Cytoskeletal toxicity of pectenotoxins in hepatic cells

Background and purpose. Pectenotoxins are macrocyclic lactones found in dinoflagellates of the genus Dinophysis, which induce severe liver damage in mice after i.p. injection. Here, we have looked for the mechanism(s) underlying this hepatotoxicity. Experimental approach. Effects of pectenotoxin (PTX)-1, PTX-2, PTX-2 seco acid (PTX-2SA) and PTX-11 were measured in a hepatocyte cell line with cancer cell characteristics (Clone 9) and in primary cultures of rat hepatocytes. Cell morphology was assessed by confocal microscopy; F- and G-actin were selectively stained and cell viability measured by Alamar Blue fluorescence. Key results. Clone 9 cells and primary hepatocytes showed a marked depolymerization of F-actin with PTX-1, PTX-2 and PTX-11 (1–1000 nM) associated with an increase in G-actin level. However, morphology was only clearly altered in Clone 9 cells. PTX-2SA had no effect on the actin cytoskeleton. Despite the potent F-actin depolymerizing effect, PTX-1, PTX-2 or PTX-11 did not decrease the viability of Clone 9 cells after 24-h treatment. Only prolonged incubation (>48 h) with PTXs induced a fall in viability, and under these conditions, morphology of both Clone 9 and primary hepatocytes was drastically changed. Conclusions and implications. Although the actin cytoskeleton was clearly altered by PTX-1, PTX-2 and PTX-11 in the hepatocyte cell line and primary hepatocytes, morphological assessments indicated a higher sensitivity of the cancer-like cell line to these toxins. However, viability of both cell types was not altered. British Journal of Pharmacology (2008) 155, 934–944; doi:10.1038/bjp.2008.323; published online 8 September 2008