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Luo R, Zhang Y, Wang H, Xu B, Qu J, Duan S, Liu R, Liu J, Li S, Li X. Radix Rehmanniae Praeparata extracts ameliorate hepatic ischemia-reperfusion injury by restoring lipid metabolism in hepatocytes. JOURNAL OF ETHNOPHARMACOLOGY 2024; 335:118702. [PMID: 39168395 DOI: 10.1016/j.jep.2024.118702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2024] [Revised: 08/06/2024] [Accepted: 08/15/2024] [Indexed: 08/23/2024]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Hepatic ischemia/reperfusion injury (HIRI) is a common occurrence during or after liver surgery, representing a major cause for postoperative complications or increased morbidity and mortality in liver diseases. Rehmanniae Radix Praeparata (RRP) is a traditional Chinese medicine frequently used and has garnered extensive attention for its therapeutic potential treating cardiovascular and hepatic ailments. Recent studies have indicated the possibility of RRP in regulating lipid accumulation and apoptosis in hepatocytes. AIM OF THE STUDY This study aimed to investigate the specific mechanisms by which RRP may impede the progression of HIRI through the regulation of lipid metabolism. MATERIALS AND METHODS High-performance liquid chromatography (HPLC) was used to identify the major components of RRP water extract. C57BL/6J mice were orally given RRP at doses of 2.5 g/kg, 5 g/kg, and 10 g/kg for a duration of 7 days before undergoing HIRI surgery. Furthermore, we established a lipid-loaded in vitro model by exposing hepatocytes to oleic acid and palmitic acid (OAPA). The anti-HIRI effect of RRP was determined through transcriptomics and various molecular biology experiments. RESULTS After identifying active ingredients in RRP, we observed that RRP exerted lipid-lowering and hepatoprotective effects on HIRI mice and OAPA-treated hepatocytes. RRP activated AMP-activated protein kinase (AMPK) and inhibited mammalian target of rapamycin (mTOR), which further on the one hand, inhibited the cleavage and activation of sterol regulatory element binding protein 2 (SREBP2) by limiting the movement of SREBPs cleavage-activating protein (SCAP)-SREBP2 complex with the help of endoplasmic reticulum lipid raft-associated protein 1 (ERLIN1) and insulin-induced gene 1 (INSIG1), and on the other hand, promoted liver X receptor α (LXRα) nuclear transportation and subsequent cholesterol efflux. Meanwhile, the anti-lipotoxic effect of RRP can be partly reversed by an LXRα inhibitor but largely blocked by the application of compound C, an AMPK inhibitor. CONCLUSION Our study elucidated that RRP served as a potential AMPK activator to alleviate HIRI by blocking SREBP2 activation and cholesterol synthesis, while also activating LXRα to facilitate cholesterol efflux. These findings shed new light on the potential therapeutic use of RRP for improving HIRI.
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Affiliation(s)
- Ranyi Luo
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 100029, China
| | - Yinhao Zhang
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 100029, China
| | - Hong Wang
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 100029, China
| | - Bing Xu
- School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing, 100029, China
| | - Jiaorong Qu
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 100029, China
| | - Shuwen Duan
- School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing, 100029, China
| | - Runping Liu
- School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing, 100029, China
| | - Jia Liu
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 100029, China
| | - Shuo Li
- School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing, 100029, China
| | - Xiaojiaoyang Li
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 100029, China.
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Moyer CL, Brown PH. Targeting nuclear hormone receptors for the prevention of breast cancer. Front Med (Lausanne) 2023; 10:1200947. [PMID: 37583424 PMCID: PMC10424511 DOI: 10.3389/fmed.2023.1200947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 06/30/2023] [Indexed: 08/17/2023] Open
Abstract
Advancements in research have led to the steady decline of breast cancer mortality over the past thirty years. However, breast cancer incidence has continued to rise, resulting in an undue burden on healthcare costs and highlighting a great need for more effective breast cancer prevention strategies, including targeted chemo preventative agents. Efforts to understand the etiology of breast cancer have uncovered important roles for nuclear receptors in the development and progression of breast cancer. Targeted therapies to inhibit estrogen receptor (ER) and progesterone receptor (PR) signaling (selective ER modulators, aromatase inhibitors and selective PR modulators) have shown great promise for the treatment and prevention of hormone receptor (HR)-positive breast cancer. However, these drugs do not prevent HR-negative disease. Therefore, recent efforts have focused on novel targeted therapies with the potential to prevent both HR-positive and HR-negative breast cancer. Among these include drugs that target other nuclear receptors, such as retinoic acid receptor (RAR), retinoid X receptor (RXR) and vitamin D receptor (VDR). In this review we provide an overview of recent preclinical and clinical trials targeting members of the nuclear receptor superfamily for the prevention of breast cancer.
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Affiliation(s)
- Cassandra L. Moyer
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Powel H. Brown
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, United States
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Na SY, Kim KS, Jung YS, Kim DK, Kim J, Cho SJ, Lee IK, Chung J, Kim JS, Choi HS. An Inverse Agonist GSK5182 Increases Protein Stability of the Orphan Nuclear Receptor ERRγ via Inhibition of Ubiquitination. Int J Mol Sci 2022; 24:ijms24010096. [PMID: 36613556 PMCID: PMC9820335 DOI: 10.3390/ijms24010096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 12/13/2022] [Accepted: 12/16/2022] [Indexed: 12/24/2022] Open
Abstract
The orphan nuclear receptor, estrogen-related receptor γ (ERRγ) is a constitutively active transcription factor involved in mitochondrial metabolism and energy homeostasis. GSK5182, a specific inverse agonist of ERRγ that inhibits transcriptional activity, induces a conformational change in ERRγ, resulting in a loss of coactivator binding. However, the molecular mechanism underlying the stabilization of the ERRγ protein by its inverse agonist remains largely unknown. In this study, we found that GSK5182 inhibited ubiquitination of ERRγ, thereby stabilizing the ERRγ protein, using cell-based assays and confocal image analysis. Y326 of ERRγ was essential for stabilization by GSK5182, as ligand-induced stabilization of ERRγ was not observed with the ERRγ-Y326A mutant. GSK5182 suppressed ubiquitination of ERRγ by the E3 ligase Parkin and subsequent degradation. The inhibitory activity of GSK5182 was strong even when the ERRγ protein level was elevated, as ERRγ bound to GSK5182 recruited a corepressor, small heterodimer partner-interacting leucine zipper (SMILE), through the activation function 2 (AF-2) domain, without alteration of the nuclear localization or DNA-binding ability of ERRγ. In addition, the AF-2 domain of ERRγ was critical for the regulation of protein stability. Mutants in the AF-2 domain were present at higher levels than the wild type in the absence of GSK5182. Furthermore, the ERRγ-L449A/L451A mutant was no longer susceptible to GSK5182. Thus, the AF-2 domain of ERRγ is responsible for the regulation of transcriptional activity and protein stability by GSK5182. These findings suggest that GSK5182 regulates ERRγ by a unique molecular mechanism, increasing the inactive form of ERRγ via inhibition of ubiquitination.
