The localisation and expression of 5 alpha-reductase types I and II mRNAs in human hyperplastic prostate and in prostate primary cultures

Yongdamsagan-tang, a traditional herbal formula, inhibits cell growth through the suppression of proliferation and inflammation in benign prostatic hyperplasia epithelial-1 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Benign prostatic hyperplasia (BPH), also called benign enlargement of the prostate, is a progressive disease that is observed in most elderly men. Yongdamsagan-tang, a traditional herbal formula, is used commonly for the treatment of inflammation-related diseases. Although the therapeutic efficacy of Yongdamsagan-tang against BPH in vivo was reported previously, its underlying mechanisms are not clearly understood.

AIM OF THE STUDY

In this study, we investigated the effect of Yongdamsagan-tang water extract (YSTE) and its mechanism on the growth of human BPH epithelial BPH-1 cells.

MATERIALS AND METHODS

YSTE was extracted from 11 herbaceous plants and its chemical composition was analyzed by High-performance liquid chromatography (HPLC). YSTE was treated in the epithelial BPH-1 cell line and then cell lysates or supernant were used to evaluate cell viability, cell cycle, proliferation and cytokine production.

RESULTS

HPLC revealed that Baicalin and gentiopicroside were involved as the major compounds of YSTE. YSTE treatment in BPH-1 cells repressed cell viability in a dose-dependent manner. Regarding the inhibitory mechanisms of YSTE on cell growth, YSTE inhibited cell proliferation via a decrease in endogenous cyclin D1 protein levels and arrest at the S phase during cell-cycle progression. Furthermore, YSTE treatment in BPH-1 cells suppressed prostaglandin E₂ production and cyclooxygenase-2 (COX-2) protein levels. The secretion of the proinflammatory cytokines, interleukin-8 and interleukin-6, was also reduced by YSTE treatment.

CONCLUSIONS

YSTE in BPH-1 cells showed antiproliferative and anti-inflammatory activities via cell-cycle arrest and downregulation of COX-2 expression, respectively. Taken together, the results of the present study will enhance our understanding of the mechanisms underlying the effect of YSTE in BPH.

Differential expression of 5-alpha reductase isozymes in the prostate and its clinical implications

The development of human benign or malignant prostatic diseases is closely associated with androgens, primarily testosterone (T) and dihydrotestosterone (DHT). T is converted to DHT by 5-alpha reductase (5-AR) isozymes. Differential expression of 5-AR isozymes is observed in both human benign and malignant prostatic tissues. 5-AR inhibitors (5-ARI) are commonly used for the treatment of benign prostatic hyperplasia (BPH) and were once promoted as chemopreventive agents for prostate cancer (PCa). This review discusses the role of the differential expression of 5-AR in the normal development of the human prostate and in the pathogenesis and progression of BPH and PCa.

Gene Expression in Prostate Cancer Cells Treated With the Dual 5 Alpha-Reductase Inhibitor Dutasteride

We sought preclinical data on the cellular and molecular effects of dutasteride in androgen-responsive, human prostate cancer (PCa) cells to better understand the mechanisms of action of 5 alpha-reductase inhibition in these cells. We used the human prostate cancer cell line LNCaP, which exhibits most features of PCa cells including androgen responsiveness. Our findings show that dutasteride kills PCa cells in vitro; it dramatically reduced viability and proliferation and disrupted genes and cellular pathways involved in metabolic, cell cycle, and apoptotic responses besides those expected in androgen-signaling pathways. Microchip gene array expression analysis revealed activation of genes in the FasL/tumor necrosis factor alpha (TNF-alpha) apoptotic and cell-survival pathways, correlating with the growth and survival effects in the LNCaP cells. Real-time polymerase chain reaction confirmed expression level changes seen by microarray analysis of candidate genes such as PLA2G2A, CDK8, CASP7, MDK, and NKX3.1. Collectively, our findings delineate the cellular and molecular effects of dutasteride in androgen-responsive PCa cells in vitro and may lead to its better therapeutic and chemopreventive use in PCa.

A multiscale, mechanism-driven, dynamic model for the effects of 5α-reductase inhibition on prostate maintenance

