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Lipotoxicity is a pivotal factor that initiates and exacerbates liver injury and is involved in the development of metabolic-associated fatty liver disease (MAFLD). However, there are few reported lipotoxicity inhibitors. Here, we identified a natural anti-lipotoxicity candidate, HN-001, from the marine fungus Aspergillus sp. C1. HN-001 dose- and time- dependently reversed palmitic acid (PA)-induced hepatocyte death. This protection was associated with IRE-1α-mediated XBP-1 splicing inhibition, which resulted in suppression of XBP-1s nuclear translocation and transcriptional regulation. Knockdown of XBP-1s attenuated lipotoxicity, but no additional ameliorative effect of HN-001 on lipotoxicity was observed in XBP-1s knockdown hepatocytes. Notably, the ER stress and lipotoxicity amelioration was associated with PLA2. Both HN-001 and the PLA2 inhibitor MAFP inhibited PLA2 activity, reduced lysophosphatidylcholine (LPC) level, subsequently ameliorated lipotoxicity. In contrast, overexpression of PLA2 caused exacerbation of lipotoxicity and weakened the anti-lipotoxic effects of HN-001. Additionally, HN-001 treatment suppressed the downstream pro-apoptotic JNK pathway. In vivo, chronic administration of HN-001 (i.p.) in mice alleviated all manifestations of MAFLD, including hepatic steatosis, liver injury, inflammation, and fibrogenesis. These effects were correlated with PLA2/IRE-1α/XBP-1s axis and JNK signaling suppression. These data indicate that HN-001 has therapeutic potential for MAFLD because it suppresses lipotoxicity, and provide a natural structural basis for developing anti-MAFLD candidates.
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ObjectiveTo analyze the induction effect of Fusobacterium nucleatum （Fn） on endoplasmic reticulum stress-related proteins Glucose-regulating protein 78（GRP78） and X-box binding protein 1（XBP1） in esophageal squamous cell carcinoma （ESCC）， and to explore its potential mechanism and clinical significance. MethodsESCC cells KYSE150 and KYSE140 were infected with Fn for 12 h， 24 h and 48 h. The oxidative stress indexes （ROS， MDA and SOD） and the expression of GRP78 and XBP1 in each group were detected by oxidative stress index kit and Western blot. The experiment was divided into Fn groups， Fn+siNC1 groups， Fn+siGRP78 groups， Fn+siNC2 groups and Fn+siXBP1 groups； the oxidative stress indexes， paclitaxel （PTX） response efficacy， abilities of proliferation， invasion and metastasis in each group were compared. The infection of Fn and the expression of GRP78 and XBP1 in 234 ESCC and paracancerous tissues were detected by RNA scope and immunohistochemistry. The correlation between each factor and clinicopathological characteristics of patients was analyzed by Chi-square test. The influence of each factor on the survival of patients was compared by Kaplan-meier survival estimate. ResultsCompared with Fn uninfected KYSE150 and KYSE140 cells， the content of ROS and MDA was gradually increased， the activity of SOD was gradually decreased， and the expression of GRP78 and XBP1 was gradually increased in Fn infected groups （12 h， 24 h and 48 h） （P < 0.05）. Compared with Fn groups， Fn+siNC1 groups， and Fn+siNC2 groups， ROS and MDA contents were decreased， SOD activity was increased， PTX response efficacy was enhanced， and abilities of proliferation， invasion and metastasis were decreased in Fn+siGRP78 and Fn+siXBP1 groups （P < 0.05）. The rates of Fn， GRP78 and XBP1 in ESCC tissues were 43.16%， 69.66% and 60.68%， respectively. And the three indexes were significantly consistent （P < 0.05）. The patients with positive Fn infection and high expression of GRP78 and XBP1 were mostly males with a history of smoking and drinking， and the tumor differentiation degree was low， the invasion degree was deep， the lymph node metastasis rate was high， and the clinical stage was mostly stage Ⅲ/Ⅳ. The 5-year survival time of patients with above positive indexes was shortened （P < 0.05）. ConclusionsFn could induce endoplasmic reticulum stress by inducing the high expression of GRP78 and XBP1， and promote the malignant evolution of ESCC.
