Antioxidant Activity, Inhibition of Intestinal Cancer Cell Growth and Polyphenolic Compounds of the Seagrass Posidonia oceanica's Extracts from Living Plants and Beach Casts.

The aim of the present study was to investigate the use of Posidonia oceanica for making products beneficial for human health. Firstly, we demonstrated that the antioxidant defense (i.e., SOD and APX activity) of P. oceanica's living leaves (LP) has low efficacy, as they partly neutralize the produced H2O2. However, high H2O2 levels led LP to produce, as a response to oxidative stress, high phenolic content, including chicoric acid, p-coumaric acid, caftaric acid, trans-cinnamic and rutin hydrate, as shown by UHPLC-DAD analysis. In addition, LP extracts inhibited intestinal cancer cell proliferation. Moreover, P. oceanica's beach casts consisting of either Wet 'Necromass' (WNP) or Dry 'Necromass' (DNP) were used for preparing extracts. Both DNP and WNP exhibited antioxidant and antiproliferative activities, although lower as compared to those of LP extracts. Although both P. oceanica's meadows and beach casts are considered priority habitats in the Mediterranean Sea due to their high ecological value, legislation framework for beach casts forbidding their removal is still missing. Our results suggested that both LP and DNP could be utilized for the production of high-added value products promoting human health, provided that a sustainability management strategy would be applied for P. oceanica's meadows and beach casts.

Transcriptome and proteome analysis reveals the anti-cancer properties of Hypnea musciformis marine macroalga extract in liver and intestinal cancer cells.

BACKGROUND: Marine seaweeds are considered as a rich source of health-promoting compounds by the food and pharmaceutical industry. Hypnea musciformis is a marine red macroalga (seaweed) that is widely distributed throughout the world, including the Mediterranean Sea. It is known to contain various bioactive compounds, including sulfated polysaccharides, flavonoids, and phlorotannins. Recent studies have investigated the potential anticancer effects of extracts from H. musciformis demonstrating their cytotoxic effects on various cancer cell lines. The anticancer effects of these extracts are thought to be due to the presence of bioactive compounds, particularly sulfated polysaccharides, which have been shown to have anticancer and immunomodulatory effects. However, further studies are needed to fully understand the molecular mechanisms that underlie their anticancer effects and to determine their potential as therapeutic agents for cancer treatment. METHODS: H. musciformis was collected from the Aegean Sea (Greece) and used for extract preparation. Transcriptome and proteome analysis was performed in liver and colon cancer human cell lines following treatment with H. musciformis seaweed extracts to characterize its anticancer effect in detail at the molecular level and to link transcriptome and proteome responses to the observed phenotypes in cancer cells. RESULTS: We have identified that treatment with the seaweed extract triggers a p53-mediated response at the transcriptional and protein level in liver cancer cells, in contrast to colon cancer cells in which the effects are more associated with metabolic changes. Furthermore, we show that in treated HepG2 liver cancer cells, p53 interacts with the chromatin of several target genes and facilitates their upregulation possibly through the recruitment of the p300 co-activator. CONCLUSIONS: Overall, the available evidence suggests that extracts from H. musciformis have the potential to serve as a source of anticancer agents in liver cancer cells mainly through activation of a p53-mediated anti-tumor response that is linked to inhibition of cellular proliferation and induction of cell death.

Antioxidant Activity and Inhibition of Liver Cancer Cells' Growth of Extracts from 14 Marine Macroalgae Species of the Mediterranean Sea.

