Levobupivacaine attenuates lipopolysaccharide‐induced acute lung injury

Levobupivacaine (LB), a kind of local anesthetic, possesses anti‐inflammatory properties. High‐mobility group box 1 (HMGB1), a nuclear DNA‐binding protein, plays a key role in the development of acute lung injury (ALI). The aim of this study was to investigate whether LB attenuates ALI by the inhibition of HMGB1 expression and to investigate the molecular mechanisms. ALI in male rats was induced by an intratracheal instillation of LPS (5 mg/kg), and male rats received mini‐osmotic pumps containing LB 30 min after LPS exposure. A549 alveolar epithelial cells were incubated with LPS in the presence or absence of LB. An enzyme‐linked immunosorbent assay was used to detect the levels of inflammatory cytokines. Western blotting was used to detect the changes in the expression of toll‐like receptor 2/4 (TLR2/4) and the activation of NF‐κB. The results showed that LB significantly protected animals from LPS‐induced ALI as evidenced by a decrease in the ratio of lung wet to dry weight, total cells, neutrophils, macrophages, and myeloperoxidase activity, associated with a reduced lung histological damage. We also found that LB post‐treatment markedly inhibited the release of HMGB1 and other pro‐inflammatory cytokines. Furthermore, LB significantly inhibited LPS‐induced TLR2/4 protein overexpression and NF‐κB activation in the lung tissues and in LPS‐stimulated A549 alveolar epithelial cells in vitro. These data indicate that LB attenuated LPS‐induced ALI by the inhibition of HMGB1 expression in rats. These benefits were associated with the inhibition of TLR2/4‐NF‐κB pathway by LB.     

Fructose-1,6-diphosphate attenuates acute lung injury induced by ischemia-reperfusion in rats

OBJECTIVE: To determine whether fructose-1,6-diphosphate (FDP) pretreatment can attenuate acute lung injury induced by ischemia-reperfusion in our isolated lung model in rats. DESIGN: Randomized, controlled study. SETTING: Animal care facility procedure room. SUBJECTS: Twenty-four adult male Sprague-Dawley rats each weighing 250-350 g. INTERVENTIONS: Typical acute lung injury in rats was induced successfully by 10 mins of hypoxia followed by 75 mins of ischemia and 50 mins of reperfusion. Ischemia-reperfusion significantly increased microvascular permeability as measured by the capillary filtration coefficient, lung weight gain, lung weight to body weight ratio, pulmonary arterial pressure, and protein concentration of bronchoalveolar lav-age fluid. MEASUREMENTS AND MAIN RESULTS: Pretreatment with FDP significantly attenuated the acute lung injury induced by ischemia-reperfusion as shown by a significant decrease in all of the assessed variables (p <.05 p <.001). The protective effect of FDP was nearly undetectable when promazine (an ecto-adenosine 5-triphosphatase inhibitor) was added before FDP pretreatment. CONCLUSIONS: Pretreatment with FDP significantly ameliorates acute lung injury induced by ischemia-reperfusion in rats.     

Reduction in alveolar macrophages attenuates acute ventilator induced lung injury in rats

Objective Alveolar macrophages are the sentinel cell for activation of the inflammatory cascade when the lung is exposed to noxious stimuli. We investigated the role of macrophages in mechanical lung injury by comparing the effect of high-volume mechanical ventilation with or without prior depletion of macrophages. Design and setting Randomized sham-controlled animal study in anesthetized rats. Methods Lung injury was induced by 15 min of mechanical ventilation (intermittent positive pressure ventilation) using high peak pressures and zero end-expiratory pressure. The mean tidal volume was 40 ± 0.7 ml/kg. One group of animals was killed immediately after this period of volutrauma (HV), while in a second group normoventilation was continued for 2 h at a tidal volume less than 10 ml/kg (HV-LV). One-half of the animals were depleted of alveolar macrophages by pretreatment with intratracheal liposomal clodronate (CL₂MDP). Measurements Arterial blood gas, blood pressure. After kill: lung static pressure volume curves, bronchoalveolar fluid concentration for protein, macrophage inflammatory protein 2, tumor necrosis factor α, and wet/dry lung weight ratio (W/D). Results During HV and HV+LV oxygenation, lung compliance, and alveolar stability were better preserved in animals pretreated with CL₂MDP. In both groups W/D ratio was significantly greater in ventilated than in nonventilated animals (4.5 ± 0.6), but the increase in W/D was significantly less in CL₂MDP treated HV and HV-LV groups (6.1 ± 0.4, 6.6 ± 0.6) than in the similarly ventilated nontreated groups (8.7 ± 0.2 and 9.2 ± 0.5). Conclusions Alveolar macrophages participate in the early phase of ventilator-induced lung injury. This research was performed at the University of South Alabama, Mobile, AL.     

