title: Gallic acid protects against endothelial injury by restoring the depletion of DNA methyltransferase 1 and inhibiting proteasome activities.
abstract: BACKGROUND
  The aim of this study was to investigate the protective effects of gallic acid, a common phenolic compound naturally present in food and nutraceuticals, on endothelial cell death and the mechanisms involved.
  
  
  METHODS
  Endothelial cell death was induced by the combination of homocysteine, adenosine and tumour necrosis factor (TNF) in human vascular endothelial cells (EAhy926 and HBEC-5i cells). The protective effects of gallic acid were evaluated against cytotoxicity, apoptosis and microparticle release. Underlying mechanisms were further investigated focusing on the involvement of DNA methyltransferase 1 (DNMT1) and proteasome activities.
  
  
  RESULTS
  Our results showed that gallic acid dose-dependently arrested cytotoxicity in EAhy926 and HBEC-5i cells induced by the combination. Gallic acid showed anti-apoptotic effects and reduced the formation of microparticles. Notably, gallic acid reversed DNMT1 depletions at the protein level. The cytoprotective and anti-apoptotic effects of gallic acid were counteracted by the pre-treatment with DNMT1 inhibitor, 5-aza-2-deoxycytidine (5-aza-dC). Treatment with gallic acid led to the accumulation of ubiquitinated protein aggregates and the reduction in chymotrypsin-like proteasome activities indicating proteasome inhibition.
  
  
  CONCLUSIONS
  Our results demonstrate for the first time that gallic acid is capable of protecting endothelial cells from injury induced by the combination of homocysteine, adenosine and TNF, at least in part, by restoring the depletion of DNMT1 and inhibiting proteasome activities.
authors.affiliation: Faculty of Pharmacy, University of Sydney, NSW 2006, Australia.
authors.forename: Antony
authors.initials: A
authors.lastname: Kam
authors.affiliation: Discipline of Pharmacology, Sydney Medical School, University of Sydney, NSW 2006, Australia.
authors.forename: Kong M
authors.initials: KM
authors.lastname: Li
authors.affiliation: Faculty of Pharmacy, University of Sydney, NSW 2006, Australia; National Institute of Complementary Medicine (NICM), University of Western Sydney, NSW 2560, Australia; School of Science and Health, University of Western Sydney, NSW 2560, Australia.
authors.forename: Valentina
authors.initials: V
authors.lastname: Razmovski-Naumovski
authors.affiliation: National Institute of Complementary Medicine (NICM), University of Western Sydney, NSW 2560, Australia; School of Science and Health, University of Western Sydney, NSW 2560, Australia.
authors.forename: Srinivas
authors.initials: S
authors.lastname: Nammi
authors.affiliation: Faculty of Pharmacy, University of Sydney, NSW 2006, Australia; National Institute of Complementary Medicine (NICM), University of Western Sydney, NSW 2560, Australia; School of Science and Health, University of Western Sydney, NSW 2560, Australia.
authors.forename: Kelvin
authors.initials: K
authors.lastname: Chan
authors.affiliation: Faculty of Pharmacy, University of Sydney, NSW 2006, Australia. Electronic address: george.li@sydney.edu.au.
authors.forename: George Q
authors.initials: GQ
authors.lastname: Li
mesh_terms: D000241:Adenosine / Q000633:toxicity; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism*; D004347:Drug Interactions; D042783:Endothelial Cells / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D005434:Flow Cytometry; D005707:Gallic Acid / Q000494:pharmacology*; D006710:Homocysteine / Q000633:toxicity; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000633:toxicity; D014665:Vasodilator Agents / Q000633:toxicity
chemical_list: D061988:Proteasome Inhibitors; D014409:Tumor Necrosis Factor-alpha; D014665:Vasodilator Agents; D006710:Homocysteine; D005707:Gallic Acid; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; D046988:Proteasome Endopeptidase Complex; D000241:Adenosine
keywords: DNMT1; Endothelial injury; Gallic acid; Proteasome