Macroalgae exhibit beneficial bioactivities for human health. Thus, the aim of the present study was to examine the antioxidant and anticancer potential of 14 macroalgae species' extracts, namely, Gigartina pistillata, Gigartina teedei, Gracilaria gracilis, Gracilaria sp., Gracilaria bursa pastoris, Colpomenia sinuosa, Cystoseira amentacea, Cystoseira barbata, Cystoseira compressa, Sargassum vulgare, Padina pavonica, Codium fragile, Ulva intestinalis, and Ulva rigida, from the Aegean Sea, Greece. The antioxidant activity was assessed using DPPH, ABTS•+, •OH, and O2•- radicals' scavenging assays, reducing power (RP), and protection from ROO•-induced DNA plasmid damage assays. Moreover, macroalgae extracts' total polyphenol contents (TPCs) were assessed. Extracts' inhibition against liver HepG2 cancer cell growth was assessed using the XTT assay. The results showed that G. teedei extract's IC50 was the lowest in DPPH (0.31 ± 0.006 mg/mL), ABTS•+ (0.02 ± 0.001 mg/mL), •OH (0.10 ± 0.007 mg/mL), O2•- (0.05 ± 0.003 mg/mL), and DNA plasmid breakage (0.038 ± 0.002 mg/mL) and exhibited the highest RP (RP0.5AU 0.24 ± 0.019 mg/mL) and TPC (12.53 ± 0.88 mg GAE/g dw). There was also a significant correlation between antioxidant activity and TPC. P. pavonica (IC50 0.93 ± 0.006 mg/mL) exhibited the highest inhibition against HepG2 cell growth. Conclusively, some of the tested extracts exhibited significant chemopreventive properties, and so they may be used for food products.

Nickel uptake kinetics and its structural and physiological impacts in the seagrass Halophila stipulacea.

The present work aims to provide insight into interactions between trace metals and higher plants, focusing on nickel uptake and its effects in seagrasses at environmentally relevant concentrations. Total and intracellular nickel accumulation kinetics, nickel effects on structural cell components, oxidative stress marker and cellular viability, and the accumulation kinetics-toxic effects relationship were investigated in leaves of Halophila stipulacea plants incubated in seawater under laboratory conditions containing nickel ions at 0.01-10 mg L-1 for 14 days. Nickel accumulation kinetics in H. stipulacea young and older apical leaves followed a Michaelis-Menten-type equation, allowing the calculation of uptake parameters; uptake rate (Vc) and equilibrium concentration (Ceq) tended to increase with the increase of nickel concentration in the medium. A dose- and uptake parameter-dependent actin filament (AF) and endoplasmic reticulum (ER) impairment was observed, whereas no effects occurred on microtubules and cell ultrastructure. AF disturbance and ER aggregation were firstly observed in differentiated cells at the lowest concentration on the 12th and 14th day, respectively, while AF disruption in meristematic cells firstly occurred at 0.05 mg L-1; the effects appeared earlier and were more acute at higher concentrations. Increased H2O2 levels were detected, while, at the highest exposures, a significant reduction in epidermal cell viability in older leaves occurred. The lowest total nickel concentrations in young leaves associated with AF disturbance onset at nickel exposure concentrations of 0.01-1 mg L-1 varied between 18.98 and 63.93 µg g-1 dry wt; importantly, they were comparable to nickel concentrations detected in seagrass leaves from various locations. The relationships between exposure concentration, uptake kinetic parameters and toxic effect onset were satisfactorily described by regression models. Our findings suggest that (a) nickel may pose a threat to seagrass meadows, (b) H. stipulacea can be regarded as an efficient biomonitor of nickel, (c) AF and ER impairment in seagrass leaves can be considered as early biomarkers of nickel-induced stress, and (d) the regression models obtained can be used as a tool to evaluate ambient nickel levels and to detect ecotoxicologically significant nickel contamination. The data presented can be utilized in the management and conservation of the coastal environment.

Cadmium uptake kinetics in parts of the seagrass Cymodocea nodosa at high exposure concentrations.

