Integrin CD11b Research Articles

Rho-GTPase Cdc42 Regulates Neutrophil Polarity Via Crosstalk Between Wiskott Aldrich Syndrome Protein (WASp), Lipid Raft Reorganization, CD11b and Microtubules

Abstract 16Neutrophils (PMNs) are the first line of immune defense by moving toward the infection site. A key event of cell migration is the maintenance of a polarized morphology characterized by a single protrusive leading edge (i.e. lamellipodia) and a contractile uropod. Using mice with a conditional Cdc42 (flox) allele, we have previously reported that the small Rho GTPase Cdc42 controls neutrophil polarity via CD11b integrin signaling at the uropod (Szczur; Blood 2009). In the present study, we seek to dissect the mechanism of Cdc42-CD11b axis in neutrophil polarity. We first examined the role of the Cdc42 effector Wiskott Aldrich Syndrome protein (WASp), as WASp−/− neutrophils showed defective neutrophil migration and integrin clustering (Yang; Immunity 2006). A Cdc42 mutant for WASp Binding (Cdc42S71P) was expressed in Cdc42−/− cells using retroviral transduction. Rescue of Cdc42 functions was analyzed compared to WT cells and Cdc42−/− cells transduced with an empty vector, and Cdc42−/− cells transduced with the wild type form of Cdc42 (wtCdc42). While expression of wtCdc42 rescued abnormal polarity and CD11b clustering in Cdc42−/− neutrophils to WT levels, expression of Cdc42S71P did not, suggesting that Cdc42 controls neutrophil polarity via WASp. We further confirmed the involvement of WASp in neutrophil polarity using WASp−/− neutrophils. WASp−/− neutrophils exhibited all characteristics of loss of polarity (ie frequent changes in direction during migration as assessed by video microscopy, multiple F-actin protrusions at the uropod). We next examined how Cdc42/WASp regulates neutrophil polarity and explored the roles of microtubules (MTs), since MTs are oriented toward the uropod in migrating WT neutrophils and Cdc42 is known to regulate MT polarity. Cdc42−/− as well as WASp−/− neutrophils showed loss of MT polarity with cells extending MT towards both the front and the uropod. They also exhibited less stabilized MTs (ie, defect in detyrosinated MT). Interestingly, MTs made contact with CD11b clusters at the uropod in WT, but not in Cdc42−/− and WASp−/− neutrophils. Enforcing CD11b clustering by CD11b antibody crosslinking in Cdc42−/− and WASp−/− neutrophils rescued polarity and MT capture at the plasma membrane to WT levels. Thus, Cdc42 regulates CD11b clustering via WASp, which, in turn, may capture and stabilize MTs at the uropod. To further examine this possibility, we examined in detail the plasma membrane of these cells. Indeed, on activation, the uropod of neutrophils reorganizes into detergent resistant membrane (DRM) domains – something, which is essential for polarity. Immunostaining with the DRM marker cholera toxin indicated loss of DRM assembly at the uropod of Cdc42−/− and WASp−/− neutrophils. Biochemistry analysis showed that DRM fraction of WT cells contained CD11b, WASp, tubulin and the microtubule end-binding protein EB1. In contrast, Cdc42−/− and WASp−/− DRMs had significantly lower amount of CD11b, WASp, tubulin, EB1 and CD11b, tubulin, EB1, respectively. Remarkably, CD11b crosslinking in WASp−/− cells rescued CD11b, tubulin and EB1 whereas CD11b crosslinking in Cdc42−/− cells rescued CD11b, tubulin and EB1 but not WASp, suggesting that Cdc42 and WASp controls DRM formation containing CD11b, and that CD11b recruits EB1 to capture and stabilize microtubules downstream of WASp.Together, our study uncovers a novel mechanism of neutrophil migration in which Cdc42 recruits WASp to the uropod to reorganize the plasma membrane into discrete DRM domains and induce CD11b clustering. CD11b clusters, in turn, capture and stabilize microtubules via EB1 – something that is critical for maintaining neutrophil polarity during directed migration. Our study thus reveals a new function for WASp in the control of neutrophil polarity via crosstalk of DRM/CD11b and microtubules.We used a 3-D migration model that mimics the extravasation cascade ex vivo to show that Cdc42/WASp/CD11b-dependent neutrophil polarity regulates the crawling step of neutrophils toward endothelial cell junction for efficient transmigration on HUVECs. Using a model of LPS-induced acute lung injury, we then show that Cdc42 loss dramatically reduced neutrophil recruitment to lung alveolar cavities as well as lung tissue inflammation – an indication for the patho-physiological importance of this pathway during the neutrophil extravasation cascade and subsequent inflammation in vivo. Disclosures:No relevant conflicts of interest to declare.

