Sex steroids modulate α1-adrenoceptor-stimulated Ca2+ elevation in human cultured prostatic stromal cells

A novel androgen signalling pathway uses dihydrotestosterone, but not testosterone, to activate the EGF receptor signalling cascade in prostate stromal cells

BACKGROUND AND PURPOSE

Human prostate growth and function are tightly controlled by androgens that are generally thought to exert their effects by regulating gene transcription. However, a rapid, non-genomic steroid action, often involving an elevation of intracellular calcium ([Ca(2+) ]i ), has also been described in a number of cell types. In this study we investigate whether androgens acutely regulate [Ca(2+) ]i in stromal cells derived from the human prostate.

EXPERIMENTAL APPROACH

Human-cultured prostatic stromal cells (HCPSCs) were loaded with the calcium-sensitive fluorophore, fura-2-acetoxymethyl ester (FURA-2AM) (10 μM). Changes in [Ca(2+) ]i in response to the androgens, dihydrotestosterone (DHT) and testosterone, as well as EGF were measured by fluorescence microscopy.

KEY RESULTS

DHT, but not testosterone (0.03-300 nM), elicited concentration-dependent elevations of [Ca(2+) ]i within 1 min of addition. These responses were blocked by the androgen receptor antagonist, flutamide (10 μM); the sarcoplasmic reticulum ATPase pump inhibitor, thapsigargin (1 μM); the inositol trisphosphate receptor inhibitor, 2-aminoethyldiphenyl borate (50 μM) and the PLC inhibitor, U-73122 (1 μM). Responses were also blocked by the L-type calcium channel blocker, nifedipine (1 μM), and by removal of extracellular calcium. A similar transient elevation of [Ca(2+) ]i was elicited by EGF (100 ng·mL(-1) ). The EGF receptor inhibitor, AG 1478 (30 nM), and the MMP inhibitor, marimastat (100 nM), blocked the DHT-induced elevation of [Ca(2+) ]i .

CONCLUSIONS AND IMPLICATIONS

These studies show that DHT elicits an androgen receptor-dependent acute elevation of [Ca(2+) ]i in HCPSC, most likely by activating EGF receptor signalling.

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.

The calcium sensor STIM1 is regulated by androgens in prostate stromal cells

BACKGROUND

Prostate development and maintenance in the adult results from an interaction of stromal and glandular components. Androgens can drive this process by direct action on the stroma. We investigated whether there was a direct link between androgens and another key regulator of stromal cells, intracellular Ca2+ ([Ca2+ ]i ).

METHODS

Prostate stromal cells were freshly obtained and cultures derived from patients with benign prostatic hyperplasia. Gene expression in dihydrotestosterone treated and untreated cells was compared using Affymetrix gene expression arrays and Ca2+ regulated features were identified by Gene Ontology (GO). Changes in [Ca2+]i were determined in Fluo-4 loaded cells. Androgen regulation was confirmed by chromatin immunoprecipitaion.

RESULTS

Stromal cell cultures were sorted for expression of integrin α1 β1 , which enriched for cells expressing the androgen receptor (AR). We identified key functional categories, within the androgen-induced gene expression signature, focusing on genes involved in calcium signaling. From this analysis, stromal interaction molecule-1 (STIM1) was identified as a significantly differentially expressed gene with four relevant associated GO terms. DNA sequence analysis showed that the promoter region of STIM1 contained putative androgen response element sequences in which AR binding ability of STIM1 was confirmed. Androgens directly regulated STIM1 expression and STIM1 effects on store-operated calcium entry were inhibited by STIM1 knock-down. Reduced STIM1 expression in prostate stromal cells led to a reduction in basal Ca2+ levels, the amount of Ca2+ released by thapsigargin and a reduction in store filling following TG-induced store depletion.

CONCLUSIONS

These results indicate that androgens modulate [Ca2+]i through the direct regulation of the STIM1 gene by AR binding to the STIM1 promoter.

Androgens regulate adenylate cyclase activity and intracellular calcium in stromal cells derived from human prostate

BACKGROUND

Increased smooth muscle tone is a significant component of benign prostatic hyperplasia, the onset of which correlates with age and declining serum testosterone levels. This study investigates the effects of androgens on key regulators of smooth muscle tone: intracellular calcium ([Ca(2+)](i)) and cyclic adenosine monophosphate (cAMP) in human cultured prostatic stromal cells (HCPSC).

METHODS

HCPSC were cultured in the absence or presence of dihydrotestosterone (DHT; 3, 30, and 300 nM) or testosterone (0.3-300 nM) alone or in the presence of flutamide (10 microM). Changes in [Ca(2+)](i) were determined in FURA-2AM (10 microM) loaded cells. Changes in cAMP were determined by Alpha Screen(R) assay.

RESULTS

Up to 32% of cultured cells exhibited spontaneous elevations of [Ca(2+)](i). The frequency of these elevations was reduced by nifedipine (10 microM), ryanodine (1 microM), and the adenylate cyclase inhibitor MDL 12,330A (20 microM). Compared to steroid-free cells, a 3-day incubation of cells with testosterone (only 3 nM) elevated basal, but not peak [Ca(2+)](i). In the presence of flutamide, all concentrations of testosterone tested elevated basal, but not peak [Ca(2+)](i). DHT (30 and 300, but not 3 nM) lowered peak and basal [Ca(2+)](i). Increased testosterone concentration dependently decreased resting cell cAMP (pIC(50): 7.64 +/- 0.29 nM).

