Increased susceptibility to bladder inflammation in smokers: targeting the PAF-PAF receptor interaction to manage inflammatory cell recruitment

Abstract

Chronic bladder inflammation can result in a significant reduction in quality of life. Smoking remains a leading preventable risk factor in many diseases. Despite the large amount of evidence supporting the risks of smoking, roughly 45 million people in the United States remain smokers. The impact of cigarette smoking on inflammation is well established, but how smoking promotes bladder inflammation is currently unknown. The aim of this study was to determine if cigarette smoke exposure impacts inflammatory cell adherence to bladder endothelial cells and if targeting the platelet-activating factor (PAF)-PAF receptor (PAFR) interaction could be beneficial in managing bladder inflammation. In response to cigarette smoke extract (CSE) incubation, bladder endothelial cells from human or mouse displayed increased PAF accumulation, decreased PAF-AH activity, and increased inflammatory cell adherence. Inhibition of endothelial cell calcium-independent phospholipase A2β (iPLA2β) with (S)-BEL, to block PAF production, prevented adherence of inflammatory cells. Pretreatment of inflammatory cells with PAFR antagonists, ginkgolide B or WEB2086 significantly reduced the number of adhered cells to bladder endothelium. Wild-type mice exposed to cigarette smoke displayed increased presence of inflammatory infiltration which was absent in iPLA2β(-/-) mice and those exposed to room air. In conclusion, cigarette smoke exposure increases endothelial cell PAF accumulation and increased inflammatory cell adherence. Inhibition of PAF accumulation or PAFR antagonism markedly attenuated inflammatory cell adherence to bladder endothelial cells. The results detailed in this study highlight to potential therapeutic targets for managing bladder inflammation.

Keywords: Endothelium; inflammation; interstitial cystitis; smoking.

Figure 1

Human bladder microvascular endothelial cells exposed to CSE (20 μg/mL). (A) PAF accumulation. (B) PAF‐AH Activity. *P < 0.05, **P < 0.01 when compared to control. n = 4. Data are means ± SE.

Figure 2

PMN Adherence to human bladder microvascular endothelial cells exposed to CSE (20 μg/mL). (A) PMN Adherence. (B) PMN adherence with iPLA ₂ inhibitors. ⁺⁺ P < 0.01 when comparing data in the presence and absence of iPLA ₂ inhibitors. (C) PMN adherence with PAF receptor antagonists. *P < 0.05, **P < 0.01 when compared to control. ⁺⁺ P < 0.01 when comparing data in the presence and absence of PAF receptor antagonists. n = 4. Data are means ± SE.

Figure 3

Cell surface expression of adhesion molecule in human bladder microvascular endothelial cells exposure to CSE (20 μg/mL). **P < 0.01 when compared to control. n = 8.

Figure 4

Change in electrical resistance of human bladder microvascular endothelial cells exposed to CSE (20 μg/mL). **P < 0.01 when compared to control. n = 5.

Figure 5

Mouse bladder endothelial cells exposed to CSE (20 μg/mL). (A) PAF accumulation. (B) PAF‐AH Activity. (C) RAW 246.7 cell adherence with PAF receptor antagonists. *P < 0.05, **P < 0.01 when compared to control. ⁺⁺ P < 0.01 when comparing data in the presence and absence of PAF receptor antagonists. n = 6. Data are means ± SE.

Figure 6

Bladder inflammation following smoke exposure. (A&C) Room Air. (B&D) 4 Weeks of Smoking. (A&B) Wild Type. (C&D) iPLA ₂ β ^−/−. n = 5–8. Arrow = Inflammatory Cells. Representative Images. Scale Bar = 20 μm.

Figure 7

Average number of lymphoid aggregates per animal group following 4 weeks of cigarette smoke exposure. *P < 0.05 when compared to wild‐type counterpart. n = 5–8.