Therapeutic potential of abalone and status of bioactive molecules: A comprehensive review

Structural and functional characterization of Hdh-HSBP1 and its involvement in heat stress and early development in Pacific abalone, Haliotis discus hannai

Heat shock factor binding protein 1 (HSBP1) is known to regulate the activity of heat shock factor 1 (HSF1) and the early development of organisms. To understand the involvement of HSBP1 in the heat shock response and embryonic and larval development of Pacific abalone (Haliotis discus hannai), the Hdh-HSBP1 gene was sequenced from the digestive gland (DG) tissue. The full-length sequence of Hdh-HSBP1 encompassed 738 nucleotides, encoding an 8.42 kDa protein consisting of 75 deduced amino acids. The protein contains an HSBP1 domain and a coiled-coil domain, which are conserved features in the HSBP1 protein family. Protein-protein molecular docking revealed that the coiled-coil region of Hdh-HSBP1 binds to the coiled-coil region of Hdh-HSF1. Tissue expression analysis demonstrated that the highest Hdh-HSBP1 expression occurred in the DG, whereas seasonal expression analysis revealed that this gene was most highly expressed in summer. In heat-stressed abalone, the highest expression of Hdh-HSBP1 occurred at 30 °C. Moreover, time-series analysis revealed that the expression of this gene began to increase significantly at 6 h post-heat stress, with higher expression observed at 12 h and 24 h post-heat stress. Furthermore, Hdh-HSBP1 mRNA expression showed a link to ROS production. Additionally, the expression of Hdh-HSBP1 showed significantly higher expression in the early stages of embryonic development in Pacific abalone. These results suggest that Hdh-HSBP1 plays a crucial role in the stress physiology of Pacific abalone by interacting with Hdh-HSF1, as well as its embryonic development.

Molecular and structural analysis of Hdh-MIRP3 and its impact on reproductive regulation in female Pacific abalone, Haliotis discus hannai

Molluscan insulin-related peptides (MIRP) play a crucial role in various biological processes, including reproduction and larval development in mollusk species. To investigate the involvement of MIRP in the ovarian development of Pacific abalone (Haliotis discus hannai), the Hdh-MIRP3 was cloned from cerebral ganglion (CG). Hdh-MIRP3 cDNA was 993 bp long, encoded a 13.22 kDa peptide, comprising 118 amino acids. Fluorescence in situ hybridization confirmed the localization of Hdh-MIRP3 in the CG and ovary. Molecular docking revealed that Hdh-MIRP3 binds to the N-terminal region of Hdh-IRP-R. Tissue expression analysis showed the highest Hdh-MIRP3 expression in the CG, followed by ovarian tissue. Hdh-MIRP3 expression was significantly upregulated in the CG and ovary during the ripe stage of seasonal ovarian development and in effective accumulative temperature conditioned abalone. Furthermore, siRNA silencing of Hdh-MIRP3 significantly downregulated the expression of four reproduction-related genes, including Hdh-GnRH, Hdh-GnRH-R, Hdh-IRP-R, and Hdh-VTG in both the CG and ovary, and Hdh-MIRP3 as well. These results indicate that Hdh-MIRP3 acts as a regulator of ovarian development in Pacific abalone. Additionally, expression analysis indicated that Hdh-MIRP3 plays a role in embryonic and larval development. Overall, the present findings elucidate the role of Hdh-MIRP3 in reproductive development in female Pacific abalone.

Bioactivity-Guided Fraction from Viscera of Abalone, Haliotis discus hannai Suppresses Cellular Basophils Activation and Anaphylaxis in Mice

Basophils and mast cells are specialized effector cells in allergic reactions. Haliotis discus hannai (abalone), is valuable seafood. Abalone male viscera, which has a brownish color and has not been previously reported to show anti-allergic activities, was extracted with acetone. Six different acetone/hexane fractions (0, 10, 20, 30, 40, and 100%) were obtained using a silica column via β-hexosaminidase release inhibitory activity-guided selection in phorbol myristate acetate and a calcium ionophore, A23187 (PMACI)-induced human basophils, KU812F cells. The 40% acetone/hexane fraction (A40) exhibited the strongest inhibition of PMACI-induced-β-hexosaminidase release. This fraction dose-dependently inhibited reactive oxygen species (ROS) production and calcium mobilization without cytotoxicity. Western blot analysis revealed that A40 down-regulated PMACI-induced MAPK (ERK 1/2, p-38, and JNK) phosphorylation, and the NF-κB translocation from the cytosol to membrane. Moreover, A40 inhibited PMACI-induced interleukin (IL)-1β, IL-6, and IL-8 production. Anti-allergic activities of A40 were confirmed based on inhibitory effects on IL-4 and tumor necrosis factor alpha (TNF-α) production in compound (com) 48/80-induced rat basophilic leukemia (RBL)-2H3 cells. A40 inhibited β-hexosaminidase release and cytokine production such as IL-4 and TNF-α produced by com 48/80-stimulated RBL-2H3 cells. Furthermore, it's fraction attenuated the IgE/DNP-induced passive cutaneous anaphylaxis (PCA) reaction in the ears of BALB/c mice. Our results suggest that abalone contains the active fraction, A40 is a potent therapeutic and functional material to treat allergic diseases.

Physiological evaluation of seasonal sperm quality in a biannual spawner, Pacific abalone: Effects on in-vitro fertilization and cryotolerance

Pacific abalone, Haliotis discus hannai, is a highly valuable gastropod mollusk commonly found in Southeast Asia. The present study aims to analyze the seminal plasma quality, sperm quality, and cryotolerance of the Pacific abalone sperm during its reproductive season. The seminal plasma quality was evaluated by analyzing biochemical and metabolite composition, enzymatic activity (superoxide dismutase, catalase, and glutathione), and lipid peroxidation (LPO) activity. The sperm quality was evaluated by analyzing motility, concentration, volume, ATP content, acrosome integrity (AI), plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), DNA integrity, and fertilization potential. The cryotolerance capacity was evaluated by analyzing post-thaw motility, AI, PMI, MMP, and DNA integrity. Seminal plasma osmolarity was significantly higher (1123.3 ± 1.5 mOsmL-1) in May compared to other reproductive periods, with Cl- (516.8 ± 0.5 mM) and Na+ (460.2 ± 0.4 mM) as the dominant ions. The seminal plasma pH remained constant at 6.8 throughout the reproductive season. Improved enzymatic activity and lower LPO were detected in May or June. Sperm quality indicators were similar in May and June, except for sperm production. The fertilization potential (May: 93.0 ± 4.4%, June: 86.0 ± 7.2%) and hatching rate (May: 86.6 ± 5.78%, June: 82.3 ± 3.2%) of Pacific abalone were significantly higher in May or June than they were in other reproductive seasons. The motility (May: 50.19 ± 2.35%, June: 49.96 ± 1.60%), AI (May: 44.02 ± 3.46%, June: 42.16 ± 3.61%), PMI (May: 54.12 ± 3.29%, June: 52.82 ± 2.58%), and MMP (May: 44.02 ± 3.46%, June: 42.16 ± 3.61%) of the cryopreserved sperm were similar in May and June compared with those preserved in other reproductive seasons. The DNA integrity of the cryopreserved sperm was similar in May (80.3 ± 6.7%) or June (78.9 ± 7.4%) and had a higher cryotolerance than in other reproductive seasons. Hence, it can be suggested that May and/or June are suitable periods for sperm physiology experiments, artificial reproduction, and sperm cryopreservation of Pacific abalone.

