Tissue-specific KO of ECM proteins

Nearly 20 years after its first description, gene targeting and generation of transgenic mice by homologous recombination in embryonic stem cells still are cutting edge tools for the postgenomic era. Understanding the function of the large number of genes encoding extracellular matrix proteins and their cellular receptors appears a daunting task that can very much profit from a genetic approach. The generation of new mutant alleles remains essential to define the different biochemical properties of such proteins. While in the past, gene targeting represented a complex procedure, restricted to few laboratories, recent breakthroughs, such as the publication of the mouse genome sequence and the perfection of recombineering techniques in bacteria, made generation of transgenic mice faster and easier. This chapter will thus focus on the recent advances in gene-targeting technology with a special eye on the study of genes involved in cell adhesion and migration.

Inflammation as a therapeutic target in heart failure? A scientific statement from the Translational Research Committee of the Heart Failure Association of the European Society of Cardiology

The increasing prevalence of heart failure poses enormous challenges for health care systems worldwide. Despite effective medical interventions that target neurohumoral activation, mortality and morbidity remain substantial. Evidence for inflammatory activation as an important pathway in disease progression in chronic heart failure has emerged in the last two decades. However, clinical trials of 'anti-inflammatory' therapies (such as anti-tumor necrosis factor-alpha approaches) have to date failed to show benefit in heart failure patients. The Heart Failure Association of the European Society of Cardiology recently organized an expert workshop to address the issue of inflammation in heart failure from a basic science, translational and clinical perspective, and to assess whether specific inflammatory pathways may yet serve as novel therapeutic targets for this condition. This consensus document represents the outcome of the workshop and defines key research questions that still need to be addressed as well as considering the requirements for future clinical trials in this area.

The anaplastic lymphoma kinase controls cell shape and growth of anaplastic large cell lymphoma through Cdc42 activation

Anaplastic large cell lymphoma (ALCL) is a non-Hodgkin's lymphoma that originates from T cells and frequently expresses oncogenic fusion proteins derived from chromosomal translocations or inversions of the anaplastic lymphoma kinase (ALK) gene. The proliferation and survival of ALCL cells are determined by the ALK activity. Here we show that the kinase activity of the nucleophosmin (NPM)-ALK fusion regulated the shape of ALCL cells and F-actin filament assembly in a pattern similar to T-cell receptor-stimulated cells. NPM-ALK formed a complex with the guanine exchange factor VAV1, enhancing its activation through phosphorylation. VAV1 increased Cdc42 activity, and in turn, Cdc42 regulated the shape and migration of ALCL cells. In vitro knockdown of VAV1 or Cdc42 by short hairpin RNA, as well as pharmacologic inhibition of Cdc42 activity by secramine, resulted in a cell cycle arrest and apoptosis of ALCL cells. Importantly, the concomitant inhibition of Cdc42 and NPM-ALK kinase acted synergistically to induce apoptosis of ALCL cells. Finally, Cdc42 was necessary for the growth as well as for the maintenance of already established lymphomas in vivo. Thus, our data open perspectives for new therapeutic strategies by revealing a mechanism of regulation of ALCL cell growth through Cdc42.

Phosphoinositide 3-kinase signalling in the vascular system

Phosphoinositide 3-kinases (PI3Ks) are protein and lipid kinases activated by different classes of membrane receptors, including G-protein coupled and tyrosine kinase receptors. Several lines of evidence have uncovered specific roles for distinct PI3K isoforms in the vascular system in both physiology and disease. The present review will summarize and discuss the most recent advances regarding PI3K-Akt signalling in endothelial cells, vascular smooth muscle cells, platelets, and inflammatory cells involved in the atherosclerotic process. Of interest, the development of novel isoform-selective PI3K inhibitor drugs offers a unique opportunity to selectively and differentially target PI3K-driven pathways in the vascular system and may give rise to new strategies for the treatment of cardiovascular diseases.

