Effectors of thioredoxin reductase: Brevetoxins and manumycin-A

The activities of two effectors, brevetoxin (PbTx) and manumycin-A (Man-A), of thioredoxin reductase (TrxR) have been evaluated against a series of fourteen TrxR orthologs originating from mammals, insects and protists and several mutants. Man-A, a molecule with numerous electrophilic sites, forms a covalent adduct with most selenocystine (Sec)-containing TrxR enzymes. The evidence also demonstrates that Man-A can form covalent adducts with some non-Sec-containing enzymes. The activities of TrxR enzymes towards various substrates are moderated by Man-A either positively or negatively depending on the enzyme. In general, the reduction of substrates by Sec-containing TrxR is inhibited and NADPH oxidase activity is activated. For non-Sec-containing TrxR the effect of Man-A on the reduction of substrates is variable, but NADPH oxidase activity can be activated even in the absence of covalent modification of TrxR. The effect of PbTx is less pronounced. A smaller subset of enzymes is affected by PbTx. With a single exception, the activities of most of this subset are activated. Although both PbTx variants can react with selenocysteine, a stable covalent adduct is not formed with any of the TrxR enzymes. The key findings from this work are (i) the identification of an alternate mechanism of toxicity for the algal toxin brevetoxin (ii) the demonstration that covalent modification of TrxR is not a prerequisite for the activation of NADPH oxidase activity of TrxR and (iii) the identification of an inhibitor which can discriminate between cytosolic and mitochondrial TrxR.

Separate and combined effects of neurotoxic and lytic compounds of Alexandrium strains on Mytilus edulis feeding activity and hemocyte function

Multiple toxic and bioactive compounds produced by Alexandrium spp. cause adverse effects on bivalves, but these effects are frequently difficult to attribute to a single compound class. To disentangle the effect of neurotoxic vs lytic secondary metabolites, we exposed blue mussels to either a paralytic shellfish toxin (PST) producing Alexandrium spp. strain, or to an exclusively lytic compound (LC) producing strain, or a strain containing both compound classes, to evaluate the time dependent effects after 3 and 7 days of feeding. Tested parameters comprised signs of paralysis, feeding activity, and immune cell integrity (hemocyte numbers and viability; lysosomal membrane destabilization) and function (ROS production). Both compound classes caused paralysis and immune impairment. The only effect attributable exclusively to PST was increased phagocytic activity after 3 days and impaired feeding activity after 7 days, which curtailed toxin accumulation in digestive glands. Lysosomal membrane destabilization were more closely, but not exclusively, matched with LC exposure. Effects on circulating hemocyte integrity and immune related functions were mostly transient or remained stable within 7 days; except for increased lysosomal labialization and decreased extracellular ROS production when mussels were exposed to the toxin combination. M. edulis displays adaptive fitness traits to survive and maintain immune capacity upon prolonged exposure to environmentally relevant concentrations of PST and/or LC producing Alexandrium strains.

The Anemonia viridis Venom: Coupling Biochemical Purification and RNA-Seq for Translational Research

Blue biotechnologies implement marine bio-resources for addressing practical concerns. The isolation of biologically active molecules from marine animals is one of the main ways this field develops. Strikingly, cnidaria are considered as sustainable resources for this purpose, as they possess unique cells for attack and protection, producing an articulated cocktail of bioactive substances. The Mediterranean sea anemone Anemonia viridis has been studied extensively for years. In this short review, we summarize advances in bioprospecting of the A. viridis toxin arsenal. A. viridis RNA datasets and toxin data mining approaches are briefly described. Analysis reveals the major pool of neurotoxins of A. viridis, which are particularly active on sodium and potassium channels. This review therefore integrates progress in both RNA-Seq based and biochemical-based bioprospecting of A. viridis toxins for biotechnological exploitation.

