Cardiovascular effect is independent of hemolytic toxicity of tentacle-only extract from the jellyfish Cyanea capillata

Identification and characterization of the key lethal toxin from jellyfish Cyanea nozakii

Jellyfish Cyanea nozakii venom is a complex mixture of various toxins, most of which are proteinous biological macromolecules and are considered to be responsible for clinical symptoms or even death after a severe sting. Previous transcriptome and proteome analysis identified hundreds of toxins in the venom, including hemolysins, C-type lectin, phospholipase A₂, potassium channel inhibitor, metalloprotease, etc. However, it is not clear which toxin in the venom plays the most important role in lethality. Herein, we isolated the key lethal toxin (Letoxcn) from jellyfish Cyanea nozakii using anion exchange chromatography, size-exclusion chromatography, and cation exchange chromatography. The molecular weight of Letoxcn is ∼50 kDa with the N-terminal sequences of QADAEKVNLPVGVCV. Peptide mass fingerprinting analysis of Letoxcn shows that it may have some motifs of phospholipase, metalloproteinase, thrombin-like enzyme, potassium channel toxin, etc. However, only metalloproteinase activity but no hemolytic, PLA₂, or blood coagulation activity was observed from in vitro toxicity analysis. Overall, this study uncovered and characterized the key lethal toxin in the venom of jellyfish Cyanea nozakii, which will not only help to reveal the molecule mechanism of the lethality, but also develop effective treatment like antivenom for this jellyfish sting in the future.

Raising Awareness on the Clinical and Forensic Aspects of Jellyfish Stings: A Worldwide Increasing Threat

Jellyfish are ubiquitous animals registering a high and increasing number of contacts with humans in coastal areas. These encounters result in a multitude of symptoms, ranging from mild erythema to death. This work aims to review the state-of-the-art regarding pathophysiology, diagnosis, treatment, and relevant clinical and forensic aspects of jellyfish stings. There are three major classes of jellyfish, causing various clinical scenarios. Most envenomations result in an erythematous lesion with morphological characteristics that may help identify the class of jellyfish responsible. In rare cases, the sting may result in delayed, persistent, or systemic symptoms. Lethal encounters have been described, but most of those cases happened in the Indo-Pacific region, where cubozoans, the deadliest jellyfish class, can be found. The diagnosis is mostly clinical but can be aided by dermoscopy, skin scrapings/sticky tape, confocal reflectance microscopy, immunological essays, among others. Treatment is currently based on preventing further envenomation, inactivating the venom, and alleviating local and systemic symptoms. However, the strategy used to achieve these effects remains under debate. Only one antivenom is currently used and covers merely one species (Chironex fleckeri). Other antivenoms have been produced experimentally but were not tested on human envenomation settings. The increased number of cases, especially due to climate changes, justifies further research in the study of clinical aspects of jellyfish envenoming.

Combined Proteome and Toxicology Approach Reveals the Lethality of Venom Toxins from Jellyfish Cyanea nozakii

Jellyfish are a type of poisonous cnidarian invertebrate that secrete lethal venom for predation or defense. Human beings often become victims of jellyfish stings accidentally while swimming or fishing and suffer severe pain, itching, swelling, inflammation, shock, and even death. Jellyfish venom is composed of various toxins, and the lethal toxin is the most toxic and hazardous component of the venom, which is responsible for deaths caused by jellyfish stings and envenomation. Our previous study revealed many toxins in jellyfish venom, including phospholipase A2, metalloproteinase, and protease inhibitors. However, it is still unknown which type of toxin is lethal and how it works. Herein a combined toxicology analysis, proteome strategy, and purification approach was employed to investigate the lethality of the venom of the jellyfish Cyanea nozakii. Toxicity analysis revealed that cardiotoxicity including acute myocardial infarction and a significant decrease in both heart rate and blood pressure is the primary cause of death. Purified lethal toxin containing a fraction of jellyfish venom was subsequently subjected to proteome analysis and bioinformation analysis. A total of 316 and 374 homologous proteins were identified, including phospholipase A2-like toxins and metalloprotease-like toxins. Furthermore, we confirmed that the lethality of the jellyfish venom is related to metalloproteinase activity but without any phospholipase A2 activity or hemolytic activity. Altogether, this study not only provides a comprehensive understanding of the lethal mechanism of jellyfish venom but also provides very useful information for the therapeutic or rescue strategy for severe jellyfish stings.

