Nicole Malet | Université Paul Sabatier de Toulouse (original) (raw)

Papers by Nicole Malet

The Journal of experimental medicine, Jan 25, 2014

Interventional strategies to treat atherosclerosis, such as transluminal angioplasty and stent im... more Interventional strategies to treat atherosclerosis, such as transluminal angioplasty and stent implantation, often cause vascular injury. This leads to intimal hyperplasia (IH) formation that induces inflammatory and fibroproliferative processes and ultimately restenosis. We show that phosphoinositide 3-kinase γ (PI3Kγ) is a key player in IH formation and is a valid therapeutic target in its prevention/treatment. PI3Kγ-deficient mice and mice expressing catalytically inactive PI3Kγ (PI3Kγ KD) showed reduced arterial occlusion and accumulation of monocytes and T cells around sites of vascular lesion. The transfer of PI3Kγ KD CD4(+) T cells into Rag2-deficient mice greatly reduced vascular occlusion compared with WT cells, clearly demonstrating the involvement of PI3Kγ 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 PI3Kγ activity, l...

Molecular and Cellular Biology, 2008

Phosphoinositide 3-kinase (PI3K) participates in extracellular signal-regulated kinase 1 and 2 (E... more Phosphoinositide 3-kinase (PI3K) participates in extracellular signal-regulated kinase 1 and 2 (ERK1-2) activation according to signal strength, through unknown mechanisms. We report herein that Gab1/Shp2 constitutes a PI3K-dependent checkpoint of ERK1-2 activation regulated according to signal intensity. Indeed, by up-and down-regulation of signal strength in different cell lines and through different methods, we observed that Gab1/Shp2 and Ras/ERK1-2 in concert become independent of PI3K upon strong epidermal growth factor receptor (EGFR) stimulation and dependent on PI3K upon limited EGFR activation. Using Gab1 mutants, we observed that this conditional role of PI3K is dictated by the EGFR capability of recruiting Gab1 through Grb2 or through the PI3K lipid product PIP 3 , according to a high or weak level of receptor stimulation, respectively. In agreement, Grb2 siRNA generates, in cells with maximal EGFR stimulation, a strong dependence on PI3K for both Gab1/Shp2 and ERK1-2 activation. Therefore, Ras/ERK1-2 depends on PI3K only when PIP 3 is required to recruit Gab1/Shp2, which occurs only under weak EGFR mobilization. Finally, we show that, in glioblastoma cells displaying residual EGFR activation, this compensatory mechanism becomes necessary to efficiently activate ERK1-2, which could probably contribute to tumor resistance to EGFR inhibitors.

Circulation Research, 2015

Estradiol (E2) exerts numerous beneficial effects in vascular disease. It regulates gene transcri... more Estradiol (E2) exerts numerous beneficial effects in vascular disease. It regulates gene transcription through nuclear estrogen receptor alpha (ERα) via two activation functions, AF1 and AF2, and can also activate membrane ERα. The role of E2 on the endothelium relies on membrane ERα activation, but the molecular mechanisms of its action on vascular smooth muscle cells (VSMC) are not fully understood. The aim of this study was to determine which cellular target and which ERα subfunction are involved in the preventive action of E2 on neointimal hyperplasia. To trigger neointimal hyperplasia of VSMC we used a mouse model of femoral arterial injury. Cre-Lox models were used to distinguish between the endothelial- and VSMC-specific actions of E2. The molecular mechanisms underlying the role of E2 were further characterized using both selective ERα agonists and transgenic mice in which the ERαAF1 function had been specifically invalidated. We found that: 1) The selective inactivation of ERα in VSMC abrogates the neointimal hyperplasia protection induced by E2, whereas inactivation of endothelial and hematopoietic ERα has no effect; 2) The selective activation of membrane ERα does not prevent neointimal hyperplasia; 3) ERαAF1 is necessary and sufficient to inhibit post-injury VSMC proliferation. Altogether, ERαAF1-mediated nuclear action is both necessary and sufficient to inhibit post-injury arterial VSMC proliferation, whereas membrane ERα largely regulates the endothelial functions of E2. This highlights the exquisite cell/tissue-specific actions of the ERα subfunctions, and helps to delineate the spectrum of action of selective ER modulators.

