Puffer fish poisoning in Bangladesh: clinical and toxicological results from large outbreaks in 2008

Physiological responses to different temperature in the liver of Takifugu rubripes larvae revealed by integrated transcriptomic and metabolomic analyses

Water temperature plays a vital role in shaping the physical conditions crucial for the growth, development and reproduction of fish species. Since limited comprehensive multi-omics analyses exploring the molecular mechanisms of temperature influences on the early life stages of fish. Here, the effects of temperature variations on the growth of Takifugu rubripes, a commercial teleost farmed in Asia were investigated. Nineteen-days-old fugu larvae were subjected to different temperature (15 °C-T15, 20 °C-T20, 25 °C-T25) for 30 days. Liver tissues were harvested at the end of the study for transcriptomic and metabolomic assessments. The T. rubripes larvae in the T15 group showed a significant decrease in total length and body weight compared to the T20 and T25 groups (p < 0.05). 1344, 416, and 2080 differentially expressed genes (DEGs) were identified in T15-vs-T20, T20-vs-T25, and T15-vs-T25 comparisons, respectively. Those DEGs were mainly enriched in metabolic, protein digestion and absorption, steroid biosynthesis, and glycerophospholipid metabolism pathways. 15 DEGs were randomly selected for RNA-seq validation, and the transcriptome results were consistent with the qPCR validation results, illustrating the accuracy of transcriptome sequencing. 340, 238, and 330 significantly different metabolites (SDMs) were identified in positive modes when comparing in T15-vs-T20, T20-vs-T25, and T15-vs-T25, respectively. Additionally, 145, 137, and 159 SDMs were identified in negative modes within the three comparisons. Those SDMs enriched in biosynthesis of secondary metabolites, glycerophospholipid metabolism, linoleic acid metabolism, and metabolic pathways. The integration of transcriptomic and metabolomic analyses indicated that DEGs and SDMs mainly enriched in metabolic pathways. These discoveries provide valuable insights into the effects of temperature on fish larvae in aquaculture, laying a foundation for future breeding approaches aimed at improving the growth of T. rubripes.

Electrocardiogram indicators for risk of respiratory failure in patients with tetrodotoxin poisoning

Tetrodotoxin blocks voltage-gated sodium channels, which are responsible for the initiation and propagation of action potentials. Impairment of action potential conduction in myocardial cells affects the cardiac conduction system and can influence electrocardiogram output. In this retrospective study, we investigated whether tetrodotoxin poisoning prolong the PR, QRS and QTc intervals, which might be used as prognostic indices of respiratory failure after tetrodotoxin poisoning. Additionally, we evaluated whether these changes correlate with tetrodotoxin concentration in the body. Eighty-four patients were divided into two groups according to the development of tetrodotoxin poisoning-related respiratory failure requiring mechanical ventilation after pufferfish ingestion. The incidence of respiratory failure was 17.9%. There was no difference in the delay between pufferfish ingestion and the onset of symptoms between the two groups. The most common electrocardiogram abnormality was QTc prolongation (23.8%), followed by PR prolongation and QRS widening. Patients with QTc prolongation had higher urinary tetrodotoxin concentrations than patients without QTc prolongation, but no differences in the plasma tetrodotoxin concentrations were observed. Two multivariate regression models indicated that the QTc interval and QTc prolongation at presentation were independent factors for the development of respiratory failure after tetrodotoxin poisoning. Tetrodotoxin poisoning can cause electrocardiogram changes indicative of changes in the cardiac conduction system. In particular, QTc prolongation was associated with the development of respiratory failure and was correlated with the urinary tetrodotoxin concentration. It is recommended that patients poisoned with tetrodotoxin who exhibit QTc prolongation undergo regular and frequent assessments of their respiration status to prevent sudden respiratory arrest.

Tetrodotoxin: The State-of-the-Art Progress in Characterization, Detection, Biosynthesis, and Transport Enrichment

Tetrodotoxin (TTX) is a neurotoxin that binds to sodium channels and blocks sodium conduction. Importantly, TTX has been increasingly detected in edible aquatic organisms. Because of this and the lack of specific antidotes, TTX poisoning is now a major threat to public health. However, it is of note that ultra-low dose TTX is an excellent analgesic with great medicinal value. These contradictory effects highlight the need for further research to elucidate the impacts and functional mechanisms of TTX. This review summarizes the latest research progress in relation to TTX sources, analogs, mechanisms of action, detection methods, poisoning symptoms, therapeutic options, biosynthesis pathways, and mechanisms of transport and accumulation in pufferfish. This review also provides a theoretical basis for reducing the poisoning risks associated with TTX and for establishing an effective system for its use and management to ensure the safety of fisheries and human health.

Determination of tetrodotoxin in human plasma and urine using online MCX SPE column cleanup coupled with liquid chromatography-tandem mass spectrometry

An efficient technique for quantitative analysis of tetrodotoxin (TTX) in human plasma and urine has been developed, which combines liquid chromatography-tandem mass spectrometry (LC-MS/MS) with online MCX solid phase extraction (SPE) cleanup. Sample preparation, including extraction with acetonitrile containing 0.5 % acetate acid, centrifugation, and filtration, was followed by online SPE cleanup. The whole run-time was less than 15 min, including online cleanup, chromatographic separation, and re-equilibration of the online SPE - LC-MS/MS system. The parameters of sample extraction, purification, separation, and detection were optimized. The matrix-matched internal standard calibration standard curves with linear regression coefficients larger than 0.9990 were established for quantification. The LOD and LOQ for this approach were determined to be 0.1 ng/mL and 0.3 ng/mL, respectively. The recoveries for varied concentrations of TTX in human plasma and urine were 84.9-104.2 % and 89.2-109.6 %, respectively. The matrix effects of TTX in human plasma and urine matrices were 85.5 % and 74.3 %, respectively, and both the inter- and intra-day precision values were less than 9.5 %. This analytical method was successfully employed for detecting TTX in biological samples from a poisoned patient who accidentally ingested the nassarius glans.

