Gene Expression and Autoradiographic Localization of Endothelin-1 and its Receptors A and B in the Different Zones of the Normal Human Prostate

Symbiotic microbes affect the expression of male reproductive genes in Glossina m. morsitans

Background

Tsetse flies (Diptera, Glossinidae) display unique reproductive biology traits. Females reproduce through adenotrophic viviparity, nourishing the growing larva into their modified uterus until parturition. Males transfer their sperm and seminal fluid, produced by both testes and male accessory glands, in a spermatophore capsule transiently formed within the female reproductive tract upon mating. Both sexes are obligate blood feeders and have evolved tight relationships with endosymbionts, already shown to provide essential nutrients lacking in their diet. However, the partnership between tsetse and its symbionts has so far been investigated, at the molecular, genomic and metabolomics level, only in females, whereas the roles of microbiota in male reproduction are still unexplored.

Results

Here we begin unravelling the impact of microbiota on Glossina m. morsitans (G. morsitans) male reproductive biology by generating transcriptomes from the reproductive tissues of males deprived of their endosymbionts (aposymbiotic) via maternal antibiotic treatment and dietary supplementation. We then compared the transcriptional profiles of genes expressed in the male reproductive tract of normal and these aposymbiotic flies. We showed that microbiota removal impacts several male reproductive genes by depressing the activity of genes in the male accessory glands (MAGs), including sequences encoding seminal fluid proteins, and increasing expression of genes in the testes. In the MAGs, in particular, the expression of genes related to mating, immunity and seminal fluid components’ synthesis is reduced. In the testes, the absence of symbionts activates genes involved in the metabolic apparatus at the basis of male reproduction, including sperm production, motility and function.

Conclusions

Our findings mirrored the complementary roles male accessory glands and testes play in supporting male reproduction and open new avenues for disentangling the interplay between male insects and endosymbionts. From an applied perspective, unravelling the metabolic and functional relationships between tsetse symbionts and male reproductive physiology will provide fundamental information useful to understanding the biology underlying improved male reproductive success in tsetse. This information is of particular importance in the context of tsetse population control via Sterile Insect Technique (SIT) and its impact on trypanosomiasis transmission.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1289-2) contains supplementary material, which is available to authorized users.

Dynamic contrast-enhanced MR imaging features of the normal central zone of the prostate

RATIONALE AND OBJECTIVES

Evaluate qualitative dynamic contrast-enhanced magnetic resonance imaging (MRI) characteristics of normal central zone based on recently described central zone MRI features.

MATERIALS AND METHODS

Institutional review board-approved, Health Insurance Portability and Accountability Act compliant study, 59 patients with prostate cancer, histopathology proven to not involve central zone or prostate base, underwent endorectal MRI before prostatectomy. Two readers independently reviewed T2-weighted images and apparent diffusion coefficient (ADC) maps identifying normal central zone based on low signal intensity and location. Next, two readers drew bilateral central zone regions of interest on dynamic contrast-enhanced magnetic resonance images in consensus and independently recorded enhancement curve types as type 1 (progressive), type 2 (plateau), and type 3 (wash-out). Identification rates of normal central zone and enhancement curve type were recorded and compared for each reviewer. The institutional review board waiver was approved and granted 05/2010.

RESULTS

Central zone identified in 92%-93% of patients on T2-weighted images and 78%-88% on ADC maps without significant difference between identification rates (P = .63 and P = .15 and inter-reader agreement (κ) is 0.64 and 0.29, for T2-weighted images and ADC maps, respectively). All central zones were rated either curve type 1 or curve type 2 by both radiologists. No statistically significant difference between the two radiologists (P = .19) and inter-reader agreement was κ = 0.37.

CONCLUSIONS

Normal central zone demonstrates either type 1 (progressive) or type 2 (plateau) enhancement curves on dynamic contrast-enhanced MRI that can be potentially useful to differentiate central zone from prostate cancer that classically demonstrates a type 3 (wash-out) enhancement curve.

Mechanisms involved in the effects of endothelin-1 in pig prostatic small arteries

