Increased lung vascular permeability is an important contributor to respiratory failure in acute lung injury (ALI). We found that a function-blocking antibody against the integrin ␣v␤5 prevented development of lung vascular permeability in two different models of ALI: ischemia-reperfusion in rats (mediated by vascular endothelial growth factor [VEGF]) and ventilation-induced lung injury (VILI) in mice (mediated, at least in part, by transforming growth factor-␤ [TGF-␤]). Knockout mice homozygous for a null mutation of the integrin ␤5 subunit were also protected from lung vascular permeability in VILI. In pulmonary endothelial cells, both the genetic absence and blocking of ␣v␤5 prevented increases in monolayer permeability induced by VEGF, TGF-␤, and thrombin. Furthermore, actin stress fiber formation induced by each of these agonists was attenuated by blocking ␣v␤5, suggesting that ␣v␤5 regulates induced pulmonary endothelial permeability by facilitating interactions with the actin cytoskeleton. These results identify integrin ␣v␤5 as a central regulator of increased pulmonary vascular permeability and a potentially attractive therapeutic target in ALI.Keywords: integrin ␣v␤5; lung vascular permeability; pulmonary endothelial barrier function Acute lung injury (ALI) is a devastating clinical syndrome characterized by development of pulmonary edema and flooding of alveolar spaces leading to impaired gas exchange, arterial hypoxemia, and respiratory failure (1). While much progress has been made in understanding the pathogenesis of ALI, it is estimated that 190,600 cases of ALI occur every year in the United States alone; these are associated with 74,500 deaths and 3.6 million hospital days (2). Effective pharmacologic therapies are not currently available and the molecular mechanisms regulating ALI remain poorly understood.Vascular permeability in the lung has long been considered a principal pathologic hallmark of ALI that is largely responsible for its characteristic pulmonary edema formation (3, 4). Recently, integrin ␣v␤5, a member of the integrin family of heterodimeric transmembrane cell surface receptors, was shown to specifically regulate increases in vascular permeability induced by vascular endothelial growth factor (VEGF) in the systemic circulation (5). Although regulation of permeability in the systemic and pulmonary circulations is often physiologically dis- CLINICAL RELEVANCEWe describe a novel role for integrin ␣v␤5 in regulating lung vascular permeability and agonist-induced endothelial permeability. Furthermore, we suggest that ␣v␤5 regulation of the actin-cytoskeleton may be a mechanism responsible for these effects.tinct, and the precise role of VEGF in ALI remains controversial, we hypothesized that ␣v␤5 could be an important regulator of vascular permeability in the lung. Therefore, we sought to determine whether ␣v␤5 could regulate lung vascular permeability in in vivo models of ALI.In this report, we used two in vivo models of ALI to examine the role of ␣v␤5 in regulating lung vascular p...

Rationale: Sepsis and acute lung injury (ALI) have devastatingly high mortality rates. Both are associated with increased vascular leak, a process regulated by complex molecular mechanisms. Objectives: We hypothesized that integrin avb3 could be an important determinant of vascular leak and endothelial permeability in sepsis and ALI. Methods: b3 subunit knockout mice were tested for lung vascular leak after endotracheal LPS, and systemic vascular leak and mortality after intraperitoneal LPS and cecal ligation and puncture. Possible contributory effects of b3 deficiency in platelets and other hematopoietic cells were excluded by bone marrow reconstitution experiments. Endothelial cells treated with avb3 antibodies were evaluated for sphingosine-1 phosphate (S1P)-mediated alterations in barrier function, cytoskeletal arrangement, and integrin localization. Measurements and Main Results: b3 knockout mice had increased vascular leak and pulmonary edema formation after endotracheal LPS, and increased vascular leak and mortality after intraperitoneal LPS and cecal ligation and puncture. In endothelial cells, avb3 antibodies inhibited barrier-enhancing and cortical actin responses to S1P. Furthermore, S1P induced translocation of avb3 from discrete focal adhesions to cortically distributed sites through Gi-and Rac1-mediated pathways. Cortical avb3 localization after S1P was decreased by avb3 antibodies, suggesting that ligation of the avb3 with its extracellular matrix ligands is required to stabilize cortical avb3 focal adhesions. Conclusions: Our studies identify a novel mechanism by which avb3 mitigates increased vascular leak, a pathophysiologic function central to sepsis and ALI. These studies suggest that drugs designed to block avb3 may have the unexpected side effect of intensifying sepsis-and ALI-associated vascular endothelial leak.Keywords: vascular endothelium; sepsis; acute lung injury; integrin Sepsis and acute lung injury (ALI) are associated with high mortality rates and worldwide healthcare burden (1-4). Development of these syndromes requires complex host responses involving multiple cell types, inflammatory mediators, and coagulation factors. One pathophysiologic hallmark common to both sepsis and ALI is increased vascular leak. Increased vascular leak in sepsis leads to redistribution of intravascular fluid to extravascular compartments, hypovolemia, hemoconcentration, and stasis of blood flow. In ALI, alveolar spaces become flooded with pulmonary edema, resulting in impaired gas exchange, arterial hypoxemia, and respiratory failure (4-6).It is generally believed that increased paracellular passage of solutes through the vascular endothelium occurs during acute inflammatory states (7,8). Frequently cited models suggest that paracellular gaps form because of disrupted homeostasis between cytoskeletal, adhesive cell-cell, and cell-matrix forces (8-10). Integrins, a large family of heterodimeric glycoprotein receptors, are important mediators of these cellular functions and have been shown to participa...

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Coordinated gastrointestinal smooth muscle contraction is critical for proper nutrient absorption and is altered in a number of medical disorders. In this work, we demonstrate a critical role for the RGD-binding integrin α8β1 in promoting nutrient absorption through regulation of gastrointestinal motility. Smooth muscle-specific deletion and antibody blockade of α8 in mice result in enhanced gastric antral smooth muscle contraction, more rapid gastric emptying, and more rapid transit of food through the small intestine leading to malabsorption of dietary fats and carbohydrates as well as protection from weight gain in a diet-induced model of obesity. Mechanistically, ligation of α8β1 by the milk protein Mfge8 reduces antral smooth muscle contractile force by preventing RhoA activation through a PTEN-dependent mechanism. Collectively, our results identify a role for α8β1 in regulating gastrointestinal motility and identify α8 as a potential target for disorders characterized by hypo- or hyper-motility.DOI: http://dx.doi.org/10.7554/eLife.13063.001

T helper (Th)17 cell responses orchestrate immunity against extracellular pathogens, but also underlie autoimmune disease pathogenesis. Here, we uncovered a distinct and critical role for miR-18a in limiting Th17 cell differentiation. miR-18a was the most dynamically upregulated miRNA of the miR-17∼92 cluster in activated T cells. miR-18a deficiency enhanced CCR6+RORγt+ Th17 cell differentiation in vitro and increased the number of tissue Th17 cells expressing CCR6, RORγt and IL-17A in airway inflammation models in vivo. Sequence-specific miR-18 inhibitors increased CCR6 and RORγt expression in both mouse and human CD4+ T cells, revealing functional conservation. miR-18a directly targeted Smad4, Hif1a, and Rora, all key transcription factors in the Th17 cell gene expression program. These findings indicate that activating signals influence the outcome of T helper cell differentiation via differential regulation of mature miRNAs within a common cluster.