Application of XBP1s Decoy Oligodeoxynucleotide Attenuates Cancerous Phenotype in Huh-7 Hepatocellular Carcinoma Cells.

OBJECTIVE: The spliced form of X-box binding protein 1 (XBP1s) is a key transcription factor in the unfolded protein response (UPR), an adaptive mechanism for cell survival. Many studies demonstrated the induced expression of XBP1s in various cancers, including hepatocellular carcinoma (HCC). Such upregulated expression is linked to an enhancement of cell proliferation, migration, and improvement of the survival rate. In this study, we aimed to assess the therapeutic potential of targeting XBP1s, by specific decoy oligodeoxynucleotide (ODN) and evaluated the cancerous phenotypes in Huh-7 cells. MATERIALS AND METHODS: In this experimental study, we transfected Huh-7 cells with XBP1s decoy oligonucleotide (ODN). Subsequently, we assess some cellular features, including viability, migration capacity, proliferation potential, and apoptosis. Therefore, various techniques included wound healing test, BrdU, and annexin/PI assays. Additionally, the colony formation capacity was evaluated. The mRNA expression levels of BAX, BCL-2, c-MYC, CCND1, MMP-9, CDH1, and CD133 were quantified by the reverse transcription-quantitative polymerase chain reaction (RT-qPCR). RESULTS: Transfection of Huh-7 cells by XBP1s decoy ODN led to significant down-regulation of c-Myc, CCND1, MMP-9, BCL-2 and CD133 and up-regulation of CDH1 and BAX transcriptional expressions in comparison with the vehicle group. Our results also demonstrated that transfection of XBP1s-decoy reduced HCC cell viability, proliferation, migration capacity as well as colonization ability in comparison with the vehicle group. CONCLUSION: These findings proposed the potential application of XBP1s-decoy ODN to reduce cancerous phenotypes such as cell proliferation, cell migration and apoptosis induction in the Huh-7 cell line. More experiments on other cell lines and primary cells could validate our results.

ALKBH5-Mediated m6A Modification of XBP1 Facilitates NSCLC Progression Through the IL-6-JAK-STAT3 Pathway.

The X-box-binding protein 1 (XBP1) is an important transcription factor during endoplasmic reticulum stress response, which was reported as an oncogene in non-small cell lung cancer (NSCLC) tumorigenesis and development. However, the regulatory mechanism of XBP1 expression in NSCLC progression was less reported. N6-methyladenosine (m6A) RNA modification is an emerging epigenetic regulatory mechanism for gene expression. This study aimed to investigate the regulatory role of the m6A modification in XBP1 expression in NSCLC. We identified XBP1 as a downstream target of ALKBH5-mediated m6A modification in A549 and PC9 cells. Knockdown of ALKBH5 increased the m6A modification and the stability of XBP1 mRNA, while overexpression of ALKBH5 had the opposite effect. Furthermore, IGF2BP3 was confirmed to be a reader of XBP1 m6A methylation and to enhance the stability of XBP1 mRNA. Additionally, IGF2BP3 knockdown significantly reversed the increase in XBP1 stability mediated by ALKBH5 depletion. In vivo and in vitro experiments demonstrated that ALKBH5/IGF2BP3 promotes the proliferation, migration, and invasion of NSCLC cells by upregulating XBP1 expression. In addition, we also showed that XBP1 promoted NSCLC cell proliferation, migration, and invasion by activating IL-6-JAK-STAT3 signaling. Our research suggested that ALKBH5-mediated m6A modification of XBP1 facilitates NSCLC progression through the IL-6-JAK-STAT3 pathway.

Alcohol promotes hepatocyte injury via ER stress sensor XBP1s mediated regulation of autophagy and lysosomal activity.