Hyperbaric oxygen attenuates lipopolysaccharide-induced acute lung injury

OBJECTIVES: To study the effect of hyperbaric oxygen therapy in alleviating acute lung injury induced by lipopolysaccharide (LPS) in rats.DESIGN AND INTERVENTIONS: The rats received an intraperitoneal injection of LPS (15 mg/kg). Animals were either breathing air at 1 ATA or subjected to hyperbaric oxygen (HBO(2)) therapy. The HBO(2) therapy was carried out in a hyperbaric chamber at a pressure of 3 ATA for 90 min. In another two groups, LPS-treated rats also received intraperitoneal injection of N(omega)-nitro-L-arginine (LNAME, 25 mg/kg) or L-N(6)-(iminoethyl)lysine (LNIL, 10 ml/kg). Another two groups of LPS-treated rats were subjected to HBO(2) exposure after the injection of L-NAME or L-NIL.MEASUREMENTS AND MAIN RESULTS: The bronchoalveolar lavage (BAL) was done into the left lung at 7.5 h after intraperitoneal injection of LPS. Parts of the right lung were excised for myeloperoxidase measurement, whereas the rest was collected for wet/dry ratio determination. LPS significantly increased the nitrite/nitrate (NO(x)(-)) concentration (34.4+/-15.7 vs 4.5+/-3.1 microM), LDH activity (66+/-17 vs 46+/-15 mAbs/min), and protein concentration (373+/-119 vs 180+/-90 mg/l) in the BAL fluid. Treatment with HBO(2) immediately after the injection of LPS enhanced the increase of NO(x)(-) production, but reduced the LDH and protein in BAL fluid to the control levels. Pretreatment with either L-NAME or L-NIL abolished the increase of NO(x)(-) in the BAL fluid and further elevated the LDH level and protein concentration.CONCLUSION: Our results suggested that HBO(2) alleviates the LPS-induced acute lung injury, which may be related to the enhancement of nitric oxide production.     

磷脂酶A2激活介导肠缺血—再灌注损伤作用机制

目的：探讨缺血再灌注（ＩＲ）损伤过程中磷脂酶Ａ２（ＰＬＡ２）激活介导肿瘤坏死因子（ＴＮＦ）等炎症介质的作用机制。方法：采用大鼠肠ＩＲ损伤模型，用放射免疫分析法测定Ｗｉｓｔａｒ大鼠肠ＩＲ损伤后血浆和肺灌洗液中ＴＮＦ、ＰＬＡ２及肝、肠组织中的ＰＬＡ２水平，并观察大鼠存活情况和脏器损伤的病理变化。结果：ＩＲ损伤后，各用药组大鼠存活时间均明显长于ＩＲ损伤组；假手术组损伤前血浆ＴＮＦ含量较损伤后变化不明显，其余各组损伤后血浆ＴＮＦ及ＰＬＡ２含量均显著高于损伤前，且各用药组血浆ＴＮＦ含量均较损伤组明显下降；损伤后肝和肠组织中ＰＬＡ２与假手术组比较均增高，用药组并无明显下降。ＩＲ损伤组肺灌洗液ＴＮＦ和ＰＬＡ２含量明显高于假手术组；用药组与损伤组比较ＰＬＡ２变化不明显。光镜和电镜下仍可见到肺组织有明显改变，但轻于ＩＲ损伤组，肺泡腔渗出较少，中性粒细胞聚集明显减轻。结论：ＰＬＡ２激活在肠ＩＲ导致的远端脏器肺损伤过程中有着重要的作用，使用ＰＬＡ２阻断剂可减轻肠ＩＲ后肺组织损伤，其机制可能与降低血浆ＴＮＦ以及肺灌洗液中ＴＮＦ和ＰＬＡ２有关。     

