Endothelin-1 changes polymorphonuclear leukocytes' deformability and CD11b expression and promotes their retention in the lung

Maximizing the Therapeutic Effect of Endothelin Receptor Antagonists in Pulmonary Fibrosis: A Paradigm for Treating the Disease

Using a lipopolysaccharide model of acute lung injury, we previously showed that endothelin-1 (ET-1), a potent mediator of vasoconstriction, may act as a "gatekeeper" for the influx of inflammatory cells into the lung. These studies provided a rationale for testing the effect of HJP272, an endothelin receptor antagonist (ERA), in hamster models of pulmonary fibrosis induced by intratracheal instillation of either bleomycin (BLM) or amiodarone (AM). To determine the temporal effects of blocking ET-1 activity, animals were given HJP272 either 1 h before initiation of lung injury or 24 h afterward. The results indicated that pretreatment with this agent caused significant reductions in various inflammatory parameters, whereas post-treatment was ineffective. This finding suggests that ERAs are only effective at a very early stage of pulmonary fibrosis and explains their lack of success in clinical trials involving patients with this disease. Nevertheless, ERAs could serve as prophylactic agents when combined with drugs that may induce pulmonary fibrosis. Furthermore, developing a biomarker for the initial changes in the lung extracellular matrix could increase the efficacy of ERAs and other therapeutic agents in preventing the progression of the disease. While no such biomarker currently exists, we propose the ratio of free to peptide-bound desmosine, a unique crosslink of elastin, as a potential candidate for detecting the earliest modifications in lung microarchitecture associated with pulmonary fibrosis.

LncRNA MALAT1 functions as a biomarker of no-reflow phenomenon in ST-segment elevation myocardial infarction patients receiving primary percutaneous coronary intervention

MALAT1 was reported to sponge miR-30e, miR-126 and miR-155 in the pathogenesis of many diseases. Plasma miR-30e can indicate the risk of no-reflow during primary percutaneous coronary intervention (pPCI), while miR-126 can be used as a predictor of coronary slow flow phenomenon. In this study, we compared the diagnostic value of above genes in the prediction of no-reflow phenomenon in ST-segment elevation myocardial infarction (STEMI) subjects receiving pPCI. Quantitative real-time PCR, ELISA, Western blot and luciferase assays were performed to explore the regulatory relationship of MALAT1/miR-30e, MALAT1/miR-126, MALAT1/miR-155, miR-126/HPSE, and miR-155/EDN1. ROC analysis was carried out to evaluate the potential value of MALAT1, miRNAs and target genes in differentiating normal reflow and no-reflow in STEMI patients receiving pPCI. Elevated MALAT1, CRP, HPSE, and EDN1 expression and suppressed miR-30e, miR-155 and miR-126 expression was found in the plasma of STEMI patients receiving pPCI who were diagnosed with no-reflow phenomenon. ROC analysis showed that the expression of MALAT1, miR-30e, miR-126 and CRP could be used as predictive biomarkers to differentiate normal reflow and no-reflow in STEMI patients receiving pPCI. MALAT1 was found to suppress the expression of miR-30e, miR-126 and miR-155, and HPSE and EDN1 were respectively targeted by miR-126 and miR-155. This study demonstrated that MALAT1 could respectively sponge the expression of miR-30e, miR-126 and miR-155. And miR-30e, miR-126 and miR-155 respectively targeted CRP, HPSE and EDN1 negatively. Moreover, MALAT1 could function as an effective biomarker of no-reflow phenomenon in STEMI patients receiving pPCI.

Lung Transplantation, Pulmonary Endothelial Inflammation, and Ex-Situ Lung Perfusion: A Review

Lung transplantation (LTx) is the gold standard treatment for end-stage lung disease; however, waitlist mortality remains high due to a shortage of suitable donor lungs. Organ quality can be compromised by lung ischemic reperfusion injury (LIRI). LIRI causes pulmonary endothelial inflammation and may lead to primary graft dysfunction (PGD). PGD is a significant cause of morbidity and mortality post-LTx. Research into preservation strategies that decrease the risk of LIRI and PGD is needed, and ex-situ lung perfusion (ESLP) is the foremost technological advancement in this field. This review addresses three major topics in the field of LTx: first, we review the clinical manifestation of LIRI post-LTx; second, we discuss the pathophysiology of LIRI that leads to pulmonary endothelial inflammation and PGD; and third, we present the role of ESLP as a therapeutic vehicle to mitigate this physiologic insult, increase the rates of donor organ utilization, and improve patient outcomes.

The Effects of Volatile Anesthetics on Lung Ischemia-Reperfusion Injury: Basic to Clinical Studies

Case reports from as early as the 1970s have shown that intravenous injection of even a small dose of volatile anesthetics result in fatal lung injury. Direct contact between volatile anesthetics and pulmonary vasculature triggers chemical damage in the vessel walls. A wide variety of factors are involved in lung ischemia-reperfusion injury (LIRI), such as pulmonary endothelial cells, alveolar epithelial cells, alveolar macrophages, neutrophils, mast cells, platelets, proinflammatory cytokines, and surfactant. With a constellation of factors involved, the assessment of the protective effect of volatile anesthetics in LIRI is difficult. Multiple animal studies have reported that with regards to LIRI, sevoflurane demonstrates an anti-inflammatory effect in immunocompetent cells and an anti-apoptotic effect on lung tissue. Scattered studies have dismissed a protective effect of desflurane against LIRI. While a single-center randomized controlled trial (RCT) found that volatile anesthetics including desflurane demonstrated a lung-protective effect in thoracic surgery, a multicenter RCT did not demonstrate a lung-protective effect of desflurane. LIRI is common in lung transplantation. One study, although limited due to its small sample size, found that the use of volatile anesthetics in organ procurement surgery involving "death by neurologic criteria" donors did not improve lung graft survival. Future studies on the protective effect of volatile anesthetics against LIRI must examine not only the mechanism of the protective effect but also differences in the effects of different types of volatile anesthetics, their optimal dosage, and the appropriateness of their use in the event of marked alveolar capillary barrier damage.

