Abstract
Ciguatoxins (CTX) and brevetoxins (BTX) are polycyclic ethereal compounds biosynthesized by the worldwide distributed planktonic and epibenthic dinoflagellates of Gambierdiscus and Karenia genera, correspondingly. Ciguatera, evoked by CTXs, is a type of ichthyosarcotoxism, which involves a variety of gastrointestinal and neurological symptoms, while BTXs cause so-called neurotoxic shellfish poisoning. Both types of toxins are reviewed together because of similar mechanisms of their action. These are the only molecules known to activate voltage-sensitive Na+-channels in mammals through a specific interaction with site 5 of its α-subunit and may compete for it, which results in an increase in neuronal excitability, neurotransmitter release and impairment of synaptic vesicle recycling. Most marine ciguatoxins potentiate Nav channels, but a considerable number of them, such as gambierol and maitotoxin, have been shown to affect another ion channel. Although the extrinsic function of these toxins is probably associated with the function of a feeding deterrent, it was suggested that their intrinsic function is coupled with the regulation of photosynthesis via light-harvesting complex II and thioredoxin. Antagonistic effects of BTXs and brevenal may provide evidence of their participation as positive and negative regulators of this mechanism.
Highlights
Ciguatera fish poisoning (CFP) is one of the most important non-bacterial disease nowadays, which is induced by consummation of fish contaminated by specific dinoflagellates of Gambierdiscus lineage [1]
The source of toxins is another unicellular dinoflagellate microalga Karenia brevis. These pathologies—CFP and Neurotoxic shellfish poisoning (NSP)—and the toxins evoking them are often considered together because on the one hand, the toxins share closely similar ladder-shape polycyclic ether structures and on the other hand, they are well known as the unique natural activators of the same target, namely voltage-gated Na+ channels (VGSC) [7,8,9]
The NSP habitat was associated with Gulf of Mexico exclusively, where the brevetoxins (BTX) produced by the dinoflagellate Karenia brevis are responsible for high fish and marine mammal mortality [41]
Summary
Ciguatera fish poisoning (CFP) is one of the most important non-bacterial disease nowadays, which is induced by consummation of fish contaminated by specific dinoflagellates of Gambierdiscus lineage [1]. Neurotoxic shellfish poisoning (NSP) [4] shows symptoms similar to CFP, this has less severe forms in humans It is highly dangerous for big marine animals, such as bottlenose dolphins [5,6]. The research field under consideration has evolved from a set of quite simple facts and ideas through step-by-step sophistication similar to the growth of areal of microalgae, producing the compounds of interest At first, these dinoflagellates were found within certain limited areas in tropical waters, their habitat seems to be much more extensive nowadays. All of the abovementioned points form the ground for the unfailing and thorough interest in the physiological, ecological and biomedical aspects of the problem of the toxins produced by these dinoflagellates It is reflected in the number of already published studies and basic reviews (see [8,12]). (v) intracellular functions of these substances in the marine algae Gambierdiscus and Karenia, which have been poorly studied until now
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