A systems-level mathematical model is presented that describes the effects of inhibiting the enzyme 5α-reductase (5aR) on the ventral prostate of the adult male rat under chronic administration of the 5aR inhibitor, finasteride. 5aR is essential for androgen regulation in males, both in normal conditions and disease states. The hormone kinetics and downstream effects on reproductive organs associated with perturbing androgen regulation are complex and not necessarily intuitive. Inhibition of 5aR decreases the metabolism of testosterone (T) to the potent androgen 5α-dihydrotestosterone (DHT). This results in decreased cell proliferation, fluid production and 5aR expression as well as increased apoptosis in the ventral prostate. These regulatory changes collectively result in decreased prostate size and function, which can be beneficial to men suffering from benign prostatic hyperplasia (BPH) and could play a role in prostate cancer. There are two distinct isoforms of 5aR in male humans and rats, and thus developing a 5aR inhibitor is a challenging pursuit. Several inhibitors are on the market for treatment of BPH, including finasteride and dutasteride. In this effort, comparisons of simulated vs. experimental T and DHT levels and prostate size are depicted, demonstrating the model accurately described an approximate 77% decrease in prostate size and nearly complete depletion of prostatic DHT following 21 days of daily finasteride dosing in rats. This implies T alone is not capable of maintaining a normal prostate size. Further model analysis suggests the possibility of alternative dosing strategies resulting in similar or greater effects on prostate size, due to complex kinetics between T, DHT and gene occupancy. With appropriate scaling and parameterization for humans, this model provides a multiscale modeling platform for drug discovery teams to test and generate hypotheses about drugging strategies for indications like BPH and prostate cancer, such as compound binding properties, dosing regimens, and target validation.

The mouse as a model to investigate sex steroid metabolism in the normal and pathological prostate

Metabolism of sex steroids within the prostate is an important factor affecting its growth and pathology. Mouse models with genetic gain- and especially loss-of-function have characterised different steroid metabolic pathways and their contribution to prostate pathology. With reference to the human prostate, this review aims to summarize the steroidogenic pathways in the mouse prostate as the basis for using the mouse as a model for intraprostatic steroid signalling. In this review we summarize the current information for three main components of the steroid signalling pathway in the mouse prostate: circulating steroids, steroid receptors and steroidogenic enzymes with regard to signalling via androgen, estrogen, progesterone and glucocorticoid pathways. This review reveals many opportunities for characterisation steroid metabolism in various mouse models. The knowledge of steroid metabolism within prostate tissue and in a lobe (rodent)/region (human) specific manner, will give valuable information for future, novel hypotheses of intraprostatic control of steroid actions. This review summarizes knowledge of steroid metabolism in the mouse prostate and its relevance to the human.

The 5 alpha-reductase isozyme family: a review of basic biology and their role in human diseases

Despite the discovery of 5 alpha-reduction as an enzymatic step in steroid metabolism in 1951, and the discovery that dihydrotestosterone is more potent than testosterone in 1968, the significance of 5 alpha-reduced steroids in human diseases was not appreciated until the discovery of 5 alpha-reductase type 2 deficiency in 1974. Affected males are born with ambiguous external genitalia, despite normal internal genitalia. The prostate is hypoplastic, nonpalpable on rectal examination and approximately 1/10th the size of age-matched normal glands. Benign prostate hyperplasia or prostate cancer does not develop in these patients. At puberty, the external genitalia virilize partially, however, secondary sexual hair remains sparse and male pattern baldness and acne develop rarely. Several compounds have been developed to inhibit the 5 alpha-reductase isozymes and they play an important role in the prevention and treatment of many common diseases. This review describes the basic biochemical properties, functions, tissue distribution, chromosomal location, and clinical significance of the 5 alpha-reductase isozyme family.

Estrogen and androgen signaling in the pathogenesis of BPH

Estrogens and androgens have both been implicated as causes of benign prostatic hyperplasia (BPH). Although epidemiological data on an association between serum androgen concentrations and BPH are inconsistent, it is generally accepted that androgens play a permissive role in BPH pathogenesis. In clinical practice, inhibitors of 5α-reductase (which converts testosterone to the more potent androgen dihydrotestosterone) have proven effective in the management of BPH, confirming an essential role for androgens in BPH pathophysiology. To date, multiple lines of evidence support a role for estrogens in BPH pathogenesis. Studies of the two estrogen receptor (ER) subtypes have shed light on their differential functions in the human prostate; ERα and ERβ have proliferative and antiproliferative effects on prostate cells, respectively. Effects of estrogens on the prostate are associated with multiple mechanisms including apoptosis, aromatase expression and paracrine regulation via prostaglandin E2. Selective estrogen receptor modulators or other agents that can influence intraprostatic estrogen levels might conceivably be potential therapeutic targets for the treatment of BPH.

