ciguatoxin-2 and Ciguatera-Poisoning

Ciguatera fish poisoning (CFP) and neurotoxic shellfish poisoning syndromes are induced by the consumption of seafood contaminated by ciguatoxins and brevetoxins. Both toxins cause sensory symptoms such as paresthesia, cold dysesthesia and painful disorders. An intense pruritus, which may become chronic, occurs also in CFP. No curative treatment is available and the pathophysiology is not fully elucidated. Here we conducted single-cell calcium video-imaging experiments in sensory neurons from newborn rats to study in vitro the ability of Pacific-ciguatoxin-2 (P-CTX-2) and brevetoxin-1 (PbTx-1) to sensitize receptors and ion channels, (i.e., to increase the percentage of responding cells and/or the response amplitude to their pharmacological agonists). In addition, we studied the neurotrophin release in sensory neurons co-cultured with keratinocytes after exposure to P-CTX-2. Our results show that P-CTX-2 induced the sensitization of TRPA1, TRPV4, PAR2, MrgprC, MrgprA and TTX-r NaV channels in sensory neurons. P-CTX-2 increased the release of nerve growth factor and brain-derived neurotrophic factor in the co-culture supernatant, suggesting that those neurotrophins could contribute to the sensitization of the aforementioned receptors and channels. Our results suggest the potential role of sensitization of sensory receptors/ion channels in the induction or persistence of sensory disturbances in CFP syndrome.

Topics: Animals; Animals, Newborn; Aquatic Organisms; Ciguatera Poisoning; Ciguatoxins; Marine Toxins; Models, Animal; Oxocins; Pacific Ocean; Pain; Pruritus; Rats; Rats, Wistar; Sensory Receptor Cells

Ciguatoxins are the major toxins responsible for ciguatera fish poisoning, a disease dominated by muco-cutaneous sensory disorders including paresthesiae, cold dysesthesia and pruritus. While the ciguatoxins are well known to target voltage-gated sodium channels (VGSCs), the ensuing molecular mechanisms underlying these sensory disorders remain poorly understood. In this study, we propose a primary sensory neuron-keratinocyte co-culture as an appropriate model to study the neuro-cutaneous effects of ciguatoxins. Using this model, we show for the first time that nanomolar concentrations of Pacific ciguatoxin-2 (P-CTX-2) induced a VGSC-dependent release of substance P (SP) and calcitonin gene-related peptide (CGRP). As these neuropeptides are known mediators of pain and itch sensations, the ciguatoxin-induced sensory disturbances in ciguatera fish poisoning may involve the release of these neuropeptides. We further determined time- and P-CTX-2 concentration-dependence of the release of SP and CGRP from the co-culture model. Moreover, we highlighted the influence of extracellular calcium on the release of neuropeptides elicited by P-CTX-2. These findings underline the usefulness of this novel in vitro model for studying the cellular and molecular mechanisms of the neuro-cutaneous effects of ciguatoxins, which may assist with identifying potential therapeutics for ciguatera fish poisoning.

Topics: Animals; Calcitonin Gene-Related Peptide; Calcium; Ciguatera Poisoning; Ciguatoxins; Coculture Techniques; Humans; Immunohistochemistry; Keratinocytes; Models, Biological; Neuropeptides; Rats; Sensory Receptor Cells