Cytosolic calcium mediates RIP1/RIP3 complex-dependent necroptosis through JNK activation and mitochondrial ROS production in human colon cancer cells.

Necroptosis is a form of programmed necrosis mediated by signaling complexes with receptor-interacting protein 1 (RIP1) and RIP3 kinases as the main mediators. However, the underlying execution pathways of this phenomenon have yet to be elucidated in detail. In this study, a RIP1/RIP3 complex was formed in 2-methoxy-6-acetyl-7-methyljuglone (MAM)-treated HCT116 and HT29 colon cancer cells. With this formation, mitochondrial reactive oxygen species (ROS) levels increased, mitochondrial depolarization occurred, and ATP concentrations decreased. This process was identified as necroptosis. This finding was confirmed by experiments showing that MAM-induced cell death was attenuated by the pharmacological or genetic blockage of necroptosis signaling, including RIP1 inhibitor necrostatin-1s (Nec-1s) and siRNA-mediated gene silencing of RIP1 and RIP3, but was unaffected by caspase inhibitor z-vad-fmk or necrosis inhibitor 2-(1H-Indol-3-yl)-3-pentylamino-maleimide (IM54). Transmission electron microscopy (TEM) analysis further revealed the ultrastructural features of MAM-induced necroptosis. MAM-induced RIP1/RIP3 complex triggered necroptosis through cytosolic calcium (Ca2+) accumulation and sustained c-Jun N-terminal kinase (JNK) activation. Both calcium chelator BAPTA-AM and JNK inhibitor SP600125 could attenuate necroptotic features, including mitochondrial ROS elevation, mitochondrial depolarization, and ATP depletion. 2-thenoyltrifluoroacetone (TTFA), which is a mitochondrial complex II inhibitor, was found to effectively reverse both MAM induced mitochondrial ROS generation and cell death, indicating the complex II was the ROS-producing site. The essential role of mitochondrial ROS was confirmed by the protective effect of overexpression of manganese superoxide dismutase (MnSOD). MAM-induced necroptosis was independent of TNFα, p53, MLKL, and lysosomal membrane permeabilization. In summary, our study demonstrated that RIP1/RIP3 complex-triggered cytosolic calcium accumulation is a critical mediator in MAM-induced necroptosis through sustained JNK activation and mitochondrial ROS production. Our study also provided new insights into the molecular regulation of necroptosis in human colon cancer cells.

Sun W ，Wu X ，Gao H ，Yu J ，Zhao W ，Lu JJ ，Wang J ，Du G ，Chen X ... -  《-》

Shikonin induces glioma cell necroptosis in vitro by ROS overproduction and promoting RIP1/RIP3 necrosome formation.

Lu B ，Gong X ，Wang ZQ ，Ding Y ，Wang C ，Luo TF ，Piao MH ，Meng FK ，Chi GF ，Luo YN ，Ge PF ... -  《-》

Inhibition of Lung Cancer by 2-Methoxy-6-Acetyl-7-Methyljuglone Through Induction of Necroptosis by Targeting Receptor-Interacting Protein 1.

Sun W ，Yu J ，Gao H ，Wu X ，Wang S ，Hou Y ，Lu JJ ，Chen X ... -  《-》

RIP1 and RIP3 contribute to shikonin-induced DNA double-strand breaks in glioma cells via increase of intracellular reactive oxygen species.

Shikonin has been reported to induce glioma cell death via necroptosis, a type of programmed necrosis primarily mediated by RIP1 and RIP3. Although RIP1 and RIP3 are found to regulate some features of necrosis such as energy depletion and cellular membrane disruption, it remains unclear whether RIP1 and RIP3 could modulate DNA double strand breaks (DSBs), which is a crucial event leading to chromatinolysis. In this study, we used glioma cell lines and mice model of xenograft glioma to investigate the roles of RIP1 and RIP3 in shikonin-induced DNA DSBs. We found that shikonin induced upregulation of RIP1 and RIP3, necrosome formation and DNA DSBs in vitro and in vivo. In vitro investigation showed that the DNA DSBs and the reduction of cellular viabilities induced by shikonin were both prevented when RIP1 or RIP3 was pharmacologically inhibited by specific inhibitor or genetically knocked down with siRNA. Then, we proved that suppression of intracellular ROS with antioxidant NAC inhibited DNA DSBs caused by either hydrogen peroxide or shikonin, suggesting that ROS played a crucial role in regulation of DNA DSBs of glioma cells induced by shikonin. Further, we found that RIP1 and RIP3 regulated shikonin-induced overproduction of ROS via causing excessive generation of mitochondrial superoxide and depletion of GSH, indicating that ROS was the downstream signal of RIP1 and RIP3. Taken together, we demonstrated that RIP1 and RIP3 contributed to shikonin-induced DNA DSBs in glioma cells via increase of intracellular ROS levels.

Zhou Z ，Lu B ，Wang C ，Wang Z ，Luo T ，Piao M ，Meng F ，Chi G ，Luo Y ，Ge P ... -  《-》

Necrostatin-1 Protects Against Paraquat-Induced Cardiac Contractile Dysfunction via RIP1-RIP3-MLKL-Dependent Necroptosis Pathway.

Zhang L ，Feng Q ，Wang T 《-》