OBJECTIVE: Endoplasmic reticulum stress (ERS) plays an important role in the development of Alcoholic liver injury (ALI), but the exact mechanism needs further exploration. This study aims to investigate the role of ERS-XBP1s in ALI, and providing new target for the treatment of liver injury. METHOD: The ALI model was constructed using the NIAAA method and was validated by several methods. ERS was detected using western-blot, RT-qPCR and immunohistochemistry. Apoptosis was measured by TUNEL staining, Hoechst staining, western-blot and Annexin V-FITC. Lysosomal function and autophagy were measured by Lyso-Tracker Green probe, western-blot and immunofluorescence, respectively. RESULTS: The ALI model was successfully constructed as demonstrated by increased liver steatosis, inflammation and oxidative stress, and higher levels of serum ALT, AST and TG. Alcohol significantly increased the expression of ERS-related molecules, such as PERK, IRE1α, GRP78 and XBP1s, and promoted the nuclear translocation of XBP1s. Moreover, alcohol significantly increased apoptosis and inhibition of XBP1s could reverse this effect in vivo and in vitro. Interestingly, we found that alcohol significantly elevated hepatocyte LC3-II/I levels and concomitantly accumulation of P62, and this phenomenon was reversed by inhibiting XBP1s both in vivo and in vitro. Mechanistically, we found that alcohol activation of ER stress sensor XBP1s which promoted liver injury via inhibiting lysosomal function and autophagy activity in hepatocytes, whereas inhibition of XBP1s reduces hepatocyte apoptosis by restoring lysosomal activity and activating of autophagy. CONCLUSION: Alcohol promotes hepatocytes injury via ER stress sensor XBP1s mediated inhibition of autophagy. Therefore, inhibition of XBP1 may protect the liver from alcohol-induced damage.

Unveiling Novel Mechanism of CIDEB in Fatty Acid Synthesis Through ChIP-Seq and Functional Analysis in Dairy Goat.

Goat milk is abundant in nutrients, particularly in milk fats, which confer health benefits to humans. Exploring the regulatory mechanism of fatty acid synthesis is highly important to understand milk composition manipulation. In this study, we used chromatin immunoprecipitation sequencing (ChIP-seq) on goat mammary glands at different lactation stages which revealed a novel lactation regulatory factor: cell death-inducing DFFA-like effector B (CIDEB). RT-qPCR results revealed that CIDEB was significantly upregulated during lactation in dairy goats. CIDEB overexpression significantly increased the expression levels of genes involved in fatty acid synthesis (ACACA, SCD1, p < 0.05; ELOVL6, p < 0.01), lipid droplet formation (XDH, p < 0.05), and triacylglycerol (TAG) synthesis (DGAT1, p < 0.05; GPAM, p < 0.01) in goat mammary epithelial cells (GMECs). The contents of lipid droplets, TAG, and cholesterol were increased (p < 0.05) in CIDEB-overexpressing GMECs, and knockdown of CIDEB led to the opposite results. In addition, CIDEB knockdown significantly decreased the proportion of C16:0 and total C18:2. Luciferase reporter assays indicated that X-box binding protein 1 (XBP1) promoted CIDEB transcription via XBP1 binding sites located in the CIDEB promoter. Furthermore, CIDEB knockdown attenuated the stimulatory effect of XBP1 on lipid droplet accumulation. Collectively, these findings elucidate the critical regulatory roles of CIDEB in milk fat synthesis, thus providing new insights into improving the quality of goat milk.

IRE1α-XBP1s axis regulates SREBP1-dependent MRP1 expression to promote chemoresistance in non-small cell lung cancer cells.

BACKGROUND: Inositol-requiring enzyme 1 (IRE1) is an endoplasmic reticulum (ER)-resident transmembrane protein that senses ER stress and mediates an essential arm of the unfolded protein response (UPR). IRE1 reduces ER stress by upregulating the expression of multiple ER chaperones through activation of X-box-binding protein 1 (XBP1). Emerging lines of evidence have revealed that IRE1-XBP1 axis serves as a multipurpose signal transducer during oncogenic transformation and cancer development. In this study, we explore how IRE1-XBP1 signaling promotes chemoresistance in lung cancer. METHODS: The expression patterns of UPR components and MRP1 were examined by Western blot. qRT-PCR was employed to determine RNA expression. The promoter activity was determined by luciferase reporter assay. Chemoresistant cancer cells were analyzed by viability, apoptosis. CUT & Tag (Cleavage under targets and tagmentation)-qPCR analysis was used for analysis of DNA-protein interaction. RESULTS: Here we show that activation of IRE1α-XBP1 pathway leads to an increase in MDR-related protein 1 (MRP1) expression, which facilitates drug extrusion and confers resistance to cytotoxic chemotherapy. At the molecular level, XBP1-induced c-Myc is necessary for SREBP1 expression, and SREBP1 binds to the MRP1 promoter to directly regulate its transcription. CONCLUSIONS: We conclude that IRE1α-XBP1 had important role in chemoresistance and appears to be a novel prognostic marker for lung cancer.