Loss of Protease-Activated Receptor 4 Prevents Inflammation Resolution and Predisposes the Heart to Cardiac Rupture After Myocardial Infarction

BACKGROUND

Cardiac rupture is a major lethal complication of acute myocardial infarction (MI). Despite significant advances in reperfusion strategies, mortality from cardiac rupture remains high. Studies suggest that cardiac rupture can be accelerated by thrombolytic therapy, but the relevance of this risk factor remains controversial.

METHODS

We analyzed protease-activated receptor 4 (Par4) expression in mouse hearts with MI and investigated the effects of Par4 deletion on cardiac remodeling and function after MI by echocardiography, quantitative immunohistochemistry, and flow cytometry.

RESULTS

Par4 mRNA and protein levels were increased in mouse hearts after MI and in isolated cardiomyocytes in response to hypertrophic and inflammatory stimuli. Par4-deficient mice showed less myocyte apoptosis, reduced infarct size, and improved functional recovery after acute MI relative to wild-type (WT). Conversely, Par4^-/- mice showed impaired cardiac function, greater rates of myocardial rupture, and increased mortality after chronic MI relative to WT. Pathological evaluation of hearts from Par4^-/- mice demonstrated a greater infarct expansion, increased cardiac hemorrhage, and delayed neutrophil accumulation, which resulted in impaired post-MI healing compared with WT. Par4 deficiency also attenuated neutrophil apoptosis in vitro and after MI in vivo and impaired inflammation resolution in infarcted myocardium. Transfer of Par4^-/- neutrophils, but not of Par4^-/- platelets, in WT recipient mice delayed inflammation resolution, increased cardiac hemorrhage, and enhanced cardiac dysfunction. In parallel, adoptive transfer of WT neutrophils into Par4^-/- mice restored inflammation resolution, reduced cardiac rupture incidence, and improved cardiac function after MI.

CONCLUSIONS

These findings reveal essential roles of Par4 in neutrophil apoptosis and inflammation resolution during myocardial healing and point to Par4 inhibition as a potential therapy that should be limited to the acute phases of ischemic insult and avoided for long-term treatment after MI.

Endothelin type B receptor promotes cofilin rod formation and dendritic loss in neurons by inducing oxidative stress and cofilin activation

Endothelin-1 (ET-1) is a neuroactive peptide produced by neurons, reactive astrocytes, and endothelial cells in the brain. Elevated levels of ET-1 have been detected in the post-mortem brains of individuals with Alzheimer's disease (AD). We have previously demonstrated that overexpression of astrocytic ET-1 exacerbates memory deficits in aged mice or in APP^K670/M671 mutant mice. However, the effects of ET-1 on neuronal dysfunction remain elusive. ET-1 has been reported to mediate superoxide formation in the vascular system via NADPH oxidase (NOX) and to regulate the actin cytoskeleton of cancer cell lines via the cofilin pathway. Interestingly, oxidative stress and cofilin activation were both reported to mediate one of the AD histopathologies, cofilin rod formation in neurons. This raises the possibility that ET-1 mediates neurodegeneration via oxidative stress- or cofilin activation-driven cofilin rod formation. Here, we demonstrate that exposure to 100 nm ET-1 or to a selective ET type B receptor (ET_B) agonist (IRL1620) induces cofilin rod formation in dendrites of primary hippocampal neurons, accompanied by a loss of distal dendrites and a reduction in dendritic length. The 100 nm IRL1620 exposure induced superoxide formation and cofilin activation, which were abolished by pretreatment with a NOX inhibitor (5 μm VAS2870). Moreover, IRL1620-induced cofilin rod formation was partially abolished by pretreatment with a calcineurin inhibitor (100 nm FK506), which suppressed cofilin activation. In conclusion, our findings suggest a role for ET_B in neurodegeneration by promoting cofilin rod formation and dendritic loss via NOX-driven superoxide formation and cofilin activation.

The Value of Combining Plasma D-Dimer and Endothelin-1 Levels to Predict No-Reflow After Percutaneous Coronary Intervention of ST-Segment Elevation in Acute Myocardial Infarction Patients with a Type 2 Diabetes Mellitus History

Background

No-reflow phenomenon is a well-known problem, often accompanying percutaneous coronary intervention (PCI) for ST-segment elevation acute myocardial infarction (STEAMI). This study investigated the value of plasma D-dimer and Endothelin-1 (ET-1) levels on admission in predicting no-reflow after primary PCI and long-term prognosis in STEAMI patients with type 2 diabetes mellitus (T2DM).

