Propofol Decreases Endoplasmic Reticulum Stress-Mediated Apoptosis in Retinal Pigment Epithelial Cells

Age-related macular degeneration (AMD) is the major cause of loss of sight globally. There is currently no effective treatment available. Retinal pigment epithelial (RPE) cells are an important part of the outer blood-retina barrier and their death is a determinant of AMD. Propofol, a common clinically used intravenous anesthetic agent, has been shown to act as an efficacious neuroprotective agent with antioxidative and anti-inflammatory properties in vivo and in vitro. However, little is known about its effects on RPE cells. The purpose of our research was to investigate whether propofol could protect RPE cells from apoptosis through endoplasmic reticulum (ER) stress–dependent pathways. To this end, prior to stimulation with thapsigargin (TG), ARPE-19 cells were pretreated with varying concentrations of propofol. A protective effect of propofol in TG-treated ARPE-9 was apparent, TUNEL and flow cytometric assays showed decreased apoptosis. We further demonstrated that propofol pretreatment attenuated or inhibited the effects caused by TG, such as upregulation of Bax, BiP, C/EBP homologous protein (CHOP), active caspase 12, and cleaved caspase 3, and downregulation of Bcl2. It also decreased the TG-induced levels of ER stress–related molecules such as p-PERK, p-eIF2α, and ATF4. Furthermore, it downregulated the expression of nuclear factor κB (NF-κB). This study elucidated novel propofol-induced cellular mechanisms for antiapoptotic activities in RPE cells undergoing ER stress and demonstrated the potential value of using propofol in the treatment of AMD.

Pituitary Adenlylate Cyclase Activating Peptide Protects Adult Neural Stem Cells from a Hypoglycaemic milieu

Hypoglycaemia is a common side-effect of glucose-lowering therapies for type-2 diabetic patients, which may cause cognitive/neurological impairment. Although the effects of hypoglycaemia in the brain have been extensively studied in neurons, how hypoglycaemia impacts the viability of adult neural stem cells (NSCs) has been poorly investigated. In addition, the cellular and molecular mechanisms of how hypoglycaemia regulates NSCs survival have not been characterized. Recent work others and us have shown that the pituitary adenylate cyclase-activating polypeptide (PACAP) and the glucagon-like peptide-1 receptor (GLP-1R) agonist Exendin-4 stimulate NSCs survival against glucolipoapoptosis. The aim of this study was to establish an in vitro system where to study the effects of hypoglycaemia on NSC survival. Furthermore, we determine the potential role of PACAP and Exendin-4 in counteracting the effect of hypoglycaemia. A hypoglycaemic in vitro milieu was mimicked by exposing subventricular zone-derived NSC to low levels of glucose. Moreover, we studied the potential involvement of apoptosis and endoplasmic reticulum stress by quantifying protein levels of Bcl-2, cleaved caspase-3 and mRNA levels of CHOP. We show that PACAP via PAC-1 receptor and PKA activation counteracts impaired NSC viability induced by hypoglycaemia. The protective effect induced by PACAP correlated with endoplasmic reticulum stress, Exendin-4 was ineffective. The results show that hypoglycaemia decreases NSC viability and that this effect can be substantially counteracted by PACAP via PAC-1 receptor activation. The data supports a potential therapeutic role of PAC-1 receptor agonists for the treatment of neurological complications, based on neurogenesis impairment by hypoglycaemia.

Low glucose dependent decrease of apoptosis and induction of autophagy in breast cancer MCF-7 cells

Cancer cells have developed a number of adaptation mechanisms involving the signal activation of the transduction pathways, which promotes the progression and metastasis. Our results showed that the percentage of apoptotic MCF-7 cells incubated in the low glucose medium for 48 h was lower in comparison to those cultured in the high glucose medium, despite the high expression of the proapoptotic transcription factor-CHOP. Furthermore, the MCF-7 cells incubated in the low glucose medium for 48 h showed a higher expression of NF-κB p100/p52 subunits compared to cells incubated in the high glucose medium. Moreover, our findings demonstrated that the shortage of glucose strongly induces autophagy in MCF-7 cells. The activation of this process is not associated with the changes in the expression of mTOR kinase. We suggest, that the antiapoptotic chaperone ORP150 induction, transcription factor NF-κB2 activation, and increased autophagy constitute mechanisms protecting the MCF-7 cells against apoptosis.

Induction of Endoplasmic Reticulum Stress via Reactive Oxygen Species Mediated by Luteolin in Melanoma Cells

BACKGROUND

This study aimed to investigate whether luteolin, a flavonoid, induces apoptosis in human melanoma cells via endoplasmic reticulum (ER) stress.

MATERIALS AND METHODS

To investigate the effects of luteolin in human melanoma cells, the anti-proliferation, apoptosis, ER stress induction and reactive oxygen species (ROS) generation were evaluated using MTT, Hoechst 33342, ER-tracker Blue White DPX and DCF-DA staining assays, respectively.

