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Neurotoxins from Marine Dinoflagellates: A Brief Review

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Dinoflagellates are not only important marine primary producers and grazers, but also the major causative agents of harmful algal blooms. It has been reported that many dinoflagellate species can produce various natural toxins. These toxins can be extremely toxic and many of them are effective at far lower dosages than conventional chemical agents. Consumption of seafood contaminated by algal toxins results in various seafood poisoning syndromes: paralytic shellfish poisoning (PSP), neurotoxic shellfish poisoning (NSP), amnesic shellfish poisoning (ASP), diarrheic shellfish poisoning (DSP), ciguatera fish poisoning (CFP) and azaspiracid shellfish poisoning (ASP). Most of these poisonings are caused by neurotoxins which present themselves with highly specific effects on the nervous system of animals, including humans, by interfering with nerve impulse transmission. Neurotoxins are a varied group of compounds, both chemically and pharmacologically. They vary in both chemical structure and mechanism of action, and produce very distinct biological effects, which provides a potential application of these toxins in pharmacology and toxicology. This review summarizes the origin, structure and clinical symptoms of PSP, NSP, CFP, AZP, yessotoxin and palytoxin produced by marine dinoflagellates, as well as their molecular mechanisms of action on voltage-gated ion channels.
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Mar. Drugs 2008, 6, 349-371; DOI: 10.3390/md20080016
Marine Drugs
ISSN 1660-3397
www.mdpi.org/marinedrugs
R
evie
w
OPEN ACCESS
Neurotoxins from Marine Dinoflagellates: A Brief Review
Da-Zhi Wang
State Key Lab of Marine Environmental Science / Environmental Science Research Center, Xiamen
University, Xiamen 361005, P.R. China
Tel.: +86-592-2186016; Fax: +86-592-2180655; E-mail: dzwang@xmu.edu.cn
Received: 9 March 2008; in revised form: 14 May 2008 / Accepted: 14 May 2008 / Published: 11 June
2008
Abstract: Dinoflagellates are not only important marine primary producers and grazers,
but also the major causative agents of harmful algal blooms. It has been reported that
many dinoflagellate species can produce various natural toxins. These toxins can be
extremely toxic and many of them are effective at far lower dosages than conventional
chemical agents. Consumption of seafood contaminated by algal toxins results in various
seafood poisoning syndromes: paralytic shellfish poisoning (PSP), neurotoxic shellfish
poisoning (NSP), amnesic shellfish poisoning (ASP), diarrheic shellfish poisoning (DSP),
ciguatera fish poisoning (CFP) and azaspiracid shellfish poisoning (ASP). Most of these
poisonings are caused by neurotoxins which present themselves with highly specific
effects on the nervous system of animals, including humans, by interfering with nerve
impulse transmission. Neurotoxins are a varied group of compounds, both chemically
and pharmacologically. They vary in both chemical structure and mechanism of action,
and produce very distinct biological effects, which provides a potential application of
these toxins in pharmacology and toxicology. This review summarizes the origin,
structure and clinical symptoms of PSP, NSP, CFP, AZP, yessotoxin and palytoxin
produced by marine dinoflagellates, as well as their molecular mechanisms of action on
voltage-gated ion channels.
Keywords: Dinoflagellates, neurotoxins, voltage-gated ion channels, molecular action
mechanism, paralytic shellfish poisoning, neurotoxic shellfish poisoning, ciguatera fish
poisoning, azaspiracid poisoning, yessotoxin, palytoxin
Mar. Drugs 2008, 6
350
1. Introduction
Over the past few decades, the occurrence of harmful algal blooms (HABs) has increased both in
frequency and in geographic distribution in many regions of the world. This has resulted in adverse
impacts on public health and the economy, and has become a global concern [1-3]. It is known that
certain HAB species can produce potent toxins that impact human health through the consumption of
contaminated shellfish, coral reef fish and finfish, or through water or aerosol exposure [4]. In many
cases, toxic species are normally present in low concentrations with no environmental or human health
impacts. However, when they are present at high cell density and are ingested by filter-feeding
shellfish, zooplankton, and herbivorous fishes, toxins are accumulated in these organisms and
transferred to higher trophic levels through the food chain, which results in various adverse effects. It
is reported that algal toxins result in more than 50,000-500,000 intoxication incidents per year, with an
overall mortality rate of 1.5% on a global basis [5]. In addition to their adverse effects on human health,
algal toxins are responsible for the death of fish and shellfish and have caused episodic mortalities of
marine mammals, birds, and other animals depending on the marine food web [6-9].
Of those causative organisms, dinoflagellates, a very large and diverse group of eukaryotic algae in
the marine ecosystem, are the major group producing toxins that impact humans [4, 10]. Dinoflagellate
toxins are structurally and functionally diverse, and many present unique biological activities. In the
past few decades, extensive studies have been devoted to the toxicology and pharmacology of
dinoflagellate toxins [11], and five major seafood poisoning syndromes caused by toxins have been
identified from the dinoflagellates (Table 1): paralytic shellfish poisoning (PSP), neurotoxic shellfish
poisoning (NSP), amnesic shellfish poisoning (ASP), diarrheic shellfish poisoning (DSP) and ciguatera
fish poisoning (CFP). Besides these well-known poisonings, several new poisoning syndromes
resulting from newly appearing dinoflagellate toxins, such as azaspiracid toxins, yessotoxin and
palytoxin have been reported and characterized recently (Table 1), and this has increased global public
concerns regarding dinoflagellate associated toxins. Dinoflagellate toxins can be functionally
categorized as neurotoxins and hepatotoxins, according to their clinical symptoms. The neurotoxicity
of dinoflagellate toxins is mediated by diverse, highly specific interactions with ion channels involved
in neurotransmission (Figure 1). This paper provides a brief overview of the origin, structure and
clinical symptoms of PSP, NSP, CFP, AZP, yessotoxin and palytoxin produced by dinoflagellates as
well as their molecular mechanisms of action on voltage-gated ion channels.
2. Voltage-gated ion channels and neurotoxins
It is known that most dinoflagellate toxins are neurotoxins, which interact with the specific
receptors associated with neurotransmitter receptors, or voltage-sensitive ion channels (Figure 1),
resulting in the observed neurotoxicity [12]. In organisms including humans, voltage-gated ion
channels, such as sodium, calcium, and potassium channels, are electrical signal generators which
control contraction of muscle, secretion of hormones, sensing of the environment, processing of
information in the brain, and output from the brain to peripheral tissues [13]. These channels share a
common structural motif containing six transmembrane segments (S1-S6) and a pore loop (Figure 1).
The voltage sensor domain consists of the S1-S4 segments with positively charged residues in the S4
segment as gating charges, while the pore is composed of the S5/S6 segments and the pore loop
Mar. Drugs 2008, 6
351
between them, which are gated by bending of the S6 segment at a hinge glycine or praline residue. In
all of these contexts, electrical signals are conducted by members of the ion channel protein super
family, a set of more than 140 structurally related pore-forming proteins [14]. Pharmacological studies
have disclosed that the functions of the voltage-gated ion channel proteins can be classified into three
complementary aspects: ion conductance, pore gating and regulation. These channel proteins are the
molecular targets for a broad range of potent neurotoxins, which strongly alter channel functions by
binding to specific receptor sites. At present, six different neurotoxin receptor sites on the channel
protein have been identified on voltage-gated ion channels using various neurotoxins [15-19].
Hydrophilic low molecular mass toxins and large polypeptide toxins block the channel pore physically
and prevent ion conductance. Alkaloid toxins and related lipid soluble toxins alter voltage-dependent
gating through binding to intramembranous receptor sites. On the contrary, poplypeptide toxins alter
channel gating through binding to extracellular sites [20, 13]. In the section below we describe the
molecular mechanisms of action of seven different neurotoxins produced by dinoflagellates.
Table 1. Seafood poisonings caused by neurotoxins identified from marine dinoflagellate species.
Type of
poisoning
Toxins Sources of toxins Primary
vector
Action target Ref.
PSP Saxitoxins and
gonyautoxins
Alexandrium spp.,
Gymnodinium spp.,
Pyrodinium spp.
Shellfish Voltage-gated
sodium channel 1
23, 27-29
NSP Brevetoxins
Kerenia brevis,
Chatonella marina,
C. antiqua,
Shellfish Voltage-gated
sodium channel 5
33,
39-41,
46, 52
Fibrocapsa
japonica,
Heterosigma
akashiwo
Yessotoxins
Protoceratium
reticulatum,
Lingulodinium
polyedrum
Shellfish Voltage-gated
calcium/sodium
channel?
94-95
Gonyaulax spinifera
CFP Ciguatoxins
Gambierdiscus
toxicus
Coral
reef fish
Voltage-gated
sodium channel 5
55, 62, 63
CFP Maitotoxins
Gambierdiscus
toxicus
Coral
reef fish
Voltage-gated
calcium channel
69, 70
AZP Azaspiracids
Protoperidinium
crassipes
Shellfish Voltage-gated
calcium channel
72, 76
Palytoxin
poisoning
Palytoxins
Ostrepsis siamensis
Shellfish Na
+
-K
+
ATPase 97,
109-111
Notes: PSP, paralytic shellfish poisoning; NSP, neurotoxic shellfish poisoning; CFP, ciguatera
fish poisoning, AZP, azaspiracid poisoning.
Mar. Drugs 2008, 6
352
Figure 1. The voltage-gated channels: The different members of the ion channel family
structurally related to the voltage-gated ion channels are illustrated as transmembrane
folding diagrams in which cylinders represent probable transmembrane alpha helices.
Green, S5-S6 pore forming segments; red, S4 voltage sensor; and gray, S1-S3
tansemembrane segments [13].
3. Paralytic shellfish poisoning (PSP)
PSP is a worldwide marine toxin disease with both neurologic and gastrointestinal symptoms,
which is caused by the consumption of shellfish contaminated by toxic dinoflagellates [21]. The first
PSP event was reported in 1927 near San Francisco, USA, and was caused by a dinoflagellate, A.
catenella, which resulted in 102 people being ill and six deaths [22]. Since then, members of three
dinoflagellate genera have been reported to be the major sources of PSP toxins: Alexandrium,
Gymnodinium, and Pyrodinium [23]. Paralytic shellfish toxins (PSTs) are produced in varying
proportions by different dinoflagellate species and even by different isolates within a species. PSP
toxins are heat-stable and water-soluble nonproteinaceous toxins. The basic structures of PSP toxins
are 3,4-propinoperhydropurine tricyclic systems. Saxitoxin and its analogues can be divided into three
categories: the carbamate compounds, which include saxitoxin, neo-saxitoxin and gonyautoxins 1-4;
the N-sulfocarbamoyl compounds, which include the C and B toxins; and finally the decarbamoyl
compounds with respect to the presence or absence of 1-N-hydroxyl, 11-hydroxysulfate, and
21-N-sulfocarbamoyl substitutions as well as epimerization at the C-11 position (Figure 2). In the past
few decades at least 24 structurally related imidazoline guanidinium PSP derivatives have been
identified and characterized from dinoflagellate species [21, 24].
