Natalia Smirnova

The activation function-1 of estrogen receptor alpha prevents arterial neointima development through a direct effect on smooth muscle cells

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PI3K signaling in arterial diseases: Non redundant functions of the PI3K isoforms.

Cardiovascular diseases are the most common cause of death around the world. This includes atherosclerosis and the adverse effects of its treatment, such as restenosis and thrombotic complications. The development of these arterial pathologies requires a series of highly-intertwined interactions between immune and arterial cells, leading to specific inflammatory and fibroproliferative cellular responses. In the last few years, the study of phosphoinositide 3-kinase (PI3K) functions has become an attractive area of investigation in the field of arterial diseases, especially since inhibitors of specific PI3K isoforms have been developed. The PI3K family includes 8 members divided into classes I, II or III depending on their substrate specificity. Although some of the different isoforms are responsible for the production of the same 3-phosphoinositides, they each have specific, non-redundant functions as a result of differences in expression levels in different cell types, activation mechanisms and specific subcellular locations. This review will focus on the functions of the different PI3K isoforms that are suspected as having protective or deleterious effects in both the various immune cells and types of cell found in the arterial wall. It will also discuss our current understanding in the context of which PI3K isoform(s) should be targeted for future therapeutic interventions to prevent or treat arterial diseases.

Targeting PI3Kγ activity decreases vascular trauma-induced intimal hyperplasia through modulation of the Th1 response

PI3Kγ plays a major role in the initiation and progression of intimal hyperplasia by specifically modulating Th1 cytokines leading to CXCL10 and RANTES production by smooth muscle cells.

Key role of PI3Kγ in monocyte chemotactic protein-1-mediated amplification of PDGF-induced aortic smooth muscle cell migration

Vascular smooth muscle cell (SMC) migration within the arterial wall is a crucial event in atherogenesis and restenosis. Monocyte chemotactic protein‐1/CC‐chemokine receptor 2 (MCP‐1/CCR2) signalling is involved in SMC migration processes but the molecular mechanisms have not been well characterized. We investigated the role of PI3Kγ in SMC migration induced by MCP‐1.

Protective Hematopoietic Effect of Estrogens in a Mouse Model of Thrombosis: Respective Roles of Nuclear Versus Membrane Estrogen Receptor α

We recently reported that chronic 17β-estradiol (E2) treatment in mice decreases platelet responsiveness, prolongs the tail-bleeding time and protects against acute thromboembolism via the hematopoietic estrogen receptor alpha (ERα), and independently of ERβ. Here, we have explored the respective roles of membrane vs nuclear actions of ERα in this process, using: 1) the selective activator of membrane ERα: estrogen dendrimer conjugate, and 2) mouse models with mutations in ERα. The selective targeting of activation function 2 of ERα provides a model of nuclear ERα loss-of-function, whereas mutation of the ERα palmitoylation site leads to a model of membrane ERα deficiency. The combination of pharmacological and genetic approaches including hematopoietic chimera mice demonstrated that absence of either membrane or nuclear ERα activation in bone marrow does not prevent the prolongation of the tail-bleeding time, suggesting a redundancy of these two functions for this E2 effect. In addition, although hematopoietic membrane ERα is neither sufficient nor necessary to protect E2-treated mice from collagen/epinephrine-induced thromboembolism, the protection against death-induced thromboembolism is significantly reduced in the absence of hematopoietic nuclear ERα activation. Overall, this study emphasizes that hematopoietic cells (likely megakaryocytes and possibly immune cells) constitute an important target in the antithrombotic effects of estrogens, and delineate for the first time in vivo the respective roles of membrane vs nuclear ERα effects, with a prominent role of the latter.

Cholesterol metabolism promotes B‐cell positioning during immune pathogenesis of chronic obstructive pulmonary disease

