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1.
Toxicon ; 184: 215-228, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32593754

RESUMO

An assessment of the major pigments and neurotoxins and a description of the phytoplankton community were carried out within the coastal region of Rio de Janeiro State (Brazil), during winter and the following spring of 2018. Overall, six stations were investigated for oceanographic conditions (with CTD casts). Filtered water samples were used to estimate the chlorophyll a (CHL-a), carotenoids (CAR), and phycobiliproteins (PHY) using UV-Vis spectrophotometry, as well as the quantification of saxitoxins (STX) and domoic acid (DA), through High Performance Liquid Chromatography (HPLC). Planktonic organisms were counted using sedimentation chambers of different volumes and an inverted microscope. A cluster analysis, SIMPER, and ANOSIM were applied to the phytoplankton data along with diversity indexes, and non-parametric statistics to phycotoxins and pigments. There was a significant difference between the winter and spring phytoplankton community, associated with the mixed layer depth (r2 = -0.626, p < 0.05) and temperature (r2 = 0.641, p < 0.05). Phytoplankton biomass and C:CHL-a indicated a higher production during the winter than in spring, with the potentially toxic genus Pseudo-nitzschia responsible for 12.79% of autotrophic abundance (SIMPER output). Pigments showed a slight increase in CAR during spring, while PHY remained at trace concentrations. Both the DA and STX were quantified in winter and spring, but with significant differences only for STX between the sampling periods. Among the 71 taxa, 11 were identified as potentially toxic with an emphasis on STX-producing dinoflagellates and cyanobacteria, such as Alexandrium sp., Gymnodinium spp. along with Trichodesmium spp. Season-related environmental variability may be the major driving force modulating the mixed assemblage of species that support different levels of phycotoxins.


Assuntos
Monitoramento Ambiental , Toxinas Marinhas/toxicidade , Fitoplâncton , Biomassa , Brasil , Clorofila A , Cianobactérias , Diatomáceas , Dinoflagelados , Ácido Caínico/análogos & derivados , Toxinas Marinhas/análise , Neurotoxinas , Estações do Ano , Água do Mar , Trichodesmium
2.
Proc Natl Acad Sci U S A ; 117(23): 12799-12805, 2020 06 09.
Artigo em Inglês | MEDLINE | ID: mdl-32457155

RESUMO

Prenylation is a common biological reaction in all domains of life wherein prenyl diphosphate donors transfer prenyl groups onto small molecules as well as large proteins. The enzymes that catalyze these reactions are structurally distinct from ubiquitous terpene cyclases that, instead, assemble terpenes via intramolecular rearrangements of a single substrate. Herein, we report the structure and molecular details of a new family of prenyltransferases from marine algae that repurposes the terpene cyclase structural fold for the N-prenylation of glutamic acid during the biosynthesis of the potent neurochemicals domoic acid and kainic acid. We solved the X-ray crystal structure of the prenyltransferase found in domoic acid biosynthesis, DabA, and show distinct active site binding modifications that remodel the canonical magnesium (Mg2+)-binding motif found in terpene cyclases. We then applied our structural knowledge of DabA and a homologous enzyme from the kainic acid biosynthetic pathway, KabA, to reengineer their isoprene donor specificities (geranyl diphosphate [GPP] versus dimethylallyl diphosphate [DMAPP]) with a single amino acid change. While diatom DabA and seaweed KabA enzymes share a common evolutionary lineage, they are distinct from all other terpene cyclases, suggesting a very distant ancestor to the larger terpene synthase family.


Assuntos
Alquil e Aril Transferases/química , Diatomáceas/enzimologia , Dimetilaliltranstransferase/química , Ácido Caínico/análogos & derivados , Neurotoxinas/biossíntese , Alquil e Aril Transferases/genética , Alquil e Aril Transferases/metabolismo , Substituição de Aminoácidos , Sítios de Ligação , Diatomáceas/metabolismo , Dimetilaliltranstransferase/genética , Dimetilaliltranstransferase/metabolismo , Ácido Glutâmico/metabolismo , Ácido Caínico/metabolismo , Magnésio/metabolismo , Prenilação , Ligação Proteica
3.
Toxicol Appl Pharmacol ; 398: 115027, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32360744

