Publications by authors named "Sebastien Augustin"

24 Publications

  • Page 1 of 1

Insulin inhibits inflammation-induced cone death in retinal detachment.

J Neuroinflammation 2020 Nov 26;17(1):358. Epub 2020 Nov 26.

Institut de la Vision, INSERM, UMR_S 968, CNRS, Sorbonne Université, 17 rue Moreau, F-75012, Paris, France.

Background: Rhegmatogenous retinal detachment (RD) involving the macula is a major cause of visual impairment despite high surgical success rate, mainly because of cone death. RD causes the infiltration of activated immune cells, but it is not clear whether and how infiltrating inflammatory cells contribute to cone cell loss.

Methods: Vitreous samples from patients with RD and from control patients with macular hole were analyzed to characterize the inflammatory response to RD. A mouse model of RD and retinal explants culture were then used to explore the mechanisms leading to cone death.

Results: Analysis of vitreous samples confirms that RD induces a marked inflammatory response with increased cytokine and chemokine expression in humans, which is closely mimicked by experimental murine RD. In this model, we corroborate that myeloid cells and T-lymphocytes contribute to cone loss, as the inhibition of their accumulation by Thrombospondin 1 (TSP1) increased cone survival. Using monocyte/retinal co-cultures and TSP1 treatment in RD, we demonstrate that immune cell infiltration downregulates rod-derived cone viability factor (RdCVF), which physiologically regulates glucose uptake in cones. Insulin and the insulin sensitizers rosiglitazone and metformin prevent in part the RD-induced cone loss in vivo, despite the persistence of inflammation CONCLUSION: Our results describe a new mechanism by which inflammation induces cone death in RD, likely through cone starvation due to the downregulation of RdCVF that could be reversed by insulin. Therapeutic inhibition of inflammation and stimulation of glucose availability in cones by insulin signaling might prevent RD-associated cone death until the RD can be surgically repaired and improve visual outcome after RD.

Trial Registration: ClinicalTrials.gov NCT03318588.
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http://dx.doi.org/10.1186/s12974-020-02039-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7694924PMC
November 2020

The 10q26 Risk Haplotype of Age-Related Macular Degeneration Aggravates Subretinal Inflammation by Impairing Monocyte Elimination.

Immunity 2020 08;53(2):429-441.e8

Sorbonne Université, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, F-75012 Paris, France. Electronic address:

A minor haplotype of the 10q26 locus conveys the strongest genetic risk for age-related macular degeneration (AMD). Here, we examined the mechanisms underlying this susceptibility. We found that monocytes from homozygous carriers of the 10q26 AMD-risk haplotype expressed high amounts of the serine peptidase HTRA1, and HTRA1 located to mononuclear phagocytes (MPs) in eyes of non-carriers with AMD. HTRA1 induced the persistence of monocytes in the subretinal space and exacerbated pathogenic inflammation by hydrolyzing thrombospondin 1 (TSP1), which separated the two CD47-binding sites within TSP1 that are necessary for efficient CD47 activation. This HTRA1-induced inhibition of CD47 signaling induced the expression of pro-inflammatory osteopontin (OPN). OPN expression increased in early monocyte-derived macrophages in 10q26 risk carriers. In models of subretinal inflammation and AMD, OPN deletion or pharmacological inhibition reversed HTRA1-induced pathogenic MP persistence. Our findings argue for the therapeutic potential of CD47 agonists and OPN inhibitors for the treatment of AMD.
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http://dx.doi.org/10.1016/j.immuni.2020.07.021DOI Listing
August 2020

CD36 Deficiency Inhibits Retinal Inflammation and Retinal Degeneration in Knockout Mice.

Front Immunol 2019 8;10:3032. Epub 2020 Jan 8.

Institut de la Vision, Sorbonne Université, INSERM, CNRS, Paris, France.

CD36, a member of the class B scavenger receptor family, participates in Toll-like receptor signaling on mononuclear phagocytes (MP) and can promote sterile pathogenic inflammation. We here analyzed the effect of CD36 deficiency on retinal inflammation and photoreceptor degeneration, the hallmarks of age-related macular degeneration (AMD), that characterize mice. We analyzed subretinal MP accumulation, and cone- and rod-degeneration in light-challenged and aged, CD36 competent or deficient, hyper-inflammatory mice, using histology and immune-stained retinal flatmounts. Monocytes (Mo) were subretinally adoptively transferred to evaluate their elimination rate from the subretinal space and Interleukin 6 (IL-6) secretion from cultured Mo-derived cells (MdCs) of the different mouse strains were analyzed. CD36 deficient mice were protected against age- and light-induced subretinal inflammation and associated cone and rod degeneration. CD36 deficiency in MPs inhibited their prolonged survival in the immune-suppressive subretinal space and reduced the exaggerated IL-6 secretion observed in MPs that we previously showed leads to increased subretinal MP survival. deficiency significantly protected hyperinflammatory mice against subretinal MP accumulation and associated photoreceptor degeneration. The observed CD36-dependent induction of pro-inflammatory IL-6 might be at least partially responsible for the prolonged MP survival in the immune-suppressive environment and its pathological consequences on photoreceptor homeostasis.
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http://dx.doi.org/10.3389/fimmu.2019.03032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6960398PMC
November 2020

IL-1β induces rod degeneration through the disruption of retinal glutamate homeostasis.

