Vascular endothelial growth factor synthesis in the acute phase of experimental and clinical lung injury.

Vascular endothelial growth factor (VEGF) is a potent angiogenic and endothelial survival factor, which is abundantly expressed in the normal lung. Conceivably, VEGF may be released by numerous cell types found around the airspaces, including alveolar type 2 cells, alveolar macrophages, and polymorphonuclear neutrophils. Using a bacteria-induced lung injury model in rats, VEGF expression in lung was investigated. Both VEGF protein and VEGF messenger ribonucleic acid (mRNA), 4 and 24 h after bacterial challenge (Pseudomonas aeruginosa), were decreased compared with sham rats. VEGF protein was also investigated in bronchoalveolar lavage (BAL) from patients studied within 7 days of acute respiratory distress syndrome (ARDS) onset and in patients without ARDS. VEGF protein levels in BAL were decreased in patients with ARDS versus those without (14.3 +/- 11.1 pg x mL(-1) versus 76.8 +/- 51.1 pg x mL(-1), p = 0.03). In aggregate, these findings show that the initial phase of acute lung injury is associated with a decrease in vascular endothelial growth factor in the lung. This downregulation may represent a protective mechanism aimed at limiting endothelial permeability, and may participate in the decrease in capillary number that is observed during early acute respiratory distress syndrome.     

A role for vascular endothelial growth factor in acute and resolving lung injury

We have previously reported, in patients with acute respiratory distress syndrome (ARDS), elevated plasma levels of vascular endothelial growth factor (VEGF) that became reduced in those who recovered. To examine the potential effect of VEGF on the epithelial side of the alveolar-capillary membrane, we compared VEGF levels in the epithelial lining fluid (ELF) of the same 40 patients with ARDS, and in 28 patients at risk of ARDS. We measured intrapulmonary VEGF levels in 23 patients on Days 1 and 4 after admission to the intensive therapy unit and related these levels to recovery. ELF from subjects with ARDS contained lower levels of VEGF than did ELF from at-risk subjects (1,076 and 7,674 pg/ml, respectively, p = 0.0004) and increased ELF levels at Day 4 were associated with recovery (p = 0.001). Alveolar macrophages from subjects with ARDS produced significantly less VEGF than those from at-risk subjects (6.3 and 13.0 pg/ml, respectively, p = 0.005). Similarly, alveolar neutrophils from subjects with ARDS produced significantly less VEGF than those at risk (13.9 and 31.5 pg/ml, respectively, p = 0.03). ELF VEGF levels inversely correlated with Lung Injury Score (p = 0.003). These studies suggest that VEGF in the alveolar space may reflect the development of, and recovery from, acute lung injury in a manner opposite to that in plasma.     

急性呼吸窘迫综合征患者肺组织细胞凋亡及Fas／FasL表达？…

目的 探讨细胞凋亡在急性呼吸窘迫综合征（ＡＲＤＳ）发病中的作用机制。方法 ＡＲＤＳ组９例,对照组５例,采用ＴＵＮＥＬ法以及免疫组织化学技术观察ＡＢＤＳ患肺组织细胞凋亡及Ｆａｓ／ＦａｓＬ系统表达的变化,结果 ＡＲＤＳ急性期患肺组织细胞凋亡率明显高于对照组,且主要表现为肺泡上皮和肺血管内皮细胞凋亡增加;Ｆａｓ抗原,ＦａｓＬ在ＡＲＤＳ急性期患肺组织中的表达与对照组比较明显下调,并且与肺组织细胞凋亡     

Angiotensin converting enzyme in bronchoalveolar lavage in ARDS

Angiotensin converting enzyme (ACE) is present in the endothelial cells of the normal lung where it converts angiotensin I to angiotensin II and inactivates bradykinin. It has been suggested that during endothelial injury ACE is sloughed into the blood, and that if the alveolar capillary membrane is injured, also into the alveolar lining fluid. Seven patients with adult respiratory distress syndrome (ARDS), were compared to 11 normal control subjects, nine patients with sarcoidosis, and six with idiopathic pulmonary fibrosis. Total, differential cell counts and ACE determinations were performed on bronchoalveolar lavage fluid in the ARDS group. ACE was detectable in the BAL of all but one ARDS patient. It was concluded that BAL ACE is elevated in some ARDS patients, especially those with infectious causes of lung injury. Increased ACE may reflect endothelial damage or local increase in ACE production in response to sepsis.     

KL-6 levels are elevated in plasma from patients with acute respiratory distress syndrome.

The acute respiratory distress syndrome (ARDS) is an extreme form of lung injury characterised by disruption to the alveolar epithelium. KL-6 is a mucin-like glycoprotein expressed on type II pneumocytes. Circulating levels of KL-6 have diagnostic and prognostic significance in a number of interstitial lung diseases, and when elevated are thought to indicate disruption of the alveolar epithelial lining. In this study, the authors sought to determine whether plasma KL-6 levels were elevated in patients with ARDS and whether these were associated with aetiology, disease severity, outcome or ventilatory strategy. Plasma samples were collected from 28 patients with ARDS, nine ventilated controls of matched illness severity and 10 healthy individuals. KL-6 concentrations were measured by enzyme-linked immunosorbent assay. Patients with ARDS had higher plasma levels of KL-6 (median 537 U x mL(-1), interquartile range (IQR) 383-1,119), as compared to ventilated controls (median 255 U x mL(-1), IQR 83-338) and normal individuals (median 215 U x mL(-1), IQR 149-307). In patients with ARDS, plasma KL-6 levels were higher in nonsurvivors than survivors, and correlated positively with oxygenation index and negatively with arterial oxygen tension:inspiratory oxygen fraction ratio. There were also significant positive correlations with mean and peak airway pressures. Elevated levels of plasma KL-6 may provide a useful marker for acute respiratory distress syndrome in ventilated patients and have possible prognostic significance. Alveolar epithelial cell damage may be influenced by the nature of mechanical ventilatory support.     

miRNA在ARDS中的作用研究进展

ARDS为常见且复杂的炎症性肺疾病,发病机制错综复杂,以肺内严重炎症反应导致肺泡上皮及毛细血管内皮损伤和功能障碍为特征,并存在细胞凋亡及肺泡液体清除异常等,最终导致肺换气功能障碍,表现为严重呼吸困难及低氧血症.微小RNA (miRNA)作为一类新型的基因调控分子,在许多疾病包括ARDS的发病过程中发挥着至关重要的作用.在肺损伤和修复过程中,特定种类的miRNA表达异常,并通过影响其靶基因的表达而调控炎症通路和免疫反应.     

G-CSF and IL-8 but not GM-CSF correlate with severity of pulmonary neutrophilia in acute respiratory distress syndrome.

Activated neutrophils play a major role in the pathogenesis of acute respiratory distress syndrome (ARDS), and persistence of pulmonary neutrophilia is related to poor survival. Interleukin (IL)-8 is implicated in recruiting neutrophils to the lungs but it has been postulated that granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF), which can promote the survival of neutrophils by delaying apoptosis, may prolong the inflammatory response. The aim of this study was to investigate the levels of GM-CSF and G-CSF in the lungs of patients with ARDS and determine their relationship relative to IL-8 with levels of neutrophils and clinical outcome. The lungs of 31 patients with ARDS were sampled by means of bronchoalveolar lavage (BAL) and assays of the three cytokines were conducted via enzyme-linked immunosorbent assay. GM-CSF, G-CSF and IL-8 were all increased in the patients compared to healthy controls but concentrations of GM-CSF were much lower than those of G-CSF and IL-8 (GM-CSF相似文献   

Tumor necrosis factor-alpha and angiostatin are mediators of endothelial cytotoxicity in bronchoalveolar lavages of patients with acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is characterized by an extensive alveolar capillary leak, permitting contact between intra-alveolar factors and the endothelium. To investigate whether factors contained in the alveolar milieu induce cell death in human lung microvascular endothelial cells, we exposed these cells in vitro to bronchoalveolar lavage fluid (BALF) supernatants from control patients, patients at risk of developing ARDS, and patients with early- and late-phase ARDS. In contrast to BALF from control patients, a significant cytotoxicity was found in BALF from patients at risk of developing ARDS, with late-phase ARDS, and especially from patients with early-phase ARDS. Subsequently, we determined the levels of factors known to exert cytotoxicity in endothelial cells, i.e., tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1, and angiostatin. BALF from patients at risk of developing ARDS, with early-phase ARDS, and with late-phase ARDS, contained increased levels of TNF-alpha and angiostatin, but not of TGF-beta1, as compared with BALF from control patients. Whereas inhibition of TGF-beta1 had no effect in this setting, neutralization of TNF-alpha or angiostatin inhibited the cytotoxic activity on endothelial cells of part of the early-phase ARDS BALF. These results indicate that TNF-alpha and angiostatin may contribute to ARDS-related endothelial injury.     

von Willebrand factor antigen as a prognostic marker in posttraumatic acute lung injury

The specific endothelial cell product von Willebrand factor antigen (vWf:Ag) was measured in plasma and lung function tests were carried out and the following lung injury parameters measured: P(a)O2/F(i)O2 ratio, static respiratory compliance and Murray's lung injury score (LIS) in a follow-up study of 36 severely traumatized patients. Injury severity score (ISS) and APACHE II scores were calculated. Patients were classified according to the presence or absence of acute respiratory distress syndrome (ARDS) complications and survival versus death. Data collection was performed on admission to hospital and after 1-3, 5, 7, 10 days of ICU stay. On all of the occasions investigated, plasma vWf:Ag levels in ARDS patients and nonsurvivors were significantly greater than those in patients without ARDS and survivors, respectively. Significant correlations were observed between initial vWf:Ag concentration and ISS, APACHE II, LIS. Our study suggests that increased concentrations of vWf:Ag in plasma are predictive of the development of ARDS and signal poor prognosis in patients following severe trauma.     

Variable tissue expression of transferrin receptors: relevance to acute respiratory distress syndrome.

Acute respiratory distress syndrome (ARDS) is associated with altered plasma and lung iron chemistry. Iron can promote microbial virulence and catalyse pro-oxidant reactions, thereby contributing to the oxidative stress that characterises the syndrome. Therefore, the expression of ferritin and transferrin receptors (TfR) were sought in the lungs and hearts of rodents treated with lipopolysaccharide (LPS), and measurements of TfR and ferritin protein expression were taken from lung biopsy specimens from patients with ARDS and appropriate controls. TfR messenger ribonucleic acid (mRNA) was significantly upregulated in the lungs and significantly downregulated in the hearts of rats 4 h after LPS. Ferritin mRNA levels (light and heavy chains) remained unaltered. Protein TfR levels were significantly upregulated in lungs and downregulated in hearts 4 h post-LPS. Ferritin protein levels were significantly downregulated in lungs compared to baseline values but were unaltered in hearts. Nonhaem iron levels were increased in lungs and decreased in hearts, and iron-regulatory-protein activity increased in hearts but not lungs. TfR protein levels were significantly increased in lung biopsies from patients with ARDS compared to controls. Transferrin receptors are upregulated in rodent lungs during inflammation but are downregulated in the heart. Transferrin receptor protein levels were significantly increased in the lungs in clinical acute respiratory distress syndrome. These findings have implications for the pathogenesis of acute respiratory distress syndrome, especially in relation to the role of iron as a mediator of oxidative stress.     

VEGF levels in the alveolar compartment do not distinguish between ARDS and hydrostatic pulmonary oedema.

