Cannabinoid Receptor Pathway in Interstitial Cystitis/Bladder Pain Syndrome

Objectives: Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic, debilitating disorder with an unclear etiology and minimally effective treatment options. Previous studies have shown an increase in proinflammatory mediators in the serum, bladder and uroepithelium of patients with IC/BPS. The endocannabinoid system (ECS), which are endogenous lipid-based neurotransmitters that exert their effect by activation of two main receptors, has been investigated fro treating various anti-inflammatory disease. Particularly, activation of the cannabinoid receptor 2 (CB2R), has been shown to inhibit proinflammatory mediators. Here, we sought to investigate the role of CB2R on inflammatory markers using an in vitro model for IC/BPS.

Methods: Primary human bladder epithelial cells (BdEC; ATCC, Manassas, VA) were exposed to varying concentrations of human recombinant tumor necrosis factor alpha (TNFα) for 24 hours, after which proinflammatory marker levels were quantified in the cultured cell supernatants. Next, experiments were conducted by simultaneously treated cells with CB2R agonist, GP1a, and TNFα for 24 hours. The mRNA expression of various inflammatory markers were measured using qRT-PCR and analyzed using the 2-ΔΔCt method. One-way ANOVA followed by Tukey’s post hoc testing was employed for statistical analysis as appropriate.

Results: TNFα treatment of BdECs resulted in significantly elevated mRNA expression of IL8, IL6, IL1α, and CXCL1 at both intermediate dose (100 ng/mL) and high dose (200 ng/mL) TNFα concentrations (Figure 1). There was no significant difference between the intermediate and high dose concentrations, hence the intermediate dose was utilized for our study. We further investigated whether TNFα treatment modulated cannabinoid receptor expression. No significant difference in CB2R mRNA levels was observed across all TNFα concentrations compared to control (p = 0.791). Although studies remain ongoing, preliminary data has shown a trend towards lower levels of IL6 expression following treatment with GP1a (Figure 2).

Conclusions: In this cellular model of IC/BPS, exposure to TNFα resulted in a significant upregulation of inflammatory markers implicated in the condition. Preliminary data indicate a decrease in these inflammatory markers following CB2R activation by the agonist GP1a. Ongoing studies are further investigating the effect of CB2R activation on TNFα-induced inflammatory marker expression. These findings could potentially identify CB2R as a therapeutic target for pharmacological interventions in IC/BPS.

Figure 1: Inflammatory response after varying concentrations of TNFα stimulation in BdEC. Shown is mean ± SEM of 2-ΔΔCt normalized to control.

Figure 2: Effect of CB2R activation on inflammatory markers after TNFα stimulation.