bims-meprid 2024-10-20 papers

Nat Commun. 2024 Oct 17. 15(1): 8971

Methionine-SAM metabolism-dependent ubiquinone synthesis is crucial for ROS accumulation in ferroptosis induction.

Chaoyi Xia, Pinghui Peng, Wenxia Zhang, Xiyue Xing, Xin Jin, Jianlan Du, Wanting Peng, Fengqi Hao, Zhexuan Zhao, Kejian Dong, Miaomiao Tian, Yunpeng Feng, Xueqing Ba, Min Wei, Yang Wang.

Ferroptosis is a cell death modality in which iron-dependent lipid peroxides accumulate on cell membranes. Cysteine, a limiting substrate for the glutathione system that neutralizes lipid peroxidation and prevents ferroptosis, can be converted by cystine reduction or synthesized from methionine. However, accumulating evidence shows methionine-based cysteine synthesis fails to effectively rescue intracellular cysteine levels upon cystine deprivation and is unable to inhibit ferroptosis. Here, we report that methionine-based cysteine synthesis is tissue-specific. Unexpectedly, we find that rather than inhibiting ferroptosis, methionine in fact plays an essential role during cystine deprivation-induced ferroptosis. Methionine-derived S-adenosylmethionine (SAM) contributes to methylation-dependent ubiquinone synthesis, which leads to lipid peroxides accumulation and subsequent ferroptosis. Moreover, SAM supplementation synergizes with Imidazole Ketone Erastin in a tumor growth suppression mouse model. Inhibiting the enzyme that converts methionine to SAM protects heart tissue from Doxorubicin-induced and ferroptosis-driven cardiomyopathy. This study broadens our understanding about the intersection of amino acid metabolism and ferroptosis regulation, providing insight into the underlying mechanisms and suggesting the methionine-SAM axis is a promising therapeutic strategy to treat ferroptosis-related diseases.

DOI: https://doi.org/10.1038/s41467-024-53380-5

Nat Metab. 2024 Oct 14.

Brown fat ATP-citrate lyase links carbohydrate availability to thermogenesis and guards against metabolic stress.

Brown adipose tissue (BAT) engages futile fatty acid synthesis-oxidation cycling, the purpose of which has remained elusive. Here, we show that ATP-citrate lyase (ACLY), which generates acetyl-CoA for fatty acid synthesis, promotes thermogenesis by mitigating metabolic stress. Without ACLY, BAT overloads the tricarboxylic acid cycle, activates the integrated stress response (ISR) and suppresses thermogenesis. ACLY's role in preventing BAT stress becomes critical when mice are weaned onto a carbohydrate-plentiful diet, while removing dietary carbohydrates prevents stress induction in ACLY-deficient BAT. ACLY loss also upregulates fatty acid synthase (Fasn); yet while ISR activation is not caused by impaired fatty acid synthesis per se, deleting Fasn and Acly unlocks an alternative metabolic programme that overcomes tricarboxylic acid cycle overload, prevents ISR activation and rescues thermogenesis. Overall, we uncover a previously unappreciated role for ACLY in mitigating mitochondrial stress that links dietary carbohydrates to uncoupling protein 1-dependent thermogenesis and provides fundamental insight into the fatty acid synthesis-oxidation paradox in BAT.

DOI: https://doi.org/10.1038/s42255-024-01143-3

Dig Med Res. 2024 Mar 30. pii: 4. [Epub ahead of print]7

Histone acylations as a mechanism for regulation of intestinal epithelial cells.

Mariane Font Fernandes, Marco Aurélio Ramirez Vinolo.

Histone post-translational modifications are reversible epigenetic mechanisms that regulate chromatin structure and gene transcription. In recent years, in addition to the well-characterized histone acetylation, new acylations such as propionylation, crotonylation, butyrylation and beta-hydroxybutyrylation have been described and explored in different cell types at contexts of health and disease. Understanding how histone acylations contribute to gene expression regulation is especially important in intestinal epithelial cells (IECs) because they receive many different signals from other cells and the external environment and must adapt to maintain essential functions such as nutrient and water absorption, maintenance of tolerance and protection against pathogens. In this review, we describe how cells regulate these modifications, how they are recognized by other proteins and impact gene expression. We summarize recent studies that explored the role of these distinct epigenetic marks in the regulation of IECs and discuss their biological importance for the intestinal epithelium's adaptations to changes in metabolism and to respond to environmental signals provided, for example, by the diet, components of the intestinal microbiota and pathogens. Finally, we discuss how the histone acylations are affected by inflammatory signals and how this knowledge may provide new targets for treatment of pathologies such as the inflammatory bowel diseases.

Keywords: Histone acetylation; colon; histone crotonylation; inflammation; microbiota

DOI: https://doi.org/10.21037/dmr-23-3

J Dent Res. 2024 Oct 12. 220345241279555

Fumarate Restrains Alveolar Bone Restoration via Regulating H3K9 Methylation.

Y Y Zhang, J Xiang, Y Y He, X Liu, H Y Ye, L Xu, H L Bai, H Zhang, H M Zhang, W Z Liu, Q M Zhai, P Ji, R D Cannon.

