Attenuated proliferation and trans-differentiation of prostatic stromal cells indicate suitability of phosphodiesterase type 5 inhibitors for prevention and treatment of benign prostatic hyperplasia

Phosphodiesterase type 5 inhibitor tadalafil reduces prostatic fibrosis via MiR-3126-3p/FGF9 axis in benign prostatic hyperplasia

Myofibroblast buildup and prostatic fibrosis play a crucial role in the development of benign prostatic hyperplasia (BPH). Treatments specifically targeting myofibroblasts could be a promising approach for treating BPH. Tadalafil, a phosphodiesterase type 5 (PDE5) inhibitor, holds the potential to intervene in this biological process. This study employs prostatic stromal fibroblasts to induce myofibroblast differentiation through TGFβ1 stimulation. As a result, tadalafil significantly inhibited prostatic stromal fibroblast proliferation and fibrosis process, compared to the control group. Furthermore, our transcriptome sequencing results revealed that tadalafil inhibited FGF9 secretion and simultaneously improved miR-3126-3p expression via TGFβ1 suppression. Overall, TGFβ1 can trigger pro-fibrotic signaling through miR-3126-3p in the prostatic stroma, and the use of tadalafil can inhibit this process.

Beyond Erectile Dysfunction: cGMP-Specific Phosphodiesterase 5 Inhibitors for Other Clinical Disorders

Cyclic guanosine monophosphate (cGMP), an important intracellular second messenger, mediates cellular functional responses in all vital organs. Phosphodiesterase 5 (PDE5) is one of the 11 members of the cyclic nucleotide phosphodiesterase (PDE) family that specifically targets cGMP generated by nitric oxide-driven activation of the soluble guanylyl cyclase. PDE5 inhibitors, including sildenafil and tadalafil, are widely used for the treatment of erectile dysfunction, pulmonary arterial hypertension, and certain urological disorders. Preclinical studies have shown promising effects of PDE5 inhibitors in the treatment of myocardial infarction, cardiac hypertrophy, heart failure, cancer and anticancer-drug-associated cardiotoxicity, diabetes, Duchenne muscular dystrophy, Alzheimer's disease, and other aging-related conditions. Many clinical trials with PDE5 inhibitors have focused on the potential cardiovascular, anticancer, and neurological benefits. In this review, we provide an overview of the current state of knowledge on PDE5 inhibitors and their potential therapeutic indications for various clinical disorders beyond erectile dysfunction.

Tadalafil and Steroid Hormones Interactions in Adipose, Bone and Prostate Tissues: Focus on Translational Perspectives

Tadalafil is a selective phosphodiesterase type-5 (PDE5) inhibitor that is approved for the treatment of men with erectile dysfunction (ED) and/or benign prostate hyperplasia (BPH) -associated symptoms. Besides its classical actions on PDE5 within the genitourinary tract, where the specific enzyme expression is maximal, it may exert different systemic effects. This is mainly due to the pleiotropic distribution of PDE5 enzyme throughout the human (and animal) body, where it can exert protective effects in different clinical conditions. Recently, it has been demonstrated that tadalafil may display novel actions on androgen receptor (AR) expression and activity and cytochrome P19a1 (Cyp19a1) and estrogen receptor β (ERβ) expression in different in vitro systems, such as adipose, bone and prostate cancer cells, where it can act as a selective modulator of steroid hormone production. This may determine novel potential mechanism(s) of control in pathophysiologic pathways. In this review, we summarize basic research and translational results applicable to the use of tadalafil in the treatment of obesity, bone loss and prostate cancer.

Benign prostatic hyperplasia/obstruction ameliorated using a soluble guanylate cyclase activator

Benign prostatic hyperplasia (BPH) is a feature of ageing males. Up to half demonstrate bladder outlet obstruction (BOO) with associated lower urinary tract symptoms (LUTS) including bladder overactivity. Current therapies to reduce obstruction, such as α1-adrenoceptor antagonists and 5α-reductase inhibitors, are not effective in all patients. The phosphodiesterase-5 inhibitor (PDE5I) tadalafil is also approved to treat BPH and LUTS, suggesting a role for nitric oxide (NO• ), soluble guanylate cyclase (sGC), and cGMP signalling pathways. However, PDE5I refractoriness can develop for reasons including nitrergic nerve damage and decreased NO• production, or inflammation-related oxidation of the sGC haem group, normally maintained in a reduced state by the cofactor cytochrome-b5-reductase 3 (CYB5R3). sGC activators, such as cinaciguat (BAY 58-2667), have been developed to enhance sGC activity in the absence of NO• or when sGC is oxidised. Accordingly, their effects on the prostate and LUT function of aged mice were evaluated. Aged mice (≥24 months) demonstrated a functional BPH/BOO phenotype, compared with adult animals (2-12 months), with low, delayed voiding responses and elevated intravesical pressures as measured by telemetric cystometry. This was consistent with outflow tract histological and molecular data that showed urethral constriction, increased prostate weight, greater collagen deposition, and cellular hyperplasia. All changes in aged animals were attenuated by daily oral treatment with cinaciguat for 2 weeks, without effect on serum testosterone levels. Cinaciguat had only transient (1 h) cardiovascular effects with oral gavage, suggesting a positive safety profile. The benefit of cinaciguat was suggested by its reversal of an overactive cystometric profile in CYB5R3 smooth muscle knockout mice that mirrors a profile of oxidative dysfunction where PDE5I may not be effective. Thus, the aged male mouse is a suitable model for BPH-induced BOO and cinaciguat has a demonstrated ability to reduce prostate-induced obstruction and consequent effects on bladder function. © 2021 The Pathological Society of Great Britain and Ireland.

Human Tissue Kallikrein 1 Is Downregulated in Elderly Human Prostates and Possesses Potential In Vitro Antioxidative and Antifibrotic Effects in Rodent Prostates

Objective

The aim of the present study was to investigate the protective effects and mechanisms of KLK1 on aging-related prostate alterations and search clues about the application of KLK1 to the treatment of human BPH.

Methods

Thirty-six rats including 26 male wild-type SD rats and 10 transgenic rats were fed to 3- or 18-month-old and divided into three groups: young WTR (yWTR) as the control (n = 16), aged WTR (aWTR) (n = 10), and aged TGR (aTGR) (n = 10). The prostates of the three groups of rats (10 rats per group) were harvested to evaluate the levels of KLK1 expression, oxidative stress, fibrosis, and involved signaling pathways, such as NO/cGMP, COX-2/PTGIS/cAMP, and TGF-β1/RhoA/ROCK1, via quantitative PCR, Western blot, histological examinations, and ELISA. Moreover, the remaining 6 yWTRs were sacrificed to obtain primary prostate fibroblast and aortic endothelial cells, and a coculture system was built with the cells for the verification of above signaling pathways in vitro. And the direct effects of bradykinin on prostate cells were detected by MTT experiment. Prostate specimens of 47 patients (age from 48 to 92 years) undergoing BPH surgery were collected after approval. Histological examinations and KLK1 IHC were preformed to analyze the relationship between KLK1 expression and age and prostate fibrosis.