Human benign prostatic hyperplasia heterotransplants as an experimental model

Benign prostatic hyperplasia is a nonmalignant adenomatous enlargement of the periurethral prostate gland. It is a common disease in older men. In addition to man, spontaneous benign prostatic hyperplasia occurs in chimpanzee and the dog. Alternatives to these spontaneous models are induced benign prostatic hyperplasia, xenografts and in vitro models. Xenografts may be induced by cells cultured in vitro or by the heterotransplantation of primary surgical specimens into immunosuppressed mice. The purpose of this review is to integrate data from more than 30 years of heterotransplantation research in the study of benign hyperplasia of the prostate. Heterotransplantation has provided data regarding the histopathology, morphology, tissue markers, androgen receptor expression, tissue kinetics, take rate and tissue vasculature for this prostate disease. There are advantages, as well as limitations, that have been identified for human prostate disease heterotransplants versus xenotransplantation of cultured cells. Overall, heterotransplanted tissue is better at retaining tissue morphology, pathology, secretory activity, expression of tissue markers and human vasculature of the patient's original specimen. Furthermore, heterotransplanted tissue preserves the three-dimensional tissular architecture of the prostate to maintain critical stromal-epithelial cell interactions.

Key targets of hormonal treatment of prostate cancer. Part 2: the androgen receptor and 5alpha-reductase

OBJECTIVE

The inhibition of 5alpha-reductase (5AR) blocks the synthesis of the most powerful intracellular androgen, dihydrotestosterone (DHT). The prostate has two 5AR isoenzymes (5AR1 and 5AR2) that change in expression and cellular location during the development of prostate cancer and tumour progression. The objective of this review is to provide an understanding of the pharmacological properties and the potential clinical benefits of 5AR inhibition.

METHODS

We searched Pubmed for data obtained from pharmacological, preclinical and clinical studies.

RESULTS

5AR1 expression increases with increasing aggressiveness and extension of malignant prostatic disease. Conversely, 5AR2 expression decreases from benign prostatic tissue to localized prostate cancer. The efficacy of 5AR2 monotherapy with finasteride alone or in combination with an androgen receptor antagonist on more final outcome measures seems to be limited. Combining an androgen receptor antagonist with a 5AR inhibitor in patients with asymptomatic, locally advanced or recurrent prostate cancer might be a reasonable first therapeutic hormonal approach. As plasma testosterone levels are maintained, beneficial effects on quality of life, potency and sexual function are expected. From studies on the dual 5AR inhibitor dutasteride, the drug produces a biochemical response in some men who progressed under androgen-deprivation therapy, and is generally well tolerated.

CONCLUSIONS

Achieving more potent suppression of intracellular DHT synthesis by 5AR inhibition is expected to provide clinical benefit to patients. Previous studies have shown that 5AR inhibition, by dutasteride in particular, halts/delays the progression of disease, and might even cause regression of disease in patients with advanced prostate cancer.

Oxytocin increases 5alpha-reductase activity of human prostate epithelial cells, but not stromal cells

BACKGROUND

Oxytocin is known to modulate 5-alpha-reductase expression and has, therefore, been implicated in the etiology and novel pharmacological treatments of benign prostatic hyperplasia (BPH). These suggestions have been made in the absence of any direct evidence that oxytocin regulates expression or activity of 5-alpha-reductase isoenzymes in the human prostate. This study evaluated the effects of oxytocin on the activity and expression of 5-alpha-reductase isoenzymes I and II of human prostate stromal (PrSC; primary site of BPH development) and epithelial (PrEC) cells.

METHODS

Cell cultures were incubated with oxytocin, or oxytocin plus a specific oxytocin antagonist for 24 hr, and conversion of (3)H-Testosterone to dihydrotestosterone used to estimate total 5-alpha-reductase activity and to determine activity of both type I and type II isoenzymes. Fully quantitative real-time RT-PCR determined levels of expression of both isoenzymes following treatments.

RESULTS

Oxytocin significantly increased the total 5-alpha-reductase activity of PrEC but not of PrSC. 5-alpha-Reductase I gene expression and enzyme activity were also increased (P<0.05) in PrEC by oxytocin. Oxytocin significantly increased type II activity, but not expression, in PrEC. Oxytocin did not significantly affect 5-alpha-reductase activity or expression in PrSC.

CONCLUSION

Both 5-alpha-reductase I and II are expressed in normal human prostate stromal and epithelial cells. Only 5-alpha-reductase isoenzymes of prostate epithelium are modulated by oxytocin.

Transcript profiling of the androgen signal in normal prostate, benign prostatic hyperplasia, and prostate cancer