Although overexpression of vascular endothelial growth factor (VEGF) 165 in the lung causes pulmonary oedema, its role in human acute lung injury (ALI) is unclear. VEGF levels are reported to be lower in bronchoalveolar lavage from ALI patients compared with normals, but these studies did not include a comparably ill control group with noninflammatory pulmonary oedema. The current authors hypothesised that VEGF levels in pulmonary oedema fluid would be lower in ALI patients compared with control patients with severe hydrostatic pulmonary oedema. VEGF was measured in pulmonary oedema fluid and plasma from 56 patients with ALI and 46 controls with severe hydrostatic pulmonary oedema. Pulmonary oedema fluid levels of VEGF did not differ between patients with hydrostatic oedema (median 799 pg x mL(-1), interquartile range (IQR) 226-2,281) and ALI (median 507, IQR 0.8-1,031). Plasma levels were also the same (median 20.5 pg x mL(-1), IQR 0-152 versus 4.8, IQR 0-99.8). There was no association between plasma or oedema fluid VEGF levels and outcomes including mortality. Vascular endothelial growth factor levels in pulmonary oedema fluid were depressed both in acute lung injury and hydrostatic pulmonary oedema. The decrease in air space concentrations of vascular endothelial growth factor in acute lung injury may not be a function of the degree of lung injury, but rather may result from alveolar flooding.     

Pulmonary epithelial permeability in ARDS and cardiogenic pulmonary oedema

Clearance of inhaled 99mTechnetium-labelled diethylene triamine pentacetate (99mTc-DTPA) from the lung, an index of pulmonary alveolar epithelial permeability (PAEP), was measured in 13 patients with cardiogenic interstitial pulmonary oedema (CIPO) and in 7 patients with adult respiratory distress syndrome (ARDS). Thirty-five normal subjects (22 nonsmokers and 13 smokers) were evaluated as controls. Half-time clearance (t0.5) values in ARDS patients (mean +/- SD: 15 +/- 2 min) were significantly lower than in CIPO patients (62 +/- 9 min). This PAEP increase in ARDS was impressive, even in comparison to heavy smokers. Loss of the PAEP vertical gradient (apical PAEP greater than base PAEP) was observed in both cardiogenic and ARDS lungs and among smokers.     

Neutrophil accumulation and structural changes in nonpulmonary organs after acute lung injury induced by phorbol myristate acetate

Multiple nonpulmonary organ failure contributes significantly to the high mortality rate associated with the adult respiratory distress syndrome (ARDS). However, little is known about specific structural and/or functional alterations that occur in nonpulmonary organs in this syndrome. Therefore, the present study was designed to test the hypothesis that inflammatory cell infiltration and structural changes occur both in the lungs and in nonpulmonary organs in ARDS. To test this hypothesis, neutrophil accumulation and structural alterations were evaluated in nonpulmonary organs from dogs with acute lung injury produced by intravenous phorbol myristate acetate (PMA) (30 micrograms/kg; n = 5). As expected, morphologic changes were present in the lungs of the PMA-treated animals and included a diffuse neutrophilic pneumonitis with interstitial, vascular, and alveolar components. PMA-treated dogs had significant increases in neutrophils (expressed as PMN/mm2 tissue section area) compared with those in control animals in the following organs: heart, 14 +/- 3 versus 4 +/- 1; brain, 2.5 +/- 0.3 versus 0.7 +/- 0.3; duodenum, 34 +/- 7 versus 10 +/- 2; liver, 397 +/- 16 versus 103 +/- 12 (p less than 0.025, all comparisons). In addition, severe necrosis and inflammation of vessels, sinusoidal thrombosis, and hepatic necrosis were noted in the liver. Like the changes noted in the lung, hepatic lesions appeared to be vascular in origin and were consistent with lesions produced by the intravascular activation of neutrophils. No microscopic lesions were detected in the brain, kidney, duodenum, and heart. Taken together, the finding of concurrent lung injury, liver injury, and nonpulmonary organ neutrophil accumulation suggests the possibility of a common pathway of injury in this model of ARDS.     

