Comparative study of the toxic effects of Chrysaora quinquecirrha (Cnidaria: Scyphozoa) and Chironex fleckeri (Cnidaria: Cubozoa) venoms using cell-based assays

Insights into the discovery and intervention of metalloproteinase in marine hazardous jellyfish

The proliferation of toxic organisms caused by changes in the marine environment, coupled with the rising human activities along the coastal lines, has resulted in an increasing number of stinging incidents, posing a serious threat to public health. Here, we evaluated the systemic toxicity of the venom in jellyfish Chrysaora quinquecirrha at both cellular and animal levels, and found that jellyfish tentacle extract (TE) has strong lethality accompanied by abnormal elevation of blood biochemical indicators and pathological changes. Joint analysis of transcriptome and proteome indicated that metalloproteinases are the predominant toxins in jellyfish. Specially, two key metalloproteinases DN6695_c0_g3 and DN8184_c0_g7 were identified by mass spectrometry of the red blood cell membrane and tetracycline hydrochloride (Tch) inhibition models. Structurally, molecular docking and kinetic analysis are employed and observed that Tch could inhibit the enzyme activity by binding to the hydrophobic pocket of the catalytic center. In this study, we demonstrated that Tch impedes the metalloproteinase activity thereby reducing the lethal effect of jellyfish, which suggests a potential strategy for combating the health threat of marine toxic jellyfish.

Fucoidan may treat jellyfish dermatitis by inhibiting the inflammatory effect of jellyfish venom

Jellyfish dermatitis is a common medical problem caused by jellyfish stings. However, there are no targeted and effective medications for their treatment. Here, the biological activity of fucoidan for treatment of jellyfish dermatitis was investigated for the first time. 3 mg/mL Fucoidan attenuated the inflammatory effects of Nemopilema nomurai nematocyst venom (NnNV), including dermal toxicity and myotoxicity. Fucoidan may decrease the inflammatory effects of NnNV by downregulating MAPK and NF-κB pathways. This may be attributed to the inhibitory effect of fucoidan on metalloproteinases and phospholipase A2 (PLA2) in NnNV. 3 mg/mL fucoidan reduced the metalloproteinase activity in NnNV from 316.33 ± 20.84 U/mg to 177.33 ± 25.36 U/mg, while the inhibition of PLA2 activity in NnNV by 1 mg/mL fucoidan could reach 37.67 ± 3.42 %. Besides, external application of 3 mg/mL fucoidan can effectively alleviate the symptoms of jellyfish dermatitis. These observations suggest that fucoidan has considerable potential for treatment of jellyfish dermatitis and could be regarded as a novel medicine for jellyfish envenomation. This study provides new ideas for treatment of jellyfish envenomation and suggests evidence for the use of fucoidan in the treatment of jellyfish dermatitis as well as broadens the potential application of fucoidan in clinical practice.

Phylogenetic and Selection Analysis of an Expanded Family of Putatively Pore-Forming Jellyfish Toxins (Cnidaria: Medusozoa)

Many jellyfish species are known to cause a painful sting, but box jellyfish (class Cubozoa) are a well-known danger to humans due to exceptionally potent venoms. Cubozoan toxicity has been attributed to the presence and abundance of cnidarian-specific pore-forming toxins called jellyfish toxins (JFTs), which are highly hemolytic and cardiotoxic. However, JFTs have also been found in other cnidarians outside of Cubozoa, and no comprehensive analysis of their phylogenetic distribution has been conducted to date. Here, we present a thorough annotation of JFTs from 147 cnidarian transcriptomes and document 111 novel putative JFTs from over 20 species within Medusozoa. Phylogenetic analyses show that JFTs form two distinct clades, which we call JFT-1 and JFT-2. JFT-1 includes all known potent cubozoan toxins, as well as hydrozoan and scyphozoan representatives, some of which were derived from medically relevant species. JFT-2 contains primarily uncharacterized JFTs. Although our analyses detected broad purifying selection across JFTs, we found that a subset of cubozoan JFT-1 sequences are influenced by gene-wide episodic positive selection compared with homologous toxins from other taxonomic groups. This suggests that duplication followed by neofunctionalization or subfunctionalization as a potential mechanism for the highly potent venom in cubozoans. Additionally, published RNA-seq data from several medusozoan species indicate that JFTs are differentially expressed, spatially and temporally, between functionally distinct tissues. Overall, our findings suggest a complex evolutionary history of JFTs involving duplication and selection that may have led to functional diversification, including variability in toxin potency and specificity.