Microparticles from apoptotic platelets promote resident macrophage differentiation

Platelets shed microparticles not only upon activation, but also upon ageing by an apoptosis-like process (apoptosis-induced platelet microparticles, PMap). While the activation-induced microparticles have widely been studied, not much is known about the (patho)physiological consequences of PMap formation. Flow cytometry and scanning electron microscopy demonstrated that PMap display activated integrins and interact to form microparticle aggregates. PMap were chemotactic for monocytic cells, bound to these cells, an furthermore stimulated cell adhesion and spreading on a fibronectin surface. After prolonged incubation, PMap promoted cell differentiation, but inhibited proliferation. Monocyte membrane receptor analysis revealed increased expression levels of CD11b (integrin αMβ2), CD14 and CD31 (platelet endothelial cell adhesion molecule-1), and the chemokine receptors CCR5 and CXCR4, but not of CCR2. This indicated that PMap polarized the cells into resident M2 monocytes. Cells treated with PMap actively consumed oxidized low-density lipoprotein (oxLDL), and released matrix metalloproteinases and hydrogen peroxide. Further confirmation for the differentiation towards resident professional phagocytes came from the finding that PMap stimulated the expression of the (ox)LDL receptors, CD36 and CD68, and the production of proinflammatory and immunomodulating cytokines by monocytes. In conclusion, interaction of PMap with monocytic cells has an immunomodulating potential. The apoptotic microparticles polarize the cells into a resident M2 subset, and induce differentiation to resident professional phagocytes.

Ezetimibe inhibe la adhesión y la migración de monocitos a través de la ruta de las proteincinasas activadas extracelularmente (p44/p42 ERK1/2

Introduction Recently, our group has demonstrated that ezetimibe, a specific inhibitor of intestinal absorption, is able to inhibit vascular inflammation in a rabbit model of atherosclerosis. In this study, we investigated the effect of ezetimibe on the adhesion and migration of human THP-1 monocytes in vitro. We also studied the involvement of the MAP kinase signalling pathway, p44/p42 ERK1/2, as a potential mechanism responsible for the observed effect. Material and methods Adhesion of THP-1 monocytes was measured as the ability of cells to bind to plates. Migration was studied using two-compartment chambers. The expression of adhesion molecules was assessed by flow cytometry. Activation of p44/p42 ERK1/2 was measured by Western Blot. Results Preincubation of THP-1 monocytes with ezetimibe prevented PMA-induced adhesion and MCP-1-induced migration in a dose-dependent manner. Preincubation of THP-1 monocytes with ezetimibe also inhibited the expression of the integrins CD11a and CD11b, as well as phosphorylation of p-p44/p42 ERK1/2 (the active form) induced by MCP-1. More than 90% of cells (evaluated through trypan blue) were viable 1 or 2 days after exposure to ezetimibe. Conclusions Our results indicate that, in addition to its lipid lowering activity, ezetimibe is able to inhibit the process of adhesion and migration of monocytes in vitro. Blocking of the p44/p42 ERK1/2 MAPK signalling pathway seems to play a role in this anti-inflammatory effect.

Activation of Adenosine A2AReceptors Inhibits Neutrophil Transuroepithelial Migration

