Mitochondrial oxidative damage in chicken skeletal muscle induced by acute heat stress

Mitochondria have long been known to play a critical role in maintaining bioenergetic status under physiological conditions. Our previous studies have shown that acute heat stress increases production of mitochondrial reactive oxygen species (ROS) in the skeletal muscle of chickens. This increased ROS production may lead to nonspecific modification of lipids and proteins, which may then result in bioenergetic dysfunctions. If increased mitochondrial ROS production in heat-stressed chickens causes oxidative damage, changes in mitochondrial peroxidized lipids and oxidatively modified proteins can be detected. To study this, 3-week-old male broiler chickens (n=4-8) were exposed to acute heat stress (34°C for 18 h) while control chickens were kept at thermoneutral condition (25°C). Skeletal muscle subsarcolemmal mitochondria were isolated and used to study mitochondrial malondialdehyde (MDA) and protein carbonyl groups. Mitochondrial thiobarbituric acid reactive substances (TBARS) formation was measured colorimetrically with 0.01% butylated hydroxytoluene (BHT) and expressed as MDA equivalent. To detect oxidation-sensitive mitochondrial proteins, polypeptides resolved by two-dimensional (2D) electrophoresis were immunostained with DNP-specific antibodies for carbonylated proteins using Western blotting. In heat-stressed chickens, mitochondrial MDA was 2.7-fold higher, and 82 mitochondrial proteins were oxidized when compared to that of control chickens. These results suggest that in heat-stressed chickens, increased mitochondrial ROS production leads to oxidative damage to mitochondrial lipids and proteins.