Amifostine reduces lung vascular permeability via suppression of inflammatory signalling

Amifostine ameliorates bleomycin-induced murine pulmonary fibrosis via NAD+/SIRT1/AMPK pathway-mediated effects on mitochondrial function and cellular metabolism

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a devastating chronic lung disease characterized by irreversible scarring of the lung parenchyma. Despite various interventions aimed at mitigating several different molecular aspects of the disease, only two drugs with limited clinical efficacy have so far been approved for IPF therapy.

OBJECTIVE

We investigated the therapeutic efficacy of amifostine, a detoxifying drug clinically used for radiation-caused cytotoxicity, in bleomycin-induced murine pulmonary fibrosis.

METHODS

C57BL6/J mice were intratracheally instilled with 3 U/kg of bleomycin. Three doses of amifostine (WR-2721, 200 mg/kg) were administered intraperitoneally on days 1, 3, and 5 after the bleomycin challenge. Bronchoalveolar lavage fluid (BALF) was collected on day 7 and day 21 for the assessment of lung inflammation, metabolites, and fibrotic injury. Human fibroblasts were treated in vitro with transforming growth factor beta 1 (TGF-β1), followed by amifostine (WR-1065, 1-4 µg/mL) treatment. The effects of TGF-β1 and amifostine on the mitochondrial production of reactive oxygen species (ROS) were assessed by live cell imaging of MitoSOX. Cellular metabolism was assessed by the extracellular acidification rate (ECAR), the oxygen consumption rate (OCR), and the concentrations of various energy-related metabolites as measured by mass spectrum (MS). Western blot analysis was performed to investigate the effect of amifostine on sirtuin 1 (SIRT1) and adenosine monophosphate activated kinase (AMPK).

RESULTS

Three doses of amifostine significantly attenuated lung inflammation and pulmonary fibrosis. Pretreatment and post-treatment of human fibroblast cells with amifostine blocked TGF-β1-induced mitochondrial ROS production and mitochondrial dysfunction in human fibroblast cells. Further, treatment of fibroblasts with TGF-β1 shifted energy metabolism away from mitochondrial oxidative phosphorylation (OXPHOS) and towards glycolysis, as observed by an altered metabolite profile including a decreased ratio of NAD + /NADH and increased lactate concentration. Treatment with amifostine significantly restored energy metabolism and activated SIRT1, which in turn activated AMPK. The activation of AMPK was required to mediate the effects of amifostine on mitochondrial homeostasis and pulmonary fibrosis. This study provides evidence that repurposing of the clinically used drug amifostine may have therapeutic applications for IPF treatment.

CONCLUSION

Amifostine inhibits bleomycin-induced pulmonary fibrosis by restoring mitochondrial function and cellular metabolism.

Monocyte Tissue Factor Expression: Lipopolysaccharide Induction and Roles in Pathological Activation of Coagulation

The coagulation system is a part of the mammalian host defense system. Pathogens and pathogen components, such as bacterial lipopolysaccharide (LPS), induce tissue factor (TF) expression in circulating monocytes that then activates the coagulation protease cascade. Formation of a clot limits dissemination of pathogens, enhances the recruitment of immune cells, and facilitates killing of pathogens. However, excessive activation of coagulation can lead to thrombosis. Here, we review studies on the mechanism of LPS induction of TF expression in monocytes and its contribution to thrombosis and disseminated intravascular coagulation. Binding of LPS to Toll-like receptor 4 on monocytes induces a transient expression of TF that involves activation of intracellular signaling pathways and binding of various transcription factors, such as c-rel/p65 and c-Fos/c-Jun, to the TF promoter. Inhibition of TF in endotoxemia and sepsis models reduces activation of coagulation and improves survival. Studies with endotoxemic mice showed that hematopoietic cells and myeloid cells play major roles in the activation of coagulation. Monocyte TF expression is also increased after surgery. Activated monocytes release TF-positive extracellular vesicles (EVs) and levels of circulating TF-positive EVs are increased in endotoxemic mice and in patients with sepsis. More recently, it was shown that inflammasomes contribute to the induction of TF expression and activation of coagulation in endotoxemic mice. Taken together, these studies indicate that monocyte TF plays a major role in activation of coagulation. Selective inhibition of monocyte TF expression may reduce pathologic activation of coagulation in sepsis and other diseases without affecting hemostasis.

WR1065 conjugated to thiol-PEG polymers as novel anticancer prodrugs: broad spectrum efficacy, synergism, and drug resistance reversal

The lack of anticancer agents that overcome innate/acquired drug resistance is the single biggest barrier to achieving a durable complete response to cancer therapy. To address this issue, a new drug family was developed for intracellular delivery of the bioactive aminothiol WR1065 by conjugating it to discrete thiol-PEG polymers: 4-star-PEG-S-S-WR1065 (4SP65) delivers four WR1065s/molecule and m-PEG6-S-S-WR1065 (1LP65) delivers one. Infrequently, WR1065 has exhibited anticancer effects when delivered via the FDA-approved cytoprotectant amifostine, which provides one WR1065/molecule extracellularly. The relative anticancer effectiveness of 4SP65, 1LP65, and amifostine was evaluated in a panel of 15 human cancer cell lines derived from seven tissues. Additional experiments assessed the capacity of 4SP65 co-treatments to potentiate the anticancer effectiveness and overcome drug resistance to cisplatin, a chemotherapeutic, or gefitinib, a tyrosine kinase inhibitor (TKI) targeting oncogenic EGFR mutations. The CyQUANT®-NF proliferation assay was used to assess cell viability after 48-h drug treatments, with the National Cancer Institute COMPARE methodology employed to characterize dose-response metrics. In normal human epithelial cells, 4SP65 or 1LP65 enhanced or inhibited cell growth but was not cytotoxic. In cancer cell lines, 4SP65 and 1LP65 induced dose-dependent cytostasis and cytolysis achieving 99% cell death at drug concentrations of 11.2 ± 1.2 µM and 126 ± 15.8 µM, respectively. Amifostine had limited cytostatic effects in 11/14 cancer cell lines and no cytolytic effects. Binary pairs of 4SP65 plus cisplatin or gefitinib increased the efficacy of each partner drug and surmounted resistance to cytolysis by cisplatin and gefitinib in relevant cancer cell lines. 4SP65 and 1LP65 were significantly more effective against TP53-mutant than TP53-wild-type cell lines, consistent with WR1065-mediated reactivation of mutant p53. Thus, 4SP65 and 1LP65 represent a unique prodrug family for innovative applications as broad-spectrum anticancer agents that target p53 and synergize with a chemotherapeutic and an EGFR-TKI to prevent or overcome drug resistance.

Schisandrin A ameliorates increased pulmonary capillary endothelial permeability accompanied with sepsis through inhibition of RhoA/ROCK1/MLC pathways

BACKGROUND

Sepsis is a systemic inflammatory response, and vascular leakage associated with acute lung injury (ALI) is an important pathophysiological process during sepsis. Schisandrin A (SchA) is a bioactive lignan which has been reported to have the anti-inflammatory effects in many studies, while whether SchA can ameliorate ALI-related vascular leakage caused by sepsis is unknown.

OBJECTIVE

To evaluate the role and the underlying mechanism of SchA in increase of pulmonary vascular permeability induced by sepsis.

METHODS

The effect of SchA on pulmonary vascular permeability was examined in rat acute lung injury model. The effect of SchA on skin vascular permeability of mice was investigated through Miles assay. MTT assay was performed to detect the cell activity, and transwell assay was used to detect the effect of SchA on cell permeability. The effects of SchA on junction proteins and RhoA/ROCK1/MLC signaling pathway were manifested by immunofluorescence staining and western blot.

RESULTS

The administration of SchA alleviated rat pulmonary endothelial dysfunction, relieved increased permeability in the mouse skin and HUVECs induced by lipopolysaccharide (LPS). Meanwhile, SchA inhibited the formation of stress fibers, reversed the decrease of expression of ZO-1 and VE-cadherin. Subsequent experiments confirmed that SchA inhibited RhoA/ROCK1/MLC canonical pathway in rat lungs and HUVECs induced by LPS. Moreover, overexpression of RhoA reversed the inhibitory effect of SchA in HUVECs, which suggested that SchA protected the pulmonary endothelial barrier by inhibiting RhoA/ROCK1/MLC pathway.

CONCLUSION

In summary, our results indicate that SchA ameliorates the increase of pulmonary endothelial permeability induced by sepsis through inhibition of RhoA/ROCK1/MLC pathway, providing a potentially effective therapeutic strategy for sepsis.

Fibrinogen Inhibits Metalloproteinase-9 Activation and Syndecan-1 Cleavage to Protect Lung Function in ApoE Null Mice After Hemorrhagic Shock

INTRODUCTION

Obesity is associated with higher mortality following trauma, although the pathogenesis is unclear. Both obesity and trauma are associated with syndecan-1 shedding and metalloproteinase-9 (MMP-9) activation, which can adversely affect endothelial cell function. We recently demonstrated that fibrinogen stabilizes endothelial cell surface syndecan-1 to reduce shedding and maintain endothelial barrier integrity. We thus hypothesized that MMP-9 activation and syndecan-1 shedding would be exacerbated by obesity after trauma but attenuated by fibrinogen-based resuscitation.

MATERIALS AND METHODS

ApoE null (^-/-) mice were fed a Western diet to induce obesity. Mice were subjected to hemorrhage shock and laparotomy then resuscitated with Lactated Ranger's (LR) or LR containing fibrinogen and compared to null and lean sham wild type mice. Mean arterial pressure (MAP) was monitored. Bronchial alveolar lavage protein as an indicator of permeability and lung histopathologic injury were assessed. Syndecan-1 protein and active MMP-9 protein were measured.

RESULTS

MAP was similar between lean sham and ApoE^-/- sham mice. However, following hemorrhage, ApoE^-/- mice resuscitated with fibrinogen had significantly higher MAP than LR mice. Lung histopathologic injury and permeability were increased in LR compared to fibrinogen resuscitated animals. Compared with lean sham mice, both active MMP-9 and cleaved syndecan-1 level were significantly higher in ApoE^-/- sham mice. Resuscitation with fibrinogen but not lactated Ringers largely reduced these changes.

