OBJECTIVEWe investigated the role of endoplasmic reticulum stress (ERS) in silica-induced apoptosis in alveolar macrophages in vitro.

METHODSRAW264.7 cells were incubated with 200 μg/mL silica for different time periods. Cell viability was assayed by the MTT assay. Cell apoptosis was evaluated by DAPI staining, flow cytometry analysis, and Western blot analysis of caspase-3. Morphological changes in the endoplasmic reticulum were observed by transmission electron microscopy. The expression of ERS markers binding protein (BiP) and CCAAT-enhancer-binding protein homologous protein (CHOP) was examined by Western blotting and real-time PCR. As an inhibitor of ERS, 4-phenylbutyric acid (4-PBA) was used in the experiments.

RESULTSSilica exposure induced nuclear condensation and caspase-3 expression in RAW264.7 cells. The number of apoptotic cells increased after silica exposure in a time-dependent manner. Silica treatment induced expansion of the endoplasmic reticulum. In addition, the expression of BiP and CHOP increased in silica-stimulated cells. Furthermore, 4-PBA treatment inhibited silica-induced endoplasmic reticulum expansion and the expression of BiP and CHOP. Moreover, 4-PBA treatment attenuated nuclear condensation, reduced apoptotic cells, and downregulated caspase-3 expression in silica-stimulated cells.

CONCLUSIONSilica-induced ERS is involved in the apoptosis of alveolar macrophages.

Animals ; Apoptosis ; drug effects ; Butylamines ; Cell Survival ; drug effects ; Endoplasmic Reticulum Stress ; physiology ; Mice ; RAW 264.7 Cells ; Silicon Dioxide ; toxicity

OBJECTIVETo study the role of lipid peroxidation injury and endoplasmic reticulum stress in Al-induced apoptosis.

METHODSNeurons from 0-3 day rats were cultured and treated with different concentrations of AlCl3.6H2O. Morphologic changes of neurons and endoplasmic reticulum were observed under fluorescent and transmission electron microscope; activities of superoxide dismutase (SOD), malondialdehyde (MDA) and ATP enzymes were detected.

RESULTSTypical morphologic changes in neurons apoptosis and endoplasmic reticulum were found under fluorescent and transmission electron microscope; SOD enzyme viability and ATP enzyme viability were significantly increased in the low-dosage group, but reduced in mid and high-dosage group (P < 0.01), whereas MDA levels decreased in the low-dosage group, but increased in mid and high-dosage group (P < 0.01).

CONCLUSIONAluminum may induce neurons apoptosis, and lipid peroxidation injury in endoplasmic reticulum plays an important role in the apoptosis progression.

Aluminum ; toxicity ; Animals ; Apoptosis ; drug effects ; Cells, Cultured ; Endoplasmic Reticulum Stress ; physiology ; Lipid Peroxidation ; physiology ; Neurons ; drug effects ; metabolism ; pathology ; Rats ; Rats, Sprague-Dawley

BACKGROUNDPodocyte apoptosis is recently indicated as an early phenomenon of diabetic nephropathy. Pancreatic β-cells exposed to saturated free fatty acid palmitate undergo irreversible endoplasmic reticulum (ER) stress and consequent apoptosis, contributing to the onset of diabetes. We hypothesized that palmitate could induce podocyte apoptosis via ER stress, which initiates or aggravates proteinuria in diabetic nephropathy.

METHODSPodocyte apoptosis was detected by 4',6-diamidio-2-phenylindole (DAPI) stained apoptotic cell count and Annexin V-PI stain. The expressions of ER molecule chaperone glucose-regulated protein 78 (GRP78), indicators of ER-associated apoptosis C/EBP homologous protein (CHOP), and Bcl-2 were assayed by Western blotting and real-time PCR. GRP78 and synaptopodin were co-localized by immunofluorescence stain.

