Hypoxia-inducible factor-1? is involved in the response to heat stress in lactating dairy cows

Hypoxia-inducible factor-1 alpha (HIF-1 alpha) is important in maintaining cellular oxygen homeostasis and cellular heat tolerance. To explore the role of HIF-1 alpha in the response to heat stress (HS) in dairy cows, 16 Chinese Holstein cows (milk yield: 32 & PLUSMN; 4 kg/d, days in milk: 272 & PLUSMN; 7 d, parity: 2-3) were used to collect coccygeal vein blood and milk samples when cows were under mild (temperature-humidity index = 77) and moderate HS (temperature-humidity index = 84), respectively. Compared to cows under mild HS, the respiratory rate (P < 0.01), rectal temperature (P < 0.01), and blood concentrations of heat shock protein (HSP)70 (P < 0.01) and HSP27 (P < 0.01) were higher, but oxygen saturation (P = 0.02) and hemoglobin (P < 0.01) were lower in cows under moderate HS. Blood HIF-1 alpha concentration was greater (P < 0.01) during moderate HS, indicating that HIF-1 alpha is involved in lactating cows' response to HS. To confirm these findings, we collected coccygeal vein blood and milk samples from 59 dairy cows under moderate HS. The HIF-1 alpha levels were correlated with the levels of heat shock transcription factor (HSF) (r = 0.7857, P < 0.01), HSP70 (r = 0.4543, P < 0.01) and HSP27 (r = 0.8782, P < 0.01). A comparison of 15 cows with higher HIF-1 alpha (> 482 ng/L) and 15 cows with lower HIF-1 alpha levels (< 439 ng/L) showed that reactive oxidative species were higher (P = 0.02), but superoxide dismutase (P < 0.01), total antioxidation capacity (P = 0.02) and glutathione peroxidase (P < 0.01) were lower in higher HIF-1 alpha cows. These results suggested that HIF-1 alpha may be indicative of the risk of oxidative stress in heat-stressed cows and may participate in the response of cows to HS by synergistically activating the expression of the HSP family with HSF.

Automated summary

HIF-1 alpha plays an important role in the response of dairy cows to heat stress. During moderate heat stress, respiratory rate, rectal temperature, and blood concentrations of HSP70 and HSP27 were higher, while oxygen saturation and hemoglobin concentration were lower compared to mild heat stress. Additionally, HIF-1 alpha concentration was higher during moderate heat stress, indicating its involvement in the response of lactating cows to heat stress. Further research confirmed these findings.