Advances in Biological Regulation, 2015

Cardiovascular diseases are the most common cause of death around the world. This includes athero... more 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.

Archives of Cardiovascular Diseases Supplements, 2015

Atherosclerosis Supplements, 2006

The Journal of experimental medicine, Jan 25, 2014

Interventional strategies to treat atherosclerosis, such as transluminal angioplasty and stent im... more Interventional strategies to treat atherosclerosis, such as transluminal angioplasty and stent implantation, often cause vascular injury. This leads to intimal hyperplasia (IH) formation that induces inflammatory and fibroproliferative processes and ultimately restenosis. We show that phosphoinositide 3-kinase γ (PI3Kγ) is a key player in IH formation and is a valid therapeutic target in its prevention/treatment. PI3Kγ-deficient mice and mice expressing catalytically inactive PI3Kγ (PI3Kγ KD) showed reduced arterial occlusion and accumulation of monocytes and T cells around sites of vascular lesion. The transfer of PI3Kγ KD CD4(+) T cells into Rag2-deficient mice greatly reduced vascular occlusion compared with WT cells, clearly demonstrating the involvement of PI3Kγ 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 PI3Kγ activity, l...

PLoS ONE, 2011

Background: Mitochondrial ATP synthase is expressed as a plasma membrane receptor for apolipoprot... more Background: Mitochondrial ATP synthase is expressed as a plasma membrane receptor for apolipoprotein A-I (apoA-I), the major protein component in High Density Lipoproteins (HDL). On hepatocytes, apoA-I binds to cell surface ATP synthase (namely ecto-F 1 -ATPase) and stimulates its ATPase activity, generating extracellular ADP. This production of extracellular ADP activates a P2Y 13 -mediated HDL endocytosis pathway. Conversely, exogenous IF1, classically known as a natural mitochondrial specific inhibitor of F 1 -ATPase activity, inhibits ecto-F 1 -ATPase activity and decreases HDL endocytosis by both human hepatocytes and perfused rat liver.

Molecular and Cellular Biology, 2008

Phosphoinositide 3-kinase (PI3K) participates in extracellular signal-regulated kinase 1 and 2 (E... more Phosphoinositide 3-kinase (PI3K) participates in extracellular signal-regulated kinase 1 and 2 (ERK1-2) activation according to signal strength, through unknown mechanisms. We report herein that Gab1/Shp2 constitutes a PI3K-dependent checkpoint of ERK1-2 activation regulated according to signal intensity. Indeed, by up-and down-regulation of signal strength in different cell lines and through different methods, we observed that Gab1/Shp2 and Ras/ERK1-2 in concert become independent of PI3K upon strong epidermal growth factor receptor (EGFR) stimulation and dependent on PI3K upon limited EGFR activation. Using Gab1 mutants, we observed that this conditional role of PI3K is dictated by the EGFR capability of recruiting Gab1 through Grb2 or through the PI3K lipid product PIP 3 , according to a high or weak level of receptor stimulation, respectively. In agreement, Grb2 siRNA generates, in cells with maximal EGFR stimulation, a strong dependence on PI3K for both Gab1/Shp2 and ERK1-2 activation. Therefore, Ras/ERK1-2 depends on PI3K only when PIP 3 is required to recruit Gab1/Shp2, which occurs only under weak EGFR mobilization. Finally, we show that, in glioblastoma cells displaying residual EGFR activation, this compensatory mechanism becomes necessary to efficiently activate ERK1-2, which could probably contribute to tumor resistance to EGFR inhibitors.

