Selma Yilmazer

A Novel Perspective for Alzheimer's Disease: Vitamin D Receptor Suppression by Amyloid-β and Preventing the Amyloid-β Induced Alterations by Vitamin D in Cortical Neurons

Amyloid-β (Aβ) is the core component of amyloid plaques of Alzheimers disease (AD). The effects of Aβ include damage to neuronal plasma membrane, disruption of Ca(2+) homeostasis, and alterations of neurotrophic factor levels. The aim of this study was to determine the effects of Aβ treatment on vitamin D receptor (VDR), L-type voltage sensitive calcium channels A1C (LVSCC A1C), NGF, and observing the effects of vitamin D treatment on Aβ induced alterations in primary cortical neurons. As to the latter, we aimed to test the suggested neuroprotective role of vitamin D as a neglected neurosteroid. The expressions of VDR and LVSCC A1C were studied with qRT-PCR and Western blotting. NGF and cytotoxicity levels were determined by ELISA. Apoptotic cell death was investigated with caspase-3 protein expression by Western blotting. Our results showed that the Aβ triggers neurodegeneration not only by inducing LVSCC A1C expression and NGF levels and but also by dramatically suppressing VDR expression. Administration of vitamin D to this model protected neurons by preventing cytotoxicity and apoptosis, and also by downregulating LVSCC A1C and upregulating VDR. Additionally, vitamin D brought NGF expression to a state of equilibrium and did not show its apoptosis inducing effects. Consequently, prevention of Aβ toxicity which was one of the major component of AD type pathology by vitamin D treatment and understanding how Aβ effects vitamin D related pathways, might open up new frontiers in clarifying molecular mechanisms of neurodegeneration and provide basis for novel perspectives in both preventing and treating AD.

The interleukin 1 alpha, interleukin 1 beta, interleukin 6 and alpha-2-macroglobulin serum levels in patients with early or late onset Alzheimer's disease, mild cognitive impairment or Parkinson's disease

Alzheimers disease (EOAD, LOAD), mild cognitive impairment (MCI), Parkinsons disease (PD) and healthy controls were included to determine the serum interleukin-1s (IL-1α, IL-1β), IL-6 and alpha-2-macroglobulin (α2M) levels using ELISA. IL-6 might be a significant contributor to the inflammatory response in LOAD. The MCI data indicate that IL-1s, α2M and BDNF are somehow related, and this relationship might allow MCI patients to be more similar to the healthy controls. A correlation analysis of multiple biomarkers in different neurodegenerative disorders might be more useful than determining the levels of a single cytokine in a single disorder.

The Effects of Vitamin D Receptor Silencing on the Expression of LVSCC-A1C and LVSCC-A1D and the Release of NGF in Cortical Neurons

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 D3 levels in Alzheimers 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 Alzheimers 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 Findings 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/Significance 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.

BDNF, TNFα, HSP90, CFH, and IL-10 Serum Levels in Patients with Early or Late Onset Alzheimer's Disease or Mild Cognitive Impairment

Identifying early-detection biomarkers have become an increasingly important approach in the treatment and prevention of Alzheimers disease (AD). In this study, we investigated the potential of brain-derived neurotrophic factor (BDNF), complement factor H (CFH), tumor necrosis factor-α (TNFα), interleukin 10 (IL-10), and heat shock protein 90 (Hsp90) as serum biomarkers for AD in a cohort of the Turkish population because they have been suggested to be associated with AD. Serum BDNF, CFH, TNFα, IL-10, and Hsp90 levels in three groups of patients, early-onset AD (EOAD; age of onset < 65; n = 22), late-onset AD (LOAD; age of onset > 65; n = 54), and mild cognitive impairment (MCI) (n = 30), were compared with age-matched healthy controls (age < 65, n = 18 and age > 65; n = 32) using ELISA. The serum BDNF levels significantly decreased and TNFα levels significantly increased in the EOAD and LOAD groups compared to the age-matched healthy controls. There was a correlation between serum TNFα and IL-10 levels in the LOAD and healthy control groups. Serum CFH levels in the LOAD and MCI patients were significantly decreased compared with controls. Serum Hsp90 levels in the EOAD, LOAD, and MCI patients were significantly decreased compared with controls. The protein misfolding, the inflammatory response, and decreased neurotrophic factor synthesis are all suggested to be related to AD type brain pathology, and our results indicate these alterations might be traced from serum samples. For accurate early diagnosis of AD, it is important to determine a profile of alterations in multiple biomarkers in large-scale population studies.

