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Abstract
Okadaic acid (OA) is a polyether fatty acid produced mainly by dinoflagellates causing
diarrhoeic shellfish poisoning (DSP) in humans. To resolve the controversies concerning
its genotoxicity in vitro, we have investigated eventual specific cellular response
in DOK, Caco-2 (Deltap53/p53(-)), HepG-2 and C6 glioma cells using the DNA damage
detection test (3d DNA repair test: nucleotide excision repair (NER) and base excision
repair (BER)), caspase-3-triggered apoptosis, neutral red (NR) and lactate dehydrogenase
(LDH) release tests. At low concentrations of OA (10nM), cytotoxicity measured by
LDH release is more marked in DOK cells, indicating necrotic cell death that occurs
only slightly in HepG-2 cells. At the same concentration, caspase-3 activation-dependent
apoptosis and DNA damage caused by OA were only detected in HepG-2 cells. This apoptosis
appears to be p53 gene dependent. Cell death occurs in the other cell types only by
necrosis at OA concentrations amended to cultures. Among the tested cell lines, HepG-2
cells are the most sensitive to OA (10-50nM) at 12 and 72h as revealed by the NR test.
The 3D test shows that only HepG-2 cells bear damaged DNA at tested concentrations.
It is concluded that the genotoxicity of OA is chiefly cell type dependent and concentration
dependent, giving sense to controversial genotoxicity data found in the literature.