Endoplasmic Reticulum Stress-related Molecules Research Articles

Honokiol Attenuates the Severity of Acute Pancreatitis and Associated Lung Injury via Acceleration of Acinar Cell Apoptosis

Severe acute pancreatitis remains a life-threatening disease with a high mortality rate among a defined proportion of those affected. Apoptosis has been hypothesized to be a beneficial form of cell death in acute pancreatitis. Honokiol, a low-molecular-weight natural product, possesses the ability of anti-inflammation and apoptosis induction. Here, we investigate whether honokiol can ameliorate severe acute pancreatitis and the associated acute lung injury in a mouse model. Mice received six injections of cerulein at 1-h intervals, then given one intraperitoneal injection of bacterial lipopolysaccharide for the induction of severe acute pancreatitis. Moreover, mice were intraperitoneally given vehicle or honokiol 10 min after the first cerulein injection. Honokiol protected against the severity of acute pancreatitis in terms of increased serum amylase and lipase levels, pancreas pathological injury, and associated acute lung injury. Honokiol significantly reduced the increases in serum tumor necrosis factor-α, interleukin 1, and nitric oxide levels 3 h and serum high-mobility group box 1 24 h after acute pancreatitis induction. Honokiol also significantly decreased myeloperoxidase activities in the pancreas and the lungs. Endoplasmic reticulum stress-related molecules eIF2α (phosphorylated) and CHOP protein expressions, apoptosis, and caspase-3 activity were increased in the pancreas of mice with severe acute pancreatitis, which was unexpectedly enhanced by honokiol treatment. These results suggest that honokiol protects against acute pancreatitis and limits the spread of inflammatory damage to the lung in a severe acute pancreatitis mouse model. The acceleration of pancreatic cell apoptosis by honokiol may play a pivotal role.

Expression profiles of endoplasmic reticulum stress-related molecules in demyelinating lesions and multiple sclerosis

Background: Increasing evidence associates the endoplasmic reticulum (ER) stress signalling pathway as a potential treatment target in multiple sclerosis (MS). Objective: To establish the expression profile of markers of ER stress both in demyelinating biopsy specimens and microdissected lesions in human post-mortem MS tissue. Methods: Immunohistochemical detection of C/EBP homologous protein (CHOP), immunoglobulin heavy chain binding protein (BiP), and hypoxia marker antigen D-110 in biopsies from three patients with MS primary or secondary progressive, three patients with clinically isolated syndrome, and one patient with lesional epilepsy was carried out. Laser capture microdissection of normal, perilesion and lesion tissue from post-mortem MS tissue and non-diseased control tissue was performed, followed by real-time PCR to detect ER stress genes. Results: In biopsy specimens, increased expression of the ER and hypoxic stress molecules in a range of cell types in most of the actively demyelinating lesions and perilesions was detected. Real-time PCR analysis demonstrated statistically significant elevated expression of the ER stress genes in normal-appearing white matter relative to control white matter. Moreover, significantly increased expression of CHOP was detected in the perilesion of active plaques (p < 0.01). Conclusions: Our results, showing detection of elevated expression of ER stress molecules in lesional tissue, offer compelling evidence for further investigation of the ER stress signalling pathway as a potential therapeutic target for the treatment of MS.

GLP-1 Can Protect Proinflammatory Cytokines Induced Beta Cell Apoptosis through the Ubiquitination

Background: Proinflammatory cytokines are one of the causes of diabetes mellitus. However, the exact molecular mechanism by which proinflammatory cytokines induce β-cell death remains to be clearly elucidated. Glucagon-like peptide-1 (GLP-1) affects the stimulation of insulin secretion and the preservation of β-cells. Additionally, it may exert an antiapoptotic effect on β cells; however, the mechanism underlying this effect has yet to be demonstrated. Therefore, we investigated the protective effects of GLP-1 in endoplasmic reticulum (ER)-mediated β-cell apoptosis using proinflammatory cytokines. Methods: To induce ER stress, hamster insulin-secreting tumor (HIT)-T15 cells were treated using a mixture of cytokines. Apoptosis was evaluated via MTT assay, Hoechst 33342 staining, and annexin/propidium iodide (PI) flow cytometry. The mRNA and protein expression levels of ER stress-related molecules were determined via PCR and Western blotting, respectively. Nitric oxide was measured with Griess reagent. The levels of inducible nitric oxide synthase (iNOS) mRNA and protein were analyzed via real-time PCR and Western blot, respectively. iNOS protein degradation was evaluated via immunoprecipitation. We pretreated HIT-T15 cells with exendin (Ex)-4 for 1 hour prior to the induction of stress. Results: We determined that Ex-4 exerted a protective effect through nitric oxide and the modulation of ER stress-related molecules (glucose-regulated protein [GRP]78, GRP94, and CCAAT/enhancer-binding protein homologous protein [CHOP]) and that Ex-4 stimulates iNOS protein degradation via the ubiquitination pathway. Additionally, Ex-4 also induced the recovery of insulin2 mRNA expression in β cells. Conclusion: The results of this study indicate that GLP-1 may protect β cells against apoptosis through the ubiquitination pathway. (Endocrinol Metab 26:142-149, 2011)

