Protection of Mouse Retinal Ganglion Cell Axons and Soma from Glaucomatous and Ischemic Injury by Cytoplasmic Overexpression of Nmnat1

Zhu, Yanli; Zhang, Lihong; Sasaki, Yo; Milbrandt, Jeffrey; Gidday, Jeffrey M.

doi:10.1167/iovs.12-10861

Cited by 59 publications

(52 citation statements)

References 46 publications

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“…Additional ligations of ≥1 presumably patent episcleral veins were performed at 24 h, and at 1 or 2 weeks following the initial surgery, if IOP was not elevated at 24 h or did not remain elevated at weekly measurement intervals, or if newly formed episcleral veins became evident. Of note, in this study and in our previous studies employing this same model [9][10][11], very few mice required additional ligation surgery at 24 h or 2 weeks after the initial ligation; rather, in most mice, new veins that became apparent by 1 week were ligated, even if IOP had not fallen below levels measured at 24 h. As described previously by us and others [9][10][11][12], IOP determinations were made between 10.00 am and 2.00 pm in both eyes prior to, and at weekly intervals following, IOP elevation using the TonoLab Rebound Tonometer system (Colonial Medical Supply, Franconia, NH, USA).…”

Section: Experimental Glaucoma Modelsupporting

confidence: 52%

“…As we described previously [9][10][11], a sustained, 3-week period of elevated IOP was achieved by repeated ligation of the episcleral veins of one eye; the fellow eye of each mouse served as a nonglaucomatous control. In brief, after ketamine/xylazine-anesthetized mice received topical application of 0.5 % proparacaine hydrochloride, the conjunctiva and Tenon's capsule were incised to expose the episcleral veins, 3-4 of which over >300°of the limbus were severed secondary to doubly ligating them with 11-0 nylon suture (Alcon Surgical, Fort Worth, TX, USA).…”

Section: Experimental Glaucoma Modelmentioning

confidence: 99%

“…Axon integrity was quantified in the postlaminar optic nerve by confocal immunofluorescence microscopy of SMI32-immunopositive axons, as described previously by us and others [10,11,[17][18][19]; SMI32 has been shown to stain the medium and large, alpha-subtype of RGCs [20,21], which, while not inclusive of all RGCs, are found evenly distributed throughout the retina [20]. In brief, after obtaining fVEP and optokinetic measurements in untreated and RHP-treated mice after 3 weeks of experimental glaucoma, animals were euthanized by transcardial perfusion, the retina was removed and Fig.…”

Section: Structural Analyses Of Glaucomatous Injury and Rh-post-mediamentioning

confidence: 99%

“…Confocal images [LSM 5 PASCAL; 40× objective (1.25 NA); Carl Zeiss, Jena, Germany] were obtained at excitation wavelengths of 405, 488, and 560 nm. Total fluorescence intensities of SMI32-positive axons within the nerve border were determined by binarizing the image after background subtraction to identify the total surface area in the nerve covered by SMI32 above threshold, calculating the total fluorescence intensity of the resulting image, and then normalizing to the total area of SMI32-positive signal, as detailed previously [10,11].…”

Section: Structural Analyses Of Glaucomatous Injury and Rh-post-mediamentioning

confidence: 99%

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Enhanced Retinal Ganglion Cell Survival in Glaucoma by Hypoxic Postconditioning After Disease Onset

et al. 2015

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The neuroprotective efficacy of adaptive epigenetics, wherein beneficial gene expression changes are induced by nonharmful "conditioning" stimuli, is now well established in several acute, preclinical central nervous system injury models. Recently, in a mouse model of glaucoma, we demonstrated retinal ganglion cell (RGC) protection by repetitively "preconditioning" with hypoxia prior to disease onset, indicating an epigenetic approach may also yield benefits in chronic neurodegenerative disease. Herein, we determined whether presenting the repetitive hypoxic stimulus after disease initiation [repetitive hypoxic "postconditioning" (RHPost)] could afford similar functional and morphologic protection against glaucomatous RGC injury. Chronic elevations in intraocular pressure (IOP) were induced unilaterally in adult male C57BL/6 mice by episcleral vein ligation. Mice were randomized to an RH-Post [1 h of systemic hypoxia (11 % oxygen) every other day, starting 4 days after IOP elevation] or an untreated control group. After 3 weeks of experimental glaucoma, the 21-27 % reduction and 5-25 % prolongation in flash visual-evoked potential amplitudes and latencies, respectively, and the 30 % impairment in visual acuity were robustly improved in RH-Post-treated mice, as was the 17 % loss in RGC soma number and 20 % reduction in axon integrity. These protective effects were observed without RH-Post affecting IOP. The present findings demonstrate that functional and morphologic protection of RGCs can be realized by stimulating epigenetic responses during the early stages of disease, and thus constitute a new conceptual approach to glaucoma therapeutics.

