Effects of acute hypoxia and lipopolysaccharide on nitric oxide synthase-2 expression in acute lung injury

Tumor Progression Locus 2 Protects against Acute Respiratory Distress Syndrome in Influenza A Virus-Infected Mice

Excessive inflammation in patients with severe influenza disease may lead to acute lung injury that results in acute respiratory distress syndrome (ARDS). ARDS is associated with alveolar damage and pulmonary edema that severely impair gas exchange, leading to hypoxia. With no existing FDA-approved treatment for ARDS, it is important to understand the factors that lead to virus-induced ARDS development to improve prevention, diagnosis, and treatment. We have previously shown that mice deficient in the serine-threonine mitogen-activated protein kinase, Tpl2 (MAP3K8 or COT), succumb to infection with a typically low-pathogenicity strain of influenza A virus (IAV; HKX31, H3N2 [x31]). The goal of the current study was to evaluate influenza A virus-infected Tpl2-/- mice clinically and histopathologically to gain insight into the disease mechanism. We hypothesized that Tpl2-/- mice succumb to IAV infection due to development of ARDS-like disease and pulmonary dysfunction. We observed prominent signs of alveolar septal necrosis, hyaline membranes, pleuritis, edema, and higher lactate dehydrogenase (LDH) levels in the lungs of IAV-infected Tpl2-/- mice compared to wild-type (WT) mice from 7 to 9 days postinfection (dpi). Notably, WT mice showed signs of regenerating epithelium, indicative of repair and recovery, that were reduced in Tpl2-/- mice. Furthermore, biomarkers associated with human ARDS cases were upregulated in Tpl2-/- mice at 7 dpi, demonstrating an ARDS-like phenotype in Tpl2-/- mice in response to IAV infection. IMPORTANCE This study demonstrates the protective role of the serine-threonine mitogen-activated protein kinase, Tpl2, in influenza virus pathogenesis and reveals that host Tpl2 deficiency is sufficient to convert a low-pathogenicity influenza A virus infection into severe influenza disease that resembles ARDS, both histopathologically and transcriptionally. The IAV-infected Tpl2-/- mouse thereby represents a novel murine model for studying ARDS-like disease that could improve our understanding of this aggressive disease and assist in the design of better diagnostics and treatments.

Protective mechanism of fdft1 in steroid hormone synthesis pathway in SD rats with acute hypoxic injury

BACKGROUND

The acute hypoxic injury caused by the plain population entering the plateau in a short period of time has become the main cause of endangering the health of the people who rush into the plateau.

OBJECTIVE

The study aimed to identify the key genes which participate in resisting the acute hypoxic injury in SD Rats by transcriptomic profile analysis.

METHODS

48 Sprague Dawley (SD) male rats were enrolled and randomly divided into four groups (0h, 24h, 48h, 72h) and housed in hypobaric hypoxia chamber with altitude 6000m for different periods of time to make them acute hypoxic injury. The transcriptomic profile of the lung tissue of the rats was analysed by RNA second-generation sequencing combined with bioinformatics analysis.

RESULTS

The results of GO and KEGG function classification analysis revealed that the differential expression genes enriched in steroid hormone synthesis pathway especially in 48h group compared to F0 group. Further analysis revealed that Farnesyl Diphosphate Farnesyl Transferase 1 (fdft1) gene encoding a rate-limiting enzyme in steroid hormone synthesis pathway was significant differently expressed between the groups. The expression levels of fdft1 gene were further verified by RT-PCR and Western-blot methods.

CONCLUSIONS

The results suggest that fdft1 gene plays an important role in responding to acute hypoxic injury by regulating steroid hormone biosynthesis.

Nuciferine Ameliorates Inflammatory Responses by Inhibiting the TLR4-Mediated Pathway in Lipopolysaccharide-Induced Acute Lung Injury

Acute lung injury (ALI) is a complex syndrome with sepsis occurring in critical patients, who usually lack effective therapy. Nuciferine is a primary bioactive component extracted from the lotus leaf, and it displays extensive pharmacological functions, including anti-cancer, anti-inflammatory, and antioxidant properties. Nevertheless, the effects of nuciferine on lipopolysaccharide (LPS)-stimulated ALI in mice has not been investigated. ALI of mice stimulated by LPS was used to determine the anti-inflammatory function of nuciferine. The molecular mechanism of nuciferine was performed on RAW264.7 macrophage cells. The results of pathological section, myeloperoxidase activity and lung wet/dry ratio showed that nuciferine alleviated LPS-induced lung injury (p < 0.05). qRT-PCR and ELISA experiments suggested that nuciferine inhibited TNF-α, IL-6, and IL-1β secretion in tissues and RAW264.7 cells but increased IL-10 secretion (p < 0.05). Molecular studies showed that TLR4 expression and nuclear factor (NF)-κB activation were both inhibited by nuciferine treatment (p < 0.05). To further investigate the anti-inflammatory mechanism of nuciferine, TLR4 was knocked down. When TLR4 was silenced, LPS induced the production of IL-1β, and TNF-α was markedly decreased by TLR4-siRNA and nuciferine treatment in LPS-induced RAW264.7 cells (p < 0.05). These results suggested that nuciferine had the ability to protect against LPS-stimulated ALI. Thus, nuciferine may be a potential drug for treating LPS-induced pulmonary inflammation.

Acute toxication of deltamethrin results in activation of iNOS, 8-OHdG and up-regulation of caspase 3, iNOS gene expression in common carp (Cyprinus carpio L.)