Results

The human KLK1 gene only existed and was expressed in aTGR. The prostate of young rats expressed more KLK1 than the aged and the expression of KLK1 in prostate decreased with age in humans (r = −0.347, P = 0.018). Compared to the aWTR group, the yWTR and aTGR groups showed milder fibrosis, less oxidative stress, upregulated NO/cGMP, and COX-2/PTGIS/cAMP signaling pathways and inhibited TGF-β1/RhoA/ROCK1 signaling pathway. In the coculture system, KLK1 suppressed TGF-β1-mediated fibroblast-to-myofibroblast transdifferentiation via cleaving LMWK to produce the BK which upregulate eNOS expression and NO production in endothelial cells. BK not only slightly stimulated the proliferation ability of prostatic stromal cells but also upregulated iNOS and inhibited TGF-β1 expression in them.

Conclusion

KLK1 protects prostate from oxidative stress and fibrosis via amplified NO/cGMP signal in aged rats. The decrease of KLK1 expression with aging is laying the groundwork for the application of KLK1 to the treatment of human BPH. The current experimental data showed that the side effects of KLK1 on the prostate cell were not obvious.

Phosphodiesterase Type-5 Inhibitor Tadalafil Modulates Steroid Hormones Signaling in a Prostate Cancer Cell Line

Background: The androgen receptor (AR) plays a key role in normal prostate homeostasis and in prostate cancer (PCa) development, while the role of aromatase (Cyp19a1) is still unclear. We evaluated the effects of a treatment with Tadalafil (TAD) on both these proteins. Methods: Androgen-sensitive human PCa cell line (LnCAP) was incubated with/without TAD (10⁻⁶ M) and bicalutamide (BCT) (10⁻⁴ M) to evaluate a potential modulation on cell proliferation, protein and mRNA expression of Cyp19a, AR and estrogen receptor-β (ERβ), respectively. Results: TAD increased early AR nuclear translocation (p < 0.05, after 15 min of exposure), and increased AR transcriptional activity (p < 0.05) and protein expression (p < 0.05) after 24 h. Moreover, after 24 h this treatment upregulated Cyp19a1 and ERβ mRNA (p < 0.05 and p < 0.005 respectively) and led to an increase in protein expression of both after 48 h (p < 0.05). Interestingly, TAD counteracted Cyp19a1 stimulation induced by BCT (p < 0.05) but did not alter the effect induced by BCT on the AR protein expression. Conclusion: We demonstrate for the first time that TAD can significantly modulate AR expression and activity, Cyp19a1 and ERβ expression in PCa cells, suggesting a specific effect of these proteins. In addition, TAD potentiates the antiproliferative activity of BCT, opening a new clinical scenario in the treatment of PCa.

Higher expression of phosphodiesterase type 5 in the anterior fibromuscular stroma of the human prostate

PURPOSE

To examine phosphodiesterase type 5 (PDE5) expression in the anterior fibromuscular stroma (AFMS) of the prostate. Although PDE5 expression was identified in the human prostate, differences in PDE5 expression in intra-prostatic regions are unknown. The AFMS in the prostate has peculiar innervations that could contribute to voiding function. Here, we examined regional differences in PDE5 expression in the prostate with special reference to the AFMS.

METHODS

A total 18 human prostate and bladder specimens were obtained. Tissue specimens were processed by hematoxylin-eosin (H&E) staining and immunohistochemistry for PDE5. Immunoreactivity with PDE5 was evaluated using computer-assisted image analysis in the following regions: the AFMS, bladder neck, stromal hyperplasia in the transition zone, glandular hyperplasia in the transition zone (TZ gland), and the peripheral zone (PZ). The correlation between PDE5 expression in the AFMS and clinical data was analysed.

RESULTS

Image analysis revealed that the median ratio of the PDE5-immunoreactive area to smooth muscle area by H&E staining was 74.7% in the AFMS. There was significantly higher PDE5 expression in the AFMS than in the TZ gland (p = 0.034) and PZ (p = 0.002). PDE5 expression in the AFMS was not significantly correlated with age, prostate volume, transition zone volume, or transition zone index. However, older men had a tendency to have higher PDE5 expression in the AFMS.

CONCLUSIONS

We found higher PDE5 expression in the AFMS compared with other prostatic regions, which suggested that the AFMS is a target region of PDE5 inhibitors in the prostate.

Long noncoding RNA DNM3OS promotes prostate stromal cells transformation via the miR-29a/29b/COL3A1 and miR-361/TGFβ1 axes

Transforming growth factor-β1 (TGFβ1)-induced differentiation into and the activation of myofibroblasts have been regarded as critical events in benign prostatic hyperplasia (BPH); however, the underlying mechanisms of BPH pathogenesis remain unclear. Microarray profiling, STRING analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway annotation, and Gene Ontology (GO) enrichment analysis were performed to confirm the candidate genes and long non-coding RNA (lncRNAs) related to BPH. Collagen Type III (COL3A1) was significantly upregulated by TGFβ1 in prostate stromal cells (PrSCs) and might be involved in DNM3OS function in myofibroblasts upon TGFβ1 stimulation. Upon TGFβ1 stimulation, COL3A1 protein was decreased by DNM3OS silencing. miR-29a and miR-29b could directly bind to the DNM3OS and COL3A1 3' untranslated region (UTR)s to negatively regulate their expression, and by serving as a competing endogenous RNAs (ceRNA), DNM3OS competed with COL3A1 for miR-29a/29b binding, therefore counteracting miR-29a/29b-mediated COL3A1 suppression. The effect of DNM3OS silencing on ECM components and TGFβ1 downstream signaling was similar to that of the TGFβ1 inhibitor SB431542. miR-361 could target DNM3OS and TGFβ1; DNM3OS competed for miR-361 binding to counteract miR-361-mediated TGFβ1 suppression. In conclusion, we identified DNM3OS as a specifically-upregulated lncRNA upon TGFβ1 stimulation in PrSCs; by serving as a ceRNA for the miR-29a/29b cluster and miR-361, DNM3OS eliminated miRNA-mediated suppression of COL3A1 and TGFβ1, thereby promoting TGFβ1-induced PrSC transformation into myofibroblasts.

Phosphodiesterase 5 (PDE5) Is Highly Expressed in Cancer-Associated Fibroblasts and Enhances Breast Tumor Progression

The overexpression of phosphodiesterase (PDE) 5 is frequently found in various human cancers, such as those of the breast. However, PDE5’s role in the tumor microenvironment is still unknown. As PDE5 represents a high-value therapeutic target, we investigated whether the expression and function of PDE5 in breast cancer-associated fibroblasts (CAFs) may be clinically relevant to malignant progression. PDE5 expression was increased in human breast cancer stroma compared with normal stroma and was correlated to a shorter overall survival. Treatment of CAFs, isolated from breast tumor biopsies, with selective PDE5 inhibitors inhibited their proliferation, motility, and invasiveness, and negatively controlled tumor–stroma interactions in both ‘in vitro’ and ‘in vivo’ models. PDE5 stable overexpression transformed immortalized mouse embryonic fibroblasts (MEFs) towards an activated fibroblast phenotype, impacting their intrinsic characteristics and paracrine effects on breast cancer cell growth and migration through an enhanced production of the C-X-C motif chemokine 16 (CXCL16). On the other hand, CAF exposure to PDE5 inhibitors was associated with reduced CXCL16 expression and secretion. Importantly, CXCL16 levels in breast cancer stroma showed a strong correlation with PDE5 levels and poor patient outcomes. In conclusion, PDE5 is overexpressed in breast cancer stroma, enhances the tumor-stimulatory activities of fibroblasts, and impacts clinical outcomes; thus, we propose this enzyme as an attractive candidate for prognosis and a potential target for treatments in breast cancer patients.

