Sulfated galactans from Gracilaria fisheri bind to shrimp haemocyte membrane proteins and stimulate the expression of immune genes

An Overview of the Biological Functions and Mechanisms of Action of Medicinal Plants and Seaweeds in the Shrimp Culture

Diseases are major constraints to developing large-scale aquaculture practices in many countries. For decades, synthetic chemotherapeutic agents have been widely applied both as prophylactics and therapeutics to inhibit and control aquatic disease outbreaks. However, their use has become more restricted due to the negative impacts they have on the environment, the host and humans, as well as their limitations in preventing the emergence of antimicrobial-resistant bacteria. Therefore, there is a growing interest in the use of medicinal plants and seaweeds as potential alternatives to antibiotics and other synthetic chemotherapeutics. Medicinal plants and seaweeds can enhance the immune systems of animals, thereby providing protection against numerous diseases while minimizing the adverse effects associated with synthetic chemotherapeutics. Furthermore, the advantages of medicinal plants and seaweeds, such as their effectiveness, easy availability and ability to be applied on a large scale, make them appealing for use in the aquaculture industry. The main goal of this study was to review the existing knowledge of the effects of medicinal plants and seaweeds, as well as their extracts, on shrimp growth, immune response and disease resistance against bacterial and viral agents. Moreover, this paper discusses the application of seaweeds in shrimp culture. We also conducted a literature review to identify gaps in the research and provide recommendations for further advancement in this field of study. Further studies should focus on evaluating other physiological aspects, such as feed and mineral utilization, enzyme activities and histological examination.

Sulfated Galactans from Agarophytes: Review of Extraction Methods, Structural Features, and Biological Activities

Agarophytes are important seaweeds of the Rhodophyta type, which have been highly exploited for industrial use as sources of a widely consumed polysaccharide of agar. In addition to that, sulfated galactans (SGs) from agarophytes, which consist of various functional sulfate groups, have attracted the attention of scientists in current studies. SGs possess various biological activities, such as anti-tumor, anticoagulant, anti-inflammatory, antioxidant, anti-obesity, anti-diabetic, anti-microbial, anti-diarrhea, and gut microbiota regulation properties. Meanwhile, the taxonomy, ecological factors, i.e., environmental factors, and harvest period, as well as preparation methods, i.e., the pretreatment, extraction, and purification conditions, have been found to influence the chemical compositions and fine structures of SGs, which have, further, been shown to have an impact on their biological activities. However, the gaps in the knowledge of the properties of SGs due to the above complex factors have hindered their industrial application. The aim of this paper is to collect and systematically review the scientific evidence about SGs and, thus, to pave the way for broader and otherwise valuable industrial applications of agarophytes for human enterprise. In the future, this harvested biomass could be sustainably used not only as a source of agar production but also as natural materials in functional food and pharmaceutical industries.

Octanoyl esterification of low molecular weight sulfated galactan enhances the cellular uptake and collagen expression in fibroblast cells

Low molecular weight sulfated galactan (LMSG) supplemented with octanoyl ester (Oct-LMSG) demonstrated superior wound healing activity compared to the unsupplemented LMSG in a fibroblast wound model. To test the hypothesis that the increased bioactivity of Oct-LMSG may depend on its penetration into the plasma membrane, its cellular uptake was investigated and collagen production in fibroblast cells was assessed for the first time. The cellular uptake of Oct-LMSG was examined using indirect immunofluorescence and a confocal laser scanning microscope. In addition, the degree of fibroblast activation associated with this uptake was evaluated. The results indicated increased LMSG internalization in fibroblasts treated with Oct-LMSG. Transmission electron micrographs revealed the ultrastructure of active protein production in fibroblasts upon treatment with Oct-LMSG. In addition, Oct-LMSG upregulated the expression of type I collagen mRNA and proteins, as well as related signaling molecules involved in collagen synthesis, including collagen type I α1 chain (Col1A1), Col1A2, phosphorylated (p)-Smad2/3 and p-Smad4. The current findings support the notion that the supplementation of LMSG with octanoyl enhanced its cellular uptake into fibroblasts and, as a result, regulated the expression of type I collagen in fibroblasts via the activation of the Smad signaling pathway. This study demonstrates the therapeutic potential of Oct-LMSG in promoting tissue regeneration.