Mechanisms of alveolar epithelial repair in acute lung injury--a translational approach

In patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS), extensive damage to the alveolar epithelial and endothelial barrier is observed, resulting in the influx of protein-rich oedema fluid into the air spaces. Efficient alveolar epithelial repair is crucial to ALI/ARDS patients' recovery. Future therapeutic strategies may therefore include acceleration of the epithelial repair process in the injured lung. However, a better understanding of the cellular and molecular mechanisms that promote alveolar epithelial repair is needed if novel therapeutic strategies are to be developed. Pulmonary oedema fluid from patients with ALI/ARDS and from patients with hydrostatic oedema as control was obtained, and the effect on alveolar epithelial repair in vitro using our alveolar epithelial wound repair bioassay was studied. In contrast to the initial hypothesis, pulmonary oedema fluid from ALI/ARDS patients increased alveolar epithelial repair in vitro by an interleukin-1beta (IL-1beta)-dependent mechanism, demonstrating a novel, possibly beneficial role for IL-1beta in patients with ALI/ARDS. Further studies using primary alveolar epithelial cells from rats revealed that IL-1beta induced alveolar epithelial repair by an epidermal growth factor (EGF)/transforming growth factor-alpha (TGF-alpha)-dependent pathway. Besides EGF and TGF-alpha, keratinocyte growth factor (KGF) and hepatocyte growth factor (HGF)--both present in pulmonary oedema fluid obtained from patients with ALI/ARDS--stimulate alveolar epithelial repair in vitro. Further experimental and clinical studies will show whether acceleration of alveolar epithelial repair by modulating cytokines and growth factors in the injured lung represents a promising new therapeutic strategy in patients with ALI/ARDS.     

Osteopontin is Strongly Expressed by Alveolar Macrophages in the Lungs of Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is characterized by an intense inflammatory response in the lung parenchyma. Recent studies suggest that excessive nitric oxide (NO) production mediated by inducible NO synthase (iNOS) in macrophages is partially involved in mediating acute lung injury in ARDS. On the other hand, osteopontin (OPN) is a cytokine which is capable of inhibiting NO production by suppressing iNOS mRNA expression in macrophages. In this study, we investigated the expression of OPN in the lungs of 10 patients with ARDS. In most patients, OPN is strongly expressed on alveolar macrophages. In addition, we produced a murine model for ARDS by intratracheal administration of lipopolysaccharide and investigated the expression of endogenous OPN and iNOS in the lungs of ARDS mice. Immunostaining demonstrated that in vivo OPN protein was coinduced with iNOS protein predominantly in the accumulating alveolar macrophages. OPN mRNA expression was also coinduced with iNOS mRNA, but was induced more slowly than iNOS mRNA in the lungs of ARDS mice. These results suggested that OPN, which may reduce NO production of macrophages by inhibiting iNOS expression, is significantly induced and expressed on alveolar macrophages in the lungs of ARDS. It is possible that OPN is partially involved in playing a protective role against excessive production of NO in ARDS.     

Production of pro-inflammatory polypeptides by airway mucous glands and its potential significance

Burn patients often develop respiratory distress and ARDS several days after injury. An ovine model allows experimental study of this problem. In sheep the injury is characterized by intense acute inflammation in the trachea and bronchi from 3 to 48h after injury, with accumulation of neutrophils, fibrin and other plasma proteins, and mucus in airway lumens. We have carried out immunostaining for multiple cytokines in this model, including interleukin-8 (IL-8), Interleukin-1 beta (IL-1beta), interleukin-1 alpha (IL-1alpha), tumor necrosis factor-alpha (TNF-alpha), and vascular endothelial growth factor (VEGF). All of these show intense immunostaining in airway mucous glands. IL-1beta and VEGF show substantial constitutive staining in the serous cells of mucous glands, while IL-8, IL-1alpha, and TNF-alpha show substantially increased expression after injury. This pattern of expression of cytokines in mucous glands, and the apparent release of cytokines into the lumen after injury, are considered potentially highly significant in the progression of injury in this model. In addition, a proinflammatory function of mucous glands might prove to be important in chronic lung diseases such as chronic bronchitis and asthma.     

