Phorbol ester-induced contractility and Ca2+ influx in human cultured prostatic stromal cells

Inhibition of human prostate smooth muscle contraction by the inhibitors of protein kinase C, GF109203X, and Go6983

INTRODUCTION

Prostate smooth muscle contraction is promoted by receptor-induced activation of intracellular signaling pathways. The presumed involvement in etiology and medical treatment of lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH) imparts a high clinical relevance to prostate smooth muscle contraction, which is contrasted by incomplete understanding at the molecular level. Involvement of protein kinase C (PKC) has been commonly assumed, but available studies were limited to nonhuman prostate smooth muscle or cell cultures. Here, we examined the effects of the PKC inhibitors Go6983 and GF109203x on contractions of human prostate tissues.

METHODS

Prostate tissues were obtained from radical prostatectomy. Contractions were induced by electric field stimulation (EFS), α₁ -adrenergic agonists (noradrenaline, phenylephrine, methoxamine), thromboxane A₂ analog U46619, endothelin-1, or calcium chloride in an organ bath.

RESULTS

GF109203X (500 nM) and Go6983 (300  nM) reduced EFS-, noradrenaline-, phenylephrine-, methoxamine-, and U46619-induced contractions of human prostate tissues, with maximum inhibitions approaching up to 55%. Using concentrations of 3 µM, GF109203X and Go6983 inhibited EFS- and noradrenaline-induced contractions, with similar effect sizes as 500 and 300 nM, respectively. Endothelin-1-induced contractions were not inhibited by GF109203X, and to neglectable extent by Go6983. After depolarization in calcium-free solution, calcium chloride-induced concentration-dependent contractions, which were inhibited by GF109203X and Go6983.

CONCLUSIONS

GF109203X and Go6983 inhibit neurogenic, α₁ -adrenergic, and thromboxane A₂ -induced smooth muscle contractions in the human prostate, suggesting a role of PKC for human prostate smooth muscle contraction. The inhibition may by be imparted by inhibition of calcium sensitivity.

Human pluripotent stem cell derived midbrain PITX3(eGFP/w) neurons: a versatile tool for pharmacological screening and neurodegenerative modeling

PITX3 expression is confined to adult midbrain dopaminergic (mDA) neurons. In this study we describe the generation and basic functional characteristics of mDA neurons derived from a human pluripotent stem cell (hPSC) line expressing eGFP under the control of the PITX3 promoter. Flow cytometry showed that eGFP was evident in 15% of the neuron population at day 12 of differentiation and this level was maintained until at least day 80. From days 20 to 80 of differentiation intracellular chloride decreased and throughout this period around ∼20% of PITX3^eGFP/w neurons exhibited spontaneous Ca²⁺ transients (from 3.3 ± 0.3 to 5.0 ± 0.1 min^-1, respectively). These neurons also responded to any of ATP, glutamate, acetylcholine, or noradrenaline with elevations of intracellular calcium. As neuronal cultures matured more dopamine was released and single PITX3^eGFP/w neurons began to respond to more than one neurotransmitter. MPP⁺ and tumor necrosis factor (TNF), but not prostaglandin E₂, caused death of the ∼50% of PITX3^eGFP/w neurons (day 80). Tracking eGFP using time lapse confocal microscopy over 24 h demonstrated significant TNF-mediated neurite retraction over time. This work now shows that these PITX3^eGFP/w neurons are amenable to flow cytometry, release dopamine and respond to multiple neurotransmitters with elevations of intracellular calcium, we believe that they represent a versatile system for neuropharmacological and neurotoxicological studies.

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.

NLK is a novel therapeutic target for PTEN deficient tumour cells

PTEN (Phosphatase and tensin homolog) is a tumour suppressor gene commonly defective in human cancer, and is thus a potentially important therapeutic target. Targeting tumour suppressor loss-of-function is possible by exploiting the genetic concept of synthetic lethality (SL). By combining the use of isogenic models of PTEN deficiency with high-throughput RNA interference (RNAi) screening, we have identified Nemo-Like Kinase (NLK) inhibition as being synthetically lethal with PTEN deficiency. This SL is likely mediated by the transcription factor FOXO1 (Forkhead box O1), an NLK substrate, as the selectivity of NLK gene silencing for PTEN deficient cells can be reversed by FOXO1 knockdown. In addition, we provide evidence that PTEN defective cells targeted by NLK gene depletion undergo senescence, suggesting that NLK function is critical for the continued proliferation of PTEN deficient cells. Taken together, these data provide new insight into the potential of targeting of NLK to treat a range of tumourigenic conditions characterised by PTEN deficiency.

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.

Protein kinase G-induced activation of K(ATP) channels reduces contractility of human prostate tissue

BACKGROUND

Human cultured prostatic stromal cells respond to protein kinase G (PKG) activators and the nitric oxide donor, sodium nitroprusside (SNP) by opening ATP-sensitive potassium channels (K(ATP) channels) to reduce nifedipine-sensitive phorbol ester-induced contractility.