Quercetin Alleviates the Progression of Chronic Rhinosinusitis Without Nasal Polyps by Inhibiting Nasal Mucosal Inflammation and Epithelial Apoptosis.

Chronic rhinosinusitis (CRS) is a common chronic inflammatory upper respiratory tract, has a major subtype of CRS without nasal polyps (CRSsNP), constituting a great global health problem. Quercetin exerts the important roles in several inflammatory diseases. However, its function in CRSsNP remains unclear. In this study, quercetin dose-dependently alleviated allergic nasal symptoms of increased frequencies of sneezing and nasal scratching in Staphylococcus aureus-constructed CRSsNP mice. Importantly, quercetin attenuated the histopathological changes of nasal mucosa tissue in model mice, including mucosal thickening, glandular hyperplasia, noticeable mast cells, and inflammatory cell infiltration. Concomitantly, quercetin alleviated the increased mucosal inflammation in CRSsNP mice by suppressing the transcripts and releases of pro-inflammatory IL-1ß, IL-6, and IL-4. Notably, quercetin restrained X-box binding protein 1 (XBP1)-mediated activation of the HIF-1α/wnt-ß-catenin axis in nasal mucosal tissues in CRSsNP model. Intriguingly, intranasal instillation of Lv-XBP1 offset the protective efficacy of quercetin against the progression of CRSsNP by suppressing the production of inflammatory cytokine IL-1ß, IL-6, and IL-4, frequency of sneezing and nasal scratching, and histopathological changes of nasal mucosa tissues. In vitro, higher expression of XBP1 was observed in human nasal epithelial cells (HNECs) of CRSsNP relative to the normal HNECs. Moreover, elevation of XBP1 by Lv-XBP1 treatment suppressed cell proliferation and increased apoptosis of CRSsNP HNECs. Mechanistically, XBP1 overexpression increased the expression of HIF-1α and ß-catenin, indicating the activation of the HIF-1α/wnt-ß-catenin axis. Nevertheless, treatment with quercetin inhibited XBP1-induced cell apoptosis and reversed XBP1-mediated inhibition in cell proliferation in HNECs, as well as the activation of the HIF-1α/wnt-ß-catenin axis. Thus, these findings reveal that quercetin may attenuate the progression of CRSsNP by inhibiting nasal mucosal inflammation and epithelial barrier dysfunction via blocking the XBP1/HIF-1α/wnt-ß-catenin pathway, supporting a promising agent against CRSsNP.

Microcystin-LR Regulates Interaction between Tumor Cells and Macrophages via the IRE1α/XBP1 Signaling Pathway to Promote the Progression of Colorectal Cancer.

Microcystin-LR (MC-LR), a cyanobacterial toxin, is a potent carcinogen implicated in colorectal cancer (CRC) progression. However, its impact on the tumor microenvironment (TME) during CRC development remains poorly understood. This study investigates the interaction between tumor cells and macrophages mediated by MC-LR within the TME and its influence on CRC progression. CRC mice exposed to MC-LR demonstrated a significant transformation from adenoma to adenocarcinoma. The infiltration of macrophages increased, and the IRE1α/XBP1 pathway was activated in CRC cells after MC-LR exposure, influencing macrophage M2 polarization under co-culture conditions. Additionally, hexokinase 2 (HK2), a downstream target of the IRE1α/XBP1 pathway, was identified, regulating glycolysis and lactate production. The MC-LR-induced IRE1α/XBP1/HK2 axis enhanced lactate production in CRC cells, promoting M2 macrophage polarization. Furthermore, co-culturing MC-LR-exposed CRC cells with macrophages, along with the IRE1α/XBP1 pathway inhibitor 4µ8C and the hexokinase inhibitor 2-DG, suppressed M2 macrophage-induced CRC cell migration, clonogenicity, and M2 macrophage polarization. This study elucidates the mechanism by which MC-LR-mediated interactions through the IRE1α/XBP1 pathway promote CRC progression, highlighting potential therapeutic targets.

