Gallic acid protects against endothelial injury by restoring the depletion of DNA methyltransferase 1 and inhibiting proteasome activities

Antony Kam; Kong M Li; Valentina Razmovski-Naumovski; Srinivas Nammi; Kelvin Chan; George Q Li

doi:10.1016/j.ijcard.2013.12.020

Gallic acid protects against endothelial injury by restoring the depletion of DNA methyltransferase 1 and inhibiting proteasome activities

Int J Cardiol. 2014 Feb 1;171(2):231-42. doi: 10.1016/j.ijcard.2013.12.020. Epub 2013 Dec 23.

Authors

Antony Kam¹, Kong M Li², Valentina Razmovski-Naumovski³, Srinivas Nammi⁴, Kelvin Chan³, George Q Li⁵

Affiliations

¹ Faculty of Pharmacy, University of Sydney, NSW 2006, Australia.
² Discipline of Pharmacology, Sydney Medical School, University of Sydney, NSW 2006, Australia.
³ 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.
⁴ 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.
⁵ Faculty of Pharmacy, University of Sydney, NSW 2006, Australia. Electronic address: george.li@sydney.edu.au.

PMID: 24388544
DOI: 10.1016/j.ijcard.2013.12.020

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.

Conclusion: 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.

Keywords: DNMT1; Endothelial injury; Gallic acid; Proteasome.

MeSH terms

Adenosine / toxicity
Cell Survival / drug effects
Cytoprotection / drug effects
DNA (Cytosine-5-)-Methyltransferase 1
DNA (Cytosine-5-)-Methyltransferases / metabolism*
Drug Interactions
Endothelial Cells / drug effects*
Endothelial Cells / enzymology
Endothelial Cells / pathology
Flow Cytometry
Gallic Acid / pharmacology*
Homocysteine / toxicity
Human Umbilical Vein Endothelial Cells
Humans
Membrane Potential, Mitochondrial / drug effects
Proteasome Endopeptidase Complex / metabolism*
Proteasome Inhibitors / pharmacology*
Tumor Necrosis Factor-alpha / toxicity
Vasodilator Agents / toxicity

Substances

Proteasome Inhibitors
Tumor Necrosis Factor-alpha
Vasodilator Agents
Homocysteine
Gallic Acid
DNA (Cytosine-5-)-Methyltransferase 1
DNA (Cytosine-5-)-Methyltransferases
DNMT1 protein, human
Proteasome Endopeptidase Complex
Adenosine