Abstract 195: Evaluation of the cell surface binding of phycocyanin and associated mechanisms causing cell death in prostate cancer cells

Plant and microbial metabolites are constantly explored to identify novel therapeutics with promising potential for treating diseases such as cancer. Marine-derived compounds are also tapped frequently for their efficacy in treating cancers and are used both in mono and combination therapies. The potential of cyanobacteria (blue-green algae) as the source of anticancer agents has been explored for many decades and, as a result of continuing efforts, several compounds have emerged as templates for the development of new anticancer drugs from these microorganisms. The C-phycocyanin (C-PC) tested in our experiments was derived from the cyanobacteria Limnothrix sp., strain 37-2-1, which is found abundantly in Florida’s Everglades. In our previous studies, this fluorescent compound was found to potentiate the cytotoxic effects of Taxol and Topotecan. In LNCaP prostate cancer cells, C-PC was able to induce apoptosis by itself through activation of the apoptotic pathway and completing DNA fragmentation. It was originally anticipated that C-PC might penetrate the cell membrane to induce mitochondrial damage and trigger the apoptotic process through activations of caspases. In order to verify this possibility, experiments were conducted to determine the uptake of C-PC using LNCaP cells. When we incubated the cells with C-PC at the concentrations of 250 and 500 µg/mL for 12 hrs and assessed the cellular uptake by capturing the fluorescence signals at the wavelength of 605 nm, using a fluorescence microscope, the signals were observed only with the periphery of the cells. Furthermore, with subsequent washes using PBS, the fluorescence signal that was seen to be associated with the plasma membrane was reduced gradually and was removed completely after the 3rd wash without any signs of penetration into the cytoplasm. The binding of C-PC to the plasma membrane was very transient and quickly dissociated at room temperature. However, after incubating the cells with the same concentrations of C-PC, there was up-regulation of proapoptotic markers such as p53 and p21 and as a result, the cells showed a significant reduction (>65%) in viability. So far, our results suggest that the cytotoxicity towards LNCaP cells might have been triggered by the binding of C-PC to the cell membrane receptors such as FasR, TRAIL-R, TNF-R, which may be linked to the mediators of extrinsic and intrinsic apoptotic signals. Hence, our findings are significant for explaining some of the apoptotic events triggered by C-PC. However, additional studies are required to identify the actual receptors involved in triggering the pathway. (The support from the Royal Dames of Cancer Research Inc., Ft. Lauderdale, Florida is gratefully acknowledged).

Citation Format: Paramjot Kaur, Sivanesan Dhandayuthapani, Shona Joseph, Syed Hussain, Miroslav Gantar, Appu Rathinavelu. Evaluation of the cell surface binding of phycocyanin and associated mechanisms causing cell death in prostate cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 195. doi:10.1158/1538-7445.AM2017-195

Carotenoid glycosides from cyanobacteria are teratogenic in the zebrafish (Danio rerio) embryo model

Toxigenicity of cyanobacteria is widely associated with production of several well-described toxins that pose recognized threats to human and ecosystem health as part of both freshwater eutrophication, and episodic blooms in freshwater and coastal habitats. However, a preponderance of evidence indicates contribution of additional bioactive, and potentially toxic, metabolites. In the present study, the zebrafish (Danio rerio) embryo was used as a model of vertebrate development to identify, and subsequently isolate and characterize, teratogenic metabolites from two representative strains of C. raciborskii. Using this approach, three chemically related carotenoids - and specifically the xanthophyll glycosides, myxol 2'-glycoside (1), 4-ketomyxol 2'-glycoside (2) and 4-hydroxymyxol 2'-glycoside (3) - which are, otherwise, well known pigment molecules from cyanobacteria were isolated as potently teratogenic compounds. Carotenoids are recognized "pro-retinoids" with retinoic acid, as a metabolic product of the oxidative cleavage of carotenoids, established as both key mediator of embryo development and, consequently, a potent teratogen. Accordingly, a comparative toxicological study of chemically diverse carotenoids, as well as apocarotenoids and retinoids, was undertaken. Based on this, a working model of the developmental toxicity of carotenoids as pro-retinoids is proposed, and the teratogenicity of these widespread metabolites is discussed in relation to possible impacts on aquatic vertebrate populations.