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Section: Experimental Glaucoma Modelsupporting

confidence: 52%

Section: Experimental Glaucoma Modelmentioning

confidence: 99%

Section: Structural Analyses Of Glaucomatous Injury and Rh-post-mediamentioning

confidence: 99%

Section: Structural Analyses Of Glaucomatous Injury and Rh-post-mediamentioning

confidence: 99%

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Enhanced Retinal Ganglion Cell Survival in Glaucoma by Hypoxic Postconditioning After Disease Onset

et al. 2015

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“…Although the neuroprotective actions of NMNATs in the mammalian brain remain largely unexplored, recent evidence suggests that NMNATs are also strongly protective against axonal and neuronal CNS degeneration. For example, increases in the expression of NMNAT1 and NMNAT3 decrease mouse retinal ganglion cell degeneration following ischemia,9, 10 and overexpression of cytoplasmic NMNAT1 protects the term‐equivalent neonatal mouse brain against the degenerative effects of cerebral H‐I via inhibition of glutamate‐dependent excitotoxic cell injury 11. In contrast, depletion of NMNAT2, the NMNAT isoform most abundant in the brain, restricts the outgrowth of retinal and cortical fibers in vitro 12.…”

Section: Introductionmentioning

confidence: 99%

NMNAT3 is protective against the effects of neonatal cerebral hypoxia‐ischemia

Galindo

Greenberg

Araki

et al. 2017

Ann Clin Transl Neurol

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ObjectiveTo determine whether the NAD+ biosynthetic protein, nicotinamide mononucleotide adenylyltransferase‐3 (NMNAT3), is a neuroprotective inducible enzyme capable of decreasing cerebral injury after neonatal hypoxia‐ischemia (H‐I) and reducing glutamate receptor‐mediated excitotoxic neurodegeneration of immature neurons.MethodsUsing NMNAT3‐overexpressing mice we investigated whether increases in brain NMNAT3 reduced cerebral tissue loss following H‐I. We then employed biochemical methods from injured neonatal brains to examine the inducibility of NMNAT3 and the mechanism of NMNAT3‐dependent neuroprotection. Using AAV8‐mediated vectors for in vitro neuronal NMNAT3 knockdown, we then examine the endogenous role of this protein on immature neuronal survival prior and following NMDA receptor‐mediated excitotoxicity.ResultsNMNAT3 mRNA and protein levels increased after neonatal H‐I. In addition, NMNAT3 overexpression decreased cortical and hippocampal tissue loss 7 days following injury. We further show that the NMNAT3 neuroprotective mechanism involves a decrease in calpastatin degradation, and a decrease in caspase‐3 activity and calpain‐mediated cleavage. Conversely, NMNAT3 knockdown of cortical and hippocampal neurons in vitro caused neuronal degeneration and increased excitotoxic cell death. The neurodegenerative effects of NMNAT3 knockdown were counteracted by exogenous upregulation of NMNAT3.ConclusionsOur observations provide new insights into the neuroprotective mechanisms of NMNATs in the injured developing brain, adding NMNAT3 as an important neuroprotective enzyme in neonatal H‐I via inhibition of apoptotic and necrotic neurodegeneration. Interestingly, we find that endogenous NMNAT3 is an inducible protein important for maintaining the survival of immature neurons. Future studies aimed at uncovering the mechanisms of NMNAT3 upregulation and neuroprotection may offer new therapies against the effects of hypoxic‐ischemic encephalopathy.

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Hidden Genetic Variation in LCA9‐Associated Congenital Blindness Explained by 5′UTR Mutations and Copy‐Number Variations of NMNAT1

et al. 2015

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Leber congenital amaurosis (LCA) is a severe autosomal‐recessive retinal dystrophy leading to congenital blindness. A recently identified LCA gene is NMNAT1, located in the LCA9 locus. Although most mutations in blindness genes are coding variations, there is accumulating evidence for hidden noncoding defects or structural variations (SVs). The starting point of this study was an LCA9‐associated consanguineous family in which no coding mutations were found in the LCA9 region. Exploring the untranslated regions of NMNAT1 revealed a novel homozygous 5′UTR variant, c.‐70A>T. Moreover, an adjacent 5′UTR variant, c.‐69C>T, was identified in a second consanguineous family displaying a similar phenotype. Both 5′UTR variants resulted in decreased NMNAT1 mRNA abundance in patients’ lymphocytes, and caused decreased luciferase activity in human retinal pigment epithelial RPE‐1 cells. Second, we unraveled pseudohomozygosity of a coding NMNAT1 mutation in two unrelated LCA patients by the identification of two distinct heterozygous partial NMNAT1 deletions. Molecular characterization of the breakpoint junctions revealed a complex Alu‐rich genomic architecture. Our study uncovered hidden genetic variation in NMNAT1‐associated LCA and emphasized a shift from coding to noncoding regulatory mutations and repeat‐mediated SVs in the molecular pathogenesis of heterogeneous recessive disorders such as hereditary blindness.

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Protection of Mouse Retinal Ganglion Cell Axons and Soma from Glaucomatous and Ischemic Injury by Cytoplasmic Overexpression of Nmnat1

Cited by 59 publications

References 46 publications

Enhanced Retinal Ganglion Cell Survival in Glaucoma by Hypoxic Postconditioning After Disease Onset

Enhanced Retinal Ganglion Cell Survival in Glaucoma by Hypoxic Postconditioning After Disease Onset

NMNAT3 is protective against the effects of neonatal cerebral hypoxia‐ischemia

Hidden Genetic Variation in LCA9‐Associated Congenital Blindness Explained by 5′UTR Mutations and Copy‐Number Variations of NMNAT1

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