Rong Jiang

Chongqing Medical University, Ch’ung-ch’ing-shih, Chongqing Shi, China

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Publications (85)194.12 Total impact

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    Preview · Article · Dec 2015 · International Journal of Molecular Sciences
  • Xiahong Chen · Xia Gong · Rong Jiang · Bin Wang · Ge Kuang · Ke Li · Jingyuan Wan
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    ABSTRACT: Acute hepatic failure involves in excessive oxidative stress and inflammatory responses, leading to a high mortality due to lacking effective therapy. Resolvin D1 (RvD1), an endogenous lipid mediator derived from polyunsaturated fatty acids, has been shown anti-inflammatory and anti-oxidative actions, however, whether RvD1 has protective effects on hepatic failure remains elusive. In this study, the roles and molecular mechanisms of RvD1 were explored in carbon tetrachloride (CCl4)-induced acute liver injury. Our results showed that RvD1 protected mice against CCl4-induced hepatic damage, as evaluated by reduced aminotransferase activities and malondialdehyde content, elevated glutathione and superoxide dismutase activities, and alleviated hepatic pathological damage. Moreover, RvD1 significantly attenuated serum tumor necrosis factor-α and interleukin-6 levels as well as hepatic myeloperoxidase activity, whereas enhanced serum IL-10 level in CCl4-administered mice. Further, RvD1 markedly up-regulated the expression and activity of heme oxygenase-1 (HO-1). However, inhibition of HO-1 activity reversed the protective effects of RvD1 on CCl4-induced liver injury. These results suggest that RvD1 could effectively prevent CCl4-induced liver injury by inhibition of oxidative stress and inflammation, and the underlying mechanism may be related to up-regulation of HO-1.
    No preview · Article · Dec 2015 · Immunopharmacology and Immunotoxicology
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    ABSTRACT: Background: We reported earlier that X-box binding protein1 spliced (XBP1S), a key regulator of the unfolded protein response (UPR), as a bone morphogenetic protein 2 (BMP2)-inducible transcription factor, positively regulates endochondral bone formation by activating granulin-epithelin precursor (GEP) chondrogenic growth factor. Under the stress of misfolded or unfolded proteins in the endoplasmic reticulum (ER), the cells can be protected by the mammalian UPR. However, the influence of activating transcription factor 6 (ATF6), another transcriptional arm of UPR, in BMP2-induced chondrocyte differentiation has not yet been elucidated. In the current study, we investigate and explore the role of ATF6 in endochondral bone formation, focus on associated molecules of hypertrophic chondrocyte differentiation, as well as the molecular events underlying this process. Methods: High-cell-density micromass cultures were used to induce ATDC5 and C3H10T1/2 cell differentiation into chondrocytes. Quantitative real-time PCR, immunoblotting analysis, and immunohistochemistry were performed to examine (1) the expression of ATF6, ATF6α, collagen II, collagen X, and matrix metalloproteinase-13 (MMP13) and (2) whether ATF6 stimulates chondrogenesis and whether ATF6 enhances runt-related transcription factor 2 (Runx2)-mediated chondrocyte hypertrophy. Culture of fetal mouse bone explants was to detect whether ATF6 stimulates chondrocyte hypertrophy, mineralization, and endochondral bone growth. Coimmunoprecipitation was employed to determine whether ATF6 associates with Runx2 in chondrocyte differentiation. Results: ATF6 is differentially expressed in the course of BMP2-triggered chondrocyte differentiation. Overexpression of ATF6 accelerates chondrocyte differentiation, and the ex vivo studies reveal that ATF6 is a potent stimulator of chondrocyte hypertrophy, mineralization, and endochondral bone growth. Knockdown of ATF6 via a siRNA approach inhibits chondrogenesis. Furthermore, ATF6 associates with Runx2 and enhances Runx2-induced chondrocyte hypertrophy. And, the stimulation effect of ATF6 is reduced during inhibition of Runx2 via a siRNA approach, suggesting that the promoting effect is required for Runx2. Conclusions: Our observations demonstrate that ATF6 positively regulates chondrocyte hypertrophy and endochondral bone formation through activating Runx2-mediated hypertrophic chondrocyte differentiation.
