Revisiting the Pharmacodynamic Uroselectivity of α 1-Adrenergic Receptor Antagonists

α1-Adrenoceptor (AR) antagonists are widely used for the relief of urinary retention secondary to benign prostatic hyperplasia (BPH). While the five Food and Drug Administration-approved α 1-AR antagonists (terazosin, doxazosin, alfuzosin, tamsulosin, and silodosin) share similar efficacy, they differ in tolerability, with reports of ejaculatory dysfunction. The aim of the present work was to revisit their α 1-AR subtype selectivity as well as of LDT5 (1-(2-methoxyphenyl)-4-[2-(3,4-dimethoxyphenyl) ethyl]piperazine monohydrochloride), a compound previously described as a multitarget antagonist of α 1A-/α 1D-AR and 5-HT1A receptors, and to estimate their affinity for D2, D3, and 5-HT1A receptors, which are putatively involved in ejaculatory dysfunction. Competition binding assays were performed with native (D2, 5-HT1A) or transfected (human α 1A-, α 1B-, α 1Dt-AR, and D3) receptors for determination of the drug's affinities. Tamsulosin and silodosin have the highest affinities for α 1A-AR, but only silodosin is clearly a selective α 1A-AR antagonist, with K i ratios of 25.3 and 50.2 for the α 1D- and α 1B-AR, respectively. Tamsulosin, silodosin, and LDT5 (but not terazosin, doxazosin, and alfuzosin) have high affinity for the 5-HT1A receptor (K i around 5-10 nM), behaving as antagonists. We conclude that the uroselectivity of tamsulosin is not explained by its too-low selectivity for the α 1A- versus α 1B-AR, and that its affinity for D2 and D3 receptors is probably too low for explaining the ejaculatory dysfunction reported for this drug. Present data also support the design of "better-than-LDT5" new multitarget lead compounds with pharmacokinetic selectivity based on poor brain penetration and that could prevent hyperplastic cell proliferation and BPH progression. SIGNIFICANCE STATEMENT: The present work revisits the uroselectivity of the five Food and Drug Administration-approved α1 adrenoceptor antagonists for the treatment of benign prostatic hyperplasia (BPH). Contrary to what has been claimed by some, our results indicate that the uroselectivity of tamsulosin is probably not fully explained by its too-weak selectivity for the α1A versus α1B adrenoceptors. We also show that tamsulosin affinity for D3 and 5-HT1A receptors is probably too low for explaining the ejaculatory dysfunction reported for this drug. Based on our lead compound LDT5, present data support the search for a multitarget antagonist of α1A-α1D and 5-HT1A receptors with poor brain penetration as an alternative for BPH treatment.

The sympathetic nervous system exacerbates carotid body sensitivity in hypertension

AIMS

The carotid bodies (CBs) of spontaneously hypertensive (SH) rats exhibit hypertonicity and hyperreflexia contributing to heightened peripheral sympathetic outflow. We hypothesized that CB hyperexcitability is driven by its own sympathetic innervation.

METHODS AND RESULTS

To test this, the chemoreflex was activated (NaCN 50-100 µL, 0.4 µg/µL) in SH and Wistar rats in situ before and after: (i) electrical stimulation (ES; 30 Hz, 2 ms, 10 V) of the superior cervical ganglion (SCG), which innervates the CB; (ii) unilateral resection of the SCG (SCGx); (iii) CB injections of an α1-adrenergic receptor agonist (phenylephrine, 50 µL, 1 mmol/L), and (iv) α1-adrenergic receptor antagonist prazosin (40 µL, 1 mmol/L) or tamsulosin (50 µL, 1 mmol/L). ES of the SCG enhanced CB-evoked sympathoexcitation by 40-50% (P < 0.05) with no difference between rat strains. Unilateral SCGx attenuated the CB-evoked sympathoexcitation in SH (62%; P < 0.01) but was without effect in Wistar rats; it also abolished the ongoing firing of chemoreceptive petrosal neurones of SH rats, which became hyperpolarized. In Wistar rats, CB injections of phenylephrine enhanced CB-evoked sympathoexcitation (33%; P < 0.05), which was prevented by prazosin (26%; P < 0.05) in SH rats. Tamsulosin alone reproduced the effects of prazosin in SH rats and prevented the sensitizing effect of the SCG following ES. Within the CB, α1A- and α1B-adrenoreceptors were co-localized on both glomus cells and blood vessels. In conscious SH rats instrumented for recording blood pressure (BP), the CB-evoked pressor response was attenuated after SCGx, and systolic BP fell by 16 ± 4.85 mmHg.

