okadaic-acid and Neurodegenerative-Diseases

Protein phosphorylation is involved in the regulation of a wide variety of physiological processes and is the result of a balance between protein kinase and phosphatase activities. Biologically active marine derived compounds have been shown to represent an interesting source of novel compounds that could modify that balance. Among them, the marine toxin and tumor promoter, okadaic acid (OA), has been shown as an inhibitor of two of the main cytosolic, broad-specificity protein phosphatases, PP1 and PP2A, thus providing an excellent cell-permeable probe for examining the role of protein phosphorylation, and PP1 and PP2A in particular, in any physiological or pathological process. In the present work, we review the use of okadaic acid to identify specific phosphoepitopes mainly in proteins relevant for neurodegeneration. We will specifically highlight those cases of highly dynamic phosphorylation-dephosphorylation events and the ability of OA to block the high turnover phosphorylation, thus allowing the detection of modified residues that could be otherwise difficult to identify. Finally, its effect on tau hyperhosphorylation and its relevance in neurodegenerative pathologies such as Alzheimer's disease and related dementia will be discussed.

Topics: Animals; Epitopes; Humans; Neurodegenerative Diseases; Okadaic Acid; Phosphorylation; Protein Phosphatase 1; Protein Phosphatase 2; tau Proteins

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by tau aggregating into neurofibrillary tangles. Targeting tau aggregation is one of the most critical strategies for AD treatment and prevention. Herein, a high-throughput screening of tau-aggregation inhibitors was performed by thioflavin T (ThT) fluorescence assay and tauR3 peptides. According to bioactivity-guided isolation, homoprejadomycin (1) was obtained from the marine bacterium Streptomyces tendae MCCC 1A01534. Two new stable derivatives, 2 and 3, were yielded in a one-step reaction. By ThT assay, transmission electron microscopy, and circular dichroism, we demonstrated that the angucyclinones 2 and 3 inhibited tau aggregation and disaggregated tau fibrils. In the presence of 2, native tauR3 peptides maintained the disorder conformation, whereas the tauR3 aggregates reduced β-sheet structures. And compound 2 was confirmed to inhibit the aggregation of full-length 2N4R tau protein. Furthermore, 2 with low cytotoxicity protected HT22 cells from okadaic acid-induced damage by suppressing tau aggregates. These results indicated that 2 was a promising lead structure with tau therapeutic potency for AD treatment.

Topics: Alzheimer Disease; Humans; Neurodegenerative Diseases; Okadaic Acid; Peptides; tau Proteins

Alzheimer's disease (AD) is a chronic and progressive neurodegenerative disease, characterized by irreversible cognitive impairment, memory loss, and behavioral disturbances, ultimately resulting in death. The critical roles of glycogen synthase kinase-3β (GSK-3β) in tau pathology have also received considerable attention. Based on molecular docking studies, a series of novel α-carboline derivatives were designed, synthesized, and evaluated as GSK-3β inhibitors for their various biological activities. Among them, compound ZCH-9 showed the most potent inhibitory activity against GSK-3β, with an IC

Topics: Alzheimer Disease; Carbolines; Glycogen Synthase Kinase 3 beta; Humans; Molecular Docking Simulation; Neuroblastoma; Neurodegenerative Diseases; Okadaic Acid; Phosphorylation; Structure-Activity Relationship; tau Proteins

Alzheimer's disease (AD) is the most common neurodegenerative disease, and it manifests as progressive memory loss and cognitive decline. However, there are no effective therapies for AD, which is an urgent problem to solve. Evodiamine, one of the main bioactive ingredients of. A protein phosphatase 2A inhibitor, okadaic acid (OA), was used to induce tau phosphorylation to mimic AD-like models in neuronal cells. Protein expression and cell apoptosis were detected using Western blotting and flow cytometry, respectively. Spatial memory/cognition was assessed using water maze, passive avoidance tests, and magnetic resonance imaging assay in OA-induced mice models, and brain slices were evaluated further by immunohistochemistry.. The results showed that evodiamine significantly reduced the expression of phosphor-tau, and further decreased tau aggregation and neuronal cell death in response to OA treatment. This inhibition was found to be via the inhibition of glycogen synthase kinase 3β, cyclin-dependent kinase 5, and mitogen-activated protein kinase pathways. In vivo results indicated that evodiamine treatment ameliorated learning and memory impairments in mice, whereas Western blotting and immunohistochemical analysis of the mouse brain also confirmed the neuroprotective effects of evodiamine.. Evodiamine can decrease the neurotoxicity of tau aggregation and exhibit a neuroprotective effect. Our results demonstrate that evodiamine has a therapeutic potential for AD treatment.