The Prevalence of Marine Lipophilic Phycotoxins Causes Potential Risks in a Tropical Small Island Developing State

Tropical small island developing states (SIDS), with their geographical isolation and limited resources, heavily rely on the fisheries industry for food and revenue. The presence of marine lipophilic phycotoxins (MLPs) poses risks to their economy and human health. To understand the contamination status and potential risks, the Republic of Kiribati was selected as the representative tropical SIDS and 55 species of 256 coral reef fish encompassing multiple trophic levels and feeding strategies were collected to analyze 17 typical MLPs. Our results showed that the potential risks of ciguatoxins were the highest and approximately 62% of fish species may pose risks for consumers. Biomagnification of ciguatoxins was observed in the food web with a trophic magnification factor of 2.90. Brevetoxin-3, okadaic acid, and dinophysistoxin-1 and -2 were first reported, but the risks posed by okadaic acid and dinophysistoxins were found to be negligible. The correlation analysis revealed that fish body size and trophic position are unreliable metrics to indicate the associated risks and prevent the consumption of contaminated fish. The potential risks of MLPs in Kiribati are of concern, and our findings can serve as valuable inputs for developing food safety policies and fisheries management strategies specific to tropical SIDS contexts.

Assessment of Human Health Impacts from Invasive Pufferfish (Attacks, Poisonings and Fatalities) across the Eastern Mediterranean

The silver-cheeked toadfish Lagocephalus sceleratus (Gmelin 1789), and to a lesser degree the orange spotted toadfish Torquigener hypselogeneion (Bleeker, 1852), pose threats to human health from physical attacks and poisonings in the Eastern Mediterranean Sea. This study reviewed human health-related impacts resulting from these pufferfish, compiling and assessing records from online sources, the peer-reviewed literature, medical records, personal interviews, and observations across the Eastern Mediterranean in the years 2004 to 2023. A total of 198 events impacting human health were documented: 28 records of physical attacks, at least 144 non-lethal poisoning episodes, and 27 human fatalities resulting from consumption. The majority of the reported incidences occurred in Syria, Türkiye, and Lebanon. Most physical attacks occurred in summer, while most poisoning events occurred during winter. The number of recorded incidents greatly increased after 2019, especially with regard to poisonings, yet whether this is related to greater media attention, or to increased fish abundance is unclear. This is the first comprehensive study to collate findings on attacks, poisonings and fatalities caused by these pufferfish in the Mediterranean Sea, and may help in improving national health policies. We urge the continuation of national campaigns to caution residents and tourists of these species' high toxicities and potential aggressiveness.

Tetrodotoxin in bivalve mollusks: An integrated study towards the comprehension of the influencing factors of a newly native phenomenon

Tetrodotoxins (TTXs) are potent neurotoxins named after the Tetraodontidae fish family. The ingestion of TTX-contaminated flesh can cause neurotoxic symptoms and can lead to death. In 2017 symptoms the European Food Safety Authority (EFSA) recognized the threat to food safety resulting from TTX exposure via food consumption and, thus, proposed a safety limit of 44 μg/kg of TTX in marine gastropods and bivalves. To date, however, TTXs have not yet been included in the list of biotoxins to be monitored within the European Union, even though, in a few cases, levels of TTX found were higher than the EFSA limit. The origin of TTX production is debated and the roles of both biotic and abiotic factors on TTX-mediated toxic events remain unclear. In order to meet these knowledge requests the present study was aimed to investigate the role of seawater temperature, pH, water conductivity, and oxygen saturation, along with the marine phytoplankton community and the bacterial community of mussels and oysters on the accumulation of TTX and analogues in the bivalves. Abiotic parameters were measured by means of a multi-parametric probe, phytoplankton community was analyzed by optic microscopy while microbial community was described by amplicon metataxonomic sequencing, TTXs concentration in the collected matrices were measured by HILIC-MS/MS. A possible role of seawater pH and temperature, among the investigated abiotic factors, in regulating the occurrence of TTXs was found. Regarding biotic variables, a possible influence of Vibrio, Shewanella and Flavobacteriaceae in the occurrence of TTXs was found. Concurrently, Prorocentrum cordatum cell numbers were correlated to the incidence of TTX in mussels. The results herein collected suggest that environmental variables play a consistent part in the occurrence of TTX in the edible bivalve habitats, and there are also indications of a potential role played by specific bacteria taxa in association with phytoplankton.

The Exploitation of Toxic Fish from the Terminal Pleistocene in Maritime Southeast Asia: A Case Study from the Mindoro Archaeological Sites, Philippines

Representatives of the Diodontidae family (porcupinefish) are known to have been fished by prehistoric Indo-Pacific populations; however, the antiquity of the use of this family is thus far unknown. We report here on the presence of Diodontidae in the archaeological sites of Bubog I, II, and Bilat in Mindoro, Philippines, dating back to c. 13,000 BP (Before Present). This evidence demonstrates the early exploitation by islanders of poisonous fish. Every part of porcupinefish can be toxic, but the toxicity is mostly concentrated in some organs, while other parts are edible. The continuous presence of Diodontidae remains throughout the stratigraphic record of these Philippines shell middens suggests that porcupinefish were prepared by human inhabitants of the sites to render them safe for consumption, indicating an advanced cultural knowledge of the preparation needed to separate the toxic principle from the edible parts. This constitutes one of the rare examples of poison processing by humans, aside from the contentious wooden stick poison applicator from Border Cave (South Africa).

