E. coli pneumonia induces CD18-independent airway neutrophil migration in the absence of increased lung vascular permeability

Advances in Targeting Drug Biological Carriers for Enhancing Tumor Therapy Efficacy

Chemotherapy drugs continue to be the main component of oncology treatment research and have been proven to be the main treatment modality in tumor therapy. However, the poor delivery efficiency of cancer therapeutic drugs and their potential off-target toxicity significantly limit their effectiveness and extensive application. The recent integration of biological carriers and functional agents is expected to camouflage synthetic biomimetic nanoparticles for targeted delivery. The promising candidates, including but not limited to red blood cells and their membranes, platelets, tumor cell membrane, bacteria, immune cell membrane, and hybrid membrane are typical representatives of biological carriers because of their excellent biocompatibility and biodegradability. Biological carriers are widely used to deliver chemotherapy drugs to improve the effectiveness of drug delivery and therapeutic efficacy in vivo, and tremendous progress is made in this field. This review summarizes recent developments in biological vectors as targeted drug delivery systems based on microenvironmental stimuli-responsive release, thus highlighting the potential applications of target drug biological carriers. The review also discusses the possibility of clinical translation, as well as the exploitation trend of these target drug biological carriers.

Differential attenuation of β2 integrin-dependent and -independent neutrophil migration by Ly6G ligation

Antibody ligation of the murine neutrophil surface protein Ly6G disrupts neutrophil migration in some contexts but not others. We tested whether this variability reflected divergent dependence of neutrophil migration on β2 integrins, adhesion molecules that interact with Ly6G at the neutrophil surface. In integrin-dependent murine arthritis, Ly6G ligation attenuated joint inflammation, even though mice lacking Ly6G altogether developed arthritis normally. By contrast, Ly6G ligation had no impact on integrin-independent neutrophil migration into inflamed lung. In peritoneum, the role of β2 integrins varied with stimulus, proving dispensable for neutrophil entry in Escherichia coli peritonitis but contributory in interleukin 1 (IL-1)-mediated sterile peritonitis. Correspondingly, Ly6G ligation attenuated only IL-1 peritonitis, disrupting the molecular association between integrins and Ly6G and inducing cell-intrinsic blockade restricted to integrin-dependent migration. Consistent with this observation, Ly6G ligation impaired integrin-mediated postadhesion strengthening for neutrophils arresting on activated cremaster endothelium in vivo. Together, these findings identify selective inhibition of integrin-mediated neutrophil emigration through Ly6G ligation, highlighting the marked site and stimulus specificity of β2 integrin dependence in neutrophil migration.

Neutrophil membranes coated, antibiotic agent loaded nanoparticles targeting to the lung inflammation

Natural cellular membranes, with the outstanding qualities of biocompatibility and specificity, have gained growing attentions in the system of drug delivery. Nanoparticles coated with cellular membranes are starting to be applied as drug-loaded-vehicles to target tumors. Here, neutrophil membranes were selected to apply in the treatment of inflammation because neutrophils can participate in various inflammatory responses and accumulate at inflammatory sites to eliminate pathogens. Through extracting neutrophil membranes from natural neutrophils without affecting their biological properties, nanoparticles loaded with sparfloxacin (SPX) were coated with these membranes and disguised as neutrophils. Compared with traditional nano-medicines, the neutrophil membrane-coated nanoparticles (NM-NP-SPX) possessed precise targeting ability just like the neutrophils could accumulate at inflammatory sites when inflammation burst. In addition, NM-NP-SPX could prolong the circulation time and had the property of controlled-release. Through in vivo experiments, we found that the concentration of three representative inflammatory cytokines in blood, bacteria and inflammatory cells in lungs of the mice with pneumonia reduced significantly in the initial 24 h after the injection of NM-NP-SPX, which meant that NM-NP-SPX could greatly reduce the risk of death for the patients with inflammation. Moreover, the infected lungs could recover rapidly without any side effects to other organs due to the low cytotoxicity of NM-NP-SPX against normal cells. Therefore, our developed drug delivery system has enormous advantages in treating inflammations. Not only that, this kind of bionic method may have greater value and application prospects in curing the inflammations arisen from cancers.