Antimicrobial and anticarcinogenic activity of bioactive peptides derived from abalone viscera (Haliotis fulgens and Haliotis corrugata)

Bioactive peptides have been studied in several sources due to their valuable potential in the pharmaceutical and food industries. Abalone viscera, which are normally discarded as byproducts, are a rich source of protein. Thus, the aim of this study was to explore the potential bioactivity of peptides derived from abalone viscera (Haliotis fulgens and Haliotis corrugata) after hydrolysis with a commercial mixture of enzymes. The hydrolysates obtained were fractionated using gel filtration chromatography. The resulting hydrolysate fractions were investigated for their antimicrobial and cytotoxic activities, including the expression of gelatinases mmp-2 and mmp-9 in human prostate cancer cell lines (PC3). Results showed antimicrobial activity for protein fractions of H. corrugata against Proteus mirabilis and Pseudomona aeuroginosa (66.2-116.25 kDa), Bacillus subtilis (6.5-21.5 kDa), and Aspergillus niger (97.4-116.25 kDa), while H. fulgens peptide fractions (200-31 kDa) displayed activity against six bacterial strains, and fractions from 116.25 to 21.5 kDa had effects on the fungus A. niger, Alternaria alternata, and Aspergillus flavus. Additionally, protein fractions displayed cytotoxic activity, inhibiting 30.4-53.8% of PC3 cellular growth. Selected fractions decreased the PMA-induced and not-induced expressions of mmp-2 and mmp-9 in PC3 cells. Abalone viscera, as byproducts, can be used as a potential source of antimicrobial and anticancer peptides.

Glutathione reductase, a biomarker of pollutant and stress in Pacific abalone

Abalone are frequently exposed to several environmental factors including heavy metal toxicity, thermal stress, H2O2-stress, starvation, viral and bacterial infection that can induce oxidative stress. Glutathione reductase is a vital enzyme in the antioxidant defense system that catalyzes the reduction of oxidized glutathione to reduced glutathione. The present study aimed to identify and localize glutathione reductase in Pacific abalone (Hdh-GR) and assess its potential role in stress physiology, heavy metal toxicity, immune response, gonadal development, and metamorphosis. The mRNA expression of Hdh-GR was upregulated in response to thermal stress, starvation, H2O2-stress, and cadmium-exposed toxicity. The induced mRNA expression was also quantified in immune-challenged abalone. Moreover, the Hdh-GR expression was significantly higher during metamorphosis. The Hdh-GR mRNA expression showed an inverse relationship with ROS production in heat stressed Pacific abalone. These results suggest that Hdh-GR has central role in the stress physiology, immune response, gonadal development, and metamorphosis of Pacific abalone.

Computer-Aided Virtual Screening and In Vitro Validation of Biomimetic Tyrosinase Inhibitory Peptides from Abalone Peptidome

Hyperpigmentation is a medical and cosmetic problem caused by an excess accumulation of melanin or the overexpression of the enzyme tyrosinase, leading to several skin disorders, i.e., freckles, melasma, and skin cancer. Tyrosinase is a key enzyme in melanogenesis and thus a target for reducing melanin production. Although abalone is a good source of bioactive peptides that have been used for several properties including depigmentation, the available information on the anti-tyrosinase property of abalone peptides remains insufficient. This study investigated the anti-tyrosinase properties of Haliotis diversicolor tyrosinase inhibitory peptides (hdTIPs) based on mushroom tyrosinase, cellular tyrosinase, and melanin content assays. The binding conformation between peptides and tyrosinase was also examined by molecular docking and dynamics study. KNN1 showed a high potent inhibitory effect on mushroom tyrosinase with an IC₅₀ of 70.83 μM. Moreover, our selected hdTIPs could inhibit melanin production through the reductions in tyrosinase activity and reactive oxygen species (ROS) levels by enhancing the antioxidative enzymes. RF1 showed the highest activity on both cellular tyrosinase inhibition and ROS reduction. leading to the lower melanin content in B16F10 murine melanoma cells. Accordingly, it can be assumed that our selected peptides exhibited high potential in medical cosmetology applications.

Identification and Characterization of Hdh-FMRF2 Gene in Pacific Abalone and Its Possible Role in Reproduction and Larva Development

FMRFamide-related peptides are neuropeptides involved in a wide range of biological processes, including reproduction and larval development. To characterize the involvement of FMRFamide in the reproduction and larval development of Pacific abalone Haliotis discus hannai, an FMRFamide cDNA (Hdh-FMRF2) was cloned from the cerebral ganglion (CG). Fluorescence in situ hybridization and qRT-PCR were performed for functional characterization. The Hdh-FMRF2 cDNA encoded 204 deduced amino acids that contained a putative signal peptide and four FaRP domains. The major population of Hdh-FMRF2 neuronal cell bodies was localized in the cortex of CG. Hdh-FMRF2 mRNA expression was significantly upregulated in CG during the mature stage of gonadal development and effective accumulative temperature (EAT) exposed abalone in both sexes. In the induced spawning event, Hdh-FMRF2 expression was significantly upregulated during spawning in males. However, no upregulation was observed in females, suggesting Hdh-FMRF2 might inhibit gamete release in female abalone. These results revealed Hdh-FMRF2 as a reproduction related peptide. Furthermore, mRNA expression in larval development suggested that this peptide was also involved in larval development during development of Pacific abalone. Collectively, this study provides evidence of possible involvement of an FMRFamide neuropeptide in the reproduction and larval development of Pacific abalone.

