Aspirin upregulates αB-Crystallin to protect the myocardium against heat stress in broiler chickens

We established in vivo and in vitro models to investigate the role of alpha B-Crystallin (CryAB) and assess the ability of aspirin (ASA) to protect the myocardium during prolonged heat stress. Thirty-day-old chickens were divided into three groups (n = 90): heat stress (HS, 40 +/- 1 degrees C); ASA(-) HS(+), 1 mg/kg ASA orally 2 h before heat stress; and ASA(+) HS(-), pretreated with aspirin, no heat stress (25 degrees C). Hearts were excised after 0, 1, 2, 3, 5, 7, 10, 15 and 24 h. Heat stress increased body temperature, though the ASA(-) HS(+) group had significantly higher temperatures than the ASA(+) HS(+) group at all time points. Compared to ASA(+) HS(+), the ASA(-) HS(+) group displayed increased sensitivity to heat stress. Pathological analysis revealed the ASA (+) HS(+) myocardium showed less severe changes (narrowed, chaotic fibers; fewer necrotic cells) than the ASA(-) HS(+) group (bleeding and extensive cell death). In vitro, ASA-pretreatment significantly increased primary chicken myocardial cell survival during heat stress. ELISAs indicated ASA induced CryAB in vivo to protect against heat stress-induced myocardial damage, but ASA did not induce CryAB in primary chicken myocardial cells. The mechanisms by which ASA induces the expression of CryAB in vivo and protects the myocardium during heat stress merit further research.