Mar. Drugs 2008, 6
353
Figure 2. Structure and species of paralytic shellfish poisoning toxins from marine
dinoflagellates [4].
N
N
N
H
H
N
R
3
R
2
OH
OH
NH
2
R
1
H
2
N
1
2
3
4
5
6
7
8
9
10
12
11
13
14
15
16
17
R
4
Toxin R1 R2 R3 R4
STX H H H OCONH
2
Neo STX OH H H OCONH
2
GTX1 OH OSO
3
-
H OCONH
2
Carbamate GTX2 H OSO
3
-
H OCONH
2
GTX3 H H OSO
3
-
OCONH
2
GTX4 OH H OSO
3
-
OCONH
2
GTX5(B1) H H H OCONHSO
3
-
GTX6(B2) OH H H OCONHSO
3
-
C1 H OSO3- H OCONHSO
3
-
N-sulfocarbamoyl C2 H H OSO
3
-
OCONHSO
3
-
C3 OH OSO3- H OCONHSO
3
-
C4 OH H OSO
3
-
OCONHSO
3
-
dcSTX H H H OH
dcNeoSTX OH H H OH
dcGTX1 OH OSO
3
-
H OH
Decarbamoyl dcGTX2 H OSO
3
-
H OH
dcGTX3 H H OSO
3
-
OH
dcGTX4 OH H OSO
3
-
OH
doSTX H H H H
Deoxydecarbamoyl doGTX2 H H OSO
3
-
H
doGTX3 H OSO
3
-
H H
Saxitoxin is the most toxic and also the most well studied among the PSP associated toxins. In mice,
its LD
50
peritoneal is 3-10 μg/kg body weight and orally is 263 μg/kg body weight. The lethal oral
dose in humans is 1 to 4 mg (5,000 to 20,000 mouse units), depending on the gender and physiological
condition of the patient. It is rapidly absorbed through the gastrointestinal tract and excreted in the
urine. The symptoms of PSP include a tickling sensation of the lips, mouth and tongue, numbness of
the extremities, gastrointestinal problems, difficulty in breathing, and a sense of dissociation followed
by complete paralysis [25]. In the case of serious intoxication, PSP leads to a variety of neurological
Mar. Drugs 2008, 6
354
symptoms culminating in respiratory arrest and cardiovascular shock or death [26]. Saxitoxin and its
analogues are very dangerous compounds, with possible military potential and have been listed by the
Organization for the Prohibition of Chemical Weapons (OPCW) as a Schedule 1 chemical intoxicant,
the manufacture, use, transfer and reuse of which are now strictly regulated by the OPCW (Chemical
Weapons Convention, September 1998, The Hague, Netherlands).
PSP toxins are the most well known potent neurotoxins that specifically and selectively bind the
sodium channels on excitable cells [27]. In 1975, Hill postulated a plugging model for the binding of
the sodium channel with saxitoxin [28]. In this model, the toxin molecular penetrates rather deeply
inside the channel and plugs it, having formed an ion pair with an anionic site thought to be located
near the bottom of the channel. However, this model could not explain the lack of anticipated steric
interactions with other structurally unfolded toxins, the gonyautoxins. Later, Kao and Walker proposed
a model which placed the toxin molecules on the outside edge of the channel with the guanidinium
group on the top of the channel entrance [29]. Meanwhile Shimizu also suggested a three-point binding
model involving two hydrogen bonds with the ketal OHs, and ion pairing of the guanidinium group
with an anionic site on the outside surface of the membrane [30]. With the success of cloning of the
sodium channel [31], more precise information regarding the toxin-binding mode has arisen from the
molecular biological studies of the sodium channel. PSP toxins are now regarded as blocking agents
that reduce the number of conducting Na
+
channels by occupying some site near the outer opening in a
1:1 high affinity specific receptor binding. The extracellular loop sections of S1-S2 (P-loops) of the
Na
+
channel are considered to be the PSP toxins-binding site. They bind to the site on the
voltage-dependent sodium channel with high affinity (Kd~2nM), which inhibits the temporary
permeability of Na
+
ions by binding tightly to receptor site 1 on the outside surface of the membrane
very close to the external orifice of the sodium channel, preventing sodium ions from passing through
the membranes of the nerve cells, and thus interfering with the transmission of signals along the nerves.
The resulting widespread blockade prevents impulse-generation in peripheral nerves and skeletal
muscles. Saxitoxin also affects skeletal muscle directly by blocking the muscle action potential without
depolarizing cells, which abolishes peripheral nerve conduction but with no curare-like action at the
neuromuscular junction. Surprisingly, selective pressure from the presence of STX in the natural
environment can select for mutations in the ion selectivity filter that cause resistance to these toxins in
the softshell clam Mya arenaria [32].
4. Neurotoxic Shellfish Poisoning (NSP)
NSP is caused by the ingestion of shellfish exposed to blooms of the dinoflagellate Kerenia brevis
(formerly Gymnodinium breve) [33, 34]. This dinoflagellate species produces two types of lipid
soluble toxins: hemolytic and neurotoxic [35], causing massive fish kills, bird deaths, and marine
mammal mortalities [36, 37]. The neurotoxic toxins are known as brevetoxins, which are a suite of
ladder-like polycyclic ether toxins. Brevetoxin congeners are of two types based on backbone structure:
brevetoxin B backbone (type 1; PbTx-2, 3, 5, 6, 8, 9) and brevetoxin A backbone (type 2; PbTx-1, 7,
10) (Figure 3). Among them, PbTx-2T is the major brevetoxin produced by K. brevis [38]. Massive
fishes are killed due to neurotoxin exposure, with the possible contribution of the hemolytic fraction.
Recently neurotoxins were also found in other fish-killing flagellate species, Chatonella marina, C.
antiqua, Fibrocapsa japonica, and Heterosigma akashiwo [39-41].
Mar. Drugs 2008, 6
355
Figure 3. Structure and species of neurotoxic shellfish poisoning toxins from marine
dinoflagellates [4].
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
CH
3
H
3
C
CH
3
CH
3
CH
3
H
3
C
R
1
O
R
2
CH
3
O
O
H
3
C
CH
3
CH
3
H
3
C
R
1
O
R
2
"head"
"tail"
"head"
"tail"
Type1 (brevetoxin B)
Type 2 (brevetoxin A)
Toxin Type R1 R2
Nominal
mass
PbTx-1 2 H CH
2
C(CH
2
)CHO 866
PbTx-2 1 H CH
2
C(CH
2
)CHO 894
PbTx-3 1 H CH
2
C(CH
2
)CH
2
OH 896
PbTx-5 1 COCH
3
K-ring acetate PbTx-2 936
PbTx-6 1 H H-ring epoxide PbTx-2 910
PbTx-7 2 H CH
2
C(CH
2
)CH
2
OH 868
PbTx-8 1 H CH
2
COCH
2
Cl 916
PbTx-9 1 H CH
2
CH(CH
3
)CH
2
OH 898
PbTx-10 2 H CH
2
CH(CH
3
)CH
2
OH 870
As with many of the known marine toxins, the brevetoxins are tasteless, odorless, and heat and acid
stable (they survive heat up to 300°C). The mouse LD
50
is 170 µg/kg body weight (0.15–0.27)
intraperitoneally, 94 µg/kg body weight intravenously and 520 µg/kg body weight orally [42].
Pathogenic dose for humans is in the order of 42-72 mouse units. NSP presents itself as a milder
gastroenteritis with neurologic symptoms compared with PSP. The symptoms of NSP include nausea,
tingling and numbness of the perioral area, loss of motor control, and severe muscular pain [43, 44].
Mar. Drugs 2008, 6
356
The mechanism of action of brevetoxins has been extensively studied, and brevetoxins are regarded
as depolarizing substances that open voltage gated sodium ion channels in cell walls, leading to
uncontrolled Na
+
influx into the cell [45]. Experiments utilizing neuroblastoma cells and rat
synaptosomes have shown that brevetoxins act on neurotoxin binding site 5 on the α-subunit of the
voltage-dependent sodium channel in a 1:1 stoichiometry [46]. This action differs from that of PSP
toxins which block the sodium channel and prevent sodium ions from passing through the membranes
of nerve cells. This enhances the inward flow of Na
+
ions into the cell by altering the membrane
properties of excitable cell types, resulting in inappropriate opening of the channel under conditions in
which it is normally closed, and it also inhibits channel inactivation [36, 45, 47-49]. The toxin appears
to produce its sensory symptoms by transforming fast sodium channels into slower ones, which results
in persistent activation and repetitive firing [50]. It was reported that brevetoxin could combine with a
separate site on the gates of the sodium channel, causing the release of neurotransmitters from
autonomic nerve endings. In particular, this can release acetylcholine, leading to smooth tracheal
contraction, as well as massive mast cell degranulation [51]. Recently, LePage et al. demonstrated that
brevetoxins also triggered Ca influx in rat cerebellar granule neurons. Derivatives PbTx-1, PbTx-2 and
PbTx-3 produced a rapid and concentration-dependent increase in cytosolic [Ca
2+
], indicating that
brevetoxin analogues display a range of efficacies to neurotoxin site 2 ligands and are activators of
neurotoxin site 5, with PbTx-1 being a full agonist and other derivatives acting as partial agonists [52].
An early investigation also reported that conformational variation of brevetoxins induces a significant
change in the gross shape of the molecule, which results in the loss of binding affinity and toxicity of
the brevetoxins [46]
5. Ciguatera Fish Poisoning (CFP)
CFP, which is the most commonly reported marine toxin disease in the world, is caused by
consumption of contaminated coral reef fishes such as barracuda, grouper, and snapper [53, 54]. It is
estimated that approximately 25,000 people are affected annually by ciguatoxins and CFP is regarded
as a world health problem [54]. The origin of ciguatera toxins has been identified in a dinoflagellate
species, Gambierdiscus toxicus, which originally produces maitotoxins (MTXs), the lipophilic
precursors of ciguatoxin [55]. These precursors are biotransformed to ciguatoxins by herbivorous
fishes and invertebrates grazing on G. toxicus and then accumulated in higher trophic levels [56]. The
ciguatoxins are a family of heat-stable, lipid-soluble, highly oxygenated, cyclic polyether molecules
with a structural framework reminiscent of the brevetoxins [57-60], and more than 20 toxins may be
involved in CFP (Figure 4) [53].
The biological activities of ciguatoxins have been studied extensively and they are regarded as the
most potent activators of sodium and/or calcium fluxes in the cytoplasm in various cells. They produce
more than 175 ciguateric symptoms, classified into four categories: gastrointestinal, neurological,
cardiovascular and general symptoms [54, 61]. It should be emphasized that the symptoms of ciguatera
vary in different oceans: in the Pacific Ocean neurological symptoms predominate, while in the
Caribbean Sea the gastrointestinal symptoms dominate due to the difference in toxin composition.