METHODS

PKG activators, SNP, diazoxide, nifedipine, isoprenaline, forskolin, and Sp-8-Br-cAMP were used to inhibit alpha(1)-adrenoceptor-induced contractions in tissue from transurethral resections of the prostate (TURP). The selective K(ATP) and large conductance Ca(2+) activated K(+) (BK(Ca)) channel inhibitors, glibenclamide and charybdotoxin, respectively were used to inhibit responses to PKG activators. RT-PCR identified the K(ATP) channel subunits present in TURP tissue and cultured cells.

RESULTS

The PKG activators, APT-cGMP (1 nM-100 microM) and PET-cGMP (1 nM-100 microM), and also SNP (1 nM-100 microM), forskolin (10 microM), diazoxide (100 microM) and nifedipine (3 microM) inhibited phenylephrine (20 microM)-induced contractions. The effect of APT-cGMP (1 nM-100 microM) could be reversed by glibenclamide, but not by charybdotoxin. TURP tissue contained mRNA for PKG Ialpha, Ibeta, and II and the K(ATP) channel subunits Kir6.1, Kir6.2, SUR2B, and SUR1. Cultured stromal cells contained only Kir6.1 and SUR2B subunit mRNA. SUR1 mRNA was detected in one of five cultured epithelial cell lines.

CONCLUSIONS

PKG activators reduce alpha(1)-adrenoceptor-induced contractility in TURP tissue via the activation of K(ATP) channels. (c) 2005 Wiley-Liss, Inc.

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

BACKGROUND

Benign prostatic hyperplasia is an age- and androgen-dependent condition of urethral compression caused by prostatic contractility and glandular enlargement. In this study we investigate whether testosterone, dihydrotestosterone and estradiol modulate the ability of human cultured prostatic stromal cells (HCPSCs) to respond to the adrenoceptor agonists, noradrenaline (30 microM) and phenylephrine (100 microM), the protein kinase C activating phorbol ester, phorbol diacetate (PDA, 10 microM), and the L-type Ca(2+) channel activator, (-)-Bay K8644 (Bay K, 10 microM) with elevations of intracellular Ca(2+) ([Ca(2+)](i)).

METHODS

Cells were loaded with the Ca(2+) sensitive fluorophore, FURA-2AM (10 microM) and changes in intracellular Ca(2+) determined before and 8-12 min after ligand addition.

RESULTS

Compared to steroid-free (SF) controls, the incubation of HCPSC with testosterone (30 and 300 pM) significantly increased responses to both noradrenaline and phenylephrine. Responses to Bay K were significantly reduced between 30 nM to 300 pM but responses to PDA were not greatly affected. Compared to SF the addition of estradiol (E(2), 100 pM) did not affect responses to phenylephrine. The concomitant addition of dihydrotestosterone (DHT) and E(2) (to give ratios from 1:1 to 1,000:1) elevated the responses to noradrenaline and phenylephrine at the extreme ranges. Responses to PDA and Bay K generally increased as DHT:E(2) approached unity.

CONCLUSIONS

These results indicate that sex steroids modulate the activities of HCPSCs through the regulation of both receptors and signal transduction processes.

Current models of human prostate contractility

1. The human prostate is a compact gland contributing to seminal fluid. With increasing age, most humans will develop benign prostatic hyperplasia, a condition of prostatic enlargement and contractility that leads to occlusion of the urethra. Over many years, investigators have used a variety of animal and cell culture models to elucidate some of the contractile and proliferative mechanisms that may be associated with the development of this condition. 2. This review briefly assesses the current state of knowledge of the mechanisms underlying human prostatic contractility and compares it with that of animal and cell culture models. It is not intended as a comprehensive methodological review, nor is it intended to indicate our preferences for either model. Our aim is to correlate findings from animal and cell culture models with the current understanding of human prostate contractility. 3. We hope that the present review will increase awareness of the suitability of the current models in developing our understanding of benign prostatic hyperplasia.

Functional role of PKC in contraction of cultured human prostatic stromal cells

The contractile activity of prostatic stromal cells contributes to symptoms of benign prostatic hyperplasia (BPH). However, the mechanisms for this contraction have not yet been fully elucidated. In this study, we investigated the role of protein kinase C (PKC) in prostatic contraction by measuring the isometric tension development of cultured human prostatic stromal cells (CHPSCs) derived from BPH patients. Fresh human BPH tissue was used only in a Western blot analysis. A ring preparation made of CHPSCs and collagen gel could develop an isometric tension during activation with various agonists. Phorbol 12,13 dibutyrate (PDBu), a PKC activator, induced a relaxation. A Western blot analysis revealed the expression of PKC-potentiated protein phosphatase-1 inhibitory protein (CPI-17) in both CHPSCs and fresh human BPH tissue to be much lower than that in the rabbit aorta. When CPI-17 was over-expressed, PDBu induced a large contraction, but the agonist-induced contraction did not become larger than expected. In alpha-toxin permeabilized preparations, PDBu induced a relaxation in control CHPSCs, while it induced a contraction at a constant [Ca2+]i in CPI-17 over-expressing CHPSCs. These results indicated that the activation of PKC in CHPSCs induces a relaxation probably due to low expression level of CPI-17 and also that the PKC-CPI-17 pathway does not appear to play a major role in the agonist-induced contraction even when CPI-17 was over-expressed.

