Estrogens increase the endothelial nitric oxide synthase (ecNOS) mRNA level in LNCaP human prostate carcinoma cells

Estrogen and Bisphenol A in Hypertension

PURPOSE OF REVIEW

Cardiovascular disease (CVD) is a non-subsiding disease that remains a leading cause of morbidity and mortality. CVD has been associated with endocrine disruptors, such as bisphenol A (BPA). This review critically summarizes existing findings on BPA and hypertension, with particular attention to genomic, non-genomic, molecular, and cellular mechanisms of action that render BPA as a cardiovascular estrogenic disruptor.

RECENT FINDINGS

Owing to its similar estrogenic structure, BPA has been shown to affect various phenotypes that are regulated by the natural hormone, estrogen. Indeed, BPA has been shown to interact with estrogen receptors, located both in the cell membrane and in the cytoplasm/nucleus. Given that estrogen plays an important role in cardiovascular physiology, a contributing role for BPA in CVD would not be unexpected. Existing literature, though limited, established BPA as a source of disruption in cardiovascular health, particularly hypertension. However, effects of BPA are largely dependent on the dose, patient gender, tissue, and developmental stage of the exposed tissue/organ. Accumulating evidence argues for an adverse effect of BPA on blood pressure, with this effect being gender, dose, and time specific. Thus, comprehensive studies which take these factors and other parameters, like epigenetic factors, into account are warranted before a thorough understanding is at hand.

Endothelial Nitric Oxide Synthase Glu298Asp Polymorphism as a Risk Factor for Prostate Cancer

Background

The endothelial form of nitric oxide synthases (eNOS) seems to have an important role in vascular development, maintenance of the vascular tone and tumor growth in human prostate cancer (PC). The purpose of this study was to investigate the association between grade and stage of disease, age of diagnosis, vascular or perineural invasion, pre-diagnostic plasma prostate-specific antigen (PSA) levels, prostate cancer risk and Glu298Asp polymorphism of the eNOS gene.

Methods

Ninety-five prostate cancer patients and 111 benign prostate hyperplasia subjects were included. The Glu298Asp polymorphism of the eNOS gene was determined by polymerase chain reaction and restriction fragment length polymorphism

Results

The odds ratio (OR) between the GT and GG polymorphism was 0.76, indicating that the presence of the GT polymorphism decreased the risk of prostate cancer of more than 20% compared to the GG polymorphism. This difference, however, was not statistically significant. The GT polymorphism had an inverse association with cancer grade compared to the reference group (OR=0.47, p value=0.2).

Conclusions

These results suggest that prostate cancer development is not associated with the Glu298Asp polymorphism of the endothelial nitric oxide synthase gene in our population. Further studies in larger samples are needed to confirm our results and characterize the molecular mechanisms by which eNOS is involved in the susceptibility to prostate cancer.

Polymorphisms in oxidative stress-related genes are associated with nasopharyngeal carcinoma susceptibility

Nasopharyngeal carcinoma (NPC) is a complex multifactorial disorder involving both genetic and environmental factors. Polymorphisms of genes encoding nitric oxide synthase (NOS) and antioxidant glutathione-S transferases (GSTs) have been associated with various tumors. We examined the combined role of NOS3, NOS2 and GST polymorphisms in NPC risk in Tunisians. We found that NOS3−786C allele and −786 CC genotype, NOS3+894T allele and +894 GT+TT genotypes, NOS2−277 G allele and −277 GG genotype, and GSTT1 del/del genotype, are more prevalent in NPC patients as compared to healthy controls. Our results suggest that genetically driven dysfunction in red–ox stress pathway could augment the risk in NPC-susceptible individuals.

Endothelial nitric oxide synthase gene polymorphisms and prostate cancer risk in Serbian population

