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Jiang L, Li J, Ji K, Lei L, Li H. MAT2A inhibition suppresses inflammation in Porphyromonas gingivalis-infected human gingival fibroblasts. J Oral Microbiol 2023; 16:2292375. [PMID: 38130504 PMCID: PMC10732205 DOI: 10.1080/20002297.2023.2292375] [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: 11/18/2022] [Accepted: 12/03/2023] [Indexed: 12/23/2023] Open
Abstract
Background Methionine adenosyl transferase II alpha (MAT2A) is the key enzyme to transform methionine into S-adenosylmethionine (SAM), the main methylgroup donor involved in the methylation. The purpose of our study wasto explore whether MAT2A-mediated methionine metabolism affected theexpression of inflammatory cytokines in human gingival fibroblasts(hGFs). Methods Both healthy and inflamed human gingiva were collected. HGFs werecultured and treated with P. gingivalis, with or without MAT2Ainhibitor (PF9366), small interference RNA (siRNA), or extrinsic SAMpretreatment. The levels of inflammatory cytokines were detected byreal-time PCR, western blotting, and ELISA. SAM levels were detectedby ELISA. The nuclear factor-kappa B (NF-κB) and mitogen-activatedprotein kinase (MAPK) pathway was explored by western blotting. Results The expression of MAT2A was increased in the inflamed tissues. P.gingivalis infection promoted the expression of MAT2A and SAM inhGFs. Meanwhile, PF9366 and MAT2A-knockdown significantly decreasedexpression of inflammatory cytokines and SAM production. PF9366inhibited activation of NF-κB/MAPK pathway in P. gingivalis-treatedhGFs. Conclusions MAT2A-mediated methionine metabolism promoted P. gingivalis-inducedinflammation in hGFs. Targeting MAT2A may provide a novel therapeuticmethod for modulating periodontitis.
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Affiliation(s)
- Lishan Jiang
- Nanjing Stomatological Hospital, Affiliated Hospital of medical School, Nanjing University, Nanjing, China
- Central Laboratory of Stomatology, Nanjing Stomatological Hospital, Affiliated Hospital of medical School, Nanjing University, Nanjing, China
| | - Jingwen Li
- Nanjing Stomatological Hospital, Affiliated Hospital of medical School, Nanjing University, Nanjing, China
- Central Laboratory of Stomatology, Nanjing Stomatological Hospital, Affiliated Hospital of medical School, Nanjing University, Nanjing, China
| | - Kun Ji
- Nanjing Stomatological Hospital, Affiliated Hospital of medical School, Nanjing University, Nanjing, China
| | - Lang Lei
- Nanjing Stomatological Hospital, Affiliated Hospital of medical School, Nanjing University, Nanjing, China
| | - Houxuan Li
- Nanjing Stomatological Hospital, Affiliated Hospital of medical School, Nanjing University, Nanjing, China
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Kitano A, Norikura T, Matsui-Yuasa I, Shimakawa H, Kamezawa M, Kojima-Yuasa A. Black carrot extract protects against hepatic injury through epigenetic modifications. J Food Biochem 2022; 46:e14292. [PMID: 35762419 DOI: 10.1111/jfbc.14292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 04/10/2022] [Accepted: 06/17/2022] [Indexed: 11/29/2022]
Abstract
We studied the epigenetic regulation of how black carrot extract (BCE) protects against ethanol-induced hepatic damage. We have shown that the butanol-extracted fraction of BCE (BCE-BuOH) increased intracellular cyclic adenosine monophosphate (cAMP) levels by suppressing the expression of phosphodiesterase 4b (PDE4b); however, the detailed mechanism remains to be elucidated. We focused on changes in histone modifications involved in the suppression of pde4 expression. The methylation level of histone H3 lysine 9 (H3K9), which regulates gene expression of PDE4b, decreased after treatment with 100 mM ethanol but was significantly increased by treatment with 400 μg/ml BCE-BuOH. In contrast, ethanol induced an increase in H3K9 acetylation. However, treatment with BCE-BuOH inhibited the increase in acetylation through an increase in Sirtuin 1 (Sirt1), a histone deacetylase. Furthermore, BCE-BuOH treatment increased the level of methionine adenosyltransferase (MAT) 2a mRNA and increased intracellular S-adenosylmethionine. The present results indicate that BCE-BuOH is useful for protection against alcohol-induced hepatic injury. PRACTICAL APPLICATIONS: We have reported that black carrot extract (BCE) suppressed liver steatosis and liver fibrosis on a rat alcoholic liver disease model. The results from this study have shown that BCE regulated the alcoholic-induced hepatic injury at the level of epigenetic modifications. These results suggested that BCE is useful for protection against alcoholic-induced hepatic injury.
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Affiliation(s)
- Atsuko Kitano
- Department of Food and Human Health Sciences, Graduate School of Human Life Science, Osaka City University, Osaka, Japan
| | - Toshio Norikura
- Department of Nutrition, Aomori University of Health and Welfare, Aomori, Japan
| | - Isao Matsui-Yuasa
- Department of Food and Human Health Sciences, Graduate School of Human Life Science, Osaka City University, Osaka, Japan
| | | | | | - Akiko Kojima-Yuasa
- Department of Food and Human Health Sciences, Graduate School of Human Life Science, Osaka City University, Osaka, Japan
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Fustin JM. Methyl Metabolism and the Clock: An Ancient Story With New Perspectives. J Biol Rhythms 2022; 37:235-248. [PMID: 35382619 PMCID: PMC9160962 DOI: 10.1177/07487304221083507] [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] [Indexed: 11/16/2022]
Abstract
Methylation, that is, the transfer or synthesis of a –CH3 group onto a target molecule, is a pervasive biochemical modification found in organisms from bacteria to humans. In mammals, a complex metabolic pathway powered by the essential nutrients vitamin B9 and B12, methionine and choline, synthesizes S-adenosylmethionine, the methyl donor in the methylation of nucleic acids, proteins, fatty acids, and small molecules by over 200 substrate-specific methyltransferases described so far in humans. Methylations not only play a key role in scenarios for the origin and evolution of life, but they remain essential for the development and physiology of organisms alive today, and methylation deficiencies contribute to the etiology of many pathologies. The methylation of histones and DNA is important for circadian rhythms in many organisms, and global inhibition of methyl metabolism similarly affects biological rhythms in prokaryotes and eukaryotes. These observations, together with various pieces of evidence scattered in the literature on circadian gene expression and metabolism, indicate a close mutual interdependence between biological rhythms and methyl metabolism that may originate from prebiotic chemistry. This perspective first proposes an abiogenetic scenario for rhythmic methylations and then outlines mammalian methyl metabolism, before reanalyzing previously published data to draw a tentative map of its profound connections with the circadian clock.
