The cytotoxic effect of Eucheuma serra agglutinin (ESA) on cancer cells and its application to molecular probe for drug delivery system using lipid vesicles

Structural study and antimicrobial and wound healing effects of lectin from Solieria filiformis (Kützing) P.W.Gabrielson

The SfL-1 isoform from the marine red algae Solieria filiformis was produced in recombinant form (rSfL-1) and showed hemagglutinating activity and inhibition similar to native SfL. The analysis of circular dichroism revealed the predominance of β-strands structures with spectra of βI-proteins for both lectins, which had Melting Temperature (Tm) between 41 °C and 53 °C. The three-dimensional structure of the rSfL-1 was determined by X-ray crystallography, revealing that it is composed of two β-barrel domains formed by five antiparallel β chains linked by a short peptide between the β-barrels. SfL and rSfL-1 were able to agglutinate strains of Escherichia coli and Staphylococcus aureus and did not show antibacterial activity. However, SfL induced a reduction in E. coli biomass at concentrations from 250 to 125 μg mL-1, whereas rSfL-1 induced reduction in all concentrations tested. Additionally, rSfL-1 at concentrations from 250 to 62.5 μg mL-1, showed a statistically significant reduction in the number of colony-forming units, which was not noticed for SfL. Wound healing assay showed that the treatments with SfL and rSfL-1 act in reducing the inflammatory response and in the activation and proliferation of fibroblasts by a larger and fast deposition of collagen.

Effects of Oncolytic Vaccinia Viruses Harboring Different Marine Lectins on Hepatocellular Carcinoma Cells

Oncolytic viruses are being developed as novel strategies for cancer therapy. Our previous studies have shown that vaccinia viruses armed with marine lectins improved the antitumor efficacy in diverse cancer types. The objective of this study was to assess the cytotoxic effects of oncoVV harboring Tachypleus tridentatus lectin (oncoVV-TTL), Aphrocallistes vastus lectin (oncoVV-AVL), white-spotted charr lectin (oncoVV-WCL), and Asterina pectinifera lectin (oncoVV-APL) on HCC. Our data revealed that the effects of recombinant viruses on Hep-3B cells were oncoVV-AVL > oncoVV-APL > oncoVV-TTL > oncoVV-WCL; oncoVV-AVL showed stronger cytotoxicity than oncoVV-APL, while oncoVV-TTL/WCL had no effect on cell killing in Huh7 cells, and PLC/PRF/5 cells exhibited sensitivity to oncoVV-AVL/TTL but not to oncoVV-APL/WCL. The cytotoxicity of oncoVV-lectins could be enhanced by apoptosis and replication in a cell-type-dependent manner. Further research revealed that AVL may mediate various pathways, including MAPK, Hippo, PI3K, lipid metabolism, and androgen pathways through AMPK crosstalk, to promote oncoVV replication in HCC in a cell-dependent manner. OncoVV-APL replication could be affected by AMPK/Hippo/lipid metabolism pathways in Hep-3B cells, AMPK/Hippo/PI3K/androgen pathways in Huh7 cells, and AMPK/Hippo pathways in PLC/PRF/5 cells. OncoVV-WCL replication was also multi-mechanistic, which could be affected by AMPK/JNK/lipid metabolism pathways in Hep-3B cells, AMPK/Hippo/androgen pathways in Huh7 cells, and AMPK/JNK/Hippo pathways in PLC/PRF/5 cells. In addition, AMPK and lipid metabolism pathways may play critical roles in oncoVV-TTL replication in Hep-3B cells, and oncoVV-TTL replication in Huh7 cells may depend on AMPK/PI3K/androgen pathways. This study provides evidence for the application of oncolytic vaccinia viruses in hepatocellular carcinoma.

Biological properties and potential of compounds extracted from red seaweeds

Macroalgae have been recently used for different applications in the food, cosmetic and pharmaceutical industry since they do not compete for land and freshwater against other resources. Moreover, they have been highlighted as a potential source of bioactive compounds. Red algae (Rhodophyta) are the largest group of seaweeds, including around 6000 different species, thus it can be hypothesized that they are a potential source of bioactive compounds. Sulfated polysaccharides, mainly agar and carrageenans, are the most relevant and exploited compounds of red algae. Other potential molecules are essential fatty acids, phycobiliproteins, vitamins, minerals, and other secondary metabolites. All these compounds have been demonstrated to exert several biological activities, among which antioxidant, anti-inflammatory, antitumor, and antimicrobial properties can be highlighted. Nevertheless, these properties need to be further tested on in vivo experiments and go in-depth in the study of the mechanism of action of the specific molecules and the understanding of the structure-activity relation. At last, the extraction technologies are essential for the correct isolation of the molecules, in a cost-effective way, to facilitate the scale-up of the processes and their further application by the industry. This manuscript is aimed at describing the fundamental composition of red algae and their most studied biological properties to pave the way to the utilization of this underused resource.

