A Doetzlhofer

Assam El-Osta

B Osterlund

BD Strahl

BR Henderson

C Van Lint

CJ Phiel

DE Newby

EA Jaffe

Erik Ulfhammer

GP Van Guilder

J Arts

JA Muldowney 3rd

JB Olesen

JM Mariadason

KN Harikrishnan

L Rossig

Lena Karlsson

M Gottlicher

M Michaelis

M Shogren-Knaak

M Takakura

MD Shahbazian

Mia Magnusson

N Gurvich

Niklas Bergh

P Ladenvall

Per-Arne Svensson

Pia Larsson

Pieter H. Reitsma

RL Medcalf

Robert L. Medcalf

S Chateauvieux

S Dunoyer-Geindre

S Kathiresan

S Kim

Sebastian Lunke

Sverker Jern

T Hrafnkelsdottir

T Kooistra

W Huang

W Ridderstrale

Y Sowa

Y Zhang

Z Marinova

PLoS ONE

English

PubMed

Epigenetic mechanisms, such as DNA methylation and histone modifications, constitute one way for a cell or an organism to respond to changes in the surrounding
environment. While histone modifications are recognized to be quite dynamic, DNA
methylation has been considered a more stable, or long-term, modification.
Ischaemic heart disease and stroke are major causes of morbidity and mortality in the Western world. In the majority of cases, these conditions are caused by intra-arterial clot formation, which can occur because the components of the haemostatic system are out of balance. This can be caused by either genetic or life-style issues. With this thesis, I have focused on epigenetic regulation of genes in endothelial cells, specifically the PLAT gene which encodes the key fibrinolytic enzyme tissue-type plasminogen
activator (t-PA).
In Study I, we found that the expression from PLAT was induced when endothelial cells were treated with the histone deacetylase inhibitor valproic acid (VPA), and that this indeed was associated with increased acetylation levels around the t-PA promoter. In patients, a defective t-PA expression results in an increased risk of suffering from myocardial infarctions, and the findings in Study I open up for a new possible treatment regimen.
In Study II and III, we used sub-culturing of primary human umbilical vein endothelial cells (HUVECs) as a model of environmental challenge to study how this affects the DNA methylation level, around the t-PA gene (Study II) as well as genome-wide (Study III). In Study II, we found that the DNA methylation level decreased in the
t-PA enhancer, but not in the promoter nor in the region immediately upstream of the promoter. This enhancer demethylation was in strong negative correlation with an increase
in t-PA gene expression. Thus, methylation in the t-PA enhancer may constitute a previously unrecognized way to regulate the expression of this essential fibrinolytic enzyme.
In Study III, we went on to examine how sub-culturing of HUVECs changed the genome-wide methylation level. We discovered that to passage 4, almost 2% of the investigated sites showed dynamic methylation, mostly displaying decreasing levels. The majority of the differentially methylated sites (DMSs) were annotated as “enhancer”. In addition, we found that several gene ontology terms were highly enriched for among the genes with DMSs situated in their enhancers. Taken together, this indicates that the demethylation process was not random, and that it occured quite fast.
We suggest that the fibrinolytic enzyme t-PA is dynamically regulated on a transcriptional
level by both histone acetylation and DNA methylation, which is important in order for the production of this key enzyme to be able to be rapidly modified locally. We also propose that DNA methylation in endothelial cells is more dynamic than previously recognized, as high levels rapidly can be erased

Magnusson, Mia

Göteborgs universitets publikationer - e-publicering och e-arkiv

Epigenetic regulation of gene expression in the vascular endothelium

 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. this substance may be a candidate for pharmacological modulation of endogenous fibrinolysis in man

Larsson Pia

Ulfhammer Erik

Magnusson Mia

Bergh Niklas

Lunke Sebastian

El-Osta Assam

Medcalf Robert L.

Svensson Per-Arne

Karlsson Lena

Jern Sverker

Public Library of Science (PLOS)

Role of Histone Acetylation in the Stimulatory Effect of Valproic Acid on Vascular Endothelial Tissue-Type Plasminogen Activator Expression

Larsson, Pia

Ulfhammer, Erik

Bergh, Niklas

Lunke, Sebastian

El-Osta, Assam

Medcalf, Robert

Svensson, Per Arne

Karlsson, Lena

Jern, Sverker

Monash University Research Repository

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

AIMS: 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. METHODS AND RESULTS: 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. CONCLUSIONS: 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

Larsson, P

Ulfhammer, E

Magnusson, M

Bergh, N

Lunke, S

El-Osta, A

Medcalf, RL

Svensson, P-A

Karlsson, L

Jern, S

University of Melbourne Institutional Repository

Aims: 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. Methods and Results: 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. Conclusions: 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

Medcalf, Robert Lindsay

Monash University Research Portal

Robert L Medcalf

Directory of Open Access Journals

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

Crossref

<div><h3>Aims</h3><p>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 <em>in vitro</em> in vascular endothelial cells, and further examined if its histone deacetylase (HDAC)-inhibitory activity is of importance for regulating t-PA expression.</p> <h3>Methods and Results</h3><p>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.</p> <h3>Conclusions</h3><p>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 <em>in vitro</em> this substance may be a candidate for pharmacological modulation of endogenous fibrinolysis in man.</p> </div

Pia Larsson (182240)

Erik Ulfhammer (182243)

Mia Magnusson (182244)

Niklas Bergh (182247)

Sebastian Lunke (182250)

Assam El-Osta (182253)

Robert L. Medcalf (7348)

Per-Arne Svensson (157540)

Lena Karlsson (182257)

Sverker Jern (182261)

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Common genetic variation in five thrombosis genes and relations to plasma hemostatic protein level and cardiovascular disease risk.

Tissue-type plasminogen activator 27,351C/T enhancer polymorphism is associated with a first myocardial infarction.

http://minerva-access.unimelb.edu.au/bitstream/11343/262879/1/PMC3282745.pdf

Role of Histone Acetylation in the Stimulatory Effect of Valproic Acid on Vascular Endothelial Tissue-Type Plasminogen Activator Expression

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Göteborgs universitets publikationer - e-publicering och e-arkiv

Public Library of Science (PLOS)

Monash University Research Repository

University of Melbourne Institutional Repository

Public Library of Science (PLOS)

Monash University Research Portal

Directory of Open Access Journals

Crossref

FigShare