C-terminal proline deletions in KCNC3 cause delayed channel inactivation and an adult-onset progressive SCA13 with spasticity

Mutations in the potassium channel gene KCNC3 (Kv3.3) cause the autosomal dominant neurological disease, spinocerebellar ataxia 13 (SCA13). In this study, we expand the genotype-phenotype repertoire of SCA13 by describing the novel KCNC3 deletion p.Pro583_Pro585del highlighting the allelic heterogeneity observed in SCA13 patients. We characterize adult-onset, progressive clinical symptoms of two afflicted kindred and introduce the symptom of profound spasticity not previously associated with the SCA13 phenotype. We also present molecular and electrophysiological characterizations of the mutant protein in mammalian cell culture. Mechanistically, the p.Pro583_Pro585del protein showed normal membrane trafficking with an altered electrophysiological profile, including slower inactivation and decreased sensitivity to the inactivation-accelerating effects of the actin depolymerizer latrunculin B. Taken together, our results highlight the clinical importance of the intracellular C-terminal portion of Kv3.3 and its association with ion channel function.

Ascidian Toxins with Potential for Drug Development

Ascidians (tunicates) are invertebrate chordates, and prolific producers of a wide variety of biologically active secondary metabolites from cyclic peptides to aromatic alkaloids. Several of these compounds have properties which make them candidates for potential new drugs to treat diseases such as cancer. Many of these natural products are not produced by the ascidians themselves, rather by their associated symbionts. This review will focus mainly on the mechanism of action of important classes of cytotoxic molecules isolated from ascidians. These toxins affect DNA transcription, protein translation, drug efflux pumps, signaling pathways and the cytoskeleton. Two ascidian compounds have already found applications in the treatment of cancer and others are being investigated for their potential in cancer, neurodegenerative and other diseases.

Biotechnological and Pharmacological Applications of Biotoxins and Other Bioactive Molecules from Dinoflagellates

The long-lasting interest in bioactive molecules (namely toxins) produced by (microalga) dinoflagellates has risen in recent years. Exhibiting wide diversity and complexity, said compounds are well-recognized for their biological features, with great potential for use as pharmaceutical therapies and biological research probes. Unfortunately, provision of those compounds is still far from sufficient, especially in view of an increasing demand for preclinical testing. Despite the difficulties to establish dinoflagellate cultures and obtain reasonable productivities of such compounds, intensive research has permitted a number of advances in the field. This paper accordingly reviews the characteristics of some of the most important biotoxins (and other bioactive substances) produced by dinoflagellates. It also presents and discusses (to some length) the main advances pertaining to dinoflagellate production, from bench to large scale-with an emphasis on material published since the latest review available on the subject. Such advances encompass improvements in nutrient formulation and light supply as major operational conditions; they have permitted adaptation of classical designs, and aided the development of novel configurations for dinoflagellate growth-even though shearing-related issues remain a major challenge.

Accumulation and Tissue Distribution of Dinophysitoxin-1 and Dinophysitoxin-3 in the Mussel Crenomytilus grayanus Feeding on the Benthic Dinoflagellate Prorocentrum foraminosum

A DTX-1-producing microalga, Prorocentrum foraminosum, from Peter the Great Bay, Sea of Japan, was fed to Gray's mussels, Crenomytilus grayanus, for 12 days. An increase in DTX-1 and 7-O-acyl-DTX-1 (DTX-3) was observed in the digestive gland, kidneys, and gills. The digestive gland accumulated 91-100% of DTX-1 + DTX-3; and kidneys and gills accumulated, up to 8.5% and 4.3%, respectively. The kidneys had a distinctive pattern of toxin accumulation where the concentration of DTX-1 did not grow significantly after the eighth day of feeding, indicating the potential of DTX-1 elimination. The digestive gland and gills predominantly accumulated DTX-1, with a dramatic increase between Days 8 and 12. The DTX-3 content was highest in the digestive gland. The composition of DTX-3 in the acyl groups was similar for the digestive gland and kidneys, and did not change during feeding. The total toxin uptake of mussels exceeded the total toxin content from ingested cells by 2.4 times, showing that toxins may have accumulated from the seawater. This assumption needs to be further proved. The muscle, gonads, and mantle remained free of toxins. No genotoxic effect was observed in the gills and digestive gland.

