Increased Lung Vascular Permeability Research Articles

A matrix metalloprotease‐PAR1 system regulates vascular integrity, systemic inflammation and death in sepsis

Sepsis is a deadly disease characterized by the inability to regulate the inflammatory–coagulation response in which the endothelium plays a key role. The cause of this perturbation remains poorly understood and has hampered the development of effective therapeutics. Matrix metalloproteases (MMPs) are involved in the host response to pathogens, but can also cause uncontrolled tissue damage and contribute to mortality. We found that human sepsis patients had markedly elevated plasma proMMP-1 and active MMP-1 levels, which correlated with death at 7 and 28 days after diagnosis. Likewise, septic mice had increased plasma levels of the MMP-1 ortholog, MMP-1a. We identified mouse MMP-1a as an agonist of protease-activated receptor-1 (PAR1) on endothelial cells. MMP-1a was released from endothelial cells in septic mice. Blockade of MMP-1 activity suppressed endothelial barrier disruption, disseminated intravascular coagulation (DIC), lung vascular permeability as well as the cytokine storm and improved survival, which was lost in PAR1-deficient mice. Infusion of human MMP-1 increased lung vascular permeability in normal wild-type mice but not in PAR1-deficient mice. These findings implicate MMP-1 as an important activator of PAR1 in sepsis and suggest that therapeutics that target MMP1-PAR1 may prove beneficial in the treatment of sepsis.

Tumor necrosis factor-α induces increased lung vascular permeability: A role for GSK3α/β

We tested the hypothesis that glycogen synthase kinase 3α/β (GSK3α/β) modulates tumor necrosis factor-a (TNF) induced increased lung vascular permeability. Rats were treated with TNF (i.v., ~ 100 ng/ml) or vehicle 0.5 h, 4.0 h and 24.0 h prior to lung isolation. Rats were co-treated with the GSK3α/β inhibitors SB216763 (0.6 mg/kg) or TDZD-8 (1.0 mg/kg). After TNF, the isolated lung was assessed for hemodynamics, wet–dry/dry weight (W–D/D) and extravascular albumin. Extravascular albumin significantly increased at TNF-24 h compared to Control. In the GSK3α/β-inhibited + TNF groups, extravascular albumin was similar to the Control and respective SB216763 and TDZD-8 groups. In separate studies, to assess GSK3α/β-activity, lung lysate was assessed for phospho-GSK3α/β-Ser 21/9, total GSK3α/β, un-phospho-β-catenin-Ser 33/37 and total β-catenin. In the TNF-4.0 h group, there was no change in GSK3α/phospho-GSK3α-Ser 21 but there was an increase in GSK3β/GSK3β-Ser 9 compared to Control, indicating GSK3β activation at TNF-4.0 h. GSK3β activation was verified because there was a decrease in un-phospho-β-catenin-Ser 33/37/β-catenin in the TNF-4.0 group, a specific outcome for GSK3β activation. In the SB216763 + TNF group, un-phospho-β-catenin-Ser 33/37 was similar to Control, indicating prevention of TNF-induced GSK3β activation. In the TNF-24 h group, there were increases in the biomarkers of inflammation phospho-eNOS-Ser 1117 and oxidized protein, which did not occur in the SB216763 + TNF-24 h and TDZD-8 + TNF-24 h groups. In the SB216763 + TNF-24 h and TDZD-8 + TNF-24 h groups, un-phospho-β-catenin-Ser 33/37 was greater than in the Control, indicating continued inhibition of GSK3β. The data indicates that pharmacologic inhibition of GSK3β inhibits TNF induced increased endothelial permeability associated with lung inflammation.

Protection of LPS-Induced Murine Acute Lung Injury by Sphingosine-1-Phosphate Lyase Suppression