Research progress in the preparation, structural characterization, bioactivities, and potential applications of sulfated agarans from the genus Gracilaria

The genus Gracilaria produces 80% of the world's industrial agar. Agar of this genus is a promising biologically active polymer, which has been used in the human diet and folk medicine, alternative for weight loss, treatment of diarrhea, etc. With more attention paid to the genus Gracilaria-sulfated agarans (GSAs), they exhibited multitudinous health benefits in antioxidant, antiviral, antibacterial, prebiotics, anti-tumor, anticoagulant, and antidiabetic. Various preparation procedures of GSAs making the diversities of structure and biological activity. Therefore, this review summarized the isolation, identification, bioactivity potentials, and applications of GSAs, providing a reference to the development of GSAs in functional food and pharmaceutical industry. PRACTICAL APPLICATIONS: The genus Gracilaria is known as a raw material for agar extraction. GSAs are food-grade agaran with the properties of thermoreversible gels at low concentrations, which are commonly used as an additive for making candies as well as raw material for making soup and snacks. They are used in folk medicine to treat diarrhea and other diseases. As an important bioactive macromolecule, GSAs have various biological activities (such as antioxidant, antiviral, antibacterial, probiotic, anti-tumor, anticoagulant, and antidiabetic activities), and have the potential to be developed as functional food and medicine. They could also be used to create innovative agar-based products such as antibacterial films and drug carriers.

Efficacy of ulvan on immune response and immuno-antioxidant gene modulation in Labeo rohita against columnaris disease

This study reports the effect of ulvan enriched diet on the influence of growth, changes in hemato-biochemical indices, improvement of antioxidant system, enhancement of innate-adaptive immunity and modification of immuno-antioxidant genes expression in Labeo rohita against Flavobacterium columnaris. The weight gain (WG) was significantly high (P > 0.05) in unchallenged normal and challenged fish fed with diets enriched with 25 and 50 mg kg^-1 ulvan; the FCR was better (P > 0.05) when fed with 50 mg kg^-1 enriched diet. In normal fish fed with or without ulvan supplementation was noted 100% survival rate (SR). In both groups, the red blood cell (RBC) and while blood cell (WBC) counts increased significantly (P > 0.05) when fed with 50 mg kg^-1 ulvan diet whereas the hemoglobin (Hb) level increased significantly on being fed with 25 and 50 mg kg^-1 ulvan diets. The SOD activity was enhanced significantly in both groups fed with any dose of ulvan diets whereas the MDA and GPx activity increased only with 25 and 50 mg kg^-1 ulvan diets. The phagocytic (PC) activity significantly increased with any enriched diet and control diet groups while the respiratory burst (RB) activity increased only with 50 mg kg^-1 ulvan diet. The alternate complement pathway (ACP), activity of lysozyme (Lyz), and immunoglobuline M (IgM) were better in both groups fed with 50 mg kg^-1 ulvan diet. The SOD and GPx antioxidant gene expression were significantly high in both groups fed with any ulvan diet while the Nrf2 gene expression was high with 50 mg kg^-1 ulvan diet. The IL-1β, TNFα, hepcidin, Lyz, and IgM cytokines or proteins mRNA expression were significant in both groups fed with all ulvan supplement diet whereas the β-2M expression was significant only with 50 mg kg^-1 ulvan diet. The present research indicates that both L. rohita groups fed with 50 mg kg^-1 ulvan diet significantly improved growth, antioxidant system, immune defense system, and immuno-antioxidant related gene expression against F. columnaris.

Chemical composition of a hot water crude extract (HWCE) from Ulva intestinalis and its potential effects on growth performance, immune responses, and resistance to white spot syndrome virus and yellowhead virus in Pacific white shrimp (Litopenaeus vannamei)

