Actin cytoskeleton of rabbit intestinal cells is a target for potent marine phycotoxins
1 Departamento de Farmacología, Facultad de Veterinaria de Lugo,
Universidad de Santiago de Compostela, 27002 Lugo, Spain
2 Departamento de Fisiología Animal, Facultad de Veterinaria de Lugo,
Universidad de Santiago de Compostela, 27002 Lugo, Spain
3 Japan Food Research Laboratories, Tama, Tokyo 206-0025, Japan
* Author for correspondence (e-mail: Luis.Botana{at}lugo.usc.es)
Accepted 22 September 2005
![]() |
Summary |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key words: brevetoxin, ciguatoxin, cytoskeleton, intestinal cell, maitotoxin, ostreocin-D, palytoxin, pectenotoxin-6, rabbit, yessotoxin
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Ciguatoxins (CTXs) and maitotoxins (MTXs) are involved in CFP
(Yasumoto et al., 1976), an
important human intoxication that produces neurological symptoms and also
gastrointestinal disorders
(Guzmán-Pérez and Park,
2000
). It is known that CTXs activate sodium channels and modify
the electrical properties of excitable cells
(Molgó et al., 1992
),
and MTXs are potent activators of Ca2+ influx in a wide variety of
cells (Gusovsky and Daly,
1990
; Escobar et al.,
1998
); however, their ability to injure intestinal cells is still
unknown. In the same way, palytoxin, one of the most potent marine
neurotoxins, produces an intoxication named clupeotoxism, whose symptomatology
is similar to ciguatera although more serious and with a high fatality rate
(Onuma et al., 2000). Recent works suggests that this toxin shows specificity
for Na+/K+ pumps in Xenopus oocyte
(Wang and Horisberger, 1997
;
Guennoun and Horisberger,
2000
), but there are no data on its biological activity in a
cellular intestinal model. By contrast, ostreocin-D is a structural analogue
of palytoxin, whose mechanism of action and toxicological effects have not yet
been elucidated, although seafood contamination with ostreocin-D is becoming
an increasing problem in some Mediterranean countries.
Ingestion of bivalve mollusks contaminated with brevetoxins (Pbtxs) causes
NSP (similar to CFP, although less severe), which is characterized by both
gastrointestinal distress and nervous alterations that begin at the same time
(Gessner, 2000). NSP is
another family of toxic marine compounds, structurally and functionally
related CTXs, which elicit their effects by activating voltage-gated sodium
channels (Wang and Wang,
2003
).
Since all of these marine toxins cause gastrointestinal disturbances or have been originally implicated in them, it is interesting to know their capacity to affect intestinal cells. Considering that (i) the cytoskeleton is involved in practically all aspects of cell behavior, and (ii) this structure is highly complex in intestinal cells, we studied the way these toxins modify the enterocyte cytoskeleton. Here we present for the first time the effect of PTX-6, YTX, CTX-3C, MTX, palytoxin, ostreocin-D, Pbtx-3 and Pbtx-9 on freshly isolated rabbit enterocytes at the level of the filamentous actin (F-actin) cytoskeleton.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The cells were isolated in modified Hanks' salt solution
(Louzao et al., 2003). For
maintenance and incubation of cells, we utilized the following salt solution
(in mmol l1): 138 NaCl, 10 Hepes, 5 D-glucose, 5
KCl, 1.5 CaCl2, 1 MgCl2, and 1 mg ml1
bovine serum albumin (BSA). Finally, each medium was adjusted to pH 7.4.
Isolation of rabbit enterocytes
One adult New Zealand White rabbit weighing 1.52.5 kg was used for
each assay. Enterocytes were isolated from duodenumjejunum by a
modification (Louzao et al.,
2003) of the method described by Brown and Sepulveda
(1985
). A section of
duodenumjejunum 2530 cm long was removed from the rabbit and
washed in ice-cold phosphate-buffered saline (PBS) containing 0.5 mmol
l1 dithiothreitol to disaggregate mucus. Then, the segment
was filled with modified Hanks' solution containing hyaluronidase (1.5 mg
ml1) and incubated at 37°C in a shaking water bath for
20 min. After this time the intestinal loop was emptied and refilled with
modified Hanks' salt solution without hyaluronidase for a second (2 min) and a
third incubation in the same conditions (5 min). The luminal content with
isolated cells was filtered through a 200 µm mesh nylon sieve before being
washed twice by centrifugation (1000 r.p.m. for 5 min, 4°C) and
resuspended with modified Hanks' salt solution. Finally, after second
centrifugation the pellet was resuspended in the salt solution for
maintenance. Viability of cells was assessed immediately after isolation
(>70%) in terms of cell membrane integrity (Trypan Blue exclusion
test).
