Sylvain Chemtob

McGill University, Montréal, Quebec, Canada

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Publications (267)1096.02 Total impact

  • Fetal and Neonatal Physiology, 5th edition edited by Richard A. Polin, 07/2016: chapter 18. Basic Pharmacologic Principles; Expert Consult.
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    ABSTRACT: G-protein coupled receptors (GPCRs) evolved as specialized sensors of the extracellular environment. Comprising the largest family of cell surface receptors, GPCRs are common therapeutic targets. Over the last 25 years, several GPCRs have been observed at the cell nucleus, suggesting the presence of intracrine GPCR signaling beyond the plasma membrane. Yet specific physiological functions of nuclear GPCRs had not been reported, until lately. We recently uncovered distinct but complementary angiogenic roles of F2rl1 (formerly known as PAR2) depending on its subcellular localization at the plasma membrane or at the nucleus. Targeting subcellular compartments to improve drug selectivity may therefore inspire novel therapeutic strategies for transmembrane receptors.
    Expert Opinion on Therapeutic Targets 06/2015; 19(6):717-21. DOI:10.1517/14728222.2015.1042365
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    ABSTRACT: Pursuing molecules that delay labour, so-called tocolytics, the prostaglandin F2α receptor (FP) was targeted, because of its roles in the stimulation of uterine contractions leading to birth and preterm birth. Previously, the indolizidinone PDC-113.824 (5) and the aza-glycinyl-proline analog 6, both were shown to delay labour in the mouse by modulating FP function, likely by an allosteric mechanism, which features biased signalling. Crystal structure and computational analyses of the indolizidin-2-one amino acid and aza-glycinyl-proline components of 5 and 6 in model peptides have shown them to adopt geometry that mimic ideal type I and II’ β-turns. To elucidate the precise turn geometry for receptor recognition, analogs 1-4 have now been synthesized: macrocycle and pyrroloazepinone mimics 1 and 2 to mimic type I, and glycinyl-proline and D-alaninyl-proline analogs 3 and 4 to favour type II’ β-turn geometry. Notably, transannular cyclization of peptide macrocycle 13 has provided diastereoselectively pyrroloazepinone 15 by a novel route that provides effective access to mimics 1 and 2 by way of a common intermediate. Among the four analogs, none exhibited efficacy nor potency on par with 5 and 6; however, D-alaninyl-proline analog 4 proved superior to the other analogs in reducing PGF2α–induced myometrial contractions and inhibiting FP modulation of cell ruffling, a response dependent on the G12/RhoA/ROCK signaling pathway. Furthermor,e Gly-Pro analog 3 potentiated the effect of PGF2α on Gq mediated ERK1/2 activation. Evidence that 4 adopted turn geometry was obtained by conformational analysis using NMR spectroscopy to characterize respectively the influences of solvent and temperature on the chemical shifts of the amide NH protons. Although mimicry of the type II’ geometry by 3, 4, 5 and 6 may favour activity, distortion from ideal geometry by the indolizidinone and aza-glycinyl residues of the latter appears to enhance their biological effects.
    Organic & Biomolecular Chemistry 05/2015; DOI:10.1039/C5OB00962F
  • Medecine sciences: M/S 04/2015; 31(4):374-6. DOI:10.1051/medsci/20153104010
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    ABSTRACT: The traditional view of G protein-coupled receptors (GPCRs) being inactivated upon their internalization has been repeatedly challenged in recent years. GPCRs, in addition to forming the largest family of cell surface receptors, can also be found on intracellular membranes such as nuclear membranes. Since the first experimental evidence of GPCRs at the nucleus in the early 1990s, approximately 30 different GPCRs have been localized at the nucleus by independent research groups, including ours. In this chapter, we describe several techniques commonly used for immuno-detection of nuclear GPCRs focusing on subcellular fractionation of proteins based on their localization and transmission electron microscopy (TEM) using primary cultured cells as well as tissue sections. We also describe the use of confocal microscopy to study nuclear calcium currents, which can further affect downstream events such as gene transcription, nuclear envelope breakdown, or its reconstruction and nucleocytoplasmic protein transport.