Sensitive and rapid detection of tetrodotoxin based on gold nanoflower-and latex microsphere-labeled monoclonal antibodies

Tetrodotoxin (TTX) could result in serious diseases due to its extremely high neurotoxicity. Thus, it is of great importance to measure TTX for food safety. In this study, an anti-TTX monoclonal antibody with good specificity and high affinity was used to develop the immunochromatographic test strips (ICTS). Gold nanoflower (AuNF) with multiple branches and latex microsphere (LM) with large particle size as signal reporters were employed for improving the sensitivity of test strips. Both AuNF and LM probes are stable, and the developed ICTS were specific to TTX, demonstrating no cross-reactivity with other marine toxins. The linear range of AuNF- and LM-based strips for TTX was 9.49-330.98 ng/mL and 5.40-443.19 ng/mL, respectively. The limit of detection (LOD) of AuNF- and LM-based strips was determined to be 9.49 ng/mL and 5.40 ng/mL, respectively. In summary, the developed ICTS based on AuNF and LM signal probes displayed enhancement of sensitivity and provided rapid and specific detection of TTX.

A Case of Puffer Fish Poisoning from United Arab Emirates

Puffer fish (Lagocephalus sceleratus) is a well-known source of deadly food poisoning due to a neurotoxin, called tetrodotoxin. Cases of tetrodotoxin poisoning are common along the coasts of East Asian countries but rare in the Arabian Gulf region. Here, we report a case of a 19-year-old man who presented with signs and symptoms suggestive of puffer fish poisoning. Dietary history was the key to diagnosis though laboratory investigations and imaging yielded normal results. Early diagnosis and proper supportive management are essential for survival.

Simultaneous analysis of paralytic shellfish toxins and tetrodotoxins in human serum by liquid chromatography coupled to Q-Exactive high-resolution mass spectrometry

Paralytic shellfish toxins (PSTs) and tetrodotoxins (TTXs) are powerful neurotoxins. Previous research reported that PSTs and TTXs are found together in seafoods and may pose a serious hazard to public health. In this study, a new analytical method combining modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) with high-performance liquid chromatography coupled to Q-Exactive Orbitrap high-resolution mass spectrometry was developed and validated for the quantification of 10 PSTs and 2 TTXs in human serum. Chromatographic separation was achieved using the HILIC TSK-Gel Amide-80 column. The mass spectrometer was operated in full scan/dd-MS²(data-dependent MS²) mode, and for quantification analysis. The dd-MS² resolution was set to 17,500 fullwidthat halfmaximum （FWHM）. Results showed that methanol with 1 % (v/v) acetic acid extraction combined with 50 mg graphitized carbon black (GCB) and 50 mg octadecyl bonded silica gel (C18) was most suitable for purification. The mean recovery for all toxins ranged from 85.3 % to 118.2 % (RSD < 12 %). The limits of detection and quantification for human serum were in the ranges of 0.67-2.61 and 2.23-8.69 ng mL^-1, respectively. The method was applied to analyze toxins in serum samples obtained from three poisoned patients in a case of poisoning caused by consumption of toxin-contaminated gastropoda (Bullacta exerata). The study has important application for rapid and accurate diagnosis of PSTs and TTXs toxin poisoning patients in clinic.

Tetrodotoxin and Its Analogues in Food: Recent Updates on Sample Preparation and Analytical Methods Since 2012

Tetrodotoxin (TTX), found in various organisms including pufferfish, is an extremely potent marine toxin responsible for numerous food poisoning accidents. Due to its serious toxicity and public health threat, detecting TTX and its analogues in diverse food matrices with a simple, fast, efficient method has become a worldwide concern. This review summarizes the advances in sample preparation and analytical methods for the determination of TTX and its analogues, focusing on the latest development over the past five years. Current state-of-the-art technologies, such as solid-phase microextraction, online technology, novel injection technology, two-dimensional liquid chromatography, high-resolution mass spectrometry, newly developed lateral flow immunochromatographic strips, immunosensors, dual-mode aptasensors, and nanomaterials-based approaches, are thoroughly discussed. The advantages and limitations of different techniques, critical comments, and future perspectives are also proposed. This review is expected to provide rewarding insights to the future development and broad application of pretreatment and detection methods for TTX and its analogues.

Rapid identification of Takifugu genus using visual loop-mediated isothermal amplification

Some Takifugu species are commonly found in the coastal areas of China, Japan, Thailand, and Korea and cause pufferfish poisoning, which is toxic and even lethal to humans. From 2010 to 2015, there were 430 cases of pufferfish poisoning worldwide, resulting in 52 deaths. Identification of Takifugu species is imperative to reduce financial losses and ensure food safety. Here, visual loop-mediated isothermal amplification (LAMP) was applied to identify Takifugu species. Conserved regions within the mitochondrial DNA among different Takifugu species were selected to design LAMP primers. In 55 min of amplification, sufficient DNA was obtained to observe the results with the naked eye, without the need for complicated instruments. The method was highly specific, with no cross-detection of 17 other fish species, namely, 7 Tetraodontiformes species and 10 commercially important fish. The method showed a detection limit of 0.1 ng Takifugu DNA and was successfully validated to detect Takifugu in cooked fish and the vomitus of poisoned patients. This rapid and visual LAMP method is a useful tool to prevent false labeling, protect consumer rights, and reduce the risk of pufferfish poisoning. PRACTICAL APPLICATION: The loop-mediated isothermal amplification method established in this study can identify cooked or digested fish products containing 1% or more of Takifugu. Therefore, it can be used for the visual detection of Takifugu products and the medical diagnosis of Takifugu poisoning.

