Further characterization of a novel EP2 and EP3 receptor dual agonist, ONO-8055, on lower urinary tract function in normal and lumbar canal stenosis rats

PGE2 receptors in detrusor muscle: Drugging the undruggable for urgency

Overactive bladder (OAB) syndrome is a prevalent condition of the lower urinary tract that causes symptoms, such as urinary frequency, urinary urgency, urge incontinence, and nocturia, and disproportionately affects women and the elderly. Current medications for OAB merely provide symptomatic relief with considerable limitations, as they are no more than moderately effective, not to mention that they may cause substantial adverse effects. Identifying novel molecular targets to facilitate the development of new medical therapies with higher efficacy and safety for OAB is in an urgent unmet need. Although the molecular mechanisms underlying the pathophysiology of OAB largely remain elusive and are likely multifactorial, mounting evidence from preclinical studies over the past decade reveals that the pro-inflammatory pathways engaging cyclooxygenases and their prostanoid products, particularly the prostaglandin E2 (PGE₂), may play essential roles in the progression of OAB. The goals of this review are to summarize recent progresses in our knowledge on the pathogenic roles of PGE₂ in the OAB and to provide new mechanistic insights into the signaling pathways transduced by its four G-protein-coupled receptors (GPCRs), i.e., EP1-EP4, in the overactive detrusor smooth muscle. We also discuss the feasibility of targeting these GPCRs as an emerging strategy to treat OAB with better therapeutic specificity than the current medications.

EP2 and EP3 receptors as therapeutic targets for underactive bladder/detrusor underactivity due to diabetic cystopathy in a type 1 diabetic rat model

OBJECTIVES

Diabetic cystopathy (DC) is recognized as one of the major etiologies of underactive bladder (UAB)/detrusor underactivity (DU). Although DC was first reported about three decades ago, there is a distinct lack of effective pharmacological management methods for UAB/DU due to DC with a robust certainty of evidence. In this study, we investigated whether EP2 and EP3 receptors are promising targets of pharmacological management of UAB/DU due to DC.

METHODS

We used streptozotocin (STZ)-induced diabetic Sprague-Dawley rats with postvoid residual urine (PVR) greater than 0.1 mL. Sixteen weeks after induction of diabetes, we performed awake single cystometry after oral administration of the vehicle, an α-blocker (tamsulosin [TAM], 0.1 and 0.3 mg/kg), a cholinesterase inhibitor (distigmine [DIS], 0.3 and 1.0 mg/kg), or an EP2/3 dual agonist (ONO-8055, 0.01 and 0.03 mg/kg). We compared cystometric parameters after administration of the vehicle and drugs using a paired t test. P < .05 was considered to be statistically significant.

RESULTS

Compared with the vehicle, TAM significantly decreased maximum intravesical pressure during voiding (Pmax), while DIS significantly increased it. However, neither drug significantly affected PVR or the residual urine rate (RUR). On the other hand, ONO-8055 significantly decreased PVR and tended to decrease RUR, although it did not significantly affect Pmax.

CONCLUSION

The present study was unable to demonstrate that stimulation of EP2 and EP3 receptors caused major improvements in UAB/DU due to DC. However, this equivocal result could arise from inherent limitations of the STZ-induced diabetic rat as a UAB/DU model.