Saccharides Influence Sperm Quality and Expressions of Motility and Fertilization-Associated Genes in Cryopreserved Sperm of Pacific Abalone, Haliotis discus hannai

Pacific abalone, Haliotis discus hannai, is a highly commercial seafood in Southeast Asia. The present study aimed to determine the influence of saccharides and vitamins on post-thaw sperm quality, ATP content, fertilization capacity, hatching capacity, and mRNA content of motility and fertilization-associated genes of Pacific abalone. Sperm cryopreserved using saccharides improved the post-thaw sperm quality including motility, acrosome integrity (AI), plasma membrane integrity (PMI), and mitochondrial membrane potential (MMP). However, vitamins (l-ascorbic acid) did not result in any significant improvement in sperm quality. Sperm cryopreserved using saccharides also improved ATP content, DNA integrity, and mRNA content of motility and fertilization-associated genes of post-thaw sperm than sperm cryopreserved without saccharides. Among sperm cryopreserved using different saccharides, post-thaw sperm quality indicators (except PMI) and mRNA content of motility and fertilization-associated genes did not show significant differences between sperm cryopreserved using 3% sucrose (S) combined with 8% dimethyl sulfoxide (DMSO) and sperm cryopreserved using 1% glucose (G) combined with 8% ethylene glycol (EG). However, sperm cryopreserved using 3% S + 8% DMSO showed higher post-thaw sperm quality (motility: 58.4 ± 2.9%, AI: 57.1 ± 3.2%, PMI: 65.3 ± 3.3%, and MMP: 59.1 ± 3.2%), ATP content (48.4 ± 1.8 nmol/ml), and % DNA in tail (2.09 ± 0.20%) than sperm cryopreserved using other saccharides. When sperms were cryopreserved using 3% S + 8% DMSO, the mRNA content of motility (heat shock protein 70, HSP70; heat shock protein 90, HSP90; protein kinase A, PKA-C; axonemal protein 66.0, Axpp66.0; and tektin-4) and fertilization-associated (sperm protein 18 kDa, SP18 kDa) genes were higher than in sperm cryopreserved using other saccharides. However, changes in the mRNA contents of these genes were insignificant between sperm cryopreserved using 3% S + 8% DMSO and 1% G + 8% EG. Taken together, these results indicate that cryopreservation using 3% S + 8% DMSO can improve post-thaw sperm quality and mRNA contents better than other examined cryoprotectants. The present study suggests that 3% S + 8% DMSO is a suitable cryoprotectant for sperm cryopreservation and molecular conservation of this valuable species.

Antioxidant Activity and Oxidative Stress-Oriented Apoptosis Pathway in Saccharides Supplemented Cryopreserved Sperm of Pacific Abalone, Haliotis discus hannai

The Pacific abalone Haliotis discus hannai is a highly commercialized seafood in Southeast Asia. The aim of the present study was to determine the antioxidant activity and oxidative stress-oriented apoptosis pathway in saccharides supplemented cryopreserved sperm of Pacific abalone. Cryopreserved sperm showed impaired antioxidant defenses due to the reduced mRNA abundance of antioxidant genes (CAT, Cu/Zn-SOD, Mn-SOD, GPx, GR, and BCL-2), apoptosis inhibitor (HSP70, and HSP90) gene, and enzymatic antioxidant activity compared to fresh sperm. Such impaired antioxidant defenses caused an increase in the mRNA expression of apoptosis genes (Bax, and Caspase-3), finally leading to apoptosis. The impaired antioxidant defense also increased O₂^•− production and lipid peroxidation (MDA) levels, which further accelerated apoptosis. Considering all the experimental findings, an apoptosis pathway of cryopreserved sperm has been adopted for the first time. Specifically, sperm cryopreserved using 3% sucrose combined with 8% dimethyl sulfoxide (DMSO) showed improved mRNA stability, enzymatic activity, and DNA integrity with reduced O₂^•− production and MDA levels compared to sperm cryopreserved with the other types of examined cryoprotectants (8% ethylene glycol + 1% glucose, 6% propylene glycol + 2% glucose, 2% glycerol + 3% glucose, and 2% methanol + 4% trehalose). The present study suggests that 3% sucrose combined with 8% DMSO is suitable to cryopreserve the sperm of this valuable species for molecular conservation.

Evaluation of Antiviral Effect against SARS-CoV-2 Propagation by Crude Polysaccharides from Seaweed and Abalone Viscera In Vitro

Crude polysaccharides, extracted from two seaweed species (Hizikia fusiforme and Sargassum horneri) and Haliotis discus hannai (abalone) viscera, were evaluated for their inhibitory effect against SARS-CoV-2 propagation. Plaque titration revealed that these crude polysaccharides efficiently inhibited SARS-CoV-2 propagation with IC₅₀ values ranging from 0.35 to 4.37 μg/mL. The crude polysaccharide of H. fusiforme showed the strongest antiviral effect, with IC₅₀ of 0.35 μg/mL, followed by S. horneri and abalone viscera with IC₅₀ of 0.56 and 4.37 μg/mL, respectively. In addition, immunofluorescence assay, western blot, and quantitative RT-PCR analysis verified that these polysaccharides could inhibit SARS-CoV-2 replication. In Vero E6 cells, treatment with these crude polysaccharides before or after viral infection strongly inhibited the expression level of SARS-CoV-2 spikes, nucleocapsid proteins, and RNA copies of RNA-dependent RNA-polymerase and nucleocapsid. These results show that these crude marine polysaccharides effectively inhibit SARS-CoV-2 propagation by interference with viral entry.

Marine Migrastatics: A Comprehensive 2022 Update

Metastasis is responsible for the bad prognosis in cancer patients. Advances in research on metastasis prevention focus attention on the molecular mechanisms underlying cancer cell motility and invasion to improve therapies for long-term survival in cancer patients. The so-called “migrastatics” could help block cancer cell invasion and lead to the rapid development of antimetastatic therapies, improving conventional cancer therapies. In the relentless search for migrastatics, the marine environment represents an important source of natural compounds due to its enormous biodiversity. Thus, this review is a selection of scientific research that has pointed out in a broad spectrum of in vitro and in vivo models the anti-cancer power of marine-derived products against cancer cell migration and invasion over the past five years. Overall, this review might provide a useful up-to-date guide about marine-derived compounds with potential interest for pharmaceutical and scientific research on antimetastatic drug endpoints.

Long-read RNA sequencing of Pacific abalone Haliotis discus hannai reveals innate immune system responses to environmental stress

Haliotis discus hannai is a commercially important mollusk species, and the abalone aquaculture sector has been jeopardized by deteriorating environmental circumstances such as bacterial infection and thermal stress during the hot summers. However, due to a paucity of genetic information, such as transcriptome resources, our understanding of their stress adaptation is restricted. In this research, using single-molecule long-read (SMRT) sequencing technology, a library composed of ten tissues (i.e., haemocytes, gills, muscle, hepatopancreas, digestive tract, mantle, mucous gland, ovary, testis and head) was constructed and sequenced. In all, 41,855 high-quality unique transcripts, among which 24,778 were successfully annotated. Additionally, 13,463 SSRs, 1,169 transcription factors, and 18,124 lncRNAs were identified in H. discus hannai transcriptome. Furthermore, multiple immune-related transcripts were identified according to KEGG annotation, and a portion of these transcripts were mapped into several classical immune-related pathways, including the PI3K-AKT signaling pathway and Toll-like receptor signaling pathway. Additionally, 24 typical sequences related to the immunity pathway were detected by RT-PCR; the results showed that most of the immune-related genes showed significantly high expression at 72 h after bacterial challenges and thermal stress, especially the expression level of genes in gills was significantly higher than that in haemocytes under V. parahaemolyticus stress at 24 h. At the same time. The analysis of alternative splicing identified several innate immunity-related functions genes, including CD109 and caspase 2. These results suggest that the complex immune system, particularly the powerful innate immunity system, was crucial for H. discus hannai response to numerous environmental challenges.