CONCLUSIONS

Fibrinogen as a resuscitative adjunct in ApoE^-/- mice after hemorrhage shock augmented MAP and reduced histopathologic injury and lung permeability, suggesting fibrinogen protects the endothelium by inhibiting MMP-9-mediated syndecan-1 cleavage in obese mice.

Novel O-benzylcinnamic acid derivative L26 treats acute lung injury in mice by MD-2

Acute lung injury (ALI) is an inflammation-mediated respiratory disease that is associated with a high mortality rate. In this study, a series of novel O-benzylcinnamic acid derivatives were designed and synthesized using cinnamic acid as the lead compound. We tested the preliminary anti-inflammatory activity of the compounds by evaluating their effect on inhibiting the activity of alkaline phosphatase (ALP) in Hek-Blue-TLR4 cells, in which compound L26 showed the best activity and 7-fold more active than CIN. ELISA, immunoprecipitation, and molecular docking indicated that L26 targeted MD-2 protein and competed with LPS to bind to MD-2, which resulted in the inhibition of inflammation. In the LPS-induced mouse model of ALI, L26 was found to decrease ALP activity and inflammatory cytokine TNF-α release to reduce lung injury by inhibiting the NF-κB signaling pathway. Acute toxicity experiments showed that high doses of L26 did not cause adverse reactions in mice, and it was safe in vivo. Also, the preliminary pharmacokinetic parameters of L26 were investigated in SD rats (T_1/2 = 4.246 h). In summary, L26 exhibited optimal pharmacodynamic and pharmacokinetic characteristics, which suggested that L26 could serve as a potential agent for the development of ALI treatment.

Amifostine analog, DRDE-30, alleviates radiation induced lung damage by attenuating inflammation and fibrosis

BACKGROUND

Radiotherapy of thoracic neoplasms and accidental radiation exposure often results in pneumonitis and fibrosis of lungs. Here, we investigated the potential of amifostine analogs: DRDE-07, DRDE-30, and DRDE-35, in alleviating radiation-induced lung damage.

METHODS

C57BL/6 mice were exposed to 13.5 Gy thoracic irradiation, 30 min after intraperitoneal administration of the analogs, and assessed for modulation of the pathological response at 12 and 24 weeks.

KEY FINDINGS

DRDE-07, DRDE-30 and DRDE-35 increased the survival of irradiated mice from 20% to 30%, 80% and 70% respectively. Reduced parenchymal opacity (X-ray CT) in the lungs of DRDE-30 pre-treated mice corroborated well with the significant decrease in Ashcroft score (p < 0.01). Two-fold increase in SOD and catalase activities (p < 0.05), coupled with a 50% increase in GSH content and a 60% decrease in MDA content (p < 0.05) suggested restoration of the antioxidant defence system. A 20% to 40% decrease in radiation-induced apoptotic and mitotic death in the lung tissue (micronuclei: p < 0.01), resulted in attenuated lung and vascular permeability (FITC-Dextran leakage) by 50% (p < 0.01), and a commensurate reduction (~50%) in leukocyte infiltration in the injured tissue (p < 0.05). DRDE-30 abrogated the activation of pro-inflammatory NF-κB and p38/MAPK signaling cascades, suppressing the release of pro-inflammatory cytokines (IL-1β: p < 0.05; TNF-α: p < 0.05; IL-6: p < 0.05) and up-regulation of CAMs on the endothelial cell surface. Reduction in hydroxyproline content (p < 0.01) and collagen suggested inhibition of lung fibrosis which was associated with attenuation of TGF-β/Smad pathway-mediated-EMT.

CONCLUSION

DRDE-30 could be a potential prophylactic agent against radiation-induced lung injury.

Auraptene, a Monoterpene Coumarin, Inhibits LTA-Induced Inflammatory Mediators via Modulating NF-κB/MAPKs Signaling Pathways

Objective

Oxidative stress-mediated inflammatory events involve in the progress of several diseases such as asthma, cancers, and multiple sclerosis. Auraptene (AU), a natural prenyloxycoumarin, possesses numerous pharmacological activities. Here, the anti-inflammatory effects of AU were investigated in lipoteichoic acid- (LTA-) induced macrophage cells (RAW 264.7).

Methods

The expression of cyclooxygenase (COX-2), tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), and inducible nitric oxide synthase (iNOS) and the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2, p38 MAPK, c-Jun N-terminal kinase (JNK), heme oxygenase (HO-1), p65, and IκBα were all identified by western blotting assay. The level of nitric oxide (NO) was measured by spectrometer analysis. The nuclear translocation of p65 nuclear factor kappa B (NF-κB) was assessed by the confocal microscopic staining method. Native polyacrylamide gel electrophoresis was performed to perceive the activity of antioxidant enzyme catalase (CAT).

Results

AU expressively reduced NO production and COX-2, TNF-α, IL-1 β, and iNOS expression in LTA-stimulated cells. AU at higher concentration (10 µM) inhibited ERK and JNK, but not p38 phosphorylation induced by LTA. Moreover, AU blocked IκB and p65 phosphorylation, and p65 nuclear translocation. However, AU pretreatment was not effective on antioxidant HO-1 expression, CAT activity, and reduced glutathione (GSH, a nonenzymatic antioxidant), in LTA-induced RAW 264.7 cells.

Conclusion

The findings of this study advocate that AU shows anti-inflammatory effects via reducing NF-κB/MAPKs signaling pathways.

Essential role for paxillin tyrosine phosphorylation in LPS-induced mitochondrial fission, ROS generation and lung endothelial barrier loss

We have shown that both reactive oxygen species (ROS) and paxillin tyrosine phosphorylation regulate LPS-induced human lung endothelial permeability. Mitochondrial ROS (mtROS) is known to increase endothelial cell (EC) permeability which requires dynamic change in mitochondrial morphology, events that are likely to be regulated by paxillin. Here, we investigated the role of paxillin and its tyrosine phosphorylation in regulating LPS-induced mitochondrial dynamics, mtROS production and human lung microvascular EC (HLMVEC) dysfunction. LPS, in a time-dependent manner, induced higher levels of ROS generation in the mitochondria compared to cytoplasm or nucleus. Down-regulation of paxillin expression with siRNA or ecto-expression of paxillin Y31F or Y118F mutant plasmids attenuated LPS-induced mtROS in HLMVECs. Pre-treatment with MitoTEMPO, a scavenger of mtROS, attenuated LPS-induced mtROS, endothelial permeability and VE-cadherin phosphorylation. Further, LPS-induced mitochondrial fission in HLMVECs was attenuated by both a paxillin siRNA, and paxillin Y31F/Y118F mutant. LPS stimulated phosphorylation of dynamin-related protein (DRP1) at S616, which was also attenuated by paxillin siRNA, and paxillinY31/Y118 mutants. Inhibition of DRP1 phosphorylation by P110 attenuated LPS-induced mtROS and endothelial permeability. LPS challenge of HLMVECs enhanced interaction between paxillin, ERK, and DRP1, and inhibition of ERK1/2 activation with PD98059 blocked mitochondrial fission. Taken together, these results suggest a key role for paxillin tyrosine phosphorylation in LPS-induced mitochondrial fission, mtROS generation and EC barrier dysfunction.

Microtubule-dependent mechanism of anti-inflammatory effect of SOCS1 in endothelial dysfunction and lung injury

Suppressors of cytokine signaling (SOCS) provide negative regulation of inflammatory reaction. The role and precise cellular mechanisms of SOCS1 in control of endothelial dysfunction and barrier compromise associated with acute lung injury remain unexplored. Our results show that siRNA-mediated SOCS1 knockdown augmented lipopolysaccharide (LPS)-induced pulmonary endothelial cell (EC) permeability and enhanced inflammatory response. Consistent with in vitro data, EC-specific SOCS1 knockout mice developed more severe lung vascular leak and accumulation of inflammatory cells in bronchoalveolar lavage fluid. SOCS1 overexpression exhibited protective effects against LPS-induced endothelial permeability and inflammation, which were dependent on microtubule (MT) integrity. Biochemical and image analysis of unstimulated EC showed SOCS1 association with the MT, while challenge with LPS or MT depolymerizing agent colchicine impaired this association. SOCS1 directly interacted with N2 domains of MT-associated proteins CLIP-170 and CLASP2. Furthermore, N-terminal region of SOCS1 was indispensable for these interactions and SOCS1-ΔN mutant lacking N-terminal 59 amino acids failed to rescue LPS-induced endothelial dysfunction. Depletion of endogenous CLIP-170 or CLASP2 abolished SOCS1 interaction with Toll-like receptor-4 and Janus kinase-2 leading to impairment of SOCS1 inhibitory effects on LPS-induced inflammation. Altogether, these findings suggest that endothelial barrier protective and anti-inflammatory effects of SOCS1 are critically dependent on its targeting to the MT.

SOCS3-microtubule interaction via CLIP-170 and CLASP2 is critical for modulation of endothelial inflammation and lung injury

Proinflammatory cytokines such as IL-6 induce endothelial cell (EC) barrier disruption and trigger an inflammatory response in part by activating the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway. The protein suppressor of cytokine signaling-3 (SOCS3) is a negative regulator of JAK-STAT, but its role in modulation of lung EC barrier dysfunction caused by bacterial pathogens has not been investigated. Using human lung ECs and EC-specific SOCS3 knockout mice, we tested the hypothesis that SOCS3 confers microtubule (MT)-mediated protection against endothelial dysfunction. SOCS3 knockdown in cultured ECs or EC-specific SOCS3 knockout in mice resulted in exacerbated lung injury characterized by increased permeability and inflammation in response to IL-6 or heat-killed Staphylococcus aureus (HKSA). Ectopic expression of SOCS3 attenuated HKSA-induced EC dysfunction, and this effect required assembled MTs. SOCS3 was enriched in the MT fractions, and treatment with HKSA disrupted SOCS3-MT association. We discovered that-in addition to its known partners gp130 and JAK2-SOCS3 interacts with MT plus-end binding proteins CLIP-170 and CLASP2 via its N-terminal domain. The resulting SOCS3-CLIP-170/CLASP2 complex was essential for maximal SOCS3 anti-inflammatory effects. Both IL-6 and HKSA promoted MT disassembly and disrupted SOCS3 interaction with CLIP-170 and CLASP2. Moreover, knockdown of CLIP-170 or CLASP2 impaired SOCS3-JAK2 interaction and abolished the anti-inflammatory effects of SOCS3. Together, these findings demonstrate for the first time an interaction between SOCS3 and CLIP-170/CLASP2 and reveal that this interaction is essential to the protective effects of SOCS3 in lung endothelium.