The Single Nucleotide Polymorphism Mal-D96N Mice Provide New Insights into Functionality of Mal in TLR Immune Responses

MyD88 adaptor-like (Mal) protein is the most polymorphic of the four key adaptor proteins involved in TLR signaling. TLRs play a critical role in the recognition and immune response to pathogens through activation of the prototypic inflammatory transcription factor NF-κB. The study of single nucleotide polymorphisms in TLRs, adaptors, and signaling mediators has provided key insights into the function of the corresponding genes but also into the susceptibility to infectious diseases in humans. In this study, we have analyzed the immune response of mice carrying the human Mal-D96N genetic variation that has previously been proposed to confer protection against septic shock. We have found that Mal-D96N macrophages display reduced cytokine expression in response to TLR4 and TLR2 ligand challenge. Mal-D96N macrophages also display reduced MAPK activation, NF-κB transactivation, and delayed NF-κB nuclear translocation, presumably via delayed kinetics of Mal interaction with MyD88 following LPS stimulation. Importantly, Mal-D96N genetic variation confers a physiological protective phenotype to in vivo models of LPS-, Escherichia coli-, and influenza A virus-induced hyperinflammatory disease in a gene dosage-dependent manner. Together, these results highlight the critical role Mal plays in regulating optimal TLR-induced inflammatory signaling pathways and suggest the potential therapeutic advantages of targeting the Mal D96 signaling nexus.

Histopathological Changes Caused by Inflammation and Oxidative Stress in Diet-Induced-Obese Mouse following Experimental Lung Injury

Obesity has been identified as a risk factor for adverse outcomes of various diseases. However, information regarding the difference between the response of obese and normal subjects to pulmonary inflammation is limited. Mice were fed with the control or high-fat diet to establish the lean and diet-induced obese (DIO) mice. Escherichia coli was intranasally instilled to reproduce non-fatal acute pneumonia model. After infection, serum samples and lung tissues were obtained at 0, 12, 24, and 72 h. DIO mice exhibited increased serum triglyceride (TG) and total cholesterol (TC) contents as well as pulmonary resistin, IL-6, and leptin levels compared with lean mice. E. coli infection caused an acute suppurative inflammation in the lung with increased lung index and serum TG and TC contents; elevated pulmonary tumor necrosis factor-α, interleukin (IL)-1β, IL-6, IL-8, and leptin levels; and oxidative stress in mice. Interestingly, almost all the above-mentioned parameters peaked at 12 h after infection in the lean-E. coli group but after 12 h in the DIO-E. coli group. These results indicated that the DIO mice presented a delayed inflammatory response and oxidative stress in non-fatal acute pneumonia induced by E. coli infection.

A Critical Role for P2X7 Receptor-Induced VCAM-1 Shedding and Neutrophil Infiltration during Acute Lung Injury

Pulmonary neutrophils are the initial inflammatory cells that are recruited during lung injury and are crucial for innate immunity. However, pathological recruitment of neutrophils results in lung injury. The objective of this study is to determine whether the novel neutrophil chemoattractant, soluble VCAM-1 (sVCAM-1), recruits pathological levels of neutrophils to injury sites and amplifies lung inflammation during acute lung injury. The mice with P2X7 receptor deficiency, or treated with a P2X7 receptor inhibitor or anti-VCAM-1 Abs, were subjected to a clinically relevant two-hit LPS and mechanical ventilation-induced acute lung injury. Neutrophil infiltration and lung inflammation were measured. Neutrophil chemotactic activities were determined by a chemotaxis assay. VCAM-1 shedding and signaling pathways were assessed in isolated lung epithelial cells. Ab neutralization of sVCAM-1 or deficiency or antagonism of P2X7R reduced neutrophil infiltration and proinflammatory cytokine levels. The ligands for sVCAM-1 were increased during acute lung injury. sVCAM-1 had neutrophil chemotactic activities and activated alveolar macrophages. VCAM-1 is released into the alveolar airspace from alveolar epithelial type I cells through P2X7 receptor-mediated activation of the metalloproteinase ADAM-17. In conclusion, sVCAM-1 is a novel chemoattractant for neutrophils and an activator for alveolar macrophages. Targeting sVCAM-1 provides a therapeutic intervention that could block pathological neutrophil recruitment, without interfering with the physiological recruitment of neutrophils, thus avoiding the impairment of host defenses.

