Distribution of tetrodotoxin, saxitoxin, and their analogs among tissues of the puffer fish Fugu pardalis

Isolation and structural determination of the first 8-epi-type tetrodotoxin analogs from the newt, Cynops ensicauda popei, and comparison of tetrodotoxin analogs profiles of this newt and the puffer fish, Fugu poecilonotus

Identification of new tetrodotoxin (TTX) analogs from TTX-possessing animals might provide insight into its biosynthesis and metabolism. In this study, four new analogs, 8-epi-5,6,11-trideoxyTTX, 4,9-anhydro-8-epi-5,6,11-trideoxyTTX, 1-hydroxy-8-epi-5,6,11-trideoxyTTX, and 1-hydroxy-4,4a-anhydro-8-epi-5,6,11-trideoxyTTX, were isolated from the newt, Cynops ensicauda popei, and their structures were determined using spectroscopic methods. These are the first 8-epi-type analogs of TTX that have been found in a natural source. Furthermore, we examined the composition of the TTX analogs in this newt and in the ovary of the puffer fish, Fugu poecilonotus, using LC/MS. The results indicate that TTX and 11-deoxyTTX were present in both sources. However, 6-epiTTX and 8-epi-type analogs were detected only in the newt, while 5,6,11-trideoxyTTX was a specific and major analog in the puffer fish. Such considerable differences among analog compositions might reflect differences in the biosynthesis or metabolism of TTX between these animals.

Toxin composition and toxicity dynamics of marine gastropod Nassarius spp. collected from Lianyungang, China

Consumption of nassariid gastropods often leads to poisoning incidents in some coastal provinces in China. To elucidate the pattern of toxicity dynamics and origin of toxins, samples of gastropod Nassarius spp. were collected from late May to early August 2007 from Lianyungang, Jiangsu province, where the poisoning incidents have been frequently reported. Toxicity was first screened with the mouse bioassay method, and tetrodotoxin and its analogues (TTXs) were analysed with high-performance liquid chromatography coupled with an ion-trap mass spectrometer (HPLC-MS(n)). The toxicity of nassariid N. semiplicatus showed an 'M'-shaped pattern of fluctuation during the sampling season. Two peaks of toxicity appeared in late May and late July. The maximum toxicity was recorded on 24 May, with the value of 846 mouse unit (MU) g(-1) of tissue (wet weight). TTX and its analogues trideoxyTTX, 4-epiTTX, anhydroTTX and oxoTTX were detected in the nassariid samples. TrideoxyTTX but not TTX was the major toxin in all the samples. No paralytic shellfish poison (PSP) was detected in the sample with the maximum toxicity by HPLC-FLD analysis. Variation of TTX content in the tissue of nassariid gastropods correlates well with the dynamics of toxicity. It is suggested that TTXs are the major toxins corresponding to the toxicity of the nassariids, and May and July are the high-risk seasons for consumption of nassariids, which is critical for the management of poisoning incidents.

Effects of puffer (Sphoeroides rubripes) supplementation on disruption of antioxidant defense systems in ethanol-treated rats

We investigated the effects of puffer (Sphoeroides rubripes) supplementation on antioxidant metabolism in ethanol-treated rats. Sprague-Dawley rats were randomly assigned into 4 groups of 7 rats each and fed (1) an AIN-93G diet (NC), (2) 25% ethanol (E), (3) 25% ethanol and an AIN-93G diet containing 1% puffer flesh (E+F), or (4) 25% ethanol and an AIN-93G diet containing 1% puffer skin (E+S) for 5 wk. At the end of the experimental period, the rats were sacrificed and their blood and organs were collected. To evaluate the effect of puffer supplementation, lipid-soluble antioxidant vitamin and conjugated diene (CD) levels, DNA damage, and mRNA expression of heme oxygenase-1 (HO-1) were assessed. Animals that were fed ethanol showed reduced plasma levels of lipid-soluble antioxidant vitamin and significantly increased levels of lipid peroxides, DNA damage, and HO-1 expression. Dietary supplementation with puffer conferred an antioxidant effect by significantly increasing the levels of γ-tocopherol, a lipid-soluble antioxidant vitamin, and by significantly decreasing the plasma levels of CD, DNA damage, and HO-1 expression. These results suggest that consumption of puffer improves the antioxidant status of ethanol-treated rats.

