Effects Of Autophagy And Cross-talk Between Autophagy And Apoptosis On Curcumin-induced Death Of K562 Cells

AIM To study the effects of autophagy and cross-talk between autophagy and apoptosis in Curcumin-induced death of K562 cellsMETHODS After treatment with Curcumin , the growth inhibition of K562 cells was assessed by MTT colorimetric assay. MDC staining was used to examine autophagy induced by Curcumin in K562 cells. Hoechest and AOEB staining were used to examine apoptosis induced by Curcumin in K562 cells. To examine the involvement of autophagy in Curcumin -induced death of K562 cells, the autophagy specific inhibitor 3-methyadenine (3-MA) was added with Curcumin and the cytotoxicity of Curcumin was measured by lactose dehydrogenase (LDH) leakage. Immunohistochemistry, flow cytometry and analysis were used to study the apoptotic and autophagic mechanisms involved in death of K562 cells.RESULTS The proliferation of K562 cells was significantly inhibited in a dose-and time-dependent manner after Curcumin treatment. Autophagy was induced in K562 cells as detected by MDC staining; A poptosis was induced in K562 cells as detected by both Hoechest and AOEB staining ; The autophagy specific inhibitor 3-MA exerted opposite effects on Curcumin -induced death of K562 cells: 3-MA potentiated Curcumin's cytotoxicitiy in K562 cells when administered 1h before Curcumin; while it attenuated Curcumin -induced death of K562 cells when administered 30 min after Curcumin. What's more, once autophagy was induced by Curcumin, LC3, the autophagic protein in mammalian cells was also activated. Moreover, pretreatment with 3-MA prior to Curcumin amplified above-mentioned apoptotic signaling pathways, but it inhibited these signaling pathways when 3-MA was administered post- Curcumin insult. CONCLUSION The proliferation of K562 cells was significantly inhibited after Curcumin treatment. Autophagy and apoptosis were induced after Curcumin treatment. Autophagic mechanism has differential contributions to Curcumin -induced apoptotic death of K562 cells at different stasges of cell death: its activation delays Curcumin -induced cell death at the initiation phase of apoptosis and accelates cell death at the later phase of apoptosis. The dual roles of autophagy in apoptotic process may occur through mitochondria mediated signaling pathway.