Advances in DNA Barcoding of Toxic Marine Organisms

There are more than 200,000 marine species worldwide. These include many important economic species, such as large yellow croaker, ribbonfish, tuna, and salmon, but also many potentially toxic species, such as blue-green algae, diatoms, cnidarians, ctenophores, Nassarius spp., and pufferfish. However, some edible and toxic species may look similar, and the correct identification of marine species is thus a major issue. The failure of traditional classification methods in certain species has promoted the use of DNA barcoding, which uses short, standard DNA fragments to assist with species identification. In this review, we summarize recent advances in DNA barcoding of toxic marine species such as jellyfish and pufferfish, using genes including cytochrome oxidase I gene (COI), cytochrome b gene (cytb), 16S rDNA, internal transcribed spacer (ITS), and Ribulose-1,5-bisphosphate carboxylase oxygenase gene (rbcL). We also discuss the application of this technique for improving the identification of marine species. The use of DNA barcoding can benefit the studies of biological diversity, biogeography, food safety, and the detection of both invasive and new species. However, the technique has limitations, particularly for the analysis of complex objects and the selection of standard DNA barcodes. The development of high-throughput methods may offer solutions to some of these issues.

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.

Evidence for an Alternative Mechanism of Toxin Production in the Box Jellyfish Alatina alata

Cubozoans (box jellyfish) have a reputation as the most venomous animals on the planet. Herein, we provide a review of cubozoan prey capture and digestion informed by the scientific literature. Like all cnidarians, box jellyfish envenomation originates from structures secreted within nematocyte post-Golgi vesicles called nematocysts. When tentacles come in contact with prey or would-be predators, a cocktail of toxins is rapidly deployed from nematocysts via a long spiny tubule that serves to immobilize the target organism. The implication has long been that toxin peptides and proteins making up the venom within the nematocyst capsule are secreted directly by nematocytes during nematogenesis. However, our combined molecular and morphological analysis of the venomous box jellyfish Alatina alata suggests that gland cells with possible dual roles in secreting toxins and toxic-like enzymes are found in the gastric cirri. These putative gland cell assemblages might be functionally important internally (digestion of prey) as well as externally (envenomation) in cubozoans. Despite the absence of nematocysts in the gastric cirri of mature A. alata medusae, this area of the digestive system appears to be the region of the body where venom-implicated gene products are found in highest abundance, challenging the idea that in cnidarians venom is synthesized exclusively in, or nearby, nematocysts. In an effort to uncover evidence for a central area enriched in gland cells associated with the gastric cirri we provide a comparative description of the morphology of the digestive structures of A. alata and Carybdea box jellyfish species. Finally, we conduct a multi-faceted analysis of the gene ontology terms associated with venom-implicated genes expressed in the tentacle/pedalium and gastric cirri, with a particular emphasis on zinc metalloprotease homologs and genes encoding other bioactive proteins that are abundant in the A. alata transcriptome.

Cnidarian Jellyfish: Ecological Aspects, Nematocyst Isolation, and Treatment Methods of Sting

Cnidarians play an important role in ecosystem functioning, in the competition among species, and for possible utilization of several active compounds against cardiovascular, nervous, endocrine, immune, infective, and inflammatory disorders or having antitumoral properties, which have been extracted from these organisms. Nevertheless, notwithstanding these promising features, the main reason for which cnidarians are known is due to their venomousness as they have a serious impact on public health as well as in economy being able to affect some human activities. For this reason a preeminent subject of the research about cnidarians is the organization of proper systems and methods of care and treatment of stinging. This chapter aims to present the data about the morphological, ecological, toxicological, epidemiological, and therapeutic aspects regarding cnidarians with the purpose to summarize the existing knowledge and to stimulate future perspectives in the research on these organisms.

