Neurotoxicology
Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw in Hankey's Clinical Neurology, 2020
Ciguatera is a unique toxicologic syndrome caused by ingestion of ciguatoxin, a poison produced by microscopic marine organisms called dinoflagellates and bioaccumulated in large reef fish such as barracuda, amberjack, sturgeon, sea bass, or grouper. The neurologic toxicity of ciguatoxin ciguatera appears similar to peripheral neuropathies with painful paresthesia of the extremities, however, it is notable for the unique finding of a sensation of hot and cold reversal (patients report cold objects feel scalding hot and vice versa). Ciguatoxin's effects are mediated by its ability to maintain sodium channels in an open position leading to continuous cell depolarization rather than neurodegeneration as with most toxic neuropathies. GI symptoms are also prominent in most cases. Treatment is primarily supportive, and no effective antidote has been identified. Some early studies appeared to show improvement with mannitol administration, but a subsequent double-blind randomized controlled trial showed no benefit.
Ciguatera: A Treating Physician's Perspective on a Global Illness
Dongyou Liu in Handbook of Foodborne Diseases, 2018
In 1993, Lewis and Holmes (53) presented comments that are well supported today. Ciguatera results from consumption of polycyclic ether toxins of the ciguatoxin class but not maitotoxins or okadaic acid. These ciguatoxins “likely arise through biotransformation and acid-catalyzed spiroisomerization of gambiertoxin-4A produced by Gambierdiscus toxicus and it is unlikely that other toxic benthic dinoflagellates are involved.” There are differences in areas of disease acquisition of a given reef for reasons unknown. Initiating events for an outbreak of ciguatera are likely environmental and/or genetic, with man-made effects on the reef suspected but not confirmed. Ciguatoxins ascend in the food chain with concentration in each predatory fish related to a variety of factors, including but not limited to rate of dietary intake, efficiency of assimilation, degree and nature of transformation of toxin(s), and rate of growth of host fish.
Macro and Micro Algal Impact on Marine Ecosystem
Gokare A. Ravishankar, Ranga Rao Ambati in Handbook of Algal Technologies and Phytochemicals, 2019
In marine environments, certain algal toxins are secreted which often reach humans in potent concentrations as they make their way up the food chain. Dinoflagellates such as Gambidiercus toxicus are mainly responsible for producing the toxins (ciguatoxin and maitotoxin) that accumulate in the flesh of over 400 species of marine predatory fish and cause ciguatera fish poisoning. Humans are affected when they consume fish whose flesh is laden with ciguatoxin (Figure 23.1) or maitotoxin. Affected individuals suffer from a host of gastrointestinal, cardiovascular and neurological disorders (Friedman et al. 2017). Paralytic shellfish poisoning is another instance of seafood-based poisoning caused by dinoflagellates like Alexandrium spp. (Van Dolah 2000). Bivalve mollusks accumulate these toxins in their tissue during filter feeding. Subsequently they are passed up the food chain and result in fatalities in humans, birds (Nisbet 1983) and humpback whales (Geraci 1989). Saxitoxin (Figure 23.1) exerts its effect by inhibiting the channel conductance of voltage gated sodium channels (Van Dolah 2000). Diarrhetic shellfish poisoning is caused by Dinophysis fortii and manifests itself with severe diarrhea and vomiting. The compounds responsible for exerting these effects are Okadaic acid (Figure 23.1), Dinophysis Toxin (DTX-1) and DTX-2. Neurotoxic shellfish poisoning is caused by brevitoxin produced by blooms of Gymnodinium breve. Symptoms include severe muscle pain, numbness and tingling of the perioral area, nausea and loss of motor control. Amnesic shellfish poisoning is the only known case of shellfish poisoning which is caused by domoic (Figure 23.1) acid from a Bacillariophyte (Pseudo-nitzschia multiseries) which results in amnesia (either permanent or temporary) and gastro-intestinal effects like nausea, vomiting, diarrhea, etc.
Nature and applications of scorpion venom: an overview
Published in Toxin Reviews, 2020
Saadia Tobassum, Hafiz Muhammad Tahir, Muhammad Arshad, Muhammad Tariq Zahid, Shaukat Ali, Muhammad Mohsin Ahsan
Toxins interact with VGSCs in two ways. It either results in a blockage of pore when the neurotoxin physically obstructs the pore and inhibits the conductance of sodium ions, or in a modification of the gating, that altered the voltage-dependence and gating kinetics of the ion channels. Toxins that interact with the site 1 use first mechanism. For example, tetrodotoxin (TTX) and sexitoxin (STX) are pore blockers of site 1. Grayanotoxin and batrachotoxin are site 2 toxins which prevent inactivation and therefore, channel remain persistently active (Stevens et al. 2011). Scorpion α-toxins and sea anemone toxins bind to site 3 and inhibit the inactivation (Possani et al. 2000). Scorpion β-toxins and spider β-toxins are site 4 toxins which shift the activation toward hyperpolarized state (Shichor et al. 2002). Site 5 toxins like ciguatoxins and brevetoxins display a real effect upon binding with VGSC, for example, inhibition of activation and the hyperpolarizing shift of voltage-dependence activation. Finally, δ-conotoxins interact with site 6 and produce similar outcomes as the site 3 neurotoxins by inhibiting inactivation (Figure 3) (Stevens et al. 2011).
Ciguatera fish poisoning in France: experience of the French Poison Control Centre Network from 2012 to 2019
Published in Clinical Toxicology, 2021
Luc de Haro, Corinne Schmitt, Sandra Sinno-Tellier, Nathalie Paret, David Boels, Gaël Le Roux, Jérôme Langrand, Nicolas Delcourt, Magali Labadie, Nicolas Simon
Ciguatera fish poisoning (CFP) is frequent in the tropics, with an estimated 50,000 to 100,000 patients poisoned per year within the endemic area [1–3]. It is caused by ingesting fish contaminated with ciguatoxins produced by dinoflagellates of the genus Gambierdiscus [1–4]. Over 400 species of fish have been involved [2,4]. The objective of this study was to discuss the experience French Poison Control Centres (French PCCs) had of ciguatera over an 8-year period with patients poisoned in endemic areas (other countries or French overseas territories) or non-endemic (Mainland France) and to emphasize territorial differences in poisonings.
Antifouling activity of portimine, select semisynthetic analogues, and other microalga-derived spirocyclic imines
Published in Biofouling, 2018
Darby G. Brooke, Gunnar Cervin, Olivier Champeau, D. Tim Harwood, Henrik Pavia, Andrew I. Selwood, Johan Svenson, Louis A. Tremblay, Patrick L. Cahill
Some of the most potent known natural products are synthesised by microalgae, such as paralytic shellfish toxins, ciguatoxins, and okadaic acid (Sasso et al. 2012). The benefit of these compounds to the producing organisms is uncertain, although in pelagic microalgae it is hypothesised that they coordinate ‘bloom’ events via quorum sensing and inter-cell communication pathways (Ianora et al. 2006). Some benthic microalgae are also known to produce biotoxins. Benthic marine organisms are subject to intense competition for space (Wahl 2009), and it is conceivable that benthic microalgae produce natural products which display AF activities.
Related Knowledge Centers
- Brevetoxin
- Depolarization
- Domoic Acid
- Nervous System
- Sodium Channel
- Toxicity
- Ether
- Ciguatera Fish Poisoning
- Blood–Brain Barrier
- Median Lethal Dose