In Silico Mapping of Essential Residues in the Catalytic Domain of PDE5 Responsible for Stabilization of Its Commercial Inhibitors

Phosphodiesterase type 5 (PDE5) is an important enzyme associated with the hydrolysis of cyclic guanosine monophosphate (cGMP) to guanosine monophosphate (GMP). Due to the relevant role of second messenger cGMP as a mediator in many physiological processes, efforts have been converged to find a safe pharmacological approach, seeking a specific, selective and potent inhibitor of the PDE5 enzyme. There are five commercial drugs with potential for clinical use: tadalafil, sildenafil, avanafil, udenafil and vardenafil. Here, we applied molecular modeling to obtain different profiles of protein–ligand interactions by adopting distinct PDE5 structures, specifically PDBid:1XOZ and two extracted from molecular dynamics (MD) simulations. The results generated by molecular docking showed several possibilities for inhibitor interactions with the catalytic pocket. Tadalafil, sildenafil and vardenafil were clearly stabilized by Gln817 via a well-oriented hydrogen bond. Another set of different interactions, such as polar, hydrophobic, π-stacking, metal–ligand and electrostatic, were responsible for accommodating avanafil and udenafil. All of the ligands are discussed in detail with consideration of the distinct protein structures, and a profile of the probability of residue–ligand contact is suggested, with the most frequently observed being: Tyr612, His613, Ser661, Thr723, Asp724, Asp764, Leu765, Val782 and Phe786. The molecular interactions displayed herein confirm findings achieved by previous authors and also present new contacts. In addition, the discussion can help researchers obtain a molecular basis for planning new selective PDE5 inhibitors, as well as explain an inhibitor’s experimental assays by considering the specific interactions occurring at the catalytic site.

Regulation of PDE5 expression in normal prostate, benign prostatic hyperplasia, and adenocarcinoma

BACKGROUND

Type 5 phosphodiesterase (PDE5) expression in the normal and pathological prostate is controversial.

OBJECTIVES

This study aimed at identifying the cell type/s, if any, expressing PDE5 in human healthy or pathological prostate sections in order to further validate the rationale of PDE5 inhibitor (PDE5i) treatment of benign prostatic hyperplasia (BPH) and their safety in the treatment of erectile dysfunction following prostate cancer (PCa) surgery.

MATERIALS AND METHODS

By immunohistochemical analysis, we studied PDE5 expression in tissue microarrays containing sections obtained from healthy, BPH, and PCa samples.

RESULTS

Our results showed that PDE5 is barely expressed in the epithelial or stromal compartment of normal human prostates, but it is highly expressed in the stromal compartment of BPH sections. We also found that a low but significant number of PCa samples (22%) expressed PDE5 in the epithelial cancer cells but not in stromal cells and that such expression was not correlated with the tumor aggressiveness, according to their Gleason score.

DISCUSSION AND CONCLUSION

PDE5 overexpression in the stromal compartment of BPH samples supports the rationale of PDE5 as a target in lower urinary tract symptoms of BPH. PDE5 expression in a significant percentage of PCa samples but the lack of correlation with the Gleason score suggests that this enzyme is not correlated with tumor aggressiveness; however, a role of PDE5 in the minimal residual disease of PCa cannot be excluded.

Tadalafil for the treatment of benign prostatic hyperplasia

INTRODUCTION

In men, lower urinary tract symptoms (LUTS) are primarily attributed to benign prostatic hyperplasia (BPH). Therapeutic options are targeted to relax prostate smooth muscle and/or reduce prostate enlargement. Areas covered: This article reviews the major preclinical and clinical data on PDE5 inhibitors with a specific focus on tadalafil. It includes details of the role of the nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) - PDE5 pathway in the LUT organs (bladder and prostate) in addition to the available data on tadalafil in patients with LUTS secondary to BPH with or without erectile dysfunction (ED). Expert opinion: Preclinical and clinical data have clearly demonstrated that PDE5 inhibitors induce bladder and prostate relaxation, which contributes to the improvement seen in storage symptoms in both animal models of bladder and prostate hypercontractility. Tadalafil is effective both as a monotherapy and add-on therapy in patients with LUTS secondary to BPH. Furthermore, as LUTS-BPH and ED are urological disorders that commonly coexist in aging men, tadalafil is more advantageous than α1-adrenoceptors and should be used as the first option. Tadalafil is a safe and tolerable therapy and unlike α1- adrenoceptors and 5-alpha reductase inhibitors, which can cause sexual dysfunctions, tadalafil improves sexual function.

Androgen Deficiency and Phosphodiesterase Type 5 Expression Changes in Aging Male: Therapeutic Implications

The age-related decline of serum T occurs in ~20-30% of adult men and it is today defined as late-onset hypogonadism (LOH). In the elderly, such decline becomes more prevalent (up to 60%) and shows-up with erectile dysfunction (ED) and hypoactive sexual desire. A large body of experimental evidences have shown that the combination of T replacement therapy (TRT) and phosphodiesterase type 5 inhibitors (PDE5i) is, usually, effective in restoring erectile function in patients with LOH and ED who have not responded to monotherapy for sexual disturbances. In fact, PDE5is potentiate the action of nitric oxide (NO) produced by endothelial cells, resulting in a vasodilator effect, while T facilitates PDE5i effects by increasing the expression of PDE5 in corpora cavernosa. Meta-analytic data have recognized to PDE5i a protective role on the cardiovascular health in patients with decreased left ventricular ejection fraction. In addition, several studies have shown pleiotropic beneficial effects of these drugs throughout the body (i.e., on bones, urogenital tract and cerebral, metabolic, and cardiovascular levels). TRT itself is able to decrease endothelial dysfunction, oxidative stress and inflammation, thus lowering the cardiovascular risk. Furthermore, untreated hypogonadism could be the cause of PDE5i ineffectiveness especially in the elderly. For these reasons, aging men complaining ED who have LOH should undergo TRT before or at the moment when PDE5i treatment is started.

Is there a relationship between phosphodiesterase type 5 inhibitors and biochemical recurrence after radical prostatectomy: a systematic review and meta-analysis

PURPOSE

Conduct a systematic review and meta-analysis of studies to evaluate the association between the use of PDE5I and biochemical recurrence (BCR) after radical prostatectomy (RP).

METHODS

We searched Embase (from 1996 to Feb 2018), PubMed (from 1996 to Feb 2018), and Cochrane library (from 1999 to Feb 2018), then manually searched the reference lists of key retrieved articles. Original studies that reported the risk of postoperative BCR for PDE5I users, as compared with non-PDE5I users, were included. Data including the characteristic of participants, the risk of BCR after RP and key criteria of study quality were collected. The pooled relative risks (RRs) were calculated with random-effects model.

RESULTS

A total of 5 cohort studies and 1 case-control study were conducted for data analysis (a total of 17752 participants). Only 1 cohort study reported adjusted RR greater than 1 (range for all derived RRs, 0.7-1.47). The meta-analysis revealed that the PDE5I users had no higher risk of BCR after RP (RR = 1.04, 95% confidence interval [CI], 0.79-1.36). Sensitivity analysis showed that the remaining pooled RR and 95% CI were not changed significantly by omitting each study. In addition, the 5-year BCR rate had no significant difference between PDE5I users and non-PDE5I users.

