Activation of A3 adenosine receptors attenuates lung injury after in vivo reperfusion

BACKGROUND: A3 adenosine receptor (AR) activation worsens or protects against renal and cardiac ischemia-reperfusion (IR) injury, respectively. The aims of the current study were to examine in an in vivo model the effect of A3AR activation on IR lung injury and investigate the mechanism by which it exerts its effect. METHODS: The arterial branch of the left lower lung lobe in intact-chest, spontaneously breathing cats was occluded for 2 h and reperfused for 3 h (IR group). Animals were treated with the selective A3 receptor agonist IB-MECA (300 microg/kg intravenously) given 15 min before ischemia or with IB-MECA as described, with pretreatment 15 min earlier with the selective A3AR antagonist MRS-1191, the nonsulfonylurea adenosine triphosphate-sensitive potassium channel-blocking agent U-37883A, or the nitric oxide synthase inhibitor N-nitro-l-arginine benzyl ester. RESULTS: IB-MECA markedly (P < 0.01) reduced the percentage of injured alveoli (IR, 48 +/- 4%; IB-MECA, 18 +/- 2%), wet:dry weight ratio (IR, 8.2 +/- 0.4; IB-MECA, 4 +/- 2), and myeloperoxidase activity (IR, 0.52 +/- 0.06 U/g; IB-MECA, 0.17 +/- 0.04 U/g). This protective effect was completely blocked by pretreatment with the selective A3AR antagonist MRS-1191 and the adenosine triphosphate-sensitive potassium channel blocking agent U-37883A but not the nitric oxide synthase inhibitor N-nitro-l-arginine benzyl ester. CONCLUSIONS: In the feline lung, the A3AR agonist IB-MECA confers a powerful protection against IR lung injury. This effect is mediated by a nitric oxide synthase-independent pathway and involves opening of adenosine triphosphate-sensitive potassium channels. Therefore, selective activation of A3AR may be an effective means of protecting the reperfused lung.     

Melatonin attenuates posttransplant lung ischemia-reperfusion injury

BACKGROUND: Melatonin, a pineal hormone, is a free radical scavenger and an antioxidant. The purpose of this study was to assess the protective effect of melatonin on posttransplant lung ischemia-reperfusion injury. METHODS: Rat single-lung transplantation was performed in two (n = 10) experimental groups after 18 hours of cold (4 degrees C) ischemia. Group I animals consisted of the ischemic control group. In group II, donor and recipient animals were treated with intraperitoneal injection of 10 mg/kg melatonin 10 minutes before harvest and reperfusion, respectively. After 2 hours of reperfusion, oxygenation, plasma, and bronchoalveolar lavage nitrite levels were measured. Lung tissue was assessed for thiobarbituric acid reactive substances and myeloperoxidase activity. Peak airway pressure was recorded throughout the reperfusion period. RESULTS: The melatonin-treated group showed significantly better oxygenation (321.8+/-33.8 mm Hg versus 86.1+/-17.4 mm Hg; p < 0.001), reduced lipid peroxidation (0.65+/-0.3 nmol/g versus 1.63+/-0.8 nmol/g; p = 0.032), and reduced myeloperoxidase activity (0.56+/-0.1 deltaOD x mg(-1) x min(-1) versus 1.01+/-0.2 deltaOD x mg(-1) x min(-1); p = 0.032). Bronchoalveolar lavage nitrite levels in the transplanted lungs were significantly lower in group II than in group I (0.34+/-0.06 micromol/L versus 1.65+/-0.6 micromol/L; p = 0.016). In group II significant reduction in peak airway pressure was noted compared with group I (p = 0.002). CONCLUSIONS: In this model, exogenously administered melatonin effectively protected lungs from reperfusion injury after prolonged ischemia.     

Inhaled nitric oxide attenuates apoptosis in ischemia-reperfusion injury of the rabbit lung

Background

Lung ischemia-reperfusion injury occurs after lung transplantation and various clinical procedures. Recently, apoptosis was reported to be induced after ischemia-reperfusion. We investigated the effects of inhaled nitric oxide (NO) on lung ischemia-reperfusion and apoptosis after ischemia-reperfusion.

