Polymethoxy-1-Alkenes Screening of Chlorella and Spirulina Food Supplements Coupled with In Vivo Toxicity Studies

Selected species of cyanobacteria and green algae have been reported to produce lipophilic polymethoxy-1-alkenes (PMAs) which were shown to exhibit in vivo teratogenicity. Considering that information on PMAs in Arthospira sp. (known commercially as Spirulina) and Chlorella sp. cultivated for food supplement production was essentially lacking, the present study screened Chlorella (n = 10) and Spirulina (n = 13) food supplements registered in the European Union. Mass spectrometry analysis of column fractionated extracts was performed. None of the four variants previously reported in some cyanobacteria and green algae, nor any potentially related structures were detected in the studied samples. Since the isolated lipophilic fractions contained various compounds, they were further screened for in vivo teratogenicity in Danio rerio embryo, and for the potential to induce oxidative stress and genotoxicity in the liver and neurotoxicity in the brain of adult zebrafish. None of the tested food supplements had detectable levels of PMAs or any potentially related structures. No teratogenicity was revealed except for spinal curvature induced by fractions obtained from two Chlorella products. Selected fractions revealed cytotoxicity as indicated by an increased level of reactive oxygen species, catalase activity, lipid peroxidation and increased frequency of DNA strand breaks in hepatic tissue. The majority (60%) of Chlorella fractions induced an increase in cholinesterase activity in zebrafish brain homogenate while exposure to 61.5% of Spirulina fractions was associated with its decrease. The present study confirms that Chlorella and Spirulina food supplements are free of teratogenic PMAs, although the observed in vivo toxicities raise questions regarding the quality of selected products

Effects of intermittent hypoxia on the cell survival and inflammatory responses in the intertidal marine bivalves Mytilus edulis and Crassostrea gigas

Hypoxia is a major stressor in estuarine and coastal habitats leading to adverse effects in aquatic organisms. Estuarine bivalves such as the blue mussels Mytilus edulis and the Pacific oysters Crassostrea gigas can survive periodic oxygen deficiency but the molecular mechanisms that underlie cellular injury during hypoxia-reoxygenation are not well understood. We examined the molecular markers of autophagy, apoptosis and inflammation during the short-term (1 day) and long-term (6 days) hypoxia and post-hypoxic recovery (1 h) in the mussels and oysters by measuring the lysosomal membrane stability, activity of a key autophagic enzyme (cathepsin D) and mRNA expression of the genes involved in the cellular survival and inflammation, including caspases 2, 3 and 8, Bcl-2, BAX, TGF-β-activated kinase 1 (TAK1), nuclear factor kappa B-1 (NF-κB), and NF-κB activating kinases IKKα and TBK1. C gigas exhibited higher hypoxia tolerance as well as blunted or delayed inflammatory and apoptotic response to hypoxia and reoxygenation shown by the later onset and/or the lack of transcriptional activation of caspases, BAX and an inflammatory effector NF-κB compared with M.edulis. Long-term hypoxia resulted in upregulation of Bcl-2 in the oysters and the mussels implying activation of the anti-apoptotic mechanisms. Our findings indicate the potential importance of the cell survival pathways in hypoxia tolerance of marine bivalves and demonstrate the utility of the molecular markers of apoptosis and autophagy for assessment of the sublethal hypoxic stress in bivalve populations

Flow cytometry as a valuable tool to study cyanobacteria:A mini-review

Flow cytometry (FCM) is routinely used in medical and veterinary diagnostics although it is also widely applied in environmental studies, including phytoplankton investigations. Cyanobacteria are wide-spread photosynthetic microorganisms that attract attention due to their ecology and potential toxicity. Therefore, novel research tools are being applied in their investigation. This paper characterizes FCM as a technique that enables photopigments (chlorophylls and phycocyanin) expressed by cyanobacteria to be excited and their emission to be subsequently detected. This feature not only allows cells to be counted in a rapid manner but also enables a wide range of potential applications in ecological and biochemical studies. The main advantages of FCM, such as rapid, automatic and precise measurements requiring small sample volumes, are also discussed in this paper along with challenges including analyses of filamentous cyanobacteria and signal overlapping. It is expected that FCM will continue to be used in some fields of cyanobacterial studies

Mitochondrial complex I in hypoxia-tolerant marine bivalves exposed to extreme hypoxia

Mitochondrial Complex I in hypoxia-tolerant marine bivalves, namely, the blue mussel Mytilus edulis, the Arctic quahog Arctica islandica and the Pacific oyster Crassostrea gigas, exposing them for one or six days to extreme hypoxia (<0.1% O2) followed by one hour of reoxygenation