Since endothelin-1 (ET-1) is involved in prostatic disorders, the current study investigated the mechanisms underlying the ET-1-induced effects in pig prostatic small arteries. The experiments were performed in rings mounted in microvascular myographs containing physiological saline solution at 37oC for isometric force recordings. On basal tension, ET-1 (0.1-30 nM) evoked concentration-dependent contractions, which were enhanced by endothelium removal. ET-1 contractions were inhibited by blockade of endothelin ETA and ETB receptors, extracellular Ca2+ removal and blockade of voltage-dependent (L-type)- and non-voltage-dependent-Ca2+ channels. On endothelium intact rings precontracted with noradrenaline, the ETB endothelin receptor agonist BQ3020 promoted a concentration-dependent relaxation which was reduced by blockade of ETB receptors, nitric oxide synthase, guanylyl cyclase and prostanoids synthesis. Endothelium removal abolished its relaxant response and unmasked a BQ3020-induced contraction. Tetraethylammonium and 4-aminopyridine, blockers of non-selective K+ channels and voltage-dependent K+ (Kv) channels, respectively, inhibited the relaxations to BQ3020. Iberiotoxin, apamin and glibenclamide, blockers of large and small Ca2+-activated- and ATP-dependent- K+ channels, respectively, failed to modify these responses. These data suggest that ET-1 promotes contraction of pig prostatic small arteries by activating vascular smooth muscle contractile endothelin ETA and ETB receptors coupled to extracellular Ca2+ entry, via voltage-dependent (L-type)- and non-voltage-dependent Ca2+ channels, also being due to intracellular Ca2+ mobilization. In addition, a population of endothelial ETB receptors mediates vasorelaxation via NO-cGMP pathway, vasodilator cyclooxygenase product(s) and Kv channels.

[Prostate biopsies endothelin-1 expression: pt3a stage prognostic factor?]

AIM

The study evaluated the immunohistochemistry expression of endothelin-1 (ET-1) by prostate cancer (PCa) in prostate biopsies as an extracapsular stage (pT3a) prognostic factor.

MATERIAL AND METHOD

Sixty-eight radical prostatectomies (RP) were performed for clinically localised PCa (35 pT2 and 33 pT3a according to the 2002 pTNM classification). Age, digital rectal examination, initial PSA, biopsy Gleason score, positive biopsies ratio, specimen Gleason score, biopsy and RP specimen perineural neoplasic invasion, PCa DNA ploidy, PCa Ki-67 DNA image cytometry and biopsy and RP specimen ET-1 immunohistochemistry expression for both group were compared. Semi-quantitative ET-1 staining assessment was realised by the same pathologist.

RESULTS

pT3a group initial PSA was higher (p=0.032). No statistically difference was noticed between pT2 and pT3a groups for positive biopsies ratio, biopsy perineural neoplastic invasion and biopsy DNA ploidy determination. Biopsy Gleason score > or =7 was predictive of a pT3a stage (p=0.03). Statistically higher intensity of ET-1 PCa expression was observed in biopsies and specimens in pT3a group than in pT2 group (p<0.001 and p=0.01). In multivariate analysis, biopsy ET-1 PCa expression was an independent risk factor of pT3a stage with specificity 79 %, sensibility 69 %, predictive positive value 77 % and negative positive value 72 %. Combined with initial PSA > or =7, values were respectively 100 %, 76.9 %, 100 % and 57.1 %.

CONCLUSION

Endothelin-1 (ET-1) prostate cancer biopsy expression in our study was an independent prognostic factor of extracapsular stage (pT3a). Further studies will assess the relevance of ET-1 expression study in clinically localised PCa for active surveillance, curative treatment or targeted adjuvant therapy management.

Current and future treatments of bone metastases

Bone metastases contribute to a significant degree of morbidity in patients with common cancers through the development of skeletal related events (SRE) such as bone pain and pathological fracture. Traditional therapy has relied on surgical removal of lesions and, with the advent of adjuvant therapies, has been combined with radiotherapy, chemotherapy, and more recently osteoclast inhibiting agents like bisphosphonates. Although these therapeutic combinations can achieve a degree of local control, and rarely cure, across the vast majority of metastatic cancers they provide only palliation. Newer molecular agents currently under investigation, combined with innovations in surgery and radiation therapy offer a more targeted approach to bone metastasis. These utilise our understanding of key steps in the metastatic cascade including chemotactic attraction to bone, secretion of proteases, the cancer supporting microenvironment of bone matrix and the RANK-RANKL interaction for osteoclast activation. Direct inhibition of metastasis progression and osteolysis with less reliance on cytotoxic agents and invasive therapy should result in improved metastatic control, longer survival and less overall morbidity.

Regional differences in the functional and biochemical properties of endothelin receptor subtypes in the rabbit prostatic urethra

OBJECTIVE

To examine the regional differences in the functional (pharmacological) and biochemical properties of endothelin (ET) receptors in the rabbit prostatic urethra.

MATERIALS AND METHODS

The properties of ET receptors in 6-month-old male rabbit prostatic urethras were examined using isolated muscle-bath and radioligand receptor-binding techniques. Using plasma membrane suspensions, saturation and inhibition experiments with [(125)I]ET-1 and unlabelled agonists and antagonists (ET(A)-selective antagonist BQ123, and ET(B)-selective agonist sarafotoxin 6c, STX6c) were done to determine the ET receptor densities and their subtype specificities in the different regions of the urethra.