In the present study, a hot water crude extract from Ulva intestinalis (Ui-HWCE) was used as a dietary supplement, and the effects on growth, immune responses, and resistance against white spot syndrome virus (WSSV) and yellowhead virus (YHV) infection in Pacific white shrimp (Litopenaeus vannamei) were investigated. Chemical analyses of Ui-HWCE revealed 13.75 ± 0.41% sulfate, 37.86 ± 5.96% uronic acid, and 46.63 ± 5.16% carbohydrate contents. The monosaccharide content of Ui-HWCE contained glucose (6.81 ± 0.94%), xylose (4.15 ± 0.11%), and rhamnose (25.84 ± 0.80%). Functional group analysis of Ui-HWCE by Fourier transform infrared (FTIR) spectroscopy revealed a typical infrared spectrum of ulvan similar to the infrared spectrum of commercially purified ulvan from Ulva armoricana (77.86 ± 2.19% similarity). Ui-HWCE was added to shrimp diets via top-dressing at 0, 1, 5, and 10 g/kg diet. After 28 days, Ui-HWCE supplementation at 5 g/kg diet efficiently improved shrimp growth performance, as indicated by weight gain, average daily growth, specific growth rates, and villus height determined by observing gut morphology. Additionally, Ui-HWCE feed supplementation at 5 g/kg diet significantly increased immune responses against a pathogenic bacterium (Vibrio parahaemolyticus AHPND stain), including phagocytic activity and clearance efficiency. Furthermore, Ui-HWCE feed supplementation upregulated the expression of several immune-related genes in the hemocytes and gills. Ui-HWCE supplementation at 1 and 5 g/kg resulted in effective anti-YHV but not anti-WSSV activity, which significantly decreased the mortality rate and YHV burden in surviving shrimp. It was concluded that Ui-HWCE supplied at 5 g/kg diet exhibits growth-promoting, immune-stimulatory, and antiviral activity that could protect L. vannamei against YHV infection.

Probing the Anti-Cancer Potency of Sulfated Galactans on Cholangiocarcinoma Cells Using Synchrotron FTIR Microspectroscopy, Molecular Docking, and In Vitro Studies

Sulfated galactans (SG) isolated from red alga Gracilaria fisheri have been reported to inhibit the growth of cholangiocarcinoma (CCA) cells, which was similar to the epidermal growth factor receptor (EGFR)-targeted drug, cetuximab. Herein, we studied the anti-cancer potency of SG compared to cetuximab. Biological studies demonstrated SG and cetuximab had similar inhibition mechanisms in CCA cells by down-regulating EGFR/ERK pathway, and the combined treatment induced a greater inhibition effect. The molecular docking study revealed that SG binds to the dimerization domain of EGFR, and this was confirmed by dimerization assay, which showed that SG inhibited ligand-induced EGFR dimer formation. Synchrotron FTIR microspectroscopy was employed to examine alterations in cellular macromolecules after drug treatment. The SR-FTIR-MS elicited similar spectral signatures of SG and cetuximab, pointing towards the bands of RNA/DNA, lipids, and amide I vibrations, which were inconsistent with the changes of signaling proteins in CCA cells after drug treatment. Thus, this study demonstrates the underlined anti-cancer mechanism of SG by interfering with EGFR dimerization. In addition, we reveal that FTIR signature spectra offer a useful tool for screening anti-cancer drugs’ effect.

Immunomodulatory and Antiviral Effects of Macroalgae Sulphated Polysaccharides: Case Studies Extend Knowledge on Their Importance in Enhancing Shellfish Health, and the Control of a Global Viral Pathogen Ostreid Herpesvirus-1 microVar

Macroalgae are the primary source of non-animal sulphated polysaccharides (SPs) in the marine environment with fucoidans derived from brown algae (Phaeophyta) and carrageenans from red algae (Rhodophyta). Much research has been carried out on SP effects on Asian shrimp species (genera Penaeus and Metapenaeus) but their effect on commercially important bivalve mollusc species is limited and in Pacific oyster Crassostrea gigas is unknown. Knowledge of their impact on bivalve pathogens and Palaemon shrimp is unknown. The objectives of this study were to assess the effects of Fucus vesiculosus (Phaeophyta), Mastocarpus stellatus (Rhodophyta) and algal derivatives (fucoidan and κ-carrageenan) on C. gigas performance, and on ostreid herpesvirus-1 microvar (OsHV-1 μVar) and bacteria Vibrio spp. development. Both pathogens have been associated with significant oyster mortalities and economic losses globally. The effects of sulphated galactan from Gracilaria fisheri (Rhodophyta) on European common prawn Palaemon serratus, an important fishery species, was also assessed. Findings indicate a rapid and prolonged increase in total blood cell count, lysozyme (enzyme that destroys pathogens), and a difference in the ratio of blood cell types in treated individuals compared to their control counterparts. A significantly lower OsHV-1 μVar prevalence was observed in treated oysters and κ-carrageenan was found to suppress viral replication (loads), while OsHV-1 μVar was not detected in the fucoidan treated oysters from Day 8 of the 26-day trial. No antibacterial effect was observed however, the oysters did not succumb to vibriosis. These findings contribute further knowledge to macroalgae sulphated polysaccharide biotherapeutic properties, their twofold effect on animal health and viral suppression.