Maitotoxin Is a Potential Selective Activator of the Endogenous Transient Receptor Potential Canonical Type 1 Channel in Xenopus laevis Oocytes

Maitotoxin (MTX) is the most potent marine toxin known to date. It is responsible for a particular human intoxication syndrome called ciguatera fish poisoning (CFP). Several reports indicate that MTX is an activator of non-selective cation channels (NSCC) in different cell types. The molecular identity of these channels is still an unresolved topic, and it has been proposed that the transient receptor potential (TRP) channels are involved in this effect. In Xenopus laevis oocytes, MTX at picomolar (pM) concentrations induces the activation of NSCC with functional and pharmacological properties that resemble the activity of TRP channels. The purpose of this study was to characterize the molecular identity of the TRP channel involved in the MTX response, using the small interference RNA (siRNA) approach and the two-electrode voltage-clamp technique (TEVC). The injection of a specifically designed siRNA to silence the transient receptor potential canonical type 1 (TRPC1) protein expression abolished the MTX response. MTX had no effect on oocytes, even at doses 20-fold higher compared to cells without injection. Total mRNA and protein levels of TRPC1 were notably diminished. The TRPC4 siRNA did not change the MTX effect, even though it was important to note that the protein level was reduced by the silencing of TRPC4. Our results suggest that MTX could be a selective activator of TRPC1 channels in X. laevis oocytes and a useful pharmacological tool for further studies on these TRP channels.

From Marine Venoms to Drugs: Efficiently Supported by a Combination of Transcriptomics and Proteomics

The potential of marine natural products to become new drugs is vast; however, research is still in its infancy. The chemical and biological diversity of marine toxins is immeasurable and as such an extraordinary resource for the discovery of new drugs. With the rapid development of next-generation sequencing (NGS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), it has been much easier and faster to identify more toxins and predict their functions with bioinformatics pipelines, which pave the way for novel drug developments. Here we provide an overview of related bioinformatics pipelines that have been supported by a combination of transcriptomics and proteomics for identification and function prediction of novel marine toxins.

Growth and toxin production of Azadinium poporum strains in batch cultures under different nutrient conditions

Azaspiracid-2 (AZA2) is the dominant toxin produced by Azadinium poporum strains AZDY06 and AZFC22 isolated from the South China Sea. Biomass and AZA2-production were examined within batch cultures with variation in experimental concentrations of nitrate (0, 88, 882, and 2647µM) or phosphate (0, 3.6, 36, and 109µM), different nitrogen sources (nitrate and urea) and media (f/2-Si, L1-Si, and K-Si) in the present study. Growth of both strains positively responded to nitrate or phosphate nutrients, but the growth status was significantly repressed by the highest additional level of phosphate (109µM). Both AZDY06 and AZFC22 grew well with higher specific growth rates, but with shorter growth periods, within f/2-Si medium spiked with urea than that within media spiked with nitrate. L1-Si medium with relatively high concentrations of trace metals was relatively favorable to both strains of A. poporum tested here. No obvious change within the toxin profile occurred in all cultures of both strains under the various nutrient conditions, although trace amounts of some suspicious derivatives of AZA2 occurred in some cultures. AZA2 cell quotas within both strains significantly (p<0.05) increased at the stationary phase under lower additional phosphate (0 and 3.6µM). Significant differences were not found within AZA2 cell quotas in cultures with additional nitrate ranging from 0 to 2647µM. The highest AZA2 cell quota and maximum AZA2 quantity per culture volume occurred in batch culture at the stationary phase under phosphate concentrations at 3.6µM. Neither A. poporum strain exhibited significant changes in AZA2 cell quotas within f/2-Si media spiked with urea or nitrate as nitrogen sources. The AZA2 cell quota of strain AZDY06 also did not change remarkably within f/2-Si, L1-Si, and K-Si media, however the AZA2 cell quota of strain AZFC22 within L1-Si medium was significantly (p<0.05) higher than that within f/2-Si medium.

New prenylated aeruginosin, microphycin, anabaenopeptin and micropeptin analogues from a Microcystis bloom material collected in Kibbutz Kfar Blum, Israel

Thirteen new and eighteen known natural products were isolated from a bloom material of an assembly of various Microcystis spp. collected in November, 2008, from a commercial fishpond near Kibbutz Kfar Blum, the Jordan Valley, Israel. The new natural products included the prenylated aeruginosin KB676 (1), microphycin KB921 (2), anabaenopeptins KB906 (3) and KB899 (4) and micropeptins KB928 (5), KB956 (6), KB970A (7), KB970B (8), KB984 (9), KB970C (10), KB1048 (11), KB992 (12) and KB1046 (13). Their structures were elucidated primarily by interpretation of their 1D and 2D nuclear magnetic resonance spectra and high-resolution mass spectrometry. Marfey's and chiral-phase high performance liquid chromatography methods were used to determine the absolute configurations of their chiral centers. Aeruginosin KB676 (1) contains the rare (2S,3aS,6S,7aS)-Choi and is the first prenylated aeruginosin derivative described in the literature. Compounds 1 and 5-11 inhibited trypsin with sub-μM IC50s, while Compounds 11-13 inhibited chymotrypsin with sub-μM IC50s. The structures and biological activities of the new natural products and our procedures of dereplication are described.