Zhimu-Huangbai herb-pair ameliorates hepatic steatosis in mice by regulating IRE1α/XBP1s pathway to inhibit SREBP-1c.

BACKGROUND: Currently, there is a lack of validated pharmacological interventions for non-alcoholic fatty liver disease (NAFLD), which is characterized by the accumulation of hepatic triglyceride. Zhimu-Huangbai (ZH) herb-pair is a traditional Chinese medicine that regulates glucose and lipid metabolism disorders. However, the precise mechanisms underlying the preventive effects of hepatic triglyceride induced by high-fat diet (HFD) remain elusive. PURPOSE: The study aimed to examine the impact of ZH herb-pair on NAFLD in mice and explore the underlying mechanisms, particularly its effects on endoplasmic reticulum (ER) stress and lipid metabolism. METHODS: NAFLD was induced in mice using HFD, and the treated mice were orally administered ZH, metformin (Glucophage) or lovastatin. The lipid metabolism factors, ER stress markers, and the unfolded protein response (UPR) branch factors were measured using immunohistochemistry, western blotting or qRT-PCR. Co-Immunoprecipitation (CoIP) was performed to reveal the connection between SCAP and SREBP-1c. Tunicamycin (TM) and plasmid delivery were used to induce acute ER stress or crease XBP1 gain function models. The main compounds in ZH binding to IRE1α protein were studied by molecular docking and cellular thermal shift assay (CETSA). RESULTS: Treatment with ZH significantly ameliorated hepatic steatosis and reduced lipid synthesis process mainly inhibiting the expression of mature active form of SREBP-1c through relieving ER stress. The expression of IRE1α and XBP1s was inhibited after treatment with ZH. In addition, ZH improved the fatty liver phenotype caused by XBP1 overexpression via decreasing srebp1c transcription. In vitro experimental results suggested that the main compounds in ZH decreased cellular TG contents. Mechanistically, ZH targeted IRE1α and inhibited XBP1s mRNA expression to relieve ER stress and inhibit SREBP-1c production. CONCLUSIONS: ZH herb-pair can protect against NAFLD by reducing the expression of SREBP-1c, in part, via regulating IRE1α/XBP1s pathway.

XBP1 Facilitating NF-κB-p65 Nuclear Translocation Promotes Macrophage-Originated Sterile Inflammation Via Regulating MT2 Transcription in the Ischemia/Reperfusion Liver.

BACKGROUND & AIMS: XBP1, most conserved transcription factor of endoplasmic reticulum stress, plays important roles in physiological and pathologic settings and has profound effects on disease progression and prognosis, so it is necessary to investigate XBP1 in macrophage-originated sterile inflammation during liver ischemia/reperfusion injury (IRI). Macrophage XBP1 expression and liver injury are analyzed in patients undergoing ischemia-related hepatectomy. METHODS: A myeloid-specific male XBP1-knockout (XBP1M-KO) strain is created for function and mechanism of XBP1 on macrophage-derived sterile inflammation in murine liver IRI with in vitro parallel research. Macrophages cocultured with hypoxia-treated hepatocytes are applied to investigate impact of XBP1 in vitro, with analysis of RNA sequencing and databases. RESULTS: Clinically, macrophage XBP1 expression significantly increases in ischemic liver tissues and positively correlates with liver injury after hepatectomy. Less hepatocellular damage is presented in XBP1M-KO mice than in XBP1-proficient (XBP1FL/FL) control animals. In vitro, XBP1 deficiency inhibits sterile inflammation and migration in macrophages cocultured with hypoxia-treated hepatocytes. Analysis of RNA sequencing and databases determines Metallothionein 2 (MT2) as XBP1 target gene, negatively regulated by binding with its promoter. XBP1 deficiency increases MT2 and IKBα expression, but inhibits nuclear factor-κB-p65 phosphorylation, markedly neutralizing XBP1M-KO-related benefits by promoting sterile inflammation during liver IRI. CONCLUSIONS: XBP1 promotes macrophage-originated sterile inflammation, increases liver IRI by binding to MT2 promoter, and regulates MT2/nuclear factor-κB pathway, potentially therapeutic for clinical liver IRI.

