Login to Access Video or Poster Abstract: MP26-09
Sources of Funding: none

Introduction

Although several studies have suggested that chronic bladder inflammation associated with oxidative stress contribute to overactive bladder (OAB), the underlying pathophysiological mechanism is unclear. Recently, the toll-like receptor (TLR) 4 has been reported to play a role in triggering chronic inflammatory conditions through activation of NLRP3 inflammasome pathways followed by production of IL1β and IL18. Although oxidative stress is one of factors that activate TLR4, it is not known whether changes in the expression of TLR4 are involved in the development of OAB caused by chronic inflammation. We therefore investigated an alteration of histopathology and expression of TLR4 and NLRP3 inflammasome-related molecules in the bladder using spontaneously hypertensive rats (SHRs) as an OAB model.

Methods

Twenty-weeks-old male SHRs and Wistar Kyoto rats (control) were used. After voiding function was analyzed by using metabolic cages, the bladder was excised for analysis of histopathology and mRNA expression. Hematoxylin eosin and Masson&[prime]s trichrome stain were performed to analyze bladder inflammatory condition and fibrosis. Immunohistostaining for NLRP3, TLR4 was also performed. Expression levels of NLRP3, IL1β, IL-18, IL6, IL8 and TGFβ mRNA in the bladder were investigated by real-time PCR. Statistical analysis was performed using Mann-Whitney U test. P value less than 0.05 was considered statistically significant.

Results

In voiding function analyses, single urine volume was significantly decreased and voiding frequency was significantly increased in SHRs compared to control rats. In histological evaluation, suburothelial fibrosis was shown in SHRs compared to controls. Furthermore, immunohistostaining showed localized expression of NLRP3 and TLR4 in the bladder urothelium in both groups. In RT-qPCR analyses, mRNA expression levels of NLRP3, TLR4, IL1β, IL-18, IL6, IL8 and TGFβ were significantly increased in SHRs in the bladder compared to controls.

Conclusions

These results suggest that activation of TLR4 associated with oxidative stress is implicated in bladder chronic inflammation, which leads to frequent urination through NLRP3 inflammasome pathways. Therefore, further clarification of interactions between TLR4 and inflammasome pathways may offer new therapeutic targets for OAB associated with chronic inflammation.

Funding

none