Novel heterologously expressed protein, AjPSPLP-3, derived from Apostichopus japonicus exhibits cell proliferation and migration activities.

Developing more effective bioactive ingredients of natural origin is imperative for promoting wound healing. Sea cucumbers have long enjoyed a good reputation as both food delicacies and traditional medicines. In this study, we heterogeneously expressed a Apostichopus japonicus derived novel protein AjPSPLP-3, which exhibits a theoretical molecular weight of 13.034 kDa, through fusion with maltose binding protein (MBP). AjPSPLP-3 contains a strict CXXCXC motif, nine extremely conserved cysteine residues and two highly conserved cysteine residues. The predicted structure of AjPSPLP-3 consists of random coil and nine ß-sheets, Cys30-Cys67, Cys38-Cys58, Cys53-Cys90, Cys56-Cys66, and Cys81-Cys102 participating in the formation of five pairs of disulfide bonds. In vitro experiments conducted on HaCaT cells proved that AjPSPLP-3 and MBP-fused AjPSPLP-3 significantly contribute to HaCaT cells proliferation and migration without exhibiting hemolytic activity on murine erythrocytes. Specifically, treatment with 10 µmol/L MBP-fused AjPSPLP-3 protein increased the viability of HaCaT cells by 12.28 % (p < 0.001), while treatment with 10 µmol/L AjPSPLP-3 protein increased viability of HaCaT cells by 6.01 % (p < 0.01). Furthermore, wound closure of MBP-fused AjPSPLP-3 and AjPSPLP-3 were 22.51 % (p < 0.01) and 7.32 % (p < 0.05) higher than that of the control groups in HaCaT cells following 24 h of incubation.

Vibrio splendidus infection promotes circRNA-FGL1-regulated coelomocyte apoptosis via competitive binding to Myc with the deubiquitinase OTUB1 in Apostichopus japonicus.

Circular RNAs (circRNAs) are involved in various physiological and pathological processes in both vertebrates and invertebrates. However, most studies on circRNAs have focused on their roles as endogenous competitive RNAs. Here, we report a novel function of circRNA derived from the Fibrinogen-like protein 1 gene (circ-FGL1) that inhibits coelomocyte apoptosis via competing with the deubiquitinase AjOTUB1 to bind AjMyc in Apostichopus japonicus during Vibrio splendidus infection. The results showed that circ-FGL1 is significantly downregulated in coelomocytes of V. splendidus-induced A. japonicus and negatively regulates coelomocyte apoptosis through the AjBax-AjCyt c pathway. Mechanistically, the deubiquitinase AjOTUB1 and circ-FGL1 could interact with the transcription factor protein AjMyc in the same region with circ-FGL1/AjMyc having greater affinity. Under normal conditions, high levels of circ-FGL1 bind directly to AjMyc, inhibiting the deubiquitylation of AjMyc by AjOTUB1 and leading to the degradation of AjMyc. After V. splendidus infection, AjMyc disassociates from the depressed expression of circ-FGL1, promoting its deubiquitylation by binding to the induced deubiquitinase AjOTUB1 to inhibit its degradation. AjMyc is then transferred to the nucleus and promotes the transcription of AjCyt c and AjBax to induce coelomocyte apoptosis. The new finding will expand our present outstanding on the functional role of circRNAs and suggest new therapeutic targets for the treatment of echinoderms during bacterial invasion.

Proteomics Analysis of the Protective Effect of Polydeoxyribonucleotide Extracted from Sea Cucumber (Apostichopus japonicus) Sperm in a Hydrogen Peroxide-Induced RAW264.7 Cell Injury Model.