J Neuroinflammation 2020 Jan 3;17(1). Epub 2020 Jan 3.

Sorbonne Université, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, F-75012, Paris, France.

Background: Age-related macular degeneration is characterized by the accumulation of subretinal macrophages and the degeneration of cones, but mainly of rods. We have previously shown that Mononuclear Phagocytes-derived IL-1β induces rod photoreceptor cell death during experimental subretinal inflammation and in retinal explants exposed to IL-1β but the mechanism is unknown.

Methods: Retinal explants were culture in the presence of human monocytes or IL-1β and photoreceptor cell survival was analyzed by TUNEL labeling. Glutamate concentration and transcription levels of gene involved in the homeostasis of glutamate were analyzed in cell fractions of explant cultured or not in the presence of IL-1β. Glutamate receptor antagonists were evaluated for their ability to reduce photoreceptor cell death in the presence of IL1-β or monocytes.

Results: We here show that IL-1β does not induce death in isolated photoreceptors, suggesting an indirect effect. We demonstrate that IL-1β leads to glutamate-induced rod photoreceptor cell death as it increases the extracellular glutamate concentrations in the retina through the inhibition of its conversion to glutamine in Müller cells, increased release from Müller cells, and diminished reuptake. The inhibition of non-NMDA receptors completely and efficiently prevented rod apoptosis in retinal explants cultured in the presence of IL-1β or, more importantly, in vivo, in a model of subretinal inflammation.

Conclusions: Our study emphasizes the importance of inflammation in the deregulation of glutamate homeostasis and provides a comprehensive mechanism of action for IL-1β-induced rod degeneration.
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http://dx.doi.org/10.1186/s12974-019-1655-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6942287PMC
January 2020

Chronic exposure to tumor necrosis factor alpha induces retinal pigment epithelium cell dedifferentiation.

J Neuroinflammation 2018 Mar 16;15(1):85. Epub 2018 Mar 16.

Sorbonne Université, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, F-75012, Paris, France.

Background: The retinal pigment epithelium (RPE) is a monolayer of pigmented cells with important barrier and immuno-suppressive functions in the eye. We have previously shown that acute stimulation of RPE cells by tumor necrosis factor alpha (TNFα) downregulates the expression of OTX2 (Orthodenticle homeobox 2) and dependent RPE genes. We here investigated the long-term effects of TNFα on RPE cell morphology and key functions in vitro.

Methods: Primary porcine RPE cells were exposed to TNFα (at 0.8, 4, or 20 ng/ml per day) for 10 days. RPE cell morphology, phagocytosis, barrier- and immunosuppressive-functions were assessed.

Results: Chronic (10 days) exposure of primary RPE cells to TNFα increases RPE cell size and polynucleation, decreases visual cycle gene expression, impedes RPE tight-junction organization and transepithelial resistance, and decreases the immunosuppressive capacities of the RPE. TNFα-induced morphological- and transepithelial-resistance changes were prevented by concomitant Transforming Growth Factor β inhibition.

Conclusions: Our results indicate that chronic TNFα-exposure is sufficient to alter RPE morphology and impede cardinal features that define the differentiated state of RPE cells with striking similarities to the alterations that are observed with age in neurodegenerative diseases such as age-related macular degeneration.
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http://dx.doi.org/10.1186/s12974-018-1106-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5857126PMC
March 2018

Neuroglobin Can Prevent or Reverse Glaucomatous Progression in DBA/2J Mice.

Mol Ther Methods Clin Dev 2017 Jun 27;5:200-220. Epub 2017 Apr 27.

Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, 75012 Paris, France.

Mitochondrial dysfunction is responsible for hereditary optic neuropathies. We wished to determine whether preserving mitochondrial bioenergetics could prevent optic neuropathy in a reliable model of glaucoma. DBA/2J mice exhibit elevated intraocular pressure, progressive degeneration of their retinal ganglion cells, and optic neuropathy that resembles glaucoma. We established that glaucoma in these mice is directly associated with mitochondrial dysfunction: respiratory chain activity was compromised in optic nerves 5 months before neuronal loss began, and the amounts of some mitochondrial proteins were reduced in retinas of glaucomatous mice. One of these proteins is neuroglobin, which has a neuroprotective function. Therefore, we investigated whether gene therapy aimed at restoring neuroglobin levels in the retina via ocular administration of an adeno-associated viral vector could reduce neuronal degeneration. The approach of treating 2-month-old mice impeded glaucoma development: few neurons died and respiratory chain activity and visual cortex activity were comparable to those in young, asymptomatic mice. When the treatment was performed in 8-month-old mice, the surviving neurons acquired new morphologic and functional properties, leading to the preservation of visual cortex activity and respiratory chain activity. The beneficial effects of neuroglobin in DBA/2J retinas confirm this protein to be a promising candidate for treating glaucoma.
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http://dx.doi.org/10.1016/j.omtm.2017.04.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5430497PMC
June 2017

Impaired vitreous composition and retinal pigment epithelium function in the FoxG1::LRP2 myopic mice.

