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Olivia J Marola, Stephanie B Syc-Mazurek, Gareth R Howell, Richard T Libby; Mechanisms of Endothelin-Induced Retinal Ganglion Cell Death. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3711.
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© ARVO (1962-2015); The Authors (2016-present)
The endothelin (EDN) system has been implicated in human glaucoma. EDN system activation has been shown to be an early, pathogenic event in animal models of glaucoma. In rodent ocular hypertensive models, pharmaceutical inhibition of EDN receptors significantly lessens glaucomatous neurodegeneration. Understanding the early signaling pathways that mediate EDN-induced retinal ganglion cell (RGC) death is critical for determining how EDN system activation contributes to the onset and progression of glaucoma. Here we examine the neuronal response to EDN insult.
Eyes of 2-4 month old DBA/2J mice were intravitreally injected with 2uL of either 1000μM EDN1 or PBS. At various time points post-injection, eyes were harvested and stained with markers for RGCs (TUJ1, RPBMS), dying cells (cleaved caspase 3; cCASP3), microglia (IBA1), and endothelial cells (CD31). Furthermore, since JUN has been shown to be involved in RGC death after glaucoma relevant injuries, eyes were examined for JUN activation (phosphorylated JUN, pJUN).
There was a significant reduction of TUJ1+ RGCs seven days after intravitreal EDN1 injection in DBA/2J mice (given as %RGC death±SEM; number of retinas; 17.3%±3.6%; n=10; p=0.001). Similar RGC loss was found 35 days after insult 11.8%±4.3%; n=4; p=0.035). Activation of JUN (pJUN) in RGCs was found at 1, 3, and 7 days after insult, and activated CASP3 (cCASP3) was found 3 and 7 days after insult (N≥ 3 for each time point). In addition, IBA1+ microglia exhibited an activated “amoeboid” morphology after EDN1 injection at these time points.
Intravitreal injection of EDN1 caused a significant loss of RGCs in DBA/2J mice. Based on RGC cell counts and neural injury markers, this death appears to occur mainly within the first week after insult. Furthermore, pJUN+ RGCs were observed during this time window, suggesting that as after an ocular hypertensive injury, JUN activation has a role in EDN-induced RGC death. It will be important to critically test the involvement of JUN in EDN-induced RGC death. Similarly, it will be important to determine how the known retinal vasoconstrictive effects of EDN are related to RGC death in this model.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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