Phosphoinositide 3-kinases gamma and delta, linkers of coordinate C5a receptor-Fcgamma receptor activation and immune complex-induced inflammation

Fcgamma receptors (FcgammaR) and the C5a receptor (C5aR) are key effectors of the acute inflammatory response to IgG immune complexes (IC). Their coordinated activation is critical in IC-induced diseases, although the significance of combined signaling by these two different receptor classes in tissue injury is unclear. Here we used the mouse model of the passive reverse lung Arthus reaction to define their requirements for distinct phosphoinositide 3-kinase (PI3K) activities in vivo. We show that genetic deletion of class IB PI3Kgamma abrogates C5aR signaling that is crucial for FcgammaR-mediated activation of lung macrophages. Thus, in PI3Kgamma(-/-) mice, IgG IC-induced FcgammaR regulation, cytokine release, and neutrophil recruitment were blunted. Notably, however, C5a production occurred normally in PI3Kgamma(-/-) mice but was impaired in PI3Kdelta(-/-) mice. Consequently, class IA PI3Kdelta deficiency caused resistance to acute IC lung injury. These results demonstrate that PI3Kgamma and PI3Kdelta coordinate the inflammatory effects of C5aR and FcgammaR and define PI3Kdelta as a novel and essential element of FcgammaR signaling in the generation of C5a in IC disease.

Phosphoinositide 3-kinase p110beta activity: key role in metabolism and mammary gland cancer but not development

The phosphoinositide 3-kinase (PI3K) pathway crucially controls metabolism and cell growth. Although different PI3K catalytic subunits are known to play distinct roles, the specific in vivo function of p110beta (the product of the PIK3CB gene) is not clear. Here, we show that mouse mutants expressing a catalytically inactive PIK3CB(K805R) mutant survived to adulthood but showed growth retardation and developed mild insulin resistance with age. Pharmacological and genetic analyses of p110beta function revealed that p110beta catalytic activity is required for PI3K signaling downstream of heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors as well as to sustain long-term insulin signaling. In addition, PIK3CB(K805R) mice were protected in a model of ERBB2-driven tumor development. These findings indicate an unexpected role for p110beta catalytic activity in diabetes and cancer, opening potential avenues for therapeutic intervention.

Essential role of phosphoinositide 3-kinase gamma in eosinophil chemotaxis within acute pulmonary inflammation

We and others have established an important role for phosphoinositide-3 kinase gamma (PI3Kgamma) in the chemotactic responses of macrophages and neutrophils. The involvement of this lipid kinase in allergic inflammatory responses is, however, yet to be fully determined. Here we compare wild-type (WT) and PI3Kgamma(-/-) (KO) mice within a model of ovalbumin (OVA) -specific pulmonary inflammation. Upon OVA aerosol challenge, cell influx into the bronchoalveolar lavage (BAL) fluid consisted of neutrophils, macrophages and, more significantly, eosinophils - which are key effector cells in allergic inflammation. Each population was reduced by up to 80% in KO mice, demonstrating a role for PI3Kgamma in cell infiltration into the airways. The mechanism of reduced eosinophilia was analysed within both development and effector stages of the immune response. Comparable levels of OVA-specific T-cell proliferation and immunoglobulin production were established in both strains. Furthermore, no significant differences between WT and KO chemokine production were observed. Having identified the critical point of PI3Kgamma involvement, KO eosinophil chemotactic dysfunction was confirmed in vitro. These data are the first to demonstrate the vital role of PI3Kgamma in acute allergic inflammation. The profound dependency of eosinophils on PI3Kgamma for pulmonary influx identifies this lipid kinase as an attractive target for the pharmacological intervention of asthma.