RESULTS

Luteolin inhibited cell proliferation and increased apoptotic body formation. Luteolin induced ER stress, as shown by ER staining and mitochondrial Ca(2+) overloading. Luteolin increased expression of the ER stress-related proteins; protein kinase RNA-like ER kinase, phospho eukaryotic translation initiation factor 2α, activating transcription factor (ATF) 6, CCAAT/enhancer-binding protein-homologous protein (CHOP), and cleaved caspase 12. Furthermore, luteolin increased the level of intracellular ROS, leading to ROS-mediated apoptosis and ER stress. However, N-acetyl cysteine, a ROS scavenger, decreased ROS levels, apoptosis, and ER stress induced by luteolin treatment. In addition, knockdown of CHOP and ATF6 by small-interfering RNA inhibited luteolin-induced cell death.

CONCLUSION

Luteolin induces apoptosis by ER stress via increasing ROS levels.

Rhododenol and raspberry ketone impair the normal proliferation of melanocytes through reactive oxygen species-dependent activation of GADD45

Rhododenol or rhododendrol (RD, 4-(4-hydroxyphenyl)-2-butanol) occurs naturally in many plants along with raspberry ketone (RK, 4-(4-hydroxyphenyl)-2-butanone), a ketone derivative, which include Nikko maple tree (Acer nikoense) and white birch (Betula platyphylla). De-pigmenting activity of RD was discovered and it was used as a brightening ingredient for the skin whitening cosmetics. Recently, cosmetics containing RD were withdrawn from the market because a number of consumers developed leukoderma, inflammation and erythema on their face, neck and hands. Here, we explored the mechanism underlying the toxicity of RD and RK against melanocytes using B16F10 murine melanoma cells and human primary epidermal melanocytes. Treatment with RD or RK resulted in the decreased cell viability in a dose-dependent manner which appeared from cell growth arrest. Consistently, ROS generation was significantly increased by RD or RK as determined by DCF-enhanced fluorescence. An antioxidant enzyme, glutathione peroxidase was depleted as well. In line with ROS generation, oxidative damages and the arrest of normal cell proliferation, GADD genes (Growth Arrest and DNA Damage) that include GADD45 and GADD153, were significantly up-regulated. Prevention of ROS generation with an anti-oxidant, N-acetylcysteine (NAC) significantly rescued RD and RK-suppressed melanocyte proliferation. Consistently, up-regulation of GADD45 and GADD153 was significantly attenuated by NAC, suggesting that increased ROS and the resultant growth arrest of melanocytes may contribute to RD and RK-induced leukoderma.

The Unfolded Protein Response Plays a Predominant Homeostatic Role in Response to Mitochondrial Stress in Pancreatic Stellate Cells

Activated pancreatic stellate cells (PaSC) are key participants in the stroma of pancreatic cancer, secreting extracellular matrix proteins and inflammatory mediators. Tumors are poorly vascularized, creating metabolic stress conditions in cancer and stromal cells that necessitate adaptive homeostatic cellular programs. Activation of autophagy and the endoplasmic reticulum unfolded protein response (UPR) have been described in hepatic stellate cells, but the role of these processes in PaSC responses to metabolic stress is unknown. We reported that the PI3K/mTOR pathway, which AMPK can regulate through multiple inputs, modulates PaSC activation and fibrogenic potential. Here, using primary and immortalized mouse PaSC, we assess the relative contributions of AMPK/mTOR signaling, autophagy and the UPR to cell fate responses during metabolic stress induced by mitochondrial dysfunction. The mitochondrial uncoupler rottlerin at low doses (0.5-2.5 μM) was added to cells cultured in 10% FBS complete media. Mitochondria rapidly depolarized, followed by altered mitochondrial dynamics and decreased cellular ATP levels. This mitochondrial dysfunction elicited rapid, sustained AMPK activation, mTOR pathway inhibition, and blockade of autophagic flux. Rottlerin treatment also induced rapid, sustained PERK/CHOP UPR signaling. Subsequently, high doses (>5 μM) induced loss of cell viability and cell death. Interestingly, AMPK knock-down using siRNA did not prevent rottlerin-induced mTOR inhibition, autophagy, or CHOP upregulation, suggesting that AMPK is dispensable for these responses. Moreover, CHOP genetic deletion, but not AMPK knock-down, prevented rottlerin-induced apoptosis and supported cell survival, suggesting that UPR signaling is a major modulator of cell fate in PaSC during metabolic stress. Further, short-term rottlerin treatment reduced both PaSC fibrogenic potential and IL-6 mRNA expression. In contrast, expression levels of the angiogenic factors HGF and VEGFα were unaffected, and the immune modulator IL-4 was markedly upregulated. These data imply that metabolic stress-induced PaSC reprogramming differentially modulates neighboring cells in the tumor microenvironment.