Production of Lectins from Marine Algae: Current Status, Challenges, and Opportunities for Non-Destructive Extraction

Marine algae are an excellent source of novel lectins. The isolation of lectins from marine algae expands the diversity in structure and carbohydrate specificities of lectins isolated from other sources. Marine algal lectins have been reported to have antiviral, antitumor, and antibacterial activity. Lectins are typically isolated from marine algae by grinding the algal tissue with liquid nitrogen and extracting with buffer and alcohol. While this method produces higher yields, it may not be sustainable for large-scale production, because a large amount of biomass is required to produce a minute amount of compound, and a significant amount of waste is generated during the extraction process. Therefore, non-destructive extraction using algal culture water could be used to ensure a continuous supply of lectins without exclusively disrupting the marine algae. This review discusses the traditional and recent advancements in algal lectin extraction methods over the last decade, as well as the steps required for large-scale production. The challenges and prospects of various extraction methods (destructive and non-destructive) are also discussed.

Can be marine bioactive peptides (MBAs) lead the future of foodomics for human health?

Marine organisms are considered a cache of biologically active metabolites with pharmaceutical, functional, and nutraceutical properties. Among these, marine bioactive peptides (MBAs) present in diverse marine species (fish, sponges, cyanobacteria, fungi, ascidians, seaweeds, & mollusks) have acquired attention owing to their broad-spectrum health-promoting benefits. Nowadays, scientists are keener exploring marine bioactive peptides precisely due to their unique structural and biological properties. These MBAs have reported ameliorating potential against different diseases like hypertension, diabetes, obesity, HIV, cancer, oxidation, and inflammation. Furthermore, MBAs isolated from various marine organisms may also have a beneficial role in the cosmetic, nutraceutical, and food industries. Few marine peptides and their derivative are approved for commercial use, while many MBAs are in various pre-clinical and clinical trials. This review mainly focuses on the diversity of marine bioactive peptides in marine organisms and their production procedures, such as chemical and enzymatic hydrolysis. Moreover, MBAs' therapeutic and biological potential has also been critically discussed herein, along with their status in drug discovery, pre-clinical and clinical trials.

A Novel C1q Domain-Containing Protein Isolated from the Mollusk Modiolus kurilensis Recognizing Glycans Enriched with Acidic Galactans and Mannans

C1q domain-containing (C1qDC) proteins are a group of biopolymers involved in immune response as pattern recognition receptors (PRRs) in a lectin-like manner. A new protein MkC1qDC from the hemolymph plasma of Modiolus kurilensis bivalve mollusk widespread in the Northwest Pacific was purified. The isolation procedure included ammonium sulfate precipitation followed by affinity chromatography on pectin-Sepharose. The full-length MkC1qDC sequence was assembled using de novo mass-spectrometry peptide sequencing complemented with N-terminal Edman's degradation, and included 176 amino acid residues with molecular mass of 19 kDa displaying high homology to bivalve C1qDC proteins. MkC1qDC demonstrated antibacterial properties against Gram-negative and Gram-positive strains. MkC1qDC binds to a number of saccharides in Ca2+-dependent manner which characterized by structural meta-similarity in acidic group enrichment of galactose and mannose derivatives incorporated in diversified molecular species of glycans. Alginate, κ-carrageenan, fucoidan, and pectin were found to be highly effective inhibitors of MkC1qDC activity. Yeast mannan, lipopolysaccharide (LPS), peptidoglycan (PGN) and mucin showed an inhibitory effect at concentrations three orders of magnitude greater than for the most effective saccharides. MkC1qDC localized to the mussel hemal system and interstitial compartment. Intriguingly, MkC1qDC was found to suppress proliferation of human adenocarcinoma HeLa cells in a dose-dependent manner, indicating to the biomedical potential of MkC1qDC protein.