Megakaryocyte maturation involves activation of the adaptive unfolded protein response.

Endoplasmic reticulum stress triggers the unfolded protein response (UPR) to promote cell survival or apoptosis. Transient endoplasmic reticulum stress activation has been reported to trigger megakaryocyte production, and UPR activation has been reported as a feature of megakaryocytic cancers. However, the role of UPR signaling in megakaryocyte biology is not fully understood. We studied the involvement of UPR in human megakaryocytic differentiation using PMA (phorbol 12-myristate 13-acetate)-induced maturation of megakaryoblastic cell lines and thrombopoietin-induced differentiation of human peripheral blood-derived progenitors. Our results demonstrate that an adaptive UPR is a feature of megakaryocytic differentiation and that this response is not associated with ER stress-induced apoptosis. Differentiation did not alter the response to the canonical endoplasmic reticulum stressors DTT or thapsigargin. However, thapsigargin, but not DTT, inhibited differentiation, consistent with the involvement of Ca2+ signaling in megakaryocyte differentiation.

Elucidation of the role of XBP1 in the progression of complete hydatidiform mole to invasive mole through RNA-seq.

OBJECTIVE: A complete hydatidiform mole (CHM) is a common disease and is known to develop post-molar gestational trophoblast neoplasia (GTN). However, the molecular mechanisms underlying the progression of CHM to post-molar GTN remain largely unknown. In this study, we investigated the molecular factors associated with the progression using RNA-seq. METHODS: We included 13 patients with CHM and performed RNA-seq using freshly frozen samples. We identified differentially expressed genes between patients who developed GTN (GTN group) and those who achieved spontaneous remission after uterine evacuation (SR group), and performed pathway analysis. Then, functional analyses were performed on choriocarcinoma (JAR and JEG-3) and CHM (Hmol1-3B and Hmol1-2C) cells. Moreover, we evaluated the in vivo tumorigenicity of XBP1-overexpressed Hmol1-3B cells. RESULTS: The gene expression profiles were separated into two groups, and an upstream regulator analysis was performed using 281 differentially expressed genes. We focused on transcription factors and identified that 33 transcription factors were activated in the GTN group. Then, excluding those with low expression levels in clinical samples and cell lines, XBP1 was selected for further analysis. Additionally, XBP1 downregulation significantly decreased the migration and invasive abilities of choriocarcinoma cells, whereas XBP1 overexpression significantly increased the migration and invasive abilities of CHM cells. Furthermore, animal experiments showed that tumor weight and blood human chorionic gonadotropin (hCG) levels were significantly higher in the XBP1-overexpressing Hmol1-3B-bearing mice than those in the control mice. CONCLUSION: RNA-seq identified XBP1 as a key factor in post-molar GTN, suggesting it contributes to the development of post-molar GTN.

The PPIase Activity of CypB Is Essential for the Activation of Both AKT/mTOR and XBP1s Signaling Pathways during the Differentiation of 3T3-L1 Preadipocytes.

In this study, we undertook an extensive investigation to determine how CypB PPIase activity affects preadipocyte differentiation and lipid metabolism. Our findings revealed that inhibition of CypB's PPIase activity suppressed the expression of crucial proteins involved in adipocyte differentiation and induced changes in proteins regulating the cell cycle. Furthermore, we clarified the impact of CypB's PPIase activity on lipid metabolism via the AKT/mTOR signaling pathway. Additionally, we demonstrated the involvement of CypB's PPIase activity in lipid metabolism through the XBP1s pathway. These discoveries offer invaluable insights for devising innovative therapeutic strategies aimed at treating and averting obesity and its related health complications. Targeting CypB's PPIase activity may emerge as a promising avenue for addressing obesity-related conditions. Furthermore, our research opens up opportunities for creating new therapeutic strategies by enhancing our comprehension of the processes involved in cellular endoplasmic reticulum stress.

Multiple unfolded protein response pathways cooperate to link cytosolic dsDNA release to stimulator of interferon gene activation.