N-Terminal Polypeptide of Annexin A2 Decreases Infection of Mycoplasma hyorhinis to Gastric Cancer Cells

Mycoplasma infection in human and its contamination in cell cultures are worldwide problems. The drugs currently available for preventing or treating mycoplasma infection suffer from low sensitivity, strong resistance and high toxicity. Our previous work showed that Mycoplasma hyorhinis (M. hyorhinis) infection was mediated by the interaction between p37 of M. hyorhinis and Annexin A2 (ANXA2) of host cells, however the translational value of this mechanism was unknown. Herein, we synthesized the N-terminal of ANXA2 polypeptide (A2PP) and found that A2PP could decrease the infection of M. hyorhinis to gastric cancer cells and block M. hyorhinis infection-induced cell migration. Furthermore, we found that A2PP could reduce M. hyorhinis contamination of passage cells. Moreover, compared with the commercial antibiotics commonly used in cell culture to prevent M. hyorhinis infection, A2PP demonstrated a more effectiveness but a low toxicity on cell growth. Thus, our study for the first time revealed A2PP’s potential for the treatment and prevention of M. hyorhinis infection.

Interleukin-22 Alleviated Palmitate-Induced Endoplasmic Reticulum Stress in INS-1 Cells through Activation of Autophagy

OBJECTIVE

Stimulation with saturated fatty acids has been shown to induce oxidative stress and endoplasmic reticulum (ER) stress in β cells and has been recognized as an important component of the pathogenesis of type 2 diabetes (T2D). Interleukin-22 (IL-22) plays a critical role in preventing β cells from oxidative and ER stress, and autophagy is associated with the survival and function of β cells. However, whether IL-22 alleviates cellular stress through activation of autophagy is unclear. In this study, we investigated the effects of IL-22 on rat insulin-secreting cells and the mechanisms underlying IL-22 and lipotoxicity-induced oxidative and ER stress in vitro.

METHODS

The levels of reactive oxygen species (ROS) were detected by flow cytometry and fluorescence microscopy. The protein expression of glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), microtubule-associated protein light chain 3B (LC3B) and Bcl-2-interacting myosin-like coiled-coil protein (Beclin-1) were evaluated by western blot. Transmission electron microscopy was utilized to observe the process of autophagy.

RESULTS

Palmitate induced increased levels of ROS and the overexpression of GRP78 and CHOP, whereas these effects were partly reversed by treatment with IL-22. Furthermore, IL-22 upregulated the protein expression of Beclin-1 and the conversion of LC3B-I to LC3B-II. Moreover, the aforementioned effects were partly suppressed by treating cells with 3-methyladenine (3-MA), an autophagy inhibitor.

CONCLUSIONS

Our results suggest that IL-22 alleviated the oxidative and ER stress induced by palmitate, which was likely mediated by autophagy. These findings could facilitate the development of novel therapeutic strategies to suppress the progression of T2D.

Intravenous Lipid Infusion Induces Endoplasmic Reticulum Stress in Endothelial Cells and Blood Mononuclear Cells of Healthy Adults

BACKGROUND

Endoplasmic reticulum (ER) stress and the subsequent unfolded protein response may initially be protective, but when prolonged, have been implicated in atherogenesis in diabetic conditions. Triglycerides and free fatty acids (FFAs) are elevated in patients with diabetes and may contribute to ER stress. We sought to evaluate the effect of acute FFA elevation on ER stress in endothelial and circulating white cells.

METHODS AND RESULTS

Twenty-one healthy subjects were treated with intralipid (20%; 45 mL/h) plus heparin (12 U/kg/h) infusion for 5 hours. Along with increased triglyceride and FFA levels, intralipid/heparin infusion reduced the calf reactive hyperemic response without a change in conduit artery flow-mediated dilation consistent with microvascular dysfunction. To investigate the short-term effects of elevated triglycerides and FFA, we measured markers of ER stress in peripheral blood mononuclear cells (PBMCs) and vascular endothelial cells (VECs). In VECs, activating transcription factor 6 (ATF6) and phospho-inositol requiring kinase 1 (pIRE1) proteins were elevated after infusion (both P<0.05). In PBMCs, ATF6 and spliced X-box-binding protein 1 (XBP-1) gene expression increased by 2.0- and 2.5-fold, respectively (both P<0.05), whereas CHOP and GADD34 decreased by ≈67% and 74%, respectively (both P<0.01). ATF6 and pIRE1 protein levels also increased (both P<0.05), and confocal microscopy revealed the nuclear localization of ATF6 after infusion, suggesting activation.

CONCLUSIONS

Along with microvascular dysfunction, intralipid infusion induced an early protective ER stress response evidenced by activation of ATF6 and IRE1 in both leukocytes and endothelial cells. Our results suggest a potential link between metabolic disturbances and ER stress that may be relevant to vascular disease.

