Endoplasmic reticulum stress and autophagy in cerebral ischemia/reperfusion injury:PERK as a potential target for intervention

Several studies have shown that activation of unfolded protein response and endoplasmic reticulum(ER)stress plays a crucial role in severe cerebral ischemia/reperfusion injury.Autophagy occurs within hours after cerebral ischemia,but the relationship between ER stress and autophagy remains unclear.In this study,we established experimental models using oxygen-glucose deprivation/reoxygenation in PC12 cells and primary neurons to simulate cerebral ischemia/reperfusion injury.We found that prolongation of oxygen-glucose deprivation activated the ER stress pathway protein kinase-like endoplasmic reticulum kinase(PERK)/eukaryotic translation initiation factor 2 subunit alpha(e IF2α)-activating transcription factor 4(ATF4)-C/EBP homologous protein(CHOP),increased neuronal apoptosis,and induced autophagy.Furthermore,inhibition of ER stress using inhibitors or by si RNA knockdown of the PERK gene significantly attenuated excessive autophagy and neuronal apoptosis,indicating an interaction between autophagy and ER stress and suggesting PERK as an essential target for regulating autophagy.Blocking autophagy with chloroquine exacerbated ER stress-induced apoptosis,indicating that normal levels of autophagy play a protective role in neuronal injury following cerebral ischemia/reperfusion injury.Findings from this study indicate that cerebral ischemia/reperfusion injury can trigger neuronal ER stress and promote autophagy,and suggest that PERK is a possible target for inhibiting excessive autophagy in cerebral ischemia/reperfusion injury.

Ferroptosis and endoplasmic reticulum stress in ischemic stroke

Ferroptosis is a form of non-apoptotic programmed cell death,and its mechanisms mainly involve the accumulation of lipid peroxides,imbalance in the amino acid antioxidant system,and disordered iron metabolism.The primary organelle responsible for coordinating external challenges and internal cell demands is the endoplasmic reticulum,and the progression of inflammatory diseases can trigger endoplasmic reticulum stress.Evidence has suggested that ferroptosis may share pathways or interact with endoplasmic reticulum stress in many diseases and plays a role in cell survival.Ferroptosis and endoplasmic reticulum stress may occur after ischemic stroke.However,there are few reports on the interactions of ferroptosis and endoplasmic reticulum stress with ischemic stroke.This review summarized the recent research on the relationships between ferroptosis and endoplasmic reticulum stress and ischemic stroke,aiming to provide a reference for developing treatments for ischemic stroke.

Treatment with β-sitosterol ameliorates the effects of cerebral ischemia/reperfusion injury by suppressing cholesterol overload, endoplasmic reticulum stress, and apoptosis

β-Sitosterol is a type of phytosterol that occurs naturally in plants.Previous studies have shown that it has anti-oxidant,anti-hyperlipidemic,anti-inflammatory,immunomodulatory,and anti-tumor effects,but it is unknown whetherβ-sitosterol treatment reduces the effects of ischemic stroke.Here we found that,in a mouse model of ischemic stroke induced by middle cerebral artery occlusion,β-sitosterol reduced the volume of cerebral infarction and brain edema,reduced neuronal apoptosis in brain tissue,and alleviated neurological dysfunction;moreover,β-sitosterol increased the activity of oxygen-and glucose-deprived cerebral cortex neurons and reduced apoptosis.Further investigation showed that the neuroprotective effects ofβ-sitosterol may be related to inhibition of endoplasmic reticulum stress caused by intracellular cholesterol accumulation after ischemic stroke.In addition,β-sitosterol showed high affinity for NPC1L1,a key transporter of cholesterol,and antagonized its activity.In conclusion,β-sitosterol may help treat ischemic stroke by inhibiting neuronal intracellular cholesterol overload/endoplasmic reticulum stress/apoptosis signaling pathways.