Methods

As a control group, the left pulmonary hilum of Japanese white rabbits (n = 10) was occluded for 120 minutes and reperfused for 120 minutes. In the inhaled NO group (n = 10), 20 parts per million nitric oxide was inhaled during reperfusion. The sham-operated group was ligated at the right hilum and perfused by the left lung only for 120 minutes. The mean pulmonary arterial pressures and Pao₂ were measured during reperfusion. The wet-to-dry weight ratio of the left lower lobe of the lung was calculated. The number of apoptotic cells was estimated using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) technique. The TUNEL staining for a time course study was done using 15 control animals that were killed by exsanguination at 15, 30, and 60 minutes after reperfusion.

Results

After 120 minutes of reperfusion, the mean pulmonary arterial pressures in the control group and in the inhaled NO group were 23.0 ± 3.2 mm Hg and 13.6 ± 2.4 mm Hg, respectively (p < 0.01). At the same time point, the Pao₂ in the control group and in the inhaled NO group were 46.1 ± 15.9 mm Hg and 88.1 ± 14.7 mm Hg, respectively (p < 0.01). The wet-to-dry weight ratios in the control group and in the inhaled NO group were 0.856 ± 0.024 and 0.808 ± 0.006, respectively (p < 0.01). Apoptotic cells appeared in the early phase of reperfusion (after 15 minutes' reperfusion). The number of apoptotic cells was significantly lower in the inhaled group than in the control group after 120 minutes' reperfusion (1.76% versus 2.87%, p < 0.01).

Conclusions

Our results suggest that the inhaled NO prevents lung ischemia-reperfusion injury and attenuates apoptosis after reperfusion in the rabbit lung.     

Cytosolic phospholipase A2 inhibition attenuates ischemia-reperfusion injury in an isolated rat lung model

BACKGROUND: Arachidonic acid metabolites and platelet-activating factor (PAF) are potentially involved in ischemia-reperfusion (IR) lung injury. A key enzyme regulating their metabolism is cytosolic phospholipase A2 (cPLA2). Arachidonyl trifluoromethyl ketone (AACOCF3) is reported to be a potent cPLA2 inhibitor. In the present study, we hypothesized that pharmacological inhibition of cPLA2 might ameliorate IR lung injury. METHODS: To test the hypothesis, we examined the effects of AACOCF3 in an isolated rat lung model. Three groups were defined (n=6, each): in the vehicle group, lungs were perfused for 2 hours without an ischemic period. In the ischemic groups, 20 mg/kg of AACOCF3 (AACOCF3 group) or saline (control group) was i.v. administered 15 min before lung harvest. Lungs were flushed with LPD solution, cold-stored 18 hours, and reperfused for 2 hours. RESULTS: IR increased cPLA2 activity mainly via alveolar macrophages, sPLA2 activity, thromboxane and leukotriene formation, and the expression of PAF receptor, whereas AACOCF3 treatment significantly reduced all of these. Compared to the vehicle group, the wet-to-dry ratio, proteins in BAL, and MPO activity increased significantly by twofold, fourfold, and threefold, respectively. Furthermore, the PO2 dropped from 615.7+/-31.2 to 452.1+/-30.9 mmHg at the end of reperfusion (P<0.001). AACOCF3 treatment maintained the PO2 at a level similar to the vehicle group throughout reperfusion and reduced significantly the alveolar-capillary leakage, edema formation, and neutrophil extravasation. CONCLUSION: Pharmacological inhibition of the cPLA2 cascade decreases bioactive lipid formation and attenuates IR-induced lung injury.     

Endotracheal calcineurin inhibition ameliorates injury in an experimental model of lung ischemia-reperfusion