Leukocyte-specific protein 1 regulates neutrophil recruitment in acute lung inflammation

The mechanisms of excessive migration of activated neutrophils into inflamed lungs, credited with tissue damage, are not fully understood. We explored the hitherto unknown expression of leukocyte-specific protein 1 (LSP1) in human and mouse lungs and neutrophils and examined its role in neutrophil migration in acute lung inflammation. Autopsied septic human lungs showed increased LSP1 labeling in epithelium, endothelium, and leukocytes, including in their nuclei compared with normal lungs. We induced acute lung inflammation through intranasal administration of E. coli lipopolysaccharide (LPS) (80 μg) in LSP1-deficient (Lsp1(-/-)) and wild-type (WT) 129/SvJ mice. Immunocytochemistry and Western blots showed increased expression of LSP1 and phosphorylated LSP1 in lungs of LPS-treated WT mice. Histology showed more congestion, inflammation, and Gr-1(+) neutrophils in lung of WT mice than Lsp1(-/-) mice. LPS-treated WT mice had significantly more neutrophils in bronchoalveolar lavage (BAL) and myeloperoxidase levels in lungs compared with Lsp1(-/-) mice. However, there were no differences in lung tissue and BAL concentrations of keratinocyte-derived chemokine, monocyte chemoattractant protein-1, macrophage inflammatory protein-1α and -1β, vascular permeability, and phosphorylated p38 MAPK between LPS-treated WT and Lsp1(-/-) mice, whereas TNF-α concentration was higher in BAL fluid from LPS-treated WT. Immunoelectron microscopy showed increased LSP1 in the nuclei of LPS-treated neutrophils. We also found increased levels of phosphorylated LSP1 associated with plasma membrane, nucleus, and cytosol at various times after LPS treatment of murine bone marrow-derived neutrophils, suggesting its role in modulation of neutrophil cytoskeleton and the membrane. These data collectively show increased expression of LSP1 in inflamed mouse and human lungs and its role in neutrophil recruitment and lung inflammation.

Prophylactic inhalation of L-alanyl-L-glutamine enhances heat shock protein 72 and attenuates endotoxin-induced lung injury in rats

Studies have demonstrated that heat shock protein 70 (HSP70) plays an important role in the protection of stressed organisms. The development of strategies for enhancing HSPs expression may provide novel means of minimizing inflammatory lung conditions, such as acute lung injury. This study aimed to examine the effect of L-alanyl-L-glutamine (GLN) inhalation in enhancing pulmonary HSP72 (inducible HSP70) expression and attenuating lung damage in a model of acute lung injury induced by lipopolysaccharide (LPS) inhalation. The experimental rats were randomly assigned to one of four experimental groups: (1) NS: saline inhalation; (2) NS-LPS: pretreatment by saline inhalation 12 h before LPS inhalation; (3) GLN: glutamine inhalation; (4) GLN-LPS: pretreatment by glutamine inhalation 12 h before LPS inhalation. The results show that GLN compared with saline administration, led to significant increase in lung HSP72 both in non LPS-treated rats and LPS-treated rats. In LPS-treated rats, pretreatment by GLN inhalation produced less lung injury as evidenced by the decrease in lung injury score and dramatic decrease in lactate dehydrogenase (LDH) activity and polymorphonuclear leukocyte cell differentiation counts (PMN %) in the bronchoalveolar lavage fluid. The study indicates that prophylactic glutamine inhalation associated with the enhancement of HSP72 synthesis attenuates tissue damage in experimental lung injury.

RhoA determines disease progression by controlling neutrophil motility and restricting hyperresponsiveness

Rho-deficient neutrophils are hyperresponsive. RhoA acts predominantly as a negative regulator of chemotaxis.

