短时长吸入一氧化氮预处理对大鼠肺缺血再灌注损伤的保护作用

目的 探讨低浓度一氧化氮(NO)预处理及其吸入时长的不同对肺缺血再灌注损伤(IRI)的影响和机制.方法 成年雄性SD大鼠77只,分为空白组(Sham组)、缺血再灌注组(I/R组)、NO预处理10 min组(NO-10 min组)、NO预处理1 min组(NO-1 min组),NO预处理60 min组(NO-60 min组),分别于不同的再灌注时间点采集标本,检测动脉血氧分压(PaO2),肺组织干/湿重比(W/D),丙二醛(MDA)浓度,髓过氧化酶(MPO)活性,肺损伤组织学评价等指标,比较前3组再灌注后2、6、24 h结果,取IRI最严重时间点,比较各组肺功能指标以及血清和左肺组织NO浓度.结果 再灌注6h肺损伤最严重;与I/R组比较,NO-10 min组各时间点指标明显改善(P＜0.05),NO吸入具有肺保护作用;NO-1 min组肺损伤无改善(P＞0.05);NO-10 min组与NO-60 min组对肺损伤保护作用相似(P＞0.05).结论 短时长吸入低浓度NO预处理可以改善IRI,但是其保护作用不与NO预处理时长成正比.     

Increased expression of nitric oxide synthase in human lung transplants after nitric oxide inhalation

BACKGROUND: The effects of the ischemia-reperfusion process of organ transplantation on nitric oxide (NO) synthase (NOS) in humans are unknown. The effects of NO inhalation on endogenous NOS expression and activity are controversial. The authors hypothesized that NO inhalation may affect ischemia-reperfusion-induced alterations of the endogenous NOS system. METHODS: The authors performed lung biopsy on patients in a randomized phase II clinical trial of NO inhalation during lung transplantation. After lung implantation, 20 ppm of NO or placebo gas was administered 10 min after the start of reperfusion. Lung tissues were collected from 20 patients (NO, n=9; placebo, n=11) after cold and warm ischemia, 1 hr and 2 hr after reperfusion. The protein levels of NOS isoforms were analyzed by Western blotting and the total NOS activity was measured. RESULTS: The protein levels of inducible NOS did not change significantly in either of the groups. In contrast, during the 2-hr reperfusion period, constitutive NOS (neuronal NOS [nNOS] and endothelial NOS) tended to decrease in the placebo group, but gradually increased in the NO group. After 2 hr of reperfusion, the nNOS protein in the NO group was significantly higher than that in the placebo group (P <0.05). However, the total NOS activity remained at low levels in both groups. CONCLUSIONS: NO inhalation-induced increase of constitutive NOS proteins indicates the interaction between inhaled NO molecules and lung tissues. However, the activity of these newly synthesized NOS proteins remains suppressed during the ischemia-reperfusion period of lung transplantation.     

Unintended inhalation of nitric oxide by contamination of compressed air: physiologic effects and interference with intended nitric oxide inhalation in acute lung injury.

BACKGROUND: Compressed air from a hospital's central gas supply may contain nitric oxide as a result of air pollution. Inhaled nitric oxide may increase arterial oxygen tension and decrease pulmonary vascular resistance in patients with acute lung injury and acute respiratory distress syndrome. Therefore, the authors wanted to determine whether unintentional nitric oxide inhalation by contamination of compressed air influences arterial oxygen tension and pulmonary vascular resistance and interferes with the therapeutic use of nitric oxide. METHODS: Nitric oxide concentrations in the compressed air of a university hospital were measured continuously by chemiluminescence during two periods (4 and 2 weeks). The effects of unintended nitric oxide inhalation on arterial oxygen tension (n = 15) and on pulmonary vascular resistance (n = 9) were measured in patients with acute lung injury and acute respiratory distress syndrome by changing the source of compressed air of the ventilator from the hospital's central gas supply to a nitric oxide-free gas tank containing compressed air. In five of these patients, the effects of an additional inhalation of 5 ppm nitric oxide were evaluated. RESULTS: During working days, compressed air of the hospital's central gas supply contained clinically effective nitric oxide concentrations (> 80 parts per billion) during 40% of the time. Change to gas tank-supplied nitric oxide-free compressed air decreased the arterial oxygen tension by 10% and increased pulmonary vascular resistance by 13%. The addition of 5 ppm nitric oxide had a minimal effect on arterial oxygen tension and pulmonary vascular resistance when added to hospital-supplied compressed air but improved both when added to tank-supplied compressed air. CONCLUSIONS: Unintended inhalation of nitric oxide increases arterial oxygen tension and decreases pulmonary vascular resistance in patients with acute lung injury and acute respiratory distress syndrome. The unintended nitric oxide inhalation interferes with the therapeutic use of nitric oxide.     

