Acute heat stress alters the expression of genes and proteins associated with the unfolded protein response pathway in the liver of broilers.

1. The aim of this study was to explore the effects of acute heat stress on serum hormone levels and the expression of genes and proteins related to the unfolded protein response (UPR) pathway and apoptotic process in the liver of broilers.2. A total of 144 Arbor Acres broilers (35-d-old) were randomly allocated to 4 different environmental-controlled chambers for acute heat exposure. The temperature of the 4 environmental chambers was adjusted to 26°C (control), 29°C, 32°C, and 35°C within 1 h, respectively. The blood and liver samples were collected after 6 h of constant heat exposure at set temperatures.3. The results showed that 6 h of acute heat stress increased serum hormone levels and up-regulated the expression of heat shock protein. The endoplasmic reticulum (ER) stress markers, GRP78 and GRP94, in the liver of broilers were significantly upregulated at the mRNA and protein levels. The PERK, IRE1, and XBP1 genes, which are involved in the unfolded protein response signalling, were significantly up-regulated at the mRNA levels. However, other pro-apoptotic genes showed no significant changes in the liver of broiler chickens in all groups except for upregulation of the anti-apoptotic gene BCL-xl.4. The results suggested that broilers have tolerance to acute heat stress to a certain extent. The UPR activation can alleviate ER stress and further prevent apoptosis in the liver of broilers under short-term exposure to high ambient temperatures.

Fas-induced caspase denitrosylation.

Only a few intracellular S-nitrosylated proteins have been identified, and it is unknown if protein S-nitrosylation/denitrosylation is a component of signal transduction cascades. Caspase-3 zymogens were found to be S-nitrosylated on their catalytic-site cysteine in unstimulated human cell lines and denitrosylated upon activation of the Fas apoptotic pathway. Decreased caspase-3 S-nitrosylation was associated with an increase in intracellular caspase activity. Fas therefore activates caspase-3 not only by inducing the cleavage of the caspase zymogen to its active subunits, but also by stimulating the denitrosylation of its active-site thiol. Protein S-nitrosylation/denitrosylation can thus serve as a regulatory process in signal transduction pathways.