Overlapping and distinct roles for PI3Kbeta and gamma isoforms in S1P-induced migration of human and mouse endothelial cells

AIMS

Sphingosine-1-phosphate (S1P), a key regulator of vascular homeostasis and angiogenesis, promotes endothelial cell migration via stimulation of phosphoinositide 3-kinase (PI3K). The aim of this study was to identify the role of PI3Kbeta and gamma isoforms and their downstream effector pathways in mediating endothelial cell migration induced by S1P.

METHODS AND RESULTS

Experiments were performed in human umbilical vein endothelial cells (HUVEC) and murine lung endothelial cells (MLEC). A combination of specific inhibitors, RNA interference, and PI3Kgamma(-/-) mice were used to investigate the role of PI3Kbeta and gamma isoforms in endothelial cell migration. Both PI3Kbeta and gamma isoforms are required for full migration induced by S1P, with Rac1 being a major mediator downstream of both isoforms. In addition, PI3Kbeta but not PI3Kgamma mediates migration via Akt but independent of Rac1 and endothelial NO synthase (eNOS). Further, a S1P-mediated activation of extracellular signal-regulated kinases (Erk) 1/2 contributes to the chemotactic response independent of PI3Kbeta or PI3Kgamma.

CONCLUSIONS

Our data demonstrate that both PI3Kbeta and PI3Kgamma isoforms are required for S1P-induced endothelial cell migration through activation of Rac1. In addition, PI3Kbeta initiates an Akt-sensitive chemotactic response which is independent of Rac1 and eNOS. Thus, PI3Kbeta and PI3Kgamma have both overlapping and distinct roles in regulating endothelial cell migration, which may underlie S1P-triggered angiogenic differentiation.

Targeting phosphoinositide 3-kinase gamma to fight inflammation and more

The family of class I phosphoinositide-3-kinase (PI3K) is composed of four lipid kinases involved at multiple levels in innate and adaptive immune responses. Class I PI3Ks are divided into two subclasses, IA and IB, sharing a similar catalytic core. Whereas class IA PI3Ks are primarily activated by receptor tyrosine kinases, the unique element of class IB PI3K (PI3Kgamma) is activated by G protein coupled receptors (GPCRs), like chemokine receptors. PI3Kgamma is mainly expressed in leukocytes where it plays a significant role in chemotaxis. Here, we report recent advances in the analysis of the role of PI3Kgamma in leukocytes and in endothelial cells. Results, derived from studies based on both pharmacological and genetic approaches, confirm PI3Kgamma as an attractive target for drug discovery. PI3Kgamma specific inhibition has gained increasing attention for the treatment of allergic, autoimmune and inflammatory diseases. Development of inhibitors has already provided series of hits, whose efficacy is currently under scrutiny worldwide.

[Epilepsy surgery in children: from a multidisciplinary network to the creation of an expertise and care centre]

We report on the experience of a network created in 1994 to evaluate children with drug-resistant epilepsies who are candidates for surgical treatment. The network includes epilepsy units from several university hospitals in France that decided to share not only their clinical expertise to better respond to the need for a multidisciplinary approach of epilepsy surgery in children, but also all the technical and human resources available in the various teams. This mode of operation has certainly provided concrete proof of its efficacy since it undoubtedly facilitated, and even accelerated, access to optimal presurgical evaluation and epilepsy surgery for hundreds of children. However, after 10 years of this very enriching practice it became evident that our approach was certainly necessary but not sufficient. It is estimated that every year in France nearly 500 children are candidates for surgical treatment, and following a presurgical evaluation, 50% of them could be operated on. Today, only 150-200 children have access to a presurgical evaluation every year. This is a highly paradoxical situation since, even if the human suffering component that such a situation generates is set aside, the direct and indirect life-time costs for every 100 nonoperated patients is estimated at 40 million euros. As a result of our cumulated experience, in 2004 we proposed a different operating model with the creation of an expertise center that will combine not only medical care services provided by a fully equipped multidisciplinary team, but also a pole of applied clinical and fundamental research, a medicosocial center managed by a lay association and an industrial development pole. The project has been recently validated by the Ministry of Health and is supported by a number of national and regional institutions. The Institute for Children and Adolescents with Epilepsy--IDEE--is designed to accelerate diagnostic procedures and, when indicated, access to optimal presurgical evaluation, while also serving as a model for a medical and economic evaluation of epilepsy care in children.