Adenosine has been identified as a significant inhibitor of inflammation by acting on adenosine A(2A) receptors. In this study, we examined the role of adenosine and A(2A) receptors in the transmigration of human neutrophils across an in vitro model of the transitional bladder urothelium. Human uroepithelial cells (UROtsa) were grown on transwell inserts; uropathogenic Escherichia coli (UPEC) and neutrophils were added to the transwell system; and the number of migrating neutrophils was evaluated. Reverse transcription-PCR (RT-PCR), immunohistochemistry, and flow cytometry were used to investigate the expression of adenosine receptors, the epithelial adhesion molecule ICAM-1, and the neutrophil integrin CD11b. Levels of proinflammatory interleukin-8 (IL-8) and phosphorylated IκBα were measured by enzyme-linked immunosorbent assays (ELISA) and Luminex assays, respectively. The neutrophils expressed all four adenosine receptor subtypes (A(1), A(2A), A(2B), and A(3) receptors), but A(3) receptors were not expressed by UROtsa cells. UPEC stimulated neutrophil transuroepithelial migration, which was significantly decreased in response to the specific A(2A) receptor agonist CGS 21680. The inhibitory effect of CGS 21680 on neutrophil migration was reversed by the A(2A) receptor antagonist SCH 58261. The production of chemotactic IL-8 and the expression of the adhesion molecule ICAM-1 or CD11b were not significantly affected by CGS 21680. However, a significant decrease in the level of phosporylated IκBα was revealed in response to CGS 21680. In conclusion, UPEC infection in vitro evoked neutrophil migration through a multilayered human uroepithelium. The UPEC-evoked neutrophil transmigration decreased in response to A(2A) receptor activation, possibly through inhibition of NF-κB signaling pathways.

13 Neutrophil activation at the culprit lesion in acute ST-segment elevation myocardial infarction with multiple complex coronary plaques

<h3>Introduction</h3> The activation of neutrophils at the culprit coronary lesion following acute plaque disruption has not been reported. We hypothesised that neutrophil activation occurs in ST elevation myocardial infarction (STEMI) prior to percutaneous intervention (PCI), and that differences in activation may be detectable locally at the culprit lesion, particularly in patients with multiple complex coronary plaques. <h3>Methods</h3> Forty STEMI patients having primary PCI were compared to 10 controls with chronic stable angina (CSA) undergoing elective PCI. The clinical, demographic and angiographic characteristics of patients and controls are shown in Abstract 13 table 1. The culprit lesion was sampled after passage of a guide wire across the lesion and use of a low profile sampling catheter (Multifunctional probing catheter, Boston Scientific Corporation, Natick, Massachusetts, USA) at the site of occlusion, prior to further mechanical intervention. Neutrophil activation was measured by flow cytometry using neutrophil intracellular myeloperoxidase content (MPO Index) and the expression of the β2- integrin CD11b, a leukocyte adhesion and activation marker at the culprit coronary lesion (CA), the aorta at the coronary ostium (Ao), the coronary sinus (CS), and femoral artery (FA) prior to primary PCI. A lower MPO content indicates the depletion of intracellular MPO and cell activation. <h3>Results</h3> A marked decrease in MPO content occurred at the CA, Ao and FA in STEMI compared to elective controls (p&lt;0.01). Furthermore, MPO content was lower at the CA (−23.1, (−25.6 to −17.1), n=37) compared to Ao (−22.0, (−24.7 to −16.2), n=37), CS (−20.6, (−24.8 to −16.9), n=30) and FA (−20.4, (−24.4 to −13.1), n=40), all p&lt;0.001 (Abstract 13 figure 1). Neutrophil MPO content was correlated with CD11b expression only at the culprit CA in STEMI (r=−0.4, p=0.03, n=31) (Abstract 13 figure 2). Neutrophil MPO content at the CA in patients with multiple complex plaques was similar to those with a single culprit however only in those with multiple complex plaques was a correlation between MPO content and CD11b (r=−0.7, p=0.02) shown. Conclusion: In acute STEMI, neutrophils are activated systemically, regionally and locally at the culprit coronary lesion. In patients with multiple complex plaques, there may be an extended local role for the activated neutrophil following acute plaque destabilisation.

Negative regulation of autoreactive B cell activation by integrin CD11b molecule (167.13)