Material/Methods

There were 822 patients with STEAMI and T2DM undergoing successful primary PCI included in this study: 418 patients showed normal re-flow after PCI, while 404 patients showed no-reflow phenomenon after PCI. The predictive value of plasma ET-1 and D-dimer level, and other clinical parameters for the no-reflow phenomenon were analyzed.

Results

The high plasma ET-1 and D-dimer levels showed predictive value for the no-reflow phenomenon in STEAMI patients with T2DM. Patients with high D-dimer and ET-1 levels showed higher risk (4.212, with 95%CI of 2.973–5.967 and 2.447 with 95%CI of 1.723–3.476, respectively) of no-reflow phenomenon compared with patients with low plasma D-dimer and ET-1 levels. Sensitivity of high plasma ET-1 and D-dimer levels in predicting no-reflow was 0.766. Both plasma D-dimer and ET-1 were adverse prognosticators for STEAMI patients with a T2DM post PCI (P<0.001).

Conclusions

In conclusion, plasma D-dimer and ET-1 levels on admission independently predict no-reflow after PCI in STEAMI patients with T2DM. When combined, the D-dimer and ET-1 levels as predictive and prognostic values are clinically promising. The plasma D-dimer and ET-1 levels provided a novel marker for treatment selection for the STEAIM patients with a T2DM history.

Time-dependent effects of HJP272, an endothelin receptor antagonist, in bleomycin-induced pulmonary fibrosis

Using a lipopolysaccharide (LPS) model of acute lung injury, we have previously shown that endothelin-1 (ET-1), a potent mediator of vasoconstriction, may act as a "gatekeeper" for the influx of inflammatory cells into the lung. To further investigate the potential of ET-1 to limit the progression of lung injury, hamsters were treated with an endothelin receptor antagonist (ERA), HJP272, either 1 h prior to intratracheal instillation of bleomycin (BLM) or 24 h afterwards. Lung injury and repair were examined by measuring the following parameters: 1) histopathological changes; 2) neutrophil content in bronchoalveolar lavage fluid (BALF); 3) lung collagen content; 4) tumor necrosis factor receptor 1 (TNFR1) expression by BALF macrophages; 5) BALF levels of: a) transforming growth factor beta-1 (TGF-β1), b) stromal cell-derived factor 1 (commonly referred to as CXCL12), and c) platelet-derived growth factor BB (PDGF-BB); 6) alveolar septal cell apoptosis (as measured by the TUNEL assay). For each of these parameters, animals pretreated with HJP272 showed significant reductions compared to those receiving BLM alone. In contrast, post-treatment with HJP272 was either ineffective or produced only marginally significant changes. The efficacy of a single pretreatment with HJP272 prior to induction of lung injury suggests that subsequent features of the disease are determined at a very early stage. This may explain why ERAs are not an effective treatment for human pulmonary fibrosis. Nevertheless, our findings suggest that they may be useful as prophylactic agents when given in combination with drugs that have fibrogenic potential.

Impaired Deformability of Copper-Deficient Neutrophils

We have previously shown that dietary copper deficiency augments neutrophil accumulation in the lung microvasculature. The current study was designed to determine whether a diet deficient in copper promotes neutrophil chemoattraction within the lung vasculature or if it alters the mechanical properties of the neutrophil, thus restricting passage through the microvessels. Sprague-Dawley rats were fed purified diets that were either copper adequate (6.3 μg Cu/g diet) or copper deficient (0.3 μg Cu/g diet) for 4 weeks. To assess neutrophil chemoattraction, bronchoalveolar lavage fluid was assayed for the neutrophil chemokine macrophage inflammatory protein-2 (MIP-2) by enzyme-linked immunosorbent assay. Neutrophil deformability was determined by measuring the pressure required to pass Isolated neutrophils through a 5-μm polycarbonate filter. The MIP-2 concentration was not significantly different between the dietary groups (Cu adequate, 435.4 ± 11.9 pg/ml; Cu deficient, 425.6 ± 14.8 pg/ml). However, compared with controls, more pressure was needed to push Cu-deficient neutrophils through the filter (Cu adequate, 0.150 ± 0.032 mm Hg/sec; Cu deficient, 0.284 0.037 mm Hg/sec). Staining of the filamentous actin (F-actin) with FITC-Phalloldin showed greater F-actin polymerization and shape change in the Cu-deficient group. These results suggest that dietary copper deficiency reduces the deformability of neutrophils by promoting F-actin polymerization. Because most neutrophils must deform during passage from arterioles to venules in the lungs, we propose that copper-deficient neutrophils accumulate in the lung because they are less deformable.

Primary Graft Dysfunction after Lung Transplantation

Primary graft dysfunction (PGD) is a severe form of acute lung injury that is a major cause of early morbidity and mortality encountered after lung transplantation. PGD is diagnosed by pulmonary oedema with diffuse alveolar damage that manifests clinically as progressive hypoxemia with radiographic pulmonary infiltrates. Inflammatory and immunological response caused by ischaemia and reperfusion is important with regard to pathophysiology. PGD affects short- and long-term outcomes, the donor organ is the leading factor affecting these adverse ramifications. To minimize the risk of PGD, reduction of lung ischaemia time, reperfusion optimisation, prostaglandin level regulation, haemodynamic control, hormone replacement therapy, ventilator management are carried out; for research regarding donor lung preparation strategies, certain procedures are recommended. In this review, recent updates in epidemiology, pathophysiology, molecular and genetic biomarkers and technical developments affecting PGD are described.

