Abstract Objective To observe the effects of exogenous hydrogen sulfide (H2S) on the expression of β-site amyloid precursor protein cleaving enzyme 1 (BACE1) and explore the possible ceDular signaling mechanism in pheochromocytoma (PC12) cells. Methods PC12 cells were exposed to different concentrations of sodium hydrosulfide (NaHS, the honor of H2S) for 24 hours. The levels of BACE1 mRNA and protein were detected by RT-PCR and Western blot,respectively. Western blot was also performed to detect the changes in the expressions of phosphorylated Akt-1 (pAkt1) and ERK1/2 (pERK1/2) proteins,which were key downstream proteins of PI3-K/Akt and MAPK/ ERK1/2 pathways,and BACE1 protein,which was affected by LY294002 and PD98059,the specific inhibitors of PD-K/Akt and MAPK/ ERK1/2 signaling pathways. The levels of AB42 in cellular culture medium was detected by ELBA. Results NaHS within the experimental concentration range decreased BACE1 expression in a dose-dependent manner, and the BACE1 expression reached the minimum level in PC12 cells exposed to 200 μmol/L NaHS. There were singificant differences in BACE1 expression between PC12 cells exposed to different concentrations of NaHS and control group (P< 0.05). LY294002 and PD98059 significantly inhibited the phosphorylation of Akt1 or ERK1/2, respectively. LY294002 attenuated the decrease in BACE1 protein expreseeion in PC 12 cells exposed to 200 μmol/L NaHS (P < 0.05), while PD98059 had no effect on the decrease in BACE1 protein expression (P > 0.05). The expression of Aβ42 showed the same trend as BACE1 whether the inhibitors were used or not. Conclusion The PI3-K/Akt signaling pathway,not the MAPK/ERK1/2 signaling pathway, may be involved in the down-regulated expression of BACE1 induced by exogenous hydrogen sulfide in PC12 cells.%目的 观察外源性硫化氢(H2S)对嗜铬细胞瘤细胞(PC12)β位淀粉样前体蛋白裂解酶1( BACE1)表达的影响,并探讨可能涉及的细胞信号机制.方法用不同浓度的硫氢化钠(NaHS)处理体外培养的PC12细胞,利用RT-PCR和Western blot法检测细胞内BACE1 mRNA及蛋白表达；继以LY294002和PD98059分别阻断磷脂酰肌醇3-激酶/丝氨酸苏氨酸蛋白激酶(PI3-K/Akt)及丝裂酶原活化蛋白激酶/细胞外信号调节激酶1/2( MAPK/ERK1/2)通路,Western blot法检测其对NaHS诱导的通路下游蛋白Akt1和ERK1/2磷酸化的影响及其对BACE1蛋白表达变化的调节；ELISA法检测细胞培养液中Aβ42水平的变化.结果NaHS在实验浓度范围内呈剂量依赖性下调BACE1mRNA及蛋白表达,200μmo/L时最明显,各NaHS组与对照组相比,差异均有统计学意义(P＜ 0.05);LY294002抑制NaHS诱导的Akt1蛋白磷酸化,削弱NaHS对BACE1蛋白的下调作用,其表达在LY294002预处理组与NaHS 200μmol/L组相比,差异具有统计学意义(P＜0.05)；而PD98059虽能抑制NaHS导致的ERK1/2蛋白磷酸化,但对其调节BACE1蛋白表达无影响,PD98059预处理与NaHS 200μmol/L组相比,差异无统计学意义(P＞0.05);不同处理条件下的Aβ42表达与BACE1变化趋势基本一致.结论外源性H2S下调PC12细胞BACE1表达,其机制可能与PI3-K/Akt信号通路的激活有关,而与MAPK/ERK1/2通路无关.
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