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Affiliation(s)
- Jean-Michel Fustin
- Centre for Biological Timing, The University of Manchester, Manchester, UK
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Dysregulated Choline, Methionine, and Aromatic Amino Acid Metabolism in Patients with Wilson Disease: Exploratory Metabolomic Profiling and Implications for Hepatic and Neurologic Phenotypes. Int J Mol Sci 2019; 20:ijms20235937. [PMID: 31779102 PMCID: PMC6928853 DOI: 10.3390/ijms20235937] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 11/22/2019] [Accepted: 11/23/2019] [Indexed: 02/07/2023] Open
Abstract
Wilson disease (WD) is a genetic copper overload condition characterized by hepatic and neuropsychiatric symptoms with a not well-understood pathogenesis. Dysregulated methionine cycle is reported in animal models of WD, though not verified in humans. Choline is essential for lipid and methionine metabolism. Defects in neurotransmitters as acetylcholine, and biogenic amines are reported in WD; however, less is known about their circulating precursors. We aimed to study choline, methionine, aromatic amino acids, and phospholipids in serum of WD subjects. Hydrophilic interaction chromatography-quadrupole time-of-flight mass spectrometry was employed to profile serum of WD subjects categorized as hepatic, neurologic, and pre-clinical. Hepatic transcript levels of genes related to choline and methionine metabolism were verified in the Jackson Laboratory toxic milk mouse model of WD (tx-j). Compared to healthy subjects, choline, methionine, ornithine, proline, phenylalanine, tyrosine, and histidine were significantly elevated in WD, with marked alterations in phosphatidylcholines and reductions in sphingosine-1-phosphate, sphingomyelins, and acylcarnitines. In tx-j mice, choline, methionine, and phosphatidylcholine were similarly dysregulated. Elevated choline is a hallmark dysregulation in WD interconnected with alterations in methionine and phospholipid metabolism, which are relevant to hepatic steatosis. The elevated phenylalanine, tyrosine, and histidine carry implications for neurologic manifestations and are worth further investigation.
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Wang K, Fang S, Liu Q, Gao J, Wang X, Zhu H, Zhu Z, Ji F, Wu J, Ma Y, Hu L, Shen X, Gao D, Zhu J, Liu P, Zhou H. TGF-β1/p65/MAT2A pathway regulates liver fibrogenesis via intracellular SAM. EBioMedicine 2019; 42:458-469. [PMID: 30926424 PMCID: PMC6491716 DOI: 10.1016/j.ebiom.2019.03.058] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 03/13/2019] [Accepted: 03/19/2019] [Indexed: 12/15/2022] Open
Abstract
Background Hepatic stellate cell (HSC) activation induced by transforming growth factor β1 (TGF-β1) plays a pivotal role in fibrogenesis, while the complex downstream mediators of TGF-β1 in such process are largely unknown. Methods We performed pharmacoproteomic profiling of the mice liver tissues from control, carbon tetrachloride (CCl4)-induced fibrosis and NPLC0393 administrated groups. The target gene MAT2A was overexpressed or knocked down in vivo by tail vein injection of AAV vectors. We examined NF-κB transcriptional activity on MAT2A promoter via luciferase assay. Intracellular SAM contents were analyzed by LC-MS method. Findings We found that methionine adenosyltransferase 2A (MAT2A) is significantly upregulated in the CCl4-induced fibrosis mice, and application of NPLC0393, a known small molecule inhibitor of TGF-β1 signaling pathway, inhibits the upregulation of MAT2A. Mechanistically, TGF-β1 induces phosphorylation of p65, i.e., activation of NF-κB, thereby promoting mRNA transcription and protein expression of MAT2A and reduces S-adenosylmethionine (SAM) concentration in HSCs. Consistently, in vivo and in vitro knockdown of MAT2A alleviates CCl4- and TGF-β1-induced HSC activation, whereas in vivo overexpression of MAT2A facilitates hepatic fibrosis and abolishes therapeutic effect of NPLC0393. Interpretation This study identifies TGF-β1/p65/MAT2A pathway that is involved in the regulation of intracellular SAM concentration and liver fibrogenesis, suggesting that this pathway is a potential therapeutic target for hepatic fibrosis. Fund This work was supported by National Natural Science Foundation of China (No. 81500469, 81573873, 81774196 and 31800693), Zhejiang Provincial Natural Science Foundation of China (No. Y15H030004), the National Key Research and Development Program from the Ministry of Science and Technology of China (No. 2017YFC1700200) and the Key Program of National Natural Science Foundation of China (No. 8153000502).