Antifreeze Proteins: Novel Applications and Navigation towards Their Clinical Application in Cryobanking

Antifreeze proteins (AFPs) or thermal hysteresis (TH) proteins are biomolecular gifts of nature to sustain life in extremely cold environments. This family of peptides, glycopeptides and proteins produced by diverse organisms including bacteria, yeast, insects and fish act by non-colligatively depressing the freezing temperature of the water below its melting point in a process termed thermal hysteresis which is then responsible for ice crystal equilibrium and inhibition of ice recrystallisation; the major cause of cell dehydration, membrane rupture and subsequent cryodamage. Scientists on the other hand have been exploring various substances as cryoprotectants. Some of the cryoprotectants in use include trehalose, dimethyl sulfoxide (DMSO), ethylene glycol (EG), sucrose, propylene glycol (PG) and glycerol but their extensive application is limited mostly by toxicity, thus fueling the quest for better cryoprotectants. Hence, extracting or synthesizing antifreeze protein and testing their cryoprotective activity has become a popular topic among researchers. Research concerning AFPs encompasses lots of effort ranging from understanding their sources and mechanism of action, extraction and purification/synthesis to structural elucidation with the aim of achieving better outcomes in cryopreservation. This review explores the potential clinical application of AFPs in the cryopreservation of different cells, tissues and organs. Here, we discuss novel approaches, identify research gaps and propose future research directions in the application of AFPs based on recent studies with the aim of achieving successful clinical and commercial use of AFPs in the future.

Analysis of Immunoreactivity of α/α2-Tropomyosin from Haliotis discus hannai, Based on IgE Epitopes and Structural Characteristics

Tropomyosin (TM) was reported to be a supercoil allergen of shellfish. However, little information is available about its link between structure and allergenicity. In this study, the subunit of TM (α-TM) and supercoil of TM (α₂-TM) were identified from Haliotis discus hannai. α₂-TM showed higher immunoreactivity than α-TM. Meanwhile, seven linear epitopes in α-TM and α₂-TM were verified, and two conformational epitopes in α₂-TM were predicted. The physicochemical properties and chemical bond assays confirmed the existence of the disulfide bond in α₂-TM. According to spectroscopy and hydrophobicity analysis, α-TM showed higher α-helix features and blueshift of the fluorescence intensity peak compared with those of α₂-TM. The structure analysis revealed the possibility of conformational epitopes in α₂-TM, which could explain the immunoreactivity differences between α-TM and α₂-TM further. These results improved the understanding of Haliotis discus hannai TM, which lay the foundation for the food processing of abalone.

Molecular Characterization of Carbonic Anhydrase II (CA II) and Its Potential Involvement in Regulating Shell Formation in the Pacific Abalone, Haliotis discus hannai

Carbonic anhydrases (CAs) are a family of metalloenzymes that can catalyze the reversible interconversion of CO₂/HCO₃^–, ubiquitously present in both prokaryotes and eukaryotes. In the present study, a CA II (designated as HdhCA II) was sequenced and characterized from the mantle tissue of the Pacific abalone. The complete sequence of HdhCA II was 1,169 bp, encoding a polypeptide of 349 amino acids with a NH₂-terminal signal peptide and a CA architectural domain. The predicted protein shared 98.57% and 68.59% sequence identities with CA II of Haliotis gigantea and Haliotis tuberculata, respectively. Two putative N-linked glycosylation motifs and two cysteine residues could potentially form intramolecular disulfide bond present in HdhCA II. The phylogenetic analysis indicated that HdhCA II was placed in a gastropod clade and robustly clustered with CA II of H. gigantea and H. tuberculata. The highest level of HdhCA II mRNA expression was detected in the shell forming mantle tissue. During ontogenesis, the mRNA of HdhCA II was detected in all stages, with larval shell formation stage showing the highest expression level. The in situ hybridization results detected the HdhCA II mRNA expression in the epithelial cells of the dorsal mantle pallial, an area known to express genes involved in the formation of a nacreous layer in the shell. This is the first report of HdhCA II in the Pacific abalone, and the results of this study indicate that this gene might play a role in the shell formation of abalone.

Inhibition of SARS-CoV-2 Virus Entry by the Crude Polysaccharides of Seaweeds and Abalone Viscera In Vitro

Much attention is being devoted to the potential of marine sulfated polysaccharides as antiviral agents in preventing COVID-19. In this study, sulfated fucoidan and crude polysaccharides, extracted from six seaweed species (Undaria pinnatifida sporophyll, Laminaria japonica, Hizikia fusiforme, Sargassum horneri, Codium fragile, Porphyra tenera) and Haliotis discus hannai (abalone viscera), were screened for their inhibitory activity against SARS-CoV-2 virus entry. Most of them showed significant antiviral activities at an IC50 of 12~289 μg/mL against SARS-CoV-2 pseudovirus in HEK293/ACE2, except for P. tenera (IC50 > 1000 μg/mL). The crude polysaccharide of S. horneri showed the strongest antiviral activity, with an IC50 of 12 μg/mL, to prevent COVID-19 entry, and abalone viscera and H. fusiforme could also inhibit SARS-CoV-2 infection with an IC50 of 33 μg/mL and 47 μg/mL, respectively. The common properties of these crude polysaccharides, which have strong antiviral activity, are high molecular weight (>800 kDa), high total carbohydrate (62.7~99.1%), high fucose content (37.3~66.2%), and highly branched polysaccharides. These results indicated that the crude polysaccharides from seaweeds and abalone viscera can effectively inhibit SARS-CoV-2 entry.

Carbonic Anhydrase in Pacific Abalone Haliotis discus hannai: Characterization, Expression, and Role in Biomineralization

Carbonic anhydrases (CAs) are universal zinc ion containing metalloenzymes that play a pivotal role in various physiological processes. In this study, a CA I (designated as Hdh CA I) was isolated and characterized from the mantle tissue of Pacific abalone, Haliotis discus hannai. The full-length cDNA sequence of Hdh CA I was 1,417-bp in length, encoding a protein of 337 amino acids with molecular weight of 37.58 kDa. Hdh CA I sequence possessed a putative signal peptide of 22 amino acids and a CA catalytic function domain. The predicted protein shared 94 and 78% sequence identities with Haliotis gigantea and Haliotis tuberculata CA I, respectively. Results of phylogenetic analysis indicated that Hdh CA I was evolutionarily close to CA I of H. gigantea and H. tuberculata with high bootstrap values. Significantly higher levels of Hdh CA I mRNA transcript were found in mantle than other examined tissues. In situ hybridization results showed strong hybridization signals in epithelial cells of the dorsal mantle pallial, an area known to synthesize and secrete proteins responsible for the nacreous layer formation of shell. This is the first study on Hdh CA I in H. discus hannai and the results may contribute to further study its physiological functions in shell biomineralization of abalone.

