Gwenaelle Le Pavec

Université Paris-Sud 11, Orsay, Île-de-France, France

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Publications (10)31.29 Total impact

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    ABSTRACT: Microglial cells are central to brain immunity and intervene in many human neurological diseases. The aim of this study was to develop a convenient cellular model for human microglial cells, suitable for HIV studies. Microglia derive from the hematogenous myelomonocytic lineage, possibly as a distinct subpopulation but in any case able to invade the CNS, proliferate, and differentiate into ameboid and then ramified microglia in the adult life. We thus attempted to derive microglia-like cells from human monocytes. When cultured with astrocyte-conditioned medium (ACM), monocytes acquired a ramified morphology, typical of microglia. They overexpressed substance P and the calcium binding protein Iba-1 and dimly expressed class II MHC, three characteristics of microglial cells. Moreover, they also expressed a potassium inward rectifier current, another microglia-specific feature. These monocyte-derived microglia-like cells (MDMi) were CD4(+)/CD14(+), evocative of an activated microglia phenotype. When treated with lipopolysaccharide (LPS), MDMi lost their overexpression of substance P, which returned to untreated monocyte-derived macrophage (MDM) level. Compared with MDM, MDMi expressed higher CD4 but lower CCR5 levels; they could be infected by HIV-1(BaL), but produced less virus progeny than MDM did. This model of human microglia may be an interesting alternative to primary microglia for large scale in vitro HIV studies and may help to better understand HIV-associated microgliosis and chronic inflammation in the brain.
    Glia 09/2006; 54(3):183-92. · 5.07 Impact Factor
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    ABSTRACT: The mechanisms of neuronal apoptosis in prion diseases are unclear. Experimental studies suggest that it may result from 2 associated mechanisms: glutamate-mediated excitotoxicity and oxidative stress. Recent studies showed that activated macrophages/microglia (AMM) express excitatory amino acid transporters (EAATs) in HIV infection, suggesting that they may play a neuroprotective role by clearing extra-cellular glutamate and producing anti-oxidant glutathione. In order to test this hypothesis in prion diseases, samples from cerebral cortex, striatum, thalamus, and cerebellum from 14 patients with Creutzfeldt-Jakob disease (8 sporadic, 2 familial, 2 iatrogenic, and 2 variant), and 4 with fatal familial insomnia (3 homozygous Met/Met at codon 129 of the PRNP gene, 1 heterozygous Met/Val), and 3 controls were immunostained for EAAT-1, GFAP, HLA-DR, CD68, IL-1, caspase 3, and PrP. In prion diseases, EAAT-1 immunopositivity was found in affected areas. Only AMM, interstitial, perivascular, perineuronal (sometimes around apoptotic neurons), or close to reactive astrocytes, expressed EAAT-1. Astrocyte EAAT-1 expression was scarcely detectable in controls and was not detected in prion disease cases. The proportion of AMM expressing EAAT-1 did not correlate with the severity of neuronal apoptosis, spongiosis, astrocytosis, microgliosis, or PrP deposition, but only with disease duration. Occasional EAAT-1 expressing AMM were found in patients with short survival, whereas diffuse EAAT-1 expression by AMM was observed in cases with long survival (24 to 33 months) that most often were heterozygous for Met/Val at codon 129 of the PRNP gene. Our findings suggest that AMM may develop a partial neuroprotective function in long-lasting prion diseases, although it does not seem to efficiently prevent neurological and neuropathological deterioration. Whether this neuroprotective function of microglia is the cause or the effect of longer survival needs to be clarified.
    Journal of Neuropathology and Experimental Neurology 11/2004; 63(10):1058-71. · 4.35 Impact Factor
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    ABSTRACT: Changes in the fine balance between matrix metalloproteinases and their tissue inhibitors, which drives extracellular matrix turnover, may be critical to central nervous system inflammation in HIV infection as well as in neurotoxicity. Although they do not produce virus when infected by HIV, astrocytes may be directly affected by the virion, because some viral proteins are known to transduce signaling in brain cells and are also sensitive to the major proinflammatory cytokine TNFalpha. We therefore studied the effects of HIV and TNFalpha on MMP-2, MMP-9 and their inhibitors, TIMP-1 and TIMP-2, in astrocytes, by zymography and ELISA, respectively, or by RT-PCR for both of them. HIV slightly increased the production of pro-MMP-2 and pro-MMP-9 by astrocytes, in a dose-dependent manner. TNFalpha strongly induced pro-MMP-9. TIMP-1 and TIMP-2 levels were affected only slightly, if at all, by HIV and TNFalpha. Thus, astrocyte/HIV contact may lead to extracellular matrix activation, which may be strongly amplified by the inflammatory response. Our data strongly suggest that, besides their physiological production of MMP-2, astrocytes would be a major source of MMP-9 in the inflamed brain.
