±0.53vs7.77±0.76(P<0.05)和6.61±0.56vs7.77±0.76(P<0.01)。病理检查见各组不同程度肺水肿、白细胞浸润,肺泡扩张度(Vv)和变异度(CV[Vv])显示肺泡中度成熟,但差异均无显著性。结论：出生早期应用iNO或联合应用PS治疗可改善早产猪氧合和机械通气效率;小剂量短时间NO吸入有利于肺液清除,没有显著改变PS成分和/或直接致肺损伤;NO通过下调NFκB可能具有抑制/调节早产肺炎症反应启动机制的作用。     

Prophylactic effects of recombinant human superoxide dismutase in neonatal lung injury induced by the intratracheal instillation of endotoxin in piglets

The efficacy of prophylactic endotracheal administration of superoxide dismutase (SOD) was assessed in an animal model of acute lung injury induced by intratracheal endotoxin in neonatal piglets. Twenty-one anesthetized piglets were studied and underwent mechanical ventilation. The animals received recombinant human SOD (5 or 20 mg/kg intratracheally) 10 min before induction of acute lung injury with intratracheal endotoxin (20 mg/kg). The PaO(2) values of the SOD-treated group remained higher than that of the control group until the end of the experiment. In contrast, the PaCO(2) values remained lower. Lung compliance remained higher. Thiobarbituric acid-reactive substances and albumin levels in the broncho-alveolar lavage fluid were more significantly increased in controls. Histologic examination showed that the degrees of atelectasis and edema in the SOD treatment group were milder than those of the control group. Thus, the present findings suggest that prophylactic treatment with SOD may be, at least in part, effective for alleviating acute lung injury caused by endotoxins.     

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.     

重组人胰岛素样生长因子1对高氧暴露下新生大鼠肺组织Clara细胞分泌蛋白表达的影响

目的探讨重组人胰岛素样生长因子1（rh-IGF-1）对高氧暴露下的新生大鼠肺损伤的影响。方法将生后2d的Wistar大鼠80只,随机分为4组。Ⅰ组：空气组;Ⅱ组：高氧组;m组：空气＋rh-IGF-1组;Ⅳ组：高氧＋rh-IGF-1组。Ⅱ组和Ⅳ组大鼠持续暴露于85％O2中,Ⅰ组和Ⅲ组大鼠呼吸空气。Ⅲ组和Ⅳ组从第3天起每日腹腔注射rh—IGF-1,1μ/Kg。于高氧暴露后7d取肺组织,用免疫组化方法检测肺内CC10表达变化,用TUNEL方法检测肺细胞凋亡。结果免疫组化结果阳性染色主要分布于终末及呼吸性细支气管上皮细胞。Ⅱ组终末和呼吸性细支气管上皮Clara细胞占上皮细胞的百分率（32．17±3．19）％和免疫阳性强度（29．45±5．56）,均明显少于Ⅰ组的测定值（68．32±2．04）％和（42．37±3．24）,差异均有统计学意义（P〈0．01）;Ⅱ组肺组织细胞凋亡指数（55．77±6．09）％明显高于Ⅰ组的测定值（16．41±4．01）％,差异有统计学意义（P〈0．01）;Ⅳ组的Clara细胞百分率（52．98±2．68）％和免疫阳性强度（41．22±6．36）较Ⅱ组明显增加,Ⅳ组的细胞凋亡指数（27．98±3．09）％明显低于Ⅱ组的测定值,差异均有统计学意义（P〈0．01）。而Ⅰ组与Ⅲ组之间差异无统计学意义（P〉0．01）。结论高氧诱导肺细胞凋亡、抑制肺内CC10分泌,而rh-IGF-1通过抑制肺细胞凋亡,能够有效抑制CC10分泌的减少,减轻气道炎症反应,抑制肺泡化阻滞,对高氧性肺损伤起保护作用。