Medusa: A Review of an Ancient Cnidarian Body Form

Medusae (aka jellyfish) have multiphasic life cycles and a propensity to adapt to, and proliferate in, a plethora of aquatic habitats, connecting them to a number of ecological and societal issues. Now, in the midst of the genomics era, affordable next-generation sequencing (NGS) platforms coupled with publically available bioinformatics tools present the much-anticipated opportunity to explore medusa taxa as potential model systems. Genome-wide studies of medusae would provide a remarkable opportunity to address long-standing questions related to the biology, physiology, and nervous system of some of the earliest pelagic animals. Furthermore, medusae have become key targets in the exploration of marine natural products, in the development of marine biomarkers, and for their application to the biomedical and robotics fields. Presented here is a synopsis of the current state of medusa research, highlighting insights provided by multi-omics studies, as well as existing knowledge gaps, calling upon the scientific community to adopt a number of medusa taxa as model systems in forthcoming research endeavors.

Functional Elucidation of Nemopilema nomurai and Cyanea nozakii Nematocyst Venoms' Lytic Activity Using Mass Spectrometry and Zymography

Background: Medusozoans utilize explosively discharging penetrant nematocysts to inject venom into prey. These venoms are composed of highly complex proteins and peptides with extensive bioactivities, as observed in vitro. Diverse enzymatic toxins have been putatively identified in the venom of jellyfish, Nemopilema nomurai and Cyanea nozakii, through examination of their proteomes and transcriptomes. However, functional examination of putative enzymatic components identified in proteomic approaches to elucidate potential bioactivities is critically needed. Methods: In this study, enzymatic toxins were functionally identified using a combined approach consisting of in gel zymography and liquid chromatography tandem mass spectrometry (LC-MS/MS). The potential roles of metalloproteinases and lipases in hemolytic activity were explored using specific inhibitors. Results: Zymography indicated that nematocyst venom possessed protease-, lipase- and hyaluronidase-class activities. Further, proteomic approaches using LC-MS/MS indicated sequence homology of proteolytic bands observed in zymography to extant zinc metalloproteinase-disintegrins and astacin metalloproteinases. Moreover, pre-incubation of the metalloproteinase inhibitor batimastat with N. nomurai nematocyst venom resulted in an approximate 62% reduction of hemolysis compared to venom exposed sheep erythrocytes, suggesting that metalloproteinases contribute to hemolytic activity. Additionally, species within the molecular mass range of 14–18 kDa exhibited both egg yolk and erythrocyte lytic activities in gel overlay assays. Conclusion: For the first time, our findings demonstrate the contribution of jellyfish venom metalloproteinase and suggest the involvement of lipase species to hemolytic activity. Investigations of this relationship will facilitate a better understanding of the constituents and toxicity of jellyfish venom.

Bioactivity of Natural and Engineered Antimicrobial Peptides from Venom of the Scorpions Urodacus yaschenkoi and U. manicatus

The spread of multidrug-resistant human pathogens has drawn attention towards antimicrobial peptides (AMPs), which are major players in the innate immune systems of many organisms, including vertebrates, invertebrates, plants and microbes. Scorpion venom is an abundant source of novel and potent AMPs. Here, we investigated natural and engineered AMPs from the scorpions Urodacus yaschenkoi and U. manicatus to determine their antimicrobial spectra as well as their hemolytic/cytotoxic activity. None of the AMPs were active against fungi, but many of them were active at low concentrations (0.25–30 µM) against seven different bacteria. Hemolytic and cytotoxic activities were determined using pig erythrocytes and baby hamster kidney cells, respectively. The amino acid substitutions in the engineered AMPs did not inhibit cytotoxicity, but reduced hemolysis and therefore increased the therapeutic indices. The phylogenetic analysis of scorpion AMPs revealed they are closely related and the GXK motif is highly conserved. The engineered scorpion AMPs offer a promising alternative for the treatment of multidrug-resistant bacterial infections and could be modified further to reduce their hemolytic/cytotoxic activity.