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Affiliation(s)
- Soon-Young Na
- School of Biological Sciences and Technology, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Ki-Sun Kim
- School of Biological Sciences and Technology, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Yoon Seok Jung
- School of Biological Sciences and Technology, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Don-Kyu Kim
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Jina Kim
- New Drug Development Center, Daegu Gyeongbuk Medical Innovation Foundation, Daegu 41061, Republic of Korea
| | - Sung Jin Cho
- Center for Brain Disorders, Brain Science Institute, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
| | - In-Kyu Lee
- Department of Internal Medicine, School of Medicine, Kyungpook National University, Kyungpook National University Hospital, Daegu 41944, Republic of Korea
- Research Institute of Aging and Metabolism, Kyungpook National University, Daegu 41940, Republic of Korea
| | - Jongkyeong Chung
- SRC Center for Systems Geroscience, Institute of Molecular Biology and Genetics, School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Jeong-Sun Kim
- Department of Chemistry, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Hueng-Sik Choi
- School of Biological Sciences and Technology, Chonnam National University, Gwangju 61186, Republic of Korea
- Correspondence: ; Tel.: +82-62-530-0503
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Li X, Sun M, Qi H, Ju C, Chen Z, Gao X, Lin Z. Identification of a Chromosome 1 Substitution Line B6-Chr1BLD as a Novel Hyperlipidemia Model via Phenotyping Screening. Metabolites 2022; 12:metabo12121276. [PMID: 36557314 PMCID: PMC9781061 DOI: 10.3390/metabo12121276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/12/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022] Open
Abstract
Hyperlipidemia is a chronic disease that seriously affects human health. Due to the fact that traditional animal models cannot fully mimic hyperlipidemia in humans, new animal models are urgently needed for basic drug research on hyperlipidemia. Previous studies have demonstrated that the genomic diversity of the wild mice chromosome 1 substitution lines was significantly different from that of laboratory mice, suggesting that it might be accompanied by phenotypic diversity. We first screened the blood lipid-related phenotype of chromosome 1 substitution lines. We found that the male HFD-fed B6-Chr1BLD mice showed more severe hyperlipidemia-related phenotypes in body weight, lipid metabolism and liver lesions. By RNA sequencing and whole-genome sequencing results of B6-Chr1BLD, we found that several differentially expressed single nucleotide polymorphism enriched genes were associated with lipid metabolism-related pathways. Lipid metabolism-related genes, mainly including Aida, Soat1, Scly and Ildr2, might play an initial and upstream role in the abnormal metabolic phenotype of male B6-Chr1BLD mice. Taken together, male B6-Chr1BLD mice could serve as a novel, polygenic interaction-based hyperlipidemia model. This study could provide a novel animal model for accurate clinical diagnosis and precise medicine of hyperlipidemia.
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Affiliation(s)
- Xu Li
- State Key Laboratory of Pharmaceutical Biotechnology, MOE Key Laboratory of Model Animals for Disease Study, Jiangsu Key Laboratory of Molecular Medicine, Model Animal Research Center, National Resource Center for Mutant Mice of China, Nanjing Drum Tower Hospital, School of Medicine, Nanjing University, Nanjing 210061, China
| | - Minli Sun
- State Key Laboratory of Pharmaceutical Biotechnology, MOE Key Laboratory of Model Animals for Disease Study, Jiangsu Key Laboratory of Molecular Medicine, Model Animal Research Center, National Resource Center for Mutant Mice of China, Nanjing Drum Tower Hospital, School of Medicine, Nanjing University, Nanjing 210061, China
| | - Hao Qi
- GemPharmatech Inc., 12 Xuefu Road, Jiangbei New Area, Nanjing 210061, China
- Correspondence: (H.Q.); (Z.L.)
| | - Cunxiang Ju
- GemPharmatech Inc., 12 Xuefu Road, Jiangbei New Area, Nanjing 210061, China
| | - Zhong Chen
- GemPharmatech Inc., 12 Xuefu Road, Jiangbei New Area, Nanjing 210061, China
| | - Xiang Gao
- State Key Laboratory of Pharmaceutical Biotechnology, MOE Key Laboratory of Model Animals for Disease Study, Jiangsu Key Laboratory of Molecular Medicine, Model Animal Research Center, National Resource Center for Mutant Mice of China, Nanjing Drum Tower Hospital, School of Medicine, Nanjing University, Nanjing 210061, China
| | - Zhaoyu Lin
- State Key Laboratory of Pharmaceutical Biotechnology, MOE Key Laboratory of Model Animals for Disease Study, Jiangsu Key Laboratory of Molecular Medicine, Model Animal Research Center, National Resource Center for Mutant Mice of China, Nanjing Drum Tower Hospital, School of Medicine, Nanjing University, Nanjing 210061, China
- Correspondence: (H.Q.); (Z.L.)
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Xu M, Chen G, Dong Y, Xiang S, Xue M, Liu Y, Song H, Song H, Wang Y. Stable expression of a truncated TLX variant drives differentiation of induced pluripotent stem cells into self-renewing neural stem cells for production of extracellular vesicles. Stem Cell Res Ther 2022; 13:436. [PMID: 36056423 PMCID: PMC9438273 DOI: 10.1186/s13287-022-03131-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 08/10/2022] [Indexed: 11/13/2022] Open
Abstract
Background Neural stem cells (NSCs)-derived extracellular vesicles (EVs) possess great potential in treating severe neurological and cerebrovascular diseases, as they carry the modulatory and regenerative ingredients of NSCs. Induced pluripotent stem cells (iPSCs)-derived NSCs culture represents a sustainable source of therapeutic EVs. However, there exist two major challenges in obtaining a scalable culture of NSCs for high-efficiency EVs production: (1) the heterogeneity of iPSC-derived NSCs culture impairs the production of high-quality EVs and (2) the intrinsic propensity of neuronal or astroglial differentiation of NSCs during prolonged culturing reduces the number of NSCs for preparing EVs. A NSCs strain that is amenable to stable self-renewal and proliferation is thus greatly needed for scalable and long-term culture. Methods Various constructs of the genes encoding the orphan nuclear receptor NR2E1 (TLX) were stably transfected in iPSCs, which were subsequently cultured in a variety of differentiation media for generation of iNSCsTLX. Transcriptomic and biomarker profile of iNSCsTLX were investigated. In particular, the positivity ratios of Sox2/Nestin and Musashi/Vimentin were used to gauge the homogeneity of the iNSCsTLX culture. The iNSCs expressing a truncated version of TLX (TLX-TP) was expanded for up to 45 passages, after which its neuronal differentiation potential and EV activity were evaluated. Results Stable expression of TLX-TP could confer the iPSCs with rapid and self-driven differentiation into NSCs through stable passaging up to 225 days. The long-term culture of NSCs maintained the highly homogenous expression of NSC-specific biomarkers and potential of neuronal differentiation. EVs harvested from the TLX-expressing NSCs cultures exhibited anti-inflammatory and neuroprotective activities. Conclusions iPSC-derived NSCs stably expressing TLX-TP is a promising cell line for scalable production of EVs, which should be further exploited for therapeutic development in neurological treatment. Supplementary Information The online version contains supplementary material available at 10.1186/s13287-022-03131-4.
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Affiliation(s)
- Mingzhi Xu
- State Key Laboratory of Proteomics, National Center for Protein Sciences(Beijing), Beijing Proteome Research Center, Beijing Institute of Lifeomics, Beijing, 102206, China
| | - Gang Chen
- State Key Laboratory of Proteomics, National Center for Protein Sciences(Beijing), Beijing Proteome Research Center, Beijing Institute of Lifeomics, Beijing, 102206, China
| | - Yanan Dong
- State Key Laboratory of Proteomics, National Center for Protein Sciences(Beijing), Beijing Proteome Research Center, Beijing Institute of Lifeomics, Beijing, 102206, China
| | - Shensi Xiang
- State Key Laboratory of Proteomics, National Center for Protein Sciences(Beijing), Beijing Proteome Research Center, Beijing Institute of Lifeomics, Beijing, 102206, China
| | - Miaomiao Xue
- State Key Laboratory of Proteomics, National Center for Protein Sciences(Beijing), Beijing Proteome Research Center, Beijing Institute of Lifeomics, Beijing, 102206, China
| | - Yongxue Liu
- Anti-Radiation Medical Laboratory, Beijing Institute of Radiation Medicine, Beijing, 100039, China
| | - Haijing Song
- Emergency Medicine, PLA Strategic Support Force Medical Center, Beijing, 100101, China.
| | - Haifeng Song
- State Key Laboratory of Proteomics, National Center for Protein Sciences(Beijing), Beijing Proteome Research Center, Beijing Institute of Lifeomics, Beijing, 102206, China.
| | - Yi Wang
- State Key Laboratory of Proteomics, National Center for Protein Sciences(Beijing), Beijing Proteome Research Center, Beijing Institute of Lifeomics, Beijing, 102206, China.
