Inhaled activated protein C attenuates lung injury induced by aerosolized endotoxin in mice

Aucubin Alleviates Chronic Obstructive Pulmonary Disease by Activating Nrf2/HO-1 Signaling Pathway

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a common chronic respiratory disease with high death rates. Aucubin is an iridoid glycoside extracted from Eucommia ulmoides with antioxidative and anti-inflammatory properties in human diseases. This study aimed to investigate its specific function in mouse and cell models of COPD.

METHODS

The COPD mouse model was established by exposing mice to a long-term cigarette smoke (CS). The number of inflammatory cells and the contents of inflammatory factors tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and IL-8 in bronchoalveolar lavage fluid (BALF) of CS-exposed mice were measured. The levels of superoxide dismutase (SOD), glutathione (GSH), malondialdehyde (MDA), and myeloperoxidase (MPO) in the lung tissues were estimated. Masson staining and hematoxylin-eosin (H&E) staining were utilized to evaluate pulmonary fibrosis and emphysema in CS-treated mice. Cell apoptosis in the lung tissues was estimated by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay. Western blot was applied to quantify protein levels of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and apoptotic markers. COPD cell model was established by exposing mouse lung epithelial cells (MLE12) with cigarette smoke extract to further verify the properties of aucubin in vitro.

RESULTS

Aucubin reduced the number of inflammatory cells and decreased the contents of TNF-α, IL-6, and IL-8 in BALF of CS-treated mice. The oxidative stress, lung emphysema, fibrosis, and lung cell apoptosis induced by CS exposure were ameliorated by aucubin administration. Aucubin activated the Nrf2/HO-1 signaling pathway in vitro and in vivo. Pretreatment with ML385, a specific Nrf2 inhibitor, antagonized the protective effects of aucubin on inflammation, oxidative stress, fibrosis, and cell apoptosis in COPD.

CONCLUSION

Aucubin alleviates inflammation, oxidative stress, apoptosis, and pulmonary fibrosis in COPD mice and CSE-treated MLE12 cells by activating the Nrf2/HO-1 signaling pathway.

Pharmacotherapy consideration of thrombolytic medications in COVID-19-associated ARDS

BACKGROUND

In late 2019, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which is responsible for coronavirus disease (COVID-19), was identified as the new pathogen to lead pneumonia in Wuhan, China, which has spread all over the world and developed into a pandemic. Despite the over 1 year of pandemic, due to the lack of an effective treatment plan, the morbidity and mortality of COVID-19 remains high. Efforts are underway to find the optimal management for this viral disease.

MAIN BODY

SARS-CoV-2 could simultaneously affect multiple organs with variable degrees of severity, from mild to critical disease. Overproduction of pro-inflammatory mediators, exacerbated cellular and humoral immune responses, and coagulopathy such as Pulmonary Intravascular Coagulopathy (PIC) contributes to cell injuries. Considering the pathophysiology of the disease and multiple microthrombi developments in COVID-19, thrombolytic medications seem to play a role in the management of the disease. Beyond the anticoagulation, the exact role of thrombolytic medications in the management of patients with COVID-19-associated acute respiratory distress syndrome (ARDS) is not explicit. This review focuses on current progress in underlying mechanisms of COVID-19-associated pulmonary intravascular coagulopathy, the historical use of thrombolytic drugs in the management of ARDS, and pharmacotherapy considerations of thrombolytic therapy, their possible benefits, and pitfalls in COVID-19-associated ARDS.

CONCLUSIONS

Inhaled or intravenous administration of thrombolytics appears to be a salvage therapy for severe ARDS associated with COVID-19 by prompt attenuation of lung injury. Considering the pathogenesis of COVID-19-related ARDS and mechanism of action of thrombolytic agents, thrombolytics appear attractive options in stable patients without contraindications.

Tanshinone IIA sodium sulfonate attenuates inflammation by upregulating circ-Sirt1 and inhibiting the entry of NF-κB into the nucleus

Inflammation is a biological process that exists in a large number of diseases. NF-κB has been proven to play a pivotal role in the development of inflammation. New drugs aimed at inhibiting the expression of NF-κB have gained attention from researchers. Sirt1 has an anti-inflammatory function, and the circRNA encoded by the Sirt1 gene may also play roles in the anti-inflammatory reaction of Sirt1. In the present study, LPS-treated RAW264.7 cells were used as an inflammatory cell model, and tanshinone IIA sodium sulfonate (TSS) was used as a therapeutic drug. We found that TSS downregulated LPS-induced TNF-α and IL-1β expression nearly threefold. LPS reduced Circ-sirt1 mRNA expression by one-third, while TSS started this phenomenon. In addition, overexpression/knockdown of Circ-sirt1 neutralized the function of TSS by regulating the translocation of NF-κB. Thus, we proved that TSS has an anti-inflammatory function by upregulating circ-Sirt1 and subsequently inhibiting the translocation of NF-κB. An in vivo experiment was also performed to confirm the protective function of TSS on inflammation. These results indicated that TSS is a potential treatment for inflammation.

Resolution of systemic complications in Schistosoma mansoni-infected mice by concomitant treatment with praziquantel and Schisandrin B

Schistosomiasis is a tropical parasitic disease, in which the major clinical manifestation includes hepatosplenomegaly, portal hypertension, and organs fibrosis. Clinically, treatment of schistosomiasis involves the use of praziquantel (PZQ) and supportive care, which does not improve the patient's outcome as liver injuries persist. Here we show the beneficial effects of using PZQ in combination with Schisandrin B (Sch B). Concomitant treatment with PZQ and Sch B resulted in a significant improvement of hepatosplenomegaly and fibrosis, compared with single-agent treatment. We also demonstrated that PZQ-Sch B treatment ameliorates injuries in the lungs and intestine better than the sole use of PZQ or Sch B. In addition, PZQ-Sch B treatment improves the survival of S. mansoni-infected mice, and the treatment combination yields better therapeutic outcomes, as indicated by a partial improvement in neurological function. These results were accompanied by a reduction in neurological injuries. Collectively, we suggest that PZQ-Sch B concomitant therapy may be useful to alleviate schistosomiasis-associated liver injuries and prevent systemic complications.

Coagulation Dysfunction in Acute Respiratory Distress Syndrome and Its Potential Impact in Inflammatory Subphenotypes

The Acute Respiratory Distress Syndrome (ARDS) has caused innumerable deaths worldwide since its initial description over five decades ago. Population-based estimates of ARDS vary from 1 to 86 cases per 100,000, with the highest rates reported in Australia and the United States. This syndrome is characterised by a breakdown of the pulmonary alveolo-epithelial barrier with subsequent severe hypoxaemia and disturbances in pulmonary mechanics. The underlying pathophysiology of this syndrome is a severe inflammatory reaction and associated local and systemic coagulation dysfunction that leads to pulmonary and systemic damage, ultimately causing death in up to 40% of patients. Since inflammation and coagulation are inextricably linked throughout evolution, it is biological folly to assess the two systems in isolation when investigating the underlying molecular mechanisms of coagulation dysfunction in ARDS. Although the body possesses potent endogenous systems to regulate coagulation, these become dysregulated and no longer optimally functional during the acute phase of ARDS, further perpetuating coagulation, inflammation and cell damage. The inflammatory ARDS subphenotypes address inflammatory differences but neglect the equally important coagulation pathway. A holistic understanding of this syndrome and its subphenotypes will improve our understanding of underlying mechanisms that then drive translation into diagnostic testing, treatments, and improve patient outcomes.

