Powerful Relaxation of Phosphodiesterase Type 4 Inhibitor Rolipram in the Pig and Human Bladder Neck

Abstract

Introduction Phosphodiesterase type 5 (PDE5) inhibitors act as effective drugs for the treatment of lower urinary tract symptom (LUTS). There is a poor information, however, about the role of the PDE4 inhibitors on the bladder outflow region contractility. Aim To investigate PDE4 expression and the relaxation induced by the PDE4 inhibitor rolipram versus that induced by the PDE5 blockers sildenafil and vardenafil, in the pig and human bladder neck. Methods Immunohistochemistry for PDE4 expression, myographs for isometric force recordings and fura-2 fluorescence for simultaneous measurements of intracellular Ca2+ concentration ([Ca2+]i) and tension for rolipram in bladder neck samples were used. Main Outcome Measures PDE4 expression and relaxations to PDE4 and PDE5 inhibitors and simultaneous measurements of [Ca2+]i and tension. Results PDE4 expression was observed widely distributed in the smooth muscle layer of the pig and human bladder neck. On urothelium-denuded phenylephrine (PhE)-precontracted strips of pig and human, rolipram, sildenafil and vardenafil produced concentration-dependent relaxations with the following order of potency: rolipram> > sildenafil>vardenafil. In pig, the adenylyl cyclase activator forskolin potentiated rolipram-elicited relaxation, whereas protein kinase A (PKA) blockade reduced such effect. On potassium-enriched physiological saline solution (KPSS)-precontracted strips, rolipram evoked a lower relaxation than that obtained on PhE-stimulated preparations. Inhibition of large (BKCa) and intermediate (IKCa) conductance Ca2+-activated K+ channels, neuronal voltage-gated Ca2+ channels, nitric oxide (NO) and hydrogen sulfide (H2S) synthases reduced rolipram responses. Rolipram inhibited the contractions induced by PhE without reducing the PhE-evoked [Ca2+]i increase. Conclusions PDE4 is present in the pig and human bladder neck smooth muscle, where rolipram exerts a much more potent relaxation than that elicited by PDE5 inhibitors. In pig, rolipram-induced response is produced through the PKA pathway involving BKCa and IKCa channel activation and [Ca2+]idesensitization-dependent mechanisms, this relaxation also being due to neuronal NO and H2S release.

Phosphodiesterase type 4 inhibition enhances nitric oxide- and hydrogen sulfide-mediated bladder neck inhibitory neurotransmission

“…Strips of pig (n = 36 pigs) and human (n = 4 individuals) bladder neck were equilibrated to a tension of 2.1 ± 0.1 g and 1.9 ± 0.1 g, respectively. PhE (1 μM) 23 , 24 , 29 produced a sustained tone of 2.4 ± 0.1 g (n = 36) and 2.3 ± 0.1 g (n = 4) in pig and human, respectively, strips.…”

“…Along with these mediators, other non-gaseous molecules, such as adenosine 5′-triphosphate (ATP) 25 , serotonin 26 and peptides, such as pituitary adenylate cyclase-activating polypeptide 38 27 , 28 , are also implicated in the bladder neck smooth muscle relaxation. Our lab has previously described a marked PDE4 expression in pig and human bladder outflow region, where the selective PDE4 inhibitor rolipram causes a powerful smooth muscle relaxation 29 . The study of the underlying mechanisms regulating the bladder neck smooth muscle tension is necessary to provide drugs causing bladder outlet region relaxation during the voiding in obstructive LUTS 20 .…”

The Role of Nitric Oxide and Hydrogen Sulfide in Urinary Tract Function

“…PDE5 inhibitors promote potent relaxations of pig and human bladder neck and urethra smooth muscle [12,27,28]. PDE5 inhibitors promote potent relaxations of pig and human bladder neck and urethra smooth muscle [12,27,28]. These drugs showed no negative impact on bladder function as measured by detrusor pressure at maximum urinary flow rate or on any other urodynamic parameter assessed and significantly improve LUTS secondary to BPH [48][49][50].…”

“…PDE5 isoenzymes are also present in the bladder out‐flow region. Thus, in the pig and human urethra, there is a high PDE5‐, cGMP‐ and PKG‐IR expression, a wide distribution of cGMP‐positive interstitial cells, smooth muscle bundles, as well as cGMP‐IR within NOS‐IR endothelium .…”

“…). Both NO and H 2 S signalling pathways are involved also in the relaxation elicited by the PDE4 inhibitor rolipram in the pig bladder neck . In human urethra, TRPA 1 immunoreactivity has been found within nerves fibres co‐expressed with TRPV 1 and CGRP, as well as in urothelial cells and interstitial cells.…”