Clinical Science, 2009

Inflammation has a central role in the pathogenesis of atherosclerosis at various stages of the d... more Inflammation has a central role in the pathogenesis of atherosclerosis at various stages of the disease. Therefore it appears of great interest to develop novel and innovative drugs targeting inflammatory proteins for the treatment of atherosclerosis. The PI3K (phosphoinositide 3-kinase) family, which catalyses the phosphorylation of the 3-OH position of phosphoinositides and generates phospholipids, controls a wide variety of intracellular signalling pathways. Recent studies provide evidence for a crucial role of this family not only in immune function, such as inflammatory cell recruitment, and expression and activation of inflammatory mediators, but also in antigen-dependent responses making it an interesting target to modulate inflammatory processes. The present review will focus on the regulation of inflammation within the vasculature during atherogenesis. We will concentrate on the different functions played by each isoform of PI3K in immune cells which could be involved in this pathology, raising the possibility that inhibition of one or more PI3K isoforms may represent an effective approach in the treatment of atherosclerosis.

Cellular and Molecular Life Sciences, 2014

ubiquitination of P2Y 13 -R and its efficient targeting to the plasma membrane. the C-terminus ta... more ubiquitination of P2Y 13 -R and its efficient targeting to the plasma membrane. the C-terminus tail exchange between P2Y 13 -R and P2Y 12 -R strongly restored plasma membrane expression of P2Y 13 -R, suggesting the involvement of the intra-cytoplasmic tail of P2Y 13 -R in expression defect. accordingly, proteasomal inhibition increased plasma membrane expression of functionally active P2Y 13 -R in hepatocytes, and consequently stimulated P2Y 13 -R-mediated hDL endocytosis. Importantly, proteasomal inhibition strongly potentiated hDL hepatic uptake (>200 %) in wildtype but not in P2Y 13 -R-deficient mice, thus reinforcing the role of P2Y 13 -R expression in regulating hDL metabolism. therefore, specific inhibition of the ubiquitin-proteasome system might be a novel powerful hDL therapy to enhance P2Y 13 -R expression and consequently promote the overall RCt.

Cardiovascular Research, 2014

Analysis of elastic fiber breakage. The autofluorescence of elastin (488 nm) was analyzed from cr... more Analysis of elastic fiber breakage. The autofluorescence of elastin (488 nm) was analyzed from cryo-sections (4 !m) of aorta samples in order to determinate elastic fiber breakage in 11-week-old ApoE -/mice and 8-week-old LDLR -/mice.

Bone, 2011

Lysophosphatidic acid (LPA) is a lipid mediator that acts in paracrine systems via interaction wi... more Lysophosphatidic acid (LPA) is a lipid mediator that acts in paracrine systems via interaction with a subset of G protein-coupled receptors (GPCRs). LPA promotes cell growth and differentiation, and has been shown to be implicated in a variety of developmental and pathophysiological processes. At least 6 LPA GPCRs have been identified to date: LPA1-LPA6. Several studies have suggested that local production of LPA by tissues and cells contributes to paracrine regulation, and a complex interplay between LPA and its receptors, LPA1 and LPA4, is believed to be involved in the regulation of bone cell activity. In particular, LPA1 may activate both osteoblasts and osteoclasts. However, its role has not as yet been examined with regard to the overall status of bone in vivo. We attempted to clarify this role by defining the bone phenotype of LPA1((-/-)) mice. These mice demonstrated significant bone defects and low bone mass, indicating that LPA1 plays an important role in osteogenesis. The LPA1((-/-)) mice also presented growth and sternal and costal abnormalities, which highlights the specific roles of LPA1 during bone development. Microcomputed tomography and histological analysis demonstrated osteoporosis in the trabecular and cortical bone of LPA1((-/-)) mice. Finally, bone marrow mesenchymal progenitors from these mice displayed decreased osteoblastic differentiation. These results suggest that LPA1 strongly influences bone development both qualitatively and quantitatively and that, in vivo, its absence results in decreased osteogenesis with no clear modification of osteoclasis. They open perspectives for a better understanding of the role of the LPA/LPA1 paracrine pathway in bone pathophysiology.

