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Crotoxin (Crtx), the main toxin in the venom of Crotalus durissus terrificus snake, is a heterodimer with a basic subunit, CB, and an acidic subunit, CA. CB is a phospholipase A2 that depends on CA to specifically bind to the cell membrane. This toxin acts in the central nervous system (CNS) causing chronic seizure effects and other cytotoxic effects. Here, we report its action on glutamate release in rat cerebral cortex synaptosomes. Aiming at a better understanding of the mechanism of action of Crtx, calcium channel blockers were used and internalization studies were performed in cerebellar granule neurons. Our results show that Crtx induces calcium-dependent glutamate release via N and P/Q calcium channels. In addition, the CB subunit of Crtx is shown to be internalized. This internalization does not depend on the presence of CA subunit neither on the PLA2 activity of CB. A correlation between CB internalization and glutamate release remains to be established.

Introduction With the aim of overcoming the high toxicity of PnTx2-6 (or δ-CNTX-Pn2a), a toxin from the venom of the armed spider (Phoneutria nigriventer), the 19-aminoacid peptide, PnPP-19 (P nigriventer potentiator peptide), was synthesized based on molecular modeling studies of PnTx2-6. PnPP-19 improved the erectile function of normotensive rats and mice, without eliciting side effects, and no signs of toxicity were observed. In addition, PnPP-19 was able to potentiate the effect of sildenafil. Aim To evaluate the efficacy of PnPP-19 in hypertensive and diabetic mouse/rat models in restoring erectile function, after topical administration; verify the biodistribution of PnPP-19 administration (topical and intravenous), permeation, and cyclic guanosine monophosphate (cGMP)/nitric oxide via implication. Methods Corpus cavernosum relaxation was evaluated using cavernous strips from male spontaneous hypertensive rats (SHR) and from streptozotocin (STZ)-diabetic mice contracted with phenylephrine and submitted to electrical field stimulation before and after incubation with PnPP-19 (10−8 mol/L, 10 minutes) or vehicle. This procedure was also used to determine cGMP/nitric oxide levels, at 8 Hz and to check the effect of PnPP-19 with sildenafil citrate. Biodistribution assays were performed using iodine 123–radiolabeled PnPP-19. In vivo erectile function was evaluated using intracavernosal pressure/main arterial pressure ratio in STZ-diabetic rats after PnPP-19 topical administration. Main Outcome Measures PnPP-19 may become a new drug able to fill the gap in the pharmacologic treatment of erectile dysfunction, especially for hypertensive and diabetic individuals Results PnPP-19 potentiated corpus cavernosum relaxation, in both control and SHR rats. SHR-cavernosal tissue treated with PnPP-19 (1–32 Hz) reached the same relaxation levels as control Wistar rats (16 and 32 Hz). PnPP-19 treatment improved cavernosal tissue relaxation in STZ-diabetic mice and rats. PnPP-19 enhanced cGMP levels in STZ-diabetic mice corpus cavernosum strips. After topical or intravenous administration in rats, 123I-PnPP-19 was mainly recruited to the penis. When topically administered (400 μg/rat), PnPP-19 restores erectile function in STZ-diabetic rats, also improving it in healthy rats by increasing the intracavernosal pressure/main arterial pressure ratio. PnPP-19 exhibited an additive effect when co-administered with sildenafil, showing a novel mode of action regardless of phosphodiesterase type 5 inhibition. Clinical Implications PnPP-19 seems to be an indicated drug to be tested to treat ED in diabetic and hypertensive patients. Strength & Limitations PnPP-19, although active by topical application and showing safety to human beings (not shown), has low permeability, about 10% of the applied dose. Conclusion Our results showed that PnPP-19 may emerge as a potent new drug that can be topically administered, becoming a promising alternative for erectile dysfunction treatment.

Bacterial keratitis is an ocular infection that can lead to severe visual disability. Staphylococcus aureus is a major pathogen of the eye. We recently demonstrated the strong antimicrobial activity of LyeTxI-b, a synthetic peptide derived from a Lycosa erithrognatha toxin. Herein, we evaluated a topical formulation (eye drops) containing LyeTxI-b to treat resistant bacterial keratitis. Keratitis was induced with intrastromal injection of 4 × 105 cells (4 µL) in New Zealand female white rabbits. Minimum inhibitory concentration (MIC) and biofilm viability were determined. LyeTxI-b ocular toxicity was evaluated through chorioallantoic membrane and Draize tests. One drop of the formulation (LyeTxI-b 28.9 µmol/L +0.5% CMC in 0.9% NaCl) was instilled into each eye four times a day, for a week. Slit-lamp biomicroscopy analysis, corneal histopathological studies and cellular infiltrate quantification through myeloperoxidase (MPO) and N-acetylglucosaminidase (NAG) detection were performed. LyeTxI-b was very effective in the treatment of keratitis, with no signs of ocular toxicity. Planktonic bacteria MIC was 3.6 µmol/L and LyeTxI-b treatment reduced biofilm viability in 90%. LyeTxI-b eliminated bacteria and reduced inflammatory cellular activity in the eyes. Healthy and treated animals showed similar NAG and MPO levels. LyeTxI-b is a potent new drug to treat resistant bacterial keratitis, showing effective antimicrobial and anti-inflammatory activity.

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