RESULTSPalmitate significantly increased the percentage of cultured apoptotic murine podocytes time-dependently when loading 0.75 mmol/L (10 hours, 13 hours, and 15 hours compared with 0 hour, P < 0.001) and dose-dependently when loading palmitate ranging from 0.25 to 1.00 mmol/L for 15 hours (compared to control, P < 0.001). Palmitate time-dependently and dose-dependently increased the protein expression of GRP78 and CHOP, and decreased that of Bcl-2. Palmitate loading ranging from 0.5 to 1.0 mmol/L for 12 hours significantly increased mRNA of GRP78 and CHOP, and decreased that of Bcl-2 compared to control (P < 0.001), with the maximum concentration being 0.75 mmol/L. Palmitate 0.5 mmol/L loading for 3 hours, 8 hours, and 12 hours significantly increased mRNA of GRP78 and CHOP, and decreased that of Bcl-2 compared to 0 hour (P < 0.001), with the maximum effect at 3 hours. Confocal microscopy demonstrated that GRP78 expression was significantly increased when exposed to 0.5 mmol/L of palmitate for 8 hours compared to control.

CONCLUSIONPalmitate could induce podocyte apoptosis via ER stress, suggesting podocyte apoptosis and consequent proteinuria caused by lipotoxic free fatty acid could be ameliorated by relief of ER stress.

Apoptosis ; drug effects ; Cells, Cultured ; Endoplasmic Reticulum Stress ; physiology ; Heat-Shock Proteins ; analysis ; physiology ; Humans ; Insulin Resistance ; Palmitic Acid ; pharmacology ; Podocytes ; drug effects ; pathology

Na+ -Ca2+ exchanger (NCX) transports Ca2+ coupled with Na+ across the plasma membrane in a bi-directional mode. Ca2+ flux via NCX mediates osteogenic processes, such as formation of extracellular matrix proteins and bone nodules. However, it is not clearly understood how the NCX regulates cellular Ca2+ movements in osteogenic processes. In this study, the role of NCX in modulating Ca2+ content of intracellular stores ([Ca2+](ER)) was investigated by measuring intracellular Ca2+ activity in isolated rat osteoblasts. Removal of extracellular Na+ elicited a transient increase of intracellular Ca2+ concentration ([Ca2+](i)). Pretreatment of antisense oligodeoxynucleotide (AS) against NCX depressed this transient Ca2+ rise and raised the basal level of [Ca2+](i). In AS-pretreated cells, the expression and activity of alkaline phosphatase (ALP), an osteogenic marker, were decreased. However, the cell viability was not affected by AS-pretreatment. Suppression of NCX activity by the AS-pretreatment decreased ATP-activated Ca2+ release from intracellular stores and significantly enhanced Ca2+ influx via store operated calcium influx (SOCI), compared to those of S-pretreated or control cells. These results strongly suggest that NCX has a regulatory role in cellular Ca2+ pathways in osteoblasts by modulating intracellular Ca2+ content.
Alkaline Phosphatase/metabolism ; Animals ; Calcium/*metabolism ; Cell Membrane/metabolism ; Cell Survival ; Cells, Cultured ; Cytoplasm/metabolism ; Endoplasmic Reticulum/metabolism ; Intracellular Space/metabolism ; Oligodeoxyribonucleotides, Antisense/pharmacology ; Osteoblasts/drug effects/*physiology ; Rats ; Signal Transduction ; Sodium/physiology ; Sodium-Calcium Exchanger/*physiology

Endoplasmic reticulum (ER) stress occurs in macrophage-rich areas of advanced atherosclerotic lesions and contributes to macrophage apoptosis and subsequent plaque necrosis. The purpose of the present study was to investigate the effects of caveolin-1 (Cav-1) on ER stress-induced apoptosis in cultured macrophages and the underlying mechanisms. RAW264.7 cells were incubated with thapsigargin (TG) to establish ER stress model. And Cav-1 expression was detected by Western blot. After being pretreated with filipin(III), a caveolae inhibitor, RAW264.7 cells were assayed with flow cytometry and confocal laser scanning microscopy to detect cell apoptosis. Moreover, p38 mitogen-activated protein kinase (MAPK) phosphorylation and C/EBP homologous protein (CHOP) expression were detected with Western blot. The results showed that Cav-1 expression was markedly increased at early stage of TG treatment (P < 0.05) and then decreased with prolonged or high dose TG treatments. The increasing of Cav-1 expression induced by TG in RAW264.7 cells was abolished under inhibition of caveolae by filipin(III) (P < 0.05). The effect of TG on apoptosis of RAW264.7 cells was further augmented after pretreatment with filipin(III) (P < 0.05). Western blotting showed that MAPK phosphorylation induced by TG was inhibited by filipin(III) in RAW264.7 cells (P < 0.05), whereas CHOP remained unchanged (P > 0.05). These results suggest that Cav-1 may play a critical role in suppressing ER stress-induced macrophages apoptosis in vitro, and one of the mechanisms may be correlated with the activation of p38 MAPK prosurvival pathway.
Animals ; Apoptosis ; drug effects ; Caveolin 1 ; genetics ; metabolism ; Cell Line ; Endoplasmic Reticulum Stress ; physiology ; Filipin ; pharmacology ; MAP Kinase Signaling System ; Macrophages ; cytology ; drug effects ; Mice ; Thapsigargin ; pharmacology ; Transcription Factor CHOP ; metabolism ; p38 Mitogen-Activated Protein Kinases ; metabolism