RESUMO

Domoic acid (DA) is a marine algal toxin that causes acute and chronic neurotoxicity in animals and humans. Prenatal exposure to DA has been associated with neuronal damage and cognitive and behavioral deficits in juvenile California sea lions, cynomolgus monkeys and rodents. Yet, the toxicokinetics (TK) of DA during pregnancy and the maternal-fetal disposition of DA have not been fully elucidated. In this study, we investigated the TK before, during, and after pregnancy and the maternal-fetal disposition of DA in 22 cynomolgus monkeys following daily oral doses of 0.075 or 0.15 mg/kg/day of DA. The AUC0-τ of DA was not changed while the renal clearance of DA was increased by 30-90% during and after pregnancy when compared to the pre-pregnancy values. DA was detected in the infant plasma and in the amniotic fluid at delivery. The infant plasma concentrations correlated positively with both the maternal plasma and the amniotic fluid concentrations. The paired infant-to-maternal plasma DA concentration ratios ranged from 0.3 to 0.6 and increased as a function of time which suggests placental efflux and longer apparent fetal half-life than the maternal half-life. The paired amniotic fluid-to-infant plasma DA concentration ratios ranged from 4.5 to 7.5 which indicates significant accumulation of DA in the amniotic fluid. A maternal-fetal TK model was developed to explore the processes that give the observed maternal-fetal disposition of DA. The final model suggests that placental transport and recirculation of DA between the fetus and amniotic fluid are major determining factors of the maternal-fetal TK of DA.


Assuntos
Ácido Caínico/análogos & derivados , Troca Materno-Fetal/fisiologia , Primatas/metabolismo , Líquido Amniótico/metabolismo , Animais , Método Duplo-Cego , Feminino , Feto/metabolismo , Ácido Caínico/metabolismo , Macaca fascicularis/metabolismo , Placenta/metabolismo , Gravidez
4.
PLoS One ; 15(4): e0231902, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32330168

RESUMO

Pseudo-nitzschia is a cosmopolitan genus, some species of which can produce domoic acid (DA), a neurotoxin responsible for the Amnesic Shellfish Poisoning (ASP). In this study, we identified P. subpacifica for the first time in Todos Santos Bay and Manzanillo Bay, in the Mexican Pacific using SEM and molecular methods. Isolates from Todos Santos Bay were cultivated under conditions of phosphate sufficiency and deficiency at 16°C and 22°C to evaluate the production of DA. This toxin was detected in the particulate (DAp) and dissolved (DAd) fractions of the cultures during the exponential and stationary phases of growth of the cultures. The highest DA concentration was detected during the exponential phase grown in cells maintained in P-deficient medium at 16°C (1.14 ± 0.08 ng mL-1 DAd and 4.71 ± 1.11 × 10-5 ng cell-1 of DAp). In P-sufficient cultures DA was higher in cells maintained at 16°C (0.25 ± 0.05 ng mL-1 DAd and 9.41 ± 1.23 × 10-7 ng cell-1 of DAp) than in cells cultured at 22°C. Therefore, we confirm that P. subpacifica can produce DA, especially under P-limited conditions that could be associated with extraordinary oceanographic events such as the 2013-2016 "Blob" in the northeastern Pacific Ocean. This event altered local oceanographic conditions and possibly generated the presence of potential harmful species in areas with economic importance on the Mexican Pacific coast.


Assuntos
Diatomáceas/genética , Diatomáceas/metabolismo , Ácido Caínico/análogos & derivados , Filogenia , Sequência de Bases , Técnicas de Cultura , Diatomáceas/classificação , Ácido Caínico/metabolismo , Laboratórios , Temperatura
5.
Environ Sci Technol ; 54(10): 6073-6081, 2020 05 19.
Artigo em Inglês | MEDLINE | ID: mdl-32302120

RESUMO

Domoic acid (DA), a potent marine toxin, is readily oxidized upon reaction with singlet oxygen (1O2). Detailed product studies revealed that the major singlet oxygenation reaction pathways were the [2 + 2] cycloaddition (60.2%) and ene reactions (39.8%) occurring at the Z double bond. Diene isomerization and [4 + 2] cycloaddition, common for conjugated diene systems, were not observed during the singlet oxygenation of DA. The bimolecular rate constant for the DA reaction with 1O2 determined by competition kinetics was 5.1 × 105 M-1 s-1. Based on the rate constant and steady-state concentrations of 1O2 in surface waters, the environmental half-life of DA due to singlet oxygen-induced transformations is between 5 and 63 days. The 1O2 reaction product mixture of DA did not exhibit significant biological activity based on ELISA studies, indicating that singlet oxygenation could be an important natural detoxification process. The characteristic oxidation products can provide valuable markers for the risk assessment of DA-contaminated natural waters.