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Objective: To explore the effect of endoplasmic reticulum stress (ERS) on neutrophil elastase (NE) induced mucin 5AC (MUC5AC) production in human airway epithelial cells. Methods: HBE16 airway epithelial cells were cultured and pretreated with reactive oxygen species (ROS) inhibitor N-acetylcysteine (NAC) or ERS inhibitor 4-phenylbutyrate (4-PBA), or transfected with small interfering RNA (siRNA) against inositolrequiring kinase 1α (IRE-1α) or X-box binding protein 1 (XBP-1), respectively before incubation with NE. NE group and blank control group were also set up. ROS production was assayed by detection kit; expression of glucose-regulated protein 78 (GRP78), phosphorylated protein kinase R-like endoplasmic reticulum kinase (pPERK), activating transcription factor 6 (ATF6), phosphorylated IRE-1α (pIRE-1α), and XBP-1 protein was detected by Western blotting; spliced XBP-1 (XBP-1s) mRNA was measured by real-time PCR; levels of MUC5AC protein in culture supernatant and cytoplasm were assayed by ELISA and immunofluorescence. Results: There was an obvious increase of ROS production with strong elevation of GRP78, ATF6, pPERK, and pIRE-1α protein in NE group cells after 24 h, compared with blank control group (P<0.05). The protein and mRNA of XBP-1s, and MUC5AC production also increased obviously (P<0.05). NAC and 4-PBA reduced ERS-related protein expression and MUC5AC production and secretion (P<0.05). Further studies showed that MUC5AC secretion was also blunted by IRE-1α siRNA or XBP-1 siRNA, accompanied with decreased expression of XBP-1s mRNA and protein (P<0.05). Conclusion: NE induces ERS by producing ROS, and increases MUC5AC protein production and secretion; IRE-1α/XBP-1 play a certain role in this process.
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Objective:To investigate the effect of X-box binding protein 1(XBP1) on the apoptosis of H9C2 cardiomyocytes under high glucose by XBP1/CHOP/Puma signaling pathway.Methods: The experiment were divided into four groups:low glucose group (LG group),high glucose group (HG group),high glucose+siRNA-NC group (HG+NC group),high glucose+siRNA-XBP1 (HG +siRNA).The expression of XBP1,C/EBP homologous protein (CHOP),p53 upregulated modulator of apoptosis(Puma), Caspase-3 in the cells after transfected were detected by Western blot;CCK-8 were used to detect the cell proliferation.Cell apoptosis was detected by flow cytometry.Results:siRNA-XBP1 reduced the expression of XBP1 in cardiomyocytes(P<0.05).Compared with LG group,the survival rate of HG group,HG +NC group and HG +siRNA group was significantly decreased (P<0.05),and the apoptosis rate was significantly increased(P<0.05).Compared with HG group,the survival rate of HG+siRNA group was significantly increased (P<0.05),and the apoptosis rate was significantly decreased(P<0.05).XBP1,CHOP,Puma in HG group,HG +NC group and HG+siRNA group was significantly higher than in LG group(P<0.05).Compared with HG group,the expression of XBP1,CHOP, Puma and Caspase-3 in HG+siRNA group was significantly lower(P<0.05).Conclusion:XBP1 inhibits cardiomyocyte apoptosis and promotes proliferation by regulating XBP1/CHOP/Puma signaling pathway.
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AIM:To investigate the effect of down-regulation of X-box binding protein 1(XBP1)expression on the viability and apoptosis of glioma cells.METHODS:The mRNA expression of XBP1 in the glioma tissues was de-tected by qPCR.Small interfering RNA(siRNA)interfering with XBP1 expression(XBP1-siRNA)was transfected into human brain glioma U251 cells.At the same time,control group(the cells without special treatment)and negative control (NC-siRNA)group(transfected with siRNA without any interference)were set up.The mRNA expression of XBP1 in the 3 groups 48 h after transfection was detected by qPCR.The protein levels of XBP1, proliferating cell nuclear antigen (PCNA),B-cell lymphoma/leukemia-2(Bcl-2),Bcl-2-associated X protein(Bax),cyclin D1(cyclin D1), phosphati-dylinositol 3-kinase(PI3K)and phosphorylated Akt(p-Akt)were determined by Western blot.The cell viability was measured by CCK-8 assay.The cell cycle distribution and apoptosis were analyzed by flow cytometry.RESULTS:The ex-pression level of XBP1 in the glioma tissues was significantly higher than that in the tumor adjacent tissues(P<0.05). The XBP1 expression at mRNA and protein levels was significantly decreased in the cells transfected with XBP1-siRNA(P<0.05).No statistically significant difference of the cell viability, cell cycle, apoptotic rate and the protein levels of PCNA,Bcl-2,Bax,cyclin D1,PI3K and p-Akt between NC-siRNA group and control group was observed.Compared with control group,the cell viability, S-phase cells and the protein levels of PCNA, Bcl-2, cyclin D1, PI3K, and p-Akt in XBP1-siRNA group were decreased significantly, and the apoptotic rate, G0/G1-phase cells and Bax protein expression were significantly increased(P<0.05).CONCLUSION:Down-regulation of XBP1 gene expression in brain glioma cells reduces the viability of cancer cells,blocks the cells in G1phase and promote apoptosis.The mechanism is related to the inhibition of PI3K/Akt signaling pathway.