Anti-oxidant and anti-inflammatory effects of auraptene on phytohemagglutinin (PHA)-induced inflammation in human lymphocytes

BACKGROUND

Inflammation is characterized as a defensive response of our body against endogenous or exogenous stimuli. Chronic inflammation and oxidative stress play an important role in the pathogenesis of various disorders such as asthma, cancers, and multiple sclerosis. Recently, diverse pharmacological activities of auraptene, a natural prenyloxycoumarin, were reported. In the present study, we aimed to evaluate the anti-oxidative and anti-inflammatory effects of auraptene on human isolated lymphocytes.

METHOD

The effects of auraptene (10, 30 and 90 μM) and dexamethasone (0.1 mM) were evaluated on cell viability, reactive oxygen species (ROS), and malondialdehyde (MDA) levels, superoxide dismutase (SOD) and catalase (CAT) activities, and total glutathione content (GSH) as well as the secretion of interleukin 6 (IL-6) and tumor necrosis factor (TNF)-α in phytohemagglutinin (PHA)-stimulated human lymphocytes.

RESULTS

Auraptene (10-90 μM) did not affect lymphocytes' viability after 48 h incubation. PHA markedly elevated ROS, MDA, IL-6, and TNF-α levels, while diminished the GSH content, and CAT and SOD activities in human lymphocytes (p < 0.001 for all cases). Treatment with auraptene (10-90 µM) significantly ameliorated ROS, MDA, IL-6, and TNF-α levels, and markedly increased GSH content, and CAT and SOD activities (p <  0.5-0.001).

CONCLUSION

Auraptene may possess promising healing effects in the different inflammatory disorders associated with activation of the acquired immune system such as multiple sclerosis and asthma.

Exosome-delivered syndecan-1 rescues acute lung injury via a FAK/p190RhoGAP/RhoA/ROCK/NF-κB signaling axis and glycocalyx enhancement

Acute lung injury (ALI) is characterized by protein-rich pulmonary edema, critical hypoxemia, and influx of pro-inflammatory cytokines and cells. There are currently no effective pharmacon therapies in clinical practice. Syndecan-1 in endothelial cells has potential to protect barrier function of endothelium and suppress inflammation response. Thus, the present study was to identify whether exosomes with encapsulation of syndecan-1 could achieve ideal therapeutic effects in ALI. Exosomes were isolated from the conditional medium of lentivirus-transfected mouse pulmonary microvascular endothelial cells (MPMVECs) and characterized by nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), and western blotting. ALI mouse models were induced via intratracheal administration of lipopolysaccharide (LPS) and treated with exosomes. Lung edema, inflammation, and glycocalyx thickness were examined. The possible mechanism was verified by immunoblotting in MPMVECs. The purified exosomes included SDC1-high-Exos and SDC1-low-Exos which loaded with up-regulated syndecan-1 and down-regulated syndecan-1 respectively. Compared with SDC1-low-Exos, administration of SDC1-high-Exos could ameliorate lung edema and inflammation, attenuate number of cells and protein levels in bronchoalveolar lavage fluid (BALF), and preserve glycocalyx. Furthermore, SDC1-high-Exos also mitigated the expression of pro-inflammatory cytokines such as IL-1β, TNF-α, and IL-6 following LPS challenge. In MPMVECs, SDC1-high-Exos decreased stress fiber formation and ameliorated monolayer hyper-permeability after LPS stimulation. Western blotting analysis demonstrated that FAK/p190RhoGAP/RhoA/ROCK/NF-κB signaling pathway may be involved in LPS-induced ALI. In conclusion, SDC1-high-Exos play a pivotal role in ameliorating LPS-stimulated ALI models and may be served as a potential therapeutic agent for clinical application in the future.

Mechanosensitive Rap1 activation promotes barrier function of lung vascular endothelium under cyclic stretch

Mechanical ventilation remains an imperative treatment for the patients with acute respiratory distress syndrome, but can also exacerbate lung injury. We have previously described a key role of RhoA GTPase in high cyclic stretch (CS)-induced endothelial cell (EC) barrier dysfunction. However, cellular mechanotransduction complexes remain to be characterized. This study tested a hypothesis that recovery of a vascular EC barrier after pathologic mechanical stress may be accelerated by cell exposure to physiologic CS levels and involves Rap1-dependent rearrangement of endothelial cell junctions. Using biochemical, molecular, and imaging approaches we found that EC pre- or postconditioning at physiologically relevant low-magnitude CS promotes resealing of cell junctions disrupted by pathologic, high-magnitude CS. Cytoskeletal remodeling induced by low CS was dependent on small GTPase Rap1. Protective effects of EC preconditioning at low CS were abolished by pharmacological or molecular inhibition of Rap1 activity. In vivo, using mice exposed to mechanical ventilation, we found that the protective effect of low tidal volume ventilation against lung injury caused by lipopolysaccharides and ventilation at high tidal volume was suppressed in Rap1 knockout mice. Taken together, our results demonstrate a prominent role of Rap1-mediated signaling mechanisms activated by low CS in acceleration of lung vascular EC barrier restoration.

Elevated truncated oxidized phospholipids as a factor exacerbating ALI in the aging lungs

As mechanisms controlling redox homeostasis become impaired with aging, exaggerated oxidant stress may cause disproportional oxidation of cell membranes and circulating phospholipids (PLs), leading to the formation of truncated oxidized PL products (Tr-OxPLs), which exhibit deleterious effects. This study investigated the role of elevated Tr-OxPLs as a factor exacerbating inflammation and lung barrier dysfunction in an animal model of aging. Mass spectrometry analysis of Tr-OxPL species in young (2-4 mo) and aging (18-24 mo) mice revealed elevated basal levels of several products [1-palmitoyl-2-(5-oxovaleroyl)- sn-glycero-phosphocholine (POVPC), 1-palmitoyl-2-glutaroyl- sn-glycero-phosphocholine, lysophosphocholine, 1-palmitoyl-2-(9-oxo-nonanoyl)- sn-glycero-3-phosphocholine, 1-palmitoyl-2-azelaoyl- sn-glycero-3-phosphocholine, O-1-O-palmitoyl-2-O-(5,8-dioxo-8-hydroxy-6-octenoyl)-l-glycero-3-phosphocholine, and others] in the aged lungs. An intratracheal (i.t.) injection of bacterial LPS caused increased generation of Tr-OxPLs in the lungs but not in the liver, with higher levels detected in the aged group. In addition, OxPLs clearance from the lung tissue after LPS challenge was delayed in the aged group. The impact of Tr-OxPLs on endothelial cell (EC) barrier compromise under inflammatory conditions was further evaluated in the 2-hit cell culture model of acute lung injury (ALI). EC barrier dysfunction caused by cell treatment with a cytokine mixture (CM) was augmented by cotreatment with low-dose Tr-OxPLs, which did not significantly affect endothelial function when added alone. Deleterious effects of Tr-OxPLs on inflamed ECs stimulated with CM were associated with further weakening of cell junctions and more robust EC hyperpermeability. Aged mice injected intratracheally with TNF-α exhibited a more pronounced elevation of cell counts and protein content in bronchoalveolar lavage (BAL) samples. Interestingly, intravenous administration of low POVPC doses-which did not affect BAL parameters alone in young mice exposed to i.t. TNF-α challenge-augmented lung injury to the levels observed in aged mice stimulated with TNF-α alone. Inhibition of Tr-OxPL generation by ectopic expression of PL-specific platelet-activating factor acetylhydrolase 2 (PAFAH2) markedly reduced EC dysfunction induced by CM, whereas PAFAH2 pharmacologic inhibition augmented deleterious effects of cytokines on EC barrier function. Moreover, exacerbating effects of PAFAH2 inhibition on TNF-α-induced lung injury were observed in vivo. These results demonstrate an age-dependent increase in Tr-OxPL production under basal conditions and augmented Tr-OxPL generation upon inflammatory stimulation, suggesting a major role for elevated Tr-OxPLs in more severe ALI and delayed resolution in aging lungs.-Ke, Y., Karki, P., Kim, J., Son, S., Berdyshev, E., Bochkov, V. N., Birukova, A. A., Birukov, K. G. Elevated truncated oxidized phospholipids as a factor exacerbating ALI in the aging lungs.

Evaluation of the anti-oxidant and anti-inflammatory effects of the methanolic extract of Ferula szowitsiana root on PHA-induced inflammation in human lymphocytes

Inflammation is defined as a defensive response of the body against either the endogenous or exogenous triggers, while this process becomes chronic leading to various disorders such as asthma, cancers, and multiple sclerosis. Recently, pharmacological properties of different constituents of F. szowitsiana have been reported. In the present study, we aimed to evaluate the anti-oxidative and anti-inflammatory effects of the methanolic extract of F. szowitsiana root on human isolated lymphocytes. The effects of either F. szowitsiana (10, 40 and 160 μg/ml) or dexamethasone (0.1 mM) were evaluated on the levels of cell proliferation, reactive oxygen species (ROS), nitric oxide (NO) production, malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT) activities, and total glutathione content (GSH) as well as the secretion of inflammatory cytokines [interleukin 6 (IL-6) and tumor necrosis factor (TNF)-α] in the presence or absence of phytohemagglutinin (PHA) stimulation (n = 8 for each group). PHA stimulation notably elevated ROS, NO, MDA, IL-6, and TNF-α levels as well as diminished GSH, CAT and SOD levels. In PHA-stimulated, the results also revealed that F. szowitsiana (10-160 µg/ml) significantly decreased MDA, ROS, NO, IL-6 and TNF-α levels as well as increased CAT, SOD and GSH levels. Collectively, F. szowitsiana is able to attenuate the overproduction of inflammatory and oxidative stress markers in the presence of PHA-stimulated T lymphocytes, while to propagate the anti-oxidative defense. Contextually, the plant has promising healing effects in the different inflammatory disorders associated with the interference of the acquired immune system such as multiple sclerosis and asthma.

