Zinc plays a role in autophagy and protects cardiac cells from
ischemia/reperfusion injury. This study aimed to test if
zinc can induce mitophagy leading to attenuation of mitochondrial
superoxide generation in the setting of
hypoxia/reoxygenation (H/R) in cardiac cells. H9c2 cells were subjected to 4 h
hypoxia followed by 2 h reoxygenation. Under normoxic conditions, treatments of cells with ZnCl2 increased both the LC3-II/LC3-I ratio and GFP-LC3 puncta, implying that
zinc induces autophagy. Further experiments showed that endogenous
zinc is required for the autophagy induced by
starvation and
rapamycin.
Zinc down-regulated TOM20, TIM23, and COX4 both in normoxic cells and the cells subjected to H/R, indicating that
zinc can trigger mitophagy.
Zinc increased ERK activity and
Beclin1 expression, and
zinc-induced mitophagy was inhibited by
PD98059 and
Beclin1 siRNA during reoxygenation.
Zinc-induced
Beclin1 expression was reversed by
PD98059, implying that
zinc promotes
Beclin1 expression via ERK. In addition,
zinc failed to induce mitophagy in cells transfected with PINK1
siRNA and stabilized PINK1 in mitochondria. Moreover,
zinc-induced PINK1 stabilization was inhibited by
PD98059. Finally,
zinc prevented mitochondrial
superoxide generation and dissipation of mitochondrial membrane potential (ΔΨm) at reoxygenation, which was blocked by both the
Beclin1 and PINK1 siRNAs, suggesting that
zinc prevents mitochondrial oxidative stress through mitophagy. In summary,
zinc induces mitophagy through PINK1 and
Beclin1 via ERK leading to the prevention of mitochondrial
superoxide generation in the setting of H/R. Clearance of damaged mitochondria may account for the cardioprotective effect of
zinc on H/R injury.