CONCLUSIONS

Our meta-analysis indicated that PDE5I treatment in men following RP did not increase the risk of BCR. The results preliminarily suggested that the use of PDE5I for erectile dysfunction after RP was oncologically safe. Nevertheless, more large sample cohort studies are needed to validate this conclusion.

Association between phosphodiesterase type 5 inhibitors and prostate cancer: A systematic review

INTRODUCTION

We aim to assess the effect of phosphodiesterase type 5 inhibitors (PDE5I) on prostate cancer risk as well on biochemical recurrence after radical prostatectomy.

METHOD

We performed a research using the following keywords "Phosphodiesterase type 5 inhibitors" and "Prostate cancer". Only trials examining the effect of PDE5I on prostate cancer risk and recurrence after radical prostatectomy were included.

RESULTS

Seventeen preclinical trials and seven clinical trials were included. Preclinical studies demonstrate a pivotal role for PDE5I as a modulator of apoptosis preventing prostate carcinogenesis. The clinical benefit of PDE5I was not demonstrated. PDE5I use was not associated with decreased prostate cancer diagnosis in two retrospective cohort studies. Biochemical recurrence after radical prostatectomy was not lower (nor higher) in patients taking PDE5I in three retrospective case match studies.

CONCLUSION

Based on this review, a change in our practice regarding pharmacological reeducation after radical prostatectomy is not justified.

New insights into the pathogenesis and treatment of non-viral hepatocellular carcinoma: a balancing act between immunosuppression and immunosurveillance

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. HCC initiates as a consequence of chronic liver damage and inflammation caused by hepatitis B and C virus infections, excessive alcohol consumption, or non-alcoholic fatty liver disease (NAFLD). Until recently, no effective treatments for advanced HCC were available and the 5-year survival rate had remained below 8% for many years. New insights into the mechanisms that drive the development of NAFLD-related HCC indicate that loss of T-cell-mediated immunosurveillance plays a cardinal role in tumor growth and malignant progression, in addition to previously identified inflammation-driven compensatory proliferation. Recently completed groundbreaking clinical studies have shown that treatments that restore antitumor immunity represent a highly effective therapeutic option for approximately 20% of advanced HCC patients. Understanding the causes of inflammation-driven immunosuppression and immune system dysfunction in the 80% of patients who fail to reignite antitumor immunity despite treatment with checkpoint inhibitors should lead to further and even more dramatic improvements in HCC immunotherapy.

Expression of a recombinant full-length LRP1B receptor in human non-small cell lung cancer cells confirms the postulated growth-suppressing function of this large LDL receptor family member

Low-density lipoprotein (LDL) receptor-related protein 1B (LRP1B), a member of the LDL receptor family, is frequently inactivated in multiple malignancies including lung cancer. LRP1B is therefore considered as a putative tumor suppressor. Due to its large size (4599 amino acids), until now only minireceptors or receptor fragments have been successfully cloned. To assess the effect of LRP1B on the proliferation of non-small cell lung cancer cells, we constructed and expressed a transfection vector containing the 13.800 bp full-length murine Lrp1b cDNA using a PCR-based cloning strategy. Expression of LRP1B was analyzed by quantitative RT-PCR (qRT-PCR) using primers specific for human LRP1B or mouse Lrp1b. Effective expression of the full length receptor was demonstrated by the appearance of a single 600 kDa band on Western Blots of HEK 293 cells. Overexpression of Lrp1b in non-small cell lung cancer cells with low or absent endogenous LRP1B expression significantly reduced cellular proliferation compared to empty vector-transfected control cells. Conversely, in Calu-1 cells, which express higher endogenous levels of the receptor, siRNA-mediated LRP1B knockdown significantly enhanced cellular proliferation. Taken together, these findings demonstrate that, consistent with the postulated tumor suppressor function, overexpression of full-length Lrp1b leads to impaired cellular proliferation, while LRP1B knockdown has the opposite effect. The recombinant Lrp1b construct represents a valuable tool to unravel the largely unknown physiological role of LRP1B and its potential functions in cancer pathogenesis.

Phosphodiesterase type 5 and cancers: progress and challenges

Cancers are an extraordinarily heterogeneous collection of diseases with distinct genetic profiles and biological features that directly influence response patterns to various treatment strategies as well as clinical outcomes. Nevertheless, our growing understanding of cancer cell biology and tumor progression is gradually leading towards rational, tailored medical treatments designed to destroy cancer cells by exploiting the unique cellular pathways that distinguish them from normal healthy counterparts. Recently, inhibition of the activity of phosphodiesterase type 5 (PDE5) is emerging as a promising approach to restore normal intracellular cyclic guanosine monophosphate (cGMP) signalling, and thereby resulting into the activation of various downstream molecules to inhibit proliferation, motility and invasion of certain cancer cells. In this review, we present an overview of the experimental and clinical evidences highlighting the role of PDE5 in the pathogenesis and prevention of various malignancies. Current data are still not sufficient to draw conclusive statements for cancer patient management, but could provide further rational for testing PDE5-targeting drugs as anticancer agents in clinical settings.

Anti-fibrotic effects of soluble guanylate cyclase stimulators and activators: A review of the preclinical evidence

It is now well established that the NO-sGC-cGMP signal transduction system mediates many different physiological functions in almost every conceivable organ system; this has been best characterized in the cardiovascular system where NO-driven cGMP production exerts a plethora of cytoprotective and anti-atherogenic effects, including dilatation, inhibition of vascular smooth muscle proliferation, blockade of leukocyte recruitment, and anti-platelet activity. Accordingly, dysfunctional NO-sGC-cGMP mediated signaling is perceived as the underlying pathophysiological cause of many cardiovascular and non-cardiovascular diseases. Due to the fundamental role of sGC in the signaling pathways triggered by NO, novel sGC 'modulators' have been identified that directly stimulate both heme-containing as well as heme-free sGC, the so-called 'sGC activators' and 'sGC stimulators', respectively. The beneficial effects of this new family of sGC 'modulators' extend beyond vasodilation, and their potential in other cardiovascular diseases aside from pulmonary arterial hypertension is promising. In animal models of hypertension and heart failure, reno-protective effects, attenuated cardiac fibrosis, and attenuated hypertrophy independent of hemodynamic effects have been shown. During recent years it has become obvious that cGMP increase by sGC modulators exerts direct antifibrotic efficacy in various organs as well as the skin. This review will provide an overview of the preclinical in vitro and in vivo studies for different fibrotic disorders including chronic renal, cardiac, liver, and lung fibrosis, as well as sclerosis and wound healing. Moreover, this review provides evidence for a new mode of action of sGC 'modulators' and its implication for clinical investigations in the treatment of fibrotic disorders such as pulmonary fibrosis and skin fibrosis.

Latest Evidence on the Use of Phosphodiesterase Type 5 Inhibitors for the Treatment of Lower Urinary Tract Symptoms Secondary to Benign Prostatic Hyperplasia

CONTEXT

Several preclinical reports, randomized controlled trials, systematic reviews, and posthoc analyses corroborate the role of phosphodiesterase type 5 inhibitors (PDE5-Is) in the treatment of men with lower urinary tract symptoms (LUTS) associated with benign prostatic enlargement (BPE).