A defining feature of acute lung injury (ALI) is the increased lung vascular permeability and alveolar flooding, which leads to associated morbidity and mortality. Specific therapies to alleviate the unremitting vascular leak in ALI are not currently clinically available; however, our prior studies indicate a protective role for sphingosine-1-phosphate (S1P) in animal models of ALI with reductions in lung edema. As S1P levels are tightly regulated by synthesis and degradation, we tested the hypothesis that inhibition of S1P lyase (S1PL), the enzyme that irreversibly degrades S1P via cleavage, could ameliorate ALI. Intratracheal instillation of LPS to mice enhanced S1PL expression, decreased S1P levels in lung tissue, and induced lung inflammation and injury. LPS challenge of wild-type mice receiving 2-acetyl-4(5)-[1(R),2(S),3(R),4-tetrahydroxybutyl]-imidazole to inhibit S1PL or S1PL(+/-) mice resulted in increased S1P levels in lung tissue and bronchoalveolar lavage fluids and reduced lung injury and inflammation. Moreover, down-regulation of S1PL expression by short interfering RNA (siRNA) in primary human lung microvascular endothelial cells increased S1P levels, and attenuated LPS-mediated phosphorylation of p38 mitogen-activated protein kinase and I-κB, IL-6 secretion, and endothelial barrier disruption via Rac1 activation. These results identify a novel role for intracellularly generated S1P in protection against ALI and suggest S1PL as a potential therapeutic target.

Differential effects of formaldehyde exposure on the cell influx and vascular permeability in a rat model of allergic lung inflammation

Exposure to air pollutants such as formaldehyde (FA) leads to inflammation, oxidative stress and immune-modulation in the airways and is associated with airway inflammatory disorders such as asthma. The purpose of our study was to investigate the effects of exposure to FA on the allergic lung inflammation. The hypothesized link between reactive oxygen species and the effects of FA was also studied. To do so, male Wistar rats were exposed to FA inhalation (1%, 90 min daily) for 3 days, and subsequently sensitized with ovalbumin (OVA)-alum by subcutaneous route. One week later the rats received another OVA-alum injection by the same route (booster). Two weeks later the rats were challenged with aerosolized OVA. The OVA challenge of rats upon FA exposure induced an elevated release of LTB 4, TXB 2, IL-1β, IL-6 and VEGF in lung cells, increased phagocytosis and lung vascular permeability, whereas the cell recruitment into lung was reduced. FA inhalation induced the oxidative burst and the nitration of proteins in the lung. Vitamins C, E and apocynin reduced the levels of LTB 4 in BAL-cultured cells of the FA and FA/OVA groups, but increased the cell influx into the lung of the FA/OVA rats. In OVA-challenged rats, the exposure to FA was associated to a reduced lung endothelial cells expression of intercellular cell adhesion molecule 1 (ICAM-1). In conclusion, our findings suggest that FA down regulate the cellular migration into the lungs after an allergic challenge and increase the ability of resident lung cells likely macrophages to generate inflammatory mediators, explaining the increased lung vascular permeability. Our data are indicative that the actions of FA involve mechanisms related to endothelium–leukocyte interactions and oxidative stress, as far as the deleterious effects of this air pollutant on airways are concerned.

Localization of increased lung vascular permeability in experimental pulmonary embolism and the role of PGI2

Localization of increased lung vascular permeability in experimental pulmonary embolism and the role of PGI2

Bone marrow-derived progenitor cells prevent thrombin-induced increase in lung vascular permeability

Since thrombin activation of endothelial cells (ECs) is well-known to increase endothelial permeability by disassembly of adherens junctions (AJs) and actinomyosin contractility mechanism involving myosin light chain (MLC) phosphorylation, we investigated the effects of bone marrow-derived progenitor cells (BMPCs) on the thrombin-induced endothelial permeability response. We observed that addition of BMPCs to endothelial monolayers at a fixed ratio prevented the thrombin-induced decrease in transendothelial electrical resistance, a measure of AJ integrity, and increased mouse pulmonary microvessel filtration coefficient, a measure of transvascular liquid permeability. The barrier protection was coupled to increased vascular endothelial cadherin expression and increased Cdc42 activity in ECs. Using small interfering RNA (siRNA) to deplete Cdc42 in ECs, we demonstrated a key role of Cdc42 in signaling the BMPC-induced endothelial barrier protection. Endothelial integrity induced by BMPCs was also secondary to inhibition of MLC phosphorylation in ECs. Thus BMPCs interacting with ECs prevent thrombin-induced endothelial hyperpermeability by a mechanism involving AJ barrier annealing, inhibition of MLC phosphorylation, and activation of Cdc42.

