252 research outputs found
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Hypoxia and neurodegeneration
No full textPeriods of chronic hypoxia, which can arise from numerous cardiorespiratory disorders, predispose individuals to the development of dementias, particularly Alzheimer's disease (AD). AD is characterized in part by the increased production of amyloid beta peptide (Abeta), which forms the extracellular plaques by which the disease can be identified post mortem. Numerous studies have now shown that hypoxia, even in vitro, can increase production of Abeta in different cell types. Evidence has been produced to indicate hypoxia alters both expression of the Abeta precursor, APP, and also the expression of the secretase enzymes, which cleave Abeta from APP. Other studies implicate reduced Abeta degradation as a possible means by which hypoxia increases Abeta levels. Such variability may be attributable to cell-specific responses to hypoxia. Further evidence indicates that some, but not all of the cellular adaptations to chronic hypoxia (including alteration of Ca(2+) homeostasis) require Abeta formation. However, other aspects of hypoxic remodeling of cell function appear to occur independently of this process. The molecular and cellular responses to hypoxia contribute to our understanding of the clinical association of hypoxia and increased incidence of AD. However, it remains to be determined whether inhibition of one or more of the effects of hypoxia may be of benefit in arresting the development of this neurodegenerative disease
TOR Signaling Couples Oxygen Sensing to Lifespan in C. elegans
No full textSummaryMetazoans adapt to a low-oxygen environment (hypoxia) through activation of stress-response pathways. Here, we report that transient hypoxia exposure extends lifespan in C. elegans through mitochondrial reactive oxygen species (ROS)-dependent regulation of the nutrient-sensing kinase target of rapamycin (TOR) and its upstream activator, RHEB-1. The increase in lifespan during hypoxia requires the intestinal GATA-type transcription factor ELT-2 downstream of TOR signaling. Using RNA sequencing (RNA-seq), we describe an ELT-2-dependent hypoxia response that includes an intestinal glutathione S-transferase, GSTO-1, and uncover that GSTO-1 is required for lifespan under hypoxia. These results indicate mitochondrial ROS-dependent TOR signaling integrates metabolic adaptations in order to confer survival under hypoxia
NF-kappa B controls energy homeostasis and metabolic adaptation by upregulating mitochondrial respiration
No full textCell proliferation is a metabolically demanding process(1,2). It requires active reprogramming of cellular bioenergetic pathways towards glucose metabolism to support anabolic growth(1,2). NF-kappa B/Rel transcription factors coordinate many of the signals that drive proliferation during immunity, inflammation and oncogenesis(3), but whether NF-kappa B regulates the metabolic reprogramming required for cell division during these processes is unknown. Here, we report that NF-kappa B organizes energy metabolism networks by controlling the balance between the utilization of glycolysis and mitochondria! respiration. NF-kappa B inhibition causes cellular reprogramming to aerobic glycolysis under basal conditions and induces necrosis on glucose starvation. The metabolic reorganization that results from NF-kappa B inhibition overcomes the requirement for tumour suppressor mutation in oncogenic transformation and impairs metabolic adaptation in cancer in vivo. This NF-kappa B-dependent metabolic pathway involves stimulation of oxidative phosphorylation through upregulation of mitochondrial synthesis of cytochrome c oxidase 2 (SCO2; ref. 4). Our findings identify NF-kappa B as a physiological regulator of mitochondrial respiration and establish a role for NF-kappa B in metabolic adaptation in normal cells and cancer.</p
ROS Function in Redox Signaling and Oxidative Stress
No full textOxidative stress refers to elevated intracellular levels of reactive oxygen species (ROS) that cause damage to lipids, proteins and DNA. Oxidative stress has been linked to a myriad of pathologies. However, elevated ROS also act as signaling molecules in the maintenance of physiological functions — a process termed redox biology. In this review we discuss the two faces of ROS — redox biology and oxidative stress — and their contribution to both physiological and pathological conditions. Redox biology involves a small increase in ROS levels that activates signaling pathways to initiate biological processes, while oxidative stress denotes high levels of ROS that result in damage to DNA, protein or lipids. Thus, the response to ROS displays hormesis, given that the opposite effect is observed at low levels compared with that seen at high levels. Here, we argue that redox biology, rather than oxidative stress, underlies physiological and pathological conditions
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