CONCLUSIONS

The sympathetic innervation of the CB is tonically activated and sensitizes the CB of SH but not Wistar rats. Furthermore, sensitization of CB-evoked reflex sympathoexcitation appears to be mediated by α1-adrenoceptors located either on the vasculature and/or glomus cells. The SCG is novel target for controlling CB pathophysiology in hypertension.

Tamsulosin attenuates abdominal aortic aneurysm growth

BACKGROUND

Tamsulosin, an α1A-adrenergic receptor inhibitor, is prescribed to treat benign prostatic hyperplasia in men >60 years of age, the same demographic most susceptible to abdominal aortic aneurysm. The goal of this study was to investigate the effect of tamsulosin on abdominal aortic aneurysm pathogenesis.

METHODS

Abdominal aortic aneurysms were induced in WT C57BL/6 male mice (n = 9-18/group), using an established topical elastase abdominal aortic aneurysm model. Osmotic pumps were implanted in mice 5 days before operation to create the model, administering either low dose (0.125 µg/day tamsulosin), high dose (0.250µg/day tamsulosin), or vehicle treatments with and without topical application of elastase. Blood pressures were measured preoperatively and on postoperative days 0, 3, 7, and 14. On postoperative day 14, aortic diameter was measured before harvest. Sample aortas were prepared for histology and cytokine analysis.

RESULTS

Measurements of systolic blood pressure did not differ between groups. Mice treated with the low dose of tamsulosin and with the high dose of tamsulosin showed decreased aortic diameter compared with vehicle-treated control (93% ± 24 versus 94% ± 30 versus 132% ± 24, respectively; P = .0003, P = .0003). Cytokine analysis demonstrated downregulation of pro-inflammatory cytokines in both treatment groups compared with the control (P < .05). Histology exhibited preservation of elastin in both low- and high-dose tamsulosin-treated groups (P = .0041 and P = .0018, respectively).

CONCLUSION

Tamsulosin attenuates abdominal aortic aneurysm formation with increased preservation of elastin and decreased production of pro-inflammatory cytokines. Further studies are necessary to elucidate the mechanism by which tamsulosin attenuates abdominal aortic aneurysm pathogenesis.

Alpha1-adrenergic blockers selectively antagonize the contractions induced by 6-nitrodopamine in the human vas deferens

6-Nitrodopamine (6-ND) is released from human vas deferens and plays a modulatory role in the male ejaculation. Therapeutical use of α1-adrenoceptor antagonists is associated with ejaculatory abnormalities. To evaluate the effect of α1-adrenoceptor antagonists on the contractions induced by 6-ND, dopamine, noradrenaline, and adrenaline in the human epididymal vas deferens (HEVD). HEVD strips were suspended in glass chambers containing heated and oxygenated Krebs-Henseleit's solution. Cumulative concentration-response curves to catecholamines (10 nM-300 μM) were constructed in HEVD strips pre-incubated (30 min) with doxazosin (0.1-1 nM), tamsulosin (1-10 nM), prazosin (10-100 nM) and/or silodosin (0.1-10 nM). The effects of these α1-adrenoceptor antagonists were also evaluated in the electric-field stimulation (EFS, 2-32 Hz)-induced contractions. Doxazosin (0.1 nM) caused significant reductions in 6-ND-induced HEVD contractions without affecting the contractions induced by dopamine, noradrenaline, and adrenaline. Similar results were observed with tamsulosin (1 nM) and prazosin (10 nM). At these concentrations, these α1-adrenoceptor antagonists largely reduced the EFS-induced contractions. Silodosin (1 nM) caused concentration-dependent rightward shifts of the concentration-response curves to 6-ND but had no effect on the contractions induced by dopamine and adrenaline. Silodosin (0.1 nM) only inhibited the contractions induced by noradrenaline. Silodosin at 1 nM, but not at 0.1 nM, caused significant reductions in the EFS-induced contractions. The results reinforce the concept that 6-ND plays a major role in the human vas deferens contractility and indicate that the ejaculation disorders caused by doxazosin, tamsulosin, prazosin and silodosin cause in man, may be due to inhibition of the contractions induced by 6-ND rather than by the classical catecholamines dopamine, noradrenaline, and adrenaline.