Influence of Tanshinone IIA on the Apoptosis of Human Esophageal Ec-109 Cells

The induced-apoptosis effect and mechanism of human esophageal cancer Ec-109 cells via tanshinone IIA was investigated. The Ec-109 cells were cultured in vitro with different concentrations of tanshinone IIA (2 µg/mL, 4 µg/mL, or 8 µg/mL) for 12, 24, 36, and 48 hours. MTT assay was used to evaluate the proliferative inhibition rate of tanshinone IIA on esophageal Ec-109 cells. After 24 hours of culturing in vitro, a control group was assigned. The apoptosis rate was detected by the AO/EB and annexin V-FITC/propidium iodide assay, and the protein levels of Caspase-4 and CHOP were determined by the Western blot technique. MTT data showed that tanshinone IIA could significantly inhibit the proliferation of Ec-109 cells with a dose- and time-dependent mode. Compared with the control group, tanshinone IIA could apparently induce apoptosis of Ec-109 cells, and the level of Caspase-4 and CHOP (p < 0.01) obviously increased. Tanshinone IIA can significantly induce the apoptosis of Ec-109 cells, which may take effect by the stress pathway of the endoplasmic reticulum.

Disruption of O-linked N-Acetylglucosamine Signaling Induces ER Stress and β Cell Failure

Nutrient levels dictate the activity of O-linked N-acetylglucosamine transferase (OGT) to regulate O-GlcNAcylation, a post-translational modification mechanism to "fine-tune" intracellular signaling and metabolic status. However, the requirement of O-GlcNAcylation for maintaining glucose homeostasis by regulating pancreatic β cell mass and function is unclear. Here, we reveal that mice lacking β cell OGT (βOGT-KO) develop diabetes and β cell failure. βOGT-KO mice demonstrated increased ER stress and distended ER architecture, and these changes ultimately caused the loss of β cell mass due to ER-stress-induced apoptosis and decreased proliferation. Akt1/2 signaling was also dampened in βOGT-KO islets. The mechanistic role of these processes was demonstrated by rescuing the phenotype of βOGT-KO mice with concomitant Chop gene deletion or genetic reconstitution of Akt2. These findings identify OGT as a regulator of β cell mass and function and provide a direct link between O-GlcNAcylation and β cell survival by regulation of ER stress responses and modulation of Akt1/2 signaling.

Causal role of oxidative stress in unfolded protein response development in the hyperthyroid state

L-3,3',5-Triiodothyronine (T3)-induced liver oxidative stress underlies significant protein oxidation, which may trigger the unfolded protein response (UPR). Administration of daily doses of 0.1mg T3 for three consecutive days significantly increased the rectal temperature of rats and liver O2 consumption rate, with higher protein carbonyl and 8-isoprostane levels, glutathione depletion, and absence of morphological changes in liver parenchyma. Concomitantly, liver protein kinase RNA-like endoplasmic reticulum (ER) kinase and eukaryotic translation initiator factor 2α were phosphorylated in T3-treated rats compared to controls, with increased protein levels of binding immunoglobulin protein and activating transcription factor 4. In addition, higher mRNA levels of C/EBP homologous protein, growth arrest and DNA damage 34, protein disulfide isomerase, and ER oxidoreductin 1α were observed, changes that were suppressed by N-acetylcysteine (0.5 g/kg) given before each dose of T3. In conclusion, T3-induced liver oxidative stress involving higher protein oxidation status has a causal role in UPR development, a response that is aimed to alleviate ER stress and promote cell survival.

ERAP2 functional knockout in humans does not alter surface heavy chains or HLA-B27, inflammatory cytokines or endoplasmic reticulum stress markers

INTRODUCTION

Single nucleotide polymorphisms in ERAP2 are strongly associated with ankylosing spondylitis (AS). One AS-associated single nucleotide polymorphism, rs2248374, causes a truncated ERAP2 protein that is degraded by nonsense-mediated decay. Approximately 25% of the populations of European ancestry are therefore natural ERAP2 knockouts. We investigated the effect of this associated variant on HLA class I allele presentation, surface heavy chains, endoplasmic reticulum (ER) stress markers and cytokine gene transcription in AS.

METHODS

Patients with AS and healthy controls with either AA or GG homozygous status for rs2248374 were studied. Antibodies to CD14, CD19-ECD, HLA-A-B-C, Valpha7.2, CD161, anti-HC10 and anti-HLA-B27 were used to analyse peripheral blood mononuclear cells. Expression levels of ER stress markers (GRP78 and CHOP) and proinflammatory genes (tumour necrosis factor (TNF), IL6, IL17 and IL22) were assessed by qPCR.

RESULTS

There was no significant difference in HLA-class I allele presentation or major histocompatibility class I heavy chains or ER stress markers GRP78 and CHOP or proinflammatory gene expression between genotypes for rs2248374 either between cases, between cases and controls, and between controls.

DISCUSSION

Large differences were not seen in HLA-B27 expression or cytokine levels between subjects with and without ERAP2 in AS cases and controls. This suggests that ERAP2 is more likely to influence AS risk through other mechanisms.