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 2008

Hydrolysis of phosphatidylcholine by phospholipase D (PLD) leads to the generation of phosphatidi... more Hydrolysis of phosphatidylcholine by phospholipase D (PLD) leads to the generation of phosphatidic acid (PA), which is itself a source of diacylglycerol (DAG). These two versatile lipid second messengers are at the centre of a phospholipid signalling network and as such are involved in several cellular functions. However, their role in T-cell activation and functions are still enigmatic. In order to elucidate this role, we generated a human and a murine T-cell line that stably overexpressed the PLD2 isoform. Analysis of the Ras-MAPK pathway upon phorbol myristate acetate (PMA) and ionomycin stimulation revealed that PLD2 promoted an early and sustained increase in ERK1/2 phosphorylation in both cell lines. This response was inhibited by 1butanol, a well known distracter of PLD activity, or upon overexpression of a dominant negative PLD2, and it was concomitant with a boost of PA/DAG production. As a functional consequence of this PLD2-dependent MAPK activation, interleukin-2 production evoked by PMA/ionomycin stimulation or CD3/CD28 engagement was enhanced in the two T-cell lines overexpressing PLD2. Thus, PLD2 emerged as an early player upstream of the Ras-MAPK-IL-2 pathway in T-cells via PA and DAG production, raising new possibilities of pharmacological manipulation in immune disorders.

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 2013

and sharing with colleagues.

Atherosclerosis Supplements, 2011

We previously showed that C3-activation is involved in vein graft disease (VGD). The role of othe... more We previously showed that C3-activation is involved in vein graft disease (VGD). The role of other complement-factors, including C5a, is unknown. We also reported a role for Mast cells (MC) in atherosclerosis. MC express receptors for complement-factor C5a, and can be activated by C5a. We here studied the effect of C5a on MC activation in VGD and subsequent accelerated atherosclerosis in ApoE-KO mice. C5a-induced MC-activation in vitro resulted in increased tryptase release of 15% (p = 0.007). In murine veingrafts (n = 3−4/time point) MC tryptase mRNA and protein levels as studied by rt-PCR and (immuno)histochemistry, decreased after surgery and increased from 7 to 28d. C5a(R) levels increased after surgery due to influx of inflammatory cells, than decreased and stabilized further on.

The Journal of experimental medicine, Jan 25, 2014

Interventional strategies to treat atherosclerosis, such as transluminal angioplasty and stent im... more Interventional strategies to treat atherosclerosis, such as transluminal angioplasty and stent implantation, often cause vascular injury. This leads to intimal hyperplasia (IH) formation that induces inflammatory and fibroproliferative processes and ultimately restenosis. We show that phosphoinositide 3-kinase γ (PI3Kγ) is a key player in IH formation and is a valid therapeutic target in its prevention/treatment. PI3Kγ-deficient mice and mice expressing catalytically inactive PI3Kγ (PI3Kγ KD) showed reduced arterial occlusion and accumulation of monocytes and T cells around sites of vascular lesion. The transfer of PI3Kγ KD CD4(+) T cells into Rag2-deficient mice greatly reduced vascular occlusion compared with WT cells, clearly demonstrating the involvement of PI3Kγ 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 PI3Kγ activity, l...

Molecular and Cellular Biology, 2008

Phosphoinositide 3-kinase (PI3K) participates in extracellular signal-regulated kinase 1 and 2 (E... more Phosphoinositide 3-kinase (PI3K) participates in extracellular signal-regulated kinase 1 and 2 (ERK1-2) activation according to signal strength, through unknown mechanisms. We report herein that Gab1/Shp2 constitutes a PI3K-dependent checkpoint of ERK1-2 activation regulated according to signal intensity. Indeed, by up-and down-regulation of signal strength in different cell lines and through different methods, we observed that Gab1/Shp2 and Ras/ERK1-2 in concert become independent of PI3K upon strong epidermal growth factor receptor (EGFR) stimulation and dependent on PI3K upon limited EGFR activation. Using Gab1 mutants, we observed that this conditional role of PI3K is dictated by the EGFR capability of recruiting Gab1 through Grb2 or through the PI3K lipid product PIP 3 , according to a high or weak level of receptor stimulation, respectively. In agreement, Grb2 siRNA generates, in cells with maximal EGFR stimulation, a strong dependence on PI3K for both Gab1/Shp2 and ERK1-2 activation. Therefore, Ras/ERK1-2 depends on PI3K only when PIP 3 is required to recruit Gab1/Shp2, which occurs only under weak EGFR mobilization. Finally, we show that, in glioblastoma cells displaying residual EGFR activation, this compensatory mechanism becomes necessary to efficiently activate ERK1-2, which could probably contribute to tumor resistance to EGFR inhibitors.