NOD2 signaling contributes to host defense in the lungs against Escherichia coli infection

Bacterial pneumonia remains a significant cause of mortality in the United States. The innate immune response is the first line of defense against invading bacteria. Neutrophil recruitment to the lungs is the first step in a multistep sequence leading to bacterial clearance. Ligand interaction with pattern-recognizing receptors (PRRs) leads to chemokine production, which drives neutrophils to the site of infection. Although we demonstrated that RIP2 is important for host defense in the lungs against Escherichia coli, the individual roles of NOD1 and NOD2 in pulmonary defense have not been addressed. Here, we explored the role of NOD2 in neutrophil-mediated host defense against an extracellular pathogen, E. coli. We found enhanced bacterial burden and reduced neutrophil and cytokine/chemokine levels in the lungs of NOD2⁻/⁻ mice following E. coli infection. Furthermore, we observed reduced activation of NF-κB and mitogen-activated protein kinases (MAPKs) in the lungs of NOD2⁻/⁻ mice upon E. coli challenge. Moreover, NOD2⁻/⁻ neutrophils show impaired intracellular bacterial killing. Using NOD2/RIP2⁻/⁻ mice, we observed bacterial burden and neutrophil accumulation in the lungs similar to those seen with NOD2⁻/⁻ mice. In addition, bone marrow-derived macrophages obtained from NOD2/RIP2⁻/⁻ mice demonstrate a reduction in activation of NF-κB and MAPKs similar to that seen with NOD2⁻/⁻ mice in response to E. coli. These findings unveil a previously unrecognized role of the NOD2-RIP2 axis for host defense against extracellular Gram-negative bacteria. This pathway may represent a novel target for the treatment of lung infection/inflammation.

Extracellular superoxide dismutase in macrophages augments bacterial killing by promoting phagocytosis

Extracellular superoxide dismutase (EC-SOD) is abundant in the lung and limits inflammation and injury in response to many pulmonary insults. To test the hypothesis that EC-SOD has an important role in bacterial infections, wild-type and EC-SOD knockout (KO) mice were infected with Escherichia coli to induce pneumonia. Although mice in the EC-SOD KO group demonstrated greater pulmonary inflammation than did wild-type mice, there was less clearance of bacteria from their lungs after infection. Macrophages and neutrophils express EC-SOD; however, its function and subcellular localization in these inflammatory cells is unclear. In the present study, immunogold electron microscopy revealed EC-SOD in membrane-bound vesicles of phagocytes. These findings suggest that inflammatory cell EC-SOD may have a role in antibacterial defense. To test this hypothesis, phagocytes from wild-type and EC-SOD KO mice were evaluated. Although macrophages lacking EC-SOD produced more reactive oxygen species than did cells expressing EC-SOD after stimulation, they demonstrated significantly impaired phagocytosis and killing of bacteria. Overall, this suggests that EC-SOD facilitates clearance of bacteria and limits inflammation in response to infection by promoting bacterial phagocytosis.

An official American Thoracic Society workshop report: features and measurements of experimental acute lung injury in animals

Acute lung injury (ALI) is well defined in humans, but there is no agreement as to the main features of acute lung injury in animal models. A Committee was organized to determine the main features that characterize ALI in animal models and to identify the most relevant methods to assess these features. We used a Delphi approach in which a series of questionnaires were distributed to a panel of experts in experimental lung injury. The Committee concluded that the main features of experimental ALI include histological evidence of tissue injury, alteration of the alveolar capillary barrier, presence of an inflammatory response, and evidence of physiological dysfunction; they recommended that, to determine if ALI has occurred, at least three of these four main features of ALI should be present. The Committee also identified key "very relevant" and "somewhat relevant" measurements for each of the main features of ALI and recommended the use of least one "very relevant" measurement and preferably one or two additional separate measurements to determine if a main feature of ALI is present. Finally, the Committee emphasized that not all of the measurements listed can or should be performed in every study, and that measurements not included in the list are by no means "irrelevant." Our list of features and measurements of ALI is intended as a guide for investigators, and ultimately investigators should choose the particular measurements that best suit the experimental questions being addressed as well as take into consideration any unique aspects of the experimental design.