Mitotane Inhibits Sterol-O-Acyl Transferase 1 Triggering Lipid-Mediated Endoplasmic Reticulum Stress and Apoptosis in Adrenocortical Carcinoma Cells

Adrenocortical carcinoma (ACC) is a rare malignancy that harbors a dismal prognosis in advanced stages. Mitotane is approved as an orphan drug for treatment of ACC and counteracts tumor growth and steroid hormone production. Despite serious adverse effects, mitotane has been clinically used for decades. Elucidation of its unknown molecular mechanism of action seems essential to develop better ACC therapies. Here, we set out to identify the molecular target of mitotane and altered downstream mechanisms by combining expression genomics and mass spectrometry technology in the NCI-H295 ACC model cell line. Pathway analyses of expression genomics data demonstrated activation of endoplasmic reticulum (ER) stress and profound alteration of lipid-related genes caused by mitotane treatment. ER stress marker CHOP was strongly induced and the two upstream ER stress signalling events XBP1-mRNA splicing and eukaryotic initiation factor 2 A (eIF2α) phosphorylation were activated by mitotane in NCI-H295 cells but to a much lesser extent in four nonsteroidogenic cell lines. Lipid mass spectrometry revealed mitotane-induced increase of free cholesterol, oxysterols, and fatty acids specifically in NCI-H295 cells as cause of ER stress. We demonstrate that mitotane is an inhibitor of sterol-O-acyl-transferase 1 (SOAT1) leading to accumulation of these toxic lipids. In ACC tissue samples we show variable SOAT1 expression correlating with the response to mitotane treatment. In conclusion, mitotane confers adrenal-specific cytotoxicity and down-regulates steroidogenesis by inhibition of SOAT1 leading to lipid-induced ER stress. Targeting of cancer-specific lipid metabolism opens new avenues for treatment of ACC and potentially other types of cancer.

Punicalagin exerts protective effect against high glucose-induced cellular stress and neural tube defects

Maternal diabetes-induced birth defects remain a significant health problem. Studying the effect of natural compounds with antioxidant properties and minimal toxicities on diabetic embryopathy may lead to the development of new and safe dietary supplements. Punicalagin is a primary polyphenol found in pomegranate juice, which possesses antioxidant, anti-inflammatory and anti-tumorigenic properties, suggesting a protective effect of punicalagin on diabetic embryopathy. Here, we examined whether punicalagin could reduce high glucose-induced neural tube defects (NTDs), and if this rescue occurs through blockage of cellular stress and caspase activation. Embryonic day 8.5 (E8.5) mouse embryos were cultured for 24 or 36 h with normal (5 mM) glucose or high glucose (16.7 mM), in presence or absence of 10 or 20 μM punicalagin. 10 μM punicalagin slightly reduced NTD formation under high glucose conditions; however, 20 μM punicalagin significantly inhibited high glucose-induced NTD formation. Punicalagin suppressed high glucose-induced lipid peroxidation marker 4-hydroxynonenal, nitrotyrosine-modified proteins, and lipid peroxides. Moreover, punicalagin abrogated endoplasmic reticulum stress by inhibiting phosphorylated protein kinase ribonucleic acid (RNA)-like ER kinase (p-PERK), phosphorylated inositol-requiring protein-1α (p-IRE1α), phosphorylated eukaryotic initiation factor 2α (p-eIF2α), C/EBP-homologous protein (CHOP), binding immunoglobulin protein (BiP) and x-box binding protein 1 (XBP1) mRNA splicing. Additionally, punicalagin suppressed high glucose-induced caspase 3 and caspase 8 cleavage. Punicalagin reduces high glucose-induced NTD formation by blocking cellular stress and caspase activation. These observations suggest punicalagin supplements could mitigate the teratogenic effects of hyperglycemia in the developing embryo, and possibly prevent diabetes-induced NTDs.

Down-regulation of PERK-ATF4-CHOP pathway by Astragaloside IV is associated with the inhibition of endoplasmic reticulum stress-induced podocyte apoptosis in diabetic rats

BACKGROUND

Endoplasmic reticulum (ER) stress-induced podocyte apoptosis plays a critical role in the development of diabetic nephropathy (DN). Here, we tested the hypothesis that suppression of PERK-ATF4-CHOP pathway by Astragaloside IV (AS-IV) is associated with inhibition of ER stress-induced podocyte apoptosis in streptozotocin (STZ)-induced diabetic rats.

METHODS

Diabetic rats were treated with AS-IV at 5 and 10 mg·kg-1·d-1, p.o., for 12 weeks. Albuminuria examination, hematoxylin & eosin staining and TUNEL analysis were performed. Immunohistochemistry, western blot, and real-time PCR were used to detect renal expression of ER chaperone GRP78 and ER-associated apoptosis proteins.

