Epigenetic upregulation of metabotropic glutamate receptor 2 in the spinal cord attenuates oestrogen-induced visceral hypersensitivity.
OBJECTIVE
Epigenetic mechanisms are potential targets to relieve somatic pain. However, little is known whether epigenetic regulation interferes with visceral pain. Previous studies show that oestrogen facilitates visceral pain. This study aimed to determine whether histone hyperacetylation in the spinal cord could attenuate oestrogen-facilitated visceral pain.


METHODS
The effect of the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) on the magnitude of the visceromotor response (VMR) to colorectal distention was examined in ovariectomised rats with/without oestrogen replacement. An additional interaction with the metabotropic glutamate receptor 2/3 (mGluR2/3) antagonist LY341495 was tested. The levels of acetylated histone and mGluR2 mRNA and protein were analysed. The binding of acetylated H3 and oestrogen receptor α (ERα) to the GRM2 promoter was measured by chromatin immunoprecipitation coupled with qPCR.


RESULTS
In ovariectomised rats, 17β-estradiol (E2), but not safflower oil, increased the magnitude of the VMR to colorectal distention. SAHA attenuated the E2-facilitated VMR, but had no effect in safflower oil-treated rats. Subsequent spinal administration of LY341495 reversed the antinociceptive effect of SAHA in E2 rats. In addition, SAHA increased mGluR2 mRNA and protein in the spinal dorsal horn following E2, but not vehicle, treatment. In contrast, neither E2 nor SAHA alone altered mGluR2 mRNA. SAHA increased binding of H3K9ac and ERα to the same regions of the GRM2 promoter in E2-SAHA-treated animals.


CONCLUSIONS
Histone hyperacetylation in the spinal cord attenuates the pronociceptive effects of oestrogen on visceral sensitivity, suggesting that epigenetic regulation may be a potential approach to relieve visceral pain.
Department of Neural and Pain Sciences, University of Maryland School of Dentistry, UM Center to Advance Chronic Pain Research, Baltimore, Maryland, USA.
Dong-Yuan
DY
Cao
Department of Neural and Pain Sciences, University of Maryland School of Dentistry, UM Center to Advance Chronic Pain Research, Baltimore, Maryland, USA.
Guang
G
Bai
Department of Neural and Pain Sciences, University of Maryland School of Dentistry, UM Center to Advance Chronic Pain Research, Baltimore, Maryland, USA.
Yaping
Y
Ji
Department of Neural and Pain Sciences, University of Maryland School of Dentistry, UM Center to Advance Chronic Pain Research, Baltimore, Maryland, USA.
Richard J
RJ
Traub
D000107:Acetylation / Q000187:drug effects; D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D004195:Disease Models, Animal; D044127:Epigenesis, Genetic / Q000187:drug effects*; D004958:Estradiol / Q000494:pharmacology; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006657:Histones / Q000378:metabolism*; D006877:Hydroxamic Acids / Q000494:pharmacology; D059225:Nociception / Q000187:drug effects / Q000502:physiology; D010052:Ovariectomy; D012333:RNA, Messenger; D051381:Rats; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects; D014781:Viscera / Q000187:drug effects / Q000503:physiopathology; D059265:Visceral Pain / Q000235:genetics* / Q000378:metabolism; D000077337:Vorinostat; D014966:Xanthenes / Q000494:pharmacology
D000596:Amino Acids; D004967:Estrogens; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D006877:Hydroxamic Acids; C114624:LY 341495; D012333:RNA, Messenger; D018094:Receptors, Metabotropic Glutamate; D014966:Xanthenes; C108822:metabotropic glutamate receptor 2; C102718:metabotropic glutamate receptor 3; D004958:Estradiol; D000077337:Vorinostat
IRRITABLE BOWEL SYNDROME; NEUROPHARMACOLOGY; SEX STEROIDS; VISCERAL HYPERSENSITIVITY; VISCERAL NOCICEPTION