Is adalimumab protective in ischemia-reperfusion injury in lung?

OBJECTIVES

Increasing cytokines and reactive oxygen species (ROS) during ischemia reperfusion (I-R) leads to the lung damage. Adalimumab (Ada) is a potent tumor necrosis factor-alpha (TNF-α) inhibitor agent. We aimed to evaluate whether Ada would prevent the lung tissue from damage development over the I-R process.

MATERIALS AND METHODS

Twenty seven Wistar albino male rats were divided into three groups (each group had 9 rats). To the control group, only laparotomy procedure was carried out. For I-R group, first infrarenal abdominal aorta was cross-clamped during 2 hr, and then reperfusion was performed for 2 hr. To I-R+Ada group, first a single dose of 50 mg/kg Ada was given intraperitoneally and 5 days later, same I-R procedure was carried out.

RESULTS

Levels of TNF-α, malondialdehyde (MDA), myeloperoxidase (MPO), endothelin-1 (ET-1) and caspase-3 enzyme activity of I-R group were higher than that of both I-R+ Ada [TNF-α (P=0.021), MDA (P=0.029), MPO (P=0.012), ET-1 (P=0.036, caspase-3 (P=0.007), respectively] and control group [TNF-α (P=0.008), MDA (P<0.001), MPO (P=0.001), ET-1 (P<0.001), caspase-3 (P<0.001), respectively]. In I-R group, severe damage was detected by hematoxylin-eosin staining. This damage was found less severe in Ada treatment group.

CONCLUSION

The release of cytokines and ET-1 in a large proportion after I-R injury, and generating of ROS in excessive quantity could cause severe damage in the lung tissue. Ada could be considered as a protective agent for lung tissue during I-R process.

HJP272, a novel endothelin receptor antagonist, attenuates lipopolysaccharide-induced acute lung injury in hamsters

INTRODUCTION

Previous studies from this laboratory indicate that endothelin-1 (ET-1), a potent vasoconstrictor, may play an important role in lipopolysaccharide (LPS)-induced release of neutrophils from the pulmonary microvasculature. To further test this concept, Syrian hamsters were treated with a novel endothelin receptor A (ETA) antagonist (HJP272) prior to intratracheal instillation of LPS.

METHODS

The effect of HJP272 on the LPS-induced inflammatory reaction was determined by measuring: (1) lung histopathological changes, (2) total neutrophils in bronchoalveolar lavage fluid (BALF), (3) expression of tumor necrosis factor receptor 1 (TNFR1) by BALF macrophages, and (4) alveolar septal cell apoptosis.

RESULTS

Treatment with HJP272 significantly reduced each of these parameters during a 24-hr period following LPS instillation, supporting the concept that limiting the activity of ET-1 may reduce the extent of lung injury. This hypothesis was further tested by giving ET-1 prior to LPS instillation, which resulted in a marked enhancement of LPS-induced lung inflammation, as measured by BALF neutrophils and TNFR1-positive macrophages. Furthermore, the increase in neutrophils resulting from treatment with ET-1 was significantly reduced by HJP272, again demonstrating the ability of ETA receptor antagonists to limit the influx of these cells into the lung.

CONCLUSIONS

These findings suggest a potential therapeutic role for these agents in diseases where neutrophils are a significant cause of lung injury, such as bronchopneumonia, respiratory distress syndrome, and chronic obstructive pulmonary disease.

Lung ischemia-reperfusion injury: a molecular and clinical view on a complex pathophysiological process

Lung ischemia-reperfusion injury remains one of the major complications after cardiac bypass surgery and lung transplantation. Due to its dual blood supply system and the availability of oxygen from alveolar ventilation, the pathogenetic mechanisms of ischemia-reperfusion injury in the lungs are more complicated than in other organs, where loss of blood flow automatically leads to hypoxia. In this review, an extensive overview is given of the molecular and cellular mechanisms that are involved in the pathogenesis of lung ischemia-reperfusion injury and the possible therapeutic strategies to reduce or prevent it. In addition, the roles of neutrophils, alveolar macrophages, cytokines, and chemokines, as well as the alterations in the cell-death related pathways, are described in detail.

The lipid moiety of haemozoin (Malaria Pigment) and P. falciparum parasitised red blood cells bind synthetic and native endothelin-1

Endothelin1 (ET-1) is a 21-amino acid peptide produced by the vascular endothelium under hypoxia, that acts locally as regulator of vascular tone and inflammation. The role of ET-1 in Plasmodium falciparum malaria is unknown, although tissue hypoxia is frequent as a result of the cytoadherence of parasitized red blood cell (pRBC) to the microvasculature. Here, we show that both synthetic and endothelial-derived ET-1 are removed by parasitized RBC (D10 and W2 strains, chloroquine sensitive, and resistant, resp.) and native haemozoin (HZ, malaria pigment), but not by normal RBC, delipidized HZ, or synthetic beta-haematin (BH). The effect is dose dependent, selective for ET-1, but not for its precursor, big ET-1, and not due to the proteolysis of ET-1. The results indicate that ET-1 binds to the lipids moiety of HZ and membranes of infected RBCs. These findings may help understanding the consequences of parasite sequestration in severe malaria.