Human prostate adenocarcinoma (CaP) and benign prostatic hyperplasia (BPH) have epithelial and stromal cell origins, respectively. To determine whether the androgen signal is processed differently in these cell types the expression of transcripts for enzymes that control ligand access to the androgen receptor (AR) were measured. Transcripts for type 2 5alpha-reductase, ketosteroid reductases [aldo-keto reductase (AKR)1C1-AKR1C4], the major oxidative 3alpha-hydroxysteroid dehydrogenase (HSD) retinol dehydrogenase (RODH)-like 3alpha-HSD (RL-HSD) and nuclear receptors [AR, estrogen receptor (ER)alpha, and ERbeta] were determined in whole human prostate and in cultures of primary epithelial cells (PEC) and primary stromal cells (PSC) from normal prostate, CaP and BPH by real-time RT-PCR. Normal PEC (n=14) had higher levels of AKR1C1 (10-fold, P<0.001), AKR1C2 (115-fold, P<0.001) and AKR1C3 (6-fold, P<0.001) than normal PSC (n=15), suggesting that reductive androgen metabolism occurs. By contrast, normal PSC had higher levels of AR (8-fold, P<0.001) and RL-HSD (21-fold, P<0.001) than normal PEC, suggesting that 3alpha-androstanediol is converted to 5alpha-dihydrotestosterone to activate AR. In CaP PEC (n=14), no significant changes in transcript levels vs. normal PEC were observed. In BPH PSC (n=21) transcripts for AR (2-fold, P<0.001), AKR1C1 (4-fold, P<0.001), AKR1C2 (10-fold P<0.001), AKR1C3 (4-fold, P<0.001) and RL-HSD (3-fold, P<0.003) were elevated to increase androgen response. Differences in the AR:ERbeta transcript ratios (eight in normal PEC vs. 280 in normal PSC) were maintained in PEC and PSC in diseased prostate. These data suggest that CaP may be more responsive to an ERbeta agonist and BPH may be more responsive to androgen ablation.

Isoenzyme type 1 of 5alpha-reductase is abundantly transcribed in normal human genital skin fibroblasts and may play an important role in masculinization of 5alpha-reductase type 2 deficient males

OBJECTIVE

5alpha-reductase enzymes reduce testosterone (T) to the most potent androgen dihydrotestosterone (DHT). Two isoenzymes are known to day. While the type 2-enzyme (5RII) is predominantly expressed in male genital tissues and mutations are known to cause a severe virilization disorder in genetic males, the role of the type 1-enzyme (5RI) in normal male androgen physiology is unclear. We investigated whether 5RI is transcribed in normal male genital skin fibroblasts (GSFs) and if the transcription is regulated by age or by androgens themselves.

METHODS

GSF from 14 normally virilized males of different ages, ranging from 8 months to 72 years, obtained at circumcision were cultured. Total RNA was isolated after incubation for 48 h with 100 nM T or without androgens. Each sample was amplified in triplicate by real-time PCR with porphobilinogen desaminase as a housekeeping gene used for semiquantification. Selected cultures were analyzed after incubation with 10 and 100 nM T and 1 and 100 nM DHT for 24, 48 and 120 h.

RESULTS

5RI was transcribed in all investigated samples with a 4.5-fold variability in the mRNA concentration of different individuals. However, neither age-related regulation nor significant influence of T or DHT on the transcription rate was discovered.

CONCLUSION

Since 5RI is abundantly transcribed in GSFs, we hypothesize that this isoenzyme may play important roles in the androgen physiology of normally virilized males and may contribute to masculinization in 5RII-deficient males at the time of puberty.

Regulation of 5alpha-reductase isoforms by oxytocin in the rat ventral prostate

Oxytocin (OT) is present in the male reproductive tract, where it is known to modulate contractility, cell growth, and steroidogenesis. Little is known about how OT regulates these processes. This study describes the localization of OT receptor in the rat ventral prostate and investigates if OT regulates gene expression and/or activity of 5alpha-reductase isoforms I and II. The ventral prostates of adult male Wistar rats were collected following daily sc administration of saline (control), OT, a specific OT antagonist or both OT plus antagonist for 3 d. Expression of the OT receptor was identified in the ventral prostate by RT-PCR and Western blot, and confirmed to be a single active binding site by radioreceptor assay. Immunohistochemistry localized the receptor to the epithelium of prostatic acini and to the stromal tissue. Real-time RT-PCR determined that OT treatment significantly reduced expression of 5alpha-reductase I but significantly increased 5alpha-reductase II expression in the ventral prostate. Activity of both isoforms of 5alpha-reductase was significantly increased by OT, resulting in increased concentration of prostatic dihydrotestosterone. In conclusion, OT is involved in regulating conversion of testosterone to the biologically active dihydrotestosterone in the rat ventral prostate. It does so by differential regulation of 5alpha-reductase isoforms I and II.