RESULTS

The ETs (ET-1 and ET-3) produced significant concentration-dependent contractile responses in the smooth muscle strips from the different regions of the urethra. Although the maximum contractile responses induced by ET-1 were similar in the different regions, the maximum contractile responses induced by ET-3 were greater in the distal region than in the proximal or middle regions, suggesting that the contractile response to ET-1 is more potent than that to ET-3 in all regions, and that there are region-specific differences in the responses to ET-3 but not ET-1. Moreover, the ET-3-induced contractile response was suppressed by BQ788 (a selective antagonist of the ET(B) receptor) suggesting that the ET(B) receptor subtype contributes to the contractile responses mediated by ET-3. The ET receptors were expressed in higher concentrations in the distal than in the proximal or middle regions. BQ123 and STX6c inhibited [(125)I]ET-1 binding in all regions with high and low affinity constants, indicating the presence of both ET(A) and ET(B) receptor subtypes. The proportions of high-affinity binding sites for BQ123, representing ET(A) receptors, were approximately 68%, 63% and 42% in the proximal, middle and distal regions, respectively. By contrast, the proportions of high-affinity binding sites for STX6c, representing ET(B) receptors, were approximately 27%, 35% and 52% in the proximal, middle, and distal regions, respectively. These data indicate the presence of regional differences in the densities and subtype specificities of ET receptor subtypes, and the existence of regional differences in the rabbit prostatic urethra.

CONCLUSION

The results suggest regional differences in ET(B) receptor subtypes that mediate contractile responses to ET-3, reflecting differences in the densities and specificities of the ET receptor subtypes in the rabbit prostatic urethra.

Pharmacotherapy for prostate cancer, with emphasis on hormonal treatments

For more than half a century, hormonal therapy has been one of the cornerstones of prostate cancer therapy. However, the position and timing of androgen deprivation therapy is continuously challenged. Nowadays, it is often combined with other types of treatment in a multi-modal approach, especially with radiation therapy. Besides the well-known luteinising hormone-releasing hormone agonists, several developments have been introduced (e.g., luteinising hormone-releasing hormone antagonists or improved depot formulations achieving a better pharmacokinetic slope and lower testosterone levels). Research developments include a better understanding of the different gonadotropin-releasing hormone isoforms, the ligand-independent transformation of the androgen receptor and androgen receptor overexpression in hormone-insensitive disease. Prostate cancer, previously thought to be chemotherapy insensitive, is now treated at the metastatic stage by taxane-based chemotherapies. The combination of hormonal therapy and chemotherapy is currently studied at various stages of the disease, as early as localised or locally advanced prostate cancer. It is very likely that, in the future, pharmacological treatment for prostate cancer will include combination therapies rather than monotherapies. The authors suggest an in-depth re-evaluation of the place of androgen deprivation therapy in prostate cancer.

Dickkopf homolog 1 mediates endothelin-1-stimulated new bone formation

Tumor-produced endothelin-1 (ET-1) stimulates osteoblasts to form new bone and is an important mediator of osteoblastic bone metastasis. The anabolic actions of ET-1 in osteoblasts were investigated by gene microarray analyses of murine neonatal calvarial organ cultures. Targets of ET-1 action were validated by real-time RT-PCR in murine primary osteoblast cultures. IL-6, IL-11, the CCN (CYR61, CTGF, NOV) family members cysteine-rich protein 61 and connective tissue growth factor, inhibin beta-A, serum/glucocorticoid regulated kinase, receptor activator of nuclear factor kappaB ligand, snail homolog 1, tissue inhibitor of metalloproteinase 3, and TG-interacting factor transcripts were increased by ET-1. ET-1 decreased the transcript for the Wnt signaling pathway inhibitor, dickkopf homolog 1 (Dkk1). Calvarial organ cultures treated with ET-1 had lower concentrations of DKK1 protein in conditioned media than control cultures. High DKK1 concentrations in bone marrow suppress bone formation in multiple myeloma. We hypothesized that the converse occurs in osteoblastic bone metastasis, where ET-1 stimulates osteoblast activity by reducing autocrine production of DKK1. Recombinant DKK1 blocked ET-1-mediated osteoblast proliferation and new bone formation in calvarial organ cultures, whereas a DKK1-neutralizing antibody increased osteoblast numbers and new bone formation. ET-1 directed nuclear translocation of beta-catenin in osteoblasts, indicating activation of the Wnt signaling pathway. The data suggest that ET-1 increases osteoblast proliferation and new bone formation by activating the Wnt signaling pathway through suppression of the Wnt pathway inhibitor DKK1.