On the origins and biosynthesis of tetrodotoxin

The potent neurotoxin tetrodotoxin (TTX) has been identified from taxonomically diverse marine organisms. TTX possesses a unique cage-like structure, however, its biosynthesis has yet to be elucidated. Biosynthetic studies in the TTX-producing newt Taricha torosa, and in bacterial genera, including Vibrio, have proven inconclusive. Indeed, very few studies have been performed that address the cellular production of TTX. Here we review the sources of TTX described to date and provide evidence for the biosynthesis of TTX by symbiotic microorganisms in higher taxa. Chemical and genetic based biosynthesis studies of TTX undertaken thus far are discussed and we outline approaches which may be useful for expanding upon the current body of knowledge. The complex biosynthesis of structurally similar toxins, that reveal clues into the biosynthetic pathway of TTX, is also presented.

LC/MS analysis of tetrodotoxin and its deoxy analogs in the marine puffer fish Fugu niphobles from the southern coast of Korea, and in the brackishwater puffer fishes Tetraodon nigroviridis and Tetraodon biocellatus from Southeast Asia

Tetrodotoxin (TTX) and its deoxy analogs, 5-deoxyTTX, 11-deoxyTTX, 6,11-dideoxyTTX, and 5,6,11-trideoxyTTX, were quantified in the tissues of three female and three male specimens of the marine puffer fish, Fugu niphobles, from the southern coast of Korea, and in the whole body of the brackishwater puffer fishes, Tetraodon nigroviridis (12 specimens) and Tetrodon biocellatus (three specimens) from Southeast Asia using LC/MS in single ion mode (SIM). Identification of these four deoxy analogs in the ovarian tissue of F. niphobles were further confirmed by LC/MS/MS. TTX and 5,6,11-trideoxyTTX were detected in all three puffer fish species as the major TTX analogs, similar to Japanese Fugu pardalis. While 6,11-dideoxyTTX was also found to be a major analog in almost all tissues of Korean F. niphobles, this analog was minor in the two Tetraodon species and Japanese F. pardalis. Among the tissues of F. niphobles, the concentrations of TTXs were highest in the ovaries (female) and skin (female and male).

Distribution and possible function of the marine alkaloid, norzoanthamine, in the zoanthid Zoanthus sp. using MALDI imaging mass spectrometry

The role of the marine alkaloid, norzoanthamine, in the colonial zoanthid Zoanthus sp. was previously unknown. High concentrations of norzoanthamine are present in the epidermal tissue of Zoanthus sp., as determined using protonated molecular ion peak mapping of norzoanthamine by matrix-assisted laser desorption/ionization mass spectrometry and high-performance liquid chromatography quantification. Sodium dodecylsulfate polyacrylamide gel electrophoresis experiments indicate that norzoanthamine increases the resistance of collagen to damage from UV light, probably not via UV light absorption, but by strengthening collagen itself, thus suggesting that collagen strengthening may be the function of norzoanthamine in Zoanthus sp.

Distribution of homologous proteins to puffer fish saxitoxin and tetrodotoxin binding protein in the plasma of puffer fish and among the tissues of Fugu pardalis examined by Western blot analysis

Puffer fish saxitoxin and tetrodotoxin binding protein (PSTBP) is a glycoprotein (200 kDa as a dimer) that we previously isolated from the plasma of Fugu pardalis (Yotsu-Yamashita et al., 2001). For the study on functions of PSTBP, here we examined distribution of homologous proteins to PSTBP in the plasma of seven species of puffer fish, and among the tissues of F. pardalis by Western blot analysis probed with a polyclonal IgG against unglycosylated PSTBP1 expressed in Echelichia coli. One or two major positive broad bands were detected at 105-140 kDa molecular weight range in the plasma (0.5 microg protein) of all species of puffer fish tested, while no band was detected in the plasma (5 microg protein) of fish other than puffer fish. Glycopeptidase F treated plasma of all species of puffer fish tested commonly showed the bands at approximately 42 kDa that was consistent to the molecular weight of unglycosylated PSTBP. These data suggest that puffer fish commonly possess glycoproteins homologous to PSTBP, but the sizes of N-glycan are specific to the species. Among soluble protein extracts (5 microg protein) from the tissues of F. pardalis, PSTBP was detected in all tissues examined, most prominently in heart, skin, and gall.

