Okadaic acid (0-100 nM; 24 hr or 48 hr) suppresses MNK-45, AGS, and Caco 2 cell growth [3]. Drp1 phosphorylation and mitochondrial fission in rat cortical neurons are increased by okadaic acid (10 nM; 8 hours) [4].

Models of Alzheimer's disease can be created with okadaic acid in animal models.

Cell proliferation assay [3]
Cell Types: AGS, MNK-45 and Caco 2 cell lines
Tested Concentrations: 0-100 nM
Incubation Duration: 24 hrs (hours) or 48 hrs (hours)
Experimental Results: Inhibition of proliferation of AGS, MNK-45, Caco 2 cells.

Absorption, Distribution and Excretion
The results in this study show... that this marine toxin is able to cross the transplacental barrier. Fetal tissue contains more okadaic acid than the liver or kidney: 5.60% compared to 1.90 and 2.55% respectively as measured by HPLC and fluorescent detection after derivatization with 9-Anthryldiazomethane (ADAM).
This study concerns the distribution of 3H-okadaic acid (OA) in organs and biological fluids of Swiss mice having received a single dose per os of OA (50 ug/kg). The determination of the intestinal tissues and contents 24 hr after administration demonstrates a slow elimination of OA. When the dose of OA was increased from 50-90 ug/kg, the concentrations of the toxin in the intestinal content and feces increased proportionally. A good correlation was found between an increase of OA in the intestinal tissue and the diarrhea in animals given 90 ug/kg orally. Moreover OA was present in liver and bile and in all organs including skin and also fluids. Altogether these results confirmed an enterohepatic circulation of OA as previously shown.
The influence of nutritional regime and water temperature on depuration rates of OA-group toxins in the wedge shell Donax trunculus was examined by exposing naturally contaminated specimens to three nutritional regimes (microalgae, commercial paste of microalgae, and starvation) for 14 days at 16 °C and 20 °C. Total OA was quantified in the whole soft tissues of the individuals collected in days 2, 4, 6, 8, 10, 12 and 14. Mortality, dry weight, condition index, gross biochemical composition and gametogenic stages were surveyed. Low variation of glycogen and carbohydrates during the experiments suggest that wedge shells were under non-dramatic stress conditions. Wedge shells fed with non-toxic diets showed similar depuration rates being 15 and 38% higher than in starvation, at 16 and 20 °C, respectively. Depuration rates under non-toxic diets at 20 °C were 71% higher than at 16 °C. These results highlight the influence of water temperature on the depuration rate of total OA accumulated by D. trunculus, even when the increase is of only 4 °C, as commonly observed in week time scales in the southern Portuguese coastal waters. These results open the possibility of a faster release of OA in harvested wedge shells translocated to depuration systems when under a slight increase of water temperature.
... acidic toxins, include okadaic acid (OA) and its derivatives named dinophysistoxins (DTXs). OA and its derivatives (DTX1, DTX2 and DTX3) are lipophilic and accumulate in the fatty tissue of shellfish. These compounds are potent phosphatase inhibitors and this property is linked to inflammation of the intestinal tract and diarrhea in humans.
Okadaic acid is known as a diarrheal shellfish poison. It is thought that there is no specific target organ for okadaic acid after it has been absorbed into the body. However, the details of its pharmacokinetics are still unknown. In this study, we demonstrated that okadaic acid was more toxic to the hepatocyte-specific uptake transporter OATP1B1- or OATP1B3-expressing cells than control vector-transfected cells. In addition, PP2A activity, which is a target molecule of okadaic acid, was more potently inhibited by okadaic acid in OATP1B1- or OATP1B3-expressing cells compared with control vector-transfected cells. The cytotoxicity of okadaic acid in OATP1B1- or OATP1B3-expressing cells was attenuated by known substrates of OATP1B1- and OATP1B3, but not in control vector-transfected cells. Furthermore, after uptake inhibition study using OATP1B3-expressing cells, Dixon plot showed that okadaic acid inhibited the uptake of hepatotoxin microcystin-LR, which is a substrate for OATP1B1 and OATP1B3, in a competitive manner. These results strongly suggested that okadaic acid is a substrate for OATP1B3 and probably for OATP1B1, and could be involved in unknown caused liver failure and liver cancer. Since okadaic acid possesses cytotoxicity and cell proliferative activity by virtue of its known phosphatase inhibition activity.