Ondansetron alleviates testosterone-induced BPH in rats through cross regulation of the 5-HT/AR/P-STAT3 and the non-canonical NF-κB pathways

Benign prostatic hyperplasia (BPH) is a widespread age-related health issue. Every year, new pathological cues are revealed in the pathogenesis of BPH, however, the role of serotonin, Janus tyrosine kinase (JAK)-2/signal transducer and activator of the transcription (STAT)-3 and non-canonical nuclear factor-kappa B (NF-κB p52) pathways and their interaction with the androgen receptor (AR) in BPH are still not fully investigated. Accordingly, the aim of the current study was to unveil the possible modulatory effect of ondansetron alone and in combination with tamsulosin on these pathways and their utilization as therapeutic targets. Five groups of rats were utilized; group 1 received corn oil to serve as normal control, while the other groups administered testosterone (3 mg/kg, subcutaneously) dissolved in corn oil for 2 weeks followed by the co-administration of either tamsulosin (0.2 mg/kg, orally), ondansetron (2 mg/kg, intraperitoneally) or their combination for another 15 days along with testosterone injections. All treatments improved kidney function (creatinine and blood urea nitrogen), decreased oxidative stress (reduced glutathione and malondialdehyde), attenuated inflammation (NF-κB, cyclooxygenase-2), decreased AR expression, NF-κB p52, P-STAT3, transforming growth factor beta-1 in addition to markers of epithelial-mesenchymal transition (alpha smooth muscle actin and vimentin) this was associated with an increase in the prostatic content of serotonin, improvement in the histopathological picture and overall shrinkage in relative prostate weight. These results show that ondansetron is a very promising treatment for BPH especially in combination with tamsulosin and unveiled NF-κB p52 and serotonin as novel therapeutic targets in the management of BPH.

The Effect of Long-Term Tamsulosin Monotherapy and Tamsulosin - Dutasteride Combination Therapy on PKC-α Enzyme Expression in Prostate Stromal Tissue

Background

The α-adrenergic receptor antagonist is the most effective medical therapy to reduce the dynamic component in patients with BPH. However, long-term administration of receptor antagonists can cause upregulation of mRNA receptor expression, resulting in tolerance of drug effectiveness. PKC-α is involved in the process of prostate smooth muscle contraction through activation of the voltage-gated Ca2+ conducted canal, influenced by androgen hormones, especially testosterone, and has an isoform with Twist1, a transcription factor that plays a role in up-regulation of androgen receptors.

Objective

The aim of the study was to compare the effect of long-term tamsulosin monotherapy and tamsulosin - dutasteride combination therapy in PKC-α enzyme expression in prostate stromal tissue of Rattus norvegicus rats of Wistar strain.

Methods

Out of 80 samples of Rattus norvegicus rats were divided into 8 groups with different interventions: negative control group, positive control group, tamsulosin monotherapy administration for 1 day, 3 day, and 6 day groups, and tamsulosin - dutasteride combination therapy for 1 day, 3 day, and 6 day groups. BPH was induced with 3 mg/kg of testosterone proprionate for 3 weeks, continued with drugs administration according to intervention grouping. Prostate stromal tissue was taken and prepared for PKC-α enzyme measurement with ELISA method.

Results

There was a significant difference (p<0.05) in the effect of tamsulosin monotherapy and tamsulosin-dutasteride combination therapy on the PKC-α expression. There was a strong positive relationship between the duration of tamsulosin-dutasteride combination therapy on the PKC-α expression, which means the longer the duration of the combination of tamsulosin-dutasteride combination the higher the PKC-α expression.

Conclusion

Administration of long-term tamsulosin - dutasteride combination therapy causes upregulation PKC-α expression more than tamsulosin only.

Therapeutic Effects of Tamsulosin in Nightmare Disorder: A Randomized, Double Blind, Placebo-Controlled, Cross-Over, Pilot Study

Nightmare disorder is associated with functional impairment, distress, and low quality of life; however, studies on pharmacotherapy of this debilitating disorder yielded mixed results. Prazosin, a non-selective α1 blocker is reported to be effective in treatment of post-traumatic stress disorder-related nightmares. We aimed at investigating therapeutic effects of tamsulosin which has higher affinity for blocking α1A and α1D adrenoceptors in treatment of nightmare disorder. A randomized, double blind, cross-over, placebo-controlled pilot study was conducted. Patients were randomly assigned to receive Tamsulosin 0.4 mg once daily or placebo for period of four weeks. Following a 2-week wash-out period, they were crossed over to the other group and received drug or placebo for duration of 4 additional weeks. Nightmare frequency and intensity measurements were carried out using Disturbing Dreams and Nightmares Severity Index (DDNSI). Blood pressure measurements were also performed. According to per protocol analysis, mean DDNSI scores decreased following administration of tamsulosin and a statistical trend towards significance was reported (p=0.065, d=0.236). Results of intention to treat analysis showed significant difference in DDNSI scores after drug use (p=0.030, d=0.651). Additionally, DDNSI scores dropped significantly following placebo use. However, intention to treat analysis showed no statistically significant difference pre and post placebo period (0.064, d=0.040). Tamsulosin may be effective in treatment of nightmare disorder. However, further larger clinical trials are recommended to clarify the effectiveness of tamsulosin and α1 subtypes in pharmacotherapy of nightmares.

