Extent Of Acute Lung Injury Research Articles

A mitochondria-targeted fluorescent sensor for imaging endogenous peroxynitrite changes in acute lung injury

Acute lung injury (ALI) is a serious pulmonary inflammatory disease resulting from excessive reactive oxygen species (ROS) which could cause the damage of the alveolar epithelial cells and capillary endothelial cells. Peroxynitrite, as one of short-lived reactive oxygen species, is closely related to the process of ALI. Thus, it is important to monitor the fluctuation of peroxynitrite in living system for understanding the process of ALI. Herein, the novel mitochondria-targeted fluorescent probe BHMT was designed to respond to peroxynitrite and pH with distinct fluorescence properties respectively. The absorption spectrum of the probe BHMT exhibited a notable red shift as the pH value declined from 8.8 to 2.6. Upon reaction with peroxynitrite, BHMT had a significant increase of fluorescence intensity (63-fold) with maintaining a detection limit of only 43.7 nM. Furthermore, BHMT could detect the levels of endogenous peroxynitrite and image the intracellular pH in ratiometric channels utilizing cell imaging. In addition, BHMT was successfully applied to revealing the relationship between the peroxynitrite and the extent of ALI. Thus, these results indicated the probe BHMT could be a potential tool for diagnosing the early stage of ALI and revealed the peroxynitrite was likely to be a crucial therapeutic target in ALI treatment.

Rev-erbα can regulate the NF-κB/NALP3 pathway to modulate lipopolysaccharide-induced acute lung injury and inflammation

Progressive lung injury and pulmonary inflammation can be induced by an intraperitoneal injection of lipopolysaccharide (LPS). Interleukin-1β (IL-1β) is a key pro-inflammatory cytokine that can further exaggerate inflammation, which is cleaved and activated by the NALP3 inflammasome. Although the nuclear receptor Rev-erbα attenuates the level of LPS-induced pulmonary inflammation, the mechanism remains unclear. In this study, we investigated the influence of LPS-induced production of IL-1β and Rev-erbα on the development of lung inflammation. Herein, we demonstrate that Rev-erbα reduces IL-1β production and lung injury following an intraperitoneal injection of LPS, which is dependent on the NF-κB/NALP3 pathway. Thus, Rev-erbα is able to decrease the extent of acute lung injury by regulating IL-1β production. This mechanism may represent a potential novel therapeutic approach for lung injury.

The mechanism underlying alpinetin-mediated alleviation of pancreatitis-associated lung injury through upregulating aquaporin-1.

Characterized by its acute onset, critical condition, poor prognosis, and high mortality rate, severe acute pancreatitis (SAP) can cause multiple organ failure at its early stage, particularly acute lung injury (ALI). The pathogenesis of ALI is diffuse alveolar damage, including an increase in pulmonary microvascular permeability, a decrease in compliance, and invasion of many inflammatory cells. Corticosteroids are the main treatment method for ALI; however, the associated high toxicity and side effects induce pain in patients. Recent studies show that the effective components in many traditional Chinese medicines can effectively inhibit inflammation with few side effects, which can decrease the complications caused by steroid consumption. Based on these observations, the main objective of the current study is to investigate the effect of alpinetin, which is a flavonoid extracted from Alpinia katsumadai Hayata, on treating lung injury induced by SAP and to explore the mechanism underlying the alpinetin-mediated decrease in the extent of ALI. In this study, we have shown through in vitro experiments that a therapeutic dose of alpinetin can promote human pulmonary microvascular endothelial cell proliferation. We have also shown via in vitro and in vivo experiments that alpinetin upregulates aquaporin-1 and, thereby, inhibits tumor necrosis factor-α expression as well as reduces the degree of lung injury. Overall, our study shows that alpinetin alleviates SAP-induced ALI. The likely molecular mechanism includes upregulated aquaporin expression, which inhibits tumor necrosis factor-α and, thus, alleviates SAP-induced ALI.

