title: α(2) noradrenergic receptor suppressed CaMKII signaling in spinal dorsal horn of mice with inflammatory pain.
abstract: Intrathecal application of α2 noradrenergic receptor agonists effectively alleviates the pathological pain induced by peripheral tissue injury. However, the spinal antinociceptive mechanisms of α2 noradrenergic receptors remain to be characterized. The present study performed immunohistochemistry and western blot to elucidate the signaling pathway initiated by α2 noradrenergic receptors in spinal dorsal horn of mice, and identified calcium/calmodulin-dependent protein kinase II (CaMKII) as an important target for noradrenergic suppression of inflammatory pain. Our data showed that intraplantar injection of Complete Freund's Adjuvant (CFA) substantially enhanced CaMKII autophosphorylation at Threonine 286, which could be abolished by intrathecal administration of α2 noradrenergic receptor agonist clonidine. Gi protein-coupled α2 noradrenergic receptor might inhibit cAMP-dependent protein kinase (PKA) to disturb CaMKII signaling. We found that pharmacological activation of PKA in intact mice also enhanced spinal CaMKII autophosphorylation level, which was completely antagonized by clonidine. Moreover, direct PKA inhibition in CFA-injected mice mimicked the suppressive effect of α2 noradrenergic receptors on CaMKII. PKA inhibition has been shown to downregulate CaMKII by enhancing protein phosphatase activity. Consistent with this notion, spinal treatment with protein phosphatase inhibitor okadaic acid ruled out clonidine-mediated CaMKII dephosphorylation in CFA-injected mice. Through PKA/protein phosphatase/CaMKII pathway, clonidine noticeably decreased CFA-evoked phosphorylation of N-methyl-d-aspartate subtype glutamate receptor GluN1 and GluN2B subunit as well as α-amino-3-hydroxy-5-methylisoxazole-4-propionic Acid subtype glutamate receptor GluA1 subunit. These data suggested that interference with CaMKII signaling might represent an important mechanism underlying noradrenergic suppression of inflammatory pain.
authors.affiliation: Department of Molecular Pharmacology, School of Pharmacy, Lanzhou University, Lanzhou 730000, Gansu, PR China.
authors.forename: Xin-Tai
authors.initials: XT
authors.lastname: Wang
authors.affiliation: Department of Molecular Pharmacology, School of Pharmacy, Lanzhou University, Lanzhou 730000, Gansu, PR China.
authors.forename: Xia
authors.initials: X
authors.lastname: Lian
authors.affiliation: Department of Molecular Pharmacology, School of Pharmacy, Lanzhou University, Lanzhou 730000, Gansu, PR China.
authors.forename: Ying-Ming
authors.initials: YM
authors.lastname: Xu
authors.affiliation: Department of Molecular Pharmacology, School of Pharmacy, Lanzhou University, Lanzhou 730000, Gansu, PR China.
authors.forename: Zhan-Wei
authors.initials: ZW
authors.lastname: Suo
authors.affiliation: Department of Molecular Pharmacology, School of Pharmacy, Lanzhou University, Lanzhou 730000, Gansu, PR China.
authors.forename: Xian
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Molecular Pharmacology, School of Pharmacy, Lanzhou University, Lanzhou 730000, Gansu, PR China. Electronic address: huxxiaodong@lzu.edu.cn.
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Hu
mesh_terms: D058647:Adrenergic alpha-2 Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D003000:Clonidine / Q000008:administration & dosage / Q000494:pharmacology*; D005620:Freund's Adjuvant; D007249:Inflammation / Q000139:chemically induced / Q000378:metabolism*; D007278:Injections, Spinal; D008297:Male; D051379:Mice; D010146:Pain / Q000139:chemically induced / Q000378:metabolism*; D020671:Posterior Horn Cells / Q000187:drug effects / Q000378:metabolism; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D005620:Freund's Adjuvant; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D003000:Clonidine
keywords: Calcium/calmodulin-dependent protein kinase II; Inflammatory pain; N-methyl-d-aspartate receptor; α(2) noradrenergic receptor; α-Amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor