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SummaryIn analogy to hemoglobin (Hb) and myoglobin (Mb), neuroglobin (Ngb) and cytoglobin (Cygb) are supposed to be involved in oxygen (O 2 ) storage and delivery. The Cygb gene harbours both conserved HREs and mRNA stabilization sites, strongly suggestive of an oxygen-dependent regulation. We examined the relative transcriptional changes of Ngb and Cygb in a situation of chronic hypoxia using real-time quantitative PCR. We could conclude that Cygb is a hypoxia-induced gene, which is transcriptionally upregulated during chronic hypoxia in a hippocampal neuronal cell line and in multiple murine metabolically active tissues. The mechanism of induction of Cygb is HIF-1a dependent. HIF-1 is unique among mammalian transcription factors with respect to the specificity and sensitivity of its induction by hypoxia. Ngb expression seems to be regulated using other response elements and is less influenced by hypoxia.

Although essentially unknown, several functions are hypothesized for neuroglobin and cytoglobin, two new members of the globin family. In this article, we try to shed more light on their possible roles in hypoxia and detoxification of reactive oxygen species in vivo. The relative transcriptional changes of neuroglobin and cytoglobin in a situation of chronic hypoxia in mice were examined using real‐time quantitative PCR. The kinetics of the hypoxic expression of neuroglobin (brain, eyes) and cytoglobin (brain, eyes, liver, heart, skeletal muscle) is organ‐specific. Moreover, reactive oxygen species production is higher in liver than in the other tissues. In eyes, the negative correlation, after reoxygenation, between neuroglobin protein level and H2O2 concentration is a first proof of a reactive oxygen species‐scavenging function for neuroglobin. In addition, apoptotic cell death after hypoxia is for the first time demonstrated in heart and liver.