Effects of Antifreeze Protein III on Sperm Cryopreservation of Pacific Abalone, Haliotis discus hannai

Pacific abalone (Haliotis discus hannai) is a highly commercial seafood in Southeast Asia. The aim of the present study was to improve the sperm cryopreservation technique for this valuable species using an antifreeze protein III (AFPIII). Post-thaw sperm quality parameters including motility, acrosome integrity (AI), plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), DNA integrity, fertility, hatchability, and mRNA abundance level of heat shock protein 90 (HSP90) were determined to ensure improvement of the cryopreservation technique. Post-thaw motility of sperm cryopreserved with AFPIII at 10 µg/mL combined with 8% dimethyl sulfoxide (DMSO) (61.3 ± 2.7%), 8% ethylene glycol (EG) (54.3 ± 3.3%), 6% propylene glycol (PG) (36.6 ± 2.6%), or 2% glycerol (GLY) (51.7 ± 3.0%) was significantly improved than that of sperm cryopreserved without AFPIII. Post-thaw motility of sperm cryopreserved with 2% MeOH and 1 µg/mL of AFPIII was also improved than that of sperm cryopreserved without AFPIII. A combination of 10 µg/mL AFPIII with 8% DMSO resulted in the highest post-thaw motility, showing AI of 60.1 ± 3.9%, PMI of 67.2 ± 4.0%, and MMP of 59.1 ± 4.3%. DNA integrity of sperm cryopreserved using 10 µg/mL AFPIII combined with 8% DMSO was not significantly (p > 0.05) different from that of fresh sperm. Cryopreservation using a combination of AFPIII with 8% DMSO improved fertilization and hatching rates of sperm compared to that of cryopreservation without supplementation of 10 µg/mL AFPIII. Sperm cryopreserved using AFPIII showed higher mRNA abundance levels of HSP90 than those cryopreserved without AFPIII. Results of the present study suggest that 10 µg/mL AFPIII combined with 8% DMSO can be used for large scale cryopreservation of Pacific abalone sperm and for hatchery production.

Preparation and antioxidant activities of polysaccharides obtained from abalone viscera by combination of enzymolysis and multiple separation methods

Abalone viscera were byproducts of the abalone processing and usually discarded as wastes. In this study, we tried to obtain functional polysaccharides from abalone viscera by a combination of enzymatic hydrolysis, membrane separation, anion exchange chromatography, and gel filtration techniques. Abalone viscera underwent successive hydrolyzation with alcalase and flavourzyme. Each enzymolysis was followed by deproteinization via membrane separation. The final yield of crude abalone viscera polysaccharide (CAVP) was 19.72%; the polysaccharide content of CAVP was 51.75%. Furthermore, three fractions of polysaccharides (AVP1, AVP2, and AVP3) were isolated from the CAVP by anion exchange chromatography and gel filtration. The molecular weights of each AVP were 14.99 kDa, 58.48 kDa, and 39.63 kDa, with a carbohydrate content of 62.75, 23.09, and 44.67%, respectively. These AVPs showed excellent antioxidant activities in vitro. Our results provide a scientific basis for the further utilization of polysaccharides from abalone viscera. PRACTICAL APPLICATION: This study demonstrated an eco-friendly approach for industrial production of high purity animal-derived polysaccharides without any environmental pollution caused by the viscera waste of abalone and promoting the comprehensive utilization of abalone resources.

Characterization of Insulin-Like Growth Factor Binding Protein 7 (Igfbp7) and Its Potential Involvement in Shell Formation and Metamorphosis of Pacific Abalone, Haliotis discus hannai

Insulin-like growth factor binding proteins (IGFBPs) are secreted proteins that play an important role in IGF regulation of growth and development of vertebrate and invertebrates. In this study, the IGFBP7 gene was cloned and characterized from mantle tissues of H. discus hannai, and designated as Hdh IGFBP7. The full-length cDNA sequence transcribed from the Hdh IGFBP7 gene was 1519-bp long with an open reading frame of 720-bp corresponding to a putative polypeptide of 239 amino acids. The molecular mass of its mature protein was approximately 23.44 KDa with an estimated isoelectric point (pI) of 5.35, and it shared significant homology with IGFBP7 gene of H. madaka. Hdh IGFBP7 has a characteristic IGFBP N-terminal domain (22–89 aa), a kazal-type serine proteinase inhibitor domain (77–128), and an immunoglobulin-like C2 domain (144–223). Furthermore, twelve cysteine residues and a signature motif of IGFBPs (XCGCCXXC) were found in its N-terminal domain. Phylogenetic analysis revealed that Hdh IGFBP7 was aligned with IGFBP7 of H. madaka. Tissue distribution analysis showed that the mRNA of Hdh IGFBP7 was expressed in all examined tissues, with the highest expression level observed in the mantle and gill tissues. The expression level of Hdh IGFBP7 mRNA was relatively higher at the juvenile stage during its metamorphosis period. In situ hybridization showed that Hdh IGFBP7 transcript was expressed in epithelial cells of the dorsal mantle pallial and mucus cells of the branchial epithelium in gill. These results provide basic information for future studies on the role of IGFBP7 in IGF regulation of shell growth, development and metamorphosis of abalone.

Characterization of Insulin-Like Growth Factor Binding Protein-5 (IGFBP-5) Gene and Its Potential Roles in Ontogenesis in the Pacific Abalone, Haliotis discus hannai

Insulin-like growth factor binding protein family is known to be involved in regulating biological actions of insulin-like growth factors (IGFs). In the present study, a full-length cDNA encoding the IGFBP-5 gene was cloned and characterized from the cerebral ganglion of Haliotis discus hannai. The 921-bp full-length sequence of Hdh IGFBP-5 cDNA transcript had an open reading frame of 411 bp encoding a predicted polypeptide of 136 amino acids, sharing high sequence identities with IGFBP-5 of H. diversicolor. The deduced Hdh IGFBP-5 protein contained a putative transmembrane domain (13-35 aa) in the N-terminal region. It also possessed a signature domain of IGFBP protein family (IB domain, 45-120 aa). Six cysteine residues (Cys-47, Cys-55, Cys-73, Cys-85, Cys-98, and Cys-118) in this cloned sequence could potentially form an intrachain disulfide bond. Phylogenetic analysis indicated that the Hdh IGFBP-5 gene was robustly clustered with IGFBP-5 of H. diversicolor. Tissue distribution analysis based on qPCR assay showed that Hdh IGFBP-5 was widely expressed in all examined tissues, with significantly (p < 0.05) higher expression in the cerebral ganglion. In male and female gametogenetic cycles, Hdh IGFBP-5 mRNA was expressed at all stages, showing significantly higher level at ripening stage. The expression level of Hdh IGFBP-5 mRNA was significantly higher in the polar body stage than in other ontogenic stages. In situ hybridization revealed that Hdh IGFBP-5 mRNA was present in the neurosecretory cells of the cerebral ganglion. This is the first study describing IGFBP-5 in H. discus hannai that might be synthesized in the neural ganglia. Our results demonstrate Hdh IGFBP-5 is involved in regulating ontogenic development and reproductive regulation of H. discus hannai.