F-actin assays
We evaluated the effect of phycotoxins on F-actin levels vs
controls by incubating 2x105 cells in each assay with PTX-6
(1 µmol l1), YTX (1 µmol l1), CTX-3C
(4 nmol l1), MTX (5 nmol l1), palytoxin
(75 nmol l1), ostreocin-D (75 nmol l1),
Pbtx-3 (250 nmol l1) or Pbtx-9 (20 nmol
l1) under agitation (120 r.p.m.) for 4 h. These incubations
when appropriate were also performed in a Ca2+-free medium.
Fluorescent labeling of actin
After incubation with toxins in the medium with or without Ca2+
was complete, cells were attached on a slide with 0.01%
poly-L-lysine for 10 min and fixed for 10 min in 3.7% formaldehyde
solution. After that cells were washed twice with PBS, then permeabilized with
0.1% Triton X-100 for 5 min. Following a brief wash in PBS, fixed cells were
incubated with 1% BSA for 30 min to reduce non-specific staining. F-actin was
specifically labeled with Oregon Green 514® phalloidin by incubating the
dye for 20 min in the dark at room temperature. This dye stains F-actin and is
a convenient probe for labeling, identifying and quantization F-actin in cell
experiments. Finally, the slides were washed twice with PBS. A coverslip was
mounted on the slide with 10 µl of a 1:1 v/v solution of PBS and glycerol
and the edges of the coverslip sealed with nail polish. Slides prepared in
this manner and stored at 4°C in the dark retained actin staining for at
least 23 days. Quantitative analysis of F-actin levels was performed
using the laser-scanning cytometer (LSC) technique.
Quantitative detection of F-actin by laser-scanning cytometry
The laser-scanning cytometer that we used (CompuCyte, Cambridge, MA, USA)
can be described as a cytofluorometer, with attributes of both flow and image
cytometry. It allows detection and quantification of the presence of cellular
markers such as Oregon Green 514® phalloidin from samples on microscope
slides. Cells mounted on slides, as described above, were excited with an
Argon ion laser (at 488 nm). To obtain a great number of single contoured
cells without losing fluorescence information the threshold level was
optimized. The parameters measured for each cell contoured were area and
maximum pixels. Between 2000 and 3000 cells were measured per slide. Note that
cells labeled with Oregon Green 514® phalloidin decrease their
fluorescence when F-actin levels fall. Scattergrams and histograms shown in
the figures display representative experiments of the effect of the toxins
obtained using LSC. Each point in a scattergram plot is an enterocyte stained
with the dye. It is important to specify that we only analyzed the
fluorescence of individual enterocytes that are found inside the region marked
in the scattergrams; points outside that region are cellular aggregates.
Confocal microscopy
Slides quantified by LSC were also viewed in a confocal microscope to
detect any change in reorganization of microfilaments or in the shape of cells
induced by the toxins. The confocal system used in this study was an MRC-1024
confocal imaging system (Bio-Rad, Hemel Hempsted, Herts, UK), a Nikon Eclipse
TE300 inverted microscope equipped with a Nikon oil objective (magnification
x60, numerical aperture 1.4), and light source was a 100 mW argon-ion
laser.
Data analysis
Results are expressed as percentage of relative fluorescence of cells
treated with toxins in relation to controls. Values are means ±
S.E.M. (standard error of the mean), N3.
|
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Measurement of fluorescence intensity was investigated in a large number of cells (between 2000 and 3000 cells per slide) by using LSC. Histograms for maximum green pixels, obtained from regions in the scattergrams, show comparative profiles between cells incubated with and without toxin. Finally, we present the results (expressed as percentage of Oregon Green 514® phalloidin relative fluorescence with respect to control cells) obtained with all the toxins studied, and show the effect of Ca2+ on toxin-induced F-actin depolymerization.