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Affiliation(s)
- Kuifeng Wang
- Department of Infectious Diseases, Affiliated Taizhou Hospital of Wenzhou Medical University, 150 Ximen Road of Linhai City, Taizhou 317000, China; Suzhou GenHouse Pharmaceutical Co., Ltd., 388 Ruoshui Road, Suzhou, Jiangsu 215123, China
| | - Shanhua Fang
- Department of Analytical Chemistry, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China; E-Institute of Shanghai Municipal Education Committee, Shanghai University of Traditional Chinese Medicine, 1200 Cailun Road, Shanghai 201203, China
| | - Qian Liu
- Department of Analytical Chemistry, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China; University of Chinese Academy of Sciences, No.19A Yuquan Road, Beijing 100049, China
| | - Jing Gao
- Department of Analytical Chemistry, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
| | - Xiaoning Wang
- E-Institute of Shanghai Municipal Education Committee, Shanghai University of Traditional Chinese Medicine, 1200 Cailun Road, Shanghai 201203, China; Key Laboratory of Liver and Kidney Diseases (Ministry of Education), Institute of Liver Diseases, Shuguang Hospital, Department of Pharmacology, Shanghai University of Traditional Chinese Medicine, 528 Zhangheng Road, Shanghai 201203, China
| | - Hongwen Zhu
- Department of Analytical Chemistry, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
| | - Zhenyun Zhu
- Department of Analytical Chemistry, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
| | - Feihong Ji
- Department of Infectious Diseases, Affiliated Taizhou Hospital of Wenzhou Medical University, 150 Ximen Road of Linhai City, Taizhou 317000, China; Suzhou GenHouse Pharmaceutical Co., Ltd., 388 Ruoshui Road, Suzhou, Jiangsu 215123, China
| | - Jiasheng Wu
- Key Laboratory of Liver and Kidney Diseases (Ministry of Education), Institute of Liver Diseases, Shuguang Hospital, Department of Pharmacology, Shanghai University of Traditional Chinese Medicine, 528 Zhangheng Road, Shanghai 201203, China
| | - Yueming Ma
- Key Laboratory of Liver and Kidney Diseases (Ministry of Education), Institute of Liver Diseases, Shuguang Hospital, Department of Pharmacology, Shanghai University of Traditional Chinese Medicine, 528 Zhangheng Road, Shanghai 201203, China
| | - Lihong Hu
- Department of Analytical Chemistry, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China; University of Chinese Academy of Sciences, No.19A Yuquan Road, Beijing 100049, China; State Key Laboratory Cultivation Base for TCM Quality and Efficacy, School of Medicine and Life Sciences, Nanjing University of Chinese Medicine, 138 Xianlin Road, Nanjing 210023, China
| | - Xu Shen
- Department of Analytical Chemistry, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China; University of Chinese Academy of Sciences, No.19A Yuquan Road, Beijing 100049, China; State Key Laboratory Cultivation Base for TCM Quality and Efficacy, School of Medicine and Life Sciences, Nanjing University of Chinese Medicine, 138 Xianlin Road, Nanjing 210023, China
| | - Daming Gao
- CAS Key Laboratory of Systems Biology, CAS Center for Excellence in Molecular Cell Science, Innovation Center for Cell Signaling Network, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Jiansheng Zhu
- Department of Infectious Diseases, Affiliated Taizhou Hospital of Wenzhou Medical University, 150 Ximen Road of Linhai City, Taizhou 317000, China.
| | - Ping Liu
- E-Institute of Shanghai Municipal Education Committee, Shanghai University of Traditional Chinese Medicine, 1200 Cailun Road, Shanghai 201203, China; Key Laboratory of Liver and Kidney Diseases (Ministry of Education), Institute of Liver Diseases, Shuguang Hospital, Department of Pharmacology, Shanghai University of Traditional Chinese Medicine, 528 Zhangheng Road, Shanghai 201203, China.
| | - Hu Zhou
- Department of Analytical Chemistry, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China; E-Institute of Shanghai Municipal Education Committee, Shanghai University of Traditional Chinese Medicine, 1200 Cailun Road, Shanghai 201203, China; University of Chinese Academy of Sciences, No.19A Yuquan Road, Beijing 100049, China.
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Abstract
Methionine adenosyltransferases (MATs) are essential for cell survival because they catalyze the biosynthesis of the biological methyl donor S-adenosylmethionine (SAMe) from methionine and adenosine triphosphate (ATP). Mammalian cells express two genes, MAT1A and MAT2A, which encode two MAT catalytic subunits, α1 and α2, respectively. The α1 subunit organizes into dimers (MATIII) or tetramers (MATI). The α2 subunit is found in the MATII isoform. A third gene MAT2B, encodes a regulatory subunit β, that regulates the activity of MATII by lowering the inhibition constant (Ki) for SAMe and the Michaelis constant (Km) for methionine. MAT1A expressed mainly in hepatocytes maintains the differentiated state of these cells whereas MAT2A and MAT2B are expressed in non-parenchymal cells of the liver (hepatic stellate cells [HSCs] and Kupffer cells) and extrahepatic tissues. A switch from the liver-specific MAT1A to MAT2A has been observed during conditions of active liver growth and de-differentiation. Liver injury, fibrosis, and cancer are associated with MAT1A silencing and MAT2A/MAT2B induction. Even though both MAT1A and MAT2A are involved in SAMe biosynthesis, they exhibit distinct molecular interactions in liver cells. This review provides an update on MAT genes and their roles in liver pathologies.
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Affiliation(s)
- Komal Ramani
- Corresponding authors: Division of Digestive and Liver
Diseases, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA,
USA (K.Ramani)
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Ramani K, Donoyan S, Tomasi ML, Park S. Role of methionine adenosyltransferase α2 and β phosphorylation and stabilization in human hepatic stellate cell trans-differentiation. J Cell Physiol 2015; 230:1075-85. [PMID: 25294683 DOI: 10.1002/jcp.24839] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 09/22/2014] [Indexed: 12/14/2022]
Abstract
Myofibroblastic trans-differentiation of hepatic stellate cells (HSCs) is an essential event in the development of liver fibrogenesis. These changes involve modulation of key regulators of the genome and the proteome. Methionine adenosyltransferases (MAT) catalyze the biosynthesis of the methyl donor, S-adenosylmethionine (SAMe) from methionine. We have previously shown that two MAT genes, MAT2A and MAT2B (encoding MATα2 and MATβ proteins respectively), are required for HSC activation and loss of MAT2A transcriptional control favors its up-regulation during trans-differentiation. Hence MAT genes are intrinsically linked to the HSC machinery during activation. In the current study, we have identified for the first time, post-translational modifications in the MATα2 and MATβ proteins that stabilize them and favor human HSC trans-differentiation. Culture-activation of human HSCs induced the MATα2 and MATβ proteins. Using mass spectrometry, we identified phosphorylation sites in MATα2 and MATβ predicted to be phosphorylated by mitogen-activated protein kinase (MAPK) family members (ERK1/2, V-Raf Murine Sarcoma Viral Oncogene Homolog B1 [B-Raf], MEK). Phosphorylation of both proteins was enhanced during HSC activation. Blocking MEK activation lowered the phosphorylation and stability of MAT proteins without influencing their mRNA levels. Silencing ERK1/2 or B-Raf lowered the phosphorylation and stability of MATβ but not MATα2. Reversal of the activated human HSC cell line, LX2 to quiescence lowered phosphorylation and destabilized MAT proteins. Mutagenesis of MATα2 and MATβ phospho-sites destabilized them and prevented HSC trans-differentiation. The data reveal that phosphorylation of MAT proteins during HSC activation stabilizes them thereby positively regulating trans-differentiation.
