Comparison of biochemical and cytotoxic activities of extracts obtained from dorsal spines and caudal fin of adult and juvenile non-native Caribbean lionfish (Pterois volitans/miles)

Fish Cytolysins in All Their Complexity

The majority of the effects observed upon envenomation by scorpaenoid fish species can be reproduced by the cytolysins present in their venoms. Fish cytolysins are multifunctional proteins that elicit lethal, cytolytic, cardiovascular, inflammatory, nociceptive, and neuromuscular activities, representing a novel class of protein toxins. These large proteins (MW 150–320 kDa) are composed by two different subunits, termed α and β, with about 700 amino acid residues each, being usually active in oligomeric form. There is a high degree of similarity between the primary sequences of cytolysins from different fish species. This suggests these molecules share similar mechanisms of action, which, at least regarding the cytolytic activity, has been proved to involve pore formation. Although the remaining components of fish venoms have interesting biological activities, fish cytolysins stand out because of their multifunctional nature and their ability to reproduce the main events of envenomation on their own. Considerable knowledge about fish cytolysins has been accumulated over the years, although there remains much to be unveiled. In this review, we compiled and compared the current information on the biochemical aspects and pharmacological activities of fish cytolysins, going over their structures, activities, mechanisms of action, and perspectives for the future.

In Silico Protein-Protein Interaction of Pterois volitans Venom with Cancer Inducers of Helicobacter pylori

Gastric cancer is a pathological condition induced by the bacteria Helicobacter pylori. Targeting the key virulence factors of H. pylori causing gastric cancer is a promising method for treating gastric cancer. Recently, research has been focused on analyzing the adrenergic, cholinergic, and anti-cancer properties of their venom proteins. Testing the anti-cancer activity of the lethal proteins in the venom of P. volitans provides a bioactive compound for cancer treatment. Still, it is also helpful to eliminate the ecological imbalance caused by these fish in the marine environment. This study focuses on an in silico approach using Z-dock to analyze the bioactive prospective of the venom proteins of P. volitans against the essential virulence proteins of H. pylori responsible for inducing cancer. Our in silico docking study using a computational model of the venom proteins and H. pylori proteins has displayed the possible interactions between these proteins. The results revealed that P. volitans hyaluronidase and PV toxin's venom proteins effectively interact with H. pylori proteins Cag A, Cag L, GGT, Cag D, and urease that may be promising proteins in cancer therapy.

Effect of pterois volitans (lionfish) venom on cholinergic and dopaminergic systems

Pterois volitans venom induces muscular fibrillation, which results from nerve transmission caused by the presence of acetylcholine (ACh). It also has cardiovascular effects that are due to its actions on muscarinic and nicotinic cholinergic receptors. In this study, we characterized the effects of P. volitans venom on nicotinic acetylcholine receptors (nAChRs) and dopaminergic neurons. After exposure to P. volitans venom, acetylcholinesterase (AChE) mRNA levels and the expression of the α2 subunit of nAChR increased in zebrafish embryos (15-20 somites). In addition, the lionfish venom blocked zebrafish α2 nAChR subunit functional expression and the ACh-induced response of human neuronal α3β2 receptors. The latter receptor was blocked by a protein fraction named F2, which was isolated from P. volitans venom using reversed phase high performance liquid chromatography (RP-HPLC). This venom causes death in dopaminergic neurons, and affects the cholinergic system. The effect of these two systems may result in retarded embryonic development of zebrafish, since the two systems function in a related manner to control growth hormone secretion.

Biochemical characterization of the venom of Central American scorpion Didymocentrus krausi Francke, 1978 (Diplocentridae) and its toxic effects in vivo and in vitro

Venoms of medically important scorpions from Buthidae family have been intensively studied, in contrast to non-buthid venoms, for which knowledge is scarce. In this work, we characterized the venom of a Diplocentridae species, Didymocentrus krausi, a small fossorial scorpion that inhabits the Tropical Dry Forest of Central America. D. krausi venom soluble fraction contains proteases with enzymatic activity on gelatin and casein. Mass spectrometry and venomic analysis confirmed the presence of elastase-like, cathepsin-O-like proteases and a neprilysin-like metalloproteinase. We did not detect phospholipase A₂, C or D, nor hyaluronidase activity in the venom. By homology-based venom gland transcriptomic analysis, NDBPs, a β-KTx-like peptide, and other putative toxin transcripts were found, which, together with a p-benzoquinone compound present in the venom, could potentially explain its direct hemolytic and cytotoxic effects in several mammalian cell lines. Cytotoxicity of D. krausi venom was higher than the effect of venoms from two buthid scorpion species distributed in Costa Rica, Centruroides edwardsii and Tityus pachyurus. Even though D. krausi venom was not lethal to mice or crickets, when injected in mouse gastrocnemius muscle at high doses it induced pathological effects at 24 h, which include myonecrosis, weak hemorrhage, and inflammatory infiltration. We observed an apparent thrombotic effect in the skin blood vessels, but no in vitro fibrinogenolytic activity was detected. In crickets, D. krausi venom induced toxicity and paralysis in short periods of time.

Advances in the characterization of the Scorpaena plumieri cytolytic toxin (Sp-CTx)

Proteins that account for the hemolytic activity found in scorpaeniform fish venoms are responsible for the majority of the effects observed upon envenomation, for instance, neurotoxic, cardiotoxic and inflammatory effects. These multifunctional toxins, described as protein lethal factors and referred to as cytolysins, are known to be extremely labile molecules. In the present work, we endeavored to overcome this constraint by determining optimal storage conditions for Sp-CTx, the major bioactive component from the scorpionfish Scorpaena plumieri venom. This cardiotoxic hemolytic cytolysin is a large dimeric glycoprotein (subunits of ≈65 kDa) with pore-forming ability. We were able to establish storage conditions that allowed us to keep the toxin partially active for up to 60 days. Stability was achieved by storing Sp-CTx at -80 and -196 °C in the presence of glycerol 10% in a pH 7.4 solution. It was demonstrated that the hemolytic activity of Sp-CTx is calcium dependent, being abolished by EDTA and zinc ions. Furthermore, the toxin exhibited its maximal hemolytic activity at pH between 8 and 9, displaying typical N- and O- linked glycoconjugated residues (galactose (1-4) N-acetylglucosamine and sialic acid (2-3) galactose in N- and/or O-glycan complexes). The hemolytic activity of Sp-CTx was inhibited by phosphatidylglycerol and phosphatidylethanolamine, suggesting a direct electrostatic interaction lipid - toxin in the pore-formation mechanism of action of this toxin. In addition, we observed that the hemolytic activity was inhibited by increasing doses of cholesterol. Finally, we were able to show, for first time, that Sp-CTx is at least partially responsible for the pain and inflammation observed upon envenomation. However, while the edema induced by Sp-CTx was reduced by pre-treatment with aprotinin and HOE-140, pointing to the involvement of the kallikrein-kinin system in this response, these drugs had no significant effect in the toxin-induced nociception. Taken together, our results could suggest that, as has been already reported for other fish cytolysins, Sp-CTx acts mostly through lipid-dependent pore formation not only in erythrocytes but also in other cell types, which could account for the pain observed upon envenomation. We believe that the present work paves the way towards the complete characterization of fish cytolysins.