Role of histone acetylation in the stimulatory effect of valproic acid on vascular endothelial tissue-type plasminogen activator expression

• Published in: PloS one Vol. 7; no. 2; p. e31573
• Main Authors: Larsson, Pia, Ulfhammer, Erik, Magnusson, Mia, Bergh, Niklas, Lunke, Sebastian, El-Osta, Assam, Medcalf, Robert L, Svensson, Per-Arne, Karlsson, Lena, Jern, Sverker
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 20.02.2012; Public Library of Science (PLoS)
• Subjects: Acetates; Acetylation; Acetylation - drug effects; Acids; Analysis; Binding sites; Biology; Cell culture; Chromatin; Chromatin Immunoprecipitation; Clinical Medicine; Consent; Coronary Vessels - cytology; Deoxyribonucleic acid; Diabetes; DNA; Education; Endothelial cells; Endothelium; Endothelium, Vascular - drug effects; Endothelium, Vascular - enzymology; Enzymes; Epigenetics; Epilepsy; Experiments; Fibrin; Fibrinolysis; Gene expression; Gene Expression Regulation - drug effects; Gene Knockdown Techniques; Growth factors; Heart attacks; Heat shock proteins; Hemostasis - drug effects; Hemostasis - genetics; Histone deacetylase; Histone Deacetylase Inhibitors - pharmacology; Histone Deacetylases - metabolism; Histones - metabolism; Human Umbilical Vein Endothelial Cells - cytology; Human Umbilical Vein Endothelial Cells - drug effects; Human Umbilical Vein Endothelial Cells - enzymology; Humans; Hypotheses; Immunoprecipitation; Klinisk medicin; Laboratories; Medical research; Medicine; Pharmacology; Promoter Regions, Genetic - genetics; Protein folding; Review boards; RNA; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA, Small Interfering - metabolism; siRNA; Thromboembolism; Thrombosis; Tissue Plasminogen Activator - genetics; Tissue Plasminogen Activator - metabolism; Tissue Plasminogen Activator - secretion; Transcription; Umbilical cord; Valproic acid; Valproic Acid - pharmacology
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0031573

Stimulated release of tissue-type plasminogen activator (t-PA) is pivotal for an intravascular fibrinolytic response and protects the circulation from occluding thrombosis. Hence, an impaired t-PA production is associated with increased risk for atherothrombotic events. A pharmacological means to stimulate the production of this enzyme may thus be desirable. We investigated if the anti-epileptic drug valproic acid (VPA) is capable of enhancing t-PA expression in vitro in vascular endothelial cells, and further examined if its histone deacetylase (HDAC)-inhibitory activity is of importance for regulating t-PA expression. Human endothelial cells were exposed to valproic acid and t-PA mRNA and protein levels were quantified. Potential changes in histone acetylation status globally and at the t-PA promoter were examined by western blot and chromatin immunoprecipitation. Valproic acid dose-dependently stimulated t-PA mRNA and protein expression in endothelial cells reaching a 2-4-fold increase at clinically relevant concentrations and 10-fold increase at maximal concentrations. Transcription profiling analysis revealed that t-PA is selectively targeted by this agent. Augmented histone acetylation was detected at the t-PA transcription start site, and an attenuated VPA-response was observed with siRNA knock of HDAC3, HDAC5 and HDAC7. Valproic acid induces t-PA expression in cultured endothelial cells, and this is associated with increased histone acetylation at the t-PA promoter. Given the apparent potency of valproic acid in stimulating t-PA expression in vitro this substance may be a candidate for pharmacological modulation of endogenous fibrinolysis in man.