Inhaled milrinone attenuates experimental acute lung injury

Purpose  To test whether inhalation of the phosphodiesterase 3 inhibitor milrinone may attenuate experimental acute lung injury (ALI). Methods  In rats, ALI was induced by infusion of oleic acid (OA). After 30 min, milrinone was inhaled either as single dose, or repeatedly in 30 min intervals. In mice, ALI was induced by intratracheal instillation of hydrochloric acid, followed by a single milrinone inhalation. Results  Four hours after OA infusion, ALI was evident as lung inflammation, protein-rich edema and hypoxemia. A single inhalation of milrinone attenuated the increase in lung wet-to-dry weight ratio and myeloperoxidase activity, and reduced protein concentration, neutrophil counts and TNF-α levels in bronchoalveolar lavage. This effect was further pronounced when milrinone was repeatedly inhaled. In mice with acid-induced ALI, milrinone attenuated hypoxemia and prevented the increase in lung myeloperoxidase activity. Conclusions  Inhalation of aerosolized milrinone may present a novel therapeutic strategy for the treatment of ALI.     

A2B adenosine receptor signaling attenuates acute lung injury by enhancing alveolar fluid clearance in mice

Although acute lung injury contributes significantly to critical illness, resolution often occurs spontaneously via activation of incompletely understood pathways. We recently found that mechanical ventilation of mice increases the level of pulmonary adenosine, and that mice deficient for extracellular adenosine generation show increased pulmonary edema and inflammation after ventilator-induced lung injury (VILI). Here, we profiled the response to VILI in mice with genetic deletions of each of the 4 adenosine receptors (ARs) and found that deletion of the A2BAR gene was specifically associated with reduced survival time and increased pulmonary albumin leakage after injury. In WT mice, treatment with an A2BAR-selective antagonist resulted in enhanced pulmonary inflammation, edema, and attenuated gas exchange, while an A2BAR agonist attenuated VILI. In bone marrow–chimeric A2BAR mice, although the pulmonary inflammatory response involved A2BAR signaling from bone marrow–derived cells, A2BARs located on the lung tissue attenuated VILI-induced albumin leakage and pulmonary edema. Furthermore, measurement of alveolar fluid clearance (AFC) demonstrated that A2BAR signaling enhanced amiloride-sensitive fluid transport and elevation of pulmonary cAMP levels following VILI, suggesting that A2BAR agonist treatment protects by drying out the lungs. Similar enhancement of pulmonary cAMP and AFC were also observed after β-adrenergic stimulation, a pathway known to promote AFC. Taken together, these studies reveal a role for A2BAR signaling in attenuating VILI and implicate this receptor as a potential therapeutic target during acute lung injury.     

Therapeutic time-window of a group IIA phospholipase A2 inhibitor in rabbit acute lung injury: correlation with lung surfactant protection

OBJECTIVE: We attempted to determine whether group IIA secretory phospholipase A2 (sPLA2-IIA) blockade after the onset of lung injury exerted therapeutic efficacy in the treatment of oleic acid (OA)-induced acute lung injury by using S-5920/LY315920Na, a novel specific inhibitor of sPLA2-IIA, with special interest in the changes of lung surfactant. DESIGN: Prospective animal study. SETTING: University laboratory. SUBJECTS: Forty Japanese white rabbits. INTERVENTIONS: The rabbits, under anesthesia, were endotracheally intubated and mechanically ventilated and then were divided into the following groups: OA + vehicle groups, intravenous infusion of OA for the first 2 hrs (0.1 mL x kg(-1) x hr(-1)) with the addition of vehicle (1 or 2 hrs after OA administration, each n = 9, total 18 rabbits); OA + S-5920/LY315920Na groups, treated identically to the OA control with the addition of S-5920/LY315920Na (1 mg/kg bolus followed by infusion at 0.5 mg x kg(-1) x hr(-1)) after OA (1 or 2 hrs after OA administration, each n = 9, total 18 rabbits); saline control groups, treated with saline instead of OA with the addition of vehicle (1 hr after OA administration, 4 rabbits). Arterial blood gas, lung mechanics, lung inflammation, lung surfactant phospholipids, and production of inflammatory mediators in the lung were measured. MEASUREMENTS AND MAIN RESULTS: Treatment with S-5920/LY315920Na 1 hr after OA infusion, but not 2 hrs after infusion, significantly attenuated the lung injury, as estimated by hypoxemia, decreased lung compliance, pulmonary edema, and vascular permeability. The therapeutic efficacy was similar to that found in our previous pretreatment study. The treatment after 1 hr dramatically inhibited OA-induced surfactant degradation in the bronchoalveolar lavage fluid (BALF), without affecting the concentrations of thromboxane A2, leukotriene B4, and interleukin-8 in BALF. The degree of surfactant degradation in BALF paralleled well with the severity of the lung injury. Furthermore, recombinant human sPLA2-IIA reproduced the similar hydrolysis pattern of isolated surfactant in vitro, which was inhibited by S-5920/LY315920Na. CONCLUSIONS: Our results indicate that therapeutic blockade of sPLA2-IIA ameliorated lung dysfunction via protection of surfactant degradation in an animal model of acute lung injury, and they suggest a new strategy in treating clinical acute lung injury.     