Endothelin-1 potentiates smoke-induced acute lung inflammation

The current study examined the role of endothelin-1 (ET-1) in mediating acute lung inflammation induced by short-term cigarette smoke exposure. Hamsters received intraperitoneal injections of ET-1, followed by a 2-hour period of smoke exposure, for 3 consecutive days. The lungs were then evaluated for inflammatory changes, using the following parameters: (1) lung histopathology, (2) neutrophil content of bronchoalveolar lavage fluid (BALF), (3) percent tumor necrosis factor receptor 1 (TNFR1)-labeled BALF macrophages, and (4) alveolar septal cell apoptosis. Results indicate that ET-1 significantly amplified the effect of smoke on each of these inflammatory markers and that these responses could be blocked by pretreatment with a novel endothelin receptor A antagonist, HJP272. In particular, exogenous ET-1 induced a marked increase in BALF neutrophils, consistent with a role for this mediator as an inflammatory cell "gatekeeper."

Preferential recruitment of neutrophils by endothelin-1 in acute lung inflammation induced by lipopolysaccharide or cigarette smoke

This study examined the role of endothelin-1 (ET-1) in recruiting inflammatory cells to the lung after induction of injury with either lipopolysaccharide (LPS) or cigarette smoke. Hamsters injected with either ET-1 or its precursor peptide (Big ET-1) prior to treatment with LPS or cigarette smoke had markedly increased concentrations of neutrophils in bronchoalveolar lavage fluid (BALF) despite a reduction in total numbers of BALF leukocytes. Furthermore, the effect of ET-1 on smoke-exposed animals was reversed by addition of an endothelin-A receptor antagonist. These results are consistent with preferential recruitment of neutrophils by ET-1, and suggest that inhibition of this proinflammatory mediator may decrease acute pulmonary inflammation associated with cigarette smoke and other pulmonary toxins.

Endothelin receptor antagonism prevents hypoxia-induced mortality and morbidity in a mouse model of sickle-cell disease

Patients with sickle-cell disease (SCD) suffer from tissue damage and life-threatening complications caused by vasoocclusive crisis (VOC). Endothelin receptors (ETRs) are mediators of one of the most potent vasoconstrictor pathways in mammals, but the relationship between vasoconstriction and VOC is not well understood. We report here that pharmacological inhibition of ETRs prevented hypoxia-induced acute VOC and organ damage in a mouse model of SCD. An in vivo ultrasonographic study of renal hemodynamics showed a substantial increase in endothelin-mediated vascular resistance during hypoxia/reoxygenation-induced VOC. This increase was reversed by administration of the dual ETR antagonist (ETRA) bosentan, which had pleiotropic beneficial effects in vivo. It prevented renal and pulmonary microvascular congestion, systemic inflammation, dense rbc formation, and infiltration of activated neutrophils into tissues with subsequent nitrative stress. Bosentan also prevented death of sickle-cell mice exposed to a severe hypoxic challenge. These findings in mice suggest that ETRA could be a potential new therapy for SCD, as it may prevent acute VOC and limit organ damage in sickle-cell patients.

Peroxisome proliferator-activated receptors ligands and ischemia-reperfusion injury

Peroxisome proliferator-activated receptors (PPARs) belong to a subfamily of transcription nuclear factors. Three isoforms of PPARs have been identified: alpha, beta/delta and gamma, encoded by different genes and distributed in various tissues. They play important roles in metabolic processes like regulation of glucose and lipid redistribution. They also have anti-atherogenic, anti-inflammatory as well as antihypertensive functions. There is good evidence that ligands of PPARs reduce tissue injury associated with ischemia and reperfusion. The potential utility of PPAR ligands in ischemia and reperfusion will be discussed in this review.

Sivelestat reduces inflammatory mediators and preserves neutrophil deformability during simulated extracorporeal circulation

BACKGROUND

Neutrophil is a major focus in efforts to ameliorate the systemic inflammatory response associated with cardiopulmonary bypass. Neutrophil elastase is a powerful proteolytic enzyme, and plays a pivotal role in the development of the inflammatory response. This study assesses the inhibitory effects of sivelestat, a highly specific neutrophil elastase inhibitor, on elastase levels, cytokine production, and the functional changes of neutrophils in a simulated extracorporeal circulation model.

METHODS

Simulated recirculation was established by recirculating heparinized (3.75 U/mL) human blood for 120 minutes in an oxygenator and a roller pump circuit with and without 100 micromol/L of sivelestat (n = 7 for each group). Neutrophil elastase and interleukin-8 were measured with an enzyme immunoassay. Neutrophil deformability was evaluated by simulated microcapillaries. The neutrophil F-actin and the expression of CD11b and L-selectin were measured by flow cytometry.

RESULTS

Sivelestat reduced both neutrophil elastase levels (p = 0.0006) and interleukin-8 production (p < 0.0001) at 120 minutes of recirculation. Sivelestat also significantly preserved neutrophil deformability (p = 0.017) and reduced F-actin expression (p = 0.0037). The drug did not modulate the changes of CD11b or L-selectin.

CONCLUSIONS

This study suggests that specific elastase inhibition with sivelestat could be a feasible therapeutic strategy for patients undergoing cardiopulmonary bypass to attenuate neutrophil-derived inflammatory response and organ injuries.