Ciguatoxin and maitotoxin are the two most common toxins associated with CFP, and they are the
most lethal natural substances known. Pharmacological studies have revealed that CTXs activate the
Mar. Drugs 2008, 6
357
voltage-sensitive sodium channel at nM to pM concentrations [61]. In mice, ciguatoxin is lethal at 0.45
μg/kg ip, and maitotoxin at a dose of 0.15 μg/kg ip. Oral intake of as little as 0.1 μg ciguatoxin can
cause illness in the human adult.
Figure 4. Structure and species of ciguatoxins from the dinoflagellate G. toxicus [62].
O
O
O
O
O
O
O
O
O
O
R
2
H
H
H
H
H
H
HO
H
3
C
H
H
H
CH
3
H
H
CH
H
H
H
H
H
H
H
H
H
CH
3
H
3
C
O
H
3
C
OH
H
H
R1
Type-1
O
O
O
O
O
O
O
O
O
O
R
1
R
2
H
H
H
H
H
H
HO
H
3
C
H
H
H
H
OH
H
H
H
H
H
H
H
H
O
O
O
CH
3
H
CH
3
H
H
H
OH
Type-2
O
O
O
O
O
O
O
O
O
O
O
O
O
HO
H
H
H
H
H
H
HO
H
3
C
H
H
H
CH
3
H
OH
CH
3
OH
H
H
H
H
H
H
H
H
H
H
H
H
3
C
H
3
C
OH
Type-3
Toxin Type R1 R2
CTX-1 1 HOCH
2
CHOH OH
CTX-2 1 HOCH
2
CHOH H
CTX-3 1 HOCH
2
CHOH H
CTX-4A 1 CH
2
=CH H
CTX-4B 1 CH
2
=CH H
CTX-2A1 2 OH OH
CTX-3C 2 H H
C-CTX-1 3 - -
Ciguatoxins exert the same action mode as brevetoxins, which selectively target the common
binding site 5 on the α-subunit of neuronal sodium channels. However, the affinity of ciguatoxins is
higher than that of brevetoxins and, thus, the affinity of CTX-1 for voltage dependent sodium channels
is around 30 times higher than that of brevetoxin. Ciguatoxins open sodium channels along the
Mar. Drugs 2008, 6
358
peripheral nerves, particularly at the nodes of Ranvier [62, 63], which results in an influx of Na
+
ions,
cell depolarization and the appearance of spontaneous action potentials in excitable cells. Consequently,
the plasma membrane is unable to maintain either the internal environment of the cells or volume
control due to the increased Na
+
permeability, which results in alteration of bioenergetic mechanisms,
cell and mitochondrial swelling and bleb formation on cell surfaces. With neurophysiological testing,
significant slowing of sensory and motor nerve conduction velocities, and F wave latencies has been
demonstrated [62, 64, 65]. This observation may be related to nodal swelling and internodal length and
volume increase, all of which have been confirmed with in vitro CTX exposure [63, 66].
Studies on cardiovascular effects of ciguatoxins reveal that ciguatoxin affects voltage-dependent
Na
+
channels causing Na
+
to move intracellularly, and normal cellular mechanisms begin to extrude
sodium and take up calcium. Calcium is the intracellular trigger for muscle contraction. Although
much of the increased calcium is buffered by the sarcoplasmic reticulum, it is likely that locally
increased calcium concentrations increase the force of cardiac muscle contraction as is observed in
ciguatoxin poisoning. A similar mechanism of ciguatoxin-induced intracellular transport of calcium
occurs in intestinal epithelial cells. The increased concentration of intracellular calcium induced by
ciguatoxin acts as a second messenger in the cell, which disrupts important ion-exchange systems,
resulting in fluid secretion and symptoms of diarrhea [67].
Figure 5. Structure of maitotoxin from the dinoflagellate G. toxicus [120].
O
O
O
O
O
O
O
O
O
O
H
H
H
H
H
OH
F'
E'
D'
C'
B'
A'
Z
Y
X
W
OH
OH
H HH HH
H
H
H
O
O
H
O
V
U
T
O
O
O
O
SR
Q
P
O
O
O
O
O
O
O
O
O
O
N
O
M
L
K
J
I
G
F
O
O
O
C
DE
O
O
BH
A
OH
OH
HO
OSO
3
Na
OH
H
HO
OH
H
H
H H
HH
H H
OH
H
OH
OH
H
OSO
3
Na
OH
H
H
H
H
H
H
OH
H
H
H
OH
H
H
H
OH
H
H
H
OH
OH
OH
H
H
OH
H
H
H
H
H
H
H
H
OH
H
OH
OH
Maitotoxin, another important neurotoxin involved in CFP, is a water soluble, ladder-shaped
polycyclic molecule with numerous hydroxyl groups and sulfate groups (Figure 5). Three forms of
MTX, MTX-1, MTX-2 and MTX-3 have been identified from G. toxicus [68]. MTX has been proved
to be the most potent toxin identified on a weight basis: the LD
50
of MTX in mice is less than 0.2
μg/Kg (intraperitoneally) and it is at least 5-fold more toxic than tetrodotoxin. Pharmacological studies
demonstrate that MTX is a potent activator of voltage-gated calcium channels which stimulates the
movement of Ca
2+
ions across biomembranes in a wide variety of organisms. As a consequence of Ca
2+
influx, maitotoxins can produce several effects: hormone and neurotransmitter secretion,
phosphoinositides breakdown, and activation of voltage gated Ca
2+
channels due to membrane
depolarization. However, the primary target of MTX still remains undefined and the molecular
Mar. Drugs 2008, 6
359
mechanism of action is not clear. It is postulated that MTX might cause a shift in voltage-dependence
of gating that favors opening of voltage-gated calcium channels at resting membrane potentials.
However, MTX activates voltage-gated calcium channels indirectly via membrane depolarization as a
consequence of activating a nonselective cation current [69]. Recently, Kakizaki et al. reported that
maitotoxin induced a profound increase in the Ca
2+
influx into cultured brainstem cells after a brief lag
period, indicating Ca
2+
permeability by acting on the calcium channel in an open state and preventing
its closing [70].
6. Azaspiracid Shellfish Poisoning (AZP)
Azaspiracid poisoning (AZP), first reported from the Netherlands but later becoming a continuing
problem in Europe [71], is a newly identified marine toxin disease. It is caused by consumption of
contaminated shellfish associated with the dinoflagellate Protoperidinium crassipes, which can
produce high intracellular concentrations of azaspiracid (AZA1), a lipophilic, polyether toxin.
Nowadays about one dozen derivatives (AZA2 to 11) of azaspiracid (AZA1) have been identified and
characterized from P. crassipes and contaminated shellfish [72-74]. AZAs differ significantly from
other dinoflagellate toxins, in that they have unique structural features characterized by a tri-spiro
assembly, an azazpiro ring fused with a 2,9-dinoxabicyclo[3.3.1] nonane and a terminal carboxylic
acid group (Figure 6).
Figure 6. Structure and species of azaspiracid poisoning toxins from marine
dinoflagellates [121].
HO
O
H
O
O
O
Me
O
H
H
H
O
M
e
Me
OH
O
O
O
H
H
NH
M
e
M
e
M
e
H
Toxin R1 R2 R3 R4
AZA1 H H Me H
AZA2 H Me Me H
AZA3 H H H H
AZA4 OH H H H
AZA5 H H H OH
Mar. Drugs 2008, 6
360
The symptoms of AZP include nausea, vomiting, severe diarrhea and stomach cramps. Neurotoxic
symptoms were also observed [72, 75, 76]. However, the extremely limited availability of the pure
toxins has impeded the necessary investigations of AZP. Some experiments carried out with mice
showed that AZP, unlike okadaic acid (OA) and its analog, dinophysistoxin-1, which need an initiator
[77], can cause lung tumor formation during repeated administration or after withdrawal of AZP
without the combined use of any initiator [78]. Also the toxin can cause necrosis in the lamina propria
of the small intestine and in lymphoid tissues such as the thymus, spleen and Peyer's patches [78]. The
action mechanism of AZAs is unknown at present. Some studies indicate that AZAs might have
different targets, since AZA1 and AZA2 increase [Ca
2+
]
i
by activation of Ca
2+
-release from internal
stores and Ca
2+
-influx, while AZA3 induces only Ca
2+
-influx. AZA5 does not modify intracellular Ca
2+
homeostasis. Recent investigation of the effect of AZA4 on cytosolic calcium concentration [Ca
2+
]
i
in
fresh human lymphocytes demonstrated that AZA4 inhibits store-operated Ca
2+
channels (SOC
channels) and Ca
2+
influx and that this process is reversible [76]. It was postulated that AZA4 inhibits
SOC channels by direct interaction with the channel pore, with another region of channel protein or
with a closely associated regulatory protein and it was also found that AZA4 acts through another type
of Ca
2+
channel, probably some non selective cation channel usually activated by MTX [76]. AZA
groups are novel inhibitors of Ca
2+
channels, SOC and non-SOC channels. Further study is needed to
determine the primary target and the molecular mechanisms of action of AZAs on Ca
2+
channels.
7. Yessotoxin (YTX)
YTX and it analogues, which are disulphated polyether compounds of increasing occurrence in
seafood, were originally isolated from the scallop Patinopecten yessoensis, collected at Mutsu Bay,
Japan [79]. Since then, YTXs have been found in Europe, South America and New Zealand, and
become a worldwide concern due to its potential risk to human health. YTXs were produced by three
dinoflagellate species, Protoceratium reticulatum, Lingulodinium polyedrum and Gonyaulax spinifera
[80-83].
YTX and its derivatives, 45-hydroxy YTX (45-OH-YTX), 45,46,47-trinor YTX, homo YTX, and
45-hydroxyhomo YTX [84, 85] are disulfated polyether lipophilic toxins originally isolated from
Japanese scallops (Figure 7) [80]. Recently several new YTX analogues: carboxyyessotoxin (with a
COOH group on the C
44
of YTX instead of a double bond); carboxyhomoyessotoxin (with a COOH
group on the C
44
of homoYTX instead of a double bond); 42,43,44,45,46,47,55-heptanor-41-oxo YTX
and 42,43,44,45,46,47,55-heptanor-41-oxohomo YTX in Adriatic mussels (M. galloprovincialis) have
been identified in dinoflagellates [86, 87].
Originally, YTXs were classified among the toxins responsible for DSP, mainly because they
appear and are extracted together with the DSP toxins, OA and the dinophysistoxins (DTXs) [80].
However, YTXs are proved to be not diarrheogenic compared to OA and its derivatives, the DTXs,
which cause intestinal fluid accumulation or inhibition of protein phosphatase 2A. Terao et al.
demonstrated that the heart is the main target organ of YTXs in mice [88]. Toxicological studies
indicated that acute oral administration at doses up to 10 mg/kg YTX or repeated (seven days) oral
exposure to high (2 mg/kg/day) doses of the toxin caused no mortality nor strong signs of toxicity in
mice [89-91]. YTX caused motor discoordination in the mouse before death due to cerebellar cortical
Mar. Drugs 2008, 6
361
alterations [90, 92, 93]. Histopathological study revealed that YTX provoked alterations in the Purkinje
cells of the cerebellum, including cytological damage to the neuronal cell body and change in the
neurotubule and neurofilament immunoreactivity [93].