The first toxins studied were PTX-6 and YTX, which have a different effect on F-actin cytoskeleton in freshly isolated intestinal cells (Fig. 1). PTX-6 (1 µmol l1) induced a decline in fluorescent phalloidin of up to 45±6.6% (Fig. 2), which indicated that PTX-6 injured the F-actin cytoskeleton. On the other hand, confocal microscopy revealed no alteration in the morphological pattern of cells treated with PTX-6, although the images reveal a decrease in the microfilament network previously quantified with LSC (Fig. 3). When the effect of 1 µmol l1 YTX was analyzed (Fig. 1), we found no significant differences on the quantity of F-actin between controls and treated cells (a decrease in fluorescence of 5±7.9% is observed in Fig. 2). In addition, changes in F-actin reorganization or in the cellular shape were not observed (data not shown).
|
|
|
|
|
|
Alterations in intracellular Ca2+ concentration can, however,
induce changes in cytoskeletal elements including microfilaments
(Fifkova, 1985;
Yin, 1987
;
Furukawa and Mattson, 1995
).
Thus it would be interesting to determine whether Ca2+ flux plays
any role in the reduction of F-actin levels caused by the toxins whose effect
involves Ca2+ movement, such as MTX and palytoxins. Enterocytes
were therefore incubated for 4 h with the toxins under the same experimental
conditions as before, but in a Ca2+ free solution. In these assays
the effects of all the toxins were quite different: LSC revealed that the
change in F-actin level induced by MTX, palytoxin and ostreocin-D was lower in
a Ca2+-free solution than in the presence of Ca2+
(Fig. 8). In fact,
quantification of the fluorescence in treated cells vs controls
showed a 10±4.9%, 26±6.3% and 25±3.2% decrease in F-actin
in cells incubated with MTX, palytoxin and ostreocin-D, respectively
(Fig. 9). Likewise, confocal
images revealed a small loss of fluorescence (very small in the case of MTX)
without any apparent modifications in F-actin distribution or in the shape of
cells exposed to toxins (data not shown).
|
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
PTXs and YTXs are marine toxins originally associated with DSP. However, it
is unclear if their toxicity causes alterations in physiology or morphology of
intestinal cells. Data obtained with both toxins were rather different. In our
hands, PTX-6 produced a large decrease in F-actin microfilaments in
enterocytes. Similar results were reported for PTX-2 in A10 rat vascular
smooth muscle cell line, where PTX-2 disrupted F-actin and sequestered actin
by forming a 1:4 complex with monomeric actin
(Hori et al., 1999). During
recent years, a number of novel and stereochemically complex macrolides that
interact with the actin cytoskeleton and sequester monomeric actin have been
isolated from different marine sources. Mycalolide B and aplyronine A are
actin depolymerizing macrolides that form 1:1 complexes with G-actin and also
may sever F-actin (Saito et al.,
1994
,
1996
;
Saito and Karaki, 1996
).
Likewise, swinholide A and bistheonellide A are unusual dimeric macrolides
that affect actin filament dynamics and bind two actin monomers
(Bubb et al., 1995
;
Saito et al., 1998
).
Interestingly, PTX-6 also belongs to one family of toxins with a macrolide
structure, and PTX-2 is the compound from which it derives
(Suzuki et al., 1998
).
Therefore, given that PTX-2 and PTX-6 are closely related it is probable that
their mechanisms for damaging F-actin cytoskeleton are similar and not related
to Ca2+ flux. This last possibility would be supported by the fact
that in other cellular models, PTX-6 do not modify cytosolic Ca2+
content (Leira et al., 2002
).
In any case, our data identify the enterocyte cytoskeleton as a target for
PTX-6. In contrast to PTX-6, our data show that YTX does not interfere with
the polymerized actin level in freshly isolated enterocytes. Recently, our
group suggested that this phycotoxin acts on cellular phosphodiesterases that
regulate adenosine 3', 5'-cyclic monophosphate (cAMP), a second
messenger implicated in intracellular signaling
(Alfonso et al., 2003
). In this
case, our study on cytoskeleton may indicate that the microfilament network in
rabbit intestinal cells is not related to the cAMP pathway.
