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Experimental Biology and Medicine... Oct 2016The aim of the study was to investigate the influence of hyperphosphorylation of tau induced by okadaic acid on the expression of nicotinic acetylcholine receptors and...
The aim of the study was to investigate the influence of hyperphosphorylation of tau induced by okadaic acid on the expression of nicotinic acetylcholine receptors and the neurotoxicity of β-amyloid peptide. Primary cultures of neurons isolated from the hippocampus of the brains of neonatal rats were exposed to okadaic acid or/and Aβ1-42 Tau phosphorylated at Ser404 and Ser202, and the protein expressions of α7, α4 and α3 nAChR subunits were quantified by Western blotting, and their corresponding mRNAs by real-time PCR. Superoxide dismutase activity was assayed biochemically and malondialdehyde by thiobarbituric acid-reactive substance. As compared to controls, phosphorylations of tau at Ser404 and Ser202 in the neurons were elevated by exposure to 20 nM okadaic acid for 48 h but not by 1 or 2 µM Aβ1-42 Treatment with 20 nM okadaic acid or 1 µM Aβ1-42 for 48 h resulted in the reduced α7, α4 and α3 proteins, and α4 and α3 mRNAs, as well as the decreased activity of superoxide dismutase and the increased malondialdehyde. Okadaic acid and Aβ1-42 together caused more pronounced changes in the expressions of α7 and α4, superoxide dismutase activity and lipid peroxidation than either alone. When pre-treatment with vitamin E or lovastatin, the neurotoxicity induced by okadaic acid was significantly attenuated. These findings indicate that hyperphosphorylation of tau induced by okadaic acid inhibits the expression of nicotinic acetylcholine receptors at both the protein and mRNA levels, as well as enhances the neurotoxicity of β-amyloid peptide.
Topics: Animals; Blotting, Western; Cells, Cultured; Neurons; Okadaic Acid; Phosphorylation; Rats; Rats, Sprague-Dawley; Real-Time Polymerase Chain Reaction; Receptors, Nicotinic; alpha7 Nicotinic Acetylcholine Receptor; tau Proteins
PubMed: 27190248
DOI: 10.1177/1535370216650759 -
Nanomaterials (Basel, Switzerland) Jun 2022We investigate a high-sensitivity surface plasmon resonance (SPR) biosensor consisting of a Au layer, four-layer MoS, and monolayer graphene. The numerical simulations,...
We investigate a high-sensitivity surface plasmon resonance (SPR) biosensor consisting of a Au layer, four-layer MoS, and monolayer graphene. The numerical simulations, by the transfer matrix method (TMM), demonstrate the sensor has a maximum sensitivity of 282°/RIU, which is approximately 2 times greater than the conventional Au-based SPR sensor. The finite difference time domain (FDTD) indicates that the presence of MoS film generates a strong surface electric field and enhances the sensitivity of the proposed SPR sensor. In addition, the influence of the number of MoS layers on the sensitivity of the proposed sensor is investigated by simulations and experiments. In the experiment, MoS and graphene films are transferred on the Au-based substrate by the PMMA-based wet transfer method, and the fabricated samples are characterized by Raman spectroscopy. Furthermore, the fabricated sensors with the Kretschmann configuration are used to detect okadaic acid (OA). The okadaic acid-bovine serum albumin bioconjugate (OA-BSA) is immobilized on the graphene layer of the sensors to develop a competitive inhibition immunoassay. The results show that the sensor has a very low limit of detection (LOD) of 1.18 ng/mL for OA, which is about 22.6 times lower than that of a conventional Au biosensor. We believe that such a high-sensitivity SPR biosensor has potential applications for clinical diagnosis and immunoassays.
PubMed: 35808053
DOI: 10.3390/nano12132219 -
Cells Oct 2021Regulation of mitochondrial morphology and motility is critical for neurons, but the exact mechanisms are unclear. Here, we demonstrate that these mechanisms may involve...