Biochim Biophys Acta Mol Basis Dis 2017 06 31;1863(6):1242-1254. Epub 2017 Mar 31.

INSERM, U968, Paris, F-75012, France; UPMC Univ Paris 06, UMR_S968, Institut de la Vision, Paris, F-75012, France; CNRS, UMR_7210, Paris, F-75012, France. Electronic address:

High myopia (HM) is one of the main causes of visual impairment and blindness all over the world and an unsolved medical problem. Persons with HM are predisposed to other eye pathologies such as retinal detachment, myopic retinopathy or glaucomatous optic neuropathy, complications that may at least partly result from the extensive liquefaction of the myopic vitreous gel. To identify the involvement of the liquid vitreous in the pathogenesis of HM we here analyzed the vitreous of the recently described highly myopic low density lipoprotein receptor-related protein 2 (Lrp2)-deficient eyes. Whereas the gel-like fraction was not apparently modified, the volume of the liquid vitreous fraction (LVF) was much higher in the myopic eyes. Biochemical and proteome analysis of the LVF revealed several modifications including a marked decrease of potassium, sodium and chloride, of proteins involved in ocular tissue homeostasis and repair as well as of ADP-ribosylation factor 4 (ARF4), a protein possibly involved in LRP2 trafficking. A small number of proteins, mainly comprising known LRP2 ligands or proteins of the inflammatory response, were over expressed in the mutants. Moreover the morphology of the LRP2-deficient retinal pigment epithelium (RPE) cells was affected and the expression of ARF4 as well as of proteins involved in degradative endocytosis was strongly reduced. Our results support the idea that impairment of the RPE structure and most likely endocytic function may contribute to the vitreal modifications and pathogenesis of HM.
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http://dx.doi.org/10.1016/j.bbadis.2017.03.022DOI Listing
June 2017

Complement Factor H Inhibits CD47-Mediated Resolution of Inflammation.

Immunity 2017 02;46(2):261-272

Institut de la Vision, 17 rue Moreau, Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, 75012 Paris, France. Electronic address:

Variants of the CFH gene, encoding complement factor H (CFH), show strong association with age-related macular degeneration (AMD), a major cause of blindness. Here, we used murine models of AMD to examine the contribution of CFH to disease etiology. Cfh deletion protected the mice from the pathogenic subretinal accumulation of mononuclear phagocytes (MP) that characterize AMD and showed accelerated resolution of inflammation. MP persistence arose secondary to binding of CFH to CD11b, which obstructed the homeostatic elimination of MPs from the subretinal space mediated by thrombospsondin-1 (TSP-1) activation of CD47. The AMD-associated CFH(H402) variant markedly increased this inhibitory effect on microglial cells, supporting a causal link to disease etiology. This mechanism is not restricted to the eye, as similar results were observed in a model of acute sterile peritonitis. Pharmacological activation of CD47 accelerated resolution of both subretinal and peritoneal inflammation, with implications for the treatment of chronic inflammatory disease.
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http://dx.doi.org/10.1016/j.immuni.2017.01.006DOI Listing
February 2017

Lebecetin, a C-type lectin, inhibits choroidal and retinal neovascularization.

FASEB J 2017 03 14;31(3):1107-1119. Epub 2016 Dec 14.

Sorbonne Universités, Université Pierre et Marie Curie, INSERM, Centre National de la Recherche Scientifique, Institut de la Vision, Paris, France;

Angiogenesis is a cause of visual impairment and blindness in the wet form of age-related macular degeneration and in ischemic retinopathies. Current therapies include use of anti-VEGF agents to reduce choroidal neovascularization (CNV) and edema. These treatments are effective in most cases, but spontaneous or acquired resistance to anti-VEGF and possible adverse effects of long-term VEGF inhibition in the retina and choroid highlight a need for additional alternative therapies. Integrins αvβ3 and αvβ5, which regulate endothelial cell proliferation and stabilization, have been implicated in ocular angiogenesis. Lebecetin (LCT) is a 30-kDa heterodimeric C-type lectin that is isolated from venom and interacts with α5β1- and αv-containing integrins. We previously showed that LCT inhibits human brain microvascular endothelial cell adhesion, migration, proliferation, and tubulogenesis. To evaluate the inhibitory effect of LCT on ocular angiogenesis, we cultured aortic and choroidal explants in the presence of LCT and analyzed the effect of LCT on CNV in the mouse CNV model and on retinal neovascularization in the oxygen-induced retinopathy model. Our data demonstrate that a single injection of LCT efficiently reduced CNV and retinal neovascularization in these models.-Montassar, F., Darche, M., Blaizot, A., Augustin, S., Conart, J.-B., Millet, A., Elayeb, M., Sahel, J.-A., Réaux-Le Goazigo, A., Sennlaub, F., Marrakchi, N., Messadi, E., Guillonneau, X. Lebecetin, a C-type lectin, inhibits choroidal and retinal neovascularization.
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http://dx.doi.org/10.1096/fj.201600351RDOI Listing
March 2017

ANGPTL4-αvβ3 interaction counteracts hypoxia-induced vascular permeability by modulating Src signalling downstream of vascular endothelial growth factor receptor 2.