LUTS treatment: Future treatment options

Lower urinary tract symptoms (LUTS) are commonly divided into storage, voiding, and postmicturition symptoms, and may occur in both men and women. Male LUTS have historically been linked to benign prostatic hyperplasia (BPH), but are not necessarily prostate related. The focus of treatment for LUTS has thus shifted from the prostate to the bladder and other extraprostatic sites. LUTS include symptoms of the overactive bladder (OAB), which are often associated with detrusor overactivity. Treatment for LUTS suggestive of BPH has traditionally involved the use of alpha(1)-adrenoceptor (AR) antagonists; 5alpha-reductase inhibitors; and phytotherapy-however, several new therapeutic principles have shown promise. Selective beta(3)-adrenoceptor agonists and antimuscarinics are potentially useful agents for treating LUTS, particularly for storage symptoms secondary to outflow obstruction. Other agents of potential or actual importance are antagonists of P2X(3) receptors, botulinum toxin type A, endothelin (ET)-converting enzyme inhibitors, and drugs acting at vanilloid, angiotensin, and vitamin D(3) receptor sites. Drugs interfering with the nitric oxide/cGMP-cAMP pathway, Rho-kinase and COX inhibitors, as well as drugs targeting receptors and mechanisms within the CNS, are also of interest and deserving of further study for the treatment of LUTS.

Endothelin receptor antagonists

Hormone refractory prostate cancer remains true to its middle name: it is largely refractory to attempts to delay its progression. New targets and new therapies are demanded. Through a review of the available literature on endothelin and several preclinical observations, the endothelin axis has emerged as one such target. In phase II and III clinical trials of atrasentan, a potent and selective endothelin receptor A subtype (ET(A)) antagonist, disease progression was delayed in some men. This well tolerated, oral agent may help convert advanced prostate cancer to a more chronic disease. This review will discuss the endothelin axis, preclinical rationale and some of the available clinical trial data on this promising new approach.

Cell specific expression of CD10/neutral endopeptidase 24.11 gene in human prostatic tissue and cells

BACKGROUND

Neutral endopeptidase (NEP/CD10) is a cell surface zinc metalloproteinase that functions as part of a regulatory loop controlling local concentrations of peptide substrates and associated peptide-mediated signal transduction processes. In contrast to the encouraging data dealing with NEP activity and regulation in prostate epithelial cells, only a few studies are available on the cellular expression and localization of neutral endopeptidase in the prostatic stromal and cancer cells. Here, we describe the cellular localization of NEP in human prostatic tissue and cells using in situ RT-PCR as a novel molecular biological approach.

METHODS

Immunofluorescence and Western blot experiments were performed to control the expression and distribution of the NEP in normal and malignant human prostatic tissues and cell lines. NEP gene expression was monitored by RT-PCR, NEP mRNA was detected in paraffin tissue sections and cultured cells of human prostate by the highly sensitive method of one step-in situ reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

NEP mRNA was detected in human prostatic tissue and in cultured cells by means of in situ RT-PCR. Prostatic tissue showed strong signals in the glandular epithelium and weak signals in the stroma, cultured cells displayed strong signals in prostate cancer cells (LNCaP) and weak signals in stromal cells (hPCPs). Western blot experiments were performed using whole cell extracts to proof the presence of NEP protein in LNCaP and hPCPs. The experiments confirm the expression of NEP by both cell types, however, the experiment with hPCPs cells showed two bands. NEP-immunofluorescence was strong in normal prostatic epithelium and confined to the apical plasma membrane. In dedifferentiated prostate cancer specimens, immunofluorescence of apical plasma membranes was lost, and both the cytoplasm and portions of the plasma membrane were immunoreactive for NEP. Prostate cancer cells (LNCaP) showed a strong immunoreaction of the plasma membrane and the cytoplasm. In comparison with LNCaP cells, only a weak cytoplasmic immunofluorescence was found in some stromal cells (hPCPs).

CONCLUSIONS

In normal prostatic tissue and specimens derived from human prostate cancer, NEP mRNA and protein are expressed mainly by the epithelial cells and to a minor extent by the stromal cells of human prostate glands. In situ RT-PCR is a powerful and straightforward approach for the routine and rapid detection of cellular specific expression of low copy genes.

Regulatory effect of castration on endothelins, their receptors and endothelin-converting enzyme in rat seminal vesicle

OBJECTIVE

To investigate the effects of castration on the expression of endothelins (ETs), ET receptors and ET converting enzyme-1 (ECE-1) in the rat seminal vesicle (RSV).

MATERIALS AND METHODS

Sprague-Dawley rats (3 months old) were surgically castrated or sham-operated, and then killed 7 days after surgery. Biochemical and pharmacological properties and the location of ET receptors in the RSV were determined by a series of binding experiments with [125I]ET-1, using membrane particulates and slide-mounted frozen sections of RSV. Expression levels of ETA and ETB receptor subtypes, ET-1, ET-3 and ECE-1 mRNAs were assessed by relative multiplex reverse-transcription polymerase chain reaction (RT-PCR).