Serenoa repens (Permixon®) inhibits the 5α‐reductase activity of human prostate cancer cell lines without interfering with PSA expression

The phytotherapeutic agent Serenoa repens is an effective dual inhibitor of 5alpha-reductase isoenzyme activity in the prostate. Unlike other 5alpha-reductase inhibitors, Serenoa repens induces its effects without interfering with the cellular capacity to secrete PSA. Here, we focussed on the possible pathways that might differentiate the action of Permixon from that of synthetic 5alpha-reductase inhibitors. We demonstrate that Serenoa repens, unlike other 5alpha-reductase inhibitors, does not inhibit binding between activated AR and the steroid receptor-binding consensus in the promoter region of the PSA gene. This was shown by a combination of techniques: assessment of the effect of Permixon on androgen action in the LNCaP prostate cancer cell line revealed no suppression of AR and maintenance of PSA protein expression at control levels. This was consistent with reporter gene experiments showing that Permixon failed to interfere with AR-mediated transcriptional activation of PSA and that both testosterone and DHT were equally effective at maintaining this activity. Our results demonstrate that despite Serenoa repens effective inhibition of 5alpha-reductase activity in the prostate, it did not suppress PSA secretion. Therefore, we confirm the therapeutic advantage of Serenoa repens over other 5alpha-reductase inhibitors as treatment with the phytotherapeutic agent will permit the continuous use of PSA measurements as a useful biomarker for prostate cancer screening and for evaluating tumour progression.

CHEMOPREVENTION OF PROSTATE CANCER IN MEN AT HIGH RISK: RATIONALE AND DESIGN OF THE REDUCTION BY DUTASTERIDE OF PROSTATE CANCER EVENTS (REDUCE) TRIAL

PURPOSE

Chemoprevention may significantly impact the natural history of prostate cancer. The most potent intraprostatic androgen, dihydrotestosterone, has a significant role in the pathophysiology of prostate cancer. It represents a biologically plausible target for chemoprevention through the inhibition of 5alpha-reductase isoenzymes.

MATERIALS AND METHODS

The Reduction by Dutasteride of Prostate Cancer Events clinical trial is an international, multicenter, double-blind, placebo controlled chemoprevention study designed to determine if dutasteride 0.5 mg daily decreases the risk of biopsy detectable prostate cancer. A total of 8,000 men will be randomized to receive dutasteride or placebo for 4 years. Eligible men must be 50 to 75 years old, have a serum prostate specific antigen of 2.5 to 10 ng/ml (ages 50 to 60 years) or 3.0 to 10 ng/ml (older than 60 years). Men must have a negative 6 to 12 core biopsy within 6 months prior to enrollment. Repeat biopsies will be taken at 2 and 4 years. The rates of prostate cancer for each treatment group will be compared. Genetic and protein biomarkers of prostate cancer, and the effect of dutasteride on benign prostatic hyperplasia and prostatitis symptomatology and histopathology will also be assessed.

RESULTS

Results remain to be determined.

CONCLUSIONS

The study will examine the effects of the dual 5alpha-reductase inhibitor dutasteride on the natural history of prostate cancer in men at increased risk for this malignancy. It affords a unique opportunity to examine biomarkers and genetic linkage for prostate cancer, and assess a range of prostate health outcome measures.

Dutasteride, the dual 5alpha-reductase inhibitor, inhibits androgen action and promotes cell death in the LNCaP prostate cancer cell line

BACKGROUND

Reduction of T to DHT by 5alphaR in the prostate enhances androgenic activity for most targets. Inhibition of 5alphaR activity with finasteride attenuates androgen action in men and animal models. The objective of this study was to compare and contrast the effects of a potent new 5alphaR inhibitor, dutasteride, with finasteride in the LNCaP prostate cancer cell line.

METHODS

LNCaP cells were incubated for varying times with T or DHT in steroid-free medium in the absence or presence of increasing doses of dutasteride or finasteride and the effects on 5alphaR activity, PSA accumulation in the medium, and on cell proliferation were determined. Drug effects on apoptosis were investigated using Annexin V staining and a cell death ELISA assay. Effects of the drugs on AR ligand-binding activity and on AR protein levels were determined.

RESULTS

Dutasteride inhibited (3)H-T conversion to (3)H-DHT and, as anticipated, inhibited T-induced secretion of PSA and proliferation. However the drug also inhibited DHT-induced PSA secretion and cell proliferation (IC(50) approximately 1 microM). Finasteride also inhibited DHT action but was less potent than dutasteride. Dutasteride competed for binding the LNCaP cell AR with an IC(50) approximately 1.5 microM. High concentrations of dutasteride (10-50 microM), but not finasteride, in steroid-free medium, resulted in enhanced cell death, possibly by apoptosis. This was accompanied by loss of AR protein and decreased AR ligand-binding activity. Occupation of AR by R1881 partly protected against cell death and loss of AR protein. PC-3 prostate cancer cells, which do not contain AR, also were killed by high concentrations of dutasteride, as well as by 50 microM finasteride.

CONCLUSIONS

Dutasteride exhibited some inhibitory actions in LNCaP cells possibly related to 5alphaR inhibition but also had antiandrogenic effects at relatively low concentrations and cell death-promoting effects at higher concentrations. Finasteride also was antiandrogenic, but less than dutasteride. The antiandrogenic effects may be mediated by the mutant LNCaP cell AR. Promotion of cell death by dutasteride can be blocked, but only in part, by androgens.