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Inhibition of ASGR1 decreases lipid levels by promoting cholesterol excretion. Nature 2022; 608:413-420. [PMID: 35922515 DOI: 10.1038/s41586-022-05006-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Accepted: 06/22/2022] [Indexed: 11/08/2022]
Abstract
High cholesterol is a major risk factor for cardiovascular disease1. Currently, no drug lowers cholesterol through directly promoting cholesterol excretion. Human genetic studies have identified that the loss-of-function Asialoglycoprotein receptor 1 (ASGR1) variants associate with low cholesterol and a reduced risk of cardiovascular disease2. ASGR1 is exclusively expressed in liver and mediates internalization and lysosomal degradation of blood asialoglycoproteins3. The mechanism by which ASGR1 affects cholesterol metabolism is unknown. Here, we find that Asgr1 deficiency decreases lipid levels in serum and liver by stabilizing LXRα. LXRα upregulates ABCA1 and ABCG5/G8, which promotes cholesterol transport to high-density lipoprotein and excretion to bile and faeces4, respectively. ASGR1 deficiency blocks endocytosis and lysosomal degradation of glycoproteins, reduces amino-acid levels in lysosomes, and thereby inhibits mTORC1 and activates AMPK. On one hand, AMPK increases LXRα by decreasing its ubiquitin ligases BRCA1/BARD1. On the other hand, AMPK suppresses SREBP1 that controls lipogenesis. Anti-ASGR1 neutralizing antibody lowers lipid levels by increasing cholesterol excretion, and shows synergistic beneficial effects with atorvastatin or ezetimibe, two widely used hypocholesterolaemic drugs. In summary, this study demonstrates that targeting ASGR1 upregulates LXRα, ABCA1 and ABCG5/G8, inhibits SREBP1 and lipogenesis, and therefore promotes cholesterol excretion and decreases lipid levels.
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Development and Validation of a Novel PPAR Signaling Pathway-Related Predictive Model to Predict Prognosis in Breast Cancer. J Immunol Res 2022; 2022:9412119. [PMID: 35692496 PMCID: PMC9184151 DOI: 10.1155/2022/9412119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Revised: 04/24/2022] [Accepted: 05/06/2022] [Indexed: 12/27/2022] Open
Abstract
This study is aimed at exploring the potential mechanism of the PPAR signaling pathway in breast cancer (BRCA) and constructing a novel prognostic-related risk model. We used various bioinformatics methods and databases to complete our exploration in this research. Based on TCGA database, we use multiple extension packages based on the R language for data conversion, processing, and statistics. We use LASSO regression analysis to establish a prognostic-related risk model in BRCA. And we combined the data of multiple online websites, including GEPIA, ImmuCellAI, TIMER, GDSC, and the Human Protein Atlas database to conduct a more in-depth exploration of the risk model. Based on the mRNA data in TCGA database, we conducted a preliminary screening of genes related to the PPAR signaling pathway through univariate Cox analysis, then used LASSO regression analysis to conduct a second screening, and successfully established a risk model consisting of ten genes in BRCA. The results of ROC curve analysis show that the risk model has good prediction accuracy. We can successfully divide breast cancer patients into high- and low-risk groups with significant prognostic differences (P = 1.92e − 05) based on this risk model. Combined with the clinical data in TCGA database, there is a correlation between the risk model and the patient's N, T, gender, and fustat. The results of multivariate Cox regression show that the risk score of this risk model can be used as an independent risk factor for BRCA patients. In particular, we draw a nomogram that can predict the 5-, 7-, and 10-year survival rates of BRCA patients. Subsequently, we conducted a series of pancancer analyses of CNV, SNV, OS, methylation, and immune infiltration for this risk model gene and used GDSC data to investigate drug sensitivity. Finally, to gain insight into the predictive value and protein expression of these risk model genes in breast cancer, we used GEO and HPA databases for validation. This study provides valuable clues for future research on the PPAR signaling pathway in BRCA.
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Kopecka J, Trouillas P, Gašparović AČ, Gazzano E, Assaraf YG, Riganti C. Phospholipids and cholesterol: Inducers of cancer multidrug resistance and therapeutic targets. Drug Resist Updat 2020; 49:100670. [DOI: 10.1016/j.drup.2019.100670] [Citation(s) in RCA: 82] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 11/14/2019] [Accepted: 11/17/2019] [Indexed: 12/13/2022]
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Kim SY, Lee JY, Jhin C, Shin JM, Kim M, Ahn HR, Yoo G, Son YJ, Jung SH, Nho CW. Reduction of Hepatic Lipogenesis by Loliolide and Pinoresinol from Lysimachia vulgaris via Degrading Liver X Receptors. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2019; 67:12419-12427. [PMID: 31610126 DOI: 10.1021/acs.jafc.9b01488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The liver X receptors (LXRs) are major regulators of lipogenesis, and their reduced activation by an inhibitor could be a treatment strategy for fatty liver disease. Small molecules originating from dietary food are considered suitable and attractive drug candidates for humans in terms of safety. In this study, an edible plant, Lysimachia vulgaris (LV), used as a traditional and medicinal food in East Asia was evaluated for lipogenesis decreasing effects. Activity-guided fractionation was performed, and the isolated compounds were identified using spectroscopic methods. We conducted in vitro real-time polymerase chain reaction (PCR) and Western blotting as well as histological and biochemical analyses following in vivo treatments. Using a high-fat diet animal model, we confirmed that LV extracts (LVE) decreased lipogenic metabolism and restored liver function to control levels. To identify active components, we conducted activity-guided fractionation and then isolated compounds. Two compounds, loliolide and pinoresinol, were identified in the dichloromethane fraction, and they significantly attenuated the expression levels of lipogenic factors including sterol regulatory element-binding protein (SREBP)-1, stearoyl-CoA desaturase 1 (SCD1), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC). Importantly, loliolide and pinoresinol significantly accelerated the protein degradation of LXRs by enhanced ubiquitination, which inhibited lipogenesis. These results suggest that loliolide and pinoresinol might be potential candidate supplementary treatments for nonalcoholic fatty liver disease (NAFLD) by reducing lipogenesis through increased ubiquitination of LXRs.
