Abstract
Purpose :
Our previous studies demonstrated that intravitreally injecting peptain-1, a peptide derived from αB-crystallin, can prevent the death of retinal ganglion cells (RGCs) in rats with ocular hypertension. Transcriptomics on RGCs of ocular hypertensive rats revealed cAMP response element-binding protein (CREB) signaling to be activated by peptain-1 conjugated with a cell-penetrating peptide (P1-CPP). This study investigated CREB phosphorylation (p-CREB) in rats with ocular hypertension following P1-CPP treatment.
Methods :
Fifteen adult male Brown Norway rats were used, with five rats in each of three groups: naïve, IOP-Vehicle, and IOP-P1-CPP. To elevate intraocular pressure (IOP), 20µl of silicone oil was injected into the anterior chamber, followed by an intravitreal injection (2µl) of either PBS (Veh) or P1-CPP (2µg/µl). On the 7th day of elevated IOP, rats were euthanized, and their retinal sections were stained with anti-CREB, p-CREB antibodies, and DAPI. Retinal sections were imaged, and integrated density measurements were done. Statistical significance was calculated using unpaired t-tests or Mann-Whitney tests in GraphPad Prism. Finally, retinal punches from post-mortem human eyes were cultured with PBS or P1-CPP (12.5µg/ml) for 48 hours, and tissue RNA was collected for qPCR analysis.
Results :
RGC counts in the IOP-Veh group revealed a 51% reduction compared to the naïve group (p<0.0001). The group that received P1-CPP after silicone oil injury (IOP-P1-CPP) exhibited a significantly lesser 23% decrease than the naïve group (p=0.0016). Assessment of integrated density for CREB expression in IOP-Veh showed a 17% increase (p=0.615) relative to the naïve group. In contrast, the IOP-P1-CPP group exhibited a substaintial 136% increase (p=0.092) compared to the naïve group. Analysis of p-CREB expression indicated a considerable 50% decrease in the IOP-Veh group compared to the naïve group (p=0.056). In contrast, the IOP-P1-CPP group displayed a significant increase compared to the IOP-Veh group (p=0.036). Lastly, RNA expression of Creb1 in human retinal tissue was increased by 1.7-fold with P1-CPP treatment compared to untreated tissue.
Conclusions :
IOP-mediated damage to RGCs in rats was reduced by P1-CPP treatment via activation of CREB signaling. P1-CPP could be used as a neuroprotective agent for glaucoma.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.