Abstract The immunological hallmark of systemic lupus erythematosus (SLE) is a loss of immune tolerance and B cell hyperactivity. Recent studies demonstrated an association between the variant of the integrin-α-M (ITGAM, also called CD11b) gene and SLE susceptibility. However, how CD11b regulates disease pathogenesis remains elusive. We found surprisingly that B cells from CD11b knock out (KO) mice exhibited hyperproliferative responsiveness to B cell receptor (BCR) cross-linking. CD11b KO autoreactive B cells had the decreased tyrosine phosphorylation including Lyn and PLCγ2 and increased p38 MAKP. Moreover, CD11b deficiency promoted B cell survival which was associated with increased BCL-xl expression. In vivo engagement of BCR by apoptotic cells resulted in significantly increased autoAb production in CD11b KO mice. Furthermore, we found that BCR cross-linking could induce CD11b activation and modulate CD11b-medited phagocytosis, suggesting ‘out-side-in’ activation of CD11b integrin by BCR crosslinking. Taken together, these results reveal the interaction between CD11b integrin and BCR signaling pathways and suggest the critical role for CD11b molecule in maintaining autoreactive B cell tolerance (This work was supported by the Alliance for Lupus Research).

Measurement of TLR-Induced Macrophage Spreading by Automated Image Analysis: Differential Role of Myd88 and MAPK in Early and Late Responses

Sensing of infectious danger by toll-like receptors (TLRs) on macrophages causes not only a reprogramming of the transcriptome but also changes in the cytoskeleton important for cell spreading and motility. Since manual determination of cell contact areas from fluorescence micrographs is very time-consuming and prone to bias, we have developed and tested algorithms for automated measurement of macrophage spreading. The two-step method combines identification of cells by nuclear staining with DAPI and cell surface staining of the integrin CD11b. Automated image analysis correlated very well with manual annotation in resting macrophages and early after stimulation, whereas at later time points the automated cell segmentation algorithm and manual annotation showed slightly larger variation. The method was applied to investigate the impact of genetic or pharmacological inhibition of known TLR signaling components. Deficiency in the adapter protein Myd88 strongly reduced spreading activity at the late time points, but had no impact early after LPS-stimulation. A similar effect was observed upon pharmacological inhibition of MEK1, the kinase activating the mitogen-activated protein kinases (MAPK) ERK1/2, indicating that ERK1/2 mediates Myd88-dependent macrophages spreading. In contrast, macrophages lacking the MAPK p38 were impaired in the initial spreading response but responded normally 8–24 h after stimulation. The dichotomy of p38 and ERK1/2 MAPK effects on early and late macrophage spreading raises the question which of the respective substrate proteins mediate(s) cytoskeletal remodeling and spreading. The automated measurement of cell spreading described here increases the objectivity and greatly reduces the time required for such investigations and is therefore expected to facilitate larger throughput analysis of macrophage spreading, e.g., in siRNA knockdown screens.

Contribution of Toll-Like Receptor Activation to Lung Damage After Donor Brain Death

Donor brain death is the first injurious event that can produce inflammatory dysfunction after pulmonary transplantation. This study was designed to determine whether stimulation of the toll-like receptor (TLR) system contributes to the changes produced by brain death. Rats were repeatedly treated with specific agonists for TLR4 or TLR2/6 to desensitize these receptors. Brain death was then induced by inflation of a balloon catheter within the extradural space. Mean arterial pressure changes and inflammatory markers were measured serially by protein and mRNA analysis. Both desensitizing pretreatments prevented the neurogenic hypotension (P<0.001) and metabolic acidosis (P<0.001) observed in control animals after brain death. These treatments also reduced the levels of tumor necrosis factor-α and CXCL1 in serum and bronchoalveolar lavage fluid, although desensitization of TLR4 produced a greater inhibition than desensitization of TLR2. Desensitization of TLR4 also reduced (P<0.05) expression of the adhesive integrin CD11b on blood neutrophils after brain death. Examination of mRNA levels in lung tissue 5 hr after brain death showed that desensitization of TLR4 limited the expression of interferon (IFN)-γ, IFNβ, and CXCL10, whereas desensitization of TLR2/6 reduced only the expression of IFNγ. These results indicate that activation of TLR signaling pathways can contribute to the lung damage produced by brain death; this may increase subsequent graft injury after transplantation.

New players in the sepsis-protective activated protein C pathway

Recombinant activated protein C (aPC) improves the survival of patients with severe sepsis, but the precise molecular and cellular targets through which it mediates this effect remain incompletely understood. In this issue of the JCI, Kerschen et al. show that endothelial cell protein C receptor (EPCR) is specifically expressed by mouse CD8+ dendritic cells and that these coordinators of host responses to systemic infection are required for aPC to provide protection against the lethality of sepsis. An additional study, by Cao and colleagues, recently published in the JCI, implicates the leukocyte integrin CD11b in the pathways by which aPC mediates antiinflammatory effects in the context of lethal sepsis in mice, suggesting a common thread of synergistic control of innate immune responses by life-saving aPC therapy.