    Preview · Article · Sep 2015 · Journal of Orthopaedic Surgery and Research
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    ABSTRACT: Eukaryotic cells possess several mechanisms to adapt to endoplasmic reticulum (ER) stress and thereby survive. ER stress activates a set of signaling pathways collectively termed as the unfolded protein response (UPR). We previously reported that Bone morphogenetic protein 2 (BMP2) mediates mild ER stress and activates UPR signal molecules in chondrogenesis. The mammalian UPR protects the cell against the stress of misfolded proteins in the endoplasmic reticulum. Failure to adapt to ER stress causes the UPR to trigger apoptosis. Glucose regulated protein 78 (GRP78), as an important molecular chaperone in UPR signaling pathways, is responsible for binding to misfolded or unfolded protein during ER stress. However the influence on GRP78 in BMP2-induced chondrocyte differentiation has not yet been elucidated and the molecular mechanism underlyng these processes remain unexplored. Herein we demonstrate that overexpression of GRP78 enhanced cell proliferation in chondrocyte development with G1 phase advance, S phase increasing and G2-M phase transition. Furthermore, overexpression of GRP78 inhibited ER stress-mediated apoptosis and then reduced apoptosis in chondrogenesis induced by BMP2, as assayed by cleaved caspase3, caspase12, C/EBP homologous protein (CHOP/DDIT3/GADD153), p-JNK (phosphorylated c-Jun N-terminal kinase) expression during the course of chondrocyte differentiation by Western blot. In addition, flow cytometry (FCM) assay, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling (TUNEL) assay and immune-histochemistry analysis also proved this result in vitro and in vivo. It was demonstrated that GRP78 knockdown via siRNA activated the ER stress-specific caspase cascade in developing chondrocyte tissue. Collectively, these findings reveal a novel critical role of GRP78 in regulating ER stress-mediated apoptosis in cartilage development and the molecular mechanisms involved.
    Preview · Article · Sep 2015 · International Journal of Molecular Sciences
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    ABSTRACT: BRAFV600E mutation is the most common activating mutation associated with aggressive behaviors in human tumors including conventional papillary thyroid carcinoma (cPTC). P-cadherin and cadherin 6 have been shown to be mesenchymal-associated cadherins and promote cancer cell invasion and metastasis. The purpose of this study was to examine BRAFV600E, P-cadherin and cadherin 6 expression in cPTC and to assess the association of their expression with clinicopathological indicators. BRAFV600E, P-cadherin and cadherin 6 protein expression in 80 cPTCs, 61 nodular hyperplasia and 76 normal thyroid tissues were examined by immunohistochemistry. The correlation of their protein expression with clinicopathological indicators of cPTC was statistically analyzed. rotein expression of BRAFV600E, P-cadherin and cadherin 6 was upregulated in cPTC. High protein expression of BRAFV600E, P-cadherin and cadherin 6 was significantly correlated with high TNM stage and lymph node metastasis (LNM) (P < 0.001). Furthermore, BRAFV600E, P-cadherin and cadherin 6 protein expression were correlated with one another. BRAFV600E high expression combined with both P-cadherin and cadherin-6 high expression had stronger correlation with high TNM stage and LNM when compared with BRAFV600E high expression combined with either P-cadherin or cadherin-6 high expression (P = 0.042, 0.017 for TNM stage and P = 0.003, 0.006 for LNM, respectively) and only BRAFV600E high expression (P < 0.001 for both TNM stage and LNM). Concomitant high expression of BRAFV600E, P-cadherin and cadherin 6 is strongly associated with high TNM stage and LNM in cPTC. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    No preview · Article · Aug 2015 · Clinical Endocrinology
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    ABSTRACT: In adults, bone hematopoietic cells are responsible for the lifelong production of all blood cells. It is affected in aging, with progressive loss of physiological integrity leading to impaired function by cellular intrinsic and extrinsic factors. However, intervention measures, which directly inhibit the aging of hematopoietic cells, remain to be investigated. In the present study, 10 µmol/l ginsenoside Rg1 (Rg1) markedly alleviated the aging phenotypes of Sca‑1+ hematopoietic cells following in vitro exposure. In addition, the protective effects of ginsenoside Rg1 on the aging of Sca‑1+ hematopoietic cells was confirmed using a serial transplantation assay in C57BL/6 mice. The mechanistic investigations revealed that Rg1‑mediated Sca‑1+ hematopoietic cell aging alleviation was linked to a series of characteristic events, including telomere end attrition compensation, telomerase activity reconstitution and the activation of genes involved in p16‑Rb signaling pathways. Based on the above results, it was concluded that ginsenoside Rg1 is a potent agent, which acts on hematopoietic cells to protect them from aging, which has implications for therapeutic approaches in hemopoietic diseases.