OBJECTIVE

Update of the latest evidence on the mechanisms of action, evaluate the current meta-analyses, and emphasize the results of pooled data analyses of PDE5-Is in LUTS/BPE.

EVIDENCE ACQUISITION

Literature analysis of basic researches on PDE5-Is, systematic literature search in PubMed and Scopus until May 2015 on reviews of trials on PDE5-Is, and collection of pooled data available on tadalafil 5mg.

EVIDENCE SYNTHESIS

Latest evidences on the pathophysiology of LUTS/BPE has provided the rationale for use of PDE5-Is: (1) improvement of LUT oxygenation, (2) smooth muscle relaxation, (3) negative regulation of proliferation and transdifferentiation of LUT stroma, (4) reduction of bladder afferent nerve activity, and (5) down-regulation of prostate inflammation are the proven mechanisms of action of PDE5-Is. Data from eight systematic reviews demonstrated that PDE5-Is allow to improve LUTS (International Prostate Symptom Score mean difference vs placebo: 2.35-4.21) and erectile function (International Index of Erectile Function mean difference vs placebo: 2.25-5.66), with negligible change in flow rate (Qmax mean difference vs placebo: 0.01-1.43). Pooled data analyses revealed that tadalafil 5mg once daily allows the clinically-meaningful improvement of LUTS and nocturnal voiding frequency independent of both erectile dysfunction severity and improvement.

CONCLUSIONS

PDE5-Is are safe and effective in improving both LUTS and erectile function in appropriately selected men with LUTS/BPE. Data on the reduction of disease progression, long-term outcomes, and cost-effectiveness analyses are still lacking.

PATIENT SUMMARY

We reviewed recent literature on phosphodiesterase type 5 inhibitors in men with lower urinary tract symptoms associated with prostatic enlargement. We found evidence to confirm that phosphodiesterase type 5 inhibitors are a valid treatment option for men affected by bothersome urinary symptoms with or without erectile dysfunction.

The Role of PDE5 Inhibitors and the NO/cGMP Pathway in Cancer

INTRODUCTION

Phosphodiesterase 5 (PDE5) inhibitors (PDE5i) have been used clinically for the treatment of erectile dysfunction, acting on the nitric oxide/cyclic guanosine monophosphate (NO/cGMP) signaling pathway. Simultaneously, researchers have elucidated the roles that this pathway plays in the regulation of cell proliferation, tumor development, and progression. As a result, our knowledge of PDE5i and cancer biology has expanded and provides an integration that holds great promise for some, but concern for others.

AIM

This review evaluates the role of PDE5i and the NO/cGMP signaling pathway in the pathogenesis and prevention of various malignancies.

METHODS

A literature review was performed with regard to the role of NO/cGMP pathway in tumor formation and prevention in preclinical and clinical studies. Studies that utilized PDE5i to further explore the involvement of this pathway also were included.

MAIN OUTCOME MEASURES

To evaluate whether PDE5i provide a potential benefit for treating and/or preventing malignancies; or if they create potential harm leading to the development of these malignancies.

RESULTS

The best available data suggest that the interactions between PDE5i and cancer are tumor- and tissue-specific. Currently, the effect of PDE5i use on melanoma development is being debated. Further clinical controversy lies in PDE5i use for penile rehabilitation after nerve-sparing prostate cancer surgery. Preclinical studies suggest that PDE5 inhibition could lead to a decreased risk of developing colorectal and breast cancer, leukemia, and myeloma. PDE5i also may provide an additional antitumor immune response. Finally, researchers have demonstrated a synergistic effect from combining PDE5i with current chemotherapeutic regimens.

CONCLUSION

Currently, there are inadequate data to make any conclusive statements regarding the role of PDE5i in cancer pathogenesis and how to alter clinical management. In order to create appropriate clinical guidelines, further experimental and clinical evidence is required.

Do baseline estrogen and testosterone affect lower urinary tract symptoms (LUTS) prior to or after pharmacologic treatment with tadalafil?

Little is known about how total testosterone and estradiol-17β influence lower urinary tract symptoms (LUTS) in men with benign prostatic hypertrophy (BPH). We analyzed data from a subset of men aged ≥18 years randomized to tadalafil 5 mg once-daily or placebo who had ≥6 month history of LUTS and an International Prostate Symptom Score (IPSS)≥13 enrolled in one of three randomized, placebo-controlled tadalafil clinical trials (N = 958). Three specific aims were addressed, as follows: (i) To characterize enrolled men by treatment randomization and testosterone level; (ii) to assess cross-sectional associations of estradiol-17β, testosterone, and LUTS prior to treatment with tadalafil; and, (iii) to assess longitudinal associations between baseline estradiol-17β and testosterone and improvements or worsening of LUTS during a 12-week period of tadalafil or placebo administration. LUTS were assessed by total IPSS, IPSS voiding sub-score (IPSS-V) and IPSS storage sub-score (IPSS-S) for cross-sectional analyses, and change in total IPSS (ΔIPSS), ΔIPSS-V, and ΔIPSS-S between baseline and 12-week visit for longitudinal analyses. Correlation analyses and linear regression examined associations. Baseline testosterone was not significantly associated with IPSS. In contrast, estradiol-17β was inversely correlated with IPSS (r = -0.08; p < 0.05) and IPSS-S (r = -0.14; p < 0.05). Tadalafil treatment resulted in greater IPSS improvements in men with lower baseline estradiol-17β versus those with higher baseline estradiol-17β. Lower baseline estradiol-17β was significantly associated with modestly improved ΔIPSS-V (p = 0.04) and Δtotal IPSS (p = 0.05) but not with ΔIPSS-S, following treatment which may substantiate the role of bladder dysfunction because of nerve and smooth muscle changes in the bladder in addition to benign prostatic enlargement in LUTS. Circulating baseline testosterone did not predict ΔIPSS. Men with lower baseline estradiol-17β levels showed greater responsiveness to tadalafil 5 mg treatment than those with higher baseline estradiol-17β levels when responsiveness was measured using total IPSS and IPSS-V.

Activators and stimulators of soluble guanylate cyclase counteract myofibroblast differentiation of prostatic and dermal stromal cells

BACKGROUND

Fibrotic diseases encompass numerous systemic and organ-specific disorders characterized by the development and persistence of myofibroblasts. TGFβ1 is considered the key inducer of fibrosis and drives myofibroblast differentiation in cells of diverse histological origin by a pro-oxidant shift in redox homeostasis associated with decreased nitric oxide (NO)/cGMP signaling. Thus, enhancement of NO/cGMP represents a potential therapeutic strategy to target myofibroblast activation and therefore fibrosis.

METHODS

Myofibroblast differentiation was induced by TGFβ1 in human primary prostatic (PrSCs) and normal dermal stromal cells (NDSCs) and monitored by α smooth muscle cell actin (SMA) and IGF binding protein 3 (IGFBP3) mRNA and protein levels. The potential of enhanced cGMP production by the sGC stimulator BAY 41-2272 or the sGC activator BAY 60-2770 to inhibit and revert myofibroblast differentiation in vitro was analyzed. Moreover, potential synergisms of BAY 41-2272 or BAY 60-2770 and inhibition of cGMP degradation by the PDE5 inhibitor vardenafil were investigated.