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Affiliation(s)
- Sun Young Kim
- Smart Farm Research Center , Korea Institute of Science and Technology (KIST) , Gangneung 25451 , Republic of Korea
| | - Joo Young Lee
- Natural Products Research Center , Korea Institute of Science and Technology (KIST) , Gangneung 25451 , Republic of Korea
| | - Changho Jhin
- Smart Farm Research Center , Korea Institute of Science and Technology (KIST) , Gangneung 25451 , Republic of Korea
| | - Ji Min Shin
- Smart Farm Research Center , Korea Institute of Science and Technology (KIST) , Gangneung 25451 , Republic of Korea
- Department of Biological Chemistry , University of Science and Technology (UST) , Daejeon 34113 , Republic of Korea
| | - Myungsuk Kim
- Smart Farm Research Center , Korea Institute of Science and Technology (KIST) , Gangneung 25451 , Republic of Korea
| | - Hong Ruyl Ahn
- Natural Products Research Center , Korea Institute of Science and Technology (KIST) , Gangneung 25451 , Republic of Korea
| | - Gyhye Yoo
- Smart Farm Research Center , Korea Institute of Science and Technology (KIST) , Gangneung 25451 , Republic of Korea
| | - Yang-Ju Son
- Smart Farm Research Center , Korea Institute of Science and Technology (KIST) , Gangneung 25451 , Republic of Korea
| | - Sang Hoon Jung
- Natural Products Research Center , Korea Institute of Science and Technology (KIST) , Gangneung 25451 , Republic of Korea
| | - Chu Won Nho
- Smart Farm Research Center , Korea Institute of Science and Technology (KIST) , Gangneung 25451 , Republic of Korea
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Zhao Q, Zhou D, You H, Lou B, Zhang Y, Tian Y, Guo N, Chen X, Liu Y, Wu Y, Yuan Z, Zhou J. IFN-γ aggravates neointimal hyperplasia by inducing endoplasmic reticulum stress and apoptosis in macrophages by promoting ubiquitin-dependent liver X receptor-α degradation. FASEB J 2017; 31:5321-5331. [PMID: 28798155 DOI: 10.1096/fj.201700327r] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 07/25/2017] [Indexed: 12/22/2022]
Abstract
Neointimal hyperplasia is the main cause of restenosis after percutaneous coronary interventions (PCIs). Both IFN-γ and macrophages play nonredundant roles in the pathogenesis of vascular intimal hyperplasia; however, the underlying mechanisms remain elusive and must be further investigated. In mouse peritoneal macrophages, IFN-γ significantly accelerated degradation and up-regulated polyubiquitination of liver X receptor (LXR)-α. Signal transducer and activator of transcription 1 (STAT1) inhibitor, fludarabine, and PIAS1 knockdown reduced ubiquitination and increased the expression of LXR-α in IFN-γ-treated macrophages. IFN-γ also increased the expression of endoplasmic reticulum (ER) stress-related proteins, including p-PERK, p-eIIF2α, and CCAAT-enhancer-binding protein homologous protein (CHOP), as well as apoptosis of macrophages. Treatment with ER stress inhibitor, 4-phenylbutyric acid (4-PBA), and LXR agonist, T0901317 (T0), alleviated IFN-γ-induced apoptosis in macrophages. Neointimal hyperplasia was significant after carotid ligation for 4 wk in ApoE-/- mice. IFN-γ mAb, T0, and 4-PBA treatment not only significantly attenuated neointimal hyperplasia but also decreased CD68+TUNEL+ double-positive macrophages in the hyperplastic neointima. Moreover, after 4-PBA or T0 administration, the number of CD68+p-eIIF2α+ and CD68+CHOP+ double-positive cells in neointimal was also apparently decreased. Taken together, these results defined an unexpected role of IFN-γ and LXR-α in the development of neointimal hyperplasia. The PIAS1/STAT1-dependent LXR-α degradation induced by IFN-γ promoted ER stress and apoptosis in macrophages, which leads to aggravated neointimal hyperplasia. LXR agonist efficiently improved neointimal hyperplasia, which may be a promising new strategy to ameliorate restenosis and vascular remodeling after PCI.-Zhao, Q., Zhou, D., You, H., Lou, B., Zhang, Y., Tian, Y., Guo, N., Chen, X., Liu, Y., Wu, Y., Yuan, Z., Zhou, J. IFN-γ aggravates neointimal hyperplasia by inducing endoplasmic reticulum stress and apoptosis in macrophages by promoting ubiquitin-dependent liver X receptor-α degradation.
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Affiliation(s)
- Qiang Zhao
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Dong Zhou
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Hongjun You
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Bowen Lou
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Yan Zhang
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Yuling Tian
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Ning Guo
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Xiaoli Chen
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Yan Liu
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Yue Wu
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Zuyi Yuan
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China; .,Key Laboratory of Environment and Genes Related to Diseases, Xi'an Jiaotong University, Ministry of Education, Xi'an, China
| | - Juan Zhou
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China; .,Key Laboratory of Molecular Cardiology of Shanxi Province, Xi'an, China
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Identification of the ER-resident E3 ubiquitin ligase RNF145 as a novel LXR-regulated gene. PLoS One 2017; 12:e0172721. [PMID: 28231341 PMCID: PMC5322959 DOI: 10.1371/journal.pone.0172721] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 02/08/2017] [Indexed: 12/12/2022] Open
Abstract
Cellular cholesterol metabolism is subject to tight regulation to maintain adequate levels of this central lipid molecule. Herein, the sterol-responsive Liver X Receptors (LXRs) play an important role owing to their ability to reduce cellular cholesterol load. In this context, identifying the full set of LXR-regulated genes will contribute to our understanding of their role in cholesterol metabolism. Using global transcriptional analysis we report here the identification of RNF145 as an LXR-regulated target gene. We demonstrate that RNF145 is regulated by LXRs in both human and mouse primary cells and cell lines, and in vivo in mice. Regulation of RNF145 by LXR depends on a functional LXR-element in its proximal promotor. Consistent with LXR-dependent regulation of Rnf145 we show that regulation is lost in macrophages and fibroblasts from Lxrαβ(-/-) mice, and also in vivo in livers of Lxrα(-/-) mice treated with the LXR synthetic ligand T0901317. RNF145 is closely related to RNF139/TRC8, an E3 ligase implicated in control of SREBP processing. However, silencing of RNF145 in HepG2 or HeLa cells does not impair SREBP1/2 processing and sterol-responsive gene expression in these cells. Similar to TRC8, we demonstrate that RNF145 is localized to the ER and that it possesses intrinsic E3 ubiquitin ligase activity. In summary, we report the identification of RNF145 as an ER-resident E3 ubiquitin ligase that is transcriptionally controlled by LXR.
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12
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Shu L, Hoo RLC, Wu X, Pan Y, Lee IPC, Cheong LY, Bornstein SR, Rong X, Guo J, Xu A. A-FABP mediates adaptive thermogenesis by promoting intracellular activation of thyroid hormones in brown adipocytes. Nat Commun 2017; 8:14147. [PMID: 28128199 PMCID: PMC5290165 DOI: 10.1038/ncomms14147] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 12/02/2016] [Indexed: 01/01/2023] Open
Abstract
The adipokine adipocyte fatty acid-binding protein (A-FABP) has been implicated in obesity-related cardio-metabolic complications. Here we show that A-FABP increases thermogenesis by promoting the conversion of T4 to T3 in brown adipocytes. We find that A-FABP levels are increased in both white (WAT) and brown (BAT) adipose tissues and the bloodstream in response to thermogenic stimuli. A-FABP knockout mice have reduced thermogenesis and whole-body energy expenditure after cold stress or after feeding a high-fat diet, which can be reversed by infusion of recombinant A-FABP. Mechanistically, A-FABP induces the expression of type-II iodothyronine deiodinase in BAT via inhibition of the nuclear receptor liver X receptor α, thereby leading to the conversion of thyroid hormone from its inactive form T4 to active T3. The thermogenic responses to T4 are abrogated in A-FABP KO mice, but enhanced by A-FABP. Thus, A-FABP acts as a physiological stimulator of BAT-mediated adaptive thermogenesis.