J Pathol 2016 12 21;240(4):461-471. Epub 2016 Oct 21.

Centre for Interdisciplinary Research in Biology (CIRB), College de France, CNRS, INSERM, PSL Research University, Paris, France.

Dynamic control of endothelial cell junctions is essential for vascular homeostasis and angiogenesis. We recently provided genetic evidence that ANGPTL4 is a key regulator of vascular integrity both during developmental and in hypoxia-induced pathological conditions. The purpose of the present study was to decipher the molecular mechanisms through which ANGPTL4 regulates vascular integrity. Using surface plasmon resonance and proximity ligation assays, we show that ANGPTL4 binds integrin αvβ3. In vitro and in vivo functional assays with Angptl4-deficient mice demonstrate that ANGPTL4-αvβ3 interaction is necessary to mediate ANGPTL4 vasoprotective effects. Mechanistically, ANGPTL4-αvβ3 interaction enhances Src recruitment to integrin αvβ3 and inhibits Src signalling downstream of vascular endothelial growth factor receptor 2 (VEFGR2), thereby repressing hypoxia-induced breakdown of VEGFR2-VE-cadherin and VEGFR2-αvβ3 complexes. We further demonstrate that intravitreal injection of recombinant human ANGPTL4 limits vascular permeability and leads to increased adherens junction and tight junction integrity. These findings identify a novel mechanism by which ANGPTL4 counteracts hypoxia-driven vascular permeability through integrin αvβ3 binding, modulation of VEGFR2-Src kinase signalling, and endothelial junction stabilization. We further demonstrate that Angptl4-deficient mice show increased vascular leakage in vivo in a model of laser-induced choroidal neovascularization, indicating that this newly identified ANGPTL4-αvβ3 axis might be a target for pharmaceutical intervention in pathological conditions. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/path.4805DOI Listing
December 2016

Activated monocytes resist elimination by retinal pigment epithelium and downregulate their OTX2 expression via TNF-α.

Aging Cell 2017 Feb 22;16(1):173-182. Epub 2016 Sep 22.

Institut de la Vision, 17 rue Moreau, 75012, Paris, France.

Orthodenticle homeobox 2 (OTX2) controls essential, homeostatic retinal pigment epithelial (RPE) genes in the adult. Using cocultures of human CD14 blood monocytes (Mos) and primary porcine RPE cells and a fully humanized system using human-induced pluripotent stem cell-derived RPE cells, we show that activated Mos markedly inhibit RPEOTX2 expression and resist elimination in contact with the immunosuppressive RPE. Mechanistically, we demonstrate that TNF-α, secreted from activated Mos, mediates the downregulation of OTX2 and essential RPE genes of the visual cycle among others. Our data show how subretinal, chronic inflammation and in particular TNF-α can affect RPE function, which might contribute to the visual dysfunctions in diseases such as age-related macular degeneration (AMD) where subretinal macrophages are observed. Our findings provide important mechanistic insights into the regulation of OTX2 under inflammatory conditions. Therapeutic restoration of OTX2 expression might help revive RPE and visual function in retinal diseases such as AMD.
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http://dx.doi.org/10.1111/acel.12540DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5242302PMC
February 2017

Subretinal mononuclear phagocytes induce cone segment loss via IL-1β.

Elife 2016 07 20;5. Epub 2016 Jul 20.

Sorbonne Universités, UPMC University Paris 06, INSERM, CNRS, Paris, France.

Photo-transduction in cone segments (CS) is crucial for high acuity daytime vision. For ill-defined reasons, CS degenerate in retinitis pigmentosa (RP) and in the transitional zone (TZ) of atrophic zones (AZ), which characterize geographic atrophy (GA). Our experiments confirm the loss of cone segments (CS) in the TZ of patients with GA and show their association with subretinal CD14(+)mononuclear phagocyte (MP) infiltration that is also reported in RP. Using human and mouse MPs in vitro and inflammation-prone Cx3cr1(GFP/GFP) mice in vivo, we demonstrate that MP-derived IL-1β leads to severe CS degeneration. Our results strongly suggest that subretinal MP accumulation participates in the observed pathological photoreceptor changes in these diseases. Inhibiting subretinal MP accumulation or Il-1β might protect the CS and help preserve high acuity daytime vision in conditions characterized by subretinal inflammation, such as AMD and RP.
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http://dx.doi.org/10.7554/eLife.16490DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4969036PMC
July 2016

Foxg1-Cre Mediated Lrp2 Inactivation in the Developing Mouse Neural Retina, Ciliary and Retinal Pigment Epithelia Models Congenital High Myopia.