    Methods in Molecular Biology 01/2015; 1234:81-97. DOI:10.1007/978-1-4939-1755-6_8
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    ABSTRACT: Ischemic retinopathies are characterized by sequential vaso-obliteration followed by abnormal intravitreal neovascularization predisposing patients to retinal detachment and blindness. Ischemic retinopathies are associated with robust inflammation that leads to generation of IL-1 beta, which causes vascular degeneration and impairs retinal revascularization in part through the Liberation of repulsive guidance cue semaphorin 3A (Sema3A). However, retinal revascularization begins as inflammation culminates in ischemic retinopathies. Because inflammation Leads to activation of proteases involved in the formation of vasculature, we hypothesized that proteinase-activated receptor (Par)-2 (official name F2r1.1) may modulate deleterious effects of IL-1 beta. Par2, detected mostly in retinal ganglion cells, was up-regulated in oxygen-induced retinopathy. Surprisingly, oxygen-induced retinopathy induced vaso-obliteration and neovascularization were unaltered in Par2 knockout mice, suggesting compensatory mechanisms. We therefore conditionally knocked down retinal Par2 with shRNA-Par2 encoded Lentivirus. Par2 knockdown interfered with normal revascularization, resulting in pronounced intravitreat neovascularization; conversely, the Par2 agonist peptide (SLIGRL) accelerated normal revascularization. In vitro and in vivo exploration of mechanisms revealed that IL-1 beta induced Par2 expression, which in turn down-regulated sequentially IL-1 receptor type I and Sema3A expression through Erk/Jnk-dependent processes. Collectively, our findings unveil an important mechanism by which IL-1 beta regulates its own endothelial cytotoxic actions by augmenting neuronal Par2 expression to repress sequentially IL-1 receptor type I and Sema3A expression. Timely activation of Par2 may be a promising therapeutic avenue in ischemic retinopathies.
    American Journal Of Pathology 12/2014; 185(2). DOI:10.1016/j.ajpath.2014.10.020
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    ABSTRACT: Premature birth (1) based on the sequence of the second extracellular loop of FP on the basis that the loop itself might modulate receptor activation. Systematic study of the structure−activity relationships of 1 generated hypotheses concerning the conformation and side-chains responsible for activity that led to the synthesis of PDC113.31 (2), a potent all d-amino acid peptide, which has successfully completed Phase 1b clinical trials. Employing indolizidinone amino acids, peptide mimics were developed that served to probe the mechanism of FP modulation. For example, PDC113.824 (9) was shown to allosterically regulate FP activity contingent on the presence of prostaglandin F2α by a mechanism implicating biased signalling. Although attempts to understand the turn geometry responsible for the activity of 9 by replacement of its indolizidin-2-one moiety with other azabicycloalkanones failed to produce biologically active analogs, employment of aza-aminoacyl-proline analogs resulted in a series of FP modulators exhibiting distinct effects on different G protein-mediated signalling pathways. Our program has thus contributed novel probes for understanding the chemical biology of FP as well as new therapeutic agents with promise for inhibiting uterine contractions and preventing preterm birth.
    Canadian Journal of Chemistry 11/2014; 92(11):1031-1040. DOI:10.1139/cjc-2014-0289
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    ABSTRACT: Neurons have an important role in retinal vascular development. Here we show that the G protein-coupled receptor (GPCR) coagulation factor II receptor-like 1 (F2rl1, previously known as Par2) is abundant in retinal ganglion cells and is associated with new blood vessel formation during retinal development and in ischemic retinopathy. After stimulation, F2rl1 in retinal ganglion cells translocates from the plasma membrane to the cell nucleus using a microtubule-dependent shuttle that requires sorting nexin 11 (Snx11). At the nucleus, F2rl1 facilitates recruitment of the transcription factor Sp1 to trigger Vegfa expression and, in turn, neovascularization. In contrast, classical plasma membrane activation of F2rl1 leads to the expression of distinct genes, including Ang1, that are involved in vessel maturation. Mutant versions of F2rl1 that prevent nuclear relocalization but not plasma membrane activation interfere with Vegfa but not Ang1 expression. Complementary angiogenic factors are therefore regulated by the subcellular localization of a receptor (F2rl1) that governs angiogenesis. These findings may have implications for the selectivity of drug actions based on the subcellular distribution of their targets.