[Epileptogenic and non-epileptogenic zones: blood flow studies of temporo-limbic seizures]

To assess the contribution of ictal SPECT to the definition of the epileptogenic zone (EZ) prior to surgery in focal drug-resistant epilepsies, we investigated the effect of the timing of injection and seizure semiology on patterns of perfusion and cerebral blood flow changes (CBF) beyond the EZ. In the rat model of amygdala-kindled seizures, we measured CBF changes with the quantitative [(14)C]-iodoantipyrine autoradiographic method during secondary generalized (SGS, n=26 fully-kindled rats) and focal seizures (FS, n=19 partially kindled rats), according to sequential timing of injection with respect to seizure onset. During SGS, the correct lateralization and rough localization of the focus within limbic structures was only possible at the early ictal and post-ictal times, in between we observed widespread rCBF increases. The switch from hyper to hypoperfusion occurred at the time of late ictal injection. The accurate localization of the EZ was obtained in the study of the more subtle FS (stage 0). At stage 1 of the kindling, there was already a remote widespread spreading of hyperperfusion. In patients surgically cured from a mesio-temporal lobe epilepsy (mean post-operative follow-up: 66 months), we retrospectively studied 26 pairs of ictal and interictal pre-operative SPECTs, classified in 3 groups according to the progression of ictal semiology. Using visual analysis of subtracted SPECTs (SISCOM) and group comparisons with a control group (using SPM), we observed more widespread combined hyper and hypoperfusion with the increasing complexity of seizures. In simple partial seizures, the SISCOM analysis allowed a correct localization of the focus in 4/8 patients, whereas the SPM analysis failed to detect significant changes, due to individual variation, spatial normalization and small magnitude of CBF changes. In complex partial seizures with automatisms, SISCOM and SPM analysis showed antero-mesial temporal hyperperfusion (overlapping the EZ), extending to the insula, basal ganglia, and thalamus in the group of patients having dystonic posturing (DP group) in addition to automatisms. Ictal hypoperfusion involved pre-frontal and parietal regions, the anterior and posterior cingulate gyri, to a greater extent in the DP group. In both human and animals studies, we observed a correlation between the extent of composite patterns of hyper/hypoperfusion and the severity of seizures, and the recruitment of remote sub-cortical structures. Hypoperfused areas belong to neural networks involved in perceptual decision making and motor planning, whose transient disruption could support purposeless actions, i.e. motor automatisms.

Genetic and pharmacological targeting of phosphoinositide 3-kinase-gamma reduces atherosclerosis and favors plaque stability by modulating inflammatory processes

BACKGROUND

The role of inflammation at all stages of the atherosclerotic process has become an active area of investigation, and there is a notable quest for novel and innovative drugs for the treatment of atherosclerosis. The lipid kinase phosphoinositide 3-kinase-gamma (PI3Kgamma) is thought to be a key player in various inflammatory, autoimmune, and allergic processes. These properties and the expression of PI3Kgamma in the cardiovascular system suggest that PI3Kgamma plays a role in atherosclerosis.

METHODS AND RESULTS

Here, we demonstrate that a specific PI3Kgamma inhibitor (AS605240) is effective in murine models of established atherosclerosis. Intraperitoneal administration of AS605240 (10 mg/kg daily) significantly decreased early atherosclerotic lesions in apolipoprotein E-deficient mice and attenuated advanced atherosclerosis in low-density lipoprotein receptor-deficient mice. Furthermore, PI3Kgamma levels were elevated in both human and murine atherosclerotic lesions. Comparison of low-density lipoprotein receptor-deficient mice transplanted with wild-type or PI3Kgamma-deficient bone marrow demonstrated that functional PI3Kgamma in the hematopoietic lineage is required for atherosclerotic progression. Alleviation of atherosclerosis by targeting of PI3Kgamma activity was accompanied by decreased macrophage and T-cell infiltration, as well as increased plaque stabilization.