RESULTS

The density of total ET receptors increased significantly in the seminal vesicle of the castrated rat. The predominance of the ETA receptor subtype in the RSV did not change with castration. Autoradiographic studies showed the presence of ET receptors on the smooth muscle and epithelium of the RSV. In addition, RT-PCR showed an up-regulation in the expression of ETA and ETB receptor subtypes, ET-1 and ECE-1 mRNAs in the seminal vesicle of the castrated rat. However, castration caused no significant change in the expression levels of ET-3 mRNA.

CONCLUSION

These findings suggest a regulatory role for testosterone in the expression of the ET receptor system in the RSV.

Pharmacological characterization of TA-0201, an endothelin receptor antagonist, with recombinant and human prostate endothelin receptors

The pharmacological profile of N-(6-(2-(5-bromopyrimidine-2-yloxy)ethoxy)-5-(4-methylphenyl)pyrimidin-4-yl)-4-(2-hydroxy-1,1-dimethylethyl) benzensulfonamide sodium salt sesquihydrate (TA-0201), a new antagonist of endothelin receptors, was examined, using human recombinant and prostate endothelin receptors. In binding experiments with [125I]endothelin-1, TA-0201 showed extremely high affinity for recombinant endothelin ET(A) receptors (pK(i)=10.7), as compared with that for recombinant endothelin ET(B) receptors (pK(i)=7.8). Endothelin ET(A) and ET(B) receptors coexisted in human prostate with different proportions (endothelin ET(A) receptor: approximately 70%), which were distinguished by TA-0201 in the same manner as with recombinant receptors. Human prostate strips contracted in response to endothelin-1 and sorafotoxin S6c, but the maximum contraction induced by endothelin-1 was approximately three times greater than that induced by sarafotoxin S6c. The response to endothelin-1, but not to sarafotoxin S6c, was inhibited by TA-0201 and cyclo(D-Asp-Pro-D-Val-Leu-D-Trp) (BQ123) (endothelin ET(A) receptor antagonist) but not by BQ788 (endothelin ET(B) receptor antagonist). These results suggest that TA-0201 is a highly selective endothelin ET(A) receptor antagonist and will be useful for understanding the physiological and pathological roles of the endothelin ET(A) receptor in human prostate and other tissues.

Estrogens affect endothelin-1 mRNA expression in LNCaP human prostate carcinoma cells

OBJECTIVE

To study effects of estrogens on endothelin-1 (ET-1) mRNA expression in the androgen-sensitive LNCaP-FGC cell line and its androgen-resistant derivative LNCaP-r. Further, if effects of estrone sulfate (E1S) are mediated via conversion to estradiol-17beta (E2). Estrogens have been shown to down-regulate ET-1, a mediator of the osteoblastic response of bone to metastatic prostate cancer.

METHODS

Cells were grown in steroid-depleted medium and incubated for 2-4 and 48 hours with 0, 1, 10, and 100 nM of either E1S or E2. mRNA levels were measured with an RT-PCR technique. Estrogen metabolism by LNCaP-FGC cells was studied by incubation with estrone (E1) and E1S at the same conditions, followed by determination of E1 and E2.

RESULTS

ET-1 mRNA expression in LNCaP-FGC cells was significantly suppressed by E2 and E1S following incubation for 2-4h but after 48 h only by E2 at 1 and 10nM and in LNCaP-r cells only by E2 at 100 nM following 2-4h of incubation. ET-1 mRNA expression was significantly higher in untreated LNCaP-r than in untreated LNCaP-FGC cells. E1 was efficiently transformed into E2 by LNCaP-FGC cells but very little to E1 and no E2 was formed from E1S.

CONCLUSION

ET-1 mRNA expression in LNCaP-FGC can be inhibited by E2, but also by its prehormone E1S. The lack of formation of E2 from E1S suggests a mode of action not related to classical steroid receptors. The higher level of ET-1 mRNA expression found in LNCaP-r cells may reflect the capability of a hormone refractory tumor to maintain activity on its own, independently of known regulatory mechanisms such as sex steroids.

Endothelin-1 production by prostate cancer cell lines is up-regulated by factors involved in cancer progression and down-regulated by androgens

BACKGROUND

Recent data demonstrate that endothelin-1 (ET-1) concentration increases in plasma of men with advanced, hormone-refractory prostate adenocarcinoma. In addition, ET-1 is involved in osteblastic remodelling and new bone formation, suggesting a role for this vasoactive peptide in the metastatic progression of prostate cancer to the bone.

METHODS

We investigated the regulation of ET-1 expression in androgen-sensitive and insensitive prostate cancer cell lines by androgens and several factors involved in progression of prostate cancer (EGF) and bone remodelling (TGFbeta-1, IL1-alpha and IGF-1).