Proteomic Investigation to Identify Anticancer Targets of Nemopilema nomurai Jellyfish Venom in Human Hepatocarcinoma HepG2 Cells

Nemopilema nomurai is a giant jellyfish that blooms in East Asian seas. Recently, N. nomurai venom (NnV) was characterized from a toxicological and pharmacological point of view. A mild dose of NnV inhibits the growth of various kinds of cancer cells, mainly hepatic cancer cells. The present study aims to identify the potential therapeutic targets and mechanism of NnV in the growth inhibition of cancer cells. Human hepatocellular carcinoma (HepG2) cells were treated with NnV, and its proteome was analyzed using two-dimensional gel electrophoresis, followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF/MS). The quantity of twenty four proteins in NnV-treated HepG2 cells varied compared to non-treated control cells. Among them, the amounts of fourteen proteins decreased and ten proteins showed elevated levels. We also found that the amounts of several cancer biomarkers and oncoproteins, which usually increase in various types of cancer cells, decreased after NnV treatment. The representative proteins included proliferating cell nuclear antigen (PCNA), glucose-regulated protein 78 (GRP78), glucose-6-phosphate dehydrogenase (G6PD), elongation factor 1γ (EF1γ), nucleolar and spindle-associated protein (NuSAP), and activator of 90 kDa heat shock protein ATPase homolog 1 (AHSA1). Western blotting also confirmed altered levels of PCNA, GRP78, and G6PD in NnV-treated HepG2 cells. In summary, the proteomic approach explains the mode of action of NnV as an anticancer agent. Further characterization of NnV may help to unveil novel therapeutic agents in cancer treatment.

Acute lion's mane jellyfish, Cyanea capillata (Cnideria: Scyphozoa), exposure to Atlantic salmon (Salmo salar L.)

Jellyfish-induced gill pathology relies upon occasional diagnostic observations yet the extent and impact of jellyfish blooms on aquaculture may be significant. Idiopathic gill lesions are often observed in apparently healthy fish. This study exposed Atlantic salmon (Salmo salar L.) smolts to macerated Cyanea capillata at 2.5 and 5 g/L for 2 hr under controlled laboratory conditions. Blood chemistry and gill histopathology were examined over a subsequent 4-week period. Fish showed an acute response to the presence of jellyfish, including characteristic external "whiplash" discoloration of the skin and acute increases in blood electrolytes and CO₂ concentration; however, these were resolved within 4 days after exposure. Histopathologically, gills showed first an acute oedema with epithelial separation followed by focal haemorrhage and thrombus formation, and then progressive inflammatory epithelial hyperplasia that progressively resolved over the 4 weeks post-exposure. Results were consistent with the envenomation of gills with cytotoxic neurotoxins and haemolysins known to be produced by C. capillata. This study suggests that many focal hyperplastic lesions on gills, especially those involving focal thrombi, may be the result of jellyfish stings. Thus, the presence of jellyfish and their impact may be severe and understated in terms of marine fish aquaculture and fish welfare.

Global Transcriptome Analysis of the Tentacle of the Jellyfish Cyanea capillata Using Deep Sequencing and Expressed Sequence Tags: Insight into the Toxin- and Degenerative Disease-Related Transcripts

BACKGROUND

Jellyfish contain diverse toxins and other bioactive components. However, large-scale identification of novel toxins and bioactive components from jellyfish has been hampered by the low efficiency of traditional isolation and purification methods.

RESULTS

We performed de novo transcriptome sequencing of the tentacle tissue of the jellyfish Cyanea capillata. A total of 51,304,108 reads were obtained and assembled into 50,536 unigenes. Of these, 21,357 unigenes had homologues in public databases, but the remaining unigenes had no significant matches due to the limited sequence information available and species-specific novel sequences. Functional annotation of the unigenes also revealed general gene expression profile characteristics in the tentacle of C. capillata. A primary goal of this study was to identify putative toxin transcripts. As expected, we screened many transcripts encoding proteins similar to several well-known toxin families including phospholipases, metalloproteases, serine proteases and serine protease inhibitors. In addition, some transcripts also resembled molecules with potential toxic activities, including cnidarian CfTX-like toxins with hemolytic activity, plancitoxin-1, venom toxin-like peptide-6, histamine-releasing factor, neprilysin, dipeptidyl peptidase 4, vascular endothelial growth factor A, angiotensin-converting enzyme-like and endothelin-converting enzyme 1-like proteins. Most of these molecules have not been previously reported in jellyfish. Interestingly, we also characterized a number of transcripts with similarities to proteins relevant to several degenerative diseases, including Huntington's, Alzheimer's and Parkinson's diseases. This is the first description of degenerative disease-associated genes in jellyfish.

CONCLUSION

We obtained a well-categorized and annotated transcriptome of C. capillata tentacle that will be an important and valuable resource for further understanding of jellyfish at the molecular level and information on the underlying molecular mechanisms of jellyfish stinging. The findings of this study may also be used in comparative studies of gene expression profiling among different jellyfish species.

Intracellular Ca(2+) overload induced by extracellular Ca(2+) entry plays an important role in acute heart dysfunction by tentacle extract from the jellyfish Cyanea capillata

The exact mechanism of acute heart dysfunction caused by jellyfish venom remains unclear for the moment. In the present study, we examined the problem caused by the tentacle extract (TE) from the jellyfish Cyanea capillata at the levels of whole animal, isolated heart, primarily cultured cardiomyocytes, and intracellular Ca(2+). The heart indexes, including HR, APs, LVPs, and MMLs, were all decreased significantly by TE in both whole animal and Langendorff-perfused isolated heart model. Imbalance of cardiac oxygen supply and demand also took place. In both Ca(2+)-containing and Ca(2+)-free bathing solutions, TE could cause obvious cytoplasmic Ca(2+) overload in NRVMs, but the cytoplasmic Ca(2+) increased faster, Ca(2+) overload peaks arrived earlier, and the morphological changes were more severe under the extracellular Ca(2+)-containing condition. L-type Ca(2+) channel blockers, as well as the inhibitor of ryanodine receptor (ryanodine), could improve the viability of NRVMs. Moreover, diltiazem significantly inhibited the acute heart dysfunction caused by TE in both Langendorff isolated heart model and whole animal. These results suggested that intracellular Ca(2+) overload induced by extracellular Ca(2+) entry plays an important role in acute heart failure by TE from the jellyfish C. capillata. Inhibition of extracellular Ca(2+) influx is a promising antagonistic alternative for heart damage by jellyfish venom.