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Affiliation(s)
- Komal Ramani
- Division of Gastroenterology and Liver Diseases, USC Research Center for Liver Diseases, Keck School of Medicine University of Southern California, Los Angeles, California
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Alleviation of alcoholic liver injury by betaine involves an enhancement of antioxidant defense via regulation of sulfur amino acid metabolism. Food Chem Toxicol 2013; 62:292-8. [PMID: 23994088 DOI: 10.1016/j.fct.2013.08.049] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 08/16/2013] [Accepted: 08/20/2013] [Indexed: 12/22/2022]
Abstract
Previous studies suggested that the hepatoprotective activity of betaine is associated with its effects on sulfur amino acid metabolism. We examined the mechanism by which betaine prevents the progression of alcoholic liver injury and its therapeutic potential. Rats received a liquid ethanol diet for 6 wk. Ethanol consumption elevated serum triglyceride and TNFα levels, alanine aminotransferase and aspartate aminotransferase activities, and lipid accumulation in liver. The oxyradical scavenging capacity of liver was reduced, and expression of CD14, TNFα, COX-2, and iNOS mRNAs was induced markedly. These ethanol-induced changes were all inhibited effectively by betaine supplementation. Hepatic S-adenosylmethionine, cysteine, and glutathione levels, reduced in the ethanol-fed rats, were increased by betaine supplementation. Methionine adenosyltransferase and cystathionine γ-lyase were induced, but cysteine dioxygenase was down-regulated, which appeared to account for the increment in cysteine availability for glutathione synthesis in the rats supplemented with betaine. Betaine supplementation for the final 2 wk of ethanol intake resulted in a similar degree of hepatoprotection, revealing its potential therapeutic value in alcoholic liver. It is concluded that the protective effects of betaine against alcoholic liver injury may be attributed to the fortification of antioxidant defense via improvement of impaired sulfur amino acid metabolism.
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Ramani K, Tomasi ML. Transcriptional regulation of methionine adenosyltransferase 2A by peroxisome proliferator-activated receptors in rat hepatic stellate cells. Hepatology 2012; 55:1942-53. [PMID: 22271545 PMCID: PMC3342421 DOI: 10.1002/hep.25594] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 12/26/2011] [Indexed: 12/11/2022]
Abstract
UNLABELLED Methionine adenosyltransferases (MATs) are critical enzymes that catalyze the formation of the methyl donor S-adenosyl methionine (SAM). The MAT2A gene, which encodes the catalytic subunit α2, is induced in dedifferentiated liver. We previously demonstrated that MAT2A expression is enhanced in activated hepatic stellate cells (HSCs) and that silencing this gene reduces HSC activation. In this study, we examined the molecular mechanisms responsible for the transcriptional regulation of the MAT2A gene in HSCs. We identified peroxisome proliferator-activated receptor (PPAR) response elements (PPREs) in the rat MAT2A promoter. The PPARγ agonist rosiglitazone (RSG) promoted quiescence in the activated rat HSC cell line (BSC) or culture-activated primary rat HSCs, decreased MAT2A expression and promoter activity, and enhanced PPARγ binding to MAT2A PPREs. In vivo HSC activation in bile duct-ligated rats lowered PPARγ interaction with MAT2A PPREs. Silencing PPARγ increased MAT2A transcription, whereas overexpressing it had the opposite effect, demonstrating that PPARγ negatively controls this gene. Site-directed mutagenesis of PPREs abolished PPARγ recruitment to the MAT2A promoter and its inhibitory effect on MAT2A transcription in quiescent HSCs. PPRE mutations decreased the basal promoter activity of MAT2A in activated HSCs independent of PPARγ, indicating that other factors might be involved in PPRE interaction. We identified PPARβ binding to wild-type but not to mutated PPREs in activated cells. Furthermore, silencing PPARβ inhibited MAT2A expression and promoter activity. Forced expression of MAT2A in RSG-treated HSCs lowered PPARγ and enhanced PPARβ expression, thereby promoting an activated phenotype. CONCLUSION We identified PPARγ as a negative regulator of MAT2A in quiescent HSCs. A switch from quiescence to activation abolishes this control and allows PPARβ to up-regulate MAT2A transcription.
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Affiliation(s)
- Komal Ramani
- Division of Gastroenterology and Liver Diseases, USC Research Center for Liver Diseases, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
| | - Maria Lauda Tomasi
- Division of Gastroenterology and Liver Diseases, USC Research Center for Liver Diseases, Keck School of Medicine University of Southern California, Los Angeles, California 90033
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Pajares MA, Markham GD. Methionine adenosyltransferase (s-adenosylmethionine synthetase). ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2011; 78:449-521. [PMID: 22220481 DOI: 10.1002/9781118105771.ch11] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- María A Pajares
- Instituto de Investigaciones Biomédicas "Alberto Sols" (CSIC-UAM), Madrid Spain
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11
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Cederbaum AI. Hepatoprotective effects of S-adenosyl-L-methionine against alcohol- and cytochrome P450 2E1-induced liver injury. World J Gastroenterol 2010; 16:1366-76. [PMID: 20238404 PMCID: PMC2842529 DOI: 10.3748/wjg.v16.i11.1366] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
S-adenosyl-L-methionine (SAM) acts as a methyl donor for methylation reactions and participates in the synthesis of glutathione. SAM is also a key metabolite that regulates hepatocyte growth, differentiation and death. Hepatic SAM levels are decreased in animal models of alcohol liver injury and in patients with alcohol liver disease or viral cirrhosis. This review describes the protection by SAM against alcohol and cytochrome P450 2E1-dependent cytotoxicity both in vitro and in vivo and evaluates mechanisms for this protection.