Assuntos
Toxinas Marinhas , Oxigênio Singlete , Ácido Caínico/análogos & derivados , Cinética
6.
Harmful Algae ; 90: 101708, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31806164

RESUMO

Within the past few decades, harmful algal blooms (HABs) have occurred frequently in Indonesian waters, resulting in environmental degradation, economic loss and human health problems. So far, HAB related studies mainly addressed ecological traits and species distribution, yet toxin measurements were virtually absent for Indonesian waters. The aim of the present study was to explore variability of the potentially toxic marine diatom genus Pseudo-nitzschia, as well as its neurotoxin domoic acid as a function of environmental conditions in Ambon Bay, eastern Indonesia. Weekly phytoplankton samples, oceanographic (CTD, nutrients) and meteorological (precipitation, wind) parameters were analyzed at 5 stations in the bay during the dry and wet seasons of 2018. Liquid chromatography - tandem mass spectrometry (LC-MS/MS) was used to detect particulate DA (pDA). Vegetative cells of Pseudo-nitzschia spp. and pDA were found in 98.6% and 51.4% of the samples, respectively. pDA levels were low, yet detected throughout the campaign, implying that Ambon Bay might potentially be subject to amnesic shellfish poisoning. The highest levels of both Pseudo-nitzschia spp. cell abundance and pDA were found in the wet season, showing a strong positive correlation between both parameters, compared to the dry season, (r = 0.87 and r = 0.66 (p < 0.01), respectively). Statistical analyses revealed that temperature and mixed layer depth positively correlated with Pseudo-nitzschia spp. and pDA during the dry season, while ammonium showed positive correlations in both seasons. This study represents the first successful investigation of the presence and variability of Pseudo-nitzschia spp. and its neurotoxin DA in Indonesian waters.


Assuntos
Diatomáceas , Cromatografia Líquida , Humanos , Indonésia , Ácido Caínico/análogos & derivados , Espectrometria de Massas em Tandem
7.
Toxicon ; 171: 62-65, 2019 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-31614156

RESUMO

Algal toxins (domoic acid, saxitoxin, okadaic acid) were monitored at seven locations off southern California using Solid Phase Adsorption Toxin Tracking. At least two types of toxins were found at all locations, with co-occurrence of two and three toxins in 12% and 10% of samples, respectively. This study expands our limited understanding of the simultaneous presence of multiple algal toxins along the coast and raises questions regarding the potential health ramifications of such co-occurrences.


Assuntos
Ácido Caínico/análogos & derivados , Ácido Okadáico/análise , Saxitoxina/análise , Adsorção , California , Monitoramento Ambiental , Proliferação Nociva de Algas , Ácido Caínico/análise , Toxinas Marinhas/análise , Água do Mar/química
8.
Mar Drugs ; 17(10)2019 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-31590222

RESUMO

Currently, animal experiments in rodents are the gold standard for developmental neurotoxicity (DNT) investigations; however, testing guidelines for these experiments are insufficient in terms of animal use, time, and costs. Thus, alternative reliable approaches are needed for predicting DNT. We chose rat neural stem cells (rNSC) as a model system, and used a well-known neurotoxin, domoic acid (DA), as a model test chemical to validate the assay. This assay was used to investigate the potential neurotoxic effects of Ochratoxin A (OTA), of which the main target organ is the kidney. However, limited information is available regarding its neurotoxic effects. The effects of DA and OTA on the cytotoxicity and on the degree of differentiation of rat rNSC into astrocytes, neurons, and oligodendrocytes were monitored using cell-specific immunofluorescence staining for undifferentiated rNSC (nestin), neurospheres (nestin and A2B5), neurons (MAP2 clone M13, MAP2 clone AP18, and Doublecortin), astrocytes (GFAP), and oligodendrocytes (A2B5 and mGalc). In the absence of any chemical exposure, approximately 46% of rNSC differentiated into astrocytes and neurons, while 40.0% of the rNSC differentiated into oligodendrocytes. Both non-cytotoxic and cytotoxic concentrations of DA and OTA reduced the differentiation of rNSC into astrocytes, neurons, and oligodendrocytes. Furthermore, a non-cytotoxic nanomolar (0.05 µM) concentration of DA and 0.2 µM of OTA reduced the percentage differentiation of rNSC into astrocytes and neurons. Morphometric analysis showed that the highest concentrations (10 µM) of DA reduced axonal length. These indicate that low, non-cytotoxic concentrations of DA and OTA can interfere with the differentiation of rNSC.