Endoplasmic reticulum stress improved chicken tenderness,promoted apoptosis and autophagy during postmortem ageing

In this study,endoplasmic reticulum(ER)stress inducer tunicamycin(TM)and inhibitor 4-phenylbutyric acid(4-PBA)were used to treat postmortem chicken breast muscle to investigate changes in tenderness and effects on apoptosis and autophagy during 5 days ageing.TM-induced ER stress reduced shear force,enhanced myofibril fragmentation index(MFI),disrupted myofibril structure,increased desmin degradation,and activatedμ-calpain and caspase-12.In addition,TM-induced ER stress increased the expression of Bax,Bim,and cytochrome c,and decreased the expression of Bcl-x L.Furthermore,TM-induced ER stress improved the conversion of LC3I to LC3II,raised the expression of Beclin-1,and decreased the expression of p62,PI3K,and m TOR.The opposite results were observed after 4-PBA treatment.These results suggested that ER stress could improve chicken tenderness,promote apoptosis and autophagy during chicken postmortem ageing.

Mechanisms underlying the role of endoplasmic reticulum stress in the placental injury and fetal growth restriction in an ovine gestation model

Background Exposure to bisphenol A(BPA),an environmental pollutant known for its endocrine-disrupting properties,during gestation has been reported to increase the risk of fetal growth restriction(FGR)in an ovine model of pregnancy.We hypothesized that the FGR results from the BPA-induced insufficiency and barrier dysfunction of the placenta,oxidative stress,inflammatory responses,autophagy and endoplasmic reticulum stress(ERS).However,precise mechanisms underlying the BPA-induced placental dysfunction,and subsequently,FGR,as well as the potential involvement of placental ERS in these complications,remain to be investigated.Methods In vivo experiment,16 twin-pregnant(from d 40 to 130 of gestation)Hu ewes were randomly distributed into two groups(8 ewes each).One group served as a control and received corn oil once a day,whereas the other group received BPA(5 mg/kg/d as a subcutaneous injection).In vitro study,ovine trophoblast cells(OTCs)were exposed to 4 treatments,6 replicates each.The OTCs were treated with 400μmol/L BPA,400μmol/L BPA+0.5μg/m L tunicamycin(Tm;ERS activator),400μmol/L BPA+1μmol/L 4-phenyl butyric acid(4-PBA;ERS antagonist)and DMEM/F12 complete medium(control),for 24 h.Results In vivo experiments,pregnant Hu ewes receiving the BPA from 40 to 130 days of pregnancy experienced a decrease in placental efficiency,progesterone(P4)level and fetal weight,and an increase in placental estrogen(E2)level,together with barrier dysfunctions,OS,inflammatory responses,autophagy and ERS in type A cotyledons.In vitro experiment,the OTCs exposed to BPA for 24 h showed an increase in the E2 level and related protein and gene expressions of autophagy,ERS,pro-apoptosis and inflammatory response,and a decrease in the P4 level and the related protein and gene expressions of antioxidant,anti-apoptosis and barrier function.Moreover,treating the OTCs with Tm aggravated BPA-induced dysfunction of barrier and endocrine(the increased E2 level and decreased P4 level),OS,inflammatory responses,autophagy,and ERS.However,treating the OTCs with 4-PBA reversed the counteracted effects of Tm mentioned above.Conclusions In general,the results reveal that BPA exposure can cause ERS in the ovine placenta and OTCs,and ERS induction might aggravate BPA-induced dysfunction of the placental barrier and endocrine,OS,inflammatory responses,and autophagy.These data offer novel mechanistic insights into whether ERS is involved in BPA-mediated placental dysfunction and fetal development.