Nonresolving inflammation causes irreversible damage to periodontal ligament stem cells (PDLSCs) and impedes alveolar bone restoration. The impaired tissue regeneration ability of stem cells is associated with abnormal mitochondrial metabolism. However, the impact of specific metabolic alterations on the differentiation process of PDLSCs remains to be understood. In this study, we found that inflammation altered the metabolic flux of the tricarboxylic acid cycle and induced the accumulation of fumarate through metabolic testing and metabolic flux analysis. Transcriptome sequencing revealed the potential of fumarate in modulating epigenetics. Specifically, histone methylation typically suppresses the expression of genes related to osteogenesis. Fumarate was found to impede the osteogenic differentiation of PDLSCs that exhibited high levels of H3K9me3. Various techniques, including assay for transposase-accessible chromatin with high-throughput sequencing, chromatin immunoprecipitation sequencing, and RNA sequencing, were used to identify the target genes regulated by H3K9me3. Mechanistically, accumulated fumarate inhibited lysine-specific demethylase 4B (KDM4B) activity and increased H3K9 methylation, thus silencing asporin gene transcription. Preventing fumarate from binding to the histone demethylase KDM4B with α-ketoglutarate effectively restored the impaired osteogenic capacity of PDLSCs and improved alveolar bone recovery. Collectively, our research has revealed the significant impact of accumulated fumarate on the regulation of osteogenesis in stem cells, suggesting that inhibiting fumarate production could be a viable therapeutic approach for treating periodontal diseases.

Keywords: citric acid cycle; histones; inflammation; mesenchymal stem cells; metabolism; osteogenesis

DOI: https://doi.org/10.1177/00220345241279555

Front Immunol. 2024 ;15 1477267

The pathological significance and potential mechanism of ACLY in cholangiocarcinoma.

Xiaoyan Sun, Xiaofang Zhao, Senyan Wang, Qi Liu, Wenjuan Wei, Jing Xu, Hongyang Wang, Wen Yang.

Background and aim: Cholangiocarcinoma (CCA) is a rare cancer, yet its incidence and mortality rates have been steadily increasing globally over the past few decades. Currently, there are no effective targeted treatment strategies available for patients. ACLY (ATP Citrate Lyase), a key enzyme in de novo lipogenesis, is aberrantly expressed in several tumors and is associated with malignant progression. However, its role and mechanisms in CCA have not yet been elucidated.
Methods: The expression of ACLY in CCA was assessed using transcriptomic profiles and tissue microarrays. Kaplan-Meier curves were employed to evaluate the prognostic significance of ACLY in CCA. Functional enrichment analysis was used to explore the potential mechanisms of ACLY in CCA. A series of assays were conducted to examine the effects of ACLY on the proliferation and migration of CCA cells. Ferroptosis inducers and inhibitors, along with lipid peroxide probes and MDA assay kits, were utilized to explore the role of ACLY in ferroptosis within CCA. Additionally, lipid-depleted fetal bovine serum and several fatty acids were used to evaluate the impact of fatty acids on ferroptosis induced by ACLY inhibition. Correlation analyses were performed to elucidate the relationship between ACLY and tumor stemness as well as tumor microenvironment.
Results: The expression of ACLY was found to be higher in CCA tissues compared to adjacent normal tissues. Patients with elevated ACLY expression demonstrated poorer overall survival outcomes. ACLY were closed associated with fatty acid metabolism and tumor-initiating cells. Knockdown of ACLY did not significantly impact the proliferation and migration of CCA cells. However, ACLY inhibition led to increased accumulation of lipid peroxides and enhanced sensitivity of CCA cells to ferroptosis inducers. Polyunsaturated fatty acids were observed to inhibit the proliferation of ACLY-knockdown cells; nonetheless, this inhibitory effect was diminished when the cells were cultured in medium supplemented with lipid-depleted fetal bovine serum. Additionally, ACLY expression was negatively correlated with immune cell infiltration and immune scores in CCA.
Conclusion: ACLY promotes ferroptosis by disrupting the balance of saturated and unsaturated fatty acids. ACLY may therefore serve as a potential diagnostic and therapeutic target for CCA.

Keywords: ACLY; cholangiocarcinoma; fatty acid metabolism; ferroptosis; immune microenvironment

DOI: https://doi.org/10.3389/fimmu.2024.1477267

Immunity. 2024 Oct 09. pii: S1074-7613(24)00457-6. [Epub ahead of print]

CRISPR screens unveil nutrient-dependent lysosomal and mitochondrial nodes impacting intestinal tissue-resident memory CD8+ T cell formation.

Nutrient availability and organelle biology direct tissue homeostasis and cell fate, but how these processes orchestrate tissue immunity remains poorly defined. Here, using in vivo CRISPR-Cas9 screens, we uncovered organelle signaling and metabolic processes shaping CD8+ tissue-resident memory T (TRM) cell development. TRM cells depended on mitochondrial translation and respiration. Conversely, three nutrient-dependent lysosomal signaling nodes-Flcn, Ragulator, and Rag GTPases-inhibited intestinal TRM cell formation. Depleting these molecules or amino acids activated the transcription factor Tfeb, thereby linking nutrient stress to TRM programming. Further, Flcn deficiency promoted protective TRM cell responses in the small intestine. Mechanistically, the Flcn-Tfeb axis restrained retinoic acid-induced CCR9 expression for migration and transforming growth factor β (TGF-β)-mediated programming for lineage differentiation. Genetic interaction screening revealed that the mitochondrial protein Mrpl52 enabled early TRM cell formation, while Acss1 controlled TRM cell development under Flcn deficiency-associated lysosomal dysregulation. Thus, the interplay between nutrients, organelle signaling, and metabolic adaptation dictates tissue immunity.

Keywords: CD8 T cell; adaptive immunity; dietary intervention; immunometabolism; lysosome; mitochondria; tissue-resident memory

DOI: https://doi.org/10.1016/j.immuni.2024.09.013