Characterization of two pituitary GH3 Cell sublines partially resistant to apoptosis induction by okadaic acid

Ritz, Vera; Marwitz, John; Richter, Elke; Ziemann, Christina; Quentin, Iris; Steinfelder, Hans Jürgen

doi:10.1016/s0006-2952(97)00397-3

Cited by 16 publications

(9 citation statements)

References 15 publications

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“…MeOk also depressed the metabolism but with a lesser potency, as the IC 50 for OA was more than sixfold lower than that for MeOk in Clone 9 cells. This potency difference is similar to that reported for MeOk-triggered apoptotic death in GH3 pituitary cells and its inhibition of secretion in rat mucosal mast cells, in each case being less potent than OA (Ritz et al, 1997;Ludowyke et al, 1998). On the other hand, we found that MeOk was more potent than OA in decreasing the metabolic activity of primary hepatocytes, which would not support the simple proposition that MeOk could be de-esterified in the cells and thus be converted into OA.…”

supporting

confidence: 64%

The methyl ester of okadaic acid is more potent than okadaic acid in disrupting the actin cytoskeleton and metabolism of primary cultured hepatocytes

Espiña

Louzao

Cagide

et al. 2010

British J Pharmacology

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The methyl ester of okadaic acid is more potent than okadaic acid in disrupting the actin cytoskeleton and metabolism of primary cultured hepatocytesb ph_512 337.. 344 Begoña Espiña Japan Food Research Laboratories, Tama, Tokyo 206-0025, JapanBackground and purpose: Okadaic acid (OA) and microcystins (MCs) are structurally different toxins with the same mechanism of action, inhibition of serine/threonine protein phosphatases (PPs). Methyl okadaate (MeOk), a methyl ester derivative of OA, was considered almost inactive due to its weak inhibition of PP1 and PP2A. Here, we have investigated the activity and potency of MeOk in hepatic cells in comparison with that of OA and MCs. Experimental approach: We tested the effects of MeOK, OA and microcystin-leucine and arginine (MC-LR) on the metabolic rate, the actin cytoskeleton and glucose uptake in a rat hepatocyte cell line (Clone 9) and in primary cultured rat hepatocytes. PP2A was assayed to compare OA and MeOk activity. Key results: MeOk disrupted the actin cytoskeleton and depressed the metabolic rate of both types of rat hepatocytes, being six-fold less potent than OA in Clone 9 cells but nearly six-fold more potent in primary cultured hepatocytes. However, unlike OA, MeOk did not change glucose uptake in these cells, suggesting a weak inhibition of PP2A, as confirmed in direct assays of PP2A activity. Conclusions and implications:Although MeOk was originally described as a weakly bioactive molecule, it clearly depressed the metabolic rate and disrupted the cytoskeleton in primary and immortalized rat hepatocytes. Furthermore, MeOk affected primary hepatocytes at much lower concentrations than those affecting immortalized cells. These effects were unrelated to PP2A inhibition. Our results suggest the risk to public health from MeOk in foodstuffs should be re-evaluated.British Journal of Pharmacology (2010) 159, 337-344; doi:10.1111/j.1476-5381.2009 published online 15 December 2009 Keywords: actin cytoskeleton; glucose uptake kinetics; metabolic rate; methyl okadaate; microcystin; okadaic acid; phycotoxins; protein phosphatase and rat hepatocytes Abbreviations: DSP, diarrheic shellfish poisoning; MC-LR, microcystin-leucine and arginine; MeOk, methyl okadaate; OA, okadaic acid; PP1, protein phosphatase-1; PP2A, protein phosphatase-2A IntroductionMany natural toxins such as okadaic acid (OA) potently inhibit the catalytic activity of serine/threonine protein phosphatases (PPs), of which PP1 and PP2A are the most abundant in cells. Both PPs have a wide spectrum of activity being able to dephosphorylate a large number of substrates in vitro (Fernandez et al., 2002). The list of PPs inhibitors includes a structurally diverse group of compounds: polyether fatty acid substances similar to okadaic acid (OA), cyclic peptides like microcystins (MCs) and nodularins, terpenoids such as cantharidin and thyrsiferyl 23-acetate and polyketides, such as tautomycin and calyculin A (Fernandez et al., 2002). OA is the best representative of the diarrheic shellfish poisoning ...