Circulation Research, 2015

Estradiol (E2) exerts numerous beneficial effects in vascular disease. It regulates gene transcri... more Estradiol (E2) exerts numerous beneficial effects in vascular disease. It regulates gene transcription through nuclear estrogen receptor alpha (ERα) via two activation functions, AF1 and AF2, and can also activate membrane ERα. The role of E2 on the endothelium relies on membrane ERα activation, but the molecular mechanisms of its action on vascular smooth muscle cells (VSMC) are not fully understood. The aim of this study was to determine which cellular target and which ERα subfunction are involved in the preventive action of E2 on neointimal hyperplasia. To trigger neointimal hyperplasia of VSMC we used a mouse model of femoral arterial injury. Cre-Lox models were used to distinguish between the endothelial- and VSMC-specific actions of E2. The molecular mechanisms underlying the role of E2 were further characterized using both selective ERα agonists and transgenic mice in which the ERαAF1 function had been specifically invalidated. We found that: 1) The selective inactivation of ERα in VSMC abrogates the neointimal hyperplasia protection induced by E2, whereas inactivation of endothelial and hematopoietic ERα has no effect; 2) The selective activation of membrane ERα does not prevent neointimal hyperplasia; 3) ERαAF1 is necessary and sufficient to inhibit post-injury VSMC proliferation. Altogether, ERαAF1-mediated nuclear action is both necessary and sufficient to inhibit post-injury arterial VSMC proliferation, whereas membrane ERα largely regulates the endothelial functions of E2. This highlights the exquisite cell/tissue-specific actions of the ERα subfunctions, and helps to delineate the spectrum of action of selective ER modulators.

Advances in Biological Regulation, 2015

Cardiovascular diseases are the most common cause of death around the world. This includes athero... more 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.

Archives of Cardiovascular Diseases Supplements, 2015

Atherosclerosis Supplements, 2006

The Journal of experimental medicine, Jan 25, 2014

Interventional strategies to treat atherosclerosis, such as transluminal angioplasty and stent im... more Interventional strategies to treat atherosclerosis, such as transluminal angioplasty and stent implantation, often cause vascular injury. This leads to intimal hyperplasia (IH) formation that induces inflammatory and fibroproliferative processes and ultimately restenosis. We show that phosphoinositide 3-kinase γ (PI3Kγ) is a key player in IH formation and is a valid therapeutic target in its prevention/treatment. PI3Kγ-deficient mice and mice expressing catalytically inactive PI3Kγ (PI3Kγ KD) showed reduced arterial occlusion and accumulation of monocytes and T cells around sites of vascular lesion. The transfer of PI3Kγ KD CD4(+) T cells into Rag2-deficient mice greatly reduced vascular occlusion compared with WT cells, clearly demonstrating the involvement of PI3Kγ 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 PI3Kγ activity, l...

PLoS ONE, 2011

Background: Mitochondrial ATP synthase is expressed as a plasma membrane receptor for apolipoprot... more Background: Mitochondrial ATP synthase is expressed as a plasma membrane receptor for apolipoprotein A-I (apoA-I), the major protein component in High Density Lipoproteins (HDL). On hepatocytes, apoA-I binds to cell surface ATP synthase (namely ecto-F 1 -ATPase) and stimulates its ATPase activity, generating extracellular ADP. This production of extracellular ADP activates a P2Y 13 -mediated HDL endocytosis pathway. Conversely, exogenous IF1, classically known as a natural mitochondrial specific inhibitor of F 1 -ATPase activity, inhibits ecto-F 1 -ATPase activity and decreases HDL endocytosis by both human hepatocytes and perfused rat liver.