Assuntos
Ácido Caínico/análogos & derivados , Células-Tronco Neurais/efeitos dos fármacos , Síndromes Neurotóxicas/etiologia , Neurotoxinas/efeitos adversos , Ocratoxinas/efeitos adversos , Animais , Astrócitos/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Células Cultivadas , Ácido Caínico/efeitos adversos , Neurônios/efeitos dos fármacos , Oligodendroglia/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley
9.
Harmful Algae ; 86: 55-63, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31358277

RESUMO

The diatom genus Pseudo-nitzschia is a common component of phytoplankton communities in the Gulf of Mexico and is potentially toxic as some species produce the potent neurotoxin domoic acid. The impact of oil and chemical dispersants on Pseudo-nitzschia spp. and domoic acid production have not yet been studied; preliminary findings from a mesocosm experiment suggest this genus may be particularly resilient. A toxicological study was conducted using a colony of Pseudo-nitzschia sp. isolated from a station off the coast of Louisiana in the Gulf of Mexico. The cultures were exposed to a water accommodated fraction (WAF) of oil and a diluted chemically enhanced WAF (DCEWAF) which was a mix of oil and dispersant (20:1). Exposure to WAF induced a lag phase but did not inhibit growth rates once in exponential growth. Cultures grown in DCEWAF did not experience a lag phase but had significantly lower growth rates than the Control and WAF cultures. The cellular quota of domoic acid was higher in cultures treated with DCEWAF and WAF relative to their control values, and half of the domoic acid had leaked out of the cells into the surrounding seawater in the DCEWAF cultures while all the domoic acid remained inside the cells in WAF-treated cultures. These results suggest that the presence of oil could lead to toxic blooms, but that the application of dispersant could decrease bioaccumulation of domoic acid through the food web.


Assuntos
Diatomáceas , Ácido Caínico , Golfo do México , Ácido Caínico/análogos & derivados , Fitoplâncton
10.
Harmful Algae ; 87: 101623, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31349885

RESUMO

As the official control laboratory for marine biotoxins within Great Britain, the Centre for Environment, Fisheries and Aquaculture Science, in conjunction with the Scottish Association for Marine Science, has amassed a decade's worth of data regarding the prevalence of the toxins associated with Amnesic Shellfish Poisoning within British waters. This monitoring involves quantitative HPLC-UV analysis of shellfish domoic acid concentration, the causative toxin for Amnesic Shellfish Poisoning, and water monitoring for Pseudo-nitzschia spp., the phytoplankton genus that produces domoic acid. The data obtained since 2008 indicate that whilst the occurrence of domoic acid in shellfish was generally below the maximum permitted limit of 20 mg/kg, there were a number of toxic episodes that breached this limit. The data showed an increase in the frequency of both domoic acid occurrence and toxic events, although there was considerable annual variability in intensity and geographical location of toxic episodes. A particularly notable increase in domoic acid occurrence in England was observed during 2014. Comparison of Scottish toxin data and Pseudo-nitzschia cell densities during this ten-year period revealed a complex relationship between the two measurements. Whilst the majority of events were associated with blooms, absolute cell densities of Pseudo-nitzschia did not correlate with domoic acid concentrations in shellfish tissue. This is believed to be partly due to the presence of a number of different Pseudo-nitzschia species in the water that can exhibit variable toxin production. These data highlight the requirement for tissue monitoring as part of an effective monitoring programme to protect the consumer, as well as the benefit of more detailed taxonomic discrimination of the Pseudo-nitzschia genus to allow greater accuracy in the prediction of shellfish toxicity.


Assuntos
Bivalves , Toxinas Marinhas , Animais , Inglaterra , Ácido Caínico/análogos & derivados , Frutos do Mar
11.
Environ Toxicol Chem ; 38(10): 2209-2223, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31343776

RESUMO

In the Northern Patagonian gulfs of Argentina (Golfo Nuevo and Golfo San José), blooms of toxigenic microalgae and the detection of their associated phycotoxins are recurrent phenomena. The present study evaluated the transfer of phycotoxins from toxigenic microalgae to mesozooplankton in Golfo Nuevo and Golfo San José throughout an annual cycle (December 2014-2015 and January 2015-2016, respectively). In addition, solid-phase adsorption toxin tracking (SPATT) samplers were deployed for the first time in these gulfs, to estimate the occurrence of phycotoxins in the seawater between the phytoplankton samplings. Domoic acid was present throughout the annual cycle in SPATT samplers, whereas no paralytic shellfish poisoning toxins were detected. Ten toxigenic species were identified: Alexandrium catenella, Dinophysis acuminata, Dinophysis acuta, Dinophysis tripos, Dinophysis caudata, Prorocentrum lima, Pseudo-nitzschia australis, Pseudo-nitzschia calliantha, Pseudo-nitzschia fraudulenta, and Pseudo-nitzschia pungens. Lipophilic and hydrophilic toxins were detected in phytoplankton and mesozooplankton from both gulfs. Pseudo-nitzschia spp. were the toxigenic species most frequent in these gulfs. Consequently, domoic acid was the phycotoxin most abundantly detected and transferred to upper trophic levels. Spirolides were detected in phytoplankton and mesozooplankton for the first time in the study area. Likewise, dinophysistoxins were found in mesozooplankton from both gulfs, and this is the first report of the presence of these phycotoxins in zooplankton from the Argentine Sea. The dominance of calanoid copepods indicates that they were the primary vector of phycotoxins in the pelagic trophic web. Environ Toxicol Chem 2019;38:2209-2223. © 2019 SETAC.


