New Insights into the Toxin Diversity and Antimicrobial Activity of the “Fire Coral” Millepora complanata

Assessing the Utility of Broad-Acting Inhibitors as Therapeutics in Diverse Venoms

Examination of venom constituent bioactivities from diverse venomous animals shows certain highly conserved classes, including enzymes (e.g., phospholipases and metalloproteinases) and pore-forming proteins. While antivenoms targeting other unique and lethal venom components have proven to be life-saving, venom-enzyme-driven tissue damage and morbidity persists. Broad-acting enzyme inhibitors demonstrate the potential to augment antivenom approaches. In this study, we investigate the potential utility of certain broad-acting inhibitors in cubozoa for the first time. Fluorogenic assays were used to determine the phospholipase A2 (PLA2) and matrix metalloproteinase (MMP) activity of the Hawaiian box jellyfish, Alatina alata, and this was compared to representative elapid, viper, and bee venoms. In vitro, evaluation of selected small-molecule inhibitors demonstrated the ability and feasibility of the broad-acting therapeutic doxycycline, which inhibited the PLA2 and MMP activity of A. alata (approximately 50% reduction at 0.1 mM (95% CI 0.06-0.15) and 2.1 mM (95% CI 1.4-3.0), respectively), in addition to both snake venoms. Additionally, copper gluconate broadly inhibited the PLA2 activity of bee, snake, and jellyfish venoms. While all venoms are complex mixtures of bioactive molecules, these studies demonstrate that targeting common class components with broad-acting inhibitors shows promise in clinical and preclinical management.

Zinc speciation promotes distinct effects on dinoflagellate growth and coral trypsin-like enzyme activity

Zinc is an essential metal to living organisms, including corals and their symbiotic microalgae (Symbiodiniaceae). Both Zn(II) deprivation and overload are capable of leading to dysfunctional metabolism, coral bleaching, and even organism death. The present work investigated the effects of chemically defined Zn species (free Zn, ZnO nanoparticles, and the complexes Zn-histidinate and Zn-EDTA) over the growth of the dinoflagellates Symbiodinium microadriaticum, Breviolum minutum, and Effrenium voratum, and on the trypsin-like proteolytic activity of the hydrocoral Millepora alcicornis. B. minutum was the most sensitive strain to any form of added Zn. For the other strains, the complex [Zn(His)2] better translated metal load into growth. This complex was the only tested compound that did not interfere with the trypsin-like activity of Millepora alcicornis extracts. Also, histidine was able to recover the activity of the enzyme inhibited by zinc. [Zn(His)2] is a potential biocarrier of zinc for microalgae or coral cultivation. These findings suggest that the control of chemical speciation of an essential metal could lead to useful compounds that assist autotrophy, while not affecting heterotrophy, in the coral holobiont.

Unlocking Antimicrobial Peptides: In Silico Proteolysis and Artificial Intelligence-Driven Discovery from Cnidarian Omics

Overcoming the growing challenge of antimicrobial resistance (AMR), which affects millions of people worldwide, has driven attention for the exploration of marine-derived antimicrobial peptides (AMPs) for innovative solutions. Cnidarians, such as corals, sea anemones, and jellyfish, are a promising valuable resource of these bioactive peptides due to their robust innate immune systems yet are still poorly explored. Hence, we employed an in silico proteolysis strategy to search for novel AMPs from omics data of 111 Cnidaria species. Millions of peptides were retrieved and screened using shallow- and deep-learning models, prioritizing AMPs with a reduced toxicity and with a structural distinctiveness from characterized AMPs. After complex network analysis, a final dataset of 3130 Cnidaria singular non-haemolytic and non-toxic AMPs were identified. Such unique AMPs were mined for their putative antibacterial activity, revealing 20 favourable candidates for in vitro testing against important ESKAPEE pathogens, offering potential new avenues for antibiotic development.