Amlodipine inhibits the proliferation and migration of esophageal carcinoma cells through the induction of endoplasmic reticulum stress

BACKGROUND L-type calcium channels are the only protein channels sensitive to calcium channel blockers,and are expressed in various cancer types.The Cancer Genome Atlas database shows that the mRNA levels of multiple L-type calcium channel subunits in esophageal squamous cell carcinoma tumor tissue are significantly higher than those in normal esophageal epithelial tissue.Therefore,we hypothesized that amlodipine,a long-acting dihydropyridine L-type calcium channel blocker,may inhibit the occurrence and development of esophageal cancer(EC).AIM To investigate the inhibitory effects of amlodipine on EC through endoplasmic reticulum(ER)stress.METHODS Cav1.3 protein expression levels in 50 pairs of EC tissues and corresponding paracancerous tissues were examined.Subsequently,the inhibitory effects of amlodipine on proliferation and migration of EC cells in vitro were detected using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide and Transwell assays.In vivo experiments were performed using murine xenograft model.To elucidate the underlying mechanisms,in vitro cell studies were performed to confirm that ER stress plays a role in inhibition proliferation and migration of EC cells treated with amlodipine.RESULTS The expression level of Cav1.3 in esophageal carcinoma was 1.6 times higher than that in paracancerous tissues.Amlodipine treatment decreased the viability of esophageal carcinoma cells in a dose-and time-dependent manner.In vivo animal experiments also clearly indicated that amlodipine inhibited the growth of EC tumors in mice.Additionally,amlodipine reduces the migration of tumor cells by inhibiting epithelial-mesenchymal transition(EMT).Mechanistic studies have demonstrated that amlodipine induces ER stress-mediated apoptosis and suppresses EMT.Moreover,amlodipine-induced autophagy was characterized by an increase in autophagy lysosomes and the accumulation of light chain 3B protein.The combination of amlodipine with the ER stress inhibitor 4-phenylbutyric acid further confirmed the role of the ER stress response in amlodipine-induced apoptosis,EMT,and autophagy.Furthermore,blocking autophagy increases the ratio of apoptosis and migration.CONCLUSION Collectively,we demonstrate for the first time that amlodipine promotes apoptosis,induces autophagy,and inhibits migration through ER stress,thereby exerting anti-tumor effects in EC.

Celastrol activates caspase-3/GSDME-dependent pyroptosis in tumor cells by inducing endoplasmic reticulum stress Author links open overlay panel

Objective:To investigate the pyroptosis-inducing effects of celastrol on tumor cells and to explore the potential mechanisms involved,specifically focusing on the role of the caspase-3/gasdermin E(GSDME)signaling pathway and the impact of endoplasmic reticulum(ER)stress and autophagy.Methods: Necrostatin-1(Nec-1),lactate dehydrogenase release(LDH)assay,and Hoechst/propidium iodide(PI)double staining were employed to validate the mode of cell death.Western blot was used to detect the cleavage of GSDME and the expression of light chain 3(LC3)and BIP.Results: Celastrol induced cell swelling with large bubbles,which is consistent with the pyroptotic phenotype.Moreover,treatment with celastrol induced GSDME cleavage,indicating the activation of GSDME-mediated pyroptosis.GSDME knockout via CRISPR/Cas9 blocked the pyroptotic morphology of celastrol in HeLa cells.In addition,cleavage of GSDME was attenuated by a specific caspase-3 inhibitor in celastrol-treated cells,suggesting that GSDME activation was induced by caspase-3.Mechanistically,celastrol induced endoplasmic reticulum(ER)stress and autophagy in HeLa cells,and other ER stress inducers produced effects consistent with those of celastrol.Conclusion: These findings suggest that celastrol triggers caspase-3/GSDME-dependent pyroptosis via activation of ER stress,which may shed light on the potential antitumor clinical applications of celastrol.

Cell division cyclin 25C knockdown inhibits hepatocellular carcinoma development by inducing endoplasmic reticulum stress