Inhibition of endotoxin-induced acute lung injury in rats by bone marrow-derived mesenchymal stem cells: Role of Nrf2/HO-1 signal axis in inhibition of NLRP3 activation

Both the Nuclear factor-erythroid 2 p45-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) antioxidant pathway and Nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) pathway are considered essential for the development of acute lung injury (ALI)/ARDS induced by sepsis. Our aim was to study the role of Nrf2/HO-1 pathway on activation of the NLRP3 in the protective effect of marrow mesenchymal stem cells (BMSCs) on LPS-induced ALI. We found that BMSCs ameliorated ALI as evidenced by 1) decreased histopathological injury, wet/dry ratio, and protein permeability index in lung; 2) decreased reactive oxygen species (ROS), malondialdehyde (MDA), and protein carbonyl content and restored the activity of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) in lung tissue; 3) reduced LPS-induced increase in inflammatory cell count and promotion of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 levels in bronchoalveolar lavage fluid (BALF); 4) improvement in the four-day survival rate of animals; and 5) enhanced expression of Nrf2 and HO-1 and decreased expression of NOD-like receptor protein 3(NLRP3) and caspase-1 (p20) in lung tissue. Of note, Nrf2 transcription factor inhibitor brusatol and HO-1 inhibitor tin protoporphyrin IX (SnppIX) reversed BMSCs induced down-expression of NLRP3 and caspase-1 (p20), and inhibited the protective effects of BMSCs. These findings demonstrated that the Nrf2-mediated HO-1 signaling pathway plays a critical role in the protective effects of BMSCs on LPS-induced ALI. BMSCs may play an anti-inflammatory effect partly through the Nrf2/HO-1-dependent NLRP3 pathway.

Anti-Inflammatory Effects of Shenfu Injection against Acute Lung Injury through Inhibiting HMGB1-NF-κB Pathway in a Rat Model of Endotoxin Shock

Shenfu injection (SFI), a Chinese herbal medicine with substances extracted from Ginseng Radix et Rhizoma Rubra and Aconiti Lateralis Radix Praeparata, is widely used as an anti-inflammatory reagent to treat endotoxin shock in China. However, the mechanism of SFI in endotoxin shock remains to be illuminated. High mobility group box 1 (HMGB1), a vital inflammatory factor in the late stage of endotoxin shock, may stimulate multiple signalling cascades, including κB (NF-κB), a nuclear transcription factor, as well as tumour necrosis factor (TNF)-α and interleukin (IL)-1β, among others in the overexpression of downstream proinflammatory cytokines. An investigation into the effects of SFI on the inhibition of the HMGB1-NF-κB pathway revealed the contribution of SFI to acute lung injury (ALI) in a rat model of endotoxin shock. To assess the anti-inflammatory activity of SFI, 5 ml/kg, 10 ml/kg, or 15 ml/kg of SFI was administered to different groups of rats following an injection of LPS, and the mean arterial pressure (MAP) at 5 h and the survival rate at 72 h were measured. 24 h after LPS injection, we observed pathological changes in the lung tissue and measured the mRNA expression, production, translocation, and secretion of HMGB1, as well as the expression of the NF-κB signal pathway-related proteins inhibitor of NF-κB (IκB)-α, P50, and P65. We also evaluated the regulation of SFI on the secretion of inflammatory factors including interleukin-1 beta (IL-1β) and TNF-α. SFI effectively prevented the drop in MAP, relieved lung tissue damage, and increased the survival rate in the endotoxin shock model in dose-dependent manner. SFI inhibited the transcription, expression, translocation, and secretion of HMGB1, increased the expression of toll-like receptor (TLR4), increased the production of IκB-α, and decreased the levels of P65, P50, and TNF-α in the lung tissue of endotoxin shock rats in a dose-dependent manner. Furthermore, SFI decreased the secretion of proinflammatory cytokines TNF-α and IL-1β. In summary, SFI improves the survival rate of endotoxin shock, perhaps through inhibiting the HMGB1-NF-κB pathway and thus preventing cytokine storm.

Bardoxolone treatment alleviates lipopolysaccharide (LPS)-induced acute lung injury through suppressing inflammation and oxidative stress regulated by Nrf2 signaling

Nuclear factor-erythroid 2 related factor 2 (Nrf2) plays critical roles in attenuating various inflammation- and oxidative stress-induced diseases, including acute lung injury (ALI). Bardoxolone (Bard), a synthetic triterpenoid based on natural product oleanolic acid, is one of the most potent Nrf2 activator. However, if Bard could prevent lipopolysaccharide (LPS)-induced ALI by inducing Nrf2 activation and its down-streaming signals, is still poorly understood. In this study, we attempted to explore the protective effect of Bard on ALI and the underlying molecular mechanisms. The results indicated that Bard significantly attenuated ALI through reducing the lung wet/dry weight ratio and protein concentration, neutrophil infiltration, malondialdehyde (MDA) and myeloperoxidase (MPO) levels, and improving superoxide dismutase (SOD) and glutathione (GSH) activities. In addition, Bard effectively ameliorated histopathological alterations, reactive oxygen species (ROS) production, pro-inflammatory cytokines release, and the expression of inducible NO synthase (iNOS), cyclooxygenase-2 (COX2) and high mobility group box 1 (HMGB1). Moreover, the inhibitory role of Bard in inflammation was also attributed to its suppression of nuclear factor-κB (NF-κB) signaling. Furthermore, the activation of mitogen-activated protein kinases (MAPKs) signaling, including p38, extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK), induced by LPS was substantially ameliorated by Bard. The beneficial effects of Bard on ALI were confirmed in LPS-incubated cells in vitro. Meanwhile, the in vitro studies also demonstrated that Bard-improved ALI was largely due to its role in inducing Nrf2 signaling through a dose-dependent manner. Importantly, we found that Bard-attenuated histological changes, inflammation, ROS production, NF-κB and MAPKs signaling in Nrf2^+/+ mice were significantly abolished in mice with Nrf2 knockout. Therefore, our study for the first time provided evidence that Bard could effectively ameliorate LPS-induced ALI by reducing oxidative stress and inflammation mainly through the activation of Nrf2 signaling.

Overexpression of Forkhead box C1 attenuates oxidative stress, inflammation and apoptosis in chronic obstructive pulmonary disease

AIM

Chronic obstructive pulmonary disease (COPD) is a disease caused by cigarette smoke, which has been emerging as a serious health problem worldwide. The aim of this study is to explore the mRNA expression profile of lung tissues from the COPD rats and to characterize the role of Forkhead box C1 (Foxc1) in COPD.