Oncolytic Vaccinia Virus Expressing White-Spotted Charr Lectin Regulates Antiviral Response in Tumor Cells and Inhibits Tumor Growth In Vitro and In Vivo

Oncolytic vaccina virus (oncoVV) used for cancer therapy has progressed in recent years. Here, a gene encoding white-spotted charr lectin (WCL) was inserted into an oncoVV vector to form an oncoVV-WCL recombinant virus. OncoVV-WCL induced higher levels of apoptosis and cytotoxicity, and replicated faster than control virus in cancer cells. OncoVV-WCL promoted IRF-3 transcriptional activity to induce higher levels of type I interferons (IFNs) and blocked the IFN-induced antiviral response by inhibiting the activity of IFN-stimulated responsive element (ISRE) and the expression of interferon-stimulated genes (ISGs). The higher levels of viral replication and antitumor activity of oncoVV-WCL were further demonstrated in a mouse xenograft tumor model. Therefore, the engineered oncoVV expressing WCL might provide a new avenue for anticancer gene therapy.

In vitro assessment of dual (antiviral and antitumor) activity of a novel lectin produced by the newly cyanobacterium isolate, Oscillatoria acuminate MHM-632 MK014210.1

A novel lectin was purified from newly cyanobacterium isolate, Oscillatoria acuminate MHM-632 MK014210.1 using affinity chromatography with a molecular weight of 120 kDa under native-PAGE and 30 kDa on reducing-PAGE, represented tetramer nature of this lectin. Oscillatorial lectin showed stability at 60 °C for 30 min, pH-dependent, with the highest activities over the pH range of 6-8, and required zinc ions to express its full activity. Oscillatorial lectin is a glycan-binding protein with a neutral carbohydrate content of 7.0% as evaluated by the phenol-sulfuric acid method. Polyols and α- glycosides polymer of mannose sugar or sugars alcohol were completely inhibited oscillatorial lectin with MIC of 0.195 mM, while β-glycosides sugars did not show any inhibition effect. The oscillatorial lectin has anti-proliferative activity against Huh-7 and MCF-7 cancer cells and inhibited their proliferation with EC₅₀ values of 106.75 µg/ml and 254.14 µg/ml, respectively. Besides the anticancer effect, oscillatorial lectin also has potent antiviral activity against HSV-1 in a dose-dependent manner via virions neutralization and inhibition of viral replication with IC₅₀ values of 90.95 ng/ml and 131.3 ng/ml, respectively. The unique carbohydrate affinity of oscillatorial lectin provides insight into its use as a promising candidate in many biotechnological applications, like fighting viral infection and combating cancer disease.Communicated by Ramaswamy H. Sarma.

Man-Specific, GalNAc/T/Tn-Specific and Neu5Ac-Specific Seaweed Lectins as Glycan Probes for the SARS-CoV-2 (COVID-19) Coronavirus

Seaweed lectins, especially high-mannose-specific lectins from red algae, have been identified as potential antiviral agents that are capable of blocking the replication of various enveloped viruses like influenza virus, herpes virus, and HIV-1 in vitro. Their antiviral activity depends on the recognition of glycoprotein receptors on the surface of sensitive host cells-in particular, hemagglutinin for influenza virus or gp120 for HIV-1, which in turn triggers fusion events, allowing the entry of the viral genome into the cells and its subsequent replication. The diversity of glycans present on the S-glycoproteins forming the spikes covering the SARS-CoV-2 envelope, essentially complex type N-glycans and high-mannose type N-glycans, suggests that high-mannose-specific seaweed lectins are particularly well adapted as glycan probes for coronaviruses. This review presents a detailed study of the carbohydrate-binding specificity of high-mannose-specific seaweed lectins, demonstrating their potential to be used as specific glycan probes for coronaviruses, as well as the biomedical interest for both the detection and immobilization of SARS-CoV-2 to avoid shedding of the virus into the environment. The use of these seaweed lectins as replication blockers for SARS-CoV-2 is also discussed.

Structure and anticancer activity of a new lectin from the cultivated red alga, Kappaphycus striatus

The red alga Kappaphycus striatus is economically important food species and extensively cultivated throughout most tropical parts of the world as a source of carrageenan. In this note, the primary structure of a new lectin KSL from this alga was elucidated by the rapid amplification method of complementary DNA (cDNA) ends, which consists of 267 amino acid residues distributed in four tandem-repeated domains of about 67 amino acids and sharing 43% of identity. The calculated molecular mass from the deduced sequence was consistent with that of natural KSL (27,826 Da) determined by electron spray ionization-mass spectrometry. The primary structure of KSL showed high similarity to those of the high mannose N-glycan specific lectins from marine red algae, ESA-2 from Eucheuma serra, EDA-2 from Eucheuma denticulatum, KSA-2 from Kappaphycus striatum, KAAs from Kappaphycus alvarezii and SfLs from Solieria filiformis, and from microorganisms, BOA from Burkholderia oklahomensis, MBHA from Myxococcus xanthus, OAA from Oscillatoria agardhii and PFL from Pseudomonas fluorescens. Furthermore, KSL showed anticancer effects against five carcinoma cell lines, HT29, Hela, MCF-7, SK-LU-1 and AGS, in a dose-dependent manner with the IC₅₀ values of 0.80-1.94 µM, whereas its inhibition activities on cancer cells were not detected in the presence of yeast mannan, an inhibitor against lectin KSL. The cultivated red alga K. striatus could also be a good source of functional lectin(s) for application as anticancer agents.

