Epigenetic changes induced by adenosine augmentation therapy prevent epileptogenesis
Rebecca L. Williams-Karnesky, Ursula S. Sandau, Theresa A. Lusardi, Nikki K. Lytle, Joseph M. Farrell, Eleanor M. Pritchard, David L. Kaplan, Detlev Boison
Rebecca L. Williams-Karnesky, Ursula S. Sandau, Theresa A. Lusardi, Nikki K. Lytle, Joseph M. Farrell, Eleanor M. Pritchard, David L. Kaplan, Detlev Boison
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Research Article Neuroscience

Epigenetic changes induced by adenosine augmentation therapy prevent epileptogenesis

Abstract

Epigenetic modifications, including changes in DNA methylation, lead to altered gene expression and thus may underlie epileptogenesis via induction of permanent changes in neuronal excitability. Therapies that could inhibit or reverse these changes may be highly effective in halting disease progression. Here we identify an epigenetic function of the brain’s endogenous anticonvulsant adenosine, showing that this compound induces hypomethylation of DNA via biochemical interference with the transmethylation pathway. We show that inhibition of DNA methylation inhibited epileptogenesis in multiple seizure models. Using a rat model of temporal lobe epilepsy, we identified an increase in hippocampal DNA methylation, which correlates with increased DNA methyltransferase activity, disruption of adenosine homeostasis, and spontaneous recurrent seizures. Finally, we used bioengineered silk implants to deliver a defined dose of adenosine over 10 days to the brains of epileptic rats. This transient therapeutic intervention reversed the DNA hypermethylation seen in the epileptic brain, inhibited sprouting of mossy fibers in the hippocampus, and prevented the progression of epilepsy for at least 3 months. These data demonstrate that pathological changes in DNA methylation homeostasis may underlie epileptogenesis and reversal of these epigenetic changes with adenosine augmentation therapy may halt disease progression.

Authors

Rebecca L. Williams-Karnesky, Ursula S. Sandau, Theresa A. Lusardi, Nikki K. Lytle, Joseph M. Farrell, Eleanor M. Pritchard, David L. Kaplan, Detlev Boison

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Figure 1

ADO regulates DNA methylation through interference with the transmethylation pathway.

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ADO regulates DNA methylation through interference with the transmethyla...
(A) Biochemistry of the transmethylation reaction. (B) A single i.c.v. bolus of ADO (5 μg) or HCY (250 μg) decreases global DNA methylation in the hippocampus at 24 hours and 5 days following the injection, whereas SAM (16 μg) increases global DNA methylation at 24 hours. (C) Reduced ADK expression leads to a decrease in hippocampal DNA methylation in vivo as seen in transgenic fb-Adk-def mice with a forebrain-selective reduction of ADK. (D) The ADK inhibitor 5-ITU (3.1 mg/kg, i.p. once daily for 5 days) reduces global DNA methylation in hippocampus of WT and homozygous ADO A1R-KO mice. (E) Coadministration of the nonselective ADO receptor antagonist caffeine (Caf, 25 mg/kg, i.p.) and ITU reduces hippocampal DNA methylation in WT mice. (F) Intraventricular ADO-releasing silk (250 ng/d) decreases hippocampal DNA methylation in naive rats 5 days after implantation. (G) Overexpression of ADK leads to DNA hypermethylation in ADK-deficient BHK cells (BHK-AK2). Western blot shows protein expression from 3 pooled experimental replicates of BHK-AK2 cells transfected with the cytoplasmic (ADK-S) or nuclear (ADK-L) isoform of ADK and nontransfected control cells. Quantification of DNA methylation was assessed using 3 experimental replicates. ADK-L increases DNA methylation to a greater extent than ADK-S. Data are displayed as average ± SEM. *P < 0.05; **P < 0.01. n = 4–9.