BACKGROUND: Seagrass species have been recommended as biomonitors of environmental condition and as tools for phytoremediation, due to their ability to concentrate anthropogenic chemicals. This study aims to provide novel information on metal accumulation in seagrasses under laboratory conditions to support their use as a tool in the evaluation and abatement of contamination in the field. We investigated the kinetics of cadmium uptake into adult leaf blades, leaf sheaths, rhizomes and roots of Cymodocea nodosa in exposure concentrations within the range of cadmium levels in industrial wastewater (0.5-40 mg L-1). RESULTS: A Michaelis-Menten-type equation satisfactorily described cadmium accumulation kinetics in seagrass parts, particularly at 0.5-5 or 10 mg L-1. However, an S equation best described the uptake kinetics in rhizomes at 5 mg L-1 and roots at 10 and 20 mg L-1. Equilibrium concentration and uptake rate tended to increase with the exposure concentration, indicating that seagrass displays a remarkable accumulation capacity of cadmium and reflect high cadmium levels in the surrounding medium. Concerning leaf blades and rhizomes, the bioconcentration factor at equilibrium (range 73.3-404.3 and 14.3-86.3, respectively) was generally lower at higher exposure concentrations, indicating a gradual reduction of available binding sites. Leaf blades and roots accumulated more cadmium with higher rate than sheaths and rhizomes. Uptake kinetics in leaf blades displayed a better fit to the Michaelis-Menten-type equation than those in the remaining plant parts, particularly at 0.5-10 mg L-1. A marked variation in tissue concentrations mainly after the steady state was observed at 20 and 40 mg L-1, indicative of the stress induced on seagrass cells. The maximum concentrations observed in seagrass parts at 5 and 10 mg L-1 were comparatively higher than those previously reported for other seagrasses incubated to similar exposure concentrations. CONCLUSIONS: Cymodocea nodosa displays a remarkable cadmium accumulation capacity and reflects high cadmium levels in the surrounding medium. Kinetic models satisfactorily describe cadmium uptake in seagrass parts, primarily in adult leaf blades, at high exposure concentrations, permitting to predict cadmium accumulation in field situations. Cymodocea nodosa appeared to be a valuable tool in the evaluation and abatement of cadmium contamination in coastal areas.

Trace element patterns in marine macroalgae.

Novel information on interspecific variation in trace element accumulation in seaweeds is provided. Concentrations and concentration factors (CFs) of a wide set of elements (As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Sr, U, V and Zn) in 26 dominant macroalgae from the Gulf of Thessaloniki, Aegean Sea were determined and compared. Uni-and multivariate data analyses were applied. Phaeophyceae showed higher concentrations and CFs of As and Sr than Rhodophyta and Chlorophyta, indicating that the accumulation of these elements is closely related to species biochemical composition. Filamentous macroalgae displayed higher concentrations and CFs of several elements, particularly Cd, Co, Cr, Cu, Mn and V than sheet-like, coarsely-branched and/or thick-leathery macroalgae, irrespective of phylogenetic relationships, indicating that the accumulation of several elements is largely related to thallus morphology and growth strategy. On a species basis, Cystoseira spp. showed both the highest concentrations and CFs of As, Padina pavonica of Sr and U, Ceramium spp. of Mn, Ceramium and Cladophora species of Co and Cu, Cladophora prolifera of Cr and Polysiphonia deusta and Ulva clathrata of Cd. Se concentration in Ulva rigida correlated positively with seawater Se concentration, and As concentration in this species with sediment As concentration. Thereby, these seaweeds could be regarded as potential biomonitors for the respective elements. A literature review was performed and global element concentrations and CFs were presented for seaweeds from genera collected during this survey. The data presented can contribute to the interpretation of biomonitoring data and the design of biomonitoring programs for the protection and management of coastal environments.

Kinetics of cadmium accumulation and its effects on microtubule integrity and cell viability in the seagrass Cymodocea nodosa.

The kinetics of cadmium accumulation and its effects on microtubule cytoskeleton and cell viability in leaf blades of the seagrass Cymodocea nodosa were investigated under laboratory conditions in exposure concentrations ranging from 0.5 to 40 mg L(-1). An initial rapid accumulation of cadmium was followed by a steady state. The Michaelis-Menten model adequately described metal accumulation; equilibrium concentration and uptake velocity tended to increase, whereas bioconcentration factor at equilibrium to decrease, as the exposure concentration increased. Cadmium depolymerized microtubules after 3-9 d of exposure, depending on trace metal concentration, indicating that microtubules could be used as an early biomarker of cadmium stress; cell death, occurring at later time than microtubule disturbance, was also observed. Microtubule depolymerization expressed as percentage of reduction of fluorescence intensity and cell mortality expressed as percentage of live cells increased with time. The lowest experimental tissue concentration associated with the onset of microtubule depolymerization and cell death (98.5-128.9µgg(-1)drywt, 0.5 mg L(-1) treatment, 7th and 9th d) was within the wide range of reported cadmium concentrations in leaves of seagrass species from various geographical areas. This lowest tissue concentration was exceeded up to the 3rd d at higher exposure concentrations, but toxic effects were generally detected at later time. The time periods required for the onset of depolymerization and for 10 and 50% of cells to die tended to decrease as the uptake velocity increased; in particular, significant negative correlations were found between these variables. These results suggest that toxicity appears to be a function of cadmium uptake rate rather than of the total tissue metal concentration. Hence, tissue residues should be interpreted in relation to the time frame of the exposure, while the estimation of metal uptake velocity could be utilized for predicting toxic effects. The data presented provide insight on the relationship between metal bioaccumulation and toxic effects in seagrasses and, overall, contribute to a better understanding of the impact of metals on aquatic organisms.

