Inositol-requiring enzyme 1α is required for gut development in Xenopus lavies embryos

AIM:To investigate the role of inositol-requiring enzyme 1α(IRE1α) in gut development of Xenopus lavies embryos.METHODS:Xenopus embryos were obtained with in vitro fertilization and cultured in 0.1 × MBSH.One and half nanogram of IRE1α,1 ng of IRE1α-GR mRNA,1 ng of IRE1αΔC-GR mRNA,and 50 ng of IRE1α morpholino oligonucleotide(MO) or XBP1(C)MO were injected into four blastomeres at 4-cell stage for scoring the phenotype and marker gene analysis.To rescue the effect of IRE1α MO,1 ng of IRE1α-GR mRNA was coinjected with 50 ng of MO.For the activation of the GR-fusion proteins,dexamethasone was prepared as 5 mmol/L stock solutions in 100% ethanol and applied to the mRNA injected embryos at desired stages in a concentration of 10 μmol/L in 0.1 × MBSH.Embryos were kept in dexamethasone up to stage 41.Whole-mount in situ hybridization was used to determine specific gene expression,such as IRE1α,IRE1β,Xbra and Xsox17α.IRE1α protein expression during Xenopus embryogenesis was detected by Western blotting.RESULTS:In the whole-mount in situ hybridization analysis,xenopus IRE1α and IRE1β showed quite different expression pattern during tadpole stage.The relatively higher expression of IRE1α was observed in the pancreas,and significant transcription of IRE1β was found in the liver.IRE1α protein could be detected at all developmental stages analyzed,from stage 1 to stage 42.Gain-of-function assay showed that IRE1α mRNA injected embryos at tailbud stage were nearly normal and the expression of the pan-mesodermal marker gene Xbra and the endodermal gene Xsox17α at stage 10.5 was not significantly changed in embryos injected with IRE1α mRNA as compared to uninjected control embryos.And at tadpole stage,the embryos injected with IRE1α-GR mRNA did not display overt phenotype,such as gut-coiling defect.Loss-of-function assay demonstrated that the IRE1α MO injected embryos were morphologically normal before the tailbud stages.We did not observe a significant change of mesodermal and endodermal marker gene expression,while after stage 40,about 80% of the MO injected embryos exhibited dramatic gut defects in which the guts did not coil,but other structures outside the gastrointestinal tract were relatively normal.To test if the phenotypes were specifically caused by the knockdown of IRE1α,a rescue experiment was performed by co-injection of IRE1α-GR mRMA with IRE1α MO.The data obtained demonstrated that the gut coiling defect was rescued.The deletion mutant of IRE1α was constructed,consisting of the N-terminal part without the C-terminal kinase and RNase domains named IRE1αΔC,to investigate the functional domain of IRE1α.Injection of IRE1αΔCGR mRNA caused similar morphological alterations with gut malformation by interfering with the function of endogenous xIRE1α.In order to investigate if IRE1α/XBP1 pathway was involved in gut development,50 ng of XBP1 MO was injected and the results showed that knockdown of XBP1 resulted in similar morphological alterations with gut-coiling defect at tadpole stage.CONCLUSION:IRE1α is not required for germ layer formation but for gut development in Xenopus lavies and it may function via XBP1-dependent pathway.

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.