Abstract A2-27: Effects of C-Phycocyanin in combination with anticancer drugs in lung cancer implanted mice

The C-Phycocyanin (C-PC) is a pigmented phycobiliprotein that is produced by the blue-green algae (cyanobacterium) named Spirulina platensis and Limnothrix sp. For the first time we have tested the anticancer properties of C-PC from the cyanobacterial isolate Limnothrix sp., that is found in Florida's Everglades, using cancer cells and xenograft tumor model. Our preliminary studies confirm that C-PC from Limnothrix have antiproliferative activity against LNCaP prostate cancer cells. However, as expected the required concentration of C-PC for anticancer activity is well above the usual doses of anticancer drugs normally used. Therefore, we speculated that C-PC could potentiate the anticancer effects of certain therapeutic agents when used in combination treatment. Initially the cytotoxic effects of C-PC and Topotecan (TPT) were confirmed using cell viability assays in A-549 lung cancer cells. Also, it was determined that C-PC treatment could significantly down regulate the levels of Bcl-2, an anti-apoptotic protein, to induce apoptosis. Furthermore, our in vivo experiments confirmed the efficacy of C-PC in potentiating the anticancer effects of Taxol, Topotecan and Cisplatin in athymic nude mice that were sub-cutaneously implanted with the xenograft tumors established from A549 lung cancer cells. During the treatment period the experimental mice had free access to C-PC dissolved in drinking water at a dose of 100 mg/Kg body weight. All the other anticancer drugs were given as intraperitoneal (i.p.) injections at a dose of 1.0 mg/kg body weight twice a week for a period of 60 days. Tumor growth was assessed once in every two weeks using caliper measurements. At the end of the treatment period the level of lung tumor biomarker CYFRA 21-1 in serum was analyzed. As a result of the treatment, the tumor growth was found to be 54%, 46% and 33% less in Taxol; TPT and Cisplatin treated groups compared to the control group. Interestingly C-PC + Taxol combination showed 75% inhibition while C-PC + TPT showed 51% and C-PC + Cisplatin showed 40% inhibition of tumor growth. Thus, the mice treated with the C-PC + Taxol combination showed an additional 21% tumor growth inhibition when compared to group treated with Taxol alone. Furthermore, the decreased level of CYFRA 21-1in serum showed a good correlation with the inhibition of tumor growth in C-PC + Taxol treated animals. Results from our study confirm that C-PC from Limnothrix sp., can significantly enhance the anticancer activity of Taxol against the A549 lung tumor in athymic nude mice possibly by decreasing the levels of Bcl-2. (This project was supported by the PFRDG grant of NSU and grants from the James & Esther King Biomedical Research Program of the State of Florida and the Royal Dames of Cancer Research Inc., Ft. Lauderdale, Florida).

Citation Format: Sivanesan Dhandayuthapani, Miroslav Gantar, Appu Rathinavelu. Effects of C-Phycocyanin in combination with anticancer drugs in lung cancer implanted mice. [abstract]. In: Proceedings of the AACR Special Conference on Translation of the Cancer Genome; Feb 7-9, 2015; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(22 Suppl 1):Abstract nr A2-27.

Identification of teratogenic polymethoxy-1-alkenes from Cylindrospermopsis raciborskii, and taxonomically diverse freshwater cyanobacteria and green algae

Cylindrospermopsis raciborskii is among the most commonly recognized toxigenic cyanobacteria associated with harmful algal blooms (HAB) in freshwater systems, and specifically associated with multiple water-soluble toxins. Lipophilic metabolites from C. raciborskii, however, were previously shown to exert teratogenicity (i.e. inhibition of vertebrate development) in the zebrafish (Danio rerio) embryo model, specifically suggesting the presence of additional bioactive compounds unrelated to the currently known toxins. In the present study, a series of known teratogenic polymethoxy-1-alkenes (PMA) were identified, purified and chemically characterized from an otherwise well-characterized strain of toxigenic C. raciborskii. Although PMA have been previously identified in other cyanobacteria, this is the first time they have been identified from this recognized HAB species. Following their identification from C. raciborskii, the taxonomic distribution of the PMA was additionally investigated by chemical screening of a freshwater algal (i.e. cyanobacteria, green algal) culture collection. Screening suggests that these compounds are distributed among phylogenetically diverse taxa. Furthermore, parallel screening of the algal culture collection, using the zebrafish embryo model of teratogenicity, the presence of PMA was found to closely correlate with developmental toxicity of these diverse algal isolates. Taken together, the data suggest PMA contribute to the toxicity of C. raciborskii, as well as apparently several other taxonomically disparate cyanobacterial and green algal genera, and may, accordingly, contribute to the toxicity of diverse freshwater HAB.

