Healthy guts exclude oxygen: Normally, the lumen of the colon lacks oxygen. Fastidiously anaerobic butyrate-producing bacteria thrive in the colon; by ablating these organisms, antibiotic treatment removes butyrate. Byndloss et al. discovered that loss of butyrate deranges metabolic signaling in gut cells (see the Perspective by Cani). This induces nitric oxidase to generate nitrate in the lumen and disables β-oxidation in epithelial cells that would otherwise mop up stray oxygen before it enters the colon. Simultaneously, regulatory T cells retreat, and inflammation is unchecked, which contributes yet more oxygen species to the colon. Then, facultative aerobic pathogens, such as Escherichia coli and Salmonella enterica , can take advantage of the altered environment and outgrow any antibiotic-crippled and benign anaerobes. Science , this issue p. 570 ; see also p. 548

Thiamine (vitamin B1) is an essential nutrient that serves as a cofactor for a number of enzymes, mostly with mitochondrial localization. Some thiamine-dependent enzymes are involved in energy metabolism and biosynthesis of nucleic acids whereas others are part of the antioxidant machinery. The brain is highly vulnerable to thiamine deficiency due to its heavy reliance on mitochondrial ATP production. This is more evident during rapid growth (i.e., perinatal periods and children) in which thiamine deficiency is commonly associated with either malnutrition or genetic defects. Thiamine deficiency contributes to a number of conditions spanning from mild neurological and psychiatric symptoms (confusion, reduced memory, and sleep disturbances) to severe encephalopathy, ataxia, congestive heart failure, muscle atrophy, and even death. This review discusses the current knowledge on thiamine deficiency and associated morbidity of neurological and psychiatric disorders, with special emphasis on the pediatric population, as well as the putative beneficial effect of thiamine supplementation in autism spectrum disorder (ASD) and other neurological conditions.

Aims: Oxidative stress is thought to be involved in Friedreich's ataxia (FRDA), yet it has not been demonstrated in the target neurons that are first to degenerate. Using the YG8R mouse model of FRDA, microarray and neuritic growth experiments were carried out in the dorsal root ganglion (DRG), the primary site of neurodegeneration in this disease. Results: YG8R hemizygous mice exhibited defects in movement, and DRG neurites had growth defects. Microarray of DRG tissue identified decreased transcripts encoding the antioxidants, including peroxiredoxins, glutaredoxins, and glutathione S-transferase, and these were confirmed by immunoblots and quantitative real-time PCR. Because the decreased gene transcripts are the known targets of the antioxidant transcription factor nuclear factor-E2-related factor-2 (Nrf2), Nrf2 expression was measured; it was significantly decreased at the transcript and protein level in both the DRG and the cerebella of the YG8R hemizygous mouse; further, frataxin expression was significantly correlated with Nrf2 expression. Functionally, in YG8R hemizygous DRG, the total glutathione levels were reduced and explanted cells were more sensitive to the thioredoxin reductase (TxnRD) inhibitor auranofin, a thiol oxidant. In cell models of FRDA, including Schwann and the DRG, frataxin deficiency caused a decreased expression of the Nrf2 protein level in the nucleus, but not a defect in its translocation from the cytosol. Further, frataxin-deficient cells had decreased enzyme activity and expression of TxnRD, which is regulated by Nrf2, and were sensitive the TxnRD inhibitor auranofin. Innovation and Conclusion: These results support a mechanistic hypothesis in which frataxin deficiency decreases Nrf2 expression in vivo, causing the sensitivity to oxidative stress in target tissues the DRG and the cerebella, which contributes to the process of neurodegeneration. Antioxid. Redox Signal. 19, 1481–1493.

