Exp Mol Med.  2018 Feb;50(2):e445. 10.1038/emm.2017.271.

Macrophage migration inhibitory factor mediates peripheral nerve injury-induced hypersensitivity by curbing dopaminergic descending inhibition

Affiliations
  • 1Department of Anesthesiology, Obstetrics and Gynecology Hospital, Affiliated to Nanjing Medical University, Nanjing, China. fred.wang@basehq.org
  • 2Department of Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
  • 3Institute of Pediatrics, Obstetrics and Gynecology Hospital, Affiliated to Nanjing Medical University, Nanjing, China.
  • 4Group of Neuropharmacology and Neurophysiology, Division of Neuroscience, The Bonoi Academy of Science and Education, Chapel Hill, NC, USA.
  • 5Department of Neurology, Qinghai Provincial People’s Hospital, Xining, China. wushizheng2005@hotmail.com

Abstract

Our previous works disclosed the contributing role of macrophage migration inhibitory factor (MIF) and dopaminergic inhibition by lysine dimethyltransferase G9a/Glp complex in peripheral nerve injury-induced hypersensitivity. We herein propose that the proinflammatory cytokine MIF participates in the regulation of neuropathic hypersensitivity by interacting with and suppressing the descending dopaminergic system. The lumbar spinal cord (L-SC) and ventral tegmental area (VTA) are two major locations with significant upregulation of MIF after chronic constriction injury (CCI) of the sciatic nerve, and they display time-dependent changes, along with a behavioral trajectory. Correspondingly, dopamine (DA) content shows the reverse characteristic change to MIF with a time-dependent curve in post-surgical behavior. The levels of both MIF and DA are reversed by the MIF tautomerase inhibitor ISO-1, and a negative relationship exists between MIF and DA. The reversed role of ISO-1 also affects tyrosine hydroxylase expression. Furthermore, CCI induces Th promoter CpG site methylation in the L-SC and VTA areas, and this effect could be abated by ISO-1 administration. G9a/SUV39H1 and H3K9me2/H3K9me3 enrichment within the Th promoter region following CCI in the L-SC and VTA was also decreased by ISO-1. In cultured dopaminergic neurons, rMIF enhanced the recruitment of G9a and SUV39H1, followed by an increase in H3K9me2/H3K9me3. These molecular changes correspondingly exhibited alterations in Th promoter CpG site methylation and pain behaviors. In summary, MIF functions as a braking factor in curbing dopaminergic descending inhibition in peripheral nerve injury-induced hypersensitivity by mediating Th gene methylation through G9a/SUV39H1-associated H3K9 methylation.


MeSH Terms

Constriction
Dopamine
Dopaminergic Neurons
Hypersensitivity*
Lysine
Macrophages*
Methylation
Negotiating
Peripheral Nerves*
Promoter Regions, Genetic
Sciatic Nerve
Spinal Cord
Tyrosine 3-Monooxygenase
Up-Regulation
Ventral Tegmental Area
Dopamine
Lysine
Tyrosine 3-Monooxygenase
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