Inhibition of DNA methyltransferases regulates cocaine self‐administration by rats: a genome‐wide DNA methylation study

Abstract

DNA methylation is a major epigenetic process which regulates the accessibility of genes to the transcriptional machinery. In the present study, we investigated whether modifying the global DNA methylation pattern in the brain would alter cocaine intake by rats, using the cocaine self-administration test. The data indicate that treatment of rats with the DNA methyltransferase inhibitors 5-aza-2'-deoxycytidine (dAZA) and zebularine enhanced the reinforcing properties of cocaine. To obtain some insights about the underlying neurobiological mechanisms, a genome-wide methylation analysis was undertaken in the prefrontal cortex of rats self-administering cocaine and treated with or without dAZA. The study identified nearly 189 000 differentially methylated regions (DMRs), about half of them were located inside gene bodies, while only 9% of DMRs were found in the promoter regions of genes. About 99% of methylation changes occurred outside CpG islands. Gene expression studies confirmed the inverse correlation usually observed between increased methylation and transcriptional activation when methylation occurs in the gene promoter. This inverse correlation was not observed when methylation took place inside gene bodies. Using the literature-based Ingenuity Pathway Analysis, we explored how the differentially methylated genes were related. The analysis showed that increase in cocaine intake by rats in response to DNA methyltransferase inhibitors underlies plasticity mechanisms which mainly concern axonal growth and synaptogenesis as well as spine remodeling. Together with the Akt/PI3K pathway, the Rho-GTPase family was found to be involved in the plasticity underlying the effect of dAZA on the observed behavioral changes.

5-Aza-2’-deoxycytidine in the medial prefrontal cortex regulates alcohol-related behavior and Ntf3-TrkC expression in rats

“…5-Aza-dc is well known to be cytotoxic and its toxicity depends on the dosage and exposure time [26]. Relevant research has shown that in the concentration range of 0.1ug/ulto 2ug /ul in specific brain region [22, 23, 27, 28], 5-Aza-dc did not interfere with the locomotor activities of rats, in line with our OFT results. In addition, our results suggest that 5-Aza-dc (1μg /0.5μl/side) in the mPFC do not affect the total fluid intake (Fig 4E) or body weight (S1 Fig) of rats.…”

DNA Methylation Dynamics and Cocaine in the Brain: Progress and Prospects

“…Using an antibody pulldown specific to 5hmC (hMeDip-seq), this group identified over 10,000 peaks of differential hydroxymethylation in the mouse NAc. As was the case with methylome studies [53,68], the majority of cocaine-induced changes in 5hmC occurred in gene bodies and intergenic regions. Combining this dataset with chromatin state information revealed that 5hmC changes were enriched at enhancer sites and regions that frequently switched chromatin states in the cocaine or control groups [47].…”

“…In a second PFC study, Fonteneau and colleagues [68] trained rats to self-administer cocaine, either alone or after intra-ventricular injections of DNMT inhibitors. As was seen in mice, self-administration resulted in numerous DMRs, most of which fell within gene bodies and intergenic regions.…”

“…Although the paradigm and brain region differ from the Fonteneau study [68], the Feng study [47] described earlier (see Section 2.4) investigated genome-wide hydroxymethylation changes in response to cocaine. Using an antibody pulldown specific to 5hmC (hMeDip-seq), this group identified over 10,000 peaks of differential hydroxymethylation in the mouse NAc.…”

Genome-Wide DNA Methylation Analysis in Male Methamphetamine Users With Different Addiction Qualities

“…Disturbances in epigenetics, particularly DNA methylation, have been implicated in the pathophysiology of several psychiatric disorders, such as eating disorders (11), depression (12), schizophrenia (13), cocaine addiction (14), and alcohol dependence (15). Epigenetic research on MA addiction is at a relatively early stage, far behind that of cancer or other complex disorders, and far behind that of cocaine, heroin, and other substance abuse.…”