Okadaic Acid: More than a Diarrheic Toxin

Abstract

Okadaic acid (OA) is one of the most frequent and worldwide distributed marine toxins. It is easily accumulated by shellfish, mainly bivalve mollusks and fish, and, subsequently, can be consumed by humans causing alimentary intoxications. OA is the main representative diarrheic shellfish poisoning (DSP) toxin and its ingestion induces gastrointestinal symptoms, although it is not considered lethal. At the molecular level, OA is a specific inhibitor of several types of serine/threonine protein phosphatases and a tumor promoter in animal carcinogenesis experiments. In the last few decades, the potential toxic effects of OA, beyond its role as a DSP toxin, have been investigated in a number of studies. Alterations in DNA and cellular components, as well as effects on immune and nervous system, and even on embryonic development, have been increasingly reported. In this manuscript, results from all these studies are compiled and reviewed to clarify the role of this toxin not only as a DSP inductor but also as cause of alterations at the cellular and molecular levels, and to highlight the relevance of biomonitoring its effects on human health. Despite further investigations are required to elucidate OA mechanisms of action, toxicokinetics, and harmful effects, there are enough evidences illustrating its toxicity, not related to DSP induction, and, consequently, supporting a revision of the current regulation on OA levels in food.

Accumulation, transformation and breakdown of DSP toxins from the toxic dinoflagellate Dinophysis acuta in blue mussels, Mytilus edulis

“…Okadaic acid and DTX are powerful inhibitors of serine/threonine protein phosphatases and may in addition cause various chronic effects (Valdiglesias et al, 2013). Pectenotoxins disrupt actin in the cytoskeleton, and may cause cell cycle arrest and cell death (Spector et al, 1999;Ares et al, 2005;Anonymous, 2009).…”

“…Hence, Dinophysis is considered the main source of DSP toxins in marine shellfish. Acute effects of DSP toxins include diarrhea, nausea, vomiting and cramps, but chronic effects have also been reported, including carcinogenic effects and effects on the immune-and nervous systems and alterations in DNA and cellular components (Valdiglesias et al, 2013).…”

Primary productivity and phytoplankton dynamics in a subtropical estuary: a multiple timescale approach

“…Although the abundance of D. acuminata complex cells was relatively low in the present study (maximum 310 cells L -1 ), they may produce large levels of toxin, so cell densities as low as 100-200 cells L -1 may be sufficient to cause hazardous outbreaks in human consumers of contaminated bivalves (Yasumoto et al 1985). In addition, diarrheic shellfish toxins may also cause immunotoxicity, genotoxicity and cytotoxicity to many cell types (reviewed in Valdiglesias et al 2013), and even tumour formation upon chronic exposure (Fujiki and Suganuma 2009).…”

Quantification and profiling of lipophilic marine toxins in microalgae by UHPLC coupled to high-resolution orbitrap mass spectrometry

“…These unicellular organisms respond to favorable conditions in monospecific events to form dense concentrations of cells. Mollusks such as filter-feeding shellfish [15,16], gastropods [17], cephalopods [18] and fish [19] ingest phytoplankton from different sources and act as a vector to humans, causing different poisoning episodes. Phycotoxins do not only affect human health but are also responsible for massive die-offs of fish, marine mammals, birds and shellfish [20].…”