OBJECTIVETo determine the activity of endoplasmic reticulum stress (ERS) and its effect on osteogenic differentiation of periodontal ligament stem cells (PDLSC) in inflammatory microenvironment.

METHODSPDLSC were obtained from the primary culture of the human tooth and cloned with limited diluted method. Real-time reverse transcription (RT)-PCR was used to examine the different expression of thapsigargin (TG) treated PDLSC and lipopolysaccharide (LPS) treated PDLSC. Real-time RT-PCR, alizarin red staining and cetyl pyridine chloride quantitative analyze were used to examine the osteogenic differentiation of PDLSC, TG + PDLSC, LPS + PDLSC and LPS + PDLSC + 4-PBA.

RESULTSProtein kinase receptor like endoplasmic reticulum kinase (PERK), glucose regulated protein 78 (GRP78), transcription activation factor 4(ATF4), CCAAT/enhancer-binding protein-homologous protein (CHOP) mRNA expression in group PDLSC + TG in 6 h were respectively 1.49 ± 0.24, 2.77 ± 0.60, 1.75 ± 0.16, 2.16 ± 0.32, which were all greater than that in group PDLSC (P < 0.05). PERK, CHOP mRNA expression reached the peak at 6 h (1.76 ± 0.08, 2.31 ± 0.17) and were greater than group PDLSC (P < 0.05). ERS could suppress osteogenic differentiation of TG + PDLSC and LPS + PDLSC. The runt-related transcription factor-2 (RUNX2), alkaline phosphatase (ALP), osteocalcin (OCN) mRNA expression of group TG + PDLSC was respectively 0.73 ± 0.06, 0.01 ± 0.00, 0.20 ± 0.06 (P < 0.05). The RUNX2, ALP, OCN mRNA expression of group LPS + PDLSC was respectively 0.80 ± 0.06, 0.48 ± 0.05, 0.29 ± 0.04 (P < 0.05). The RUNX2, ALP, OCN mRNA expression of group PDLSC + TG + 4-PBA was respectively 1.10 ± 0.09, 0.74 ± 0.05, 0.67 ± 0.13, which were greater higher than that of group LPS + PDLSC (P < 0.05).

CONCLUSIONSERS was activated in PDLSC and suppressed osteogenic differentiation of PDLSC, which can simulate inflammatory microenvironment in vitro. This effect can be recovered by using ERS inhibitor 4-PBA.

Alkaline Phosphatase ; metabolism ; Butylamines ; pharmacology ; Cell Differentiation ; Cellular Microenvironment ; Core Binding Factor Alpha 1 Subunit ; metabolism ; Endoplasmic Reticulum Stress ; physiology ; Humans ; Osteocalcin ; metabolism ; Osteogenesis ; Periodontal Ligament ; cytology ; metabolism ; Polysaccharides ; pharmacology ; RNA, Messenger ; metabolism ; Stem Cells ; drug effects ; physiology ; Thapsigargin ; pharmacology