RESULTS

BAY 41-2272 and BAY 60-2770 at doses of 30µM significantly inhibited induction of SMA and IGFBP3 levels in PrSCs and reduced myofibroblast marker levels in TGFβ1-predifferentiated cells. At lower concentrations (3 and 10µM) only BAY 41-2272 but not BAY 60-2770 significantly inhibited and reverted myofibroblast differentiation. In NDSCs both substances significantly inhibited differentiation at all concentrations tested. Attenuation of SMA expression was more pronounced in NDSCs whereas reduction of IGFBP3 levels by BAY 41-2272 appeared more efficient in PrSCs. Moreover, administration of BAY 41-2272 or BAY 60-2770 enhanced the efficiency of the PDE5 inhibitor vardenafil to inhibit and revert myofibroblast differentiation in vitro.

CONCLUSIONS

Increase of cGMP by sGC stimulation/activation significantly inhibited and reverted myofibroblast differentiation. This effect was even more pronounced when a combination treatment with a PDE5 inhibitor was applied. Thus, enhancement of NO/cGMP-signaling by sGC stimulation/activation is a promising strategy for the treatment of fibrotic diseases. Whereas, in NDSCs BAY 60-2770 and BAY 41-2272 exerted similar effects on myofibroblast differentiation, higher potency of BAY 41-2272 was observed in PrSCs, indicating phenotypical differences between fibroblasts form different organs that should be taken into account in the search for antifibrotic therapies.

Tissue injury and hypoxia promote malignant progression of prostate cancer by inducing CXCL13 expression in tumor myofibroblasts

Prostate cancer (PC) is a slowly progressing malignancy that often responds to androgen ablation or chemotherapy by becoming more aggressive, acquiring a neuroendocrine phenotype, and undergoing metastatic spread. We found that B lymphocytes recruited into regressing androgen-deprived tumors by C-X-C motif chemokine 13 (CXCL13), a chemokine whose expression correlates with clinical severity, play an important role in malignant progression and metastatic dissemination of PC. We now describe how androgen ablation induces CXCL13 expression. In both allografted and spontaneous mouse PC, CXCL13 is expressed by tumor-associated myofibroblasts that are activated on androgen ablation through a hypoxia-dependent mechanism. The same cells produce CXCL13 after chemotherapy. Myofibroblast activation and CXCL13 expression also occur in the normal prostate after androgen deprivation, and CXCL13 is expressed by myofibroblasts in human PC. Hypoxia activates hypoxia-inducible factor 1 (HIF-1) and induces autocrine TGF-β signaling that promotes myofibroblast activation and CXCL13 induction. In addition to TGF-β receptor kinase inhibitors, myofibroblast activation and CXCL13 induction are blocked by phosphodiesterase 5 (PDE5) inhibitors. Both inhibitor types and myofibroblast immunodepletion block the emergence of castration-resistant PC in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model of spontaneous metastatic PC with neuroendocrine differentiation.

Stimulation of the soluble guanylate cyclase (sGC) inhibits fibrosis by blocking non-canonical TGFβ signalling

OBJECTIVES

We have previously described the antifibrotic role of the soluble guanylate cyclase (sGC). The mode of action, however, remained elusive. In the present study, we describe a novel link between sGC signalling and transforming growth factor β (TGFβ) signalling that mediates the antifibrotic effects of the sGC.

METHODS

Human fibroblasts and murine sGC knockout fibroblasts were treated with the sGC stimulator BAY 41-2272 or the stable cyclic guanosine monophosphate (cGMP) analogue 8-Bromo-cGMP and stimulated with TGFβ. sGC knockout fibroblasts were isolated from sGCI(fl/fl) mice, and recombination was induced by Cre-adenovirus. In vivo, we studied the antifibrotic effects of BAY 41-2272 in mice overexpressing a constitutively active TGF-β1 receptor.

RESULTS

sGC stimulation inhibited TGFβ-dependent fibroblast activation and collagen release. sGC knockout fibroblasts confirmed that the sGC is essential for the antifibrotic effects of BAY 41-2272. Furthermore, 8-Bromo-cGMP reduced TGFβ-dependent collagen release. While nuclear p-SMAD2 and 3 levels, SMAD reporter activity and transcription of classical TGFβ target genes remained unchanged, sGC stimulation blocked the phosphorylation of ERK. In vivo, sGC stimulation inhibited TGFβ-driven dermal fibrosis but did not change p-SMAD2 and 3 levels and TGFβ target gene expression, confirming that non-canonical TGFβ pathways mediate the antifibrotic sGC activity.

CONCLUSIONS

We elucidated the antifibrotic mode of action of the sGC that increases cGMP levels, blocks non-canonical TGFβ signalling and inhibits experimental fibrosis. Since sGC stimulators have shown excellent efficacy and tolerability in phase 3 clinical trials for pulmonary arterial hypertension, they may be further developed for the simultaneous treatment of fibrosis and vascular disease in systemic sclerosis.

Redox signaling as a therapeutic target to inhibit myofibroblast activation in degenerative fibrotic disease

Degenerative fibrotic diseases encompass numerous systemic and organ-specific disorders. Despite their associated significant morbidity and mortality, there is currently no effective antifibrotic treatment. Fibrosis is characterized by the development and persistence of myofibroblasts, whose unregulated deposition of extracellular matrix components disrupts signaling cascades and normal tissue architecture leading to organ failure and death. The profibrotic cytokine transforming growth factor beta (TGFβ) is considered the foremost inducer of fibrosis, driving myofibroblast differentiation in diverse tissues. This review summarizes recent in vitro and in vivo data demonstrating that TGF β-induced myofibroblast differentiation is driven by a prooxidant shift in redox homeostasis. Elevated NADPH oxidase 4 (NOX4)-derived hydrogen peroxide (H2O2) supported by concomitant decreases in nitric oxide (NO) signaling and reactive oxygen species scavengers are central factors in the molecular pathogenesis of fibrosis in numerous tissues and organs. Moreover, complex interplay between NOX4-derived H2O2 and NO signaling regulates myofibroblast differentiation. Restoring redox homeostasis via antioxidants or NOX4 inactivation as well as by enhancing NO signaling via activation of soluble guanylyl cyclases or inhibition of phosphodiesterases can inhibit and reverse myofibroblast differentiation. Thus, dysregulated redox signaling represents a potential therapeutic target for the treatment of wide variety of different degenerative fibrotic disorders.

Dickkopf-related protein 3 promotes pathogenic stromal remodeling in benign prostatic hyperplasia and prostate cancer

BACKGROUND

Compartment-specific epithelial and stromal expression of the secreted glycoprotein Dickkopf-related protein (Dkk)-3 is altered in age-related proliferative disorders of the human prostate. This study aimed to determine the effect of Dkk-3 on prostate stromal remodeling that is stromal proliferation, fibroblast-to-myofibroblast differentiation and expression of angiogenic factors in vitro.

METHODS

Lentiviral-delivered overexpression and shRNA-mediated knockdown of DKK3 were applied to primary human prostatic stromal cells (PrSCs). Cellular proliferation was analyzed by BrdU incorporation ELISA. Expression of Dkk-3, apoptosis-related genes, cyclin-dependent kinase inhibitors and angiogenic factors were analyzed by qPCR, Western blot analysis or ELISA. Fibroblast-to-myofibroblast differentiation was monitored by smooth muscle cell actin and insulin-like growth factor binding protein 3 mRNA and protein levels. The relevance of Wnt/β-catenin and PI3K/AKT signaling pathways was assessed by cytoplasmic/nuclear β-catenin levels and phosphorylation of AKT.