Bioencapsulation efficacy of sulfated galactans in adult Artemia salina for enhancing immunity in shrimp Litopenaeus vannamei

Live food organisms like Artemia have been used for delivery of different substances such as nutrients, probiotics and immune-stimulants to aquatic animals. Previously, we reported that sulfated galactans (SG) from the red seaweed Gracilaria fisheri (G. fisheri) increased immune activity in shrimp. In the present study we further investigated the capacity and efficiency of bioencapsulation of SG in adult Artemia for delivery to tissues and potentially boosting the expression of immune genes in post larvae shrimp. SG were labelled with FITC (FITC-SG) for in vivo tracking in shrimp. Bioencapsulation of adult Artemia with FITC-SG (0-100 μg mL^-1) was performed and the fluorescence intensity was detected in the gut lumen after enrichment periods of 30 min, 1 h, 2 h, 6 h and 24 h. The results showed the Artemia took up SG over time in a concentration-dependent manner. Shrimp were fed with the bioencapsulated Artemia (FITC-SG, 20 μg mL^-1) and the shrimp were evaluated under a stereo-fluorescent microscope. At 24 h after administration, FITC-SG was located in gills and hepatopancreas and also bound with haemocytes. With daily SG administration, the genes IMD, IKKβ were up-regulated (after 1 day) while genes dicer and proPO-I were up-regulated later (after 7 days). Moreover, continued monitoring of shrimp fed for 3 consecutive days only with SG at the dose of 0.5 mg g^-1 BW showed increases in the expression of IMD, IKKβ genes on day 1 and which gradually declined to normal levels on day 14, while the expression of dicer and proPO-I was increased on day 3 and remained high on day 14. These results demonstrate that bioencapsulation of SG in adult Artemia successfully delivers SG to shrimp tissues, which then bind with haemocytes and subsequently activate immune genes, and potentially increase immunity in shrimp. In addition, the present study suggests that a 3-consecutive-day regimen of SG supplemented in Artemia (0.5 mg g^-1 BW) may boost and sustain the enhanced immune functions in post larvae shrimp.

Inhibition of N-myristoyltransferase1 affects dengue virus replication

Dengue virus (DENV) causes dengue fever, a self‐limiting disease that could be fatal due to serious complications. No specific treatment is currently available and the preventative vaccine is only partially protective. To develop a potential drug target for dengue fever, we need to understand its biology and pathogenesis thoroughly. N‐myristoyltransferase (NMT) is an N‐terminal protein lipidation enzyme that catalyzes the covalent cotranslational attachment of fatty acids to the amino‐terminal glycine residue of a number of proteins, leading to the modulation of various signaling molecules. In this study, we investigated the interaction of dengue viral proteins with host NMT and its subsequent effect on DENV. Our bioinformatics, molecular docking, and far‐western blotting analyses demonstrated the interaction of viral envelope protein (E) with NMT. The gene expression of NMT was strongly elevated in a dependent manner during the viral replication phase in dendritic cells. Moreover, NMT gene silencing significantly inhibited DENV replication in dendritic cells. Further studies investigating the target cell types of other host factors are suggested.

Application of marine-derived polysaccharides as immunostimulants in aquaculture: A review of current knowledge and further perspectives

The use of antibiotics in the feeds of cultivable aquatic animals has been generally practised to reduce infectious diseases as well as to improve the survival and growth. In recent years, many countries ban to aquatic animals due to the use of large amount of antibiotics and chemotherapies, thus alternative novel strategies are need to promote the growth of aquatic animals and control the pathogens. Dietary supplementation of marine-derived polysaccharides (MDPs) is one of the potential substitutes for antibiotics in aquatic animal feeds. Recently, the use of dietary MDPs in the aquaculture animals has been focused with much interest. In aquaculture, MDPs are used as prebiotic substance which is mostly accepted as a nutritional component for improving the growth performance and health conditions. Hence, present review is a comprehensive and an updated collection of available research reports on different MDPs (alginate, fucoidan, carrageenan, laminarin, ulvan, galactan, agar, chitin and chitosan), route of administration, dosage and applications for improving aqua feeds with emphasis on its effects on growth, biochemical indices, immune response, gut microbiota and disease resistance of aquaculture animals. This review describes the sustainability of global aquaculture production by providing a best alternative to harmful antibiotics, thereby meeting the emerging consumer demand for antibiotic-free aquatic food products.