RESULTS

Treatment with AS-IV ameliorated albuminuria and renal histopathology in diabetic rats. Diabetic rats had significant increment in podocyte apoptosis as well as phosphorylated PERK and eIF2α in the kidneys, which were attenuated by AS-IV treatment. Furthermore, diabetic rats were found to have increased protein and mRNA expressions of GRP78 and ER-associated apoptosis proteins, such as ATF4, CHOP and TRB3, which were also attenuated by AS-IV treatment. Increased Bax expression and decreased Bcl-2 expression were detected in diabetic rats, and these changes were partially restored by AS-IV treatment.

CONCLUSION

The protective effect of AS-IV on ER stress-induced podocyte apoptosis is associated with inhibition of PERK-ATF4-CHOP pathway. Down-regulation of PERK- ATF4-CHOP pathway by AS-IV may be a novel strategy for the treatment of DN.

The balance between adaptive and apoptotic unfolded protein responses regulates β-cell death under ER stress conditions through XBP1, CHOP and JNK

Endoplasmic reticulum (ER) stress and the subsequent unfolded protein response (UPR) have been implicated in β-cell death in type 1 and type 2 diabetes. However, the UPR is also a fundamental mechanism required for β-cell adaptation and survival. The mechanisms regulating the transition from adaptive to apoptotic UPR remain to be clarified. Here, we investigated the relationships between XBP1, CHOP and JNK in the transition from adaptive to apoptotic UPR and β-cell death in models of type 1 and type 2 diabetes. XBP1 inhibition potentiated cell death induced by pro-inflammatory cytokines or the saturated fatty acid palmitate in MIN6 β-cells. This response was prevented by CHOP inhibition. IRE1/XBP1 inhibition led to alterations in islets from diabetes-resistant ob/ob mice that resemble those found in diabetes, including increases in cell death and inflammation and antioxidant gene expression. Similarly, IRE1/XBP1 inhibition increased cell death in islets from NOD mice. On the other hand, JNK inhibition: 1) increased adaptive UPR and reduced cell death in islets from diabetic db/db mice, and 2) restored adaptive UPR while protecting against apoptotic UPR gene expression and β-cell death and dysfunction following cytokine exposure. These findings suggest that the balance between XBP1-mediated adaptive and CHOP-dependent apoptotic UPR is critically important for β-cell survival during ER stress. JNK activation regulates the transition from adaptive to apoptotic UPR, thus providing a mechanism for β-cell propensity to cell death rather than ER stress adaptation in type 1 and type 2 diabetes.

Exendin-4 protects rat islets against loss of viability and function induced by brain death

Islet quality loss after isolation from brain-dead donors still hinders the implementation of human islet transplantation for treatment of type 1 diabetes. In this scenario, systemic inflammation elicited by donor brain death (BD) is among the main factors influencing islet viability and functional impairment. Exendin-4 is largely recognized to promote anti-inflammatory and cytoprotective effects on β-cells. Therefore, we hypothesized that administration of exendin-4 to brain-dead donors might improve islet survival and insulin secretory capabilities. Here, using a rat model of BD, we demonstrate that exendin-4 administration to the brain-dead donors increases both islet viability and glucose-stimulated insulin secretion. In this model, exendin-4 treatment produced a significant decrease in interleukin-1β expression in the pancreas. Furthermore, exendin-4 treatment increased the expression of superoxide dismutase-2 and prevented BD-induced elevation in uncoupling protein-2 expression. Such observations were accompanied by a reduction in gene expression of two genes often associated with endoplasmic reticulum (ER) stress response in freshly isolated islets from treated animals, C/EBP homologous protein and immunoglobulin heavy-chain binding protein. As ER stress response has been shown to be triggered by and to participate in cytokine-induced β-cell death, we suggest that exendin-4 might exert its beneficial effects through alleviation of pancreatic inflammation and oxidative stress, which in turn could prevent islet ER stress and β-cell death. Our findings might unveil a novel strategy to preserve islet quality from brain-dead donors. After testing in the human pancreatic islet transplantation setting, this approach might sum to the ongoing effort to achieve consistent and successful single-donor islet transplantation.

[Preventive effect of misoprostol against nonsteroidal anti-inflammatory drug-induced enteropathy in mice]

OBJECTIVE

To investigate the preventive effect of misoprostol against non-steroidal anti-inflammatory drug (NSAID)-induced intestinal injury in mice.

METHODS

NSAID-induced intestinal injury model was established through diclofenac sodium. Sixty specific-pathogen-free (SPF) BABL/c male mice were randomly divided into the following five groups: normal, model and three misoprostol groups with different concentrations (200, 400, 800 μg/kg). Misoprostol was given to aforementioned three misoprostol groups by gavage once a day for 6 days. In the fourth day afternoon, 5 mg/kg (10 mL/kg) diclofenac was fed to all mice by gavage except for normal group. On the seventh day, all mice were sacrificed and intestinal permeability was detected using FITC labeled dextran. The intestinal tissues were taken for detecting the mRNA and protein expressions of intestinal glucose regulated protein 78 (GRP78), C/EBP homologous protein (CHOP) and tumor necrosis factor alpha (TNF-α) through HE staining, reverse transcription PCR and Western blotting, respectively.