吸入NO对肺灌洗诱导的急性肺损伤家猪血液动力学及肺气体交换的影响

目的评价吸入一氧化氮(NO)对肺灌洗诱导的急性肺损伤(ALI)气体交换及血液动力学的影响.方法16头健康家猪,麻醉后经气管导管肺内以生理盐水反复灌洗,直至动脉氧分压(PaO2)＜100mmHg达1h,记录气体交换及血液动力学各参数作为急性肺损伤的基础值.随机分为NO组及对照组,NO组吸入20ppm的NO,对照组不予治疗,记录各组每小时的气体交换及血液动力学参数,并观察高铁血红蛋白(MetHb)的改变.结果NO组的MPAP在整个实验过程中显著低于对照组.NO组吸入NO1h后,PaO2即呈上升趋势,4h后从ALI的(65.29±14.37)mmHg升至(114.52±36.5)mmHg,较对照组显著升高.同时Qs/Qt及AaDO2降低.MAP及SVR相对于对照组无显著性改变.MetHb无显著升高.结论在肺灌洗诱导的急性肺损伤家猪,吸入20ppm的NO选择性降低肺动脉压,改善肺氧合,并不引起高铁血红蛋白血症.     

The nitric oxide synthase cofactor tetrahydrobiopterin reduces allograft ischemia-reperfusion injury after lung transplantation.

OBJECTIVE: Exogenous nitric oxide reduces ischemia-reperfusion injury after solid organ transplantation. Tetrahydrobiopterin, an essential cofactor for nitric oxide synthases, may restore impaired endothelium-dependent nitric oxide synthesis. We evaluated whether tetrahydrobiopterin administration to the recipient attenuates lung reperfusion injury after transplantation in swine. METHODS: Unilateral left lung transplantation was performed in 15 weight-matched pigs (24-31 kg). Donor lungs were flushed with 1.5 L cold (1 degrees C) low-potassium-dextran solution and preserved for 20 hours. Group I animals served as controls. Group II and III animals were treated with a bolus of tetrahydrobiopterin (20 mg/kg). In addition, in group III a continuous infusion of tetrahydrobiopterin (10 mg/kg per hour over 5 hours) was given. One hour after reperfusion, the recipient right lung was occluded. Cyclic guanosine monophosphate levels were measured in the pulmonary venous and central venous blood. Extravascular lung water index, hemodynamic variables, lipid peroxidation, and neutrophil migration to the allograft were assessed. RESULTS: In group III a significant reduction of extravascular lung water was noted in comparison with the controls (P =.0047). Lipid peroxidation in lung allograft tissue was significantly reduced in group II (P =.0021) and group III ( P =. 0077) in comparison with group I. Pulmonary venous levels of cyclic guanosine monophosphate increased up to 23 +/- 1 pmol/mL at 5 hours in group II and up to 40 +/- 1 pmol/mL in group III (group I, 4.1 +/- 0.5 pmol/mL [I vs III]; P <.001), whereas central venous levels of cyclic guanosine monophosphate were unchanged in all groups. CONCLUSION: Tetrahydrobiopterin administration during lung allograft reperfusion may reduce posttransplantation lung edema and oxygen-derived free radical injury in the graft. This effect is mediated by local enhancement of the nitric oxide/cyclic guanosine monophosphate pathway.     