Sea cucumber viscera contain various naturally occurring active substances, but they are often underutilized during sea cucumber processing. Polydeoxyribonucleotide (PDRN) is an adenosine A2A receptor agonist that activates the A2A receptor to produce various biological effects. Currently, most studies on the activity of PDRN have focused on its anti-inflammatory, anti-apoptotic, and tissue repair properties, yet relatively few studies have investigated its antioxidant activity. In this study, we reported for the first time that PDRN was extracted from the sperm of Apostichopus japonicus (AJS-PDRN), and we evaluated its antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS), and hydroxyl radical scavenging assays. An in vitro injury model was established using H2O2-induced oxidative damage in RAW264.7 cells, and we investigated the protective effect of AJS-PDRN on these cells. Additionally, we explored the potential mechanism by which AJS-PDRN protects RAW264.7 cells from damage using iTRAQ proteomics analysis. The results showed that AJS-PDRN possessed excellent antioxidant activity and could significantly scavenge DPPH, ABTS, and hydroxyl radicals. In vitro antioxidant assays demonstrated that AJS-PDRN was cytoprotective and significantly enhanced the antioxidant capacity of RAW264.7 cells. The results of GO enrichment and KEGG pathway analysis indicate that the protective effects of AJS-PDRN pretreatment on RAW264.7 cells are primarily achieved through the regulation of immune and inflammatory responses, modulation of the extracellular matrix and signal transduction pathways, promotion of membrane repair, and enhancement of cellular antioxidant capacity. The results of a protein-protein interaction (PPI) network analysis indicate that AJS-PDRN reduces cellular oxidative damage by upregulating the expression of intracellular selenoprotein family members. In summary, our findings reveal that AJS-PDRN mitigates H2O2-induced oxidative damage through multiple pathways, underscoring its significant potential in the prevention and treatment of diseases caused by oxidative stress.

The nuclear receptor coactivator 4 regulates ferritinophagy induced by vibrio splendidus in coelomocytes of Apostichopus japonicus.

Iron homeostasis is vital for the host's defense against pathogenic invasion and the ferritinophagy is a crucial mechanism in maintaining intracellular iron homeostasis by facilitating the degradation and recycling of stored iron. The nuclear receptor coactivator 4 (NCOA4) serves as a ferritinophagy receptor, facilitating the binding and delivery of ferritin to the autophagosome and lysosome. However, NCOA4 of the sea cucumber Apostichopus japonicus (AjNCOA4) has not been reported until now. In this study, we identified and characterized AjNCOA4 in A. japonicus. This gene encodes a polypeptide containing 597 amino acids with an open reading frame of 1794 bp. The inferred amino acid sequence of AjNCOA4 comprises an ARA70 domain. Furthermore, a multiple sequence alignment demonstrated varying degrees of sequence homology between AjNCOA4 from A. japonicus and other NCOA4 orthologs. The phylogenetic tree of NCOA4 correlates with the established timeline of metazoan evolution. Expression analysis revealed that AjNCOA4 is expressed in all tested tissues, including the body wall, muscle, intestine, respiratory tree, and coelomocytes. Following challenge with Vibrio splendidus, the coelomocytes exhibited a significant increase in AjNCOA4 mRNA levels, peaking at 24 h. We successfully obtained recombinant AjNCOA4 protein through prokaryotic expression and prepared a specific polyclonal antibody. Immunofluorescence and co-immunoprecipitation experiments demonstrated an interaction between AjNCOA4 and AjFerritin in coelomocytes. RNA interference-mediated knockdown of AjNCOA4 expression resulted in elevated iron ion levels in coelomocytes. Bacterial stimulation enhanced ferritinophagy in coelomocytes, while knockdown of AjNCOA4 reduced the occurrence of ferritinophagy. These findings suggest that AjNCOA4 modulates ferritinophagy induced by V. splendidus in coelomocytes of A. japonicus.

Response and adaptation mechanisms of Apostichopus japonicus to single and combined anthropogenic stresses of polystyrene microplastics or cadmium.