Mechanisms of attenuation of abdominal sepsis induced acute lung injury by ascorbic acid

Bacterial infections of the lungs and abdomen are among the most common causes of sepsis. Abdominal peritonitis often results in acute lung injury (ALI). Recent reports demonstrate a potential benefit of parenteral vitamin C [ascorbic acid (AscA)] in the pathogenesis of sepsis. Therefore we examined the mechanisms of vitamin C supplementation in the setting of abdominal peritonitis-mediated ALI. We hypothesized that vitamin C supplementation would protect lungs by restoring alveolar epithelial barrier integrity and preventing sepsis-associated coagulopathy. Male C57BL/6 mice were intraperitoneally injected with a fecal stem solution to induce abdominal peritonitis (FIP) 30 min prior to receiving either AscA (200 mg/kg) or dehydroascorbic acid (200 mg/kg). Variables examined included survival, extent of ALI, pulmonary inflammatory markers (myeloperoxidase, chemokines), bronchoalveolar epithelial permeability, alveolar fluid clearance, epithelial ion channel, and pump expression (aquaporin 5, cystic fibrosis transmembrane conductance regulator, epithelial sodium channel, and Na(+)-K(+)-ATPase), tight junction protein expression (claudins, occludins, zona occludens), cytoskeletal rearrangements (F-actin polymerization), and coagulation parameters (thromboelastography, pro- and anticoagulants, fibrinolysis mediators) of septic blood. FIP-mediated ALI was characterized by compromised lung epithelial permeability, reduced alveolar fluid clearance, pulmonary inflammation and neutrophil sequestration, coagulation abnormalities, and increased mortality. Parenteral vitamin C infusion protected mice from the deleterious consequences of sepsis by multiple mechanisms, including attenuation of the proinflammatory response, enhancement of epithelial barrier function, increasing alveolar fluid clearance, and prevention of sepsis-associated coagulation abnormalities. Parenteral vitamin C may potentially have a role in the management of sepsis and ALI associated with sepsis.

Isoflurane Preconditioning Ameliorates Endotoxin-Induced Acute Lung Injury and Mortality in Rats

The effects of isoflurane pretreatment on pulmonary proinflammatory cytokines and survival in severe endotoxin-induced acute lung injury (ALI) have not been studied systemically. We investigated the effect of preadministration of isoflurane on ALI induced by lipopolysaccharide (LPS) in rats. Male Sprague-Dawley rats weighing 250-300 g were randomly assigned to 1 of 4 groups: sham rats (injected intraperitoneally [IP] with saline) pretreated with vehicle (100% O(2)) (sham-vehicle); sham rats pretreated with isoflurane (sham-ISO); LPS rats (injected IP with LPS) pretreated with vehicle (vehicle-LPS); and LPS rats pretreated with isoflurane (ISO-LPS). Endotoxemia was induced by IP injection of LPS. Isoflurane 1.4% was administered 30 min before LPS injection. The animals were then observed for 6 h. We monitored arterial blood pressure, heart rate, and blood gas. The extent of ALI was evaluated by lung wet/dry ratio, Evans blue dye extravasation, and histologic examination. We also measured pulmonary nitric oxide (NO), tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6 levels. In addition, survival statistics and pulmonary inducible NO synthase (iNOS) gene expression were also determined. LPS caused systemic hypotension and severe ALI, as evidenced by the increases in the extent of ALI, impairment of pulmonary functions, and increases in pulmonary NO, TNF-alpha, IL-1beta, and IL-6. Isoflurane preconditioning mitigated systemic hypotension and the development of ALI. Isoflurane preconditioning also attenuated the LPS-induced increases in pulmonary nitrate/nitrite and proinflammatory cytokine release and improved survival of rats with severe sepsis. The expression of iNOS was upregulated by LPS and reduced by isoflurane pretreatment. Isoflurane preconditioning can attenuate pulmonary proinflammatory cytokine release and decrease the mortality induced by severe sepsis. Early protection seems to be mediated partly through inhibition of iNOS-NO pathway activation.

Intravascular FC-77 attenuates phorbol myristate acetate-induced acute lung injury in isolated rat lungs