    No preview · Article · Jun 2015 · Molecular Medicine Reports
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    ABSTRACT: Leukemia is a clonal disorder with blocked normal differentiation and cell death of hematopoietic progenitor cells. Traditional modalities with most used radiation and chemotherapy are nonspecific and toxic which cause adverse effects on normal cells. Differentiation inducing therapy forcing malignant cells to undergo terminal differentiation has been proven to be a promising strategy. However, there is still scarce of potent differentiation inducing agents. We show here that Angelica sinensis polysaccharide (ASP), a major active component in Dong quai (Chinese Angelica sinensis), has potential differentiation inducing activity in human chronic erythro- megakaryoblastic leukemia K562 cells. MTT assays and flow cytometric analysis demonstrated that ASP inhibited K562 cell proliferation and arrested the cell cycle at the G0/G1 phase. ASP also triggered K562 cells to undergo erythroid differentiaton as revealed by morphological changes, intensive benzidine staining and hemoglobin colorimetric reaction, as well as increased expression of glycophorin A (GPA) protein. ASP induced redistribution of STAT5 protein from the cytoplasm to the nucleus. Western blotting analysis further identified that ASP markedly sensitized K562 cells to exogenous erythropoietin (EPO) by activating EPO-induced JAK2/ STAT5 tyrosine phosphorylation, thus augmenting the EPO-mediated JAK2/STAT5 signaling pathway. On the basis of these findings, we propose that ASP might be developed as a potential candidate for chronic myelogenous leukemia inducing differentiation treatment.
    No preview · Article · May 2015 · Asian Pacific journal of cancer prevention: APJCP

  • No preview · Article · Apr 2015 · Journal of Biological Chemistry
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    ABSTRACT: Aminotriazole (ATZ) is commonly used as a catalase (CAT) inhibitor. We previously found ATZ attenuated oxidative liver injury, but the underlying mechanisms remain unknown. Acetaminophen (APAP) overdose frequently induces life-threatening oxidative hepatitis. In the present study, the potential hepatoprotective effects of ATZ on oxidative liver injury and the underlying mechanisms were further investigated in a mouse model with APAP poisoning. The experimental data indicated that pretreatment with ATZ dose- and time-dependently suppressed the elevation of plasma aminotransferases in APAP exposed mice, these effects were accompanied with alleviated histological abnormality and improved survival rate of APAP-challenged mice. In mice exposed to APAP, ATZ pretreatment decreased the CAT activities, hydrogen peroxide (H2O2) levels, malondialdehyde (MDA) contents, myeloperoxidase (MPO) levels in liver and reduced TNF-α levels in plasma. Pretreatment with ATZ also downregulated APAP-induced cytochrome P450 2E1 (CYP2E1) expression and JNK phosphorylation. In addition, posttreatment with ATZ after APAP challenge decreased the levels of plasma aminotransferases and increased the survival rate of experimental animals. Posttreatment with ATZ had no effects on CYP2E1 expression or JNK phosphorylation, but it significantly decreased the levels of plasma TNF-α. Our data indicated that the LD50 of ATZ in mice was 5367.4 mg/kg body weight, which is much higher than the therapeutic dose of ATZ in the present study. These data suggested that ATZ might be effective and safe in protect mice against APAP-induced hepatotoxicity, the beneficial effects might resulted from downregulation of CYP2E1 and inhibiton of inflammation.