Microplastics (MPs) have become pervasive in marine ecosystems, exerting detrimental effects on marine life. The concurrent presence and interaction of MPs and heavy metals in aquatic environments could engender more insidious toxicological impacts. This study aimed to elucidate the potential impacts and underlying mechanisms of polystyrene microplastics (PS-MPs), cadmium (Cd), and their combined stress (MPs-Cd) on sea cucumbers (Apostichopus japonicus). It focused on the growth, Cd bioaccumulation, oxidative stress responses, immunoenzymatic activities, and metabolic profiles, specifically considering PS-MPs sizes preferentially ingested by these organisms. The high-dose MPs (MH) treatment group exhibited an increase in cadmium bioavailability within the sea cucumbers. Exposure to PS-MPs or Cd triggered the activation of antioxidant defenses and immune responses. PS-MPs and Cd exhibited a synergistic effect on lysozyme (LZM) activity. A total of 149, 316, 211, 197, 215, 619, 434, and 602 differentially expressed metabolites were identified, distinguishing the low-dose MPs (ML), high-dose MPs (MH), low-dose Cd (LCd), low-dose MPs and low-dose Cd (MLLCd), high-dose MPs and low-dose Cd (MHLCd), high-dose Cd (HCd), low-dose MPs and high-dose Cd (MLHCd), high-dose MPs and high-dose Cd (MHHCd) groups, respectively. Metabolomic analyses revealed disruptions in lipid metabolism, nervous system function, signal transduction, and transport and catabolism pathways following exposure to PS-MPs, Cd, and MPs-Cd. Correlation analyses among key differentially expressed metabolites (DEMs) underscored the interregulation among these metabolic pathways. These results offer new perspectives on the distinct and synergistic toxicological impacts of microplastics and cadmium on aquatic species, highlighting the complex interplay between environmental contaminants and their effects on marine life.

Fucoidan from Apostichopus japonicus ameliorates alcoholic liver disease by regulating gut-liver axis homeostasis.

Long-term and excessive alcohol consumption can lead to the development of alcoholic liver disease (ALD), characterized by oxidative damage, intestinal barrier injury, and disruption of intestinal microbiota. In this study, we extracted fucoidan (Aj-FUC) from Apostichopus japonicus using enzymatic methods and characterized its structure. The ALD model was established in male Balb/c mice using 56° Baijiu, with silymarin as a positive control. Mice were orally administered 100 mg/kg·bw and 300 mg/kg·bw of Aj-FUC for 28 days to evaluate its effects on liver injury in ALD mice and explore its potential role in modulating the gut-liver axis. The results showed significant improvements in histopathological changes and liver disease in the Aj-FUC group. Aj-FUC treatment significantly increased the levels of glutathione (GSH) and glutathione peroxidase (GSH-Px) while weakly reduced the elevation of malondialdehyde (MDA) induced by ALD. It also regulated the Nrf2/HO-1 signaling pathway, collectively alleviating hepatic oxidative stress. Aj-FUC intervention upregulated the expression of ZO-1 and Occludin, thus contributing to repair the intestinal barrier. Additionally, Aj-FUC increased the content of short-chain fatty acids (SCFAs) and regulated the imbalance in gut microbiota. These results suggested that Aj-FUC alleviates ALD by modulating the gut-liver axis homeostasis. It may prove to be a useful dietary supplement in the treatment of alcoholic liver damage.

Polyphenol oxidase mediates (-)-epigallocatechin gallate to inhibit endogenous cathepsin activity in Apostichopus japonicus.

Apostichopus japonicus (A. japonicus) has rich nutritional value and is an important economic crop. Due to its rich endogenous enzyme system, fresh A. japonicus is prone to autolysis during market circulation and storage, resulting in economic losses. In order to alleviate this phenomenon, we investigated the effect of polyphenol oxidase (PPO) mediated (-)-epigallocatechin gallate (EGCG) on the activity and structure of endogenous cathepsin series protein (CEP) from A. japonicus. Research on cathepsin activity showed that PPO mediated EGCG could significantly reduce enzyme activity, resulting in a decrease in enzymatic reaction rate. SDS-PAGE and scanning electron microscopy results showed that PPO mediates EGCG could induce CEP aggregation to form protein aggregates. Various spectral results indicated that EGCG caused changes in the structure of CEP. Meanwhile, the conjugates formed by PPO mediated EGCG had lower thermal stability. In conclusion, PPO mediated EGCG was an effective method to inhibit the endogenous enzyme activity.