The clinical syndrome produced by CTXs includes gastrointestinal and
neurological symptoms (Connell and
Colquhoun, 2003). CTX-3C and MTX are marine toxins associated with
CFP, but their mechanism of action is different and also their effect on the
cytoskeleton. Our results indicated that MTX causes an important decrease in
actin filaments. This toxin induces a Ca2+ influx in many cellular
models by activating voltage-gated Ca2+ channels
(Takahashi et al., 1982
;
Xi et al., 1992
) and
Ca2+-permeable non-selective cation channels
(Daly et al., 1995
;
Bielfeld-Ackermann et al.,
1998
). It is known that Ca2+ is a second messenger able
to induce diverse cellular responses, among them cytoskeleton modifications
(Yin and Stossel, 1979
;
Puius et al., 1998
). In this
sense, we found that the action of MTX on actin cytoskeleton is highly related
to Ca2+ influx, which would be consistent with recent reports
suggesting that the toxic effects of MTX are secondary to Ca2+
entry (Gusovsky and Daly,
1990
; Escobar et al.,
1998
; De la Rosa et al.,
2001
). CTX-3C did not otherwise modify actin polymerization or
enterocyte structure. In agreement with this lack of any structural effect,
data obtained with ileum tissues showed that CTXs stimulated intestinal fluid
secretion without any accompanying tissue damage
(Fasano et al., 1991
). CTX-3C
has greater toxic potency but similar biological activity and effect on
cytoskeleton to Pbtx-3 and Pbtx-9 (Lombet
et al., 1987
; Van Dolah, 2000). We found that Pbtx-3 and Pbtx-9
have no effect on the actin cytoskeleton in enterocytes. CTXs and Pbtxs bind
specifically to site 5 of sodium channel, resulting in persistent activation
or prolonged channel opening (Poli et al.,
1986
; Lombet et al.,
1987
; Baden, 1989
;
Lewis et al., 1991
). We
previously found that nanomolar concentrations of CTX-3C, Pbtx-3 and Pbtx-9
change the membrane potential of excitable cell membranes
(Louzao et al., 2004
).
Voltage-gated Na+ channels do not express in non-excitable cells
(Parekh, 1998
), as would occur
in intestinal cells; however, recent studies revealed that Pbtxs could have a
secondary effect in addition to voltage-gated Na+ channel
activation. Related to this, several studies showed that Pbtx-2 induced a
Na+ entry in tissues in which voltage-gated Na+ channels
are absent or scarce (Rodriguez et al.,
1994
), and this phenomenon was also observed in artificial
membranes (Matile and Nakanishi,
1996
). Taken together, our data with CTX-3C, Pbtx-3 and Pbtx-9
suggest that actin cytoskeleton dynamics is not related to sodium movement in
isolated intestinal cells.
The pharmacological target of palytoxin in excitable cells seems to be the
Na+/K+ pump, which is converted in an open channel that
permits K+ efflux and influx of monovalent cations
(Ishida et al., 1983;
Habermann, 1989
). Studies
analyzing the palytoxin-induced ionic fluxes in erythrocytes suggested that
the palytoxin-induced channel in non-excitable cells is similar to one in
excitable cells (Habermann,
1989
; Tosteson et al.,
1991
; Frelin and Van
Renterghem, 1995
). It is known that changes in the intracellular
concentration of ions caused by palytoxin implicate Ca2+. In fact,
previous investigations revealed that the palytoxin effect on cytosolic
Ca2+ is dependent on extracellular Ca2+
(Frelin and Van Renterghem,
1995
; Amano et al.,
1997
; Ishii et al.,
1997
; Satoh et al.,
2003
). Within this context, and taking into account that palytoxin
administered intraperitoneally caused intestinal injuries in mice
(Ito et al., 1996
), it would
be interesting to see the effect of palytoxin and ostreocin-D on the
microfilament network of intestinal cells and also to study whether
Ca2+ movements are playing any role in this effect. Enterocytes
incubated with palytoxin in a Ca2+-containing medium reduced the
polymerized actin level 52±4.4% compared to the control. Enterocytes
treated with ostreocin-D showed a decrease of 47±6.8%. However, when
extracellular Ca2+ was omitted, this effect was reduced by almost
half. In our case, it is clear that the activity of palytoxin on actin
cytoskeleton of intestinal cells is partially modulated by a signaling pathway
involving Ca2+ influx. Likewise, the data obtained with ostreocin-D
suggest an action mechanism targeting intestinal cells, similar to that of the
parent compound, palytoxin. It is important to note that these are the first
cellular data concerning the biological activity of ostreocin-D.
Alterations in the actin level are not always related to disorders in the
morphological pattern of cells and vice versa. There is evidence that
treatment of HeLa cells with adenovirus infection or trypsin/EDTA, which lead
to modifications in cell shape (rounding up) and motility, are not coupled to
an alteration in the actin content
(Blikstad and Carlsson, 1982).