MAIN METHODS

Wistar rats were exposed to cigarette smoke during 16 weeks for COPD model establishment. The microarray was used to identify the differential gene expression in the lung of rats. Adenovirus carrying Foxc1 was administered to rats by intratracheally instillation once a week for 16 weeks. Human bronchial epithelial cell line (16HBE) cells were transfected with Foxc1 siRNA followed by incubation in the presence of CSE (10%) for 24 h. Subsequently, the pathological changes, fibrosis, apoptosis, inflammatory cytokines and oxidative stress were detected.

KEY FINDINGS

Microarray results showed an upregulation of Foxc1 in lung tissues in COPD rats. Overexpression of Foxc1 mitigated the lung injury, as evidenced by reducing alveolar fusion, inflammatory cell infiltration and oxidative stress. Additionally, the apoptosis was remarkably increased in the lung in rats exposed to cigarette smoke, which was suppressed by Foxc1 overexpression. Furthermore, downregulation of Foxc1 aggravated the inflammation, oxidative stress and apoptosis in 16HBE cells with CSE treatment.

SIGNIFICANCE

Overexpression of Foxc1 could prevent oxidative stress, inflammation responses and cell apoptosis and knockdown of Foxc1 has the opposite effect, suggesting that Foxc1 may be available for lung protection during COPD.

Paeonol attenuates acute lung injury by inhibiting HMGB1 in lipopolysaccharide-induced shock rats

High-mobility group box 1 (HMGB1) is a highly conserved DNA-binding nuclear protein that facilitates gene transcription and the DNA repair response. However, HMGB1 may be released by necrotic cells as well as activated monocytes and macrophages following stimulation with lipopolysaccharide (LPS), interleukin-1β (IL-1β), or tumor necrosis factor-α (TNF-α). Extracellular HMGB1 plays a critical role in the pathogenesis of acute lung injury (ALI) through activating the nuclear transcription factor κB (NF-κB) P65 pathway, thus, it may be a promising therapeutic target in shock-induced ALI. Paeonol (Pae) is the main active component of Paeonia suffruticosa, which has been used to inhibit the inflammatory response in traditional Chinese medicine. We have proven that Pae inhibits the expression, relocation and secretion of HMGB1 in vitro. However, the role of Pae in the HMGB1-NF-κB pathway remains unknown. We herein investigated the role of Pae in LPS-induced ALI rats. In this study, LPS induced a marked decrease in the mean arterial pressure (MAP) and survival rate (only 25% after 72 h), and induced severe pathological changes in the lung tissue of rats, which was accompanied by elevated expression of HMGB1 and its downstream protein NF-κB P65. Treatment with Pae significantly improved the survival rate (>60%) and MAP, and attenuated the pathological damage to the lung tissue in ALI rats. Western blotting revealed that Pae also inhibited the total expression of HMGB1, NF-κB P65 and TNF-α in the lung tissue of ALI rats. Moreover, Pae increased the expression of HMGB1 in the nucleus, inhibited the production of HMGB1 in the cytoplasm, and decreased the expression of P65 both in the nucleus and cytoplasm of lung tissue cells in LPS-induced ALI rats. The results were in agreement with those observed in the in vitro experiment. These findings indicate that Pae may be a potential treatment for ALI through its repression of the HMGB1-NF-κB P65 signaling pathway.

Activated Protein C has No Effect on Pulmonary Capillary Endothelial Function in Septic Patients with Acute Respiratory Distress Syndrome: Association of Endothelial Dysfunction with Mortality

INTRODUCTION

Pulmonary capillary endothelium-bound (PCEB) angiotensin-converting enzyme (ACE) activity is a direct and quantifiable index of pulmonary endothelial function that decreases early in acute respiratory distress syndrome (ARDS) and correlates with its severity. Endothelial dysfunction is a major pathophysiology that underlies sepsis-related ARDS. Recombinant human activated protein C (rhAPC), now withdrawn from the market, has been used in the recent past as an endothelial-protective treatment in patients with septic organ dysfunction.

METHODS

We investigated the effect of rhAPC on pulmonary endothelial function in 19 septic patients suffering from ARDS. Applying indicator-dilution type techniques, we measured single-pass transpulmonary percent metabolism (%M) and hydrolysis (v) of the synthetic, biologically inactive, and highly specific for ACE substrate, ³H-benzoyl-Phe-Ala-Pro (BPAP), under first-order reaction conditions, and calculated lung functional capillary surface area before and after treatment with rhAPC.

RESULTS

Pulmonary endothelium ACE activity was severely impaired in septic patients with ARDS, and was not affected by rhAPC treatment. Additionally, poor outcome was related to a more profound decrease in PCEB-ACE activity. Angiotensin-converting enzyme-substrate utilization was statistically significantly lower in non-survivors as compared to survivors, with no changes over time within each group: BPAP %M: 32.7 ± 3.4% at baseline to 25.6 ± 2.9% at day 7 in survivors versus 20.8 ± 2.8 to 15.5 ± 5%, respectively, in non-survivors (p = 0.044), while hydrolysis (v): 0.41 ± 0.06 at baseline to 0.30 ± 0.04 at day 7 in survivors compared to 0.24 ± 0.04 to 0.18 ± 0.06, respectively, in non-survivors (p = 0.049).

CONCLUSION

rhAPC administration in septic patients with ARDS did not improve PCEB-ACE activity indices. However, these indices might be useful in the early recognition of septic patients with ARDS at high risk of mortality.

Anticoagulant therapy in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) presents a complex pathophysiology characterized by pulmonary activated coagulation and reduced fibrinolysis. Despite advances in supportive care of this syndrome, morbidity and mortality remains high, leading to the need of novel therapies to combat this disease. Focus these therapies in the inhibition of ARDS development pathophysiology is essential. Beneficial effects of anticoagulants in ARDS have been proved in preclinical and clinical trials, thanks to its anticoagulant and anti-inflammatory properties. Moreover, local administration by nebulization in the alveolar compartment increases local efficacy and does not produce systemic bleeding. In this review the coagulation and fibrinolytic pathway and its pharmacological targets to treat ARDS are summarized.

Nebulized anticoagulants in lung injury in critically ill patients-an updated systematic review of preclinical and clinical studies

Pneumonia, inhalation trauma and acute respiratory distress syndrome (ARDS), typical causes of lung injury in critically ill patients, are all three characterized by dysregulated inflammation and coagulation in the lungs. Nebulized anticoagulants are thought to have beneficial effects as they could attenuate pulmonary coagulopathy and maybe even affect pulmonary inflammation. A systematic search of the medical literature was performed using terms referring to aspects of the condition ('pneumonia', 'inhalation trauma' and 'ARDS'), the intervention ('nebulized', 'vaporized', and 'aerosolized') and anticoagulants limited to agents that are commercially available and frequently given or tested in critically ill patients ['heparin', 'danaparoid', 'activated protein C' (APC), 'antithrombin' (AT) and 'tissue factor pathway inhibitor' (TFPI)]. The systematic search identified 16 articles reporting on preclinical studies and 11 articles reporting on human trials. All nebulized anticoagulants attenuate pulmonary coagulopathy in preclinical studies using various models for lung injury, but the effects on inflammation are less consistent. Nebulized heparin, danaparoid and TFPI, but not APC and AT also reduced systemic coagulation. Nebulized heparin in lung injury patients shows contradictory results, and there is concern over systemic side effects of this strategy. Future studies need to focus on the way to nebulize anticoagulants, as well as on efficient but safe dosages, and other side effects.

