PI3K modulates estrogen‐dependent facilitation of colon‐to‐urethra cross‐organ reflex sensitization in ovariectomized female rats

Abstract

J. Neurochem. (2010) 10.1111/j.1471‐4159.2010.06577.x Abstract To determine the role of 17β‐estradiol and involvement of intracellular phosphatidylinositol‐3‐kinase signaling in cross‐organ sensitization between the descending colon and the urethra, we analyzed urethra reflex activity and protein expressions in lumbosacral (L6–S2) spinal dorsal horn in response to mustard oil instillation into the descending colon in ovariectomized female rats. When compared with vehicle solution, intracolonic mustard oil sensitized the NMDA receptor NR2B subunit‐dependent reflex activity and increased expression levels of phosphorylated Akt (pAkt) and phosphorylated NR2B (pNR2B) in dorsal horn. Facilitation of reflex sensitization and increases in protein expressions of pAkt and pNR2B in dorsal horn were induced after pre‐treatment with a subcutaneous injection of 17β‐estradiol (5 μg/kg), 6 h ahead of time, when compared with vehicle solution. This phenomenon was reversed both by intrathecal pre‐treatment with ICI 182780 (0.25 mg/kg, i.t.) and LY294002 (50 mg/kg, i.t.). Immunoprecipitation of dorsal horn tissue revealed a protein‐protein interaction between pAkt and pNR2B increases, 6 h following the subcutaneous 17β‐estradiol when compared with vehicle injections. Results indicate 17β‐estradiol may activate the phosphatidylinositol‐3‐kinase cascade, which subsequently phosphorylates the NR2B subunit, via spinal estrogen receptors ERα/ERβ, to facilitate NMDA‐dependent cross‐organ sensitization, which is presumed to underlie pelvic viscero‐visceral referred pain.

Estrogen receptor (ER)-α, β and progesterone receptor (PR) mediates changes in relaxin receptor (RXFP1 and RXFP2) expression and passive range of motion of rats’ knee

“…Since serum 17 beta-estradiol concentrations vary markedly throughout the menstrual cycle, different doses of this hormone (0.2, 2, 20 and 50 g/kg), progesterone (4 mg/kg) (Gholami et al, 2013) were injected subcutaneously at the neck cuff with a 24-interval for 3 days consequently. Associated injections with the non-selective estrogen receptor (ER) antagonist ICI 182/780 25 mg/kg (Peng et al, 2010;Wakeling et al, 1991), a selective estrogen receptor beta antagonist (ER␤), 4-[2-phenyo-5,7-bis-(trifluoromrthyl)pyrazolo(1,5-a)pyrimidin-3-yl]phenol (PHTPP) 25 mg/kg, a selective estrogen receptor ␣ antagonist (1,3-bis-(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1N-pyrazole dihydrochloride) MPP 25 mg/kg (Al-Nakkash, 2012), and mifepristone 7.5 mg/kg (Baan et al, 2005) were injected subcutaneously at the neck cuff 30 min before physiologic doses of estrogen and progesterone injection. The doses of hormones administrated were based on physiological levels and antagonists doses were selected based on effective dose of previous studies.…”

EphrinB2 induces pelvic-urethra reflex potentiation via Src kinase-dependent tyrosine phosphorylation of NR2B

“…In the last decade, studies have demonstrated that the interactions between EphBRs and their ephrinB ligands modulate neural plasticity induction in the mammalian central nervous system, mainly, but not exclusively, via exhibiting effects on NMDAR (8,12). A recent study also demonstrated that, in association with thermal hyperalgesia, EphBR activation caused by immunoglobulin fusion protein of ephrinB2 (ephrinB2-Fc)-induced, Src kinase-dependent NR2B phosphorylation in the spinal cord (2), suggesting that ephrinB2-EphBR tyrosine kinase interactions could probably modulate pain signaling via spinal Src-dependent NMDAR phosphorylation (2).Although further proof is still needed for the physiological and/or pathophysiological relevance, the induction of pelvicurethra reflex potentiation (15, 16), a form of NR2B phosphorylation-dependent neural plasticity (5,25,31,41), has been linked to the development of visceral pain from pelvic organs (26,27,30,32,33). Studies have shown that the activation of nociceptive afferent fibers expressing transient receptor potential vanilloid/transient receptor potential ankyrin by the instillation of irritants into the uterus (32, 33) and the descending colon (29) facilitated pelvic-urethra reflex activity in a crossorgan manner.…”

“…Although further proof is still needed for the physiological and/or pathophysiological relevance, the induction of pelvicurethra reflex potentiation (15, 16), a form of NR2B phosphorylation-dependent neural plasticity (5,25,31,41), has been linked to the development of visceral pain from pelvic organs (26,27,30,32,33). Studies have shown that the activation of nociceptive afferent fibers expressing transient receptor potential vanilloid/transient receptor potential ankyrin by the instillation of irritants into the uterus (32, 33) and the descending colon (29) facilitated pelvic-urethra reflex activity in a crossorgan manner.…”

Sex differences and hormonal modulation of deep tissue pain

“…Stimulation of the pelvic nerve (either electrically or via colonic inflammation) increased urethra activity. The reflex was more robust in rats in proestrus compared to metestrus and was decreased by ovariectomy (Peng et al, 2010; Peng et al, 2008). The reflex was blocked by APV with greater effect in ovariectomized rats (Lin et al, 2006).…”