Different early ER-stress responses in the CLN8 mnd mouse model of neuronal ceroid lipofuscinosis

Neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative disorders characterized by epilepsy, progressive motor and cognitive decline, blindness, and by the accumulation of autofluorescent lipopigment. Late-infantile onset forms (LINCL) include those linked to mutations in CLN8 gene, encoding a transmembrane protein at the endoplasmic reticulum (ER). In the motor neuron degeneration (mnd) mouse model of the CLN8-LINCL (CLN8 mnd ), we carried out an analysis of ER stress-related molecules in CNS structures that exhibit a variable rate of disease progression (early retinal degeneration and delayed brain and motoneuron dysfunction). At the presymptomatic state of 1-month-old CLN8 mnd mice, we found an upregulation of GRP78 and activation of the transcription factor-6 (ATF6) in all structures examined, an activation of a CHOP-dependent pathway in the cerebellum, hippocampus and retina, a caspase-12-dependent pathway in the retina and no activation of these two pathways in the cerebral cortex and spinal cord. An increased CHOP expression was detected in the cortex and spinal cord at the early symptomatic state (4 months). Caspase-3 cleavage occurred presymptomatically in the cerebellum, hippocampus and retina, and symptomatically in the cerebral cortex and spinal cord. We also monitored activation of NF-κB, which is engaged in the alarming phase of ER stress, together with increased levels of TRAF2, TNF-α and TNFR1, and no activation of ASK-1/JNK signalling pathway, all over mnd structures. The results suggest that early ER-stress responses distinctly combined and ER-stress pathways integrated with inflammatory responses may contribute to the progression of the CLN8 mnd disease in CNS structures.

Sodium 4-phenylbutyrate protects against spinal cord ischemia by inhibition of endoplasmic reticulum stress

Delayed paraplegia after operation on the thoracoabdominal aorta is considered to be related to vulnerability of motor neurons to ischemia. Previous studies have demonstrated the relationship between neuronal vulnerability and endoplasmic reticulum (ER) stress after transient ischemia in the spinal cord. The aim of this study was to investigate whether sodium 4-phenylbutyrate (PBA), a chemical chaperone that reduces the load of mutant or unfolded proteins retained in the ER during cellular stress, can protect against ischemic spinal cord damage. Spinal cord ischemia was induced in rabbits by direct aortic cross-clamping (below the renal artery and above the bifurcation) for 15 minutes at normothermia. Group A (n = 6) was a sham operation control group. In group B (n = 6) and group C (n = 6), vehicle or 15 mg/kg/h of sodium 4-PBA was infused intravenously, respectively, from 30 minutes before the induction of ischemia until 30 minutes after reperfusion. Neurologic function was assessed at 8 hours, and 2 and 7 days after reperfusion with a Tarlov score. Histologic changes were studied with hematoxylin-eosin staining. Immunohistochemistry analysis for ER stress-related molecules, including caspase12 and GRP78 were examined. The mean Tarlov scores were 4.0 in every group at 8 hours, but were 4.0, 2.5, and 3.9 at 2 days; and 4.0, 0.7, and 4.0 at 7 days in groups A, B, and C, respectively. The numbers of intact motor neurons at 7 days after reperfusion were 47.4, 21.5, and 44.9 in groups A, B, and C, respectively. There was no significant difference in terms of viable neurons between groups A and C. Caspase12 and GRP78 immunoreactivities were induced in motor neurons in group B, whereas they were not observed in groups A and C. Reduction in ER stress-induced spinal cord injury was achieved by the administration of 4-PBA. 4-PBA may be a strong candidate for use as a therapeutic agent in the treatment of ischemic spinal cord injury.