GLYCOCALYX PROTECTION REDUCES LEUKOCYTE ADHESION AFTER ISCHEMIA/REPERFUSION

Adhesion of polymorphonuclear neutrophils (PMN) to coronary endothelium is a key event for cardiac ischemia/reperfusion injury. Adhesion molecules are normally harbored within the glycocalyx, clothing every healthy vascular endothelium, but shed by ischemia/reperfusion. Our aim was to show whether protection of the glycocalyx with either hydrocortisone or antithrombin can reduce postischemic leukocyte adhesion. Isolated guinea pig hearts, perfused with Krebs-Henseleit buffer, were subjected to 20 min of warm (37 degrees C) no-flow ischemia and consecutive 10 min of reperfusion, either in the absence or presence of hydrocortisone (10 microg/mL) or antithrombin (1 U/mL). An intracoronary bolus of 3 x 10 PMN was applied at the end of reperfusion but without prior contact to the drugs. The sequestration of PMN was calculated from the difference between coronary input and output of cells. Expression of the integrin CD11b on PMN was measured before and after coronary passage. Ischemia/reperfusion induced severe degradation of the glycocalyx (coronary venous syndecan-1 release, 171 +/- 15 ng/g heart vs. basal, 19 +/- 2 ng/g; heparan sulfate, 5.27 +/- 0.28 microg/g vs. basal, 0.26 +/- 0.06 microg/g) and increased PMN adhesion (38.1% +/- 3.5% vs. basal, 11.7% +/- 3.1%). Hydrocortisone and antithrombin both not only reduced glycocalyx shedding (syndecan-1 release, 34 +/- 6 ng/g and 26 +/- 5 ng/g; heparan sulfate, 1.96 +/- 0.24 microg/g and 1.28 +/- 0.2 microg/g, respectively), but also PMN adhesion (17.3% +/- 2.2% and 25.4% +/- 3.3%, respectively) after ischemia/reperfusion. Electron microscopy revealed a mostly intact coronary glycocalyx after pretreatment with either drug. Activation of PMN upon coronary passage was not influenced. Preservation of the glycocalyx mitigates postischemic PMN adhesion. Preconditioning with either hydrocortisone or antithrombin should, thus, alleviate vascular leakage, tissue edema, and inflammation.

Integrin CD11b negatively regulates TLR-triggered inflammatory responses by activating Syk and promoting degradation of MyD88 and TRIF via Cbl-b

Integrins are critical for the migration and function of leukocytes in inflammation. However, the interaction between integrin alpha(M) (CD11b), which has high expression in monocytes and macrophages, and Toll-like receptor (TLR)-triggered innate immunity remains unclear. Here we report that CD11b deficiency enhanced TLR-mediated responses in macrophages, rendering mice more susceptible to endotoxin shock and Escherichia coli-caused sepsis. CD11b was activated by TLR-triggered phosphatidylinositol 3-OH kinase (PI(3)K) and the effector RapL and fed back to inhibit TLR signaling by activating the tyrosine kinases Src and Syk. Syk interacted with and induced tyrosine phosphorylation of MyD88 and TRIF, which led to degradation of these adaptor molecules by the E3 ubiquitin ligase Cbl-b. Thus, TLR-triggered, active CD11b integrin engages in crosstalk with the MyD88 and TRIF pathways and subsequently inhibits TLR signaling in innate immune responses.

Short-term IL-1β blockade reduces monocyte CD11b integrin expression in an IL-8 dependent fashion in patients with type 1 diabetes

Interleukin 1-beta (IL-1beta) is a major inflammatory cytokine. Blockade of the IL-1beta pathway is therapeutically efficacious in type 2 diabetes, but the mechanistic effects on the immune system are incompletely understood. We administered an IL-1 receptor antagonist, anakinra, to 7 type 1 diabetes patients in order to investigate the immunologic and metabolic effects of this drug. Mechanistic assays were performed before and after drug administration. A novel signature was observed, with reduced serum interleukin 8 (IL-8) levels and reduced CD11b integrin expression on monocytes associated with increased CXCR1 expression. This set of linked phenotypes suggests that blockade of the IL-1beta pathway results in the reduced ability of mononuclear cells to traffic to sites of inflammation. Mechanistic studies from large scale trials using IL-1 blockade in type 1 diabetes should focus on changes in monocyte trafficking and the IL-8 pathway.