Antitumor Potential of Marine and Freshwater Lectins

Often, even the most effective antineoplastic drugs currently used in clinic do not efficiently allow complete healing due to the related toxicity. The reason for the toxicity lies in the lack of selectivity for cancer cells of the vast majority of anticancer agents. Thus, the need for new potent anticancer compounds characterized by a better toxicological profile is compelling. Lectins belong to a particular class of non-immunogenic glycoproteins and have the characteristics to selectively bind specific sugar sequences on the surface of cells. This property is exploited to exclusively bind cancer cells and exert antitumor activity through the induction of different forms of regulated cell death and the inhibition of cancer cell proliferation. Thanks to the extraordinary biodiversity, marine environments represent a unique source of active natural compounds with anticancer potential. Several marine and freshwater organisms, ranging from the simplest alga to the most complex vertebrate, are amazingly enriched in these proteins. Remarkably, all studies gathered in this review show the impressive anticancer effect of each studied marine lectin combined with irrelevant toxicity in vitro and in vivo and pave the way to design clinical trials to assess the real antineoplastic potential of these promising proteins. It provides a concise and precise description of the experimental results, their interpretation as well as the experimental conclusions that can be drawn.

Mannose-Specific Lectins from Marine Algae: Diverse Structural Scaffolds Associated to Common Virucidal and Anti-Cancer Properties

To date, a number of mannose-specific lectins have been isolated and characterized from seaweeds, especially from red algae. In fact, man-specific seaweed lectins consist of different structural scaffolds harboring a single or a few carbohydrate-binding sites which specifically recognize mannose-containing glycans. Depending on the structural scaffold, man-specific seaweed lectins belong to five distinct structurally-related lectin families, namely (1) the griffithsin lectin family (β-prism I scaffold); (2) the Oscillatoria agardhii agglutinin homolog (OAAH) lectin family (β-barrel scaffold); (3) the legume lectin-like lectin family (β-sandwich scaffold); (4) the Galanthus nivalis agglutinin (GNA)-like lectin family (β-prism II scaffold); and, (5) the MFP2-like lectin family (MFP2-like scaffold). Another algal lectin from Ulva pertusa, has been inferred to the methanol dehydrogenase related lectin family, because it displays a rather different GlcNAc-specificity. In spite of these structural discrepancies, all members from the five lectin families share a common ability to specifically recognize man-containing glycans and, especially, high-mannose type glycans. Because of their mannose-binding specificity, these lectins have been used as valuable tools for deciphering and characterizing the complex mannose-containing glycans from the glycocalyx covering both normal and transformed cells, and as diagnostic tools and therapeutic drugs that specifically recognize the altered high-mannose N-glycans occurring at the surface of various cancer cells. In addition to these anti-cancer properties, man-specific seaweed lectins have been widely used as potent human immunodeficiency virus (HIV-1)-inactivating proteins, due to their capacity to specifically interact with the envelope glycoprotein gp120 and prevent the virion infectivity of HIV-1 towards the host CD4+ T-lymphocyte cells in vitro.

Overview of the Structure⁻Function Relationships of Mannose-Specific Lectins from Plants, Algae and Fungi

To date, a number of mannose-binding lectins have been isolated and characterized from plants and fungi. These proteins are composed of different structural scaffold structures which harbor a single or multiple carbohydrate-binding sites involved in the specific recognition of mannose-containing glycans. Generally, the mannose-binding site consists of a small, central, carbohydrate-binding pocket responsible for the "broad sugar-binding specificity" toward a single mannose molecule, surrounded by a more extended binding area responsible for the specific recognition of larger mannose-containing N-glycan chains. Accordingly, the mannose-binding specificity of the so-called mannose-binding lectins towards complex mannose-containing N-glycans depends largely on the topography of their mannose-binding site(s). This structure⁻function relationship introduces a high degree of specificity in the apparently homogeneous group of mannose-binding lectins, with respect to the specific recognition of high-mannose and complex N-glycans. Because of the high specificity towards mannose these lectins are valuable tools for deciphering and characterizing the complex mannose-containing glycans that decorate both normal and transformed cells, e.g., the altered high-mannose N-glycans that often occur at the surface of various cancer cells.