Soluble mediators from endotoxin‐stimulated stellate cells cause sustained JNK activation, ER stress and apoptosis of hepatocytes

Cells respond to various injurious stimuli by undergoing endoplasmic reticulum (ER) stress that is utilized as a survival or death mechanism. Bacterial lipopolysaccharide (LPS)‐stimulated hepatic stellate cells (HSCs) produce mediators that inhibit DNA synthesis and induce apoptosis of hepatocytes. Our objective was to investigate whether (a) LPS causes ER stress and apoptosis of hepatocytes in vivo, and (b) soluble mediators released by LPS‐stimulated HSCs cause ER stress leading to apoptosis of hepatocytes in vitro. LPS (10 mg/kg; ip) treatment of rats for 6h was found to cause ER stress/autophagy, activation of JNK MAPK and activation/expression of ER stress‐related molecules PERK, eIF2á and CHOP, and activation of caspase‐3 in hepatocytes. In vitro, soluble mediators released by LPS (10–1000ng/ml)‐stimulated HSCs in serum‐free condition caused cytosolic vacuolization associated with activation/increased expression of PERK, eIF2á and CHOP. LPS‐stimulated HSCs also caused activation of p38‐ and JNK‐MAPK in hepatocytes. However, blockage of JNK but not p38 activation ameliorated ER stress, inhibition of DNA synthesis and caspase‐3 activation caused by LPS‐stimulated HSCs. The results suggest that the ER stress induced by mediators released by LPS‐stimulated HSCs in hepatocytes may be an important mechanism that dictates their survival or death. Supported by an NIH grant (DK 54411).

Inhibition of Colon Carcinogenesis by 2-Methoxy-5-Amino-N-Hydroxybenzamide, a Novel Derivative of Mesalamine

Mesalamine has been reported to protect against inflammatory bowel disease-related colorectal cancer (CRC), but several drug-related issues have limited its use in chemopreventive programs. We evaluated the antineoplastic properties of mesalamine derivatives using in vitro and in vivo models of CRC. CRC cell proliferation and cell-cycle progression were evaluated by flow cytometry after exposure to mesalamine or mesalamine derivatives. Cyclins, cyclin-dependent kinases, and endoplasmic reticulum stress-related molecules were examined by immunoblotting. The in vivo antineoplastic effect of 2-methoxy-5-amino-N-hydroxybenzamide (2-14) was evaluated in a syngenic, CT26-derived xenograft mouse model of CRC and in the azoxymethane/dextran sulfate sodium-induced mouse model of colitis-associated CRC. The mesalamine derivative 2-14 was 10-fold more potent than mesalamine in inhibiting CRC cell proliferation. After exposure to 2-14, cyclin D1 expression was reduced and G0/G1 phase cells accumulated. These events were preceded by activation of eukaryotic translation initiation factor 2-alpha kinase 3 (pancreatic endoplasmic reticulum eIF2alpha kinase), phosphorylation of eukaryotic translation initiation factor 2alpha, induction of activating transcription factor 4, and splicing of X-box binding protein 1 messenger RNA, events that define endoplasmic reticulum stress. Silencing of PERK restored cyclin D1 levels, allowing cells to overcome the cell-cycle block induced by 2-14. Mice injected with 2-14 developed fewer CRC xenograft-derived tumors. Moreover, 2-14 injection reduced the development of neoplastic lesions induced by azoxymethane and dextran sulfate sodium in mice. The mesalamine derivative 2-14 inhibited CRC cell proliferation in vitro and prevented CRC progression in mouse models.