巨噬细胞移动抑制因子在急性呼吸窘迫综合征发病中的作用

目的 探讨巨噬细胞移动抑制因子（MIF）在急性呼吸窘迫综合征（ARDS）中的表达和作用。方法 ARDS组12例，对照组20例，用ELISA法测定患者血清MIF水平，采用流式细胞仪检测外周血单个核细胞（PBMC）MIF的表达，用免疫组织化学双重染色和原位杂交技术观察肺组织中MIF mRNA和蛋白表达水平。结果 ARDS患者外周血清MIF水平和PBMC MIF表达率明显高于正常人（P＜0.01)。原位杂交和免疫组化染色结果显示，正常肺组织中未见MIF mRNA和蛋白表达，而在ARDS肺组织中MIF表达水平明显增高，肺间质、肺泡腔内可见巨噬细胞浸润并见有MIF表达，病理损伤较严重处MIF表达更强且与巨噬细胞浸润数量明显相关。结论 ARDS患者血清MIF水平和外周血单个核细胞表达MIF增多，肺组织存在MIF表达增多及巨噬细胞浸润情况，提示MIF在ARDS发病中起重要作用。     

Occurrence of the adult respiratory distress syndrome in neutropenic patients

Neutrophils are believed to play an essential role in the pathogenesis of the adult respiratory distress syndrome (ARDS). This concept is largely based on the observation that neutrophil depletion protects against altered pulmonary vascular permeability in several models of acute lung injury produced in laboratory animals. Four patients who developed ARDS during periods of profound neutropenia are presented. These patients met commonly accepted clinical and roentgenographic criteria for the syndrome, and each had the characteristic findings of diffuse alveolar damage by lung histologic examination. The failure of this degree of neutropenia to protect against ARDS in humans raises questions about whether neutrophils or neutrophil products are essential in the pathogenesis of the syndrome.     

Current concepts regarding adult respiratory distress syndrome

Adult respiratory distress syndrome (ARDS) is a multietiologic acute and progressive pulmonary dysfunction that may be precipitated by any of a number of pathogenic agents. Clinical and experimental studies suggest that activation of complement and blood neutrophils plays a significant role in the development of pulmonary vascular injury, which is an important pathophysiological feature of ARDS. Although the specific cellular and biochemical mechanisms resulting in the development of ARDS are unknown, it has been suggested that oxygen-derived free radicals generated from complement-activated granulocytes may be involved, directly or indirectly, in the destruction of lung vascular endothelium and alveolar tissue matrix. This hypothesis is supported by recent experimental studies showing that acute lung injury secondary to systemic complement activation can largely be prevented by interventions that scavenge for hydroxyl radicals or restrict availability of ionic iron.     

Fibroproliferative phase of ARDS. Clinical findings and effects of corticosteroids

Most patients with adult respiratory distress syndrome (ARDS) survive the initial insult which caused respiratory failure only to succumb later to sepsis caused by nosocomial pneumonia or to pulmonary fibrosis. Clinical criteria and analysis of the tracheal aspirate are notoriously inadequate for establishing a diagnosis of ventilator-associated pneumonia. We implemented a comprehensive diagnostic protocol to determine the cause of sepsis in ARDS patients who had been ventilated for more than three days and who had no bronchoscopic evidence of pneumonia. Nine patients with late ARDS who had fever (89 percent), leukocytosis (89 percent), a new localized infiltrate (78 percent), purulent tracheal secretions (89 percent), low systemic vascular resistance (50 percent), and marked uptake of gallium in the lungs (100 percent) had no source of infection identified. Open-lung biopsy specimens from seven patients showed the fibroproliferative phase of diffuse alveolar damage and confirmed absence of pneumonia. Treatment with prolonged high doses of corticosteroids was associated with a marked and rapid improvement in lung injury score (p less than 0.003 at five days). Our findings indicate that the fibroproliferative process occurring in the lungs of patients with late ARDS gives rise to clinical manifestations identical to those of pneumonia and is potentially responsive to steroid treatment.