OBJECTIVES: We previously demonstrated that calcineurin inhibitors given intravenously ameliorate experimental lung ischemia-reperfusion injury. This study evaluates whether these effects can be achieved when these agents are delivered endotracheally. METHODS: Left lungs of Long Evans rats were rendered ischemic for 90 minutes and reperfused for up to 4 hours. Treated animals received tacrolimus endotracheally at doses of 0.2, 0.1, or 0.025 mg/kg 60 minutes before ischemia. Injury was quantitated in terms of vascular permeability. Additional animals treated at a dose of 0.1 mg/kg were assessed for lung tissue myeloperoxidase content and bronchoalveolar lavage leukocyte content. Bronchoalveolar lavage fluid was assessed for cytokine and chemokine content by enzyme-linked immunosorbent assay. Tissue samples were processed for nuclear factor-kappaB activation, and blood levels of tacrolimus were measured in treated animals. RESULTS: Left lung vascular permeability was reduced in treated animals in a dose-dependent fashion compared with controls. The protective effects correlated with a 47% (0.50% +/- 0.06% vs 0.27% +/- 0.08%, respectively) reduction in tissue myeloperoxidase content (P <.004) and marked reductions in bronchoalveolar lavage leukocyte accumulation. This protection was also associated with decreased nuclear factor-kappaB activation and diminished expression of proinflammatory mediators. Blood tacrolimus levels in treated animals at 4 hours of reperfusion were undetectable. CONCLUSIONS: Tacrolimus administered endotracheally is protective against lung ischemia-reperfusion injury in our model. This protection is associated with a decrease in nuclear factor-kappaB activation. This route of tacrolimus administration broadens its potential clinical use and decreases concerns about systemic and renal toxicity. It may be a useful therapy in lung donors to protect against lung ischemia-reperfusion injury.     

静脉应用抑肽酶对大鼠肺移植模型缺血再灌注损伤的作用

目的 探讨静脉应用抑肽酶对肺移植后肺缺血再灌注损伤的作用和机制.方法 利用移植肺冷缺血14 h建立的大鼠肺移植缺血再灌注损伤模型,考察抑肽酶对缺血再灌注损伤的影响,并检测细胞因子等指标探讨机制.结果 抑肽酶组较对照组移植肺氧合好、湿干比小,同时支气管肺泡灌洗液中白细胞介素(IL)-2[(113±32)μg/L和(162±43)μg/L,P＜0.05]、血清中IL-8[(7.26±1.01)ng/L和(9.43±0.97)ng/L,P＜0.05]和肿瘤坏死因子(TNF)-α[(152.3±36.4)ng/L和(211.6±52.7)ng/L,P＜0.05]、肺组织中髓过氧化物酶活性[(2.36±0.62)U/g和(3.98±0.36)U/g,P＜0.05]都显著降低.结论 静脉应用抑肽酶能够减轻缺血再灌注损伤,机制可能包括:减少IL-2的释放、抑制TNF-α活化和IL-8产生,抑制中性粒细胞的聚集、激活和脱颗粒.     

白细胞介素12在大鼠肺缺血再灌注损伤中的作用

目的 评价白细胞介素12(IL-12)在大鼠肺缺血再灌注损伤中的作用.方法 健康成年雄性SD大鼠24只,8-10周龄,体重250-280 g,采用随机数字表法,将大鼠随机分为3组(n=8):假手术组(S组),肺缺血再灌注损伤组([/R组),IL-12单克隆抗体组(IL-12组).S组只分离肺门不夹闭;I/R组夹闭肺门60 min后,恢复灌注2 h;IL-12组于夹闭肺门前1h尾静脉注射IL-12单克隆抗体200μg/kg.于再灌注结束时采集血样和肺绀织,测定血浆TNF-α浓度、辅助性T细胞(Th)1和Th2水平、肺组织湿干重(W/D)比、髓过氧化物酶(MPO)活性、MDA含量及动脉血氧分压(PaO2)及二氧化碳分压(PaCO2).光镜下观察肺组织病理学改变.结果 与S组比较,I/R组和IL-12组肺组织W/D比、MDA含量、MPO活性、血浆TNF-α浓度升高,I/R组PaO2降低,PaCO2、Th1水平和Th1/Th2升高(P＜0.01),Th2水平差异无统计学意义(P＞0.05),IL-12组PaO2、PaCO2、Th1、Th2水平及Th1/Th2差异无统计学意义(P＞0.05);与I/R组比较,IL-12组PaCO2、肺组织W/D比、MDA含量、MPO活性、血浆TNF-α浓度、Th1水平和Th1/Th2降低,Th2水平和PaO2升高(P＜0.01).I/R组肺组织损伤明显,IL-12组肺组织损伤程度明显减轻.结论IL-12通过使Tn1/Th2失衡而参与肺缺血再灌注损伤.