New Drugs from the Sea: Pro-Apoptotic Activity of Sponges and Algae Derived Compounds

Natural compounds derived from marine organisms exhibit a wide variety of biological activities. Over the last decades, a great interest has been focused on the anti-tumour role of sponges and algae that constitute the major source of these bioactive metabolites. A substantial number of chemically different structures from different species have demonstrated inhibition of tumour growth and progression by inducing apoptosis in several types of human cancer. The molecular mechanisms by which marine natural products activate apoptosis mainly include (1) a dysregulation of the mitochondrial pathway; (2) the activation of caspases; and/or (3) increase of death signals through transmembrane death receptors. This great variety of mechanisms of action may help to overcome the multitude of resistances exhibited by different tumour specimens. Therefore, products from marine organisms and their synthetic derivates might represent promising sources for new anticancer drugs, both as single agents or as co-adjuvants with other chemotherapeutics. This review will focus on some selected bioactive molecules from sponges and algae with pro-apoptotic potential in tumour cells.

Lectins from red algae and their biomedical potential

Lectins are unique proteins or glycoproteins of non-immune origin that bind specifically to carbohydrates. They recognise and interact reversibly to either free carbohydrates or glycoconjugates, without modifying their structure. Lectins are highly diverse and widely distributed in nature and have been extensively reported from various red algae species. Numerous red algae species have been reported to possess lectins having carbohydrate specificity towards complex glycoproteins or high-mannose N-glycans. These lectin-glycan interactions further trigger many biochemical responses which lead to their extensive use as valuable tools in biomedical research. Thus, owing to their exceptional glycan recognition property, red algae lectins are potential candidate for inhibition of various viral diseases. Hence, the present report integrates existing information on the red algae lectins, their carbohydrate specificity, and characteristics of purified lectins. Further, the review also reports the current state of research into their anti-viral activity against various enveloped viruses such as HIV, hepatitis, influenza, encephalitis, coronavirus and herpes simplex virus and other biomedical activities such as anti-cancer, anti-microbial, anti-inflammatory, anti-nociceptive and acaricidal activities.

Structural characterization of two isolectins from the marine red alga Solieria filiformis (Kützing) P.W. Gabrielson and their anticancer effect on MCF-7 breast cancer cells

As described in the literature, Solieria filiformis lectin (SfL) from the marine red alga S. filiformis was found to have antinociceptive and anti-inflammatory effects. In this study, we characterized two SfL variants, SfL-1 and SfL-2, with molecular mass of 27,552Da and 27,985Da, respectively. The primary structures of SfL-1 and SfL-2 consist of four tandem-repeat protein domains with 67 amino acids each. SfL-1 and -2 showed high similarity to OAAH-family lectins. 3D structure prediction revealed that SfL-1 and -2 are composed of two β-barrel-like domains formed by five antiparallel β-strands, which are connected by a short peptide linker. Furthermore, the mixture of isoforms (SfLs) showed anticancer effect against MCF-7 cells. Specifically, SfLs inhibited 50% of viability in MCF-7 cells after treatment at 125μg.mL^-1, while the inhibition of Human Dermal Fibroblasts (HDF) was 34% with the same treatment. Finally, 24h after treatment, 25% of MCF-7 cells were in early apoptosis and 35% in late apoptosis. Evaluation of pro- and anti-apoptotic gene expression of MCF-7 cells revealed that SfLs induced caspase-dependent apoptosis within 24h.

Marine lectins and their medicinal applications

Marine organisms have been extensively explored for the last several decades as potential sources of novel biologically active compounds, and extensive research has been conducted on lectins. Lectins derived from marine organisms are structurally diverse and also differ from those identified from terrestrial organisms. Marine lectins appear to be particularly useful in some biological applications. They seem to induce negligible immunogenicity because they have a relatively small size, are more stable due to extensive disulfide bridge formation, and have high specificity for complex glyco-conjugates and carbohydrates instead of simple sugars. It is clear that many of them have not yet been extensively studied when compared with their terrestrial counterparts. Marine lectins can be used to design and develop new potentially useful therapeutic agents. This review encompasses recent research on the isolation and identification of marine lectins with potential value in medicinal applications.

Marine lectins and their medicinal applications

Marine organisms have been extensively explored for the last several decades as potential sources of novel biologically active compounds, and extensive research has been conducted on lectins. Lectins derived from marine organisms are structurally diverse and also differ from those identified from terrestrial organisms. Marine lectins appear to be particularly useful in some biological applications. They seem to induce negligible immunogenicity because they have a relatively small size, are more stable due to extensive disulfide bridge formation, and have high specificity for complex glyco-conjugates and carbohydrates instead of simple sugars. It is clear that many of them have not yet been extensively studied when compared with their terrestrial counterparts. Marine lectins can be used to design and develop new potentially useful therapeutic agents. This review encompasses recent research on the isolation and identification of marine lectins with potential value in medicinal applications.