To evaluate whether intravascular Fluorinert (FC-77) attenuates phorbol myristate acetate (PMA)-induced acute lung injury in rats. Randomized, controlled animal study. Animal care facility procedure room in a medical center. Thirty-six adult male Sprague-Dawley rats each weighing 250-350 g. PMA (2 microg/kg) was injected into lung perfusate and induced acute lung injury. Different doses of FC-77 were given before PMA administration. The isolated rat lungs were randomly assigned to two control groups (saline and 1% FC-77 only) and four PMA groups (PMA, 0.1% FC-77 + PMA, 0.5% FC-77+PMA, and 1% FC-77+PMA); each condition was maintained for 60 mins. The extent of acute lung injury was assessed by microvascular permeability (measured using the capillary filtration coefficient), lung weight gain, wet lung-to-body weight ratio, pulmonary arterial pressure, and protein concentration of the bronchoalveolar lavage fluid. The concentration of tumor necrosis factor-alpha in lung perfusate was determined. Parts of the right lung were excised for myeloperoxidase and malondialdehyde measurements, whereas the rest was examined for histopathological changes. PMA produced a significant increase in the capillary filtration coefficient, lung weight gain, wet lung-to-body weight ratio, pulmonary arterial pressure, and protein concentration of the bronchoalveolar lavage fluid. Tumor necrosis factor-alpha in lung perfusate and myeloperoxidase and malondialdehyde in lung tissue were also significantly increased. In addition, the pathologic picture showed increased neutrophil infiltration in lung tissues. In contrast, pretreatment with intravascular FC-77 significantly attenuated these variables in a dose-dependent manner compared with the PMA group. Intravascular FC-77 significantly ameliorated acute lung injury induced by PMA in rats in a dose-dependent manner. The protective mechanism may act, in part, by decreasing neutrophil infiltration, inhibiting proinflammatory cytokine production, and preventing the release of free radicals.

Protective effects of propofol on acute lung injury induced by oleic acid in conscious rats*

Oleic acid has been used to induce acute lung injury (ALI) in animals. In patients with acute respiratory distress syndrome (ARDS), the blood level of oleic acid was increased. The mechanism and therapeutic regimen of ARDS and oleic acid-induced ALI remain undefined. In the present study, we investigated the oleic acid-induced changes in lung variables for the measure of ALI, inflammatory mediators, and neutrophil-derived substances. We evaluated the effects of pretreatment and posttreatment with propofol. Randomized, controlled animal study. University research laboratory. Fifty adult male Sprague-Dawley rats weighing 250-300 g. We employed a conscious and unrestrained rat model. Oleic acid at a dose of 100 mg/kg was administered intravenously. Propofol (30 mg/kg) was given by intravenous infusion (6 mg/kg/min for 5 mins) 30 mins before (pretreatment) and 30 mins after (posttreatment) oleic acid. We monitored the arterial pressure, heart rate, and blood gas. The lung weight changes, exhaled nitric oxide, protein concentration in bronchoalveolar lavage, and Evans blue content in lung tissue were determined. The plasma nitrate/nitrite, methylguanidine, cytokines (tumor necrosis factor-alpha, interleukin-1beta, interleukin-6, and interleukin-10), neutrophil elastase, myeloperoxidase, malondialdehyde, and sodium- and potassium-activated adenosine triphosphatase (Na+-K+-ATPase) were detected. Histopathological examination of the lung was performed. Oleic acid caused systemic hypotension and severe ALI as evidenced by the increases in the extent of ALI, impairment of pulmonary functions (blood gas variables), and lung pathology. In addition, oleic acid significantly increased inflammatory mediators and neutrophil-derived factors but depressed Na+-K+-ATPase. The inducible nitric oxide synthase was up-regulated. Pre- or posttreatment with propofol was capable of reversing the oleic acid-induced changes and attenuating the extent of ALI. Oleic acid resulted in sepsis-like responses including ALI, inflammatory reaction, and increased neutrophil-derived factors. It depressed the Na+-K+-ATPase activity but up-regulated inducible nitric oxide synthase. Treatment with propofol abrogated or reversed the oleic acid-induced changes.

N-Acetylcysteine attenuates acute lung injury induced by fat embolism*

Fat embolism syndrome is a clinical issue in subjects with long-bone fracture. It may lead to acute lung injury. The mechanisms and therapeutic regimen remain unclear. The present study was designed to investigate the pathologic and biochemical changes after fat embolization in isolated rat lungs, and to test the effects of posttreatment with N-acetylcysteine (NAC). Prospective, randomized, controlled animal study. University research laboratory. A total of 36 perfused lungs isolated from Sprague-Dawley rats. The isolated lungs were randomly assigned to receive physiologic saline solution (vehicle group), fat embolism (FE group), or FE with NAC posttreatment (FE + NAC group). There were 12 isolated lungs in each group. FE was produced by introduction of corn oil micelles. NAC at a dose 150 mg/kg was given 10 mins after FE. The extent of acute lung injury was evaluated by lung weight change, protein concentration in bronchoalveolar lavage, and exhaled nitric oxide. We also measured the pulmonary arterial pressure and capillary filtration coefficient and determined the nitrate/nitrite, methylguanidine, tumor necrosis factor-alpha, and interleukin-1beta in lung perfusate. Histopathologic changes of the lung were examined and quantified. The levels of neutrophil elastase and myeloperoxidase were determined. The expression of inducible nitric oxide synthase was detected. FE caused acute lung injury as evidenced by the lung weight changes, increases in exhaled nitric oxide and protein concentration in bronchoalveolar lavage, pulmonary hypertension, increased capillary filtration coefficient, and lung pathology. The insult also increased nitrate/nitrite, methylguanidine, tumor necrosis factor-alpha, and interleukin-1beta in lung perfusate, increased neutrophil elastase and myeloperoxidase levels, and upregulated inducible nitric oxide synthase expression. Posttreatment with NAC abrogated these changes induced by FE. FE caused acute lung injury and associated biochemical changes. Posttreatment with NAC was effective to alleviate the pathologic and biochemical changes caused by FE.

