Intracellular aggregation of abnormally phosphorylated tau in neurofibrillary tangles (NFTs) is a major neuropathological hallmark of Tauopathies such as Alzheimer’s disease. Tau phosphorylation is controlled by the homeostasis of glycogen synthase kinase-3β (GSK-3β) and protein phosphatase-2A (PP2A). Okadaic acid (OKA) is a potent inhibitor of PP2A, leading to abnormal tau phosphorylation. Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family and is selectively downregulated in AD brain. In this study, we investigated the effects of tau phosphorylation on secreted and cellular BDNF levels in primary cortical neurons. Primary cortical neurons were prepared from embryonic day 16 (E16) Sprague-Dawley rat embryos. After 7 days in vitro, neurons were treated with 25 nM OKA for inducing tau hyperphosphorylation. Tau phosphorylation was assessed by Western blot using antibody against phospho-Thr231 and non-phosphorylated tau protein was detected with the Tau-1 antibody. Levels of BDNF secreted to the culture medium were determined by ELISA at the 4th, 8th and 24th hours of treatment. Cellular localization and the protein expression of BNDF were determined by immunofluorescent labeling and fluorescent intensity measurements.
Our results show that after 8 hours of OKA treatment, tau phosphorylation at Thr231 increased, whereas Tau-1 signal decreased (p<0.0001) Compared with the control groups, BDNF levels in the OKA treated group were significantly lower after 4 and 24 hours of treatment (p<0.0001) but were not significantly different at 8 hours of treatment (p>0.05). While prominent BDNF immunoreactivity was seen in cytoplasm and neurites of the neurons in control groups, BDNF immunoreactivity significantly decreased in the OKA treated group (p<0.0001) and this attenuation was significant especially at neurites.
Our results suggested that decreased BDNF protein levels might depend on the defects in axonal transport as a result of disrupted microtubule structure caused by tau hyperphosphorylation.
To cite this abstract:İREM L. ATASOY, SELMA YILMAZER, ERDİNÇ DURSUN, DERYA METİN ARMAĞAN, MELEK ÖZTÜRK, DUYGU GEZEN-AK; OKA-induced tau hyperphosphorylation decrease BDNF protein levels in primary cortical neuron cultures. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/oka-induced-tau-hyperphosphorylation-decrease-bdnf-protein-levels-in-primary-cortical-neuron-cultures/. Accessed: May 26, 2020
EMC Abstracts - https://emc-proceedings.com/abstract/oka-induced-tau-hyperphosphorylation-decrease-bdnf-protein-levels-in-primary-cortical-neuron-cultures/