RESULTS

Northern analysis and radio immunoassay demonstrated that all the ET-1 pathways are tuned off in the androgen-sensitive LNCaP cell line when compared to the androgen-insensitive PC-3 and DU145. In PC-3 cells transfected with a full-length androgen receptor expression vector (PC-3-AR), treatment with androgens reduced gene expression and secretion of ET-1 without affecting the gene expression of ET-3. Collectively, these data support a role for androgens in the regulation of ET-1 production by prostate adenocarcinoma cells. In PC-3 and DU145 cells, ET-1 gene expression and secretion were up-regulated by TGFbeta-1, EGF and IL1-alpha, whereas IGF-1 was ineffective. Conversely, none of the treatments affected ECE-1 or ET-3 gene expression.

CONCLUSIONS

In conclusion, ET-1 production by prostate adenocarcinoma cells is down-regulated by androgens and up-regulated by factors involved in tumour progression indicating a role for this peptide in the biology of prostate cancer. In view of the role exerted by ET-1 in the process of bone metastasis, our data suggest the use of ET-1 receptor antagonists in the treatment of advanced prostate cancer.

Endothelin-1 in human prostatic carcinoma treated with androgen withdrawal: an immunohistochemical study

BACKGROUND

Various reports suggest a role for endothelin-1 in prostatic carcinoma. The objective of the current study was to evaluate the changes of the immunodetectable endothelin-1 in prostatic carcinomas characterized by different grades of regression due to total androgen withdrawal.

METHODS

An immunohistochemical study was made on eleven prostatic carcinomas treated with neoadjuvant hormonal therapy for 3 months, followed by radical prostatectomy. Another ten specimens of untreated carcinomas were studied for comparison. An appraisal of androgen receptors was associated. A highly specific polyclonal antibody against endothelin-1 and a commercial monoclonal mouse antibody for androgenic receptors were used.

RESULTS

In all cases, a prevalent quantity of androgenic receptor-positive tumor cells were present. Neoplastic cells of untreated carcinomas showed a strong and heterogeneous staining for endothelin -1. In unregressed areas of treated cases, the features of endothelin-1 and androgen-receptor staining were the same as those of untreated cases. In areas characterized by moderate histologic regression, the endothelin-1 staining became more heterogeneous. In areas of strong histologic regression, a diffuse membrane staining was often noted. Only in completely regressed cancer cells was a definite loss of immunodetectable endothelin-1 and androgenic receptors observed.

CONCLUSIONS

Endothelin-1 is one of the proteins intrinsic to prostatic epithelial cells, both benign and malignant. In cases treated with androgen withdrawal, histologic regression is not uniform. In unmodified areas, immunodetectable endothelin-1 and androgenic receptors also are unmodified, thus suggesting some mechanism that substitutes for the action of androgen. Only neoplastic cells with complete histologic regression also lose androgenic receptors and endothelin-1, whereas the preserved immunostaining in deeply modified prostatic neoplastic cells seems to indicate that these cells still are potentially active.

Expression of endothelin receptor a associated with prostate cancer progression

PURPOSE

We determined the role of endothelin receptors in prostate cancer progression.

MATERIALS AND METHODS

We examined 51 prostate cancer specimens obtained at surgery or biopsy for the relationship of endothelin receptor expression determined by immunohistochemical staining with malignant potential.

RESULTS

The positive staining rate of endothelin receptor A in the 51 specimens was significantly higher than of endothelin B (71% versus 24%, p <0.0001). The staining rate of receptor A in Gleason score 5 to 10 disease was significantly higher than in Gleason 2 to 4 disease (91% versus 29%, p <0.0001). The overall staining rate of endothelin receptor A in nonorgan confined disease without bone metastasis but with extraprostatic disease was 87% in 23 cases, including 16 of 19 stage T3 (84%) and all 4 stage T4 (100%) cases. This rate was significantly higher than that of organ confined cancer (29%, p = 0.0003). All patients with bone metastasis had positive staining for endothelin receptor A. An especially high rate of intensely positive staining was observed for endothelin receptor A in biopsy specimens with bone metastasis or Gleason sum 8 to 10. Moreover, positive staining was stronger in cancer cells penetrating the prostatic capsule than in those at the primary foci. However, the positive staining rate of endothelin receptor B was not significantly different in organ and nonorgan confined cancer without bone metastasis (12% versus 26%, p = 0.4284), bone metastatic and nonmetastatic cancer (20% versus 36%, p = 0.2619) or the Gleason sum groups (p = 0.0874).

CONCLUSIONS

Our results indicate that endothelin receptor A expression may serve as a marker for and have an important role in prostate cancer progression.