Baicalein is one of the major flavonoids in Scutellaria baicalensis Georgi and possesses various effects, including cytoprotection and anti-inflammation. Because endoplasmic reticulum (ER) stress has been implicated in neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and cerebral ischemia, we investigated the effects of baicalein on apoptotic death of HT22 mouse hippocampal neuronal cells induced by thapsigargin (TG) and brefeldin A (BFA), two representative ER stress inducers. Apoptosis, reactive oxygen species (ROS) production, and mitochondrial membrane potential (MMP) were measured by flow cytometry. Expression level and phosphorylation status of ER stress-associated proteins and activation and cleavage of apoptosis-associated proteins were analyzed by Western blot. Baicalein reduced TG- and BFA-induced apoptosis of HT22 cells and activation and cleavage of apoptosis-associated proteins, such as caspase-12 and -3 and poly(ADP-ribose) polymerase. Baicalein also reduced the TG- and BFA-induced expression of ER stress-associated proteins, including C/EBP homologous protein (CHOP) and glucose-regulated protein 78, the cleavage of X-box binding protein-1 and activating transcription factor 6alpha, and the phosphorylation of eukaryotic initiation factor-2alpha and mitogen-activated protein kinases, such as p38, JNK, and ERK. Knock-down of CHOP expression by siRNA transfection and specific inhibitors of p38 (SB203580), JNK (SP600125), and ERK (PD98059) as well as anti-oxidant (N-acetylcysteine) reduced TG- or BFA-induced cell death. Baicalein also reduced TG- and BFA-induced ROS accumulation and MMP reduction. Taken together, these results suggest that baicalein could protect HT22 neuronal cells against ER stress-induced apoptosis by reducing CHOP induction as well as ROS accumulation and mitochondrial damage.
Animals ; *Apoptosis ; Brefeldin A/pharmacology ; Cell Line ; Cytoprotection ; DNA-Binding Proteins/metabolism ; Endoplasmic Reticulum/drug effects/*physiology ; Flavanones/*pharmacology ; Heat-Shock Proteins/biosynthesis ; Hippocampus/cytology ; Membrane Potential, Mitochondrial/drug effects ; Mice ; Mitogen-Activated Protein Kinases/metabolism ; Neurons/*drug effects/physiology ; Reactive Oxygen Species/*metabolism ; Signal Transduction/drug effects ; Thapsigargin/pharmacology ; Transcription Factor CHOP/*biosynthesis ; Transcription Factors/metabolism ; Unfolded Protein Response/drug effects

OBJECTIVETo explore the role of Bid protein in the mitochondria and endoplasmic reticulum (ER) associated apoptotic pathway.

METHODSApoptosis of MUTZ-1 cells induced by homoharringtonine (HHT) was measured by FACS. Mitochondria and ER associated apoptotic pathway was detected by RT-PCR and Western blotting. And the translocation of Bid protein was measured by laser scanning confocal microscope (LSCM).

RESULTSAfter exposure of MUTZ-1 to HHT at 0.05 microg/ml for 24 h, typical ER-stress phenomenon induced apoptotic cells and release of Ca2+ from the cytosolic Ca2+ storage and the loss of mitochondrial membrane potential were observed. RT-PCR analysis revealed that mRNAs for ER stress-associated proapoptotic factor were markedly increased at 4 h after 0.05 microg/ml HHT treatment and peaked at 12 h, then decreased steady. Activation of caspase protein was also observed at 8 h. The translocation of Bid protein from ER to mitochondria was observed at 12 h after HHT treatment.

CONCLUSIONHHT can induce MUTZ-1 cells apoptosis. The cell death may be likely mediated by the ER stress pathway as well as mitochondrial pathway and Bid protein may be the cross talk of the two apoptotic pathways.

Apoptosis ; drug effects ; physiology ; BH3 Interacting Domain Death Agonist Protein ; metabolism ; physiology ; Calcium ; metabolism ; Caspase 3 ; metabolism ; Caspases, Initiator ; metabolism ; Cell Line ; DNA-Binding Proteins ; metabolism ; Endoplasmic Reticulum ; metabolism ; physiology ; Harringtonines ; pharmacology ; Humans ; Mitochondria ; metabolism ; physiology ; Regulatory Factor X Transcription Factors ; Transcription Factors ; metabolism

BACKGROUNDAccumulated evidence shows that hypoxia can induce endothelial apoptosis, however the mechanism is still unknown. We hypothesized whether intermittent or persistent hypoxia could induce endoplasmic reticular stress, leading to endothelial apoptosis.