Staphylococcus aureus-induced endothelial permeability and inflammation are mediated by microtubule destabilization

Staphylococcus aureus is a major etiological agent of sepsis and induces endothelial cell (EC) barrier dysfunction and inflammation, two major hallmarks of acute lung injury. However, the molecular mechanisms of bacterial pathogen-induced EC barrier disruption are incompletely understood. Here, we investigated the role of microtubules (MT) in the mechanisms of EC barrier compromise caused by heat-killed S. aureus (HKSA). Using a customized monolayer permeability assay in human pulmonary EC and MT fractionation, we observed that HKSA-induced barrier disruption is accompanied by MT destabilization and increased histone deacetylase-6 (HDAC6) activity resulting from elevated reactive oxygen species (ROS) production. Molecular or pharmacological HDAC6 inhibition rescued barrier function in HKSA-challenged vascular endothelium. The HKSA-induced EC permeability was associated with impaired MT-mediated delivery of cytoplasmic linker-associated protein 2 (CLASP2) to the cell periphery, limiting its interaction with adherens junction proteins. HKSA-induced EC barrier dysfunction was also associated with increased Rho GTPase activity via activation of MT-bound Rho-specific guanine nucleotide exchange factor-H1 (GEF-H1) and was abolished by HDAC6 down-regulation. HKSA activated the NF-κB proinflammatory pathway and increased the expression of intercellular and vascular cell adhesion molecules in EC, an effect that was also HDAC6-dependent and mediated, at least in part, by a GEF-H1/Rho-dependent mechanism. Of note, HDAC6 knockout mice or HDAC6 inhibitor-treated WT mice were partially protected from vascular leakage and inflammation caused by both HKSA or methicillin-resistant S. aureus (MRSA). Our results indicate that S. aureus-induced, ROS-dependent up-regulation of HDAC6 activity destabilizes MT and thereby activates the GEF-H1/Rho pathway, increasing both EC permeability and inflammation.

Berberine alleviates endothelial glycocalyx degradation and promotes glycocalyx restoration in LPS-induced ARDS

In the pathogenesis of acute respiratory distress syndrome (ARDS), an increase in vascular endothelial permeability may trigger pulmonary edema and ultimately lead to respiratory failure. Endothelial glycocalyx damage is an important factor that causes an increase in vascular endothelial permeability. Berberine (BBR) is an isoquinoline alkaloid extracted from Coptis chinensis, a plant used in traditional Chinese medicine that exerts multiple pharmacological effects. In this study, pretreatment with BBR inhibited the increase in vascular endothelial permeability in mice with lipopolysaccharide (LPS)-induced ARDS. BBR pretreatment inhibited the shedding of syndecan-1 (SDC-1) and heparan sulfate (HS), which are important components of the endothelial glycocalyx that lessen endothelial glycocalyx damage. BBR further significantly inhibited increases in important endothelial glycocalyx damage factors, including reactive oxygen species (ROS), heparanase (HPA), and matrix metalloproteinase 9 (MMP9) in LPS-induced ARDS mice and in LPS-stimulated human umbilical vein endothelial cells. BBR pretreatment also decreased the production of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and inhibited NF-κB signaling pathway activation in LPS-induced ARDS. In addition, BBR promoted the recovery of SDC-1 and HS content in injured endothelial glycocalyx after LPS treatment and accelerated its restoration. This is the first report of BBR maintaining the integrity of endothelial glycocalyx. These results provide a new theoretical basis for the use of BBR in the treatment of ARDS and other diseases related to endothelial glycocalyx damage.

Inhibitory effects on the production of inflammatory mediators and reactive oxygen species by Mori folium in lipopolysaccharide-stimulated macrophages and zebrafish

Mori folium, the leaf of Morus alba L. (Moraceae), has been traditionally used for various medicinal purposes from ancient times to the present. In this study, we examined the effects of water extract of Mori folium (WEMF) on the production of inflammatory mediators, such as nitric oxide (NO) and prostaglandin E2 (PGE2), and reactive oxygen species (ROS) in lipopolysaccharide (LPS)-stimulated murine RAW 264.7 macrophages. Our data indicated that WEMF significantly suppressed the secretion of NO and PGE2 in RAW 264.7 macrophages without any significant cytotoxicity. The protective effects were accompanied by a marked reduction in their regulatory gene expression at the transcription level. WEMF attenuated LPS-induced intracellular ROS production in RAW 264.7 macrophages. It inhibited the nuclear translocation of the nuclear factor-kappa B p65 subunit and the activation of mitogen-activated protein kinases in LPS-treated RAW 264.7 macrophages. Furthermore, WEMF reduced LPS-induced NO production and ROS accumulation in zebrafish. Although more efforts are needed to fully understand the critical role of WEMF in the inhibition of inflammation, the findings of the present study may provide insights into the approaches for Mori folium as a potential therapeutic agent for inflammatory and antioxidant disorders.

Incorporation of iloprost in phospholipase-resistant phospholipid scaffold enhances its barrier protective effects on pulmonary endothelium

Correction of barrier dysfunction and inflammation in acute lung injury (ALI) represents an important problem. Previous studies demonstrate barrier-protective and anti-inflammatory effects of bioactive lipid prostacyclin and its stable analog iloprost (ILO). We generated a phospholipase resistant synthetic phospholipid with iloprost attached at the sn-2 position (ILO-PC) and investigated its biological effects. In comparison to free ILO, ILO-PC caused sustained endothelial cell (EC) barrier enhancement, linked to more prolonged activation of Rap1 and Rac1 GTPases and their cytoskeletal and cell junction effectors: cortactin, PAK1, p120-catenin and VE-cadherin. ILO and ILO-PC equally efficiently suppressed acute, Rho GTPase-dependent EC hyper-permeability caused by thrombin. However, ILO-PC exhibited more sustained barrier-protective and anti-inflammatory effects in the model of chronic EC dysfunction caused by bacterial wall lipopolysacharide (LPS). ILO-PC was also more potent inhibitor of NFκB signaling and lung vascular leak in the murine model of LPS-induced ALI. Treatment with ILO-PC showed more efficient ALI recovery over 3 days after LPS challenge than free ILO. In conclusion, this study describes a novel synthetic phospholipid with barrier-enhancing and anti-inflammatory properties superior to existing prostacyclin analogs, which may be used as a prototype for future development of more efficient treatment for ALI and other vascular leak syndromes.

Sirt1 Protects Endothelial Cells against LPS-Induced Barrier Dysfunction

Sepsis is a threatening health problem and characterized by microvascular dysfunction. In this study, we verified that LPS caused the downregulation of Sirt1 and the hyperpermeability of endothelial cells. Inhibition of Sirt1 with ex527 or Sirt1 siRNA displayed a higher permeability, while activation of Sirt1 with SRT1720 reversed the LPS-induced hyperpermeability, formation of fiber stress, and disruption of VE-cadherin distribution. In pulmonary microvascular vein endothelial cells isolated from wild-type mice, Sirt1 was attenuated upon LPS, while Sirt1 was preserved in a receptor of advanced glycation end product-knockout mice. The RAGE antibody could also diminish the downregulation and ubiquitination of Sirt1 in LPS-exposed human umbilical vein endothelial cells. An LPS-induced decrease in Sirt1 activity was attenuated by the RAGE antibody and TLR4 inhibitor. In vivo study also demonstrated the attenuating role of Sirt1 and RAGE knockout in LPS-induced increases in dextran leakage of mesenteric venules. Furthermore, activation of Sirt1 prevented LPS-induced decreases in the activity and expression of superoxide dismutase 2, as well as the increases in NADPH oxidase 4 and reactive oxygen species, while inhibition of Sirt1 aggravated the SOD2 decline. It also demonstrated that Sirt1-deacetylated p53 is required for p53 inactivation, which reversed the downregulation of β-catenin caused by LPS.

Effects of prostaglandin lipid mediators on agonist-induced lung endothelial permeability and inflammation

Prostaglandins (PG), the products of cyclooxygenase-mediated conversion of arachidonic acid, become upregulated in many situations including allergic response, inflammation, and injury, and exhibit a variety of biological activities. Previous studies described barrier-enhancing and anti-inflammatory effects of PGE₂ and PGI₂ on vascular endothelial cells (EC). Yet, the effects of other PG members on EC barrier and inflammatory activation have not been systematically analyzed. This study compared effects of PGE₂, PGI₂, PGF_2α, PGA₂, PGJ₂, and PGD₂ on human pulmonary EC. EC permeability was assessed by measurements of transendothelial electrical resistance and cell monolayer permeability for FITC-labeled tracer. Anti-inflammatory effects of PGs were evaluated by analysis of expression of adhesion molecule ICAM1 and secretion of soluble ICAM1 and cytokines by EC. PGE₂, PGI₂, and PGA₂ exhibited the most potent barrier-enhancing effects and most efficient attenuation of thrombin-induced EC permeability and contractile response, whereas PGI₂ effectively suppressed thrombin-induced permeability but was less efficient in the attenuation of prolonged EC hyperpermeability caused by interleukin-6 or bacterial wall lipopolysaccharide, LPS. PGD₂ showed a modest protective effect on the EC inflammatory response, whereas PGF_2α and PGJ₂ were without effect on agonist-induced EC barrier dysfunction. In vivo, PGE₂, PGI₂, and PGA₂ attenuated LPS-induced lung inflammation, whereas PGF_2α and PGJ₂ were without effect. Interestingly, PGD₂ exhibited a protective effect in the in vivo model of LPS-induced lung injury. This study provides a comprehensive analysis of barrier-protective and anti-inflammatory effects of different prostaglandins on lung EC in vitro and in vivo and identifies PGE₂, PGI₂, and PGA₂ as prostaglandins with the most potent protective properties.