Regulation of mitochondrial morphology and motility is critical for neurons, but the exact mechanisms are unclear. Here, we demonstrate that these mechanisms may involve collapsin response mediator protein 2 (CRMP2). CRMP2 is attached to neuronal mitochondria and binds to dynamin-related protein 1 (Drp1), Miro 2, and Kinesin 1 light chain (KLC1). Treating neurons with okadaic acid (OA), an inhibitor of phosphatases PP1 and PP2A, resulted in increased CRMP2 phosphorylation at Thr509/514, Ser522, and Thr555, and augmented Drp1 phosphorylation at Ser616. The CRMP2-binding small molecule (S)-lacosamide ((S)-LCM) prevented an OA-induced increase in CRMP2 phosphorylation at Thr509/514 and Ser522 but not at Thr555, and also failed to alleviate Drp1 phosphorylation. The increased CRMP2 phosphorylation correlated with decreased CRMP2 binding to Drp1, Miro 2, and KLC1. (S)-LCM rescued CRMP2 binding to Drp1 and Miro 2 but not to KLC1. In parallel with CRMP2 hyperphosphorylation, OA increased mitochondrial fission and suppressed mitochondrial traffic. (S)-LCM prevented OA-induced alterations in mitochondrial morphology and motility. Deletion of CRMP2 with a small interfering RNA (siRNA) resulted in increased mitochondrial fission and diminished mitochondrial traffic. Overall, our data suggest that the CRMP2 expression level and phosphorylation state are involved in regulating mitochondrial morphology and motility in neurons.
Topics: Animals; Cells, Cultured; Corpus Striatum; Gene Deletion; Intercellular Signaling Peptides and Proteins; Kinesins; Mice; Mitochondria; Mitochondrial Dynamics; Nerve Tissue Proteins; Neurons; Okadaic Acid; Phosphoprotein Phosphatases; Phosphorylation
PubMed: 34685760
DOI: 10.3390/cells10102781 -
Toxicon: X Sep 2023Oysters () were screened for 12 phycotoxins over two years in nearshore waters to collect baseline phycotoxin data and to determine prevalence of phycotoxin...
Oysters () were screened for 12 phycotoxins over two years in nearshore waters to collect baseline phycotoxin data and to determine prevalence of phycotoxin co-occurrence in the commercially and ecologically-relevant species. Trace to low concentrations of azaspiracid-1 and -2 (AZA1, AZA2), domoic acid (DA), okadaic acid (OA), and dinophysistoxin-1 (DTX1) were detected, orders of magnitude below seafood safety action levels. Microcystins (MCs), MC-RR and MC-YR, were also found in oysters (maximum: 7.12 μg MC-RR/kg shellfish meat wet weight), warranting consideration of developing action levels for freshwater phycotoxins in marine shellfish. Oysters contained phycotoxins that impair shellfish health: karlotoxin1-1 and 1-3 (KmTx1-1, KmTx1-3), goniodomin A (GDA), and pectenotoxin-2 (PTX2). Co-occurrence of phycotoxins in oysters was common (54%, n = 81). AZAs and DA co-occurred most frequently of the phycotoxins investigated that are a concern for human health (n = 13) and PTX2 and KmTxs co-occurred most frequently amongst the phycotoxins of concern for shellfish health (n = 9). Various harmful algal bloom (HAB) monitoring methods and tools were assessed for their effectiveness at indicating levels of phycotoxins in oysters. These included co-deployed solid phase adsorption toxin tracking (SPATT) devices, toxin levels in particulate organic matter (POM, >1.5 μm) and whole water samples and cell concentrations from water samples as determined by microscopy and quantitative real-time PCR (qPCR). The dominant phycotoxin varied between SPATTs and all other phycotoxin sample types, and out of the 11 phycotoxins detected in oysters, only four and seven were detected in POM and whole water respectively, indicating phycotoxin profile mismatch between ecosystem compartments. Nevertheless, there were correlations between DA in oysters and whole water (simple linear regression [LR]: R = 0.6, p < 0.0001, n = 40), and PTX2 in oysters and SPATTs (LR: R = 0.3, p = 0.001, n = 36), providing additional monitoring tools for these phycotoxins, but oyster samples remain the best overall indicators of seafood safety.
PubMed: 37448555
DOI: 10.1016/j.toxcx.2023.100166 -
Brain Research Bulletin Jun 2016Intraneuronal aggregates of neurofibrillary tangles (NFTs), together with beta-amyloid plaques and astrogliosis, are histological markers of Alzheimer's disease (AD)....
Intraneuronal aggregates of neurofibrillary tangles (NFTs), together with beta-amyloid plaques and astrogliosis, are histological markers of Alzheimer's disease (AD). The underlying mechanism of sporadic AD remains poorly understood, but abnormal hyperphosphorylation of tau protein is suggested to have a role in NFTs genesis, which leads to neuronal dysfunction and death. Okadaic acid (OKA), a strong inhibitor of protein phosphatase 2A, has been used to induce dementia similar to AD in rats. We herein investigated the effect of intracerebroventricular (ICV) infusion of OKA (100 and 200ng) on hippocampal tau phosphorylation at Ser396, which is considered an important fibrillogenic tau protein site, and on glucose uptake, which is reduced early in AD. ICV infusion of OKA (at 200ng) induced a spatial cognitive deficit, hippocampal astrogliosis (based on GFAP increment) and increase in tau phosphorylation at site 396 in this model. Moreover, we observed a decreased glucose uptake in the hippocampal slices of OKA-treated rats. In vitro exposure of hippocampal slices to OKA altered tau phosphorylation at site 396, without any associated change in glucose uptake activity. Taken together, these findings further our understanding of OKA neurotoxicity, in vivo and vitro, particularly with regard to the role of tau phosphorylation, and reinforce the importance of the OKA dementia model for studying the neurochemical alterations that may occur in AD, such as NFTs and glucose hypometabolism.