    Nature Medicine 09/2014; 20(10). DOI:10.1038/nm.3669
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    ABSTRACT: Purpose Pathological choroidal neovascularization (CNV) is the major cause of severe vision loss in patients with age-related macular degeneration (AMD). Inflammation is a key component in AMD, and macrophages play an important role in CNV generation. We have demonstrated that human T-lymphocyte-derived microparticles (LMPs) significantly inhibit angiogenesis in several models of ocular neovascularization. In this study, we investigated whether LMPs modulate angiogenic microenvironment by altering macrophages activitiesMethods LMPs were produced from apoptotic human T lymphocytes after treated with actinomycin D. The effects of LMPs on cell viability and cell migration were studied in apoptosis assay and migration assay respectively. Cell growth of human retinal microvascular endothelial cells was assessed after cells were co-cultured with LMPs pre-treated macrophages. A laser-induced CNV model was used to determine labelled choroidal flat-mounts.Results LMPs dose-dependently inhibited macrophages cell growth without altering cell death. In addition, LMPs dramatically abrogated VEGF-induced macrophages migration. LMPs-pretreated macrophages exhibited strong inhibitory effect on endothelial cell growth and this effect was associated with the increased expression of IL-12, CD36 and HIF-1α. In vivo, intravitreal injection of LMPs significantly suppressed laser-induced CNV and reduced macrophages infiltration at the lesion sites.Conclusion These results suggest that LMPs are potent antiangiogenic therapeutic agent. In addition to the direct effects on endothelial cells, LMPs may interfere the proangiogenic environment through modulation of macrophages function during pathophysiological conditions.
    Acta ophthalmologica 09/2014; 92(s253). DOI:10.1111/j.1755-3768.2014.F012.x
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    ABSTRACT: IL-23 is part of the IL-12 family of cytokines and is composed of the p19 subunit specific to IL-23 and the p40 subunit shared with IL-12. IL-23 specifically contributes to the inflammatory process of multiple chronic inflammatory autoimmune disorders, including psoriasis, multiple sclerosis, inflammatory bowel disease and rheumatoid arthritis. So far, one antibody targeting the shared p40 subunit of IL-12 and IL-23, Ustekinumab, is approved clinically to treat psoriasis. However, there are no treatments inhibiting specifically the IL-23 pro-inflammatory response. We have developed small IL-23R specific antagonists by designing all D-peptides arising from flexible regions of IL-23R. Of these peptides, we selected 2305 (teeeqqly), since in addition to its soluble properties, it inhibited IL-23-induced STAT3 phosphorylation in spleen cells. Peptide 2305 specifically binds to IL-23R/IL-12Rβ1-expressing HEK293 cells and not to cells devoid of the receptor. Peptide 2305 showed functional selectivity by modulating IL-23-induced gene expression in IL-23R/IL-12Rβ1-expressing cells and in Jurkat cells; 2305 does not inhibit IL-12-induced cytokine expression in IL-12Rβ-IL-12Rβ2-HEK293 cells. Finally, in comparison with anti-p40 treatment, 2305 effectively and selectively inhibits IL-23-induced inflammation in three in vivo mouse models: IL-23-induced ear inflammation, anti-CD40 induced systemic inflammatory response and collagen-induced arthritis. We hereby describe the discovery and characterization of a potent IL-23R small peptide modulator, 2305 (teeeqqly), that is effective in vivo. 2305 may be more convenient, less cumbersome, less costly, and most importantly more specific than current biologics for the treatment of inflammatory conditions, and conceivably complement the actual therapies for these chronic and debilitating inflammatory diseases.
