title: Original Research: Influence of okadaic acid on hyperphosphorylation of tau and nicotinic acetylcholine receptors in primary neurons.
abstract: 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.
authors.affiliation: Department of Pathology at the Affiliated Hospital, Guizhou Medical University, Guiyang 550004, Guizhou, PR China.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhao
authors.affiliation: The Key Laboratory of Medical Molecular Biology, Guizhou Medical University, Guiyang 550004, Guizhou, PR China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Xiao
authors.affiliation: The Key Laboratory of Medical Molecular Biology, Guizhou Medical University, Guiyang 550004, Guizhou, PR China.
authors.forename: Xiao-Liang
authors.initials: XL
authors.lastname: Wang
authors.affiliation: KI-Alzheimer Disease Research Center, Karolinska Institutet, Novum, SE14186 Huddinge, Sweden.
authors.forename: Jinjing
authors.initials: J
authors.lastname: Pei
authors.affiliation: Department of Pathology at the Affiliated Hospital, Guizhou Medical University, Guiyang 550004, Guizhou, PR China The Key Laboratory of Medical Molecular Biology, Guizhou Medical University, Guiyang 550004, Guizhou, PR China zhizhongguan@yahoo.com.
authors.forename: Zhi-Zhong
authors.initials: ZZ
authors.lastname: Guan
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D019319:Okadaic Acid / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000378:metabolism; D064569:alpha7 Nicotinic Acetylcholine Receptor / Q000187:drug effects / Q000378:metabolism; D016875:tau Proteins / Q000187:drug effects* / Q000378:metabolism
chemical_list: D019319:Okadaic Acid; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; D016875:tau Proteins
keywords: Okadaic acid; neurotoxicity; nicotinic acetylcholine receptor; primary neurons; tau protein; β-amyloid peptide