Assuntos
Toxinas Marinhas/toxicidade , Microalgas/química , Zooplâncton/metabolismo , Adsorção , Animais , Argentina , Biomassa , Diatomáceas/efeitos dos fármacos , Dinoflagelados/efeitos dos fármacos , Geografia , Ácido Caínico/análogos & derivados , Ácido Caínico/análise , Fitoplâncton/efeitos dos fármacos , Estações do Ano , Água do Mar , Zooplâncton/efeitos dos fármacos
12.
Arch Biochem Biophys ; 671: 52-61, 2019 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-31220431

RESUMO

Kainate receptors play an important role in the brain. They contribute to postsynaptic depolarization, modulate the release of neurotransmitters such as GABA and glutamate, affect the development of the neuronal network. At the same time, their functions depend not only on the type of neuron expressing them but also on their localization (pre- or postsynaptic). It has been shown in present work that activation of kainate receptors by domoic acid stimulates the secretion of both glutamate and GABA. This effect is observed at a concentration of 100 nM. At higher levels (200-500 nM), domoic acid selectively activates a specific population of GABAergic neurons. The peculiarity of these neurons is increased excitability in the network. This phenomenon can be explained by the weak GABA(A)R-mediated inhibition, as well as by the lower activation threshold of voltage-gated channels. Moreover, activation of these GABAergic neurons by domoic acid leads to the suppression of activity in the network under ammonium-induced hyperexcitation. As shown by inhibitory analysis, this effect is mediated by GABA(A) receptors. The obtained data may be of interest since the suppression of hyperexcitation via the selective activation of GABAergic neurons can be considered as a new potential approach to the treatment of diseases accompanied by increased neuronal activity such as epilepsy, ischemia and hepatic encephalopathy.


Assuntos
Neurônios GABAérgicos/efeitos dos fármacos , Ácido Caínico/análogos & derivados , Receptores de Ácido Caínico/metabolismo , Cloreto de Amônio/farmacologia , Animais , Bicuculina/farmacologia , Cálcio/metabolismo , Neurônios GABAérgicos/metabolismo , Ácido Glutâmico/metabolismo , Hipocampo/metabolismo , Ácido Caínico/farmacologia , Ratos Sprague-Dawley , Receptores de GABA-A/metabolismo , Ácido gama-Aminobutírico/metabolismo
13.
Toxicon ; 167: 101-105, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31125620

RESUMO

Domoic acid (DA) or Amnesic Shellfish Poisoning (ASP) produced by the genus Pseudo-nitzschia diatom was investigated in two seasonal periods in fishing areas of Katsuwonus pelamis in the South Atlantic Ocean. Higher DA concentrations were found in spring compared to winter. Pseudo-nitzschia spp. more quantified in winter than in spring, while P. pungens, a species among the most reported for an AD toxic potential, was only found in spring.


Assuntos
Monitoramento Ambiental , Ácido Caínico/análogos & derivados , Fitoplâncton/química , Água do Mar/química , Oceano Atlântico , Brasil , Ácido Caínico/análise , Estações do Ano
14.
Toxins (Basel) ; 11(5)2019 05 23.
Artigo em Inglês | MEDLINE | ID: mdl-31126088