Toxocara canis: Prospective activity of Quercetin and venom of Cassiopea andromeda (Cnidaria: Cassiopeidae) against third-stage larvae in vitro

Toxocariasis is a zoonotic parasitic infection with worldwide distribution and high impact on human health. It has a limited clinical resolution with the available drugs, making it challenging to treat. Quercetin, which possesses biological and pharmacological qualities including antiparasitic, antioxidant, and anticancer activities, is a possible substitute for the current medications. Marine invertebrates can produce a vast array of different molecules, many of which are biologically active substances with distinct characteristics. In this study, we assessed the in vitro nematocidal effect of both quercetin and venom of Cassiopea andromeda (jellyfish) against third larvae of Toxocara canis. In microplates with Roswell Park Memorial Institute-1640 medium, larvae were incubated with ethanolic extract of quercetin (0.01, 0.02, 0.05, 0.08, 0.1, 0.25, and 0.5 mM/mL) and water extract of C. andromeda venom (15, 20, 25, 30, 35, 40, and 60 µg/mL) to evaluate their larvicidal effect. A scanning electron microscopy has investigated the possible effect of lethal concentration (LC90) of both extracts on the body wall of cultivated larvae, in comparison with those cultivated in albendazole. Our study revealed the effects of both quercetin and C. andromeda venom exposure on the mortality rate and the ultrastructure of T. canis third larva in comparison with control and albendazole-treated groups.

Marine Envenomation in Okinawa: Overview and Treatment Concept

Okinawa prefecture is a popular tourist destination due to its beaches and reefs. The reefs host a large variety of animals, including a number of venomous species. Because of the popularity of the reefs and marine activities, people are frequently in close contact with dangerous venomous species and, thus, are exposed to potential envenomation. Commonly encountered venomous animals throughout Okinawa include the invertebrate cone snail, sea urchin, crown-of-thorns starfish, blue-ringed octopus, box jellyfish, and fire coral. The vertebrates include the stonefish, lionfish, sea snake, and moray eel. Treatment for marine envenomation can involve first aid, hot water immersion, antivenom, supportive care, regional anesthesia, and pharmaceutical administration. Information on venomous animals, their toxins, and treatment should be well understood by prehospital care providers and physicians practicing in the prefecture.

Transcriptomic and proteomic analyses reveal the first occurrence of diverse toxin groups in Millepora alcicornis

Millepora alcicornis is a reef-forming cnidarian widely distributed in the Mexican Caribbean. Millepora species or "fire corals" inflict a painful stinging reaction in humans when touched. Even though hundreds of organic and polypeptide toxins have been characterized from sea anemones and jellyfish, there are few reports regarding the diversity of toxins synthesized by fire corals. Here, based on transcriptomic analysis of M. alcicornis, several predicted proteins that show amino acid sequence similarity to toxins were identified, including neurotoxins, metalloproteases, hemostasis-impairing toxins, serin proteases, cysteine-rich venom proteins, phospholipases, complement system-impairing toxins, phosphodiesterases, pore-forming toxins, and L-aminoacid oxidases. The soluble nematocyst proteome of this organism was shown to induce hemolytic, proteolytic, and phospholipase A2 effects by gel zymography. Protein bands or spots on 1D- and 2D-PAGE gels corresponding to zones of hemolytic and enzymatic activities were excised, subjected to in-gel digestion with trypsin, and analyzed by mass spectrometry. These proteins exhibited sequence homology to PLA2s, metalloproteinases, pore-forming toxins, and neurotoxins, such as actitoxins and CrTX-A. The complex array of venom-related transcripts that were identified in M. alcicornis, some of which are first reported in "fire corals", provide novel insight into the structural richness of Cnidarian toxins and their distribution among species. SIGNIFICANCE: Marine organisms are a promising source of bioactive compounds with valuable contributions in diverse fields such as human health, pharmaceuticals, and industrial application. Currently, not much attention has been paid to the study of fire corals, which possess a variety of molecules that exhibit diverse toxic effects and therefore have great pharmaceutical and biotechnological potential. The isolation and identification of novel marine-derived toxins by classical approaches are time-consuming and have low yields. Thus, next-generation strategies, like base-'omics technologies, are essential for the high-throughput characterization of venom compounds such as those synthesized by fire corals. This study moves the field forward because it provides new insights regarding the first occurrence of diverse toxin groups in Millepora alcicornis. The findings presented here will contribute to the current understanding of the mechanisms of action of Millepora toxins. This research also reveals important information related to the potential role of toxins in the defense and capture of prey mechanisms and for designing appropriate treatments for fire coral envenomation. Moreover, due to the lack of information on the taxonomic identification of Millepora, the insights presented here can advise the taxonomic classification of the species of this genus.