Identification and characterization of neutral endopeptidase (EC 3. 4. 24. 11) from human prostasomes--localization in prostatic tissue and cell lines

BACKGROUND

An antibody directed against a 100 kDa protein was immunoselected from a polyvalent antiserum against human prostasomes. The antibody as well as biochemical characteristics of the respective antigen were used to study the structural relationship of the latter with prostate membrane specific antigen (PMSA), another 100 kDa membrane protein of the prostate.

METHODS

The isolated purified 100 kDa protein was characterized by tryptic degradation, aminoacid-sequencing and mass spectroscopy peptide-fingerprinting as well as mono-saccharide analysis and lectin binding and identified as a prostasomal neutral endopeptidase (NEP, EC 3.4.24.11). Immunohistochemistry, immunoelectron microscopy, in situ hybridization, and RT-PCR were performed to analyze the expression and distribution of the protein in normal and malignant human prostatic tissues and cell lines.

RESULTS

Prostatic NEP, which has no relationship with PMSA, is a glycosylated, integral membrane protein type II. The prevalent glycosyl residues are NeuNAc, GlcNAc, GalNAc, Gal, Man, Fuc. NEP-mRNA is expressed in human prostatic epithelial and some stromal cells. NEP-immunoreactivity is strong in normal prostatic epithelium and confined to the apical plasma membrane. During apocrine secretion, the enzyme is released from the secretory cells, contributing to the formation of prostasomes. In prostate cancer specimens, immunoreactivity of apical plasma membranes is lost, while generalized cytoplasmic immunoreactivity develops.

CONCLUSIONS

Prostatic secretory cells contain a membrane-bound, highly glycosylated neutral endopeptidase which is restricted to the apical plasma membrane. The enzyme is released from the cells in an apocrine fashion and contributes to the formation of prostasomes. In prostate cancer cells a preferential cytoplasmic localization is observed, pointing to alterations in intracellular targeting.

The contractile effects of endothelins on the smooth muscle of the rat prostate gland

Endothelin-1 elicited tonic contractions of rat prostatic smooth muscle that were unaffected by prazosin (0.5 microM), tetrodotoxin (1 microM) or guanethidine (10 microM). The rank order of potency of the endothelin isopeptides was endothelin-1>endothelin-2> or =endothelin-3. Sarafotoxin S6B was approximately equipotent with endothelin-1 in eliciting tonic contractions, but neither of the selective endothelin ET(B) receptor-agonists, sarafotoxin S6C (0.1 nM-0.3 microM) and BQ3020 (Ac-[Ala (11,15)]endothelin-1(6-21); 0.1 nM-0.3 microM), affected prostatic smooth muscle tone. The selective endothelin ET(A) receptor antagonist, BQ123 (cyclo(D-Asp-L-Pro-D-Val-L-Leu-D-Trp; 1 microM), attenuated responses to endothelin-1, -2 and -3, while the non-selective endothelin receptor antagonist bosentan (1 microM) and the selective endothelin ET(B) receptor antagonist BQ788, (Dmpc-gamma-MeLeu(9)-D-Trp(l-CO(2)CH(3))-D-Nle-OH; 1 microM) attenuated responses to endothelin-3 only. Contractions induced by exogenous administration of noradrenaline were unaffected by preincubation of tissues in BQ123 (1 microM) indicating the selectivity of this antagonist. These data suggest that endothelins mediate contractions of the rat prostate by action at endothelin ET(A) receptors.

Potential role of endothelin and nitric oxide in physiology and pathophysiology of the lower urinary tract

Endothelium-derived vasoactive mediators (endothelin-1 with its vasoconstrictive and mitogenic properties and nitric oxide with its vasodilatory and antiproliferative properties) play an important role in the regulation of vascular smooth muscle tone and cellular proliferation. Several recent studies have now demonstrated the presence of these vasoactive agents in the urinary tract where they are thought to play a prominent role in urinary tract physiology and disease. This article reviews the synthesis, localisation and actions of endothelin and nitric oxide in the lower urinary tract and examines the possible role of these mediators in disease.

Altered endothelin-3 and endothelin-B receptor mRNA expression in Hirschsprung's disease

BACKGROUND

Recently, the endothelin-3 (EDN3) and endothelin-B receptor (EDNRB) gene have been recognized as susceptibility genes for Hirschsprung's disease (HD). However, gene mutations have been observed only in limited cases, and the role of EDN3 in the pathogenesis and motility dysfunction in HD is not understood fully. To evaluate the possible implication of EDN3 and EDNRB for the development of HD, we examined the EDN3 and EDNRB mRNA level in bowel specimens of HD patients.

METHODS

Entire resected specimens of colon were obtained from 14 patients with HD. Eight age-matched control patients without gastroenteric disorders also were examined. mRNA was extracted from ganglionic and aganglionic segments of the HD specimens and normal colons. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to evaluate the relative amount of EDN3 and EDNRB mRNA.