RESUMO

Domoic acid (DA)-producing harmful algal blooms (HABs) have been present at unprecedented geographic extent and duration in recent years causing an increase in contamination of seafood by this common environmental neurotoxin. The toxin is responsible for the neurotoxic illness, amnesic shellfish poisoning (ASP), that is characterized by gastro-intestinal distress, seizures, memory loss, and death. Established seafood safety regulatory limits of 20 µg DA/g shellfish have been relatively successful at protecting human seafood consumers from short-term high-level exposures and episodes of acute ASP. Significant concerns, however, remain regarding the potential impact of repetitive low-level or chronic DA exposure for which there are no protections. Here, we report the novel discovery of a DA-specific antibody in the serum of chronically-exposed tribal shellfish harvesters from a region where DA is commonly detected at low levels in razor clams year-round. The toxin was also detected in tribal shellfish consumers' urine samples confirming systemic DA exposure via consumption of legally-harvested razor clams. The presence of a DA-specific antibody in the serum of human shellfish consumers confirms long-term chronic DA exposure and may be useful as a diagnostic biomarker in a clinical setting. Adverse effects of chronic low-level DA exposure have been previously documented in laboratory animal studies and tribal razor clam consumers, underscoring the potential clinical impact of such a diagnostic biomarker for protecting human health. The discovery of this type of antibody response to chronic DA exposure has broader implications for other environmental neurotoxins of concern.


Assuntos
Anticorpos/sangue , Técnicas Biossensoriais , Ácido Caínico/análogos & derivados , Toxinas Marinhas/imunologia , Neurotoxinas/imunologia , Monitoramento Biológico , Biomarcadores/sangue , Exposição Dietética/análise , Humanos , Índios Norte-Americanos , Ácido Caínico/imunologia , Ácido Caínico/urina , Toxinas Marinhas/urina , Neurotoxinas/urina , Frutos do Mar , Ressonância de Plasmônio de Superfície , Washington
15.
Neurotoxicology ; 72: 114-124, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30826346

RESUMO

Domoic acid (DA) is an excitatory neurotoxin produced by marine algae and responsible for Amnesiac Shellfish Poisoning in humans. Current regulatory limits (˜0.075-0.1 mg/kg/day) protect against acute toxicity, but recent studies suggest that the chronic consumption of DA below the regulatory limit may produce subtle neurotoxicity in adults, including decrements in memory. As DA-algal blooms are increasing in both severity and frequency, we sought to better understand the effects of chronic DA exposure on reproductive and neurobehavioral endpoints in a preclinical nonhuman primate model. To this end, we initiated a long-term study using adult, female Macaca fascicularis monkeys exposed to daily, oral doses of 0.075 or 0.15 mg/kg of DA for a range of 321-381, and 346-554 days, respectively. This time period included a pre-pregnancy, pregnancy, and postpartum period. Throughout these times, trained data collectors observed intentional tremors in some exposed animals during biweekly clinical examinations. The present study explores the basis of this neurobehavioral finding with in vivo imaging techniques, including diffusion tensor magnetic resonance imaging and spectroscopy. Diffusion tensor analyses revealed that, while DA exposed macaques did not significantly differ from controls, increases in DA-related tremors were negatively correlated with fractional anisotropy, a measure of structural integrity, in the internal capsule, fornix, pons, and corpus callosum. Brain concentrations of lactate, a neurochemical closely linked with astrocytes, were also weakly, but positively associated with tremors. These findings are the first documented results suggesting that chronic oral exposure to DA at concentrations near the current human regulatory limit are related to structural and chemical changes in the adult primate brain.


Assuntos
Encéfalo/efeitos dos fármacos , Encéfalo/patologia , Ácido Caínico/análogos & derivados , Toxinas Marinhas/toxicidade , Neurotoxinas/toxicidade , Animais , Imagem de Tensor de Difusão , Feminino , Ácido Caínico/administração & dosagem , Ácido Caínico/toxicidade , Macaca fascicularis , Toxinas Marinhas/administração & dosagem , Neurotoxinas/administração & dosagem , Período Pós-Parto , Gravidez , Tremor/induzido quimicamente
16.
Eur J Pharmacol ; 851: 25-35, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30790558

RESUMO

Alzheimer's disease (AD) is characterized by abnormal accumulation of extracellular amyloid beta protein (Aß) plaques and intracellular neurofibrillary tangles, as well as by a state of chronic inflammation in the central nervous system (CNS). Adverse activation of microglia, the brain immune cells, is believed to contribute to AD pathology including excessive neuronal death. Thus, normalizing immune functions of microglia could slow neurodegeneration, and identification of novel compounds capable of modifying microglial functions is an important goal. Since kainic acid (KA) has been shown to modulate microglial morphology and immune functions, we synthesized six new KA analogs (KAAs) and tested their effects on select microglial functions by using three different cell types as microglia models. Four of the KAAs at low micromolar concentrations inhibited secretion of cytotoxins, monocyte chemoattractant protein (MCP)-1, reactive oxygen species and nitric oxide (NO) by immune-stimulated microglia-like cells. We hypothesize that the effects of the novel KAAs on microglia-like cells are not mediated by KA receptors since their biological activity was distinct from that of KA in all assays performed. A structural similarity search identified aldose reductase (AR) as a potential target for the novel KAAs. This hypothesis was supported by use of AR inhibitor zopolrestat, which abolished the inhibitory effects of two KAAs on microglial secretion of NO. Since the newly developed KAAs inhibited pro-inflammatory and cytotoxic functions of microglia, they should be further investigated for their potential beneficial effect on neuroinflammation and neurodegeneration in AD animal models.