Genome-wide association studies (GWAS) have identified over 46 SNPs associated with human prostate cancer (PCa). Some studies have shown correlation of the nitric oxide synthase (NOS) NOS3 gene polymorphisms with the risk and/or progression of PCa. This study aimed to evaluate the association of NOS3 gene polymorphisms (-786T>C, -764A>G, -714G>T, -690C>T, -649G>A and 894G>T) with PCa risk and progression. 150 patients with PCa, 150 patients with BPH and 100 age-matched healthy controls were recruited in this study. Genotyping of promoter polymorphisms was performed by bi-directional DNA sequencing, and for 894G>T by RFLP analysis. There was no significant association between the alleles and genotypes of these genetic variants and PCa risk. For -786T>C polymorphism, we found that C allele is associated with absence of metastases, assuming dominant genetic model (P = 0.049; OR, 0.50; 95% CI, 0.25-1.00). It was found that, compared with NOS3 -690C>T variant CC genotype, CT and TT genotypes confer decreased risk of developing metastases (dominant model, P = 0.015, OR, 0.24; 95% CI, 0.07-0.88) and show association with low clinical tumour stage, compared with stages T3 and T4 (dominant model, P = 0.046, OR, 0.20; 95% CI, 0.04-1.02). Genetic variants -764A>G, -714G>T, -649G>A were not detected in our study group. There is evidence of an inverse correlation of the NOS3 894G>T minor allele with high serum PSA (>20 ng/ml) (dominant model, P = 0.013, OR, 0.37; 95% CI, 0.17-0.82). Our results suggest that NOS3 gene polymorphisms are genetic susceptibility factors for the progression of PCa and patient outcome.

Influence of angiotensin I-converting enzyme gene polymorphism on hepatocellular carcinoma risk in China

Growing evidence suggests that the angiotensin-converting enzyme (ACE) and endothelial nitric oxide synthase (eNOS) genes are associated with risk in a wide range of cancers. The objective of this study was to examine whether two DNA polymorphisms at the ACE insertion/deletion (I/D) and the variable number of tandem repeats in NOS intron 4 (4a/4b) were linked to the risk of developing hepatocellular carcinoma (HCC) in a Chinese population. The polymorphisms at ACE I/D and eNOS 4a/4b were genotyped in 293 HCC patients and 384 healthy control subjects using polymerase chain reaction. The frequencies of the D allele (p=0.003, OR=0.72, 95% CI=0.58-0.90) in the ACE gene of HCC patients were significantly different from the healthy controls, and a significantly decreased HCC risk was associated with the DD genotype in both the recessive (p<0.001, OR=0.19, 95% CI=0.11-0.34) and codominant models (p<0.001, OR=0.26, 95% CI=0.14-0.48). This study provided evidence that the ACE I/D polymorphism is associated with HCC, indicating that the ACE I/D polymorphism contributes to HCC progression in the Chinese population.

eNOS activation by physical forces: from short-term regulation of contraction to chronic remodeling of cardiovascular tissues

Nitric oxide production in response to flow-dependent shear forces applied on the surface of endothelial cells is a fundamental mechanism of regulation of vascular tone, peripheral resistance, and tissue perfusion. This implicates the concerted action of multiple upstream "mechanosensing" molecules reversibly assembled in signalosomes recruiting endothelial nitric oxide synthase (eNOS) in specific subcellular locales, e.g., plasmalemmal caveolae. Subsequent short- and long-term increases in activity and expression of eNOS translate this mechanical stimulus into enhanced NO production and bioactivity through a complex transcriptional and posttranslational regulation of the enzyme, including by shear-stress responsive transcription factors, oxidant stress-dependent regulation of transcript stability, eNOS regulatory phosphorylations, and protein-protein interactions. Notably, eNOS expressed in cardiac myocytes is amenable to a similar regulation in response to stretching of cardiac muscle cells and in part mediates the length-dependent increase in cardiac contraction force. In addition to short-term regulation of contractile tone, eNOS mediates key aspects of cardiac and vascular remodeling, e.g., by orchestrating the mobilization, recruitment, migration, and differentiation of cardiac and vascular progenitor cells, in part by regulating the stabilization and transcriptional activity of hypoxia inducible factor in normoxia and hypoxia. The continuum of the influence of eNOS in cardiovascular biology explains its growing implication in mechanosensitive aspects of integrated physiology, such as the control of blood pressure variability or the modulation of cardiac remodeling in situations of hemodynamic overload.

The -786T>C promoter polymorphism of the NOS3 gene is associated with prostate cancer progression

Background

There is no biological or epidemiological data on the association between NOS3 promoter polymorphisms and prostate cancer. The polymorphisms in the promoter region of NOS3 gene may be responsible for variations in the plasma NO, which may promote cancer progression by providing a selective growth advantage to tumor cells by angiogenic stimulus and by direct DNA damage.