Abstract 5314: Evaluation of C-phycocyanin and anticancer drug combination for inducing apoptosis in LNCaP prostate cancer cells

Natural products have been used for thousands of years by different culture and civilization to fight against diseases such as cancer. Modern medicine has begun to recognize the need to evaluate these natural products in terms of their potential therapeutic value with less toxic side effects. The discovery of novel natural anti-tumor compounds such as C-phycocyanin (C-PC) from the cyanobacterium Limnothrix sp., shows significant potential for inclusion in future drug regimens. C-PC is a pigment found in blue-green algae that have been proven to have antioxidant, anti-inflammatory and hepatoprotective properties. This cycanobacterium is relatively abundant in the estuaries and coastal waters of Florida's Everglades and the compound can be easily extracted from this natural resource. Mapping apoptosis mediated cancer cell death pathway can assist in paving way for the creation of future drug regimens with less toxic side effects in conjugation with a more potent therapeutic response. The main objective of our study was to evaluate apoptosis mediated cancer cell death against LNCaP prostate cancer cells using C-PC in combination with the well-known anti-cancer drug Topotecan (TPT). For this purpose several in vitro experiments were conducted in our laboratory to test whether lower than normal doses of the potent anticancer drug TPT can offer the same level of cytotoxicity as normal doses when combined with C-PC. Our experiments verified that when 10% of a typical dose of TPT was combined with C-PC, the cytotoxic effects towards LNCaP cancer cells were significantly higher than when TPT was used alone at its full dose. It is suspected that generation of ROS may play a crucial role in the overall process. However, the ultimate activation of key apoptotic proteases such as caspase-9 and caspase-3 appears to play a major part in the overall process. It was also observed that DNA fragmentation was more pronounced when both TPT and C-PC were used in combination for treatment. Furthermore, the expression level of the pro- and anti-apoptotic proteins such as Bcl-2 and Bax were also significantly modulated in cancer cells treated with C-PC and TPT combination. Higher levels of ROS generation as well as an increase in the activities of caspase-9 and caspase-3 detected in the combination treatments suggest that C-PC can augment apoptosis mediated cancer cell death and the therapeutic potentials of TPT.  In that respect, we suggest that C-PC can improve the anticancer effects of several other anti-cancer drugs that are currently available and therefore could help to diminish many of the harsh side effects experienced by cancer patients undergoing chemotherapy. (This project was supported by the PFRDG grant of NSU and grants from the James & Esther King Biomedical Research Program of the State of Florida and The Royal Dames of Cancer Research Inc., Ft. Lauderdale, Florida).

Citation Format: Amal Khallouki, Hasan Azad, Sivanesan Dhandayuthapani, Miroslav Gantar, Appu Rathinavelu. Evaluation of C-phycocyanin and anticancer drug combination for inducing apoptosis in LNCaP prostate cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5314. doi:10.1158/1538-7445.AM2015-5314

Abstract 5318: Effect of C-phycocyanin on the anticancer properties of taxol and topotecan in lung cancer implanted athymic nude mice

The biodiversity of marine environment and the associated chemical multiplicity offers unlimited resource for discovering new antitumor agents. For the first time we have tested the anticancer properties of C-phycocyanin (C-PC) isolated from a unique cyanobacterial strain named Limnothrix sp., which is found in Florida's Everglades. Our preliminary studies originally confirmed antiproliferative activity of C-PC against LNCaP prostate cancer cells and subsequently against A549 lung cancer cells also. Therefore, we speculated that C-PC could potentiate the anticancer effects of certain therapeutic agents when used in combination treatments. For this purpose the cytotoxic effects of C-PC and topotecan were confirmed using cell viability assays in A549 lung cancer cells. Subsequently, our in vivo experiments confirmed the efficacy of C-PC in potentiating the anticancer effects of taxol and topotecan in athymic nude mice that were sub-cutaneously implanted with the xenograft tumors established from A549 lung cancer cells. During the treatment period the experimental mice had free access to C-PC that was dissolved in drinking water at a dose of 100 mg/kg body weight. The anticancer drugs were given as intraperitoneal injections at a dose of 1.0 mg/kg body weight twice a week for a period of 60 days. The tumor growth was assessed once in every two weeks using caliper measurements. At the end of the treatment period the levels of lung tumor biomarkers CYFRA 21-1 (Cytokeratin 19 fragments) and CEA (Carcino Embryonic Antigen) in serum were analyzed. As a result of the treatment, the tumor growth was found to be 54% and 46% less in taxol and topotecan treated groups compared to the control group. Interestingly C-PC + taxol combination showed 75% inhibition of tumor growth. Thus, the mice treated with the C-PC + taxol combination showed an additional 21% tumor growth inhibition when compared to the group treated with taxol alone. Furthermore, the levels of the tumor biomarkers CYFRA 21-1 and CEA in serum were significantly reduced by the treatment showing a good correlation with the inhibition of tumor growth in C-PC + taxol treated animals. The C-PC + taxol combination treated animals showed 91% decrease while C-PC alone was able to reduce the levels of CYFRA 21-1 by 85%. Similarly, the CEA levels were reduced by 97% following the C-PC + taxol combination treatment. It was further determined that C-PC treatment could significantly down regulate the levels of anti-apoptotic protein such as Bcl-2 to trigger apoptosis in lung cancer cells. Thus, results from our study confirm that C-PC from Limnothrix sp., can significantly enhance the anticancer activity of taxol against the A549 lung tumor in athymic nude mice possibly by decreasing the levels of Bcl-2. (Project was supported by the PFRDG grant of NSU, James & Esther King Biomedical Research Program of the State of Florida and The Royal Dames of Cancer Research Inc., Ft. Lauderdale, Florida).