Deltamethrin is a widely used synthetic pyrethroid pesticide that protects agricultural yields, including crops, fruits, and vegetables from insect-pests. It is known that deltamethrin toxication leads to metabolic disorders and has detrimental effects on the brain and liver in different organisms. However, the harmful effects of deltamethrin toxication on aquatic animals remain unclear. In the present study, we aimed to evaluate the adverse effects of deltamethrin toxication by performing a histopathological examination, an immunofluorescence assay, and a qRT-PCR on common carp. We observed that a low-dose (0.04μM) and a high-dose (0.08μM) of deltamethrin exposure caused lamellar cells hyperplasia and inflammatory cells infiltration in the gills, hyperemia, diffuse hydropic degenerations and focal necrosis in the hepatocytes, necrotic changes in the neurons, and also induced activation of inducible Nitric Oxide Synthase (iNOS) and 8-hydroxy-2-deoxyguanosine (8-OHdG) in the gills, liver, and brain depending on the exposure time (24h, 48h, 72h and 96h). In addition, deltamethrin toxication caused the up-regulation of caspase-3 and the inducible Nitric Oxide Synthase (iNOS) of the gene expression depending on the dose (0.04μM and 0.08μM) and the exposure time in the brain (p<0.05, p<0.01, p<0.001). Our results indicated that long-term deltamethrin exposure could lead to inflammation, oxidative stress, DNA damage, and apoptosis on the different organs in common carp. Thus, deltamethrin toxication is dangerous for common carp populations, and the usage of deltamethrin should be controlled and restricted in agricultural areas.

The role of inflammation in hypoxic pulmonary hypertension: from cellular mechanisms to clinical phenotypes

Hypoxic pulmonary hypertension (PH) comprises a heterogeneous group of diseases sharing the common feature of chronic hypoxia-induced pulmonary vascular remodeling. The disease is usually characterized by mild to moderate pulmonary vascular remodeling that is largely thought to be reversible compared with the progressive irreversible disease seen in World Health Organization (WHO) group I disease. However, in these patients, the presence of PH significantly worsens morbidity and mortality. In addition, a small subset of patients with hypoxic PH develop "out-of-proportion" severe pulmonary hypertension characterized by pulmonary vascular remodeling that is irreversible and similar to that in WHO group I disease. In all cases of hypoxia-related vascular remodeling and PH, inflammation, particularly persistent inflammation, is thought to play a role. This review focuses on the effects of hypoxia on pulmonary vascular cells and the signaling pathways involved in the initiation and perpetuation of vascular inflammation, especially as they relate to vascular remodeling and transition to chronic irreversible PH. We hypothesize that the combination of hypoxia and local tissue factors/cytokines ("second hit") antagonizes tissue homeostatic cellular interactions between mesenchymal cells (fibroblasts and/or smooth muscle cells) and macrophages and arrests these cells in an epigenetically locked and permanently activated proremodeling and proinflammatory phenotype. This aberrant cellular cross-talk between mesenchymal cells and macrophages promotes transition to chronic nonresolving inflammation and vascular remodeling, perpetuating PH. A better understanding of these signaling pathways may lead to the development of specific therapeutic targets, as none are currently available for WHO group III disease.

Therapeutic Effect of the Tuber of Alisma orientale on Lipopolysaccharide-Induced Acute Lung Injury

Although Alisma orientale, an ethnic herb, has been prescribed for treating various diseases in Asian traditional medicine, experimental evidence to support its therapeutic effects is lacking. Here, we sought to determine whether A. orientale has a therapeutic effect on acute lung injury (ALI). Ethanol extract of the tuber of A. orientale (EEAO) was prepared and fingerprinted by HPLC for its constituents. Mice received an intraperitoneal (i.p.) injection of lipopolysaccharide (LPS) for the induction of ALI. At 2 h after LPS treatment, mice received an intratracheal (i.t.) spraying of various amounts of EEAO to the lung. Bioluminescence imaging of transgenic NF- κ B/luciferase reporter mice shows that i.t. EEAO posttreatment suppressed lung inflammation. In similar experiments with C57BL/6 mice, EEAO posttreatment significantly improved lung inflammation, as assessed by H&E staining of lung sections, counting of neutrophils in bronchoalveolar lavage fluid, and semiquantitative RT-PCR analyses of proinflammatory cytokines and Nrf2-dependent genes in the inflamed lungs. Furthermore, EEAO posttreatment enhanced the survival of mice that received a lethal dose of LPS. Together, our results provide evidence that A. orientale has a therapeutic effect on ALI induced by sepsis.

Growth of human bronchial epithelial cells at an air-liquid interface alters the response to particle exposure

Background

We tested the hypothesis that normal human bronchial epithelial (NHBE) cells 1) grown submerged in media and 2) allowed to differentiate at air-liquid interface (ALI) demonstrate disparities in the response to particle exposure.

Results

Following exposure of submerged NHBE cells to ambient air pollution particle collected in Chapel Hill, NC, RNA for IL-8, IL-6, heme oxygenase 1 (HOX1) and cyclooxygenase 2 (COX2) increased. The same cells allowed to differentiate over 3, 10, and 21 days at ALI demonstrated no such changes following particle exposure. Similarly, BEAS-2B cells grown submerged in media demonstrated a significant increase in IL-8 and HOX1 RNA after exposure to NIST 1648 particle relative to the same cells exposed after growth at ALI. Subsequently, it was not possible to attribute the observed decreases in the response of NHBE cells to differentiation alone since BEAS-2B cells, which do not differentiate, showed similar changes when grown at ALI. With no exposure to particles, differentiation of NHBE cells at ALI over 3 to 21 days demonstrated significant decrements in baseline levels of RNA for the same proteins (i.e. IL-8, IL-6, HOX1, and COX2). With no exposure to particles, BEAS-2B cells grown at ALI showed comparable changes in RNA for IL-8 and HOX1. After the same particle exposure, NHBE cells grown at ALI on a transwell in 95% N₂-5% CO₂ and exposed to NIST 1648 particle demonstrated significantly greater changes in IL-8 and HOX1 relative to cells grown in 95% air-5% CO₂.