Figure 7. Structure and species of yessotoxins from marine dinoflagellates [122].
O
S
O
O
HO
O
O
O
O
O
O
O
O
O
O
53
O
S
HO
O
O
1
4
8
3
6
H
H
7
9
1
2
1
5
1
6
H
H
H
49
50
H
H
52
H
H
54
OH
R
H
H
O
H
1
9
H
H
51
2
3
2
8
2
6
3
0
H
3
2
H
OH
3
4
H
3
6
3
7
4
0
4
1
42
41a
O
NH
44
46
47
47a
OH
HO
1'
2'
3'
OH
55
1 R= H m/z=1290
2 R= CH3 m/z=1304
O
O
O
O
O
O
O
O
O
O
O
R
2
47
O
O
G
F
E
D
C
B
A
H
I
J
K
R
1
S
O
HO
O
S
O
O
HO
n
3
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
OH
OH
41
42
40
45
Toxin R R1 R2
YTX 1 CH
2
H
45-hydroxyYTX 1 CH
2
OH
carboxyYTX 1 CO
2
H H
homoYTX 2 CH
2
H
45-hydroxyhomoYTX 2 CH
2
OH
carboxyhomoYTX 2 CO
2
H H
Recently it was demonstrated that YTX is a potent neurotoxin to neuronal cells. However, the
action site and the mechanism are unknown [94]. YTX was observed to induce a two-fold increase in
cytosolic calcium in cerebellar neurons that was prevented by the voltage-sensitive calcium channel
Mar. Drugs 2008, 6
362
antagonists nifedipine and verapamil. These results suggest YTX might interact with calcium channels
and/or sodium channels directly. Previous studies also showed that YTX activated nifedipine-sensitive
calcium channels in human lymphocytes [95], and YTX was postulated to activate non-capacitative
calcium entry and inhibit capacitive calcium entry by emptying of internal calcium stores.
8. Palytoxin (PTX)
PTX is a polyhydroxylated compound that shows remarkable biological activity at an extremely
low concentration [96]. This toxin was first isolated from the soft coral Palythoa toxica and
subsequently from many other organisms such as seaweeds and shellfish. Recently, palytoxin was also
found in a benthic dinoflagellate, Ostrepsis siamensis, which caused blooms along the coast of Europe
[97-102], extensive death of edible mollusks and echinoderms [99, 100] and human illnesses [98, 99].
Cases of death resulting from PTX have been reported to be due to consumption of contaminated crabs
in the Philippines [103], sea urchins in Brazil [104] and fish in Japan [105-107]. PTX has become of
worldwide concern due to its potential impact on animals including humans.
PTX is a large, very complex molecule with both lipophilic and hydrophilic regions, and has the
longest chain of continuous carbon atoms in any known natural product (Figure 8). Recently several
analogues, ostreocin-D (42-hydroxy-3, 26-didemethyl-9,44-dideoxypalytoxin) and mascarenotoxins
were identified in O. siamensis. PTX is regarded as one of the most potent toxins so far known [108],
the LD
50
s 24 h after intravenous injection vary from 0.025 μg/kg in rabbits and about the same in dogs
to 0.45 μg/kg in mice, with monkeys, rats and guinea pigs around 0.9 μg/kg. Toxic symptoms include
fever inaction, ataxia, drowsiness, and weakness of limbs followed by death.
Over the past few decades much effort has been devoted to define the action mechanisms of PTXs,
however these have not been identified. Pharmacological and electrophysiological studies have
demonstrated that PTXs act as a haemolysin and alter the function of excitable cells. PTX selectively
binds to the Na
+
, K
+
-ATPase with a Kd of 20 pM [109] and transforms the pump into a channel
permeable to monovalent cations with a single-channel conductance of 10 pS [110–113]. Presently,
three primary sites of action of PTXs have been postulated: PTX first opens a small conductance,
non-selective cationic channel which results in membrane depolarization, K
+
efflux and Na
+
influx.
Subsequently, the membrane depolarization may open voltage dependent Ca
2+
channels in synaptic
nerve terminals, cardiac cells and smooth muscle cells, while Na
+
influx may load cells with Na
+
and
favor Ca
2+
uptake by the Na
+
/Ca
2+
exchanger in synaptic terminals, cardiac cells and vascular smooth
muscle cells. Then the increase of [Ca
2+
l
i
stimulates the release of neurotransmitters by nerve terminals,
of histamine by mast cells and of vasoactive factors by vascular endothelial cells as a signal. It also
induces contractions of striated and smooth muscle cells. Additional effects of a rise in [Ca
2+
]
i
may be
activation of phospholipase C [114] and phospholipase A2 [115]. There are reports that PTX opens an
H
+
conductive pathway which results in activation of the Na
+
/H
+
exchanger [116, 117]. Other
investigators suggest that PTX raises [Ca
2+
]
i
independently of the activity of voltage dependent Ca
2+
channels and Na
+
/Ca
’+
exchange [118]. The last two actions might act as the opening of H
+
specific
and Ca
2+
specific channels. Overall, PTX might posses more than one site of action in excitable cells
and act as an agonist for low conductance channels conducting Na
+
/K
+
, Ca
2+
and H
+
ions.
Mar. Drugs 2008, 6
363
Figure 8. Structure of palytoxin from marine dinoflagellates [123].
O
H
2
N
OH
O
O
OH
OH
O
OH
HO
OH
HO
OH
OH
OH
OH
OH
OH
OH
O
OH
OH
OH
HO
O
OH
OH
HO
H
OH
OH
OH
O
OH
HO
OH
OH
OH
HO N
H
N
H
O O
OH
OH OH
O
HO
OH
HO
OH
OH
H
OH
OH
OH
OH
O
O
9. Summary
This paper briefly outlines the origin, structure, symptoms and molecular action mechanisms of
neurotoxins produced by marine dinoflagellates. These toxins vary in chemical structure and
mechanism of action, and produce very distinct biological effects, which provides a potential
application of these toxins in pharmacology and toxicology. However, some of them have not been
well studied due to the limited supply of pure toxins and their molecular action mechanisms are
unknown. Moreover, novel species of neurotoxins produced by dinoflagellates have been found and
identified, which provide a challenge for the characterization of their toxin mechanisms and their
effects on marine organisms and humans. Further work using the cell-based approach is needed to
determine the precise mode of action of these novel neurotoxins from marine dinoflagellates.
Acknowledgements
The authors thank Prof. John Hodgkiss for helping to revise the manuscript. This work was partially
supported by research grants from the Ministry of Science and Technology of the People’s Republic of
China (Project No. 2005DFA20430), the National Natural Science Foundation of China (40376032
and 40476053), Fujian Provincial Department or Science and Technology, the Excellent Group and the
Program for New Century Excellent Talents in Xiamen University to Prof. D.-Z. Wang.
Mar. Drugs 2008, 6
364
References and Notes
1. Anderson, D. M. Toxic algal blooms and red tides: a global perspective. In: Red Tides: Biology,
Environmental Science and Toxicology; Okaichi. T.; Anderson, D. M.; Nemoto, T., Ed; Elsevier:
New York, 1989; pp. 11-16.
2. Smayda T. J. Novel and nuisance phytoplankton blooms in the sea: evidence for a global
epidemic. In: Toxic Marine Phytoplankton; Graneli, E.; Sundstrom, B.; Edler, L.; Anderson, D.
M., Ed; Elsevier: New York, 1990; pp. 29-40
3. Hallegraeff, G. M. Harmful algal blooms: a Global review. In: Manual on Harmful Marine
Microalgae; Hallegraeff, G. M.; Anderson, D. M.; Cembella, A. D., Ed; UNESCO: Landais,
France, 2005; pp. 25-49
4. Van Dolah, F. M. Diversity of Marine and Freshwater Algal Toxins. In: Seafood Toxicology:
Pharmacology, Physiology and Detection; Botana, L., Ed; Marcel Dekker: New York, 2000; pp.
19-43.
5. Quod, J. P.; Turquet, J. Ciguatera fish poisoning in Reunion island (SW Indian Ocean):
epidemiology and clinical patterns. Toxicon 1996, 34, 779-785
6. Geraci, J. R.; Anderson, D. M.; Timperi, R. J; St Aubin, D. J.; Early, G. A.; Prescott, J. H.; Mayo,
C. A. Humpback whales (Megaoetera novaeangliae) fatally poisoned by dinoflagellate toxin.
Can. J. Fish. Aq. Sc. 1989, 46, 1895-1898.
7. Landsberg, J. H.; Steidinger, K. A historical review of red tide events caused by Gymnodinium
breve as related to mass mortalities of the endangered manatee (Trichechus manatus latirostris)
in Florida, USA. In: Harmful Microalgae; Reguera, B.; Blanco, J.; Fernandez, M. L.; Wyatt, T.,
Ed; IOC of UNESCO and Xunta de Galicia, Spain, 1998; pp. 97–100.
8. Scholin, C. A.; Gulland, F.; Doucette, G. J.; Benson, S.; Busman, M.; Chavez, F. P.; Cordaro, J.;
DeLong, R.; De Vogelaere, A.; Harvey, J.; Haulena, M.; Lefebvre, K.; Lipscomb, T.; Loscutoff,
S.; Lowenstine, L. J.; Marin III, R.; Miller, P. E.; McLellan, W. A.; Moeller, P. D. R.; Powell, C.
L.; Rowles, T.; Silvagni, P.; Silver, M.; Spraker, T.; Trainer, V.; Van Dolah, F. M. Mortality of
sea lions along the central California coast linked to a toxic diatom bloom. Nature 2000, 430,
80-84.
9. Flewelling, L. J; Naar, J. P; Abbott, J. P; Baden, D. G; Barros, N. B; Bossart, G. D; Bottein, M.
Y; Hammond, D. G; Haubold, E. M; Heil, C. A; Henry, M. S; Jacocks, H. M; Leighfield, T. A;
Pierce, R. H; Pitchford, T. D; Rommel, S. A; Scott, P. S; Steidinger, K. A; Truby, E. W; Van
Dolah, F. M; Landsberg, J. H. Brevetoxicosis: red tides and marine mammal mortalities. Nature
2005, 435, 755-756.
10. Trainer, V. L.; Baden, D. G. High affinity binding of red tide neurotoxins to marine mammal
brain. Aquat. Toxicol.; 1999, 46, 139-128.
11. Botana, L. M. Seafood and Freshwater toxins: pharmacology, physiology, and detection. Marcel
Dekker: New York, 2000.