Increased Expression of Endoplasmic Reticulum Stress-Related Signaling Pathway Molecules in Multiple Sclerosis Lesions

Activation of endoplasmic reticulum (ER) stress-related cell signals has been reported in several neurologic disorders and may contribute to neurodegeneration. Endoplasmic reticulum stress is also linked to ischemic injury. However, activation of an ER stress response has not been investigated in multiple sclerosis (MS) lesions. We detected increased expression of ER stress-associated C/EBP homologous protein, immunoglobulin heavy chain-binding protein, and X-box-binding protein 1 in multiple cell types, including oligodendrocytes, astrocytes, T cells, and microglia in active MS lesions. Semiquantitative analysis of expression in active, chronic active, and chronic inactive lesions indicated that levels of immunoglobulin heavy chain-binding protein were significantly higher in acute lesions than in non-MS controls or MS normal-appearing white matter, and that ER stress-associated C/EBP homologous protein was upregulated to the greatest extent at the edges of chronic active lesions. Because demyelination may be triggered by a tissue response to ischemia-like conditions, changes in the hypoxia-related antigen D-110 were also investigated, and it was found that increased ER stress-associated C/EBP homologous protein expression can occur in either the presence or absence of D-110. A possible link between a perturbed ER and lesion development in MS suggests a signaling pathway that may represent a new therapeutic target in MS.

Protective Effects of Glucagon Like Peptide-1 on HIT-T15 β Cell Apoptosis via ER Stress Induced by 2-deoxy-D-glucose

Background: The characteristic feature of pancreatic β cells is highly developed endoplasmic reticulum (ER) due to a heavy engagement in insulin secretion. The ER serves several important function, including post-translational modification, folding, and assembly of newly synthesized secretory proteins, and its proper function is essential to cell survival. Various stress conditions can interfere with ER function. Pancreatic β cells may be particularly vulnerable to ER stress that causes to impair insulin biosynthesis and β cell survival through apoptosis. Glucagon like peptide-1 (GLP-1) is a new drug for treatment of type 2 diabetes and has effects on stimulation of insulin secretion and β cell preservation. Also, it may have an antiapoptotic effect on β cells, but detailed mechanisms are not proven. Therefore, we investigated the protective mechanism of GLP-1 in β cells through ER stress response induced by 2-deoxy-D-glucose (2DG). Methods: For induction of the ER stress, HIT-T15 cells (hamster β cell line) were treated with 2DG (10 mM). Apoptosis was evaluated with MTT assay, hoechst 33342 staining and Annexin/PI flow cytometry. Expression of ER stress-related molecules was determined by real-time PCR or western blot. For blocking ER stress, we pretreated HIT-T15 cells with exendin-4 (Ex-4; GLP-1 receptor agonist) for 1 hour before stress induction. Results: After induction with ER stress (2DG), β cells were lost by apoptosis. We found that Ex-4 had a protective effect through ER stress related molecules (GRP78, GRP94, XBP-1, eIF2α, CHOP) modulation. Also, Ex-4 recovered the expression of insulin2 mRNA in β cells. Conclusion: These results suggest that GLP-1 may protect β cells apoptosis through ER stress modulation. (KOREAN DIABETES J 32:477-487, 2008)

Impact of the endoplasmic reticulum stress response in spinal cord after transient ischemia

Background Delayed paraplegia after operation of the thoracic aorta is considered to be related to vulnerability of motor neurons to ischemia. Recently, endoplasmic reticulum (ER) stress has been reported to participate in neuronal cell death. In the present study, we investigate the expression of ER stress-related molecules and discuss the relationship between neuronal vulnerability and ER stress after transient ischemia in the spinal cord. Methods A rabbit spinal cord ischemia model was generated using a balloon catheter. In this model, spinal motor neurons show selectively delayed neuronal death whereas other spinal neuron, such as interneurons, survive. Immunohistochemical analysis and Western blotting for ER stress-related molecules, including phosphorylated eukaryotic initiation factor 2 alpha (p-eIF2α), activating transcription factor 4 (ATF4), glucose-regulated protein 78 (GRP78) and inositol-requiring ER transmembrane RNAse α isoform (IRE1α), were examined. Results P-eIF2α, which inhibits protein synthesis and modulates ER stress, was induced only in interneurons after 6 h of reperfusion. ATF4, which is specifically activated by PERK-eIF2α, was induced only in interneurons between 6 h and 1 day after reperfusion. GRP78 was induced strongly both in interneurons and motor neurons at an early stage of reperfusion, but prolonged expression was observed only in interneurons. IRE1α, which is supposed to transduce an ER stress-related death signal, was expressed more strongly and over a more prolonged period in motor neurons. Conclusions These results indicate that the vulnerability of motor neurons in the spinal cord might be partially attributed to an ER stress response to transient ischemia.