Nafamostat preserves neutrophil deformability and reduces microaggregate formation during simulated extracorporeal circulation

BACKGROUND

Initial sequestration of activated neutrophils and platelet microaggregates in capillaries are responsible for the inflammatory response associated with cardiopulmonary bypass. The study assesses the inhibitory effects of nafamostat mesilate on neutrophil and platelet activation, and on the neutrophil deformability change and microaggregate formation during simulated extracorporeal circulation.

METHODS

Fresh heparinized human blood was recirculated for 120 minutes in a membrane oxygenator and a roller pump with and without nafamostat (1.0 mg bolus plus 8.0 mg/h infusion; n = 10 for each group). Neutrophil and platelet counts and platelet aggregation were measured. CD11b, L-selectin, and cytoplasmic F-actin of neutrophils were measured by flow cytometry. The microchannel transit time of whole blood was measured as a marker of neutrophil deformability and microaggregate formation. Neutrophil elastase and complement C4d were measured using enzyme immunoassay.

RESULTS

Nafamostat preserved platelet counts and inhibited platelet aggregation. Nafamostat significantly reduced neutrophil elastase release at 120 minutes of recirculation, and F-actin expression at 30 and 60 minutes. The drug did not modulate the changes of CD11b, L-selectin, or C4d. Whole blood filterability was significantly preserved by nafamostat at 30 and 120 minutes.

CONCLUSIONS

Nafamostat preserves blood filterability during recirculation, possibly by suppression of F-actin expression and platelet activation. Nafamostat may reduce neutrophil sequestration and microaggregate formation in the microcirculation during cardiopulmonary bypass.

Phosphodiesterase type 4 inhibitor rolipram inhibits activation of monocytes during extracorporeal circulation

OBJECTIVE

Cardiopulmonary bypass is associated with systemic inflammatory response syndrome and risk of multiorgan injury mediated by activated leukocytes. Phosphodiesterase type 4 is the predominant phosphodiesterase isozyme in leukocytes and plays a key role in the regulation of leukocyte activation. The aim of this study was to examine the effect of rolipram, a selective phosphodiesterase type 4 inhibitor, on functional changes of monocytes during simulated extracorporeal circulation.

METHODS AND RESULTS

Simulated extracorporeal circulation was established by recirculating heparinized human blood for 120 minutes on a membrane oxygenator with or without 10 micromol/L of rolipram. L-selectin and CD11b expression of monocytes were measured with flow cytometry. C4d fragment, Bb fragment, C5b-9, and interleukin-6 were measured with enzyme immunoassay. Rolipram reduced the increase in CD11b expression and the decrease in L-selectin expression of monocytes in response to simulated extracorporeal circulation. Rolipram inhibited the increase in C4d fragment and interleukin-6, but it did not affect the increase in Bb fragment or C5b-9.

CONCLUSION

Rolipram inhibited changes in adhesion molecule expression and interleukin-6 release by activated monocytes in simulated extracorporeal circulation. This study suggests that phosphodiesterase type 4 inhibition could be feasible therapeutic strategy to prevent exaggerated inflammatory response and organ injury in patients undergoing cardiopulmonary bypass.

Inhibition of c-Jun N-Terminal Kinase Limits Lipopolysaccharide-induced Pulmonary Neutrophil Influx

The influx of neutrophils into the lung is a sentinel event in LPS-induced acute lung inflammation. Previous studies have shown that systemic inhibition of p38 decreases LPS-induced neutrophil influx into the alveolar space but has no effect on pulmonary parenchymal neutrophil accumulation or on microvascular leak, indicating other pathways are important in LPS-induced acute lung inflammation. This study examined the role of c-Jun N-terminal kinase in LPS-induced acute lung inflammation. Systemic inhibition of c-Jun N-terminal kinase, with the specific c-Jun N-terminal kinase inhibitor SP600125, decreased the LPS-induced accumulation of neutrophils into the lung parenchyma and alveolar space. In addition, increases in microvascular leak after LPS exposure were diminished by c-Jun N-terminal kinase inhibition. To determine mechanisms by which systemic c-Jun N-terminal kinase inhibition decreased pulmonary neutrophil influx, LPS and tumor necrosis factor alpha (TNF-alpha-)-induced neutrophil actin assembly and retention were examined. Neutrophil actin assembly was decreased after LPS and TNF-alpha stimulation with SP600125 pretreatment, as well as LPS-induced neutrophil retention. Finally, c-Jun N-terminal kinase inhibition decreased Cdc42 activation after LPS or TNF-alpha stimulation, thereby providing one mechanism by which c-Jun N-terminal kinase inhibition decreased actin assembly, and thereby pulmonary neutrophil accumulation.