An Updated Review of Tetrodotoxin and Its Peculiarities

Tetrodotoxin (TTX) is a crystalline, weakly basic, colorless organic substance and is one of the most potent marine toxins known. Although TTX was first isolated from pufferfish, it has been found in numerous other marine organisms and a few terrestrial species. Moreover, tetrodotoxication is still an important health problem today, as TTX has no known antidote. TTX poisonings were most commonly reported from Japan, Thailand, and China, but today the risk of TTX poisoning is spreading around the world. Recent studies have shown that TTX-containing fish are being found in other regions of the Pacific and in the Indian Ocean, as well as the Mediterranean Sea. This review aims to summarize pertinent information available to date on the structure, origin, distribution, mechanism of action of TTX and analytical methods used for the detection of TTX, as well as on TTX-containing organisms, symptoms of TTX poisoning, and incidence worldwide.

Tetrodotoxin in live bivalve mollusks from Europe: Is it to be considered an emerging concern for food safety?

Tetrodotoxins (TTXs) are a group of potent neurotoxins named after the Tetraodontidae fish family (pufferfish). TTXs have been reported in several animal taxa, both terrestrial and marine. The ingestion of TTX-contaminated flesh can cause serious neurotoxic symptomatology and can eventually lead to death. Traditionally, TTXs have been associated with Asian countries, in particular with pufferfish consumption. However, they have also been reported in bivalve mollusks farmed in the Pacific area and, recently, in European seas. In Europe, different countries have reported TTXs, especially those bordering the Mediterranean Sea. As a consequence, in 2017 the European Food Safety Authority (EFSA) released an opinion with reference to TTX present in marine gastropods and bivalves, proposing a safety limit of 44 µg/kg TTXs in shellfish meat, below which no adverse effects should be observed in humans. Nevertheless, this limit has been exceeded on many occasions in European shellfish and, while for bivalves there have been no registered human intoxications, that is not the case for marine gastropods. However, TTXs have not yet been included in the list of marine biotoxins officially monitored in live bivalve mollusks within the European Union (EU). Thus, the aims of this manuscript are to discuss the increasing occurrence of TTXs in live bivalve mollusks from European sea waters, to acknowledge the still ongoing knowledge gaps that should be covered and to stimulate constructive debate on the eventuality of adopting a shared regulatory context, at least in the EU, for monitoring and managing this potential threat to food safety.

Pufferfish poisoning from Arothron stellatus: The first confirmed case in India with exact DNA sequencing-based species identification

A puffer fish poisoning case was reported from the coastal city of Veraval in the Gujarat state of India with patient reporting symptoms of giddiness, vertigo, aphasia and heaviness of head following consumption of cooked fish. Treatment was purely symptomatic and supportive. The patient was discharged from the hospital in a stable condition after 4 days. The suspected fish species was later identified using DNA (Deoxyribonucleic Acid) sequencing as Arothron stellatus with 100% identity.

From Poison to Promise: The Evolution of Tetrodotoxin and Its Potential as a Therapeutic

Tetrodotoxin (TTX) is a potent neurotoxin that was first identified in pufferfish but has since been isolated from an array of taxa that host TTX-producing bacteria. However, determining its origin, ecosystem roles, and biomedical applications has challenged researchers for decades. Recognized as a poison and for its lethal effects on humans when ingested, TTX is primarily a powerful sodium channel inhibitor that targets voltage-gated sodium channels, including six of the nine mammalian isoforms. Although lethal doses for humans range from 1.5-2.0 mg TTX (blood level 9 ng/mL), when it is administered at levels far below LD₅₀, TTX exhibits therapeutic properties, especially to treat cancer-related pain, neuropathic pain, and visceral pain. Furthermore, TTX can potentially treat a variety of medical ailments, including heroin and cocaine withdrawal symptoms, spinal cord injuries, brain trauma, and some kinds of tumors. Here, we (i) describe the perplexing evolution and ecology of tetrodotoxin, (ii) review its mechanisms and modes of action, and (iii) offer an overview of the numerous ways it may be applied as a therapeutic. There is much to be explored in these three areas, and we offer ideas for future research that combine evolutionary biology with therapeutics. The TTX system holds great promise as a therapeutic and understanding the origin and chemical ecology of TTX as a poison will only improve its general benefit to humanity.

Awareness on tetrodotoxin of illegal activity: forensic issue from a rare homicide case report and literature review

The authors describe an extremely rare case of homicide by injecting tetrodotoxin (TTX) as lethal neurotoxin found in puffer fish. After a thorough investigation, the male victim was found to have a broken stalk from syringe needle in the subcutaneous tissue of left buttock and severe asphyxia confirmed by the main pathological findings at autopsy. During tortuous toxicological analysis，TTX was revealed by ultra high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) as well as acute intoxication confirmed from forensic examination. The literature of qualitative and quantitative determination of TTX from human fluids was also reviewed to expect widely acceptable detection strategies. This case highlighted the importance of TTX toxicant with chemical formula name purchased through e-commerce，so as to improve particular emphasis and supervision on harmful substances possibly using hidden information or illegal means. Histopathological and toxicological results demonstrated here provided a reference and other useful information to the challenges of forensic casework. In general, the case report illustrates medico-legal issues of more attention to the possibility of TTX poisoning in rapid death and the need of routine postmortem tox screening in future practice.