Role of nitric oxide in myocardial dysfunction after combined burn and smoke inhalation injury

This study tested the hypothesis that nitric oxide (NO) synthesized from inducible NO synthase (iNOS) is responsible for the cardiac dysfunction observed after burn and smoke inhalation injury. Twelve sheep received 40% third-degree burn and smoke inhalation under halothane anesthesia. The animals were divided into two groups: a MEG group [iNOS was inhibited with mercaptoethylguanidine (MEG), a selective inhibitor of iNOS, n=6] and a control group (n=6). The control group showed a significant increase in NO₂⁻/NO₃⁻ (NO_x) concentration, metabolite of NO, in plasma after 24 h, whereas the MEG group did not. In the control group, cardiac depression was observed immediately after injury associated with hemoconcentration. Cardiac function returned to a normal level within 6 h following injury. In the control group cardiac dysfunction was observed again after 24 h although the hemoconcentration peaked at 24 h after injury and then began to resolve. In the MEG group, cardiac depression and hemoconcentration were not observed. The present data suggest that cardiac depression seen with this combination injury consists of two phases and that the later phase is mediated by iNOS–NO.     

一氧化氮和一氧化氮合成酶在急性肺损伤的作用

急性肺损伤(acute lung injury,ALI)是一种发病率和死亡率都很高的常见临床疾病. 目前,对ALI病理生理学基础和临床研究方面的了解越来越多,但并没有提出新的治疗策略能够明显改善ALI的治疗.在ALI的动物模型和患者中,一氧化氮合成酶(nitric oxide synthases,NOS)表达及活性增强和一氧化氮(NO)的增多在ALI的病理生理过程中有重要作用;但临床抑制NO生成以及选择性抑制NOS并没有对ALI的治疗有明显效果.目前提出了不同细胞源性NO的概念,这种NO的细胞源性差异可能对ALI的治疗有潜在的意义.现综述NO和NOS在ALI中的作用.     

Rat gastric injury after lipopolysaccharide: role of inducible nitric oxide synthase

BACKGROUND: Short-term treatment with lipopolysaccharide (LPS) causes morphologic, but not macroscopic, gastric injury and decreases gastric injury caused by a subsequent challenge with a luminal irritant. This effect is abrogated by inducible nitric oxide synthase (iNOS) inhibition. The effects of long-term treatment with LPS on gastric injury are unknown as is the role of iNOS. We hypothesized that LPS would cause macroscopic gastric injury at later time points through an iNOS-dependent pathway. METHODS: Conscious rats were given saline or LPS (1 or 20 mg/kg intraperitoneal) as a single intraperitoneal injection and killed 24 to 72 hours after injection. Macroscopic gastric injury (computerized planimetry), gastric luminal fluid volume and pH, and iNOS protein levels were assessed. RESULTS: When compared with saline, high-dose but not low-dose LPS caused macroscopic gastric injury, increased gastric luminal fluid and pH, and up-regulated iNOS at 24 and 48 hours. All assessments returned to baseline by 72 hours. Inhibition of iNOS with 1400W (1 mg/kg intraperitoneal) given 15 minutes before saline or LPS (20 mg/kg) attenuated the deleterious effects of LPS on gastric injury and pH, but not fluid accumulation. CONCLUSIONS: These data suggest that prolonged treatment with high-dose LPS causes gastric injury through an iNOS-mediated pathway.     

Safety of inhaled nitric oxide after lung transplantation.

