Cyclic guanosine monophosphate-enhancing reduces androgenic extracellular regulated protein kinases-phosphorylation/Rho kinase II-activation in benign prostate hyperplasia.

OBJECTIVES: To investigate whether 7-[2-[4-(2-chlorophenyl) piperazinyl] ethyl]-1,3-di-methylxanthine (KMUP-1) inhibits the effects of testosterone on the development of benign prostatic hyperplasia and sensitizes prostate contraction.

METHODS: A benign prostatic hyperplasia animal model was established by subcutaneous injections of testosterone (3 mg/kg/day, s.c.) for 4 weeks in adult male Sprague-Dawley rats. Animals were divided into six groups: control, testosterone, testosterone with KMUP-1 (2.5, 5 mg/kg/day), sildenafil (5 mg/kg/day) or doxazosin (5 mg/kg/day). After 4 weeks, the animals were killed, and prostate tissues were prepared for isometric tension measurement and western blotting analysis. KMUP-1, Y27632, zaprinast, doxazosin or tamsulosin were used at various concentrations to determine the contractility sensitized by phenylephrine (10 μmol/L).

RESULTS: KMUP-1 inhibited testosterone-induced phosphorylation of extracellular signal-regulated phosphorylated protein kinase and mitogen-activated protein kinase kinase and Rho kinase-II activation. Sildenafil and doxazosin significantly decreased benign prostatic hyperplasia-induced mitogen-activated protein kinase kinase and Rho kinase-II activation. The decreased expressions of soluble guanylate cyclase α1 was reversed by KMUP-1, doxazosin and sildenafil. Soluble guanylate cyclase β1 and protein kinase G were increased by KMUP-1, doxazosin, and sildenafil in the testosterone-treated benign prostatic hyperplasia group. Phosphodiesterase-5A was increased by testosterone and inhibited by KMUP-1 (5 mg/kg/day) or sildenafil (5 mg/kg/day). KMUP-1 inhibited phenylephrine-sensitized prostate contraction of rats treated with testosterone.

CONCLUSIONS: Mitogen-activated protein kinase 1/extracellular regulated protein kinases kinase, soluble guanylate cyclase/cyclic guanosine monophosphate, protein kinase/protein kinase G and Rho kinase-II are related to prostate smooth muscle tone and proliferation induced by testosterone. KMUP-1 inhibits testosterone-induced prostate hyper-contractility and mitogen-activated protein kinase 1/extracellular regulated protein kinases kinase-phosphorylation, and it inactivates Rho kinase-II by cyclic guanosine monophosphate, protein kinase and α1A-adenergic blockade. Thus, KMUP-1 might be a beneficial pharmacotherapy for benign prostatic hyperplasia.