Marine bromophenol bis (2,3-dibromo-4,5-dihydroxy-phenyl)-methane inhibits the proliferation, migration, and invasion of hepatocellular carcinoma cells via modulating β1-integrin/FAK signaling

Bis (2,3-dibromo-4,5-dihydroxy-phenyl)-methane (BDDPM) is a natural bromophenol compound derived from marine algae. Previous reports have shown that BDDPM possesses antimicrobial activity. In the present study, we found that BDDPM has cytotoxic activity on a wide range of tumor cells, including BEL-7402 cells (IC₅₀ = 8.7 μg/mL). Further studies have shown that prior to the onset of apoptosis, the BDDPM induces BEL-7402 cell detachment by decreasing the adherence of cells to the extracellular matrix (ECM). Detachment experiments have shown that the treatment of BEL-7402 cells with low concentrations of BDDPM (5.0 μg/mL) significantly inhibits cell adhesion to fibronectin and collagen IV as well as cell migration and invasion. High doses of BDDPM (10.0 μg/mL) completely inhibit the migration of BEL-7402 cells, and the expression level of MMPs (MMP-2 and MMP-9) is significantly decreased. Moreover, the expression of β1-integrin and focal adhesion kinase (FAK) is found to be down-regulated by BDDPM. This study suggests that BDDPM has a potential to be developed as a novel anticancer therapeutic agent due to its anti-metastatic activity and also indicates that BDDPM, which has a unique chemical structure, could serve as a lead compound for rational drug design and for future development of anticancer agents.

Isolation, structure elucidation, relative LC-MS response, and in vitro toxicity of azaspiracids from the dinoflagellate Azadinium spinosum

We identified three new azaspiracids (AZAs) with molecular weights of 715, 815, and 829 (AZA33 (3), AZA34 (4), and AZA35, respectively) in mussels, seawater, and Azadinium spinosum culture. Approximately 700 μg of 3 and 250 μg of 4 were isolated from a bulk culture of A. spinosum, and their structures determined by MS and NMR spectroscopy. These compounds differ significantly at the carboxyl end of the molecule from known AZA analogues and therefore provide valuable information on structure-activity relationships. Initial toxicological assessment was performed using an in vitro model system based on Jurkat T lymphocyte cytotoxicity, and the potencies of 3 and 4 were found to be 0.22- and 5.5-fold that of AZA1 (1), respectively. Thus, major changes in the carboxyl end of 1 resulted in significant changes in toxicity. In mussel extracts, 3 was detected at low levels, whereas 4 and AZA35 were detected only at extremely low levels or not at all. The structures of 3 and 4 are consistent with AZAs being biosynthetically assembled from the amino end.

Effects of in vitro exposure to diarrheic toxin producer Prorocentrum lima on gene expressions related to cell cycle regulation and immune response in Crassostrea gigas

Background

Crassostrea gigas accumulates diarrheic shellfish toxins (DSP) associated to Prorocentrum lima of which Okadaic acid (OA) causes specific inhibitions of serine and threonine phosphatases 1 and 2A. Its toxic effects have been extensively reported in bivalve mollusks at cellular and physiological levels, but genomic approaches have been scarcely studied.

Methodology/Principal Findings

Acute and sub-chronic exposure effects of P. lima were investigated on farmed juvenile C. gigas (3–5 mm). The Pacific oysters were fed with three dinoflagellate concentrations: 0.3, 3, and 30×10³ cells mL⁻¹ along with a nontoxic control diet of Isochrysis galbana. The effects of P. lima on C. gigas were followed by analyzing expression levels of a total of four genes, three involved in cell cycle regulation and one in immune response by polymerase chain reaction and real time quantitative PCR, where changes in time and cell concentration were found. The highest expression levels were found in oysters fed 3×10³ cells mL⁻¹ at 168 h for the cycle regulator p21 protein (9 fold), chromatin assembly factor 1 p55 subunit (8 fold), elongation factor 2 (2 fold), and lipopolysaccharide/β-1, 3 glucan binding protein (13 fold above base line). Additionally, the transcript level of all the genes decreased in oysters fed wich the mixed diet 30×10³ cells mL⁻¹ of dinoflagellate after 72 h and was lowest in the chromatin assembly factor 1 p55 subunit (0.9 fold below baseline).

