Inflammatory-linked changes in CpG island methylation of three opioid peptide genes in a rat model for pain.

Charlotte Louise Justine Jacobi,Christoph Stein,Robert Blum

doi:10.1371/journal.pone.0191698

Charlotte Louise Justine Jacobi, Christoph Stein + Show 1 more

Open Access

https://doi.org/10.1371/journal.pone.0191698

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Journal: PloS one	Publication Date: Jan 19, 2018
Citations: 5	License type: CC BY 4.0

Affiliation: Charité - Universitätsmedizin Berlin

Abstract

Expression of the opioid peptide genes proopiomelanocortin (Pomc), proenkephalin (Penk), and prodynorphin (Pdyn), in immune cells plays a key role in endogenous pain control. In a rat model of painful unilateral paw inflammation, we isolated cells from popliteal lymph nodes and evaluated the role of CpG island C5-methylation on the transcriptional activation of those genes. Using methylated DNA immunoprecipitation, we sorted gDNA into methylated (me) and non-me fractions and then determined the CpG island methylation status of each fraction via quantitative Real Time-PCR (qRT-PCR). In silico analysis by MethPrimer software identified one CpG island in Pdyn and three each in Pomc and Penk. No substantial changes in C5-methylation of any gene were observed. In conclusion, the CpG island methylation status does not seem to be a key regulator of opioid gene activation in immune cells during peripheral tissue inflammation.

Highlights

The expression of endogenous opioid peptides in peripheral tissue can play an important role in pain control [1,2,3]
The opioid peptides END, MENK and Dynorphin A (DynA) are encoded by proopiomelanocortin (Pomc), proenkephalin (Penk) and prodynorphin (Pdyn), respectively
Using the MethPrimer software for identifying CpG islands within the three opioid peptide coding rat genes, three CpG islands were found in each Pomc and Penk, and one in Pdyn (Fig 1A) (Table 1)

Summary

Introduction

The expression of endogenous opioid peptides in peripheral tissue can play an important role in pain control [1,2,3]. Immune cells express the three opioid peptides beta-endorphin (END), Met-enkephalin (MENK) and Dynorphin A (DynA) [4,5,6,7,8,9,10]. Upon their release, antinociception is triggered through binding of the opioid peptides to their corresponding receptors on peripheral sensory nerve endings [11,12]. The opioid peptides END, MENK and DynA are encoded by proopiomelanocortin (Pomc), proenkephalin (Penk) and prodynorphin (Pdyn), respectively. All endogenous opioids are synthesized site- in various organs [16,17,18,19]

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