title: Homocysteine accelerates senescence of endothelial cells via DNA hypomethylation of human telomerase reverse transcriptase.
abstract: OBJECTIVE
  Homocysteine can accelerate the senescence of endothelial progenitor cells or endothelial cells (ECs) via telomerase inactivation and length shortening. However, the underlying mechanism is unclear. Here, we investigated whether homocysteine promotes endothelial senescence by reducing the expression and activity of human telomerase reverse transcriptase (hTERT) by DNA methylation to reduce ECs telomerase activity.
  
  
  RESULTS
  When compared with primary human umbilical vein endothelial cells grown under standard conditions, ECs with chronic homocysteine treatment showed accelerated upregulation of p16, p21, and p53, markers of cellular senescence, during 6 to 10 passages. Interestingly, homocysteine-stimulated but not angiotensin II-stimulated ECs senescence could be reversed by hypermethylation induced by folic acid or s-adenosylmethionine supplementation. Meanwhile, homocysteine promoted the shortening of telomere length specifically related to restoration of hTERT transcriptional expression and CCCTC-binding factor binding sites with hTERT promoter hypomethylation, as detected by quantitative real-time polymerase chain reaction, Western blot, methylation-specific polymerase chain reaction, and bisulfite sequencing assay. Electrophoretic mobility shift assay and chromatin immunoprecipitation results showed that homocysteine-reduced telomere activity and homocysteine-induced EC senescence might contribute to hTERT promoter demethylation by increasing CCCTC-binding factor repression and interfering in the SP1 binding to the demethylated hTERT promoter, which might relate with reduced of DNA methyltransferase 1. Furthermore, the CCCTC-binding factor-dependent mechanism of homocysteine-reduced hTERT expression via DNA demethylation was confirmed in aortic endothelia of mice with hyperhomocysteine levels.
  
  
  CONCLUSIONS
  CCCTC-binding factor and SP1 cross talk may contribute to homocysteine-reduced hTERT DNA methylation and expression in endothelial senescence.
authors.affiliation: From the Department of Clinical Laboratory, Peking Union Medical College and Peking Union Medical College Hospital, Beijing, China (D.Z., W.C.); Department of Physiology and Pathophysiology, Key Laboratory of Cardiovascular Science of Ministry of Education, Peking University Health Science Center, Beijing, China (W.C.); Cardiovascular Research Center, Shantou University Medical College, Shantou, Guangdong, China (D.Z., J.L., X.X.); and Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China (Y.Z.).
authors.forename: Donghong
authors.initials: D
authors.lastname: Zhang
authors.affiliation: From the Department of Clinical Laboratory, Peking Union Medical College and Peking Union Medical College Hospital, Beijing, China (D.Z., W.C.); Department of Physiology and Pathophysiology, Key Laboratory of Cardiovascular Science of Ministry of Education, Peking University Health Science Center, Beijing, China (W.C.); Cardiovascular Research Center, Shantou University Medical College, Shantou, Guangdong, China (D.Z., J.L., X.X.); and Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China (Y.Z.).
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Sun
authors.affiliation: From the Department of Clinical Laboratory, Peking Union Medical College and Peking Union Medical College Hospital, Beijing, China (D.Z., W.C.); Department of Physiology and Pathophysiology, Key Laboratory of Cardiovascular Science of Ministry of Education, Peking University Health Science Center, Beijing, China (W.C.); Cardiovascular Research Center, Shantou University Medical College, Shantou, Guangdong, China (D.Z., J.L., X.X.); and Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China (Y.Z.).
authors.forename: Jianlan
authors.initials: J
authors.lastname: Liu
authors.affiliation: From the Department of Clinical Laboratory, Peking Union Medical College and Peking Union Medical College Hospital, Beijing, China (D.Z., W.C.); Department of Physiology and Pathophysiology, Key Laboratory of Cardiovascular Science of Ministry of Education, Peking University Health Science Center, Beijing, China (W.C.); Cardiovascular Research Center, Shantou University Medical College, Shantou, Guangdong, China (D.Z., J.L., X.X.); and Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China (Y.Z.).
authors.forename: Xina
authors.initials: X
authors.lastname: Xie
authors.affiliation: From the Department of Clinical Laboratory, Peking Union Medical College and Peking Union Medical College Hospital, Beijing, China (D.Z., W.C.); Department of Physiology and Pathophysiology, Key Laboratory of Cardiovascular Science of Ministry of Education, Peking University Health Science Center, Beijing, China (W.C.); Cardiovascular Research Center, Shantou University Medical College, Shantou, Guangdong, China (D.Z., J.L., X.X.); and Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China (Y.Z.). zhuyi@tijmu.edu.cn cuiw@pumch.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Cui
authors.affiliation: From the Department of Clinical Laboratory, Peking Union Medical College and Peking Union Medical College Hospital, Beijing, China (D.Z., W.C.); Department of Physiology and Pathophysiology, Key Laboratory of Cardiovascular Science of Ministry of Education, Peking University Health Science Center, Beijing, China (W.C.); Cardiovascular Research Center, Shantou University Medical College, Shantou, Guangdong, China (D.Z., J.L., X.X.); and Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China (Y.Z.). zhuyi@tijmu.edu.cn cuiw@pumch.cn.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhu
mesh_terms: D000804:Angiotensin II / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D000076246:CCCTC-Binding Factor; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000187:drug effects*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D019175:DNA Methylation / Q000187:drug effects*; D004195:Disease Models, Animal; D005492:Folic Acid / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D006710:Homocysteine / Q000494:pharmacology*; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D020138:Hyperhomocysteinemia / Q000097:blood / Q000201:enzymology / Q000235:genetics; D008297:Male; D008810:Mice, Inbred C57BL; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000494:pharmacology; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D016615:Telomere / Q000187:drug effects* / Q000378:metabolism; D059506:Telomere Shortening / Q000187:drug effects; D013997:Time Factors; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D000076246:CCCTC-Binding Factor; C493956:CDKN1A protein, human; C000619697:CTCF protein, human; C000619698:Ctcf protein, mouse; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D012097:Repressor Proteins; D016329:Sp1 Transcription Factor; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D006710:Homocysteine; D000804:Angiotensin II; D012436:S-Adenosylmethionine; D005492:Folic Acid; C509186:TERT protein, human; D019098:Telomerase; C509187:Tert protein, mouse
keywords: aging; endothelial cells; homocysteine; telomerase reverse transcriptase, human