Development and validation of a specific and sensitive liquid chromatography tandem mass spectrometry method for determination of tetrodotoxin in human urine and its pharmacokinetic study

Tetrodotoxin (TTX) exhibits the therapeutic potential in blocking pain and in low doses can safely relieve severe pain. The urinary excretion profiles of TTX in humans have not been reported due to the extremely low lethal dose. In this study, a rapid and specific method based on protein precipitation coupled to liquid chromatography tandem mass spectrometry was developed to determine the level of TTX in human urine samples. 11-Deoxytetrodotoxin was used as an internal standard (IS). Multiple reaction monitoring mode was used for quantification using target fragment ions m/z 320.0 → 162.1 for TTX and m/z 304.0 → 176.0 for 11-deoxyTTX. The separation of analytes was achieved on a hydrophilic interaction liquid chromatography column (250 × 4.6 mm, 5.0 μm). The mobile phase consisted of 5 mM ammonium formate in water (pH = 4.50) and 5 mM ammonium formate in acetonitrile (pH = 4.50). The flow rate was set at 0.80 mL/min in a gradient condition. Calibration plots were linear throughout the range 0.986-98.6 ng/mL of TTX in human urine. The intra-assay accuracies and precisions were within the acceptable range. The method was successfully applied to a urinary excretion study after intravenous administration of TTX to healthy volunteers. The developed method will be helpful for future pharmacological studies of TTX.

Accumulation and Elimination of Tetrodotoxin in the Pufferfish Takifugu obscurus by Dietary Administration of the Wild Toxic Gastropod Nassarius semiplicata

To investigate pufferfish accumulation, elimination, and distribution of tetrodotoxin (TTX), Takifugu obscurus was fed with wild TTX-containing gastropod Nassarius semiplicata to simulate the natural food chain. Three-month-old non-poisonous T. obscurus was fed with wild toxic N. semiplicata at three exposure dose for 28 days, and later, with toxin-free food until day 67. Three fish individuals from each treatment were sampled, and the distribution of TTX in different tissues was measured. The results showed that the accumulation ratio of TTX in the three exposure dose groups ranged from 35.76% to 40.20%. The accumulation ratio in the skin and liver was the highest amongst all tissues, accounting for more than 85% of the total TTX, whereas that in the kidney and gallbladder was the lowest (0.11–0.78%). Studies on the kinetic of TTX accumulation and elimination revealed that the skin was the tissue with the highest accumulation speed constant (8.06), while the liver, kidney, and intestinal tract showed the highest speed of TTX elimination. The time required for TTX reduction to reach the safety limit could be predicted by using standard elimination equations. Qualitative analysis by UPLC-MS/MS revealed the occurrence of seven TTX derivatives in T. obscurus; of these TTX, 5-deoxy TTX, 11-deoxy TTX, 4,9-anhydro TTX were found in all tested tissues.

Tetrodotoxin in marine bivalves and edible gastropods: A mini-review

Tetrodotoxin (TTX) is a potent neurotoxin responsible for countless human intoxications and deaths around the world. The distribution of TTX and its analogues is diverse and the toxin has been detected in organisms from both marine and terrestrial environments. Increasing detections seafood species, such as bivalves and gastropods, has drawn attention to the toxin, reinvigorating scientific interest and regulatory concerns. There have been reports of TTX in 21 species of bivalves and edible gastropods from ten countries since the 1980's. While TTX is structurally dissimilar to saxitoxin (STX), another neurotoxin detected in seafood, it has similar sodium channel blocking action and potency and both neurotoxins have been shown to have additive toxicities. The global regulatory level for the STX group toxins applied to shellfish is 800 μg/kg. The presence of TTX in shellfish is only regulated in one country; The Netherlands, with a regulatory level of 44 μg/kg. Due to the recent interest surrounding TTX in bivalves, the European Food Safety Authority established a panel to assess the risk and regulation of TTX in bivalves, and their final opinion was that a concentration below 44 μg of TTX per kg of shellfish would not result in adverse human effects. In this article, we review current knowledge on worldwide TTX levels in edible gastropods and bivalves over the last four decades, the different methods of detection used, and the current regulatory status. We suggest research needs that will assist with knowledge gaps and ultimately allow development of robust monitoring and management protocols.

Marine Tetrodotoxin as a Risk for Human Health

Tetrodotoxin (TTX) is a toxin mainly occurring naturally in contaminated puffer fish, which are a culinary delicacy in Japan. It is also detected in various marine organisms like globefish, starfish, sunfish, stars, frogs, crabs, snails, Australian blue-ringed octopuses, and bivalve molluscs. TTX is produced by marine bacteria that are consumed mainly by fish of the Tetraodontidae family and other aquatic animals. TTX poisoning through consuming marine snails has recently begun to occur over a wider geographical extent through Taiwan, China, and Europe. This neurotoxin causes food intoxication and poses an acute risk to public health. The aim of this review is to present the most recent information about TTX and its analogues with particular regard to toxicity, methods of analysis, and risk to humans of exposure.

Neurobiology and therapeutic utility of neurotoxins targeting postsynaptic mechanisms of neuromuscular transmission

The neuromuscular junction (NMJ) is the principal site for the translation of motor neurochemical signals to muscle activity. Therefore, the release and sensing machinery of acetylcholine (ACh) along with muscle contraction are two of the main targets of natural toxins and pathogens, causing paralysis. Given pharmacology and medical advances, the active ingredients of toxins that target postsynaptic mechanisms have become of major interest, showing promise as drug leads. Herein, we review key facets of prevalent toxins modulating the mechanisms of ACh sensing and generation of the postsynaptic response, with muscle contraction. We consider the correlation between their outstanding selectivity and potency plus effects on motor function, and discuss emerging data advocating their usage for the development of therapies alleviating neuromuscular dysfunction.

