Increased cell apoptosis of urothelium mediated by inflammation in interstitial cystitis/painful bladder syndrome

Abstract

Objective: To investigate whether bladder inflammation could directly modulate the signaling pathway of increased urothelial cell apoptosis in interstitial cystitis/painful bladder syndrome (IC/PBS). Chronic inflammation and impaired urothelial homeostasis are possible pathogenesis of IC/PBS.

Methods: A total of 29 patients with IC/PBS and 5 control patients were enrolled in the present study. Double stain, protein array analysis, and Western blotting were performed to analyze the alterations of caspase 3, Bad, Bax, phospho-p53, phospho-p38α, and tumor necrosis factor-α (TNF-α) in bladder mucosa specimens from patients with IC/PBS and control patients. The intensities of the proteins in the arrays and Western blots were quantified using ImageJ processing. Inflammatory molecule-treated urothelial cells were analyzed using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling staining and Western blotting for the level of molecules involved in apoptosis.

Results: Phospho-p38 and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling double staining indicated that inflammatory and apoptotic events coexisted in the IC/PBS bladder. Protein-antibody array analysis showed that several inflammatory molecules were increased in the IC/PBS samples. We also found that the levels of pro-apoptotic proteins, including phospho-p53 (Ser 15), Bad, Bax, and cleaved caspase-3 were significantly increased in the IC/PBS bladders. These results were confirmed by immunoblotting and suggested that the tissue damage and abnormal urothelium in the IC/PBS bladder might be regulated concurrently by inflammatory signals, such as p38 mitogen-activated protein kinase and TNF-α. The in vitro analysis also showed that the apoptotic process could be induced by TNF-α treatment and anisomycin stimulation in normal urothelial cells.

Conclusion: Apoptosis of urothelial cells in patients with IC/PBS could result from upregulation of inflammatory signals, including p38 mitogen-activated protein kinase and TNF-α.