Protection of pancreatic β-cells by exendin-4 may involve the reduction of endoplasmic reticulum stress; in vivo and in vitro studies

The aim of this study was to investigate the in vivo and in vitro effects of exendin-4, a potent glucagon-like peptide 1 agonist, on the protection of the pancreatic beta-cells against their cell death. In in vivo experiments, we used beta-cell-specific calmodulin-overexpressing mice where massive apoptosis takes place in their beta-cells, and we examined the effects of chronic treatment with exendin-4. Chronic and s.c. administration of exendin-4 reduced hyperglycemia. The treatment caused significant increases of the insulin contents of the pancreas and islets, and retained the insulin-positive area. Dispersed transgenic islet cells lived only shortly, and several endoplasmic reticulum (ER) stress-related molecules such as immunoglobulin-binding protein (Bip), inositol-requiring enzyme-1alpha, X-box-binding protein-1 (XBP-1), RNA-activated protein kinase-like endoplasmic reticulum kinase, activating transcription factor-4, and C/EBP-homologous protein (CHOP) were more expressed in the transgenic islets. We also found that the spliced form of XBP-1, a marker of ER stress, was also increased in beta-cell-specific calmodulin-overexpressing transgenic islets. In the quantitative real-time PCR analyses, the expression levels of Bip and CHOP were reduced in the islets from the transgenic mice treated with exendin-4. These findings suggest that excess of ER stress occurs in the transgenic beta-cells, and the suppression of ER stress and resultant protection against cell death may be involved in the anti-diabetic effects of exendin-4.

Early activation of endoplasmic reticulum stress is associated with arginine-induced acute pancreatitis

Endoplasmic reticulum (ER) stress mechanisms have been found to play critical roles in a number of diseases states, such as diabetes mellitus and Alzheimer disease, but whether they are involved in acute pancreatitis is unknown. Here we show for the first time that all major ER stress sensing and signaling mechanisms are present in exocrine acini and are activated early in the arginine model of experimental acute pancreatitis. Pancreatitis was induced in rats by intraperitoneal injection of 4.0 g/kg body wt arginine. Pancreatitis severity was assessed by analysis of serum amylase, pancreatic trypsin activity, water content, and histology. ER stress-related molecules PERK, eIF2alpha, ATF6, XBP-1, BiP, CHOP, and caspase-12 were analyzed. Arginine treatment induced rapid and severe pancreatitis, as indicated by increased serum amylase, pancreatic tissue edema, and acinar cell damage within 4 h. Arginine treatment also caused an early activation of ER stress, as indicated by phosphorylation of PERK and its downstream target eIF2alpha, ATF6 translocation into the nucleus (within 1 h), and upregulation of BiP (within 4 h). XBP-1 splicing and CHOP expression were observed within 8 h. After 24 h, increased activation of the ER stress-related proapoptotic molecule caspase-12 was observed along with an increase in caspase-3 activity and TdT (terminal deoxynucleotidyl transferase)-mediated dUDP nick-end labeling (TUNEL) staining in exocrine acini. These results indicate that ER stress is an important early acinar cell event that likely contributes to the development of acute pancreatitis in the arginine model.

The protective effect of dantrolene on ischemic neuronal cell death is associated with reduced expression of endoplasmic reticulum stress markers

The endoplasmic reticulum (ER) plays an important role in ischemic neuronal cell death. In order to determine the effect of dantrolene, a ryanodine receptor antagonist, on ER stress response and ischemic brain injury, we investigated changes in ER stress-related molecules, that is phosphorylated form of double-stranded RNA-activated protein kinase (PKR)-like ER kinase (p-PERK), phosphorylated form of eukaryotic initiation factor 2α (p-eIF2α), activating transcription factor-4 (ATF-4), and C/EBP-homologous protein (CHOP), as well as terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) in the peri-ischemic area and ischemic core region of rat brain after transient middle cerebral artery occlusion (MCAO). In contrast to the cases treated with vehicle, the infarct volume and TUNEL-positive cells were significantly reduced at 24 h of reperfusion by treatment with dantrolene. The immunoreactivities for p-PERK, p-eIF2α, ATF-4, and CHOP were increased at the ischemic peripheral region after MCAO, which were partially inhibited by dantrolene treatment. The present results suggest that dantrolene significantly decreased infarct volume and provided neuroprotective effect on rats after transient MCAO by reducing ER stress-mediated apoptotic signal pathway activation in the ischemic area.