    Preview · Article · Apr 2015 · PLoS ONE
  • Li Ma · Xia Gong · Ge Kuang · Rong Jiang · Rongchun Chen · Jingyuan Wan
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    ABSTRACT: Sesamin has been described to exert anti-oxidant and anti-inflammatory properties. In present study, we investigated the potential effects and mechanisms of sesamin on lipopolysaccharide (LPS)-induced fulminant hepatic failure (FHF) in D-galactosamine (D-GalN)-sensitized mice. Our results showed that pretreatment with sesamin dose-dependently improved LPS/D-GalN-induced mortality and liver injury as indicated by reduced serum levels of aminotransferases and alleviated pathological damage as well as hepatocyte apoptosis in mice. Additionally, sesamin markedly attenuated LPS/D-GalN-induced adhesion molecules expression, and decreased neutrophils recruitment. Furthermore, sesamin inhibited LPS-induced tumor necrosis factor-alpha (TNF-α) production, p38 mitogen-activated protein kinases (MAPK) and NF-κB activation, and Toll like receptor (TLR) 4 expression in mice and in RAW264.7 macrophage cells. In summary, these results demonstrate that sesamin protects mice from LPS-induced FHF and the molecular mechanisms may down-regulate the expression of TLR4, block MAPK and NF-κB activation, decrease the production of TNF-α. Copyright © 2015 Elsevier Inc. All rights reserved.
    No preview · Article · Apr 2015 · Biochemical and Biophysical Research Communications
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    ABSTRACT: To investigate the effect of running exercise on myelinated fibers in the dentate gyrus (DG) of the hippocampus during Alzheimer's disease (AD), 6-month-old male APP/PS1 transgenic mice were randomly assigned to control or running groups. The running groups were subjected to a running protocol for four months. The behaviors of the mice from both groups were then assessed using the Morris water maze, and the total volume of the DG and the related quantitative parameters with characteristics of the myelinated nerve fiber and the myelin sheath in the DG were investigated using unbiased stereological techniques and electron microscopy. Learning and spatial memory performances were both significantly increased in the running group compared with the control group. There was no significant difference in the g-ratio of the myelinated axons between the two groups. However, the DG volume, the myelinated fiber length and volume in the DG, and the myelin sheath volume and thickness in the DG were all significantly increased in the running group mice compared with the control group mice. These results indicated that running exercise was able to prevent DG atrophy and delay the progression of the myelinated fiber loss and the demyelination of the myelin sheaths in the DG in an AD mouse model, which may underlie the running-induced improvement in learning and spatial memory. Taken together, these results demonstrated that running exercise could delay the progression of AD.
    No preview · Article · Mar 2015 · Current Alzheimer research
  • Qian Che · Ling Lin · Qing Ai · Pu Ge · Jie Dai · Rong Jiang · Dan Zhou · Jingyuan Wan · Li Zhang
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    ABSTRACT: The glycolytic inhibitor 2-deoxyglucose (2-DG) is a calorie restriction (CR) mimetic produces CR-like beneficial effects in both acute and chronic pathological processes, but whether 2-DG is also helpful in critical and life-threatening situation is not known. In the present study, the potential benefits of 2-DG in lipopolysaccharide/D-galactosamine (LPS/D-Gal)-induced lethal liver injury were investigated. The results indicated that treatment with 2-DG suppressed the elevation of plasma aminotransferases, alleviated the histopathological abnormalities and improved the survival rate of LPS/D-Gal-exposed mice. Treatment with 2-DG also suppressed the production of pro-apoptotic cytokine TNF-α, the phosphorylation of JNK, the activation of caspase cascade and the count of TUNEL-positive apoptotic hepatocytes. These data suggested that the CR mimetic 2-DG could also provide beneficial effects in lethal pathological process such as LPS/D-Gal-induced fulminant liver injury. Copyright © 2015. Published by Elsevier Inc.