LC-ICP-MS analysis of arsenic compounds in dominant seaweeds from the Thermaikos Gulf (Northern Aegean Sea, Greece).

The content of total arsenic and arsenic compounds in the dominant seaweed species in the Thermaikos Gulf, Northern Aegean Sea was determined in samples collected in different seasons. Total arsenic was determined by acid digestion followed by ICP-MS. Arsenic speciation was analyzed by water extraction followed by LC-ICP-MS. Total arsenic concentrations in the seaweeds ranged from 1.39 to 55.0 mg kg(-1). Cystoseira species and Codium fragile showed the highest total As contents, while Ulva species (U. intestinalis, U. rigida,U. fasciata) had the lowest Arsenosugars, the most common arsenic species in seaweeds, were found in all samples, and glycerol-arsenosugar was the most common form; however, phosphate-arsenosugar and sulfate-arsenosugar were also present. Inorganic arsenic was measured in seven algae species and detected in another. Arsenate was the most abundant species in Cystoseira barbata (27.0 mg kg(-1)). Arsenobetaine was measured in only one sample. Methylated arsenic species were measured at very low concentrations. The information should contribute to further understanding the presence of arsenic compounds in dominant seaweeds from the Thermaikos Gulf.

Effects of cadmium, zinc and nitrogen status on non-protein thiols in the macroalgae Enteromorpha spp. from the Scheldt Estuary (SW Netherlands, Belgium) and Thermaikos Gulf (N Aegean Sea, Greece).

Enteromorpha prolifera (Scheldt Estuary) and E. linza (Thermaikos Gulf) were incubated at three salinities with 100 and 200microgL(-1)Cd and Zn. The objective was to measure effects of Cd, Zn and nitrogen (N) status on the pools of metal-binding non-protein thiols: glutathione and phytochelatins, (gamma-glutamyl-cysteinyl)(n)-glycine (PC). In E. linza, ammonium pools were higher, but amino acid pools, total N and protein contents were lower than in E. prolifera. Reduced glutathione (GSH) pools were positively correlated with free glutamate and protein contents. In E. linza GSH pools increased and the ratio of reduced to oxidized glutathione (GSH:(GSH+0.5GSSG)), an indicator of oxidative stress, decreased with Cd contents, indicating Cd-induced glutathione oxidation. Total glutathione pools (reduced plus oxidized) ranged from 16nmolSgdwt(-1) in controls (at 0.5micromolCdgdwt(-1)) to 179nmolSgdwt(-1) (at 1.9micromolCdgdwt(-1)) at the highest cadmium dosage. Cadmium stimulated PC synthesis in E. prolifera which suggests that in N-rich algae, glutathione pools were high enough for PC synthesis. In both species GSH and protein increased with Zn contents, whereas GSH:(GSH+0.5GSSG) decreased, which would indicate Zn-induced oxidative stress; in E. linza, at the highest salinity the glutathione redox ratio decreased from 0.61 (at 2.9micromolZngdwt(-1)) to 0.26 (at 4.9nmolSgdwt(-1)) (at 0.5molCdgdwt(-1)). PCs were not synthesized in response to Zn, which may have resulted in Zn-induced GSH oxidation. The presence of both oxidative effects (Cd, Zn) and detoxification (Cd) could be identified by observing the responses of glutathione and PC pools to metal stress.