RESULTS

Knockdown of DKK3 significantly attenuated PrSC proliferation as well as fibroblast-to-myofibroblast differentiation and increased the expression of the vessel stabilizing factor angiopoietin-1. DKK3 knockdown did not affect subcellular localization or levels of β-catenin but attenuated AKT phosphorylation in PrSCs. Consistently the PI3K/AKT inhibitor LY294002 mimicked the effects of DKK3 knockdown.

CONCLUSIONS

Dkk-3 promotes fibroblast proliferation and myofibroblast differentiation and regulates expression of angiopoietin-1 in prostatic stroma potentially via enhancing PI3K/AKT signaling. Thus, elevated Dkk-3 in the stroma of the diseased prostate presumably regulates stromal remodeling by enhancing proliferation and differentiation of stromal cells and contributing to the angiogenic switch observed in BPH and PCa. Therefore, Dkk-3 represents a potential therapeutic target for stromal remodeling in BPH and PCa.

Stromal insulin-like growth factor binding protein 3 (IGFBP3) is elevated in the diseased human prostate and promotes ex vivo fibroblast-to-myofibroblast differentiation

Dysregulation of the IGF axis is implicated in the development of benign prostatic hyperplasia (BPH) and prostate cancer (PCa), 2 of the most common diseases affecting elderly males. PCa is the second leading cause of male-related cancer death in Western societies. Although distinct pathologies, BPH and PCa are both characterized by extensive stromal remodeling, in particular fibroblast-to-myofibroblast differentiation, thought to be induced by elevated local production of TGFβ1. We previously showed that TGFβ1-mediated fibroblast-to-myofibroblast differentiation of primary human prostatic stromal cells resulted in the dsyregulation of several components of the IGF axis, including the induction of IGF binding protein 3 (IGFBP3). Using isoform-specific lentiviral-mediated knockdown, we demonstrate herein that IGFBP3 is essential for TGFβ1-mediated differentiation. Although recombinant human IGFBP3 alone was not sufficient to induce differentiation, IGFBP3 synergistically potentiated TGFβ1-mediated stromal remodeling predominantly via an IGF-independent mechanism. Consistent with these in vitro findings, IGFBP3 immunohistochemistry revealed elevated levels of IGFBP3 in the hyperplastic fibromuscular stroma of BPH specimens and in the tumor-adjacent stroma of high-grade PCa. Collectively these data indicate that the dysregulation of the stromal IGF axis, in particular elevated IGFBP3, plays a crucial role in fibroblast-to-myofibroblast differentiation in the diseased prostatic stroma and indicate the therapeutic potential of inhibiting stromal remodeling and the resulting dysregulation of the stromal IGF axis as a novel strategy for the treatment of advanced PCa and BPH.

The use of a single daily dose of tadalafil to treat signs and symptoms of benign prostatic hyperplasia and erectile dysfunction

A strong and independent association between lower urinary tract symptoms suggestive of benign prostatic hyperplasia (LUTS/BPH) and erectile dysfunction (ED) has been widely evidenced in several clinical epidemiologic studies. Preclinical animal models have provided a great deal of information on potential common pathogenic mechanisms underlying these two clinical identities. Although the efficacy of the most commonly used treatments for LUTS/BPH is well defined, the negative impact of these treatments on sexual function – in particular, on ED – has triggered the search for new treatment options. In this regard, a new role for phosphodiesterase type 5 inhibitors in the treatment of LUTS/BPH and ED has been claimed. Tadalafil is one of the most extensively investigated phosphodiesterase type 5 inhibitors for this new indication. All evidence reported to date suggests that tadalafil 5 mg once daily is a safe and effective treatment option for both LUTS/BPH and ED.

Incidence rate of prostate cancer in men treated for erectile dysfunction with phosphodiesterase type 5 inhibitors: retrospective analysis

The purpose of this study was to determine the incidence rate of prostate cancer among men with erectile dysfunction (ED) treated with phosphodiesterase type 5 inhibitors (PDE-5i) over a 7-year period vs. men with ED of the same age and with similar risk factors who were not treated with PDE-5i. In a retrospective review of electronic medical records and billing databases between the years 2000 and 2006, men with ED between the ages of 50 and 69 years and no history of prostate cancer prior to 2000 were identified. These individuals were divided into two groups: 2362 men who had treatment with PDE-5i, and 2612 men who did not have treatment. Demographic data in each group were compared. During the study period, 97 (4.1%) men with ED treated with PDE-5i were diagnosed with prostate cancer compared with 258 (9.9%) men with ED in the non-treated group (P<00001). A higher percentage of African Americans were treated with PDE-5i vs. those who were not (10.5% vs. 7.1%; P<0.0001). The PDE-5i group had lower documented diagnosis of elevated prostate-specific antigen (10.0% vs. 13.1%; P=0.0008) and higher percentage of benign prostatic hyperplasia (38.4% vs. 35.1%; P=0.0149). Men with ED treated with PDE-5i tended to have less chance (adjusted odds ratio: 0.4; 95% confidence intervals: 0.3-0.5; P<0.0001) of having prostate cancer. Our data suggest that men with ED treated with PDE-5i tended to have less of a chance of being diagnosed with prostate cancer. Further research is warranted.

Mechanism of action of phosphodiesterase type 5 inhibition in metabolic syndrome-associated prostate alterations: an experimental study in the rabbit

BACKGROUND

Phosphodiesterase type 5 (PDE5) inhibitors improve benign prostatic hyperplasia (BPH)-related lower urinary tract symptoms (LUTS), often associated with metabolic syndrome (MetS). This study investigated the effects of PDE5 inhibition in the prostate of rabbits fed a high fat diet (HFD) for 12 weeks. HFD-rabbits develop the most important features of human MetS (glucose intolerance, dyslipidemia, increased abdominal adiposity, and hypertension), along with hypogonadism and LUT abnormalities (prostate and bladder inflammation/tissue remodeling).

METHODS

Gene expression was evaluated by quantitative RT-PCR. Prostate morphological changes and oxygenation were evaluated by immunohistochemistry.

RESULTS

HFD prostates showed increased PDE5 expression, suggesting a peculiar sensitivity of prostate to the action of PDE5 inhibitors during MetS. Accordingly, prostate PDE5 mRNA was negatively associated to plasma testosterone/estradiol ratio, whose reduction characterizes MetS, and positively with the expression in prostate of several genes exploring pathogenetic processes for BPH/LUTS, such as inflammation, leukocyte infiltration, and fibrosis/myofibroblast activation. Most of these genes was up-regulated by HFD, and significantly reduced by PDE5 inhibition, through either chronic (12 weeks) or, at a lower extent, acute (1-week) tadalafil dosing. Tadalafil was also able to reduce blood pressure and visceral fat in HFD rabbits, without changing any other MetS parameter. Interestingly, 1-week tadalafil administration to HFD rabbits, significantly blunted prostate inflammation (increased CD45 immunopositivity), fibrosis (reduced muscle/fiber ratio) and hypo-oxygenation, thus suggesting a potential curative effect of PDE5 inhibition on MetS-related prostate alterations.