Conclusions

On C. gigas the whole cell ingestion of P lima caused a clear mRNA modulation expression of the genes involved in cell cycle regulation and immune system. Over-expression could be related to DNA damage, disturbances in cell cycle continuity, probably a genotoxic effect, as well as an activation of its innate immune system as first line of defense.

Cytotoxic effects of three new metabolites from Red Sea marine sponge, Petrosia sp

Marine sponges represent an affluent source of biogenetically unprecedented array of biologically active compounds. This study revealed the isolation of ten compounds from marine sponge of Petrosia sp. Their chemical structures were determined by using 1D and 2D NMR, UV, IR and MS measurements. A polyoxygenated steroid (3β,7β,9α-trihydroxycholest-5-en (1), a purine-derivative (3,7-dimethyl-2-(methylamino)-3H-purin-6(7H)-one (2) and a sphingolipid (N-((3S,E)-1,3-dihydroxytetracos-4-en-2-yl)stearamide (3) proved to be new compounds. Meanwhile, seven known compounds; (4-10) were also identified. The cytotoxicity of the total extract and the isolated compounds were subjected to cytotoxicity evaluation employing two cancer cell lines; HepG2 and MCF-7. All tested compounds exhibited cytotoxic effect on both cancer cell lines with IC(50) in range of 20-500 μM. The proposed mechanism of cytotoxic activities was examined through its molecular affinity to the DNA. Compound 5 showed the highest affinity to the DNA with IC(50) 30 μg/mL.

Cyclic marinopyrrole derivatives as disruptors of Mcl-1 and Bcl-x(L) binding to Bim

A series of novel cyclic marinopyrroles were designed and synthesized. Their activity to disrupt the binding of the pro-apoptotic protein, Bim, to the pro-survival proteins, Mcl-1 and Bcl-x(L), was evaluated using ELISA assays. Both atropisomers of marinopyrrole A (1) show similar potency. A tetrabromo congener 9 is two-fold more potent than 1. Two novel cyclic marinopyrroles (3 and 4) are two- to seven-fold more potent than 1.

Shellfish toxins targeting voltage-gated sodium channels

Voltage-gated sodium channels (VGSCs) play a central role in the generation and propagation of action potentials in excitable neurons and other cells and are targeted by commonly used local anesthetics, antiarrhythmics, and anticonvulsants. They are also common targets of neurotoxins including shellfish toxins. Shellfish toxins are a variety of toxic secondary metabolites produced by prokaryotic cyanobacteria and eukaryotic dinoflagellates in both marine and fresh water systems, which can accumulate in marine animals via the food chain. Consumption of shellfish toxin-contaminated seafood may result in potentially fatal human shellfish poisoning. This article provides an overview of the structure, bioactivity, and pharmacology of shellfish toxins that act on VGSCs, along with a brief discussion on their pharmaceutical potential for pain management.

Cyanobacteria and cyanotoxins: from impacts on aquatic ecosystems and human health to anticarcinogenic effects

Cyanobacteria or blue-green algae are among the pioneer organisms of planet Earth. They developed an efficient photosynthetic capacity and played a significant role in the evolution of the early atmosphere. Essential for the development and evolution of species, they proliferate easily in aquatic environments, primarily due to human activities. Eutrophic environments are conducive to the appearance of cyanobacterial blooms that not only affect water quality, but also produce highly toxic metabolites. Poisoning and serious chronic effects in humans, such as cancer, have been described. On the other hand, many cyanobacterial genera have been studied for their toxins with anticancer potential in human cell lines, generating promising results for future research toward controlling human adenocarcinomas. This review presents the knowledge that has evolved on the topic of toxins produced by cyanobacteria, ranging from their negative impacts to their benefits.

