Comparative toxicological study of the novel protein phosphatase inhibitor 19-Epi-okadaic acid in primary cultures of rat cerebellar cells

• Published in: Toxicological sciences Vol. 132; no. 2; pp. 409 - 418
• Main Authors: Fernández-Sánchez, Maria-Teresa, Cabrera-García, David, Ferrero-Gutierrez, Amaia, Pérez-Gómez, Anabel, Cruz, Patricia G, Daranas, Antonio H, Fernández, José J, Norte, Manuel, Novelli, Antonello
• Format: Journal Article
• Language: English
• Published: United States 01.04.2013
• Subjects: Animals; Apoptosis - drug effects; Cells, Cultured; Cerebellum - cytology; Cerebellum - drug effects; Enzyme Activation; Gene Expression - drug effects; Okadaic Acid - analogs & derivatives; Okadaic Acid - toxicity; Phosphoprotein Phosphatases - antagonists & inhibitors; Protein Kinases - metabolism; Rats
• ISSN: 1096-6080; 1096-0929
• DOI: 10.1093/toxsci/kft006

Okadaic acid (OKA) and analogues are frequent contaminants of coastal waters and seafood. Structure analysis of the isolated OKA analogue 19-epi-OKA showed important conformation differences expected to result in lower protein phosphatase (PP) inhibitory potencies than OKA. However, 19-epi-OKA and OKA inhibitory activities versus PP2A were unexpectedly found to be virtually equipotent. To investigate the toxicological relevance of these findings, we tested the effects of 19-epi-OKA on cultured cerebellar cells and compared them with those of OKA and its isomer dinophysistoxin-2. 19-epi-OKA caused degeneration of neurites and neuronal death with much lower potency than its congeners. The concentration of 19-epi-OKA that reduced after 24h the maximum neuronal survival (EC5024) by 50% was ~300nM compared with ~2nM and ~8nM for OKA and dinophysistoxin-2, respectively. Exposure to 19-epi-OKA resulted also in less toxicity for cultured glial cells (EC5024,19-epi-OKA ~ 600nM; EC5024,OKA ~ 20nM). 19-epi-OKA induced apoptotic condensation and fragmentation of chromatin, activation of caspases, and activation of ERK1/2 MAP kinases, features previously reported for OKA and dinophysistoxin-2. Also, differential sensitivity to 19-epi-OKA was observed between neuronal and glial cells, a specific characteristic shared by OKA and dinophysistoxin-2 but not by other toxins. Our results are consistent with 19-epi-OKA being included among the group of toxins of OKA and derivatives and support the suitability of cellular bioassays for the detection of these compounds.