Prostaglandin E receptor-4 receptor mediates endothelial barrier-enhancing and anti-inflammatory effects of oxidized phospholipids

Unlike other agonists that cause transient endothelial cell (EC) response, the products of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (PAPC) oxidation that contain cyclopenthenone groups, which recapitulate prostaglandin-like structure, cause sustained enhancement of the pulmonary EC barrier. The mechanisms that drive the sustained effects by oxidized PAPC (OxPAPC) remain unexplored. On the basis of the structural similarity of isoprostanoid moieties that are present in full-length oxygenated PAPC species, we used an inhibitory approach to perform the screening of prostanoid receptors as potential candidates that mediate OxPAPC effects. Results show that only prostaglandin E receptor-4 (EP4) was involved and mediated the sustained phase of the barrier-enhancing effects of OxPAPC that are associated with the activation of Rac GTPase and its cytoskeletal targets. EC incubation with OxPAPC also induced EP4 mRNA expression in pulmonary ECs and lung tissue. EP4 knockdown using gene-specific small interfering RNA did not affect the rapid phase of OxPAPC-induced EC barrier enhancement or the protective effects against thrombin-induced EC permeability, but abolished the advanced barrier enhancement phase and suppressed the protective effects of OxPAPC against more sustained EC barrier dysfunction and cell inflammatory response caused by TNF-α. Endothelial-specific knockout of the EP4 receptor in mice attenuated the protective effect of intravenous OxPAPC administration in the model of acute lung injury caused by intratracheal injection of LPS. Taken together, these results demonstrate a novel role for prostaglandin receptor EP4 in the mediation of barrier-enhancing and anti-inflammatory effects caused by oxidized phospholipids.-Oskolkova, O., Gawlak, G., Tian, Y., Ke, Y., Sarich, N., Son, S., Andreasson, K., Bochkov, V. N., Birukova, A. A., Birukov, K. G. Prostaglandin E receptor-4 receptor mediates endothelial barrier-enhancing and anti-inflammatory effects of oxidized phospholipids.

Anti-Inflammatory Effects of OxPAPC Involve Endothelial Cell-Mediated Generation of LXA4

RATIONALE

Oxidation of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (OxPAPC) generates a group of bioactive oxidized phospholipid products with a broad range of biological activities. Barrier-enhancing and anti-inflammatory effects of OxPAPC on pulmonary endothelial cells are critical for prevention of acute lung injury caused by bacterial pathogens or excessive mechanical ventilation. Anti-inflammatory properties of OxPAPC are associated with its antagonistic effects on Toll-like receptors and suppression of RhoA GTPase signaling.

OBJECTIVE

Because OxPAPC exhibits long-lasting anti-inflammatory and lung-protective effects even after single administration in vivo, we tested the hypothesis that these effects may be mediated by additional mechanisms, such as OxPAPC-dependent production of anti-inflammatory and proresolving lipid mediator, lipoxin A4 (LXA4).

METHODS AND RESULTS

Mass spectrometry and ELISA assays detected significant accumulation of LXA4 in the lungs of OxPAPC-treated mice and in conditioned medium of OxPAPC-exposed pulmonary endothelial cells. Administration of LXA4 reproduced anti-inflammatory effect of OxPAPC against tumor necrosis factor-α in vitro and in the animal model of lipopolysaccharide-induced lung injury. The potent barrier-protective and anti-inflammatory effects of OxPAPC against tumor necrosis factor-α and lipopolysaccharide challenge were suppressed in human pulmonary endothelial cells with small interfering RNA-induced knockdown of LXA4 formyl peptide receptor-2 (FPR2/ALX) and in mFPR2^-/- (mouse formyl peptide receptor 2) mice lacking the mouse homolog of human FPR2/ALX.

CONCLUSIONS

This is the first demonstration that inflammation- and injury-associated phospholipid oxidation triggers production of anti-inflammatory and proresolution molecules, such as LXA4. This lipid mediator switch represents a novel mechanism of OxPAPC-assisted recovery of inflamed lung endothelium.

Mechanisms that determine nanocarrier targeting to healthy versus inflamed lung regions

Inflamed organs display marked spatial heterogeneity of inflammation, with patches of inflamed tissue adjacent to healthy tissue. To investigate how nanocarriers (NCs) distribute between such patches, we created a mouse model that recapitulates the spatial heterogeneity of the inflammatory lung disease ARDS. NCs targeting the epitope PECAM strongly accumulated in the lungs, but were shunted away from inflamed lung regions due to hypoxic vasoconstriction (HVC). In contrast, ICAM-targeted NCs, which had lower whole-lung uptake than PECAM/NCs in inflamed lungs, displayed markedly higher NC levels in inflamed regions than PECAM/NCs, due to increased regional ICAM. Regional HVC, epitope expression, and capillary leak were sufficient to predict intra-organ of distribution of NCs, antibodies, and drugs. Importantly, these effects were not observable with traditional spatially-uniform models of ARDS, nor when examining only whole-organ uptake. This study underscores how examining NCs' intra-organ distribution in spatially heterogeneous animal models can guide rational NC design.

Regulation of lung endothelial permeability and inflammatory responses by prostaglandin A2: role of EP4 receptor

PGA2 exhibits anti-inflammatory and barrier-protective effects on endothelial cells and in two mouse models of acute lung injury. PGA2-induced cytoskeletal remodeling and suppression of the NFκB pathway is mediated by prostanoid receptor EP4. Endothelial-specific EP4 knockout abolishes PGA2-protective effects in vitro and in vivo.

The role of prostaglandin A2 (PGA2) in modulation of vascular endothelial function is unknown. We investigated effects of PGA2 on pulmonary endothelial cell (EC) permeability and inflammatory activation and identified a receptor mediating these effects. PGA2 enhanced the EC barrier and protected against barrier dysfunction caused by vasoactive peptide thrombin and proinflammatory bacterial wall lipopolysaccharide (LPS). Receptor screening using pharmacological and molecular inhibitory approaches identified EP4 as a novel PGA2 receptor. EP4 mediated barrier-protective effects of PGA2 by activating Rap1/Rac1 GTPase and protein kinase A targets at cell adhesions and cytoskeleton: VE-cadherin, p120-catenin, ZO-1, cortactin, and VASP. PGA2 also suppressed LPS-induced inflammatory signaling by inhibiting the NFκB pathway and expression of EC adhesion molecules ICAM1 and VCAM1. These effects were abolished by pharmacological or molecular inhibition of EP4. In vivo, PGA2 was protective in two distinct models of acute lung injury (ALI): LPS-induced inflammatory injury and two-hit ALI caused by suboptimal mechanical ventilation and injection of thrombin receptor–activating peptide. These protective effects were abolished in mice with endothelial-specific EP4 knockout. The results suggest a novel role for the PGA2–EP4 axis in vascular EC protection that is critical for improvement of pathological states associated with increased vascular leakage and inflammation.

Potential strategies to ameliorate risk of radiotherapy-induced second malignant neoplasms

This review is aimed at the issue of radiation-induced second malignant neoplasms (SMN), which has become an important problem with the increasing success of modern cancer radiotherapy (RT). It is imperative to avoid compromising the therapeutic ratio while addressing the challenge of SMN. The dilemma is illustrated by the role of reactive oxygen species in both the mechanisms of tumor cell kill and of radiation-induced carcinogenesis. We explore the literature focusing on three potential routes of amelioration to address this challenge. An obvious approach to avoiding compromise of the tumor response is the use of radioprotectors or mitigators that are selective for normal tissues. We also explore the opportunities to avoid protection of the tumor by topical/regional radioprotection of normal tissues, although this strategy limits the scope of protection. Finally, we explore the role of the bystander/abscopal phenomenon in radiation carcinogenesis, in association with the inflammatory response. Targeted and non-targeted effects of radiation are both linked to SMN through induction of DNA damage, genome instability and mutagenesis, but differences in the mechanisms and kinetics between targeted and non-targeted effects may provide opportunities to lessen SMN. The agents that could be employed to pursue each of these strategies are briefly reviewed. In many cases, the same agent has potential utility for more than one strategy. Although the parallel problem of chemotherapy-induced SMN shares common features, this review focuses on RT associated SMN. Also, we avoid the burgeoning literature on the endeavor to suppress cancer incidence by use of antioxidants and vitamins either as dietary strategies or supplementation.

Molecular mechanisms in lipopolysaccharide-induced pulmonary endothelial barrier dysfunction

The confluent pulmonary endothelium plays an important role as a semi-permeable barrier between the vascular space of blood vessels and the underlying tissues, and it contributes to the maintenance of circulatory fluid homeostasis. Pulmonary endothelial barrier dysfunction is a pivotal early step in the development of a variety of high mortality diseases, such as acute lung injury (ALI). Endothelium barrier dysfunction in response to inflammatory or infectious mediators, including lipopolysaccharide (LPS), is accompanied by invertible cell deformation and interendothelial gap formation. However, specific pharmacological therapies aiming at ameliorating pulmonary endothelial barrier function in patients are still lacking. A full understanding of the fundamental mechanisms that are involved in the regulation of pulmonary endothelial permeability is essential for the development of barrier protective therapeutic strategies. Therefore, this review summarizes several important molecular mechanisms involved in LPS-induced changes in pulmonary endothelial barrier function. As for barrier-disruption, the activation of myosin light chain kinase (MLCK), RhoA and tyrosine kinases; increase of calcium influx; and apoptosis of the endothelium lead to an elevation of lung endothelial permeability. Additionally, the activation of Rac1, Cdc42, protease activated receptor 1 (PAR1) and adenosine receptors (ARs), as well as the increase of cyclic AMP and sphingosine-1-phosphate (S1P) content, protect against LPS-induced lung endothelial barrier dysfunction. Furthermore, current regulatory factors and strategies against the development of LPS-induced lung endothelial hyper-permeability are discussed.