Conclusions

We conclude that growth of NHBE cells at ALI is associated with a diminished biological effect following particle exposure relative to cells submerged in media. This decreased response showed an association with increased oxygen availability.

Acute lung injury and acute respiratory distress syndrome: experimental and clinical investigations

Acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) can be associated with various disorders. Recent investigation has involved clinical studies in collaboration with clinical investigators and pathologists on the pathogenetic mechanisms of ALI or ARDS caused by various disorders. This literature review includes a brief historical retrospective of ALI/ARDS, the neurogenic pulmonary edema due to head injury, the long-term experimental studies and clinical investigations from our laboratory, the detrimental role of NO, the risk factors, and the possible pathogenetic mechanisms as well as therapeutic regimen for ALI/ARDS.

Acute respiratory distress syndrome and lung injury: Pathogenetic mechanism and therapeutic implication

To review possible mechanisms and therapeutics for acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). ALI/ARDS causes high mortality. The risk factors include head injury, intracranial disorders, sepsis, infections and others. Investigations have indicated the detrimental role of nitric oxide (NO) through the inducible NO synthase (iNOS). The possible therapeutic regimen includes extracorporeal membrane oxygenation, prone position, fluid and hemodynamic management and permissive hypercapnic acidosis etc. Other pharmacological treatments are anti-inflammatory and/or antimicrobial agents, inhalation of NO, glucocorticoids, surfactant therapy and agents facilitating lung water resolution and ion transports. β-adrenergic agonists are able to accelerate lung fluid and ion removal and to stimulate surfactant secretion. In conscious rats, regular exercise training alleviates the endotoxin-induced ALI. Propofol and N-acetylcysteine exert protective effect on the ALI induced by endotoxin. Insulin possesses anti-inflammatory effect. Pentobarbital is capable of reducing the endotoxin-induced ALI. In addition, nicotinamide or niacinamide abrogates the ALI caused by ischemia/reperfusion or endotoxemia. This review includes historical retrospective of ALI/ARDS, the neurogenic pulmonary edema due to head injury, the detrimental role of NO, the risk factors, and the possible pathogenetic mechanisms as well as therapeutic regimen for ALI/ARDS.

Oxygen-dependent regulation of nitric oxide production by inducible nitric oxide synthase

Inducible nitric oxide synthase (iNOS) catalyzes the reaction that converts the substrates O(2) and l-arginine to the products nitric oxide (NO) and l-citrulline. Macrophages, and many other cell types, upregulate and express iNOS primarily in response to inflammatory stimuli. Physiological and pathophysiological oxygen tension can regulate NO production by iNOS at multiple levels, including transcriptional, translational, posttranslational, enzyme dimerization, cofactor availability, and substrate dependence. Cell culture techniques that emphasize control of cellular PO(2), and measurement of NO or its stable products, have been used by several investigators for in vitro study of the O(2) dependence of NO production at one or more of these levels. In most cell types, prior or concurrent exposure to cytokines or other inflammatory stimuli is required for the upregulation of iNOS mRNA and protein by hypoxia. Important transcription factors that target the iNOS promoter in hypoxia include hypoxia-inducible factor 1 and/or nuclear factor κB. In contrast to the upregulation of iNOS by hypoxia, in most cell types NO production is reduced by hypoxia. Recent work suggests a prominent role for O(2) substrate dependence in the short-term regulation of iNOS-mediated NO production.

A new experimental murine model for lipopolysaccharide-mediated lethal shock with lung injury

We have recently established a new experimental murine model for lipopolysaccharide (LPS)-mediated lethal shock with lung-specific injury. Severe lung injury is induced by administration of LPS into α-galactosylceramide (α-GalCer)-sensitized mice; the mice died with acute lung injury and respiratory distress within 24 h. α-GalCer activates natural killer T (NKT) cells in the lungs and liver, and induces the production of interferon (IFN)-γ. However, IFN-γ signaling is only triggered in the lungs and makes them susceptible to LPS. On the other hand, IFN-γ signaling is inhibited in liver and results in few hepatic lesions. Unlike liver NKT cells, lung NKT cells fail to produce interleukin (IL)-4, which down-regulates the IFN-γ signaling, in response to α-GalCer. The differential cytokine profile between lung and liver NKT cells may lead to organ-specific lung lesions. The experimental system using α-GalCer sensitization could be a useful experimental model for clinical endotoxic or septic shock as it presents respiratory failure, a typical manifestation in severe septic patients. In this review, key evidence and the introducuction of the detailed mechanism of LPS-mediated lung-specific injury in α-GalCer-sensitized mice is provided. In particular, the molecular background of organ-specific development of lung injury in the model is focused on.

The value of the lipopolysaccharide-induced acute lung injury model in respiratory medicine

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a syndrome characterized by pulmonary edema and acute inflammation. Lipopolysaccharide (LPS), a major component in Gram-negative bacteria, has been used to induce ALI/ARDS. LPS-induced animal models highlight ways to explore mechanisms of multiple diseases and provide useful information on the discovery of novel biomarkers and drug targets. However, each model has its own merits and drawbacks. The goal of this article is to summarize and evaluate the results of experimental findings in LPS-induced ALI/ARDS, and the possible mechanisms and treatments elucidated. Advantages and disadvantages of such models in pulmonary research and new directions for future investigations are also discussed.