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OBJECTIVE: To investigate the effect of curcumol on the apoptosis inhibition of TRAF2 and XBP1 controled by IRE1 in rats with obstructive nephropathy. METHODS: Rats were randomly divided into sham control group, model control group and enalapril group as well as high, medium and low formononetin groups. Animal model of RIF was established by unilateral ureteral obstruction (UUO). The rats were sacrificed at 14 d after UUO, and blood samples were collected. Levels of serum creatinine (Scr) and blood urea nitrogen (BUN) were examined. Renal tubular damage index was determined by H&E staining. The area of RIF was determined by Masson staining. Expressions of GRP78,IRE1,p-IRE1,TRAF2 and XBP1 in kidney were determined by Western blotting analysis. Apoptosis of tubular epithelial cells was detected by TUNEL assay. RESULTS: Levels of Scr and BUN, tubulointerstitial injury index, RIF and apoptotic index as well as expressions of GRP78,IRE1,p-IRE1,TRAF2 and XBP1 were different between the model control and treatment groups (P<0.05, P<0.01). Compared with the enalapril group, tubulointerstitial injury index and RIF as well as the levels of Scr and BUN were decreased (P < 0.05) in the high curcumol group. CONCLUSION: The curcumol can block the apoptosis of renal tubular epithelial cells through interfering IRE1-XBP1 signaling pathway by inhibiting TRAF2 protein expression mediated by IRE1 phosphorylation. Ultimately, development of RIF was postponed.
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OBJECTIVE To identify the valid targets and new drugs of ulcerative colitis (UC), a recurrent and intractable inflammatory bowel disease. METHODS and RESULTS In an in vivo mouse model of DSS-induced colitis, HLJ2 decreased weight loss, colon contracture, disease activity index (DAI), colon mucosa damage index (CMDI) and histopathological index (HI). HLJ2 also decreased myelo?peroxidase(MPO) activity and reduced production of the inflammatory cytokines TNF- α, IL- 1β, andIL- 6. HLJ2 improved intestinal mucosa damage induced by dextran sodium sulfate (DSS) and increased the expression of ZO-1 and claudin-1. Fecal 16s rRNA high-throughput sequencing demon?strated a significant improvement in UC intestinal dysbacteriosis in mice treated with HLJ2, including increased abundance of probiotics such as Lachnospiraceae, Prevotellaceae, and Lactobacillaceae. At the same time there was a reduction in the abundance of pathogenic or conditional pathogenic microor?ganisms such as Bacteroidaceae, Porphyromonadaceae, Deferribacteraceae, and Pseudomonadaceae in HLJ2- treated mice compared with untreated mice. CONCLUSION Our results demonstrated that the XBP1 agonist HLJ2 inhibits inflammation, regulates the intestinal flora, and protects the intestinal mucosa. It is thus a potential therapeutic agent for ulcerative colitis.
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X-box binding protein -1(XBP-1)is a newly found protein that plays significant roles in protein folding and endoplasmic reticulum construction .The expression of XBP-1 is widely displayed in various kinds of tumor and is shown to take part in tumorigenesis and tumor progression .This review briefly summarizes the biology of XBP-1 and focuses on recent findings concerning its role in immune evasion ,tumorigenesis ,devel-opment of cancer ,angiogenesis ,hypoxia ,invasion and metastasis .
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Objective:To determine the effect of hypoxic stress on glioma cell XBP1 expression, the relationship between XBP1 expres-sion and sugar metabolism, the influence of XBP1 repression on the survival rate of glioma cells under normoxia and hypoxia, and the influence of XBP1 on glioma cell glycolysis. Methods:We tested XBP1 activation in human glioma cell lines cultured under normoxia and hypoxia. XBP1 expression was repressed with siRNA technology. Cells were treated with oxidative phosphorylation inhibitor. We then detected the variation in cell apoptosis, sugar metabolism mode, and cell apoptosis and glycolysis products under normoxia and hypoxia. Results:XBP1 activation increased under hypoxia. Silencing XBP1 expression reduced glioma cell survival level, ATP and lactic acid production, and glucose consumption under hypoxia. After inhibiting cell oxidative phosphorylation, XBP1 repression significantly reduced the survival level of glioma cells. Conclusion:Hypoxia can activate XBP1 in glioma cells. Under hypoxia, XBP1 silencing de-presses cell activity and glycolysis. Glycolysis of glioma cells under hypoxia depends on XBP1 activation.
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Nicotinamide adenine dinucleotide phosphate oxidase ( NOXs) contributes to the production of reactive oxygen species ( ROS) in liver fibrosis, resulting in the activation of endoplas-mic reticulum stress ( ERS ) and IRE1α-XBP1 signaling path-way. ROS is a series of oxygen metabolites and its derivatives, produced by the single electron reduction of molecular oxygen ( O2 ) , including superoxide anion ( O2- ) , hydroxyl radical (-OH) , hydrogen peroxide ( H2 O2 ) , hypochlorite ion ( OCl-) and so on. They can interact with a large number of molecules, including small inorganic molecules, proteins, lipids, carbohy-drates and nucleic acids, resulting in lipid peroxidation of cell damaging molecules. And as a second messenger, ROS can also affect the proliferation and activation of HSC in liver fibrosis, and induce the hepatocyte apoptosis through a variety of cellular signal transduction. Here we review the current status of the study on the mechanism of NOXs in liver fibrosis.