BACKGROUND: The present study tests the hypothesis that therapy with inhaled nitric oxide (iNO) at the time of lung transplantation in patients undergoing bilateral angle lung transplantation: (i) is safe; and (ii) does not increase either the duration of mechanical ventilation or the incidence of acute graft dysfunction. METHODS: We conducted a prospective, non-randomized trial of iNO at 20 parts per million. The treatment group was comprised of 14 patients (10 females, 4 males) undergoing lung transplantation to address severe end-stage lung disease and pulmonary hypertension (mean pulmonary artery pressure > 30 mmHg). Clinical and histologic parameters were compared with 22 historical control subjects who were matched with the study population for age, diagnosis and disease severity (17 females, 5 males) and had undergone lung transplantation in the preceding 2-year time period. No significant differences were noted between the 2 study groups at baseline. RESULTS: No toxic effect of iNO treatment was evident. Although the incidence of acute graft dysfunction was the same in both groups, the occurrence of acute graft rejection in the initial 4 weeks after transplant was less frequent in the iNO group than in the control group (7% vs 32%, p = 0.05). Fifty percent of the treatment group, as compared with 22% of the control group, were discharged from the hospital within 2 weeks of the procedure (p = 0.05). CONCLUSIONS: Early initiation of iNO in lung transplant patients with pulmonary hypertension is safe and may decrease the incidence of acute graft rejection. We speculate that iNO may exert an immunomodulatory effect.     

Acute inhalation of cigarette smoke increases lower respiratory tract nitric oxide concentrations

BACKGROUND—Cigarettesmoking is associated with a number of common pulmonary diseasesincluding chronic airflow limitation and bronchial carcinoma. Lowerrespiratory tract (LRT) nitric oxide (NO) concentrations are reduced inhabitual cigarette smokers between cigarettes, and although thisfinding has been implicated in the pathogenesis of smoking relateddisease, the underlying mechanisms are unclear. A study was undertakento determine the nature and time course for changes in LRT NOconcentrations following acute inhalation of cigarette smoke.
METHODS—Twenty fourhealthy habitual smokers were studied. The concentration of LRT NO inexhaled breath before, one and ten minutes after smoking a singlecigarette was measured using chemiluminescence.
RESULTS—LRT NOconcentrations increased in all subjects from a mean (SE) of 2.6 (0.27)to 4.8 (0.26) ppb (p<0.0001) at one minute, and at 10 minutes remainedsignificantly raised above the baseline level at 3.2 (0.25) ppb (p = 0.003). The mean (95% CI) increases in NO concentrations were 2.2 (1.7 to 2.7) and 0.6 (0.2 to 1.0) ppb, respectively.
CONCLUSIONS—Thesefindings were unexpected in both their direction and time course. Theysuggest a novel mechanism for the handling of NO in the human lung. Wehypothesise that NO is trapped in the epithelial lining fluid (ELF) ofthe normal human respiratory tract in bioequivalent forms such asS-nitrosothiols or peroxynitrite and that this trapping mechanism issensitive to the redox state of the ELF. LRT NO concentrations willthus increase with oxidant exposure and decline as pulmonaryantioxidant defence mechanisms take effect. These findings may haveimplications for the pathogenesis and diagnosis of oxidant mediatedpulmonary disease.

     

Uptake of inhaled nitric oxide in acute lung injury

Background: Despite the widespread use of inhaled nitric oxide (NO), little is known of its pulmonary uptake in patients with acute respiratory failure.
Methods: Fourteen patients with acute lung injury (ALI) and ongoing NO therapy were studied. Three doses of NO (5, 10 and 40 ppm) were given for 20 min and at each dose level the following parameters were recorded: minute ventilation, inspiratory NO cone, mixed expired NO cone, end-tidal NO cone, mixed expired CO₂ cone, end-tidal CO₂ cone and arterial CO₂ tension. Total uptake was calculated and correlated to the total amount of NO inhaled, the amount of NO administered to the alveolar space, and the amount of NO administered to the perfused alveolar space.
Results: About 35% of the total amount of NO delivered is taken up by the lungs, 70% of NO administered to the alveolar space is taken up, and 95–100% of the NO administered to perfused alveolar space is taken up. The size of the alveolar dead space varied between 10 and60% of the alveolar space. At 40 ppm of inhaled NO there was no difference between inspired and mixed expired NO₂ concentration, indicating that there is no significant NO₂ formation taking place in the lungs during NO inhalation at the concentrations studied.
Conclusions: Practically all NO administered to the perfused alveolar space is taken up. The total uptake differs from that of healthy persons probably because of differences in the alveolar dead space.     