METHODSTwenty-four 8-week male Sprague Dawley (SD) rats were divided into three groups: normoxia (NC) group, intermittent hypoxia (IH) group and persistent hypoxia (PH) group. TUNEL staining was performed to detect aortic arch endotheliar apoptosis, and immunohistochemistry for BIP, CHOP and caspase12 to test protein expression; human umbilical vein endothelial cells (HUVECs) of the line ECV304 were cultured (with or without taurodeoxycholic acid (TUDCA) 10 mmol/L, 100 mmol/L) and divided into four groups: NC group (20.8% O2 for 4 hours), PH1 group (5% O2 for 4 hours), PH2 group (5% O2 for 12 hours) and IH group (20.8% O2 and 5% O2 alternatively for 8 hours). Annexin V-fluorescein-isothiocyanate/propidium iodide flow cytometry was used to assess apoptosis in each group. The expressions of GRP78, CHOP and caspase12 were detected by real-time quantitative reverse-transcription PCR. Result Intermittent and persistent hypoxia could increase the rate of endothelium apoptosis and the expressions of GRP78, CHOP and caspase12 compared with the control, induction by intermittent hypoxia was slightly higher than persistent hypoxia. In the HUVEC experiment, TUDCA significantly reduced apoptosis and the expressions of GRP78, CHOP and caspase12.

CONCLUSIONHypoxia, especially intermittent, can induce endothelial cell apoptosis possibly through endoplasmic reticulum stress pathway, which can be attenuated by taurodeoxycholic acid.

Animals ; Apoptosis ; drug effects ; genetics ; physiology ; Caspase 12 ; genetics ; Endoplasmic Reticulum Stress ; drug effects ; genetics ; physiology ; Heat-Shock Proteins ; genetics ; Human Umbilical Vein Endothelial Cells ; Humans ; Hypoxia ; genetics ; physiopathology ; Male ; Rats ; Rats, Sprague-Dawley ; Taurodeoxycholic Acid ; pharmacology ; Transcription Factor CHOP ; genetics

OBJECTIVETo study the effects of erythropoietin (EPO) on cardiomyocyte apoptosis and endoplasmic reticulum stress (ERS)-related proteins, glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP), in neonatal rats with asphyxia.

METHODSA total of 120 newborn Sprague-Dawley rats (7 days old) were randomly divided into sham-operated (n=40), asphyxia (n=40) and EPO-treated asphyxia groups (n=40). A neonatal rat model of normobaric asphyxia was established in the asphyxia and EPO-treated asphyxia groups. The rats in the EPO-treated asphyxia group received intraperitoneal injection of recombinant human erythropoietin (500 U/mL) immediately after the model was established, while the other two groups received the same volume of normal saline (0.9%). Heart blood and myocardial tissue samples were collected from 8 rats in each group at 2, 6, 12, 24 or 48 hours after the model was established. Serum creatine kinase (CK) and lactate dehydrogenase (LDH) levels were measured; cardiomyocyte apoptosis was evaluated, and expression of myocardial GRP78 and CHOP was measured.

RESULTSCompared with the sham-operated and EPO-treated asphyxia groups, the asphyxia group had significantly increased serum CK and LDH levels, number of apoptotic cells, and expression of myocardial GRP78 and CHOP at each time point (P<0.01), and all the indices were significantly higher in the EPO-treated asphyxia group than in the sham-operated group (P<0.01). At 24 hours after asphyxia, the expression of myocardial CHOP was positively correlated with the myocardial apoptosis index (r=0.944, P<0.01).

CONCLUSIONSEPO exerts a protective effect on the myocardium of neonatal rats with hypoxic-ischemic injury by regulating ERS-related proteins GRP78 and CHOP and reducing cardiomyocyte apoptosis.

Animals ; Animals, Newborn ; Apoptosis ; drug effects ; Asphyxia Neonatorum ; drug therapy ; pathology ; Creatine Kinase ; blood ; Endoplasmic Reticulum Stress ; physiology ; Erythropoietin ; pharmacology ; Heat-Shock Proteins ; analysis ; L-Lactate Dehydrogenase ; blood ; Myocytes, Cardiac ; drug effects ; pathology ; Rats ; Rats, Sprague-Dawley ; Transcription Factor CHOP ; analysis