Effects of Dietary Zinc on Growth Performance, Digestive Enzyme Activities, Antioxidant Status, and Immune Responses of Sea Cucumber Apostichopus japonicus.

Zinc is an essential micronutrient for organisms involved in regulating various biological processes. This study evaluated the effects of dietary zinc on growth performance, digestive enzyme activities, antioxidant status, and immune responses of sea cucumber Apostichopus japonicus. Five experimental diets were formulated with graded levels of zinc (0, 20, 40, 60, and 80 mg/kg, respectively), and the actual dietary zinc values were 31.4, 51.0, 68.2, 91.9, and 110.8 mg/kg diet, respectively. Sea cucumbers were fed with diets for 2 months. The results showed the growth performance, amylase, and trypsin activities of sea cucumber increased significantly with zinc supplementation, and the best growth performance and enzyme activities were observed at 40 mg/kg zinc diet. Zinc supplementation significantly increased activities of superoxide dismutase, catalase, anti-superoxide anion, and inhibiting hydroxyl radical, while significantly reduced the malondialdehyde content. Furthermore, the higher zinc supplementation levels resulted in significantly upregulated immune-related genes of hsp90, p105, rel, and lsz, suggesting that excessive zinc caused oxidative stress. The broken-line regression analysis of specific growth rate indicated dietary zinc requirement in juvenile sea cucumber was ~ 66.3 mg/kg diet. Overall, dietary zinc contributes to the growth and immune resistance of juvenile sea cucumber, and our study will provide insights into the rational use of dietary zinc in aquaculture.

Chemical substances and their activities in sea cucumber Apostichopus japonicus: A review.

Apostichopus japonicus, also known as Stichopus japonicus, with medicinal and food homologous figures, is a globally recognized precious ingredient with extremely high nutritional value. There is no relevant review available through literature search, so this article selects the research articles through the keywords "sea cucumber" and "Apostichopus japonicus (Stichopus japonicus)" in six professional databases, such as Wiley, PubMed, ScienceDirect, ACS, Springer, and Web of Science, from 2000 to the present, summarizing the extraction, isolation, and purification methods for the four major categories (polysaccharides, proteins and peptides, saponins, and other components) of the A. japonicus chemical substances and 10 effective biological activities of A. japonicus. Included are anticoagulation, anticancer/antitumor activities, hematopoiesis, regulation of gut microbiota, and immune regulatory activities that correspond to traditional efficacy. Literature support is provided for the development of medicines and functional foods and related aspects that play a leading role in future directions.

Comprehensive metabolomics of Philippine Stichopus cf. horrens reveals diverse classes of valuable small molecules for biomedical applications.

Stichopus cf. horrens is an economically important sea cucumber species in Southeast Asia due to their presumed nutritional and medicinal benefits. However, compared to other sea cucumbers such as Apostichopus japonicus, there are no biochemical studies on which compounds contribute to the purported bioactivities of S. cf. horrens. To address this, a high-throughput characterization of the global metabolite profile of the species was performed through LC-MS/MS experiments and utilizing open-access platforms such as GNPS, XCMS, and metaboAnalyst. Bioinformatics-based molecular networking and chemometrics revealed the abundance of phospholipids such as phosphatidylcholines (PCs), phosphatidylethanolamines (PEs), phosphatidylinositols (PIs), and phosphatidylserines (PSs) in the crude samples. Body wall extracts were observed to have higher levels of structural, diacylated PCs, while the viscera have higher relative abundance of single-tail PCs and PEs that could be involved in digestion via nutrient absorption and transport for sea cucumbers. PEs and sphingolipids could also be implicated in the ecological response and morphological transformations of S. cf. horrens in the presence of predatory and other environmental stress. Interestingly, terpenoid glycosides and saponins with reported anti-cancer benefits were significantly localized in the body wall. The sulfated alkanes and sterols present in S. cf. horrens bear similarity to known kairomones and other signaling molecules. All in all, the results provide a baseline metabolomic profile of S. cf. horrens that may further be used for comparative and exploratory studies and suggest the untapped potential of S. cf. horrens as a source of bioactive molecules.