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Ramani K, Yang H, Kuhlenkamp J, Tomasi L, Tsukamoto H, Mato JM, Lu SC. Changes in the expression of methionine adenosyltransferase genes and S-adenosylmethionine homeostasis during hepatic stellate cell activation. Hepatology 2010; 51:986-95. [PMID: 20043323 PMCID: PMC2905860 DOI: 10.1002/hep.23411] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
UNLABELLED Hepatic stellate cell (HSC) activation is an essential event during liver fibrogenesis. Methionine adenosyltransferase (MAT) catalyzes biosynthesis of S-adenosylmethionine (SAMe), the principle methyl donor. SAMe metabolism generates two methylation inhibitors, methylthioadenosine (MTA) and S-adenosylhomocysteine (SAH). Liver cell proliferation is associated with induction of two nonliver-specific MATs: MAT2A, which encodes the catalytic subunit alpha2, and MAT2beta, which encodes a regulatory subunit beta that modulates the activity of the MAT2A-encoded isoenzyme MATII. We reported that MAT2A and MAT2beta genes are required for liver cancer cell growth that is induced by the profibrogenic factor leptin. Also, MAT2beta regulates leptin signaling. The strong association of MAT genes with proliferation and leptin signaling in liver cells led us to examine the role of these genes during HSC activation. MAT2A and MAT2beta are induced in culture-activated primary rat HSCs and HSCs from 10-day bile duct ligated (BDL) rat livers. HSC activation led to a decline in intracellular SAMe and MTA levels, a drop in the SAMe/SAH ratio, and global DNA hypomethylation. The decrease in SAMe levels was associated with lower MATII activity during activation. MAT2A silencing in primary HSCs and MAT2A or MAT2beta silencing in the human stellate cell line LX-2 resulted in decreased collagen and alpha-smooth muscle actin (alpha-SMA) expression and cell growth and increased apoptosis. MAT2A knockdown decreased intracellular SAMe levels in LX-2 cells. Activation of extracellular signal-regulated kinase and phosphatidylinositol-3-kinase signaling in LX-2 cells required the expression of MAT2beta but not that of MAT2A. CONCLUSION MAT2A and MAT2beta genes are induced during HSC activation and are essential for this process. The SAMe level falls, resulting in global DNA hypomethylation.
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Affiliation(s)
- Komal Ramani
- Division of Gastroenterology and Liver Diseases, USC Research Center for Liver Diseases, HMR Bldg., 413, Department of Medicine, Keck School of Medicine USC, 2011 Zonal Ave., Los Angeles, CA 90033, USA.
| | - Heping Yang
- Division of Gastroenterology and Liver Diseases, USC Research Center for Liver Diseases, Keck School of Medicine University of Southern California, Los Angeles, California 90033
| | - John Kuhlenkamp
- Division of Gastroenterology and Liver Diseases, USC Research Center for Liver Diseases, Keck School of Medicine University of Southern California, Los Angeles, California 90033
| | - Lauda Tomasi
- Division of Gastroenterology and Liver Diseases, USC Research Center for Liver Diseases, Keck School of Medicine University of Southern California, Los Angeles, California 90033
| | - Hidekazu Tsukamoto
- Southern California Research Center for Alcoholic Liver and Pancreatic Diseases and Cirrhosis, Keck School of Medicine University of Southern California, Los Angeles, California 90033
| | - José M. Mato
- CIC bioGUNE, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (Ciberehd), Technology, Park of Bizkaia, 48160 Derio, Bizkaia, Spain
| | - Shelly C. Lu
- Division of Gastroenterology and Liver Diseases, USC Research Center for Liver Diseases, Keck School of Medicine University of Southern California, Los Angeles, California 90033, Southern California Research Center for Alcoholic Liver and Pancreatic Diseases and Cirrhosis, Keck School of Medicine University of Southern California, Los Angeles, California 90033
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Llacuna L, Marí M, Lluis JM, García-Ruiz C, Fernández-Checa JC, Morales A. Reactive oxygen species mediate liver injury through parenchymal nuclear factor-kappaB inactivation in prolonged ischemia/reperfusion. THE AMERICAN JOURNAL OF PATHOLOGY 2009; 174:1776-85. [PMID: 19349371 DOI: 10.2353/ajpath.2009.080857] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Nuclear factor (NF)-kappaB participates in ischemia/reperfusion (I/R) hepatic signaling, stimulating both protective mechanisms and the generation of inflammatory cytokines. After analyzing NF-kappaB activation during increasing times of ischemia in murine I/R, we observed that the nuclear translocation of p65 paralleled Src and IkappaB tyrosine phosphorylation, which peaked after 60 minutes of ischemia. After extended ischemic periods (90 to 120 minutes) however, nuclear p65 levels were inversely correlated with the progressive induction of oxidative stress. Despite this profile of NF-kappaB activation, inflammatory genes, such as tumor necrosis factor (TNF) and interleukin (IL)-1beta, predominantly induced by Kupffer cells, increased throughout time during ischemia (30 to 120 minutes), whereas protective NF-kappaB-dependent genes, such as manganese superoxide dismutase (Mn-SOD), expressed in parenchymal cells, decreased. Consistent with this behavior, gadolinium chloride pretreatment abolished TNF/IL-1beta up-regulation during ischemia without affecting Mn-SOD levels. Interestingly, specific glutathione (GSH) up-regulation in hepatocytes by S-adenosylmethionine increased Mn-SOD expression and protected against I/R-mediated liver injury despite TNF/IL-1beta induction. Similar protection was achieved by administration of the SOD mimetic MnTBAP. In contrast, indiscriminate hepatic GSH depletion by buthionine-sulfoximine before I/R potentiated oxidative stress and decreased both nuclear p65 and Mn-SOD expression levels, increasing TNF/IL-1beta up-regulation and I/R-induced liver damage. Thus, the divergent role of NF-kappaB activation in selective liver cell populations underlies the dichotomy of NF-kappaB in hepatic I/R injury, illustrating the relevance of specifically maintaining NF-kappaB activation in parenchymal cells.