Citation Format: Sivanesan Dhandayuthapani, Miroslav Gantar, Thanigaivelan Kanagasabai, Manasa Subbarao, Appu Rathinavelu. Effect of C-phycocyanin on the anticancer properties of taxol and topotecan in lung cancer implanted athymic nude mice. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5318. doi:10.1158/1538-7445.AM2015-5318

Indole alkaloids from Fischerella inhibit vertebrate development in the zebrafish (Danio rerio) embryo model

Cyanobacteria are recognized producers of toxic or otherwise bioactive metabolite associated, in particular, with so-called “harmful algal blooms” (HABs) and eutrophication of freshwater systems. In the present study, two apparently teratogenic indole alkaloids from a freshwater strain of the widespread cyanobacterial genus, Fischerella (Stigonemataceae), were isolated by bioassay-guided fractionation, specifically using the zebrafish (Danio rerio) embryo, as a model of vertebrate development. The two alkaloids include the previously known 12-epi-hapalindole H isonitrile (1), and a new nitrile-containing variant, 12-epi-ambiguine B nitrile (2). Although both compounds were toxic to developing embryos, the former compound was shown to be relatively more potent, and to correlate best with the observed embryo toxicity. Related indole alkaloids from Fischerella, and other genera in the Stigonemataceae, have been widely reported as antimicrobial compounds, specifically in association with apparent allelopathy. However, this is the first report of their vertebrate toxicity, and the observed teratogenicity of these alkaloids supports a possible contribution to the toxicity of this widespread cyanobacterial family, particularly in relation to freshwater HABs and eutrophication.

Ecology and Physiology of the Pathogenic Cyanobacterium Roseofilum reptotaenium

Roseofilum reptotaenium is a gliding, filamentous, phycoerythrin-rich cyanobacterium that has been found only in the horizontally migrating, pathogenic microbial mat, black band disease (BBD) on Caribbean corals. R. reptotaenium dominates the BBD mat in terms of biomass and motility, and the filaments form the mat fabric. This cyanobacterium produces the cyanotoxin microcystin, predominately MC-LR, and can tolerate high levels of sulfide produced by sulfate reducing bacteria (SRB) that are also associated with BBD. Laboratory cultures of R. reptotaenium infect coral fragments, suggesting that the cyanobacterium is the primary pathogen of BBD, but since this species cannot grow axenically and Koch's Postulates cannot be fulfilled, it cannot be proposed as a primary pathogen. However, R. reptotaenium does play several major pathogenic roles in this polymicrobial disease. Here, we provide an overview of the ecology of this coral pathogen and present new information on R. reptotaenium ecophysiology, including roles in the infection process, chemotactic and other motility responses, and the effect of pH on growth and motility. Additionally, we show, using metabolomics, that exposure of the BBD microbial community to the cyanotoxin MC-LR affects community metabolite profiles, in particular those associated with nucleic acid biosynthesis.

Effects of cyanobacterial lipopolysaccharides from microcystis on glutathione-based detoxification pathways in the zebrafish (Danio rerio) embryo

Cyanobacteria ("blue-green algae") are recognized producers of a diverse array of toxic secondary metabolites. Of these, the lipopolysaccharides (LPS), produced by all cyanobacteria, remain to be well investigated. In the current study, we specifically employed the zebrafish (Danio rerio) embryo to investigate the effects of LPS from geographically diverse strains of the widespread cyanobacterial genus, Microcystis, on several detoxifying enzymes/pathways, including glutathione-S-transferase (GST), glutathione peroxidase (GPx)/glutathione reductase (GR), superoxide dismutase (SOD), and catalase (CAT), and compared observed effects to those of heterotrophic bacterial (i.e., E. coli) LPS. In agreement with previous studies, cyanobacterial LPS significantly reduced GST in embryos exposed to LPS in all treatments. In contrast, GPx moderately increased in embryos exposed to LPS, with no effect on reciprocal GR activity. Interestingly, total glutathione levels were elevated in embryos exposed to Microcystis LPS, but the relative levels of reduced and oxidized glutathione (i.e., GSH/GSSG) were, likewise, elevated suggesting that oxidative stress is not involved in the observed effects as typical of heterotrophic bacterial LPS in mammalian systems. In further support of this, no effect was observed with respect to CAT or SOD activity. These findings demonstrate that Microcystis LPS affects glutathione-based detoxification pathways in the zebrafish embryo, and more generally, that this model is well suited for investigating the apparent toxicophore of cyanobacterial LPS, including possible differences in structure-activity relationships between heterotrophic and cyanobacterial LPS, and teleost fish versus mammalian systems.