The neurodegenerative disorder Friedreich’s ataxia (FRDA) is caused by mutations in frataxin, a mitochondrial protein whose function remains controversial. Using co-immunoprecipitation and mass spectrometry we identified multiple interactors of mitochondrial frataxin in mammalian cells. One interactor was mortalin/GRP75, a homolog of the yeast ssq1 chaperone that integrates iron–sulfur clusters into imported mitochondrial proteins. Another interactor was ISD11, recently identified as a component of the eukaryotic complex Nfs1/ISCU, an essential component of iron–sulfur cluster biogenesis. Interactions between frataxin and ISD11, and frataxin and GRP75 were confirmed by co-immunoprecipitation experiments in both directions. Immunofluorescence analysis demonstrated that ISD11 co-localized with both frataxin and with mitochondria. The point mutations I154F and W155R in frataxin cause FRDA and are clustered to one surface of the protein, and these mutations decrease the interaction of frataxin with ISD11. The frataxin/ISD11 interaction was also decreased by the chelator EDTA, and was increased by supplementation with nickel but not other metal ions. Nickel supplementation rescued the defective interaction of mutant frataxin I154F and W155R with ISD11. Upon ISD11 depletion by siRNA in HEK293T cells, the amount of the Nfs1/ISCU protein complex declined, as did the activity of the iron–sulfur cluster enzyme aconitase, while the cellular iron content was increased, as seen in tissues from FRDA patients. Furthermore, ISD11 mRNA levels were decreased in FRDA patient cells. These data suggest that frataxin binds the iron–sulfur biogenesis Nfs1/ISCU complex through ISD11, that the interaction is nickel-dependent, and that multiple consequences of frataxin deficiency are duplicated by ISD11 deficiency.

Mesenchymal stem cells (MSCs) from adult and neonatal tissues are intensively investigated for their use in regenerative medicine. The purpose of this study was to compare the onset of replicative senescence in MSCs isolated from equine bone marrow (BMSC), adipose tissue (ASC), and umbilical cord tissue (UCMSC). MSC proliferation (cell doubling), senescence-associated β-galactosidase staining, telomere length, Sox-2 , and lineage-specific marker expression were assessed for MSCs harvested from tissues of 4 different donors. The results show that before senescence ensued, all cell types proliferated at ∼1 day/cell doubling. BMSCs significantly increased population doubling rate by passage 10 and ceased proliferation after a little >30 total population doublings, whereas UCMSCs and ASCs achieved about 60 to 80 total population doublings. UCMSC and ASCs showed marked β-galactosidase staining after ∼70 population doublings, whereas BMSCs stained positive by ∼30 population doublings. The onset of senescence was associated with a significant reduction in telomere length averaging 10.2 kbp at passage 3 and 4.5 kbp in senescent cultures. MSCs stained intensively for osteonectin at senescence compared with earlier passages, whereas vimentin and low levels of smooth muscle actin were consistently expressed. Sox-2 gene expression was consistently noted in all 3 MSC types. In conclusion, equine BMSCs appear to senesce much earlier than ASCs and UCMSCs. These results demonstrate the limited passage numbers of subcultured BMSCs available for use in research and tissue engineering and suggest that adipose tissue and umbilical cord tissue may be preferable for tissue banking purposes.

Cancer is frequently characterized histologically by the appearance of large cells that are either aneuploid or polyploid. Aneuploidy and polyploidy are hallmarks of radiation-induced mitotic catastrophe (MC), a common phenomenon occurring in tumor cells with impaired p53 function following exposure to various cytotoxic and genotoxic agents. MC is characterized by altered expression of mitotic regulators, untimely and abnormal cell division, delayed DNA damage, and changes in morphology. We report here that cells undergoing radiation-induced MC are more plastic with regards to ploidy and that this plasticity allows them to reorganize their genetic material through reduction division to produce smaller cells which are morphologically indistinguishable from control cells. Experiments conducted with the large-scale digital cell analysis system are discussed and show that a small fraction of polyploid cancer cells formed via radiation-induced MC can survive and start a process of depolyploidization that yields various outcomes. Although most multipolar divisions failed and cell fusion occurred, some of these divisions were successful and originated a variety of cell progeny characterized by different ploidy. Among these ploidy phenotypes, a progeny of small mononucleated cells, indistinguishable from the untreated control cells, is often seen. We report here evidence that meiosis-specific genes are expressed in the polyploid cells during depolyploidization. Tumor cells might take advantage of the temporary change from a promitotic to a promeiotic division regimen to facilitate depolyploidization and restore the proliferative state of the tumor cell population. These events might be mechanisms by which tumor progression and resistance to treatment occur in vivo. [Cancer Res 2009;69(6):2296–304]