Fyn limits the protease activating receptor‐1 (PAR‐1)‐induced increase in lung microvascular permeability by inducing FAK activation

We showed that focal adhesion kinase (FAK) is required to reverse the thrombin‐induced increase in endothelial permeability. Fyn is a non‐receptor Src family tyrosine kinase, which phosphorylates FAK. We investigated the role of Fyn in regulating lung microvascular permeability using Fyn deficient mice. First, we determined whether activation of PAR‐1 by specific activating peptide (TFLLRN), alters FAK activity in lungs. Lungs of WT or Fyn−/− mice received i.v. injection of either control or PAR‐1 activating peptide were homogenized for determination of FAK phosphorylation. We observed that PAR‐1 agonist peptide increased FAK phosphorylation at Y397 and Y576 in WT mice lungs, but failed to induce FAK phosphorylation in lungs of Fyn−/− mice. Next, we determined microvessel filtration coefficient (Kf,c) in lungs isolated from WT and Fyn−/− mice. We observed that basal Kf,,c was significantly higher in Fyn−/− lungs than WT lungs. We also determined Evans blue albumin extravasation and lung wet‐ to dry weight ratio following PAR‐1 activation to assess the role of Fyn in regulating lung edema formation. Injection of PAR‐1 peptide produced significantly greater increase in lung vascular permeability in Fyn−/− mice, indicating that Fyn limits the PAR‐1‐induced pulmonary edema. We next addressed whether rescuing FAK activation could restore lung vascular permeability in Fyn−/− mice. Liposomes conjugated with FAK double phospho‐mimicing mutant (Y397D/Y576D) were injected in Fyn−/− mice and lung vascular permeability was determined after confirmation of FAK mutant expression. We show that rescuing FAK phosphorylation markedly suppressed PAR‐1 induced lung vascular permeability in Fyn−/− mice. These studies identify Fyn as the critical tyrosine kinase that by inducing FAK activation maintains lung vascular barrier function.

TRPC1‐Mediated Ca2+ Entry Increases Lung Microvascular Permeability

Despite the evidence that transient receptor potential canonical (TRPC1) channel can mediate Ca2+ entry in endothelial cells the role of TRPC1 activity in the mechanism of increased lung vascular permeability remains unclear. We isolated lungs from TRPC1−/− and wild type (WT) mice and activated Ca2+ entry by two independent mechanisms to determine the role of TRPC1 in regulating lung microvascular permeability. We perfused lungs with either thapsigargin, that activates Ca2+ entry by depleting intracellular stores or diacylglycerol (DAG), that activate Ca2+ entry independent of store depletion. We determined lung microvascular permeability by determining filtration co‐efficient (Kfc), a measure of hydraulic conductivity across endothelial exchange barrier. We show that in WT lungs thapsigargin increased lung Kfc whereas thapsigargin failed to increase Kfc in lungs isolated from TRPC1−/− mice. Interestingly, OAG, a cell permeable analog of DAG, increased Kfc in TRPC1−/− mice but the Kfc response was significantly lower than that observed in WT mice lungs. We next determined the contribution of TRPC1 in regulating lung microvascular permeability in response to thrombin ligation of protease activating receptor 1 (PAR‐1) which activate Ca2+ entry both by store‐dependent and DAG‐dependent manner. We show that PAR‐1 activation by specific PAR‐1 peptide increased Kfc in WT lungs whereas it failed to induce a response in lungs isolated from TRPC1−/− mice. We also address the role of TRPC1 in the lung inflammatory response to sepsis induced by i.p. injection of LPS. Prevention of lung injury in TRPC1−/− mice was associated with decreased mortality in response to LPS challenge. Thus, TRPC1 through its ability to regulate Ca2+ entry is a crucial determinant of increased lung microvascular permeability and inflammatory response.

Microparticle (MP) formation and matrix metalloproteinase (MMP) activation during ventilator induced lung injury (VILI)

Ventilation with high peak inflation pressures (PIP) induces increased lung vascular permeability. Activation of MMP causes proteolytic breakdown of cell adhesion proteins and contributes to the increased permeability in VILI. MPs are membrane enclosed particles less than 1 micron diameter, produced by cell activation, exocytosis or apoptosis, and are known to produce endothelial cell dysfunction. To determine a possible link between MP and MMP activation, we ventilated C57/BL6 mice at 50 cmH2O PIP for 2 hours. Plasma MP numbers increased eightfold compared to unventilated controls while MP counts in BAL were similar. Using flow cytometry for surface proteins, 30% of plasma MP expressed CD31, CD54 and CD61, whereas approximately 50% expressed CD106, CD147, and E‐cadherin. In lungs ventilated with high PIP compared to low PIP (9 cmH2O), MMP‐2 activity increased 2‐fold in lung tissue and 25‐fold in BAL; MMP‐9 activity increased 2‐fold in lung tissue and 4‐fold in plasma, and tissue inhibitor of metalloproteinase (TIMP) decreased by 30% in lung tissue. Collagenase activity was approximately 2‐fold higher in MP compared to supernatant in both plasma and BAL. These data indicate that MP increased during VILI and possess surface proteins and MMP activity to bind to and degrade junctional proteins. MP may serve as targeted agents which contribute to increased vascular permeability during VILI. Supported by P01 HL66299.

