April 2011
Volume 52, Issue 14
ARVO Annual Meeting Abstract  |   April 2011
Intracellular Accumulation of A2E in Retinal Microglia Influences Neuroprotection and Cellular Migration
Author Affiliations & Notes
  • Wenxin Ma
    NEI, Bethesda, Maryland
  • Steven Coon
    Program in Developmental Endocrinology and Genetics, NICHHD, Bethesda, Maryland
  • Zhongshu Tang
    Unit Retinal Vascular Neurobiology,
    NEI, Bethesda, Maryland
  • Robert Fariss
    Imaging Core Unit,
    NEI, Bethesda, Maryland
  • Wai Wong
    NEI, Bethesda, Maryland
  • Footnotes
    Commercial Relationships  Wenxin Ma, None; Steven Coon, None; Zhongshu Tang, None; Robert Fariss, None; Wai Wong, None
  • Footnotes
    Support  NEI Intramural Research
Investigative Ophthalmology & Visual Science April 2011, Vol.52, 2288. doi:
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      Wenxin Ma, Steven Coon, Zhongshu Tang, Robert Fariss, Wai Wong; Intracellular Accumulation of A2E in Retinal Microglia Influences Neuroprotection and Cellular Migration. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2288.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : The age-dependent accumulation of microglia/macrophages in the subretinal space has been implicated in the pathogenesis of age-related macular degeneration (AMD). Aged microglia in the subretinal space become juxtaposed with photoreceptors and RPE cells and accumulate autofluorescent intracellular deposits of lipofuscin. We investigated the effect of A2E, a major fluorophore of lipofuscin, on the physiology of cultured microglia in vitro to discover pathological implications of aged microglia in the subretinal space.

Methods: : A2E was synthesized from all-trans retinal and ethanolamine and purified by HPLC. Primary microglia cultured from mouse retina were incubated with A2E (6µM for 6 hours) to achieve intracellular loading. Microglia were harvested for mRNA gene expression analysis (rtPCR and Nanostring nCounter) and cellular migration assessed using a Boyden chamber assay. Conditioned media of A2E-loaded microglia were assessed for neuroprotective effects on 661W photoreceptor cells experiencing H202-mediated oxidative stress.

Results: : Cultured microglial accumulate A2E at sublethal doses as intracellular autofluorescent deposits akin to those observed in aged microglia in vivo. A2E loading of microglia induced morphological alteration from a ramified to a more rounded morphology. mRNA gene expression changes included decreased levels of growth factors (BDNF, CNTF, NGF, GDNF) and chemokine receptors (CCR1, CCR5). mRNA levels for proinflammatory factors TNFα were increased but those for IL1β and IL6 were not significantly altered. Functionally, A2E-loaded microglia demonstrated lower levels of cell division, lower rates of cellular migration in response to a chemokine (CCL2, CCL3) gradient, and provided lower levels of neuroprotection to photoreceptors experiencing H202-induced oxidative stress.

Conclusions: : Exposure of primary retinal microglia to A2E resulted in an accumulation of autofluorescent intracellular deposits and alterations in morphology that resembled those occurring in aged microglia found in the subretinal space. A2E-loaded microglia demonstrated altered physiological properties that may relate to the progressive accumulation of subretinal microglia in vivo and pathological changes observed in the aging retina.

Keywords: age-related macular degeneration • inflammation • gene/expression 

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