title: Endogenous PI3K/Akt and NMDAR act independently in the regulation of CREB activity in lumbosacral spinal cord in cystitis.
abstract: The integral interaction of signaling components in the regulation of visceral inflammation-induced central sensitization in the spinal cord has not been well studied. Here we report that phosphoinositide 3-kinase (PI3K)-dependent Akt activation and N-methyl-d-aspartic acid receptor (NMDAR) in lumbosacral spinal cord independently regulate the activation of cAMP response element-binding protein (CREB) in vivo in a rat visceral pain model of cystitis induced by intraperitoneal injection of cyclophosphamide (CYP). We demonstrate that suppression of endogenous PI3K/Akt activity with a potent PI3K inhibitor LY294002 reverses CYP-induced phosphorylation of CREB, however, it has no effect on CYP-induced phosphorylation of NR1 at Ser(897) and Ser(896); conversely, inhibition of NMDAR in vivo with MK801 fails to block CYP-induced Akt activation but significantly attenuates CYP-induced CREB phosphorylation in lumbosacral spinal cord. This novel interrelationship of PI3K/Akt, NMDAR, and CREB activation in lumbosacral spinal cord is further confirmed in an ex vivo spinal slice culture system exposed to an excitatory neurotransmitter calcitonin gene-related peptide (CGRP). Consistently we found that CGRP-triggered CREB activation can be blocked by both PI3K inhibitor LY294002 and NMDAR antagonists MK801 and D-AP5. However, CGRP-triggered Akt activation cannot be blocked by MK801 or D-AP5; vice versa, LY294002 pretreatment that suppresses the Akt activity fails to reverse CGRP-elicited NR1 phosphorylation. These results suggest that PI3K/Akt and NMDAR independently regulate spinal plasticity in visceral pain model, and target of a single pathway is necessary but not sufficient in treatment of visceral hypersensitivity.
authors.affiliation: Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia.
authors.forename: Jarren C
authors.initials: JC
authors.lastname: Kay
authors.affiliation: Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia.
authors.forename: Chun-Mei
authors.initials: CM
authors.lastname: Xia
authors.affiliation: Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia.
authors.forename: Miao
authors.initials: M
authors.lastname: Liu
authors.affiliation: Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia.
authors.forename: Shanwei
authors.initials: S
authors.lastname: Shen
authors.affiliation: Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia.
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Yu
authors.affiliation: Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia.
authors.forename: Chulwon
authors.initials: C
authors.lastname: Chung
authors.affiliation: Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia.
authors.forename: Li-Ya
authors.initials: LY
authors.lastname: Qiao
mesh_terms: D000818:Animals; D015153:Blotting, Western; D059333:Central Nervous System Sensitization / Q000502:physiology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D003556:Cystitis / Q000378:metabolism* / Q000503:physiopathology; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D008161:Lumbosacral Region; D008297:Male; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013116:Spinal Cord / Q000378:metabolism*
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D016194:Receptors, N-Methyl-D-Aspartate; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt
keywords: Akt; CREB; Central sensitization; NMDAR; Spinal cord