Kallistatin protects against sepsis-related acute lung injury via inhibiting inflammation and apoptosis

Kallistatin, an endogenous plasma protein, exhibits pleiotropic properties in inhibiting inflammation, oxidative stress and apoptosis, as evidenced in various animal models and cultured cells. Here, we demonstrate that kallistatin levels were positively correlated with the concentration of total protein in bronchoalveolar lavage fluids (BALF) from patients with sepsis-related acute respiratory distress syndrome (ARDS), indicating a compensatory mechanism. Lower ratio of kallistatin to total protein in BALF showed a significant trend toward elevated neutrophil counts (P = 0.002) in BALF and increased mortality (P = 0.046). In lipopolysaccharide (LPS)-treated mice, expression of human kallistatin in lung by gene transfer with human kallistatin-encoding plasmid ameliorated acute lung injury (ALI) and reduced cytokine/chemokine levels in BALF. These mice exhibited attenuated lung epithelial apoptosis and decreased Fas/FasL expression compared to the control mice. Mouse survival was improved by kallistatin gene transfer or recombinant human kallistatin treatment after LPS challenge. In LPS-stimulated A549 human lung epithelial cells, kallistatin attenuated apoptosis, down-regulated Fas/FasL signaling, suppressed intracellular reactive oxygen species (ROS) and inhibited ROS-mediated NF-κB activation and inflammation. Furthermore, LPS-induced apoptosis was blocked by antioxidant N-acetylcysteine or NF-κB inhibitor via down-regulating Fas expression. These findings suggest the therapeutic potential of kallistatin for sepsis-related ALI/ARDS.

Attenuation of lipopolysaccharide-induced lung vascular stiffening by lipoxin reduces lung inflammation

Reversible changes in lung microstructure accompany lung inflammation, although alterations in tissue micromechanics and their impact on inflammation remain unknown. This study investigated changes in extracellular matrix (ECM) remodeling and tissue stiffness in a model of LPS-induced inflammation and examined the role of lipoxin analog 15-epi-lipoxin A4 (eLXA4) in the reduction of stiffness-dependent exacerbation of the inflammatory process. Atomic force microscopy measurements of live lung slices were used to directly measure local tissue stiffness changes induced by intratracheal injection of LPS. Effects of LPS on ECM properties and inflammatory response were evaluated in an animal model of LPS-induced lung injury, live lung tissue slices, and pulmonary endothelial cell (EC) culture. In vivo, LPS increased perivascular stiffness in lung slices monitored by atomic force microscopy and stimulated expression of ECM proteins fibronectin, collagen I, and ECM crosslinker enzyme, lysyl oxidase. Increased stiffness and ECM remodeling escalated LPS-induced VCAM1 and ICAM1 expression and IL-8 production by lung ECs. Stiffness-dependent exacerbation of inflammatory signaling was confirmed in pulmonary ECs grown on substrates with high and low stiffness. eLXA4 inhibited LPS-increased stiffness in lung cross sections, attenuated stiffness-dependent enhancement of EC inflammatory activation, and restored lung compliance in vivo. This study shows that increased local vascular stiffness exacerbates lung inflammation. Attenuation of local stiffening of lung vasculature represents a novel mechanism of lipoxin antiinflammatory action.

Oxidized phospholipids protect against lung injury and endothelial barrier dysfunction caused by heat-inactivated Staphylococcus aureus

Increased endothelial cell (EC) permeability and vascular inflammation along with alveolar epithelial damage are key features of acute lung injury (ALI). Products of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine oxidation (OxPAPC) showed protective effects against inflammatory signaling and vascular EC barrier dysfunction induced by gram-negative bacterial wall lipopolysaccharide (LPS). We explored the more general protective effects of OxPAPC and investigated whether delayed posttreatment with OxPAPC boosts the recovery of lung inflammatory injury and EC barrier dysfunction triggered by intratracheal injection of heat-killed gram-positive Staphylococcus aureus (HKSA) bacteria. HKSA-induced pulmonary EC permeability, activation of p38 MAP kinase and NF-κB inflammatory cascades, secretion of IL-8 and soluble ICAM1, fibronectin deposition, and expression of adhesion molecules ICAM1 and VCAM1 by activated EC were significantly attenuated by cotreatment as well as posttreatment with OxPAPC up to 16 h after HKSA addition. Remarkably, posttreatment with OxPAPC up to 24 h post-HKSA challenge dramatically accelerated lung recovery by restoring lung barrier properties monitored by Evans blue extravasation and protein content in bronchoalveolar lavage (BAL) fluid and reducing inflammation reflected by decreased MIP-1, KC, TNF-α, IL-13 levels and neutrophil count in BAL samples. These studies demonstrate potent in vivo and in vitro protective effects of posttreatment with anti-inflammatory oxidized phospholipids in the model of ALI caused by HKSA. These results warrant further investigations into the potential use of OxPAPC compounds combined with antibiotic therapies as a treatment of sepsis and ALI induced by gram-positive bacterial pathogens.

Prostacyclin post-treatment improves LPS-induced acute lung injury and endothelial barrier recovery via Rap1

Protective effects of prostacyclin (PC) or its stable analog beraprost against agonist-induced lung vascular inflammation have been associated with elevation of intracellular cAMP and Rac GTPase signaling which inhibited the RhoA GTPase-dependent pathway of endothelial barrier dysfunction. This study investigated a distinct mechanism of PC-stimulated lung vascular endothelial (EC) barrier recovery and resolution of LPS-induced inflammation mediated by small GTPase Rap1. Efficient barrier recovery was observed in LPS-challenged pulmonary EC after prostacyclin administration even after 15 h of initial inflammatory insult and was accompanied by the significant attenuation of p38 MAP kinase and NFκB signaling and decreased production of IL-8 and soluble ICAM1. These effects were reproduced in cells post-treated with 8CPT, a small molecule activator of Rap1-specific nucleotide exchange factor Epac. By contrast, pharmacologic Epac inhibitor, Rap1 knockdown, or knockdown of cell junction-associated Rap1 effector afadin attenuated EC recovery caused by PC or 8CPT post-treatment. The key role of Rap1 in lung barrier restoration was further confirmed in the murine model of LPS-induced acute lung injury. Lung injury was monitored by measurements of bronchoalveolar lavage protein content, cell count, and Evans blue extravasation and live imaging of vascular leak over 6 days using a fluorescent tracer. The data showed significant acceleration of lung recovery by PC and 8CPT post-treatment, which was abrogated in Rap1a(-/-) mice. These results suggest that post-treatment with PC triggers the Epac/Rap1/afadin-dependent mechanism of endothelial barrier restoration and downregulation of p38MAPK and NFκB inflammatory cascades, altogether leading to accelerated lung recovery.

Asef mediates HGF protective effects against LPS-induced lung injury and endothelial barrier dysfunction

Increased vascular endothelial permeability and inflammation are major pathological mechanisms of pulmonary edema and its life-threatening complication, the acute respiratory distress syndrome (ARDS). We have previously described potent protective effects of hepatocyte growth factor (HGF) against thrombin-induced hyperpermeability and identified the Rac pathway as a key mechanism of HGF-mediated endothelial barrier protection. However, anti-inflammatory effects of HGF are less understood. This study examined effects of HGF on the pulmonary endothelial cell (EC) inflammatory activation and barrier dysfunction caused by the gram-negative bacterial pathogen lipopolysaccharide (LPS). We tested involvement of the novel Rac-specific guanine nucleotide exchange factor Asef in the HGF anti-inflammatory effects. HGF protected the pulmonary EC monolayer against LPS-induced hyperpermeability, disruption of monolayer integrity, activation of NF-kB signaling, expression of adhesion molecules intercellular adhesion molecule-1 and vascular cell adhesion molecule-1, and production of IL-8. These effects were critically dependent on Asef. Small-interfering RNA-induced downregulation of Asef attenuated HGF protective effects against LPS-induced EC barrier failure. Protective effects of HGF against LPS-induced lung inflammation and vascular leak were also diminished in Asef knockout mice. Taken together, these results demonstrate potent anti-inflammatory effects by HGF and delineate a key role of Asef in the mediation of the HGF barrier protective and anti-inflammatory effects. Modulation of Asef activity may have important implications in therapeutic strategies aimed at the treatment of sepsis and acute lung injury/ARDS-induced gram-negative bacterial pathogens.

Asef controls vascular endothelial permeability and barrier recovery in the lung

This is the first report of Asef involvement in the regulation of endothelial vascular permeability in vitro and in vivo. Asef activation in endothelial cells by hepatocyte growth factor suppressed the Rho-dependent pathway of agonist-induced endothelial permeability and promoted Rac1-dependent endothelial barrier recovery.

Increased levels of hepatocyte growth factor (HGF) in injured lungs may reflect a compensatory response to diminish acute lung injury (ALI). HGF-induced activation of Rac1 GTPase stimulates endothelial barrier protective mechanisms. This study tested the involvement of Rac-specific guanine nucleotide exchange factor Asef in HGF-induced endothelial cell (EC) cytoskeletal dynamics and barrier protection in vitro and in a two-hit model of ALI. HGF induced membrane translocation of Asef and stimulated Asef Rac1-specific nucleotide exchange activity. Expression of constitutively activated Asef mutant mimicked HGF-induced peripheral actin cytoskeleton enhancement. In contrast, siRNA-induced Asef knockdown or expression of dominant-negative Asef attenuated HGF-induced Rac1 activation evaluated by Rac-GTP pull down and FRET assay with Rac1 biosensor. Molecular inhibition of Asef attenuated HGF-induced peripheral accumulation of cortactin, formation of lamellipodia-like structures, and enhancement of VE-cadherin adherens junctions and compromised HGF-protective effect against thrombin-induced RhoA GTPase activation, Rho-dependent cytoskeleton remodeling, and EC permeability. Intravenous HGF injection attenuated lung inflammation and vascular leak in the two-hit model of ALI induced by excessive mechanical ventilation and thrombin signaling peptide TRAP6. This effect was lost in Asef^−/− mice. This study shows for the first time the role of Asef in HGF-mediated protection against endothelial hyperpermeability and lung injury.