PLoS One 2015 24;10(6):e0129518. Epub 2015 Jun 24.

INSERM, U968, Paris, F-75012, France; UPMC Univ Paris 06, UMR_S968, Institut de la Vision, Paris, F-75012, France; CNRS, UMR_7210, Paris, F-75012, France.

Myopia is a common ocular disorder generally due to increased axial length of the eye-globe. Its extreme form high myopia (HM) is a multifactorial disease leading to retinal and scleral damage, visual impairment or loss and is an important health issue. Mutations in the endocytic receptor LRP2 gene result in Donnai-Barrow (DBS) and Stickler syndromes, both characterized by HM. To clearly establish the link between Lrp2 and congenital HM we inactivated Lrp2 in the mouse forebrain including the neural retina and the retinal and ciliary pigment epithelia. High resolution in vivo MRI imaging and ophthalmological analyses showed that the adult Lrp2-deficient eyes were 40% longer than the control ones mainly due to an excessive elongation of the vitreal chamber. They had an apparently normal intraocular pressure and developed chorioretinal atrophy and posterior scleral staphyloma features reminiscent of human myopic retinopathy. Immunomorphological and ultrastructural analyses showed that increased eye lengthening was first observed by post-natal day 5 (P5) and that it was accompanied by a rapid decrease of the bipolar, photoreceptor and retinal ganglion cells, and eventually the optic nerve axons. It was followed by scleral thinning and collagen fiber disorganization, essentially in the posterior pole. We conclude that the function of LRP2 in the ocular tissues is necessary for normal eye growth and that the Lrp2-deficient eyes provide a unique tool to further study human HM.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0129518PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4480972PMC
April 2016

Nuclear expression of mitochondrial ND4 leads to the protein assembling in complex I and prevents optic atrophy and visual loss.

Mol Ther Methods Clin Dev 2015 25;2:15003. Epub 2015 Feb 25.

INSERM, U968 , Paris, France ; Sorbonne Universités, UPMC Univ Paris 06, UMR_S 968, Institut de la, Vision , Paris, France ; CNRS, UMR_7210 , Paris, France.

Leber hereditary optic neuropathy is due to mitochondrial DNA mutations; in ~70% of all cases, a point mutation in the mitochondrial NADH dehydrogenase subunit 4, ND4, gene leads to central vision loss. We optimized allotopic expression (nuclear transcription of a gene that is normally transcribed inside the mitochondria) aimed at designing a gene therapy for ND4; its coding sequence was associated with the cis-acting elements of the human COX10 mRNA to allow the efficient mitochondrial delivery of the protein. After ocular administration to adult rats of a recombinant adeno-associated viral vector containing the human ND4 gene, we demonstrated that: (i) the sustained expression of human ND4 did not lead to harmful effects, instead the human protein is efficiently imported inside the mitochondria and assembled in respiratory chain complex I; (ii) the presence of the human protein in the experimental model of Leber hereditary optic neuropathy significantly prevents retinal ganglion cell degeneration and preserves both complex I function in optic nerves and visual function. Hence, the use of optimized allotopic expression is relevant for treating mitochondrial disorders due to mutations in the organelle genome.
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http://dx.doi.org/10.1038/mtm.2015.3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4444999PMC
June 2015

Gene therapy for mitochondrial diseases: Leber Hereditary Optic Neuropathy as the first candidate for a clinical trial.

C R Biol 2014 Mar 24;337(3):193-206. Epub 2014 Feb 24.

INSERM, U968, Paris 75012, France; Sorbonne Universités, UPMC université Paris 6, UMR_S 968, Institut de la vision, Paris 75012, France; CNRS, UMR_7210, Paris 75012, France. Electronic address:

Mitochondrial disorders cannot be ignored anymore in most medical disciplines; indeed their minimum estimated prevalence is superior to 1 in 5000 births. Despite the progress made in the last 25 years on the identification of gene mutations causing mitochondrial pathologies, only slow progress was made towards their effective treatments. Ocular involvement is a frequent feature in mitochondrial diseases and corresponds to severe and irreversible visual handicap due to retinal neuron loss and optic atrophy. Interestingly, three clinical trials for Leber Congenital Amaurosis due to RPE65 mutations are ongoing since 2007. Overall, the feasibility and safety of ocular Adeno-Associated Virus delivery in adult and younger patients and consistent visual function improvements have been demonstrated. The success of gene-replacement therapy for RPE65 opens the way for the development of similar approaches for a broad range of eye disorders, including those with mitochondrial etiology such as Leber Hereditary Optic Neuropathy (LHON).
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http://dx.doi.org/10.1016/j.crvi.2013.11.011DOI Listing
March 2014

Neuroglobin gene therapy prevents optic atrophy and preserves durably visual function in Harlequin mice.

