Cell Permeable Peptain for Neuroprotection in Glaucoma

Abstract

Purpose : To determine if intravitreal administration of the core peptide of α-B crystallin, peptain-1 (P1) conjugated to a cell permeable peptide CPP (P1-CPP) could inhibit retinal ganglion cell (RGC) loss and functional decline in a rodent model of glaucoma.

Methods : Primary RGCs were isolated from post-natal day 4-6 rat pups. The cultured RGCs were deprived of neurotrophic factors for 48 h in the presence of either P1-CPP (12.5 µg/ml) or vehicle, following which RGC survival was assessed by CytoCalcein™ Violet 450. In a different set of experiments, intraocular pressure (IOP) was elevated in one eye of Brown Norway (BN) rats and intravitreally injected with 2 µl of either P1-CPP (2µg per eye) or vehicle, once in a week for a period of 6 weeks. RGC function was assessed by the pattern electroretinogram (PERG) amplitude and compared between all the treatment groups. Following the treatments, the rats were euthanized by approved methods, retinal flat mounts obtained were stained with an antibody to the RGC marker, Brn3a, to assess RGC counts. Retinal flat mounts were imaged and surviving RGCs were counted.

Results : In primary RGCs neurotrophic factor deprivation treatment for 48h led to 83% of RGC loss compared to cells grown in complete medium (p<0.0001). P1-CPP treatment significantly lowered the neurotrophic factor-mediated RGC loss by 64% (p<0.0001). IOP elevated and vehicle injected animals had 1192 ± 279 per mm² surviving RGCs in eccentricity 2 and 700 ± 246 per mm² in eccentricity 3, while P1-CPP treated rats had significantly higher RGC counts (1482 ± 388 and 1054 ± 343 respectively; **p<0.01). P1-CPP treatment also promoted axonal protection during IOP elevation. IOP elevation caused 63% decline in the PERG amplitude (*p<0.03) in comparison with naïve rats, which was sustained by P1-CPP treatment.

Conclusions : Intravitreal administration of P1-CPP provides cellular as well as functional protection of RGCs, and has the potential to facilitate neuroprotection in glaucoma.

This is a 2021 ARVO Annual Meeting abstract.