Methods

This study aimed evaluating the NOS3 promoter polymorphisms by PCR-SSCP and sequencing, associating genotypes and haplotypes with NOS3 expression levels through semi-quantitative RT-PCR, and with PCA3 mRNA detection, a specific tumor biomarker, in the peripheral blood of pre-surgical samples from 177 patients; 83 PCa and 94 BPH.

Results

Three novel SNPs were identified -764A>G, -714G>T and -649G>A in the NOS3 gene promoter region, which together with the -786T>C generated four haplotypes (N, T, C, A). NOS3 gene expression levels were affected by the -786T>C polymorphism, and there was a 2-fold increase in NOS3 levels favored by the incorporation of each C allele. NOS3 levels higher than 80% of the constitutive gene expression level (B2M) presented a 4-fold increase in PCa occurrence.

Conclusion

The -786T>C polymorphism was the most important promoter alteration of the NOS3 gene that may affect the PCa progression, but not its occurrence, and the incorporation of the C allele is associated with increased levels of NOS3 transcripts. The NOS3 transcript levels presented a bimodal behavior in tumor development and may be used as a biomarker together with the PCA3 marker for molecular staging of the prostate cancer.

Sex hormones induce direct epithelial and inflammation-mediated oxidative/nitrosative stress that favors prostatic carcinogenesis in the noble rat

Oxidative and nitrosative stress have been implicated in prostate carcinogenesis, but the cause(s) of redox imbalance in the gland remains poorly defined. We and others have reported that administration of testosterone plus 17beta-estradiol to Noble rats for 16 weeks induces dysplasia and stromal inflammation of the lateral prostate (LP) but not the ventral prostate. Here, using laser capture microdissected specimens, we found that the combined hormone regimen increased the expression of mRNA of specific members of NAD(P)H oxidase (NOX-1, NOX-2, and NOX4), nitric-oxide synthase [NOS; inducible NOS and endothelial NOS], and cyclooxygenase (COX-2) in the LP epithelium and/or its adjacent inflammatory stroma. Accompanying these changes was the accumulation of 8-hydroxy-2'-deoxyguanosine, 4-hydroxynonenal protein adducts, and nitrotyrosine, primarily in the LP epithelium, suggesting that NOX, NOS, and COX may mediate hormone-induced oxidative/nitrosative stress in epithelium. We concluded that the oxidative/nitrosative damage resulting from the testosterone-plus-17beta-estradiol treatment is not solely derived from stromal inflammatory lesions but likely also originates from the epithelium per se. In this context, the up-regulation of COX-2 from epithelium represents a potential mechanism by which the hormone-initiated epithelium might induce inflammatory responses. Thus, we link alterations in the hormonal milieu with oxidative/nitrosative/inflammatory damage to the prostate epithelium that promotes carcinogenesis.

The endothelial nitric oxide synthase Glu-298-Asp polymorphism and its mRNA expression in the peripheral blood of patients with prostate cancer and benign prostatic hyperplasia

BACKGROUND

The endothelial nitric oxide synthase (ecNOS) has an important role in vascular development and in the carcinogenesis process of prostate cancer (PCa). The nitric oxide (NO) production may promote cancer progression by providing a selective growth advantage to tumor cells, by angiogenic stimulus and by direct DNA damage.

METHODS

The present study aimed at evaluating the ecNOS Glu-298-Asp polymorphism by the PCR-RFLP technique, associating genotypes with gene expression levels and the tumor biomarker, Prostate Cancer Antigen (DD3), through semi-quantitative RT-PCR. Pre-surgical peripheral blood samples from 160 patients were analyzed: 84 PCa, 11 prostate intraepithelial neoplasia (PIN) and 65 benign prostatic hyperplasia (BPH).

RESULTS

The GG and GT Glu-298-Asp genotypes were associated with positive DD3 expression in the peripheral blood, presenting a 3.32-fold higher risk of PCa occurrence. There was no association between genotypes and ecNOS mRNA expression levels; however, the presence of the G allele is closely related to the hematogenous dissemination event of tumoral cells, as evidenced by the DD3 positivity. The higher G allele frequency among pT3 and pT4 staged PCa patients suggests that this would be associated with advanced phenotypes of the disease and may also be contributing to higher NO levels, causing cancer progression.

CONCLUSIONS

The G allele may have a secondary influence on the prostate cancer predisposition, but an essential role on the event of tumor cells hematogenous dissemination, probably due to the angiogenic stimulus.