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Metabolism / Metabolites
The ingestion of seafood contaminated with the marine biotoxin okadaic acid (OA) can lead to diarrhetic shellfish poisoning with symptoms like nausea, vomiting and abdominal cramps. Both rat and the human hepatic cytochrome P450 monooxygenases (CYP) metabolize OA. However, liver cell toxicity of metabolized OA is mainly unclear. The aim of our study was to detect the cellular effects in HepG2 cells exposed to OA in the presence of recombinant CYP enzymes of both rat and human for the investigation of species differences. The results should be set in correlation with a CYP-specific metabolite pattern. Comparative metabolite profiles of OA after incubation in rat and human recombinant CYP enzymes were established by using LC-MS/MS technique. Results demonstrated that metabolism of OA to oxygenated metabolites correlates with detoxification which was mainly catalyzed by human CYP3A4 and CYP3A5. Detoxification by rat Cyp3a1 was lower compared to human CYP3A enzymes and activation of OA by Cyp3a2 was observed, coincident with minor overall conversion capacity of OA. By contrast human and rat CYP1A2 seem to activate OA into cytotoxic intermediates. In conclusion, different mechanisms of OA metabolism may occur in the liver. At low OA doses, the human liver is likely well protected against cytotoxic OA, but for high shellfish consumers a potential risk cannot be excluded.
Four metabolites of okadaic acid were generated by incubation with human recombinant cytochrome P450 3A4. The structures of two of the four metabolites have been determined by MS/MS experiments and 1D and 2D NMR methods using 94 and 133 ug of each metabolite. The structure of a third metabolite was determined by oxidation to a metabolite of known structure. Like okadaic acid, the metabolites are inhibitors of protein phosphatase PP2A. Although one of the metabolites does have an alpha,beta unsaturated carbonyl with the potential to form adducts with an active site cysteine, all of the metabolites are reversible inhibitors of PP2A.

Toxicity Summary
IDENTIFICATION AND USE: Okadaic acid (OA) is a solid. 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 used as a biochemical tool as tumor promoter and probe of cellular regulation. HUMAN STUDIES: 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. Induction of DNA adducts by OA was shown in human keratinocytes and human bronchial epithelial cells. ANIMAL STUDIES: In mice after 7 days of oral administration of 1 mg/kg/day OA induced diarrhea, body weight loss, reduced food consumption, and death. OA was a tumor promoter in two-stage experiments on mouse skin. OA can induce disorganization in cytoskeletal architecture and cell-cell contact, cause chromosome loss, apoptosis, DNA damage and inhibit phosphatases, suggesting its potential embryotoxicity. OA is used as a pharmacologically induced model of Alzheimer's disease in different species. In rats intrahippocampal bilateral microinjection of OA led to a spatial memory impairment. A significantly higher frequency of micronuclei was observed in hemocytes from the OA-exposed group of the mussel Perna perna compared to control. Induction of DNA adducts by OA was shown in Baby Hamster Kidney (BHK) cells, also the induction of DNA adducts in zebra fish embryos was demonstrated. ECOTOXICITY STUDIES: The blue mussel, Mytilus edulis and the pacific oyster, Crassostrea gigas were exposed in vivo to OA and impacts on DNA fragmentation were measured. A significant increase in DNA fragmentation was observed in the two cell types from both species relative to the controls. This increase was greater in the pacific oyster at the higher toxin concentration. In mussel Mytilus galloprovincialis mussel gill cells display higher sensitivity to early OA-mediated genotoxicity than hemocytes. In maize cells, OA caused the cell cycle arrest at preprophase, leading to seedling growth inhibition.