BACKGROUND Cell division cyclin 25C(CDC25C)is a protein that plays a critical role in the cell cycle,specifically in the transition from the G2 phase to the M phase.Recent research has shown that CDC25C could be a potential therapeutic target for cancers,particularly for hepatocellular carcinoma(HCC).However,the specific regulatory mechanisms underlying the role of CDC25C in HCC tumorigenesis and development remain incompletely understood.AIM To explore the impact of CDC25C on cell proliferation and apoptosis,as well as its regulatory mechanisms in HCC development.METHODS Hepa1-6 and B16 cells were transduced with a lentiviral vector containing shRNA interference sequences(LV-CDC25C shRNA)to knock down CDC25C.Subsequently,a xenograft mouse model was established by subcutaneously injecting transduced Hepa1-6 cells into C57BL/6 mice to assess the effects of CDC25C knockdown on HCC development in vivo.Cell proliferation and migration were evaluated using a Cell Counting Kit-8 cell proliferation assays and wound healing assays,respectively.The expression of endoplasmic reticulum(ER)stress-related molecules(glucose-regulated protein 78,X-box binding protein-1,and C/EBP homologous protein)was measured in both cells and subcutaneous xenografts using quantitative real-time PCR(qRT-PCR)and western blotting.Additionally,apoptosis was investigated using flow cytometry,qRT-PCR,and western blotting.RESULTS CDC25C was stably suppressed in Hepa1-6 and B16 cells through LV-CDC25C shRNA transduction.A xenograft model with CDC25C knockdown was successfully established and that downregulation of CDC25C expression significantly inhibited HCC growth in mice.CDC25C knockdown not only inhibited cell proliferation and migration but also significantly increased the ER stress response,ultimately promoting ER stress-induced apoptosis in HCC cells.CONCLUSION The regulatory mechanism of CDC25C in HCC development may involve the activation of ER stress and the ER stress-induced apoptosis signaling pathway.

SIRT1 inhibits apoptosis of human lens epithelial cells through suppressing endoplasmic reticulum stress in vitro and in vivo

AIM:To explore the effect of silent information regulator factor 2-related enzyme 1(SIRT1)on modulating apoptosis of human lens epithelial cells(HLECs)and alleviating lens opacification of rats through suppressing endoplasmic reticulum(ER)stress.METHODS:HLECs(SRA01/04)were treated with varying concentrations of tunicamycin(TM)for 24h,and the expression of SIRT1 and C/EBP homologous protein(CHOP)was assessed using real-time quantitative polymerase chain reaction(RT-PCR),Western blotting,and immunofluorescence.Cell morphology and proliferation was evaluated using an inverted microscope and cell counting kit-8(CCK-8)assay,respectively.In the SRA01/04 cell apoptosis model,which underwent siRNA transfection for SIRT1 knockdown and SRT1720 treatment for its activation,the expression levels of SIRT1,CHOP,glucose regulated protein 78(GRP78),and activating transcription factor 4(ATF4)were examined.The potential reversal of SIRT1 knockdown effects by 4-phenyl butyric acid(4-PBA;an ER stress inhibitor)was investigated.In vivo,age-related cataract(ARC)rat models were induced by sodium selenite injection,and the protective role of SIRT1,activated by SRT1720 intraperitoneal injections,was evaluated through morphology observation,hematoxylin and eosin(H&E)staining,Western blotting,and RT-PCR.RESULTS:SIRT1 expression was downregulated in TMinduced SRA01/04 cells.Besides,in SRA01/04 cells,both cell apoptosis and CHOP expression increased with the rising doses of TM.ER stress was stimulated by TM,as evidenced by the increased GRP78 and ATF4 in the SRA01/04 cell apoptosis model.Inhibition of SIRT1 by siRNA knockdown increased ER stress activation,whereas SRT1720 treatment had opposite results.4-PBA partly reverse the adverse effect of SIRT1 knockdown on apoptosis.In vivo,SRT1720 attenuated the lens opacification and weakened the ER stress activation in ARC rat models.CONCLUSION:SIRT1 plays a protective role against TM-induced apoptosis in HLECs and slows the progression of cataract in rats by inhibiting ER stress.These findings suggest a novel strategy for cataract treatment focused on targeting ER stress,highlighting the therapeutic potential of SIRT1 modulation in ARC development.