Role of coagulation pathways and treatment with activated protein C in hyperoxic lung injury

Background:Activated protein C (APC) significantly decreases mortality in severe sepsis, but its role in acute lung injury from non-infectious aetiologies is unclear. The role of APC in hyperoxic acute lung...

Impact of acute kidney injury on lung injury

classic animal models of critical illness have focused on injury of a single end-organ, with the goal of better understanding and attenuating that injury, and ultimately developing novel disease-focused therapies. For example, acute lung injury (ALI) can be induced in animal models by administration

Uremic lung: new insights into a forgotten condition

The high mortality rate of acute kidney injury (AKI) despite advances in dialysis led to a renewed appreciation of the impact of AKI on distant organ dysfunction. Mechanistic studies demonstrated that AKI induces increased lung vascular permeability, soluble and cellular inflammation, and dysregulated salt and water channels. AKI also affects the brain, heart, liver, bone marrow, and gastrointestinal tract. Klein et al. now demonstrate that interleukin-6 is a direct mediator of AKI-induced lung changes.

Magnitude-dependent effects of cyclic stretch on HGF- and VEGF-induced pulmonary endothelial remodeling and barrier regulation

Mechanical ventilation at high tidal volumes compromises the blood-gas barrier and increases lung vascular permeability, which may lead to ventilator-induced lung injury and pulmonary edema. Using pulmonary endothelial cell (ECs) exposed to physiologically [5% cyclic stretch (CS)] and pathologically (18% CS) relevant magnitudes of CS, we evaluated the potential protective effects of hepatocyte growth factor (HGF) on EC barrier dysfunction induced by CS and vascular endothelial growth factor (VEGF). In static culture, HGF enhanced EC barrier function in a Rac-dependent manner and attenuated VEGF-induced EC permeability and paracellular gap formation. The protective effects of HGF were associated with the suppression of Rho-dependent signaling triggered by VEGF. Five percent CS promoted HGF-induced enhancement of the cortical F-actin rim and activation of Rac-dependent signaling, suggesting synergistic barrier-protective effects of physiological CS and HGF. In contrast, 18% CS further enhanced VEGF-induced EC permeability, activation of Rho signaling, and formation of actin stress fibers and paracellular gaps. These effects were attenuated by HGF pretreatment. EC preconditioning at 5% CS before HGF and VEGF further promoted EC barrier maintenance. Our data suggest synergistic effects of HGF and physiological CS in the Rac-mediated mechanisms of EC barrier protection. In turn, HGF reduced the barrier-disruptive effects of VEGF and pathological CS via downregulation of the Rho pathway. These results support the importance of HGF-VEGF balance in control of acute lung injury/acute respiratory distress syndrome severity via small GTPase-dependent regulation of lung endothelial permeability.

Critical role of Cdc42 in mediating endothelial barrier protection in vivo

Activation of the Rho GTPase Cdc42 has been shown in endothelial cell monolayers to prevent disassembly of interendothelial junctions and the increase in endothelial permeability. Here, we addressed the in vivo role of Cdc42 activity in mediating endothelial barrier protection in lungs by generating mice expressing the dominant active mutant V12Cdc42 protein in vascular endothelial cells targeted via the VE-cadherin promoter. These mice developed normally and exhibited constitutively active GTP-bound Cdc42. The increase in lung vascular permeability and gain in tissue water content in response to intraperitoneal lipopolysaccharide challenge (7 mg/kg) were markedly attenuated in the transgenic mice. To address the basis of the protective effect, we observed that expression of V12Cdc42 mutant in endothelial monolayers reduced the decrease in transendothelial electrical resistance, a measure of opening of interendothelial junctions, thus indicating that Cdc42 activity preserved junctional integrity. RhoA activity in V12Cdc42-expressing endothelial monolayers was reduced compared with untransfected cells, suggesting that activated Cdc42 functions by counteracting the canonical RhoA-mediated mechanism of endothelial hyperpermeability. Therefore, Cdc42 activity of microvessel endothelial cells is a critical determinant of junctional barrier restrictiveness and may represent a means of therapeutically modulating increased lung vascular permeability and edema formation.