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Affiliation(s)
- Laura Llacuna
- Liver Unit, Hospital Clinic, Institut de Investigacions Biomèdiques August Pi-Sunyer, Centro de Investigaciones Biomédicas Esther Koplowitz, Universitat de Barcelona, Barcelona, Spain
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Ikeda R, Nishida T, Watanabe F, Shimizu-Saito K, Asahina K, Horikawa S, Teraoka H. Involvement of CCAAT/enhancer binding protein-beta (C/EBPbeta) in epigenetic regulation of mouse methionine adenosyltransferase 1A gene expression. Int J Biochem Cell Biol 2008; 40:1956-69. [PMID: 18346930 DOI: 10.1016/j.biocel.2008.02.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Revised: 01/23/2008] [Accepted: 02/11/2008] [Indexed: 12/31/2022]
Abstract
Methionine adenosyltransferase (MAT) catalyzes the synthesis of S-adenosylmethionine, the main methyl donor in cellular transmethylation reactions and the aminopropyl moiety in polyamine biosynthesis. In mammals, two different genes, MAT1A and MAT2A, encode catalytic polypeptides of liver-specific MAT I/III and ubiquitous MAT II, respectively. Reverse transcription-polymerase chain reaction showed that MAT1A gene expression was at a detectable level in embryonic day 14 mouse fetal liver and subsequently increased. Bisulfite genomic sequencing indicated that the methylation status of 10CpG sites in the MAT1A promoter proximal region was appreciably correlated with the gene expression in mouse developing liver and in adult hepatic cells; hepatic stellate cells and hepatocytes. When mouse hepatoma-derived Hepa-1 cells showing extremely low expression of MAT1A gene were treated with 5-aza-2'-deoxycytidine and trichostatin A, MAT1A gene expression was enhanced. In addition, in vitro methylation of the MAT1A promoter region suppressed the MAT1A promoter activity in reporter assay. Next, we performed electrophoretic mobility shift assay and found that the transcriptional factor CCAAT/enhancer binding protein-beta (C/EBPbeta) specifically binds to a putative binding site of C/EBPbeta in the MAT1A promoter. Suppression of C/EBPbeta expression by short hairpin RNA decreased the MAT1A promoter activity and MAT1A gene expression, and inhibition of C/EBPbeta binding to MAT1A by site-directed mutagenesis also showed similar results. Western blot analysis and chromatin immunoprecipitation assay indicated that C/EBPbeta binding is dependent on DNA methylation status. Based on these findings, we conclude that C/EBPbeta plays an important role in epigenetic regulation of the mature hepatic gene MAT1A.
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Affiliation(s)
- Reiko Ikeda
- Department of Pathological Biochemistry, Medical Research Institute, Tokyo Medical and Dental University, 2-3-10 Kandasurugadai, Chiyoda-ku, Tokyo 101-0062, Japan
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15
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Cao Q, Mak KM, Lieber CS. DLPC and SAMe combined prevent leptin-stimulated TIMP-1 production in LX-2 human hepatic stellate cells by inhibiting HO-mediated signal transduction. Liver Int 2006; 26:221-31. [PMID: 16448461 DOI: 10.1111/j.1478-3231.2005.01204.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACKGROUND/AIMS Both dilinoleoylphosphatidylcholine (DLPC) and S-adenosylmethionine (SAMe) have antioxidant properties and antifibrogenic actions. Because H2O2 mediates signal transduction-stimulating liver fibrogenesis, we investigated whether DLPC and SAMe attenuate the production of tissue inhibitor of metalloproteinase (TIMP)-1 by inhibiting H2O2 formation. METHODS LX-2 human hepatic stellate cells were treated with leptin with or without DLPC, SAMe or various inhibitors. RESULTS Leptin-stimulated TIMP-1 mRNA and its protein were diminished by DLPC or SAMe alone, and the response was fully prevented by the combination of DLPC and SAMe. H2O2 was increased while glutathione was decreased; these changes were prevented by AG490, suggesting a Janus kinases (JAK)-mediated process. Up-regulation of leptin receptor and activation of JAK1 and 2 were not affected by DLPC+SAMe, whereas phosphorylation of ERK1/2 and p38 was blocked by DLPC+SAMe or catalase, suggesting an H2O2-dependent mechanism. These treatments also suppressed leptin-stimulated TIMP-1 promoter activity and decreased TIMP-1 mRNA stability, contributing to TIMP-1 mRNA down-regulation. PD098059, an ERK1/2 inhibitor, suppressed TIMP-1 promoter activity, whereas SB203580, a p38 inhibitor, decreased TIMP-1 message stability; both resulted in a partial reduction of TIMP-1 mRNA. CONCLUSION As decreased TIMP-1 production may enhance collagen deposition, the combined administration of DLPC+SAMe should be considered for the prevention of H2O2-mediated signaling and the resulting fibrosis.
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Affiliation(s)
- Qi Cao
- Alcohol Research and Treatment Center, Bronx Veterans Affairs Medical Center and Mount Sinai School of Medicine, Bronx, NY 10468, USA
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Nieto N, Cederbaum AI. S-adenosylmethionine blocks collagen I production by preventing transforming growth factor-beta induction of the COL1A2 promoter. J Biol Chem 2005; 280:30963-74. [PMID: 15983038 DOI: 10.1074/jbc.m503569200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
To study the anti-fibrogenic mechanisms of S-adenosylmethionine (AdoMet), transgenic mice harboring the -17 kb to +54 bp of the collagen alpha2 (I) promoter (COL1A2) cloned upstream from the beta-gal reporter gene were injected with carbon tetrachloride (CCl4) to induce fibrosis and coadministered either AdoMet or saline. Control groups received AdoMet or mineral oil. AdoMet lowered the pathology in CCl4-treated mice as shown by transaminase levels, hematoxylin and eosin, Masson's trichrome staining, and collagen I expression. beta-Galactosidase activity indicated activation of the COL1A2 promoter in stellate cells from CCl4-treated mice and repression of such activation by AdoMet. Lipid peroxidation, transforming growth factor-beta (TGFbeta) expression, and decreases in glutathione levels were prevented by AdoMet. Incubation of primary stellate cells with AdoMet down-regulated basal and TGFbeta-induced collagen I and alpha-smooth muscle actin proteins. AdoMet metabolites down-regulated collagen I protein and mRNA levels. AdoMet repressed basal and TGFbeta-induced reporter activity in stellate cells transfected with COL1A2 promoter deletion constructs. AdoMet blocked TGFbeta induction of the -378 bp region of the COL1A2 promoter and prevented the phosphorylation of extracellular signal-regulated kinase 1/2 and the binding of Sp1 to the TGFbeta-responsive element. These observations unveil a novel mechanism by which AdoMet could ameliorate liver fibrosis.
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Affiliation(s)
- Natalia Nieto
- Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, New York, New York 10029, USA.