Transcriptome analysis reveals key transcription factors and pathways of polian vesicle associated with cell proliferation in Vibrio splendidus-challenged Apostichopus japonicus.

Polian vesicle is thought to produce coelomocytes and contribute to the sea cucumber's immune system. Our previous work has indicated that polian vesicle was responsible for cell proliferation at 72 h post pathogenic challenge. However, the transcription factors related to the activation of effector factors and the molecular process behind this remained unknown. In this study, to reveal the early functions of polian vesicle in response to the microbe, a comparative transcriptome sequencing of polian vesicle in V. splendidus-challenged Apostichopus japonicus, including normal group (PV 0 h), pathogen challenging for 6 h (PV 6 h) and 12 h (PV 12 h) was performed. Compared PV 0 h to PV 6 h, PV 0 h to PV 12 h, and PV 6 h to PV 12 h, we found 69, 211, and 175 differentially expressed genes (DEGs), respectively. KEGG enrichment analysis revealed the DEGs, including several transcription factors such as fos, FOS-FOX, ATF2, egr1, KLF2, and Notch3 between PV 6 h and PV 12 h were consistently enriched in MAPK, Apelin and Notch3 signaling pathways related to cell proliferation compared with that in PV 0 h. Important DEGs involved in cell growth were chosen, and their expression patterns were almost the same as the transcriptome profile analysis by qPCR. Protein interaction network analysis indicated that two DEGs of fos and egr1 were probably significant as key candidate genes controlling cell proliferation and differentiation in polian vesicle after pathogenic infection in A. japonicus. Overall, our analysis demonstrates that polian vesicles may play an essential role in regulating proliferation via transcription factors-mediated signaling pathway in A. japonicus and provide new insights into hematopoietic modulation of polian vesicles in response to pathogen infection.

Polyphenol extracts from Ascophyllum nodosum protected sea cucumber (Apostichopus japonicas) body wall against thermal degradation during tenderization.

To retard the protein degradation during sea cucumber processing, polyphenol extracts from Ascophyllum nodosum (PhE) was used as a potential antioxidant to maintain the structural integrity of sea cucumber body wall. Accordingly, the protection effects of PhE (0, 0.5, 1.0 and 1.5 mg PhE/g SFBW) against thermal degradation of the solid fragments of body wall (SFBW) have been investigated in order to evaluate their impact on the oxidation level and structural changes. Electronic Spin Resonance results showed that PhE could significantly inhibit the occurrence of oxidation by scavenging the free radicals. The effect of PhE on chemical analysis of soluble matters in SFBW was characterized by SDS-PAGE and HPLC. Compared with thermally treated SFBW, samples with PhE presented a decrease in protein dissolution. Thermal treatment resulted in the disintegration of collagen fibrils and fibril bundles in SFBW samples, while the density of collagen fibrils was increased, and the porosity decreased in samples with PhE. The results of FTIR and intrinsic tryptophan fluorescence confirmed that the structures of SFBW were modified by PhE. Besides, the denaturing temperature and decomposition temperature were both improved with the addition of PhE. These results suggested that PhE appeared to have a positive effect on lowering oxidation and improving thermostability and structural stability of SFBW, which could provide a theoretical basis for protecting sea cucumber body wall against degradation during thermal tenderization.

