Purchase this article with an account.
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.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
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.
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.
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.
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.
This PDF is available to Subscribers Only