Antithrombin III Diminishes Production of Oxygen Radical in Endotoxin-Infused Rat Lung

The interaction of antithrombin III (AT) with cell surface glycosaminoglycans is known to have an inhibitory effect on inflammatory processes. We evaluated the effect of AT on endotoxin-induced production of oxygen radical in the pulmonary circulation using a fluorescent imaging technique. Also measured was the myeloperoxidase content of the lung, which served as an index of neutrophil accumulation, and neutrophil F-actin levels. Four groups of rats were infused for 2 h with endotoxin at 4.5 mg/kg/h (Et group), physiological saline (CT group), 100 U/kg of AT + endotoxin (AT group), or 100 U/kg of low-heparin-affinity latent-AT + endotoxin (L-AT group), respectively. Production of oxygen radical, neutrophil accumulation, and neutrophil F-actin levels were all significantly higher in the ET and L-AT groups than in the CT or AT group. Moreover; the levels of myeloperoxidase within the lung were well correlated with levels of oxygen radical production, which was consistent with the electron microscopic finding that cerium was deposited almost exclusively around neutrophils. Thus, it appears that AT most likely reduces F-actin formation in neutrophil by binding to glycosaminoglycans (e.g., syndecan-4) on the neutrophil, thereby reducing neutrophil accumulation in the lung, which would in turn inhibit oxygen radical production in the lung.

Continuous subcutaneous injection reduces polymorphonuclear leukocyte activation by granulocyte colony-stimulating factor

The use of granulocyte colony stimulating factor (G-CSF) for recovery from neutropenia has been established; however, acute lung injury due to G-CSF-induced polymorphonuclear leukocyte (PMN) activation is a serious complication. This study was designed to compare the activation of PMN with single bolus administration and continuous administration of G-CSF. Healthy volunteers (age 33.8 ± 1.4 yr; n = 6) received a single bolus injection of 50 μm/m2of G-CSF (SI; n = 6) or continuous subcutaneous injection of 50 μm/m2of G-CSF for 24 h (CI; n = 6) and were followed for 48 h. Circulating leukocyte counts, markers of activation on PMN, and circulating levels of G-CSF, IL-6, and PMN elastase were measured. SI rapidly increased serum G-CSF levels, which peaked at 4 h, whereas CI gradually increased G-CSF levels, which remained at a steady level from 8 to 24 h. SI caused a rapid decrease in PMN counts at 0.5 h followed by sustained increase to peak at 12 h. CI gradually increased PMN counts, which peaked at 24 h, but the peak values were not significantly different between the groups. SI-induced activation of PMN, which was characterized by increased expression of CD11b, decreased expression of L-selectin, and increased F-actin content, led to increases in serum IL-6 and PMN elastase level. Such changes were all attenuated with CI ( P < 0.05). We conclude that continuous subcutaneous injection of G-CSF resulted in a marrow response similar to that to a single injection but yielded reduced PMN activation.

Activated neutrophils and platelet microaggregates impede blood filterability through microchannels during simulated extracorporeal circulation

BACKGROUND

Neutrophil sequestration and platelet microaggregates in organ capillaries have been implicated in the inflammatory response associated with cardiopulmonary bypass. We examined the filterability of neutrophils and platelet microaggregates through silicon microchannels during simulated extracorporeal circulation. We hypothesize that blood contact with artificial surfaces over time decreases the ability of neutrophils, platelets, and their aggregates to pass through microchannels.

METHODS

Fresh human blood from donors (n = 9) was recirculated for 120 minutes in a simulated extracorporeal circuit. Blood samples were obtained from a donor at 0, 30, 60, and 120 minutes of recirculation. The microchannel transit time and the flow behavior of blood cells were evaluated by a silicon microchannel array flow analyzer. CD11b, L-selectin, and F-actin of neutrophils were measured by flow cytometry. Neutrophil and platelet counts and platelet aggregation to adenosine diphosphate were measured.

RESULTS

The microchannel transit time was prolonged during recirculation, reaching 185.9% +/- 25.6% of baseline at 120 minutes. The video microscope showed that neutrophils and platelet microaggregates plugged the microchannels. CD11b, L-selectin, and F-actin levels changed significantly by 120 minutes. Platelet counts decreased and platelet aggregability was attenuated.

CONCLUSIONS

Simulated extracorporeal circulation caused a progressive loss in the ability of neutrophils, platelets, and their aggregates to pass through the microchannels independent of neutrophil adhesion molecule expression.

Ischemia-reperfusion-induced lung injury

Ischemia-reperfusion-induced lung injury is characterized by nonspecific alveolar damage, lung edema, and hypoxemia occurring within 72 hours after lung transplantation. The most severe form may lead to primary graft failure and remains a significant cause of morbidity and mortality after lung transplantation. Over the past decade, better understanding of the mechanisms of ischemia-reperfusion injury, improvements in the technique of lung preservation, and the development of a new preservation solution specifically for the lung have been associated with a reduction in the incidence of primary graft failure from approximately 30 to 15% or less. Several strategies have also been introduced into clinical practice for the prevention and treatment of ischemia-reperfusion-induced lung injury with various degrees of success. However, only three randomized, double-blinded, placebo-controlled trials on ischemia-reperfusion-induced lung injury have been reported in the literature. In the future, the development of new agents and their application in prospective clinical trials are to be expected to prevent the occurrence of this potentially devastating complication and to further improve the success of lung transplantation.

Phosphodiesterase type 4 inhibition of activated polymorphonuclear leukocytes in a simulated extracorporeal circulation model

OBJECTIVES

Cardiopulmonary bypass is associated with a systemic inflammatory response syndrome and the risk of multiorgan injuries mediated by activated polymorphonuclear leukocytes. Phosphodiesterase type 4 is the predominant phosphodiesterase isozyme in polymorphonuclear leukocytes and plays a key role in the regulation of polymorphonuclear leukocyte activation. The aim of this study was to examine the effect of rolipram, a selective phosphodiesterase type 4 inhibitor, on the functional changes of polymorphonuclear leukocytes by using simulated extracorporeal circulation.