NITRIC OXIDE MODULATES AIR EMBOLISM‐INDUCED LUNG INJURY IN RATS WITH NORMOTENSION AND HYPERTENSION

1. Air embolism the in lungs induces microvascular obstruction, mediator release and acute lung injury (ALI). Nitrite oxide (NO) plays protective and pathological roles in ALI produced by various causes, but its role in air embolism-induced ALI has not been fully investigated. 2. The purpose of the present investigation was to elucidate the involvement of NO and pro-inflammatory cytokines in the pathogenesis of ALI following air infusion into isolated perfused lungs from spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto (WKY) rats. 3. The extent of ALI was evaluated by changes in lung weight, Evans blue dye leakage, the protein concentration in the bronchoalveolar lavage and pathological examination. We also measured nitrite/nitrate (NO(x)), tumour necrosis factor (TNF)-alpha and interleukin (IL)-1beta concentrations in lung perfusate and determined cGMP in lung tissue. 4. The NO synthase (NOS) inhibitors N(G)-nitro-l-arginine methyl ester (l-NAME) and l-N(6)-(1-iminoethyl)-lysine (l-Nil), as well as the NO donors sodium nitroprusside (SNP) and s-nitroso-N-acetylpenicillamine (SNAP), were administered 30 min before air embolism at a concentration of 10(-3) mol/L in the lung perfusate. 5. Air embolism-induced ALI was enhanced by pretreatment with l-NAME or l-Nil, but was alleviated by SNP or SNAP pretreatment, in both SHR and WKY rats. In both SHR and WKY rats, AE elevated levels of NO(x) (2.6 and 28.7%, respectively), TNF-alpha (52.7 and 158.6%, respectively) and IL-1beta (108.4 and 224.1%, respectively) in the lung perfusate and cGMP levels in lung tissues (35.8 and 111.2%, respectively). Pretreatment with l-LAME or l-Nil exacerbated, whereas SNP or SNAP abrogated, the increases in these factors, except in the case of NO(x) (levels were decreased by l-LAME or l-Nil pretreatment and increased by SNP or SNAP pretreatment). 6. Air embolism caused increases in the lung weight (LW)/bodyweight ratio, LW gain, protein concentration in bronchoalveolar lavage and Evans blue dye leakage. These AE-induced changes were less in lungs isolated from SHR compared with normotensive WKY rats. 7. The results suggest that ALI and associated changes following air embolism in lungs isolated from SHR are less than those in WKY rats. Nitric oxide production through inducible NOS isoforms reduces air embolism-induced lung injury and associated changes. Spontaneously hypertensive rats appear to be more resistant than WKY rats to air embolism challenge.

