Search Results (215)

Tetrodotoxin (TTX), widely known as pufferfish venom, is a low-molecular-weight guanidinium neurotoxin. It can accumulate to extremely high concentrations in certain animals, including pufferfish, blue-ringed octopuses, flatworms, and nemerteans. However, the origin of TTX and the mechanisms that enable such extreme accumulation in these animals remain poorly understood. In this study, using confocal laser scanning microscopy combined with electron immunocytochemistry and ultrastructural analysis, we demonstrate the presence of TTX-positive bacteria associated with specialized cellular structures—type II phagosomes of gut enterocytes—in the highly toxic nemertean Cephalothrix cf. simula. We hypothesize that TTX production in C. cf. simula results from interactions between the nemertean host and its endosymbionts. These findings clarify the origin and accumulation of the toxin in nemerteans and have broader implications for other TTX-bearing species. Full article

This study documents the presence of two uncommon tetraodontiform fishes and reviews the occurrence of species from this order in Spanish marine waters. Two tetraodontid specimens (Family Tetraodontidae) were caught in the Atlantic waters off the coast of Galicia, northwestern Spain. A specimen of Sphoeroides pachygaster was collected in 2021 off the Costa da Vela, while a specimen of Ephippion guttifer was captured in 2025 in the Ría de Pontevedra, both locations situated in southern Galicia. Morphological analyses, supported by photographic evidence and DNA barcoding, confirmed the preliminary taxonomic identification of the two species. Histological reproductive analysis of the Ephippion guttifer specimen revealed a female in the spawning-capable phase. These findings constitute the first verified record of S. pachygaster and the second of E. guttifer in Galician waters. An updated comprehensive list of tetraodontiform species found in Spanish waters across five geographical demarcations was compiled. Historically, a total of 26 species across five families have been reported in Spanish waters, with 22 in the Canary Islands and 15 in the Spanish Iberian Peninsula and Balearic Islands. Additionally, a review of the presence of neurotoxic tetrodotoxins (TTXs) or paralytic shellfish toxins (PSTs) in each species is included, providing an up-to-date overview of a largely unexplored field in European waters. The increasing occurrence of tetraodontiform fishes in Spanish waters provides further evidence of the progressive tropicalization of the Spanish marine environment. Full article

Depression remains a major global health challenge, with a significant proportion of patients failing to respond to conventional antidepressants. This study aimed to evaluate the potential antidepressant effects and toxicological profile of a novel tetrodotoxin (TTX) oral film formulation in a mouse model of chronic unpredictable mild stress (CUMS). Male C57BL/6J mice were subjected to CUMS and treated daily with TTX oral film at doses of 10, 20, and 40 μg/kg, with fluoxetine (18 mg/kg) serving as a positive control. Behavioral assessments, including sucrose preference test, open field test, forced swimming test, elevated plus maze, and novel object recognition, demonstrated that TTX oral film administration alleviated depression- and anxiety-like behaviors and improved cognitive function. Furthermore, TTX oral film treatment restored hippocampal serotonin levels, which were depleted in CUMS mice, and showed no adverse effects on organ indexes after long-term use. Toxicological evaluation through acute toxicity testing revealed an oral LD₅₀ of 919 μg/kg, indicating a substantially improved safety profile compared to pure TTX and a wide therapeutic window. These findings suggest that the TTX oral film possesses significant antidepressant activity with favorable toxicological properties, supporting its potential as a novel and safe treatment for depression. Full article