Single and combined effects of microplastics and cadmium on the sea cucumber Apostichopus japonicus.

Microplastic pollution of the ocean has received extensive attention as plastic pollution increases globally, but the potential ecological risks caused by microplastic interactions with trace metals still require further research. In this study, Apostichopus japonicus was used to explore the individual and combined toxicities of cadmium (Cd) and microplastics and their effects on growth, Cd tissue accumulation, digestive enzymes, and gut microbes. The body weight gain and specific growth rate of animals exposed to a combination of high concentrations of Cd and microplastics decreased. The addition of high concentrations of cadmium to the diet led to an increase in cadmium content in the respiratory tree, digestive tract and body wall. Amylase, lipase and trypsin decreased to different degrees in the group treated with high concentrations of Cd/microplastics. Firmicutes were significantly reduced across multiple treatment groups, with the order Lactobacillales being the most significantly affected. Cd is the pollutant causing the greatest negative impact, but the presence of microplastics undoubtedly increases its toxicity.

Bioaccumulation of functionalized polystyrene nanoplastics in sea cucumber Apostichopus japonicus (Selenka, 1867) and their toxic effects on oxidative stress, energy metabolism and mitochondrial pathway.

Micro/nano-plastics (M/NPs) are emerging contaminants in aquatic environment, however, little knowledge regarding the adverse effects of functionalized NPs has been documented so far. This study investigated the accumulation of different polystyrene nanoplastics (PS-NPs, i.e., plain PS, carboxyl-functional PS-COOH and amino-functional PS-NH2) at two particle sizes of 100 nm and 200 nm, and evaluated the impacts on oxidative stress, energy metabolism and mitochondrial pathway responses in intestine and respiratory tree of Apostichopus japonicus during the 20-d exposure experiment. The results showed that there were significant interactions of particle size and nanoplastic type on the accumulation of different PS-NPs. Exposure to NPs significantly increased the production of malondialdehyde, glutathione and reactive oxygen species, as well as the activities of antioxidant enzymes including glutathione reductase, superoxide dismutase and catalase, resulting in various degrees of oxidative damage in sea cucumber. The significant decrease in adenosine triphosphate content and increases in alkaline phosphatase and lactate dehydrogenase activities suggested that NPs impaired energy metabolism and modified their energy allocation. After 20-d exposure, the complex I, II and III activities in mitochondrial respiratory chain were significantly inhibited. Meanwhile, the Bax and Caspase-3 gene expression were significantly up-regulated, and Bacl-2 was down-regulated, indicating the toxicity on mitochondrial pathway of A. japonicus. The calculated IBR values elucidated the greater detriment to mitochondrial pathway than oxidative stress and energy metabolism. For 100 nm particle size, plain PS has stronger influence on all the biomarkers compared to PS-COOH/NH2, however, the opposite trends were observed in 200 nm PS-NPs. Furthermore, 100 nm PS-NPs were recognized to be more hazardous to sea cucumber than 200 nm microbeads. These findings provide new insights for understanding the differentiated toxic effects of functionalized NPs in marine invertebrates.

TMT-based proteomics analysis of growth advantage of triploid Apostichopus japonicus.