Exosomes derived from microglia overexpressing miR-124-3p alleviate neuronal endoplasmic reticulum stress damage after repetitive mild traumatic brain injury

We previously reported that miR-124-3p is markedly upregulated in microglia-derived exosomes following repetitive mild traumatic brain injury.However,its impact on neuronal endoplasmic reticulum stress following repetitive mild traumatic brain injury remains unclear.In this study,we first used an HT22 scratch injury model to mimic traumatic brain injury,then co-cultured the HT22 cells with BV2 microglia expressing high levels of miR-124-3p.We found that exosomes containing high levels of miR-124-3p attenuated apoptosis and endoplasmic reticulum stress.Furthermore,luciferase reporter assay analysis confirmed that miR-124-3p bound specifically to the endoplasmic reticulum stress-related protein IRE1α,while an IRE1αfunctional salvage experiment confirmed that miR-124-3p targeted IRE1αand reduced its expression,thereby inhibiting endoplasmic reticulum stress in injured neurons.Finally,we delivered microglia-derived exosomes containing miR-124-3p intranasally to a mouse model of repetitive mild traumatic brain injury and found that endoplasmic reticulum stress and apoptosis levels in hippocampal neurons were significantly reduced.These findings suggest that,after repetitive mild traumatic brain injury,miR-124-3 can be transferred from microglia-derived exosomes to injured neurons,where it exerts a neuroprotective effect by inhibiting endoplasmic reticulum stress.Therefore,microglia-derived exosomes containing miR-124-3p may represent a novel therapeutic strategy for repetitive mild traumatic brain injury.

Sirtuin 1 alleviates endoplasmic reticulum stress-mediated apoptosis of intestinal epithelial cells in ulcerative colitis

BACKGROUND Sirtuin 1(SIRT1)is a nicotinamide adenine dinucleotide(NAD+)-dependent protein deacetylase that is involved in various diseases,including cancers,metabolic diseases,and inflammation-associated diseases.However,the role of SIRT1 in ulcerative colitis(UC)is still confusing.AIM To investigate the role of SIRT1 in intestinal epithelial cells(IECs)in UC and further explore the underlying mechanisms.METHODS We developed a coculture model using macrophages and Caco-2 cells.After treatment with the SIRT1 activator SRT1720 or inhibitor nicotinamide(NAM),the expression of occludin and zona occludens 1(ZO-1)was assessed by Western blot analysis.Annexin V-APC/7-AAD assays were performed to evaluate Caco-2 apoptosis.Dextran sodium sulfate(DSS)-induced colitis mice were exposed to SRT1720 or NAM for 7 d.Transferase-mediated dUTP nick-end labeling(TUNEL)assays were conducted to assess apoptosis in colon tissues.The expression levels of glucose-regulated protein 78(GRP78),CCAAT/enhancerbinding protein homologous protein(CHOP),caspase-12,caspase-9,and caspase-3 in Caco-2 cells and the colon tissues of treated mice were examined by quantitative real-time PCR and Western blot.RESULTS SRT1720 treatment increased the protein levels of occludin and ZO-1 and inhibited Caco-2 apoptosis,whereas NAM administration caused the opposite effects.DSS-induced colitis mice treated with SRT1720 had a lower disease activity index(P<0.01),histological score(P<0.001),inflammatory cytokine levels(P<0.01),and apoptotic cell rate(P<0.01),while exposure to NAM caused the opposite effects.Moreover,SIRT1 activation reduced the expression levels of GRP78,CHOP,cleaved caspase-12,cleaved caspase-9,and cleaved caspase-3 in Caco-2 cells and the colon tissues of treated mice.CONCLUSION SIRT1 activation reduces apoptosis of IECs via the suppression of endoplasmic reticulum stress-mediated apoptosis-associated molecules CHOP and caspase-12.SIRT1 activation may be a potential therapeutic strategy for UC.

Role of endoplasmic reticulum stress in the pathogenesis of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease(NAFLD)has emerged as a common public health problem in recent decades.However,the underlying mechanisms leading to the development of NAFLD are not fully understood.The endoplasmic reticulum(ER)stress response has recently been proposed to play a crucial role in both the development of steatosis and progression to nonalcoholic steatohepatitis.ER stress is activated to regulate protein synthesis and restore homeostatic equilibrium when the cell is stressed due to the accumulation of unfolded or misfolded proteins.However,delayed or insufficient responses to ER stress may turn physiological mechanisms into pathological consequences,including fat accumulation,insulin resistance,inflammation,and apoptosis,all of which play important roles in the pathogenesis of NAFLD.Therefore,understanding the role of ER stress in the pathogenesis of NAFLD has become a topic of intense investigation.This review highlights the recent findings linking ER stress signaling pathways to the pathogenesis of NAFLD.