Mol Ther 2014 Jun 13;22(6):1096-1109. Epub 2014 Mar 13.

INSERM, U968, Paris, France; Sorbonne Universités, UPMC Univ Paris, Institut de la Vision, Paris, France; Centre national de la recherche scientifique, Paris, France. Electronic address:

Neuroglobin (NGB) is considered as an endogenous neuroprotective molecule against stroke, since the protein alleviates the adverse effects of hypoxic and ischemic insults. We previously demonstrated the functional link between NGB and mitochondria since it is required for respiratory chain function. Thus, here, we evaluated the relevance of this effect in the Harlequin (Hq) mouse strain, which exhibits retinal ganglion cell (RGC) loss and optic atrophy due to a respiratory chain complex I (CI) defect. A twofold decrease of NGB amounts was observed in Hq retinas. We constructed a recombinant adeno-associated virus which combines to the mouse NGB open reading frame, its 5' and 3'UTR, for guarantying mRNA stability and translation capacity. The vector was administrated intravitreally to Hq mice and NGB expression was stable for up to 7 months without negative effect on retinal architecture or function. On the contrary, RGCs and their axons were substantially preserved from degeneration; consequently, CI activity in optic nerves was protected conferring improvements in vision. Hence, we established that NGB prevents respiratory chain impairment, therefore, protecting visual function otherwise compromised by mitochondrial energetic failure.
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http://dx.doi.org/10.1038/mt.2014.44DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4048897PMC
June 2014

Neuroglobin involvement in visual pathways through the optic nerve.

Biochim Biophys Acta 2013 Sep 29;1834(9):1772-8. Epub 2013 Apr 29.

INSERM, U968, Paris F-75012, France.

Neuroglobin is a member of the globin superfamily proposed to be only expressed in neurons and involved in neuronal protection from hypoxia or oxidative stress. A significant fraction of the protein localizes within the mitochondria and is directly associated with mitochondrial metabolism and integrity. The retina is the site of the highest concentration for neuroglobin and has been reported to be up to 100-fold higher than in the brain. Since neuroglobin was especially abundant in retinal ganglion cell layer, we investigated its abundance in optic nerves. Remarkably in optic nerves, neuroglobin is observed, as expected, in retinal ganglion cell axon profiles but also astrocyte processes, in physiological conditions, possess high levels of the protein. Neuroglobin mRNA and protein levels are ~10-fold higher in optic nerves than in retinas, indicating an important accumulation of neuroglobin in these support cells. Additionally, neuroglobin levels increase in Müller cells during reactive gliosis in response to eye injury. This suggests the pivotal role of neuroglobin in retinal glia involved in neuronal support and/or healing. This article is part of a Special Issue entitled: Oxygen Binding and Sensing Proteins.
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http://dx.doi.org/10.1016/j.bbapap.2013.04.014DOI Listing
September 2013

Neuroglobin involvement in respiratory chain function and retinal ganglion cell integrity.

Biochim Biophys Acta 2012 Dec 2;1823(12):2261-73. Epub 2012 Oct 2.

Inserm, U968, Paris, 75012, France.

Neuroglobin is a member of the globin superfamily expressed in vertebrate brain and retina. The protein is thought to be involved in neuronal protection from hypoxia or oxidative stress and could represent a key element of Alzheimer disease pathogenesis. Our aim was to determine whether neuroglobin could be directly associated with mitochondrial metabolism and integrity. We identified three different forms of neuroglobin in the retina, varying in their apparent molecular masses; all forms are abundant in mitochondrial fractions. This indicates that a significant fraction of the protein localizes within the organelle either in the matrix or in the matrix side of the inner membrane. Since neuroglobin was especially abundant in the ganglion cell layer, we transduced retinal ganglion cells with an anti-neuroglobin short hairpin RNA using in vivo electroporation. Neuroglobin knockdown leads to reduced activities of respiratory chain complexes I and III, degeneration of retinal ganglion cells, and impairment of visual function. The deleterious effect on cell survival was confirmed in primary retinal ganglion cells subjected to inhibition of neuroglobin expression. Hence, neuroglobin should be considered as a novel mitochondrial protein involved in respiratory chain function which is essential for retinal ganglion cell integrity.
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http://dx.doi.org/10.1016/j.bbamcr.2012.09.009DOI Listing
December 2012

Downregulation of apoptosis-inducing factor in Harlequin mice induces progressive and severe optic atrophy which is durably prevented by AAV2-AIF1 gene therapy.

Brain 2012 Jan 26;135(Pt 1):35-52. Epub 2011 Nov 26.

INSERM, U968, Paris, F-75012, France.