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17
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Lu SC, Mato JM. Role of methionine adenosyltransferase and S-adenosylmethionine in alcohol-associated liver cancer. Alcohol 2005; 35:227-34. [PMID: 16054984 DOI: 10.1016/j.alcohol.2005.03.011] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Accepted: 03/27/2005] [Indexed: 12/22/2022]
Abstract
Two genes (MAT1A and MAT2A) encode for the essential enzyme methionine adenosyltransferase (MAT), which catalyzes the biosynthesis of S-adenosylmethionine (SAMe), the principal methyl donor and, in the liver, a precursor of glutathione. MAT1A is expressed mostly in the liver, whereas MAT2A is widely distributed. MAT2A is induced in the liver during periods of rapid growth and dedifferentiation. In human hepatocellular carcinoma (HCC) MAT1A is replaced by MAT2A. This is important pathogenetically because MAT2A expression is associated with lower SAMe levels and faster growth, whereas exogenous SAMe treatment inhibits growth. Rats fed ethanol intragastrically for 9 weeks also exhibit a relative switch in hepatic MAT expression, decreased SAMe levels, hypomethylation of c-myc, increased c-myc expression, and increased DNA strand break accumulation. Patients with alcoholic liver disease have decreased hepatic MAT activity owing to both decreased MAT1A expression and inactivation of the MAT1A-encoded isoenzymes, culminating in decreased SAMe biosynthesis. Consequences of chronic hepatic SAMe depletion have been examined in the MAT1A knockout mouse model. In this model, the liver is more susceptible to injury. In addition, spontaneous steatohepatitis develops by 8 months, and HCC develops by 18 months. Accumulating evidence shows that, in addition to being a methyl donor, SAMe controls hepatocyte growth response and death response. Whereas transient SAMe depletion is necessary for the liver to regenerate, chronic hepatic SAMe depletion may lead to malignant transformation. It is interesting that SAMe is antiapoptotic in normal hepatocytes, but proapoptotic in liver cancer cells. This should make SAMe an attractive agent for both chemoprevention and treatment of HCC.
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Affiliation(s)
- Shelly C Lu
- USC Research Center for Liver Diseases, USC-UCLA Research Center for Alcoholic Liver and Pancreatic Diseases, Keck School of Medicine USC, Los Angeles, CA 90033, USA.
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Martínez-Chantar ML, García-Trevijano ER, Latasa MU, Martín-Duce A, Fortes P, Caballería J, Avila MA, Mato JM. Methionine adenosyltransferase II beta subunit gene expression provides a proliferative advantage in human hepatoma. Gastroenterology 2003; 124:940-8. [PMID: 12671891 DOI: 10.1053/gast.2003.50151] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND & AIMS Of the 2 genes (MAT1A, MAT2A) encoding methionine adenosyltransferase, the enzyme that synthesizes S-adenosylmethionine, MAT1A, is expressed in liver, whereas MAT2A is expressed in extrahepatic tissues. In liver, MAT2A expression associates with growth, dedifferentiation, and cancer. Here, we identified the beta subunit as a regulator of proliferation in human hepatoma cell lines. The beta subunit has been cloned and shown to lower the K(m) of methionine adenosyltransferase II alpha2 (the MAT2A product) for methionine and to render the enzyme more susceptible to S-adenosylmethionine inhibition. METHODS Methionine adenosyltransferase II alpha2 and beta subunit expression was analyzed in human and rat liver and hepatoma cell lines and their interaction studied in HuH7 cells. beta Subunit expression was up- and down-regulated in human hepatoma cell lines and the effect on DNA synthesis determined. RESULTS We found that beta subunit is expressed in rat extrahepatic tissues but not in normal liver. In human liver, beta subunit expression associates with cirrhosis and hepatoma. beta Subunit is expressed in most (HepG2, PLC, and Hep3B) but not all (HuH7) hepatoma cell lines. Transfection of beta subunit reduced S-adenosylmethionine content and stimulated DNA synthesis in HuH7 cells, whereas down-regulation of beta subunit expression diminished DNA synthesis in HepG2. The interaction between methionine adenosyltransferase II alpha2 and beta subunit was demonstrated in HuH7 cells. CONCLUSIONS Our findings indicate that beta subunit associates with cirrhosis and cancer providing a proliferative advantage in hepatoma cells through its interaction with methionine adenosyltransferase II alpha2 and down-regulation of S-adenosylmethionine levels.
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Affiliation(s)
- Maria L Martínez-Chantar
- División de Hepatología y Terapia Génica, Departamento de Medicina Interna, Universidad de Navarra, Pamplona, Spain
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Abstract
Methionine catabolism occurs mostly in the liver through the formation of S-adenosylmethionine (SAM) in a reaction catalyzed by methionine adenosyltransferase (MAT). S-adenosylmethionine is the principal biologic methyl donor, a precursor for polyamines, and in liver, it is also a precursor for reduced glutathione (GSH). Liver-specific and non-liver-specific MAT are products of two different genes, MAT1A and MAT2A, respectively. Mature liver expresses MAT1A, whereas MAT2A is expressed in extrahepatic tissues and induced during liver growth and de-differentiation. The type of MAT expressed by the cell affects the steady-state SAM level, DNA methylation, and growth rate. This has been demonstrated further by using the MAT1A knockout mouse model in which hepatic SAM and GSH levels decrease, the liver becomes larger and more susceptible to injury, and steatohepatitis develops spontaneously. Altered methionine metabolism in alcoholic liver disease results in decreased transmethylation and transsulfuration, changes that may play important pathogenic roles. Major changes include a relative switch in MAT expression; decreased hepatic SAM, GSH, and DNA methylation levels; decreased homocysteine metabolism; and hyperhomocysteinemia. Consequences of hepatic DNA hypomethylation include increased expression of c-myc and DNA strand break accumulation. One possible consequence of hyperhomocysteinemia is increased fibrogenesis. Abnormal methionine metabolism may also occur in Kupffer cells, which express both forms of MAT. If SAM levels also decrease in these cells, this may contribute to the induction of tumor necrosis factor (TNF) expression and release. In summary, altered hepatic methionine metabolism can have serious consequences that affect not only hepatocytes, but also hepatic stellate and Kupffer cells. These changes can lead to impaired antioxidant defense, altered gene expression, promotion of fibrogenesis, and even hepatocarcinogenesis.
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Affiliation(s)
- Shelly C Lu
- USC Liver Disease Research Center, USC-UCLA Research Center for Alcoholic Liver and Pancreatic Diseases, Keck School of Medicine USC, Los Angeles, CA 90033, USA.
