Avaliação da atividade neuroprotetora da Parawixina 11 isolada da peçonha da aranha Parawixia bistriata (Araneae, Araneidae), em ratos Wistar submetidos a um modelo de glaucoma agudo / Neuroprotective activity analysis of Parawixin 11, isolated from Parawixia bistriata (Araneae, Araneidae) spider venom, in Wistar rats submitted to an model of acute glaucoma

Marcela Nunes Rosa

Glaucoma is defined as a typical optic neuropathy characterized by ganglion cells loss and consequent optic nerve damage, resulting in a gradual reduction of the visual field and eventual blindness. In regard to compounds present in spider venoms, they represent an interesting source of bioactive molecules and the study about the possible neuroprotective effects of these substances, in experimental models of glaucoma, is an important step to developed new drugs to treating this disease. Therefore, our research group has investigated neuroactive compounds isolated from Parawixia bistriata spider venom. Nowadays, three purified molecules, PbTx1.2.3 (Parawixin 1), FrPbAII (Parawixin 2) and Parawixin 10 showed anticonvulsant and neuroprotective effects. They enhance the L-gluatamate uptake (Parawixin 1 and 10) or inhibit the GABA uptake (Parawixin 2). In addition these compounds, we also isolated the Parawixin 11 (PW11). So far, the results with PW11 showed the anticonvulsant effect in rats after seizures drug-induced and neuroprotetive effect after Status epilepticus pilocarpine -induced. Nevertheless, this study was to exemine if Pw11 could also be neuroprotective in acute glaucoma model and attempt to infer the mechanism of action, comparing it and associating it to muscimol, nipecotic acid, ALX 5407 and riluzole. For this, the model used was the intraocular pressure (IOP) elevation, disrupting the blood flow in retina and causing ischemia. It was used a system with air pressure, comprising of a 27G venous puncture needle connected to an air reservoir coupled to a manometer. Male Wistar rats (200-250 g) were anesthetized and each group (n=4) received an intravitreal injection (volumn = 1,2 µL) in the left eye of one of the following substances: deionized water (VE1); DMSO 4,7%, 0,05 µg/µL of PW11; 0,10 µg/µL of PW11; 0,20 µg/µL of PW11; 5 µg/µL of muscimol;3µg/µL of nipecotic acid; 0,30 µg/µL of ALX 5407;23,45 µg/µL of riluzole. Other groups received an injection (volumn = 2,4 µL) with one of the following associations: 0,10 µg/µL of PW11+muscimol; 0,10 µg/µL of PW11+nipecotic acid; 0,10 µg/µL of PW11+ALX 5407 and 0,10 µg/µL of PW11+riluzole. Fifteen minutes later, the IOP was raised up to 120 mmHg for 45 min, inducing retinal ischemia. Some animals, which were ischemia group (ISCH), were sacrificed immediately thereafter. The ischemia/reperfusion (ISCH/REP) group animals had IOP normalizedduring 15 min, after ischemia, making possible the blood flow return and, then, they were euthanized. Then, the eyes were removed and fixed in ALFAC solution. The ischemic retinas with or without reperfusion showed piknotic nuclei, citoplasmatic vacuolization, edema and disorganization of the retinal layers, characteristics of this lesion type. After ISCH, treatments with 0.1 and 0.2 µg/µL of PW11 preserved, respectively, 17.51 and 37.45% of cells in the INL if compared with VE1 group. In the GCL, when PW11 was associated to muscimol, a GABAA receptor agonist, and to nipecotic acid, a GAT-1 transporter inhibtor, there was significant protection of 37.07 and 44.81%, respectively, if compared with VE1 group, indicating nonspecificity of PW11 in gabaergic system. After ISCH/REP, cell densities in GCL of treated retinas with 0.05, 0.10 ad 0.20 µg/µL of PW11 were 32.88, 24.05 and 28.27% higher than that of VE1 group retinas, respectively. In INL, the cell densities after PW11 treatments were 38.78, 35.25 and 30.96% higher than that of VE1 group retinas, respectively. Regarding the presence of Fluoro-Jade C (FJC) stained degenerating neurons, retinas from treated animals showed less FJC-positive neurons in INL, IPL and GCL if compared with those of VE1 and DMSO groups. In view of these effects, it is concluded that the PW11 can be a useful tool to developed therapies that combine different drugs in glaucoma and other neuropathology treatments.

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