CONCLUSIONS

These findings demonstrate that some HCPSC have the ability to spontaneously and transiently elevate [Ca(2+)](i). The magnitude of these [Ca(2+)](i) peaks, along with resting levels of calcium and cAMP, appear to be regulated by androgens.

Protective actions of sex steroid hormones in Alzheimer's disease

Risk for Alzheimer's disease (AD) is associated with age-related loss of sex steroid hormones in both women and men. In post-menopausal women, the precipitous depletion of estrogens and progestogens is hypothesized to increase susceptibility to AD pathogenesis, a concept largely supported by epidemiological evidence but refuted by some clinical findings. Experimental evidence suggests that estrogens have numerous neuroprotective actions relevant to prevention of AD, in particular promotion of neuron viability and reduction of beta-amyloid accumulation, a critical factor in the initiation and progression of AD. Recent findings suggest neural responsiveness to estrogen can diminish with age, reducing neuroprotective actions of estrogen and, consequently, potentially limiting the utility of hormone therapies in aged women. In addition, estrogen neuroprotective actions are also modulated by progestogens. Specifically, continuous progestogen exposure is associated with inhibition of estrogen actions whereas cyclic delivery of progestogens may enhance neural benefits of estrogen. In recent years, emerging literature has begun to elucidate a parallel relationship of sex steroid hormones and AD risk in men. Normal age-related testosterone loss in men is associated with increased risk to several diseases including AD. Like estrogen, testosterone has been established as an endogenous neuroprotective factor that not only increases neuronal resilience against AD-related insults, but also reduces beta-amyloid accumulation. Androgen neuroprotective effects are mediated both directly by activation of androgen pathways and indirectly by aromatization to estradiol and initiation of protective estrogen signaling mechanisms. The successful use of hormone therapies in aging men and women to delay, prevent, and or treat AD will require additional research to optimize key parameters of hormone therapy and may benefit from the continuing development of selective estrogen and androgen receptor modulators.

beta(2) and beta(3)-adrenoceptor inhibition of alpha(1)-adrenoceptor-stimulated Ca(2+) elevation in human cultured prostatic stromal cells

Prostatic beta-adrenoceptors inhibit alpha(1)-adrenoceptor-stimulated contractility. This study examines the effects of beta-adrenoceptor stimulation upon phenylephrine-induced elevations of intracellular Ca(2+)([Ca(2+)](i)) in human cultured prostatic stromal cells, and contractility of human prostatic tissue. Human cultured prostatic stromal cells were used for [(3)H]-cAMP accumulation studies or were loaded with 5-oxazolecarboxylic acid, 2-(6-(bis(2-((acetyloxy)methoxy)-2-oxoethyl)amino)-5-(2-(2-(bis(2-((acetyloxy)methoxy)-2-oxoethyl)amino)-5-methylphenoxy)ethoxy)-2-benzofuranyl)-, (acetyloxy)methyl ester (FURA-2AM, 10 microM) for Ca(2+) imaging studies. The beta-adrenoceptor agonist isoprenaline increased the accumulation of [(3)H]-cAMP (pEC(50)+/-S.E.M. 6.58+/-0.11) in human cultured prostatic stromal cells, an effect antagonized by the beta(2)-adrenoceptor antagonist (+/-)-1-[2,3-(dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol (ICI 118,551), but not by the beta(1)-adrenoceptor antagonist, atenolol. Isoprenaline (3 microM), the adenylyl cyclase activator, forskolin (20 microM) and the phosphodiesterase-4 inhibitor, rolipram (10 microM) inhibited the elevation of [Ca(2+)](i) elicited by phenylephrine (20 microM). The effect of isoprenaline could be blocked by ICI 118,551 (100 nM), the adenylyl cyclase inhibitor cis-N-(2-phenylcyclopentyl)-azacyclotridec-1-en-2-amine (MDL 12,330A, 20 microM) and the K(Ca) channel blocker, iberiotoxin (100 nM), but not by atenolol (1 microM) or the K(ATP) channel blocker, glibenclamide (3 microM). Agonists selective for beta(1)-(xamoterol and prenalterol), beta(2)-(procaterol and salbutamol) and beta(3)-((+/-)-(R(*), R(*))-[4-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]amino]propyl]phenoxy]acetic acid, BRL37344) adrenoceptors inhibited the elevation of [Ca(2+)](i) elicited by phenylephrine (20 microM) with a rank order of BRL37344> or =xamoterol> or =isoprenaline>procaterol> or =prenalterol>salbutamol. The xamoterol effect was reversed by ICI 118,551 (100 nM), but not by 1-(2-ethylphenoxy)-3-[[(1S)-1,2,3,4-tetrahydro-1-naphthalenyl]amino]-(2S)-2-propanol (SR59230A, 100 nM) or atenolol (1 microM). The BRL37344 effect was reversed by SR59230A (100 nM), but not by atenolol (1 microM) or ICI 118,551 (100 nM). Both xamoterol and BRL37344 inhibited phenylephrine-induced tissue contractility. This study shows that both xamoterol and BRL37344 are effective inhibitors of phenylephrine-induced effects in human cultured prostatic stromal cells and in prostatic tissue.