Copper or/and arsenic induces autophagy by oxidative stress-related PI3K/AKT/mTOR pathways and cascaded mitochondrial fission in chicken skeletal muscle

Abstract

Autophagy is an ubiquitin proteasome system for degradation of intracellular damaged proteins and organelles. Both as environmental pollutants, flourishing data show arsenic (As) and copper (Cu) as robust oxidative stress inducers. Whether this kind of damage correlates with autophagy through the phosphoinositide-3-kinase/protein kinase b/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway still remains elusive. A 12-week exposures of Cu or/and As to chicken time-dependently displayed significant element residue in the pectoralis. Aligning with previous results, a strong pro-oxidant nature of Cu and As was clearly indicated by enzyme/nonenzyme antioxidants. Fragmented mitochondria induced by oxidative damage were accompanied by overexpressed dynamin related protein-1 and decreased mitochondrial fusion-related genes. Upon comparative analysis, time-dependent conversion of light chain 3 (LC3)-I to LC3-II, increases in autophagy-related genes such as Bcl-2-interacting protein (Beclin-1) and inhibited PI3K/AKT/mTOR pathway firmly supported the fact that Cu or/and As induces autophagy. These results further coincided with ultrastructure showing clusters of vesicles and autophagosome in the skeletal muscle. Interestingly, the time-dependently elevated heat shock proteins observed in Cu or/and As treated chicken suggest the continuous adaptation and physiological acclimation of organisms to this stress responses. Interestingly, the combination of copper and arsenic elicited more serious oxidative damage and its-cascaded injuries than their individuals. Together, our results showed that after Cu or/and As insult and accumulation, inhibited PI3K/AKT/mTOR pathway activated autophagy and disturbed mitochondrial dynamic, forming a positive feedback with redox disorder.