Cytotoxicity, fractionation and dereplication of extracts of the dinoflagellate Vulcanodinium rugosum, a producer of pinnatoxin G

Pinnatoxin G (PnTX-G) is a marine toxin belonging to the class of cyclic imines and produced by the dinoflagellate Vulcanodinium rugosum. In spite of its strong toxicity to mice, leading to the classification of pinnatoxins into the class of “fast-acting toxins”, its hazard for human health has never been demonstrated. In this study, crude extracts of V. rugosum exhibited significant cytotoxicity against Neuro2A and KB cells. IC₅₀ values of 0.38 µg mL⁻¹ and 0.19 µg mL⁻¹ were estimated on Neuro2A cells after only 24 h of incubation and on KB cells after 72 h of incubation, respectively. In the case of Caco-2 cells 48 h after exposure, the crude extract of V. rugosum induced cell cycle arrest accompanied by a dramatic increase in double strand DNA breaks, although only 40% cytotoxicity was observed at the highest concentration tested (5 µg mL⁻¹). However, PnTX-G was not a potent cytotoxic compound as no reduction of the cell viability was observed on the different cell lines. Moreover, no effects on the cell cycle or DNA damage were observed following treatment of undifferentiated Caco-2 cells with PnTX-G. The crude extract of V. rugosum was thus partially purified using liquid-liquid partitioning and SPE clean-up. In vitro assays revealed strong activity of some fractions containing no PnTX-G. The crude extract and the most potent fraction were evaluated using full scan and tandem high resolution mass spectrometry. The dereplication revealed the presence of a major compound that could be putatively annotated as nakijiquinone A, N-carboxy-methyl-smenospongine or stachybotrin A, using the MarinLit™ database. Further investigations will be necessary to confirm the identity of the compounds responsible for the cytotoxicity and genotoxicity of the extracts of V. rugosum.

Interpreting the possible ecological role(s) of cyanotoxins: compounds for competitive advantage and/or physiological aide?

To date, most research on freshwater cyanotoxin(s) has focused on understanding the dynamics of toxin production and decomposition, as well as evaluating the environmental conditions that trigger toxin production, all with the objective of informing management strategies and options for risk reduction. Comparatively few research studies have considered how this information can be used to understand the broader ecological role of cyanotoxin(s), and the possible applications of this knowledge to the management of toxic blooms. This paper explores the ecological, toxicological, and genetic evidence for cyanotoxin production in natural environments. The possible evolutionary advantages of toxin production are grouped into two main themes: That of "competitive advantage" or "physiological aide". The first grouping illustrates how compounds produced by cyanobacteria may have originated from the need for a cellular defence mechanism, in response to grazing pressure and/or resource competition. The second grouping considers the contribution that secondary metabolites make to improved cellular physiology, through benefits to homeostasis, photosynthetic efficiencies, and accelerated growth rates. The discussion also includes other factors in the debate about possible evolutionary roles for toxins, such as different modes of exposures and effects on non-target (i.e., non-competitive) species. The paper demonstrates that complex and multiple factors are at play in driving evolutionary processes in aquatic environments. This information may provide a fresh perspective on managing toxic blooms, including the need to use a "systems approach" to understand how physico-chemical conditions, as well biological stressors, interact to trigger toxin production.

Antibacterial and antifungal activities of polyketide metabolite from marine Streptomyces sp. AP-123 and its cytotoxic effect