Isolation, characterization and antioxidative activity of C-phycocyanin from Limnothrix sp. strain 37-2-1

C-phycocyanin (C-PC) is a blue colored accessory photosynthetic pigment found in cyanobacteria. Some of the medicinal properties of Spirulina have been attributed to this pigment, which includes anticancer, antioxidant, and anti-inflammatory activity. We have screened cyanobacteria isolated from freshwater habitats in Florida for their high content of C-PC. Of 125 strains tested, one filamentous strain identified as Limnothrix sp. was selected for further research. This strain produced 18% C-PC of total dry biomass. Here we describe a simple method for obtaining C-PC of high purity without the use of ion exchange chromatography. The procedure is based on pigment precipitation from the cell lysate with an appropriate concentration of ammonium sulfate, then purification with activated carbon and chitosan, followed by a sample concentration using tangential flow filtration. We have shown that when the lower concentration of ammonium sulfate was used, C-PC with higher purity index was recovered. Characterization of C-PC from Limnothrix showed that it had an absorbance maximum at 620nm and fluorescence at 639nm. The molecular mass of intact C-PC was estimated to be ~50kDa with α and β subunits forming dimmers. When C-PC content per unit biomass was compared to that of marketed Spirulina powder, we found that Limnothrix was superior. C-phycocyanin from Limnothrix had an antioxidative activity on DPPH free radicals similar to that found in a natural antioxidant - rutin.

Microcystin production and ecological physiology of Caribbean black band disease cyanobacteria

Molecular studies of black band disease (BBD), a coral disease found on tropical and subtropical reefs worldwide, have shown that one 16S rRNA gene sequence is ubiquitous. This sequence has been reported to be a member of the cyanobacterial genus Oscillatoria. In this study, extracts of two cultured laboratory strains of BBD Oscillatoria, and for comparison two strains of BBD Geitlerinema, all isolated from reefs of the wider Caribbean, were analysed using Ultra-Performance Liquid Chromatography-Tandem Quad Mass Spectrometry (UPLC-MS/MS). The cyanotoxin microcystin-LR (MC-LR) was found in all strains, and one Geitlerinema strain additionally produced MC-YR. Growth experiments that monitored toxin production using enzyme-linked immunosorbent assay (ELISA) showed that BBD Oscillatoria produced yields of MC-LR equivalent (0.02-0.04 mg g(-1)) independent of biomass and culture conditions (varying temperature, pH, light and organic carbon). This pattern is different from BBD Geitlerinema, which increased production of MC-LR equivalent in the presence of organic carbon in the light and dark and at a relatively lower temperature. These results indicate that different species and strains of BBD cyanobacteria, which can occur in the same BBD infection, may contribute to BBD pathobiology by producing different toxins and different amounts of toxin at different stages in the disease process. This is the first detailed study of laboratory cultures of the ubiquitous BBD cyanobacterium Oscillatoria sp. isolated from Caribbean reefs.

Molecular aspects of microcystin-induced hepatotoxicity and hepatocarcinogenesis

It is known that microcystin (MC) is a cyanotoxin that is a potent environmental inhibitor of eucariotic protein serine/threonine phosphatase 1 and 2A, both in vitro and in vivo. Consequently, these cyanobacterial toxins (MC-IARC group 2B carcinogen, MC extracts-group 3) are potent tumor promoters and there is an indication that they may also act as tumor initiators. The ability of microcystin-LR (MC-LR) to act as a tumor initiator is based on fact that it can induce DNA damage either by direct interaction with DNA or by indirect mechanisms through formation of reactive oxygen species (ROS). Both acute and chronic exposures, to either low or high doses of MC-LR, can activate apoptotic pathways. Chronic exposure to low concentrations of MC-LR contributes to increased risk for cancer development. Epidemiological studies, in certain areas of China, have suggested that MC is one of the risk factors for the high incidence of primary liver cancer (PLC). Recently, we have reported a correlation between PLC and cyanobacterial "blooms" in reservoirs used as a source for drinking water supply in central Serbia. It appears that the combination of acute and chronic exposures to both high and low doses of MC can lead to PLC initiation and promotion. Based on this, we propose that the requirement for the co-factors such as aflatoxin B1 and other mycotoxins, HBV, HCV, alcohol, etc. is not needed for initiation and promotion of PLC by MC-LR as was suggested earlier. The possible mechanisms of the genotoxicity of MC and its role as a hepatocarcinogen are outlined in this review. Furthermore, we show that the exposure of hepatocytes to MC can lead either to malignant proliferation or apoptosis.