Cytogenetic and expression profiles associated with transformation to androgen-resistant prostate cancer

BACKGROUND

The mechanisms underlying the progression of prostate cancer to androgen-resistant cancer are still not fully understood. Here, we studied the genetic events associated with this transformation.

METHODS

The androgen sensitive prostate cancer cells line LNCaP-FGC and its androgen resistant subline LNCaP-r were investigated using SKY, CGH, and cDNA microarray.

RESULTS

Karyotypically, several additional chromosomal aberrations were seen in LNCaP-r as compared to the parental line. CGH also revealed unique net chromosomal alterations in LNCaP-r compared to LNCaP-FGC, including gain of 2p13-23, 2q21-32, and 13q and loss of 6p22-pter. cDNA microarray analysis identified several genes involved in DNA methylation, such as DNMT2, DNMT3a, and methyl-CpG binding domain protein 2 and 4 that were higher expressed in LNCaP-r. Interestingly, androgen responsiveness of LNCaP-r was restored after treated with DNA methyltransferase inhibitor.

CONCLUSIONS

Our findings may serve as a basis for molecular dissection of the mechanisms involved in development of androgen resistant prostate cancer.

Comparison of proposed frameworks for grouping polychlorinated biphenyl congener data applied to a case-control pilot study of prostate cancer

Although the commercial synthesis of polychlorinated biphenyls (PCBs) has been banned in the United States for several decades, they are persistent in the environment with exposure mainly being through diet. The biologic and toxic effects of PCBs and their metabolites are due in part to their ability to interact with several cellular and nuclear receptors, thereby altering signaling pathways and gene transcription. These effects include endocrine modulation and disruption. Therefore, the natural history of cancer in tissues expressing these receptors may be modulated by PCB congeners, which are known to have estrogenic, antiestrogenic, and other hormonal effects. Several frameworks for grouping PCB congeners based on these interactions have been proposed. We conducted a hospital-based, case-control pilot study of 58 prostate cancer cases and 99 controls to evaluate the association between the proposed PCB groupings and the risk of prostate cancer. Serum samples were analyzed for a total of 30 PCBs. In multivariate analyses, the odds of prostate cancer among men with the highest concentrations of moderately chlorinated PCBs or PCBs with phenobarbital-like activities (constitutively active receptor (CAR) agonists) was over two times that among men with the lowest concentrations. Increasing trends in risk across the concentration levels were also observed. These results suggest that a higher burden of PCBs that are CAR agonists may be positively associated with an increased risk of prostate cancer and they encourage further research in this area.

Relationship between upregulated oestrogen receptors and expression of growth factors in cultured, human, prostatic stromal cells exposed to estradiol or dihydrotestosterone

This study investigated the hypothesis that, in benign prostatic hyperplasia (BPH), upregulated oestrogen receptors (ER) and the action of androgens differentially regulate expression of stromal growth factors. Eight human prostatic stromal cell strains were subjected to a procedure to upregulate their ER by exposing them to 1 micromol 17beta-estradiol for 10 days followed by passage and growth in the absence of steroids. Four of the cell strains instead received 100 nmol dihydrotestosterone for 48 h. Immunoexpression of ERalpha, AR and six growth factors was quantified by flow cytometry in each case. Expression of ERalpha was significantly increased in six of eight cell strains. Expressions of six growth factors (FGF-2, FGF-7, IGF-1, TGF-beta1 NGF and e NOS) were elevated but only for FGF-7 was it significant. There was a significant positive correlation between the change in ERalpha and the change in FGF-2 and FGF-7, but not the other growth factors. Exposure to dihydrotestosterone reduced expression of ERalpha and all six growth factors, compared with oestrogen-treated cells but not significantly. It is concluded that upregulated ERalpha in prostatic stroma may have a greater modulating influence on synthesis of certain growth factors than the direct action of androgens and, by enhancing synthesis of FGF-2 and FGF-7, could play a significant role in the development of BPH.

Influence of estrogen and polyamines on mifepristone-induced apoptosis in prostate cancer cells

PURPOSE

Although androgens are the main steroids controlling the growth of prostate glands, estrogens are also important in the regulation of its growth. Prostate cancer cells, like other cancer cells, maintain high levels of polyamines. In LNCaP cells, apoptosis is induced by mifepristone. During the process of cell death, the regulation of ROS production, caspase-3 activation and poly (ADP-ribose) polymerase cleavage were investigated in the presence of estrogen and polyamines to identify their possible roles.