The efficacy of activated protein C in murine endotoxemia is dependent on integrin CD11b.

Activated protein C (APC), the only FDA-approved biotherapeutic drug for sepsis, possesses anticoagulant, antiinflammatory, and barrier-protective activities. However, the mechanisms underlying its anti-inflammatory functions are not well defined. Here, we report that the antiinflammatory activity of APC on macrophages is dependent on integrin CD11b/CD18, but not on endothelial protein C receptor (EPCR). We showed that CD11b/CD18 bound APC within specialized membrane microdomains/lipid rafts and facilitated APC cleavage and activation of protease-activated receptor-1 (PAR1), leading to enhanced production of sphingosine-1-phosphate (S1P) and suppression of the proinflammatory response of activated macrophages. Deletion of the gamma-carboxyglutamic acid domain of APC, a region critical for its anticoagulant activity and EPCR-dependent barrier protection, had no effect on its antiinflammatory function. Genetic inactivation of CD11b, PAR1, or sphingosine kinase-1, but not EPCR, abolished the ability of APC to suppress the macrophage inflammatory response in vitro. Using an LPS-induced mouse model of lethal endotoxemia, we showed that APC administration reduced the mortality of wild-type mice, but not CD11b-deficient mice. These data establish what we believe to be a novel mechanism underlying the antiinflammatory activity of APC in the setting of endotoxemia and provide clear evidence that the antiinflammatory function of APC is distinct from its barrier-protective function and anticoagulant activities.

PO-26 Coagulation activation in myeloid leukemia: the role of integrin CD11b, leukocytosis, blast cells and promyelocytes

PO-26 Coagulation activation in myeloid leukemia: the role of integrin CD11b, leukocytosis, blast cells and promyelocytes

Reduced CD11b Integrin Expression with Short-term Administration of an IL-1R Antagonist in Type 1 Diabetes Patients

Reduced CD11b Integrin Expression with Short-term Administration of an IL-1R Antagonist in Type 1 Diabetes Patients

The attenuation of platelet and monocyte activation in a rabbit model of extracorporeal circulation by a nitric oxide releasing polymer

Nitric oxide (NO) has been shown to reduce thrombogenicity by decreasing platelet and monocyte activation by the surface glycoprotein, P-selectin and the integrin, CD11b, respectively. In order to prevent platelet and monocyte activation with exposure to an extracorporeal circulation (ECC), a nitric oxide releasing (NORel) polymeric coating composed of plasticized polyvinyl chloride (PVC) blended with a lipophilic N-diazeniumdiolate was evaluated in a 4 h rabbit thrombogenicity model using flow cytometry. The NORel polymer significantly reduced ECC thrombus formation compared to polymer control after 4 h blood exposure (2.8 ± 0.7 NORel vs 6.7 ± 0.4 pixels/cm 2 control). Platelet count (3.4 ± 0.3 NORel vs 2.3 ± 0.3 × 10 8/ml control) and function as measured by aggregometry (71 ± 3 NORel vs 17 ± 6% control) were preserved after 4 h exposure in NORel versus control ECC. Plasma fibrinogen levels significantly decreased in both NORel and control groups. Platelet P-selectin mean fluorescence intensity (MFI) as measured by flow cytometry was attenuated after 4 h on ECC to ex vivo collagen stimulation (27 ± 1 NORel vs 40 ± 2 MFI control). Monocyte CD11b expression was reduced after 4 h on ECC with NORel polymer (87 ± 14 NORel vs 162 ± 30 MFI control). These results suggest that the NORel polymer coatings attenuate the increase in both platelet P-selectin and monocytic CD11b integrin expression in blood exposure to ECCs. These NO-mediated platelet and monocytic changes were shown to improve thromboresistance of these NORel-polymer-coated ECCs for biomedical devices.