Crucial involvement of the CX3CR1-CX3CL1 axis in dextran sulfate sodium-mediated acute colitis in mice

Ingestion of DSS solution can induce in rodents acute colitis with a massive infiltration of neutrophils and macropahges, mimicking pathological changes observed in the acute phase of UC patients. Concomitantly, DSS ingestion enhanced the expression of a potent macrophage-tropic chemokine, CX3CL1/fractalkine, and its receptor, CX3CR1, in the colon. WT but not CX3CR1-deficient mice exhibited marked body weight loss and shortening of the colon after DSS ingestion. Moreover, inflammatory cell infiltration was attenuated in CX3CR1-deficient mice together with reduced destruction of glandular architecture compared with WT mice. DSS ingestion enhanced intracolonic iNOS expression by macrophages and nitrotyrosine generation in WT mice, but iNOS expression and nitrotyrosine generation were attenuated in CX3CR1-deficient mice. The analysis on bone marrow chimeric mice revealed that bone marrow-derived but not non-bone marrow-derived CX3CR1-expressing cells were a major source of iNOS. These observations would indicate that the CX3CL1-CX3CR1 axis can regulate the expression of iNOS, a crucial mediator of DSS-induced colitis. Thus, targeting the CX3CL1-CX3CR1 axis may be effective for the treatment of IBDs such as UC.

pO(2)-dependent NO production determines OPPC activity in macrophages

Stimulated macrophages produce nitric oxide (NO) via inducible nitric oxide synthase (iNOS) using molecular O(2), L-arginine, and NADPH. Exposure of macrophages to hypoxia decreases NO production within seconds, suggesting substrate limitation as the mechanism. Conflicting data exist regarding the effect of pO(2) on NADPH production via the oxidative pentose phosphate cycle (OPPC). Therefore, the present studies were developed to determine whether NADPH could be limiting for NO production under hypoxia. Production of NO metabolites (NOx) and OPPC activity by RAW 264.7 cells was significantly increased by stimulation with lipopolysaccharide (LPS) and interferon gamma (IFNgamma) at pO(2) ranging from 0.07 to 50%. OPPC activity correlated linearly with NOx production at pO(2)>0.13%. Increased OPPC activity by stimulated RAW 264.7 cells was significantly reduced by 1400 W, an iNOS inhibitor. OPPC activity was significantly increased by concomitant treatment of stimulated RAW 264.7 cells with chemical oxidants such as hydroxyethyldisulfide or pimonidazole, at 0.07 and 50% O(2), without decreasing NOx production. These results are the first to investigate the effect of pO(2) on the relationship between NO production and OPPC activity, and to rule out limitations in OPPC activity as a mechanism by which NO production is decreased under hypoxia.

Lipopolysaccharide plus hypoxia and reoxygenation synergistically reduce electrical coupling between microvascular endothelial cells by dephosphorylating connexin40

We showed that lipopolysaccharide (LPS) or hypoxia and reoxygenation (H/R) decreases electrical coupling between microvascular endothelial cells by targeting the gap junction protein connexin40 (Cx40), tyrosine kinase-, ERK1/2-, and PKA-dependently. Since LPS can compromise microvascular blood flow, resulting in micro-regional H/R, the concurrent LPS + H/R could reduce coupling to a much greater extent than LPS or H/R alone. We examined this possibility in a model of cultured microvascular endothelial cells (mouse skeletal muscle origin) in terms of electrical coupling and the phosphorylation status of Cx40. To assess coupling, we measured the spread of electrical current injected into the cell monolayer and computed the intercellular resistance as an inversed measure of coupling. In wild type cells, but not in Cx40 null cells, concurrent LPS + H/R synergistically increased resistance by approximately 270%, well above the level observed for LPS or H/R alone. Cx37 and Cx43 protein expression did not differ between Cx40 null and wild type cells. LPS + H/R increased resistance PKA- and PKC-dependently. By immunoprecipitating Cx40, we found that LPS + H/R reduced serine phosphorylation to a much greater degree than that observed for LPS or H/R alone. Further, PKA-specific, but not PKC-specific serine phosphorylation of Cx40 was also significantly reduced following LPS + H/R. This reduction was prevented by tyrosine kinase and MEK1/2 inhibition, by PKA activation, and mimicked in control cells by PKA inhibition. We conclude that LPS + H/R initiates tyrosine kinase- and ERK1/2-sensitive signaling that synergistically reduces inter-endothelial electrical coupling by dephosphorylating PKA-specific serine residues of Cx40.

Pulmonary pathology in patients associated with scrub typhus

AIMS

Scrub typhus is a zoonotic disease caused by Orientia tsutsugamushi. Severe cases resulting in mortality from this disease have rarely been reported. We present two scrub typhus cases (a man and a girl) who died of acute respiratory distress syndrome (ARDS).

METHODS

Autopsies were performed. Histopathological and immunohistochemical stains were employed using specific antibody for O. tsutsugamushi and inducible nitric oxide synthase (iNOS).

RESULTS

These subjects developed respiratory distress shortly after admission, and expired following respiratory failure. At autopsy, generalised lymphadenopathy was observed. The lung weight was about two-fold the normal value. Gross inspection revealed oedematous and haemorrhagic lungs. Microscopic examination revealed diffuse alveolar damage with hyaline membrane formation and interstitial pneumonitis with infiltration of inflammatory cells. Immunohistochemical stain showed O. tsutsugamushi antigen depositions in the endothelial cells. We also demonstrated iNOS in the alveolar macrophages and lung tissue debris in both cases.

CONCLUSION

Scrub typhus is usually a mild infectious disease. Our cases present the most dramatic example of sudden death due to ARDS in a short period of time. The clinical investigation and analysis suggest direct endothelial cell invasion of the organism and marked iNOS expression may be involved in the pathogenesis of ARDS associated with scrub typhus.