Angiogenesis depends on Ca²⁺-mediated endothelial cell migration. The increase in intracellular Ca²⁺ concentration ([Ca²⁺]_i) is coordinated by caveolae and the Cx43 hemichannel opening. However, the functional coupling of voltage-dependent Na⁺ channels (Na_v) with Na⁺-Ca²⁺ exchanger reverse mode (NCXrm) activation may contribute to the response, which was evaluated using the wound-healing assay in primary cultures of rat mesenteric endothelial cells. Changes in [Ca²⁺]_i, the hemichannel opening and the association of Na_v channels with caveolin-1, a caveolae structural protein, were analyzed. Both endothelial cell migration and the associated Ca²⁺ signaling were inhibited by tetrodotoxin (TTX), a Na_v channel blocker, lamotrigine, a preferential Na_v1.2 inhibitor, or 4,9-anhydro-TTX, a specific Na_v1.6 blocker. A similar result was found by disrupting caveolae organization with methyl-β-cyclodextrin or blocking NCXrm with SEA0400. TTX and SEA0400 also prevented Cx43 hemichannel opening, and tubular-like structure formation depended on Na_v channels. An analysis using a proximity ligation assay showed that endothelial cell migration was paralleled by the progressive association of caveolin-1 with Na_v1.2, but not Na_v1.6, channels. These results suggest that the functional coupling of Na_v1.2 and Na_v1.6 channels with the activation of NCXrm and Cx43 hemichannels mediates the Ca²⁺ signaling associated with endothelial cell migration and angiogenesis, which provides new targets to modulate angiogenesis in physiological or pathological conditions. Full article

Tetrodotoxin (TTX) is a potent marine neurotoxin, necessitating sensitive and user-friendly on-site assays. To address long workflows of traditional immunoassays and limited signal amplification in colorimetric microfluidics, we developed a nanozyme-catalyzed colorimetric magnetic microfluidic immunosensor (Nano-CMI). This platform combines an aptamer–antibody sandwich capture format with catalytic amplification via AuNR@Pt@m-SiO₂ (APMS) nanozymes on a magnetically actuated microfluidic chip. Magnetic actuation simplifies sample handling and washing, while APMS catalysis enhances sensitivity and visual readout. The Nano-CMI has been used for the detection of TTX samples ranging from 0.2 to 20 ng/mL with a detection limit of 0.2 ng/mL in 10 min, following the linear equation: y = −31.14ln x + 110.15, and the entire “capture-reaction-detection” workflow can be completed within 1 h. With rapid response, minimal hands-on time, and robust performance, this platform offers a practical, high-sensitivity solution for on-site TTX screening in food safety and customs inspection. Full article

Background/Objectives: Glucose Transporter 1 Deficiency Syndrome (GLUT1-DS) is a neurodevelopmental disorder caused by mutations in the gene encoding glucose transporter 1 (GLUT1), which leads to impaired glucose transport into the brain and is characterized by drug-resistant epilepsy. Limited glucose supply disrupts neuronal and astrocytic energy homeostasis, but how hypometabolism translates into network hyperexcitability remains poorly understood. Here, we used induced pluripotent stem cells (iPSCs)-derived brain organoids to examine how reduced metabolic substrate availability shapes epileptiform dynamics in human neuronal circuits from GLUT1-DS. Methods: Brain organoids were generated from a healthy donor or a GLUT1-DS patient and interfaced with multielectrode arrays (MEA) for recording of neuronal activity. A unified Python (v3.10)-based analytical pipeline was developed to quantify spikes, bursts, and power spectral density (PSD) across frequency bands of neuronal activity. Organoids were challenged with reduced glucose, pentylenetetrazol (PTZ), potassium chloride (KCl), and tetrodotoxin (TTX) to assess metabolic and pharmacological modulation of excitability. Results: GLUT1-DS organoids exhibited elevated baseline hyperexcitability compared to healthy control, characterized by increased spike rates, prolonged bursts, increased spikes per burst, and elevated PSD. Reduced glucose availability further amplified these features selectively in GLUT1-DS. Conclusions: Human brain organoids reproduce the pathological coupling between hypometabolism and hyperexcitability in GLUT1-DS. Our platform provides a mechanistic model and quantification tool for evaluating metabolic and anti-epileptic therapeutic strategies. Full article