Vitamin D inquiry in hippocampal neurons: consequences of vitamin D-VDR pathway disruption on calcium channel and the vitamin D requirement

Vitamin D receptor (VDR) and the enzymes involved in bioactivation of vitamin D, shown to be expressed in the central nervous system, particularly in areas affected by neurodegenerative disorders, especially in hippocampus. We showed that amyloid beta (Aβ) pathology includes VDR protein depletion and vitamin D-VDR pathway disruption either induced by Aβ or by VDR siRNA have very similar effects on cortical neurons. The goal of this study is to show the presence of 25 hydroxy vitamin D3-24 hydroxylase (24OHase) which is essential for vitamin D catabolism in hippocampal and cortical neurons. Additional goal is to compare the expression pattern of VDR and 24OHase both in hippocampal and in cortical neurons and to investigate the effects of VDR suppression in hippocampal neurons in order to see whether similar mechanisms work in hippocampus and cerebral cortex. Primary neuronal cultures were prepared from Sprague–dawley rat embryos. qRT-PCR was performed to determine VDR, 24OHase, and LVSCC-A1C mRNA expression levels. Cytotoxicity levels were determined by ELISA. Our findings illustrate that 24OHase mRNA was present both in hippocampal and in cortical neurons. VDR and 24OHase mRNA were higher in hippocampal neurons than the cortical ones. LVSCC-A1C mRNA levels increased in hippocampal neurons when VDR is down-regulated. Our results indicate that hippocampal neurons response to VDR suppression similar as cortical neurons, regarding calcium channel regulation. Higher gene expression of 24OHase and VDR might indicate “higher requirement of vitamin D” in hippocampus and potential consequences of vitamin D deficiency in cognitive decline, neurodegeneration, and Alzheimer’s disease.

Vitamin D receptor alleles, bone mineral density and turnover in postmenopausal osteoporotic and healthy women.

Objective: Vitamin D receptor (VDR) gene polymorphisms and bone metabolic markers were investigated as potential genetic markers for osteoporosis in postmenopausal Turkish women. The relationship between their VDR gene polymorphisms and bone states was determined. Materials and Methods: Restriction fragment length polymorphisms at the VDR gene locus (i.e., for BsmI, ApaI, and TaqI) was investigated in 75 postmenopausal osteoporotic (53.16 ± 1.31 years) and 66 healthy (52.62 ± 1.69 years) Turkish women and the genotypes were related to bone mineral density (BMD) at femoral neck (FN), lumbar spine (L1–4), trochanter, Ward’s triangle (Ward’s) and metabolic parameters of bone turnover. Results: In osteoporotic women, TaqI genotype-related differences of the VDR gene were found to be significant at all BMD sites; TT genotype had higher L1–4 BMD values than Tt and tt (p < 0.05); tt genotype had significantly lower BMD at FN (p < 0.05), trochanter (p < 0.01), and Ward’s (p < 0.05) compared to TT genotype. The tt genotype was found to be associated with higher (p < 0.05) serum osteocalcin levels compared to Tt and TT genotypes in the osteoporotic women, whereas no such association was found for the healthy women. Conclusion: Our data showed an association between VDR TaqI genotype and BMD at the FN, L1–4, trochanter and Ward’s triangle in nonobese postmenopausal osteoporotic women. Thus the VDR gene Taql polymorphism modulates differences in BMD in the postmenopausal osteoporotic women.

A New Mechanism for Amyloid-β Induction of iNOS: Vitamin D-VDR Pathway Disruption

The inflammatory process in Alzheimers disease (AD) has been suggested to include oxidative and nitrosative damage caused by elevated levels of nitric oxide (NO) and inducible nitric oxide synthase (iNOS). Here, we investigated iNOS expression in cortical neurons following amyloid-β (Aβ) treatment, vitamin D treatment, Aβ combined with vitamin D treatment, and vitamin D signaling disruption via silencing of nuclear (vitamin D receptor-VDR) or membrane vitamin D (1,25-MARRS) receptors. We observed that Aβ induced iNOS expression. Vitamin D prevented Aβ-induced cytotoxicity and iNOS upregulation in cortical neurons. Our silencing experiments suggest that vitamin D regulates iNOS via VDR, not 1,25-MARRS, in cortical neurons. Consequently, VDR absence induces iNOS expression in either the absence or presence of Aβ. While our previous work demonstrates that Aβ pathology includes VDR suppression, our present work demonstrates that Aβ induces iNOS and that this effect is mediated via disruption of the vitamin D-VDR pathway. These data suggest the existence of crosstalk between Aβ pathology and VDR. Thus, vitamin D supplementation should be considered a candidate in both the treatment and prevention of AD.