A new transcriptome and transcriptome profiling of adult and larval tissue in the box jellyfish Alatina alata: an emerging model for studying venom, vision and sex

Background

Cubozoans (box jellyfish) are cnidarians that have evolved a number of distinguishing features. Many cubozoans have a particularly potent sting, effected by stinging structures called nematocysts; cubozoans have well-developed light sensation, possessing both image-forming lens eyes and light-sensitive eye spots; and some cubozoans have complex mating behaviors, including aggregations, copulation and internal fertilization. The cubozoan Alatina alata is emerging as a cnidarian model because it forms predictable monthly nearshore breeding aggregations in tropical to subtropical waters worldwide, making both adult and larval material reliably accessible. To develop resources for A. alata, this study generated a functionally annotated transcriptome of adult and larval tissue, applying preliminary differential expression analyses to identify candidate genes involved in nematogenesis and venom production, vision and extraocular sensory perception, and sexual reproduction, which for brevity we refer to as “venom”, “vision” and “sex”.

Results

We assembled a transcriptome de novo from RNA-Seq data pooled from multiple body parts (gastric cirri, ovaries, tentacle (with pedalium base) and rhopalium) of an adult female A. alata medusa and larval planulae. Our transcriptome comprises ~32 K transcripts, after filtering, and provides a basis for analyzing patterns of gene expression in adult and larval box jellyfish tissues. Furthermore, we annotated a large set of candidate genes putatively involved in venom, vision and sex, providing an initial molecular characterization of these complex features in cubozoans. Expression profiles and gene tree reconstruction provided a number of preliminary insights into the putative sites of nematogenesis and venom production, regions of phototransduction activity and fertilization dynamics in A. alata.

Conclusions

Our Alatina alata transcriptome significantly adds to the genomic resources for this emerging cubozoan model. This study provides the first annotated transcriptome from multiple tissues of a cubozoan focusing on both the adult and larvae. Our approach of using multiple body parts and life stages to generate this transcriptome effectively identified a broad range of candidate genes for the further study of coordinated processes associated with venom, vision and sex. This new genomic resource and the candidate gene dataset are valuable for further investigating the evolution of distinctive features of cubozoans, and of cnidarians more broadly.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2944-3) contains supplementary material, which is available to authorized users.

Tentacle Transcriptome and Venom Proteome of the Pacific Sea Nettle, Chrysaora fuscescens (Cnidaria: Scyphozoa)

Jellyfish venoms are rich sources of toxins designed to capture prey or deter predators, but they can also elicit harmful effects in humans. In this study, an integrated transcriptomic and proteomic approach was used to identify putative toxins and their potential role in the venom of the scyphozoan jellyfish Chrysaora fuscescens. A de novo tentacle transcriptome, containing more than 23,000 contigs, was constructed and used in proteomic analysis of C. fuscescens venom to identify potential toxins. From a total of 163 proteins identified in the venom proteome, 27 were classified as putative toxins and grouped into six protein families: proteinases, venom allergens, C-type lectins, pore-forming toxins, glycoside hydrolases and enzyme inhibitors. Other putative toxins identified in the transcriptome, but not the proteome, included additional proteinases as well as lipases and deoxyribonucleases. Sequence analysis also revealed the presence of ShKT domains in two putative venom proteins from the proteome and an additional 15 from the transcriptome, suggesting potential ion channel blockade or modulatory activities. Comparison of these potential toxins to those from other cnidarians provided insight into their possible roles in C. fuscescens venom and an overview of the diversity of potential toxin families in cnidarian venoms.