Assessment of the effects of sulfated polysaccharides extracted from the red seaweed Irish moss Chondrus crispus on the immune-stimulant activity in mussels Mytilus spp

Seaweeds contain a number of health enhancing and antimicrobial bioactive compounds including sulfated polysaccharides (SP). In the present study, SP extracted from a European red seaweed Irish moss Chondrus crispus was chemically analyzed, SP content extracted and the immune-response effect on wild Irish mussels Mytilus spp. investigated for the first time. A high percent yield of SP was extracted from C. crispus and the immune-stimulant activity of SP was assessed in a laboratory trial with mussels exposed to three different treatments of low (10 μg mL^-1), medium (20 μg mL^-1) and high (50 μg mL^-1) SP dose concentrations and a control mussel group with no exposure to SP. An initial mussel sample was processed prior to the trial commencing and mussels were subsequently sampled on Days 1, 2, 3, 4, 7, and 10 post SP exposure. Both cell, humoral and immune related gene responses including haemocyte cell viability, haemocyte counts, lysozyme activity and expression of immune related genes (defensin, mytimycin and lysozyme mRNA) were assessed. No mussel mortalities were observed in either the treated or non-treated groups. Mussels exposed with SP showed an increase in haemocyte cell viability and the total number of haemocytes compared to control mussels. Lysozyme activity was also higher in treated mussels. Additionally, up-regulated expression of defensin, mytimycin and lysozyme mRNA was observed in SP treated mussels shortly after exposure (on Days 1, 2, and 3) to SP. These results indicate that a high quality yield of SP can be readily extracted from C. crispus and more importantly based on the animal model used in this study, SP extracted from C. crispus can rapidly induce health enhancing activities in Mytilus spp. at a cellular, humoral and molecular level and with a prolonged effect up to ten days post treatment.

Sulfated galactans from the red seaweed Gracilaria fisheri exerts anti-migration effect on cholangiocarcinoma cells

BACKGROUND

Seaweeds have a long history of use in Asian countries as functional foods, medicinal herbs, and the treatment of cancer. Polysaccharides from various seaweeds have shown anti-tumor activity. Cholangiocarcinoma (CCA), often with metastatic disease, is highly prevalent in Thailand as a consequence of liver fluke infection. Recently, we extracted sulfated galactans (SG) from Gracilaria fisheri (G. fisheri), a south east Asian seaweed, and found it exhibited anti-proliferation effect on CCA cells.

PURPOSE

In the present study, we evaluated the anti-migration activity of SG on CCA cells and its underlined mechanism.

METHODS

CCA cells were treated with SG alone or drugs targeting to epidermal growth factor (EGF) receptor (EGFR) or pretreated with SG prior to incubation with EGF. Anti-migration activity was determined using a scratch wound-healing assay and zymography. Immunofluorescence staining and western blotting were used to investigate EGFR signaling mediators.

RESULTS

Under basal condition, SG reduced the migration rate of CCA, which was correlated with a decrease in the active-form of matrix metalloproteinases-9. SG decreased expression of phosphorylated focal adhesion kinase (FAK), but increased expression of E-cadherin to promote cells stasis. Moreover, phosphorylation of EGFR and extracellular signal-regulated kinases (ERK), known to stimulate growth of cancer cells, was blocked in a comparable way to EGFR inhibitors Cetuximab and Erlotinib. Pretreatment cells with SG attenuated EGF induced phosphorylation of EGFR, ERK and FAK.

CONCLUSION

This study reveals that SG from G. fisheri retards migration of CCA cells, and its mechanism of inhibition is mediated, to some extent, by inhibitory effects on MAPK/ERK signal transduction pathway. Our findings suggest that there may be a therapeutic potential of SG in CCA treatment.