Anti-inflammatory effect of SQC-beta-CD on lipopolysaccharide-induced acute lung injury

AIM OF THE STUDY

Shuang-Qing-Cao (SQC) is a folk Chinese medicinal formula. The therapeutic effects of inclusion complexation of SQC extract in beta-cyclodextrin (SQC-beta-CD) against lipopolysaccharide (LPS)-induced acute lung injury (ALI) were studied in mice.

MATERIALS AND METHODS

Two protocols were designed for administration of SQC-beta-CD (10 and 20 mg/kg body weight) or DEX (2 mg/kg). According to Protocol A we intraperitoneally injected diluent (saline with 0.5% Tween 80), SQC-beta-CD or DEX respectively into mice 30 min and 3h after LPS challenge. Alternatively, in Protocol B we administered diluent, SQC-beta-CD or DEX 3h before and 30 min after LPS challenge.

RESULTS

The histological results showed that SQC-beta-CD (20 mg/kg) protected mice from LPS-induced ALI such as oedema, haemorrhage, blood vessel and alveolar structural damage. Furthermore, SQC-beta-CD inhibited LPS-increased pulmonary MPO activity and migration of polymorphonuclear neutrophils (PMNs) into bronchoalveolar lavage fluid (BALF). Immunohistochemical experiment demonstrated that SQC-beta-CD decreased inducible nitric oxide synthase (iNOS) expression in lung 24h after LPS administration. Consequently, SQC-beta-CD prevented LPS-induced nitric oxide (NO) release in BALF.

CONCLUSIONS

The results indicated that SQC-beta-CD is greatly effective in inhibiting ALI. The present study indicated that SQC-beta-CD acted as a potential therapeutic reagent for treating ALI.

Nitric oxide mediates acute lung injury caused by fat embolism in isolated rat's lungs

BACKGROUND

The involvement of nitric oxide (NO) in acute lung injury (ALI) induced by fat embolism (FE) has not been investigated. The present study elucidated the role of NO in ALI because of FE.

METHODS

FE was produced by introduction of fatty acid (corn oil micelles) into the isolated rat's lungs. Nonselective NO synthase (NOS) and selective inducible NOS (iNOS) inhibitors, N-nitro-l-arginine methyl ester (l-NAME) and l-N(1-iminoethyl)-lysine (l-Nil) as well as NO donors, sodium nitroprusside (SNP), and S-nitroso-N-acetylpenicillamine (SNAP) at a dose of 10 mol/L were given 60 minutes before FE. There were six groups of isolated lungs randomly assigned to receive vehicle (physiologic saline solution), FE, FE with pretreatment of l-NAME, l-Nil, SNP, or SNAP. Each group was observed for 4 hours.

RESULTS

FE significantly increased the lung weight changes, pulmonary arterial pressure, and microvascular permeability. The concentration of nitrate or nitrite, methyl guanidine, tumor necrosis factor-alpha, and interleukin-1beta was significantly elevated after FE. Hisotopathologic examination revealed lung edema with multiple fatty droplets in lung tissue. Pretreatment with l-NAME or l-Nil attenuated, whereas SNP or SNAP exacerbated most of the FE-induced changes. Addition of NO donors (SNP or SNAP) into the isolated lungs did not produce significant changes in the lungs, suggesting that NO donation alone without FE does not exerts harmful effect.

CONCLUSIONS

Our results suggest that NO production through the iNOS isoform plays a detrimental role in the FE-induced ALI. Free radical and proinflammatory cytokines may also be involved in the pathogenesis of ALI because of FE.

N-acetylcysteine attenuates acute lung injury induced by fat embolism

OBJECTIVES

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).

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

A total of 36 perfused lungs isolated from Sprague-Dawley rats.

INTERVENTIONS

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.

MEASUREMENTS AND MAIN RESULTS

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.

CONCLUSION

FE caused acute lung injury and associated biochemical changes. Posttreatment with NAC was effective to alleviate the pathologic and biochemical changes caused by FE.

The mechanism of development of acute lung injury in lethal endotoxic shock using alpha-galactosylceramide sensitization

The mechanism underlying acute lung injury in lethal endotoxic shock induced by administration of lipopolysaccharide (LPS) into alpha-galactosylceramide (alpha-GalCer)-sensitized mice was studied. Sensitization with alpha-GalCer resulted in the increase of natural killer T (NK T) cells and the production of interferon (IFN)-gamma in the lung. The IFN-gamma that was produced induced expression of adhesion molecules, especially vascular cell adhesion molecule-1 (VCAM-1), on vascular endothelial cells in the lung. Anti-IFN-gamma antibody inhibited significantly the VCAM-1 expression in alpha-GalCer-sensitized mice. Very late activating antigen-4-positive cells, as the counterpart of VCAM-1, accumulated in the lung. Anti-VCAM-1 antibody prevented LPS-mediated lethal shock in alpha-GalCer-sensitized mice. The administration of LPS into alpha-GalCer-sensitized mice caused local production of excessive proinflammatory mediators, such as tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6 and nitric oxide. LPS caused microvascular leakage of proteins and cells into bronchoalveolar lavage fluid. Taken together, sensitization with alpha-GalCer was suggested to induce the expression of VCAM-1 via IFN-gamma produced by NK T cells and recruit a number of inflammatory cells into the lung. Further, LPS was suggested to lead to the production of excessive proinflammatory mediators, the elevation of pulmonary permeability and cell death. The putative mechanism of acute lung injury in LPS-mediated lethal shock using alpha-GalCer sensitization is discussed.