    No preview · Article · Mar 2015 · Biochemical and Biophysical Research Communications
  • Xiao-Qi Liu · Rong Jiang · Si-Qi Li · Jing Wang · Fa-Ping Yi
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    ABSTRACT: Prostate cancer is the most common cancer in men. In this study, we investigated immune responses of cytotoxic T lymphocytes (CTLs) against TRAMP-C2 prostate cancer cells after activation by dendritic cells (DCs) loaded with TRAMP-C2 freeze-thaw antigen and/or PEP-3 peptide in vitro. Bone marrow-derived DC from the bone marrow of the C57BL/6 were induced to mature by using the cytokine of rhGM-CSF and rhIL-4, and loaded with either the freeze-thaw antigen or PEP-3 peptide or both of them. Maturation of DCs was detected by flow cytometry. The killing efficiency of the CTLs on TRAMP-C2 cells were detected by flow cytometry, CCK8, colony formation, transwell migration, and wound-healing assay. The levels of the IFN-γ, TNF-β and IL-12 were measured by enzyme-linked immunosorbent assay (ELISA). Compared with the unloaded DCs, the loaded DCs had significantly increased expression of several phenotypes related to DC maturation. CTLs activated by DCs loaded with freeze-thaw antigen and PEP-3 peptide had more evident cytotoxicity against TRAMP-C2 cells in vitro. The secretion levels of IFN-γ, TNF-β and IL-12, secreted by DCs loaded with antigen and PEP-3 and interaction with T cells, were higher than in the other groups. Our results suggest that the CTLs activated by DCs loaded with TRAMP-C2 freeze-thaw antigen and PEP-3 peptide exert a remarkable killing efficiency against TRAMP-C2 cells in vitro.
    No preview · Article · Feb 2015 · Asian Pacific journal of cancer prevention: APJCP
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    ABSTRACT: It is extremely difficult to discriminate between follicular thyroid carcinoma (FTC) and follicular thyroid adenoma (FTA) before surgery, because the morphologies of carcinoma cells and adenoma cells obtained by fine needle aspiration biopsy (FNAB) are similar. Molecular markers may be helpful on this issue. The purpose of this study was to assess the role of GPER1, EGFR and CXCR1 in differential diagnosis between FTC and FTA. GPER1, EGFR and CXCR1 mRNA expression levels were examined in 15 FTCs and 10 FTAs using real-time RT-PCR. FTC showed to have significantly increased mRNA levels of the three molecules compared to FTA (P < 0.001 for all the three molecules). GPER1, EGFR and CXCR1 protein expression in 106 FTCs and 128 FTAs were analyzed using immunohistochemistry. The rates of GPER1, EGFR and CXCR1 high expression were 73.6%, 72.6% and 70.8% in FTC and 30.5%, 28.1% and 27.3% in FTA, respectively. Statistical analysis showed that GPER1, EGFR and CXCR1 protein expression were correlated with one another in FTC and concomitant high expression of the three molecules had stronger correlation with the occurrence of FTC than did each alone. The positive predictive values (PPV) for concomitant high expression of the three molecules for discriminating between FTC and FTA were 91.0% for GPER1/EGFR, 93.8% for GPER1/CXCR1, 92.3% for EGFR/CXCR1 and 98.2% for GPER1/EGFR/CXCR1, respectively. These results indicated that the evaluation of GPER1, EGFR and CXCR1 concomitant high expression may be helpful in differential diagnosis between FTC and FTA.
    No preview · Article · Jan 2015 · International journal of clinical and experimental pathology
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    ABSTRACT: Purpose The purpose of this study was to assess the improved absorption and in vivo kinetic characteristics of a novel water-in-oil nanoemulsion containing evodiamine–phospholipid nanocomplex (NEEPN) when administered orally. Methods NEEPN was fabricated by loading an evodiamine–phospholipid nanocomplex into a water-in-oil nanoemulsive system. The gastrointestinal absorption of NEEPN was investigated using an in situ perfusion method. The modified in vivo kinetic characteristics of evodiamine (EDA) in NEEPN were also evaluated. Results Compared with EDA or conventional nanoemulsions containing EDA instead of evodiamine–phospholipid complex, NEEPN with its favorable in vivo kinetic characteristics clearly enhanced the gastrointestinal absorption and oral bioavailability of EDA; for example, the relative bioavailability of NEEPN to free EDA was calculated to be 630.35%, and the effective permeability of NEEPN in the colon was 8.64-fold that of EDA. Conclusion NEEPN markedly improved the oral bioavailability of EDA, which was probably due to its increased gastrointestinal absorption. NEEPN also increased efficacy and reduced adverse effects for oral delivery of EDA. Such finding demonstrates great clinical significance as an ideal drug delivery system demands high efficacy and no adverse effects.