Molecular Identification, Characterization, and Expression Analysis of a Gonadotropin-Releasing Hormone Receptor (GnRH-R) in Pacific Abalone, Haliotis discus hannai

A full-length cDNA sequence encoding a GnRH receptor was cloned from the pleuropedal ganglion of the Pacific abalone, Haliotis discus hannai. The cloned sequence is 1499-bp in length encoding a protein of 460 amino acid residues, with a molecular mass of 52.22 kDa and an isoelectric point (pI) of 9.57. The architecture of HdhGnRH-R gene exhibited key features of G protein-coupled receptors (GPCRs), including seven membrane spanning domains, putative N-linked glycosylation motifs, and phosphorylation sites of serine and threonine residues. It shared 63%, 52%, and 30% sequence identities with Octopus vulgaris, Limulus polyphemus, and Mizuhopecten yessoensis GnRH-R II sequences, respectively. Phylogenetic analysis indicated that HdhGnRH-R gene was clustered with GnRH-R II of O. vulgaris and O. bimaculoides. qPCR assay demonstrated that the mRNA expression level of this receptor was significantly higher in the pleuropedal ganglion than that in any other examined tissue. Transcriptional activities of this gene in gonadal tissues were significantly higher in the ripening stage. The mRNA expression of this gene was significantly higher in pleuropedal ganglion, testis, and ovary at higher effective accumulative temperature (1000 °C). In situ hybridization revealed that HdhGnRH-R mRNA was expressed in neurosecretory cells of pleuropedal ganglion. Our results suggest that HdhGnRH-R gene synthesized in the neural ganglia might be involved in the control of gonadal maturation and gametogenesis of H. discus hannai. This is the first report of GnRH-R in H. discus hannai and the results may contribute to further studies of GPCRs evolution or may useful for the development of aquaculture method of this abalone species.

Molecular characterization and spatiotemporal expression of prohormone convertase 2 in the Pacific abalone, Haliotis discus hannai

Prohormone convertases (PCs) are subtilisin-like proteases responsible for the intracellular processing of prohormones and proneuropeptides in vertebrates and invertebrates. The full-length PC2 cDNA sequence was cloned from pleuropedal ganglion of Haliotis discus hannai, consisted of 2254-bp with an open reading frame of 1989-bp and encoded a protein of 662 amino acid residues. The architecture of Hdh PC2 displayed key features of PCs, including a signal peptide, a pro-segment domain with sites for autocatalytic activation, a catalytic domain, and a pro-protein domain (P-domain). It shares the highest homology of its amino acid sequence with the PC2 from H. asinina and to lesser extent with that of Homo sapiens and Rana catesbeiana PC2. Sequence alignment analysis indicated that Hdh PC2 was highly conserved in the catalytic domain, including a catalytic triad of serine proteinases of the subtilisin family at positions Asp-195, His-236, and Ser-412. The cloned sequence contained a canonical integrin binding sequence, and four cysteine residues involved in the formation of an intramolecular disulfide link. Phylogenetic analysis revealed that the Hdh PC2 is robustly clustered with the Has PC2. Quantitative PCR assay demonstrated that the Hdh PC2 was predominantly expressed in the pleuropedal ganglion rather than in other examined tissues. Although PC2 mRNA was expressed throughout the gametogenetic cycle of male and female abalone, the expression level was significantly higher in the ripening stage of female abalone. Also, a significantly higher expression was observed in the pleuropedal ganglion and gonadal tissues at a higher effective accumulative temperature (1000°C). In situ hybridization revealed that the PC2 mRNA expressing neurosecretory cells were distributed in the cortex region of the pleuropedal ganglion. According to the results, it can be concluded that pleuropedal ganglion is the highest site of PC2 activity, and this enzyme might be involved in the abalone reproduction process.

Identification, characterization, and expression analysis of a serotonin receptor involved in the reproductive process of the Pacific abalone, Haliotis discus hannai

Serotonin receptor (5-HT) is a biogenic amine acting as a neurotransmitter and neuromodulator that mediates various aspects of reproduction and gametogenesis. The full-length nucleotide sequence of Haliotis discus hannai encodes a protein of 417 amino acids with a predicted molecular mass of 46.54 kDa and isoelectric point of 8.94. The structural profile of 5-HT_Hdh displayed key features of G protein-coupled receptors, including seven hydrophobic transmembrane domains, putative N-linked glycosylation sites, and several phosphorylation consensus motifs. It shares the highest homology of its amino acid sequence with the 5-HT receptor from Haliotis asinina, and to lesser extent of human 5-HT receptor. The cloned sequence possesses two cysteine residues (Cys-115 and Cys-193), which are likely to form a disulfide bond. Phylogenetic comparison with other known 5-HT receptor genes revealed that the 5-HT_Hdh is most closely related to the 5-HT_Ha receptor. The three-dimensional structure of the 5-HT_Hdh showed multiple alpha helices which is separated by a helix-loop-helix (HLH) structure. Quantitative PCR demonstrated that the receptor mRNA was predominantly expressed in the pleuropedal ganglion. Significant differences in the transcriptional activity of the 5-HT_Hdh gene were observed in the ovary at the ripening stage. An exclusive expression was detected in pleuropedal ganglion, testis, and ovary at higher effective accumulative temperature (1000 °C). In situ hybridization showed that the 5-HT_Hdh expressing neurosecretory cells were distributed in the cortex of the pleuropedal ganglion. Our results suggest that 5-HT_Hdh synthesized in the neural ganglia may be involved in oocyte maturation and spawning of H. discus hannai.

Antimicrobial resistance of pathogenic Aeromonas spp. isolated from marketed Pacific abalone (Haliotis discus hannai) in Korea

AIMS

The object of this study was to identify potential health concerns of the Aeromons spp. isolated from marketed Pacific abalone (Haliotis discus hannai) with respect to their virulence and antimicrobial resistance patterns.

METHODS AND RESULTS

We identified 29 strains of aeromonads consisting of five species; Aeromonas hydrophila (n = 9), Aeromonas enteropelogenes (n = 14), Aeromonas veronii (n = 3), Aeromonas salmonicida (n = 2) and Aeromonas sobria (n = 1), by employing series of biochemical tests and gene sequencing. In the phenotypic virulence assays, all isolates showed gelatinase and caseinase activities, while lipase formation (69%), phospholipase production (90%), DNase formation (82%), slime production (49%) and haemolysis activity (α = 18% and β = 82%) were also detected among isolates. Prevalence of virulence genes; aerA (100%), fla (66%), ahyB (73%), act (52%), alt (42%), ast (35%), ser (52%), gcat (69%), ascV (43%), hlyA (83%), lip (52%) and exu (59%) were detected by PCR assays. In disc diffusion test, 100% resistance was detected against ampicillin while cephalothin, rifampicin, oxytetracycline, colistine sulphate, nalidixic acid and piperaciliin were resisted by 86, 73, 42, 35, 28, 20 and 20% of the isolates respectively. Thirteen (45%) of the isolates showed multiple antimicrobial resistance (MAR) indices ≥ 0·2.