RESULTS

Compared with the normal group, intestinal mucosa in the model group was seriously damaged and intestinal permeability significantly increased. The intestinal mucosal villus degeneration, necrosis, shedding, and inflammatory cell infiltration occurred in the model group. Yet, intestinal mucosal injury in different misoprostol groups was less severe. Their intestinal mucosal permeability was improved. The expressions of GRP78 protein and TNF-α, CHOP mRNAs on intestine were significantly reduced compared with those of the model group.

CONCLUSION

Misoprostol has preventive effect against NSAID-induced intestinal diseases.

Se-Methyl-L-selenocysteine Induces Apoptosis via Endoplasmic Reticulum Stress and the Death Receptor Pathway in Human Colon Adenocarcinoma COLO 205 Cells

Selenomethionine (SeMet) and Se-methyl-L-selenocysteine (MSeC) are natural organoselenium compounds found in garlic, onion, and broccoli. In addition, these compounds have lower toxicity and better anticancer activities than inorganic Se. This study investigated the effects of MSeC treatment on the growth of COLO 205 human colorectal adenocarcinoma cells and evaluated the mechanisms related to the MSeC-induced effects. When COLO 205 cells were treated with 200 μM MSeC for 24 h, MSeC caused 80% apoptosis in cells. MSeC increased the expression of Fas and FasL, followed by the cleavage of caspase-3, caspase-8, DNA fragmentation factor (DFF45), and poly(ADP-ribose) polymerase (PARP). MSeC also increased the levels of Bax protein and decreased the levels of Bid and Bcl-2 proteins. However, MSeC did not cause apoptosis through reactive oxygen species (ROS) stress but instead through endoplasmic reticulum (ER) stress. The cleavage of caspase-12 and caspase-9 was shown to increase the growth arrest and protein levels of DNA-damage inducible genes (GADD) 153 and 45. MSeC also downregulated the ERK1/2 and PI3K/AKT protein levels and upregulated the p38 and JNK protein levels in COLO 205 cells. These results showed that the mechanism by which MSeC induced apoptosis in COLO 205 cells involved caspase activation, the extrinsic apoptotic pathway, and the regulation of ER-stress-induced apoptosis.

Inhibitory Effects of Verrucarin A on Tunicamycin-Induced ER Stress in FaO Rat Liver Cells

Endoplasmic reticulum (ER) stress is linked with development and maintenance of cancer, and serves as a therapeutic target for treatment of cancer. Verrucarin A, isolated from the broth of Fusarium sp. F060190, showed potential inhibitory activity on tunicamycin-induced ER stress in FaO rat liver cells. In addition, the compound decreased tunicamycin-induced GRP78 promoter activity in a dose dependent manner without inducing significant inhibition of luciferase activity and cell growth for 6 and 12 h. Moreover, the compound decreased the expression of GRP78, CHOP, XBP-1, and suppressed XBP-1, and reduced phosphorylation of IRE1α in FaO rat liver cells. This evidence suggests for the first time that verrucarin A inhibited tunicamycin-induced ER stress in FaO rat liver cells.

Involvement of iron depletion in palmitate-induced lipotoxicity of beta cells

High levels of plasma free fatty acid are thought to contribute to the loss of pancreatic beta-cells in type 2 diabetes. In particular, saturated fatty acid such as palmitate or stearate can induce apoptosis in cultured beta cells (lipotoxicity). Endoplasmic reticulum stress is a critical mediator of free fatty acid-induced lipotoxicity. Recently, disorders in mitochondrial respiratory metabolism have been linked to lipotoxicity. Since iron is a critical component of respiratory metabolism, this study is initiated to determine whether abnormal iron metabolism is involved in palmitate-induced beta cell death. Immunoblotting analysis showed that treatment of INS-1 beta cells with palmitate reduced the level of transferrin receptor 1 (TfR1), but increased the level of heavy chain ferritin (FTH). In addition, palmitate reduced intracellular labile iron pool. Whereas iron depletion through treatment with iron-chelators deferoxamine or deferasirox augmented palmitate-induced cell death, iron supplementation with ferric chloride, ferrous sulfate, or holo-transferrin significantly protected cells against palmitate-induced death. Furthermore, overexpression of TfR1 reduced palmitate-induced cell death, whereas knockdown of TfR1 augmented cell death. In particular, treatment with deferoxamine increased the level of endoplasmic reticulum (ER) stress markers phospho-PERK, phospho-eIF2α, CHOP and phospho-c-Jun N-terminal kinase. Treatment with chemical chaperone significantly protected cells against deferoxamine-induced apoptosis. Iron supplementation also protected cells against palmitate-induced primary islet death. These data suggest that iron depletion plays an important role in palmitate-induced beta cell death through inducing ER stress. Therefore, attempts to block iron depletion might be able to prevent beta cell loss in type 2 diabetes.

