Abstract
Purpose :
Our goal was to study the endogenous antioxidant response of the retina to elevation in intraocular pressure (IOP).
Methods :
To elevate IOP, we injected polystyrene beads into the anterior chamber of 3-month old male and female C57Bl/6 mice. We quantified superoxide levels in vivo using dihydroethidium. Post-collection, we quantified expression of antioxidant proteins using a PCR microarray and quantified total and phosphorylated Nrf2 via western blot analysis. In order to determine which upstream signaling pathway was involved in Nrf2 activation, we also quantified total and phosphorylated PI3K, GSK3B, JNK, and AkT.
Results :
There was a 225% increase in dihydroethidium fluorescence one week after IOP elevation (p<0.0001), a 193% increase two weeks after IOP elevation (p<0.0001), and a 76% increase three weeks after IOP elevation (p=0.0086). There was no difference in Nrf2 protein or mRNA levels between groups, but there was 63% increase in phosphorylated Nrf2 at two weeks after IOP elevation in comparison to all timepoints as well as saline-injected controls (p<0.0001 compared to all other groups). Additionally, there was a 41% increase in peroxiredoxin transcripts two weeks after IOP elevation (p=0.026) and a 64% increase in thioredoxin transcripts two weeks after IOP elevation (p=0.04). Finally, levels of phosphorylated AkT were increased by 50% at one week after IOP elevation (p<0.05), but there was no change in levels of phosphorylated PI3K between groups (p=0.32).
Conclusions :
Elevated IOP results in increased oxidative stress, followed by an endogenous response of increased Nrf2 phosphorylation and upregulation of antioxidant response element-driven transcripts at 2 weeks following IOP elevation. To date, our data suggests a possible role for AkT, but not PI3K in this response.
This is a 2020 ARVO Annual Meeting abstract.