METHODS

Simulated extracorporeal circulation was established by recirculating heparinized human blood for 120 minutes on a membrane oxygenator with and without 10 micro mol/L rolipram. F-actin content and L-selectin and CD11b expression of polymorphonuclear leukocytes were measured by means of flow cytometry. Polymorphonuclear leukocyte deformability was evaluated with a microchannel array flow analyzer that had a similar diameter as the capillaries. Polymorphonuclear leukocyte elastase was measured with an enzyme immunoassay.

RESULTS

Rolipram reduced the increase of F-actin content of polymorphonuclear leukocytes and the increase of transit time of 100 micro L of blood sample through a microchannel. Rolipram reduced the increase of CD11b expression and the decrease of L-selectin expression of polymorphonuclear leukocytes. Rolipram reduced the release of elastase from polymorphonuclear leukocytes.

CONCLUSION

Rolipram inhibited the deformability change mediated by F-actin assembly, the changes in adhesion molecules, and the release of elastase from activated polymorphonuclear leukocytes in simulated extracorporeal circulation. This study suggests that phosphodiesterase type 4 inhibition could be a feasible therapeutic strategy to prevent the exaggerated inflammatory response related to cardiopulmonary bypass.

Phosphodiesterase type 4 inhibitor reduces the retention of polymorphonuclear leukocytes in the lung

Phosphodiesterase (PDE) type 4 is the predominant PDE isozyme in polymorphonuclear leukocytes (PMN) and plays a key role in the regulation of PMN activation. The aim of this study was to examine the effect of a PDE type 4 inhibitor, rolipram, on the functional changes and the retention of PMN in the lung. In vitro, F-actin content and L-selectin and CD11b expression of PMN stimulated by N-formyl-Met-Leu-Phe were measured by flow cytometry. PMN deformability was evaluated using silicon microchannels. Rolipram reduced the increase of F-actin and CD11b but did not change the decrease of L-selectin. Rolipram inhibited the increase of the transit time of PMN through the microchannel. We evaluated the retention of PMN in the lung in vivo by infusing labeled blood into the vena cava and examining the recovery into aortic root samples in rabbits. Rolipram inhibited the retention of stimulated PMN in the lung. In conclusion, a PDE type 4 inhibitor, rolipram, reduces the retention of PMN in the lung by reducing deformability change and CD11b upregulation of PMN.

Pulmonary adrenomedullin counteracts deterioration of coronary flow and myocardial performance evoked by pulmonary endothelins in experimental acute respiratory distress syndrome

OBJECTIVES

We recently showed that pulmonary endothelins may affect coronary circulation under various experimental and clinical conditions. Here, we investigated the effect of pulmonary mediators on coronary tone in experimental acute respiratory distress syndrome. We focused particularly on pulmonary endothelin-1, a major vasoconstrictor in acute respiratory distress syndrome, and on adrenomedullin, a potent vasodilator that is up-regulated by inflammatory stimuli.

DESIGN

Controlled experiment that used isolated organs.

SETTING

Experimental laboratory.

SUBJECTS

Wistar rats.

INTERVENTIONS

The saline effluent from an isolated lung was used to serially perfuse the coronary vessels of an isolated heart. We compared serial perfusion after 2-hr pretreatment of lungs with vehicle or endotoxin (50 microg/mL), and we used the following drugs to elucidate the coronary response observed: the endothelin type A receptor antagonist BQ-123 (2 microM), the endothelin type B antagonist A-192621 (500 nM), the endothelin-converting enzyme inhibitor phosphoramidon (50 microM), the calcitonin gene-related peptide type-1 receptor antagonist hCGRP(8-37) (2 microM), and the adrenomedullin receptor antagonist hAM(22-52) (200 nM) (n = 6 each).

MEASUREMENTS AND MAIN RESULTS

In controls, serial perfusion decreased coronary flow to 87 +/- 3% of baseline (p < .05). BQ-123 and phosphoramidon prevented this effect, whereas blockade of endothelin type B and adrenomedullin-binding receptors had no effect. After endotoxin challenge, coronary flow significantly increased to 110 +/- 2%. This response was augmented by BQ-123 (124 +/- 2%) and phosphoramidon (123 +/- 3%); A-192621 had no effect. Application of hCGRP(8-37) and hAM(22-52) significantly decreased coronary flow to 81 +/- 3% and 88 +/- 2%, respectively. Flow decrease after blockade of both adrenomedullin-binding receptors (73 +/- 2%) significantly deteriorated peak left ventricular pressure, to 82 +/- 6% of baseline; rate of pressure increase, to 81 +/- 5%; and rate of pressure decline, to 77 +/- 6%. Endotoxin pretreatment elevated pulmonary venous big endothelin-1 (three-fold), endothelin-1 (two-fold), and adrenomedullin (five-fold).

CONCLUSION

In experimental acute respiratory distress syndrome, pulmonary adrenomedullin--via calcitonin gene-related peptide type-1 receptor and adrenomedullin receptor--outweighs the coronary vasoconstrictor impact of pulmonary big endothelin-1 exerted via endothelin type A receptors after conversion to mature endothelin-1. The consequence is prevention of flow-related deterioration of myocardial performance.