By contrast, in mesangial cells 1 µmol l1 of cytochalasin
B (a well known actin-depolymerizing toxin) causes a marked loss of F-actin,
but has no effect on cell morphology
(Patel et al., 2003
). In
agreement with this, we found that the morphology of intestinal cells did not
seem to be affected by any of the toxins that induced a notable effect on
actin levels. Even though in many cases variations in morphology have been
associated with new distributions in microfilaments
(Maier et al., 1995
;
Fiorentini et al., 1996
), this
was not observed in our study.
In conclusion, our results indicate that toxins whose action mechanism is
closely associated with the cytoskeleton, such as PTX-6, or to Ca2+
movement, as in the case of MTX, palytoxin and ostreocin-D, are potent natural
actin-depolymerizing compounds in rabbit isolated intestinal cells although
they produce no change in cell morphology. It is known that gastrointestinal
toxicity is associated with very different mechanisms of action of the toxic
agent, such as blocking protein synthesis, stimulating guanylate cyclase or
modifying the cytoskeleton dynamics
(Fasano, 2002). Clearly
further studies are necessary, but our approach is a starting point for
elucidating the links between cellular targets and gastrointestinal toxicity
of these four toxins.
List of abbreviations
![]() |
Acknowledgments |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Alfonso, A., De la Rosa, L., Vieytes, M., Yasumoto, T. and Botana, L. (2003). Yessotoxin, a novel phycotoxin, activates phosphodiesterase activity. Effect of yessotoxin on cAMP levels in human lymphocytes. Biochem. Pharmacol. 65,193 -208.[CrossRef][Medline]
Amano, K., Sato, K., Hori, M., Ozaki, H. and Karaki, H. (1997). Palytoxin-induced increase in endothelial Ca2+ concentration in the rabbit aortic valve. Naunyn Schmiedebergs Arch. Pharmacol. 355,751 -758.[Medline]
Baden, D. G. (1989). Brevetoxins: unique
polyether dinoflagellate toxins. FASEB J.
3,1807
-1817.
Bielfeld-Ackermann, A., Range, C. and Korbmacher, C. (1998). Maitotoxin (MTX) activates a non-selective cation channel in Xenopus laevis oocytes. Pflugers Arch. 436,329 -337.[CrossRef][Medline]
Blikstad, I. and Carlsson, L. (1982). On the
dynamics of the microfilament system in HeLa cells. J. Cell
Biol. 93,122
-128.
Brown, P. D. and Sepulveda, F. V. (1985). A rabbit jejunal isolated enterocyte preparation suitable for transport studies. J. Physiol. 863,257 -270.
Bubb, M. R., Spector, I., Bershadsky, A. D. and Korn, E. D.
(1995). Swinholide A is a microfilament disrupting marine toxin
that stabilizes actin dimers and severs actin filaments. J. Biol.
Chem. 270,3463
-3466.
Connell, J. E. and Colquhoun, D. (2003). Risk of ciguatera fish poisoning: impact on recommendations to eat more fish. Asia Pac. J. Clin. Nutr. 12, S67.
Daly, J. W., Lueders, J., Padgett, W. L., Shin, Y. and Gusovsky, F. (1995). Maitotoxin-elicited calcium influx in cultured cells. Effect of calcium-channel blockers. Biochem. Pharmacol. 50,1187 -1197.[CrossRef][Medline]
De la Rosa, L., Alfonso, A., Vilarino, N., Vieytes, M., Yasumoto, T. and Botana, L. (2001). Maitotoxin-induced calcium entry in human lymphocytes: modulation by yessotoxin, Ca(2+) channel blockers and kinases. Cell Signal. 13,711 -716.[CrossRef][Medline]
Escobar, L. I., Salvador, C., Martinez, M. and Vaca, L. (1998). Maitotoxin, a cationic channel activator. Neurobiology 6,59 -74.[Medline]
Fasano, A. (2002). Toxins and the gut: role in human disease. Gut 50,1119 -1114.
Fasano, A., Hokama, Y., Russell, R. and Morris, J. G., Jr (1991). Diarrhoea in ciguatera fish poisoning: preliminary evaluation of pathophysiological mechanisms. Gastroenterology 100,471 -476.[Medline]
Fifkova, E. (1985). Actin in the nervous system. Brain Res. 356,187 -215.[Medline]
Fiorentini, C., Matarrese, P., Fattorossi, A. and Donelli, G. (1996). Okadaic acid induces changes in the organization of F-actin in intestinal cells. Toxicon 34,937 -945.[CrossRef][Medline]
Frelin, C. and Van Renterghem, C. (1995). Palytoxin. Recent electrophysiological and pharmacological evidence for several mechanisms of action. Gen. Pharmacol. 26, 33-37.[CrossRef][Medline]
Freudenthal, A. R. and Jijina, J. L. (1985). Shellfish poisoning episodes involving or coincidental with dinoflagellates. In Toxic Dinoflagellates (ed. D. M. Anderson, A. W. White and D. G. Baden), pp. 461-466. New York: Elsevier.