12. Gessner, B. D. Neurotoxic toxins. In: Seafood and Freshwater toxins: Pharmacology,
Physiology and Detection; Botana, L. M., Ed; Marcel Dekker: New York, 2000; pp. 65-90.
13. Catterall, W. A.; Cestele, S.; Yarov-Yarovoy, V.; Yu, F. H.; Konoki, K.; Scheuer, T.
Voltage-gated channels and gating modifier toxins. Toxicon 2007, 49, 124-141
Mar. Drugs 2008, 6
365
14. Yu, F. H.; Catterall, W. A. The VGL-chanome: a protein superfamily specialized for electrical
signaling and ionic homeostasis. Science STKE. 2004, re 15
15. Catterall, W. A. Neurotoxins that act on voltage-sensitive sodium channels in excitable
membranes. Annu. Rev. Pharmacol. Toxicol. 1980, 20, 15-43.
16. Martin-Eauclaire, M. F.; Couraud, F. Scorpion neurotoxins: effects and mechanisms. In:
Handbook of Neurotoxicology; Chang, L. W.; Dyer, R. S., Ed; Marcel-Dekker: New York, USA,
1992; pp. 683-716.
17. Catterall W. A.; Risk, M. Toxin T46 from Ptychodiscus brevis (formerly Gymnodinium breve)
enhances activation of voltage-sensitive sodium channels by veratridine. Mol. Pharmacol. 1981,
19, 345-348.
18. Poli, M. A.; Mende, T. J.; Baden, D. G. Brevetoxins, unique activators of voltage-sensitive
sodium channels, bind to specific sites in rat brain synaptosones. Mol. Pharmacol. 1986, 30,
129-135.
19. Fainzillber, M.; Kofman, O.; Zoltkin, E.; Gordon, D. A new neurotoxin receptor site on sodium
channels is identified by a conotoxin that affects sodium channel inactivation in mollusks and
acts as an antagonist in rat brain. J. Biol. Chem. 1994, 269, 2574-2580
20. Cestele, S.; Catterall, W. A. Molecular mechanisms of neurotoxin action on voltage-gated
sodium channels. Biochimie 2000, 82, 883-892.
21. Kodama, M. Ecology, classification, and origin. In: Seafood and freshwater toxins:
Pharmacology, Physiology and Detection; Botana, L., Ed; Marcel Dekker: New York, 2000; pp.
125-150
22. Sommer, H.; Meyer, K. F. Paralytic shellfish poisoning. Arch. Pathol. 1937, 24, 560-598.
23. Shumway, S. E. A review of the effects of algal blooms on shellfish and aquaculture. J. World
Aquac. Soc. 1990, 21, 65-104.
24. Shimizu, Y. Microalgal metabolites: a respective. Ann. Rev. Microbiol. 1996, 50, 431–465.
25. Halsetead, B. W. Poisonous and venomous marine animals of the world. Princeton: Darwin,
1978.
26. Lagos N.; Andrinolo, D. Paralytic shellfish poisoning (PSP): toxicology and kinetics. In: Seafood
and Freshwater Toxins: Pharmacology, Physiology and Detection; Botana, L.M; Ed; Marcel
Dekker: New York, USA, 2000, pp. 203–215.
27. Kao, C. Y. Tetrodotoxin, saxitoxin and their significance in the study of excitation phenomena.
Pharmacol. Rev. 1966, 18, 997-1049.
28. Hill, B. The receptor for tetrodotoxin and saxitoxin: a structural hypothesis. Biophys. J. 1975, 15,
615-619.
29. Kao, C. Y.; Walkwe, S. E. Active groups of saxitoxin and tetrodotoxin as deduced from action of
saxitoxin analogs on frog muscle and squid axon. J. Physiol. 1982, 323, 619-637.
30. Shimizu, Y. Recent progress in marine toxin research. Pure. Appl. Chem. 1980, 54, 1973-1980
31. Numa, S.; Noda, M. Molecular structure of sodium channels. Ann. NY. Acad. Sci. 1986. 479,
338-355.
32. Bricelj, V. M.; Connel, L.; Konoki, K.; Macquarrie, S. P.; Scheuer, T.; Catterall, W. A.; Trainer,
V. L. Sodium channel mutation leading to saxitoxin res
istance in clams increase risk of PSP.
Nature 2005, 434, 763-767.
Mar. Drugs 2008, 6
366
33. Steidinger, K. A. Phytoplankton ecology: A conceptual review based on eastern. Gulf of Mexico
research. CRC Crit. Rev. Microbiol. 1973, 3, 49–67.
34. Baden, D. G. Marine food-borne dinoflagellate toxins. Int. Rev. Cytol. 1983, 82, 99-150.
35. Baden, D. G.; Mende, T. J. Toxicity of two toxins from the Florida red tide marine dinoflagellate,
Gymnodinium breve. Toxicon 1982, 20, 457-461.
36. Poli, M.; Mende, T. J.; Baden, D. G. Brevetoxins, unique activators of voltage-sensitive sodium
channels bind to specific sites in rat brain synaptosomes. Mol. Pharmacol. 1986, 30, 129-135.
37. Baden, D.; Fleming, L. E.; Bean, J. A. Chapter: Marine Toxins. In: Handbook of Clinical
Neurology: Intoxications of the Nervous System Part H. Natural Toxins and Drugs; deWolf, F. A;
Ed.; Elsevier: Amsterdam, 1995; pp. 141-175.
38. Baden, D. G.; Bourdelais, A. J.; Jacocks, H.; Michelliza, S.; Naar, J. Natural and Derivative
Brevetoxins: Historical Background, Multiplicity, and Effects. Environ. Health Persp. 2005,
113.
39. Sagir Ahmed, M. D.; Arakawa, O.; Onoue, Y. Toxicity of cultured Chatonella marina. In:
Harmful Marine Algal Blooms; Lassus, P.; Arzul, G.; Erhard, E.; Gentien, P.; Marcaillou, C; Ed.;
Lavoisier: Paris, 1995, pp. 499-504
40. Khan, S.; Arakawa, O.; Onoue, Y. Neurotoxins in a toxic red tide of Heterosigma akashiwo
(Raphidophyceae) in Kagoshima Bay, Japan. Aquacul. Res. 1997, 28, 9-14.
41. Hallegraeff, G. M.; Munday, B. L.; Baden, D. G.; Whitney, P. L. Chatonnella maria
raphidophyte bloom associated with mortality of cultured bluefin tuna (Thunnus maccoyii) in
south Australia. In:Harmful algae; Reguera, B.; Blanco, J.; Ferandz, M. L.; Wyatt, T. Ed.; Xunta
de Galacia and IOC: Santiago de Compostela, Spain, 1998; pp. 93-96.
42. Kirkpatrick, B.; Fleming, L. E.; Squicciarini, D.; Backer, L. C.; Clark, R.; Abraham,W.; Benson,
J.; Chenge, Y. S.; Johnson, D.; Pierce, R.; Zaias, J.; Bossart, G. D.; Baden, D. G. Literature
review of Florida red tide: Implications for human health effects. Harmful algae, 2004, 3, 99-115
43. Morris, P. D.; Campbell, D. S.; Taylor, T. J.; Freeman, J. I. Clinical and epidemiological features
of neurotoxic shellfish poisoning in North Carolina. Am. J. Public Health, 1991, 81, 4, 471-474
44. Baden, D. G.; Adams, D. J. Brevetoxins: Chemistry, mechanism of action, and methods of
detection. In: Seafood and Freshwater Toxins: Pharmacology, Physiology and Detection; Botana,
L. M; Ed, 2000, Marcel Dekker: New York, pp. 505–532.
45. Baden, D.G. Marine food-born dinoflagellate toxins. Int. Rev. Cytol. 1983, 82, 99-150.
46. Rein, K. S.; Baden, D. G.; Gawley, R. E. Conformational analysis of the sodium channel
modulator, brevetoxin A, comparison with brevetoxin B conformations, and a hypothesis about
the common pharmacophore of the “site” toxins. J. Org. Chem. 1994, 59, 2101-2106.
47. Gallagher, P.; Shinnick-Gallagher, P. Effect of brevetoxin in the rat phrenic nerve diaphragm
preparation. Brit. J. Pharmacol. 1980, 69, 367-372.
48. Halstead, B. W. Poisonous and Venomous Marine Animals of the World. Darwin Press:
Princeton, 1988.
49. Trainer, V. L.; Thomsen, W. J.; Catterall, W. A.; Baden, D. G. Photoaffinity labeling of the
brevetoxin receptor on sodium channels in rat brain synaptosomes. Mol. Pharmacol. 1991, 40,
988-994.
50. Watters, M. R. Organic neurotoxins in seafoods. Clin. Neurol. Neurosurg. 1995, 97, 119-124
Mar. Drugs 2008, 6
367
51. Fleming, L. E.; Baden, D. G. Neurotoxic Shellfish Poisoning: Public Health and Human Health
Effects. White Paper for the Proceedings of the Texas Conference on Neurotoxic Shellfish
Poisoning, Proceedings of the Texas NSP Conference, Corpus Christi (Texas), April, 1998, pp.
27-34.
52. LePage,K. T.; Baden, D. G.; Murray,T. F. Brevetoxin derivatives act as partial agonists at
neurotoxin site 5 on the voltage-gated Na
+
channel. Brain Res. 2003, 959, 120-127
53. Guzman-Perez, S. E.; Park, D. L. Ciguatera toxins: Chemistry and diction. In: Seafood and
Freshwater Toxins: Pharmacology, Physiology and Detection; Botana, L., Ed; Marcel Dekker:
New York, 2000; pp. 401-418.
54. Terao, K. Ciguatera toxins: toxicology. In: Seafood and Freshwater Toxins: Pharmacology,
Physiology and Detection; Botana, L., Ed; Marcel Dekker: New York, 2000; pp. 449-472.
55. Yasumoto, T.; Nakajima, I.; Bagnis, R.; Adachi, R. Finding of a dinoflagellate as a likely culprit
of ciguatera. Jpn. Soc. Sci. Fish. 1977, 43, 1021–1026.
56. Legrand, A.M. 1998. Ciguatera toxins: origin, transfer through the food chain and toxicity to
humans. In: Harmful Algae, Proceedings of the VIII International Conference on Harmful Algae;
Reguera, B.; Blanco, J.; Fernandez, M.; Wyatt, T; Eds., Xunta de Galicia and IOC of UNESCO:
Vigo, Spain, 1999, pp. 39-43.
57. Scheuer, P. J.; Takahashi, W.; Tsutsumi, J.; Yoshida, T. Ciguatoxin: isolation and chemical
nature. Science 1967, 155, 1267-1268.
58. Tachibana, K.; Nukina, M.; John, Y. D.; Scheuer, P. J. Recent developments in the molecular
structure of ciguatoxin. Biol. Bull. 1987, 172, 122-127.
59. Murata, M.; Legrand, A.M.; Ishibashi, Y.; Yasumoto, T. Structures and configurations of
ciguatoxin from the moray eel Gymnothorax javanicus and its likely precursor from the
dinoflagellate Gambierdiscus toxicus. J. Am. Chem. Soc. 1990, 112, 4380–4386.