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supporting

confidence: 64%

The methyl ester of okadaic acid is more potent than okadaic acid in disrupting the actin cytoskeleton and metabolism of primary cultured hepatocytes

Espiña

Louzao

Cagide

et al. 2010

British J Pharmacology

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“…In another report, p38 MAP kinase is activated in GH3 cells during bromocryptine-induced apoptosis [26]. The apoptosis of GH3 cells was also observed following treatment with a dopaminergic neurotoxin, 1-methyl-4-phenylpyridinium ion [27], and with inhibitors of serine/threonine phosphatases 1 and 2A [28,29].…”

Section: Discussionmentioning

confidence: 91%

Effect of Therapeutic Doses of Ionising Radiation on the Somatomammotroph Pituitary Cell Line, GH3

Mareková

Vokurková

et al. 2003

Endocr J

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Abstract. Ionising radiation is used for the treatment of pituitary tumours as fractionated radiotherapy, where the total dose reaching the tumour area is in the range of 40-50 Gy, or during stereotactic radiosurgery, where the total dose reaching the tumour area during one session is in the range of 20-90 Gy. In this study, we investigated the effect of ionising radiation of 60 Co (dose rate of 3 Gy/min, similar to that used during gamma knife procedure) on the mode of cell death of the somatomammotroph pituitary cell line, GH3, an immortalized cell line derived from a rat pituitary adenoma. We found that the basic mechanism of cell death induced by irradiation of this GH3 cell line by g-rays was programmed cell death -apoptosis. Doses of 20-50 Gy were shown to inhibit proliferation in these cells. 24 hours after irradiation with a dose of 20 and 50 Gy, cells were shown to accumulate in the G 2 /M phase of cell cycle. This cell cycle arrest lasted for at least ten days. Apoptosis was detected 72 hours towards until the end of the study (10 days). However, a significant number of cells were still alive ten days following irradiation. We conclude that ionising radiation doses of 20 and 50 Gy induce pituitary GH3 cell apoptosis following cell cycle arrest in the G 2 /M phase.

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“…Moreover, the fact that nonphosphatase targets are not known for OA does not mean that they do not exist. In fact, OA effects apparently not related to PP2A ⁄ PP1 inhibition have been reported occasionally [14][15][16]39,40].…”

Section: Discussionmentioning

confidence: 99%

“…This toxin stimulated contraction in rat uterine smooth muscle similar to the contraction triggered by OA [14]. It has been also reported that methyl okadaate induces apoptotic death in GH3 pituitary cells [15] and inhibits secretion in rat mucosal mast cells [16], although in these cases less efficiently than OA.…”

mentioning

confidence: 91%

Induction of actin cytoskeleton rearrangement by methyl okadaate – comparison with okadaic acid

Vilariño¹,

Ares²,

Cagide³

et al. 2008

The FEBS Journal

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Methyl okadaate is a derivative of the lipophilic polyether okadaic acid (OA), a well-known inducer of apoptosis. OA inhibits Ser/Thr protein phosphatases (PPs), among them types 1 and 2A (PP1 and PP2A), whereas methyl okadaate lacks PP1/PP2A inhibitory activity in vitro. As progressive loss of neuronal cytoarchitecture is a major event that precedes neuronal death, in this work we studied comparatively the effects of both toxins on actin cytoskeleton organization in human neuroblastoma cells by filamentous actin (F-actin) labeling with the specific dye Oregon Green 514 Phalloidin. Neither methyl okadaate nor OA modified the amount of F-actin per cell. However, confocal microscopy imaging showed that methyl okadaate induced reorganization of actin cytoskeleton, loss of the typical flattened morphology and adoption of a round shape, and a reduction in the number of neurites, with a consequent loss of cell attachment. These effects were identical to those induced by OA, although methyl okadaate potency was approximately 10-fold lower. In order to investigate the role of membrane potential and cytosolic Ca2+ concentration in morphological changes induced by these toxins, the cells were stained with bis-(1,3-dibutylbarbituric acid)-trimethine oxonol and fura-2. No toxin effect was detected on membrane potential or calcium influx, indicating that these two signals are not responsible for cytoskeletal/morphological change induction. Methyl okadaate induced an increase of Ser/Thr phosphorylation of cellular proteins detected by western blot, showing similar phosphorylation profiles to OA. Our data suggest that methyl okadaate is an active compound that shares a pharmacological target with OA that may be a Ser/Thr phosphatase, probably different from PP1 and PP2A.

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Characterization of two pituitary GH3 Cell sublines partially resistant to apoptosis induction by okadaic acid

Cited by 16 publications

References 15 publications

The methyl ester of okadaic acid is more potent than okadaic acid in disrupting the actin cytoskeleton and metabolism of primary cultured hepatocytes

The methyl ester of okadaic acid is more potent than okadaic acid in disrupting the actin cytoskeleton and metabolism of primary cultured hepatocytes

Effect of Therapeutic Doses of Ionising Radiation on the Somatomammotroph Pituitary Cell Line, GH3

Induction of actin cytoskeleton rearrangement by methyl okadaate – comparison with okadaic acid

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