Role of microtubules in attenuation of PepG-induced vascular endothelial dysfunction by atrial natriuretic peptide

Apart from control of circulating fluid, atrial natriuretic peptide (ANP) exhibits anti-inflammatory effects in the lung. However, molecular mechanisms of ANP anti-inflammatory effects are not well-understood. Peripheral microtubule (MT) dynamics is essential for agonist-induced regulation of vascular endothelial permeability. Here we studied the role of MT-dependent signaling in ANP protective effects against endothelial cell (EC) barrier dysfunction and acute lung injury induced by Staphylococcus aureus-derived peptidoglican-G (PepG). PepG-induced vascular endothelial dysfunction was accompanied by MT destabilization and disruption of MT network. ANP attenuated PepG-induced MT disassembly, NFκB signaling and activity of MT-associated Rho activator GEF-H1 leading to attenuation of EC inflammatory activation reflected by expression of adhesion molecules ICAM1 and VCAM1. ANP-induced EC barrier preservation and MT stabilization were linked to phosphorylation and inactivation of MT-depolymerizing protein stathmin. Expression of stathmin phosphorylation-deficient mutant abolished ANP protective effects against PepG-induced inflammation and EC permeability. In contrast, siRNA-mediated stathmin knockdown prevented PepG-induced peripheral MT disassembly and endothelial barrier dysfunction. ANP protective effects in a murine model of PepG-induced lung injury were associated with increased phosphorylation of stathmin, while exacerbated lung injury in the ANP knockout mice was accompanied by decreased pool of stable MT. Stathmin knockdown in vivo reversed exacerbation of lung injury in the ANP knockout mice. These results show a novel MT-mediated mechanism of endothelial barrier protection by ANP in pulmonary EC and animal model of PepG-induced lung injury via stathmin-dependent control of MT assembly.

Adiponectin protects against hyperoxic lung injury and vascular leak

Adiponectin (Ad), an adipokine exclusively secreted by the adipose tissue, has emerged as a paracrine metabolic regulator as well as a protectant against oxidative stress. Pharmacological approaches of protecting against clinical hyperoxic lung injury during oxygen therapy/treatment are limited. We have previously reported that Ad inhibits the NADPH oxidase-catalyzed formation of superoxide from molecular oxygen in human neutrophils. Based on this premise, we conducted studies to determine whether (i) exogenous Ad would protect against the hyperoxia-induced barrier dysfunction in the lung endothelial cells (ECs) in vitro, and (ii) endogenously synthesized Ad would protect against hyperoxic lung injury in wild-type (WT) and Ad-overexpressing transgenic (AdTg) mice in vivo. The results demonstrated that exogenous Ad protected against the hyperoxia-induced oxidative stress, loss of glutathione (GSH), cytoskeletal reorganization, barrier dysfunction, and leak in the lung ECs in vitro. Furthermore, the hyperoxia-induced lung injury, vascular leak, and lipid peroxidation were significantly attenuated in AdTg mice in vivo. Also, AdTg mice exhibited elevated levels of total thiols and GSH in the lungs as compared with WT mice. For the first time, our studies demonstrated that Ad protected against the hyperoxia-induced lung damage apparently through attenuation of oxidative stress and modulation of thiol-redox status.

Stiffness-activated GEF-H1 expression exacerbates LPS-induced lung inflammation

Acute lung injury (ALI) is accompanied by decreased lung compliance. However, a role of tissue mechanics in modulation of inflammation remains unclear. We hypothesized that bacterial lipopolysacharide (LPS) stimulates extracellular matrix (ECM) production and vascular stiffening leading to stiffness-dependent exacerbation of endothelial cell (EC) inflammatory activation and lung barrier dysfunction. Expression of GEF-H1, ICAM-1, VCAM-1, ECM proteins fibronectin and collagen, lysyl oxidase (LOX) activity, interleukin-8 and activation of Rho signaling were analyzed in lung samples and pulmonary EC grown on soft (1.5 or 2.8 kPa) and stiff (40 kPa) substrates. LPS induced EC inflammatory activation accompanied by expression of ECM proteins, increase in LOX activity, and activation of Rho signaling. These effects were augmented in EC grown on stiff substrate. Stiffness-dependent enhancement of inflammation was associated with increased expression of Rho activator, GEF-H1. Inhibition of ECM crosslinking and stiffening by LOX suppression reduced EC inflammatory activation and GEF-H1 expression in response to LPS. In vivo, LOX inhibition attenuated LPS-induced expression of GEF-H1 and lung dysfunction. These findings present a novel mechanism of stiffness-dependent exacerbation of vascular inflammation and escalation of ALI via stimulation of GEF-H1-Rho pathway. This pathway represents a fundamental mechanism of positive feedback regulation of inflammation.

Resolvin D1 reverts lipopolysaccharide-induced TJ proteins disruption and the increase of cellular permeability by regulating IκBα signaling in human vascular endothelial cells

Tight Junctions (TJ) are important components of paracellular pathways, and their destruction enhances vascular permeability. Resolvin D1 (RvD1) is a novel lipid mediator that has treatment effects on inflammatory diseases, but its effect on inflammation induced increase in vascular permeability is unclear. To understand whether RvD1 counteracts the lipopolysaccharide (LPS) induced increase in vascular cell permeability, we investigated the effects of RvD1 on endothelial barrier permeability and tight junction reorganization and expression in the presence or absence of LPS stimulation in cultured Human Vascular Endothelial Cells (HUVECs). Our results showed that RvD1 decreased LPS-induced increased in cellular permeability and inhibited the LPS-induced redistribution of zo-1, occludin, and F-actin in HUVECs. Moreover, RvD1 attenuated the expression of IκBα in LPS-induced HUVECs. The NF-κB inhibitor PDTC enhanced the protective effects of RvD1 on restoration of occludin rather than zo-1 expression in LPS-stimulated HUVECs. By contrast, the ERK1/2 inhibitor PD98059 had no effect on LPS-induced alterations in zo-1 and occludin protein expressions in HUVECs. Our data indicate that RvD1 protects against impairment of endothelial barrier function induced by LPS through upregulating the expression of TJ proteins in HUVECs, which involves the IκBα pathway but not the ERK1/2 signaling.

Cell-type-specific crosstalk between p38 MAPK and Rho signaling in lung micro- and macrovascular barrier dysfunction induced by Staphylococcus aureus-derived pathogens

Lung inflammation and alterations in endothelial cell (EC) micro- and macrovascular permeability are key events to development of acute lung injury. Using ECs derived from human pulmonary artery and lung microvasculature, we investigated the interplay between p38 stress mitogen-activated protein kinase (MAPK) and Rho guanosine triphosphatase signaling in inflammatory and hyperpermeability responses. Both cell types were treated with Staphylococcus aureus-derived peptidoglycan (PepG) and lipoteichoic acid (LTA) with or without pretreatment with p38 MAPK or Rho kinase inhibitors. LTA and PepG increased permeability markedly in both pulmonary macrovascular and microvascular ECs. Agonist-induced hyperpermeability was accompanied by cytoskeletal remodeling, disruption of cell-cell contacts, formation of paracellular gaps, and activation of p38 MAPK, nuclear factor kappa-B (NFκB), and Rho/Rho kinase signaling. In macrovascular ECs, pharmacologic inhibition of Rho kinase with Y27632 suppressed p38 MAP kinase cascade activation significantly, whereas inhibition of p38 MAPK with SB203580 had no effect on Rho activation. In contrast, inhibition of p38 MAPK in microvascular ECs suppressed LTA/PepG-induced activation of Rho, whereas the Rho inhibitor suppressed activation of p38 MAPK. Inhibition of either p38 MAPK or Rho kinase attenuated activation of NFκB signaling substantially. These results demonstrate cell-type-specific differences in signaling induced by Staphylococcus aureus-derived pathogens in pulmonary endothelium. Thus, although Gram-positive bacterial compounds caused barrier dysfunction in both EC types, it was induced by a different pattern of crosstalk between Rho, p38 MAPK, and NFκB signaling. These observations may have important implications in defining microvasculature-specific therapeutic strategies aimed at the treatment of sepsis and acute lung injury induced by Gram-positive bacterial pathogens.

Effect of serum from patients with severe acute pancreatitis on vascular endothelial permeability

OBJECTIVE

This study aimed to investigate the effect of serum taken from patients with severe acute pancreatitis (SAP) on vascular endothelial permeability.

METHODS

The monolayer permeability of endothelial cells (ECs) was assessed. Morphological changes in ECs, induced by serum from patients with SAP were assessed. Expressions of RhoA, myosin light chain (MLC) phosphorylation, and VE-cadherin protein were detected by Western blot.

RESULTS

Compared with the control group, 20% SAP serum significantly increased endothelial monolayer permeability (P < 0.01), markedly induced transcellular F-actin redistribution with stress fiber formation and VE-cadherin derangement with fragmentations located at the cell borders, and increased gaps between ECs. Furthermore, Western blotting showed that SAP serum induced rapid activation of Rho protein, and markedly increased the level of phosphorylated MLC. However, pretreatment with Y-27632 (an inhibitor for Rho kinase) significantly inhibited endothelial hyperpermeability and the morphological changes of F-actin rearrangement and VE-cadherin redistribution. This was associated with a down-regulation of Rho protein expression and a reduction in the level of MLC phosphorylation.

CONCLUSIONS

The SAP serum induces the loss of vascular endothelial monolayer integrity, with endothelial F-actin stress fiber formation and VE-cadherin redistribution. One of the mechanisms for this process involves the activation of the Rho/Rho kinase signaling pathway.

Reactive oxygen species by isoflurane mediates inhibition of nuclear factor κB activation in lipopolysaccharide-induced acute inflammation of the lung

BACKGROUND

Although anesthetic-induced inhibition of lipopolysaccharide (LPS)-induced lung injury has been recognized, the underlying mechanism is obscure. Some studies suggest that reactive oxygen species (ROS) by isoflurane play a crucial role for anesthetic-induced protective effects on the brain or the heart; however, it still remains controversial. In this study, we examined the role of isoflurane-derived ROS in isoflurane-induced inhibition of lung injury and nuclear factor κB (NFκB) activation in LPS-challenged rat lungs.