    AJP Regulatory Integrative and Comparative Physiology 08/2014; DOI:10.1152/ajpregu.00540.2013
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    ABSTRACT: IL-12 and IL-23 cytokines respectively drive Th1 and Th17 type responses. Yet, little is known regarding the biology of these receptors. As the IL-12 and IL-23 receptors share a common subunit, it has been assumed that these receptors are co-expressed. Surprisingly, we find that the expression of each of these receptors is restricted to specific cell types, in both mouse and human. Indeed, although IL-12Rβ2 is expressed by NK cells and a subset of γδ T cells, the expression of IL-23R is restricted to specific T cell subsets, a small number of B cells and innate lymphoid cells. By exploiting an IL-12- and IL-23-dependent mouse model of innate inflammation, we demonstrate an intricate interplay between IL-12Rβ2 NK cells and IL-23R innate lymphoid cells with respectively dominant roles in the regulation of systemic versus local inflammatory responses. Together, these findings support an unforeseen lineage-specific dichotomy in the in vivo role of both the IL-12 and IL-23 pathways in pathological inflammatory states, which may allow more accurate dissection of the roles of these receptors in chronic inflammatory diseases in humans.
    PLoS ONE 02/2014; 9(2):e89092. DOI:10.1371/journal.pone.0089092
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    ABSTRACT: Prompt post-hypoxia-ischemia (HI) revascularization has been suggested to improve outcome in adults and newborn subjects. Other than hypoxia-inducible factor, sensors of metabolic demand remain largely unknown. During HI, anaerobic respiration is arrested resulting in accumulation of carbohydrate metabolic intermediates. As such succinate readily increases, exerting its biological effects via a specific receptor, G-protein-coupled receptor (GPR) 91. We postulate that succinate/GPR91 enhances post-HI vascularization and reduces infarct size in a model of newborn HI brain injury. The Rice-Vannucci model of neonatal HI was used. Succinate was measured by mass spectrometry, and microvascular density was evaluated by quantification of lectin-stained cryosection. Gene expression was evaluated by real-time polymerase chain reaction. Succinate levels rapidly increased in the penumbral region of brain infarcts. GPR91 was foremost localized not only in neurons but also in astrocytes. Microvascular density increased at 96 hours after injury in wild-type animals; it was diminished in GPR91-null mice leading to an increased infarct size. Stimulation with succinate led to an increase in growth factors implicated in angiogenesis only in wild-type mice. To explain the mode of action of succinate/GPR91, we investigated the role of PGE2-prostaglandin E receptor 4, previously proposed in neural angiogenesis. Succinate-induced vascular endothelial growth factor expression was abrogated by a cyclooxygenase inhibitor and a selective prostaglandin E receptor 4 antagonist. This antagonist also abolished succinate-induced neovascularization. We uncover a dominant metabolic sensor responsible for post-HI neurovascular adaptation, notably succinate/GPR91, acting via PGE2-prostaglandin E receptor 4 to govern expression of major angiogenic factors. We propose that pharmacological intervention targeting GPR91 could improve post-HI brain recovery.