Requirement of alpha(4)beta(1) and alpha(5)beta(1) integrin expression in bone-marrow-derived progenitor cells in preventing endotoxin-induced lung vascular injury and edema in mice

The goal of this study was to determine the role of integrin-mediated adhesion of bone-marrow-derived progenitor cells (BMPCs) as a requirement for the endothelial barrier protection in a lung injury model. C57BL mice were used as the source for BMPCs, which were characterized as CD34(+) and fetal liver kinase-1 (Flk1)(+) and also an expression of a repertoire of integrins. We used a mouse model of bacterial lipopolysaccharide (LPS)-induced lung vascular injury and edema formation to test the effects of BMPC integrin expression in preventing endothelial barrier injury. Adhesion of BMPCs to purified extracellular matrix proteins induced focal adhesion kinase (Fak) phosphorylation and formation of branching point structures in a alpha(4) and alpha(5) integrin-dependent manner. BMPCs expressing red fluorescent protein (RFP) were administered via the retro-orbital venous route in mice treated intraperitonially with LPS (7.5 mg/kg body weight). We observed increased retention of RFP-labeled Flk1(+) and CD34(+) BMPCs for up to 8 weeks in mice injured with LPS. BMPC transplantation increased survival by 50% (at 72-96 hours after LPS) and reduced lung vascular injury and extravascular water content induced by LPS. However, blocking with anti-alpha(4) or anti-alpha(5) integrin antibody or shRNA-mediated silencing of alpha(4) or alpha(5) integrins in donor BMPCs failed to prevent the vascular injury or edema formation and mortality. Thus, alpha(4) and alpha(5) integrin-dependent adhesion of BMPCs in lung tissue plays a critical role in preventing lung vascular injury and increasing survival in a mouse model of LPS-induced acute lung injury.

Protective effects of a superoxide dismutase/catalase mimetic compound against paraquat pneumotoxicity in rat lung

BACKGROUND AND OBJECTIVE

EUK-134 is one of the most promising of the superoxide dismutase (SOD)/catalase mimetic compounds. The antioxidant effects of EUK-134 were tested in a rat model of paraquat pneumotoxicity.

METHODS

Male Wistar rats (n = 72) were divided into three groups: group 1, controls; group 2, paraquat alone; group 3, paraquat + EUK-134. Paraquat dichloride was administered per os at a dose of 80 mg/kg. EUK-134 was injected intraperitoneally at 10 mg/kg 2 h before the paraquat and again 4 h later at 5 mg/kg.

RESULTS

On days 1, 3 and 5 after treatment with paraquat alone the LDH activity increased (P = 0.0001, P = 0.00001 and P = 0.03, respectively), and the total protein content increased (P = 0.00002, P = 0.001 and P = 0.01, respectively). The levels of acid phosphatase (AcP) in BAL fluid increased on days 1 and 3 (P = 0.006 and P = 0.04). In lung homogenates paraquat alone increased SOD activity on day 1 and decreased it on days 3 and 5. Combined treatment with paraquat and EUK-134 elevated LDH activity on day 3 (significantly less than paraquat alone) and day 5, elevated the total protein content on day 5 only, and did not change AcP activity. The combination of both agents did not alter SOD activity and decreased catalase activity on day 5 significantly less than treatment with paraquat alone (P = 0.05).

CONCLUSIONS

EUK-134, a superoxide dismutase/catalase mimetic compound decreased the pneumotoxic effect of paraquat in rats.

Neutrophil-mediated lung permeability and host defense proteins

Neutrophil recruitment to the alveolar space is associated with increased epithelial permeability. The present study investigated in mice whether neutrophil recruitment to the lung leads to accumulation of plasma-derived host defense proteins in the alveolar space and whether respiratory burst contributes to this increase in permeability. Albumin, complement C1q, and IgM were increased in bronchoalveolar lavage (BAL) fluid 6 h after intratracheal LPS challenge. Neutrophil depletion before LPS treatment completely prevented this increase in BAL fluid protein concentration. Respiratory burst was not detected in neutrophils isolated from BAL fluid, and BAL proteins were increased in mice deficient in a key subunit of the respiratory burst apparatus, gp91(phox), similar to wild-type mice. Neutrophil recruitment elicited by intratracheal instillation of the chemokines macrophage inflammatory protein-2 and keratinocyte-derived chemokine was also accompanied by accumulation of albumin, C1q, and IgM. During neutrophil recruitment to the alveolar space, epithelial permeability facilitates delivery of host defense proteins. The observed increase in epithelial permeability requires recruitment of neutrophils, but not activation of the respiratory burst, and occurs with chemokine-induced neutrophil migration independent of LPS exposure.

