The heme oxygenase-1 inhibitor ZnPPIX induces non-canonical, Beclin 1-independent, autophagy through p38 MAPK pathway.

Zinc protoporphyrin IX (ZnPPIX), a heme oxygenase-1 enzyme inhibitor, has been reported to induce apoptosis and to have antitumor properties. Here, we report that ZnPPIX triggers autophagy and causes defective autophagy flux in HeLa cells. Autophagosome formation was independent of Beclin 1, indicating non-canonical autophagy activity in ZnPPIX-treated cells. Furthermore, western blot results indicated that p38 MAPK (mitogen-activated protein kinase) was phosphorylated in treated cells. Consistently, SB203580 (a p38 inhibitor) obviously inhibited the accumulation of autophagosomes. Our results indicated that p38 MAPK may be a key regulator for non-canonical Beclin1-independent autophagy.