The double-stranded DNA (dsDNA) sensor STING has been increasingly implicated in responses to "sterile" endogenous threats and pathogens without nominal DNA or cyclic di-nucleotide stimuli. Previous work showed an endoplasmic reticulum (ER) stress response, known as the unfolded protein response (UPR), activates STING. Herein, we sought to determine if ER stress generated a STING ligand, and to identify the UPR pathways involved. Induction of IFN-ß expression following stimulation with the UPR inducer thapsigargin (TPG) or oxygen glucose deprivation required both STING and the dsDNA-sensing cyclic GMP-AMP synthase (cGAS). Furthermore, TPG increased cytosolic mitochondrial DNA, and immunofluorescence visualized dsDNA punctae in murine and human cells, providing a cGAS stimulus. N-acetylcysteine decreased IFN-ß induction by TPG, implicating reactive oxygen species (ROS). However, mitoTEMPO, a mitochondrial oxidative stress inhibitor did not impact TPG-induced IFN. On the other hand, inhibiting the inositol requiring enzyme 1 (IRE1) ER stress sensor and its target transcription factor XBP1 decreased the generation of cytosolic dsDNA. iNOS upregulation was XBP1-dependent, and an iNOS inhibitor decreased cytosolic dsDNA and IFN-ß, implicating ROS downstream of the IRE1-XBP1 pathway. Inhibition of the PKR-like ER kinase (PERK) pathway also attenuated cytoplasmic dsDNA release. The PERK-regulated apoptotic factor Bim was required for both dsDNA release and IFN-ß mRNA induction. Finally, XBP1 and PERK pathways contributed to cytosolic dsDNA release and IFN-induction by the RNA virus, Vesicular Stomatitis Virus (VSV). Together, our findings suggest that ER stressors, including viral pathogens without nominal STING or cGAS ligands such as RNA viruses, trigger multiple canonical UPR pathways that cooperate to activate STING and downstream IFN-ß via mitochondrial dsDNA release.

Vernonia amygdalina Leaf Extract Induces Apoptosis in HeLa Cells: A Metabolomics and Proteomics Study.

Medicinal plants produce various bioactive molecules with potential anti-cancer properties with favorable safety profiles. We aimed to investigate the comprehensive composition of Vernonia amygdalina leaf extract and its cytotoxic effects via apoptosis in HeLa cells. The metabolomics approach using LC-MS/MS was conducted to gather the metabolite profile of the extract. Proteomics was performed to understand the comprehensive mechanistic pathways of action. The apoptosis was visualized by cellular staining and the apoptotic proteins were evaluated. V. amygdalina leaf extract exhibited dose-dependent cytotoxic effects on both HeLa and Vero cells after 24 h of exposure in the MTT assay with the IC50 values of 0.767 ± 0.0334 and 4.043 ± 0.469 µg mL-1, respectively, which demonstrated a higher concentration required for Vero cell cytotoxicity. The metabolomic profile of 112 known metabolites specified that the majority of them were alkaloids, phenolic compounds, and steroids. Among these metabolites, deacetylvindoline and licochalcone B were suggested to implicate cytotoxicity. The cytotoxic pathways involved the response to stress and cell death which was similar to doxorubicin. The upstream regulatory proteins, phosphatase and tensin homolog deleted on chromosome ten (PTEN) and X-box binding protein 1 (XBP1), were significantly altered, supporting the regulation of apoptosis and cell death. The levels of apoptotic proteins, c-Jun N-terminal kinases (JNK), p53, and caspase-9 were significantly increased. The novel insights gained from the metabolomic profiling and proteomic pathway analysis of V. amygdalina leaf extract have identified crucial components related to apoptosis induction, highlighting its potential to develop future chemotherapy.

Mechanistic study of PD-L1 regulation of metastatic proliferation in non-small cell lung cancer through modulation of IRE1α/XBP-1 signaling pathway in tumor-associated macrophages.