60. Lewis, R. J.; Vernoux, J. -P.; Brereton, I. M. Structure of Caribbean ciguatoxin isolated from
Caranx latus. J. Am. Chem. Soc. 1998, 120, 5914–5920.
61. Lewis, R. J.; Molgo, J.; Ada
ms, D. J. Pharmacology of toxins involved in ciguatera and related
fish poisonings. In: Seafood and Freshwater Toxins: Pharmacology, Physiology and Detection;
Botana, L., Ed.; Marcel Dekker, Inc., New York, 2000. pp. 419–447.
62. Cameron J: Effects of ciguatoxin on nerve excitability in rats (part I). J. Neurol. Sci. 1991, 101,
87-92.
63. Mattei, C.; Dechraoui, M. Y.; Molgó, J.; Meunier, F. A.; Legrand, A. M.; Benoit, E. Neurotoxins
targetting receptor site 5 of voltage-dependent sodium channels increase the nodal volume of
myelinated axons. J. Neurosci. Res. 1999, 55, 666–673.
64. Allsop, J. L.; Martini, L.; Lebris, H.; Pollard, J.; Walsh, J.; Hodgkinson, S. Neurologic
manifestations of ciguatera. 3 cases with a neurophysiologic study and examination of one nerve
biopsy. Rev. Neurol. 1986, 142, 590–597.
65. Cameron, J. Electrophysiological studies on ciguatera poisoning in man (part II). J. Neurol. Sci.
1991, 101, 93-97.
66. Benoit, E. Nodal swelling produced by ciguatoxin-induced selective activation of sodium
channels in myelinated nerve fibers. Neuroscience 1996, 71, 1121-1131.
Mar. Drugs 2008, 6
368
67. Lehane, L.; Lewis, R. J. Ciguatera: recent advances but the risk remains. Int. J. Food Microbiol.
2000, 61, 91–125.
68. Holmes, M.J., Lewis, R.J. Purification characterization of large and small maitotoxins from
cultured Gambierdiscus toxicus. Nat. Toxins 1994, 2, 64–72.
69. Estacion, M. Ciguatera toxins: Mechanism of action and pharmacology of maitotoxin. In:
Seafood and Freshwater Toxins: Pharmacology, Physiology and Detection; Botana, L., Ed.;
Marcel Dekker, Inc., New York, 2000. pp. 473-504
70. Kakizaki, A.; Takahashi, M.; Akagi, H.; Tachikawa, E.; Yamamoto, T.; Taira, E.; Yamakuni T.;
Ohizumi, Y. Ca
2+
channel activating action of maitotoxin in cultured brainstem neurons. Eur. J.
Pharmacol. 2006, 536, 223-231
71. Statake, M.; Ofuji, K.; Naoki, H.; James, K. J.; Furey, A.; McMahon, T. Azaspiracid, a new
marine toxin having unique spiro ring assembles, isolated from Irish mussels, Mytilus edulis. J.
Am. Chem. Soc. 1998, 120, 9967-9968
72. Oufji, K.; Statake, M.; McMahon, T.; Silker, J.; James, K. J.; Naoki, H. Two analogs of
azaspiracid isolated from mussels, Mytilus edulis, involved in human intoxication in Ireland. Nat.
Toxins 1999, 7, 99-102
73. James, K.; Lehane, M.; Moroney, C.; Fernandez-Puente, P.; Statake, M.; Yasumoto, T.
Azaspiracid shellfish poisoning: unusual toxin dynamics in shellfish and the increased risk of
acute human intoxications. Food Addit. Contam. 2002, 19, 555-561.
74. James, K.; Sierra, M. D.; Lehane, M.; Brana Magdalena, A.; Furey, A. Detection of five newly
hydroxyl analogues of azaspiracids in shellfish using multiple tandem mass spectrometry.
Toxicon 2003, 41, 277-283.
75. Ito, E.; Statake, M.; Ofuji, K.; Kurita, N.; McMahon, T.; James, K. Multiple organ damage
caused by a new toxin azaspiracid, isolated from mussels produced in Ireland. Toxicon 2000, 38,
917-930.
76. Alfonso, A.; Roman, Y.; Vieytes, M. R.; Ofuji, K.; Statake, M.; Yasumoto, T.; Botana, L. M.
Azaspiracid-4 inhibits Ca2+ entry by stored operated channels in human T lymphocytes.
Biochem. Pharmacol. 2005, 69, 1627-1636.
77. Suganuma, M.; Fujiki, H.; Suguri, H.; Yoshizawa, S.; Hirota, M.; Nakayasu, M.; Ojika, M.;
Wakamatsu, K.; Yamada, K.; Sugimura, T. Specific binding of okadaic acid, a new tumor
promoter. Proc. Natl. Acad. Sci. USA 1988, 85, 1768-1771.
78. Ito, E.; Statake, M.; Ofuji, K.; Higashi, M.; Harigaya, K.; McMahon, T. Chronic effects in mice
caused by oral administration of sublethal doses of azaspiracid, a new marine toxin isolated from
mussels. Toxicon 2002, 40, 193-202.
79. Murata, M.; Kumagai, M.; Lee, J. S.; Yasumoto, T. Isolation and structure of yessotoxin, a novel
polyether compound implicated in diarrheic shellfish poisoning. Tetrahedron Lett. 1987, 28,
5869-5872.
80. Draisci, R.;, Ferretti, E.; Palleschi, L; Marchiafava, C.; Poletti,R.; Milandri, A.; Ceredi, A.;
Pompei, M. High levels of yessotoxin in mussels and presence of yessotoxin and
homoyessotoxin in dinoflagellates of the Adriatic Sea. Toxicon 1999, 37, 1187–1193.
Mar. Drugs 2008, 6
369
81. Paz, B.; Riobó, P.; Luisa Fernández, M.; Fraga, S,; Franco, J. M. Production and release of
yessotoxins by the dinoflagellates Protoceratium reticulatum and Lingulodinium polyedrum in
culture. Toxicon 2004, 44, 251-258
82. Satake, M.; Ichimura, T.; Sekiguchi, K.; Yoshimatsu, S.; Oshima, Y. Confirmation of yessotoxin
and 45, 46, 47-trinoryessotoxin production by Protoceratium reticulatum collected in Japan. Nat.
Toxins 1999, 7, 147-150.
83. Rhodes, L.; McNabb, P.; de Salas, M.; Briggs, L.; Beuzenberg, V.; Gladstone, M.; Yessotoxin
production by Gonyaulax spinifera. Harmful Algae 2006, 5, 148–155.
84. Satake, M.; Terasawa, K.; Kadowaki, Y.; Yasumoto, T. Relative configuration of yessotoxin and
isolation of two new analogs from toxic scallops. Tetrahedron Lett. 1996, 37, 5955–5958.
85. Satake, M.; Viviani, R.; Yasumoto, T. Yessotoxin in mussels of the northern Adriatic Sea.
Toxicon 1997, 35, 177–183.
86. Ciminiello, P.; Fattorusso, E.; Forino, M.; Poletti, R. 42,43,44,45,46,47,55-
Heptanor-41-oxohomoyessotoxin, a new biotoxin from mussels of the northern Adriatic sea,
Chem. Res. Toxicol. 2001, 14, 596–599.
87. Ciminiello, P.; Dell’Aversano, C.; Fattorusso, E.; Forino, M.; Magno, S.; Poletti, R. Direct
detection of yessotoxin and its analogues by liquid chromatography coupled with electrospray
ion trap mass spectrometry. J. Chromatogr. A, 2002, 968, 61-69
88. Tarao, K.; Ito, E.; Oarada, M.; Murata, M.; Yasumoto, T. Histopathiological studies on
experimental marine toxin poisoning-5. The effects in mice of yessotoxin isolated from
Patinopecten yessoessis and a desulfated derivative. Toxicon 1990, 28, 1095-1104.
89. Aune, T.; Sørby, R.; Yasumoto, T.; Ramstad, H.; Landsverk, T. Comparison of oral and
intraperitoneal toxicity of yessotoxin towards mice. Toxicon 2002, 40, 77–82.
90. Tubaro, A.; Sosa, S.; Carbonatto, M.; Altinier, G.; Vita, F.; Melato, M.; Satake, M.; Yasumoto, T.
Oral and intraperitoneal acute toxicity studies of yessotoxin and homoyessotoxins in mice.
Toxicon 2003, 41, 783–792.
91. Tubaro, A.; Sosa, S.; Altinier, G.; Soranzo, M. R.; Satake, M;, Della Loggia, R.; Yasumoto, T.
Short-term toxicity of homoyessotoxins, yessotoxin and okadaic acid in mice. Toxicon 2004, 43,
439–445.
92. Wolf, L. W.; Laregina, M. C.; Tolbert, D. L. A behavioural study of the development of
hereditary cerebellar ataxia in the shaker rat mutant. Behav. Brain Res. 1996, 75, 67-81.
93. Franchini, A.; Marchesini, E.; Poletti, R.; Ottaviani, E. Acute toxic effect of the algal yessotoxin
on Purkinje cells from the cerebellum of Swiss CDq mice. Toxicon 2004, 43, 347-352.
94. Perez-Gomez, A.; Ferrero-Gutierrez, A.; Novelli, A.; Franco, J. M.; Paz, B,; Fernandez-Sanchze,
M. T. Potent neurotoxic action of the shellfish biotoxin yessotoxin on cultured cerebellar neurons.
Toxicol. Sci. 2006, 90, 168-177.
95. De la Rosa, L. A.; Alfonso, A.; Vieytes, M. R.; Botana, L. M. Modulation of cytosolic calcium
levels of human lymphocytes by yessotoxin, a novel marine phycotoxin. Biochem. Pharmacol.
2001, 61, 827-833.
96. Moore, R. E.; Scheuer, P. J. Palytoxin: a new marine toxin from a coelenterate. Science 1971,
172, 495-498
Mar. Drugs 2008, 6
370
97. Penna, A.; Vila, M.; Fraga, S.; Giacobbe, M. G.; Andreoni, F.; Riobó, P.; Veronesi, C.
Characterization of Ostreopsis and Coolia (Dinophyceae) isolates in the western Mediterranean
Sea based on morphology, toxicity, and internal transcribed spacer 5.8S rDNA sequences. J.
Phycol. 2005, 41, 212–225.
98. Gallitelli, M.; Ungaro, N.; Addante, L. M.; Gentiloni, N.; Sabbà, C. Respiratory illness as a
reaction to tropical algal blooms occurring in a temperate climate, JAMA. 2005, 293, 2599–2600.
99. Sansoni, G.; Borghini, B.; Camici, G.; Casotti, M.; Righini, P.; Rustighi, C.; Fioriture algali di
Ostreopsis Ovata (Gonyaulacales: Dinophyceae): Unproblema emergente. Biol. Ambientale
2003, 17, 17–23.
