Background

Overexpression of the transsulfuration enzyme cystathionine-β-synthase (CBS), and overproduction of its product, hydrogen sulfide (H₂S) are recognized as potential pathogenetic factors in Down syndrome (DS). The purpose of the study was to determine how the mitochondrial function and core metabolic pathways are affected by DS and how pharmacological inhibition of CBS affects these parameters.

Methods

8 human control and 8 human DS fibroblast cell lines have been subjected to bioenergetic and fluxomic and proteomic analysis with and without treatment with a pharmacological inhibitor of CBS.

Results

DS cells exhibited a significantly higher CBS expression than control cells, and produced more H₂S. They also exhibited suppressed mitochondrial electron transport and oxygen consumption and suppressed Complex IV activity, impaired cell proliferation and increased ROS generation. Inhibition of H₂S biosynthesis with aminooxyacetic acid reduced cellular H₂S, improved cellular bioenergetics, attenuated ROS and improved proliferation. ¹³C glucose fluxomic analysis revealed that DS cells exhibit a suppression of the Krebs cycle activity with a compensatory increase in glycolysis. CBS inhibition restored the flux from glycolysis to the Krebs cycle and reactivated oxidative phosphorylation. Proteomic analysis revealed no CBS-dependent alterations in the expression level of the enzymes involved in glycolysis, oxidative phosphorylation and the pentose phosphate pathway. DS was associated with the dysregulation of several components of the autophagy network; CBS inhibition normalized several of these parameters.

Conclusions

Increased H₂S generation in DS promotes pseudohypoxia and contributes to cellular metabolic dysfunction by causing a shift from oxidative phosphorylation to glycolysis.

中文翻译：

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胱硫醚β-合酶/H2S途径在唐氏综合症细胞代谢功能障碍和假性缺氧发展中的作用

背景

转硫酶胱硫醚-β-合酶（CBS）的过度表达及其产物硫化氢（H ₂ S）的过度产生被认为是唐氏综合症（DS）的潜在致病因素。本研究的目的是确定 DS 如何影响线粒体功能和核心代谢途径，以及 CBS 的药理学抑制如何影响这些参数。

方法

对 8 个人类对照细胞系和 8 个人类 DS 成纤维细胞系进行了生物能、通量组学和蛋白质组学分析，无论是否经过 CBS 药理学抑制剂处理。

结果

DS细胞表现出比对照细胞显着更高的CBS表达，并产生更多的H ₂ S。它们还表现出线粒体电子传递和耗氧量受到抑制、复合物IV活性受到抑制、细胞增殖受损和ROS生成增加。用氨氧乙酸抑制H _{2 S生物合成可减少细胞H 2} S，改善细胞生物能，减弱ROS并改善增殖。¹³ C葡萄糖流组学分析表明，DS细胞表现出三羧酸循环活性的抑制以及糖酵解的代偿性增加。CBS 抑制恢复了从糖酵解到克雷布斯循环的通量，并重新激活了氧化磷酸化。蛋白质组学分析显示，参与糖酵解、氧化磷酸化和磷酸戊糖途径的酶的表达水平没有出现依赖于 CBS 的变化。DS 与自噬网络的多个组成部分的失调有关。CBS 抑制使其中几个参数正常化。

结论

DS 中H ₂ S 生成的增加会促进假性缺氧，并通过导致从氧化磷酸化转变为糖酵解而导致细胞代谢功能障碍。