Elevated levels of DNA methylation at the OPRM1 promoter in blood and sperm from male opioid addicts

Abstract

Objective The OPRM1 gene was studied for DNA methylation in opioid dependence and possible paternal contribution to epigenetic inheritance of altered methylation profiles. Participants and methods DNA was extracted from blood and sperm from 13 male opioid addicts and 21 male control subjects. DNA methylation was determined by pyrosequencing in 24 CpG sites at the OPRM1 promoter region. Results The authors found significantly increased overall methylation in blood DNA from addicted subjects (Kruskal-Wallis [K-W] p = 0.013) Seven CpG sites showed significantly hypermethylated blood DNA from cases when compared with blood DNA controls (p < 0.05 at CpGs 5, 9, 10, 11, 18, 23, and 24). In sperm-derived DNA from addicts, the methylation was significantly increased at CpG 2 (p = 0.012), and overall methylation did not reach significant difference ( K-W p = 0.523). Conclusions Increased DNA methylation in the OPRM1 gene is associated with opioid dependence. Hypermethylated CpG sites located in OPRM1 promoter may potentially block the binding of Sp1 and other transcription activators, thus leading to OPRM1 silencing. The increased DNA methylation in sperm may suggest a way of epigenetic heritability of opioid abuse or dependence phenotypes.

Multigenerational and transgenerational inheritance of drug exposure: The effects of alcohol, opiates, cocaine, marijuana, and nicotine

“…Hypomethylation at LINE-1 retrotransposons has been identified in leukocytes of chronic heroin users (Doehring et al, 2013) and in neuronal cell lines (Trivedi et al, 2014); consequently, LINE-1 mRNA expression increases (Trivedi et al, 2014). In contrast, increased CpG methylation has been reported in lymphocytes, blood, and sperm of chronic heroin users in the promoter region of the OPRM1 gene (Chorbov et al, 2011; Nielsen et al, 2008). Thus, morphine administration can lead to both increased and decreased DNA methylation in a gene-dependent manner in the individual user.…”

“…In addition to methylation and acetylation modifications of histones, morphine exposure induces methylation changes on DNA directly (Nielsen et al, 2008; Chorbov et al, 2011; Doehring et al, 2013; Trivedi et al, 2014). Morphine modulates cellular oxidative stress and methyl group donation through the antioxidant glutathione and the methyl donor SAM, respectively (Trivedi et al, 2014).…”

OPRM1 Methylation Contributes to Opioid Tolerance in Cancer Patients

“…Our finding of OPRM1 hypermethylation in peripheral leukocytes from cancer patients receiving opioids is consistent with previous studies that found OPRM1 hypermethylation in peripheral leukocytes of opioid-addicted patients. 2 The statistical methods for the analysis of DNA methylation are evolving. A persistent challenge in estimating biological differences in DNA methylation is that CpG sites rarely act independently, but rather neighboring clusters of CpG are jointly methylated.…”

“…17 Studies of heroin users found that high opioid use correlates with downregulation of the mu-opioid receptor on circulating leukocytes. 2 In addition, we showed in a cancer mouse model that the mu-opioid receptor is downregulated on the dorsal root ganglia (DRG) that innervate the cancer, even in opioid-naive animals. 31 Moreover, we demonstrated that epigenetic silencing of the mu-opioid receptor gene ( OPRM1 ) in cancer cells exacerbates cancer pain, and that reversal of OPRM1 gene silencing in the cancer produces antinociception.…”

Epigenetically modified nucleotides in chronic heroin and cocaine treated mice

“…Most of the studies published until today, focus on specific genes (Barros et al, 2013), with a special interest in the OPRM1 (Nielsen et al, 2009. In one case it was reported that the OPRM1 gene was significantly hypermethylated not only in blood, but also in sperm-derived DNA, suggesting that this epigenetic phenomenon may be the mechanism by which opioid abuse and dependence phenotypes are transferred to the next generation (Chorbov et al, 2011). In another study, it was shown that in the brain of chronic opiate addicts, enhanced methylation of the OPRM1 DNA hinders the μ-opioid receptor upregulation.…”