RESULTS

In normal colon, constant EDN3 and EDNRB mRNA expression was observed. In HD, EDN3 and EDNRB mRNA expression was observed. In HD, EDN3 and EDNRB mRNA levels were decreased both in ganglionic and aganglionic segment in 2 cases. In 6 cases, EDN3 mRNA expression was decreased in aganglionic segment and in another 2 cases, EDNRB mRNA expression was decreased in aganglionic segment. In the remaining 4 cases, EDN3 and EDNRB mRNA levels were similar to controls.

CONCLUSION

The authors' findings indicate that loss of EDN3 and EDNRB function may be involved in the maldevelopment of neural crest-derived cells causing HD in many patients.

Pharmacological characterization of endothelin receptor subtypes in the guinea-pig prostate gland

Experiments have been conducted to investigate the actions of endothelins on the guinea-pig prostate gland. Saturation experiments with [125I]-endothelin-1 (2-800 pM) in guinea-pig prostatic homogenates indicated the presence of high affinity binding sites with an equilibrium dissociation constant (KD) of 230+/-50 pM, a maximum number of binding sites (Bmax) of 52+/-16 fmol mg(-1) protein or 269+/-61 fmol g(-1) tissue and a Hill coefficient (nH) of 1.01+/-0.03 (n = 3). Competition experiments revealed that binding of [125I]-endothelin-1 (20 pM) was inhibited with the following order of potency: endothelin-1 >>BQ-788 (N-cis-2,6-dimethylpiperidinocarbonyl-L-gamma-methyl-Leu-D-Trp[1-+ ++CO2CH3-D-Nle-ONa])> BQ-123 (cyclo-D-Asp-L-Pro-D-Val-Leu-D-Trp) > or = sarafotoxin S6c. At concentrations with negligible influence on smooth muscle tone, endothelin-1, endothelin-2 and sarafotoxin S6b (1 nM-0.1 microM) produced concentration-dependent potentiation of the contractions evoked by electrical field stimulation with trains of 20 pulses at 10 Hz every 50 s, 0.5 ms pulse width and a dial setting of 60 V. In contrast, the endothelin ET(B) receptor-preferring agonist endothelin-3 (1 nM- 1 microM) was much less potent, and the endothelin ET(B) receptor-selective agonists sarafotoxin S6c and BQ-3020 (Ac-[Ala11,15]-endothelin-1 (6-21)), up to 1 microM, were without effect. The endothelin ET(A) receptor antagonist BQ-123 (1 microM) markedly inhibited the potentiation induced by endothelin-1, endothelin-2 and sarafotoxin S6b while the endothelin ET(B) receptor antagonist BQ-788 (1 microM) was less effective. While our binding data indicates the presence of ET(A) and ET(B) binding sites in the guinea-pig prostate, the endothelin-induced facilitation of neurotransmission to the prostatic smooth muscle is mediated largely via activation of endothelin receptors of the ET(A) subtype.

Prostate stroma: physiology

BACKGROUND

The separate structural and functional activities of the prostatic stroma were only recently discovered and are still poorly understood.

METHODS

This review summarizes recent literature on the structure, and on the angiogenic, contractile, proliferative, and secretory activities mediated by the prostatic stroma and its agents.

RESULTS

The stroma undergirds the acinar epithelium through its fibromuscular substance. Neovascularization of its hypoxic cells, a process driven by cytokines, especially vascular endothelial growth factor, provides fuel for glycolytic empowerment of smooth muscle contraction, growth, and secretion. Signals from the stromal complement of cholinergic and adrenergic fibers, modulated by also-elaborated nitric oxide, provide tight regulation of uroflow. Apparently, autonomic control is independent of that of the powerful endothelin, secreted by the epithelium. Superimposed on these intrinsic elements of prostatic stromal control are the effects of steroid hormones and their effectors.

CONCLUSIONS

The illumination of the stroma's role in prostatic physiology, coupled with advances in knowledge of its pharmacology, should aid in our understanding, management, and prevention of prostatic disease.

Endothelin receptors in testosterone-induced prostatic hypertrophy in rats

Endothelin receptors were characterized in rat prostate and potential modification of these receptors was investigated in prostatic hypertrophy induced by testosterone. Both ET(A) and ET(B) endothelin receptor mRNA were detected in rat prostate, whereas binding experiments show the presence of only ET(A) receptors. Testosterone administration produced a 75% increase in prostate weight. Although the density of prostatic endothelin receptors was decreased from 348 +/- 75.0 fmol/mg protein in control rats to 252 +/- 39.9 fmol/mg protein in testosterone-treated animals, the total amount of receptors per prostate was unchanged. The steady-state level of ET(A)- and ET(B)-receptor mRNA was not altered by testosterone treatment. These results suggest that endothelin receptors are not affected in prostatic hypertrophy induced by testosterone.