Search

Highlights • Malignant gliomas are extremely resistant to therapies that induce apoptosis. • Malignant gliomas are less resistant to therapies that induce autophagy. • Curcumin induces ROS-dependent induction of autophagy in malignant glioma cells. • Curcumin induces up-regulation of Par-4 in human malignant glioma cells. • Curcumin induces tumor suppressive lipid, ceramide in malignant glioma cells., Malignant gliomas are extremely resistant to therapies that induce apoptosis, but are less resistant to therapies that induce autophagy. Therefore, drugs targeting autophagy are promising in the management of malignant gliomas. In this study, we investigated the anti-glioma potential of curcumin in vitro, and further examined the molecular mechanisms of curcumin-induced cell death in human malignant glioma. Here, we provide evidence that curcumin is cytotoxic against human malignant glioma cell lines, and the mechanism of cell death caused by curcumin is associated with features of autophagy. Curcumin suppresses the growth of human malignant glioma cells via ROS-dependent prostate apoptosis response-4 (Par-4) induction and ceramide generation. Extracellular supplementation of antioxidants such as glutathione and N-acetylcysteine to glioma cells abrogated the Par-4 induction, ceramide generation, and in turn, prevented curcumin-induced autophagic cell death. Moreover, tumor cells transfected with Par-4 gene sensitized the curcumin-induced autophagic cell death. Overall, this study describes a novel signaling pathway by which curcumin induces ROS-dependent Par-4 activation and ceramide generation, leading to autophagic cell death in human malignant glioma cells.

Graphical abstract, Highlights • RIPK-dependent necrosis is involved in acetaminophen (APAP)-induced hepatotoxicity. • Necrostatin-1 (Nec-1) protects mice against APAP-induced acute liver damage. • Nec-1 suppresses APAP-induced ROS generation in hepatocytes. • Nec-1 promotes resistance to oxidative stress in hepatocytes., Excessive acetaminophen (APAP) use is one of the most common causes of acute liver failure. Various types of cell death in the damaged liver are linked to APAP-induced hepatotoxicity, and, of these, necrotic cell death of hepatocytes has been shown to be involved in disease pathogenesis. Until recently, necrosis was commonly considered to be a random and unregulated form of cell death; however, recent studies have identified a previously unknown form of programmed necrosis called receptor-interacting protein kinase (RIPK)-dependent necrosis (or necroptosis), which is controlled by the kinases RIPK1 and RIPK3. Although RIPK-dependent necrosis has been implicated in a variety of disease states, including atherosclerosis, myocardial organ damage, stroke, ischemia–reperfusion injury, pancreatitis, and inflammatory bowel disease. However its involvement in APAP-induced hepatocyte necrosis remains elusive. Here, we showed that RIPK1 phosphorylation, which is a hallmark of RIPK-dependent necrosis, was induced by APAP, and the expression pattern of RIPK1 and RIPK3 in the liver overlapped with that of CYP2E1, whose activity around the central vein area has been demonstrated to be critical for the development of APAP-induced hepatic injury. Moreover, a RIPK1 inhibitor ameliorated APAP-induced hepatotoxicity in an animal model, which was underscored by significant suppression of the release of hepatic enzymes and cytokine expression levels. RIPK1 inhibition decreased reactive oxygen species levels produced in APAP-injured hepatocytes, whereas CYP2E1 expression and the depletion rate of total glutathione were unaffected. Of note, RIPK1 inhibition also conferred resistance to oxidative stress in hepatocytes. These data collectively demonstrated a RIPK-dependent necrotic mechanism operates in the APAP-injured liver and inhibition of this pathway may be beneficial for APAP-induced fulminant hepatic failure.

Ebselen is a synthetic, lipid-soluble seleno-organic compound. The high electrophilicity of ebselen enables it to react with multiple cysteine residues of various proteins. Despite extensive research on ebselen, its target molecules and mechanism of action remains less understood. We performed biochemical as well as in vivo experiments employing budding yeast as a model organism to understand the mode of action of ebselen. The growth curve analysis and FACS (florescence activated cell sorting) assays revealed that ebselen exerts growth inhibitory effects on yeast cells by causing a delay in cell cycle progression. We observed that ebselen exposure causes an increase in intracellular ROS levels and mitochondrial membrane potential, and that these effects were reversed by addition of antioxidants such as reduced glutathione (GSH) or N-acetyl-l-cysteine (NAC). Interestingly, a significant increase in ROS levels was noticed in gdh3-deleted cells compared to wild-type cells. Furthermore, we showed that ebselen inhibits GDH function by interacting with its cysteine residues, leading to the formation of inactive hexameric GDH. Two-dimensional gel electrophoresis revealed protein targets of ebselen including CPR1, the yeast homolog of Cyclophilin A. Additionally, ebselen treatment leads to the inhibition of yeast sporulation. These results indicate a novel direct connection between ebselen and redox homeostasis., Graphical Abstract, Highlights • Ebselen treatment causes an increase in intracellular ROS levels and mitochondrial membrane potential. • Ebselen inactivates GDH3 and Cyclophilin A by interacting with their cysteine residues. • The ebselen-induced increase in ROS levels leads to inhibition of sporulation in yeast. • Yeast gdh3 deletion potentiates ROS generation upon ebselen treatment.

Sensor histidine kinases (HKs) are important factors that control cellular growth in response to environmental conditions. The expression of 15 HKs from Aspergillus nidulans was analyzed by quantitative real-time PCR under vegetative, asexual, and sexual growth conditions. Most HKs were highly expressed during asexual growth. All HK gene-disrupted strains produced reactive oxygen species (ROS). Three HKs are involved in the control of ROS: HysA was the most abundant under the restricted oxygen condition, NikA is involved in fungicide sensing, and FphA inhibits sexual development in response to red light. Phosphotransfer signal transduction via HysA is essential for ROS production control., Highlights • Most histidine kinases in Aspergillus nidulans are expressed during asexual development. • ROS were generated in some histidine kinase (HK)-gene disrupted strains. • The phosphorylation activities of HKs are essential to control ROS generation.