Freudenthal, A. R. and Jijina, J. L. (1988). Potential hazards of Dinophysis to consumers and shellfisheries. J. Shellfish Res. 7,695 -701.
Furukawa, K. and Mattson, M. P. (1995). Cytochalasins protect hippocampal neurons against amyloid beta-peptide toxicity: evidence that actin depolymerization suppresses Ca2+ influx. J. Neurochem. 65,1061 -1068.[Medline]
Gessner, B. D. (2000). Neurotoxic toxins. In Seafood and Freshwater Toxins. Pharmacology, Physiology and Detection (ed. L. M. Botana), pp. 65-90. New York: Marcel Dekker Inc.
Guennoun, S. and Horisberger, J. D. (2000). Structure of the 5th transmembrane segment of the Na,K-ATPase alpha subunit: a cysteine-scanning mutagenesis study. FEBS Lett. 482,144 -148.[CrossRef][Medline]
Gusovsky, F. and Daly, J. W. (1990). Maitotoxin: a unique pharmacological tool for research on calcium-dependent mechanisms. Biochem. Pharmacol. 39,1633 -1639.[CrossRef][Medline]
Guzmán-Pérez, S. E. and Park, D. L. (2000). Ciguatera toxins: chemistry and detection. In Seafood and Freshwater Toxins: Pharmacology, Physiology and Detection (ed. L. M. Botana), pp.401 -418. New York: Marcel Dekker Inc.
Habermann, E. (1989). Palytoxin acts through Na+,K+-ATPase. Toxicon 27,1171 -1187.[CrossRef][Medline]
Holleran, E. A. and Holzbaur, E. L. (1998). Speculating about spectrin: new insights into the Golgi-associated cytoskeleton. Trends Cell Biol. 8, 26-29.[CrossRef][Medline]
Hori, M., Matsuura, Y., Yoshimoto, R., Ozaki, H. Y. T. and Karaki, H. (1999). Actin depolymerizing action by marine toxin, pectenotoxin-2. Nippon Yakurigaku Zasshi 114,225 -229.
Ishida, Y., Takagi, K., Takahashi, M., Satake, N. and Shibata,
S. (1983). Palytoxin isolated from marine coelenterates. The
inhibitory action on (Na,K)-ATPase. J. Biol. Chem.
258,7900
-7902.
Ishii, K., Ito, K. M., Uemura, D. and Ito, K.
(1997). Possible mechanism of palytoxin-induced Ca++
mobilization in porcine coronary artery. J. Pharmacol. Exp.
Ther. 281,1077
-1084.
Ito, E., Ohkusu, M. and Yasumoto, T. (1996). Intestinal injuries caused by experimental palytoxicosis in mice. Toxicon 34,643 -652.[CrossRef][Medline]
Jung, J., Sim, C. and Lee, C. (1995). Cytotoxic compounds from a two sponge association. J. Nat. Prod. 58,1722 -1726.[CrossRef][Medline]
Kamal, A. and Goldstein, L. S. (2000). Connecting vesicle transport to the cytoskeleton. Curr. Opin. Cell Biol. 12,503 -508.[CrossRef][Medline]
Kirkpatrick, B., Fleming, L. E., Squicciarini, D., Backer, L. C., Clark, R., Abraham, W., Benson, J., Cheng, Y. S., Johnson, D., Pierce, R. et al. (2004). Literature review of Florida red tide: implications for human health effects. Harmful Algae 3, 99-115.[CrossRef]
Leira, F., Cabado, A., Vieytes, M., Roman, Y., Alfonso, A., Botana, L., Yasumoto, T., Malaguti, C. and Rossini, G. (2002). Characterization of F-actin depolymerization as a major toxic event induced by pectenotoxin-6 in neuroblastoma cells. Biochem. Pharmacol. 63,1979 -1988.[CrossRef][Medline]
Lewis, R. J., Sellin, M., Poli, M. A., Norton, R. S., MacLeod, J. K. and Sheil, M. M. (1991). Purification and characterization of ciguatoxins from moray eel (Lycodontis javanicus, Muraenidae). Toxicon 29,1115 -1127.[CrossRef][Medline]
Lombet, A., Bidard, J. N. and Lazdunski, M. (1987). Ciguatoxin and brevetoxins share a common receptor site on the neuronal voltage-dependent Na+ channel. FEBS Lett. 219,355 -359.[CrossRef][Medline]
Louzao, M. C., Vieytes, M. R., Fontal, O. I. and Botana, L. M. (2003). Glucose uptake in enterocytes: A test for molecular targets of okadaic acid. J. Recept. Signal Transduct. Res. 23,211 -224.[CrossRef][Medline]
Louzao, M. C., Vieytes, M. R., Yasumoto, T. and Botana, L. M. (2004). Detection of sodium channel activators by a rapid fluorimetric microplate assay. Chem. Res. Toxicol. 17,572 -578.[CrossRef][Medline]
Maekawa, M., Ishizaki, T., Boku, S., Watanabe, N., Fujita, A.,
Iwamatsu, A., Obinata, T., Ohashi, K., Mizuno, K. and Narumiya, S.