OBJECTIVE: To explore the related research of PD-L1 in IRE1α/XBP-1 signaling pathway on non-small cell lung cancer. METHODS: The tumor model of mice was established and divided into four groups; after successful modeling, the tumor tissue of mice was removed for subsequent experiments; the bought THP-1 cells were grouped into four different groups, a control group, nivolumab intervention group, IRE1α inhibition group, and nivolumab intervention + IRE1α inhibition group; after co-culture of the four groups of THP-1 cells with A549, THP-1 cell protein levels in the four groups were analyzed using Western blot; A549 cell migration, invasion and proliferation were assessed using the scratch assay, Transwell method, monoclonal experiment and CCK-8 method. RESULTS: In vivo studies indicated that the stimulation of nivolumab could strongly check the progress of NSCLC (non-small cell lung); two groups treated with 4 µ8c showed obvious effects on check point of NSCLC; In vitro experiments including Western-blot experiment, Scratch experiment, Transwell method, Monoclonal experiment and CCK-8 experiment suggest that nivolumab could inhibit migration, invasion and proliferation of NSCLC tumor cells and it. CONCLUSION: PD-L1 is capable of controlling metastatic and proliferative potential of NSCLC by the way of the modification of IRE1α/XBP-1 signaling in tumor-associated macrophages.

Semaglutide Ameliorates Hepatocyte Steatosis in a Cell Co-Culture System by Downregulating the IRE1α-XBP1-C/EBPα Signaling Pathway in Macrophages.

INTRODUCTION: Non-alcoholic fatty liver disease (NAFLD) is currently the most common type of chronic liver disease. Semaglutide is a glucose-lowering drug administered for the treatment of type 2 diabetes mellitus (T2DM) and is clinically effective in the treatment of NAFLD. X-box binding protein 1 (XBP1) is related to the pathogenesis of both NAFLD and T2DM. The aim of the present study was to demonstrate whether the underlying mechanism of semaglutide treatment for NAFLD is via downregulation of the inositol-requiring transmembrane kinase/endonuclease-1α (IRE1α)-XBP1-CCAAT/enhancer binding protein α (C/EBPα) signaling pathway in macrophages. METHODS: In the present study, NAFLD cell modeling was induced by oleic acid (0.4 mm) and palmitic acid (0.2 mm). Hepatocytes (AML12) and macrophages (RAW264.7) were co-cultured in 6-well Transwell plates. Semaglutide (60 or 140 nm) was administrated for 24 h, while pioglitazone (2 µm) and toyocamycin (200 nm) were used as a positive control drug and a XBP1 inhibitor, respectively. Autophagy and apoptosis of AML12 cells were detected by transmission electron microscopy and Western blotting (WB). Hepatocyte steatosis was evaluated by adopting total intracellular triglyceride determination, analysis of the relative expression of proteins and genes associated with lipid metabolism and hepatocyte Oil red O staining. Detection of inflammation factors was conducted by ELISA and WB. To explore the underlying mechanism of NAFLD treatment with semaglutide, the relative expression of related proteins and genes were tested. RESULTS: Our study demonstrated that semaglutide treatment improved autophagy and inhibited apoptosis of hepatocytes, while notably ameliorating steatosis of hepatocytes. In addition, inflammation was attenuated in the NAFLD cell co-culture model after semaglutide administration. Semaglutide also significantly reduced the protein and gene expression levels of the IRE1α-XBP1-C/EBPα signaling pathway in macrophages. CONCLUSION: Semaglutide partially ameliorated NAFLD by downregulating the IRE1α-XBP1-C/EBPα signaling pathway in macrophages. These findings may provide a potential theoretical basis for semaglutide therapy for NAFLD.

Upregulation of Xbp1 in NPY/AgRP neurons reverses diet-induced obesity and ameliorates leptin and insulin resistance.

The molecular mechanisms underlying neuronal leptin and insulin resistance in obesity and diabetes are not fully understood. In this study, we show that induction of the unfolded protein response transcription factor, spliced X-box binding protein 1 (Xbp1s), in Agouti-Related Peptide (AgRP) neurons alone, is sufficient to not only protect against but also significantly reverse diet-induced obesity (DIO) as well as improve leptin and insulin sensitivity, despite activation of endoplasmic reticulum stress. We also demonstrate that constitutive expression of Xbp1s in AgRP neurons contributes to improved insulin sensitivity and glucose tolerance. Together, our results identify critical molecular mechanisms linking ER stress in arcuate AgRP neurons to acute leptin and insulin resistance as well as liver glucose metabolism in DIO and diabetes.