A Gram positive, filamentous, spore forming antagonistic Streptomyces sp. AP-123 derived from marine region of Andra Pradesh, India, was studied for its medical importance. Among the 210 Streptomyces strains screened at 64.3% exhibited activity against Gram positive bacteria, 48.5% showed activity towards Gram negative bacteria, 38.8% exhibited both Gram positive and negative bacteria and 80.85% strains revealed significant antifungal activity. However, primary screening revealed that Streptomyces sp. AP-123 exhibited significant antimicrobial activity against all the tested bacteria compared to other Streptomyces strains. The presence of l-diaminopimelic acid and glycine in the cell wall hydrolysates and streptomycin resistance indicated the strain belonged to Streptomyces genus. The 16S rDNA gene based phylogenetic affiliation was determined by using bioinformatic tools and it was identified as Streptomyces sp. AP-123 with 99% sequence similarity to Streptomyces flavogriseus. The antimicrobial substances were extracted by hexane and ethyl acetate from spent medium in which Streptomyces sp. AP-123 was cultivated at 30 °C for 5 d. The antimicrobial activity was assessed using broth micro-dilution technique. A compound was obtained by eluting the crude extract using varying concentrations of solvents followed by the chromatographic purification. Based on the IR, (13)C NMR and (1)H NMR spectral data, the compound was identified as polyketide related antibiotic. It exhibited significant antibacterial activity against Gram positive and Gram negative bacteria and also showed a potent cytotoxic activity against cell lines viz. Vero (Green monkey kidney) and HEP2 (laryngeal carcinoma cells) in vitro. The lowest Minimum Inhibitory Concentration (MIC) of the compound against Bacillus subtilis and Staphylococcus aureus were 25 and 37.5 μg mL(-1), respectively. Against Escherichia coli and Pseudomonas aeruginosa it exhibited MIC of 50 and 37.58 μg mL(-1), respectively. However, against Candida albicans and filamentous fungus, Aspergillus niger the MIC values were 12.5 and 25 μg mL(-1), respectively. Cloning and sequence analysis of ketoacyl synthase (KS) gene revealed similarity to the type II polyketide synthase (PKS) gene of Streptomyces species.

Cardiotoxic effects of venom fractions from the Australian box jellyfish Chironex fleckeri on human myocardiocytes

An investigation into the cardiotoxic effects in human cardiomyocytes of different fractions (as produced from an FPLC) of the venom from Chironex fleckeri showed that whole venom caused cardiac cell death in minutes, measured as cell detachment using xCELLigence technology. However, only one fraction of the venom was responsible for this effect. When all extracted venoms were recombined a similar result was seen for the toxic fraction, however these effects were slower than unfractionated venom alone even though the concentrations were similar. The difference in the results between fractioned and unfractionated venom may have been caused by compounds remaining in the FPLC column, which may interact with the toxic fraction to cause rapid cell detachment or death.

Cellular and transcriptional responses of Crassostrea gigas hemocytes exposed in vitro to brevetoxin (PbTx-2)

Hemocytes mediate a series of immune reactions essential for bivalve survival in the environment, however, the impact of harmful algal species and their associated phycotoxins upon bivalve immune system is under debate. To better understand the possible toxic effects of these toxins, Crassostrea gigas hemocytes were exposed to brevetoxin (PbTx-2). Hemocyte viability, monitored through the neutral red retention and MTT reduction assays, and apoptosis (Hoechst staining) remained unchanged during 12 h of exposure to PbTx-2 in concentrations up to 1000 µg/L. Despite cell viability and apoptosis remained stable, hemocytes incubated for 4 h with 1000 µg/L of PbTx-2 revealed higher expression levels of Hsp70 (p < 0.01) and CYP356A1 (p < 0.05) transcripts and a tendency to increase FABP expression, as evaluated by Real-Time quantitative PCR. The expression of other studied genes (BPI, IL-17, GSTO, EcSOD, Prx6, SOD and GPx) remained unchanged. The results suggest that the absence of cytotoxic effects of PbTx-2 in Crassostrea gigas hemocytes, even at high concentrations, allow early defense responses to be produced by activating protective mechanisms associated to detoxification (CYP356A1 and possibly FABP) and stress (Hsp70), but not to immune or to antioxidant (BPI, IL-17, EcSOD, Prx6, GPx and SOD) related genes.

New cytotoxic cembranolides from the soft coral Lobophytum michaelae

Six new cembranolides, michaolides L–Q (1–6), and a known cembranolide, lobomichaolide (7) were isolated from the CH₂Cl₂ extract of the soft coral Lobophytum michaelae. Their structures were established by extensive spectral analysis. The anti-HCMV (human cytomegalovirus) activity of 1–7 and their cytotoxicity against selected cell lines were evaluated.

Sea-originated cytotoxic substances

Cancer accounted for huge number of deaths, which represents about 13% of all deaths worldwide, and the number of the deaths due to cancer is increasing. Natural products and their synthetic analogs are widely used as antitumor drugs. As represented by these drugs, many anticancer drugs originated from cytotoxic compounds. Marine natural products are a gold mine of strong bioactive compounds with unique structures created in evolution of organisms over hundred million years. However, in the field of drug discovery, most studies have focused on plant essences and bacterial metabolites, and candidate compounds from marine origin are still remaining relatively unexplored.