Sulfide, microcystin, and the etiology of black band disease

Black band disease (BBD) consists of a cyanobacterial-dominated, sulfide-rich microbial mat that migrates across coral colonies, degrading coral tissue. The mat contains diverse bacteria that include photoautotrophs (cyanobacteria), sulfate-reducers, sulfide-oxidizers, and organoheterotrophs. BBD sulfate-reducers contribute to BBD pathobiology by production of sulfide, which causes coral tissue lysis and death, and the cyanotoxin microcystin is produced by BBD cyanobacteria. Here we used a model system of coral fragments to investigate the roles of sulfide and microcystin in BBD by exposure to the metabolic inhibitors sodium molybdate and 3-(3', 4'-dichlorophenyl)-1, 1-dimethylurea (DCMU), which inhibit sulfate reduction and oxygenic photosynthesis, respectively. Exposure of BBD inocula to sodium molybdate prior to inoculation prevented infection of healthy fragments but did not prevent continued band migration and coral tissue lysis by active BBD infections. Exposure to DCMU did not inhibit either the initiation of BBD or continued migration of active BBD. Exposure of healthy coral fragments to sulfide, purified microcystin, and a combination of both revealed that both microcystin and sulfide are toxic to coral and act synergistically. Measurement of growth of bacteria isolated from BBD and the healthy coral surface mucopolysaccharide layer (SML) during exposure to microcystin revealed that growth of relatively more BBD than SML isolates was stimulated, although effects were not uniform and the majority exhibited no effect. Our results indicate that sulfide is required for initiation of BBD, both microcystin and sulfide are involved in BBD pathobiology, and microcystin may structure the BBD bacterial community.

Cyanotoxins from black band disease of corals and from other coral reef environments

Many cyanobacteria produce cyanotoxins, which has been well documented from freshwater environments but not investigated to the same extent in marine environments. Cyanobacteria are an obligate component of the polymicrobial disease of corals known as black band disease (BBD). Cyanotoxins were previously shown to be present in field samples of BBD and in a limited number of BBD cyanobacterial cultures. These toxins were suggested as one of the mechanisms contributing to BBD-associated coral tissue lysis and death. In this work, we tested nine cyanobacterial isolates from BBD and additionally nine isolated from non-BBD marine sources for their ability to produce toxins. The presence of toxins was determined using cell extracts of laboratory grown cyanobacterial cultures using ELISA and the PP2A assay. Based on these tests, it was shown that cyanobacterial toxins belonging to the microcystin/nodularin group were produced by cyanobacteria originating from both BBD and non-BBD sources. Several environmental factors that can be encountered in the highly dynamic microenvironment of BBD were tested for their effect on both cyanobacterial growth yield and rate of toxin production using two of the BBD isolates of the genera Leptolyngbya and Geitlerinema. While toxin production was the highest under mixotrophic conditions (light and glucose) for the Leptolyngbya isolate, it was highest under photoautotrophic conditions for the Geitlerinema isolate. Our results show that toxin production among marine cyanobacteria is more widespread than previously documented, and we present data showing three marine cyanobacterial genera (Phormidium, Pseudanabaena, and Spirulina) are newly identified as cyanotoxin producers. We also show that cyanotoxin production by BBD cyanobacteria can be affected by environmental factors that are present in the microenvironment associated with this coral disease.

MICROALGAE AND CYANOBACTERIA: FOOD FOR THOUGHT(1)

In non-Western civilizations, cyanobacteria have been part of the human diet for centuries. Today, microalgae and cyanobacteria are either produced in controlled cultivation processes or harvested from the natural habitats and marketed as food supplements around the world. Cyanobacteria produce a vast array of different biologically active compounds, some of which are expected to be used in drug development. The fact that some of the active components from cyanobacteria potentially have anticancer, antimicrobial, antiviral, anti-inflammatory, and other effects is being used for marketing purposes. However, introduction of these products in the form of whole biomass for alimentary purposes raises concerns regarding the potential toxicity and long-term effects on human health. Here, we review data on the use of cyanobacteria and microalgae in human nutrition and searched for available information on legislature that regulates the use of these products. We have found that, although the quality control of these products is most often self-regulated by the manufacturers, different governmental agencies are introducing strict regulations for placing novel products, such as algae and cyanobacteria, on the market. The existing regulations require these products to be tested for the presence of toxins, such as microcystin; however, other, sometimes novel, toxins remain undetected, and their long-term effects on human health remain unknown.