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Interactions
/The authors/ generated a neuroblastoma (SH-SY5Y) cell system in which cytoskeletal proteins are abnormally phosphorylated resulting in microtubule disruption due to the marked inhibition of protein phosphatase activities by okadaic acid (OA). OA-induced declines in cell viability and mitochondrial metabolic activity were remarkably prevented by melatonin. In addition, the hyperphosphorylation/accumulation of neurofilament-(NF-) H/M subunits and the disruption of microtubules, induced by OA, were significantly inhibited by melatonin.
In awake rats the microinjection into the hippocampus of okadaic acid, a potent inhibitor of protein phosphatases 1 and 2A, induces in about 20 min intense electroencephalographic and behavioral limbic-type seizures, which are suppressed by the systemic administration of the NMDA receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo-[a,d]cyclohepten-5,10-imine hydrogen maleate and by the intrahippocampal administration of 1-(5-isoquinolinesulfonyl)-2-methylpiperazine, an inhibitor of protein kinases.
Okadaic acid (OA) is a marine toxin, a tumor promoter and an inducer of apoptosis. It mainly inhibits protein-phosphatases, protein synthesis and enhances lipid peroxidation. Caco-2 cells were treated exclusively by OA (15 ng/mL) or cadmium (Cd) (0.625 and 5 ug/mL) for 24 hr, protein synthesis was inhibited (by 42 +/- 5%, 18 +/- 13%, and 90 +/- 4% respectively) while /malondialdehyde/ (MDA) production was 2,235 +/- 129, 1710 +/- 20, and 11,496 +/-1,624 pmol/mg protein respectively. In addition, each toxicant induced modified bases in DNA; increases in oxidised bases and methylated dC. The combination of OA and cadmium was more cytotoxic and caused more DNA base modifications; the ratio m(5)dC/(m(5)dC + dC) was increased from 3 +/- 0.15 to 9 +/- 0.15 and the ratio 8-(OH)-dG/10(5) dG also (from 36 +/- 2 to 76 +/- 6). The combination of OA and Cd also increased the level of MDA (1,6874 +/- 2,189 pmole/mg protein). The present results strongly suggest that DNA damage resulting from the oxidative stress induced by these two toxicants may significantly contribute to increasing their carcinogenicity via epigenetic processes.
25 nM okadaic acid promotes DNA fragmentation in B16 melanoma, increasing cell detachment as well as pigmentation, a characteristic of melanocytic cell differentiation. At lower levels, okadaic acid synergizes with UV exposure to increase DNA fragmentation.
For more Interactions (Complete) data for Okadaic acid (20 total), please visit the HSDB record page.

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Non-Human Toxicity Values
LD50 Mouse ip 185.6 ug/kg
LD50 Mouse ip 192 ug/kg

[1]. Kleppe R, et al. Cell Death Inducing Microbial Protein Phosphatase Inhibitors--Mechanisms of Action. Mar Drugs. 2015 Oct 22;13(10):6505-20.
[2]. Valdiglesias V, et al. Okadaic acid: more than a diarrheic toxin. Mar Drugs. 2013 Oct 31;11(11):4328-49.
[3]. del Campo M, et al. Okadaic acid toxin at sublethal dose produced cell proliferation in gastric and colon epithelial cell lines. Mar Drugs. 2013;11(12):4751-4760.
[4]. Cho MH, et al. Increased phosphorylation of dynamin-related protein 1 and mitochondrial fission in okadaic acid-treated neurons. Brain Res. 2012 May 15;1454:100-10.
[5]. Baker S, et al. A local insult of okadaic acid in wild-type mice induces tau phosphorylation and protein aggregation in anatomically distinct brain regions. Acta Neuropathol Commun. 2016;4:32.