    Arteriosclerosis Thrombosis and Vascular Biology 11/2013; 34(2). DOI:10.1161/ATVBAHA.113.302131
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    ABSTRACT: Purpose:Perinatal inflammatory stress in preterm babies is associated with increased rates of severe retinopathy of prematurity (ROP) and adverse neurological dysfunction. While sustained perinatal systemic inflammation is known to perturb and damage the cerebral neurovascular unit, the precise impact on the neurovascular retina remains ill-defined. In this study, we set out to determine the consequences of severe systemic inflammatory stress on developmental retinal vascularization and evaluate the subsequent outcome on retinal function in later life. Methods:Systemic inflammatory stress was induced in C57BL/6J mouse pups by an intraperitoneal injection of lipopolysaccharide (LPS; 1 mg/kg) at post-natal day 4. A detailed and systematic analysis of retinal microglial infiltration, retinal vascular morphology, density and growth rate was performed at key time-points throughout retinal vascularization. Retinal function in adult life was assessed with the electroretinogram at 6 weeks post-injection. Results: As early as 48 hours after intra-peritoneal administration of LPS, a significant increase in retinal vascular densities was noted throughout the retina. A pronounced increase in the number of activated microglial cell was observed in the retinal ganglion cell layer and in the outer plexiform layer just prior to their vascularization; direct physical contact between activated microglia and sprouting vessels suggested that microglia partake in promoting the aberrant retinal vascularization. With maturity, animals subjected to perinatal inflammatory stress displayed depleted retinal vascular beds and had significantly decreased retinal function as determined by electroretinograms. Conclusions: Our data reveal that early severe post-natal inflammatory stress leads to abnormal retinal vascular development, increased vessel anastomosis and ultimately, permanently compromises retinal function. The aberrant and initially exaggerated retinal vascularization observed is associated with microglial activation, providing a cellular mechanism by which perinatal sepsis predisposes to ROP.
    Investigative ophthalmology & visual science 11/2013; 54(13). DOI:10.1167/iovs.13-12496
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    ABSTRACT: Angiogenesis of the microvasculature is central to the etiology of many diseases including proliferative retinopathy, age-related macular degeneration and cancer. A mouse model of microvascular angiogenesis would be very valuable and enable access to a wide range of genetically manipulated tissues that closely approximate small blood vessel growth in vivo. Vascular endothelial cells cultured in vitro are widely used, however, isolating pure vascular murine endothelial cells is technically challenging. A microvascular mouse explant model that is robust, quantitative and can be reproduced without difficulty would overcome these limitations. Here we characterized and optimized for reproducibility an organotypic microvascular angiogenesis mouse and rat model from the choroid, a microvascular bed in the posterior of eye. The choroidal tissues from C57BL/6J and 129S6/SvEvTac mice and Sprague Dawley rats were isolated and incubated in Matrigel. Vascular sprouting was comparable between choroid samples obtained from different animals of the same genetic background. The sprouting area, normalized to controls, was highly reproducible between independent experiments. We developed a semi-automated macro in ImageJ software to allow for more efficient quantification of sprouting area. Isolated choroid explants responded to manipulation of the external environment while maintaining the local interactions of endothelial cells with neighboring cells, including pericytes and macrophages as evidenced by immunohistochemistry and fluorescence-activated cell sorting (FACS) analysis. This reproducible ex vivo angiogenesis assay can be used to evaluate angiogenic potential of pharmacologic compounds on microvessels and can take advantage of genetically manipulated mouse tissue for microvascular disease research.
    PLoS ONE 08/2013; 8(7):e69552. DOI:10.1371/journal.pone.0069552
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    ABSTRACT: Background: Choroidal neovascularization (CNV) is a major cause of vision loss in which choroidal vessels penetrate the retinal pigment epithelium (RPE)-an important source of growth factors, including nerve growth factor (NGF), whose activation via the p75NTR receptor promotes apoptosis and inhibits angiogenesis. We previously demonstrated that human T-lymphocyte-derived microparticles (LMPs) significantly inhibit angiogenesis in several models of ocular neovascularization. We herein investigated how LMPs modulate pro and antiangiogenic microenvironments during choroidal angiogenesis. Methods: Antiangiogenic effects of LMPs were investigated using a rat model of choroidal angiogenesis. The impact of LMPs on expression of major angiogenic factors was assessed by real-time qPCR. To determine whether p75NTR signalling was implicated in LMPs-induced activities, we used a specific antibody and shRNA targeting p75NTR. Cellular apoptosis was determined via evaluation of activated caspase-3 and annexin V binding. Results: LMPs time-dependently inhibited choroidal angiogenesis by more than 64% after 48 hours of treatment. Removal of the RPE from choroidal explants abolished the antiangiogenic effects of LMPs. mRNA levels of pigment epithelium-derived factor (PEDF) and NGF were significantly increased following LMPs treatment of intact, but not RPE-removed choroids. Downregulation of PEDF and p75NTR significantly blocked the antiangiogenic effects of LMPs. Finally, induction of choroidal endothelial cell apoptosis by LMPs was dependent on p75NTR. Conclusions: We demonstrate for the first time that LMPs markedly inhibit choroidal angiogenesis via mechanisms that are dependent on the integrity of the RPE and that are largely mediated by the PEDF and proapoptotic activities of p75NTR.