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Affiliation(s)
- Lingling Shu
- State Key Laboratory of Pharmaceutical Biotechnology, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Ruby L. C. Hoo
- State Key Laboratory of Pharmaceutical Biotechnology, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Xiaoping Wu
- State Key Laboratory of Pharmaceutical Biotechnology, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Yong Pan
- State Key Laboratory of Pharmaceutical Biotechnology, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Ida P. C. Lee
- State Key Laboratory of Pharmaceutical Biotechnology, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Lai Yee Cheong
- State Key Laboratory of Pharmaceutical Biotechnology, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Department of Pharmacology and Pharmacy, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | | | - Xianglu Rong
- Joint Laboratory of Guangdong and Hong Kong on Metabolic Diseases, Guangdong Pharmaceutical University, 510000 Guangzhou, China
| | - Jiao Guo
- Joint Laboratory of Guangdong and Hong Kong on Metabolic Diseases, Guangdong Pharmaceutical University, 510000 Guangzhou, China
| | - Aimin Xu
- State Key Laboratory of Pharmaceutical Biotechnology, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Department of Pharmacology and Pharmacy, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
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13
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Lee HJ, Ryu JM, Jung YH, Lee SJ, Kim JY, Lee SH, Hwang IK, Seong JK, Han HJ. High glucose upregulates BACE1-mediated Aβ production through ROS-dependent HIF-1α and LXRα/ABCA1-regulated lipid raft reorganization in SK-N-MC cells. Sci Rep 2016; 6:36746. [PMID: 27829662 PMCID: PMC5103190 DOI: 10.1038/srep36746] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 10/20/2016] [Indexed: 01/07/2023] Open
Abstract
There is an accumulation of evidence indicating that the risk of Alzheimer’s disease is associated with diabetes mellitus, an indicator of high glucose concentrations in blood plasma. This study investigated the effect of high glucose on BACE1 expression and amyloidogenesis in vivo, and we present details of the mechanism associated with those effects. Our results, using ZLC and ZDF rat models, showed that ZDF rats have high levels of amyloid-beta (Aβ), phosphorylated tau, BACE1, and APP-C99. In vitro result with mouse hippocampal neuron and SK-N-MC, high glucose stimulated Aβ secretion and apoptosis in a dose-dependent manner. In addition, high glucose increased BACE1 and APP-C99 expressions, which were reversed by a reactive oxygen species (ROS) scavenger. Indeed, high glucose increased intracellular ROS levels and HIF-1α expression, associated with regulation of BACE1 and Liver X Receptor α (LXRα). In addition, high glucose induced ATP-binding cassette transporter A1 (ABCA1) down-regulation, was associated with LXR-induced lipid raft reorganization and BACE1 localization on the lipid raft. Furthermore, silencing of BACE1 expression was shown to regulate Aβ secretion and apoptosis of SK-N-MC. In conclusion, high glucose upregulates BACE1 expression and activity through HIF-1α and LXRα/ABCA1-regulated lipid raft reorganization, leading to Aβ production and apoptosis of SK-N-MC.
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Affiliation(s)
- Hyun Jik Lee
- Department of Veterinary Physiology, College of Veterinary Medicine, Research Institute for Veterinary Science and BK21 PLUS Program for Creative Veterinary Science Research Center, Seoul National University, Seoul 08826, Korea
| | - Jung Min Ryu
- Department of Veterinary Physiology, College of Veterinary Medicine, Chonnam National University, Gwangju 61186, Korea
| | - Young Hyun Jung
- Department of Veterinary Physiology, College of Veterinary Medicine, Research Institute for Veterinary Science and BK21 PLUS Program for Creative Veterinary Science Research Center, Seoul National University, Seoul 08826, Korea
| | - Sei-Jung Lee
- Department of Veterinary Physiology, College of Veterinary Medicine, Research Institute for Veterinary Science and BK21 PLUS Program for Creative Veterinary Science Research Center, Seoul National University, Seoul 08826, Korea
| | - Jeong Yeon Kim
- Department of Veterinary Physiology, College of Veterinary Medicine, Research Institute for Veterinary Science and BK21 PLUS Program for Creative Veterinary Science Research Center, Seoul National University, Seoul 08826, Korea
| | - Sang Hun Lee
- Medical Science Research Institute, Soonchunhyang University Seoul Hospital, Seoul, Republic of Korea.,Department of Biochemistry, Soonchunhyang University College of Medicine, Cheonan, 330-930, Republic of Korea
| | - In Koo Hwang
- BK21 PLUS Program for Creative Veterinary Science Research, and Research Institute for Veterinary Science; Seoul National University and Korea Mouse Phenotyping Center (KMPC), Seoul, Korea.,Department of Anatomy and Cell Biology; Korea Mouse Phenotyping Center (KMPC); College of Veterinary Medicine; Seoul National University, Seoul, Korea
| | - Je Kyung Seong
- BK21 PLUS Program for Creative Veterinary Science Research, and Research Institute for Veterinary Science; Seoul National University and Korea Mouse Phenotyping Center (KMPC), Seoul, Korea.,Department of Anatomy and Cell Biology; Korea Mouse Phenotyping Center (KMPC); College of Veterinary Medicine; Seoul National University, Seoul, Korea
| | - Ho Jae Han
- Department of Veterinary Physiology, College of Veterinary Medicine, Research Institute for Veterinary Science and BK21 PLUS Program for Creative Veterinary Science Research Center, Seoul National University, Seoul 08826, Korea
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14
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Lee JH, Kim H, Park SJ, Woo JH, Joe EH, Jou I. Small heterodimer partner SHP mediates liver X receptor (LXR)–dependent suppression of inflammatory signaling by promoting LXR SUMOylation specifically in astrocytes. Sci Signal 2016; 9:ra78. [DOI: 10.1126/scisignal.aaf4850] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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15
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Zhao JF, Shyue SK, Lee TS. Excess Nitric Oxide Activates TRPV1-Ca(2+)-Calpain Signaling and Promotes PEST-dependent Degradation of Liver X Receptor α. Int J Biol Sci 2016; 12:18-29. [PMID: 26722214 PMCID: PMC4679395 DOI: 10.7150/ijbs.13549] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 11/05/2015] [Indexed: 12/17/2022] Open
Abstract
Excess nitric oxide (NO) deregulates cholesterol metabolism in macrophage foam cells, yet the underlying molecular mechanism is incompletely understood. To investigate the mechanism, we found that in macrophages, treatment with NO donors S-nitroso-N-acetyl-D,L-penicillamine (SNAP) or diethylenetriamine/nitric oxide induced LXRα degradation and reduced the expression of the downstream target of LXRα, ATP-binding cassette transporter A1 (ABCA1), and cholesterol efflux. In addition, SNAP induced calcium (Ca2+) influx into cells, increased calpain activity and promoted the formation of calpain-LXRα complex. Pharmacological inhibition of calpain activity reversed the SNAP-induced degradation of LXRα, down-regulation of ABCA1 and impairment of cholesterol efflux in macrophages. SNAP increased the formation of calpain-LXRα complex in a Pro-Glu-Ser-Thr (PEST) motif-dependent manner. Truncation of the PEST motif in LXRα abolished the calpain-dependent proteolysis. Removal of extracellular Ca2+ by EGTA or pharmacological inhibition of TRPV1 channel activity diminished SNAP-induced increase in intracellular Ca2+, calpain activation, LXRα degradation, ABCA1 down-regulation and impaired cholesterol efflux. In conclusion, excess NO may activate calpain via TRPV1-Ca2+ signaling and promote the recognition of calpain in the PEST motif of LXRα, thereby leading to degradation of LXRα and, ultimately, downregulated ABCA1 expression and impaired ABCA1-dependent cholesterol efflux in macrophages.
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Affiliation(s)
- Jin-Feng Zhao
- 1. Department of Physiology, National Yang-Ming University, Taipei, 11221, Taiwan
| | - Song-Kun Shyue
- 2. Cardiovascular Division, Institute of Biomedical Sciences, Academia Sinica, Taipei, 11529, Taiwan
| | - Tzong-Shyuan Lee
- 1. Department of Physiology, National Yang-Ming University, Taipei, 11221, Taiwan. ; 3. Genome Research Center, National Yang-Ming University, Taipei, 11221, Taiwan
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16
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Botez G, Piraino G, Hake PW, Ledford JR, O'Connor M, Cook JA, Zingarelli B. Age-dependent therapeutic effects of liver X receptor-α activation in murine polymicrobial sepsis. Innate Immun 2015; 21:609-18. [PMID: 25956304 PMCID: PMC4509881 DOI: 10.1177/1753425915569367] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 01/05/2015] [Indexed: 12/29/2022] Open
Abstract
The severity of sepsis is significantly affected by advanced age; however, age-dependent molecular mechanisms of this susceptibility are unknown. Nuclear liver X receptor-α (LXRα) is a regulator of lipid metabolism with associated anti-inflammatory properties. Here, we investigated the role of LXRα in age-dependent lung injury and outcome of sepsis. Male C57BL/6, LXRα-deficient (LXRα−/−) and wild type (WT) (LXRα+/+) mice of different ages were subjected to sepsis by cecal ligation and puncture (CLP). In pharmacological studies, treatment with the LXRα ligand T0901317 reduced lung neutrophil infiltration in C57BL/6 mice aged from 1 to 8 mo when compared with vehicle-treated animals subjected to CLP. The LXRα ligand improved survival in young mice (2–3 mo old) but did not affect survival or neutrophil infiltration in mature adult mice (11–13 mo old). Immunoblotting revealed an age-dependent decrease of lung LXRα levels. Young LXRα−/− mice (2–3 mo old) exhibited earlier mortality than age-matched WT mice after CLP. Lung damage and neutrophil infiltration, lung activation of the pro-inflammatory NF-κB and plasma IL-6 levels were higher in LXRα−/− mice 18 h after CLP compared with LXRα+/+ mice. This study suggests that the anti-inflammatory properties of LXRα in sepsis are age-dependent and severely compromised in mature adult animals.
