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Hypoxia‐inducible factor (HIF‐1) as the primary factor mediating gene‐dependent cellular responses to hypoxia represents an attractive target for the therapeutic interventions. The current Editorial comments on an as yet underestimated facet of HIF‐1–related research. The activity of HIF‐1 is being regulated by the availability of its α‐subunit HIF‐1α, which undergoes quick degradation. The process of degradation is initiated by prolyl 4‐hydroxylase (PHD). PHD is an oxygen‐dependent enzyme and therefore is inactivated in hypoxia, in turn resulting in HIF‐1α stabilization, its dimerization with HIF‐1β subunit thereby producing the transcriptionally active factor. It has been suggested that pharmacological inhibition of PHD activity might give the same results. Indeed, a large body of evidence on beneficial effects of PHD inhibitors has been accumulated in multiple laboratory and clinical trials. In addition to them, a paper by Li and colleagues published in this issue of Journal of Neurochemistry also reports that inhibition of PHD by adaptaquin reduces hypoxic‐ischemic brain injury in a neonatal mouse model. When dissecting the underlying molecular mechanisms, Li and colleagues surprisingly found that the observed effects appear to be independent of HIF‐1. These findings draw attention back to the question about possible HIF‐1 effects independent of PHD inhibitors, which has been raised several years ago but has not received sufficient attention so far, and is being discussed in this Editorial. One of the possible mechanisms might be ascribed to the ferroptosis pathway affected by PHD inhibitors but this question needs further careful studies, as well as clarification of other mechanisms possibly involved. Even if they represent a prospective therapeutic strategy, the lack of current knowledge about endogenous targets of PHD inhibitors, except for PHD, calls for a careful and balanced approach toward their clinical use. [ABSTRACT FROM AUTHOR]

Abstract: The microbiome and its cross‐talk with the brain have drawn increasing attention lately, since imbalances in the gut microbiota's composition may result in pathogenic dysfunctions affecting brain functioning up to development of neurodegenerative and mental diseases. The current Editorial discusses a study by Gao and coworkers in the current issue of the Journal of Neurochemistry in which the authors use a model of antibiotic‐induced dysbiosis ‐ targeted infusion of antibiotics into the gut ‐ to assess if microbiotic metabolites exert effects on local neurotransmitter expression or contribute to the gut‐brain axis. The authors mechanistically link distal ileal infusion of antibiotics with a change in the levels of microbial metabolites that affect the expression of neurotransmitters in the brain and thereby can participate in the fine‐tuning of the hypothalamic functions, including regulation of visceral and neuroendocrine processes, stress responses, mood and anxiety. Their study thus represents an important step towards our understanding of the brain‐gut axis, with the potential to advance therapeutics. [ABSTRACT FROM AUTHOR]

Preconditioning using mild repetitive hypobaric hypoxia is known to increase a tolerance of brain neurons to severe hypoxia and other injurious exposures. In the present study, the effects of mild hypoxic preconditioning on the expression of transcription factors NF-κB and phosphorylated CREB (pCREB) has been studied in the neocortex of rats exposed to severe hypobaric hypoxia. As revealed by quantitative immunocytochemistry, the injurious severe hypobaric hypoxia (180 Torr, 3 h) remarkably reduced the neocortical levels of pCREB and NF-κB. The three-trial hypoxic preconditioning (360 Torr, 2 h, 3 days) induced persistent up-regulation of pCREB and NF-κB expression in the neocortex of rats 3–24 h following the severe hypoxia. In addition, the preconditioning alone which was not followed by the severe hypoxia, considerably increased neocortical pCREB and NF-κB levels. The findings suggest a role for transcription factors cAMP response element-binding protein and NF-κB in the neuroprotective mechanisms activated by the hypoxic preconditioning. [ABSTRACT FROM AUTHOR]

Abstract Thioredoxins are a class of small redox-regulating proteins that have been implicated in the control of various aspects of cellular functions and seem to be one of the key regulators of signalling in the cellular responses to various stresses. Thioredoxin-2 (Trx2) is a novel mammalian thioredoxin which, in contrast to previously known cytosolic thioredoxin (Trx1), has been localized to the mitochondria. Trx2 is abundantly expressed in skeletal muscle, heart and adrenal gland, as well as in some other peripheral tissues with high metabolic activity. Using in situ hybridization and immunohistochemistry, we have studied the distribution and regulation of Trx2 expression in the rat brain. Trx2 mRNA and protein are highly expressed in the neurons in several brain regions, including the olfactory bulb, frontal cortex, hippocampus, some hypothalamic and thalamic nuclei, cerebellum and numerous brainstem nuclei. In addition, the Trx2 mRNA expression in paraventricular hypothalamic nucleus and reticular thalamic nucleus was found to be sensitive to peripheral glucocorticoids, as dexamethasone treatment caused significant elevation of Trx2 mRNA level in this area. No changes in other brain areas were observed after dexamethasone treatment. These findings implicate a significant regulatory and/or protective function of Trx2 in the nervous system. [ABSTRACT FROM AUTHOR]

Intermittent hypoxia (IH) is commonly associated with pathological conditions, particularly obstructive sleep apnoea. However, IH is also increasingly used to enhance health and performance and is emerging as a potent non‐pharmacological intervention against numerous diseases. Whether IH is detrimental or beneficial for health is largely determined by the intensity, duration, number and frequency of the hypoxic exposures and by the specific responses they engender. Adaptive responses to hypoxia protect from future hypoxic or ischaemic insults, improve cellular resilience and functions, and boost mental and physical performance. The cellular and systemic mechanisms producing these benefits are highly complex, and the failure of different components can shift long‐term adaptation to maladaptation and the development of pathologies. Rather than discussing in detail the well‐characterized individual responses and adaptations to IH, we here aim to summarize and integrate hypoxia‐activated mechanisms into a holistic picture of the body's adaptive responses to hypoxia and specifically IH, and demonstrate how these mechanisms might be mobilized for their health benefits while minimizing the risks of hypoxia exposure. [ABSTRACT FROM AUTHOR]

The article presents an abstract of the study "Expression of Trap220 in Developing and Adult Rat Central Nervous System." The study will be presented at a joint meeting of the International Society for Neurochemistry and the European Society for Neurochemistry which will be organized in Berlin, Germany, from August 8-14, 1999. The study revealed the significant role played by thyroid hormone receptor-associated protein in processes of growth and differentiation of neural tissues.