METHODS

Male Sprague-Dawley rats were subjected to inhalation of 1.0 minimum alveolar concentration of isoflurane for 60 minutes, and intratracheal LPS 0.1 mg was administered 60 minutes later. In some cases, ROS scavenger, 2-mercaptopropinyl glycine or N-acetylcysteine was given 30 minutes before isoflurane. ROS generation was measured by fluorometer before LPS challenge and 4 hours after. Isoflurane's preconditioning effect was assessed by histologic examination, protein content, neutrophil recruitment, and determination of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 levels in bronchoalveolar lavage fluid and lung tissue. Western blotting measured phosphorylation of inhibitory κB α (ser 32/36), NFκB p65, and inducible nitric oxide synthase (iNOS). TNF-α and IL-6 mRNA expression and immunofluorescence staining for iNOS were also assessed.

RESULTS

Isoflurane preconditioning reduced inflammatory lung injury and TNF-α, IL-1β, and IL-6 release in the lung. Isoflurane upregulated ROS generation before LPS but inhibited a ROS burst after LPS challenge. ROS scavenger administration before isoflurane abolished the isoflurane preconditioning effect as well as isoflurane-induced inhibition of phosphorylation of inhibitory κBα, NFκB p65, iNOS activation, and mRNA expression of TNF-α and IL-6 in acute LPS-challenged lungs.

CONCLUSIONS

This study suggests a crucial role of upregulated ROS generation by isoflurane for modification of inflammatory pathways by isoflurane preconditioning in acute inflammation of the lung.

Oxidative stress contributes to lung injury and barrier dysfunction via microtubule destabilization

Oxidative stress is an important part of host innate immune response to foreign pathogens, such as bacterial LPS, but excessive activation of redox signaling may lead to pathologic endothelial cell (EC) activation and barrier dysfunction. Microtubules (MTs) play an important role in agonist-induced regulation of vascular endothelial permeability, but their impact in modulation of inflammation and EC barrier has not been yet investigated. This study examined the effects of LPS-induced oxidative stress on MT dynamics and the involvement of MTs in the LPS-induced mechanisms of Rho activation, EC permeability, and lung injury. LPS treatment of pulmonary vascular EC induced elevation of reactive oxygen species (ROS) and caused oxidative stress associated with EC hyperpermeability, cytoskeletal remodeling, and formation of paracellular gaps, as well as activation of Rho, p38 stress kinase, and NF-κB signaling, the hallmarks of endothelial barrier dysfunction. LPS also triggered ROS-dependent disassembly of the MT network, leading to activation of MT-dependent signaling. Stabilization of MTs with epothilone B, or inhibition of MT-associated guanine nucleotide exchange factor (GEF)-H1 activity by silencing RNA-mediated knockdown, suppressed LPS-induced EC barrier dysfunction in vitro, and attenuated vascular leak and lung inflammation in vivo. LPS disruptive effects were linked to activation of Rho signaling caused by LPS-induced MT disassembly and release of Rho-specific GEF-H1 from MTs. These studies demonstrate, for the first time, the mechanism of ROS-induced Rho activation via destabilization of MTs and GEF-H1-dependent activation of Rho signaling, leading to pulmonary EC barrier dysfunction and exacerbation of LPS-induced inflammation.

Iloprost improves endothelial barrier function in lipopolysaccharide-induced lung injury

The protective effects of prostacyclin and its stable analogue iloprost are mediated by elevation of intracellular cyclic AMP (cAMP) leading to enhancement of the peripheral actin cytoskeleton and cell-cell adhesive structures. This study tested the hypothesis that iloprost may exhibit protective effects against lung injury and endothelial barrier dysfunction induced by bacterial wall lipopolysaccharide (LPS). Endothelial barrier dysfunction was assessed by measurements of transendothelial permeability, morphologically and by analysis of LPS-activated inflammatory signalling. In vivo, C57BL/6J mice were challenged with LPS with or without iloprost or 8-bromoadenosine-3',5'-cyclic monophosphate (Br-cAMP) treatment. Lung injury was monitored by measurements of bronchoalveolar lavage protein content, cell count and Evans blue extravasation. Iloprost and Br-cAMP attenuated the disruption of the endothelial monolayer, and suppressed the activation of p38 mitogen-activated protein kinase (MAPK), the nuclear factor (NF)-κB pathway, Rho signalling, intercellular adhesion molecular (ICAM)-1 expression and neutrophil migration after LPS challenge. In vivo, iloprost was effective against LPS-induced protein and neutrophil accumulation in bronchoalveolar lavage fluid, and reduced myeloperoxidase activation, ICAM-1 expression and Evans blue extravasation in the lungs. Inhibition of Rac activity abolished the barrier-protective and anti-inflammatory effects of iloprost and Br-cAMP. Iloprost-induced elevation of intracellular cAMP triggers Rac signalling, which attenuates LPS-induced NF-κB and p38 MAPK inflammatory pathways and the Rho-dependent mechanism of endothelial permeability.

CCAAT/enhancer-binding protein δ facilitates bacterial dissemination during pneumococcal pneumonia in a platelet-activating factor receptor-dependent manner

CCAAT/enhancer-binding protein δ (C/EBPδ) recently emerged as an essential player in the inflammatory response to bacterial infections. C/EBPδ levels increase rapidly after a proinflammatory stimulus, and increasing C/EBPδ levels seem to be indispensable for amplification of the inflammatory response. Here we aimed to elucidate the role of C/EBPδ in host defense in community-acquired pneumococcal pneumonia. We show that C/EBPδ(-/-) mice are relatively resistant to pneumococcal pneumonia, as indicated by delayed and reduced mortality, diminished outgrowth of pneumococci in lungs, and reduced dissemination of the infection. Moreover, expression of platelet-activating factor receptor (PAFR), which is known to potentiate bacterial translocation of gram-positive bacteria, was significantly reduced during infection in C/EBPδ(-/-) mice compared with WT controls. Importantly, cell stimulation experiments revealed that C/EBPδ potentiates PAFR expression induced by lipoteichoic acid and pneumococci. Thus, C/EBPδ exaggerates bacterial dissemination during Streptococcus pneumoniae-induced pulmonary infection, suggesting an important role for PAFR-dependent bacterial translocation.

Stimulation of Rho signaling by pathologic mechanical stretch is a "second hit" to Rho-independent lung injury induced by IL-6

Most patients with acute lung injury (ALI) and acute respiratory distress syndrome of septic and nonseptic nature require assisted ventilation with positive pressure, which at suboptimal range may further exacerbate lung dysfunction. Previous studies described enhancement of agonist-induced Rho GTPase signaling and endothelial cell (EC) permeability in EC cultures exposed to pathologically relevant cyclic stretch (CS) magnitudes. This study examined a role of pathologic CS in modulation of pulmonary EC permeability caused by IL-6, a cytokine increased in sepsis and acting in a Rho-independent manner. IL-6 increased EC permeability, which was associated with activation of Jak/signal transducers and activators of transcription, p38 MAP kinase, and NF-κB signaling and was augmented by EC exposure to 18% CS. Rho kinase inhibitor Y-27632 suppressed the synergistic effect of 18% CS on IL-6-induced EC monolayer disruption but did not alter the IL-6 effects on static EC culture. 18% CS also increased IL-6-induced ICAM-1 expression by pulmonary EC and neutrophil adhesion, which was attenuated by Y-27632. Intratracheal IL-6 administration in C57BL/6J mice increased protein content and cell count in bronchoalveolar lavage fluid. These changes were augmented by high tidal volume mechanical ventilation (HTV; 30 ml/kg, 4 h). Intravenous injection of Y-27632 suppressed IL6/HTV-induced lung injury. In conclusion, this study proposes a novel mechanism contributing to two-hit model of ALI: in addition to synergistic effects on Rho-dependent endothelial hyper-permeability triggered by thrombin, TNFα, LPS, or other agonists, ventilator-induced lung injury-relevant CS may also exacerbate Rho-independent mechanisms of EC permeability induced by other inflammatory mediators such as IL-6 via mechanisms involving Rho activity.

Induction of cellular antioxidant defense by amifostine improves ventilator-induced lung injury

OBJECTIVES

To test the hypothesis that preconditioning animals with amifostine improves ventilator-induced lung injury via induction of antioxidant defense enzymes. Mechanical ventilation at high tidal volume induces reactive oxygen species production and oxidative stress in the lung, which plays a major role in the pathogenesis of ventilator-induced lung injury. Amifostine attenuates oxidative stress and improves lipopolysaccharide-induced lung injury by acting as a direct scavenger of reactive oxygen and nitrogen species. This study tested effects of chronic amifostine administration on parameters of oxidative stress, lung barrier function, and inflammation associated with ventilator-induced lung injury.

DESIGN

Randomized and controlled laboratory investigation in mice and cell culture.

SETTING

University laboratory.

SUBJECTS

C57BL/6J mice.

INTERVENTIONS

Mice received once-daily dosing with amifostine (10-100 mg/kg, intraperitoneal injection) 3 days consecutively before high tidal volume ventilation (30 mL/kg, 4 hrs) at day 4. Pulmonary endothelial cell cultures were exposed to pathologic cyclic stretching (18% equibiaxial stretch) and thrombin in a previously verified two-hit model of in vitro ventilator-induced lung injury.

MEASUREMENTS AND MAIN RESULTS

Three-day amifostine preconditioning before high tidal volume attenuated high tidal volume-induced protein and cell accumulation in the alveolar space judged by bronchoalveolar lavage fluid analysis, decreased Evans Blue dye extravasation into the lung parenchyma, decreased biochemical parameters of high tidal volume-induced tissue oxidative stress, and inhibited high tidal volume-induced activation of redox-sensitive stress kinases and nuclear factor-kappa B inflammatory cascade. These protective effects of amifostine were associated with increased superoxide dismutase 2 expression and increased superoxide dismutase and catalase enzymatic activities in the animal and endothelial cell culture models of ventilator-induced lung injury.

CONCLUSIONS

Amifostine preconditioning activates lung tissue antioxidant cell defense mechanisms and may be a promising strategy for alleviation of ventilator-induced lung injury in critically ill patients subjected to extended mechanical ventilation.