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Mato JM, Corrales FJ, Lu SC, Avila MA. S-Adenosylmethionine: a control switch that regulates liver function. FASEB J 2002; 16:15-26. [PMID: 11772932 DOI: 10.1096/fj.01-0401rev] [Citation(s) in RCA: 311] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Genome sequence analysis reveals that all organisms synthesize S-adenosylmethionine (AdoMet) and that a large fraction of all genes is AdoMet-dependent methyltransferases. AdoMet-dependent methylation has been shown to be central to many biological processes. Up to 85% of all methylation reactions and as much as 48% of methionine metabolism occur in the liver, which indicates the crucial importance of this organ in the regulation of blood methionine. Of the two mammalian genes (MAT1A, MAT2A) that encode methionine adenosyltransferase (MAT, the enzyme that makes AdoMet), MAT1A is specifically expressed in adult liver. It now appears that growth factors, cytokines, and hormones regulate liver MAT mRNA levels and enzyme activity and that AdoMet should not be viewed only as an intermediate metabolite in methionine catabolism, but also as an intracellular control switch that regulates essential hepatic functions such as regeneration, differentiation, and the sensitivity of this organ to injury. The aim of this review is to integrate these recent findings linking AdoMet with liver growth, differentiation, and injury into a comprehensive model. With the availability of AdoMet as a nutritional supplement and evidence of its beneficial role in various liver diseases, this review offers insight into its mechanism of action.
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Affiliation(s)
- Jose M Mato
- Division of Hepatology and Gene Therapy, School of Medicine, University of Navarra, 31008 Pamplona, Spain.
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Abstract
Alcoholic liver disease (ALD) develops as a consequence of priming and sensitizing mechanisms rendered by cross-interactions of primary mechanistic factors and secondary risk factors. This concept, albeit not novel, is becoming widely accepted by the field, and more research is directed toward identifying and characterizing the interfaces of the cross-interactions to help understand individual predisposition to the disease. Another pivotal development is the beginning of cell type-specific research to elucidate specific contributions not only of hepatocytes, but also of hepatic macrophages, liver-associated lymphocytes, sinusoidal endothelial cells, and hepatic stellate cells to sensitizing and priming mechanisms. In particular, the critical role of hepatic macrophages has been highlighted and the priming mechanisms concerning this paracrine effect have been proposed. Glutathione depletion in hepatocyte mitochondria is considered the most important sensitizing mechanism. One of the contributing factors is decreased methionine metabolism. Remaining key questions include how altered methionine metabolism contribute to the pathogenesis of ALD; how cross-talk among nonparenchymal liver cells or between nonparenchymal cells and hepatocytes leads to ALD; how dysfunctional mitochondria determine the type of cell death in ALD; and what secondary factors are critical for the development of advanced ALD such as alcoholic hepatitis and cirrhosis.
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Affiliation(s)
- H Tsukamoto
- USC-UCLA Research Center for Alcoholic Liver and Pancreatic Diseases, USC Research Center for Liver Diseases, Department of Pathology, Keck School of Medicine of USC, Los Angeles, California 90033, USA.
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Ito K, Ikeda S, Kojima N, Miura M, Shimizu-Saito K, Yamaguchi I, Katsuyama I, Sanada K, Iwai T, Senoo H, Horikawa S. Correlation between the expression of methionine adenosyltransferase and the stages of human colorectal carcinoma. Surg Today 2001; 30:706-10. [PMID: 10955733 DOI: 10.1007/s005950070081] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Methionine adenosyltransferase (MAT) catalyzes the synthesis of S-adenosylmethionine (AdoMet) from ATP and L-methionine. AdoMet is the major methyl donor in most transmethylation reactions in vivo, and it is also the propylamino donor in the biosynthesis of polyamines. In the present study, we assessed MAT activity in human colons with colorectal carcinoma and the values were compared with those of morphologically normal adjacent mucosa. Higher levels of MAT activity were observed in the colorectal carcinoma than in the normal colon. The ratio of MAT activity in tumor tissue versus normal tissue seemed to be correlated well will the stage of the colorectal tumor. Furthermore, immunoblot analysis showed that the high levels of MAT activity observed in colorectal carcinoma were due to the increased amounts of MAT protein. Immunohistochemical analysis revealed that MAT was most abundant in goblet cells, particularly in granules in the supranuclear area of these cells. In the colorectal carcinoma tissues, MAT was strongly stained in the cancerous cells and localized in granules in the supranuclear region. The results of this preliminary study suggest that determination of the relative ratio of MAT activity in both normal and tumor regions in human colorectal carcinoma could be a clinically useful tool for determining the stage of malignancy of colorectal carcinomas.
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Affiliation(s)
- K Ito
- Department of Surgery, Tsuchiura Kyodo Hospital, Japan
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Lu SC, Huang ZZ, Yang H, Mato JM, Avila MA, Tsukamoto H. Changes in methionine adenosyltransferase and S-adenosylmethionine homeostasis in alcoholic rat liver. Am J Physiol Gastrointest Liver Physiol 2000; 279:G178-85. [PMID: 10898761 DOI: 10.1152/ajpgi.2000.279.1.g178] [Citation(s) in RCA: 131] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Liver-specific and non-liver-specific methionine adenosyltransferase (MAT) are products of two genes, MAT1A and MAT2A, respectively, that catalyze the formation of S-adenosylmethionine (SAM). We previously showed that MAT2A expression was associated with more rapid cell growth. Changes in MAT expression have not been examined in animal models of alcoholic liver injury, which is the focus of the current study. After rats were fed intragastrically with ethanol and high fat for 9 wk, the mRNA level of both MAT forms doubled but only the protein level of MAT2A increased. Although liver-specific MAT activity did not change, it was 32% lower after one and 68% lower after eight weekly enteral doses of lipopolysaccharide. Hepatic levels of methionine, SAM, and DNA methylation fell by approximately 40%. c-myc was hypomethylated, and its mRNA level increased. Genome-wide DNA strand break increased. Thus in the prefibrotic stage of alcoholic liver injury, there is already a switch in MAT expression, global DNA hypomethylation, increased c-myc expression, and genome-wide DNA strand break. These changes may be important in predisposing this liver disease to malignant degeneration.
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Affiliation(s)
- S C Lu
- Division of Gastrointestinal and Liver Diseases, University of Southern California-University of California, Los Angeles 90033, USA
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