Okadaic acid is a polycyclic ether that is produced by several species of dinoflagellates, and is known to accumulate in both marine sponges and shellfish. A polyketide, polyether derivative of a C38 fatty acid, it is one of the primary causes of diarrhetic shellfish poisoning (DSP). It is a potent inhibitor of specific protein phosphatases and is known to have a variety of negative effects on cells. It has a role as a marine metabolite, an EC 3.1.3.16 (phosphoprotein phosphatase) inhibitor and a calcium ionophore.
A specific inhibitor of phosphoserine/threonine protein phosphatase 1 and 2a. It is also a potent tumor promoter. (Thromb Res 1992;67(4):345-54 & Cancer Res 1993;53(2):239-41)
Okadaic acid has been reported in Prorocentrum belizeanum, Dinophysis acuta, and other organisms with data available.
A specific inhibitor of phosphoserine/threonine protein phosphatase 1 and 2a. It is also a potent tumor promoter. It is produced by DINOFLAGELLATES and causes diarrhetic SHELLFISH POISONING.

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Mechanism of Action
Microcystins, potent heptapeptide hepatotoxins produced by certain bloom-forming cyanobacteria, are strong protein phosphatase inhibitors. They covalently bind the serine/threonine protein phosphatases 1 and 2A (PP1 and PP2A), thereby influencing regulation of cellular protein phosphorylation. The paralytic shellfish poison, okadaic acid, is also a potent inhibitor of these PPs. Inhibition of PP1 and PP2A has a dualistic effect on cells exposed to okadaic acid or microcystin-LR, with both apoptosis and increased cellular proliferation being reported.

C44H68O13

805.0029

804.466

78111-17-8

Okadaic acid ammonium salt;175522-42-6;Okadaic acid sodium;209266-80-8

446512

Colorless to light yellow liquid

1.3±0.1 g/cm3

921.6±65.0 °C at 760 mmHg

164-166ºC

269.4±27.8 °C

0.0±0.6 mmHg at 25°C

1.585

4.21

5

13

10

57

1520

17

O1[C@@]2([H])[C@@]([H])(C(=C([H])[H])[C@]([H])([C@]([H])(C([H])([H])[C@]([H])(C([H])([H])[H])[C@@]3([H])[C@]([H])(C([H])([H])[H])C([H])([H])C([H])([H])[C@]4(C([H])([H])C([H])([H])C([H])([H])C([H])([H])O4)O3)O[H])O[C@]2([H])C([H])([H])C([H])([H])[C@]21C([H])([H])C([H])([H])C([H])(/C(/[H])=C(\[H])/C([H])(C([H])([H])[H])[C@]1([H])C([H])([H])C(C([H])([H])[H])=C([H])[C@]3([C@@]([H])(C([H])([H])C([H])([H])[C@@]([H])(C([H])([H])[C@@](C(=O)O[H])(C([H])([H])[H])O[H])O3)O[H])O1)O2)O[H]

QNDVLZJODHBUFM-WFXQOWMNSA-N

InChI=1S/C44H68O13/c1-25-21-34(55-44(23-25)35(46)12-11-31(54-44)24-41(6,50)40(48)49)26(2)9-10-30-14-18-43(53-30)19-15-33-39(57-43)36(47)29(5)38(52-33)32(45)22-28(4)37-27(3)13-17-42(56-37)16-7-8-20-51-42/h9-10,23,26-28,30-39,45-47,50H,5,7-8,11-22,24H2,1-4,6H3,(H,48,49)/b10-9+/t26-,27-,28+,30+,31+,32+,33-,34+,35-,36-,37+,38+,39-,41-,42+,43-,44-/m1/s1

(2R)-3-[(2S,6R,8S,11R)-2-[(E,2R)-4-[(2S,2'R,4R,4aS,6R,8aR)-4-hydroxy-2-[(1S,3S)-1-hydroxy-3-[(2S,3R,6S)-3-methyl-1,7-dioxaspiro[5.5]undecan-2-yl]butyl]-3-methylidenespiro[4a,7,8,8a-tetrahydro-4H-pyrano[3,2-b]pyran-6,5'-oxolane]-2'-yl]but-3-en-2-yl]-11-hydroxy-4-methyl-1,7-dioxaspiro[5.5]undec-4-en-8-yl]-2-hydroxy-2-methylpropanoic acid

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)