The Incidence of Marine Toxins and the Associated Seafood Poisoning Episodes in the African Countries of the Indian Ocean and the Red Sea

The occurrence of Harmful Algal Blooms (HABs) and bacteria can be one of the great threats to public health due to their ability to produce marine toxins (MTs). The most reported MTs include paralytic shellfish toxins (PSTs), amnesic shellfish toxins (ASTs), diarrheic shellfish toxins (DSTs), cyclic imines (CIs), ciguatoxins (CTXs), azaspiracids (AZTs), palytoxin (PlTXs), tetrodotoxins (TTXs) and their analogs, some of them leading to fatal outcomes. MTs have been reported in several marine organisms causing human poisoning incidents since these organisms constitute the food basis of coastal human populations. In African countries of the Indian Ocean and the Red Sea, to date, only South Africa has a specific monitoring program for MTs and some other countries count only with respect to centers of seafood poisoning control. Therefore, the aim of this review is to evaluate the occurrence of MTs and associated poisoning episodes as a contribution to public health and monitoring programs as an MT risk assessment tool for this geographic region.

The Incidence of Tetrodotoxin and Its Analogs in the Indian Ocean and the Red Sea

Tetrodotoxin (TTX) is a potent marine neurotoxin with bacterial origin. To date, around 28 analogs of TTX are known, but only 12 were detected in marine organisms, namely TTX, 11-oxoTTX, 11-deoxyTTX, 11-norTTX-6(R)-ol, 11-norTTX-6(S)-ol, 4-epiTTX, 4,9-anhydroTTX, 5,6,11-trideoxyTTX, 4-CysTTX, 5-deoxyTTX, 5,11-dideoxyTTX, and 6,11-dideoxyTTX. TTX and its derivatives are involved in many cases of seafood poisoning in many parts of the world due to their occurrence in different marine species of human consumption such as fish, gastropods, and bivalves. Currently, this neurotoxin group is not monitored in many parts of the world including in the Indian Ocean area, even with reported outbreaks of seafood poisoning involving puffer fish, which is one of the principal TTX vectors know since Egyptian times. Thus, the main objective of this review was to assess the incidence of TTXs in seafood and associated seafood poisonings in the Indian Ocean and the Red Sea. Most reported data in this geographical area are associated with seafood poisoning caused by different species of puffer fish through the recognition of TTX poisoning symptoms and not by TTX detection techniques. This scenario shows the need of data regarding TTX prevalence, geographical distribution, and its vectors in this area to better assess human health risk and build effective monitoring programs to protect the health of consumers in Indian Ocean area.

Kidney toxicity related to herbs and dietary supplements: Online table of case reports. Part 3 of 5 series

BACKGROUND

No tabular summary of potentially life-threatening, kidney-toxic dietary supplements (DS; includes herbs) based on PubMed case reports is currently available online and continually updated to forewarn United States consumers, clinicians, and companies manufacturing DS. The purpose of this review was to create an online research summary table of kidney toxicity case reports related to DS.

METHODS

Documented PubMed case reports (1966 to May 2016, and cross-referencing) of DS appearing to contribute to kidney toxicity were listed in "DS Toxic Tables." Keywords included "herb" or "dietary supplement" combined with "kidney" to generate an overview list, and possibly "toxicity" to narrow the selection. Case reports were excluded if they involved herb combinations (some exceptions), Chinese herb mixtures, teas of mixed herb contents, mushrooms, poisonous plants, self-harm, excessive doses (except vitamins/minerals), legal or illegal drugs, drug-herbal interactions, and confounders of drugs or diseases. Since commercial DS often include a combination of ingredients, they were treated separately; so were foods. A few foods with kidney-toxic effects were listed in a fourth table. The spectrum of herbal or DS-induced kidney injuries included kidney stones, nephritis, nephrotic syndrome, necrosis, acute kidney injury (AKI; previously known as acute renal failure [ARF]), chronic kidney disease, kidney transplant, and death.

RESULTS

Approximately 7 herbs (minus 4 no longer for sale) and 10 dietary supplements (minus 3 excluded due to excessive doses + germanium that is no longer sold) have been related to kidney injury case reports published in PubMed (+crosslisting) in the last 50 + years (1966 to May 2016). The implicated herbs include Chinese yew (Taxus celbica) extract, impila (Callilepis laureola), morning cypress (Cupressus funebris Endl), St. John's wort (Hypericum perforatum), thundergod vine (Tripterygium wilfordii hook F), tribulus (Tribulus terrestris) and wormwood (Artemisia herba-alba). No longer sold in the United States are chocolate vine or mu tong (Caulis aristolochiae), guang fang ji (Aristolochia fangchi), ma huang (Ephedra sinica), and Tenshin Tokishigyaku-ka-goshuyu-shokyo-to. The DS include bile (sheep), chlorella, chromium (Cr), CKLS, creatine, gallbladder (fish), glucosamine, hydrazine, N.O.-Xplode, Spanish fly, and excess intakes of vitamins A, C, and D. Germanium (Ge) is not available for sale. The top two DS with the largest number of reported publications, but not always case reports, in descending order, were the aristolochic acid-containing herbs guang fang ji (mistaken identity) and chocolate vine or mu tong. The remaining DS featured one to three publications over a 50+ year period. Numerous case reports were reported for kidney-toxic foods: djenkol bean, gallbladders (carp fish, pufferfish, & snake), and star fruit (only in chronic kidney disease patients), and uncooked yam powder or juice.

CONCLUSION

This online "DS Toxic Table" provides clinicians, consumers, and manufacturers with a list of herbs that could potentially contribute to kidney injuries.