Chloroquine attenuates paraquat-induced lung injury in mice by altering inflammation, oxidative stress and fibrosis

Paraquat is one of the most extensively used herbicides and has high toxicity for humans and animals. However, there is no effective treatment for paraquat poisoning. The aim of the present study was to evaluate the effects of chloroquine on paraquat-induced lung injury in mice. Mice received a single intraperitoneal injection of paraquat and a daily intraperitoneal injection of the indicated dosages of chloroquine or dexamethasone. The histological changes, inflammation and oxidative stress in the lungs were examined at day 3, and the degree of pulmonary fibrosis was examined at day 28. H&E staining showed that chloroquine markedly attenuated lung injury induced by paraquat. In addition, the inflammatory responses induced by paraquat were inhibited after treatment with chloroquine, as indicated by the decreased number of leukocytes, the reduced levels of TNF-α, IL-1β and IL-6 in the bronchoalveolar lavage fluid, the reduced NO content, and downregulation of iNOS expression in lung tissues. No different effect was found between high-dose chloroquine and dexamethasone. Additionally, the treatment with chloroquine increased the activity of SOD and decreased the level of MDA in the lung tissues. The expressions of the anti-oxidative proteins, Nrf2, HO-1 and NQO1, were also upregulated by chloroquine treatment. The high-dose chloroquine was more effective than dexamethasone in its anti-oxidation ability. Finally, the results of Masson's staining illustrated that chloroquine markedly attenuated fibrosis in the paraquat-exposed lungs. Immunohistochemistry staining showed that the expressions of the pro-fibrotic proteins TGF-β and α-SMA were downregulated after treatment with chloroquine. In conclusion, chloroquine effectively attenuated paraquat-induced lung injury in mice.

Absence of the Adenosine A2A Receptor Confers Pulmonary Arterial Hypertension Through RhoA/ROCK Signaling Pathway in Mice

Numerous evidence suggests that RhoA/Rho kinase (ROCK) signaling pathway plays an important role in the pathogenesis of pulmonary arterial hypertension (PAH), but little is known about its effects on the development of PAH in mice with absence of the adenosine A2A receptor (A2AR). Eight A2AR knockout (KO) and 8 wild-type mice were used. Morphometric analysis of pulmonary arterioles included right ventricle/left ventricle plus ventricular septum (Fulton index), vessel wall thickness/total vascular diameter (WT%), and vessel wall area/total vascular area (WA%). The expression of RhoA and ROCK1 mRNA was determined by real-time polymerase chain reaction. The expression of RhoA, ROCK1, and phosphorylation of myosin phosphatase target subunit 1 proteins in pulmonary tissue was tested by Western blot. The position of ROCK1 protein was evaluated by immunohistochemistry. Compared with wild-type mice, A2AR KO mice displayed (1) increased Fulton index, WT%, and WA% (P < 0.01); (2) increased mRNA expression of RhoA and ROCK1 (each P < 0.05); (3) increased protein expression of RhoA, ROCK1, and phosphorylation of myosin phosphatase target subunit 1 (each P < 0.01); (4) increased location of ROCK1 protein in endothelial and smooth muscle cells of pulmonary artery, bronchial, and alveolar epithelial cells. Activation of RhoA/ROCK signaling pathway may cause pulmonary vascular constriction, pulmonary artery remodeling, and PAH in adenosine A2A receptor KO mice.

Autotaxin and Endotoxin-Induced Acute Lung Injury

Acute Lung Injury (ALI) is a life-threatening, diffuse heterogeneous lung injury characterized by acute onset, pulmonary edema and respiratory failure. Lipopolysaccharide (LPS) is a common cause of both direct and indirect lung injury and when administered to a mouse induces a lung phenotype exhibiting some of the clinical characteristics of human ALI. Here, we report that LPS inhalation in mice results in increased bronchoalveolar lavage fluid (BALF) levels of Autotaxin (ATX, Enpp2), a lysophospholipase D largely responsible for the conversion of lysophosphatidylcholine (LPC) to lysophosphatidic acid (LPA) in biological fluids and chronically inflamed sites. In agreement, gradual increases were also detected in BALF LPA levels, following inflammation and pulmonary edema. However, genetic or pharmacologic targeting of ATX had minor effects in ALI severity, suggesting no major involvement of the ATX/LPA axis in acute inflammation. Moreover, systemic, chronic exposure to increased ATX/LPA levels was shown to predispose to and/or to promote acute inflammation and ALI unlike chronic inflammatory pathophysiological situations, further suggesting a differential involvement of the ATX/LPA axis in acute versus chronic pulmonary inflammation.

Recombinant human brain natriuretic peptide ameliorates trauma-induced acute lung injury via inhibiting JAK/STAT signaling pathway in rats

BACKGROUND

JAK/STAT signal pathway plays an important role in the inflammation process of acute lung injury (ALI). This study aimed to investigate the correlation between recombinant human brain natriuretic peptide (rhBNP) and the JAK/STAT signaling pathway and to explore the protective mechanism of rhBNP against trauma-induced ALI.

METHODS

The arterial partial pressure in oxygen, lung wet-dry weight ratios, protein content in bronchoalveolar lavage fluid, the histopathologic of the lung, as well as the protein expressions of STAT1, JAK2, and STAT3 were detected.

RESULTS

Sprague-Dawley rats were randomly divided into five groups: a control group, a sham-operated group, an ALI group, an ALI + rhBNP group, and an ALI + AG490 group. At 4 hours, 12 hours, 1 day, 3 days, and 7 days after injury, injured lung specimens were harvested. rhBNP pretreatment significantly ameliorated hypoxemia and histopathologic changes and alleviated pulmonary edema in trauma-induced ALI rats. rhBNP pretreatment reduced the phosphorylated protein and total protein level of STAT1. Similarly to JAK-specific inhibitor AG490, rhBNP was shown to significantly inhibit the phosphorylation of JAK2 and STAT3 in rats with trauma-induced ALI.

CONCLUSION

Our experimental findings indicated that rhBNP can protect rats against trauma-induced ALI and that its underlying mechanism may be related to the inhibition of JAK/STAT signaling pathway activation.

Inhibition of HMGCoA reductase by simvastatin protects mice from injurious mechanical ventilation

BACKGROUND

Mortality from severe acute respiratory distress syndrome exceeds 40% and there is no available pharmacologic treatment. Mechanical ventilation contributes to lung dysfunction and mortality by causing ventilator-induced lung injury. We explored the utility of simvastatin in a mouse model of severe ventilator-induced lung injury.

