Qianqian Wang

Jellyfish stings are the most common type of marine life injuries. However, at present, the treatment measures against jellyfish stings are mostly empirical and supportive, with uncertain therapeutic outcomes, and there is a lack of specific antidotes based on the toxic mechanism of jellyfish venom in clinical practice. In our previous study, polyphenol epigallocatechin-3-gallate (EGCG) was found to neutralize the toxicity of jellyfish Nemopilema nomurai venom (NnV) in vivo and in vitro. Herein we further demonstrated that EGCG exerted its antagonistic effect against NnV through inhibiting the oxidative stress, pro-apoptotic proteins, and systemic inflammatory responses. Subsequently, we constructed a polyethylene glycol (PEG)-EGCG/tetracycline hydrochloride (HTC) co-loaded micellar nanocomplex in order to enhance the stability and bioavailability of EGCG in vivo, which successfully integrated the membrane-repair function of PEG, the enzyme inhibitory effect of HTC and the antioxidant properties of EGCG. Notably, this micellar nanocomplex demonstrated significant protective effects against both functional damage and pathological alterations in a non-lethal NnV-envenomed mouse model. When administered 1 h after NnV envenomation, EGCG (40 mg/kg), HTC and PEG-EGCG (containing 40 mg/kg EGCG) only partially improved abnormal blood biochemical indicators and moderately alleviated histopathologic damage, and PEG-EGCG/HTC containing merely 8 mg/kg EGCG completely mitigated the toxic reactions in envenomed mice. In the preventive regimen, the administration of EGCG, HTC or PEG-EGCG 30 min before exposure showed no significant improvement in abnormal blood biochemical indicators and histopathologic damage, while PEG-EGCG/HTC could still significantly improve the functional impairments and histopathologic damage of the heart and liver in NnV-envenomed mice. These findings suggest the clinical translational potential of PEG-EGCG/HTC against jellyfish envenomation.

Excessive ultraviolet B (UVB) exposure is the leading environmental contributor to the development of skin aging, also referred to as photoaging. We previously obtained a group of modified antioxidant peptides (WP5, LW5 and YY6), which were derived from marine organisms, through a single amino acid substitution, and demonstrated that the antioxidant peptides exhibited apparent protective effects against UVB-induced oxidative damage in human keratinocyte cells. Nonetheless, it remains uncertain whether they can alleviate skin photoaging caused by UVB. This research aims to investigate the anti-photoaging effects of the antioxidant peptides in vitro and in vivo and the underlying molecular mechanisms. We found that the antioxidant peptides significantly alleviated the senescence of HDF-a cells induced by UVB and suppressed the expression of matrix metalloproteinases (MMPs) and the degradation of collagen I, and the mitogen-activated protein kinase (MAPK) pathways, particularly the p38 MAPK pathway, might involve in anti-photoaging effects of the antioxidant peptides in HDF-a cells. Furthermore, an emulsion containing antioxidant peptides was prepared, and it was also found to inhibit the expression of MMPs and inflammation factors IL-6 and IL-1β in the mice exposed to UVB. Our results suggest that these antioxidant peptides might be applied as effective components in cosmetics for retarding skin photoaging in the future.

Nemopilema nomurai is a species of common large toxic jellyfish in China seas, and its tentacle tissues contain various types of nematocysts. However, the correlation between the morphology and function of nematocysts still remains unclear. In this study, we first obtained two monomorphic nematocysts with high-purity from N. nomurai, namely Anisorhizas and O-isorhizas, by density gradient centrifugation: the Anisorhizas is small and rod-shaped and the O-isorhizas is larger and spherical. Upon deionized water stimulation, O-isorhizas exhibited a stronger discharge capability than Anisorhizas. The nematocyst contents of Anisorhizas (AnC) and O-isorhizas (OnC) were extracted separately, and their composition and bioactivities were analyzed simultaneously. The protein bands by SDS-PAGE revealed similar distributions in AnC and OnC, except that the protein band distribution in OnC was more extensive. OnC showed stronger cytotoxicity, hemolytic activity, metalloprotease activity, and serine protease activity than AnC. In contrast, AnC exhibited a higher antioxidant activity and significant proinflammatory activity. Both AnC and OnC exhibited antimicrobial activities against certain marine pathogenic Vibrios. These results suggest that O-isorhizas, with the larger capsule capability, stronger discharge ability and toxicity, likely plays a major role in inducing toxic effects and tissue damage, while Anisorhizas, being smaller and less toxic, may undertake preferentially other functions, such as synergistic predation, environmental stress adaptation, and energy balance maintenance. This study provides insights into the morpho-functional relationship between various types of nematocysts, and also lays a foundation for further exploration of the functional diversity of nematocysts and the mechanisms underlying jellyfish envenomation.

Nemopilema nomurai is a species of common large toxic jellyfish in China seas, and its tentacle tissues contain various types of nematocysts. However, the correlation between the morphology and function of nematocysts still remains unclear. In this study, we first obtained two monomorphic nematocysts with high-purity from N. nomurai, namely Anisorhizas and O-isorhizas, by density gradient centrifugation: the Anisorhizas is small and rod-shaped and the O-isorhizas is larger and spherical. Upon deionized water stimulation, O-isorhizas exhibited a stronger discharge capability than Anisorhizas. The nematocyst contents of Anisorhizas (AnC) and O-isorhizas (OnC) were extracted separately, and their composition and bioactivities were analyzed simultaneously. The protein bands by SDS-PAGE revealed similar distributions in AnC and OnC, except that the protein band distribution in OnC was more extensive. OnC showed stronger cytotoxicity, hemolytic activity, metalloprotease activity, and serine protease activity than AnC. In contrast, AnC exhibited a higher antioxidant activity and significant proinflammatory activity. Both AnC and OnC exhibited antimicrobial activities against certain marine pathogenic Vibrios. These results suggest that O-isorhizas, with the larger capsule capability, stronger discharge ability and toxicity, likely plays a major role in inducing toxic effects and tissue damage, while Anisorhizas, being smaller and less toxic, may undertake preferentially other functions, such as synergistic predation, environmental stress adaptation, and energy balance maintenance. This study provides insights into the morpho-functional relationship between various types of nematocysts, and also lays a foundation for further exploration of the functional diversity of nematocysts and the mechanisms underlying jellyfish envenomation.

Tetrodotoxin (TTX) is a highly fatal marine biotoxin. Constantly increasing intoxications and the lack of specific antitoxic drugs in clinical applications highlight the need for further research into the toxic effects of TTX. Current reports on poisoning cases and the TTX toxicity mechanism suggest that the blocking of voltage-gated sodium channels (VGSCs) by TTX is probably reversible, but direct evidence of this is lacking, as far as we are aware. This study explored the acute toxic effects of TTX at sub-lethal doses via different routes, analyzing variations in muscle strength and TTX concentration in the blood in mice. We found that the loss of muscle strength in mice caused by TTX was dose-dependent and reversible, and the death time and muscle strength variations after oral gavage with TTX appeared to occur later and were more variable than those after intramuscular injection. In conclusion, we systematically compared the acute toxic effects of TTX for two different administration routes at sub-lethal doses, directly verifying the reversible reaction of TTX blocking VGSCs and speculating that averting a complete block of VGSCs by TTX could be an effective strategy for preventing death from TTX poisoning. This work may provide data for the diagnosis and treatment of TTX poisoning.