Vitamin D is a secosteroid hormone mediating its functions via vitamin D receptor (VDR) and an endoplasmic reticulum chaperone, protein disulfide isomerase A3 (PDIA3). From a physiological perspective, there is also a well-established association of cholesterol and vitamin D synthesis, since both share a common metabolic substrate, 7 dehydrocholesterol (7-DHC). Yet, the potential basic pathways, of the biological interplay of DHCR24 and vitamin D equilibrium, on neuronal level, are yet to be determined. In this study, we aimed to investigate the relation between vitamin D pathways and DHCR24 in primary cortical neuron cultures. The neocortex of Sprague–Dawley rat embryos (E16) was used for the preparation of primary cortical neuron cultures. DHCR24 mRNA and protein expression levels were determined by qRT-PCR, Western blotting, and immunofluorescent labeling in 1,25-dihydroxyvitamin D3-treated or VDR/PDIA3-silenced primary cortical neurons. The mRNA expression of DHCR24 was significantly decreased in the cortical neurons treated with 10^-8M 1,25-dihydroxyvitamin D₃ (p<0.001). In parallel with the mRNA results, DHCR24 protein expression in cortical neurons treated with 10^-8M 1,25-dihydroxyvitamin D₃ was also significantly lower than untreated neurons (p<0.05). These data were also confirmed with immunofluorescent labeling and fluorescence intensity measurements of DHCR24 (p<0.001). Finally, DHCR24 mRNA expression level was significantly increased in PDIA3 siRNA-treated neurons (p<0.05). Similar to the mRNA results, the DHCR24 protein expression of PDIA3 siRNA-treated neurons was also statistically higher than the other groups (p<0.05). Results of this mechanistic experimental basic study demonstrate that DHCR24 mRNA expression and protein concentrations attenuated in response to vitamin D treatment. Furthermore, we observed that PDIA3 might be involved in this modulatory effect. Our findings indicate a complex interaction of DHCR24 and vitamin D equilibrium, through the involvement of PDIA3 and vitamin D in the modulation of cholesterol metabolism in neuronal cells, requiring future studies on the field.

维生素 D 是一种分泌类固醇激素，通过维生素 D 受体 (VDR) 和内质网伴侣蛋白二硫键异构酶 A3 (PDIA3) 介导其功能。从生理角度来看，胆固醇和维生素 D 合成之间也存在明确的关联，因为两者都有共同的代谢底物 7 脱氢胆固醇 (7-DHC)。然而，DHCR24 和维生素 D 平衡在神经元水平上的生物相互作用的潜在基本途径仍有待确定。在本研究中，我们旨在研究原代皮质神经元培养物中维生素 D 途径与 DHCR24 之间的关系。 Sprague-Dawley 大鼠胚胎 (E16) 的新皮质用于制备原代皮质神经元培养物。通过 qRT-PCR、蛋白质印迹和免疫荧光标记测定 1,25-二羟基维生素 D3 处理或 VDR/PDIA3 沉默的原代皮质神经元中的 DHCR24 mRNA 和蛋白表达水平。 10 ^-8 M 1,25-二羟基维生素 D ₃处理的皮层神经元中 DHCR24 的 mRNA 表达显着降低（p<0 id=14>-8 M 1,25-二羟基维生素 D ₃也显着低于未处理的神经元） (p<0.05)。最后，DHCR24 mRNA 表达水平在 PDIA3 siRNA 处理的神经元中显着增加 (p<0.05)。 mRNA 结果显示，PDIA3 siRNA 处理的神经元的 DHCR24 蛋白表达也显着高于其他组 (p<0.05)。该机制实验基础研究的结果表明，DHCR24 mRNA 表达和蛋白浓度响应维生素 D 处理而减弱。 此外，我们观察到 PDIA3 可能参与这种调节作用。我们的研究结果表明，DHCR24 和维生素 D 平衡之间存在复杂的相互作用，通过 PDIA3 和维生素 D 参与神经元细胞胆固醇代谢的调节，需要该领域的进一步研究。