100. Ciminiello, P.; Dell’Aversano, C.; Fattorusso, E.; Forino, M.; Magno, G. S.; Tartaglione, L.;
Grillo, C.; Melchiorre, N. The Genoa 2005 outbreak: Determination of putative palytoxin in
Mediterranean Ostreopsis ovata by a new liquid chromatography tandem mass spectrometry
method, Anal. Chem. 2006, 78, 6153–6159.
101. Riobó, P.; Paz, B.; Franco, J. M. Analysis of palytox-in- like in Ostreopsis cultures by liquid
chromatography with precolumn derivatization and fluorescence detection, Anal. Chim. Acta
2006, 566, 217–223.
102. Monti, M.; Minocci, M.; Beran, A.; Ivena, L. First record of Ostreopsis cfr. Ovata on
macroalgae in the northern Adriatic. Sea, Mar. Pol. Bull. 2007, 54, 598–601.
103. Alcala, A.C.; Alcala, L.C.; Garth, J.S.; Yasumura, D.; Yasumoto, T. Human fatality due to
ingestion of the crab Demania reynaudii contained a palytoxin-like toxin. Toxicon 1998, 26,
105–107.
104. Granéli, E.; Ferreira, C. E. L.; Yasumoto, T.; Rodrigues, E.; Neves, M. H. B. Sea urchins
poisoning by the benthic dinoflagellate Ostreopsis ovata on the Brazilian coast. In: Book of
Abstracts of Xth International Conference on Harmful Algae, Florida, 2002.
105. Fukui, M.; Murata, M.; Inoue, A.; Gawel, M.; Yasumoto, T. Occurrence of palytoxin in the
Trigger fish Melichtys vidua. Toxicon 1987, 25, 1121–1124.
106. Onuma, Y.; Satake, M.; Ukena, T.; Roux, J.; Chanteau, S.; Rasolofonirina, N.; Ratsimaloto, N.;
Naoki, H.; Yasumoto, T. Identification of putative palytoxin as the cause of clupeotoxism.
Toxicon 1999, 37, 55–65.
107. Taniyama, S.; Arakawa, O.; Terada, M.; Nishio, S.; Takatani, T.; Mahmud, Y.; Noguchi, T.
Ostreopsis sp., a possible origin of palytoxin (PTX) in parrotfish Scarus ovifrons. Toxicon 2003,
42, 29–33.
108. Moore, R. E. Bartolini, G,; Barchi, J.; Bothmer-By, A. A.; Dadok, J.; Ford, J. Absolute
stereochemistry of palytoxin. J. Am. Chem. Soc. 1982, 104, 3776-3779
109. Bottinger, H,; Beress, L.; Habermann, E. Involvement of (Na
+
, K
+
-ATPase) in binding and
actions of palytoxin on human erythrocytes. Biochim. Biophys. Acta 1986, 861, 164–176.
110. Habermann, E. Palytoxin acts through the Na
+
, K
+
-ATPase. Toxicon 1989, 27, 1171–1187.
111. Kim, S. Y.; Marx, K. A.; Wu, C.H. Involvement of the Na
+
, K
+
-ATPase in the introduction of
ion channels by palytoxin. Naunyn-Schmiedeberg’s Arch. Pharmacol. 1995, 351, 542– 554.
112. Hirsh, J. K.; Wu, C. H. Palytoxin-induced single-channel currents from the sodium pump
synthesized by in vitro expression. Toxicon 1997, 35, 169-176
Mar. Drugs 2008, 6
371
113. Scheiner-Bobis, G.; Meyer zu Heringdorf, D.; Christ, M.; Habermann, E. Palytoxin induces K
+
efflux from yeast cells expressing the mammalian sodium pump. Mol. Pharmacol. 1994, 45,
1132– 1136.
114. Habermann, E.; Laux, M. Depolarization increases inositol phosphate production in a particulate
preparation from rat brain. Naunyn-Schmiederberg’s Arch. Pharmac. 1986, 334, l-15.
115. Levine, L.; Fujiki, H. Stimulation of arachidonic acid metabolism by different types of tumor
promoters. Carcinogenesis 1985, 6, 1631-1635.
116. Frelin C.; Vigne, P.; Breittmayer, J. P. Mechanism of the cardiotoxic action of palytoxin. Mol.
Pharmacol. 1991, 38, 904-909.
117. Yoshizumi, M.; Houchi, H.; Ishimura, Y.; Masuda, Y.; Morita, K.; Oka, M. Mechanism of
palytoxin induced Na
+
influx into cultured bovine adrenal chromaffin cells: possible involvement
of Na
+
/H
+
exchange system. Neurosci. Left. 1991, 130, 103-l 06.
118. Satoh, E.; Nakazato, Y. Mode of action of palytoxin on the release of acetylcholine from rat
cerebrocortical synaptosomes. J. Neurochem. 1991, 57, 1276-1280.
119. Tsumuraya, T.; Fujii, I; Inoue, M.; Tatami, A.; Miyazaki, K.; Hirama, M. Production of
monoclonal antibodies for sandwich immunoassay detection of ciguatoxin 51-hydroxyCTX3C.
Toxicon 2006, 48, 287-294
120. Ishikawa, Y; Nishiyama, S. Synthesis of the BCD ring system of azaspiracid: construction of the
trispiro ring structure by the thioether approach. Tetrahedron Lett. 2004, 45, 351-354
121. Miles, C. O.; Samdal, I. A; Aasen, J. A. G.; Jensen, D. J.; Quilliam, M. A.; Petersen, D.; Briggs, L.
M.; Wilkins, A. L.; Rise, F.; Cooney, J. M.; MacKenzie, A. L.. Evidence for numerous analogs of
yessotoxin in Protoceratium reticulatum. Harmful Algae 2005, 6, 1075-1091
122. Cha, J. K.; Christ, W. J.; Finan, J. M.; Fujiko, H.; Kishi, Y.; Klein, L. L.; Ko, S. S.; Leder, J.;
McWhorter Jr, W. W.; Pfaff, K. P.; Yonaga, M.; Uemura, D.; Hirata, Y. Stereochemistry of
palytoxin. Complete structure. J. Am. Chem. Soc. 1982, 104, 7369-7371.
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... Dinophysis acuminata and Prorocentrum minimum). Dinoflagellates are responsible for the majority of toxic HA blooms (Sopanen et al., 2011) and are often associated with major environmental and economic issues (Hallegraeff, 1993;Anderson et al., 2012;Hallegraeff et al., 2021) and causing disease and death in a variety of marine animals, including fish, seabirds, and mammals (Wang, 2008;Jensen et al., 2015;Kershaw et al., 2021). ...
... HA toxins will not necessarily have a significant impact on invertebrates, including crustaceans and bivalves, but they may accumulate within their tissues and transmit toxins to vertebrates higher up the food chain. However, HA can strongly impact vertebrates, such as fish, birds, marine mammals and humans (Robineau et al., 1991;Durbin et al., 2002;Doucette et al., 2006;Wang et al., 2008;Fire et al., 2021;Kershaw et al., 2021;Marampouti et al., 2021). The decentralization of the invertebrate nervous system compared to vertebrates is one of the possible reasons that result in this difference (Turner, 2014). ...
... Saxitoxins inhibit nerve transmission by blocking watersoluble sodium channels (Luckas, Erler, and Krock, 2015). The consumption of shellfish contaminated with PSP toxins can cause difficulty in breathing, gastrointestinal problems, and a sense of dissociation followed by complete paralysis in humans and other vertebrates (Wang, 2008); however, how PSP toxin exposure/consumption affects invertebrate fitness remains unclear. ...
Thesis
Copepods form an important link between phytoplankton and higher trophic levels. Several species of phytoplankton, including dinoflagellates of the genus Alexandrium, produce neurotoxins commonly known as paralytic shellfish toxins (PSTs). The toxins from harmful algae (HA) may impact copepod survival, eeding, and fitness by acting as a feeding deterrent and/or by causing physical incapacitation. However, copepods may be able to overcome these toxic effects and/or become tolerant to toxicity by partial metabolism. Published information on how HA affect survival, feeding and other physiological processes in opepods are difficult to compare due to the different concentrations of HA used as food, the level of toxins in the food, and the various responses measured on different copepod species from different locations. Very few experiments have examined how HA toxins influence the survival, feeding and fecundity of copepods within UK waters. This thesis aims to address this knowledge gap whilst also choosing organisms of wider geographical relevance. This study examined the effects of a toxin-producing dinoflagellate, Alexandrium catenella, on two physiologically different copepods: Acartia tonsa, a pelagic coastal copepod that is found in the UK and other coastal waters including Northern & Southern America and Australia, and Calanus helgolandicus, which is spread across the North East Atlantic with high numbers on the European shelf and in oceanic waters. In Chapter 3, short-term (24 h) survival and feeding experiments revealed that adult female A. tonsa can survive exposure to field-recorded bloom concentrations of toxic A. catenella. Survival only decreased when exposure levels exceed reported environmental concentrations by two orders of magnitude. The lethal median concentration (LC50) was 12.45 ng STX eq L−1. Ingestion rates were higher when offered A. catenella in the absence of alternative prey, potentially suggesting compensatory feeding. A. tonsa actively selected non-toxic Rhodomonas sp. over toxic A. catenella when offered a mixed diet. Chapter 4 demonstrated that the survival of female A. tonsa is not affected by prolonged (10 days) exposure to toxic A. catenella. However, additional feeding and egg production experiments suggested that whilst A. tonsa can obtain enough energy from ingesting toxic A. catenella to survive, it suffers reproductive impairment when feeding on this prey alone. In Chapter 5, C. helgolandicus showed a decrease in feeding rate when feeding on toxic A. catenella compared to when feeding on the non-toxic congener, Alexandrium tamarense. On the other hand, the egg production and hatching success rates were not affected by the relative abundance of toxic A. catenella and non-toxic A. tamarense in diet, suggesting they may have used biomass reserves to sustain egg production. Body toxin analysis of C. helgolandicus showed they may bioaccumulate toxins in their bodies; however, the retention efficiency was very low. Full toxin profiles for A. catenella, including 8 to 12 PSTs, are presented in all experiments. This study furthers our understanding of PST-producing HA-copepod interactions, and how they may be affected by the increased frequency and magnitude of HA blooms.
... Phytoplankton toxins are mostly neurotoxins with various chemical structures, ranging from comparatively simple alkaloids and amino acids to polyketides, a family of extremely diverse compound structures and toxic effects. In addition, maitotoxin and palytoxin are toxins generated by the dinoflagellates Ostreopsis siamensis and Gambierdiscus toxicus [11]. Toxins accumulate in filterfeeding fish and shellfish, causing PSP, ASP, DSP, CFP, and azaspiracid shellfish poisoning (AZP). ...
... In addition, these toxins exhibit cancer-causing properties and are associated with other stress-related diseases. Alexandrium, Gymnodinium, and Pyrodinium are toxin-producing dinoflagellates [11]. Their toxins, disease-causing clinical symptoms, and potential targets, including molecular mechanisms, are summarized in (Table 2). ...