Polyploid breeding can produce new species with a faster growth rate, higher disease resistance, and higher survival rate, and has achieved significant economic benefits. This study investigated the protein differences in the body wall of triploid Apostichopus japonicus and diploid A. japonicus using isotope-labeled relative and absolute quantitative Tandem Mass Tag technology. A total of 21,096 independent peptides and 4621 proteins were identified. Among them, there were 723 proteins with significant expression differences, including 413 up-regulated proteins and 310 down-regulated proteins. The differentially expressed proteins (DEPs) were enriched in 4519 Gene Ontology enrichment pathways and 320 Kyoto Encyclopedia of Genes and Genomes enrichment pathways. Twenty-two key DEPs related to important functions such as growth and immunity of triploid A. japonicus were screened from the results, among which 20 were up-regulated, such as cathepsin L2 cysteine protease and fibrinogen-like protein A. Arylsulfatase A and zonadhesin were down-regulated. The up-regulated proteins were mainly involved in oxidative stress response, innate immune response, and collagen synthesis in triploid A. japonicus, and the down-regulated proteins were mainly associated with the sterility of triploid A. japonicus. In addition, the transcriptome and proteome were analyzed jointly to support proteome data. In this study, the differences in protein composition between triploid and diploid A. japonicus were analyzed for the first time, and the results revealed the underlying reasons for the growth advantage of triploid A. japonicus.

Cloning and functional analysis of a pacifastin-like protein from the sea cucumber, Apostichopus japonicus.

Pacifastin family proteins play a crucial role in regulating innate immune responses such as phagocytosis in invertebrates. However, the function of the Ajpacifastin-like counterpart in the sea cucumber Apostichopus japonicus remains elusive. In this study, the pacifastin gene of A. japonicus was cloned, characterized and named Ajpacifastin-like. The open reading frame of Ajpacifastin-like is 1497 bp in length and encodes a polypeptide containing 498 amino acid residues. Structural analysis revealed that the protein encoded by Ajpacifastin-like contains two pacifastin light chain domains (amino acids 287-322 and amino acids 376-407). Real-time reverse transcriptase PCR showed that Ajpacifastin-like mRNA is ubiquitously expressed in all tissues examined, with the highest expression in muscle. Ajpacifastin-like mRNA expression was significantly upregulated to 3.27-fold after challenge with Vibrio splendidus for 24 h. To explore the function of the Ajpacifastin-like protein in the immune response of A. japonicus, dsRNA interference with Ajpacifastin-like expression and with the expression of its postulated target gene was performed. Flow cytometry analysis showed that the rate of phagocytosis by coelomocytes increased to 1.21-fold in individuals treated with specific Ajpacifastin-like siRNA. However, rate of phagocytosis by coelomocytes decreased to 86% in individuals treated with Ajphenoloxidase siRNA. These results show that the Ajpacifastin-like gene is ubiquitously expressed in almost all tissues and that Ajpacifastin-like protein acts as an immunomodulatory factor via phenoloxidase to mediate phagocytosis by coelomocytes in pathogen-challenged A. japonicus.

The effect of 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47) on locomotor behaviour and muscle physiology of the sea cucumber Apostichopus japonicus.

The 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) is the predominant congener of polybrominated diphenyl ethers, and it is also a persistent organic pollutant that with a higher detection rate in samples from environment and animals. To date, there have been few studies of the effects of BDE-47 on locomotion in sea cucumbers. In this study, we investigated the influence of different concentrations of BDE-47 (low: 0.1 µg/L; moderate: 1.0 µg/L; high: 10.0 µg/L) on locomotion of Apostichopus japonicus and evaluated changes in their muscle physiology using ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry. The behavioural studies showed that the average and maximum velocity of movement decreased significantly in both the moderate and high BDE-47 groups after 1 day of exposure. In addition, levels of 55 metabolites were identified and characterized in the longitudinal muscle of A. japonicus exposed to BDE-47. The alteration of taurine and norepinephrine levels indicated that BDE-47 had drastic physiological effects on the longitudinal muscle of A. japonicus.

Potential of Epidermal Growth Factor-like Peptide from the Sea Cucumber Stichopus horrens to Increase the Growth of Human Cells: In Silico Molecular Docking Approach.