    Full-text · Article · Sep 2014 · International Journal of Nanomedicine
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    ABSTRACT: Bone morphogenetic protein 2(BMP2) is known to activate unfolded protein response (UPR) signal molecules in chondrogenesis. Inositol-requiring enzyme-1α (IRE1α),as one of three unfolded protein sensors in UPR signaling pathways, can be activated during ER stress. However, the influence on IRE1α in chondrocyte differentiation has not yet been elucidated. Here we present evidence demonstrating that overexpression of IRE1α inhibits chondrocyte differentiation, as revealed by reduced expression of collagen II (ColII), Sox9, collagen X (ColX), matrix metalloproteinase 13 (MMP-13), Indian hedgehog (IHH), Runx2 and enhanced expression of parathyroid hormone-related peptide (PTHrP). Furthermore, IRE1α-mediated inhibition of chondrogenesis depends on its enzymatic activity, since its point mutant lacking enzymatic activity completely loses this activity. The RNase and Kinase domains of IRE1α C-terminal are necessary for its full enzymatic activity and inhibition of chondrocyte differentiation. Mechanism studies demonstrate that granulin–epithelin precursor(GEP), a growth factor known to stimulate chondrogenesis, induced IRE1α expression in chondrogenesis. The expression of IRE1α is depended on GEP signaling, and IRE1α expression is hardly detectable in GEP−/− embryos. In addition, IRE1α inhibits GEP-mediated chondrocyte differentiation as a negative regulator. Altered expression of IRE1α in chondrocyte hypertrophy was accompanied by altered levels of IHH and PTHrP. Collectively, IRE1α may be a novel regulator of chondrocyte differentiation by 1) inhibition GEP-mediated chondrocyte differentiation as a negative regulator; 2) promoting IHH/PTHrP signaling.
    No preview · Article · Sep 2014 · Cellular Signalling
  • Xinru Yin · Xia Gong · Rong Jiang · Ge Kuang · Bin Wang · Li Zhang · Ge Xu · Jingyuan Wan
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    ABSTRACT: Emodin has been reported to possess anti-inflammatory and anti-oxidant activities. The aim of this study was to explore the effect and mechanism of emodin on lipopolysaccharide (LPS)-induced fulminant hepatic failure (FHF) in D-galactosamine (D-GalN)-sensitized mice. Our results showed that pretreatment with emodin inhibited the elevation of plasma aminotransferases, alleviated the hepatic histopathological abnormalities and improved the survival rate of LPS/D-GalN-primed mice. Moreover, emodin markedly attenuated the increased serum and hepatic tumor necrosis factor-α (TNF-α) production, and activated hepatic p38 mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) signal pathways in LPS/D-GalN-challenged mice. Furthermore, using an in vitro experiment, we found that emodin dose-dependently suppressed TNF-α production, dampened AP-1 and NF-κB activation, and blocked toll-like receptor (TLR) 4/myeloid differentiation factor (MD) 2 complex expression in LPS-elicited RAW264.7 mouse macrophage cells. Taken together, these data suggested that emodin could effectively prevent LPS-induced FHF, which might be mediated by inhibition of TNF-α production, deactivation of MAPKs and NF-κB, and blockade of TLR4/MD2 complex expression.
    No preview · Article · Aug 2014 · International Immunopharmacology
  • Feng Jin Guo · Fei Xia · Rong Jiang · Mei Ling Li
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    ABSTRACT: We present evidences demonstrating that overexpression of IRE1a inhibits chondrocyte differentiation, as revealed by reduced expression of Col, SOX9, Col X, MMP-13, IHH, Runx2. Furthmore, IRE1a-mediated inhibition of chondrogenesis depends on its enzymatic activity, since its point mutant lacking enzymatic activity completely loses this activity. The RNase and Kinase domains of IRE1a C-terminal is necessary for its full enzymatic activity and inhibition of chondrocyte differentiation. Mechanism studies demonstrate that granulin-epithelin precursor(GEP),a growth factor known to stimulate chondrogenesis, induced IRE1a expression in chondrogenesis. In addition, IRE1a inhibits GEP-mediated chondrocyte differentiation as a negative regulator. Altered expression of IRE1a in chondrocyte hypertrophy was accompanied by altered levels of IHH and PTHrP.Collectively,IRE1a may be a novel regulator of chondrocyte differentiation by 1) inhibition GEP-mediated chondrocyte differentiation as a negative regulator; 2) promoting IHH/PTHrP signaling.