Pulmonary oedema in isolated lung lobe after inhalation injury

Pulmonary oedema was produced in isolated lung lobes with steam and provided direct continuous measurements of transudation as it occurred. Transvascular flux (Q_f) and weight gain (G_w) of the lobe increased immediately and the transudation reached its peak within half an hour after inhalation injury. Studies of protein content, colloid osmotic pressure of bronchial exudate and water content of lung, reconfirmed the increase in pulmonary capillary permeability. Marked haemoconcentration was revealed. Plasma leaked 113g (25 per cent), plasma protein leaked 1.96g (9.7 per cent) during the experiment. Based on the measured arterial pressure (P_a), vein pressure (P_v), arterial occlusion (P_ao), venous occlusion (P_vo), double occlusion (P_do) and blood flow through the lobe (Q_t), the total vascular (R_t), arterial (R_a), middle compartment (R_mid) and venous (R_v) resistances were calculated. All the resistances were increased and the Q_t showed a decrease after inhalation injury.     

Preventive influence of inhaled nitric oxide on lung ischemia-reperfusion injury

n = 9). The control group was not administered NO (group II, n = 8). Severe ischemia-reperfusion injury occurred as evidenced by hypoxia and lung edema. PaO₂ at 120 min after reperfusion was 325 ± 41 mmHg in group I and 40 ± 6 mmHg in group II. The pulmonary blood flow of the left lung at 120 min after reperfusion was 51% ± 3% in group I and 20% ± 5% in group II. The wet-to-dry weight ratio was 5.5 ± 0.2 for the right lungs, 5.8 ± 0.8 for the left lung in group I, and 6.1 ± 0.4 for the left lung in group II. Histopathologically, marked hemorrhage, hyaline membrane formation, and leukocyte infiltration were observed in group II but not in group I. These data suggested that inhaled NO reduced warm ischemia-reperfusion injury in the lung, and also contributed to a better preserved lung function. (Received for publication on July, 13, 1998; accepted on Mar. 11, 1999)     

Role of nitric oxide in treatment of acute lung injury after surgery with extracorporeal circulation

Postoperative acute lung injury (ALI) compromises oxygen transfer across alveolar-capillary membrane with consecutive hypoxia, one of its indicators being reduction of oxygenation index PaO2/FiO2 below 40 kPa (300 mm Hg). Management of ALI includes different procedures like mechanical lung ventilation (MLV), drugs and others. One of the new possibilities for treatment of ALI is nitric oxide (NO) inhalation. The aim of this prospective study was to examine the role of NO inhalation in treatment of ALI. 14 patients with ALI developed immediately after operation with extracorporeal circulation (ECC) were included in the study. Group A (n = 8) inhaled NO and group B (n = 6) did not inhale NO during treatment of ALI. All other therapeutic measures were the same in both groups. The groups were similar in relation to demographic data, type of surgery and duration of ECC. PaO2/FiO2 was calculated before operation (T1), immediately after surgery (T2) and after lung recovery, when the need for MLV stopped (T3). The duration of MLV was also registered. PaO2/FiO2 (kPa) in referent times was in group A 54.9 +/- 1.6, 33.8 +/- 1.2 and 46.2 +/- 0.8 and in group B 52.2 +/- 1.1, 33.5 +/- 1.5 and 47.3 +/- 0.9, respectively. There was a statistically significant decrease of PaO2/FiO2 in T2 and T3 vs T1 in both groups (p < 0.05), while the difference between the groups was not statistically significant. The duration of MLV (h) in group B (28.5 +/- 1.6) was statistically significantly shorter than in group A (63.1 +/- 8.7) (p < 0.01). According to the results of this study we conclude that NO inhalation during ALI after surgery with ECC significantly reduces the duration of MVL and improves pulmonary recovery.