Cannabinoid receptor expression in the bladder is altered in detrusor overactivity

Area of Science:

• Urology
• Pharmacology
• Neuroscience

Background:

• Cannabinoid receptors (CB) are present in the human bladder and can inhibit detrusor muscle contraction.
• The precise mechanism of this inhibition and the role of CB in detrusor overactivity (DO) are not fully understood.

Purpose of the Study:

• To compare cannabinoid receptor (CB) expression in normal versus DO human bladders.
• To characterize the role of CB in the pathophysiology of DO.

Main Methods:

• Polymer chain reaction (PCR) to analyze CB gene transcripts.
• Immunohistochemistry (IHC) to assess CB protein levels.
• Immunofluorescence (IF) to evaluate CB co-localization with nerve fibers.
• Radioligand binding assays to determine receptor density and affinity.

Main Results:

• CB1 transcripts were elevated in the urothelium but reduced in the detrusor of DO bladders compared to normal bladders.
• Radioligand binding showed a CB density of 421 ± 104 fmol/mg protein in normal bladders.
• CB1 receptors co-localized with cholinergic nerves (ChAT) in the detrusor and with PGP9.5 in both urothelium and detrusor.
• CB2 receptors co-localized with ChAT and PGP9.5 in both urothelium and detrusor.

Conclusions:

• Reduced cannabinoid receptor expression in the detrusor of DO patients may contribute to the disease's pathophysiology.
• Co-localization of CB receptors with cholinergic nerves suggests a role in neurotransmitter regulation.
• Cannabinoid agonists show potential as a therapeutic strategy for overactive bladder.