Irisin attenuates intestinal injury,oxidative and endoplasmic reticulum stress in mice with L-arginine-induced acute pancreatitis

BACKGROUND Acute pancreatitis(AP)is often associated with intestinal injury,which in turn exaggerates the progression of AP.Our recent study has shown that a low level of serum irisin,a novel exercise-induced hormone,is associated with poor outcomes in patients with AP and irisin administration protects against experimental AP.However,the role of irisin in intestinal injury in AP has not been evaluated.AIM To investigate the effect of irisin administration on intestinal injury in experimental AP.METHODS AP was induced in male adult mice by two hourly intraperitoneal injections of Larginine.At 2 h after the last injection of L-arginine,irisin(50 or 250μg/kg body weight)or 1 mL normal saline(vehicle)was administered through intraperitoneal injection.The animals were sacrificed at 72 h after the induction of AP.Intestinal injury,apoptosis,oxidative and endoplasmic reticulum(ER)stress were evaluated.RESULTS Administration of irisin significantly mitigated intestinal damage,reduced apoptosis,and attenuated oxidative and ER stress in AP mice.In addition,irisin treatment also effectively downregulated serum tumor necrosis factor-alpha and interleukin-6 levels and alleviated injury in the pancreas,liver and lung of AP mice.CONCLUSION Irisin-mediated multiple physiological events attenuate intestinal injury following an episode of AP.Irisin has a great potential to be further developed as an effective treatment for patients with AP.

Ulinastatin suppresses endoplasmic reticulum stress and apoptosis in the hippocampus of rats with acute paraquat poisoning

Lung injury is the main manifestation of paraquat poisoning. Few studies have addressed brain damage after paraquat poisoning. Ulinastatin is a protease inhibitor that can effectively stabilize lysosomal membranes, prevent cell damage, and reduce the production of free radicals. This study assumed that ulinastatin would exert these effects on brain tissues that had been poisoned with paraquat. Rat models of paraquat poisoning were intraperitoneally injected with ulinastatin. Simultaneously, rats in the control group were administered normal saline. Hematoxylin-eosin staining showed that most hippocampal cells were contracted and nucleoli had disappeared in the paraquat group. Fewer cells in the hippocampus were concentrated and nucleoli had dis- appeared in the ulinastatin group. Western blot assay showed that expressions of GRP78 and cleaved-caspase-3 were significantly lower in the ulinastatin group than in the paraquat group. Immunohistochemical findings showed that CHOP immunoreactivity was significantly lower in the ulinastatin group than in the paraquat group. Terminal deoxynucleotidyl transferase-medi- ated dUTP nick end labeling staining showed that the number of apoptotic cells was reduced in the paraquat and ulinastatin groups. These data confirmed that endoplasmic reticular stress can be induced by acute paraqnat poisoning. Ulinastatin can effectively inhibit this stress as well as cell apoptosis, thereby exerting a neuroprotective effect.

Role of PERK/eIF2α/CHOP Endoplasmic Reticulum Stress Pathway in Oxidized Low-density Lipoprotein Mediated Induction of Endothelial Apoptosis