METHODS

Male C57BL6 mice (n = 7/group) were pretreated with simvastatin or saline and received protective (8 mL/kg) or injurious (25 mL/kg) ventilation for four hours. Three doses of simvastatin (20 mg/kg) or saline were injected intraperitoneally on days -2, -1 and 0 of the experiment. Lung mechanics, (respiratory system elastance, tissue damping and airway resistance), were evaluated by forced oscillation technique, while respiratory system compliance was measured with quasi-static pressure-volume curves. A pathologist blinded to treatment allocation scored hematoxylin-eosin-stained lung sections for the presence of lung injury. Pulmonary endothelial dysfunction was ascertained by bronchoalveolar lavage protein content and lung tissue expression of endothelial junctional protein Vascular Endothelial cadherin by immunoblotting. To assess the inflammatory response in the lung, we determined bronchoalveolar lavage fluid total cell content and neutrophil fraction by microscopy and staining in addition to Matrix-Metalloprotease-9 by ELISA. For the systemic response, we obtained plasma levels of Tumor Necrosis Factor-α, Interleukin-6 and Matrix-Metalloprotease-9 by ELISA. Statistical hypothesis testing was undertaken using one-way analysis of variance and Tukey's post hoc tests.

RESULTS

Ventilation with high tidal volume (HVt) resulted in significantly increased lung elastance by 3-fold and decreased lung compliance by 45% compared to low tidal volume (LVt) but simvastatin abrogated lung mechanical alterations of HVt. Histologic lung injury score increased four-fold by HVt but not in simvastatin-pretreated mice. Lavage pleocytosis and neutrophilia were induced by HVt but were significantly attenuated by simvastatin. Microvascular protein permeability increase 20-fold by injurious ventilation but only 4-fold with simvastatin. There was a 3-fold increase in plasma Tumor Necrosis Factor-α, a 7-fold increase in plasma Interleukin-6 and a 20-fold increase in lavage fluid Matrix-Metalloprotease-9 by HVt but simvastatin reduced these levels to control. Lung tissue vascular endothelial cadherin expression was significantly reduced by injurious ventilation but remained preserved by simvastatin.

CONCLUSION

High-dose simvastatin prevents experimental hyperinflation lung injury by angioprotective and anti-inflammatory effects.

Protein C and acute inflammation: a clinical and biological perspective

The protein C system plays an active role in modulating severe systemic inflammatory processes such as sepsis, trauma, and acute respiratory distress syndrome (ARDS) via its anticoagulant and anti-inflammatory properties. Plasma levels of activated protein C (aPC) are lower than normal in acute inflammation in humans, except early after severe trauma when high plasma levels of aPC may play a mechanistic role in the development of posttraumatic coagulopathy. Thus, following positive results of preclinical studies, a clinical trial (PROWESS) with high continuous doses of recombinant human aPC given for 4 days demonstrated a survival benefit in patients with severe sepsis. This result was not confirmed by subsequent clinical trials, including the recently published PROWESS-SHOCK trial in patients with septic shock and a phase II trial with patients with nonseptic ARDS. A possible explanation for the major difference in outcome between PROWESS and PROWESS-SHOCK trials is that lung-protective ventilation was used for the patients included in the recent PROWESS-SHOCK, but not in the original PROWESS trial. Since up to 75% of sepsis originates from the lung, aPC treatment may not have added enough to the beneficial effect of lung-protective ventilation to show lower mortality. Thus whether aPC will continue to be used to modulate the acute inflammatory response in humans remains uncertain. Because recombinant human aPC has been withdrawn from the market, a better understanding of the complex interactions between coagulation and inflammation is needed before considering the development of new drugs that modulate both coagulation and acute inflammation in humans.

Caveolar uptake and endothelial-protective effects of nanostructured lipid carriers in acid aspiration murine acute lung injury

PURPOSE

Nanostructured lipid carriers (NLC), nanosized phospholipids/triglyceride particles developed for drug delivery, are considered biologically inactive. We assessed the efficacy of unloaded NLC as experimental treatment for acute lung injury (ALI).

METHODS

To induce ALI, C57Black/6 male mice received intratracheal injections of HCl or saline; A single dose of 16 mg/Kg NLC or saline was injected intravenously concomitantly with HCl challenge. NLC uptake mechanisms and effects on endothelial permeability and signaling were studied in cultured endothelial cells and neutrophils.

RESULTS

NLC pre-treatment attenuated pulmonary microvascular protein leak, airspace inflammatory cells, thrombin proteolytic activity and histologic lung injury score 24 h post insult. Using fluorescence measurements and flow cytometry in mouse lung microvascular endothelial cell culture homogenates, we determined that NLC rendered fluorescent by curcumin labeling are taken up by endothelial cells from mice expressing caveolin-1, the coat protein of caveolar endocytic vesicles, but not from caveolin-1 gene-disrupted mice, which lack caveolae. In contrast, conventional emulsions (CE), consisting of larger particles, were not incorporated. In addition, NLC pre-treatment of cultured human lung microvascular endothelial cells abrogated thrombin-induced activation of p44/42, albumin permeability response, actin cytoskeletal remodeling and interleukin-6 production. Finally, NLC but not CE abrogated lipopolysaccharide-triggered interleukin-8 release.

CONCLUSIONS

NLC are engulfed by endothelial caveolae and possess endothelial-protective effects. These novel properties may be of potential utility in ALI.

Activated protein C in the treatment of acute lung injury and acute respiratory distress syndrome

BACKGROUND

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) frequently necessitate mechanical ventilation in the intensive care unit. The syndromes have a high mortality rate and there is at present no treatment specifically directed at the underlying pathogenesis. Central in the pathophysiology of ALI/ARDS is alveolocapillary inflammation leading to permeability edema. As a result of the crosstalk between inflammation and coagulation, activation of proinflammatory and procoagulant/antifibrinolytic pathways contributes to disruption of the endothelial barrier. Protein C (PC) plays a central role in maintaining the equilibrium between coagulation and inflammation. Additionally, natural anticoagulants, such as PC, are depleted, both in blood as well as in the lung. Therefore, the PC system is of interest as a therapeutic target in patients with ALI/ARDS.

METHOD

This review is based on a Medline search of relevant basic and clinical studies.

OBJECTIVE

It discusses the potential role of activated PC in modulating the proinflammatory/procoagulant state for enhancing endothelial barrier function in animal models and human ALI/ARDS.

Barrier-protective effects of activated protein C in human alveolar epithelial cells

Acute lung injury (ALI) is a clinical manifestation of respiratory failure, caused by lung inflammation and the disruption of the alveolar-capillary barrier. Preservation of the physical integrity of the alveolar epithelial monolayer is of critical importance to prevent alveolar edema. Barrier integrity depends largely on the balance between physical forces on cell-cell and cell-matrix contacts, and this balance might be affected by alterations in the coagulation cascade in patients with ALI. We aimed to study the effects of activated protein C (APC) on mechanical tension and barrier integrity in human alveolar epithelial cells (A549) exposed to thrombin. Cells were pretreated for 3 h with APC (50 µg/ml) or vehicle (control). Subsequently, thrombin (50 nM) or medium was added to the cell culture. APC significantly reduced thrombin-induced cell monolayer permeability, cell stiffening, and cell contraction, measured by electrical impedance, optical magnetic twisting cytometry, and traction microscopy, respectively, suggesting a barrier-protective response. The dynamics of the barrier integrity was also assessed by western blotting and immunofluorescence analysis of the tight junction ZO-1. Thrombin resulted in more elongated ZO-1 aggregates at cell-cell interface areas and induced an increase in ZO-1 membrane protein content. APC attenuated the length of these ZO-1 aggregates and reduced the ZO-1 membrane protein levels induced by thrombin. In conclusion, pretreatment with APC reduced the disruption of barrier integrity induced by thrombin, thus contributing to alveolar epithelial barrier protection.