Allelopathic activity among Cyanobacteria and microalgae isolated from Florida freshwater habitats

We evaluated allelopathic interactions between strains of Cyanobacteria and green algae isolated from south and central Florida. Allelopathy, including inhibition or stimulation of growth, was assessed by cocultivation of each of the isolated strains, as well as by evaluation of extracts prepared from the isolates. All of the strains of Cyanobacteria, and four of the six isolates of green algae, showed some allelopathic activity (i.e. inhibition or stimulation of the growth of other strains). Of these, the most pronounced activity was observed for the cyanobacterial isolate Fischerella sp. strain 52-1. In the cocultivation experiments this cyanobacterium inhibited the growth of all tested green algae and Cyanobacteria. The crude lipophilic extracts from Fischerella sp. strain 52-1 isolated from both the biomass and the culture liquid inhibited photosynthesis of the green alga Chlamydomonas sp. in a concentration- and time-dependent manner and caused extensive loss of ultrastructural cell organization. Preliminary chemical characterization of compounds extracted from Fischerella sp. strain 52-1 indicated the presence of indole alkaloids, and further characterization has confirmed that these compounds belong to the hapalindoles previously isolated from other species of Fischerella and related genera. Further chemical characterization of these compounds, and further investigation of their apparent role in allelopathy is ongoing.

Occurrence and distribution of novel botryococcene hydrocarbons in freshwater wetlands of the Florida Everglades

A high abundance of isoprenoid hydrocarbons, the botryococcenes, with carbon numbers from 32 to 34 were detected in the Florida Everglades freshwater wetlands. These compounds were present in varying amounts up to 106microg/gdw in periphyton, 278microg/gdw in floc, and 46microg/gdw in soils. Their structures were determined based on comparison to standards, interpretation of their mass spectra and those of their hydrogenation products, and comparison of Kovats indexes to those reported in the literature. A total of 26 cyclic and acyclic botryococcenes with 8 skeletons were identified, including those with fewer degrees of unsaturation, which are proposed as early diagenetic derivatives from the natural products. This is the first report that botryococcenes occur in the Everglades freshwater wetlands. Their potential biogenetic sources from green algae and cyanobacteria were examined, but neither contained botryococcenes. Thus, the source implication of botryococcenes in this ecosystem needs further study.

The presence of the cyanobacterial toxin microcystin in black band disease of corals

Black band disease (BBD) is a migrating, cyanobacterial dominated, sulfide-rich microbial mat that moves across coral colonies lysing coral tissue. While it is known that BBD sulfate-reducing bacteria contribute to BBD pathogenicity by production of sulfide, additional mechanisms of toxicity may be involved. Using HPLC/MS, the cyanotoxin microcystin was detected in 22 field samples of BBD collected from five coral species on nine reefs of the wider Caribbean (Florida Keys and Bahamas). Two cyanobacterial cultures isolated from BBD, Geitlerinema and Leptolyngbya sp. contained microcystin based on HPLC/MS, with toxic activity confirmed using the protein phosphatase inhibition assay. The gene mcyA from the microcystin synthesis complex was detected in two field samples and from both BBD cyanobacterial cultures. Microcystin was not detected in six BBD samples from a different area of the Caribbean (St Croix, USVI) and the Philippines, suggesting regional specificity for BBD microcystin. This is the first report of the presence of microcystin in a coral disease.

Structures of pahayokolides A and B, cyclic peptides from a Lyngbya sp

The isolation and structure elucidation of two cyclic peptides, pahayokolides A (1) and B (2), is described. Structural features determined for these compounds include a pendent N-acetyl-N-methyl leucine, both E- and Z-dehydrobutyrines, a homophenylalanine, and an unusual polyhydroxy amino acid that is most likely of mixed polyketide synthase/nonribosomal peptide synthase origin. These peptides were purified from a new species of cyanobacteria of the genus Lyngbya, which was isolated from a periphyton mat from the Florida Everglades.

The zebrafish (Danio rerio) embryo as a model system for identification and characterization of developmental toxins from marine and freshwater microalgae

The zebrafish (Danio rerio) embryo has emerged as an important model of vertebrate development. As such, this model system is finding utility in the investigation of toxic agents that inhibit, or otherwise interfere with, developmental processes (i.e. developmental toxins), including compounds that have potential relevance to both human and environmental health, as well as biomedicine. Recently, this system has been applied increasingly to the study of microbial toxins, and more specifically, as an aquatic animal model, has been employed to investigate toxins from marine and freshwater microalgae, including those classified among the so-called "harmful algal blooms" (HABs). We have developed this system for identification and characterization of toxins from cyanobacteria (i.e. "blue-green algae") isolated from the Florida Everglades and other freshwater sources in South and Central Florida. Here we review the use of this system as it has been applied generally to the investigation of toxins from marine and freshwater microalgae, and illustrate this utility as we have applied it to the detection, bioassay-guided fractionation and subsequent characterization of developmental toxins from freshwater cyanobacteria.

Epidemiology of recreational exposure to freshwater cyanobacteria--an international prospective cohort study

BACKGROUND

Case studies and anecdotal reports have documented a range of acute illnesses associated with exposure to cyanobacteria and their toxins in recreational waters. The epidemiological data to date are limited; we sought to improve on the design of some previously conducted studies in order to facilitate revision and refinement of guidelines for exposure to cyanobacteria in recreational waters.