    Investigative ophthalmology & visual science 08/2013; 54(9). DOI:10.1167/iovs.13-11896
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    ABSTRACT: Purpose Age-related macular degeneration (AMD) represents the leading cause of vision loss in the elderly. The cumulative oxidative injury induces retinal pigment epithelium (RPE) membrane microparticles production, RPE cell death and cellular senescence. The RPE blebs are implicated in the formation of sub-retinal deposit. Nonetheless, the pathophysiological roles of RPE microparticles (RMPs) remain largely unexplored. This study was designed to investigate whether RMPs participate in the retinal cells dysfunction. Methods RMPs and fluorescent DiI-labelled RMPs were isolated from cultured ARPE-19 cells under oxidative stress. RMPs-treated RPE cells were subjected to WST-1, cellular senescent, apoptotic assay and FACS cell cycle analysis respectively. The antibody against CD36 was used in uptake experiment to determine the involvement of scavenger receptor CD36. Results Our study revealed that uptake of RMPs by RPE cells is time-dependent, and this process is partially dependent on CD36 evidenced by an approximately 50% decrease of RMPs uptake caused by CD36 antibody treatment. In addition, RMPs significantly reduced RPE cell viability in a dose-dependent manner. RMPs in a concentration of 5% µg/ml significantly induced RPE cell-cycle arrest at G0/G1 phase. RMPs-treated cells exhibited a 19% increase in G0/G1 phase, with associated increases of the senescence-associated β-galactosidase activity. Conclusion We demonstrated for the first time that RPE cells uptake microparticles derived from RPE cells under oxidative stress. These findings strongly suggest that RMPs function as mediators to exacerbate the oxidative damages to RPE cells, and indicate a pathological role of RMPs in AMD.
    Acta ophthalmologica 08/2013; 91(s252). DOI:10.1111/j.1755-3768.2013.4774.x
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    ABSTRACT: Age-related macular degeneration (AMD) is a prominent cause of blindness in the Western world. To date, its molecular pathogenesis as well as the sequence of events leading to retinal degeneration remain largely ill-defined. While the invasion of choroidal neovessels in the retina is the primary mechanism that precipitates loss of sight, an earlier dry form precedes it. Here we provide the first evidence for the protective role of the Retinal Pigment Epithelium (RPE)-resident metabolite receptor, succinate receptor 1 (SUCNR1; G-Protein coupled Receptor-91 (GPR91), in preventing dry AMD-like lesions of the outer retina. Genetic analysis of 925 patients with geographic atrophy and 1199 AMD-free peers revealed an increased risk of developing geographic atrophy associated with intronic variants in theSUCNR1 gene. In mice, outer retinal expression of SUCNR1 is observed in the RPE as well as microglial cells and decreases progressively with age. Accordingly, Sucnr1-/- mice show signs of premature sub-retinal dystrophy with accumulation of oxidized-LDL, abnormal thickening of Bruch's membrane and a buildup of subretinal microglia. The accumulation of microglia in Sucnr1-deficient mice is likely triggered by the inefficient clearance of oxidized lipids by the RPE as bone marrow transfer of wild-type microglia into Sucnr1-/- mice did not salvage the patho-phenotype and systemic lipolysis was equivalent between wild-type and control mice. Our findings suggest that deficiency in SUCNR1 is a possible contributing factor to the pathogenesis of dry AMD and thus broaden our understanding of this clinically unmet need.