Topics: Animals; Cognition; Dose-Response Relationship, Drug; Enzyme Inhibitors; Glial Fibrillary Acidic Protein; Glucose; Glutamate-Ammonia Ligase; Glutamic Acid; Glutathione; Hippocampus; In Vitro Techniques; Injections, Intraventricular; Male; Motor Activity; Okadaic Acid; Rats; Rats, Wistar; S100 Calcium Binding Protein beta Subunit; tau Proteins
PubMed: 27108544
DOI: 10.1016/j.brainresbull.2016.04.014 -
Toxins Nov 2018The identification and quantification of okadaic acid (OA)/dinophysistoxin (DTX) analogues and pectenotoxins (PTXs) in samples collected from coastal locations around...
The identification and quantification of okadaic acid (OA)/dinophysistoxin (DTX) analogues and pectenotoxins (PTXs) in samples collected from coastal locations around Japan were evaluated by liquid chromatography mass spectrometry. The species identified and analyzed included , , (), , , , , (), and . The dominant toxin found in was PTX2 although some samples contained DTX1 as a minor toxin. specimens isolated from the southwestern regions (Takada and Hiroshima) showed characteristic toxin profiles, with only OA detected in samples collected from Takada. In contrast, both OA and DTX1, in addition to a larger proportion of PTX2, were detected in from Hiroshima. showed a toxin profile dominated by PTX2 although this species had higher levels of DTX1 than . OA was detected as a minor toxin in some samples collected from Yakumo, Noheji, and Hakata. PTX2 was also the dominant toxin found among other species analyzed, such as , , and , although some pooled picked cells of these species contained trace levels of OA or DTX1. The results obtained in this study re-confirm that cellular toxin content and profiles are different even among strains of the same species.
Topics: Alveolata; Aquatic Organisms; Chromatography, Liquid; Environmental Monitoring; Japan; Marine Toxins; Okadaic Acid; Seawater; Tandem Mass Spectrometry
PubMed: 30404158
DOI: 10.3390/toxins10110457 -
Toxins Sep 2023Okadaic acid (OA) and its analogues cause diarrhetic shellfish poisoning (DSP) in humans, and risk assessments of these toxins require toxicity equivalency factors...
Okadaic acid (OA) and its analogues cause diarrhetic shellfish poisoning (DSP) in humans, and risk assessments of these toxins require toxicity equivalency factors (TEFs), which represent the relative toxicities of analogues. However, no human death by DSP toxin has been reported, and its current TEF value is based on acute lethality. To properly reflect the symptoms of DSP, such as diarrhea without death, the chronic toxicity of DSP toxins at sublethal doses should be considered. In this study, we obtained acute oral LD values for OA and dinophysistoxin-1 (DTX-1) (1069 and 897 μg/kg, respectively) to set sublethal doses. Mice were treated with sublethal doses of OA and DTX-1 for 7 days. The mice lost body weight, and the disease activity index and intestinal crypt depths increased. Furthermore, these changes were more severe in OA-treated mice than in the DTX-1-treated mice. Strikingly, ascites was observed, and its severity was greater in mice treated with OA. Our findings suggest that OA is at least as toxic as DTX-1 after repeated oral administration at a low dose. This is the first study to compare repeated oral dosing of DSP toxins. Further sub-chronic and chronic studies are warranted to determine appropriate TEF values for DSP toxins.
Topics: Humans; Animals; Mice; Okadaic Acid; Lethal Dose 50; Shellfish Poisoning; Diarrhea; Pyrans
PubMed: 37888618
DOI: 10.3390/toxins15100587 -
Translational Cancer Research Jun 2019Okadaic acid (OA) and hematein are both able to inhibit the proliferation of human lung adenocarcinoma A549 cells. However, it is largely unknown about their combined...
BACKGROUND
Okadaic acid (OA) and hematein are both able to inhibit the proliferation of human lung adenocarcinoma A549 cells. However, it is largely unknown about their combined effects on proliferation and apoptosis of A549 cells.