    No preview · Article · Jul 2014
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    ABSTRACT: We previously report that BMP2 mediates mild ER stress-activated ATF6 and directly regulates XBP1S splicing in the course of chondrogenesis. The mammalian unfolded protein response (UPR) protects the cell against the stress of misfolded proteins in the endoplasmic reticulum (ER). Failure to adapt to ER stress causes the UPR to trigger apoptosis. The transcription factor activating transcription factor 6 (ATF6), a key regulator of the UPR, is known to be important for ER stress-mediated apoptosis and cell growth, but the molecular mechanism underlying these processes remains unexplored. In this study, we demonstrate that ATF6 is differentially expressed during BMP2-stimulated chondrocyte differentiation and exhibits prominent expression in growth plate chondrocytes. ATF6 can enhance the level of IRE1a-spliced XBP1S protein in chondrogenesis. IRE1a and ATF6 can synergistically regulate endogenous XBP1S gene expression in chondrogenesis. Furthermore, overexpression ATF6 inhibited, while ATF6-knockdown enhanced, the cell proliferation in chondrocyte development with G1 phase arresting, S phase reducing and G2-M phase delaying. Besides, Ad-ATF6 can activate, whereas knockdown ATF6 by an siRNA-silencing approach inhibited, ER stress-mediated apoptosis in chondrogenesis induced by BMP2, as assayed by cleaved caspase3, CHOP, p-JNK expression in the course of chondrocyte differentiation. On the other hand, FCM, TUNEL assay and immunohistochemistry analysis also proved this result in vitro and in vivo. It was demonstrated that Ad-ATF6 activation of the ER stress-specific caspase cascade in developing chondrocyte tissue. Collectively, these findings reveal a novel critical role of ATF6 in regulating ER stress-mediated apoptosis in chondrocyte differentiation and the molecular mechanisms involved.
    No preview · Article · Jun 2014 · Histochemie
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    F-J Guo · R Jiang · Z Xiong · F Xia · M Li · L Chen · C-J Liu
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    ABSTRACT: Bone morphogenetic protein 2 (BMP2) is known to activate unfolded protein response (UPR) signaling molecules, such as BiP (IgH chain-binding protein), PERK (PKR-like ER-resistant kinase), and IRE1α. Inositol-requiring enzyme-1a (IRE1a), as one of three unfolded protein sensors in UPR signaling pathways, can be activated during ER stress. Granulin-epithelin precursor (GEP) is an autocrine growth factor that has been implicated in embryonic development, tissue repair, tumorigenesis, and inflammation. However, the influence on IRE1a in BMP2-induced osteoblast differentiation has not yet been elucidated. Herein we demonstrate that overexpression of IRE1a inhibits osteoblast differentiation, as revealed by reduced activity of alkaline phosphatase (ALP) and osteocalcin; however, knockdown of IRE1a via the RNAi approach stimulates osteoblastogenesis. Mechanistic studies revealed that the expression of IRE1a during osteoblast was a consequence of JunB transcription factor binding to several AP1 sequence (TGAG/CTCA) in the 5'-flanking regulatory region of the IRE1a gene, followed by transcription. In addition, GEP induces IRE1a expressions and this induction of IRE1a by GEP depends on JunB. Furthermore, IRE1a inhibition of GEP-induced osteoblastogenesis relies on JunB. Besides, GEP is required for IRE1a inhibition of BMP2-induced bone formation. Collectively, these findings demonstrate that IRE1a negatively regulates BMP2-induced osteoblast differentiation and this IRE1a inhibition effect depends on GEP growth factor. Thus, IRE1a, BMP2, GEP growth factor, and JunB transcription factor form a regulatory loop and act in concert in the course of osteoblastogenesis.
    Preview · Article · May 2014 · Cell Death & Disease