Effect of okadaic acid on cultured clam heart cells: involvement of MAPkinase pathways

Abstract

SummaryOkadaic acid (OA) is one of the main diarrhetic shellfish poisoning toxins and a potent inhibitor of protein phosphatases 1 and 2A. The downstream signal transduction pathways following the protein phosphatase inhibition are still unknown and the results of most of the previous studies are often conflicting. The aim of the present study was to evaluate the effects of OA on heart clam cells and to analyse its possible mechanisms of action by investigating the signal transduction pathways involved in OA cytotoxicity. We showed that OA at 1 µM after 24 h of treatment induces disorganization of the actin cytoskeleton, rounding and detachment of fibroblastic cells. Moreover, treatment of heart cells revealed a sequential activation of MAPK proteins depending on the OA concentration. We suggest that the duration of p38 and JNK activation is a critical factor in determining cell apoptosis in clam cardiomyocytes. In the opposite, ERK activation could be involved in cell survival. The cell death induced by OA is a MAPK modulated pathway, mediated by caspase 3-dependent mechanism. OA was found to induce no significant effect on spontaneous beating rate or inward L-type calcium current in clam cardiomyocytes, suggesting that PP1 was not inhibited even by the highest dose of OA.

Proteomic profile in Perna viridis after exposed to Prorocentrum lima, a dinoflagellate producing DSP toxins

“…However, according to the proteomics analysis, the P. lima exposure significantly changed expression of a great number of proteins, which are potentially involved in multiple physiological processes in mussel, including detoxification, cytoskeleton assembling, metabolism and signal transduction, suggesting the deleterious effects of DSP toxins on P. viridis. In fact, consistent with our results, a growing number of studies have found the genotoxic and cytotoxic effects of OA in bivalves in molecular level (Hanana et al, 2012;Prego-Faraldo et al, 2013).…”

“…Using a mussel cDNA microarray, Manfrin et al (2010) found that 9% of up-regulated transcripts in mussel induced by OA exposure were potentially involved in cytoskeleton organization. Hanana et al (2012) observed that the exposure of clam heart to OA at 1 mM for 24 h could induce disorganization of the actin cytoskeleton, rounding and detachment of the fibroblastic cells.…”

“…Combined with down-regulation of annexins and actin-related protein 2, 3, we speculated that P. lima and associated DSP toxins might induce cytoskeletonal disorganization of mussel gills. Actually, OA-induced changes in cytoskeletal architecture and cellecell contact have been extensively reported (Leira et al, 2001;Espiña and Rubiolo, 2008;Vale and Botana, 2008;Vilariño et al, 2008;Espiña et al, 2010;Wang et al, 2011;Hanana et al, 2012;Huang et al, 2013;Opsahl et al, 2013). Using a mussel cDNA microarray, Manfrin et al (2010) found that 9% of up-regulated transcripts in mussel induced by OA exposure were potentially involved in cytoskeleton organization.…”

“…OA is the best representative of the DSP toxins (Espiña et al, 2010). It is found that OA is a highly selective inhibitor of protein phosphatase types 1 (PP1) and 2A (PP2A), which can produce a marked increase in phosphorylation of several proteins, thus leading to deleterious effects on organisms (Talarmin et al, 2008;Hanana et al, 2012). Low concentrations of OA are reported to be cytotoxic in a vast range of cell culture systems.…”

A roadmap for hazard monitoring and risk assessment of marine biotoxins on the basis of chemical and biological test systems

“…In addition, protein phosphatase independent effects of DSP toxins are suggested that could possibly be employed to describe human symptomatology that is more likely to be present as a result of sub-acute toxic or at subchronic exposure levels: the latter could also be addressed via functional assays, e.g., cytotoxicity of OA in t lymphocytes (Martin-lopez et al, 2012), caspase-3 independent apoptosis (Hanana et al, 2012;Jayaraj et al, 2009), OA induced neuro-inflammation (Kamat et al, 2012), and granulation of tubulin in cytoplasma of hepatocytes (Rubiolo et al, 2012).…”