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Affiliation(s)
- Gabriela Botez
- Division of Critical Care Medicine, Cincinnati Children's Hospital Medical Center, Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Giovanna Piraino
- Division of Critical Care Medicine, Cincinnati Children's Hospital Medical Center, Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Paul W Hake
- Division of Critical Care Medicine, Cincinnati Children's Hospital Medical Center, Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, OH, USA Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA
| | - John R Ledford
- Division of Critical Care Medicine, Cincinnati Children's Hospital Medical Center, Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Michael O'Connor
- Division of Critical Care Medicine, Cincinnati Children's Hospital Medical Center, Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - James A Cook
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA
| | - Basilia Zingarelli
- Division of Critical Care Medicine, Cincinnati Children's Hospital Medical Center, Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, OH, USA
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17
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Hwang I, Park YJ, Kim YR, Kim YN, Ka S, Lee HY, Seong JK, Seok YJ, Kim JB. Alteration of gut microbiota by vancomycin and bacitracin improves insulin resistance via glucagon-like peptide 1 in diet-induced obesity. FASEB J 2015; 29:2397-411. [PMID: 25713030 DOI: 10.1096/fj.14-265983] [Citation(s) in RCA: 158] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2014] [Accepted: 02/03/2015] [Indexed: 12/13/2022]
Abstract
Firmicutes and Bacteroidetes, 2 major phyla of gut microbiota, are involved in lipid and bile acid metabolism to maintain systemic energy homeostasis in host. Recently, accumulating evidence has suggested that dietary changes promptly induce the alteration of abundance of both Firmicutes and Bacteroidetes in obesity and its related metabolic diseases. Nevertheless, the metabolic roles of Firmicutes and Bacteroidetes on such disease states remain unclear. The aim of this study was to determine the effects of antibiotic-induced depletion of Firmicutes and Bacteroidetes on dysregulation of energy homeostasis in obesity. Treatment of C57BL/6J mice with the antibiotics (vancomycin [V] and bacitracin [B]), in the drinking water, before diet-induced obesity (DIO) greatly decreased both Firmicutes and Bacteroidetes in the gut as revealed by pyrosequencing of the microbial 16S rRNA gene. Concomitantly, systemic glucose intolerance, hyperinsulinemia, and insulin resistance in DIO were ameliorated via augmentation of GLP-1 secretion (active form; 2.03-fold, total form; 5.09-fold) independently of obesity as compared with untreated DIO controls. Furthermore, there were increases in metabolically beneficial metabolites derived from the gut. Together, our data suggest that Firmicutes and Bacteroidetes potentially mediate insulin resistance through modulation of GLP-1 secretion in obesity.
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Affiliation(s)
- Injae Hwang
- *Department of Biological Sciences, Institute of Molecular Biology and Genetics, Department of Biophysics and Chemical Biology, College of Veterinary Medicine, and College of Medicine, Seoul National University, Seoul, Korea
| | - Yoon Jeong Park
- *Department of Biological Sciences, Institute of Molecular Biology and Genetics, Department of Biophysics and Chemical Biology, College of Veterinary Medicine, and College of Medicine, Seoul National University, Seoul, Korea
| | - Yeon-Ran Kim
- *Department of Biological Sciences, Institute of Molecular Biology and Genetics, Department of Biophysics and Chemical Biology, College of Veterinary Medicine, and College of Medicine, Seoul National University, Seoul, Korea
| | - Yo Na Kim
- *Department of Biological Sciences, Institute of Molecular Biology and Genetics, Department of Biophysics and Chemical Biology, College of Veterinary Medicine, and College of Medicine, Seoul National University, Seoul, Korea
| | - Sojeong Ka
- *Department of Biological Sciences, Institute of Molecular Biology and Genetics, Department of Biophysics and Chemical Biology, College of Veterinary Medicine, and College of Medicine, Seoul National University, Seoul, Korea
| | - Ho Young Lee
- *Department of Biological Sciences, Institute of Molecular Biology and Genetics, Department of Biophysics and Chemical Biology, College of Veterinary Medicine, and College of Medicine, Seoul National University, Seoul, Korea
| | - Je Kyung Seong
- *Department of Biological Sciences, Institute of Molecular Biology and Genetics, Department of Biophysics and Chemical Biology, College of Veterinary Medicine, and College of Medicine, Seoul National University, Seoul, Korea
| | - Yeong-Jae Seok
- *Department of Biological Sciences, Institute of Molecular Biology and Genetics, Department of Biophysics and Chemical Biology, College of Veterinary Medicine, and College of Medicine, Seoul National University, Seoul, Korea
| | - Jae Bum Kim
- *Department of Biological Sciences, Institute of Molecular Biology and Genetics, Department of Biophysics and Chemical Biology, College of Veterinary Medicine, and College of Medicine, Seoul National University, Seoul, Korea
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18
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Sharpe LJ, Cook ECL, Zelcer N, Brown AJ. The UPS and downs of cholesterol homeostasis. Trends Biochem Sci 2014; 39:527-35. [PMID: 25220377 DOI: 10.1016/j.tibs.2014.08.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 08/18/2014] [Accepted: 08/21/2014] [Indexed: 11/26/2022]
Abstract
An emerging theme in the regulation of cholesterol homeostasis is the role of the ubiquitin proteasome system (UPS), through which proteins are ubiquitylated and then degraded in response to specific signals. The UPS controls all aspects of cholesterol metabolism including its synthesis, uptake, and efflux. We review here recent work uncovering the ubiquitylation and degradation of key players in cholesterol homeostasis. This includes the low-density lipoprotein (LDL) receptor, transcription factors (sterol regulatory element binding proteins and liver X receptors), flux-controlling enzymes in cholesterol synthesis (3-hydroxy-3-methylglutaryl-CoA reductase and squalene monooxygenase), and cholesterol exporters (ATP-binding cassette transporters ABCA1 and ABCG1). We explore which E3 ligases are involved, and identify areas deserving of further research.
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Affiliation(s)
- Laura J Sharpe
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW 2052, Australia
| | - Emma C L Cook
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105AZ Amsterdam, The Netherlands
| | - Noam Zelcer
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105AZ Amsterdam, The Netherlands.
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW 2052, Australia.