Rapid screening and multi-toxin profile confirmation of tetrodotoxins and analogues in human body fluids derived from a puffer fish poisoning incident in New Caledonia

In August 2014, a puffer fish poisoning incidence resulting in one fatality was reported in New Caledonia. Although tetrodotoxin (TTX) intoxication was established from the patients' signs and symptoms, the determination of TTX in the patient's urine, serum or plasma is essential to confirm the clinical diagnosis. To provide a simple cost-effective rapid screening tool for clinical analysis, a maleimide-based enzyme-linked immunosorbent assay (mELISA) adapted for the determination of TTX contents in human body fluids was assessed. The mELISA was applied to the analysis of urine samples from two patients and a response for the presence of TTX and/or structurally similar analogues was detected in all samples. The analysis by LC-MS/MS confirmed the presence of TTX but also TTX analogues (4-epiTTX, 4,9-anhydroTTX and 5,6,11-trideoxyTTX) in the urine. A change in the multi-toxin profile in the urine based on time following consumption was observed. LC-MS/MS analysis of serum and plasma samples also revealed the presence of TTX (32.9 ng/mL) and 5,6,11-trideoxyTTX (374.6 ng/mL) in the post-mortem plasma. The results provide for the first time the TTX multi-toxin profile of human samples from a puffer fish intoxication and clearly demonstrate the implication of TTX as the causative agent of the reported intoxication case.

Guanidinium Toxins and Their Interactions with Voltage-Gated Sodium Ion Channels

Guanidinium toxins, such as saxitoxin (STX), tetrodotoxin (TTX) and their analogs, are naturally occurring alkaloids with divergent evolutionary origins and biogeographical distribution, but which share the common chemical feature of guanidinium moieties. These guanidinium groups confer high biological activity with high affinity and ion flux blockage capacity for voltage-gated sodium channels (NaV). Members of the STX group, known collectively as paralytic shellfish toxins (PSTs), are produced among three genera of marine dinoflagellates and about a dozen genera of primarily freshwater or brackish water cyanobacteria. In contrast, toxins of the TTX group occur mainly in macrozoa, particularly among puffer fish, several species of marine invertebrates and a few terrestrial amphibians. In the case of TTX and analogs, most evidence suggests that symbiotic bacteria are the origin of the toxins, although endogenous biosynthesis independent from bacteria has not been excluded. The evolutionary origin of the biosynthetic genes for STX and analogs in dinoflagellates and cyanobacteria remains elusive. These highly potent molecules have been the subject of intensive research since the latter half of the past century; first to study the mode of action of their toxigenicity, and later as tools to characterize the role and structure of NaV channels, and finally as therapeutics. Their pharmacological activities have provided encouragement for their use as therapeutants for ion channel-related pathologies, such as pain control. The functional role in aquatic and terrestrial ecosystems for both groups of toxins is unproven, although plausible mechanisms of ion channel regulation and chemical defense are often invoked. Molecular approaches and the development of improved detection methods will yield deeper understanding of their physiological and ecological roles. This knowledge will facilitate their further biotechnological exploitation and point the way towards development of pharmaceuticals and therapeutic applications.

Urinary Excretion of Tetrodotoxin Modeled in a Porcine Renal Proximal Tubule Epithelial Cell Line, LLC-PK₁

This study examined the urinary excretion of tetrodotoxin (TTX) modeled in a porcine renal proximal tubule epithelial cell line, LLC-PK₁. Time course profiles of TTX excretion and reabsorption across the cell monolayers at 37 °C showed that the amount of TTX transported increased linearly for 60 min. However, at 4 °C, the amount of TTX transported was approximately 20% of the value at 37 °C. These results indicate that TTX transport is both a transcellular and carrier-mediated process. Using a transport inhibition assay in which cell monolayers were incubated with 50 µM TTX and 5 mM of a transport inhibitor at 37 °C for 30 min, urinary excretion was significantly reduced by probenecid, tetraethylammonium (TEA), l-carnitine, and cimetidine, slightly reduced by p-aminohippuric acid (PAH), and unaffected by 1-methyl-4-phenylpyridinium (MPP+), oxaliplatin, and cefalexin. Renal reabsorption was significantly reduced by PAH, but was unaffected by probenecid, TEA and l-carnitine. These findings indicate that TTX is primarily excreted by organic cation transporters (OCTs) and organic cation/carnitine transporters (OCTNs), partially transported by organic anion transporters (OATs) and multidrug resistance-associated proteins (MRPs), and negligibly transported by multidrug and toxic compound extrusion transporters (MATEs).

Risks for public health related to the presence of tetrodotoxin (TTX) and TTX analogues in marine bivalves and gastropods

Tetrodotoxin (TTX) and its analogues are produced by marine bacteria and have been detected in marine bivalves and gastropods from European waters. The European Commission asked EFSA for a scientific opinion on the risks to public health related to the presence of TTX and TTX analogues in marine bivalves and gastropods. The Panel on Contaminants in the Food Chain reviewed the available literature but did not find support for the minimum lethal dose for humans of 2 mg, mentioned in various reviews. Some human case reports describe serious effects at a dose of 0.2 mg, corresponding to 4 μg/kg body weight (bw). However, the uncertainties on the actual exposure in the studies preclude their use for derivation of an acute reference dose (ARfD). Instead, a group ARfD of 0.25 μg/kg bw, applying to TTX and its analogues, was derived based on a TTX dose of 25 μg/kg bw at which no apathy was observed in an acute oral study with mice, applying a standard uncertainty factor of 100. Estimated relative potencies for analogues are lower than that of TTX but are associated with a high degree of uncertainty. Based on the occurrence data submitted to EFSA and reported consumption days only, average and P95 exposures of 0.00-0.09 and 0.00-0.03 μg/kg bw, respectively, were calculated. Using a large portion size of 400 g bivalves and P95 occurrence levels of TTX, with exception of oysters, the exposure was below the group ARfD in all consumer groups. A concentration below 44 μg TTX equivalents/kg shellfish meat, based on a large portion size of 400 g, was considered not to result in adverse effects in humans. Liquid chromatography with tandem mass spectroscopy (LC-MS/MS) methods are the most suitable for identification and quantification of TTX and its analogues, with LOQs between 1 and 25 μg/kg.

