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

BackgroundRecent 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 D3 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.Methodology/Principal FindingsqRT-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/SignificanceOur 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.

Vitamin D Receptor Gene Haplotype Is Associated with Late-Onset Alzheimer's Disease

“…Our recent in vitro experiments also provided some explanation for the biological function of the vitamin D-VDR pathway in AD and neurodegeneration Gezen-Ak et al 2011). We showed that amyloid beta suppressed the expression of VDR in cortical neurons and suggested that vitamin D supplementation may prevent amyloid induced cytotoxicity ).…”

Vitamin D in Neurological Diseases: A Rationale for a Pathogenic Impact

“…The knock-out model of VDR-/-has an accelerated aging process in all the organs, and in the brain [17][18], with a significant in-brain decrease of NGF [19] and of other neurotransmitters, such as acetylcholine [20][21][22][23][24]. Congenital deficiency of vitamin D significantly reduces the activity of glutamic acid decarboxylase (GAD) 65/67 (key enzymes in GABAergic inter-neurons) and the levels of glutamate and glutamine in brain tissue [25].…”

Assessing the Magnitude and Effect of Various Risk Factors Associated with Vitamin D Deficiency among Females in the UAE

“…The variables required descriptive nominal and ordinal possible answer choices in order to facilitate the response method of individuals, due to the study relying on personal response and opinion rather than numerical data or accurate serum analyses. The variables represented and mentioned in the objectives above are, respectively: sun exposure (or not) during a specific timing (between 10 am and 3 pm), type of Sun protection factor (SPF) (8,15, more than 15, none), frequency of Sun protection factor application (frequently, usually/sometimes, rarely), frequency of practicing sunbathing (frequently, sometimes/during holidays, rarely), type of clothes and coverage (covering the whole body with religious "Hijab", not covering the whole body with arms, face, or legs uncovered), daily work/educational environment (indoors or a mix of outdoors and indoors according to the type of daily transportation used), nature of physical activity usually practiced (active lifestyle, usually practicing outdoor activities, sedentary lifestyle), types of food containing natural and fortified Vitamin D and choice of more than one type frequently consumed (cod liver oil, salmon, tuna, sardines, liver/beef, orange juice, milk, yoghurt, and readymade cereals), and finally current weight range (underweight, normal weight, overweight, obese).…”

“…It's important to have "sun exposure between the hours of 10:00 and 15:00 in the spring, summer, and autumn, because this is the only time when enough UVB photons reach the earth's surface to produce vitamin D 3 in the skin" 13 The amount of sunbathing, in accordance with skin pigmentation, mainly affects the degree of being exposed to the sun where one practicing sunbathing will often result in achieving the recommended intake of Vitamin D as opposed to not sunbathing, however it is notable that lighter pigmented people absorb more than dark pigmented due to the latter requiring a larger amount of exposure to reach levels of the former 14 Furthermore, sunscreens with an Sun protection factor factor of 8 reduce the skin's synthesis of vitamin D 3 by >95% whereas an Sun protection factor factor of 15 reduces synthesis by >98%. 15 The frequency of sunscreen application is also of great significance in relation to causing Vitamin D deficiency, especially due to the possibility of women using it much more than men.…”