Efeito neuroprotetor de peptídeos derivados da aranha armadeira (Phoneutria nigriventer) em doenças da retina.

Abstract

The retina is highly demanding energetically, and its functioning comprises the activation of several signaling cascades. Therefore, events that undermine such cascade processes lead to the increase of the oxidation stress and give rise to inflammatory processes resulting in pathologies such as the age-related macular degeneration and glaucoma. In view of this, peptides derived from the venom of the Phoneutria nigriventer spider have stood out for presenting pharmacological action through mechanisms associated to neuroprotective effects. Hence, the goal of the present work was to investigate the safety and the neuroprotectant action of peptides derived from the venom of the Phoneutria nigriventer spider in ocular neurodegenerative diseases and evaluate the efficacy of a nanostructured formulation in the improvement of the bioavailability of peptides. A wide range of doses of the PnPa11 and PnPa13 was tested, and the 1.25 µg/mL concentration was determined to be the safest and was therefore utilized in the subsequent tests. The studies on the retina degeneration promoted by the blue LED light revealed that both selected peptides were able to protect the retina from the induced damage. The analysis of the electroretinogram showed larger preservation of the amplitude of the a and b waves (response of Müller cells, bipolar cells and photoreceptors) and this effect was also observed in the morphological analysis. The western blot analyses reinforce the hypothesis that such peptides are able to protect the retina against apoptosis. In a second approach, the neuroprotectant activity of PnPP-19, a nitric oxide (NO) donor peptide, and the safety of its use were analyzed. The obtained results showed that PnPP-19 did not induce toxicity signs in tested doses. Besides, the assay of PnPP-19 tagged with FITC showed that this peptide can permeate the cornea layers. Moreover, it was observed that the peptide was capable of promoting NO release, leading to the reduction of the intraocular pressure (IOP). During the evaluation of the neuroprotective activity of such peptide, it was observed that a pre-treatment with the PnPP-19 was able to avoid induced damages in the retina through ischemia. Thus, it is supposed that the neuroprotective effect of the PnPP-19 by an association of the hypotensive effect and the antioxidation effects by the increase of NO production. Thus, the efficacy of a system of drug nano-reservoir in the ocular delivery of the peptide was tested. The device was able to extend the peptide delivery in the ocular surface. This effect was noted through a rise in the fluorescence of the ocular surface and an improvement of the hypotensive capacity of the peptide. We also observed the capability of the device to increase the bioavailability of this peptide for a posterior segment. Our results enable a new perspective in the treatment of degenerative diseases in the retina and point to uncountable pathways for the use of peptides in ocular diseases. The studied device is promising, as it is capable to offer an improved non-invasive treatment that can increase the bioavailability of the peptides for the ocular tissues.