CYLD is a crucial negative regulator of innate immune response in Escherichia coli pneumonia

Bacteraemic pneumonia is a common cause of sepsis in critically ill patients today and is characterized by dysregulation of inflammation. The genetic factors predisposing to bacteraemic pneumonia are not yet fully understood. Innate immunity is pivotal for host defence against invading bacteria, and nuclear factor-kappa B (NF-kappaB) is central to bacteria-induced inflammation and immune responses. The deubiquitinating enzyme CYLD has been identified as a key negative regulator for NF-kappaB. In the present study, we investigated the role of CYLD in innate immune response in Escherichia coli pneumonia. Upon E. coli inoculation, Cyld(-/-) mice were hypersusceptible to E. coli pneumonia with higher mortality. Innate immune response to E. coli was enhanced in Cyld(-/-) cells and mice. Cyld(-/-) cells exhibited enhanced NF-kappaB activation upon E. coli inoculation, and the enhanced NF-kappaB activation by E. coli was abolished by perturbing IkappaB kinase (IKK) signalling. Furthermore, IKK inhibitor rescued Cyld(-/-) mice from lethal infection during E. coli pneumonia along with reduced inflammation. Taken together, these data showed that CYLD acts as a crucial negative regulator for E. coli pneumonia by negatively regulating NF-kappaB. These findings provide novel insight into the regulation of bacteraemic pneumonia and related diseases and may help develop novel therapeutic strategies for these diseases.

Augmented inducible nitric oxide synthase expression and increased NO production reduce sepsis-induced lung injury and mortality in myeloperoxidase-null mice

The myeloperoxidase (MPO)-hydrogen peroxide-halide system is an efficient oxygen-dependent antimicrobial component of polymorphonuclear leukocyte (PMN)-mediated host defense. However, MPO deficiency results in few clinical consequences indicating the activation of compensatory mechanisms. Here, we determined possible mechanisms protecting the host using MPO(-/-) mice challenged with live gram-negative bacterium Escherichia coli. We observed that MPO(-/-) mice unexpectedly had improved survival compared with wild-type (WT) mice within 5-12 h after intraperitoneal E. coli challenge. Lungs of MPO(-/-) mice also demonstrated lower bacterial colonization and markedly attenuated increases in microvascular permeability and edema formation after E. coli challenge compared with WT. However, PMN sequestration in lungs of both groups was similar. Basal inducible nitric oxide synthase (iNOS) expression was significantly elevated in lungs and PMNs of MPO(-/-) mice, and NO production was increased two- to sixfold compared with WT. Nitrotyrosine levels doubled in lungs of WT mice within 1 h after E. coli challenge but did not change in MPO(-/-) mice. Inhibition of iNOS in MPO(-/-) mice significantly increased lung edema and reduced their survival after E. coli challenge, but iNOS inhibitor had the opposite effect in WT mice. Thus augmented iNOS expression and NO production in MPO(-/-) mice compensate for the lack of HOCl-mediated bacterial killing, and the absence of MPO-derived oxidants mitigates E. coli sepsis-induced lung inflammation and injury.

Inactivation of CD11b in a mouse transgenic model protects against sepsis-induced lung PMN infiltration and vascular injury

To inactivate chronically the beta2-integrin CD11b (Mac-1), we made a transgenic model in mice in which we expressed the CD11b antagonist polypeptide neutrophil inhibitory factor (NIF). Using these mice, we determined the in vivo effects of CD11b inactivation on polymorphonuclear leukocyte (PMN) function and acute lung injury (ALI) induced by Escherichia coli septicemia. In wild-type PMNs, CD11b expression was induced within 1 h after E. coli challenge, whereas this response was significantly reduced in NIF(+/+) PMNs. Coimmunoprecipitation studies showed that NIF associated with CD11b in NIF(+/+) PMNs. To validate the effectiveness of CD11b blockade, we compared PMN function in NIF(+/+) and Mac-1-deficient (Mac-1(-/-)) mice. Adhesion of both Mac-1(-/-) and NIF(+/+) PMNs to endothelial cells in response to LPS was reduced in both types of PMNs and fully blocked only by the addition of anti-CD11a monoclonal antibody. This finding is indicative of intact CD11a function in the NIF(+/+) PMNs but the blockade of CD11b function. CD11b inactivation in NIF(+/+) mice interfered with lung PMN infiltration induced by E. coli and prevented the increase in lung microvessel permeability and edema formation, with most of the protection seen in the 1-h period after the E. coli. Thus our results demonstrate that CD11b plays a crucial role in mediating lung PMN sequestration and vascular injury in the early phase of gram-negative septicemia. The NIF(+/+) mouse model, in which CD11b is inactivated by binding to NIF, is a potentially useful model for in vivo assessment of the role of PMN CD11b in the mechanism of vascular inflammation.