    Aging 06/2013; 5(6).
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    ABSTRACT: OBJECTIVE: Proinflammatory cytokines contribute to the development of retinal vasculopathies. However, the role of these factors and the mechanisms by which they elicit their effects in retina are not known. We investigated whether activated microglia during early stages of ischemic retinopathy produces excessive interleukin-1β (IL-1β), which elicits retinal microvascular degeneration not directly but rather by triggering the release of the proapoptotic/repulsive factor semaphorin-3A (Sema3A) from neurons. APPROACH AND RESULTS: Sprague Dawley rats subjected to retinopathy induced by hyperoxia (80% O2; O2-induced retinopathy) exhibited retinal vaso-obliteration associated with microglial activation, NLRP3 upregulation, and IL-1β and Sema3A release; IL-1β was mostly generated by microglia. Intraperitoneal administration of IL-1 receptor antagonists (Kineret, or rytvela [101.10]) decreased these effects and enhanced retinal revascularization; knockdown of Sema3A resulted in microvessel preservation and, conversely, administration of IL-1β caused vaso-obliteration. In vitro, IL-1β derived from activated primary microglial cells, cultured under hyperoxia, stimulated the release of Sema3A in retinal ganglion cells-5, which in turn induced apoptosis of microvascular endothelium; antagonism of IL-1 receptor decreased microglial activation and on retinal ganglion cells-5 abolished the release of Sema3A inhibiting ensuing endothelial cell apoptosis. IL-1β was not directly cytotoxic to endothelial cells. CONCLUSIONS: Our findings suggest that in the early stages of O2-induced retinopathy, retinal microglia are activated to produce IL-1β, which sustains the activation of microglia and induces microvascular injury through the release of Sema3A from adjacent neurons. Interference with IL-1 receptor or Sema3A actions preserves the microvascular bed in ischemic retinopathies and, consequently, decreases ensued pathological preretinal neovascularization.
    Arteriosclerosis Thrombosis and Vascular Biology 06/2013; 33(8). DOI:10.1161/ATVBAHA.113.301331
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    ABSTRACT: OBJECTIVE: Nitro-oxidative stress exerts a significant role in the genesis of hypoxic-ischemic (HI) brain injury. We previously reported that the ω-6 long chain fatty acids, transarachidonic acids (TAAs), which are nitrative stress-induced nonenzymatically generated arachidonic acid derivatives, trigger selective microvascular endothelial cell death in neonatal neural tissue. The primary molecular target of TAAs remains unidentified. GPR40 is a G protein-coupled receptor activated by long chain fatty acids, including ω-6; it is highly expressed in brain, but its functions in this tissue are largely unknown. We hypothesized that TAAs play a significant role in neonatal HI-induced cerebral microvascular degeneration through GPR40 activation.Approach and Results-Within 24 hours of a HI insult to postnatal day 7 rat pups, a cerebral infarct and a 40% decrease in cerebrovascular density was observed. These effects were associated with an increase in nitrative stress markers (3-nitrotyrosine immunoreactivity and TAA levels) and were reduced by treatment with nitric oxide synthase inhibitor. GPR40 was expressed in rat pup brain microvasculature. In vitro, in GPR40-expressing human embryonic kidney (HEK)-293 cells, [(14)C]-14E-AA (radiolabeled TAA) bound specifically, and TAA induced calcium transients, extracellular signal-regulated kinase 1/2 phosphorylation, and proapoptotic thrombospondin-1 expression. In vivo, intracerebroventricular injection of TAAs triggered thrombospondin-1 expression and cerebral microvascular degeneration in wild-type mice, but not in GPR40-null congeners. Additionally, HI-induced neurovascular degeneration and cerebral infarct were decreased in GPR40-null mice. CONCLUSIONS: GPR40 emerges as the first identified G protein-coupled receptor conveying actions of nonenzymatically generated nitro-oxidative products, specifically TAAs, and is involved in (neonatal) HI encephalopathy.