    Microbes and Infection 03/2004; 6(2):157-63. · 2.92 Impact Factor
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    ABSTRACT: Microglial cells and macrophages are the only cells within the central nervous system, in which productive HIV infection has been unquestionably demonstrated. Those cells play a key role in the origin of the neuronal dysfunction underlying HIV-related cognitive disorders. The neurotoxicity of the cells is both direct, related to HIV proteins, and indirect, through the release by activated macrophages and microglial cells (AMM) of multiple neurotoxic factors. The mechanisms of neuronal damage, the final irreversible stage of which is neuronal apoptosis, are only partly understood but appear to involve oxidative stress and glutamate-receptor mediated toxicity. On the other hand, recent experimental in vitro and in vivo studies, and neuropathological studies in HIV infected patients at different stages of the disease, tend to show that AMM express excitatory amino acid transporters (EAAT) suggesting that in addition to their neurotoxic properties, they also have a neuroprotective role by clearing extra-cellular glutamate and producing antioxidant glutathione. This neuroprotective role could counteract, at least in the early stages of the disease, the neurotoxicity of AMM explaining the discrepancy between the conspicuous microglial activation at that stage and the absence of cognitive disorder, neuronal loss and neuronal apoptosis. It could also explain the regression of the cognitive disorders in some patients who received highly active antiretroviral treatment.
    Annales de Pathologie 03/2004; 24(1):31-44. · 0.24 Impact Factor
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    ABSTRACT: Microglial cells and macrophages are the only cells within the central nervous system, in which productive HIV infection has been unquestionably demonstrated. Those cells play a key role in the origin of the neuronal dysfunction underlying HIV-related cognitive disorders. The neurotoxicity of the cells is both direct, related to HIV proteins, and indirect, through the release by activated macrophages and microglial cells (AMM) of multiple neurotoxic factors. The mechanisms of neuronal damage, the final irreversible stage of which is neuronal apoptosis, are only partly understood but appear to involve oxidative stress and glutamate-receptor mediated toxicity. On the other hand, recent experimental in vitro and in vivo studies, and neuropathological studies in HIV infected patients at different stages of the disease, tend to show that AMM express excitatory amino acid transporters (EAAT) suggesting that in addition to their neurotoxic properties, they also have a neuroprotective role by clearing extra-cellular glutamate and producing antioxidant glutathione. This neuroprotective role could counteract, at least in the early stages of the disease, the neurotoxicity of AMM explaining the discrepancy between the conspicuous microglial activation at that stage and the absence of cognitive disorder, neuronal loss and neuronal apoptosis. It could also explain the regression of the cognitive disorders in some patients who received highly active antiretroviral treatment.
    Annales de Pathologie 02/2004; 24(1):17. · 0.24 Impact Factor
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    Revue Neurologique - REV NEUROL. 01/2004; 160(8):846-846.
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    ABSTRACT: Recent experimental studies showed that activated macrophages/microglia (AMM) express excitatory amino acid transporters (EAATs), suggesting that, in addition to their neurotoxic properties, they also have a neuroprotective role by clearing extracellular glutamate and producing antioxidant glutathione. To test this hypothesis in human, the brain of 12 HIV-positive patients and 3 controls were immunostained for EAAT-1. EAAT-1 was expressed by AMM in all HIV-infected cases but not in HIV-negative controls. Expression varied according to the disease stage. In 5 cases with active HIV-encephalitis (HIVE), AMM strongly expressed EAAT-1 in the white matter and basal ganglia, analogous to HLA-DR and CD68 expression. There was weaker expression in the cortex and perineuronal microglial cells were not involved. In a case with "burnt out" HIVE following highly active antiretroviral therapy (HAART), EAAT-1 expression was mild, identical to that of HLA-DR and CD68 in the white matter and cortex and involved perineuronal microglial cells. In 3 AIDS patients without HIVE and in 3 pre-AIDS cases, EAAT-1 expression in the white matter was weaker than HLA-DR and CD68 expression; there was stronger correlation in the gray matter where perineuronal microglial cells were stained predominantly. Our findings in humans tend to confirm that AMM, particularly perineuronal microglial cells, play a neuroprotective role in the early stages of HIV infection and, possibly, following treatment. This is in keeping with the early microglial activation seen in pre-AIDS cases, and the late occurrence of neuronal loss. It may also explain the reversible cognitive disorders following treatment in some cases.
