title: The effects of vitamin D receptor silencing on the expression of LVSCC-A1C and LVSCC-A1D and the release of NGF in cortical neurons.
abstract: BACKGROUND
  Recent studies have suggested that vitamin D can act on cells in the nervous system. Associations between polymorphisms in the vitamin D receptor (VDR), age-dependent cognitive decline, and insufficient serum 25 hydroxyvitamin D(3) levels in Alzheimer's patients and elderly people with cognitive decline have been reported. We have previously shown that amyloid β (Aβ) treatment eliminates VDR protein in cortical neurons. These results suggest a potential role for vitamin D and vitamin D-mediated mechanisms in Alzheimer's disease (AD) and neurodegeneration. Vitamin D has been shown to down-regulate the L-type voltage-sensitive calcium channels, LVSCC-A1C and LVSCC-A1D, and up-regulate nerve growth factor (NGF). However, expression of these proteins when VDR is repressed is unknown. The aim of this study is to investigate LVSCC-A1C, LVSCC-A1D expression levels and NGF release in VDR-silenced primary cortical neurons prepared from Sprague-Dawley rat embryos.
  
  
  RESULTS
  qRT-PCR and western blots were performed to determine VDR, LVSCC-A1C and -A1D expression levels. NGF and cytotoxicity levels were determined by ELISA. Apoptosis was determined by TUNEL. Our findings illustrate that LVSCC-A1C mRNA and protein levels increased rapidly in cortical neurons when VDR is down-regulated, whereas, LVSCC-A1D mRNA and protein levels did not change and NGF release decreased in response to VDR down-regulation. Although vitamin D regulates LVSCC-A1C through VDR, it may not regulate LVSCC-A1D through VDR.
  
  
  CONCLUSIONS
  Our results indicate that suppression of VDR disrupts LVSCC-A1C and NGF production. In addition, when VDR is suppressed, neurons could be vulnerable to aging and neurodegeneration, and when combined with Aβ toxicity, it is possible to explain some of the events that occur during neurodegeneration.
authors.affiliation: Istanbul University, Cerrahpasa Faculty of Medicine, Department of Medical Biology, Istanbul, Turkey.
authors.forename: Duygu
authors.initials: D
authors.lastname: Gezen-Ak
authors.forename: Erdinç
authors.initials: E
authors.lastname: Dursun
authors.forename: Selma
authors.initials: S
authors.lastname: Yilmazer
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002117:Calcitriol / Q000494:pharmacology; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D002540:Cerebral Cortex / Q000166:cytology*; D005786:Gene Expression Regulation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D020868:Gene Silencing / Q000187:drug effects; D020932:Nerve Growth Factor / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018167:Receptors, Calcitriol / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C504728:Cacna1c protein, rat; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018167:Receptors, Calcitriol; C093712:Cacna1d protein, rat; D020932:Nerve Growth Factor; D002117:Calcitriol