Algal lectins as promising biomolecules for biomedical research

Lectins are natural bioactive ubiquitous proteins or glycoproteins of non-immune response that bind reversibly to glycans of glycoproteins, glycolipids and polysaccharides possessing at least one non-catalytic domain causing agglutination. Some of them consist of several carbohydrate-binding domains which endow them with the properties of cell agglutination or precipitation of glycoconjugates. Lectins are rampant in nature from plants, animals and microorganisms. Among microorganisms, algae are the potent source of lectins with unique properties specifically from red algae. The demand of peculiar and neoteric biologically active substances has intensified the developments on isolation and biomedical applications of new algal lectins. Comprehensively, algal lectins are used in biomedical research for antiviral, antinociceptive, anti-inflammatory, anti-tumor activities, etc. and in pharmaceutics for the fabrication of cost-effective protein expression systems and nutraceutics. In this review, an attempt has been made to collate the information on various biomedical applications of algal lectins.

Membrane interaction between Span 80 vesicle and phospholipid vesicle (liposome): Span 80 vesicle can perturb and hemifuse with liposomal membrane

We have focused on the interaction between the Span 80 vesicle and phospholipid vesicle (liposome). The Span 80 vesicle was mixed with a phospholipid vesicle (liposome), used as a simplified model of plasma membrane. From calcein leakage experiments, it was revealed that the interaction between the Span 80 vesicles and the liposomes could perturb the liposome membrane. In the experiments based on fluorescence resonance energy transfer, the lipid mixing between Span 80 vesicle and liposome was observed. The above phenomena were also supported by the fluorescence spectroscopic analysis using laurdan, resulting in the variation in the membrane properties of liposome after its mixing with Span 80 vesicle. These results suggest that the Span 80 vesicles can easily interact and hemifuse with the liposome membrane, which depend on the membrane properties of the Span 80 vesicle, "flexible" and "molecular structure" of the components.

Active Targeting to Osteosarcoma Cells and Apoptotic Cell Death Induction by the Novel Lectin Eucheuma serra Agglutinin Isolated from a Marine Red Alga

Previously, we demonstrated that the novel lectin Eucheuma serra agglutinin from a marine red alga (ESA) induces apoptotic cell death in carcinoma. We now find that ESA induces apoptosis also in the case of sarcoma cells. First, propidium iodide assays with OST cells and LM8 cells showed a decrease in cell viability after addition of ESA. With 50 μg/ml ESA, the viabilities after 24 hours decreased to 54.7 ± 11.4% in the case of OST cells and to 41.7 ± 12.3% for LM8 cells. Second, using fluorescently labeled ESA and flow cytometric and fluorescence microscopic measurements, it could be shown that ESA does not bind to cells that were treated with glycosidases, indicating importance of the carbohydrate chains on the surface of the cells for efficient ESA-cell interactions. Third, Span 80 vesicles with surface-bound ESA as active targeting ligand were shown to display sarcoma cell binding activity, leading to apoptosis and complete OST cell death after 48 hours at 2 μg/ml ESA. The findings indicate that Span 80 vesicles with surface-bound ESA are a potentially useful drug delivery system not only for the treatment of carcinoma but also for the treatment of osteosarcoma.

Algal chemodiversity and bioactivity: sources of natural variability and implications for commercial application

There has been significant recent interest in the commercial utilisation of algae based on their valuable chemical constituents many of which exhibit multiple bioactivities with applications in the food, cosmetic, agri- and horticultural sectors and in human health. Compounds of particular commercial interest include pigments, lipids and fatty acids, proteins, polysaccharides and phenolics which all display considerable diversity between and within taxa. The chemical composition of natural algal populations is further influenced by spatial and temporal changes in environmental parameters including light, temperature, nutrients and salinity, as well as biotic interactions. As reported bioactivities are closely linked to specific compounds it is important to understand, and be able to quantify, existing chemical diversity and variability. This review outlines the taxonomic, ecological and chemical diversity between, and within, different algal groups and the implications for commercial utilisation of algae from natural populations. The biochemical diversity and complexity of commercially important types of compounds and their environmental and developmental control are addressed. Such knowledge is likely to help achieve higher and more consistent levels of bioactivity in natural samples and may allow selective harvesting according to algal species and local environmental conditions for different groups of compounds.

