L-Cysteine promotes the proliferation and differentiation of neural stem cells via the CBS/H₂S pathway

Homocysteine induces cytotoxicity and proliferation inhibition in neural stem cells via DNA methylation in vitro

Mild to moderate hyperhomocysteinemia has been implicated in neurodevelopmental disorders and neurodegenerative diseases in human studies. Although the molecular mechanisms underlying the effects of homocysteine (Hcy) neurotoxicity on the nervous system are not yet fully understood, inhibition of neural stem cell (NSC) proliferation and alterations in DNA methylation may be involved. The aim of the present study was to characterize the effects of Hcy on DNA methylation in NSCs, and to explore how Hcy-induced changes in DNA methylation patterns affect NSC proliferation. We found that D,L-Hcy (30-1000 μm) but not L-cysteine inhibited cell proliferation and reduced levels of global DNA methylation in NSCs from neonatal rat hippocampus and increased cell injury. High levels of Hcy also induced an increase in S-adenosylhomocysteine (SAH), a decrease in the ratio of S-adenosylmethionine (SAM) to SAH, and a reduction in protein expression of the DNA methyltransferases DNMT1, DNMT3a and DNMT3b and their enzymatic activity. Moreover, the DNMT inhibitor zebularine reduced the global DNA methylation level and inhibited NSC proliferation. Our results suggest that alterations in DNA methylation may be an important mechanism by which high levels of Hcy inhibit NSC viability in vitro. Hcy-induced DNA hypomethylation may be caused by a reduction in the DNMT activity which is regulated by the cellular concentrations of SAM and SAH, or their protein expression levels. Our results also suggest that Hcy may play a role in the pathogenesis of certain nervous system diseases via a molecular mechanism that involves negative regulation of NSC proliferation and alterations in DNA methylation.

Palmitic acid affects proliferation and differentiation of neural stem cells in vitro

High-lipid diet composed of saturated fatty acids (SFAs) has significant detrimental effects on brain homeostasis, and deleterious effects of SFAs on various cells have been well documented. However, the effects of SFAs on neural stem Cells (NSCs) function have not been fully explored. The aim of this study was to determine whether palmitic acid (PA) affected the proliferation and differentiation of murine-derived NSCs. The results showed that PA dose dependently suppressed viability of NSCs and was cytotoxic at high concentrations. The toxic levels of PA inhibited the proliferation of NSCs as shown by reduced bromodeoxyuridine labeling of NSCs, which is correlated with reactive oxygen species generation. Pretreatment of the cells with the antioxidant N-acetyl-L-cysteine inhibitor significantly attenuated the effects of PA on the proliferation of NSCs. Furthermore, nontoxic levels of PA promoted astrocytogenesis in the differentiated NSCs, associated with Stat3 activation and altered expression of serial of basic helix-loop-helix transcription factor genes. Altogether, our data have demonstrated that PA has a significant impact on proliferation and differentiation of NSCs in vitro and may be useful for elucidating the role of SFAs in regulating NSCs fate in physiological and pathological settings.

A metabolic signature of colon cancer initiating cells

Colon cancer initiating cells (CCICs) are more tumorigenic and metastatic than the majority of colorectal cancer (CRC) cells. CCICs have also been associated with stem cell-like properties. However, there is a lack of system-level understanding of what mechanisms distinguish CCICs from common CRC cells. We compared the transcriptomes of CD133+ CCICs and CD133- CRC cells from multiple sources, which identified a distinct metabolic signature for CD133(high) CCICs. High-resolution unbiased metabolomics was then performed to validate this CCIC metabolic signature. Specifically, levels of enzymes and metabolites involved in glycolysis, the citric acid (TCA) cycle, and cysteine and methionine metabolism are altered in CCICs. Analyses of the alterations further suggest an epigenetic link. This metabolic signature provides mechanistic insights into CCIC phenotypes and may serve as potential biomarkers and therapeutic targets for future CRC treatment.