Glioblastoma (GBM) is the most aggressive primary cancer with poor survival. In the absence of an effective treatment and a high probability of recurrence, new therapeutic approaches are urgently needed. This study focused on targeting microRNA-10b (miR-10b) highly expressed in GBM cells that has been identified as one of the key drivers of GBM progression. Inhibiting miR-10b using antisense oligonucleotides (ASOs) has shown promise, but its delivery is challenging due to short circulation half-life, degradation by nucleases, and limited blood–brain barrier (BBB) permeability. To overcome these barriers, we employed a magnetic nanoparticle (MN) platform to deliver anti-miR-10b ASOs (MN-anti-miR10b). In addition to serving as a delivery vehicle, these nanoparticles can be used for monitoring delivery using magnetic resonance imaging (MRI). In therapeutic studies in orthotopic models of GBM presented here we used MN-anti-miR10b as well as TTX-MC138, a clinically tested anti-miR10b nanotherapeutic now in Phase I trials in patients with solid (non-GBM) cancers. Both formulations showed efficient delivery, as demonstrated by imaging and improved survival, leading to target inhibition and increased apoptosis. This approach may offer a novel strategy for delivering therapeutics to GBM and improving patient outcomes in one of the most aggressive and treatment-resistant forms of brain cancer. Full article

The Isles of Scilly are an archipelago of islands in the far southwest of the UK which contain numerous beds of wild bivalve molluscs which are recreationally harvested for local consumption. However, the islands have never previously been assessed for the presence of harmful algae and their shellfish toxin metabolites which can cause serious human health impacts. This study sought to address these knowledge gaps through the analysis of seawater and shellfish tissues for microalgae and toxins utilizing portable and lab-based microscopy, nanopore sequencing, chemical analysis and immunoassay kits. The study design was affected by the national COVID-19 lockdown which enforced implementation of citizen-led sampling and in-field microscopy. Microscopy and sequencing approaches led to the confirmation of multiple HAB species of concern, including those potentially responsible for production of neurotoxic and diarrhetic shellfish toxins. A portable microscope was successfully utilized in the field for recognition of microalgae and for early warning of potential shellfish toxicity events. Chemical analysis of cockle, clam and mussel samples confirmed the detection of paralytic, diarrhetic and amnesic shellfish toxins, with an unusual okadaic acid group toxin profile reaching a maximum toxicity of approximately half the regulatory limit as defined by EU law. The Sensoreal Alert Lateral Flow Assay was used to screen and highlight samples containing higher concentrations of DSP toxins. Furthermore, Tetrodotoxin was detected for the first time in the UK in cockle and grooved carpet shells. Multiple saxitoxin analogues were also detected in two echinoderm species, with this providing the first ever report of paralytic shellfish toxins in the spiny starfish, Marthasterias glacialis. The toxin profiles in the two species varied significantly with a dominance of GTX4 in Luidia ciliaris as opposed to a dominance of STX in Marthasterias glacialis. Overall, the study showed that a multi-method assessment of a previously unexplored region within the UK territory contained microalgae and toxins of concern to human health, and that a citizen-led programme could be instigated using portable microscopy and rapid toxin testing to assess the early warning for potentially harmful microalgae and toxins in the region, with confirmatory analysis being conducted to establish actual levels of risk for local consumers of seafood. Full article

Tetrodotoxin (TTX) is an extremely potent neurotoxin, a selective blocker of voltage-gated sodium (NaV) channels, produced by bacteria and accumulated across a wide range of taxa. Several TTX-bearing animals have developed molecular adaptations in their NaV channels that provide TTX resistance, making this toxin one of the factors of molecular evolution. However, the molecular basis of TTX resistance in NaV channels of a significant proportion of tetrodotoxic species remains poorly studied. Nemertea is a phylum of marine worms, comprising both TTX-bearing and non-TTX-bearing species. Here, we analyzed the amino acid sequences of the NaV1 channel regions responsible for TTX binding from 22 species of nemerteans. Substitutions previously characterized as conferring TTX resistance in other taxa were detected in sixteen nemerteans; local clustering was observed within several families. These findings suggest that TTX resistance in nemerteans evolved multiple times independently and may serve as either as an adaptation facilitating TTX accumulation for subsequent use for defense and predation, or as a mechanism allowing consumption of tetrodotoxic prey without toxin accumulation. Full article

