Piperlongumine selectively kills glioblastoma multiforme cells via reactive oxygen species accumulation dependent JNK and p38 activation

Abstract

Piperlongumine (PL), a natural alkaloid isolated from the long pepper, may have anti-cancer properties. It selectively targets and kills cancer cells but leaves normal cells intact. Here, we reported that PL selectively killed glioblastoma multiforme (GBM) cells via accumulating reactive oxygen species (ROS) to activate JNK and p38. PL at 20μM could induce severe cell death in three GBM cell lines (LN229, U87 and 8MG) but not astrocytes in cultures. PL elevated ROS prominently and reduced glutathione levels in LN229 and U87 cells. Antioxidant N-acetyl-L-cysteine (NAC) completely reversed PL-induced ROS accumulation and prevented cell death in LN229 and U87 cells. In LN229 and U87 cells, PL-treatment activated JNK and p38 but not Erk and Akt, in a dosage-dependent manner. These activations could be blocked by NAC pre-treatment. JNK and p38 specific inhibitors, SB203580 and SP600125 respectively, significantly blocked the cytotoxic effects of PL in LN229 and U87 cells. Our data first suggests that PL may have therapeutic potential for one of the most malignant and refractory tumors GBM.

Keywords: 2′-,7′-dichlorofluorescin diacetate; 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; Apoptosis; Brain tumor; Cancer therapy; DCFH-DA; DMEM; DMSO; Dulbecco’s modified Eagle’s medium; FBS; FCM; GBM; GSH; Glioma; JNK; MTT; N-acetyl-l-cysteine; NAC; Oxidative stress; PBS; PI; PL; Piplartine; ROS; c-jun N-terminal kinase; dimethyl sulfoxide; fetal bovine serum; flow cytometry; glioblastoma multiforme; glutathione; phosphate buffered saline; piperlongumine; propidium iodide; reactive oxygen species.