Changes of intracellular Ca2+ in quercetin-induced autophagy progression.

Quercetin was previously reported to exhibit significant anti-proliferative activities, and its major effect on tumors was to induce cell apoptosis or autophagy. However, the specific mechanism remains controversial. In this study, autophagy induced by quercetin was determined with various methods. Intracellular Ca2+ ([Ca2+]i) was measured after being incubated with Fluo-3 acetoxymethyl (AM). At the same time, the relationship between the intracellular Ca2+ and autophagy induced by quercetin was further analyzed. These results showed that autophagy induced by quercetin (0-50 µg/ml) in HepG2 cells was in a dose-dependent manner. Meanwhile, when autophagy was induced by quercetin, [Ca2+]i was significantly increased. And after being incubated with calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N-tetraacetic acid-AM, autophagy was suppressed, which implied that [Ca2+]i elevation appeared to be the cause for autophagy induction. These results suggested that calcium from intracellular calcium storage may play an important role in quercetin-induced autophagy.