A1 and A2A adenosine receptor modulation of alpha 1-adrenoceptor-mediated contractility in human cultured prostatic stromal cells

1. This study investigated the possibility that adenosine receptors modulate the alpha(1)-adrenoceptor-mediated contractility of human cultured prostatic stromal cells (HCPSC). 2. The nonselective adenosine receptor agonist, 5'-N-ethylcarboxamido-adenosine (NECA; 10 nm-10 microm), and the A(1) adenosine receptor selective agonist, cyclopentyladenosine (CPA; 10 nm-10 microm), elicited significant contractions in HCPSC, with maximum contractile responses of 18+/-3% and 17+/-2% reduction in initial cell length, respectively. 3. In the presence of a threshold concentration of phenylephrine (PE) (100 nm), CPA (1 nm-10 microm) caused contractions, with an EC(50) of 124+/-12 nm and maximum contractile response of 37+/-4%. The A(1) adenosine receptor-selective antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX 100 nm) blocked this effect. In the presence of DPCPX (100 nm), NECA (1 nm-10 microm) inhibited contractions elicited by a submaximal concentration of PE (10 microm), with an IC(50) of 48+/-2 nm. The A(2A) adenosine receptor-selective antagonist 4-(2-[7-amino-2-[furyl][1,2,4]triazolo[2,3-alpha][1,3,5,]triazin-5-yl amino]ethyl)phenol (Zm241385 100 nm) blocked this effect. 4. In BCECF-AM (10 microm)-loaded cells, both CPA (100 pM-1 microm) and NECA (100 pm-10 microm) elicited concentration-dependent decreases in intracellular pH (pH(i)), with EC(50) values of 3.1+/-0.3 and 6.0+/-0.3 nm, respectively. The response to NECA was blocked by Zm241385 (100 nm; apparent pK(B) of 9.4+/-0.4), but not by DPCPX (100 nm). The maximum response to CPA was blocked by DPCPX (100 nm), and unaffected by Zm241385 (100 nm). 5. NECA (10 nm-10 microm) alone did not increase [(3)H]-cAMP in HCPSC. In the presence of DPCPX (100 nm), NECA (10 nm-10 microm) caused a concentration dependent increase in [(3)H]-cAMP, with an EC(50) of 1.2+/-0.1 microm. This response was inhibited by Zm241385 (100 nm). CPA (10 nm-10 microm) had no effect on cAMP, in the presence or absence of forskolin (1 microm). 6. These findings are consistent with a role for adenosine receptors in the modulation of adrenoceptor-mediated contractility in human prostate-derived cells.

Alpha 1-adrenoceptor effects mediated by protein kinase C alpha in human cultured prostatic stromal cells

1 We have investigated the effects of alpha(1)-adrenoceptor stimulation upon contractility, Ca(2+) influx, inositol phosphate production, and protein kinase C (PKC) translocation in human cultured prostatic stromal cells (HCPSC). 2 The alpha(1)-adrenoceptor selective agonist phenylephrine elicited contractile responses of HCPSC, i.e. a maximal cell shortening of 45+/-6% of initial cell length, with an EC(50) of 1.6+/-0.1 microM. The alpha(1)-adrenoceptor selective antagonists prazosin (1 microM) and terazosin (1 microM) both blocked contractions to phenylephrine (10 microM). The L-type calcium channel blocker nifedipine (10 microM), and the PKC inhibitors Gö 6976 (1 microM) and bisindolylmaleimide (1 microM) also inhibited phenylephrine-induced contractions. 3 Phenylephrine caused a concentration dependent increase in inositol phosphate production (EC(50) 119+/-67 nM). This response was blocked by terazosin (1 microM). 4 Phenylephrine caused the translocation of the PKC alpha isoform, but not the beta, delta, gamma, epsilon or lambda isoforms, from the cytosolic to the particulate fraction of HCPSC, with an EC(50) of 5.7+/-0.5 microM. 5 In FURA-2AM (5 microM) loaded cells, phenylephrine elicited concentration dependent increases in [Ca(2+)](i), with an EC(50) of 3.9+/-0.4 microM. The response to phenylephrine (10 microM) was blocked by prazosin (1 microM), bisindolymaleimide (1 microM), and nifedipine (10 microM). 6 In conclusion, this study has shown that HCPSC express functional alpha(1)-adrenoceptors, and that the intracellular pathways responsible for contractility may be largely dependent upon protein kinase C activation and subsequent opening of L-type calcium channels.