Project description:Human monocyte-derived dendritic cells (moDCs) have been used as an in vitro model for studying tolerance and immunity. However, the underlying metabolic states of tolerogenic (dexamethasone and vitamin D3-treated), immature and immunogenic (mature, LPS-treated) moDCs have not been completely characterized. Through transcriptomic analyses, we determined that tolerogenic moDCs exhibit augmented catabolic pathways with respect to oxidative phosphorylation (OXPHOS), fatty acid oxidation (FAO) and glycolysis. Functionally, tolerogenic moDCs showed the highest mitochondrial membrane potential, production of reactive oxygen species and superoxide, and increased mitochondrial spare respiratory capacity. Tolerogenic and mature moDCs manifested differential FAO gene expression with FAO activity being significantly higher in tolerogenic and immature moDCs than in mature. In addition, tolerogenic and mature moDCs demonstrated similar levels of glycolytic rate, but not glycolytic capacity and reserve, which were more pronounced in tolerogenic and immature moDCs. Finally, tolerogenic and immature moDCs, but not mature moDCs, showed high plasticity to compensate the intracellular ATP content after inhibition of different energetic metabolic pathways. Overall, tolerogenic moDCs exhibit a metabolic signature of increased, stable OXPHOS programing and high plasticity for metabolic adaptation. These findings provide a framework for future research of metabolic properties of human DCs. Total RNA of sixteen samples from four moDC types (tolerogenic, LPS-tolerogenic, immature and mature) were extracted by Trizol (Invitrogen) followed by a clean-up procedure using RNeasy Micro Kit (Qiagen). All RNA samples had an integrity number ≥9.6 assessed by Agilent Bioanalyzer. Total RNA samples were amplified using TargetAmp™ and the biotinilated cRNA was prepared by Nano-g™ Biotin-aRNA Labeling Kit for the Illumina® System (Epicentre). After the hybridization to the Illumina Human HT-12 v4 Beadchips for 17 h at 58°C, the arrays were washed, stained (Illumina Wash Protocol) and then scanned using BeadArray Scanner 500GX. Array data were extracted at the probe level without background correction using Illumina GenomeStudio software. These raw data were quantile normalized and log2 transformed. Technical replicates were obtained from the hybridization in duplicate of three samples. Pearson correlation analysis showed high correlation between the technical replicates (r>0.99). Differentially expressed genes (DEGs) were identified using Limma16 with Benjamini-Hochberg multiple testing correction (p<0.05). DEGs were further clustered into different groups according to the patterns of expression change among the different moDC types using STEM software17. The analysis was performed in R v.2.12.2 (http://www.R-project.org) with Bioconductor 2.12 (http://www.bioconductor.org) and enabled by Pipeline Pilot (www.accelrys.com).

Project description:When the yeast Saccharomyces cerevisiae is subjected to increasing glycolytic fluxes under aerobic conditions, there is a threshold value of the glucose uptake rate at which the metabolism shifts from being purely respiratory to mixed respiratory and fermentative. This shift is characterized by ethanol production, a phenomenon known as the Crabtree effect due to its analogy with lactate overflow in cancer cells. It is well known that at high glycolytic fluxes there is glucose repression of respiratory pathways resulting in a decrease in the respiratory capacity. Despite many years of detailed studies on this subject, it is not known whether the onset of the Crabtree effect (or overflow metabolism) is due to a limited respiratory capacity or caused by glucose-mediated repression of respiration. We addressed this issue by increasing respiration in S. cerevisiae by introducing a heterologous alternative oxidase, and observed reduced aerobic ethanol formation. In contrast, increasing non-respiratory NADH oxidation by overexpression of a water-forming NADH oxidase reduced aerobic glycerol formation. The metabolic response to elevated alternative oxidase occurred predominantly in the mitochondria, while NADH oxidase affected genes that catalyze cytosolic reactions. Moreover, NADH oxidase restored the deficiency of cytosolic NADH dehydrogenases in S. cerevisiae. These results indicate that NADH oxidase localizes in the cytosol, while alternative oxidase is directed to the mitochondria. The onset of aerobic ethanol formation is demonstrated to be a consequence of an imbalance in mitochondrial redox balancing. In addition to answering fundamental physiological questions, our findings are relevant for all biomass derived applications of S. cerevisiae. Experiment Overall Design: Heterologous gene expression in chemostats using Affymetrix Yeast Genome 2.0 arrays. Total RNA extraction and sample preparation, hybridization was done according to the manufacturer's protocol.

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Homo sapiens

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