The Harlequin mutant mouse, characterized by loss of function of apoptosis-inducing factor, represents a reliable genetic model that resembles pathologies caused by human mitochondrial complex I deficiency. Therefore, we extensively characterized the retinal morphology and function of Harlequin mice during the course of neuronal cell death leading to blindness, with the aim of preventing optic atrophy. Retinas and optic nerves from these mice showed an isolated respiratory chain complex I defect correlated with retinal ganglion cell loss, optic atrophy, glial and microglial cell activation. All of these changes led to irreversible vision loss. In control mice, retinas AIF1 messenger RNA was 2.3-fold more abundant than AIF2, both messenger RNAs being sorted to the mitochondrial surface. In Harlequin mouse retinas, there was a 96% decrease of both AIF1 and AIF2 messenger RNA steady-state levels. We attained substantial and long-lasting protection of retinal ganglion cell and optic nerve integrity, the preservation of complex I function in optic nerves, as well as the prevention of glial and microglial responses after intravitreal administration of an AAV2 vector containing the full-length open reading frame and the 3' untranslated region of the AIF1 gene. Therefore, we demonstrate that gene therapy for mitochondrial diseases due to mutations in nuclear DNA can be achieved, so long as the 'therapeutic gene' permits the accurate cellular localization of the corresponding messenger RNA.
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http://dx.doi.org/10.1093/brain/awr290DOI Listing
January 2012

In vivo observation of the locomotion of microglial cells in the retina.

Glia 2010 Nov;58(14):1663-8

Inserm, UMR_S968, Institut de la Vision, Paris, France.

Microglial cells (MCs) are active sensors and reactive phagocytes of neural tissues. They are known to migrate and accumulate in areas of neuronal damage. Thus, microglial locomotion is an essential feature of the inflammatory reaction in neural tissue. Yet, to our knowledge there has been no report of direct in vivo observation of the migration of MCs. Here, we show that intravitreally injected cyanine dyes (DiO, DiI, and indocyanine green) are sequestrated in MCs during several months, and subsequently in vivo images of these fluorescent MCs can be obtained by confocal scanning laser ophthalmoscopy. This enabled noninvasive, time-lapse observation of the migrating behavior of MCs, both in the basal state and following laser damage. In the basal state, a slow, intermittent, random-like locomotion was observed. Following focal laser damage, MCs promptly (i.e., within 1 h) initiated centripetal, convergent migration. MCs up to 400 μm away migrated into the scar at velocities up to 7 μm/min. This early phase of centripetal migration was followed by a more prolonged phase of nontargeted locomotion around and within injured sites during at least 24 h. Cyanine-positive cells persisted within the scar during several weeks. To our knowledge, this is the first in vivo observation of the locomotion of individual MCs. Our results show that the locomotion of MCs is not limited to translocation to acutely damaged area, but may also be observed in the basal state and after completion of the recruitment of MCs into scars.
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http://dx.doi.org/10.1002/glia.21037DOI Listing
November 2010

Matrix metalloproteinases are involved in both type I (apoptosis) and type II (autophagy) cell death induced by sodium phenylacetate in MDA-MB-231 breast tumour cells.

Anticancer Res 2009 Apr;29(4):1335-43

U553 INSERM Hôpital Saint-Louis 1, Paris, France.

The effects of sodium phenylacetate (NaPa), an antitumoral molecule, on cell death and matrix metalloproteinase (MMP) activities and synthesis were investigated in two metastatic breast tumour cell lines, MDA-MB-231 and MDA-MB-435, cultured on three-dimensional type I collagen gels (3-D cultures). In both cell lines, NaPa inhibited cell proliferation and induced apoptotic cell death as measured by TUNEL assay, with an IC(30) of 20 mM and 10 mM for MDA-MB-231 and MDA-MB-435 cells, respectively. In MDA-MB-231 cells, NaPa also induced (i) an autophagic process evidenced by the appearance of autophagic vacuoles and an increased phosphatase acid activity, (ii) the formation of pseudopodia and (iii) an increase in MMP-1 and MMP-9 secretion without affecting MT1-MMP. In NaPa-treated MDA-MB-435 cells, no autophagic vacuoles were formed but F-actin depolymerisation was observed. MMP-1, MMP-9 and MT1-MMP levels were strongly enhanced in these cells but MMPs were not secreted and accumulated intracellularly. When breast cancer cells were treated with NaPa in the presence of an MMP inhibitor (GM6001), apoptotic cell death decreased and the induction of autophagic vacuoles in MDA-MB-231 cells was inhibited. Taken together, these data suggest that MMPs are involved in the autophagic cell death and/or apoptosis of breast tumour cells.
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April 2009

Optimized allotopic expression of the human mitochondrial ND4 prevents blindness in a rat model of mitochondrial dysfunction.

Am J Hum Genet 2008 Sep 4;83(3):373-87. Epub 2008 Sep 4.

Institut de la Vision, Université Pierre et Marie Curie-Paris6, Unité mixte de recherche S 592, 17 rue Moreau, Paris F-75012, France.

