Incomplete autophagy and increased cholesterol synthesis during neuronal cell death caused by a synthetic cannabinoid, CP-55,940

There is a propensity for synthetic cannabinoid abuse to spread worldwide. CP-55,940, a synthetic cannabinoid having the ability to activate both CB1 and CB2 receptors, has been shown to induce cell death in neurons as well as other cells. Here we investigate molecular events underling the adverse effects of CP-55,940 on neuronal cells. Exposure of mouse neuroblastoma Neuro2a cells to 10–50 µM CP-55,940 results in concentration-dependent cell death that is not accompanied by an induction of apoptosis. CP-55,940 also stimulates autophagy, but the stimulation is not followed by an increase in autophagic degradation. Transcriptome analysis using DNA microarray revealed the increased expression of genes for the cholesterol biosynthesis pathway that is associated with the activation of SREBP-2, the master transcriptional regulator of cholesterol biosynthesis. However, free cholesterol is localized mainly to cytoplasmic structures, although it is localized to the plasma membrane in healthy cells. Thus, cellular trafficking of cholesterol seems to be somewhat disrupted in CP-55,940 stimulated cells. These results show for the first time that CP-55,940 stimulates autophagy as well as cholesterol biosynthesis, although not all the processes involved in the cellular response to CP-55,940 seem to be complete in these cells.