脱氢皮质酮对大鼠海马神经元的毒性作用及其机制的探讨

Neurotoxic effect of 11β-dehydrocorticosterone on hippocampal neuron and its mechanism

目的 :研究糖皮质激素的代谢产物 11-脱氢皮质酮对大鼠海马神经元的毒性作用及其机制。 方法 :采用 Westernblotting、放射性酶活性测定及 MTT染色测定法进行实验。 结果 :Western blotting和放射性酶活性测定均证明了原代培养大鼠海马神经元内存在使 11-脱氢皮质酮转化为皮质酮的酶 ,即 型 11β-羟基类固醇脱氢酶 (11β- HSD1)。 11-脱氢皮质酮能够促进 11β- HSD1蛋白的表达。细胞存活实验表明 :11-脱氢皮质酮 (10 - 6 m ol/ L )可对无血清 DMEM培养的大鼠海马神经元产生损伤作用 ,此作用不仅可为 11β- HSD1抑制剂甘珀酸 (carbenoxolone,CBX)所阻断 ,还能为糖皮质激素受体 (glucocorticoidreceptor,GR)拮抗剂阻断 ,但不能为肾上腺皮质激素受体 (m ineralocorticoid receptor,MR)拮抗剂所阻断。结论 :11-脱氢皮质酮能够对大鼠海马神经元产生毒性作用 ,此毒性作用是由 11β- HSD1参与并由 GR受体介导的。 11-脱氢皮质酮使 11β- HSD1蛋白表达增加 ,又反过来促进 11-脱氢皮质酮向皮质酮的转化 ,此正反馈作用可能在应激性迟发性神经元死亡中发挥一定的作用。

Objective:To study the toxicity of 11 dehydrocorticosterone on hippocampal neurons and to determine whether 11β hydroxysteroid dehydrogenase (11β HSD1) is involved in the neurotoxity. Methods:Western blotting, radiometric enzyme activity assay and MTT assay were employed in this study. Results:Both 11β HSD1 protein and bioactivity were positive in the hippocampal neurons as demonstrated by Western blotting and radiometric enzyme activity assay. At concentration of 10 -6 mol/L, 11 dehydrocorticosterone was neurontoxic to hippocampal neurons cultured in serum free DMEM medium. This neurotoxic effect of 11 dehydrocorticosterone was blocked by 11β HSD1 inhibitor carbenoxolone (CBX) and glucocorticoid receptor (GR) antagonist RU38486, but not by mineralcocorticoid receptor (MR) antagonist spironolatone. Corticosterone and its derivative 11 dehydrocorticosterone up regulated 11β HSD1 level. Conclusion:11 dehydrocorticosterone has toxicity on hippocampal neurons, and it can be blocked by CBX, suggesting 11β HSD1 may convert biologically inactive 11 dehydrocorticosterone to active corticosterone. The up regulation of 11β HSD1 by glucocorticoids in return exaggerates the neurotoxic effect of corticosterone, which may play a positive role in the delayed neuron death during stress.