Effects of steroids on oxytocin secretion by the human prostate in vitro

Oxytocin (OT) concentrations are elevated in prostate tissue of patients with benign prostatic hyperplasia (BPH). Oxytocin specifically increases growth, 5 alpha-reductase activity and contractility in the prostate. In the rat prostatic OT concentrations are regulated by gonadal steroids, with androgens reducing but oestrogens increasing OT concentrations. The regulation of prostatic oxytocin in man is not understood. This study investigates the effects of gonadal steroids on oxytocin production by the human prostate. Primary explants (approx. 1 mm3) of prostate tissue from patients with BPH were incubated in Dulbecco's modified Eagle's media in the absence or presence of 10 nmol/L testosterone (T), 10 nmol/L dihydrotestosterone (DHT), T or DHT plus 100 nmol/L of the anti-androgen cyproterone acetate (CPA), 55 pmol/L diethylstilbestrol (DES), or DES plus DHT. The amount of oxytocin secreted into the media after 3 days was measured by radioimmunoassay. Testosterone and DHT significantly increased oxytocin concentrations secreted into the media from 0.86 +/- 0.11 ng/g of tissue (control) to 1.51 +/- 0.14 ng/g (p < 0.01) and 1.54 +/- 0.13 ng/g (p < 0.05), respectively. Incubation of tissue samples with CPA resulted in oxytocin concentrations similar to control levels. Treatment with DES caused a significant increase from 1.99 +/- 0.71 to 3.98 +/- 1.36 ng/g (p < 0.05). A similar increase was measured in media of tissue incubated in DES plus DHT (p < 0.001). The results demonstrate that, unlike the rat where androgens decrease oxytocin, in hyperplastic human prostate tissue both androgens and oestrogens increase oxytocin. This imbalance in the regulation of oxytocin may result in promoting prostatic overgrowth in the pathogenesis of BPH.

Messenger RNA levels and enzyme activities of 5 alpha-reductase types 1 and 2 in human benign prostatic hyperplasia (BPH) tissue

BACKGROUND

Benign prostatic hyperplasia (BPH) development requires testicular androgens and aging. The principle prostatic androgen is dihydrotestosterone (DHT). Testosterone is converted to DHT by the enzyme 5 alpha-reductase. Two distinct 5 alpha-reductase enzymes, types 1 and 2, have been identified. While some studies have suggested that type 2 isoenzyme predominates in the prostate, studies on the prostatic localization of the two isoenzymes are controversial. The purpose of this study was to determine the quantitative expressions of 5 alpha-reductase types 1 and 2 in BPH tissues.

METHODS

We examined the localizations of types 1 and 2 isoenzymes in BPH tissues using immunohistochemical staining and a real-time quantitative RT-PCR assay using the TaqMan system. We measured the enzyme activities of types 1 and 2 at pH values of 7.5 and 5.0, respectively.

RESULTS

Our immunohistochemical study showed that type 1 isoenzyme was expressed predominantly in epithelial cells, whereas type 2 isoenzyme was expressed in both stromal and epithelial cells. The real-time RT-PCR assay demonstrated that the copy numbers of type 1 isoenzyme mRNA were significantly higher than those of type 2 isoenzyme mRNA. There were significant associations between enzyme activity at pH 7.5 and type 1 isoenzyme mRNA expression, and between the activity at pH 5.0 and type 2 mRNA expressions.

CONCLUSIONS

We demonstrated that 5 alpha-reductase type 1 had a specific enzyme activity in the prostate, which supports the hypothesis that the type 1 isoenzyme may play a significant role in maintaining prostate enlargement along with the type 2 isoenzyme.

5α-Reductase Type 1 Immunostaining is Enhanced in Some Prostate Cancers Compared With Benign Prostatic Hyperplasia Epithelium

PURPOSE

In the prostate testosterone is converted to the more potent androgen dihydrotestosterone by the enzymes 5alpha-reductase (5alphaR) types 1 (5alphaR1) and 2 (5alphaR2). Since 5alphaR2 is the dominant prostatic enzyme, the 5alphaR2 selective inhibitor finasteride has been widely used to treat benign prostatic hyperplasia (BPH). However, inhibition of both 5alphaR enzymes provides a greater decrease in serum dihydrotestosterone. We developed a specific antibody to 5alphaR1 and assessed expression in BPH and prostate cancer (pCa) tissue. The presence of this isoenzyme in localized prostate cancer would provide a rationale for assessing the efficacy of dual inhibition for prostate cancer prevention.