The effect of alcohol and hydrogen peroxide on liver hepcidin gene expression in mice lacking antioxidant enzymes, glutathione peroxidase-1 or catalase

This study investigates the regulation of hepcidin, the key iron-regulatory molecule, by alcohol and hydrogen peroxide (H2O2) in glutathione peroxidase-1 (gpx-1(-/-)) and catalase (catalase(-/-)) knockout mice. For alcohol studies, 10% ethanol was administered in the drinking water for 7 days. Gpx-1(-/-) displayed significantly higher hepatic H2O2 levels than catalase(-/-) compared to wild-type mice, as measured by 2'-7'-dichlorodihydrofluorescein diacetate (DCFH-DA). The basal level of liver hepcidin expression was attenuated in gpx-1(-/-) mice. Alcohol increased H2O2 production in catalase(-/-) and wild-type, but not gpx-1(-/-), mice. Hepcidin expression was inhibited in alcohol-fed catalase(-/-) and wild-type mice. In contrast, alcohol elevated hepcidin expression in gpx-1(-/-) mice. Gpx-1(-/-) mice also displayed higher level of basal liver CHOP protein expression than catalase(-/-) mice. Alcohol induced CHOP and to a lesser extent GRP78/BiP expression, but not XBP1 splicing or binding of CREBH to hepcidin gene promoter, in gpx-1(-/-) mice. The up-regulation of hepatic ATF4 mRNA levels, which was observed in gpx-1(-/-) mice, was attenuated by alcohol. In conclusion, our findings strongly suggest that H2O2 inhibits hepcidin expression in vivo. Synergistic induction of CHOP by alcohol and H2O2, in the absence of gpx-1, stimulates liver hepcidin gene expression by ER stress independent of CREBH.

Bevacizumab induces A549 cell apoptosis through the mechanism of endoplasmic reticulum stress in vitro

AIMS

To observe the effect of bevacizumab on human A549 cells and explore its mechanism.

METHODS

After different concentrations (0 μM, 1 μM, 5 μM, 25 μM) of bevacizumab treating in A549 cells, CCK8 assay detect the impact of bevacizumab on A549 cell proliferation and flow cytometry determine the effect of bevacizumab on human A549 cells apoptosis. Real-time PCR and Western blotting detect the changing expression of the target gene (CHOP, caspase-4, IRE1, XBP-1) on mRNA and Protein level.

RESULTS

Treatment with bevacizumab for 24-hr have induced cell death in a does-dependent manner dramatically (P<0.05). In terms of the mRNA level, expression of XBP-1 has increased obviously in each group (1 μM, 5 μM, 25 μM) (P<0.01); the expression of CHOP (25 μM) and caspase-4 (5 μM) have increased slightly (P<0.05). In terms of the protein level, the expression of CHOP has increased obviously in each group (1 μM, 5 μM, 25 μM) when compared with the control group (0 μM) (P<0.05). As for caspase-4 (5 μM, 25 μM), the expression have increased slightly when compared with the control group (0 μM) (P<0.05).

CONCLUSION

Bevacizumab can induce A549 cell apoptosis through the mechanism of endoplasmic reticulum stress.

Endoplasmic reticulum stress-mediated apoptotic pathway is involved in corpus luteum regression in rats

Endoplasmic reticulum stress (ERS), which is a novel pathway of regulating cellular apoptosis and the function of ERS during corpus luteum (CL) regression, is explored. Early-luteal stage (day 2), mid-luteal stage (day 7), and late-luteal stage (day 14 and 20) were induced, and the apoptosis of luteal cells was detected by a terminal 2'-deoxyuridine 5'-triphosphate nick-end labeling (TUNEL) assay. The apoptotic cells were increased with the regression of CL, especially during the late-luteal stage. The ERS markers glucose-regulated protein 78 (Grp78), CCAAT/enhancer-binding protein homologous protein (CHOP), X-box binding protein 1 (XBP1), activating transcription factor 6α (ATF6α), eukaryotic initiation factor 2α (eIF2α), inositol-requiring protein 1α (IRE1α), caspase 12, and apoptosis marker caspase 3 were analyzed by real-time polymerase chain reaction (PCR) and immunohistochemistry, in agreement with the results of the TUNEL assay; the expression levels of CHOP, caspase 12, and caspase 3 were increased during the process of CL regression. Luteal cells were isolated and cultured in vitro, and the apoptosis of luteal cells was induced by prostaglandin F2α. The ERS was attenuated by the ERS inhibitor tauroursodeoxycholic acid, and the apoptotic rate was analyzed by flow cytometry. The ERS markers Grp78, CHOP, XBP1s, ATF6α, eIF2α, IRE1α, caspase 12, and apoptotic execute marker caspase 3 were analyzed by real-time PCR and immunofluorescence, and the results suggested that the expression of CHOP, caspase 12, and caspase 3 were increased, and there was increased apoptosis of luteal cells. But the expression of IRE1α/XBP1s and eIF2α was not detected. Taken together, the ERS is involved in the CL regression of rats through the CHOP and caspase 12 pathway.