磷脂酶A2在小儿急性肺损伤中的作用及意义

目的探讨磷脂酶A2在急性肺损伤(ALI)恶化进程中的作用及意义.方法结合危重病例评分,采用ELISA检测28例ALI患儿血清PLA2含量,并监测患儿脏器功能及动脉血气.结果 ALI患儿血清PLA2含量明显高于正常组(P＜0.001),低于多脏器功能衰竭(MOF)组(P＜0.01).结论 PLA2参与ALI的病理生理过程,与ALI的病情有关,并可作为早期警示ALI及MOF的实验室参数.     

A rat model of acute lung injury induced by cardiopulmonary bypass.

Impaired lung function is still a major complication after cardiac surgery with cardiopulmonary bypass. The purpose of the present study was to develop an experimental model of acute pulmonary injury induced by cardiopulmonary bypass in Wistar rats. Cardiopulmonary bypass was performed for 60 min using a non-pulsatile roller pump and a membrane oxygenator (n = 8 for cardiopulmonary bypass group and n = 7 for control rats). We measured tracheal pressure, airflow, and lung volume changes and obtained pulmonary resistance and dynamic elastance. After the cardiopulmonary bypass, lungs were submitted to a quick-freezing protocol and morphometric analysis was performed. There was a time-dependent increase in dynamic elastance, but not pulmonary resistance, only in the rats submitted to cardiopulmonary bypass (P = 0.005). Lungs from animals submitted to cardiopulmonary bypass showed significantly more alveolar hemorrhage (P = 0.025) and edema (P = 0.021), as well as perivascular edema (P = 0.003) when compared to control rats. In our experimental model, rats submitted to cardiopulmonary bypass developed acute pulmonary changes similar to the early phase of acute pulmonary distress syndrome. Cardiopulmonary bypass resulted in an increase in pulmonary elastance without changes in resistance. This experimental model is suitable for studies concerning the mechanisms of acute lung injury induced by cardiopulmonary bypass.     

Heparanase pretreatment attenuates endotoxin-induced acute lung injury in rats

A central event of systemic inflammation and septic organ injury is infiltration of tissues with polymorphonuclear neutrophils, likely modulated by the integrity of the extracellular matrix underlying the vascular endothelium. In the present study, the effect of matrix-modifying endoglycosidase (heparanase) on endotoxin (LPS)-induced inflammatory lung injury was investigated in rats. Animals were treated with heparanase or LPS or pretreated with heparanase before LPS injection, and acute lung injury was verified histologically and characterized by analysis of bronchoalveolar lavage fluids. Pretreatment with heparanase attenuated the mortality of animals and preserved the histological structure of the lungs. Furthermore, polymorphonuclear neutrophil accumulation and activation, analyzed by myeloperoxidase release and reactive oxygen species production associated with lung injury, were significantly reduced upon heparanase pretreatment. In addition, heparanase pretreatment elevated the IL-10 levels in the pulmonary compartment. Moreover, results from in vitro experiments have identified monocyte-derived IL-10 as an important mediator used by heparanase to suppress inflammatory reactions. The protective effect of heparanase may indicate a novel therapeutic strategy for sepsis.     