CONCLUSIONS

Our findings suggest that the potential health risk posed by the abalone-borne Aeromonas spp. should not be underestimated.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first time to evaluate possible public health risks upon consumption of abalone harbored Aeromonas spp. and also to isolate potential pathogenic and multidrug-resistant Aeromonas spp. from Pacific abalone in Korea.

Boiled Abalone Byproduct Peptide Exhibits Anti-Tumor Activity in HT1080 Cells and HUVECs by Suppressing the Metastasis and Angiogenesis in Vitro

Abalone (Haliotis discus hannai) is a precious seafood in the market. It has been reported that biological active substances derived from abalone have anti-oxidative, anti-inflammatory, anti-bacterial, and anti-thrombosis potential. However, there were few studies to assess whether they have anti-cancer potential. In this study, we evaluated the anti-metastasis and anti-pro-angiogenic factors and mechanism of action of boiled abalone byproduct peptide (BABP, EMDEAQDPSEW) in human fibrosarcoma (HT1080) cells and human umbilical vein endothelial cells (HUVECs). The results demonstrated that BABP treatment significantly lowers migration and the invasion of HT1080 cells and HUVECs. BABP inhibits phorbol 12-myristate 13-acetate (PMA)-induced matrix metalloproteinase (MMP) expression and activity by blocking mitogen-activated protein kinases (MAPKs) and NF-κB signaling and hypoxia-induced vascular endothelial growth factor (VEGF) secretion and hypoxia inducible factor (HIF)-1α accumulation through suppressing the AKT/mTOR signal pathway. BABP treatment inhibits VEGF-induced VEGFR-2 expression and tube formation in HUVECs. The effect of BABP on anti-metastatic and anti-vascular activity in HT1080 cells and HUVECs revealed that BABP may be a potential pharmacophore for tumor therapy in the future.

Abalone Collagen Extracts Potentiate Stem Cell Properties of Human Epidermal Keratinocytes

Stem cell activities in human tissues are critical for tissue integrity and function. Maintaining keratinocyte stem cells (KSCs) stemness helps sustain healthy skin by supporting keratinocyte renewal, involving the formation of epidermal barriers. In this study, abalone collagen (AC) extracts with molecular weights of 3 kDa (AC 1) and 300 kDa (AC 2) were compared to the epidermal growth factor (EGF) for their effects on cell proliferation, cell migration (wound healing), spheroid formation, and the expression level of stem cell markers on human keratinocytes (HaCaT cells). Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cell proliferation was quantified by ATP and DNA content analysis and Sulforhodamine B (SRB) assays. Cell migration assay was determined using the scratch wound healing test. Spheroid formation was evaluated and the expression level of stem cell markers was investigated by western blot analysis. The results showed that AC 1 at the concentration of 100 µg/mL could stimulate HaCaT cell proliferation, migration, spheroid formation, and the expression level of stem cell markers (keratin 19, β-catenin, ALDH1A1) compared to the control. In conclusion, a smaller molecular weight of abalone collagen extract exhibits a better effect on keratinocytes proliferation, migration, and stemness, which could be a potential active ingredient in cosmeceutical products.

Isolation and Comparative Study on the Characterization of Guanidine Hydrochloride Soluble Collagen and Pepsin Soluble Collagen from the Body of Surf Clam Shell (Coelomactra antiquata)

The aim of this study was to characterize the collagens from the body of surf clam shell (Coelomactra antiquata). Guanidine hydrochloride and pepsin were used to extract collagens. Guanidine hydrochloride soluble collagen (GSC) and pepsin soluble collagen (PSC) were separately isolated from the body of surf clam shell. Results showed that the moisture, protein, carbohydrate, and ash contents of the body of surf clam shell were 82.46%, 11.56%, 3.05%, and 2.38%, respectively, but the fat content was only 0.55%. The yields were 0.59% for GSC and 3.78% for PSC. Both GSC and PSC were composed of α₁ and α₂ chains and a β chain, however, GSC and PSC showed distinct differences from each other and the type I collagen from grass carp muscle on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). GSC and PSC contained glycine as the major amino acid and had imino acid of 150 and 155 residues/1000 residues, respectively. Fourier transform infrared spectroscopy (FTIR) spectra of GSC and PSC revealed the presence of a triple helix. The GSC appeared to have a dense sheet-like film linked by random-coiled filaments and PSC had fine globular filaments under scanning electron microscopy (SEM). The maximum transition temperature (Tmax) of GSC and PSC was 33.05 °C and 31.33 °C, respectively. These results provide valuable scientific information for the texture study and development of surf clam shell or other bivalve mollusks.

Marine glycosaminoglycan-like carbohydrates as potential drug candidates for infectious disease

Glycosaminoglycans (GAGs), present in the extracellular matrix, are exploited by numerous, distinct microbes for cellular attachment, adhesion, invasion and evasion of the host immune system. Glycosaminoglycans, including the widely used, clinical anticoagulant heparin and semi-synthetic analogues thereof, have been reported to inhibit and disrupt interactions between microbial proteins and carbohydrates present on the surface of host cells. However, the anticoagulant properties of unmodified, pharmaceutical heparin preparations preclude their capabilities as therapeutics for infectious disease states. Here, unique Glycosaminoglycan-like saccharides from various, distinct marine species are reported for their potential use as therapeutics against infectious diseases; many of which possess highly attenuated anticoagulant activities, while retaining significant antimicrobial properties.

Genome sequence of pacific abalone (Haliotis discus hannai): the first draft genome in family Haliotidae

Background: Abalones are large marine snails in the family Haliotidae and the genus Haliotis belonging to the class Gastropoda of the phylum Mollusca. The family Haliotidae contains only one genus, Haliotis, and this single genus is known to contain several species of abalone. With 18 additional subspecies, the most comprehensive treatment of Haliotidae considers 56 species valid [1]. Abalone is an economically important fishery and aquaculture animal that is considered a highly prized seafood delicacy. The total global supply of abalone has increased 5-fold since the 1970s and farm production increased explosively from 50 mt to 103 464 mt in the past 40 years. Additionally, researchers have recently focused on abalone given their reported tumor suppression effect. However, despite the valuable features of this marine animal, no genomic information is available for the Haliotidae family and related research is still limited. To construct the H. discus hannai genome, a total of 580-G base pairs using Illumina and Pacbio platforms were generated with 322-fold coverage based on the 1.8-Gb estimated genome size of H. discus hannai using flow cytometry. The final genome assembly consisted of 1.86 Gb with 35 450 scaffolds (>2 kb). GC content level was 40.51%, and the N50 length of assembled scaffolds was 211 kb. We identified 29 449 genes using Evidence Modeler based on the gene information from ab initio prediction, protein homology with known genes, and transcriptome evidence of RNA-seq. Here we present the first Haliotidae genome, H. discus hannai, with sequencing data, assembly, and gene annotation information. This will be helpful for resolving the lack of genomic information in the Haliotidae family as well as providing more opportunities for understanding gastropod evolution.

