Mo2033 Allergic Inflammation-Induced Up-Regulation of Acid and TRPV1 Sensing in Vagal Afferent Neurons in a Guinea Pig Model of Eosinophilic Esophagitis

Abstract

pathways downstream of BDNF in bladder afferent neuronal activation in trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats. The METHODS used include induction of colitis with intracolonic instillation of TNBS (1.5 mL/kg of 60 mg/mL solution in 50 % EtOH) and Fast Blue labeling of bladder afferent neurons in these animals. TrkB was examined by immunohistochemistry and polymerase chain reaction (PCR). The intracellular signaling molecules downstream of BDNF including phospholipase C (PLC)γ, Akt, extracellular signalregulated kinase (ERK), and cAMP response element-binding (CREB) were examined by immunohistochemistry in bladder afferent neurons. We also used single cell calcium imaging and cultural of DRG neuron and glia for ex vivo studies. Our RESULTS showed that TrkB was expressed in small to medium-sized DRG neurons; in comparison, TrkB was not expressed by DRG glial cells. This was consistent with that BDNF (50 ng/mL) stimulation increased intracellular calcium level in cultured small to medium-sized DRG neurons but not in DRG glial cells, and a selective TrkB agonist 7,8-Dihydroxyflavone (1 μM) had the same effect in these cells. At 7 days of colitis, the elevated level of TrkB in bladder afferent neurons may enhance the responsiveness of these neurons to BDNF. Among the intracellular signaling molecules downstream of BDNF/TrkB, the expression level of PLCγ (not Akt or ERK) was increased in specifically labeled bladder afferent neurons during colitis, suggesting an involvement of calcium pathways in colitis-induced bladder afferent activation. At 7 days of colitis, the phosphorylation (activation) level of CREB, a calcium-dependent transcription factor, was also increased in bladder afferent neurons. BDNF stimulation of DRG explants increased the level of phospho-CREB in DRG neurons. CONCLUSION: BDNF-mediated bladder overactivity during colitis involves activation of the PLCγ/calcium pathways in bladder afferent neurons.