METHODS
The combined effects of the two drugs on proliferation of A549 cells and the responses of mitochondria and endoplasmic reticulum (ER) apoptosis pathways were investigated.
RESULTS
MTT assay showed that both OA and hematein significantly inhibited proliferation of A549 cells, and the combined drugs could further increase the inhibition ratio with lower dosages. Inverted phase contrast microscope and scanning electron microscope (SEM) analysis indicated that the combined drugs aggravated the appearance of apoptotic bodies and damaged cells. Compared to the single drug treated groups, reactive oxygen species (ROS) contents were significantly higher in the groups treated by the combined drugs, and mitochondrial membrane potential was significant lower. Western blot indicated that pro-apoptotic Bax that involved in mitochondrial apoptosis pathway increased, the anti-apoptotic protein Bcl-2 decreased, and the ER apoptosis-related proteins CHOP, Calpain2, JNK1 and IRE1 increased.
CONCLUSIONS
This work demonstrates that OA combined hematein can more effectively inhibit proliferation of A549 cells, and induce apoptosis of A549 cells via mitochondria and ER dependent pathways.
PubMed: 35116836
DOI: 10.21037/tcr.2019.06.05 -
Marine Drugs Jan 2021Okadaic acid (OA) and its main structural analogs dinophysistoxin-1 (DTX1) and dinophysistoxin-2 (DTX2) are marine lipophilic phycotoxins distributed worldwide that can...
Okadaic acid (OA) and its main structural analogs dinophysistoxin-1 (DTX1) and dinophysistoxin-2 (DTX2) are marine lipophilic phycotoxins distributed worldwide that can be accumulated by edible shellfish and can cause diarrheic shellfish poisoning (DSP). In order to study their toxicokinetics, mice were treated with different doses of OA, DTX1, or DTX2 and signs of toxicity were recorded up to 24 h. Toxin distribution in the main organs from the gastrointestinal tract was assessed by liquid chromatography-mass spectrometry (LC/MS/MS) analysis. Our results indicate a dose-dependency in gastrointestinal absorption of these toxins. Twenty-four hours post-administration, the highest concentration of toxin was detected in the stomach and, in descending order, in the large intestine, small intestine, and liver. There was also a different toxicokinetic pathway between OA, DTX1, and DTX2. When the same toxin doses are compared, more OA than DTX1 is detected in the small intestine. OA and DTX1 showed similar concentrations in the stomach, liver, and large intestine tissues, but the amount of DTX2 is much lower in all these organs, providing information on DSP toxicokinetics for human safety assessment.
Topics: Animals; Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Female; Intestines; Marine Toxins; Mass Spectrometry; Mice; Mice, Inbred C57BL; Okadaic Acid; Shellfish; Shellfish Poisoning; Stomach; Tissue Distribution; Toxicokinetics
PubMed: 33430011
DOI: 10.3390/md19010023 -
International Journal of Molecular... Dec 2022Male fertility relies on the ability of spermatozoa to fertilize the egg in the female reproductive tract (FRT). Spermatozoa acquire activated motility during epididymal... (Review)
Review
Male fertility relies on the ability of spermatozoa to fertilize the egg in the female reproductive tract (FRT). Spermatozoa acquire activated motility during epididymal maturation; however, to be capable of fertilization, they must achieve hyperactivated motility in the FRT. Extensive research found that three protein phosphatases (PPs) are crucial to sperm motility regulation, the sperm-specific protein phosphatase type 1 (PP1) isoform gamma 2 (PP1γ2), protein phosphatase type 2A (PP2A) and protein phosphatase type 2B (PP2B). Studies have reported that PP activity decreases during epididymal maturation, whereas protein kinase activity increases, which appears to be a requirement for motility acquisition. An interplay between these PPs has been extensively investigated; however, many specific interactions and some inconsistencies remain to be elucidated. The study of PPs significantly advanced following the identification of naturally occurring toxins, including calyculin A, okadaic acid, cyclosporin, endothall and deltamethrin, which are powerful and specific PP inhibitors. This review aims to overview the protein phosphorylation-dependent biochemical pathways underlying sperm motility acquisition and hyperactivation, followed by a discussion of the PP inhibitors that allowed advances in the current knowledge of these pathways. Since male infertility cases still attain alarming numbers, additional research on the topic is required, particularly using other PP inhibitors.
Topics: Humans; Male; Female; Sperm Motility; Calcineurin; Semen; Epididymis; Protein Phosphatase 2; Spermatozoa; Protein Phosphatase 1; Enzyme Inhibitors; Phosphorylation
PubMed: 36499559
DOI: 10.3390/ijms232315235