MATERIALS AND METHODS

A polyclonal antibody to 5alphaR1 was developed and validated using 5alphaR1 and 5alphaR2 transfected COS-1 cells. A total of 26 BPH and 53 pCa specimens were assessed for 5alphaR1 protein expression using immunocytochemical methods. Also, 29 BPH and 37 pCa specimens were assayed for 5alphaR1 and 5alphaR2 enzyme activity.

RESULTS

Specificity of the 5alphaR1 antibody was confirmed using transfected COS-1 cells. Cells transfected with 5alphaR1 showed specific staining in immunocytochemistry experiments and on Western blotting of cell lysates the expected 24 kDa band was observed. High intensity immunoreactivity for 5alphaR1 was observed in the tumor epithelium of 28% of pCa specimens. No high intensity epithelial staining was observed in BPH specimens. In 19% of pCa and 7% of BPH specimens 5alphaR1 enzyme activity was detected.

CONCLUSIONS

The presence of increased 5alphaR1 in some prostatic malignancies suggests that it is worthwhile to investigate the use of a dual 5alphaR inhibitor to prevent or treat early stage prostate cancer.

Induction of 5alpha-reductase type II mRNA transcription in primary cultured prostate epithelial cells by a soluble factor produced by primary cultured prostate fibroblast cells

The role of DHT in the development of BPH has resulted in the formulation of several drugs, which have been designed to inhibit the formation of DHT by the 5alpha-reductase enzymes (5alpha-reductase type I (5alpha-RI) & 5alpha-reductase type II (5alpha-RII)). Although the function of these enzymes is well understood, the biochemical stimulus for initiation of 5alpha-RI and II gene expression has not been described. Study of a co-culture model indicated the presence of a diffusible factor secreted by prostatic fibroblast cells, which is responsible for the transcription of 5alpha-II mRNA in primary prostatic epithelial cells. In this study, we describe the partial characterisation of a fibroblast-secreted, soluble factor which we believe induces the transcription of 5alpha-RII mRNA in long-term primary cultures of prostate epithelial cells which can no longer transcribe 5alpha-RII mRNA.

Development of a new in vitro model for the study of benign prostatic hyperplasia

BACKGROUND

The search for novel agents for the treatment of the lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH) is dependent on an increased understanding of the pathophysiology of the disease. Unfortunately, in vitro and animal models have been of limited value.

METHODS

This article describes a novel model system in which the interactions of the stromal and epithelial components of the prostate gland can be determined.

RESULTS

The coculture system provides a simple model of the cellular interactions occurring in the adult human prostate.

CONCLUSIONS

This coculture system could potentially be used to determine the precise molecular site of action of agents such as terazosin on prostatic apoptosis.

Cultured stromal cells: an in vitro model of prostatic mesenchymal biology

BACKGROUND

Initial efforts to develop in vitro models to study prostatic biology focused on the culture and characterization of epithelial cells. Recently, attention has turned towards inclusion of stromal cells in experimental systems.

METHODS

Improved methods to isolate and culture stromal cells have been developed. An array of markers are employed to characterize subtypes of stromal cells, with particular interest in smooth muscle differentiation.

RESULTS

Defined, serum-free media are available for certain experimental applications. Conditions that promote smooth muscle differentiation have been identified. Investigators have characterized hormonal and peptide factors that regulate the growth of prostatic stromal cells, and have also described paracrine factors produced by stromal cells that influence epithelial biology.

CONCLUSIONS

Prostatic stromal-cell cultures are now widely employed by a large number of investigators for a diverse array of experimental purposes. While further refinement is required to obtain model systems that fully mimic in vivo processes, the availability of stromal- and epithelial-cell cultures provides a valuable resource for studying normal prostatic biology as well as benign prostatic hyperplasia (BPH) and cancer.

Estrogen in the etiopathogenesis of BPH

BACKGROUND

While the androgen-dependence of the prostate gland has long been accepted, the participation of estrogen, mediated via the stroma in the elicitation of benign prostatic hyperplasia (BPH), has only recently been recognized. Its mode of action is still uncertain.

METHODS

This review first outlines the regulation of gene expression via hormones, growth factors, and other ligands in the coordination of cell growth, differentiation, and function. Focus is next directed to factors particularly involved in phosphorylation of estrogen receptors. Then, the access of sex steroids, especially of estrogen to the cell and to the transduction machinery, is described, preparatory to examining the hypotheses by which this access causes the process of BPH to occur.

RESULTS

It becomes clear that the necessary phosphorylative activities which transmit signals to nuclear receptors and thence transcription of target genes can be performed by steroids or mimicked by proxy molecules and by cross-talk between discrete pathways. The character and concentration of the available estrogen are determined by the extent of its biosynthesis, its penetration of the cell, and its subsequent metabolism. In addition, the estrogen affects its own access through stimulation of facilitating peptide hormones, prolactin, and sex hormone-binding globulin. Finally, the induction of BPH is shown to be determined by the androgen/estrogen ratio and the change in stromal/epithelial balance accompanying aging.