Assuntos
Ácido Caínico/análogos & derivados , Ácido Caínico/farmacologia , Microglia/efeitos dos fármacos , Benzotiazóis/farmacologia , Células HL-60 , Humanos , Microglia/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Óxido Nítrico/metabolismo , Ftalazinas/farmacologia , Espécies Reativas de Oxigênio/metabolismo
17.
BMC Mol Biol ; 20(1): 7, 2019 02 26.
Artigo em Inglês | MEDLINE | ID: mdl-30808304

RESUMO

BACKGROUND: A major cause of phytoplankton mortality is predation by zooplankton. Strategies to avoid grazers have probably played a major role in the evolution of phytoplankton and impacted bloom dynamics and trophic energy transport. Certain species of the genus Pseudo-nitzschia produce the neurotoxin, domoic acid (DA), as a response to the presence of copepod grazers, suggesting that DA is a defense compound. The biosynthesis of DA comprises fusion of two precursors, a C10 isoprenoid geranyl pyrophosphate and L-glutamate. Geranyl pyrophosphate (GPP) may derive from the mevalonate isoprenoid (MEV) pathway in the cytosol or from the methyl-erythritol phosphate (MEP) pathway in the plastid. L-glutamate is suggested to derive from the citric acid cycle. Fragilariopsis, a phylogenetically related but nontoxic genus of diatoms, does not appear to possess a similar defense mechanism. We acquired information on genes involved in biosynthesis, precursor pathways and regulatory functions for DA production in the toxigenic Pseudo-nitzschia seriata, as well as genes involved in responses to grazers to resolve common responses for defense strategies in diatoms. RESULTS: Several genes are expressed in cells of Pseudo-nitzschia when these are exposed to predator cues. No genes are expressed in Fragilariopsis when treated similarly, indicating that the two taxa have evolved different strategies to avoid predation. Genes involved in signal transduction indicate that Pseudo-nitzschia cells receive signals from copepods that transduce cascading molecular precursors leading to the formation of DA. Five out of seven genes in the MEP pathway for synthesis of GPP are upregulated, but none in the conventional MEV pathway. Five genes with known or suggested functions in later steps of DA formation are upregulated. We conclude that no gene regulation supports that L-glutamate derives from the citric acid cycle, and we suggest the proline metabolism to be a downstream precursor. CONCLUSIONS: Pseudo-nitzschia cells, but not Fragilariopsis, receive and respond to copepod cues. The cellular route for the C10 isoprenoid product for biosynthesis of DA arises from the MEP metabolic pathway and we suggest proline metabolism to be a downstream precursor for L-glutamate. We suggest 13 genes with unknown function to be involved in diatom responses to grazers.


Assuntos
Diatomáceas/genética , Diatomáceas/metabolismo , Ácido Caínico/análogos & derivados , Toxinas Marinhas/genética , Toxinas Marinhas/metabolismo , Redes e Vias Metabólicas/genética , Eritritol/análogos & derivados , Eritritol/metabolismo , Herbivoria , Ácido Caínico/metabolismo , Fosfatos de Poli-Isoprenil/metabolismo , Fosfatos Açúcares/metabolismo
18.
Genome Biol Evol ; 11(3): 731-747, 2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30778535

RESUMO

Untangling the functional basis of divergence between closely related species is a step toward understanding species dynamics within communities at both the evolutionary and ecological scales. We investigated cellular (i.e., growth, domoic acid production, and nutrient consumption) and molecular (transcriptomic analyses) responses to varying nutrient concentrations across several strains belonging to three species of the toxic diatom genus Pseudo-nitzschia. Three main results were obtained. First, strains from the same species displayed similar transcriptomic, but not necessarily cellular, responses to the experimental conditions. It showed the importance of considering intraspecific diversity to investigate functional divergence between species. Second, a major exception to the first finding was a strain recently isolated from the natural environment and displaying contrasting gene expression patterns related to cell motility and domoic acid production. This result illustrated the profound modifications that may occur when transferring a cell from the natural to the in vitro environment and asks for future studies to better understand the influence of culture duration and life cycle on expression patterns. Third, transcriptomic responses were more similar between the two species displaying similar ecology in situ, irrespective of the genetic distance. This was especially true for molecular responses related to TCA cycle, photosynthesis, and nitrogen metabolism. However, transcripts related to phosphate uptake were variable between species. It highlighted the importance of considering both overall genetic distance and ecological divergence to explain functional divergence between species.