A sulfated galactans supplemented diet enhances the expression of immune genes and protects against Vibrio parahaemolyticus infection in shrimp

A sulfated galactans (SG) supplemented diet was evaluated for the potential to stimulate immune activity in shrimp Penaeus vannamei (P. vannamei). Shrimp given the SG supplemented diet (0.5, 1 and 2% w/w) for 7 days showed enhanced expression of the downstream signaling mediator of lipopolysaccharide and β-1,3-glucan binding protein (LGBP) and immune related genes including p-NF-κB, IMD, IKKβ and IKKε, antimicrobial peptide PEN-4, proPO-I and II. Following immersion with Vibrio parahaemolyticus (V. parahaemolyticus) for 14 days, the shrimp given the SG supplemented diet (1 and 2% w/w) showed a decrease in bacterial colonies and bacterial toxin gene expression, compared to shrimp given a normal diet, and they reached 50% mortality at day 14. However, shrimp given the normal diet and challenged with the bacteria reached 100% mortality at day 6. SG-fed shrimp increased expression of immune genes related to LGBP signaling at day 1 after the bacterial immersion compared to control (no immersion), which later decreased to control levels. Shrimp on the normal diet also increased expression of immune related genes at day 1 after immersion which however decreased below control levels by day 3. Taken together, the results indicate the efficacy of the SG supplemented diet to enhance the immune activity in shrimp which could offer protection from V. parahaemolyticus infection.

Sulfated Galactans from Red Seaweed Gracilaria fisheri Target EGFR and Inhibit Cholangiocarcinoma Cell Proliferation

Cholangiocarcinoma (CCA) is increasing in incidence worldwide and is resistant to chemotherapeutic agents, making treatment of CCA a major challenge. Previous studies reported that natural sulfated polysaccharides (SPs) disrupted growth factor receptor activation in cancer cells. The present study, therefore, aimed at investigating the antiproliferation effect of sulfated galactans (SG) isolated from the red seaweed Gracilaria fisheri (G. fisheri) on CCA cell lines. Direct binding activity of SG to CCA cells, epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR) were determined. The effect of SG on proliferation of CCA cells was investigated. Cell cycle analyses and expression of signaling molecules associated with proliferation were also determined. The results demonstrated that SG bound directly to EGFR. SG inhibited proliferation of various CCA cell lines by inhibiting EGFR and extracellular signal-regulated kinases (ERK) phosphorylation, and inhibited EGF-induced increased cell proliferation. Cell cycle analyses showed that SG induced cell cycle arrest at the G0/G1 phase, down-regulated cell cycle genes and proteins (cyclin-D, cyclin-E, cdk-4, cdk-2), and up-regulated the tumor suppressor protein P53 and the cyclin-dependent kinase inhibitor P21. Taken together, these data demonstrate that SG from G. fisheri inhibited proliferation of CCA cells, and its mechanism of inhibition is mediated, to some extent, by inhibitory effects on EGFR activation and EGFR/ERK signaling pathway. SG presents a potential EGFR targeted molecule, which may be further clinically developed in a combination therapy for CCA treatment.

Innate immune-stimulating and immune genes up-regulating activities of three types of alginate from Sargassum siliquosum in Pacific white shrimp, Litopenaeus vannamei

The Total Haemocyte Count (THC), phenoloxidase (PO), Superoxide Dismutase (SOD) activity, Phagocytic Activity/Index and Total Protein Plasma (TPP) were examined after feeding the white shrimp Litopenaeus vannamei with diets supplemented with three different types of alginates (acid, calcium and sodium alginates). Immune-related genes expression was evaluated by quantitative Real Time PCR (qRT-PCR). Results indicated that the immune parameters directly increased according to the doses of alginates and time. The 2.0 g kg(-1) of acid and sodium alginate treatments were gave better results. Four immune-related genes expression i.e. LGBP, Toll, Lectin, proPO were up regulated. It is therefore concluded that the supplementation of alginate of Sargassum siliquosum on the diet of L. vannamei enhanced the innate immunity as well as the expression of immune-related genes. It is the first report on the simultaneous evaluation of three alginate types to enhance innate immune parameters and immune-related genes expression in L. vannamei.