Di(2-ethylhexyl) phthalate-induced apoptosis in rat INS-1 cells is dependent on activation of endoplasmic reticulum stress and suppression of antioxidant protection.

Di(2-ethylhexyl) phthalate (DEHP) is used as plasticizer and is ubiquitously found in the environment. Exposure to DEHP has been linked to an increased incidence of type 2 diabetes. Pancreatic β-cell dysfunction is a hallmark of type 2 diabetes; however, it is unknown whether DEHP exposure contributes to this risk. Here, we aimed to investigate the cytotoxic effects of DEHP on INS-1 cells and to further explore the related underlying mechanisms. INS-1 cells were exposed to 0, 5, 25, 125 or 625 μM DEHP for 24 hrs. Cell viability, glucose-stimulated insulin secretion, reactive oxygen species (ROS) generation, cellular antioxidant response, Ca(2+) homoeostasis and the levels of genes and proteins involved in endoplasmic reticulum (ER) stress were measured. The results showed that DEHP decreased insulin secretion and content and induced apoptosis in INS-1 cells in a dose-dependent manner. Furthermore, ROS generation was increased and Nrf2-dependent antioxidant defence protection was dysregulated in INS-1 cells after DEHP exposure. Most importantly, DEHP effectively depleted ER Ca(2+) and triggered the ER stress response as demonstrated by the elevated transcription and translation of the ER chaperone GRP78 and GRP94, the increased phosphorylation of protein kinase R-like endoplasmic reticulum kinase (PERK) and its downstream substrate eukaryotic translation initiation factor 2α (eIF2α), as well as the increased levels of activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP). Taken together, DEHP exerted toxic effects on INS-1 cells by inducing apoptosis, which is dependent on the activation of the PERK-ATF4-CHOP ER stress signalling pathway and the suppression of Nrf2-dependent antioxidant protection.

Sun X ，Lin Y ，Huang Q ，Shi J ，Qiu L ，Kang M ，Chen Y ，Fang C ，Ye T ，Dong S ... -  《-》

ROS-mediated PERK-eIF2α-ATF4 pathway plays an important role in arsenite-induced L-02 cells apoptosis via regulating CHOP-DR5 signaling.

Chronic exposure to arsenic remains a worldwide environmental health issue, affecting hundreds of millions of people. Although, arsenic-induced oxidative stress and apoptosis have been determined, the underlying apoptosis mechanism has not been fully elucidated yet. Oxidative stress integrated-ER stress plays an important role in Life-and-Death decision of cells. The current study was to investigate whether NaAsO2 utilizes oxidative stress integrated-ER stress signaling to exert pro-apoptotic activity in L-02 cells. Results showed that death receptor 5 (DR5) was a mediator of NaAsO2 -induced apoptosis by enhancing construction of the death-inducing signaling complex (DISC). NaAsO2 -sensitized DR5 elevation required maintainable transcription and its transcription factor C/EBP homologous protein (CHOP). Further results showed that NaAsO2 increased expression in biomarker of endoplasmic reticulum (ER) stress and activated the protein kinase R-like ER kinase (PERK)-eukaryotic translation initiation 2α (eIF2α)-activating transcription factor 4 (ATF4) pathway. PERK inhibitor and ATF4 siRNA significantly attenuated NaAsO2 -induced CHOP and DR5 expressions. In addition, the antioxidant N-acetyl-l-cysteine (NAC) treatment led to amelioration of NaAsO2 -induced production of reactive oxygen species (ROS) and some ER stress- and apoptosis- related protein levels and cell viability. Taken together, the results indicate that ROS-mediated PERK-eIF2α-ATF4 pathway activated by NaAsO2 is the critical upstream event for subsequent apoptosis induction via regulating CHOP-DR5 signaling in L-02 cells when chronic exposure to arsenic, and support that antioxidants might be potential therapeutic agents for preventing or delaying the onset and progress of arsenic-induced hepatotoxicity.

Liu C ，Zhang A 《-》

Involvement of endoplasmic reticulum stress-activated PERK-eIF2α-ATF4 signaling pathway in T-2 toxin-induced apoptosis of porcine renal epithelial cells.

T-2 toxin is a highly toxic trichothecene that can induce toxic effects in a variety of organs and tissues, but the pathogenesis of its nephrotoxicity has not been elucidated. In this study, we assessed the involvement of protein kinase RNA-like ER kinase (PERK)-mediated endoplasmic reticulum (ER) stress and apoptosis in PK-15 cells cultured at different concentrations of T-2 toxin. Cell viability, antioxidant capacity, intracellular calcium (Ca2+) content, apoptotic rate, levels of ER stress, and apoptosis-related proteins were studied. T-2 toxin inhibited cell proliferation; increased the apoptosis rate; and was accompanied by increased cleaved caspase-3 expression, altered intracellular oxidative stress marker levels, and intracellular Ca2+ overloading. The ER stress inhibitor 4-phenylbutyrate (4-PBA) and PERK selective inhibitor GSK2606414 prevented the decrease of cell activity and apoptosis caused by T-2 toxin. The altered expression of glucose regulatory protein 78 (GRP78), C/EBP homologous protein (CHOP), and caspase-12 proved that ER stress was involved in cell injury triggered by T-2 toxin. T-2 toxin activated the phosphorylation of PERK and the alpha subunit of eukaryotic initiation factor 2 (eIF2α) and upregulated the activating transcription factor 4 (ATF4), thereby triggering ER stress via the GRP78/PERK/CHOP signaling pathway. This study provides a new perspective for understanding the nephrotoxicity of T-2 toxin.

Liu X ，Wang Z ，Wang X ，Yan X ，He Q ，Liu S ，Ye M ，Li X ，Yuan Z ，Wu J ，Yi J ，Wen L ，Li R ... -  《-》

Pollen Typhae Total Flavone Inhibits Endoplasmic Reticulum Stress-Induced Apoptosis in Human Aortic-Vascular Smooth Muscle Cells through Down-Regulating PERK-eIF2α-ATF4-CHOP Pathway.

Chen MT ，Huang RL ，Ou LJ ，Chen YN ，Men L ，Chang X ，Wang L ，Yang YZ ，Zhang Z ... -  《-》

Cytokine-induced beta-cell death is independent of endoplasmic reticulum stress signaling.

Akerfeldt MC ，Howes J ，Chan JY ，Stevens VA ，Boubenna N ，McGuire HM ，King C ，Biden TJ ，Laybutt DR ... -  《-》