Granulocyte-macrophage colony-stimulating factor (GM-CSF) is released by female mouse bladder urothelial cells and expressed by the urothelium as an early response to lipopolysaccharides (LPS)

Aims: We studied in vitro and in vivo response of primary mouse bladder urothelial cells (mBUC) and bladder urothelium to lipopolysaccharides (LPS), focusing on granulocyte-macrophage colony-stimulating factor (GM-CSF) signaling. Methods: Female C57BL/6 mBUC were exposed for 12 hr to differing concentrations of LPS (100 ng/ml to 10 µg/ml). mBUC were also exposed to a single dose of LPS (1 µg/ml) for 3, 6, 12 hr. Neutralizing GM-CSF antibody (0.1 μg/ml) was used block GM-CSF activity in vitro. In vivo experiments were performed, whereby, LPS (1 mg/ml) was instilled intravesically and left to dwell for 30 min followed by harvest of bladder urothelium 3 to 18 hr later. ELISA measured GM-CSF. qPCR quantitated mRNA for GM-CSF, vascular endothelial growth factor-A (VEGF-A), cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), and tumor necrosis factor α (TNF-α). RT-PCR was used to detect mRNA for GM-CSF, GM-CSFRα, and β in bladder tissues. Immunohistofluorescence and Western blots for GM-CSFRα were performed on bladder tissues. Results: LPS induced a dose-dependent release of GM-CSF by mBUC. Mouse bladder urothelium did not express GM-CSF mRNA at baseline, but expressed GM-CSF mRNA 3 hr after in vivo LPS exposure, with GM-CSF mRNA expression disappearing 18 hr later. GM-CSFRα expression was confirmed in bladder urothelium. GM-CSF neutralizing antibody significantly diminished LPS-induced increases of VEGF and COX-2 mRNA expression. Conclusions: Urothelium and mBUC secreted GM-CSF as an early response to LPS. GM-CSF mediated downstream expression of VEGF and COX-2. Urothelial GM-CSF may function as a signaling mediator for both inflammation and pain transduction. Neurourol. Urodynam. 36:1020–1025, 2017.