Intercellular Adhesion Molecule-1–Dependent Neutrophil Adhesion to Endothelial Cells Induces Caveolae-Mediated Pulmonary Vascular Hyperpermeability

We investigated the role of caveolae in the mechanism of increased pulmonary vascular permeability and edema formation induced by the activation of polymorphonuclear neutrophils (PMNs). We observed that the increase in lung vascular permeability induced by the activation of PMNs required caveolin-1, the caveolae scaffold protein. The permeability increase induced by PMN activation was blocked in caveolin-1 knockout mice and by suppressing caveolin-1 expression in rats. The response was also dependent on Src phosphorylation of caveolin-1 known to activate caveolae-mediated endocytosis in endothelial cells. To address the role of PMN interaction with endothelial cells, we used an intercellular adhesion molecule (ICAM)-1 blocking monoclonal antibody. Preventing the ICAM-1-mediated PMN binding to endothelial cells abrogated Src phosphorylation of caveolin-1, as well as the increase in endothelial permeability. Direct ICAM-1 activation by crosslinking recapitulated these responses, suggesting that ICAM-1 activates caveolin-1 signaling responsible for caveolae-mediated endothelial hyperpermeability. Our results provide support for the novel concept that a large component of pulmonary vascular hyperpermeability induced by activation of PMNs adherent to the vessel wall is dependent on signaling via caveolin-1 and increased caveolae-mediated transcytosis. Thus, it is important to consider the role of the transendothelial vesicular permeability pathway that contributes to edema formation in developing therapeutic interventions against PMN-mediated inflammatory diseases such as acute lung injury.

Negative-Feedback Loop Attenuates Hydrostatic Lung Edema via a cGMP-Dependent Regulation of Transient Receptor Potential Vanilloid 4

Although the formation of hydrostatic lung edema is generally attributed to imbalanced Starling forces, recent data show that lung endothelial cells respond to increased vascular pressure and may thus regulate vascular permeability and edema formation. In combining real-time optical imaging of the endothelial Ca(2+) concentration ([Ca(2+)](i)) and NO production with filtration coefficient (K(f)) measurements in the isolated perfused lung, we identified a series of endothelial responses that constitute a negative-feedback loop to protect the microvascular barrier. Elevation of lung microvascular pressure was shown to increase endothelial [Ca(2+)](i) via activation of transient receptor potential vanilloid 4 (TRPV4) channels. The endothelial [Ca(2+)](i) transient increased K(f) via activation of myosin light-chain kinase and simultaneously stimulated NO synthesis. In TRPV4 deficient mice, pressure-induced increases in endothelial [Ca(2+)](i), NO synthesis, and lung wet/dry weight ratio were largely blocked. Endothelial NO formation limited the permeability increase by a cGMP-dependent attenuation of the pressure-induced [Ca(2+)](i) response. Inactivation of TRPV4 channels by cGMP was confirmed by whole-cell patch-clamp of pulmonary microvascular endothelial cells and intravital imaging of endothelial [Ca(2+)](i). Hence, pressure-induced endothelial Ca(2+) influx via TRPV4 channels increases lung vascular permeability yet concomitantly activates an NO-mediated negative-feedback loop that protects the vascular barrier by a cGMP-dependent attenuation of the endothelial [Ca(2+)](i) response. The identification of this novel regulatory pathway gives rise to new treatment strategies, as demonstrated in vivo in rats with acute myocardial infarction in which inhibition of cGMP degradation by the phosphodiesterase 5 inhibitor sildenafil reduced hydrostatic lung edema.

Deletion of PKCalpha in mice attenuates the thrombin‐induced increase in lung vascular permeability

We addressed the role of protein kinase Cα (PKCα) in signaling the increase in lung vascular permeability induced by the mediator thrombin. We used PKCα knockout mice to determine the effect of PKCα deletion on changes in endothelial permeability and adherens junction proteins. We determined microvessel filtration coefficient (Kfc) using the isolated‐perfused mouse lung preparation. Stimulation with PAR‐1 agonist peptide (10 μM) increased Kfc 50% less in the knockout mice than control wild type mice. We quantified vascular endothelial (VE) cadherin levels in mouse lung endothelial cells (MLECs) by Western blot analysis. Thrombin rapidly diminished VE‐cadherin levels in MLECs. PKCα deletion abrogated the VE‐cadherin disruption induced by thrombin. As PKCα activation was known to inhibit Akt, we observed higher Akt activity in PKCα‐deleted MLECs. We also observed that activated PKCζ was markedly increased in PKCα‐deleted MLECs, suggesting compensatory activation of PKCζ. The data demonstrate that PKCα is required to elicit the increase in lung vascular permeability. The mechanism of PKCα‐mediated increase in vascular permeability may involve signaling at the level of VE‐cadherin that promotes the disassembly of adherens junctions.This study is supported by NIH # HL45638

