Arsenic induces reactive oxygen species-caused neuronal cell apoptosis through JNK/ERK-mediated mitochondria-dependent and GRP 78/CHOP-regulated pathways.

Arsenic (As), a well-known high toxic metal, is an important environmental and industrial contaminant, and it induces oxidative stress, which causes many adverse health effects and diseases in humans, particularly in inorganic As (iAs) more harmful than organic As. Recently, epidemiological studies have suggested a possible relationship between iAs exposure and neurodegenerative disease development. However, the toxicological effects and underlying mechanisms of iAs-induced neuronal cell injuries are mostly unknown. The present study demonstrated that iAs significantly decreased cell viability and induced apoptosis in Neuro-2a cells. iAs also increased oxidative stress damage (production of malondialdehyde (MDA) and ROS, and reduction of Nrf2 and thioredoxin protein expression) and induced several features of mitochondria-dependent apoptotic signals, including: mitochondrial dysfunction, the activations of PARP and caspase cascades, and the increase in caspase-3 activity. Pretreatment with the antioxidant N-acetylcysteine (NAC) effectively reversed these iAs-induced responses. iAs also increased the phosphorylation of JNK and ERK1/2, but did not that p38-MAPK, in treated Neuro-2a cells. NAC and the specific JNK inhibitor (SP600125) and ERK1/2 inhibitor (PD98059) abrogated iAs-induced cell cytotoxicity, caspase-3/-7 activity, and JNK and ERK1/2 activation. Additionally, exposure of Neuro-2a cells to iAs triggered endoplasmic reticulum (ER) stress identified through several key molecules (GRP 78, CHOP, XBP-1, and caspase-12), which was prevented by NAC. Transfection with GRP 78- and CHOP-specific si-RNA dramatically suppressed GRP 78 and CHOP expression, respectively, and attenuated the activations of caspase-12, -7, and -3 in iAs-exposed cells. Therefore, these results indicate that iAs induces ROS causing neuronal cell death via both JNK/ERK-mediated mitochondria-dependent and GRP 78/CHOP-triggered apoptosis pathways.

Lu TH ，Tseng TJ ，Su CC ，Tang FC ，Yen CC ，Liu YY ，Yang CY ，Wu CC ，Chen KL ，Hung DZ ，Chen YW ... -  《-》

Luteolin induces apoptosis through endoplasmic reticulum stress and mitochondrial dysfunction in Neuro-2a mouse neuroblastoma cells.

Luteolin, a dietary flavonoid, induces apoptosis in various types of cancer cells. However, its role in neuroblastoma and the underlying mechanisms remain to be elucidated. In the present study, we investigated the molecular mechanisms of the anti-cancer effect of luteolin in Neuro-2a mouse neuroblastoma cells. Luteolin induced apoptotic cell death and activation of caspase-12, -9, and -3, and knockdown of caspase-12 by siRNA transfection reduced luteolin-induced cell death. Luteolin also induced expression of endoplasmic reticulum (ER) stress-associated proteins, including C/EBP homologous protein (CHOP) and glucose-regulated proteins (GRP) 94 and 78, cleavage of ATF6α, and phosphorylation of eIF2α. CHOP knockdown or ER stress inhibitor, 4-phenylbutyric acid, reduced luteolin-induced cell death. These results suggest involvement of ER stress in luteolin-induced neuroblastoma cell death. We then showed that luteolin induced accumulation of reactive oxygen species and that the anti-oxidant N-acetylcysteine reduced luteolin-induced cell death and expression of CHOP and GRP78. We also demonstrated rapid reduction of mitochondrial membrane potential by luteolin, and N-acetylcysteine, as well as 4-phenylbutyric acid or CHOP siRNA transfection ameliorated luteolin-induced late loss, but not early loss of mitochondrial membrane potential. Finally, we showed that luteolin induced activation of mitogen-activated protein kinases such as JNK, p38, and ERK, and inhibitors of mitogen-activated protein kinases reduced luteolin-induced cell death and CHOP expression, as well as mitochondrial Bax translocation and cytochrome c release. Collectively, our results suggest that luteolin induces apoptosis through ER stress and mitochondrial dysfunction in Neuro-2a mouse neuroblastoma cells.

Choi AY ，Choi JH ，Yoon H ，Hwang KY ，Noh MH ，Choe W ，Yoon KS ，Ha J ，Yeo EJ ，Kang I ... -  《-》

Arsenic induces pancreatic β-cell apoptosis via the oxidative stress-regulated mitochondria-dependent and endoplasmic reticulum stress-triggered signaling pathways.

Arsenic (As), a ubiquitous toxic metal, is an important environmental and industrial pollutant throughout the world. Inorganic As (iAs) is usually more harmful than organic ones and with a high risk of diabetes incidence by exposure. However, the toxicological effects of iAs on growth and function of pancreatic β-cells still remain unclear. Here, we found that iAs significantly decreased insulin secretion and cell viability, and increased ROS and MDA formation in pancreatic β-cell-derived RIN-m5F cells. iAs also induced the increases in sub-G1 hypodiploids, annexin V-Cy3 binding, and caspase-3 activity in RIN-m5F cells, indicating that iAs could induce β-cell apoptosis. Moreover, iAs induced MAPKs activation, mitochondria dysfunction, p53 up-regulation, Bcl-2 and Mdm-2 down-regulation, PARP, and caspase cascades, which displayed features of mitochondria-dependent apoptotic signals. In addition, exposure of RIN-m5F cells to iAs, could trigger ER stress as indicated by the enhancement in ER stress-related molecules induction (such as GRP78, GRP94, CHOP, and XBP1), procaspase-12 cleavage, and calpain activation. The iAs-induced apoptosis and its-related signalings could be effectively reversed by antioxidant N-acetylcysteine. We next observed that exposure of mice to iAs in drinking water for 6 consecutive weeks significantly decreased decreased the plasma insulin, elevated glucose intolerance and plasma lipid peroxidation, and induced islet cells apoptosis, which accompanied with arsenic accumulation in the whole blood and pancreas. N-acetylcysteine effectively antagonized the iAs-induced responses in mice. Taken together, these results suggest that iAs-induced oxidative stress causes pancreatic β-cells apoptosis via the mitochondria-dependent and ER stress-triggered signaling pathways.

Lu TH ，Su CC ，Chen YW ，Yang CY ，Wu CC ，Hung DZ ，Chen CH ，Cheng PW ，Liu SH ，Huang CF ... -  《-》

Indomethacin induces apoptosis in 786-O renal cell carcinoma cells by activating mitogen-activated protein kinases and AKT.

Ou YC ，Yang CR ，Cheng CL ，Raung SL ，Hung YY ，Chen CJ ... -  《EUROPEAN JOURNAL OF PHARMACOLOGY》

Cadmium induces apoptosis in pancreatic β-cells through a mitochondria-dependent pathway: the role of oxidative stress-mediated c-Jun N-terminal kinase activation.

Chang KC ，Hsu CC ，Liu SH ，Su CC ，Yen CC ，Lee MJ ，Chen KL ，Ho TJ ，Hung DZ ，Wu CC ，Lu TH ，Su YC ，Chen YW ，Huang CF ... -  《PLoS One》