Intravitreal injection of peptides PnPa11 and PnPa13, derivatives of spider venom, prevents retinal damage.

Background: PnPa11 and PnPa13 are synthetic peptides derived from spider venom, which display antinociceptive and neuroprotective properties. In this work, we evaluated the safety of intravitreal use and the neuroprotective effect of these peptides.

Methods: The cytotoxicity and the antiangiogenic activity of these peptides were evaluated by the sulforhodamine-B method and chicken chorioallantoic membrane (CAM) assay, respectively. The safety was analyzed in Wistar rats that were intravitreally injected with different doses (0.50; 1.25; 2.50; 3.75 and 5.00 µg/mL) of these peptides (right eye, n = 6). The retinal function was assessed by electroretinography exams (ERG), intraocular pressure (IOP), and histological analyzes. In order to investigate the neuroprotective effect, Wistar rats received intravitreal injections (right eye, n = 6) of peptides at 1.25 µg/mL and then were exposed to blue LED light. In addition, the visual function and the retinal microstructure were verified.

Results: Cytotoxicity analyses demonstrated that the peptides did not present any toxicity over ARPE-19 (adult retinal pigmented epithelial) cell line and the antiangiogenic study highlighted that the peptides promoted the reduction of blood vessels. The intravitreal injection did not cause major changes, neither induced any irreversible damage. In the retinal degeneration assay, the ERG records demonstrated that the prior treatment with PnPa11 and PnPa13 protected the retina from damage. Morphological analyses confirmed the ERG findings. Immunoblotting analyses revealed that PnPa11 increased Erk1/2, NR2A, and NR2B retinal expression after the light stress model, but did not cause Akt1 activation, while PnPa13 prevented Erk1/2 and Akt1 dephosphorylation.

Conclusions: The intraocular administration of these peptides was well tolerated and presented protective activity against retinal degeneration, suggesting the potential use of these peptides as neuroprotectors in the ophthalmological field.