The involvement of nitric oxide, nitric oxide synthase, neutrophil elastase, myeloperoxidase and proinflammatory cytokines in the acute lung injury caused by phorbol myristate acetate

Phorbol myristate acetate (PMA) causes acute lung injury (ALI). The present study was designed to elucidate the role of nitric oxide (NO), inducible NO synthase (iNOS), neutrophil elastase (NE) and other mediators in the ALI caused by PMA. In isolated rat's lungs, PMA at various doses (1, 2 and 4 mug/g lung weight) was added into the lung perfusate. Vehicle group received dimethyl sulfoxide (the solvent for PMA) 100 mug/g. We measured the lung weight changes, pulmonary arterial pressure, capillary filtration coefficient, exhaled NO, protein concentration in bronchoalveolar lavage (PCBAL) and Evan blue dye leakage. Nitrate/nitrite, methyl guanidine, proinflammatory cytokines, NE and myeloperoxidase (MPO) in lung perfusate were determined. Histopathological examination was performed. We detected the iNOS mRNA expression in lung tissue. PMA caused dose-dependent increases in variables for lung changes, and nitrate/nitrite, methyl guanidine, proinflammatory cytokines, NE and MPO in lung perfusate. The pathology was characterized by alveolar hemorrhagic edema with inflammatory cell infiltration. Scanning electron microscopy revealed endothelial damage. PMA upregulated the expression of iNOS mRNA. Our results suggest that neutrophil activation by PMA causes release of NE, upregulation of iNOS and a series of inflammatory responses leading to endothelial damage and ALI.

Physiological and hypoxic O2 tensions rapidly regulate NO production by stimulated macrophages

Nitric oxide (NO) production by inducible NO synthase (iNOS) is dependent on O(2) availability. The duration and degree of hypoxia that limit NO production are poorly defined in cultured cells. To investigate short-term O(2)-mediated regulation of NO production, we used a novel forced convection cell culture system to rapidly (response time of 1.6 s) and accurately (+/-1 Torr) deliver specific O(2) tensions (from <1 to 157 Torr) directly to a monolayer of LPS- and IFNgamma-stimulated RAW 264.7 cells while simultaneously measuring NO production via an electrochemical probe. Decreased O(2) availability rapidly (<or=30 s) and reversibly decreased NO production with an apparent K(m)O(2) of 22 (SD 6) Torr (31 microM) and a V(max) of 4.9 (SD 0.4) nmol min(-1) 10(-6) cells. To explore potential mechanisms of decreased NO production during hypoxia, we investigated O(2)-dependent changes in iNOS protein concentration, iNOS dimerization, and cellular NO consumption. iNOS protein concentration was not affected (P = 0.895). iNOS dimerization appeared to be biphasic [6 Torr (P = 0.008) and 157 Torr (P = 0.258) >36 Torr], but it did not predict NO production. NO consumption was minimal at high O(2) and NO tensions and negligible at low O(2) and NO tensions. These results are consistent with O(2) substrate limitation as a regulatory mechanism during brief hypoxic exposure. The rapid and reversible effects of physiological and pathophysiological O(2) tensions suggest that O(2) tension has the potential to regulate NO production in vivo.

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.

Clinical and pathological features of fat embolism with acute respiratory distress syndrome

FES (fat embolism syndrome) is a clinical problem, and, although ARDS (acute respiratory distress syndrome) has been considered as a serious complication of FES, the pathogenesis of ARDS associated with FES remains unclear. In the present study, we investigated the clinical manifestations, and biochemical and pathophysiological changes, in subjects associated with FES and ARDS, to elucidate the possible mechanisms involved in this disorder. A total of eight patients with FES were studied, and arterial blood pH, PaO(2) (arterial partial pressure of O(2)), PaCO(2) (arterial partial pressure of CO(2)), biochemical and pathophysiological data were obtained. These subjects suffered from crash injuries and developed FES associated with ARDS, and each died within 2 h after admission. In the subjects, chest radiography revealed that the lungs were clear on admission, and pulmonary infiltration was observed within 2 h of admission. Arterial blood pH and PaO(2) declined, whereas PaCO(2) increased. Plasma PLA(2) (phospholipase A(2)), nitrate/nitrite, methylguanidine, TNF-alpha (tumour necrosis factor-alpha), IL-1beta (interleukin-1beta) and IL-10 (interleukin-10) were significantly elevated. Pathological examinations revealed alveolar oedema and haemorrhage with multiple fat droplet depositions and fibrin thrombi. Fat droplets were also found in the arterioles and/or capillaries in the lung, kidney and brain. Immunohistochemical staining identified iNOS (inducible nitric oxide synthase) in alveolar macrophages. In conclusion, our clinical analysis suggests that PLA(2), NO, free radicals and pro-inflammatory cytokines are involved in the pathogenesis of ARDS associated with FES. The major source of NO is the alveolar macrophages.

Inhibition of inducible nitric oxide synthase attenuates acute endotoxin-induced lung injury in rats

1. In the present study, we investigated the effects of the inducible nitric oxide (iNOS) inhibitors S-methylisothiourea (SMT) and l-N(6)-(1-iminoethyl)-lysine (l-Nil) on endotoxin-induced acute lung injury (ALI), as well as the associated physiological, biomedical and pathological changes, in anaesthetized Sprague-Dawley rats and in rat isolated perfused lungs. 2. Endotoxaemia was induced by an intravenous (i.v.) infusion of lipopolysaccharide (LPS; Escherichia coli 10 mg/kg). Lipopolysaccharide produced systemic hypotension and tachycardia. It also increased the lung weight/bodyweight ratio, lung weight gain, exhaled nitric oxide (NO), the protein concentration in bronchoalveolar lavage and microvascular permeability. 3. Following infusion of LPS, plasma nitrate/nitrite, methyl guanidine, pro-inflammatory cytokines (tumour necrosis factor-alpha and interleukin-1beta) were markedly elevated. Pathological examination revealed severe pulmonary oedema and inflammatory cell infiltration. Pretreatment with SMT (3 mg/kg, i.v.) or l-Nil (3 mg/kg, i.v.) significantly attenuated the LPS-induced changes and ALI. 4. The results suggest that the inflammatory responses and ALI following infusion of LPS are due to the production of NO, free radicals and pro-inflammatory cytokines through the iNOS system. Inhibition of iNOS is effective in mitigating the endotoxaemic changes and lung pathology. Inhibitors of iNOS may be potential therapeutic agents for clinical application in patients with acute respiratory distress syndrome.