Interleukin-1β Causes Acute Lung Injury via αvβ5 and αvβ6 Integrin–Dependent Mechanisms

Interleukin (IL)-1beta has previously been shown to be among the most biologically active cytokines in the lungs of patients with acute lung injury (ALI). Furthermore, there is experimental evidence that lung vascular permeability increases after short-term exposure to IL-1 protein, although the exact mechanism is unknown. Therefore, the objective of this study was to determine the mechanisms of IL-1beta-mediated increase in lung vascular permeability and pulmonary edema following transient overexpression of this cytokine in the lungs by adenoviral gene transfer. Lung vascular permeability increased with intrapulmonary IL-1beta production with a maximal effect 7 days after instillation of the adenovirus. Furthermore, inhibition of the alphavbeta6 integrin and/or transforming growth factor-beta attenuated the IL-1beta-induced ALI. The results of in vitro studies indicated that IL-1beta caused the activation of transforming growth factor-beta via RhoA/alphavbeta6 integrin-dependent mechanisms and the inhibition of the alphavbeta6 integrin and/or transforming growth factor-beta signaling completely blocked the IL-1beta-mediated protein permeability across alveolar epithelial cell monolayers. In addition, IL-1beta increased protein permeability across lung endothelial cell monolayers via RhoA- and alphavbeta5 integrin-dependent mechanisms. The final series of in vivo experiments demonstrated that pretreatment with blocking antibodies to both the alphavbeta5 and alphavbeta6 integrins had an additive protective effect against IL-1beta-induced ALI. In summary, these results demonstrate a critical role for the alphavbeta5/beta6 integrins in mediating the IL-1beta-induced ALI and indicate that these integrins could be a potentially attractive therapeutic target in ALI.

Epithelium: sticking it out, together

some cells live within a community of neighboring cells, restricted in time and space, most prominently interacting with cells of similar functions. Some cells live within fixed positions, surrounded on all sides by a loose forest of matrix proteins. Some cells live as nomads, wandering throughout

Protective role of vascular endothelial growth factor in endotoxin-induced acute lung injury in mice

BackgroundVascular endothelial growth factor (VEGF), a substance that stimulates new blood vessel formation, is an important survival factor for endothelial cells. Although overexpressed VEGF in the lung induces pulmonary edema with increased lung vascular permeability, the role of VEGF in the development of acute lung injury remains to be determined.MethodsTo evaluate the role of VEGF in the pathogenesis of acute lung injury, we first evaluated the effects of exogenous VEGF and VEGF blockade using monoclonal antibody on LPS-induced lung injury in mice. Using the lung specimens, we performed TUNEL staining to detect apoptotic cells and immunostaining to evaluate the expression of apoptosis-associated molecules, including caspase-3, Bax, apoptosis inducing factor (AIF), and cytochrome C. As a parameter of endothelial permeability, we measured the albumin transferred across human pulmonary artery endothelial cell (HPAEC) monolayers cultured on porous filters with various concentrations of VEGF. The effect of VEGF on apoptosis HPAECs was also examined by TUNEL staining and active caspase-3 immunoassay.ResultsExogenous VEGF significantly decreased LPS-induced extravascular albumin leakage and edema formation. Treatment with anti-VEGF antibody significantly enhanced lung edema formation and neutrophil emigration after intratracheal LPS administration, whereas extravascular albumin leakage was not significantly changed by VEGF blockade. In lung pathology, pretreatment with VEGF significantly decreased the numbers of TUNEL positive cells and those with positive immunostaining of the pro-apoptotic molecules examined. VEGF attenuated the increases in the permeability of the HPAEC monolayer and the apoptosis of HPAECs induced by TNF-α and LPS. In addition, VEGF significantly reduced the levels of TNF-α- and LPS-induced active caspase-3 in HPAEC lysates.ConclusionThese results suggest that VEGF suppresses the apoptosis induced by inflammatory stimuli and functions as a protective factor against acute lung injury.