Comparison of the acute inhibitory effects of Tetrodotoxin (TTX) in rat and human neuronal networks for risk assessment purposes

Tetrodotoxin (TTX) is an extremely toxic marine neurotoxin. TTX inhibits voltage-gated sodium channels, resulting in a potentially lethal inhibition of neurotransmission. Despite numerous intoxications in Asia and Europe, limited (human) toxicological data are available for TTX. Additionally, the degree of interspecies differences for TTX is not well established, hampering the use of available (animal) data for human risk assessment and establishing regulatory limits for TTX concentrations in (shell)fish. We therefore used micro-electrode array (MEA) recordings as an integrated measure of neurotransmission to demonstrate that TTX inhibits neuronal electrical activity in both primary rat cortical cultures and human-induced pluripotent stem cell (hIPSC)-derived iCell^® neurons in co-culture with hIPSC-derived iCell^® astrocytes, with IC₅₀ values of 7 and 10nM, respectively. From these data combined with LD₅₀ values and IC₅₀ concentrations of voltage-gated sodium channels derived from literature it can be concluded that interspecies differences are limited for TTX. Consequently, we used experimental animal data to derive a human acute reference dose of 1.33μg/kg body weight, which corresponds to maximum concentration of TTX in shellfish of 200μg/kg.

Development and validation of a high-throughput online solid phase extraction - Liquid chromatography - Tandem mass spectrometry method for the detection of tetrodotoxin in human urine

Tetrodotoxin (TTX) is an extremely potent paralytic toxin responsible for yearly illness and death around the world. A clinical measurement is necessary to confirm exposure because symptoms of TTX intoxication cannot be distinguished from other paralytic toxins. Our group has developed an online solid phase extraction hydrophilic interaction liquid chromatography (HILIC) method for the analysis of TTX in human urine with tandem mass spectrometry. The reportable range for the method was 2.80 - 249 ng/mL in urine with precision and accuracy within 15% as determined for all quality control samples. No isotopically-labeled internal standard is available for TTX; thus a surrogate internal standard, voglibose, was investigated to compensate for matrix effects and ionization suppression. However, upon evaluation, voglibose was ineffective for this purpose. This new online method rapidly identifies TTX, facilitating the work of public health authorities and providing support to monitoring programs worldwide.

Development of standardized methodology for identifying toxins in clinical samples and fish species associated with tetrodotoxin-borne poisoning incidents

Tetrodotoxin (TTX) is a naturally occurring toxin in food, especially in puffer fish. TTX poisoning is observed frequently in South East Asian regions. In TTX-derived food poisoning outbreaks, the amount of TTX recovered from suspicious fish samples or leftovers, and residual levels from biological fluids of victims are typically trace. However, liquid chromatography–mass spectrometry and liquid chromatography–tandem mass spectrometry methods have been demonstrated to qualitatively and quantitatively determine TTX in clinical samples from victims. Identification and validation of the TTX-originating seafood species responsible for a food poisoning incident is needed. A polymerase chain reaction-based method on mitochondrial DNA analysis is useful for identification of fish species. This review aims to collect pertinent information available on TTX-borne food poisoning incidents with a special emphasis on the analytical methods employed for TTX detection in clinical laboratories as well as for the identification of TTX-bearing species.

Tetrodotoxin, an Extremely Potent Marine Neurotoxin: Distribution, Toxicity, Origin and Therapeutical Uses

Tetrodotoxin (TTX) is a potent neurotoxin responsible for many human intoxications and fatalities each year. The origin of TTX is unknown, but in the pufferfish, it seems to be produced by endosymbiotic bacteria that often seem to be passed down the food chain. The ingestion of contaminated pufferfish, considered the most delicious fish in Japan, is the usual route of toxicity. This neurotoxin, reported as a threat to human health in Asian countries, has spread to the Pacific and Mediterranean, due to the increase of temperature waters worldwide. TTX, for which there is no known antidote, inhibits sodium channel producing heart failure in many cases and consequently death. In Japan, a regulatory limit of 2 mg eq TTX/kg was established, although the restaurant preparation of “fugu” is strictly controlled by law and only chefs qualified are allowed to prepare the fish. Due to its paralysis effect, this neurotoxin could be used in the medical field as an analgesic to treat some cancer pains.

Tetrodotoxin and Its Analogues in the Pufferfish Arothron hispidus and A. nigropunctatus from the Solomon Islands: A Comparison of Their Toxin Profiles with the Same Species from Okinawa, Japan

Pufferfish poisoning has not been well documented in the South Pacific, although fish and other seafood are sources of protein in these island nations. In this study, tetrodotoxin (TTX) and its analogues in each organ of the pufferfish Arothron hispidus and A. nigropunctatus collected in the Solomon Islands were investigated using high resolution LC-MS. The toxin profiles of the same two species of pufferfish from Okinawa, Japan were also examined for comparison. TTXs concentrations were higher in the skin of both species from both regions, and relatively lower in the liver, ovary, testis, stomach, intestine, and flesh. Due to higher TTX concentrations (51.0 and 28.7 µg/g at highest) detected in the skin of the two species from the Solomon Islands (saxitoxin was <0.02 µg/g), these species should be banned from consumption. Similar results were obtained from fish collected in Okinawa, Japan: TTX in the skin of A. hispidus and A. nigropunctatus were 12.7 and 255 µg/g, respectively, at highest, and saxitoxin was also detected in the skin (2.80 µg/g at highest) and ovary of A. hispidus. TTX, 5,6,11-trideoxyTTX (with its 4-epi form), and its anhydro forms were the most abundant, and 11-oxoTTX was commonly detected in the skin.