(1999). Signaling from Rho to the actin cytoskeleton through
protein kinases ROCK and LIM-kinase. Science
285,895
-898.
Mahajan, V. B., Pai, K. S., Lau, A. and Cunningham, D. D.
(2000). Creatine kinase, an ATP-generating enzyme, is required
for thrombin receptor signaling to the cytoskeleton. Proc. Natl.
Acad. Sci. USA 97,12062
-12067.
Maier, G. D., Wright, M. A., Lozano, Y., Djordjevic, A., Matthews, J. P. and Young, M. R. (1995). Regulation of cytoskeletal organization in tumor cells by protein phosphatases-1 and -2A. Int. J. Cancer 61,54 -61.[Medline]
Matile, S. and Nakanishi, K. (1996). Selective caption movement across lipid belayers containing brevetoxin B. Angew. Chem. Int. Ed. Engl. 35,757 -759.[CrossRef]
Molgó, J., Benoit, E., Comella, J. X. and Legrand, A. M. (1992). Ciguatoxin: a tool for research on sodium-dependent mechanisms. In Methods in Neuroscience. Neurotoxins, Vol. 8 (ed. P. M. Conn), pp.149 -164. New York: Academic Press.
Oliver, C. J., Terry-Lorenzo, R. T., Elliot, E., Bloomer, W. A. C., Li, S., Brautigan, D. L., Colbran, R. J. and Shenolikar, S. (2002). Targeting protein phosphatase 1 (PP1) to the actin cytoskeleton: the neurabin I/PP1 complex regulates cell morphology. Mol. Cell. Biol.4690 -4701.
Onuma, Y., Satake, M., Ukena, T., Roux, S., Chanteau, S., Rasolofonirina, N., Ratsimaloto, M., Naoki, H. and Yasumoto, T. (1999). Identification of putative palytoxin as the cause of clupeotoxism. Toxicon 37, 55-65.[CrossRef][Medline]
Parekh, A. B. (1998). Voltage-dependent conductance changes in a nonvoltage-activated sodium current from a mast cell line. J. Membr. Biol. 165,145 -151.[CrossRef][Medline]
Patel, K., Harding, P., Haney, L. B. and Glass, W. F., 2nd (2003). Regulation of the mesangial cell myofibroblast phenotype by actin polymerization. J. Cell. Physiol. 195,435 -445.[CrossRef][Medline]
Pearce-Pratt, R., Malamud, D. and Phillips, D. M. (1994). Role of the cytoskeleton in cell-to-cell transmission of human immunodeficiency virus. J. Virol. 68,2898 -2905.[Abstract]
Poli, M. A., Mende, T. J. and Baden, D. G.
(1986). Brevetoxins, unique activators of voltage-sensitive
sodium channels, bind to specific sites in rat brain synaptosomes.
Mol. Pharmacol. 30,129
-135.
Puius, Y. A., Mahoney, N. M. and Almo, S. C. (1998). The modular structure of actin-regulatory proteins. Curr. Opin. Cell Biol. 10, 23-34.[CrossRef][Medline]
Rodriguez, F. A., Escobales, N. and Maldonado, C. (1994). Brevetoxin-3 (PbTx-3) inhibits oxygen consumption and increases Na+ content in mouse liver slices through a tetrodotoxin-sensitive pathway. Toxicon 32,1385 -1395.[CrossRef][Medline]
Saito, S. and Karaki, H. (1996). A family of novel actin-inhibiting marine toxins. Clin. Exp. Pharmacol. Physiol. 23,743 -746.[Medline]
Saito, S., Watabe, S., Ozaki, H., Fusetani, N. and Karaki,
H. (1994). Mycalolide B, a novel actin depolymerizing agent.
J. Biol. Chem. 269,29710
-29714.
