Highlighting curcumin-induced crosstalk between autophagy and apoptosis: A biochemical approach coupling impedancemetry, imaging, and flow cytometry

Curcumin, a major active component of turmeric ( Curcuma longa, L. ), is known to have various effects on both healthy and cancerous tissues. In vitro studies suggest that curcumin inhibits cancer cell growth by activating apoptosis, but the mechanism underlying the anticancer effects of curcumin is still unclear. Since there is a consensus about endoplasmic reticulum (ER) stress being involved in the cytotoxicity of many natural compounds, we investigated by Amnis®Imaging flow cytometry the mechanistic aspects of curcumin’s destabilization of the ER, but also the status of the lysosomal compartment involved in curcumin-associated apoptosis. Curcumin induces ER stress thereby causing an unfolded protein response (UPR) and calcium release which destabilize the mitochondrial compartment and induce apoptosis. These events are also associated with secondary lysosomal membrane permeabilization and activation of caspase-8, mediated by activation of cathepsins and calpains. We previously showed that sequence lead to the generation of truncated tBid and disruption of mitochondrial homeostasis. These two pathways of different intensities and momentum converge towards an amplification of cell death that still needs to be studied in more detail. It has been suggested that it may be possible to exploit autophagy for cancer therapy. There is a complex interplay involving early autophagy as soon as mitochondria produce superoxide anions and hydrogen peroxide. Treatments with 10 µM to 20 µM curcumin induce autophagosome formation, while only early events of cell death are detectable.In the present study, curcumin-induced autophagy failed to rescue all cells since most cells underwent type II cell death following initial autophagic processes. However, a small number of cells blocked in the cell cycle escaped and were rescued to give rise to a novel proliferation phase.