ENDOTOXIN‐INDUCED ACUTE LUNG INJURY AND ORGAN DYSFUNCTION ARE ATTENUATED BY PENTOBARBITAL ANAESTHESIA

1. Acute lung injury (ALI) as a result of sepsis is a major cause of mortality. Certain anaesthetic agents have been reported to suppress pro-inflammatory cytokines and inducible nitric oxide (NO) synthase (iNOS) activities. We investigated the effects of pentobarbital on ALI and organ functions after the administration of endotoxin. 2. Intravenous (i.v.) pentobarbital (20 or 40 mg/kg) was administered 5 min after lipopolysaccharide (LPS; 10 or 30 mg/kg via i.v. infusion). To avoid hypoxia and/or hypercapnia following anaesthesia, we installed a special chamber connected to a rodent ventilator to provide ventilation with 95% oxygen content and 5% nitrogen. The animal was kept at eucapnic conditions (arterial PCO2 at an average of 38 +/- 2 mmHg). 3. We monitored the arterial pressure (AP) and heart rate (HR). Acute lung injury was evaluated by lung weight changes, protein concentration in bronchoalveolar lavage, and Evans blue leakage. Plasma nitrate/nitrite, methyl guanidine and biochemical factors were determined. Pathological and immunofluorescent examinations were performed to observe the lung changes and to determine the activities of pro-inflammatory cytokines, nitrotyrosine and iNOS. 4. Lipopolysaccharide caused dose-dependent systemic hypotension with an increase in the extent of ALI. The lung pathology included oedema and inflammatory cell infiltration. Accompanying the ALI, LPS elevated plasma nitrate/nitrite, methyl guanidine, blood urea nitrogen, lactic dehydrogenase, creatinine phosphokinase, glutamic transaminase and amylase. The lung tissue content of tumour necrosis factor-alpha, interleukin-lbeta, iNOS and nitrotyrosine was increased following LPS administration. These changes were abrogated by pentobarbital anaesthesia. 5. Our results indicated that pentobarbital anaesthesia significantly augmented the LPS-induced systemic hypotension. However, it attenuated the LPS-induced ALI and organ dysfunctions. This agent also improved the survival rate following LPS at high and low doses. This mechanism may be related to the inhibitory effects on the increases in the production or activity of NO, free radicals, pro-inflammatory cytokines, nitrotyrosine and iNOS.

EFFECTS OF INITIAL PASSAGE OF ENDOTOXIN THROUGH THE LIVER ON THE EXTENT OF ACUTE LUNG INJURY IN A RAT MODEL

We hypothesized that the extent of acute lung injury (ALI) caused by lipopolysaccharide (LPS) is modified with its initial passage through the liver. We tested this hypothesis by administering LPS, 5 mg/kg, or saline to 120 male Wistar rats via the portal vein (PV) or the inferior vena cava (IVC) over 1 h. Four experimental groups of rats were administered saline into the PV, saline into the IVC, LPS into the PV (LPS-PV group), and LPS into the IVC (LPS-IVC group), respectively. At 15 and 30 min after onset of 51Chromium-LPS infusion, the gamma counts in the liver were higher in the LPS-PV group than that in the LPS-IVC group. The ratio of 125Iodine-albumin counts in lung tissue to that in plasma per unit of weight (as an assessment of pulmonary microvascular permeability) at 240 min after onset of LPS stimulation, the accumulation of polymorphonuclear cell (assessed by myeloperoxidase activity) and the concentration of tumor necrosis factor alpha in the lung at 60 and 240 min after onset of LPS infusion, were higher in the LPS-IVC group than in the LPS-PV group. Significant differences in several factors indicative of inflammation and in the extent of LPS-induced ALI were observed after the onset of LPS infusion, depending on whether it was delivered via the PV or the IVC. These observations suggest that the entrapping of LPS during its initial passage through the hepatic circulation may attenuate LPS-induced ALI within 4 h of initiation of LPS stimulation.

Insulin attenuates endotoxin-induced acute lung injury in conscious rats

To investigate the effects of insulin on the acute lung injury induced by lipopolysaccharide using a conscious rat model. Prospective, randomized, controlled animal study. University research laboratory. A total of 190 adult male Sprague-Dawley rats weighing 250-300 g. 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. 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. 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.

The Intensity of Chronic Lung Inflammation and Fibrosis after Bleomycin Is Directly Related to the Severity of Acute Injury

Interstitial lung disease is thought to result from progression of an initial lung injury and alveolitis into a chronic inflammatory process that produces fibrosis. However, the relationship between the severity of the initial phase of acute injury and alveolitis and the amount of subsequent chronic inflammation and fibrosis remains unclear. We induced a wide spectrum of acute lung injury in rabbits by using various amounts of intratracheal bleomycin (5 or 10 U/kg) with and without oxygen supplementation (100% O2 for 2 min). The arterial oxygen tension on Day 12 after the bleomycin correlated with the extent of acute lung injury, as well as with the amount of chronic inflammation and fibrosis present on Day 56, as determined by physiologic parameters (lung volume, DLCO/VA, and PO2), and morphometry (volume proportions abnormal parenchyma made up of intra-alveolar macrophages, intra-alveolar granulocytes, abnormal alveoli, abnormal airways, fibrosis, consolidation, and honeycombing). We conclude that in bleomycin-induced interstitial lung disease in the rabbit, there is a direct relationship between the severity of acute lung injury after intratracheal bleomycin and the amount of subsequent chronic inflammation and fibrosis. This suggests that the mechanisms regulating the development of fibrosis are directly influenced by the extent of initial injury.