Temperature regulates hypoxia-inducible factor-1 (HIF-1) in a poikilothermic vertebrate, crucian carp (Carassius carassius)

Abstract

SUMMARY Hypoxia-inducible transcription factor-1 (HIF-1) is a master regulator of hypoxia-induced gene responses. To find out whether HIF-1 function is involved in gene expression changes associated with temperature acclimation as well as in hypoxia adaptation in poikilotherms, we studied HIF-1 DNA binding activity and HIF-1α expression in normoxia and during hypoxia (0.7 mg l–1 O2) in crucian carp at temperatures of 26, 18 and 8°C. Temperature had a marked influence on HIF-1 in normoxia. Although HIF-1α mRNA levels remained unaltered, cold acclimation (8°C)increased HIF-1α protein amounts in the liver, gills and heart and HIF-1 DNA binding activity in the heart, gills and kidney of crucian carp by two- to threefold compared to warm acclimated fish (26°C). In the heart and kidney HIF-1 activity was already significantly increased in the 18°C acclimated fish. Temperature also affected hypoxic regulation of HIF-1. Although hypoxia initially increased amounts of HIF-1α protein in all studied tissues at every temperature, except for liver at 18°C, HIF-1 activity increased only in the heart of 8°C acclimated and in the gills of 18°C acclimated fish. At 8°C HIF-1α mRNA levels increased transiently in the gills after 6 h of hypoxia and in the kidney after 48 h of hypoxia. In the gills at 26°C HIF-1α mRNA levels increased after 6 h of hypoxia and remained above normoxic levels for up to 48 h of hypoxia. These results show that HIF-1 is involved in controlling gene responses to both oxygen and temperature in crucian carp. No overall transcriptional control mechanism has been described for low temperature acclimation in poikilotherms, but the present results suggest that HIF-1 could have a role in such regulation. Moreover, this study highlights interaction of the two prime factors defining metabolism,temperature and oxygen, in the transcriptional control of metabolic homeostasis in animals.

Effects of seasonal and latitudinal cold on oxidative stress parameters and activation of hypoxia inducible factor (HIF-1) in zoarcid fish

“…In this study as well as in earlier investigations of HIF response to hypoxia and temperature change in fish, HIF1a protein levels and HIF-1 DNA binding activity were detected also under normoxic, unstressed conditions in vivo (Stroka et al 2001;Rissanen et al 2006;Heise et al 2006a, b). This contrasts findings in mammalian cellular systems (e.g.…”

“…Therefore, the supershift assay could not be carried out for the Antarctic eelpout. The specificity of the observed band has been determined in three fish species in the laboratory of M. Nikinmaa (see also Soitamo et al 2001;Rissanen et al 2006). Further, the signal of the complex band appeared at the same location as that found in North Sea eelpout, indicating the band to have the molecular size of the HIF-1-EPO enhancer complex.…”

“…A role for HIF-responses is also discussed in thermal adaptation. In insect larvae HIF-1a transcripts as well as protein levels increase in response to seasonal cold exposure and freezing (Morin et al 2005), and recent studies by Rissanen et al (2006) and Heise et al (2006a, b) suggested that HIF may play a role in cold tolerance in eurythermal freshwater and marine fish. Rissanen et al (2006) exposed extremely hypoxia tolerant crucian carp to controlled cooling over several weeks and found increased HIF protein expression and/or DNA-binding activity (in band shift assays) in liver, heart, gill and kidney, which was associated with a marked increase in HSP70 and 90 levels.…”

“…In insect larvae HIF-1a transcripts as well as protein levels increase in response to seasonal cold exposure and freezing (Morin et al 2005), and recent studies by Rissanen et al (2006) and Heise et al (2006a, b) suggested that HIF may play a role in cold tolerance in eurythermal freshwater and marine fish. Rissanen et al (2006) exposed extremely hypoxia tolerant crucian carp to controlled cooling over several weeks and found increased HIF protein expression and/or DNA-binding activity (in band shift assays) in liver, heart, gill and kidney, which was associated with a marked increase in HSP70 and 90 levels. We have investigated the HIF response to cold shock in North Sea eelpout (Heise et al 2006a) and found HIF-1 DNA binding in liver tissue (the only organ we investigated) significantly enhanced following 2 h cold exposure to 1 and 5°C, compared to control fish kept at 12°C.…”

“…Proteasomal degradation of HIF-1a abrogates the hypoxic response in a tissue under physiological normoxia conditions (see Wenger 2000;Huang and Bunn 2003) and the PHDs are therefore ascribed cellular oxygen sensor functions . While most studies have suggested that HIF levels are regulated via oxygen-dependent breakdown, recent studies on hypoxia-tolerant animals from different vertebrate groups suggest that also HIF mRNA levels may be regulated (Shams et al 2004;Rissanen et al 2006;Law et al 2006).…”