Objective PERK/elF2/CHOP is a major signaling pathway mediating endoplasmic reticulum （ER） stress related with atherosclerosis. Oxidized LDL （ox-LDL） also induces endothelial apoptosis and plays a vital role in the initiation and progression of atherosclerosis. The present study was conducted to explore the regulatory effect of ox-LDL on PERK/elF2a/CHOP signaling pathway in vascular endothelial cells. Methods The effects of ox-LDL on PERK and p-elF2a protein expression of primary human umbilical vein endothelial cells （HUVECs） were investigated by Western blot analysis. PERK gene silencing and selective elF2a phosphatase inhibitor, salubrinal were used to inhibit the process of ox-LDL induced endothelial cell apoptosis, caspase-3 activity, and CHOP mRNA level. Results Ox-LDL treatment significantly increased the expression of PERK, PERK-mediated inactivation of elF2a phosphorylation, and the expression of CHOP, as well as the caspase-3 activity and apoptosis. The effects of ox-LDL were markedly decreased by knocking down PERK with stable transduction of lentiviral shRNA or by selective elF2a phosphatase inhibitor, salubrinal. Conclusion This study provides the first evidence that ox-LDL induces apoptosis in vascular endothelial cells mediated largely via the PERK/elF2a/CHOP ER-stress pathway. It adds new insights into the molecular mechanisms underlying the pathogenesis and progression of atherosclerosis.

N-acetylcysteine protects against cadmium-induced germ cell apoptosis by inhibiting endoplasmic reticulum stress in testes

Cadmium （Cd） is a reproductive toxicant that induces germ cell apoptosis in the testes. Previous studies have demonstrated that endoplasmic reticulum （ER） stress is involved in Cd-induced germ cell apoptosis. The aim of the present study was to investigate the effects of N-acetylcysteine （NAC）, an antioxidant, on Cd-induced ER stress and germ cell apoptosis in the testes. Male CD-1 mice were intraperitoneally injected with CdCl2 （2.0 mg kg^-1）. As expected, acute Cd exposure induced germ cell apoptosis in the testes, as determined by terminal dUTP nick-end labelling （TUNEL）. However, the administration of NAC alleviated Cd-induced germ ceil apoptosis in the testes. Further analysis showed that NAC attenuated the Cd-induced upregulation of testicular glucose-regulated protein 78 （GRP78）, an important ER molecular chaperone. Moreover, NAC inhibited the Cd-induced phosphorylation of testicular eukaryotic translation initiation factor 2a （elF2a）, a downstream target of the double-stranded RNA-activated kinase-like ER kinase （PERK） pathway. In addition, NAC blocked the Cd-induced activation of testicular X binding protein （XBP）-1, indicating that NAC attenuates the Cd-induced ER stress and the unfolded protein response （UPR）. Interestingly, NAC almost completely prevented the Cd-induced elevation of C/EBP homologous protein （CHOP） and phosphorylation of c-Jun N-terminal kinase （.INK）, two components of the ER stress-mediated apoptotic pathway. In conclusion, NAC protects against Cd-induced germ cell apoptosis by inhibiting endoplasmic reticulum stress in the testes.

Hyperhomocysteinemia, endoplasmic reticulum stress, and alcoholic liver injury

Deficiencies in vitamins or other factors(B6,B12,folic acid, betaine)and genetic disorders for the metabolism of the non-protein amino acid-homocysteine(Hcy)lead to hyperhomocysteinemia(HHcy).HHcy is an integral component of several disorders including cardiovascular disease,neurodegeneration,diabetes and alcoholic liver disease.HHcy unleashes mediators of inflammation such as NFκB,IL-1β,IL-6,and IL-8,increases production of intracellular superoxide anion causing oxidative stress and reducing intracellular level of nitric oxide(NO),and induces endoplasrnic reticulum(ER)stress which can explain many processes of Hcy-promoted cell injury such as apoptosis, fat accumulation,and inflammation.Animal models have played an important role in determining the biological effects of HHcy.ER stress may also be involved in other liver diseases such as α_1-antitrypsin(α_1-AT)deficiency and hepatitis C and/or B virus infection.Future research should evaluate the possible potentiative effects of alcohol and hepatic virus infection on ER stress-induced liver injury,study potentially beneficial effects of lowering Hcy and preventing ER stress in alcoholic humans,and examine polymorphisrn of Hcy metabolizing enzymes as potential risk-factors for the development of HHcy and liver disease.