... In humans, the lethal oral dose ranges from 1 to 4 mg, depending on the sex and physiological state of the patient. It is quickly absorbed and eliminated via the urine after passing through the intestinal tract [11]. ...
Article
Full-text available
Phytoplankton are photosynthetic microorganisms in aquatic environments that produce many bioactive substances. However, some of them are toxic to aquatic organisms via filter-feeding and are even poisonous to humans through the food chain. Human poisoning from these substances and their serious long-term consequences have resulted in several health threats, including cancer, skin disorders, and other diseases, which have been frequently documented. Seafood poisoning disorders triggered by phytoplankton toxins include paralytic shellfish poisoning (PSP), neurotoxic shellfish poisoning (NSP), amnesic shellfish poisoning (ASP), diarrheic shellfish poisoning (DSP), ciguatera fish poisoning (CFP), and azaspiracid shellfish poisoning (AZP). Accordingly, identifying harmful shellfish poisoning and toxin-producing species and their detrimental effects is urgently required. Although the harmful effects of these toxins are well documented, their possible modes of action are insufficiently understood in terms of clinical symptoms. In this review, we summarize the current state of knowledge regarding phytoplankton toxins and their detrimental consequences, including tumor-promoting activity. The structure, source, and clinical symptoms caused by these toxins, as well as their molecular mechanisms of action on voltage-gated ion channels, are briefly discussed. Moreover, the possible stress-associated reactive oxygen species (ROS)-related modes of action are summarized. Finally, we describe the toxic effects of phytoplankton toxins and discuss future research in the field of stress-associated ROS-related toxicity. Moreover, these toxins can also be used in different pharmacological prospects and can be established as a potent pharmacophore in the near future.
... Phytoplankton are responsible for the production of harmful toxins [14][15][16]. Although phytoplankton toxins can be hazardous to aquatic ecosystems and human health, some aquatic organisms are not affected by the toxins and may even contribute to several biomedical applications [17]. Not only cancer, but also diabetes, inflammation, and ROS-related diseases are among the most common health concerns in the United States and other countries, and no satisfactory treatment strategies are currently available [1,18]. ...
... Dinoflagellates are unicellular and planktonic and are a promising source of biologically active toxins that have an impact on the safety of seafood and human health. Due to HABs, dinoflagellates have been identified as potent natural physiologically active toxin makers in marine environments [17]. The dinoflagellate toxin not only harms the marine environment, but it is also detrimental to economic activities (such as aquaculture, fisheries, and tourism) [119]. ...
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Phytoplankton are prominent organisms that contain numerous bioactive substances and secondary metabolites, including toxins, which can be valuable to pharmaceutical, nutraceutical, and biotechnological industries. Studies on toxins produced by phytoplankton such as cyanobacteria, diatoms, and dinoflagellates have become more prevalent in recent years and have sparked much interest in this field of research. Because of their richness and complexity, they have great potential as medicinal remedies and biological exploratory probes. Unfortunately, such toxins are still at the preclinical and clinical stages of development. Phytoplankton toxins are harmful to other organisms and are hazardous to animals and human health. However, they may be effective as therapeutic pharmacological agents for numerous disorders, including dyslipidemia, obesity, cancer, diabetes, and hypertension. In this review, we have focused on the properties of different toxins produced by phytoplankton, as well as their beneficial effects and potential biomedical applications. The anticancer properties exhibited by phytoplankton toxins are mainly attributed to their apoptotic effects. As a result, phytoplankton toxins are a promising strategy for avoiding postponement or cancer treatment. Moreover, they also displayed promising applications in other ailments and diseases such as Alzheimer’s disease, diabetes, AIDS, fungal, bacterial, schizophrenia, inflammation, allergy, osteoporosis, asthma, and pain. Preclinical and clinical applications of phytoplankton toxins, as well as future directi
... Dinoflagellates make a variety of natural products that have largely been identified based on their impact to human and animal health [1][2][3][4]. The actual biological and/or ecological roles are largely unknown and require further study. ...
... In many ways, this study is a bridge between dinoflagellate biology, focusing on ecology and species diversity, and natural product research, a biochemical approach to discovering and harnessing useful compounds. This marriage seems a foregone conclusion given that dinoflagellates make compounds that affect human health negatively [4] but potentially positively as therapeutic agents, with neosaxitoxin being the first phycotoxin to be used clinically [68]. The difficult biology of dinoflagellates has made this area of research slow-moving although with the production of the polyunsaturated fatty acid DHA from Crypthecodinium cohnii [69] and the subsequent efforts for genetic engineering [60] being a notable exception. ...
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Photosynthetic dinoflagellates synthesize many toxic but also potential therapeutic compounds therapeutics via polyketide/non-ribosomal peptide synthesis, a common means of producing natural products in bacteria and fungi. Although canonical genes are identifiable in dinoflagellate transcriptomes, the biosynthetic pathways are obfuscated by high copy numbers and fractured synteny. This study focuses on the carrier domains that scaffold natural product synthesis (thiolation domains) and the phosphopantetheinyl transferases (PPTases) that thiolate these carriers. We replaced the thiolation domain of the indigoidine producing BpsA gene from Streptomyces lavendulae with those of three multidomain dinoflagellate transcripts and coexpressed these constructs with each of three dinoflagellate PPTases looking for specific pairings that would identify distinct pathways. Surprisingly, all three PPTases were able to activate all the thiolation domains from one transcript, although with differing levels of indigoidine produced, demonstrating an unusual lack of specificity. Unfortunately, constructs with the remaining thiolation domains produced almost no indigoidine and the thiolation domain for lipid synthesis could not be expressed in E. coli. These results combined with inconsistent protein expression for different PPTase/thiolation domain pairings present technical hurdles for future work. Despite these challenges, expression of catalytically active dinoflagellate proteins in E. coli is a novel and useful tool going forward.
... Over the past few decades, substantial research effort has been devoted to Gambierdiscus and its toxins [16][17][18], and great advancements have been made in deciphering its taxonomy, phylogenetics, geographic distribution, toxin detection method, biosynthesis, toxicology, and pharmacology [19][20][21][22]. Notably, the occurrence and geographic distribution of CFP have undergone a considerable expansion due to intensive anthropogenic activities and global climate change, rendering it a worldwide concern [23]. ...
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Gambierdiscus is a dinoflagellate genus widely distributed throughout tropical and subtropical regions. Some members of this genus can produce a group of potent polycyclic polyether neurotoxins responsible for ciguatera fish poisoning (CFP), one of the most significant food-borne illnesses associated with fish consumption. Ciguatoxins and maitotoxins, the two major toxins produced by Gambierdiscus, act on voltage-gated channels and TRPA1 receptors, consequently leading to poisoning and even death in both humans and animals. Over the past few decades, the occurrence and geographic distribution of CFP have undergone a significant expansion due to intensive anthropogenic activities and global climate change, which results in more human illness, a greater public health impact, and larger economic losses. The global spread of CFP has led to Gambierdiscus and its toxins being considered an environmental and human health concern worldwide. In this review, we seek to provide an overview of recent advances in the field of Gambierdiscus and its associated toxins based on the existing literature combined with re-analyses of current data. The taxonomy, phylogenetics, geographic distribution, environmental regulation, toxin detection method, toxin biosynthesis, and pharmacology and toxicology of Gambierdiscus are summarized and discussed. We also highlight future perspectives on Gambierdiscus and its associated toxins.
... Several microalgae are known to secrete phycotoxins. In particular dinoflagellates are known as a major source of toxins in the marine environment (Wang, 2008). These toxins, including the alkaloid saxitoxin that is considered the most toxic among them, have been associated with neurotoxicity. ...
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Microalgae comprise a phylogenetically very diverse group of photosynthetic unicellular pro‐ and eukaryotic organisms growing in marine and other aquatic environments. While they are well explored for the generation of biofuels, their potential as a source of antimicrobial and prebiotic substances have recently received increasing interest. Within this framework, microalgae may offer solutions to the societal challenge we face, concerning the lack of antibiotics treating the growing level of antimicrobial resistant bacteria and fungi in clinical settings. While the vast majority of microalgae and their associated microbiota remain unstudied, they may be a fascinating and rewarding source for novel and more sustainable antimicrobials and alternative molecules and compounds. In this review, we present an overview of the current knowledge on health benefits of microalgae and their associated microbiota. Finally, we describe remaining issues and limitation, and suggest several promising research potentials that should be given attention. Microalgae may offer solutions to the societal challenge we face concerning the lack of antibiotics treating the growing level of antimicrobial resistant bacteria and fungi in clinical and industrial settings. While the vast majority of microalgae and their associated microbiota are unstudied, they may be a fascinating and rewarding source for novel and more sustainable antimicrobials and alternative molecules and compounds. In this review we present an overview of the current knowledge on health benefits of microalgae and their microbiota.
... Nevertheless, dinoflagellates can also cause massive and persistent harmful algal blooms (HABs) that pose a threat to other organisms in the environment [9]. In fact, dinoflagellates are among the most toxigenic HAB species [9]; they are able to produce a wide range of compounds that can be bioaccumulated through the food web to cause disease and death of marine organisms and negatively impact human health [10,11]. The HAB dinoflagellate Karlodinium veneficum is a mixotrophic species that has caused harmful algal blooms worldwide for decades [12]. ...
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... Their toxins (2022) 1-17 4 are among the most powerful natural poisons known. Toxic species are normally existing in low densities with no environmental or human health influences; however, at high cell density, they can be ingested by filter-feeding shellfish, zooplankton, and herbivorous fishes, leading to bioaccumulation and biomagnification of toxic chemicals in various organisms at each trophic level of the food chain, causing multiple adverse impacts [16]. The algal toxin has been reported to be responsible for more than 50,000 intoxication incidents per year, with an overall death rate of 1.5% on a worldwide scale [17]. ...
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... Dinoflagellates are a group of protists comprised of ~2,400 modern species [19] that cause the majority of marine harmful algal blooms (HABs) [20], producing a variety of toxins that threaten the public and ecosystem health [21,22], and also support the growth of coral reefs due to endosymbiotic existence within corals [23]. ...
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The extraordinary chemical diversity seen in the cyanobacteria (blue-green algae) is especially pronounced in the ubiquitous tropical marine species, Lyngbya majuscula. The gene clusters responsible for the production of some of the secondary metabolites have recently been elucidated. The clinoflagellates, which are lower eukaryotic algae, also demonstrate chemical diversity and produce unique polycyclic ethers of polyketide origin. A new mechanism for the formation of the truncated polyketide backbones has recently been proposed. The toxicogenicity of clinoflagellates of the genus Pfiesteria has been the focus of controversy - are they 'killer organisms', as alleged? A recent investigation of Pfiesteria genes seems to rule out the presence of polyketide synthase, which is the gene responsible for the production of most dinoflagellate toxins.
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