Abstract

Benign prostatic hyperplasia (BPH) is characterized by stromal cell proliferation and contraction of the periurethral smooth muscle, causing lower urinary tract symptoms. Current BPH treatment, based on monotherapy with α_1A-adrenoceptor antagonists, is helpful for many patients, but insufficient for others, and recent reports suggest that stimulation of α_1D-adrenoceptors and 5-hydroxytryptamine (serotonin) (5-HT)_1A receptors contributes to cell proliferation. In this study, we investigated the potential of three N-phenylpiperazine derivatives (LDT3, LDT5, and LDT8) as multi-target antagonists of BPH-associated receptors. The affinity and efficacy of LDTs were estimated in isometric contraction and competition-binding assays using tissues (prostate and aorta) and brain membrane samples enriched in specific on- or off-target receptors. LDTs’ potency was estimated in intracellular Ca²⁺ elevation assays using cells overexpressing human α₁-adrenoceptor subtypes. The antiproliferative effect of LDTs on prostate cells from BPH patients was evaluated by viable cell counting and 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide assays. We also determined LDTs’ effects on rat intraurethral and arterial pressure. LDT3 and LDT5 are potent antagonists of α_1A-, α_1D-adrenoceptors, and 5-HT_1A receptors (K_i values in the nanomolar range), and fully inhibited phenylephrine- and 5-HT–induced proliferation of BPH cells. In vivo, LDT3 and LDT5 fully blocked the increase of intraurethral pressure (IUP) induced by phenylephrine at doses (ED₅₀ of 0.15 and 0.09 μg.kg⁻¹, respectively) without effect on basal mean blood pressure. LDT3 and LDT5 are multi-target antagonists of key receptors in BPH, and are capable of triggering both prostate muscle relaxation and human hyperplastic prostate cell growth inhibition in vitro. Thus, LDT3 and LDT5 represent potential new lead compounds for BPH treatment.