Maturation-associated changes in toxicity of the pufferfish Takifugu poecilonotus

From October 2006 to December 2007, wild specimens of the pufferfish Takifugu poecilonotus (93 females, 45 males) were collected from the Ariake Sea. Tissue toxicity was examined by mouse bioassay, and tetrodotoxin (TTX) content in the blood plasma by enzyme-linked immunosorbent assay. The relationship between toxicity and maturation was investigated based on changes in the gonadosomatic index: December-March in females and November-March in males, the 'maturation period'; April, 'just after spawning'; and the other months, the 'ordinary period'. Toxicity of both sexes was high throughout the year, but sharply declined in April. In all tissues examined (skin, liver, and ovary) other than testis, toxicity exceeded 1000 MU/g or 10,000 MU/individual in many individuals. Seasonal profiles of tissue toxicity differed markedly between sexes. In females, liver toxicity was high during the ordinary period, and ovary toxicity was high during the maturation period. In males, little maturation-associated change in the toxin distribution was observed. Plasma TTX levels were similar between the sexes (1.59-15.1 MU/ml), and fluctuated largely throughout the year without corresponding changes in tissue toxicity. The percentage of TTX binding to high molecular-weight substances in the plasma varied in association with maturation; the binding ratio fluctuated at relatively low levels during the ordinary period, and stabilized at a high level during the maturation period.

Examination of transformation among tetrodotoxin and its analogs in the living cultured juvenile puffer fish, kusafugu, Fugu niphobles by intramuscular administration

In puffer fish, tetrodotoxin (TTX) exists as the major toxin with chemically equilibrium analogs (4-epiTTX, 4,9-anhydroTTX) and chemically non-equilibrium analogs (deoxy analogs, 11-oxoTTX, 4-S-cysteinylTTX). There are two purposes to this study: 1) to search for the reason why TTX is the most major analog in puffer fish, even 4,9-anhydroTTX is chemically more stable, 2) to investigate whether or not chemically non-equilibrium analogs are transformed in puffer fish, because these were predicted to be biosynthetic intermediates. Pure TTX, 4-epiTTX, 4,9-anhydroTTX, and 11-oxoTTX were separately administrated to the cultured non-toxic juvenile puffer fish kusafugu, Fugu niphobles by intramuscular injection. Sixteen days after administration, TTX analogs in the whole fish were analyzed by LC-fluorescent detection and LC/MS. By the administration of TTX, 4-epiTTX, and 4,9-anhydroTTX, 34-40% of the administrated doses of the toxins were accumulated, and 4,9-anhydroTTX has become the major toxin after inter-conversion. This result indicates discrepancy from the previous ones wherein TTX was predominantly accumulated when TTXs were administrated through diets; this suggests that dietary administration might be necessary to accumulate TTX as the major toxin, and not 4,9-anhydroTTX. Transformations from TTX to deoxy analogs or 11-oxoTTX, or from 11-oxoTTX to TTX were not detected in this study.

First toxicity report of tetrodotoxin and 5,6,11-trideoxyTTX in the trumpet shell Charonia lampas lampas in Europe

Tetrodotoxin (TTX) is one of the most potent toxins already isolated, which occurs in a wide variety of animals. In this work, the occurrence of TTX and analogues was examined using mass spectrometry, confocal microscopy, liquid chromatography-mass spectrometry (LC-MS), and mouse bioassay in a trumpet shell (Charonia lampas lampas) and in the fluids of a patient poisoned by consuming this shell. Retention time data in the LC-MS system within the enhanced mass spectrum (EMS) mode indicated the presence of TTX and the analogue 5,6,11-trideoxyTTX; the enhanced product ion (EPI) mode confirmed the existence of both toxins with the formation of characteristic daughter ions from the fragment pattern of each molecule. TTX and 5,6,11-trideoxyTTX were only detected in the digestive gland of the trumpet shell and also in the urine and serum of the patient. The concentration of 5,6,11-trideoxyTTX checked in the samples by LC-MS was 3 times higher than TTX. However, the results obtained by mouse bioassay showed that the analogue is much less toxic than TTX. In vitro toxicity was checked using cerebellar cells; in these experiments the trumpet shell sample showed high toxicity, but the level was lower than in vivo results probably due to some competition between analogues. This paper shows for first time the presence and toxicity of TTX and 5,6,11-trideoxyTTX in a trumpet shell collected in the European coasts. The LC-MS method is a useful tool to confirm the presence of TTX and the further identification of TTX analogues.

