Assessment of Neuronal Cell-Based Cytotoxicity of Neurotoxins from an Estuarine Nemertean in the Han River Estuary

Nemertea is a phylum of marine worms whose members bear various toxins, including tetrodotoxin (TTX) and its analogues. Despite the more than 30 years of studying TTXs in nemerteans, many questions regarding their functions and the mechanisms ensuring their accumulation and usage remain unclear. In the nemertean Kulikovia alborostrata, we studied TTX and 5,6,11-trideoxyTTX concentrations in body extracts and in released mucus, as well as various aspects of the TTX-positive-cell excretion system and voltage-gated sodium (Nav1) channel subtype 1 mutations contributing to the toxins’ accumulation. For TTX detection, an immunohistological study with an anti-TTX antibody and HPLC-MS/MS were conducted. For Nav1 mutation searching, PCR amplification with specific primers, followed by Sanger sequencing, was used. The investigation revealed that, in response to an external stimulus, subepidermal TTX-positive cells released secretions actively to the body surface. The post-release toxin recovery in these cells was low for TTX and high for 5,6,11-trideoxyTTX in captivity. According to the data obtained, there is low probability of the targeted usage of TTX as a repellent, and targeted 5,6,11-trideoxyTTX secretion by TTX-bearing nemerteans was suggested as a possibility. The Sanger sequencing revealed identical sequences of the P-loop regions of Nav1 domains I–IV in all 17 studied individuals. Mutations comprising amino acid substitutions, probably contributing to nemertean channel resistance to TTX, were shown.

Section: Discussionmentioning

confidence: 97%

Tetrodotoxins Secretion and Voltage-Gated Sodium Channel Adaptation in the Ribbon Worm Kulikovia alborostrata (Takakura, 1898) (Nemertea)

Vlasenko

Kuznetsov

Malykin

et al. 2021

“…In most of the species, including Amphiporus sp., Malacobdella japonica, Nipponnemertes punctatula, Lineus alborostratus (=Kulikovia alborostrata), Lineus fuscoviridis, and Lineus torquatus, only equilibrium TTX analogues-4-epiTTX and 4,9-anhydroTTX-were found [17]. However, nonequilibrium analogues were also found in some nemertean species: 5-deoxyTTX, 11-deoxyTTX, and 5,6,11-trideoxyTTX were detected in Kulikovia manchenkoi [8] and 11-norTTX-6 (S)-ol and 5,11-dideoxyTTX were detected in Yininemertes pratensis [18]. Previously in nemerteans from the Cephalothrix simula s. l group, the nonequilibrium analogues 5-deoxyTTX, 11-deoxyTTX, 5,6,11-trideoxyTTX [16], 11-norTTX-6(S)-ol, 11-norTTX-6(R)-ol [8], 6,11-dideoxyTTX, 11-oxoTTX, 4,9-anhydro -5,6,11-trideoxyTTX, and 4,9-anhydro-11-oxoTTX [11] were previously found, along with TTX and its equilibrium analogues.…”

Section: Discussionmentioning

confidence: 99%

Tetrodotoxin and Its Analogues in Cephalothrix cf. simula (Nemertea: Palaeonemertea) from the Sea of Japan (Peter the Great Gulf): Intrabody Distribution and Secretions

Vlasenko

Magarlamov

2020

Some nemertean species from the genus Cephalothrix accumulate tetrodotoxin (TTX) in extremely high concentrations. The current study is the first to provide high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) data on tetrodotoxin and its analogues (TTXs) profile and concentration in different regions and organs of Cephalothrix cf. simula, and its secretions produced in response to stimulation. Different specimens of C. cf. simula possessed 7–11 analogues, including nine previously found in this species and two new for nemerteans—4,9-anhydro-8-epi-5,6,11-trideoxyTTX and 1-hydroxy-8-epi-5,6,11-trideoxyTTX. The study of the toxins’ distribution in different regions and organs of nemerteans revealed the same qualitative composition of TTXs throughout the body but differences in the total concentration of the toxins. The total concentration of TTXs was highest in the anterior region of the body and decreased towards the posterior; the ratio of the analogues also differed between regions. The data obtained suggest a pathway of TTXs uptake in C. cf. simula and the role of toxins in the life activity of nemerteans.

“…Several masses corresponding to known TTX derivatives were found, as was cytotoxicity in certain fractions. However, correlation between the two was poor, again raising the question of the origin of activity [84].…”

Section: Ribbon Worm Toxinsmentioning

confidence: 99%

The Toxins of Nemertean Worms

Göransson

Jacobsson

Strand

et al. 2019

Most ribbon worms (phylum: Nemertea) are found in marine environments, where they act as predators and scavengers. They are characterized by an eversible proboscis that isused to hunt for prey and thick mucus covering their skin. Both proboscis and epidermal mucus mediate toxicity to predators and preys. Research into the chemical nature of the substances that render toxicity has not been extensive, but it has nevertheless led to the identification of several compounds of potential medicinal use or for application in biotechnology. This review provides a complete account of the current status of research into nemertean toxins.