MATERIALS AND METHODS

The cell growth was assessed using the MTT assay, and the intracellular ROS production by the DCFH-DA assay. The p53 protein expression, activation of caspase-3 and PARP cleavage were checked by Western blotting, with specific antibodies to each.

RESULTS

The growth and viability of the cells were significantly inhibited, in a dose- and time-dependent manners, by mifepristone (MIF) treatment. The production of ROS were dependent on the MIF dosage. The activation of caspase-3 and cleavage of PARPalso increased with the duration of MIF treatment. The expression of p53 protein also increased with increases in the MIF incubation time. E(2) severely inhibited the ROS production, caspase-3 activation and PARP cleavage. However, polyamines only inhibited the ROS production, without influencing the caspase-3 activation or PARP cleavage.

CONCLUSION

In LNCaP cells, MIF induces apoptosis through ROS production. The expression of p53 protein, caspase-3 activation and PARP cleavage accompanied the process of apoptosis. The apoptotic processes were inhibited by E(2), but polyamines only inhibited the ROS production, implying the multifunctional role of E(2), in addition to its role as a free radical scavenger.

Lipid profiles and endothelial function with low-dose hormone replacement therapy in postmenopausal women at risk for coronary artery disease: a randomized trial

AIMS

To compare the effect of low (0.3 mg) and commonly prescribed (0.625 mg) doses of conjugated equine estrogens (CEE) on brachial artery flow-mediated dilation and lipid profiles.

METHODS AND RESULTS

Twenty-five postmenopausal women (mean age, 65+/-6 years) at risk for coronary artery disease (CAD) (> or =2 established risk factors) entered a double-blind crossover study. Brachial artery endothelial function was evaluated by means of high-resolution vascular echography. Both CEE doses significantly decreased total cholesterol (-13%, 0.3 mg; -15%, 0.625 mg), low-density lipoprotein-cholesterol (LDL-C) (-15%, 0.3 mg; -16%, 0.625 mg), and lipoprotein(a) (-28%, 0.3 mg; -39%, 0.625 mg) values from baseline levels. Both treatments increased high-density lipoprotein-cholesterol (HDL-C) (5%, 0.3 mg; 7%, 0.625 mg) and triglycerides (3%, 0.3 mg; 8%, 0.625 mg). There was no dose effect for changes in the LDL-C/HDL-C ratio (-21%, 0.3 mg; -23%, 0.625 mg). Both doses improved brachial artery dilation during reactive hyperemia by 63% over baseline.

CONCLUSION

In women at risk for CAD, low-dose hormone replacement treatment (HRT) improves lipid profiles and brachial artery endothelial function comparably to the most commonly prescribed dose. The benefit:risk ratio of low-dose HRT provides an attractive option for postmenopausal women at risk for CAD.

Endothelial nitric oxide synthase gene polymorphisms and the shedding of circulating tumour cells in the blood of prostate cancer patients

The involvement of endothelial nitric oxide synthase (ecNOS) gene polymorphisms (ecNOS4a/b and Glu-Asp298) on the shedding of tumor cells in the blood of 61 patients with prostate cancer (PCa), was analyzed. Hematogenous micrometastasis with blood circulating tumor cells (CTCs) may be an early event in the natural history of PCa metastization. CTCs can be detected by the presence of messenger RNA prostate specific membrane antigen by reverse transcription-polymerase chain reaction. We found an association between ecNOS4a/b genotypes presenting the a allele (ab/aa) with the presence of CTCs in the blood of PCa under the age of 67 years (P=0.003) and with localized disease (P=0.012). This association was not found for Glu-Asp298 genotypes. In summary, we have identified a nitric oxide related genetic factor associated with micrometastization of prostate cancer. We hypothesize that genotypes with the a allele of the ecNOS4a/b polymorphism may facilitate the survival of CTCs in the blood of cancer patients.