Acid-induced acute lung injury in mice is associated with P44/42 and c-Jun N-terminal kinase activation and requires the function of tumor necrosis factor α receptor I

Aspiration of hydrochloric acid (HCl)-containing gastric juice leads to acute lung injury (ALI) and hypoxemic respiratory failure due to an exuberant inflammatory response associated with pulmonary edema from increased vascular and epithelial permeability. The aim of this study was to determine the role and signaling mechanisms of tumor necrosis factor α (TNF-α) in experimental ALI from HCl aspiration using a combination of genetic animal models and pharmacologic inhibition strategies. To this end, HCl was instilled intratracheally to mice, followed by respiratory system elastance measurement, bronchoalveolar lavage, and lung tissue harvesting 24 h after injection. Hydrochloric acid instillation induced an inflammatory response in the lungs of wild-type mice, evidenced as increased bronchoalveolar lavage total cells, neutrophils, and total protein; histologic lung injury score; and respiratory system elastance, whereas TNF-α receptor I mRNA levels were maintained. These alterations could be prevented by pretreatment with etanercept or genetic deletion of the 55-kd TNF-α receptor I, but not by deletion of the TNF-α gene. Hydrochloric acid induced a 6-fold increase in apoptotic, caspase 3-positive cells in lung sections from wild-type mice, which was abrogated in mice lacking TNF-α receptor I. In immunoblotting and immunohistochemistry studies, HCl stimulated signaling via p44/42 and c-Jun N-terminal kinase, which was blocked in TNF-α receptor I knockout mice. In conclusion, ALI induced by HCl requires TNF-α receptor I function and associates with activation of downstream proinflammatory signaling pathways p44/42 and c-Jun N-terminal kinase.

Bronchoalveolar hemostasis in lung injury and acute respiratory distress syndrome

Enhanced intrapulmonary fibrin deposition as a result of abnormal broncho-alveolar fibrin turnover is a hallmark of acute respiratory distress syndrome (ARDS), pneumonia and ventilator-induced lung injury (VILI), and is important to the pathogenesis of these conditions. The mechanisms that contribute to alveolar coagulopathy are localized tissue factor-mediated thrombin generation, impaired activity of natural coagulation inhibitors and depression of bronchoalveolar urokinase plasminogen activator-mediated fibrinolysis, caused by the increase of plasminogen activator inhibitors. There is an intense and bidirectional interaction between coagulation and inflammatory pathways in the bronchoalveolar compartment. Systemic or local administration of anticoagulant agents (including activated protein C, antithrombin and heparin) and profibrinolytic agents (such as plasminogen activators) attenuate pulmonary coagulopathy. Several preclinical studies show additional anti-inflammatory effects of these therapies in ARDS and pneumonia.

Nebulized anticoagulants for acute lung injury - a systematic review of preclinical and clinical investigations

Background

Data from interventional trials of systemic anticoagulation for sepsis inconsistently suggest beneficial effects in case of acute lung injury (ALI). Severe systemic bleeding due to anticoagulation may have offset the possible positive effects. Nebulization of anticoagulants may allow for improved local biological availability and as such may improve efficacy in the lungs and lower the risk of systemic bleeding complications.

Method

We performed a systematic review of preclinical studies and clinical trials investigating the efficacy and safety of nebulized anticoagulants in the setting of lung injury in animals and ALI in humans.

Results

The efficacy of nebulized activated protein C, antithrombin, heparin and danaparoid has been tested in diverse animal models of direct (for example, pneumonia-, intra-pulmonary lipopolysaccharide (LPS)-, and smoke inhalation-induced lung injury) and indirect lung injury (for example, intravenous LPS- and trauma-induced lung injury). Nebulized anticoagulants were found to have the potential to attenuate pulmonary coagulopathy and frequently also inflammation. Notably, nebulized danaparoid and heparin but not activated protein C and antithrombin, were found to have an effect on systemic coagulation. Clinical trials of nebulized anticoagulants are very limited. Nebulized heparin was found to improve survival of patients with smoke inhalation-induced ALI. In a trial of critically ill patients who needed mechanical ventilation for longer than two days, nebulized heparin was associated with a higher number of ventilator-free days. In line with results from preclinical studies, nebulization of heparin was found to have an effect on systemic coagulation, but without causing systemic bleedings.

Conclusion

Local anticoagulant therapy through nebulization of anticoagulants attenuates pulmonary coagulopathy and frequently also inflammation in preclinical studies of lung injury. Recent human trials suggest nebulized heparin for ALI to be beneficial and safe, but data are very limited.

Activated protein C inhalation: a novel therapeutic strategy for acute lung injury

Acute lung injury (ALI) is a critical illness syndrome with a mortality rate of 25–40%. Despite recent advances of our understanding of the pathophysiology of ALI, no pharmacologic therapies have been proven effective. The key pathogenesis of ALI is the activation of the coagulation cascade and impaired fibrinolysis, resulting in extensive fibrin and hyaline membrane deposition. Activated protein C (APC), an endogenous protein that promotes fibrinolysis and inhibits thrombosis, can modulate the coagulation and inflammation associated with ALI. It is therefore reasonable to suggest that preventing the progression of pulmonary coagulopathy, by restoring normal intraalveolar levels of protein C, will be of therapeutic benefit to patients with ALI. However, a recent clinical trial demonstrated that APC did not improve outcomes from ALI, raising the possibility that the method of APC administration, intravenous infusion or inhalation, may influence the outcomes. In this article we propose the hypothesis that APC inhalation might be a promising and novel choice in the treatment of ALI.

Pretreatment with atorvastatin attenuates lung injury caused by high-stretch mechanical ventilation in an isolated rabbit lung model

OBJECTIVE

We hypothesized that pretreatment with atorvastatin improves alveolar capillary permeability and hemodynamics and, thus, confers protection against lung injury caused by high-stretch mechanical ventilation.

METHODS

Twenty-four isolated sets of normal rabbit lungs were utilized. Treated animals received atorvastatin (20 mg/kg body weight/day by mouth) for 3 days before surgery. Lungs were perfused constantly (300 mL/min) and ventilated for 1 hr with pressure-control ventilation at either 23 (high pressure; resulting in tidal volume approximately 22 mL/kg) or 11 (low pressure; tidal volume approximately 10 mL/kg) cm H2O peak inspiratory pressure and positive end-expiratory pressure of 3 cm H2O. Four groups were examined: high pressure-no statin, high pressure-statin pretreatment, low pressure-no statin, and low pressure-statin pretreatment.