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19
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Sim WC, Park S, Lee KY, Je YT, Yin HQ, Choi YJ, Sung SH, Park SJ, Park HJ, Shin KJ, Lee BH. LXR-α antagonist meso-dihydroguaiaretic acid attenuates high-fat diet-induced nonalcoholic fatty liver. Biochem Pharmacol 2014; 90:414-24. [PMID: 24955981 DOI: 10.1016/j.bcp.2014.06.013] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Revised: 06/14/2014] [Accepted: 06/16/2014] [Indexed: 01/17/2023]
Abstract
Collaborative regulation of liver X receptor (LXR) and sterol regulatory element binding protein (SREBP)-1 are main determinants in hepatic steatosis, as shown in both animal models and human patients. Recent studies indicate that selective intervention of overly functional LXRα in the liver shows promise in treatment of fatty liver disease. In the present study, we evaluated the effects of meso-dihydroguaiaretic acid (MDGA) on LXRα activation and its ability to attenuate fatty liver in mice. MDGA inhibited activation of the LXRα ligand-binding domain by competitively binding to the pocket for agonist T0901317 and decreased the luciferase activity in LXRE-tk-Luc-transfected cells. MDGA significantly attenuated hepatic neutral lipid accumulation in T0901317- and high fat diet (HFD)-induced fatty liver. The effect of MDGA was so potent that treatment with 1mg/kg for 2 weeks completely reversed the lipid accumulation induced by HFD feeding. MDGA reduced the expression of LXRα co-activator protein RIP140 and LXRα target gene products associated with lipogenesis in HFD-fed mice. These results demonstrate that MDGA has the potential to attenuate nonalcoholic steatosis mediated by selective inhibition of LXRα in the liver in mice.
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Affiliation(s)
- Woo-Cheol Sim
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 151-742, Republic of Korea
| | - Sora Park
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 151-742, Republic of Korea
| | - Kang-Yo Lee
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 151-742, Republic of Korea
| | - Young-Tae Je
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 151-742, Republic of Korea
| | - Hu-Quan Yin
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 151-742, Republic of Korea
| | - You-Jin Choi
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 151-742, Republic of Korea
| | - Sang Hyun Sung
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 151-742, Republic of Korea
| | - So-Jung Park
- School of Pharmacy, Sungkyunkwan University, Seobu-ro 2066, Jangan-gu, Suwon 440-746, Republic of Korea
| | - Hyun-Ju Park
- School of Pharmacy, Sungkyunkwan University, Seobu-ro 2066, Jangan-gu, Suwon 440-746, Republic of Korea
| | - Kye Jung Shin
- College of Pharmacy, The Catholic University, Bucheon 420-743, Republic of Korea
| | - Byung-Hoon Lee
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 151-742, Republic of Korea.
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20
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Arora M, Kaul D, Sharma YP. Blood cellular mutant LXR-α protein stability governs initiation of coronary heart disease. World J Cardiol 2013; 5:305-312. [PMID: 24009820 PMCID: PMC3761184 DOI: 10.4330/wjc.v5.i8.305] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 04/29/2013] [Accepted: 07/19/2013] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the role of [breast and ovarian cancer susceptibility 1 (BRCA1)-associated RING domain 1 (BARD1)]/BRCA1 E3-ubiquitin ligase complex in governing the stability of mutant liver X receptor-α (LXR-α) protein in coronary heart disease (CHD) subjects.
METHODS: The expression analysis of various genes was carried out by quantitative real time polymerase chain reaction and western blotting within blood mononuclear cells of human CHD subjects at various stages of coronary occlusion and their corresponding normal healthy counterparts. Immunoprecipitation experiments were performed to establish protein interactions between LXR-α and BARD1. Peripheral blood mononuclear cells were cultured and exposed to Vitamin D3 and Cisplatin to validate the degradation of mutant LXR-α protein in CHD subjects by BARD1/BRCA1 complex.
RESULTS: The expression of mutant LXR-α protein in CHD subjects was found to decrease gradually with the severity of coronary occlusion exhibiting a strong negative correlation, r = -0.975 at P < 0.001. Further, the expression of BARD1 and BRCA1 also increased with the disease severity, r = 0.895 and 0.873 respectively (P < 0.001). Immunoprecipitation studies established that BARD1/BRCA1 complex degrades mutant LXR-αvia ubiquitination. The absence of functional LXR-α protein resulted in increased expression of inflammatory cytokines such as interleukin (IL)-6, IL-8 and interferon-γ and decreased expression of ABCA1 (ATP-binding cassette A1) (r = 0.932, 0.949, 0.918 and -0.902 with respect to Gensini score; P < 0.001). Additionally, cell culture experiments proved that Vitamin D3 could prevent the degradation of mutant LXR-α and restore its functional activity to some extent.
CONCLUSION: Mutant LXR-α protein in CHD subjects is degraded by BARD1/BRCA1 complex and Vitamin D3 can rescue and restore its function.
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21
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Steffensen KR, Jakobsson T, Gustafsson JÅ. Targeting liver X receptors in inflammation. Expert Opin Ther Targets 2013; 17:977-90. [PMID: 23738533 DOI: 10.1517/14728222.2013.806490] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
INTRODUCTION The two oxysterol receptors, 'liver X receptors (LXRs)' LXRα and LXRβ, are amongst the emerging newer drug targets within the nuclear receptor family and targeting LXRs represents novel strategies needed for prevention and treatment of diseases where current therapeutics is inadequate. AREAS COVERED This review discusses the current understanding of LXR biology with an emphasis on the molecular aspects of LXR signalling establishing their potential as drug targets. Recent advances of their transcriptional mechanisms in inflammatory pathways and their physiological roles in inflammation and immunity are described. EXPERT OPINION The new discoveries of LXR-regulated inflammatory pathways have ignited new promises for LXRs as drug targets. The broad physiological roles of LXRs involve a high risk of unwanted side effects. Recent insights into LXR biology of the brain indicate a highly important role in neuronal development and a clinical trial testing an LXR agonist reported adverse neurological side effects. This suggests that drug development must focus on limiting the range of LXR signalling - possibly achieved through subtype, tissue specific, promoter specific or pathway specific activation of LXRs where a successful candidate drug must be carefully studied for its effect in the central nervous system.
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Affiliation(s)
- Knut R Steffensen
- Karolinska Institutet, Center for Biosciences, Department of Biosciences and Nutrition, S-14183 Stockholm, Sweden.
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22
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Mouzat K, Baron S, Marceau G, Caira F, Sapin V, Volle DH, Lumbroso S, Lobaccaro JM. Emerging roles for LXRs and LRH-1 in female reproduction. Mol Cell Endocrinol 2013; 368:47-58. [PMID: 22750099 DOI: 10.1016/j.mce.2012.06.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 06/18/2012] [Accepted: 06/19/2012] [Indexed: 01/05/2023]
Abstract
Nutritional status is known to control female reproductive physiology. Many reproductive pathologies such as anorexia nervosa, dystocia and preeclampsia, have been linked to body mass index and to metabolic syndrome. Lipid metabolism has also been associated with ovarian, uterine and placental functions. Among the regulators of lipid homeostasis, the Liver X Receptors (LXRs) and the Liver Receptor Homolog-1 (LRH-1), two members of the nuclear receptor superfamily, play a central role. LXRs are sensitive to intracellular cholesterol concentration and decrease plasma cholesterol, allowing to considering them as "cholesterol sensors". LRH-1 shares many target-genes with LXRs and has been considered for a long time as a real orphan nuclear receptor, but recent findings showed that phospholipids are ligands for this nuclear receptor. Acting in concert, LXRs and LRH-1 could thus be sensitive to slight modifications in cellular lipid balance, tightly maintaining their cellular concentrations. These last years, the use of transgenic mice clarified the roles of these nuclear receptors in many physiological functions. This review will be focused on the roles of LXRs and LRH-1 on female reproduction. Their contribution to ovarian endocrine and exocrine functions, as well as uterine and placental physiology will be discussed. The future challenge will thus be to target these nuclear receptors to prevent lipid-associated reproductive diseases in women.
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Affiliation(s)
- Kevin Mouzat
- Laboratoire de Biochimie, Centre Hospitalier Universitaire de Nîmes, Hôpital Carémeau, Place du Pr. Robert Debré, F-30029 Nimes, France.