Bioactive toxins from stinging jellyfish

Jellyfish blooms occur throughout the world. Human contact with a jellyfish induces a local reaction of the skin, which can be painful and leave scaring. Systemic symptoms are also observed and contact with some species is lethal. A number of studies have evaluated the in vitro biological activity of whole jellyfish venom or of purified fractions. Hemolytic, cytotoxic, neurotoxic or enzymatic activities are commonly observed. Some toxins have been purified and characterized. A family of pore forming toxins specific to Medusozoans has been identified. There remains a need for detailed characterization of jellyfish toxins to fully understand the symptoms observed in vivo.

Hemolytic venoms from marine cnidarian jellyfish - an overview

Cnidarian jellyfish are viewed as an emergent problem in several coastal zones throughout the world. Recurrent outbreaks pose a serious threat to tourists and bathers, as well as to sea-workers, involving health and economical aspects. As a rule, cnidarian stinging as a consequence of nematocyst firing induces merely local symptoms but cardiovascular or neurological complications can also occur. Hemolysis is a frequent effect of cnidarian stinging; this dangerous condition is known to be caused by several venoms and can sometimes be lethal. At present, the bulk of data concerning hemolytic cnidarian venoms comes from the study of benthic species, such as sea anemones and soft corals, but hemolytic factors were found in venoms of several siphonophore, cubozoan and scyphozoan jellyfish, which are mainly involved in the envenomation of bathers and sea-workers. Therefore, the aim of this paper is to review the scientific literature concerning the hemolytic venoms from cnidarian jellyfish taking into consideration their importance in human pathology as well as health implications and possible therapeutic measures.

Pharmacological studies of tentacle extract from the jellyfish Cyanea capillata in isolated rat aorta

Our previous studies demonstrated that tentacle extract (TE) from the jellyfish, Cyanea capillata, could cause a dose-dependent increase of systolic blood pressure, which seemed to be the result of direct constriction of vascular smooth muscle (VSM). The aim of this study is to investigate whether TE could induce vasoconstriction in vitro and to explore its potential mechanism. Using isolated aorta rings, a direct contractile response of TE was verified, which showed that TE could induce concentration-dependent contractile responses in both endothelium-intact and -denuded aortas. Interestingly, the amplitude of contraction in the endothelium-denuded aorta was much stronger than that in the endothelium-intact one, implying that TE might also bring a weak functional relaxation in addition to vasoconstriction. Further drug intervention experiments indicated that the functional vasodilation might be mediated by nitric oxide, and that TE-induced vasoconstriction could be attributed to calcium influx via voltage-operated calcium channels (VOCCs) from the extracellular space, as well as sarcoplasmic reticulum (SR) Ca²⁺ release via the inositol 1,4,5-trisphosphate receptor (IP₃R), leading to an increase in [Ca²⁺](c), instead of activation of the PLC/DAG/PKC pathway or the sympathetic nerve system.

Lipid peroxidation is another potential mechanism besides pore-formation underlying hemolysis of tentacle extract from the jellyfish Cyanea capillata

This study was performed to explore other potential mechanisms underlying hemolysis in addition to pore-formation of tentacle extract (TE) from the jellyfish Cyanea capillata. A dose-dependent increase of hemolysis was observed in rat erythrocyte suspensions and the hemolytic activity of TE was enhanced in the presence of Ca2+, which was attenuated by Ca2+ channel blockers (Diltiazem, Verapamil and Nifedipine). Direct intracellular Ca2+ increase was observed after TE treatment by confocal laser scanning microscopy, and the Ca2+ increase could be depressed by Diltiazem. The osmotic protectant polyethylenglycol (PEG) significantly blocked hemolysis with a molecular mass exceeding 4000 Da. These results support a pore-forming mechanism of TE in the erythrocyte membrane, which is consistent with previous studies by us and other groups. The concentration of malondialdehyde (MDA), an important marker of lipid peroxidation, increased dose-dependently in rat erythrocytes after TE treatment, while in vitro hemolysis of TE was inhibited by the antioxidants ascorbic acid-Vitamin C (Vc)-and reduced glutathione (GSH). Furthermore, in vivo hemolysis and electrolyte change after TE administration could be partly recovered by Vc. These results indicate that lipid peroxidation is another potential mechanism besides pore-formation underlying the hemolysis of TE, and both Ca2+ channel blockers and antioxidants could be useful candidates against the hemolytic activity of jellyfish venoms.