    Arteriosclerosis Thrombosis and Vascular Biology 03/2013; 33(5). DOI:10.1161/ATVBAHA.112.300943
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    ABSTRACT: Acute renal failure (ARF) is a serious medical complication characterized by an abrupt and sustained decline in renal function. Despite significant advances in supportive care there is currently no effective treatment to restore renal function. Prostaglandin E(2) (PGE(2)) is a lipid hormone mediator abundantly produced in the kidney where it acts locally to regulate renal function; several studies suggest that modulating EP(4) receptor activity could improve renal function following kidney injury. An optimized peptidomimetic ligand of EP(4) receptor, THG213.29, was tested for its efficacy to improve renal function (glomerular filtration rate, renal plasma flow and urine output) and histological changes in a model of ARF induced by either cisplatin or renal artery occlusion in Sprague-Dawley rats. THG213.29 modulated PGE(2) binding dissociation kinetics, indicative of an allosteric binding mode. Consistently, THG213.29 antagonized EP(4)-mediated relaxation of piglet saphenous vein rings, partially inhibited EP(4)-mediated cAMP production, but did not affect Gαi activation or ß-arrestin recruitment. In vivo, THG213.29 significantly improved renal function and histological changes in cisplatin- and renal artery occlusion-induced ARF models. THG213.29 increased mRNA expression of heme-oxygenase 1, Bcl2 and fibroblast growth factor 2 (FGF-2) in renal cortex; correspondingly in EP(4)-transfected HEK293 cells, THG213.29 augmented FGF-2, and abrogated EP(4)-dependent overexpression of inflammatory IL-6 and of apoptotic DAXX and BAD. Our results demonstrate that THG213.29 represents a novel class of diuretic agent with noncompetitive allosteric modulator effects on EP(4) receptor resulting in improved renal function and integrity following acute renal failure.
    AJP Regulatory Integrative and Comparative Physiology 11/2012; DOI:10.1152/ajpregu.00138.2012

Publication Stats

6k Citations
1,096.02 Total Impact Points

Institutions

  • 1985–2015
    • McGill University
      • • Department of Pharmacology and Therapeutics
      • • Division of Ophthalmology
      Montréal, Quebec, Canada
  • 2014
    • Centre Hospitalier Universitaire de Québec (CHUQ)
      Quebec City, Quebec, Canada
  • 1996–2014
    • CHU Sainte-Justine
      • Department of Ophthalmology
      Montréal, Quebec, Canada
  • 1993–2013
    • Université de Montréal
      • • Department of Pediatrics
      • • Department of Ophthalmology
      • • Center for Mathematical Research
      Montréal, Quebec, Canada
  • 2011
    • Assistance Publique – Hôpitaux de Paris
      Lutetia Parisorum, Île-de-France, France
  • 2010
    • Hôpital Maisonneuve-Rosemont
      Montréal, Quebec, Canada
  • 2009
    • Université René Descartes - Paris 5
      Lutetia Parisorum, Île-de-France, France
  • 2008
    • New York Medical College
      • Department of Pharmacology
      New York, New York, United States
  • 2006
    • University of Texas at Dallas
      • Biochemistry
      Richardson, Texas, United States
  • 1989–2006
    • Université du Québec à Montréal
      Montréal, Quebec, Canada
  • 1999–2003
    • University of California, San Francisco
      • Cardiovascular Research Institute
      San Francisco, California, United States
  • 1997
    • California State University, Long Beach
      Long Beach, California, United States
  • 1992–1993
    • University of Iowa
      • Department of Pediatrics
      Iowa City, IA, United States