Cdc42 regulates adherens junction stability and endothelial permeability by inducing alpha-catenin interaction with the vascular endothelial cadherin complex

The endothelial adherens junctions (AJs) consist of trans-oligomers of membrane spanning vascular endothelial (VE)-cadherin proteins, which bind beta-catenin through their cytoplasmic domain. beta-Catenin in turn binds alpha-catenin and connects the AJ complex with the actin cytoskeleton. We addressed the in vivo effects of loss of VE-cadherin interactions on lung vascular endothelial permeability and the role of specific Rho GTPase effectors in regulating the increase in permeability induced by AJ destabilization. We used cationic liposomes encapsulating the mutant of VE-cadherin lacking the extracellular domain (DeltaEXD) to interfere with AJ assembly in mouse lung endothelial cells. We observed that lung vascular permeability (quantified as microvessel filtration coefficient [K(f,c)]) was increased 5-fold in lungs expressing DeltaEXD. This did not occur to the same degree on expression of the VE-cadherin mutant, DeltaEXDDeltabeta, lacking the beta-catenin-binding site. The increased vascular permeability was the result of destabilization of VE-cadherin homotypic interaction induced by a shift in the binding of beta-catenin from wild-type VE-cadherin to the expressed DeltaEXD mutant. Because DeltaEXD expression in endothelial cells activated the Rho GTPase Cdc42, we addressed its role in the mechanism of increased endothelial permeability induced by AJ destabilization. Coexpression of dominant-negative Cdc42 (N17Cdc42) prevented the increase in K(f,c) induced by DeltaEXD. This was attributed to inhibition of the association of alpha-catenin with the DeltaEXD-beta-catenin complex. The results demonstrate that Cdc42 regulates AJ permeability by controlling the binding of alpha-catenin with beta-catenin and the consequent interaction of the VE-cadherin/catenin complex with the actin cytoskeleton.

Toll-IL-1 Receptor Domain-Containing Adaptor Protein Is Critical for Early Lung Immune Responses against Escherichia coli Lipopolysaccharide and Viable Escherichia coli

Pulmonary bacterial diseases are a leading cause of mortality in the U.S. Innate immune response is vital for bacterial clearance from the lung, and TLRs play a critical role in this process. Toll-IL-1R domain-containing adaptor protein (TIRAP) is a key molecule in the TLR4 and 2 signaling. Despite its potential importance, the role of TIRAP-mediated signaling in lung responses has not been examined. Our goals were to determine the role of TIRAP-dependent signaling in the induction of lung innate immune responses against Escherichia coli LPS and viable E. coli, and in lung defense against E. coli in mice. LPS-induced neutrophil sequestration; NF-kappaB translocation; keratinocyte cell-derived chemokine, MIP-2, TNF-alpha, and IL-6 expression; histopathology; and VCAM-1 and ICAM-1 expression were abolished in the lungs of TIRAP-/- mice. A cell-permeable TIRAP blocking peptide attenuated LPS-induced lung responses. Furthermore, immune responses in the lungs of TIRAP-/- mice were attenuated against E. coli compared with TIRAP+/+ mice. TIRAP-/- mice also had early mortality, higher bacterial burden in the lungs, and more bacterial dissemination following E. coli inoculation. Moreover, we used human alveolar macrophages to examine the role of TIRAP signaling in the human system. The TIRAP blocking peptide abolished LPS-induced TNF-alpha, IL-6, and IL-8 expression in alveolar macrophages, whereas it attenuated E. coli-induced expression of these cytokines and chemokines. Taken together, this is the first study illustrating the crucial role of TIRAP in the generation of an effective early immune response against E. coli LPS and viable E. coli, and in lung defense against a bacterial pathogen.