Mitochondrial diseases due to mutations in mitochondrial DNA can no longer be ignored in most medical areas. With prevalence certainly higher than one in 6000, they probably represent the most common form of metabolic disorders. Despite progress in identification of their molecular mechanisms, little has been done with regard to therapy. We have recently optimized the allotopic expression for the mitochondrial genes ATP6, ND1, and ND4 and obtained a complete and long-lasting rescue of mitochondrial dysfunction in the human fibroblasts in which these genes were mutated. However, biosafety and benefit to mitochondrial function must be validated in animal models prior to clinical applications. To create an animal model of Leber Hereditary Optic Neuropathy (LHON), we introduced the human ND4 gene harboring the G11778A mutation, responsible of 60% of LHON cases, to rat eyes by in vivo electroporation. The treatment induced the degeneration of retinal ganglion cells (RGCs), which were 40% less abundant in treated eyes than in control eyes. This deleterious effect was also confirmed in primary cell culture, in which both RGC survival and neurite outgrowth were compromised. Importantly, RGC loss was clearly associated with a decline in visual performance. A subsequent electroporation with wild-type ND4 prevented both RGC loss and the impairment of visual function. Hence, these data provide the proof-of-principle that optimized allotopic expression can be an effective treatment for LHON, and they open the way to clinical studies on other devastating mitochondrial disorders.
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http://dx.doi.org/10.1016/j.ajhg.2008.08.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2556433PMC
September 2008

The optimized allotopic expression of ND1 or ND4 genes restores respiratory chain complex I activity in fibroblasts harboring mutations in these genes.

Biochim Biophys Acta 2008 Oct 6;1783(10):1707-17. Epub 2008 May 6.

Institut de la Vision, Université Pierre et Marie Curie-Paris, INSERM UMR-S 592, 17 rue Moreau, Paris, F-75012 France.

Leber's Hereditary Optic Neuropathy (LHON) was the first maternally inherited mitochondrial disease identified and is now considered the most prevalent mitochondrial disorder. LHON patients harbor mutations in mitochondrial DNA (mtDNA). In about 90% of cases, the genes involved encode proteins of the respiratory chain complex I. Even though the molecular bases are known since 20 years almost all remains to be done regarding physiopathology and therapy. In this study, we report a severe decrease of complex I activity in cultured skin fibroblasts isolated from two LHON patients harboring mutations in ND4 or ND1 genes. Most importantly, we were able to restore sustainably (a) the ability to grow on galactose, (b) the ATP synthesis rate and (c) the complex I activity, initially impaired in these cells. Our strategy consisted of forcing mRNAs from nuclearly-encoded ND1 and ND4 genes to localize to the mitochondrial surface. The rescue of the respiratory chain defect observed was possible by discreet amounts of hybrid mRNAs and fusion proteins demonstrating the efficiency of their mitochondrial import. Hence, we confirmed here for two mitochondrial genes located in the organelle that the optimized allotopic expression approach represents a powerful tool that could ultimately be applied in human therapy for LHON.
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http://dx.doi.org/10.1016/j.bbamcr.2008.04.018DOI Listing
October 2008

Allotopic mRNA localization to the mitochondrial surface rescues respiratory chain defects in fibroblasts harboring mitochondrial DNA mutations affecting complex I or v subunits.

Rejuvenation Res 2007 Jun;10(2):127-44

Laboratoire de Physiopathologie Cellulaire et Moléculaire de la Rétine, INSERM U592, Université Pierre et Marie Curie (UPMC-Paris6), Hôpital St. Antoine-Bât. Kourilsky, 184 rue du Faubourg Saint-Antoine, 75571 Paris Cedex 12, France.

The possibility of synthesizing mitochondrial DNA (mtDNA)-coded proteins in the cytosolic compartment, called allotopic expression, provides an attractive option for genetic treatment of human diseases caused by mutations of the corresponding genes. However, it is now appreciated that the high hydrophobicity of proteins encoded by the mitochondrial genome represents a strong limitation on their mitochondrial import when translated in the cytosol. Recently, we optimized the allotopic expression of a recoded ATP6 gene in human cells, by forcing its mRNA to localize to the mitochondrial surface. In this study, we show that this approach leads to a long-lasting and complete rescue of mitochondrial dysfunction of fibroblasts harboring the neurogenic muscle weakness, ataxia and retinitis Pigmentosa T8993G ATP6 mutation or the Leber hereditary optic neuropathy G11778A ND4 mutation. The recoded ATP6 gene was associated with the cis-acting elements of SOD2, while the ND4 gene was associated with the cis-acting elements of COX10. Both ATP6 and ND4 gene products were efficiently translocated into the mitochondria and functional within their respective respiratory chain complexes. Indeed, the abilities to grow in galactose and to produce adenosine triphosphate (ATP) in vitro were both completely restored in fibroblasts allotopically expressing either ATP6 or ND4. Notably, in fibroblasts harboring the ATP6 mutation, allotopic expression of ATP6 led to the recovery of complex V enzymatic activity. Therefore, mRNA sorting to the mitochondrial surface represents a powerful strategy that could ultimately be applied in human therapy and become available for an array of devastating disorders caused by mtDNA mutations.
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http://dx.doi.org/10.1089/rej.2006.0526DOI Listing
June 2007
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