    Journal of Neuropathology and Experimental Neurology 06/2003; 62(5):475-85. · 4.35 Impact Factor
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    ABSTRACT: It is now widely accepted that neuronal damage in HIV infection results mainly from microglial activation and involves apoptosis, oxidative stress and glutamate-mediated neurotoxicity. Glutamate toxicity acts via 2 distinct pathways: an excitotoxic one in which glutamate receptors are hyperactivated, and an oxidative one in which cystine uptake is inhibited, resulting in glutathione depletion and oxidative stress. A number of studies show that astrocytes normally take up glutamate, keeping extracellular glutamate concentration low in the brain and preventing excitotoxicity. This action is inhibited in HIV infection, probably due to the effects of inflammatory mediators and viral proteins. Other in vitro studies as well as in vivo experiments in rodents following mechanical stimulation, show that activated microglia and brain macrophages express high affinity glutamate transporters. These data have been confirmed in chronic inflammation of the brain, particularly in SIV infection, where activated microglia and brain macrophages also express glutamine synthetase. Recent studies in humans with HIV infection show that activated microglia and brain macrophages express the glutamate transporter EAAT-1 and that expression varies according to the disease stage. This suggests that, besides their recognized neurotoxic properties in HIV infection, these cells also have a neuroprotective function, and may partly make up for the inhibited astrocytic function, at least temporarily. This hypothesis might explain the discrepancy between microglial activation which occurs early in the disease, and neuronal apoptosis and neuronal loss which is a late event. In this review article, we discuss the possible neuroprotective and neurotrophic roles of activated microglia and macrophages that may be generated by the expression of high affinity glutamate transporters and glutamine synthetase, 2 major effectors of glial glutamate metabolism, and the implications for HIV-induced neuronal dysfunction, the underlying cause of HIV dementia.
    Brain Pathology 05/2003; 13(2):211-22. · 4.74 Impact Factor
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    ABSTRACT: Na+-dependent transporters for glutamate (excitatory amino acid transporters, EAATs) clear extracellular glutamate in the brain and prevent excitotoxic neuronal damage. Glutamine synthetase (GS) provides metabolic support for neurones by producing the neurotrophic amino acid glutamine. EAAT and GS expression has recently been demonstrated in macrophages and microglial cells in vitro, and in two models of acute inflammation in vivo. This observation might modify our current understanding of brain inflammation, which considers activated microglia and brain macrophages as the main neurotoxic cells through their production of a variety of neurotoxins, including glutamate. EAAT and GS expression by these cells would entail neuroprotective and neurotrophic properties, counterbalancing the deleterious consequences of microglial activation. Macaque infection by the simian immunodeficiency virus (SIV) is considered the most relevant model for human acquired immunodeficiency syndrome (AIDS), including chronic inflammation of the brain at the early asymptomatic stage of the infection, followed by an AIDS-like disease where neuronal death occurs. We studied the expression of EAAT-2 and GS in the brains of three SIVmac251-infected and two noninfected cynomolgus macaques. We found that both microglia and brain macrophages expressed EAAT-2 and GS in infected primates, suggesting that these cells might, like astrocytes, clear extracellular glutamate and provide glutamine to neurones. Microglia and macrophages could thus have neuroprotective and neurotrophic properties in addition to their production of neurotoxins. This finding might explain the contrast between early intense microglial activation and the late occurrence of neuronal apoptotic cell death, which is mainly observed at the terminal stage of the disease.
    Neuropathology and Applied Neurobiology 11/2002; 28(5):410-7. · 4.84 Impact Factor
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    ABSTRACT: We assessed the anti-human immunodeficiency virus (anti-HIV) activity in vitro of new platelet-activating factor (PAF) receptor antagonists, as PAF and viral replication are thought to be involved in HIV neuropathogenesis. We found that PMS-601 inhibited proinflammatory cytokine synthesis and HIV replication in macrophages and potentiated the antiretroviral activity of zidovudine. These results suggest that PMS-601 is of potential value as an adjuvant treatment for HIV infection.
    Antimicrobial Agents and Chemotherapy 12/2000; 44(11):3150-4. · 4.57 Impact Factor