Molecular and Cellular Biology, 2008

Phosphoinositide 3-kinase (PI3K) participates in extracellular signal-regulated kinase 1 and 2 (E... more Phosphoinositide 3-kinase (PI3K) participates in extracellular signal-regulated kinase 1 and 2 (ERK1-2) activation according to signal strength, through unknown mechanisms. We report herein that Gab1/Shp2 constitutes a PI3K-dependent checkpoint of ERK1-2 activation regulated according to signal intensity. Indeed, by up-and down-regulation of signal strength in different cell lines and through different methods, we observed that Gab1/Shp2 and Ras/ERK1-2 in concert become independent of PI3K upon strong epidermal growth factor receptor (EGFR) stimulation and dependent on PI3K upon limited EGFR activation. Using Gab1 mutants, we observed that this conditional role of PI3K is dictated by the EGFR capability of recruiting Gab1 through Grb2 or through the PI3K lipid product PIP 3 , according to a high or weak level of receptor stimulation, respectively. In agreement, Grb2 siRNA generates, in cells with maximal EGFR stimulation, a strong dependence on PI3K for both Gab1/Shp2 and ERK1-2 activation. Therefore, Ras/ERK1-2 depends on PI3K only when PIP 3 is required to recruit Gab1/Shp2, which occurs only under weak EGFR mobilization. Finally, we show that, in glioblastoma cells displaying residual EGFR activation, this compensatory mechanism becomes necessary to efficiently activate ERK1-2, which could probably contribute to tumor resistance to EGFR inhibitors.

Clinical Science, 2009

Inflammation has a central role in the pathogenesis of atherosclerosis at various stages of the d... more Inflammation has a central role in the pathogenesis of atherosclerosis at various stages of the disease. Therefore it appears of great interest to develop novel and innovative drugs targeting inflammatory proteins for the treatment of atherosclerosis. The PI3K (phosphoinositide 3-kinase) family, which catalyses the phosphorylation of the 3-OH position of phosphoinositides and generates phospholipids, controls a wide variety of intracellular signalling pathways. Recent studies provide evidence for a crucial role of this family not only in immune function, such as inflammatory cell recruitment, and expression and activation of inflammatory mediators, but also in antigen-dependent responses making it an interesting target to modulate inflammatory processes. The present review will focus on the regulation of inflammation within the vasculature during atherogenesis. We will concentrate on the different functions played by each isoform of PI3K in immune cells which could be involved in this pathology, raising the possibility that inhibition of one or more PI3K isoforms may represent an effective approach in the treatment of atherosclerosis.

Cellular and Molecular Life Sciences, 2014

ubiquitination of P2Y 13 -R and its efficient targeting to the plasma membrane. the C-terminus ta... more ubiquitination of P2Y 13 -R and its efficient targeting to the plasma membrane. the C-terminus tail exchange between P2Y 13 -R and P2Y 12 -R strongly restored plasma membrane expression of P2Y 13 -R, suggesting the involvement of the intra-cytoplasmic tail of P2Y 13 -R in expression defect. accordingly, proteasomal inhibition increased plasma membrane expression of functionally active P2Y 13 -R in hepatocytes, and consequently stimulated P2Y 13 -R-mediated hDL endocytosis. Importantly, proteasomal inhibition strongly potentiated hDL hepatic uptake (>200 %) in wildtype but not in P2Y 13 -R-deficient mice, thus reinforcing the role of P2Y 13 -R expression in regulating hDL metabolism. therefore, specific inhibition of the ubiquitin-proteasome system might be a novel powerful hDL therapy to enhance P2Y 13 -R expression and consequently promote the overall RCt.

Cardiovascular Research, 2014

Analysis of elastic fiber breakage. The autofluorescence of elastin (488 nm) was analyzed from cr... more Analysis of elastic fiber breakage. The autofluorescence of elastin (488 nm) was analyzed from cryo-sections (4 !m) of aorta samples in order to determinate elastic fiber breakage in 11-week-old ApoE -/mice and 8-week-old LDLR -/mice.