Assuntos
Evolução Biológica , Diatomáceas/fisiologia , Ácido Caínico/análogos & derivados , Ácido Caínico/metabolismo , Família Multigênica , Nutrientes , Fenótipo
19.
Toxins (Basel) ; 11(2)2019 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-30717167

RESUMO

Domoic acid (DA) is a neurotoxin associated with amnesic shellfish poisoning (ASP). Though LC coupled to tandem mass spectrometry (LC-MS/MS) has become the preferred method for DA determination, traditional sample pretreatment is still labor-intensive. In this study, a simple, efficient and selective method for LC-MS/MS analysis of DA in shellfish was established by optimizing clean-up procedures on a self-assembly immunoaffinity column (IAC). Shellfish was extracted with 75% methanol twice and diluted with phosphate buffered saline (PBS, 1:2). The mixture was purified on IAC as follows: preconditioned with PBS, loaded with sample, washed by 50% MeOH, and eluted with MeOH containing 2% ammonium hydroxide. Concentrated analyte was monitored by multiple reaction monitoring (MRM) using electrospray (ESI) positive ion mode throughout the LC gradient elution. Based on the post-extraction addition method, matrix effects for various shellfish matrices were found to be less than 8%. The developed method was fully validated by choosing mussel as the representative matrix. The method had a limit of detection (LOD) of 0.02 µg·g-1, showed excellent linear correlation in the range of 0.05⁻40 µg·g-1, and obtained ideal recoveries (91⁻94%), intra-day RSDs (6⁻8%) and inter-day RSDs (3⁻6%). The method was successfully applied to DA determination in 59 shellfish samples, with a detection rate of 10% and contaminated content of 0.1⁻14.9 µg·g-1.


Assuntos
Bivalves/química , Contaminação de Alimentos/análise , Ácido Caínico/análogos & derivados , Frutos do Mar/análise , Animais , China , Cromatografia Líquida de Alta Pressão , Ácido Caínico/análise , Espectrometria de Massas por Ionização por Electrospray , Espectrometria de Massas em Tandem
20.
Toxins (Basel) ; 11(2)2019 02 06.
Artigo em Inglês | MEDLINE | ID: mdl-30736356

RESUMO

Some species of the genus Pseudo-nitzschia produce the toxin domoic acid, which causes amnesic shellfish poisoning (ASP). Given that bivalve mollusks are filter feeders, they can accumulate these toxins in their tissues. To elucidate the transcriptional response of the queen scallop Aequipecten opercularis after exposure to domoic acid-producing Pseudo-nitzschia, the digestive gland transcriptome was de novo assembled using an Illumina HiSeq 2000 platform. Then, a differential gene expression analysis was performed. After the assembly, 142,137 unigenes were obtained, and a total of 10,144 genes were differentially expressed in the groups exposed to the toxin. Functional enrichment analysis found that 374 Pfam (protein families database) domains were significantly enriched. The C1q domain, the C-type lectin, the major facilitator superfamily, the immunoglobulin domain, and the cytochrome P450 were among the most enriched Pfam domains. Protein network analysis showed a small number of highly connected nodes involved in specific functions: proteasome components, mitochondrial ribosomal proteins, protein translocases of mitochondrial membranes, cytochromes P450, and glutathione S-transferases. The results suggest that exposure to domoic acid-producing organisms causes oxidative stress and mitochondrial dysfunction. The transcriptional response counteracts these effects with the up-regulation of genes coding for some mitochondrial proteins, proteasome components, and antioxidant enzymes (glutathione S-transferases, thioredoxins, glutaredoxins, and copper/zinc superoxide dismutases).


Assuntos
Trato Gastrointestinal/efeitos dos fármacos , Ácido Caínico/análogos & derivados , Toxinas Marinhas/toxicidade , Pectinidae/efeitos dos fármacos , Transcriptoma/efeitos dos fármacos , Animais , Diatomáceas , Trato Gastrointestinal/metabolismo , Ácido Caínico/toxicidade , Pectinidae/genética , RNA-Seq
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