Shellfish: Nutritive Value, Health Benefits, and Consumer Safety

Shellfish is a major component of global seafood production. Specific items include shrimp, lobsters, oysters, mussels, scallops, clams, crabs, krill, crayfish, squid, cuttlefish, snails, abalone, and others. Shellfish, in general, contain appreciable quantities of digestible proteins, essential amino acids, bioactive peptides, long-chain polyunsaturated fatty acids, astaxanthin and other carotenoids, vitamin B₁₂ and other vitamins, minerals, including copper, zinc, inorganic phosphate, sodium, potassium, selenium, iodine, and also other nutrients, which offer a variety of health benefits to the consumer. Although shellfish are generally safe for consumption, their exposure to diverse habitats, the filter feeding nature of shellfish such as oysters, clams, and mussels, and unhealthy farming and handling practices may occasionally entail health risks because of possible presence of various hazards. These hazards include pathogenic organisms, parasites, biotoxins, industrial and environmental pollutants, heavy metals, process-related additives such as antibiotics and bisulfite, and also presence of allergy-causing compounds in their bodies. Most of the hazards can be addressed by appropriate preventive measures at various stages of harvesting, farming, processing, storage, distribution, and consumption. Furthermore, consumer safety of shellfish and other seafood items is strictly monitored by international, governmental, and local public health organizations. This article highlights the nutritional value and health benefits of shellfish items and points out the various control measures to safeguard consumer safety with respect to the products.

Anti-Coagulant and Anti-Thrombotic Properties of Blacklip Abalone (Haliotis rubra): In Vitro and Animal Studies

Sulphated polysaccharides with anti-thrombotic and anti-coagulant activities have been found in various marine biota. In this study, a previously characterised anti-thrombotic and anti-coagulant extract from blacklip abalone was fractionated by anion exchange chromatography (AEC), pooled (on a sulphated polysaccharide basis) and administered to Wistar rats via oral gavage (N = 8) for assessment as an oral therapeutic. To ensure that the preparation had anti-coagulant activity prior to oral administration, it was assessed in rat blood by thromboelastography (TEG) significantly increasing reaction (R) time (or time until clot formation). Following in vitro confirmation of anti-coagulant activity, 40 mg of the preparation was orally administered to rats with blood samples collected at 2, 4, and 6 h post-gavage. Assessment of all blood samples by TEG showed some prolongation of R time from 355 to 380 s after 4 h. Dosing of the post-gavage blood samples with the abalone preparation to confirm anti-thrombotic activity in vitro revealed residual anti-coagulant activity, further suggesting that oral administration did increase anti-coagulant potential in the collected blood but that bioavailability was low. Assessment of tissues and haematological parameters showed no obvious harmful effects of the abalone preparation in animals. In summary, even though oral administration of fractionated and pooled blacklip abalone extract to rats delayed clotting after 4 h, bioavailability of the preparation appeared to be low and may be more appropriate for intravenous administration as an anti-thrombotic or anti-coagulant therapeutic.

In vitro anti-thrombotic and anti-coagulant properties of blacklip abalone (Haliotis rubra) viscera hydrolysate

Abalone viscera contain sulphated polysaccharides with anti-thrombotic and anti-coagulant activities. In this study, a hydrolysate was prepared from blacklip abalone (Haliotis rubra) viscera using papain and bromelain and fractionated using ion exchange and size exclusion chromatography. Hydrolysates and fractions were investigated for in vitro thrombin inhibition mediated through heparin cofactor II (HCII) as well as anti-coagulant activity in plasma and whole blood. On the basis of sulphated polysaccharide concentration, the hydrolysate inhibited thrombin through HCII with an inhibitor concentration at 50% (IC50) of 16.5 μg/mL compared with 2.1 μg/mL for standard heparin. Fractionation concentrated HCII-mediated thrombin inhibition down to an IC50 of 1.8 μg/mL and improved anti-coagulant activities by significantly delaying clotting time. This study confirmed the presence of anti-thrombotic and anti-coagulant molecules in blacklip abalone viscera and demonstrated that these activities can be enriched with a simple chromatography regime. Blacklip abalone viscera warrant further investigation as a source of nutraceutical or functional food ingredients. Graphical abstract Schematic showing preparation of bioactive extracts and fractions from blacklip abalone.

Alternative Splicing Profile and Sex-Preferential Gene Expression in the Female and Male Pacific Abalone Haliotis discus hannai

In order to characterize the female or male transcriptome of the Pacific abalone and further increase genomic resources, we sequenced the mRNA of full-length complementary DNA (cDNA) libraries derived from pooled tissues of female and male Haliotis discus hannai by employing the Iso-Seq protocol of the PacBio RSII platform. We successfully assembled whole full-length cDNA sequences and constructed a transcriptome database that included isoform information. After clustering, a total of 15,110 and 12,145 genes that coded for proteins were identified in female and male abalones, respectively. A total of 13,057 putative orthologs were retained from each transcriptome in abalones. Overall Gene Ontology terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways analyzed in each database showed a similar composition between sexes. In addition, a total of 519 and 391 isoforms were genome-widely identified with at least two isoforms from female and male transcriptome databases. We found that the number of isoforms and their alternatively spliced patterns are variable and sex-dependent. This information represents the first significant contribution to sex-preferential genomic resources of the Pacific abalone. The availability of whole female and male transcriptome database and their isoform information will be useful to improve our understanding of molecular responses and also for the analysis of population dynamics in the Pacific abalone.

In vitro Anti-Thrombotic Activity of Extracts from Blacklip Abalone (Haliotis rubra) Processing Waste

Waste generated from the processing of marine organisms for food represents an underutilized resource that has the potential to provide bioactive molecules with pharmaceutical applications. Some of these molecules have known anti-thrombotic and anti-coagulant activities and are being investigated as alternatives to common anti-thrombotic drugs, like heparin and warfarin that have serious side effects. In the current study, extracts prepared from blacklip abalone (Haliotis rubra) processing waste, using food grade enzymes papain and bromelain, were found to contain sulphated polysaccharide with anti-thrombotic activity. Extracts were found to be enriched with sulphated polysaccharides and assessed for anti-thrombotic activity in vitro through heparin cofactor-II (HCII)-mediated inhibition of thrombin. More than 60% thrombin inhibition was observed in response to 100 μg/mL sulphated polysaccharides. Anti-thrombotic potential was further assessed as anti-coagulant activity in plasma and blood, using prothrombin time (PT), activated partial thromboplastin time (aPTT), and thromboelastography (TEG). All abalone extracts had significant activity compared with saline control. Anion exchange chromatography was used to separate extracts into fractions with enhanced anti-thrombotic activity, improving HCII-mediated thrombin inhibition, PT and aPTT almost 2-fold. Overall this study identifies an alternative source of anti-thrombotic molecules that can be easily processed offering alternatives to current anti-thrombotic agents like heparin.