RESULTS

The high-pressure-no statin group sustained more damage than the low-pressure groups. In high-pressure groups, lungs of statin-pretreated vs. no statin-pretreated animals sustained a significantly lower increase in ultrafiltration coefficient (an accurate marker of alveolar capillary permeability; high-pressure-statin pretreatment vs. high-pressure-no statin, -0.013 +/- 0.017 g/min/mm Hg/100g vs. 1.723 +/- 0.495 g/min/mm Hg/100g; p < .001), lower weight gain (i.e., less edema formation; 4.62 +/- 1.50 grams vs. 17.75 +/- 4.71 grams; p = .005), improved hemodynamics (i.e., lower increase in mean pulmonary artery pressure; 0.56 +/- 0.51 mm Hg vs. 5.62 +/- 1.52 mm Hg; p = .04), lower protein concentration in bronchoalveolar lavage fluid (p < .001), and fewer histologic lesions (p = .013). Apoptosis of lung parenchyma cells was not different (p = .97). There was no difference between low-pressure-statin pretreatment and low-pressure-no statin groups regarding these outcomes.

CONCLUSION

In this model, atorvastatin improves alveolar capillary permeability and hemodynamics and, thus, attenuates lung injury caused by high-stretch mechanical ventilation.

Inhaled activated protein C: a new therapy for the prevention of ventilator-induced lung injury?

Systemic administration of activated protein C (APC) has been shown to reduce pulmonary inflammation in preclinical models of acute lung injury. However, there is only limited information concerning the effects of inhaled APC in modulating the severity of pulmonary inflammation. In a study reported in this issue of Critical Care, Maniatis and colleagues show that pretreatment of mice with inhaled APC is protective against ventilator-induced lung injury. While the mechanisms responsible for this effect require additional elucidation, inhaled APC appears to be a potentially useful intervention in diminishing the severity of ventilator-induced lung injury and other forms of acute lung injury.

Inhaled activated protein C protects mice from ventilator-induced lung injury

INTRODUCTION

Activated Protein C (APC), an endogenous anticoagulant, improves tissue microperfusion and endothelial cell survival in systemic inflammatory states such as sepsis, but intravenous administration may cause severe bleeding. We have thus addressed the role of APC delivered locally by inhalation in preventing acute lung injury from alveolar overdistention and the subsequent ventilator-induced lung injury (VILI). We also assessed the effects of APC on the activation status of Extracellular- Regulated Kinase 1/2 (ERK) pathway, which has been shown to be involved in regulating pulmonary responses to mechanical stretch.

METHODS

Inhaled APC (12.5 microg drotrecogin-alpha x 4 doses) or saline was given to tracheotomized C57/Bl6 mice starting 20 min prior to initiation of injurious mechanical ventilation with tidal volume 25 mL/Kg for 4 hours and then hourly thereafter; control groups receiving inhaled saline were ventilated with 8 mL/Kg for 30 min or 4 hr. We measured lung function (respiratory system elastance H), arterial blood gases, surrogates of vascular leak (broncho-alveolar lavage (BAL) total protein and angiotensin-converting enzyme (ACE)-activity), and parameters of inflammation (BAL neutrophils and lung tissue myeloperoxidase (MPO) activity). Morphological alterations induced by mechanical ventilation were examined in hematoxylin-eosin lung tissue sections. The activation status of ERK was probed in lung tissue homogenates by immunoblotting and in paraffin sections by immunohistochemistry. The effect of APC on ERK signaling downstream of the thrombin receptor was tested on A549 human lung epithelial cells by immunoblotting. Statistical analyses were performed using ANOVA with appropriate post-hoc testing.

RESULTS

In mice subjected to VILI without APC, we observed hypoxemia, increased respiratory system elastance and inflammation, assessed by BAL neutrophil counts and tissue MPO activity. BAL total protein levels and ACE activity were also elevated by VILI, indicating compromise of the alveolo-capillary barrier. In addition to preserving lung function, inhaled APC prevented endothelial barrier disruption and attenuated hypoxemia and the inflammatory response. Mechanistically, we found a strong activation of ERK in lung tissues by VILI, which was prevented by APC, suggestive of pathogenetic involvement of the Mitogen-Activated Kinase pathway. In cultured human lung epithelial cells challenged by thrombin, APC abrogated the activation of ERK and its downstream effector, cytosolic Phospholipase A2.

CONCLUSIONS

Topical application of APC by inhalation may effectively reduce lung injury induced by mechanical ventilation in mice.

NAC is associated with additional alleviation of lung injury induced by invasive pulmonary aspergillosis in a neutropenic model

AIM

Neutropenic individuals are at high risk for invasive pulmonary aspergillosis (IPA), a life-threatening infection. To evaluate the therapeutic potential of antioxidants, IPA was induced in neutropenic mice and the effect of N-acetyl-l-cysteine (NAC) on oxidative stress levels and lung injury was analyzed.

METHODS

Mice were pretreated with three daily intraperitoneal injections of 150 mg/kg cyclophosphamide, followed by intratracheal inoculation with 4.5x10(6) conidia of Aspergillus fumigatus. The infected mice were then randomly assigned to an amphotericin B (AMB) group, an AMB plus NAC group, or an untreated control (C) group. In each group, the duration of treatment was 24, 48, or 72 h, and activities such as appearance, feeding, and dermal temperature were observed throughout the experiment. Sera and lung tissues were collected and analyzed by quantitative enzyme-linked immunosorbent assay (ELISA) for total protein, superoxide dismutase (SOD), malondialdehyde (MDA), tumor necrosis factor-alpha (TNF-alpha), and interleukin-10 (IL-10) levels. The wet/dry weight ratio of the lung was also calculated and lung sections were stained with hematoxylin-eosin for pathological examination and with methenamine silver stain for fungus detection.

RESULTS

Compared with the mice untreated with NAC, mice in the AMB plus NAC group had increased SOD and reduced MDA levels both systemically and locally at 24, 48, and 72 h after inoculation with conidia. NAC treatment also decreased the pulmonary protein content at 48 and 72 h and the lung wet/dry weight ratio at 24 and 48 h. Additionally, NAC enhanced pulmonary production of TNF-alpha and IL-10 at 24 h and 48 h.

CONCLUSION

In combination with antifungal therapy, NAC treatment can alleviate oxidative stress and lung injury associated with IPA in neutropenic mice.Acta Pharmacologica Sinica (2009) 30: 980-986; doi: 10.1038/aps.2009.83.

Protective mechanisms of activated protein C in severe inflammatory disorders

The protein C system is an important natural anticoagulant mechanism mediated by activated protein C (APC) that regulates the activity of factors VIIIa and Va. Besides well-defined anticoagulant properties, APC also demonstrates anti-inflammatory, anti-apoptotic and endothelial barrier-stabilizing effects that are collectively referred to as the cytoprotective effects of APC. Many of these beneficial effects are mediated through its co-receptor endothelial protein C receptor, and the protease-activated receptor 1, although exact mechanisms remain unclear and are likely pleiotropic in nature. Increased insight into the structure-function relationships of APC facilitated design of APC variants that conserve cytoprotective effects and reduce anticoagulant features, thereby attenuating the risk of severe bleeding with APC therapy. Impairment of the protein C system plays an important role in acute lung injury/acute respiratory distress syndrome and severe sepsis. The pathophysiology of both diseases states involves uncontrolled inflammation, enhanced coagulation and compromised fibrinolysis. This leads to microvascular thrombosis and organ injury. Administration of recombinant human APC to correct the dysregulated protein C system reduced mortality in severe sepsis patients (PROWESS trial), which stimulated further research into its mechanisms of action. Several other clinical trials evaluating recombinant human APC have been completed, including studies in children and less severely ill adults with sepsis as well as a study in acute lung injury. On the whole, these studies have not supported the use of APC in these populations and challenge the field of APC research to search for additional answers.