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23
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Macrophage glucose-6-phosphate dehydrogenase stimulates proinflammatory responses with oxidative stress. Mol Cell Biol 2013; 33:2425-35. [PMID: 23572562 DOI: 10.1128/mcb.01260-12] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Glucose-6-phosphate dehydrogenase (G6PD) is a key enzyme that regulates cellular redox potential. In this study, we demonstrate that macrophage G6PD plays an important role in the modulation of proinflammatory responses and oxidative stress. The G6PD levels in macrophages in the adipose tissue of obese animals were elevated, and G6PD mRNA levels positively correlated with those of proinflammatory genes. Lipopolysaccharide (LPS) and free fatty acids, which initiate proinflammatory signals, stimulated macrophage G6PD. Overexpression of macrophage G6PD potentiated the expression of proinflammatory and pro-oxidative genes responsible for the aggravation of insulin sensitivity in adipocytes. In contrast, when macrophage G6PD was inhibited or suppressed via chemical inhibitors or small interfering RNA (siRNA), respectively, basal and LPS-induced proinflammatory gene expression was attenuated. Furthermore, macrophage G6PD increased activation of the p38 mitogen-activated protein kinase (MAPK) and NF-κB pathways, which may lead to a vicious cycle of oxidative stress and proinflammatory cascade. Together, these data suggest that an abnormal increase of G6PD in macrophages promotes oxidative stress and inflammatory responses in the adipose tissue of obese animals.
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24
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Chen Y, Duan Y, Kang Y, Yang X, Jiang M, Zhang L, Li G, Yin Z, Hu W, Dong P, Li X, Hajjar DP, Han J. Activation of liver X receptor induces macrophage interleukin-5 expression. J Biol Chem 2012; 287:43340-50. [PMID: 23150660 DOI: 10.1074/jbc.m112.403394] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
IL-5 stimulates production of T15/EO6 IgM antibodies that can block the uptake of oxidized low density lipoprotein by macrophages, whereas a deficiency in macrophage IL-5 expression accelerates development of atherosclerosis. Liver X receptors (LXRs) are ligand-activated transcription factors that can induce macrophage ABCA1 expression and cholesterol efflux, thereby inhibiting the development of atherosclerosis. However, it remains unknown whether additional mechanisms, such as the regulation of macrophage IL-5 expression, are related to the anti-atherogenic properties of LXR. We initially defined IL-5 expression in macrophages where the LXR ligand (T0901317) induced macrophage IL-5 protein expression and secretion. The overexpression of LXR increased, whereas its knockdown inhibited IL-5 expression. Furthermore, we found that LXR activation increased IL-5 transcripts, promoter activity, formation of an LXR·LXR-responsive element complex, and IL-5 protein stability. In vivo, we found that T0901317 increased IL-5 and total IgM levels in plasma and IL-5 expression in multiple tissues in wild type mice. In LDL receptor knock-out (LDLR(-/-)) mice, T0901317 increased IL-5 expression in the aortic root area. Taken together, our studies demonstrate that macrophage IL-5 is a target gene for LXR activation, and the induction of macrophage IL-5 expression can be related to LXR-inhibited atherosclerosis.
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Affiliation(s)
- Yuanli Chen
- State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300071, China
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Jakobsson T, Treuter E, Gustafsson JÅ, Steffensen KR. Liver X receptor biology and pharmacology: new pathways, challenges and opportunities. Trends Pharmacol Sci 2012; 33:394-404. [PMID: 22541735 DOI: 10.1016/j.tips.2012.03.013] [Citation(s) in RCA: 240] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 03/05/2012] [Accepted: 03/26/2012] [Indexed: 01/12/2023]
Abstract
Nuclear receptors (NRs) are master regulators of transcriptional programs that integrate the homeostatic control of almost all biological processes. Their direct mode of ligand regulation and genome interaction is at the core of modern pharmacology. The two liver X receptors LXRα and LXRβ are among the emerging newer drug targets within the NR family. LXRs are best known as nuclear oxysterol receptors and physiological regulators of lipid and cholesterol metabolism that also act in an anti-inflammatory way. Because LXRs control diverse pathways in development, reproduction, metabolism, immunity and inflammation, they have potential as therapeutic targets for diseases as diverse as lipid disorders, atherosclerosis, chronic inflammation, autoimmunity, cancer and neurodegenerative diseases. Recent insights into LXR signaling suggest future targeting strategies aiming at increasing LXR subtype and pathway selectivity. This review discusses the current status of our understanding of LXR biology and pharmacology, with an emphasis on the molecular aspects of LXR signaling that constitute the potential of LXRs as drug targets.
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Affiliation(s)
- Tomas Jakobsson
- Center for Biosciences, Department of Biosciences and Nutrition, Karolinska Institutet, S-14183 Stockholm, Sweden
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26
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Viennois E, Pommier AJC, Mouzat K, Oumeddour A, Hajjaji FZE, Dufour J, Caira F, Volle DH, Baron S, Lobaccaro JMA. Targeting liver X receptors in human health: deadlock or promising trail? Expert Opin Ther Targets 2011; 15:219-32. [DOI: 10.1517/14728222.2011.547853] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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27
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Weedon-Fekjær M, Johnsen G, Anthonisen E, Sugulle M, Nebb H, Duttaroy A, Staff A. Expression of Liver X Receptors in Pregnancies Complicated by Preeclampsia. Placenta 2010; 31:818-24. [DOI: 10.1016/j.placenta.2010.06.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Revised: 05/27/2010] [Accepted: 06/24/2010] [Indexed: 10/19/2022]
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28
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Nedumaran B, Kim GS, Hong S, Yoon YS, Kim YH, Lee CH, Lee YC, Koo SH, Choi HS. Orphan nuclear receptor DAX-1 acts as a novel corepressor of liver X receptor alpha and inhibits hepatic lipogenesis. J Biol Chem 2010; 285:9221-32. [PMID: 20080977 DOI: 10.1074/jbc.m109.073650] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
DAX-1 (dosage-sensitive sex reversal adrenal hypoplasia congenital critical region on X chromosome, gene 1) is a member of the nuclear receptor superfamily that can repress diverse nuclear receptors and has a key role in adreno-gonadal development. Our previous report has demonstrated that DAX-1 can inhibit hepatocyte nuclear factor 4alpha transactivity and negatively regulate gluconeogenic gene expression (Nedumaran, B., Hong, S., Xie, Y. B., Kim, Y. H., Seo, W. Y., Lee, M. W., Lee, C. H., Koo, S. H., and Choi, H. S. (2009) J. Biol. Chem. 284, 27511-27523). Here, we further expand the role of DAX-1 in hepatic energy metabolism. Transfection assays have demonstrated that DAX-1 can inhibit the transcriptional activity of nuclear receptor liver X receptor alpha (LXRalpha). Physical interaction between DAX-1 and LXRalpha was confirmed Immunofluorescent staining in mouse liver shows that LXRalpha and DAX-1 are colocalized in the nucleus. Domain mapping analysis shows that the entire region of DAX-1 is involved in the interaction with the ligand binding domain region of LXRalpha. Competition analyses demonstrate that DAX-1 competes with the coactivator SRC-1 for repressing LXRalpha transactivity. Chromatin immunoprecipitation assay showed that endogenous DAX-1 recruitment on the SREBP-1c gene promoter was decreased in the presence of LXRalpha agonist. Overexpression of DAX-1 inhibits T7-induced LXRalpha target gene expression, whereas knockdown of endogenous DAX-1 significantly increases T7-induced LXRalpha target gene expression in HepG2 cells. Finally, overexpression of DAX-1 in mouse liver decreases T7-induced LXRalpha target gene expression, liver triglyceride level, and lipid accumulation. Overall, this study suggests that DAX-1, a novel corepressor of LXRalpha, functions as a negative regulator of lipogenic enzyme gene expression in liver.
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Affiliation(s)
- Balachandar Nedumaran
- Hormone Research Center, School of Biological Science and Technology, Chonnam National University, Gwangju 500-757, Korea
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