METHODS

A prospective cohort study was conducted to investigate the incidence of acute symptoms in individuals exposed, through recreational activities, to low (cell surface area < 2.4 mm2/mL), medium (2.4-12.0 mm2/mL) and high (> 12.0 mm2/mL) levels of cyanobacteria in lakes and rivers in southeast Queensland, the central coast area of New South Wales, and northeast and central Florida. Multivariable logistic regression analyses were employed; models adjusted for region, age, smoking, prior history of asthma, hay fever or skin disease (eczema or dermatitis) and clustering by household.

RESULTS

Of individuals approached, 3,595 met the eligibility criteria, 3,193 (89%) agreed to participate and 1,331 (37%) completed both the questionnaire and follow-up interview. Respiratory symptoms were 2.1 (95%CI: 1.1-4.0) times more likely to be reported by subjects exposed to high levels of cyanobacteria than by those exposed to low levels. Similarly, when grouping all reported symptoms, individuals exposed to high levels of cyanobacteria were 1.7 (95%CI: 1.0-2.8) times more likely to report symptoms than their low-level cyanobacteria-exposed counterparts.

CONCLUSION

A significant increase in reporting of minor self-limiting symptoms, particularly respiratory symptoms, was associated with exposure to higher levels of cyanobacteria of mixed genera. We suggest that exposure to cyanobacteria based on total cell surface area above 12 mm2/mL could result in increased incidence of symptoms. The potential for severe, life-threatening cyanobacteria-related illness is likely to be greater in recreational waters that have significant levels of cyanobacterial toxins, so future epidemiological investigations should be directed towards recreational exposure to cyanotoxins.

Pharmacology and toxicology of pahayokolide A, a bioactive metabolite from a freshwater species of Lyngbya isolated from the Florida Everglades

The genus of filamentous cyanobacteria, Lyngbya, has been found to be a rich source of bioactive metabolites. However, identification of such compounds from Lyngbya has largely focused on a few marine representatives. Here, we report on the pharmacology and toxicology of pahayokolide A from a freshwater isolate, Lyngbya sp. strain 15-2, from the Florida Everglades. Specifically, we investigated inhibition of microbial representatives and mammalian cell lines, as well as toxicity of the compound to both invertebrate and vertebrate models. Pahayokolide A inhibited representatives of Bacillus, as well as the yeast, Saccharomyces cerevisiae. Interestingly, the compound also inhibited several representatives of green algae that were also isolated from the Everglades. Pahayokolide A was shown to inhibit a number of cancer cell lines over a range of concentrations (IC50 varied from 2.13 to 44.57 microM) depending on the cell-type. When tested against brine shrimp, pahayokolide was only marginally toxic at the highest concentrations tested (1 mg/mL). The compound was, however, acutely toxic to zebrafish embryos (LC50=2.15 microM). Possible biomedical and environmental health aspects of the pahayokolides remain to be investigated; however, the identification of bioactive metabolites such as these demonstrates the potential of the Florida Everglades as source of new toxins and drugs.

Colonization of wheat (Triticum vulgare L.) by N2 -fixing cyanobacteria: IV. Dark nitrogenase activity and effects of cyanobacteria on natural 15 N abundance in the plants

Two cyanobacterial soil isolates, Nostoc 2S9B and Anabaena C5, that had previously been shown to form different types of association with the roots of wheat plants grown in liquid culture, were tested for heterotrophic nitrogenase activity and the ability to colonize the roots of plants grown in sand. Nostoc 2S9B showed substantial nitrogenase activity when associated with the roots of plants grown in liquid culture in medium free of combined N, even with the roots maintained and with assays performed in the dark (29 % of the rate shown by root-associated Nostoc 2S9B grown and assayed in the light). When grown heterotrophically in the dark, at the expense of fructose, free-living Nostoc 2S9B showed a similar nitrogenase activity to root-associated Nostoc 2S9B in the dark. In contrast, Anabaena C5 showed no nitrogenase activity in the dark, under these conditions. When three different wheat cultivars were grown in sand that had previously been surface-inoculated with Nostoc 2S9B or with the cultured symbiotic cyanobacterium Nostoc LBG1, isolated from the bryophyte Anthoceros, there was colonization of the plant roots; there was no colonization of roots by Anabaena C5 under these conditions. Some increases in plant biomass and nitrogen content were observed, but these were dependent on the wheat cultivar and cyanobacterial inoculum used. Wheat plants grown in sand that had been pre-inoculated with Nostoc 2S9B, Nostoc LBG1 or Anabaena C5 in medium free of combined N had lower δ¹⁵ N values in both roots and shoots than plants grown under identical conditions without a cyanobacterial inoculum. The observed ¹⁵ N/¹⁴ N fractionation indicates that N₂ fixed by the cyanobacteria contributed to the nitrogen economy of the wheat plants, irrespective of whether they were closely associated with the plant roots.