Abstract
Sea anemones are a rich source of biologically active substances. In crayfish muscle fibers, Bunodosoma cangicum whole venom selectively blocks the I K(Ca) currents. In the present study, we report for the first time powerful hemolytic and neuroactive effects present in two different fractions obtained by gel-filtration chromatography from whole venom of B. cangicum. A cytolytic fraction (Bcg-2) with components of molecular mass ranging from 8 to 18 kDa elicited hemolysis of mouse erythrocytes with an EC50 = 14 microg/ml and a maximum dose of 22 microg/ml. The effects of the neuroactive fraction, Bcg-3 (2 to 5 kDa), were studied on isolated crab nerves. This fraction prolonged the compound action potentials by increasing their duration and rise time in a dose-dependent manner. This effect was evident after the washout of the preparation, suggesting the existence of a reversible substance that was initially masking the effects of an irreversible one. In order to elucidate the target of Bcg-3 action, the fraction was applied to a tetraethylammonium-pretreated preparation. An additional increase in action potential duration was observed, suggesting a blockade of a different population of K+ channels or of tetraethylammonium-insensitive channels. Also, tetrodotoxin could not block the action potentials in a Bcg-3-pretreated preparation, suggesting a possible interaction of Bcg-3 with Na+ channels. The present data suggest that B. cangicum venom contains at least two bioactive fractions whose activity on cell membranes seems to differ from the I K(Ca) blockade described previously.
Highlights
Sea anemones contain a variety of biologically active substances including polypeptide toxins which affect sodium and potassium channels [1,2]
Sea anemone neurotoxins that affect sodium channels slow down the inactivation phase of the currents without affecting the activation process, so that the channels remain open for a longer period of time leading to a prolongation of the action potential duration [1,3]
The present results show the presence of powerful hemolytic and neuroactive substances in two fractions obtained by gelfiltration chromatography of B. cangicum whole venom
Summary
Sea anemones contain a variety of biologically active substances including polypeptide toxins which affect sodium and potassium channels [1,2]. Cytolysins that act on cell membranes (pore-forming toxins) have been described [3,4]. All these types of peptides have been isolated from different species such as Anemonia sulcata [5], Stoichactis helianthus [6], Actinia equina [7], Bunodosoma granulifera [2,8,9] and Bunodosoma caissarum [10,11]. The venom inhibits the binding of radiolabeled DTX to synaptosomal membranes [13] These studies [13,15] described interesting neuroactive effects of whole venom, no attempt was made to purify the toxin(s) responsible for such actions on ionic channels. The presence of cytolytic toxins in the venom has not been explored previously
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