Abstract
Purpose :
Recent studies in our laboratory demonstrated that oxygen and glucose deprivation resulted in losses of retinal ganglion cells (RGCs) and that activation of the sigma-1 receptors restored the numbers of RGCs via inhibition of caspase 3/7 activity. In these studies, we examined the signaling mechanisms involved in RGC losses in an optic nerve crush mouse model (ONC).
Methods :
ONC was performed in C57BL/6 mice. Briefly, the left optic nerve (ON) was exposed intraorbitally through a small window made between the surrounding muscles. The ON was crushed approximately 1mm behind the globe with self-closing forceps for 4 seconds under visualization. The contralateral eye was used as controls for ONC. Termination experiments include immunohistochemical analysis of phosphorylated (p) c Jun, c Jun and Caspase 3.
Results :
Phosphorylated c Jun and c Jun were observed in RGCs 16 hours, 24 hours, 3 days and 7 days post ONC. P-c-Jun was localized in the periphery and cytoplasm of the cells while c-Jun was localized to the nucleus. In some instances, p-c-Jun co-localized with c-Jun. Contralateral control, without ONC, did not stain for either P-c-Jun or c-Jun. Most interestingly, caspase 3 expression was only observed 7 days post ONC.
Conclusions :
These findings suggest that the apoptotic pathway is involved in RGC losses seen in ONC model. The findings that p-c-Jun and c-Jun are expressed at 16 hours after ONC, suggest that this is a relatively early response gene. That caspase 3 is expressed seven days after ONC, suggest a later response in the apoptotic pathway, and correlates with marked decreases in the number of RGCs observed seven days after ONC. Given the ability of the sigma-1 receptor to rescue RGCs by inhibiting caspase 3/7 activity in primary RGCs subjected to OGD, the possibility exists that activation of the sigma-1 receptor in ONC models would also rescue RGCs, via inhibition of caspase 3. Future experiments will confirm this.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.