Topics: Alzheimer Disease; Animals; Apoptosis; Brain; Cell Line; Cognition; Cognition Disorders; Disease Models, Animal; Humans; Male; Maze Learning; Mice; Mice, Inbred ICR; Neurodegenerative Diseases; Neurons; Neuroprotection; Neuroprotective Agents; Okadaic Acid; Phosphorylation; Quinazolines; Spatial Memory; tau Proteins; Tauopathies

In recent studies, it has been shown that the Transient Receptor Potential Melastatin-2 Channels (TRPM2) and Phospholipases A2 (PLA. OKA (200ng/10μl) was administered bilateral intracerebroventricularly as a single injection.. OKA-treated rats showed significant impairments of spatial memory in Morris Water Maze Test. OKA-induced memory-impaired rats showed increased numbers of degenerated neurons and Caspase-3, tau phosphorylated ser396, β-amyloid positive cells in the hippocampus and cerebral cortex. Furthermore, OKA-treated rats exhibited significantly increased MDA, TNF-α levels, and decreased SOD, GSH-PX enzyme activates and GSH levels of the tissues. ACA administration ameliorated OKA-induced memory impairment in rats. The ACA treatment also increased SOD and GSH-PX enzyme activation and GSH levels, and conversely decreased the levels of MDA, TNF-α. It was found that the numbers of the degenerated neurons and Caspase-3 positive cells of cortex and hippocampus regions were significantly reduced.. ACA administration attenuates the oxidative stress and neuroinflammation of OKA-induced neurodegeneration; and ameliorates the cognitive decline and neurodegeneration.

Topics: Animals; Caspase 3; Cerebral Cortex; Hippocampus; Male; Maze Learning; Memory; Neurodegenerative Diseases; Okadaic Acid; ortho-Aminobenzoates; Phospholipase A2 Inhibitors; Phospholipases A2; Rats; Rats, Sprague-Dawley; TRPM Cation Channels

Failures in neurotrophic support and signalling play key roles in Alzheimer's disease (AD) pathogenesis. We previously demonstrated that downregulation of the neurotrophin effector Kinase D interacting substrate (Kidins220) by excitotoxicity and cerebral ischaemia contributed to neuronal death. This downregulation, triggered through overactivation of N-methyl-D-aspartate receptors (NMDARs), involved proteolysis of Kidins220 by calpain and transcriptional inhibition. As excitotoxicity is at the basis of AD aetiology, we hypothesized that Kidins220 might also be downregulated in this disease. Unexpectedly, Kidins220 is augmented in necropsies from AD patients where it accumulates with hyperphosphorylated tau. This increase correlates with enhanced Kidins220 resistance to calpain processing but no higher gene transcription. Using AD brain necropsies, glycogen synthase kinase 3-β (GSK3β)-transgenic mice and cell models of AD-related neurodegeneration, we show that GSK3β phosphorylation decreases Kidins220 susceptibility to calpain proteolysis, while protein phosphatase 1 (PP1) action has the opposite effect. As altered activities of GSK3β and phosphatases are involved in tau aggregation and constitute hallmarks in AD, a GSK3β/PP1 imbalance may also contribute to Kidins220 decreased clearance, accumulation and hampered neurotrophin signalling from early stages of the disease pathogenesis. These results encourage searches for mutations in Kidins220 gene and their possible associations to dementias. Finally, our data support a model where the effects of excitotoxicity drastically differ when occurring in cerebral ischaemia versus progressively sustained toxicity along AD progression. The striking differences in Kidins220 stability resulting from chronic versus acute brain damage may also have important implications for the therapeutic intervention of neurodegenerative disorders.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Animals; Brain Ischemia; Calpain; Cell Death; Cells, Cultured; Disease Models, Animal; Down-Regulation; Female; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; HEK293 Cells; Humans; Male; Membrane Proteins; Mice; Mice, Transgenic; Nerve Growth Factors; Nerve Tissue Proteins; Neurodegenerative Diseases; Neurons; Okadaic Acid; Phosphorylation; Protein Phosphatase 1; Proteolysis; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Signal Transduction; tau Proteins