Calcipotriol inhibits α‐synuclein aggregation in SH‐SY5Y neuroblastoma cells by a Calbindin‐D28k‐dependent mechanism

Abstract

Many neurodegenerative diseases are characterized by the formation of microscopically visible intracellular protein aggregates. a-Synuclein is the key aggregating protein in Parkinson's disease which is characterized by neuronal cytoplasmic Lewy body inclusions. Previous studies have shown relative sparing of neurons in Parkinson's disease and dementia with Lewy bodies that are positive for the vitamin D-dependent calcium-buffering protein, calbindin-D28k, and that a-synuclein aggregates are excluded from calbindin-D28k-positive neurons. Recent cell culture studies have shown that a-synuclein aggregation can be induced by raised intracellular-free Ca(II) and demonstrated that raised intracellular calcium and oxidative stress can act synergistically to promote a-synuclein aggregation. We hypothesized that calcipotriol, a potent vitamin D analogue used pharmaceutically, may be able to suppress calcium-dependent a-synuclein aggregation by inducing calbindin-D28k expression. Immunofluorescence and western blot analysis showed that calcipotriol potently induced calbindin-D28k in a dose-dependent manner in SH-SY5Y human neuroblastoma cells. Calcipotriol significantly decreased the frequency of a-synuclein aggregate positive cells subjected to treatments that cause raised intracellularfree Ca(II) (potassium depolarization, KCl/H 2 O 2 combined treatment, and rotenone) in a dose-dependent manner and increased viability. Suppression of calbindin-D28k expression in calcipotriol-treated cells using calbindin-D28k-specific siRNA showed significantly higher a-synuclein aggregation levels, indicating that calcipotriol-mediated blocking of calcium-dependent a-synuclein aggregation was dependent on the induction of calbindin-D28k expression. These data indicate that targeting raised intraneuronal-free Ca(II) in the brain by promoting the expression of calbindin-D28k at the transcriptional level using calcipotriol could prevent a-synuclein aggregate formation and ameliorate Parkinson's disease pathogenesis.

The relationships of vitamin D, vitamin D receptor gene polymorphisms, and vitamin D supplementation with Parkinson’s disease

“…In the 6-OHDA-induced PD model, pre- or post-treatment with 1,25(OH) 2 D 3 reduced tissue immunopositivity for TNF-α, partially restored tyrosine hydroxylase (TH) immunoreactivity, and prevented the decrease of VDR immunoreactivity in the lesioned striatum [ 133 , 134 ]. Cell culture studies revealed that the increased intracellular free calcium can induce the aggregation of α-synuclein, and proved that the increase of intracellular calcium and oxidative stress can act cooperatively to promote α-synuclein aggregation [ 135 – 138 ]. By reducing the expression of L -type Ca 2+ channels and increasing the expression of the plasma membrane Ca 2+ ATP-ase, NCX1, anti-apoptotic factor Bcl-2 and buffering protein calbindin D28k, 1,25(OH) 2 D 3 can maintain the low cytosolic Ca 2+ concentrations and thereby protect against Ca 2+ -induced oxidative damage in SN dopaminergic neurons [ 106 , 129 ].…”

The Effects of Vitamin D Deficiency on Neurodegenerative Diseases

“…Causal link [63] Transcription [62] Causal relationship [63] Regulatory T cells ↑ [112] Vit. D2 as suitable therapeutic candidate [128] Potential role of the VDR [138] Benefits after supplementation [139,140] Vit [92] Immunomodulatory effects [113] Ca 2+ homeostasis [114] Reduced oligomerization of prions [128] Inflammation [141] Ca 2+ homeostasis [142] Potential transcriptional regulation of HTT gene [150] Intervention studies Beneficial [58] Beneficial in dependence of genotype [87] Beneficial [115][116][117][118] Vit. D as genetic and environmental risk factor [ diseases and reduced Vitamin D level; however, it has to be emphasized that many aspects of vitamin D remain obscure in these diseases.…”

“…Furthermore vitamin D 3 administration was shown to prevent zinc-induced oxidative stress in substantia nigra of rat brain [91]. Oxidative stress and elevated intracellular-free calcium promote the aggregation of α-synuclein synergistically, and a recent study could show that the vitamin D 3 analogue calcipotriol is able to induce the expression of calbindin-D28k, thereby inhibiting the calcium-mediated aggregation of α-synuclein in human neuroblastoma cells [92].…”

Association Between Serum Vitamin D Levels and Parkinson's Disease: A Systematic Review and Meta-Analysis

“…Third, lewy bodies are abnormal aggregates of alpha synuclein that develops in neurons in PD. Vitamin D analogs can decrease intracellular-free Ca (II) and downregulate the expression of calbindin-D28k to reduce α-synuclein aggregation ( 48 ). However, so far its pathogenesis has not been completely figured out.…”