Insulin attenuates endotoxin-induced acute lung injury in conscious rats

OBJECTIVES: To investigate the effects of insulin on the acute lung injury induced by lipopolysaccharide using a conscious rat model. DESIGN: Prospective, randomized, controlled animal study. SETTING: University research laboratory. SUBJECTS: A total of 190 adult male Sprague-Dawley rats weighing 250-300 g. INTERVENTIONS: Endotoxemia was induced by intravenous infusion of lipopolysaccharide. Lipopolysaccharide at various doses (0, 1, 5, 10, 20, and 30 mg/kg, n=10 for each dose) was administered intravenously in 20 mins. Insulin infusion at doses of 0.5, 1, and 5 microU/kg/min was given 5 mins before lipopolysaccharide administration. Plasma glucose was clamped at 90-110 mg/dL by infusion of 10-80% glucose solution. Insulin and glucose infusion (0.01 mL/min) was started 5 mins before lipopolysaccharide and continued for 120 mins. The rats received a total of 60, 120, and 600 microU/kg insulin as well as 0.12, 0.36, and 0.96 g of glucose in respective groups. The animals were then observed for 4 hrs. MEASUREMENTS AND MAIN RESULTS: The extent of acute lung injury was evaluated by lung weight/body weight ratio, lung weight gain, protein concentration in bronchoalveolar lavage, and exhaled nitric oxide. We also measured plasma nitrate/nitrite and methyl guanidine. In addition, histopathologic changes of the lung were examined. Lipopolysaccharide caused systemic hypotension and severe acute lung injury with increases in plasma nitrate/nitrite and methyl guanidine. Pretreatment with insulin infusion at doses of 0.5, 1, and 5 microU/kg/min mitigated or prevented systemic hypotension and the development of acute lung injury, depending on the dose. Insulin also attenuated the lipopolysaccharide-induced increases in nitrate/nitrite and methyl guanidine. CONCLUSIONS: Insulin is effective in reducing or preventing the lipopolysaccharide-induced increases in plasma nitrate/nitrite and methyl guanidine and the occurrence of acute lung injury.     

Generation of lyso-phospholipids from surfactant in acute lung injury is mediated by type-II phospholipase A2 and inhibited by a direct surfactant protein A-phospholipase A2 protein interaction.

Lyso-phospholipids exert a major injurious effect on lung cell membranes during Acute Respiratory Distress Syndrome (ARDS), but the mechanisms leading to their in vivo generation are still unknown. Intratracheal administration of LPS to guinea pigs induced the secretion of type II secretory phospholipase A2 (sPLA2-II) accompanied by a marked increase in fatty acid and lyso-phosphatidylcholine (lyso-PC) levels in the bronchoalveolar lavage fluid (BALF). Administration of LY311727, a specific sPLA2-II inhibitor, reduced by 60% the mass of free fatty acid and lyso-PC content in BALF. Gas chromatography/mass spectrometry analysis revealed that palmitic acid and palmitoyl-2-lyso-PC were the predominant lipid derivatives released in BALF. A similar pattern was observed after the intratracheal administration of recombinant guinea pig (r-GP) sPLA2-II and was accompanied by a 50-60% loss of surfactant phospholipid content, suggesting that surfactant is a major lung target of sPLA2-II. In confirmation, r-GP sPLA2-II was able to hydrolyze surfactant phospholipids in vitro. This hydrolysis was inhibited by surfactant protein A (SP-A) through a direct and selective protein-protein interaction between SP-A and sPLA2-II. Hence, our study reports an in vivo direct causal relationship between sPLA2-II and early surfactant degradation and a new process of regulation for sPLA2-II activity. Anti-sPLA2-II strategy may represent a novel therapeutic approach in lung injury, such as ARDS.     

单侧肺滴入酸后急性肺损伤的研究

目的：观察酸滴入侧的急性肺损伤（ＡＬＩ）的形成及对测肺有无损伤形成。方法：１８只新西兰兔随机分为生理盐水（ＮＳ）滴入对照组和盐酸入损伤组。以向右肺内滴入ＮＳ或ＨＣｌ后的血气、气道压力、动静态顺应性、肺湿／干比（Ｗ／Ｄ）和支气管肺泡灌洗液（ＢＡＬＦ）中总蛋白（ＴＰ）、总磷脂（ＴＰＬ）、饱和磷脂占总磷脂比（ＤＳＰＣ／ＴＰＬ）及肺组织形态学来判断有无ＡＬＩ及其严重程度。结果：损伤组在酸滴入后ＰａＯ２较基