The small Rho GTPase Cdc42 regulates neutrophil polarity via CD11b integrin signaling

AbstractNeutrophil migration to sites of infection is the first line of cellular defense. A key event of migration is the maintenance of a polarized morphology, which is characterized by a single leading edge of filamentous actin and a contractile uropod devoid of filamentous actin protrusions. Using a mouse model of high Cdc42 activity, we previously demonstrated the importance of Cdc42 activity in neutrophil migration. However, the specific functions of Cdc42 in this process remain to be understood. Using neutrophils genetically deficient in Cdc42, we show that Cdc42 regulates directed migration by maintaining neutrophil polarity. Although it is known to be activated at the front, Cdc42 suppresses protrusions at the uropod. Interestingly, Cdc42 makes use of the integrin CD11b during this process. Cdc42 determines the redistribution of CD11b at the uropod. In turn, using CD11b-null cells and CD11b crosslinking experiments, we show that CD11b modulates myosin light chain phosphorylation to suppress lateral protrusions. Our results uncover a new mechanism in which Cdc42 regulates the uropod through CD11b signaling to maintain polarity in migrating neutrophils. It also reveals new functions for CD11b in neutrophil polarity.

ATTENUATION OF PULMONARY INFLAMMATION AFTER EXPOSURE TO BLAST OVERPRESSURE BY N-ACETYLCYSTEINE AMIDE

Lung contusion is a common problem from blunt chest trauma caused by mechanical forces and by exposure to blast overpressure, often with fatal consequences. Lung contusion is also a risk factor for the development of pneumonia, severe clinical acute lung injury (ALI), and acute respiratory distress syndrome (ARDS). Infiltrating neutrophils are considered to be central mediators of lung injuries after blunt trauma. Recent studies have demonstrated that antioxidants reduced pulmonary inflammation in different models of lung damage. This study examined the effect of antioxidant N-acetylcysteine amide (NACA) on the progression of lung inflammation after exposure to a moderate level of blast overpressure (140 kPa). Rats were administered with NACA (i.p. 100 mg/kg) or placebo (PBS) 30, 60 min and 24 h after exposure. Nonblasted sham-injected animals served as controls. Neutrophil infiltration measured by myeloperoxidase (MPO) activity in the lung was significantly increased at 2 days after blast and returned to controls at 8 days. This increase corresponded with activation of integrin CD11b mRNA and lung inflammatory chemokine mRNA expression; macrophage inflammatory protein-1 (MIP-1), monocyte chemotactic peptide-1 (MCP-1), and cytokine-induced neutrophil chemoattractant-1 (CINC-1). At 8 days, all inflammatory mediators returned to control levels. In addition, expression of heme oxygenase-1 (HO-1) mRNA increased at 2 days after exposure. No changes were detected in the lung manganase superoxide dismutase (MnSOD) or glutathione reductase (GR) mRNA expression after blast. N-Acetylcysteine amide significantly reduced infiltration of neutrophils and CD11b mRNA activation in lungs, and completely blocked activation of MIP-1, MCP-1 and CINC-1 mRNA. The relatively higher inhibition of chemokine mRNAs compared with reduction in MPO activity and CD11b is in accordance with an antioxidant effect of NACA on reactive oxygen species (ROS) accumulation, rather than by an effect on neutrophil sequestration. The inhibition of HO-1 mRNA activation after blast was likely also related to the drug antioxidant effect.

Complete resolution of leukemia cutis with sorafenib in an acute myeloid leukemia patient with FLT3‐ITD mutation