Estrogen modulation of endothelial nitric oxide synthase

Over the past decade, clinical and basic research has demonstrated that estrogen has a dramatic impact on the response to vascular injury and the development of atherosclerosis. Further work has indicated that this is at least partially mediated by an enhancement in nitric oxide (NO) production by the endothelial isoform of NO synthase (eNOS) due to increases in both eNOS expression and level of activation. The effects on eNOS abundance are primarily mediated at the level of gene transcription, and they are dependent on estrogen receptors (ERs), which classically serve as transcription factors, but they are independent of estrogen response element action. Estrogen also has potent nongenomic effects on eNOS activity mediated by a subpopulation of ERalpha localized to caveolae in endothelial cells, where they are coupled to eNOS in a functional signaling module. These observations, which emphasize dependence on cell surface-associated receptors, provide evidence for the existence of a steroid receptor fast-action complex, or SRFC, in caveolae. Estrogen binding to ERalpha on the SRFC in caveolae leads to G(alphai) activation, which mediates downstream events. The downstream signaling includes activation of tyrosine kinase-MAPK and Akt/protein kinase B signaling, stimulation of heat shock protein 90 binding to eNOS, and perturbation of the local calcium environment, leading to eNOS phosphorylation and calmodulin-mediated eNOS stimulation. These unique genomic and nongenomic processes are critical to the vasoprotective and atheroprotective characteristics of estrogen. In addition, they serve as excellent paradigms for further elucidation of novel mechanisms of steroid hormone action.

Endothelial nitric oxide synthase gene polymorphisms and genetic susceptibility to prostate cancer

The endothelial cell-specific form of nitric oxide synthases (ecNOS) is localized at 7q35-q36 and is involved in vascular development and tumour growth in human prostate cancer. We have conducted a case-control study to investigate the prevalence of two polymorphisms at intron 4 (ecNOS4a/b) and exon 7 (Glu-Asp298) of ecNOS gene in 125 prostate cancer (PCa) patients and in 153 controls. We observed that the a-allele (aa or ab genotypes from ecNOS4a/b) was over-presented in the group of PCa with Gleason histological grade >or=7 (P=0.041). With regard to the Glu-Asp298 polymorphism, patients with the T-allele were younger than patients with no T-allele (P=0.037), and a statistically significant difference was noted in the Glu-Asp298 genotype distribution between cases with advanced disease and cases with localized disease (P=0.0013). When comparing cases and controls with logistic regression analysis we observed that the presence of the a-allele is associated with prostate cancer risk (odds ratio (OR) 1.83; 95% confidence interval (CI) 1.06-3.17; P=0.029), to high histological grade (Gleason >or=7) of PCa (OR 2.18; 95% CI 0.95-4.98; P=0.062) and with the risk of progression of the cancer disease (OR 2.85; 95% CI 1.19-6.82; P=0.018). Furthermore, we found that carriers with the combination of the a-allele (aa and ab ecNOS4a/b genotypes) and T-allele (GT and TT from Glu-Asp298) have a threefold increase in prostate cancer risk (OR 3.13; 95% CI 1.41-6.91, P=0.004). In summary, we have identified an NO-related genetic risk factor for prostate cancer that may help in understanding the molecular mechanism involved in the individual susceptibility to prostate cancer.

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.

Cholinergic innervation and function in the prostate gland

The mammalian prostate is densely innervated by hypogastric and pelvic nerves that play an important role in regulating the growth and function of the gland. While there has been much interest in the role of the noradrenergic innervation and adrenoceptors in prostate function, the role of cholinergic neurones in prostate physiology and pathophysiology is not well understood. This review focuses on the role of acetylcholine and cholinoceptors in prostate function. Nitric oxide, vasoactive intestinal polypeptide, and/or neuropeptide Y are co-localised with cholinesterase and/or acetylcholine transporter in some of the nerve fibres supplying the prostate. Their roles are also briefly discussed in this review. A dense network of cholinesterase-staining fibres supplies both prostate epithelium and stroma, suggesting a role of acetylcholine and/or co-localised neuropeptides in the modulation of prostatic secretions, as well as smooth muscle tone. A predominantly epithelial location for prostate muscarinic receptors indicated a major secretomotor role for acetylcholine. The muscarinic receptor subtype mediating muscarinic agonist-induced smooth muscle contraction or enhancement of contractions evoked by nerve stimulation differs in different species. In the human, there is evidence for M(1) receptors on the epithelium, M(2) receptors on the stroma, and both M(1) and M(3) receptors in some prostate cancer cell lines. Several recent investigations indicate that muscarinic receptors may also mediate or modulate normal, benign, and malignant prostate growth. The role of muscarinic agonists and their receptors and the influences of age, testicular, and other steroids in regulating the effects are reviewed.