mtROS-mediated Akt/AMPK/mTOR pathway was involved in Copper-induced autophagy and it attenuates Copper-induced apoptosis in RAW264.7 mouse monocytes

Abstract

Copper (Cu) is a trace element necessary in animals as well as human beings. However, excessive Cu is toxic to immunocytes, but the precise mechanism is largely unclear so far. This work was conducted aiming to examine the Cu-mediated autophagy mechanism together with its role in Cu toxicology in RAW264.7 cells. Here, we demonstrated that CuSO₄ reduced the cell viability depending on its dose. CuSO₄ could obviously increase autophagy in RAW264.7 cells. According to the obtained results, CuSO₄ induced autophagy through Akt/AMPK/mTOR pathway which characterized by down regulation of p-Akt (Ser473)/Akt, p-mTOR/mTOR, p-ULK1(Ser757)/ULK1 and subsequent up-regulation of p-AMPKα/AMPKα and p-ULK1(Ser555)/ULK1. Furthermore, CuSO₄ significantly induced the production of mitochondrial reactive oxygen species (mtROS). In addition, CuSO₄-mediated apoptosis and autophagy might be suppressed through suppressing mtROS generation by exposure to Mito-TEMPO. Intriguingly, autophagy promotion with rapamycin could decrease the apoptosis and the inhibition of autophagy with knock down Atg5 could enhance the apoptosis induced by CuSO₄. Moreover, our results suggested that mtROS is the original cause in CuSO₄-induced apoptosis and autophagy. Additionally, CuSO₄ induced autophagy through mtROS-dependent Akt/AMPK/mTOR signalling pathwayin RAW264.7 cells. Moreover, autophagy activation might potentially generate a protection mechanism for improving CuSO₄-induced RAW264.7 cell apoptosis.

Keywords: Apoptosis; Autophagy; CuSO(4); RAW264.7 cells; mtROS.