American Journal of HematologyVolume 84, Issue 10 p. 701-702 CorrespondenceFree Access Complete resolution of leukemia cutis with sorafenib in an acute myeloid leukemia patient with FLT3-ITD mutation† Sung Ho Lee, Sung Ho Lee Department of Medical Oncology, New York Medical College, Bronx, New YorkSearch for more papers by this authorElisabeth Paietta, Elisabeth Paietta Department of Medical Oncology, New York Medical College, Bronx, New YorkSearch for more papers by this authorJanis Racevskis, Janis Racevskis Department of Medical Oncology, New York Medical College, Bronx, New YorkSearch for more papers by this authorPeter H. Wiernik, Peter H. Wiernik Department of Medical Oncology, New York Medical College, Bronx, New YorkSearch for more papers by this author Sung Ho Lee, Sung Ho Lee Department of Medical Oncology, New York Medical College, Bronx, New YorkSearch for more papers by this authorElisabeth Paietta, Elisabeth Paietta Department of Medical Oncology, New York Medical College, Bronx, New YorkSearch for more papers by this authorJanis Racevskis, Janis Racevskis Department of Medical Oncology, New York Medical College, Bronx, New YorkSearch for more papers by this authorPeter H. Wiernik, Peter H. Wiernik Department of Medical Oncology, New York Medical College, Bronx, New YorkSearch for more papers by this author First published: 25 July 2009 https://doi.org/10.1002/ajh.21511Citations: 25 † Conflict of interest: Nothing to report. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL References 1 Zhang W,Konopleva M,Shi YX, et al. Mutant FLT3: A direct target of sorafenib in acute myelogenous leukemia. J Natl Cancer Inst 2008; 100: 184– 198. 2 Paietta E,Andersen J,Yunis J, et al. Acute myeloid leukemia expressing the leucocyte integrin CD11b—A new leukemic syndrome with poor prognosis: Result of an ECOG database analysis. Br J Haematol 1998; 100: 265– 272. 3 Nakao M,Yokota S,Iwai T, et al. Internal tandem duplication of the flt3 gene found in acute myeloid leukemia. Leukemia 1996; 10: 1911– 1918. 4 Kottaridis PD,Gale RE,Frew ME, et al. The presence of a FLT3 internal tandem duplication in patients with acute myeloid leukemia (AML) adds important prognostic information to cytogenetic risk group and response to the first cycle of chemotherapy: Analysis of 854 patients from the United Kingdom medical research council AML 10 and 12 trials. Blood 2001; 98: 1752– 1759. 5 Safaian NN,Czibere A,Bruns I, et al. Sorafenib (Nexavar®) induces molecular remission and regression of extramedullary disease in a patient with FLT3-ITD acute myeloid leukemia. Leuk Res 2009; 33: 348– 350. 6 Metzelder S,Wang Y,Wollmer E, et al. Compassionate use of sorafenib in FLT3-ITD-positive acute myeloid leukemia: Sustained regression before and after allogenic stem cell transplantation. Blood 2009; 113: 6567– 6571. 7 Hu S,Niu H,Minkin P, et al. Comparison of antitumor effects of multitargeted tyrosine kinase inhibitors in acute myelogenous leukemia. Mol Cancer Ther 2008; 7: 1110– 1120. 8 Zhang W,Konopleva M,Ruvolo VR, et al. Sorafenib induces apoptosis of AML cells via Bim-mediated activation of the intrinsic apoptotic pathway. Leukemia 2008; 22: 808– 818. Citing Literature Volume84, Issue10October 2009Pages 701-702 ReferencesRelatedInformation

The β2 integrin CD11b attenuates polyinosinic:Polycytidylic acid–induced hepatitis by negatively regulating natural killer cell functions #

The beta2 integrins play a key role in inflammation and immune responses. The beta2 integrin CD11b has been shown recently to be important in the maintenance of tolerance; however, the underlying mechanisms remain to be fully understood. Natural killer (NK) cells are an important effector of innate immunity but are also a regulator of adaptive immune response. How the activating and inhibitory signals are balanced to determine NK cell function needs to be further identified. CD11b expression was dramatically up-regulated on NK cells once they matured and became activated; therefore, we investigated the role of inducible CD11b in the regulation of NK cells. Neutralizing anti-CD11b antibody enhanced cytotoxicity, interferon-gamma (IFN-gamma) and granzyme B production of Toll-like receptor 3 (TLR3)-triggered NK cells. CD11b-deficient NK cells stimulated with or without the TLR3 ligand polyinosinic:polycytidylic acid [poly(I:C)] exhibited more potent cytotoxicity, and higher production of IFN-gamma and granzyme B. Through in vivo depletion of NK cells and adoptive transfer of CD11b-deficient NK cells, we demonstrated that CD11b-mediated suppression of NK cell function was responsible for attenuation of poly(I:C)-induced acute hepatitis by CD11b. Our findings demonstrate that CD11b negatively regulates NK cell activation and thus attenuates poly(I:C)-induced acute hepatitis. Our study provides a new mechanistic explanation for maintenance of tolerance and control of inflammation by CD11b.