A high proportion of Baltic Sea benthic cyanobacterial isolates contain apoptogens able to induce rapid death of isolated rat hepatocytes.
To assess the potential hepatotoxicity of benthic cyanobacteria, we isolated 41 strains from the Baltic Sea. The bacteria were differentially extracted with solvents of decreasing polarity. The extracts were tested for ability to induce death of primary rat hepatocytes in suspension culture. Mainly morphological criteria were used to discriminate between cell death with apoptotic features (shrinkage, chromatin hypercondensation, budding) or necrotic features (swelling, loss of plasma membrane integrity). The 24 isolates containing hepatotoxic compounds were of the genus Anabaena. The non-toxic isolates were mainly Nostoc and Calothrix. The toxicity was not due to the known hepatotoxic cyanobacterial protein phosphatase inhibitors microcystin or nodularin, as demonstrated by lacking competition with microcystin for PP2A binding. Apoptotic cell death was rapid, being evident from 10 to 60 min after the addition of extract. Sometimes the initial apoptosis was followed by secondary necrosis. Three cyanobacterial extracts produced apoptosis with unusual cell morphology including actin rearrangements. It will be of interest to know if they contain substance(s) acting through novel death pathways. We conclude that benthic Anabaena cyanobacteria represent a rich source of apoptogenic toxins, presumably directed against competitors or predators in the aquatic environment, but obviously able also to induce cell death in mammalian parenchymal liver cells.
Herfindal
Lars
L
Section for Anatomy and Cell Biology, Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009 Bergen, Norway.
Oftedal
Linn
L
Selheim
Frode
F
Wahlsten
Matti
M
Sivonen
Kaarina
K
Døskeland
Stein Ove
SO
D000199:Actins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001427:Bacterial Toxins / Q000302:isolation & purification / Q000633:toxicity*; D001454:Baltic States; D002478:Cells, Cultured; D000458:Cyanobacteria / Q000737:chemistry*; D000087522:Cyanobacteria Toxins; D004791:Enzyme Inhibitors / Q000494:pharmacology; D022781:Hepatocytes / Q000187:drug effects* / Q000473:pathology; D008387:Marine Toxins / Q000302:isolation & purification / Q000633:toxicity*; D052998:Microcystins; D010456:Peptides, Cyclic / Q000037:antagonists & inhibitors / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D011485:Protein Binding; D051381:Rats; D012623:Seawater; D013997:Time Factors
D000199:Actins; D001427:Bacterial Toxins; D000087522:Cyanobacteria Toxins; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D052998:Microcystins; D010456:Peptides, Cyclic; C063998:nodularin; C078588:microcystin; D010749:Phosphoprotein Phosphatases