Research articleCerebral dopamine neurotrophic factor alleviates Aβ25-35-induced endoplasmic reticulum stress and early synaptotoxicity in rat hippocampal cells
Introduction
Alzheimer’s disease (AD), the major cause of dementia, is the most common age-related neurodegenerative disorder. Neuropathological features of AD include extracellular deposits of amyloid-β (Aβ) peptide and intracellular neurofibrillary tangles of hyperphosphorylated tau proteins [1]. Mounting evidence suggests that cognitive deficits in AD begin with subtle alterations of synaptic function before overt neuronal loss is detectable [2]. As the etiology of AD remains unclear, there are currently no effective treatments. Therefore, novel therapies for slowing disease progressions, and particularly those early strategies to prevent synaptic dysfunctions are urgently needed.
Neurotrophic factors (NTF) are a family of growth factors that promote the cell survival, and regulate brain plasticity and neuroregeneration. A new comer of NTF, cerebral dopamine neurotrophic factor (CDNF), which is located in endoplasmic reticulum (ER) and involved in unfolded protein response (UPR) in ER stress [3], [4], displays strong protective and restorative effects in dopaminergic neurons [5], [6]. Recent studies showed overexpression of CDNF could alleviate cell damage and promote nerve regeneration [7], [8]. In addition, gene therapy with CDNF displayed the potential to improve long term memory in APP/PS1 transgenic animals [9]. Although growing body of evidence suggests ER stress is implicated in AD, few are related to Aβ synaptotoxicity [10], [11], [12]. Furthermore, the effects of CDNF on Aβ-induced synaptotoxicity and the related molecular mechanisms remain unclear. Our present report demonstrates the protective effects of CDNF on Aβ-induced synaptotoxicity and ER stress.
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Materials
CDNF protein was from R&D (MN, USA). Aβ25-35 was purchased from American Peptide (CA, USA), dissolved in DMSO (Sigma-Aldrich, MO, USA) and stored in −20 °C. Neurobasal A, B27, Dulbecco’s-Modified Eagle Media/F12 (DMEM/F12), fetal bovine serum (FBS), trypsin and PDL were obtained from Gibco (MO, USA). Basic fibroblast growth factor (bFGF) (NY, USA) and Lipofectamine-2000 (CA, USA) were from Invitrogen.
Aβ25-35 preparation
Aβ25-35 was dissolved in 2 mM DMSO, diluted 1:10 in sterile PBS, vortexed (30 min, room
CDNF expression in rat primary hippocampal cells
Previous studies have indicated that CDNF is expressed in most tissues of brain, especially in hippocampus, but have not confirmed the accurate cell types [5], [8], [17]. The results of immunofluorescence displayed some CDNF-immunolabled cells coexpressed GFAP (marker of astrocytes) or Tuj1 (marker of neurons), suggesting that CDNF was expressed in both astrocytes and neurons (Fig. 2A). In addition, we also verified the expression of CDNF in hippocampal cells using western blot analysis (Fig. 2
Discussion
CDNF is a new member of the novel evolutionary conserved neurotrophic factor family. Currently, most studies on CDNF are mainly in PD disease, and a significant neuroprotective and neurorestorative effect of CDNF has been identified in the mouse PD models [18], [19], which motivated some researchers to investigate its potential therapeutic effect in AD animal models. To our knowledge, only one study so far has addressed the potential of CDNF in AD models [9]. In 2015, Kemppainen reported that
Acknowledgements
The authors are grateful to Prof. Weiming Duan for his kind assistance. This work was supported by the Program for New Century Excellent Talents in University (NCET-10-0015), the Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions (CIT&TCD201304175), Beijing BaiQianWan Talents Program (2015002), Beijing Natural Science Foundation (5152004), National Natural Science Foundation of China (81301100).
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