CONCLUSIONS

Despite a growing knowledge of hormone levels, metabolism, and activities in the prostate, and the variety of processes and factors they affect, our explanation of BPH is still fanciful.

Serenoa repens (Permixon): a 5alpha-reductase types I and II inhibitor-new evidence in a coculture model of BPH

BACKGROUND

The aim of this study was to determine the effect of the phytotherapeutic agent, Permixon, on a novel coculture model of benign prostatic hyperplasia (BPH) in an effort to better understand the mode of action of the drug in vivo.

METHODS

The effect of Permixon, at the calculated therapeutic concentration, on the activity of 5alpha-reductase isoenzymes was evaluated utilizing a pH-specific assay. Prostate-specific antigen (PSA) secretions into the medium were measured in the presence and absence of Permixon and quantified by an ELISA assay. The morphological patterns before and following Permixon treatment were also examined by electron microscopy. All results were compared to controls.

RESULTS

Permixon at a concentration of 10 micrograms/ml (calculated plasma concentration in patient receiving recommended therapeutic dosage) was shown to be an effective inhibitor of both 5alpha-reductase types I and II isoenzymes without influencing the secretion of PSA by the epithelial cells, even after stimulation with testosterone. The morphology of Permixon-treated cells was found to be markedly different from that of untreated controls. Cells which had been treated with the drug demonstrated extensive accumulation of lipids in the cytoplasm and widespread damage of intracellular membranes, including mitochondrial and nuclear membranes.

CONCLUSIONS

Permixon is an effective dual inhibitor of 5alpha-reductase isoenzyme activities in the prostate. Unlike other 5alpha-reductase inhibitors, Permixon induces this effect without interfering with the cells' capacity to secrete PSA, thus permitting the continued use of PSA measurements for prostate cancer screening.

Localization of type 5 17beta-hydroxysteroid dehydrogenase, 3beta-hydroxysteroid dehydrogenase, and androgen receptor in the human prostate by in situ hybridization and immunocytochemistry

An important source of androgens in the human prostate are those synthesized locally from the inactive adrenal precursor dehydroepiandrosterone (DHEA) and its sulfated derivative DHEA-S. Three beta-HSD (hydroxysteroid dehydrogenase) converts DHEA into androstenedione (4-dione), whereas type 5 17beta-HSD catalyzes the reduction of 4-dione into testosterone in the human prostate and other peripheral intracrine tissues. In the present study, we have used two complementary approaches, namely in situ hybridization and immunocytochemistry, to identify the cells that contain the type 5 17beta-HSD messenger RNA and enzyme in human benign prostatic hyperplasia (BPH). Localization of 3beta-HSD and of the androgen receptor (AR) was also investigated by immunostaining in the same tissue. To find out whether there are any differences between BPH and normal prostate tissue, the localization of type 5 17beta-HSD was reexamined by immunocytochemistry in the normal human prostate samples and also in normal prostate epithelial cell line (PrEC). The in situ hybridization results obtained with a tritiated uridine triphosphate (3H-UTP)-labeled type 5 17beta-HSD riboprobe are in agreement with the immunostaining data obtained with a specific antibody to the enzyme. The immunostaining results obtained from normal prostate tissue and BPH were found to be similar. Thus, in the glandular epithelium, basal cells highly express the messenger RNA and the enzyme, whereas luminal cells show a much lower and variable level of expression. In the stroma and walls of blood vessels, fibroblasts and the endothelial cells lining the blood vessels show positive staining. Similar results are observed when the cellular distribution of 3beta-HSD is investigated. AR immunoreactivity, however, shows a different distribution because, in the epithelium, most of the nuclei of basal cells are negative, whereas the majority of nuclei of the luminal cells show positive staining. A strong reaction for AR is also found in most stromal cell nuclei and in the nuclei of most endothelial cells, as well as in some other cells of the walls of blood vessels. In conclusion, human type 5 17beta-HSD, as well as 3beta-HSD, are highly expressed, not only in the basal epithelial cells and stromal fibroblasts but also in the endothelial cells and fibroblasts of the blood vessels. AR, on the other hand, is highly expressed in the luminal cells. The present data suggest that DHEA is transformed in the basal cells of the glandular epithelium into 4-dione by 3beta-HSD and then into testosterone by type 5 17beta-HSD, whereas dihydrotestosterone is synthesized in the luminal cells after diffusion of testosterone from the underlying layer of basal cells. The potential role of androgen formation and action in blood vessels is unknown and opens new avenues of investigation for a better understanding of the multiple roles of androgens.