Journal Article

Endogenous analgesia mediated by CD4+ T lymphocytes is dependent on enkephalins in mice

Deraison, Céline, Boué, Jérôme, Dietrich, Gilles, Vergnolle, Nathalie, Basso, Lilian, Blanpied, Catherine, Robiou-du-Pont, Sébastien, Mahiddine, Karim

2016

Overview

Background T cell-derived opioids play a key role in the control of inflammatory pain. However, the nature of opioids produced by T cells is still matter of debate in mice. Whereas β-endorphin has been found in T lymphocytes by using antibody-based methods, messenger RNA (mRNA) quantification shows mainly mRNA encoding for enkephalins. The objective of the study is to elucidate the nature of T cell-derived opioids responsible for analgesia and clarify discrepancy of the results at the protein and genetic levels. Methods CD4 + T lymphocytes were isolated from wild-type and enkephalin-deficient mice. mRNA encoding for β-endorphin and enkephalin was quantified by RT-qPCR. The binding of commercially available polyclonal anti-endorphin antibodies to lymphocytes from wild-type or enkephalin knockout mice was assessed by cytofluorometry. Opioid-mediated analgesic properties of T lymphocytes from wild-type and enkephalin-deficient mice were compared in a model of inflammation-induced somatic pain by measuring sensitivity to mechanical stimuli using calibrated von Frey filaments. Results CD4 + T lymphocytes expressed high level of mRNA encoding for enkephalins but not for β-endorphin in mice. Anti-β-endorphin polyclonal IgG antibodies are specific for β-endorphin but cross-react with enkephalins. Anti-β-endorphin polyclonal antibodies bound to wild-type but not enkephalin-deficient CD4 + T lymphocytes. Endogenous regulation of inflammatory pain by wild-type T lymphocytes was completely abolished when T lymphocytes were deficient in enkephalins. Pain behavior of immune-deficient (i.e., without B and T lymphocytes) mice was superimposable to that of mice transferred with enkephalin-deficient lymphocytes. Conclusions Rabbit polyclonal anti-β-endorphin serum IgG bind to CD4 + T lymphocytes because of their cross-reactivity towards enkephalins. Thus, staining of T lymphocytes by anti-β-endorphin polyclonal IgG reported in most of studies in mice is because of their binding to enkephalins. In mice, CD4 + T lymphocytes completely lose their analgesic opioid-mediated activity when lacking enkephalins.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V
• Subject: Amino Acid Sequence / Analgesia - methods / Animals / Biomedical and Life Sciences / Biomedicine / CD4-Positive T-Lymphocytes - immunology / CD4-Positive T-Lymphocytes - metabolism / Chronic pain / Enkephalins / Enkephalins - genetics / Enkephalins - immunology / Enkephalins - metabolism / Immunoglobulin G / Immunology / Influence / Life Sciences / Male / Mice / Mice, 129 Strain / Mice, Inbred C57BL / Mice, Knockout / Neurobiology / Neurology / Neurosciences / Pain - immunology / Pain - metabolism / Pain - prevention & control / Pain Measurement - methods / Rabbits / Random Allocation / Risk factors