The development of chronic obstructive pulmonary disease (COPD) pathogenesis remains unclear, but emerging evidence supports a crucial role for inducible bronchus‐associated lymphoid tissue (iBALT) in disease progression. Mechanisms underlying iBALT generation, particularly during chronic CS exposure, remain to be defined. Oxysterol metabolism of cholesterol is crucial to immune cell localization in secondary lymphoid tissue. Here, we demonstrate that oxysterols also critically regulate iBALT generation and the immune pathogenesis of COPD. In both COPD patients and cigarette smoke (CS)‐exposed mice, we identified significantly upregulated CH25H and CYP7B1 expression in airway epithelial cells, regulating CS‐induced B‐cell migration and iBALT formation. Mice deficient in CH25H or the oxysterol receptor EBI2 exhibited decreased iBALT and subsequent CS‐induced emphysema. Further, inhibition of the oxysterol pathway using clotrimazole resolved iBALT formation and attenuated CS‐induced emphysema in vivo therapeutically. Collectively, our studies are the first to mechanistically interrogate oxysterol‐dependent iBALT formation in the pathogenesis of COPD, and identify a novel therapeutic target for the treatment of COPD and potentially other diseases driven by the generation of tertiary lymphoid organs.

0377 : Phosphoinositide 3-kinase gamma: a potential clinical target in the prevention of vascular damages inuced by arterial injury

Context Angioplasty with stent placement, used to treat symptomatic atherosclerosis plaques, is frequently complicated by restenosis. This pathology is characteried by fibroproliferative and immuno-inflammatory mechanisms of the arterial wall, called intimal hyperplasia (IH). Aims Our previous results demonstrated that phosphoinositide 3-kinase (??(PI3K(??) was a key mediator of inflammatory processes of the arterial wall leading to atherosclerosis. We now proposed this enzyme as a potential clinical target to prevent vascular damages occuring after arterial lesion leading to IH. As cellular and molecular aspects of IH are still incompletely described, we intended to offer a better understanding ofimmune responses involved in this pathology. Results Using a mouse model of arterial mechanical injury, we showed that PI3K(?-deficient mice and mice expressing a catalytically-inactive PI3K(?(PI3K(?KD) showed reduced arterial occlusion and accumulation of monocytes and T cells around site of vascular lesion. The transfer of PI3K(?KD CD4 + T cells into Rag2-deficient mice greatly reduced vascular occlusion compared to WT cells, clearly demonstrating the involvement of PI3K(?in CD4 + T cells during IH formation. In addition, we found that IH is associated with increased levels of Th1 and Th17 cytokines. A specific decrease in the Th1 response was observed in the absence of PI3K(?activity, leading to decreased chemokine production by smooth muscle cells. Finally, we show that a short period of treatment with a PI3K(?inhibitor decreased IH development in arterial mechanical injury in mice but also in a rat carotid artery balloon injury model demonstrating the therapeutic potential of this inhibitor. Conclusion Our work pintpoint PI3K(?as a good target for IH prevention and brings new insights in the immune biology of the disease.

026 La translocation de bactéries intestinales vers les tissus adipeux initie l’inflammation et le diabète induits par un régime gras chez la souris

Rationnel Un regime riche en graisses modifie le microbiote intestinal, initie une inflammation a bas bruit, une resistance a l’insuline et un diabete de type 2. Mais les mecanismes associant microbiote et inflammation metabolique ne sont pas connus. Materiels et methodes Resultats Nos travaux demontrent qu’apres une semaine de regime gras (avant l’apparition du diabete), le nombre de bacteries commensales intestinales viables augmente de plus de 100 fois dans le tissu adipeux et le sang des souris. Cette translocation de bacteries vivantes est prevenue chez des souris dont les recepteurs aux motifs bacteriens Nod1 ou CD14 ont ete invalides. Ces souris ne developpent ensuite pas de diabete. A l’inverse chez la souris ob/ob, la translocation de bacteries viables vers les tissus est spontanement tres augmentee. Cette « bacteriemie metabolique » est notamment associee a une augmentation de l’adherence d’Escherichia coli a la muqueuse intestinale et a sa colocalisation avec les cellules dendritiques de la lamina propria. Afin de diminuer l’adherence et la translocation bacterienne nous avons traite pendant six semaines des souris diabetiques avec le probiotique Bifidobacterium animalis subsp. lactis 420. Ce traitement a reduit l’inflammation metabolique, l’intolerance au glucose et la sensibilite a l’insuline. Conclusion Nos resultats demontrent que le developpement d’un etat diabetique sous regime gras chez la souris, est precede par une augmentation de la translocation bacterienne depuis l’intestin vers les tissus, alimentant ainsi en continu bacteriemie et inflammation metaboliques. De nouvelles perspectives therapeutiques sont ainsi envisagees pour le traitement du diabete de type 2.