Beta Amyloid Suppresses the Expression of the Vitamin D Receptor Gene and Induces the Expression of the Vitamin D Catabolic Enzyme Gene in Hippocampal Neurons

Background/Aims: The beta amyloid aggregations present in Alzheimers disease affect neurons through various toxic alterations. The aim of this study was to determine the expression of the vitamin D receptor (VDR), 25-hydroxyvitamin D3 24-hydroxylase (an accelerator of vitamin D catabolism), and the L-type voltage-sensitive calcium channel A1C (LVSCC-A1C) in hippocampal neurons in response to beta amyloid and vitamin D treatments to test the protective effects of vitamin D and the probable effects of beta amyloid on vitamin D catabolism. Methods: The expression of the VDR, 24-hydroxylase (24OHase) and LVSCC-A1C mRNAs were studied using quantitative real-time polymerase chain reaction, and the cytotoxicity levels were determined by an ELISA in primary hippocampal neuron cultures prepared from Sprague-Dawley rat embryos. Results: Our results demonstrated that beta amyloid suppressed the expression of VDR mRNA and induced the expression of 24OHase and LVSCC-A1C mRNAs. Conclusion: Beta amyloid may disrupt the vitamin D-VDR pathway and cause defective utilization of vitamin D by suppressing the level of the VDR and elevating the level of 24OHase.

Detection of c-erbB-2 mRNAs using dig-labelled oligonucleotide probe with in situ hybridisation in human breast carcinoma: Comparison with immunohistochemical results

Amplification and overexpression of the c-erbB-2 oncogene are of prognostic significance in human breast cancer. Overexpression of c-erbB-2 is the result of gene amplification. However, increased transcript levels of c-erbB-2 are also detected in the absence of gene amplification. In this study for the detection of the overexpression mRNA in situ hybridisation (ISH) and immunohistochemistry (IHC) were used. Our aim was to develop the suitable mRNA ISH protocol for formalin-fixed paraffin-embedded material and to compare the localisation of transcripts and protein products in 20 primary breast carcinomas. Sections were immunostained with monoclonal c-erbB-2 antibody. In ISH method digoxigenin-labelled oligoprobe was used for the detection of c-erbB-2 mRNAs. We determined optimal condition for the ISH procedure (e.g., probe concentration, digestion, post washing). c-erbB-2 protein overproduction was detected in 11/20 cases with IHC. The mRNA signals were observed in malignant cell cytoplasm in 6/20 cases by ISH. ISH positive signals were found in only one case without detected overexpression of the protein. There were cell to cell variations in the hybridisation signals even within individual tumours. The ISH and IHC positive signals for c-erbB-2 was observed mostly in infiltrating ductal carcinomas that belong to aggressive lesions.

Interleukin-1α –889 C/T Polymorphism in Turkish Patients with Late-Onset Alzheimer’s Disease

Background/Aims: The polymorphism (rs1800587) in the 5′-flanking regulatory region at –889 of the interleukin-1α gene has been shown to be associated with inflammatory diseases and Alzheimer’s disease (AD). The aim of the current study is to determine whether there is an association between the promoter region polymorphism of the interleukin-1α gene and late-onset AD in a cohort of Turkish patients. Methods: One hundred and four subjects with dementia of the Alzheimer type and 103 age-matched controls were genotyped according to the PCR with confronting two-pair primers method. Results: Although the distribution of genotypes did not significantly differ (p = 0.107), the difference between allelic frequency was nearly significant according to a χ2 test (p = 0.05) when the controls and patients were compared. Conclusion: Our results showed that there is no association between the –889 C/T transition on the interleukin-1α gene and late-onset AD in the Turkish population.