The detection of tetrodotoxins (TTXs) in European shellfish led the European Union to request a risk assessment from the European Food Safety Authority (EFSA). EFSA set a reference limit of 44 µg TTX equivalents kg⁻¹ and called for more data on TTX occurrence, especially in gastropods, which can accumulate in TTXs but remain poorly studied. Recently, preliminary monitoring has revealed the recurrent presence of TTXs in mussels in three areas along the North–Central Adriatic coast of Italy, while research on non-bivalve organisms has not yet been carried out. This study presents a preliminary survey, conducted from January 2023 to March 2025, on the presence of TTXs in gastropods, echinoderms, and arthropods collected from this area. A method in Hydrophilic Interaction Liquid Chromatography coupled with tandem Mass Spectrometry (HILIC-MS/MS) for detecting TTXs in bivalve mollusks was first tested through an international proficiency test, then optimized for the other invertebrates, the object of this study. TTX levels in all gastropods and arthropod samples were undetectable, while traces (~5 µg kg⁻¹) were found in one echinoderm sample (Paracentrotus lividus), marking the first reported occurrence of TTX in this species. Sea urchins are widely consumed in Italy; therefore, this finding is of particular importance from a public health perspective and deserves further investigation. Some gastropod genera or species sampled (e.g., Nassarius, Rapana venosa) have been identified as TTX carriers in other regions; therefore, the negative results obtained in this study may be related to seasonal or geographic variability. These results provide valuable data to EFSA’s call for monitoring emerging risks, particularly as climate change may increase TTX prevalence in European waters as well as worldwide. Full article

Normal alcohols (n-alcohols) exhibit contrasting effects on neuronal excitability; specifically, ethanol enhances neuronal firing, while hexanol suppresses it. Both compounds are known to inhibit sodium currents, yet the mechanisms behind their differing effects remain unclear. Our previous studies demonstrated that Kv7 channels are modulated differently by alcohol chain length, prompting investigation into their role in these contrasting effects. We conducted whole-cell patch clamp recordings on neonatal (P5-P7) rat superior cervical ganglion neurons to assess alcohol impacts on action potential firing and ionic currents, utilizing tetrodotoxin (TTX), XE991, and retigabine (RTG). Ethanol (100 mM) increased action potential frequency, whereas hexanol (3 mM) decreased it, despite both inhibiting sodium currents by 12% and 45%, respectively. Notably, ethanol inhibited Kv7 currents by 16%, while hexanol enhanced them by 29%. TTX alone did not affect firing frequency until sodium current inhibition exceeded 76%, indicating moderate sodium channel blockade cannot fully explain the effects of alcohol. XE991 increased firing frequency and depolarized the resting membrane potential, while retigabine produced opposite effects. The combination of TTX with Kv7 modulators replicated the effects observed with each alcohol. These findings suggest Kv7 channel modulation plays an important role in the chain length-dependent effects of alcohol on neuronal excitability. Full article

Pufferfish are an economically important food in Asia despite the potential risk of tetrodotoxin (TTX) poisoning. To promote food safety by ensuring the correct identification of pufferfish species, we developed common and species-specific primer sets for four Lagocephalus species (Lagocephalus spadiceus, Lagocephalus cheesemanii, Lagocephalus wheeleri, and Lagocephalus inermis) based on analysis of mitochondrial DNA cytochrome c oxidase subunit I (COI) in various pufferfish species commonly distributed and/or legally sold in Korea. The common primers were developed based on complete sequence data acquired from GenBank. The total length of fragments amplified by the common primer set was 1280 bp. Then, species-specific multiplex polymerase chain reaction (PCR) amplification was conducted for the four target species, obtaining 980 bp for L. spadiceus, 859 bp for L. cheesemanii, 672 bp for L. wheeleri, and 563 bp for L. inermis. Multiplex PCR is an important tool for the simple, rapid, accurate, and simultaneous identification of target species. The newly developed primer sets will contribute to reducing the occurrence of TTX poisoning and protect consumer rights by eradicating the mislabeling or fraudulent use of pufferfish products. Full article