CONCLUSIONS

These data identify PI3Kgamma as a new target in atherosclerosis with the potential to modulate multiple stages of atherosclerotic lesion formation, such as fatty streak constitution, cellular composition, and final fibrous cap establishment.

Magnetically enriched bone marrow-derived macrophages loaded in vitro with iron oxide can migrate to inflammation sites in mice

In vitro labelling of cells permits incorporation of large amounts of iron oxide and consequently high detection sensitivity, but it remains controversial whether labelled cells would respond normally to stimuli. This question was addressed by differentiating bone marrow-derived macrophages (BMDMs) in vitro, labelling cells with high concentrations of Endorem in vitro, and eliminating unlabelled cells by magnetic enrichment. To explore their acute inflammatory response, enriched cells were injected into mice with carrageenan-induced inflammation, the 'air pouch model'. Cells recovered from the inflammation site 16 h after intravenous BMDM injection into the tail vein were analysed by in vitro MRI and fluorescent microscopy. With both assays, Endorem-labelled cells were detectable. This indicates that BMDMs, loaded with high concentrations of iron oxide in vitro, can still respond to chemokine gradients and infiltrate inflamed tissue in mice. Furthermore, by using genetically modified mice as BMDM donors, it should be possible to study the role of individual genes in macrophage recruitment.

Phosphoinositide 3-kinase gamma participates in T cell receptor-induced T cell activation

Class I phosphoinositide 3–kinases (PI3Ks) constitute a family of enzymes that generates 3-phosphorylated polyphosphoinositides at the cell membrane after stimulation of protein tyrosine (Tyr) kinase–associated receptors or G protein–coupled receptors (GPCRs). The class I PI3Ks are divided into two types: class I_A p85/p110 heterodimers, which are activated by Tyr kinases, and the class I_B p110γ isoform, which is activated by GPCR. Although the T cell receptor (TCR) is a protein Tyr kinase–associated receptor, p110γ deletion affects TCR-induced T cell stimulation. We examined whether the TCR activates p110γ, as well as the consequences of interfering with p110γ expression or function for T cell activation. We found that after TCR ligation, p110γ interacts with Gα_q/11, lymphocyte-specific Tyr kinase, and ζ-associated protein. TCR stimulation activates p110γ, which affects 3-phosphorylated polyphosphoinositide levels at the immunological synapse. We show that TCR-stimulated p110γ controls RAS-related C3 botulinum substrate 1 activity, F-actin polarization, and the interaction between T cells and antigen-presenting cells, illustrating a crucial role for p110γ in TCR-induced T cell activation.

The p110delta catalytic isoform of PI3K is a key player in NK-cell development and cytokine secretion

The signal transduction pathways that lead activated natural killer (NK) cells to produce cytokines, releases cytotoxic granules, or do both, are not clearly dissected. For example, phosphoinositide 3-kinases (PI3Ks) are key players in the execution of both functions, but the relative contribution of each isoform is unknown. We show here that the catalytic isoform p110δ, not p110γ, was required for interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), and granulocyte macrophage colony-stimulating factor (GM-CSF) secretion, whereas neither was necessary for cytotoxicity. Yet, when both p110δ and p110γ isoforms were inactivated by a combination of genetic and biochemical approaches, cytotoxicity was decreased. NK-cell numbers were also affected by the lack of p110δ but not p110γ and more severely so in mice lacking both subunits. These results provide genetic evidence that p110δ is the dominant PI3K isoform for cytokine secretion by NK cells and suggest that PI3Ks cooperate during NK-cell development and cytotoxicity.