Induction of Endoplasmic Reticulum Stress by Cadmium and Its Regulation on Nrf2 Signaling Pathway in Kidneys of Rats

Objective This study was conducted to investigate the regulation of endoplasmic reticulum stress on Nrf2 signaling pathway in the kidneys of rats. Methods Rats were divided into twelve groups of six animals each. Some groups were pre-administered with bacitracin or tauroursodeoxycholic acid(TUDCA), and all of them were treated with 5-20 μmol/kg cadmium(Cd) for 48 h. The oxidative stress levels were analyzed using kits. The mRNA and protein expression levels of endoplasmic reticulum stress-related factors and Nrf2 signaling pathway-related factors were determined using RT-PCR and western blot. Results Cd exposure resulted in oxidative stress in the kidneys of rats and upregulated the expression of endoplasmic reticulum stress(ERS)-related factors and Nrf2 signaling pathway-related factors, especially at doses of 10 and 20 μmol/kg Cd, and the expression changes were particularly obvious. Moreover, after pretreatment with bacitracin, Cd upregulated the expression of ERS-related factors to a certain extent and, at higher doses, increased the mRNA expression of Nrf2. After pretreatment with TUDCA, Cd reduced the level of ERS to a certain extent; however, at these doses, there were no significant changes in the expression of Nrf2. Conclusion Cadmium can result in ERS and oxidative stress in the kidneys of rats, activate Nrf2, and upregulate the transcriptional expression of phase II detoxification enzymes under these experimental conditions. ERS has a positive regulation effect on Nrf2 signaling pathway but has little effect on the negative regulation of Nrf2 signaling pathway in cadmium toxicity.

Endoplasmic reticulum stress-induced apoptosis in the penumbra aggravates secondary damage in rats with traumatic brain injury

Neuronal apoptosis is mediated by intrinsic and extrinsic signaling pathways such as the membrane-mediated,mitochondrial,and endoplasmic reticulum stress pathways.Few studies have examined the endoplasmic reticulum-mediated apoptosis pathway in the penumbra after traumatic brain injury,and it remains unclear whether endoplasmic reticulum stress can activate the caspase-12-dependent apoptotic pathway in the traumatic penumbra.Here,we established rat models of fluid percussion-induced traumatic brain injury and found that protein expression of caspase-12,caspase-3 and the endoplasmic reticulum stress marker 78 k Da glucose-regulated protein increased in the traumatic penumbra 6 hours after injury and peaked at 24 hours.Furthermore,numbers of terminal deoxynucleotidyl transferase-mediated d UTP nick end labeling-positive cells in the traumatic penumbra also reached peak levels 24 hours after injury.These findings suggest that caspase-12-mediated endoplasmic reticulum-related apoptosis is activated in the traumatic penumbra,and may play an important role in the pathophysiology of secondary brain injury.

Neuroprotective effects of Activin A on endoplasmic reticulum stress-mediated apoptotic and autophagic PC12 cell death

Activin A, a member of the transforming growth factor-beta superfamily, plays a neuroprotective role in multiple neurological diseases. Endoplasmic reticulum（ER） stress-mediated apoptotic and autophagic cell death is implicated in a wide range of diseases, including cerebral ischemia and neurodegenerative diseases. Thapsigargin was used to induce PC12 cell death, and Activin A was used for intervention. Our results showed that Activin A significantly inhibited morphological changes in thapsigargin-induced apoptotic cells, and the expression of apoptosis-associated proteins [cleaved-caspase-12, C/EBP homologous protein（CHOP） and cleaved-caspase-3] and biomarkers of autophagy（Beclin-1 and light chain 3）, and downregulated the expression of thapsigargin-induced ER stress-associated proteins [inositol requiring enzyme-1（IRE1）, tumor necrosis factor receptor-associated factor 2（TRAF2）, apoptosis signal-regulating kinase 1（ASK1）, c-Jun N-terminal kinase（JNK） and p38]. The inhibition of thapsigargin-induced cell death was concentration-dependent. These findings suggest that administration of Activin A protects PC12 cells against ER stress-mediated apoptotic and autophagic cell death by inhibiting the activation of the IRE1-TRAF2-ASK1-JNK/p38 cascade.