Characteristics of α1-adrenoceptor antagonists-induced ejaculatory dysfunction on spontaneous seminal emission in rats

Although α1-adrenoceptor (α1-AR) antagonists used to treat benign prostatic hyperplasia can cause ejaculation disorders, the aetiology of this adverse event is still controversial. Therefore, we investigated the effects of antagonists with different affinities for α1-AR subtypes on ejaculatory function and their mechanisms of action in normal rats. In the spontaneous seminal emission (SSE) test, systemically administered prazosin, terazosin, tamsulosin and naftopidil decreased the weight of ejaculated seminal material in a dose-dependent manner; the potency order was as follows: tamsulosin > terazosin > prazosin > naftopidil. The selective α1D-AR antagonist BMY7378 had no effect on SSE. Intrathecal tamsulosin and naftopidil did not inhibit SSE. Tamsulosin, the most potent, was ineffective as a single dose and significantly increased seminal vesicle fluid in rats treated for 2 weeks but did not significantly change retrograde ejaculation. These results indicated that the difference in inhibitory potency of the five α1-AR antagonists against SSE was due to the involvement of α1A-AR subtypes. Our results further suggested that α1-AR antagonist-induced ejaculatory dysfunction at the peripheral level was mainly due to the loss of seminal emission, although some retrograde ejaculation may also be involved.

Evaluation of the Effect of an α-Adrenergic Blocker, a PPAR-γ Receptor Agonist, and a Glycemic Regulator on Chronic Kidney Disease in Diabetic Rats

Diabetic nephropathy (DN) is a globally widespread complication of diabetes mellitus (DM). Research indicates that pioglitazone and linagliptin mitigate the risk of DN by reducing inflammation, oxidative stress, and fibrosis. The role of tamsulosin in DN is less studied, but it may contribute to reducing oxidative stress and inflammatory responses. The protective effects of combining pioglitazone, linagliptin, and tamsulosin on the kidneys have scarcely been investigated. This study examines the individual and combined effects of these drugs on DN in Wistar rats. Diabetic rats were treated with tamsulosin, pioglitazone, and linagliptin for six weeks. We assessed food and water intake, estimated glomerular filtration rate (eGFR), histological markers, urea, creatinine, glucose, NF-κB, IL-1, IL-10, TGF-β, and Col-IV using immunofluorescence and qPCR. The DN group exhibited hyperglycaemia, reduced eGFR, and tissue damage. Tamsulosin and linagliptin improved eGFR, decreased urinary glucose, and repaired tissue damage. Pioglitazone and its combinations restored serum and urinary markers and reduced tissue damage. Linagliptin lowered serum creatinine and tissue injury. In conclusion, tamsulosin, linagliptin, and pioglitazone demonstrated renoprotective effects in DN.

The alpha1A antagonist tamsulosin impairs memory acquisition, consolidation and retrieval in a novel object recognition task in mice

Tamsulosin is an α1-adrenoceptor antagonist used to treat benign prostatic hyperplasia. This drug exhibits high affinity for α1A- and α1D-adrenoceptor subtypes, which are also expressed in the brain. While dementia symptoms have been reported after administration of tamsulosin in humans, studies on its effects on the rodent brain are still rare. The present study investigated the effects of tamsulosin (and biperiden, an amnesic drug) on cognitive performance in the object recognition task (ORT). Tamsulosin (0.001-0.01 mg/kg) was orally administrated in mice at three distinct time points: pre-training, post-training and pre-test session. Tamsulosin 0.01 mg/kg impaired object recognition regardless of when it was injected, whereas at lower doses did not affect mouse performance in the ORT. Biperiden also impaired acquisition and consolidation of object recognition in mice. Furthermore, the effects of tamsulosin on locomotion, motivation and anxiety were excluded as potential confounding factors. At all doses tested, tamsulosin did not alter distance moved, time spent exploring objects in the ORT, and anxiety-related behaviors in the elevated plus-maze test. By contrast, diazepam evoked a significant reduction of anxiety-like behaviours. In conclusion, tamsulosin impaired memory acquisition, consolidation and retrieval in an object recognition task in mice, thus affecting memory performance in a non-specific phase manner. These findings contribute to our understanding of the potential adverse effects of tamsulosin, and shed light on the role played by α1-adrenoceptors, particularly α1A- subtype, in cognitive processes.