The real-time, cost-effective detection of marine toxins like tetrodotoxin (TTX) remains a significant challenge for the scientific community. Traditional methods, including cell-based assays (CBAs), high-performance liquid chromatography (HPLC), and automated patch clamp (APC), are time-consuming, requiring expensive lab-based equipment and highly trained personnel. Enzyme-linked immunosorbent assays (ELISAs), lateral flow assays (LFAs), and immunosensors may not be suitable for toxin analogues. Thus, a simplified approach has been developed in this study, which involves the electrophysiological and electrochemical interrogation of N2a cells grown on ITO-coated glass electrodes by measuring extracellular field potentials (EFP) in conjunction with whole-cell patch clamp recordings and electrochemical impedance spectroscopy (EIS) measurements both before and after incubation with TTX. The ITO substrate proved biocompatible and non-toxic for N2a cells. TTX exposure caused 102% inhibition in EFP values at 300 nM, confirmed by sodium current inhibition of 93% at 300 nM and 22% at 1 nM in patch clamp studies (IC₅₀ = 6.7 nM). EIS measurements indicated concentration-dependent impedance changes in the range of 6–300 nM. This research aims to provide a proof-of-concept for integration of electrophysiological and electrochemical approaches to simplify toxin detection systems. Full article

This study investigated whether marine toxin poisonings reported to U.S. Poison Centers changed during the height of the pandemic period (April 2020 to December 2021). The National Poison Data System was queried for single-substance human exposure calls between 1 January 2000 and 31 March 2022 pertaining to ichthyosarcotoxins. Incidence rate ratios for exposure calls were calculated using mixed-effects negative binomial regression. Call counts were aggregated by year and regressed on a binary indicator for occurrence during pandemic restrictions. During the peak pandemic period, exposure calls decreased for several toxins: ciguatera poisoning: 0.57 (0.43, 0.76); clupeotoxic fish poisoning: 0.12 (0.04, 0.39); diarrhetic shellfish poisoning: 0.28 (0.16, 0.49); paralytic shellfish poisoning: 0.23 (0.17, 0.33); scombroid fish poisoning: 0.46 (0.36, 0.57). However, palytoxin poisoning (1.94 (1.32, 2.84)) and tetrodotoxin poisoning (1.73 (1.46, 2.04)) exposure calls appear to have increased. All results were Bonferroni-significant (p ≤ 0.0009). Sensitivity analyses suggest the PLTX increase began prior to pandemic restrictions, whereas the TTX increase appeared to be directly associated with the restrictions. Both men and women reported increases in TTX exposure calls. The TTX increase could be associated with potentially increased participation in outdoor activities, as TTX exposures are linked to amphibia, echinoderms, fish, and mollusks, among other animals. Full article

Background: The concentration of antigen-specific antibodies in serum is usually measured in international units/mL. Therefore, the actual concentration of virus-specific antibodies in sera is unknown. Objectives: The aim of the study was to determine conversion factors for concentrations of IgG against hepatitis B surface antigen (HBs), SARS-CoV-2 receptor binding domain (RBD) and nucleoprotein (NP) as well as tetanus toxin (Ttx) in serum and to compare antigen-specific IgG concentrations in serum samples. Methods: Absorption equivalence ELISAs were used to determine conversion factors for international units (IU) for anti-HBs, anti-SARS-CoV-2-RBD and NP and for anti-Ttx immunoglobulin G. The antigen-specific IgG concentrations in serum samples were then measured in units/mL and the ratio of IgG concentrations in the sera was determined using the conversion factors. Results: One IU of anti-HBs IgG corresponded to 24.4 BAU of anti-CoV-2 RBD IgG, 6.87 BAU of anti-CoV-2 NP and 14 mIU of anti-Ttx IgG. One BAU anti-SARS-CoV-2 NP-specific IgG is equivalent to 3.5 BAU SARS-CoV-2 RBD-specific IgG. Conversion of international units showed that median serum anti-Ttx-IgG concentrations were 50 times higher and anti-CoV-2-RBD-IgG concentrations were 390 times higher than median anti-HBs-IgG concentrations. In addition, after SARS-CoV-2 infection, the concentration of NP-specific IgG in serum was generally higher than that of RBD-specific IgG. Conclusions: The study provides conversion factors for serum concentrations of IgG against HBs, SARS-CoV-2 RBD and NP, as well as Ttx-IgG. This offers new insights into serum IgG concentrations and allows conclusions to be drawn about plasma cell pools. Full article