Preparation of cationic immunovesicles containing cationic Peptide lipid for specific drug delivery to target cells

The cationic vesicle composed of Span80 and cationic peptide lipid (CPL) was prepared. The cytotoxicity of the Span80-CPL cationic vesicle was very low compared with Span80 vesicle. Antibody was able to be immobilized on vesicle surface by mediation of protein A. The antigen targeting ability of the antibody-immobilized vesicle (immunovesicle) derived from antibody was evaluated. Our results suggested that the Span80-CPL immunovesicles specifically associate with target cells by the antibody mediation, and the substance capsulated in immunovesicle was transferred into the target cells. This means that the Span80-CPL immunovesicle is expected to achieve a high local concentration of an encapsulated drug at the target.

High-mannose N-glycan-specific lectin from the red alga Kappaphycus striatum (Carrageenophyte)

From a fresh sample (1 kg) of cultivated red alga Kappaphycus striatum, three isolectins, KSA-1 (15.1 mg), KSA-2 (58.0 mg) and KSA-3 (6.9 mg), were isolated by a combination of extraction with aqueous ethanol, ethanol precipitation, and ion exchange chromatography. Isolated KSAs were monomeric proteins of about 28kDa having identical 20N-terminal amino acid sequences to each other. Their hemagglutination activities were not inhibited by monosaccharides, but inhibited by glycoproteins bearing high-mannose N-glycans. In a binding experiment with pyridylaminated oligosaccharides by centrifugal ultrafiltration-HPLC assay, the isolectin KSA-2 was exclusively bound to high-mannose type N-glycans, but not to other glycans. Including complex types and a pentasaccharide core of N-glycans, indicating that it recognized branched oligomannosides. The binding activity of KSA-2 was slightly different among high-mannose N-glycans examined, indicating that the lectin has a higher affinity for those having the exposed (α1-3) Man in the D2 arm. On the other hand, KSA-2 did not bind to a free oligomannose that is a constituent of the branched oligomannosides, implying that the portion of the core GlcNAc residue(s) of the N-glycans is also essential for binding. Thus, KSA-2 appears to recognize the extended carbohydrate structure with a minimal length of a tetrasaccharide, Man(α1-3)Man(α1-6)Man(β1-4)GlcNAc. This study indicates that K. striatum, which has extensively been cultivated as a source of carrageenan, is a good source of a valuable lectin(s) that is strictly specific for high-mannose N-glycans.

BIOACTIVE PROTEINS, PEPTIDES, AND AMINO ACIDS FROM MACROALGAE(1)

Macroalgae are a diverse group of marine organisms that have developed complex and unique metabolic pathways to ensure survival in highly competitive marine environments. As a result, these organisms have been targeted for mining of natural biologically active components. The exploration of marine organisms has revealed numerous bioactive compounds that are proteinaceous in nature. These include proteins, linear peptides, cyclic peptides and depsipeptides, peptide derivatives, amino acids, and amino acid-like components. Furthermore, some species of macroalgae have been shown to contain significant levels of protein. While some protein-derived bioactive peptides have been characterized from macroalgae, macroalgal proteins currently still represent good candidate raw materials for biofunctional peptide mining. This review will provide an overview of the important bioactive amino-acid-containing compounds that have been identified in macroalgae. Moreover, the potential of macroalgal proteins as substrates for the generation of biofunctional peptides for utilization as functional foods to provide specific health benefits will be discussed.

In vitro and in vivo anti-tumor effects of novel Span 80 vesicles containing immobilized Eucheuma serra agglutinin

The lectin Eucheuma serra agglutinin (ESA) is known from previous studies to specifically bind to high-mannose type N-glycans and to induce apoptotic cancer cell death in vitro. In this study, Span 80 vesicles, with an average diameter between about 200 and 400 nm, containing immobilized ESA were prepared from the nonionic surfactant Span 80, also known as sorbitan monooleate. The vesicles were investigated in vitro and in vivo to evaluate the vesicles's potential applicability as novel drug delivery system. The results obtained are promising since the following was observed: (i) vesicular ESA had the same hemagglutinating activity as free ESA, demonstrating its biological activity when bound to the vesicles; (ii) vesicles containing immobilized ESA decreased the viability of Colo201 cancer cells in vitro while the growth of normal cells was not affected; (iii) the vesicles showed binding to Colo201 cells in vitro and caused inhibition of cancer cell growth in nude mice to which the vesicle-treated cells were added; (iv) the vesicles diminished tumor growth after intravenous administration to nude mice which contained an implanted Colo201 tumor; (v) the vesicles showed a tendency to accumulate at the site of the tumor 6h after i.v. administration to nude mice. Thus, all measurements carried out indicate that this type of Span 80 vesicle can be considered as promising alternatives to conventional phospholipid-based vesicles.