HIF-1alpha expression in response to lipopolysaccaride mediates induction of hepatic inflammatory cytokine TNFalpha

HIF-1alpha is a transcription factor that acts as a master regulator of gene expression induced by hypoxia. Recent studies have demonstrated that the potent inflammatory factor, lipopolysaccharide (LPS), can also activate HIF-1alpha in myeloid cells. However, the molecular mechanisms at the transcriptional level of HIF-1alpha induction by LPS remained undefined. Here, we investigated the regulatory mechanism of HIF-1alpha expression by LPS in hepatocytes and identified that LPS-induced HIF-1alpha mediate gene transcription of a typical inflammatory mediator, tumor-necrosis factor alpha (TNFalpha). Increased HIF-1alpha gene expression by LPS was defined in a series of hepatic cell lines by RT-PCR, Western blotting and promoter transactivation assay. The JNK signaling and c-Jun activation were required to induce the HIF-1alpha gene transcription by LPS. The finding that a cascade transcriptional activation of distinct set of transcription factors, c-Jun and HIF-1alpha, in response to LPS stimulation associates with induction of TNFalpha gene transcription lends new insights into the functional mechanisms by which complex patterns of gene regulation on LPS-derived HIF activation are achieved.

Histochemical Alterations in One Lung Ventilation

BACKGROUND

One lung ventilation is a commonly performed surgical procedure. Although there have been several reports showing that one-lung ventilation can cause pathophysiological alterations such as pulmonary hypoxic vasoconstriction and intrapulmonary shunting, there have been virtually no reports on the effects of one-lung ventilation on lung histology.

MATERIALS AND METHODS

Yorkshire pigs (11-17 kg) were anesthetized, a tracheotomy performed and a tracheal tube inserted. The chest was opened and one lung ventilation (OLV), was induced by clamping of the right main bronchus. OLV was continued for 60 min before the clamp was removed and two lung ventilation (TLV) started. TLV was continued for 30 to 60 min. Blood and lung biopsies were taken immediately before OLV, 30 min and 60 min of OLV and after restoration of TLV.

RESULTS

Histological analyses revealed that the non-ventilated lung was totally collapsed during OLV. On reventilation, there was clear evidence of vascular congestion and alveolar wall thickening at 30 min after TLV. At 60 min of TLV, there was still vascular congestion. Serum nitrite levels (as an index of nitric oxide production) showed steady decline over the course of the experimental period, reaching a significantly low level on reventilation (compared with baseline levels before OLV). Lung MPO activity (marker of neutrophil sequestration) and serum TNFalpha levels were not raised during the entire experimental period.

CONCLUSIONS

These results suggest that there was lung vascular injury after OLV, which was associated with reduced levels of nitric oxide production and not associated with an inflammatory response.

Upregulation of hypoxia-induced mitogenic factor in bacterial lipopolysaccharide-induced acute lung injury

Hypoxia-induced mitogenic factor (HIMF), also known as FIZZ1 (found in inflammatory zone), plays important roles in lung inflammation. We found that intraperitoneal injection of lipopolysaccharide (LPS) induced intensive HIMF production exclusively in mouse lung, but not in the heart, liver, spleen or kidney. This HIMF production, at least partly, contributes to LPS-induced vascular cell adhesion molecule-1 (VCAM-1) upregulation and mononuclear cell sequestration to lung parenchyma, while protecting alveolar type II cells from LPS-resulted decrease in surfactant protein-C production and cell death. These data indicate that HIMF participates in LPS-induced acute lung injury and inflammation through modulating VCAM-1 and SP-C expression.

Hypoxia aggravates lipopolysaccharide-induced lung injury

The animal model of inflammatory response induced by intratracheal application of lipopolysaccharide includes many typical features of acute lung injury or the acute respiratory distress syndrome. A number of experimental investigations have been performed to characterize the nature of this injury more effectively. In inflammatory conditions, hypoxia occurs frequently before and in parallel with pulmonary and non-pulmonary pathological events. This current study was designed to examine the in vivo effect of hypoxia as a potentially aggravating condition in endotoxin-induced lung injury. Lipopolysaccharide, 150 microg, was instilled intratracheally into rat lungs, and thereafter animals were exposed to either normoxia or hypoxia (10% oxygen). Lungs were collected 2, 4, 6 and 8 h later. Inflammatory response and tissue damage were evaluated by quantitative analysis of inflammatory cells and mediators, surfactant protein and vascular permeability. A significantly enhanced neutrophil recruitment was seen in lipopolysaccharide-animals exposed to hypoxia compared to lipopolysaccharide-animals under normoxia. This increased neutrophil accumulation was triggered by inflammatory mediators such as tumour necrosis factor-alpha and macrophage inflammatory protein-1beta, secreted by alveolar macrophages. Determination of vascular permeability and surfactant protein-B showed enhanced concentrations in lipopolysaccharide-lungs exposed to hypoxia, which was absent in animals previously alveolar macrophage-depleted. This study demonstrates that hypoxia aggravates lipopolysaccharide injury and therefore represents a second hit injury. The additional hypoxia-induced inflammatory reaction seems to be predominantly localized in the respiratory compartment, underlining the compartmentalized nature of the inflammatory response.

