September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
RhoA Signaling and Synaptic Damage Occur within Hours in a Live Pig Model of Retinal Detachment
Author Affiliations & Notes
  • Jianfeng Wang
    Department of Pharmacology, Physiology & Neurosciences, Rutgers - New Jersey Medical School, Newark, New Jersey, United States
  • Marco A Zarbin
    Institute of Ophthalmology & Visual Science, Rutgers - New Jersey Medical School, Newark, New Jersey, United States
  • Ilene Sugino
    Institute of Ophthalmology & Visual Science, Rutgers - New Jersey Medical School, Newark, New Jersey, United States
  • Ian Whitehead
    UH Cancer Center, Rutgers - New Jersey Medical School, Newark, New Jersey, United States
  • Ellen Townes-Anderson
    Department of Pharmacology, Physiology & Neurosciences, Rutgers - New Jersey Medical School, Newark, New Jersey, United States
    Institute of Ophthalmology & Visual Science, Rutgers - New Jersey Medical School, Newark, New Jersey, United States
  • Footnotes
    Commercial Relationships   Jianfeng Wang, None; Marco Zarbin, None; Ilene Sugino, None; Ian Whitehead, None; Ellen Townes-Anderson, None
  • Footnotes
    Support  1R01EY021542
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 5372. doi:
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      Jianfeng Wang, Marco A Zarbin, Ilene Sugino, Ian Whitehead, Ellen Townes-Anderson; RhoA Signaling and Synaptic Damage Occur within Hours in a Live Pig Model of Retinal Detachment. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5372.

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

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Abstract

Purpose : Although inhibition of RhoA reduces rod presynaptic plasticity in vitro, RhoA activation after retinal injury has not been examined in vivo. We have used a model of retinal detachment in live pig to determine whether RhoA signaling is present in detachment in vivo, and whether blocking this pathway helps prevent axonal retraction by rod cells as an initial step towards a therapy to stabilize synaptic connections after detachment.

Methods : Under anesthesia, adult Yorkshire pigs underwent pars plana vitrectomy; detachments were created by injecting balanced salt solution or 0.1, 1, or 10 mM Y27632, a ROCK inhibitor, subretinally. The animals were kept under anesthesia for 2 hrs, and then sacrificed for enucleation. Neural explants from detached and non-detached retinal areas were lysed for GTPase activity assays and western blot analysis. Remaining tissue was fixed for morphology and quantification of axonal retraction.

Results : Western blots showed that RhoA activity increased significantly with detachment, more than 1.5-fold, compared to eyes with only a vitrectomy (surgical control). Increased phosphorylation of myosin light chain, a RhoA effector, also occurred. Immunohistochemical analysis demonstrated that rod cells concurrently retract their terminals towards their cell bodies, disrupting the photoreceptor-to-bipolar synapse and producing significant numbers of rod spherules with SV2 immunolabel in the outer nuclear layer of the retina. In eyes with detachment, distant retina that remained attached also showed significant increases in RhoA activity and synaptic disjunction. Increased Rac1 activity and GFAP were not specific for detachment and sprouting of bipolar dendrites was not seen. Finally, using the Rho kinase inhibitor Y27632 at 1 and 10mM, axonal retraction by rod cells was significantly reduced.

Conclusions : Activation of the RhoA pathway occurs quickly after injury and promotes synaptic damage but can be controlled by Rho kinase inhibition. Although prompt repair of detachment is accepted practice, these studies suggest that retinal detachment joins a list of CNS injuries, such as stroke and spinal cord injury, which may benefit from very rapid therapeutic intervention.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

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