血必净注射液经肌醇需求酶1α信号通路影响组织因子凝血活性

目的：探讨不同浓度血必净注射液对内毒素诱导大鼠内皮细胞组织因子（tissue factor, TF）凝血活性的影响。方法：随机将内皮细胞分为对照组、脂多糖（lipopolysaccharide，LPS）组（500 ng/ml）、血必净组（1、5、25 μl /ml）、LPS＋血必净组（1、5、25 μl/ml），培养24、48和72 h后采用CCK-8法检测细胞增殖；留取上清，检测乳酸脱氢酶（lactic dehydrogenase，LDH）释放量；以刺激72 h为观察点，采用Western blot技术检测肌醇需求酶1α（inositol-requiring enzyme 1α，IRE1α）、未剪接型X盒结合蛋白（unspliced-box binding protein-1, uXBP-1）、剪接型X盒结合蛋白（spliced-box binding protein-1, sXBP-1）及蛋白质二硫化物异构酶（protein disulfide isomerase，PDI）的表达水平；加入Ca2＋、凝血因子（coagulation factor，F）Ⅶ和FⅩ，用发色底物法检测活化FⅩa水平。结果：与对照组相比，LPS组细胞增殖能力下降，LDH释放增多（P〈0.05）, IRE1α、uXBP1、sXBP1、PDI表达均上调，差异具有统计学意义（P〈0.05）。与对照组相比，血必净组细胞增殖能力增强，LDH释放减少（P〈0.05或P〈0.01），随着时间增加，此效应逐渐增强；LPS＋血必净组较LPS组细胞增殖活性升高，LDH释放下降（P〈0.05或P〈0.01），RE1α、uXBP1、sXBP1和PDI表达均明显减弱（P〈0.01），FⅩa产生随IRE1α、XBP1、PDI表达水平降低而减少（P〈0.05），其中LPS＋5 μl/ml血必净组降低FⅩa效果尤为明显（P〈0.05）。结论：血必净注射液能通过阻断IRE1α-XBP1通路，降低PDI的表达，影响内皮细胞TF凝血活性。

Coronavirus transmissible gastroenteritis virus antagonizes the antiviral effect of the microRNA miR-27b via the IRE1 pathway

Although the functional parameters of micro RNAs(mi RNAs)have been explored to some extent,the roles of these molecules in coronavirus infection and the regulatory mechanism of mi RNAs in virus infection are still unclear.Transmissible gastroenteritis virus(TGEV)is an enteropathgenic coronavirus and causes high morbidity and mortality in suckling piglets.Here,we demonstrated that microRNA-27b-3p(miR-27b-3p)suppressed TGEV replication by directly targeting porcine suppressor of cytokine signaling 6(SOCS6),while TGEV infection downregulated miR-27b-3p expression in swine testicular(ST)cells and in piglets.Mechanistically,the decrease of miR-27b-3p expression during TGEV infection was mediated by the activated inositolrequiring enzyme 1(IRE1)pathway of the endoplasmic reticulum(ER)stress.Further studies showed that when ER stress was induced by TGEV,IRE1 acted as an RNase activated by autophosphorylation and unconventionally spliced m RNA encoding a potent transcription factor,X-box-binding protein 1(Xbp1s).Xbp1s inhibited the transcription of miR-27 and ultimately reduced the production of miR-27b-3p.Therefore,our findings indicate that TGEV inhibits the expression of an anti-coronavirus micro RNA through the IRE1 pathway and suggest a novel way in which coronavirus regulates the host cell response to infection.

Endoplasmic reticulum stress and liver diseases

Endoplasmic reticulum(ER)stress occurs when ER homeostasis is perturbed with accumulation of unfolded/misfolded protein or calcium depletion.The unfolded protein response(UPR),comprising of inositol-requiring enzyme 1 a(IRE1 a),double-stranded RNA-dependent protein kinase(PKR)-like ER kinase(PERK)and activating transcription factor 6(ATF6)signaling pathways,is a protective cellular response activated by ER stress.However,UPR activation can also induce cell death upon persistent ER stress.The liver is susceptible to ER stress given its synthetic and other biological functions.Numerous studies from human liver samples and animal disease models have indicated a crucial role of ER stress and the UPR signaling pathways in the pathogenesis of liver diseases,including non-alcoholic fatty liver disease(NAFLD),alcoholic liver disease(ALD),alpha-1 antitrypsin(AAT)deficiency(AATD),cholestatic liver disease,drug-induced liver injury,ischemia/reperfusion(I/R)injury,viral hepatitis and hepatocel-lular carcinoma(HCC).Extensive investigations have demonstrated the potential underlying mechanisms of the induction of ER stress and the contribution of the UPR pathways during the development of the diseases.Moreover,ER stress and the UPR proteins and genes have become emerging therapeutic targets to treat liver diseases.