Saito, S., Watabe, S., Ozaki, H., Kigoshi, H., Yamada, K., Fusetani, N. and Karaki, H. (1996). Novel actin depolymerizing macrolide aplyronine A. J. Biochem. (Tokyo) 120,552 -555.[Abstract]
Saito, S. Y., Watabe, S., Ozaki, H., Kobayashi, M., Suzuki, T., Kobayashi, H., Fusetani, N. and Karaki, H. (1998). Actin-depolymerizing effect of dimeric macrolides, bistheonellide A and swinholide A. J. Biochem. (Tokyo) 123,571 -578.[Abstract]
Salmon, E. D. and Way, M. (1999). Cytoskeleton. Curr. Opin. Cell Biol. 11, 15-17.[CrossRef]
Satoh, E., Ishii, T. and Nishimura, M. (2003). Palytoxin-induced increase in cytosolic-free Ca(2+) in mouse spleen cells. Eur. J. Pharmacol. 465, 9-13.[CrossRef][Medline]
Schreider, C., Peignon, G., Thenet, S., Chambaz, J. and
Pincon-Raymond, M. (2002). Integrin-mediated functional
polarization of Caco-2 cells through E-cadherinactin complexes.
J. Cell Sci. 115,543
-552.
Smith, P. R., Saccomani, G., Joe, E. H., Angelides, K. J. and
Benos, D. J. (1991). Amiloride-sensitive sodium channel is
linked to the cytoskeleton in renal epithelial cells. Proc. Natl.
Acad. Sci. USA 88,6971
-6975.
Suzuki, T., Mitsuya, T., Matsubara, H. and Yamasaki, M. (1998). Determination of pectenotoxin-2 after solid phase extraction from seawater and from the dinoflagellate Dinophysis fortii by liquid chromatography with electrospray mass spectrometry and ultraviolet detection: evidence of oxidation of pectenotoxin-2 to pectenotoxin-6 in scallops. J. Chromatogr. A 815,155 -160.[CrossRef][Medline]
Takahashi, M., Ohizumi, Y. and Yasumoto, T.
(1982). Maitotoxin, a Ca2+ channel activator
candidate. J. Biol. Chem.
257,7287
-7289.
Tosteson, M. T. (2000). Mechanism of action. pharmacology and toxicology. In Seafood and Freshwater Toxins: Pharmacology, Physiology and Detection (ed. L. M. Botana), pp.549 -566. New York: Marcel Dekker Inc.
Tosteson, M. T., Halperin, J. A., Kishi, Y. and Tosteson, D. C. (1991). Palytoxin induces an increase in the cation conductance of red cells. J. Gen. Physiol. 98,969 -985.[Abstract]
Wang, S. Y. and Wang, G. K. (2003). Voltage-gated sodium channels as primary targets of diverse lipid-soluble neurotoxins. Cell Signal. 15,151 -159.[CrossRef][Medline]
Wang, X. and Horisberger, J. D. (1997). Palytoxin effects through interaction with the Na,K-ATPase in Xenopus oocyte. FEBS Lett. 409,391 -395.[CrossRef][Medline]
Xi, D., Van Dolah, F. M. and Ramsdell, J. S.
(1992). Maitotoxin induces a calcium-dependent membrane
depolarization in GH4C1 pituitary cells via activation of type L
voltage-dependent calcium channels. J. Biol. Chem.
267,25025
-25031.
Yasumoto, T., Bagnis, R. and Vernoux, J. P. (1976). Toxicity study of surgeon fishes-II: properties of the principal water-soluble toxin. Bull. Jap. Soc. Sci. Fish. 42,359 -365.
Yin, H. L. (1987). Gelsolin: calcium- and polyphosphoinositide-regulated actin-modulating protein. BioEssays 7,176 -179.[CrossRef][Medline]
Yin, H. L. and Stossel, T. P. (1979). Control of cytoplasmic actin gel-sol transformation by gelsolin, a calcium-dependent regulatory protein. Nature 281,583 -586.[Medline]