Delivery of miR-214 via extracellular vesicles downregulates Xbp1 expression and pro-inflammatory cytokine genes in macrophages.

Aim: Tumor-infiltrating macrophages are tumor-promoting and show activation of the unfolded protein response (UPR). The transcription factor X-box binding protein 1 (XBP1) is a conserved element of the UPR. Upon activation, the UPR mediates the transcriptional activation of pro-inflammatory cytokines and immune suppressive factors, hence contributing to immune dysregulation in the tumor microenvironment (TME). miR-214 is a short non-coding miRNA that targets the 3'-UTR of the Xbp1 transcript. Here, we tested a new method to efficiently deliver miR-214 to macrophages as a potential new therapeutic approach. Methods: We generated miR-214-laden extracellular vesicles (iEV-214) in a murine B cell and demonstrated that iEV-214 were enriched in miR-214 between 1,500 - 2,000 fold relative to control iEVs. Results: Bone marrow-derived macrophages (BMDM) treated with iEV-214 for 24 h underwent a specific enrichment in miR-214, suggesting transfer of the miR-214 payload from the iEVs to macrophages. iEV-214 treatment of BMDM markedly reduced (> 50%) Xbp1 transcription under endoplasmic reticulum stress conditions compared to controls. Immune-related genes downstream of XBP1s (Il-6, Il-23p19, and Arg1) were also reduced by 69%, 51%, and 34%, respectively. Conclusions: Together, these data permit to conclude that iEV-214 are an efficient strategy to downregulate the expression of Xbp1 mRNA and downstream genes in macrophages. We propose miRNA-laden iEVs are a new approach to target macrophages and control immune dysregulation in the TME.

The IRE1α/XBP1 signaling axis drives myoblast fusion in adult skeletal muscle.

Skeletal muscle regeneration involves a signaling network that regulates the proliferation, differentiation, and fusion of muscle precursor cells to injured myofibers. IRE1α, one of the arms of the unfolded protein response, regulates cellular proteostasis in response to ER stress. Here, we demonstrate that inducible deletion of IRE1α in satellite cells of mice impairs skeletal muscle regeneration through inhibiting myoblast fusion. Knockdown of IRE1α or its downstream target, X-box protein 1 (XBP1), also inhibits myoblast fusion during myogenesis. Transcriptome analysis revealed that knockdown of IRE1α or XBP1 dysregulates the gene expression of molecules involved in myoblast fusion. The IRE1α-XBP1 axis mediates the gene expression of multiple profusion molecules, including myomaker (Mymk). Spliced XBP1 (sXBP1) transcription factor binds to the promoter of Mymk gene during myogenesis. Overexpression of myomaker in IRE1α-knockdown cultures rescues fusion defects. Inducible deletion of IRE1α in satellite cells also inhibits myoblast fusion and myofiber hypertrophy in response to functional overload. Collectively, our study demonstrates that IRE1α promotes myoblast fusion through sXBP1-mediated up-regulation of the gene expression of multiple profusion molecules, including myomaker.

XBP1 splicing contributes to endoplasmic reticulum stress-induced human islet amyloid polypeptide up-regulation.

As a pathological hallmark of type 2 diabetes mellitus (T2DM), islet amyloid is formed by the aggregation of islet amyloid polypeptide (IAPP). Endoplasmic reticulum (ER) stress interacts with IAPP aggregates and has been implicated in the pathogenesis of T2DM. To examine the role of ER stress in T2DM, we cloned the hIAPP promoter and analyzed its promoter activity in human ß-cells. We found that ER stress significantly enhanced hIAPP promoter activity and expression in human ß-cells via triggering X-box binding protein 1 (XBP1) splicing. We identified a binding site of XBP1 in the hIAPP promoter. Disruption of this binding site by substitution or deletion mutagenesis significantly diminished the effects of ER stress on hIAPP promoter activity. Blockade of XBP splicing by MKC3946 treatment inhibited ER stress-induced hIAPP up-regulation and improved human ß-cell survival and function. Our study uncovers a link between ER stress and IAPP at the transcriptional level and may provide novel insights into the role of ER stress in IAPP cytotoxicity and the pathogenesis of T2DM.