Strict specificity for high-mannose type N-glycans and primary structure of a red alga Eucheuma serra lectin

We have elucidated the carbohydrate-binding profile of a non-monosaccharide-binding lectin named Eucheuma serra lectin (ESA)-2 from the red alga Eucheuma serra using a lectin-immobilized column and a centrifugal ultrafiltration-high performance liquid chromatography method with a variety of fluorescence-labeled oligosaccharides. In both methods, ESA-2 exclusively bound with high-mannose type (HM) N-glycans, but not with any of other N-glycans including complex type, hybrid type and core pentasaccharides, and oligosaccharides from glycolipids. These findings indicate that ESA-2 recognizes the branched oligomannosides of the N-glycans. However, ESA-2 did not bind with any of the free oligomannoses examined that are constituents of the branched oligomannosides implying that the portion of the core N-acetyl-D-glucosamine (GlcNAc) residue(s) of the N-glycans is also essential for binding. Thus, the algal lectin was strictly specific for HM N-glycans and recognized the extended carbohydrate structure with a minimum size of the pentasaccharide, Man(alpha1-3)Man(alpha1-6)Man(beta1-4)GlcNAc(beta1-4) GlcNAc. Kinetic analysis of binding with a HM heptasaccharide (M5) showed that ESA-2 has four carbohydrate-binding sites per polypeptide with a high association constant of 1.6x10(8) M-1. Sequence analysis, by a combination of Edman degradation and mass analyses of the intact protein and of peptides produced by its enzymic digestions, showed that ESA-2 is composed of 268 amino acids (molecular weight 27950) with four tandemly repeated domains of 67 amino acids. The number of repeats coincided with the number of carbohydrate-binding sites in the monomeric molecule. Surprisingly, the marine algal lectin was homologous to hemagglutinin from the soil bacterium Myxococcus xanthus.

The anti-tumor effect of Euchema serra agglutinin on colon cancer cells in vitro and in vivo

Eucheuma serra agglutinin (ESA) is a lectin derived from a marine red alga E. serra and binds specifically to mannose-rich sugar chains. Previous reports have indicated that ESA associates with several cancer cells via sugar chains on cell surfaces and induces apoptotic cell death. In this study, we investigated the effect of ESA on Colon26 mouse colon adenocarcinoma cells both in vitro and in vivo. ESA induced cell death against Colon26 cells in vitro, and the expression of caspase-3 and the translocation of phosphatidylserine in ESA-treated Colon26 cells suggested that this cell death was induced through apoptosis. An intravenous injection of ESA significantly inhibited the growth of Colon26 tumors in BALB/c mice; moreover, DNA fragmentation was detected in tumor cells following ESA treatment. These results indicated that ESA is effective as an anti-cancer drug not only in vitro but also in vivo. The side-effects of ESA were not considered to be serious because the decrease in body weight of the mice injected with it was negligible. These observations suggest that ESA has the potential to be an effective anti-tumor drug.

Double-Modification of Lectin Using Two Distinct Chemistries for Fluorescent Ratiometric Sensing and Imaging Saccharides in Test Tube or in Cell

The site-selective incorporation of two different fluorophores into a naturally occurring protein (lectin, a sugar-binding protein) has been successfully carried out using two distinct orthogonal chemical methods. By post-photoaffinity labeling modification, Con A, a glucose- and mannose-selective lectin, was modified with fluorescein in the proximity of the sugar binding site (Tyr100 site), and the controlled acylation reaction provided the site-selective attachment of coumarin at Lys114. In this doubly modified Con A, the fluorescein emission changed upon the binding to the corresponding sugars, such as the glucose or mannose derivatives, whereas the coumarin emission was constant. Thus, the doubly modified Con A fluorescently sensed the glucose- and mannose-rich saccharides in a ratiometric manner while retaining the natural binding selectivity and affinity, regardless of the double modification. On the benefit of the ratiometric fluorescent analysis using two distinct probes, the sugar trimming process of a glycoprotein can be precisely monitored by the engineered Con A. Furthermore, the doubly modified Con A can be used not only for the convenient fluorescent imaging of saccharides localized on a cell surface, such as the MCF-7, a breast cancer cell having rich high-mannose branch, but also for the ratiometric fluorescent sensing of the glucose concentration inside HepG2 cells. These results demonstrated that the semisynthetic lectin modified doubly by two distinct chemistries is superior to the singly modified one in function, and thus, it may be potentially useful in cell, as well as in test tube.