鋰鹽抑制 C6 神經膠瘤細胞增生之機制
Mechanisms by which Lithium inhibits C6
中文摘要鋰鹽(Lithium Chloride)經常被長期用於治療憂鬱症及躁鬱症。近來的研究發現鋰 鹽可以抑制細胞週期的運行及誘導細胞計劃性死亡(apoptosis)。鋰鹽還可抑制 Glycogen synthase kinase-3 活性並保護細胞免於 apoptosis。本研究發現鋰鹽 (LiCl)可抑制細胞的生長和 DNA 合成,並且 20 mM LiCl 可造成 cyclinB、Cyclin E 增加及 cdk-2 減少。使用 10 mM LiCl 隨著處理時間增加,可發現其可暫時的 抑制 p-Akt,可造成 p21CIP-1 及 Cyclin E 的增加。LiCl 使 C6 神經膠瘤細胞的 細胞週期停滯於 S 階段,以 Flow cytometry 分析,發現細胞並無 apoptosis 的現 象。除此之外,並且可抑制 DNA 合成。這個現象同時伴隨著可誘導 p21CIP-1、 抑制 P27KIP-1 蛋白表現和抑制 AKT/PKB Thr308 和 Ser473 的磷酸化,處理 24 小時的過程中發現 10 及 21 小時 p-Akt 表現及活性均有受到抑制的現象。一旦使 細胞內的 Akt/PKB 過度表現時可影響由鋰鹽(LiCl)所抑制的 Akt/PKB 磷酸化,也 改變了由鋰鹽(LiCl)所刺激的 p21CIP-1 的現象。但是,Thymidine incorporation 時 Akt/PKB 過度表現時並有改善鋰鹽所造成的抑制現象,因此認為鋰鹽對細胞可能 仍透過其他機制抑制細胞 DNA 的合成。MTT 的實驗中發現給予外源性 inositol 時並不影響因 LiCl 所抑制細胞生長的現象,因此,認為鋰鹽的抑制作用並非因 抑制 PI-Cycle 而導致細胞內 inositol 循環再利用不足所致。綜合以上結果,鋰鹽 抑制 C6 神經膠瘤細胞生長作用中,且其中鋰鹽抑制 Akt/PKB 的作用扮演了一重 要的角色。 英文摘要
Lithium has been widely used to treat manic depression and bipolar disorder behavior. Recently, lithium has been shown to inhibit cell cycle progression and induced
programmed cell death. In contrast, lithium inhibits glycogen synthase kinase-3 activity and provides protection against cell apoptosis. Here, we show that lithium inhibits cell cycle progression at S phase without inducing apoptosis in C6 glioma cells. The effects were parallelled with induction of p21cip-1 and suppression of p27KIP-1 protein expressions. The time course of p21cip-1 induction correlates with inhibition of Akt/PKB phosphorylation on Thr308 and Ser473 regulatory sites. Overexpression of Akt/PKB abolished the lithium-mediated inhibtion of Akt/PKB phosphorylation, reversed the lithium-mediated p21cip induction. Overexpression of Akt/PKB did not reverse the lithium inhibition of DNA synthesis. Supplement with exogenous inositol had no effect on the lithium-mediated inhibition of Akt/PKB phosphorylation, indicating that the mechanism of the lithium is not due to inositol
depletion. Taken together, these data indicated that inhibition of Akt/PKB signaling is involved in the modulation of cell cycle progression by Lithium in C6 glioma cells.