Oxygenation inhibits the physiological tissue-protecting mechanism and thereby exacerbates acute inflammatory lung injury

Acute respiratory distress syndrome (ARDS) usually requires symptomatic supportive therapy by intubation and mechanical ventilation with the supplemental use of high oxygen concentrations. Although oxygen therapy represents a life-saving measure, the recent discovery of a critical tissue-protecting mechanism predicts that administration of oxygen to ARDS patients with uncontrolled pulmonary inflammation also may have dangerous side effects. Oxygenation may weaken the local tissue hypoxia-driven and adenosine A2A receptor (A2AR)-mediated anti-inflammatory mechanism and thereby further exacerbate lung injury. Here we report experiments with wild-type and adenosine A2AR-deficient mice that confirm the predicted effects of oxygen. These results also suggest the possibility of iatrogenic exacerbation of acute lung injury upon oxygen administration due to the oxygenation-associated elimination of A2AR-mediated lung tissue-protecting pathway. We show that this potential complication of clinically widely used oxygenation procedures could be completely prevented by intratracheal injection of a selective A2AR agonist to compensate for the oxygenation-related loss of the lung tissue-protecting endogenous adenosine. The identification of a major iatrogenic complication of oxygen therapy in conditions of acute lung inflammation attracts attention to the need for clinical and epidemiological studies of ARDS patients who require oxygen therapy. It is proposed that oxygen therapy in patients with ARDS and other causes of lung inflammation should be combined with anti-inflammatory measures, e.g., with inhalative application of A2AR agonists. The reported observations may also answer the long-standing question as to why the lungs are the most susceptible to inflammatory injury and why lung failure usually precedes multiple organ failure.

Simultaneous analysis of host and pathogen interactions during an in vivo infection reveals local induction of host acute phase response proteins, a novel bacterial stress response, and evidence of a host-imposed metal ion limited environment

A fundamental goal in the study of infections is to understand the dynamic interplay between host and pathogen; however, direct in vivo interrogation of this disease process via transcriptional profiling has been lacking. Here we describe the development and application of novel bacterial RNA amplification technology to simultaneously identify key elements of both host and pathogen responses in a murine infection model. On the bacterial side, we found induction of an unusual pattern of stress response genes, a response to host-induced metal ion limitation, and a failure to achieve stationary phase in vivo. On the mammalian side, we observed the surprising induction of several genes encoding acute phase response proteins including hepcidin, haptoglobin, complement C3 and metallothionein 1 at the site of infection, as well as other mediators of innate immunity. Thus, our results reveal host-pathogen cross-talk not predicted by previous in vitro analyses and provide the framework to eavesdrop on a broad array of host-pathogen interactions in vivo. As described here, the comprehensive examination of host-pathogen interactions during an infection is critical to the discovery of novel approaches for intervention not predicted by current models.

Nitric Oxide (NO) in normal and hypoxic vascular regulation of the spiny dogfish,Squalus acanthias

Nitric oxide (NO) is a potent vasodilator in terrestrial vertebrates, but whether vascular endothelial-derived NO plays a role in vascular regulation in fish remains controversial. To explore this issue, a study was made of spiny dogfish sharks (Squalus acanthias) in normoxia and acute hypoxia (60 min exposure to seawater equilibrated with 3% oxygen) with various agents known to alter NO metabolism or availability. In normoxia, nitroprusside (a NO donor) reduced blood pressure by 20%, establishing that vascular smooth muscle responds to NO. L-arginine, the substrate for NO synthase, had no hemodynamic effect. Acetylcholine, which stimulates endothelial NO and prostaglandin production in mammals, reduced blood pressure, but also caused marked bradycardia. L-NAME, an inhibitor of all NO synthases, caused a small 10% rise in blood pressure, but cell-free hemoglobin (a potent NO scavenger and hypertensive agent in mammals) had no effect. Acute hypoxia caused a 15% fall in blood pressure, which was blocked by L-NAME and cell-free hemoglobin. Serum nitrite, a marker of NO production, rose with hypoxia, but not with L-NAME. Results suggest that NO is not an endothelial-derived vasodilator in the normoxic elasmobranch. The hypertensive effect of L-NAME may represent inhibition of NO production in the CNS and nerves regulating blood pressure. In acute hypoxia, there is a rapid up-regulation of vascular NO production that appears to be responsible for hypoxic vasodilation.

Adrenomedullin expression in a rat model of acute lung injury induced by hypoxia and LPS

Adrenomedullin (ADM) is upregulated independently by hypoxia and LPS, two key factors in the pathogenesis of acute lung injury (ALI). This study evaluates the expression of ADM in ALI using experimental models combining both stimuli: an in vivo model of rats treated with LPS and acute normobaric hypoxia (9% O2) and an in vitro model of rat lung cell lines cultured with LPS and exposed to hypoxia (1% O2). ADM expression was analyzed by in situ hybridization, Northern blot, Western blot, and RIA analyses. In the rat lung, combination of hypoxia and LPS treatments overcomes ADM induction occurring after each treatment alone. With in situ techniques, the synergistic effect of both stimuli mainly correlates with ADM expression in inflammatory cells within blood vessels and, to a lesser extent, to cells in the lung parenchyma and bronchiolar epithelial cells. In the in vitro model, hypoxia and hypoxia + LPS treatments caused a similar strong induction of ADM expression and secretion in epithelial and endothelial cell lines. In alveolar macrophages, however, LPS-induced ADM expression and secretion were further increased by the concomitant exposure to hypoxia, thus paralleling the in vivo response. In conclusion, ADM expression is highly induced in a variety of key lung cell types in this rat model of ALI by combination of hypoxia and LPS, suggesting an essential role for this mediator in this syndrome.