Bone, 2011

Lysophosphatidic acid (LPA) is a lipid mediator that acts in paracrine systems via interaction wi... more Lysophosphatidic acid (LPA) is a lipid mediator that acts in paracrine systems via interaction with a subset of G protein-coupled receptors (GPCRs). LPA promotes cell growth and differentiation, and has been shown to be implicated in a variety of developmental and pathophysiological processes. At least 6 LPA GPCRs have been identified to date: LPA1-LPA6. Several studies have suggested that local production of LPA by tissues and cells contributes to paracrine regulation, and a complex interplay between LPA and its receptors, LPA1 and LPA4, is believed to be involved in the regulation of bone cell activity. In particular, LPA1 may activate both osteoblasts and osteoclasts. However, its role has not as yet been examined with regard to the overall status of bone in vivo. We attempted to clarify this role by defining the bone phenotype of LPA1((-/-)) mice. These mice demonstrated significant bone defects and low bone mass, indicating that LPA1 plays an important role in osteogenesis. The LPA1((-/-)) mice also presented growth and sternal and costal abnormalities, which highlights the specific roles of LPA1 during bone development. Microcomputed tomography and histological analysis demonstrated osteoporosis in the trabecular and cortical bone of LPA1((-/-)) mice. Finally, bone marrow mesenchymal progenitors from these mice displayed decreased osteoblastic differentiation. These results suggest that LPA1 strongly influences bone development both qualitatively and quantitatively and that, in vivo, its absence results in decreased osteogenesis with no clear modification of osteoclasis. They open perspectives for a better understanding of the role of the LPA/LPA1 paracrine pathway in bone pathophysiology.

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 2008

Hydrolysis of phosphatidylcholine by phospholipase D (PLD) leads to the generation of phosphatidi... more Hydrolysis of phosphatidylcholine by phospholipase D (PLD) leads to the generation of phosphatidic acid (PA), which is itself a source of diacylglycerol (DAG). These two versatile lipid second messengers are at the centre of a phospholipid signalling network and as such are involved in several cellular functions. However, their role in T-cell activation and functions are still enigmatic. In order to elucidate this role, we generated a human and a murine T-cell line that stably overexpressed the PLD2 isoform. Analysis of the Ras-MAPK pathway upon phorbol myristate acetate (PMA) and ionomycin stimulation revealed that PLD2 promoted an early and sustained increase in ERK1/2 phosphorylation in both cell lines. This response was inhibited by 1butanol, a well known distracter of PLD activity, or upon overexpression of a dominant negative PLD2, and it was concomitant with a boost of PA/DAG production. As a functional consequence of this PLD2-dependent MAPK activation, interleukin-2 production evoked by PMA/ionomycin stimulation or CD3/CD28 engagement was enhanced in the two T-cell lines overexpressing PLD2. Thus, PLD2 emerged as an early player upstream of the Ras-MAPK-IL-2 pathway in T-cells via PA and DAG production, raising new possibilities of pharmacological manipulation in immune disorders.

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 2013

and sharing with colleagues.

Atherosclerosis Supplements, 2011

We previously showed that C3-activation is involved in vein graft disease (VGD). The role of othe... more We previously showed that C3-activation is involved in vein graft disease (VGD). The role of other complement-factors, including C5a, is unknown. We also reported a role for Mast cells (MC) in atherosclerosis. MC express receptors for complement-factor C5a, and can be activated by C5a. We here studied the effect of C5a on MC activation in VGD and subsequent accelerated atherosclerosis in ApoE-KO mice. C5a-induced MC-activation in vitro resulted in increased tryptase release of 15% (p = 0.007). In murine veingrafts (n = 3−4/time point) MC tryptase mRNA and protein levels as studied by rt-PCR and (immuno)histochemistry, decreased after surgery and increased from 7 to 28d. C5a(R) levels increased after surgery due to influx of inflammatory cells, than decreased and stabilized further on.