Alterations in the human lung proteome with lipopolysaccharide

Background

Recombinant human activated protein C (rhAPC) is associated with improved survival in high-risk patients with severe sepsis; however, the effects of both lipopolysaccharide (LPS) and rhAPC on the bronchoalveolar lavage fluid (BALF) proteome are unknown.

Methods

Using differential in gel electrophoresis (DIGE) we identified changes in the BALF proteome from 10 healthy volunteers given intrapulmonary LPS in one lobe and saline in another lobe. Subjects were randomized to pretreatment with saline or rhAPC.

Results

An average of 255 protein spots were detected in each proteome. We found 31 spots corresponding to 8 proteins that displayed abundance increased or decreased at least 2-fold after LPS. Proteins that decreased after LPS included surfactant protein A, immunoglobulin J chain, fibrinogen-γ, α₁-antitrypsin, immunoglobulin, and α₂-HS-glycoprotein. Haptoglobin increased after LPS-treatment. Treatment with rhAPC was associated with a larger relative decrease in immunoglobulin J chain, fibrinogen-γ, α₁-antitrypsin, and α₂-HS-glycoprotein.

Conclusion

Intrapulmonary LPS was associated with specific protein changes suggesting that the lung response to LPS is more than just a loss of integrity in the alveolar epithelial barrier; however, pretreatment with rhAPC resulted in minor changes in relative BALF protein abundance consistent with its lack of affect in ALI and milder forms of sepsis.

Short-term administration of a high oxygen concentration is not injurious in an ex-vivo rabbit model of ventilator-induced lung injury

BACKGROUND

Mechanical ventilation and administration of a high oxygen concentration are simultaneously used in the management of respiratory failure. We conducted this study to evaluate the effect of a high inspired oxygen concentration on ventilator-induced lung injury.

METHODS

Forty sets of isolated/perfused rabbit lungs were randomized for 60 min of pressure-control ventilation at a plateau inspiratory pressure of 25 or 15 cm H(2)O and positive end-expiratory pressure of 3 cm H(2)O while receiving 100% or 21% O(2). The temperature, pH, and partial pressure of CO(2) in the perfusate were maintained the same in all groups (n = 10 for each group). The outcome measures used to assess lung injury included: the change in weight gain and ultrafiltration coefficient, the frequency of vascular failure, the histological lesions and the concentration of tumor necrosis factor-alpha and malondialdehyde in the bronchoalveolar lavage fluid.

RESULTS

The two groups ventilated at the higher inspiratory pressure/tidal volume experienced greater weight gain and increases in the ultrafiltration coefficient, more frequently suffered vascular failure, and presented higher composite scores of histological damage than the two groups ventilated at the lower inspiratory pressure/tidal volume. Hyperoxia was not found to further increase any of the monitored markers of lung injury. No difference was noticed among the four experimental groups in the alveolar lavage fluid levels of tumor necrosis factor-alpha or malondialdehyde.

CONCLUSIONS

These findings suggest that short-term administration of a high oxygen concentration is not a major determinant of ventilator-induced lung injury in this experimental model.

A review of pulmonary coagulopathy in acute lung injury, acute respiratory distress syndrome and pneumonia

Enhanced bronchoalveolar coagulation is a hallmark of many acute inflammatory lung diseases such as acute lung injury, acute respiratory distress syndrome and pneumonia. Intervention with natural anticoagulants in these diseases has therefore become a topic of interest. Recently, new data on the role of pulmonary coagulation and inflammation has become available. The aim of this review is to summarize these findings. Furthermore, the results of anticoagulant therapeutic interventions in these disorders are discussed.

New therapeutic applications for the anticoagulant, activated protein C

BACKGROUND

Activated protein C (APC) is derived from its precursor, protein C (PC). Originally thought to be synthesised exclusively by the liver, recent reports have shown that PC is also produced by endothelial cells, smooth muscle cells, keratinocytes and some leukocytes.

OBJECTIVE

To provide an update on the emerging therapeutic effects of APC.

RESULTS/CONCLUSION

APC functions as an anticoagulant with cytoprotective, anti-inflammatory and antiapoptotic properties. In vitro and preclinical data have revealed that APC exerts its protective effects via an intriguing mechanism requiring endothelial protein C receptor and protease activated receptor-1. Approved as a therapeutic agent for severe sepsis, APC is emerging as a potential treatment for a number of autoimmune and inflammatory diseases including spinal cord injury, asthma, chronic wounds and possibly rheumatoid arthritis. The future therapeutic uses of APC look very promising.

Endothelial pathomechanisms in acute lung injury

Acute lung injury (ALI) and its most severe extreme the acute respiratory distress syndrome (ARDS) refer to increased-permeability pulmonary edema caused by a variety of pulmonary or systemic insults. ALI and in particular ARDS, are usually accompanied by refractory hypoxemia and the need for mechanical ventilation. In most cases, an exaggerated inflammatory and pro-thrombotic reaction to an initial stimulus, such as systemic infection, elicits disruption of the alveolo-capillary membrane and vascular fluid leak. The pulmonary endothelium is a major metabolic organ promoting adequate pulmonary and systemic vascular homeostasis, and a main target of circulating cells and humoral mediators under injury; pulmonary endothelium is therefore critically involved in the pathogenesis of ALI. In this review we will discuss mechanisms of pulmonary endothelial dysfunction and edema generation in the lung with special emphasis on the interplay between the endothelium, the immune and hemostatic systems, and highlight how these principles apply in the context of defined disorders and specific insults implicated in ALI pathogenesis.

The endothelium in acute lung injury/acute respiratory distress syndrome

PURPOSE OF REVIEW

Since pulmonary edema from increased endothelial permeability is the hallmark of acute lung injury, a frequently encountered entity in critical care medicine, the study of endothelial responses in this setting is crucial to the development of effective endothelial-targeted treatments.

RECENT FINDINGS

From the enormous amount of research in the field of endothelial pathophysiology, we have focused on work delineating endothelial alterations elicited by noxious stimuli implicated in acute lung injury. The bulk of the material covered deals with molecular and cellular aspects of the pathogenesis, reflecting current trends in the published literature. We initially discuss pathways of endothelial dysfunction in acute lung injury and then cover the mechanisms of endothelial protection. Several experimental treatments in animal models are presented, which aid in the understanding of the disease pathogenesis and provide evidence for potentially useful therapies.

SUMMARY

Mechanistic studies have delivered several interventions, which are effective in preventing and treating experimental acute lung injury and have thus provided objectives for translational studies. Some of these modalities may evolve into clinically useful tools in the treatment of this devastating illness.