Magrassi L, Adorni L, Montorfano G, Rapelli S, Butti G, Berra B, Milanesi G
Department of Surgery, University of Pavia-IRCCS Policlinico S. Matteo, Italy.
Acta Neurochir (Wien). 1998;140(7):707-13; discussion 713-4. doi: 10.1007/s007010050166.
1 alpha, 25-dihydroxyvitamin D3 was previously shown to induce cell death in brain tumour cell lines when added to the medium at micromolar concentration. In this paper we show that Cholecalciferol, a poor ligand of the vitamin D receptor, also induces cell death of HU197 human glioblastoma cell line and early passages cultures derived from a recurrent human glioblastoma. This finding suggests that the effects of vitamin D metabolites on brain tumour cells are at least partially independent from the activation of the classic nuclear receptor pathway. Vitamin D metabolites have been shown to activate the sphingomyelin pathway inducing an increase in cellular ceramide concentration. We determined the levels of sphingomyelin ceramide and ganglioside GD3 in Hu197 cells after treatment with cholecalciferol. A significant increase in ceramide concentration and a proportional decrease in sphingomyelin was already present after 6 hours of cholecalciferol treatment when no morphological changes were visible in the cultures. Treatment with ceramides (N-acetylsphingosine or natural ceramide from bovine brain) of the same cells also induces cell death. Similarly, treatment of the same cells with bacterial Sphingomyelinase also results in cell death. The demonstration of an increase in intracellular ceramide after cholecalciferol treatment and the ability of ceramide to induce cell death suggest that the sphingomyelin pathway may be implicated in the effect of vitamin D metabolites on human glioblastoma cells. Inhibition of ceramide biosynthesis by fumonisin B1 treatment did not alter the dose response curve of HU197 cells to cholecalciferol. Insensitivity to fumonisin B1 together with a decrease in sphingomyelin content after cholecalciferol treatment indicate that activation of sphingomyelinase should be responsible for the increase in intracellular ceramide concentration.
先前的研究表明，当以微摩尔浓度添加到培养基中时，1α,25 - 二羟基维生素D3可诱导脑肿瘤细胞系发生细胞死亡。在本文中，我们发现维生素D受体的不良配体胆钙化醇也可诱导HU197人胶质母细胞瘤细胞系以及源自复发性人胶质母细胞瘤的早期传代培养物发生细胞死亡。这一发现表明，维生素D代谢产物对脑肿瘤细胞的作用至少部分独立于经典核受体途径的激活。维生素D代谢产物已被证明可激活鞘磷脂途径，导致细胞内神经酰胺浓度增加。我们测定了胆钙化醇处理后Hu197细胞中鞘磷脂、神经酰胺和神经节苷脂GD3的水平。在胆钙化醇处理6小时后，当培养物中未见形态学变化时，神经酰胺浓度显著增加，鞘磷脂成比例减少。用神经酰胺（N - 乙酰鞘氨醇或来自牛脑的天然神经酰胺）处理相同细胞也会诱导细胞死亡。同样，用细菌鞘磷脂酶处理相同细胞也会导致细胞死亡。胆钙化醇处理后细胞内神经酰胺增加以及神经酰胺诱导细胞死亡的能力表明，鞘磷脂途径可能与维生素D代谢产物对人胶质母细胞瘤细胞的作用有关。用伏马菌素B1处理抑制神经酰胺生物合成并未改变HU197细胞对胆钙化醇的剂量反应曲线。对伏马菌素B1不敏感以及胆钙化醇处理后鞘磷脂含量降低表明，鞘磷脂酶的激活应是细胞内神经酰胺浓度增加的原因。
