Prophylactic effect of tadalafil on bladder function in a rat model of chronic bladder ischemia

PURPOSE

We investigated the effect of tadalafil on chronic ischemia related bladder dysfunction.

MATERIALS AND METHODS

Adult male Sprague-Dawley® rats were divided into control, arterial endothelial injury and arterial endothelial injury with tadalafil treatment groups. The arterial injury and arterial injury-tadalafil groups underwent endothelial injury of the iliac arteries and received a 2% cholesterol diet after injury. Arterial injury-tadalafil rats received tadalafil (2 mg/kg per day) orally for 8 weeks after injury. The control group received a regular diet. At 8 weeks urodynamic investigation was performed. Bladder tissue was harvested for pharmacological studies, and histological examination of the iliac arteries and bladders was performed.

RESULTS

Iliac arteries from arterial injury and arterial injury-tadalafil rats showed neointimal formation and luminal occlusion. In the arterial injury group the micturition interval was significantly shorter (mean ± SEM 5.4 ± 0.5 vs 11.1 ± 1.1 minutes), and bladder capacity and voided volume were less than in controls. Contractile responses of bladder strips to KCl, electrical field stimulation and carbachol were significantly less after arterial injury than in controls. The arterial injury group showed a significantly increased percent of collagen compared with controls (mean 37.4% ± 1.8% vs 21.5% ± 1.8%). In the arterial injury-tadalafil group intimal formation and luminal occlusion were not prevented. However, there were significant improvements in all functional and morphological parameters compared with the arterial injury group.

CONCLUSIONS

Arterial occlusive disease may lead to chronic bladder ischemia and bladder hyperactivity. Chronic treatment with tadalafil protects bladder function and morphology, resulting in decreased bladder hyperactivity. If valid for humans, the data support phosphodiesterase 5 inhibition as treatment for chronic ischemia related bladder dysfunction.

The effect of hypercholesterolemia on carbachol-induced contractions of the detrusor smooth muscle in rats: increased role of L-type Ca2+ channels

To investigate a possible relation between hypercholesterolemia and detrusor smooth muscle function, we studied the contractile response to potassium challenge, carbachol (CCh), and the components of CCh-induced contractile mechanism in high-cholesterol diet-fed rats. Adult male Sprague-Dawley rats were fed with standard (control group, N = 17) or 4 % cholesterol diet (hypercholesterolemia group (HC), N = 16) for 4 weeks. Spontaneous contractions of detrusor muscle strips and their responses to potassium chloride (KCl) or cumulative dose-contraction curves to CCh were recorded. The effects of muscarinic receptor antagonists (methoctramin and/or 4-diphenylacetoxy-N-methylpiperidine), L-type Ca(+2) channel blocker (nifedipine), and/or rho-kinase inhibitor Y-27632 were investigated. Blood cholesterol level was increased in the HC group with no sign of atherosclerosis. The KCl-induced detrusor smooth muscle contractions were higher in HC, whereas spontaneous and CCh-induced responses were similar in both groups. Preincubation with receptor antagonist for M(3) but not for M(2) attenuated contraction significantly, shifting the dose-response curve to the right. This response was similar in both groups. Among two effector mechanisms of M(3)-mediated detrusor smooth muscle contraction, rho-kinase pathway was not affected by hypercholesterolemia, whereas blockade of L-type Ca(+2) channels potently reduced contractions. The results of this study point out a relation between hypercholesterolemia and contractile mechanism of detrusor smooth muscle likely to change urinary bladder function, via altering L-type Ca(+2) channels. Taken together with escalating incidence of hypercholesterolemia and lower urinary tract symptoms, it is a field which deserves to be investigated further.

Suppression of bladder overactivity and oxidative stress by the phytotherapeutic agent, Eviprostat, in a rat model of atherosclerosis-induced chronic bladder ischemia

OBJECTIVES

To clarify the mechanism by which chronic bladder ischemia causes bladder functional changes, and to investigate the involvement of oxidative stress and pro-inflammatory cytokines, and the effects of the phytotherapeutic drug, Eviprostat, on these biochemical marker levels and bladder function.

METHODS

Male Sprague-Dawley rats aged 15 weeks were divided into three groups. Arterial injury was experimentally induced by balloon endothelial injury of the iliac arteries, and a 2% cholesterol diet was given for 8 weeks. Rats in the arterial-injury group were given daily oral vehicle or Eviprostat, whereas sham-operated animals on a regular diet (0.09% cholesterol) were given vehicle for the last 2 weeks. Eight weeks after surgery, the levels of bladder pro-inflammatory cytokines, as well as bladder and urinary oxidative-stress markers, were determined. Cystometrograms were carried out without anesthesia or restraint.

RESULTS

Bladder and urinary oxidative-stress markers, and bladder pro-inflammatory cytokine levels were significantly increased in the arterial-injury group, and Eviprostat markedly suppressed these increase. The cystometrograms showed that arterial injury decreased the intermicturition interval without affecting the micturition pressure. This decrease was reversed by Eviprostat treatment.

CONCLUSIONS

Oxidative stress and pro-inflammatory cytokines might be involved in the development of overactive bladder by atherosclerosis-induced chronic bladder ischemia. Eviprostat might provide an attractive treatment option for individuals with bladder dysfunction due to chronic bladder ischemia because of its anti-oxidant and anti-inflammatory properties.