Accumulation of tetrodotoxin and 4,9-anhydrotetrodotoxin in cultured juvenile kusafugu Fugu niphobles by dietary administration of natural toxic komonfugu Fugu poecilonotus liver

Non-toxic cultured juvenile kusafugu Fugu niphobles were fed with a diet containing highly toxic natural komonfugu Fugu poecilonotus liver until the 30th day (8.0 microg of TTX and 3.7 microg of 4,9-anhydroTTX/fish/day), and then fed with a non-toxic diet until the 240th day. During the 30-240th day, five or six fish were periodically sampled six times, and the contents of TTX and 4,9-anhydroTTX in each tissue were determined. The total TTX and 4,9-anhydroTTX accumulated in all tissues tested was not significantly changed during the experimental period, both being kept at 70% of administrated doses. However, in the liver, the TTX content accounted to be 120 microg (50% of administrated) on the 30th day, and then it gradually decreased to 50 microg until the 240th day, while 4,9-anhydroTTX content was kept at approximately 40 microg (40% of administrated) during all the experimental periods. In contrast to the liver, in the skin, TTX and 4,9-anhydroTTX were 40 and 5 microg, respectively, on the 30th day, and then gradually increased to 80 and 24 microg, respectively, until the 240th day. In the intestine, TTX and 4,9-anhydroTTX contents were kept at 25 and 12 microg, respectively, during all the experimental periods. According to these results, we assumed that a part of TTX accumulated in the liver was slowly transferred to the skin.

Toxin-resistant sodium channels: parallel adaptive evolution across a complete gene family

Approximately 75% of vertebrate proteins belong to protein families encoded by multiple evolutionarily related genes, a pattern that emerged as a result of gene and genome duplications over the course of vertebrate evolution. In families of genes with similar or related functions, adaptation to a strong selective agent should involve multiple adaptive changes across the entire gene family. However, we know of no evolutionary studies that have explicitly addressed this point. Here, we show how 4 taxonomically diverse species of pufferfishes (Tetraodontidae) each evolved resistance to the guanidinium toxins tetrodotoxin (TTX) and saxitoxin (STX) via parallel amino acid replacements across all 8 sodium channels present in teleost fish genomes. This resulted in diverse suites of coexisting sodium channel types that all confer varying degrees of toxin resistance, yet show remarkable convergence among genes and phylogenetically diverse species. Using site-directed mutagenesis and expression of a vertebrate sodium channel, we also demonstrate that resistance to TTX/STX is enhanced up to 15-fold by single, frequently observed replacements at 2 sites that have not previously been implicated in toxin binding but show similar or identical replacements in pufferfishes and in distantly related vertebrate and nonvertebrate animals. This study presents an example of natural selection acting upon a complete gene family, repeatedly arriving at a diverse but limited number of adaptive changes within the same genome. To be maximally informative, we suggest that future studies of molecular adaptation should consider all functionally similar paralogs of the affected gene family.

6,11-Dideoxytetrodotoxin from the puffer fish, Fugu pardalis

The presence of an unknown dideoxy analog of tetrodotoxin was suggested on the liquid chromatography/electrospray ionization-mass spectrometry mass chromatogram of the ovaries of the puffer fish, Fugu pardalis, in single ion monitoring mode to detect at m/z 288. We succeeded to isolate this analog (approximately 0.4 mg) from 200 g of the ovaries and the structure was determined as 6,11-dideoxytetrodotoxin by spectroscopic methods (high resolution-fast atom bombardment-MS and NMR spectroscopy). The discovery of the new analog is highly significant with respect to the biosynthesis or metabolism of tetrodotoxin. We also roughly determined the value of IC(50) (mice, intraperitoneal) for 6,11-dideoxytetrodotoxin as 420 microg/kg and thus it is 42 times less toxic than tetrodotoxin.

Determination of tetrodotoxin and its analogs in the puffer fish Takifugu oblongus from Bangladesh by hydrophilic interaction chromatography and mass-spectrometric detection

Tetrodotoxin (TTX) and its analogs (TTXs), widely distributed among marine as well as terrestrial animals, induce dangerous intoxications. These highly potential toxins are also known as the causative agent of puffer fish poisoning. A newly developed highly sensitive method for determination of TTXs based on hydrophilic interaction chromatography and mass-spectrometric detection is presented. TTX, anhydrotetrodotoxin, 11-deoxytetrodotoxin and trideoxytetrodotoxin were determined in separated tissues of Bangladeshi marine puffers, Takifugu oblongus. TTX was predominant in skin, muscle and liver, whereas trideoxytetrodotoxin preponderated in the ovary. The toxicity of the various tissues was determined by a mouse bioassay.