The sea cucumber is prominent as a traditional remedy among Asians for wound healing due to its high capacity for regeneration after expulsion of its internal organs. A short peptide consisting of 45 amino acids from transcriptome data of Stichopus horrens (Sh-EGFl-1) shows a convincing capability to promote the growth of human melanoma cells. Molecular docking of Sh-EGFl-1 peptide with human epidermal growth factor receptor (hEGFR) exhibited a favorable intermolecular interaction, where most of the Sh-EGFl-1 residues interacted with calcium binding-like domains. A superimposed image of the docked structure against a human EGF-EGFR crystal model also gave an acceptable root mean square deviation (RMSD) value of less than 1.5 Å. Human cell growth was significantly improved by Sh-EGFl-1 peptide at a lower concentration in a cell proliferation assay. Gene expression profiling of the cells indicated that Sh-EGFl-1 has activates hEGFR through five epidermal growth factor signaling pathways; phosphoinositide 3-kinase (PI3K), mitogen-activated protein kinase (MAPK), phospholipase C gamma (PLC-gamma), Janus kinase-signal transducer and activator of transcription (JAK-STAT) and Ras homologous (Rho) pathways. All these pathways triggered cells' proliferation, differentiation, survival and re-organization of the actin cytoskeleton. Overall, this marine-derived, bioactive peptide has the capability to promote proliferation and could be further explored as a cell-growth-promoting agent for biomedical and bioprocessing applications.

A Peptide HEPFYGNEGALR from Apostichopus japonicus Alleviates Acute Alcoholic Liver Injury by Enhancing Antioxidant Response in Male C57BL/6J Mice.

Liver-related disease caused by alcohol is a frequent disorder of the hepatic tract. Heavy consumption of alcohol in a short period causes oxidative damage to the liver. Sea cucumber is abundant in nutrients and its various extracts have been studied for antioxidant properties. One peptide was isolated and identified from Apostichopus japonicus in our recent study. We investigated the benefits of the peptide in a model of acute ethanol-induced male C57BL/6J mice. Dietary intake of the peptide could attenuate hepatomegaly, hepatitis and the accumulation of lipid droplets, and increase antioxidant enzyme activities in mice with acute alcoholic liver injury. The results indicated that a 20 mg/kg peptide supplement could activate the Nrf2/HO-1 pathway and block the nuclear translocation of NF-κB to alleviate oxidative stress and inflammation. In addition, the preventive effects of peptide supplementation may be related to autophagy. This study suggests that dietary supplementation with a sea cucumber-derived peptide is one of the potential candidates to alleviate acute alcoholic liver injury.

Oral administration of sea cucumber (Stichopus japonicus) protein exerts wound healing effects via the PI3K/AKT/mTOR signaling pathway.

This study aimed to investigate the effect of the oral administration of sea cucumber protein (SCP) on wound healing. SCP was isolated and purified from the body wall of Stichopus japonicus. A mouse skin incision model was operated on to evaluate the wound repair effect of SCP. The histological changes in the skin at the wound sites of BALB/c mice were observed by staining with haematoxylin and eosin (H&E) and Masson's trichrome. The enzyme-linked immunosorbent assay (ELISA) was used to analyze the expression of inflammatory cytokines in BALB/c mice. The boost cell migration ability was detected by a scratch assay after HaCaT cells were cultured with digested SCP (dSCP). Western blotting and RT-PCR assays were performed to determine the mechanism of SCP promoting wound healing. As a result, the wound healing rate in the SCP high dose group was 1.3-fold, compared to that in the blank group on day 14. Also, increased epidermal thickness and 1.79-fold collagen deposition contrasted with the blank group. Additionally, SCP could up-regulate the levels of pro-inflammatory factors (IL-1ß, IL-6, TNF-α) from day 3 to 7 firstly and decreased from day 7 to 14. IL-8 expression continuously decreased while the level of anti-inflammatory factor (IL-10) increased during the healing stage. Furthermore, the cell closure area reached 67% after being treated with 50 µg mL-1 of dSCP for 48 h. Cell proliferation was associated with the dSCP-activated PI3K/AKT/mTOR pathway. Taken together, SCP can be orally used as an effective agent for wound repair.