CONCLUSIONS

Our data provide the experimental evidences to support the multiple potentiality of PDE5 inhibitors as a useful therapeutic tool in LUTS.

Phosphodiesterase-5 expression and function in the lower urinary tract: a critical review

Both clinical and preclinical studies have mostly shown beneficial effects for Phosphodiesterase-5 (PDE-5) inhibitors in the treatment of lower urinary tract symptoms. Molecular studies have consistently shown abundant PDE-5 expression in bladder smooth muscle. Data concerning urethral PDE-5 expression have been surprising because striated muscle was not only positively identified, but also found to express more PDE-5 than the smooth muscle. In the prostate, highly variable results have been obtained. For PDE-5 expression, the data have ranged from extremely low to highly abundant. PDE-5 has been found in the glandular epithelium, vascular smooth muscle, endothelium, and fibromuscular stroma.

Phosphodiesterase type 5 inhibition reverts prostate fibroblast-to-myofibroblast trans-differentiation

Phosphodiesterase type 5 (PDE5) inhibitors have been demonstrated to improve lower urinary tract symptoms secondary to benign prostatic hyperplasia (BPH). Because BPH is primarily driven by fibroblast-to-myofibroblast trans-differentiation, this study aimed to evaluate the potential of the PDE5 inhibitor vardenafil to inhibit and reverse trans-differentiation of primary human prostatic stromal cells (PrSC). Vardenafil, sodium nitroprusside, lentiviral-delivered short hairpin RNA-mediated PDE5 knockdown, sodium orthovanadate, and inhibitors of MAPK kinase, protein kinase G, Ras homolog family member (Rho) A, RhoA/Rho kinase, phosphatidylinositol 3 kinase and protein kinase B (AKT) were applied to PrSC treated with basic fibroblast growth factor (fibroblasts) or TGFβ1 (myofibroblasts) in vitro, in chicken chorioallantoic membrane xenografts in vivo, and to prostatic organoids ex vivo. Fibroblast-to-myofibroblast trans-differentiation was monitored by smooth muscle cell actin and IGF binding protein 3 mRNA and protein levels. Vardenafil significantly attenuated TGFβ1-induced PrSC trans-differentiation in vitro and in chorioallantoic membrane xenografts. Enhancement of nitric oxide/cyclic guanosine monophosphate signaling by vardenafil, sodium nitroprusside, or PDE5 knockdown reduced smooth muscle cell actin and IGF binding protein 3 mRNA and protein levels and restored fibroblast-like morphology in trans-differentiated myofibroblast. This reversal of trans-differentiation was not affected by MAPK kinase, protein kinase G, RhoA, or RhoA/Rho kinase inhibition, but vardenafil attenuated phospho-AKT levels in myofibroblasts. Consistently, phosphatidylinositol 3 kinase or AKT inhibition induced reversal of trans-differentiation, whereas the tyrosine phosphatase inhibitor sodium orthovanadate abrogated the effect of vardenafil. Treatment of prostatic organoids with vardenafil ex vivo reduced expression of myofibroblast markers, indicating reverse remodeling of stroma towards a desired higher fibroblast/myofibroblast ratio. Thus, enhancement of the nitric oxide/cyclic guanosine monophosphate signaling pathway by vardenafil attenuates and reverts fibroblast-to-myofibroblast trans-differentiation, hypothesizing that BPH patients might benefit from long-term therapy with PDE5 inhibitors.

Therapeutic targeting of redox signaling in myofibroblast differentiation and age-related fibrotic disease

Myofibroblast activation plays a central role during normal wound healing. Whereas insufficient myofibroblast activation impairs wound healing, excessive myofibroblast activation promotes fibrosis in diverse tissues (including benign prostatic hyperplasia, BPH) leading to organ dysfunction and also promotes a stromal response that supports tumor progression. The incidence of impaired wound healing, tissue fibrosis, BPH, and certain cancers strongly increases with age. This paper summarizes findings from in vitro fibroblast-to-myofibroblast differentiation systems that serve as cellular models to study fibrogenesis of diverse tissues. Supported by substantial in vivo data, a large body of evidence indicates that myofibroblast differentiation induced by the profibrotic cytokine transforming growth factor beta is driven by a prooxidant shift in redox homeostasis due to elevated production of NADPH oxidase 4 (NOX4)-derived hydrogen peroxide and supported by concomitant decreases in nitric oxide/cGMP signaling and reactive oxygen species (ROS) scavenging enzymes. Fibroblast-to-myofibroblast differentiation can be inhibited and reversed by restoring redox homeostasis using antioxidants or NOX4 inactivation as well as enhancing nitric oxide/cGMP signaling via activation of soluble guanylyl cyclases or inhibition of phosphodiesterases. Current evidence indicates the therapeutic potential of targeting the prooxidant shift in redox homeostasis for the treatment of age-related diseases associated with myofibroblast dysregulation.

PAGE4 positivity is associated with attenuated AR signaling and predicts patient survival in hormone-naive prostate cancer

Aberrant activation of the androgen receptor (AR) plays a key role during prostate cancer (PCa) development and progression to castration-resistant prostate cancer (CR-PCa) after androgen deprivation therapy, the mainstay systemic treatment for PCa. New strategies to abrogate AR activity and biomarkers that predict aggressive tumor behavior are essential for improved therapeutic intervention. PCa tissue microarrays herein reveal that prostate-associated gene 4 (PAGE4), an X-linked cancer/testis antigen, is highly up-regulated in the epithelium of preneoplastic lesions compared with benign epithelium, but subsequently decreases with tumor progression. We show that AR signaling is attenuated in PAGE4-expressing cells both in vitro and in vivo, most likely via impaired androgen-induced AR nuclear translocation and subsequently reduced AR protein stabilization and phosphorylation at serines 81 and 213. Consistently, epithelial PAGE4 protein levels inversely correlated with AR activation status in hormone-naive and CR-PCa clinical specimens. Moreover, PAGE4 impaired the development of CR-PCa xenografts, and strong PAGE4 immunoreactivity independently predicted favorable patient survival in hormone-naive PCa. Collectively, these data suggest that dysregulation of epithelial PAGE4 modulates AR signaling, thereby promoting progression to advanced lethal PCa and highlight the potential value of PAGE4 as a prognostic and therapeutic target.

Testosterone regulates smooth muscle contractile pathways in the rat prostate: emphasis on PDE5 signaling

Testosterone (T) plays a permissive role in the development of benign prostatic hyperplasia (BPH), and phosphodiesterase 5 inhibitors (PDE5is) have been found to be effective for BPH and lower urinary tract symptoms (LUTS) in clinical trials. This study investigated the effect of T on smooth muscle (SM) contractile and regulatory signaling pathways, including PDE5 expression and functional activity in prostate in male rats (sham-operated, surgically castrated, and castrated with T supplementation). In vitro organ bath studies, real-time RT-PCR, Western blot analysis, and immunohistochemistry were performed. Castration heavily attenuated contractility, including sensitivity to phenylephrine with SM myosin immunostaining revealing a disrupted SM cell arrangement in the stroma. PDE5 was immunolocalized exclusively in the prostate stroma, and orchiectomy signficantly reduced PDE5 immunopositivity, mRNA, and protein expression, along with nNOS and ROKβ mRNA, whereas it increased eNOS plus α(1a) and α(1b) adrenoreceptor expression in castrated animals. The PDE5i zaprinast significantly increased prostate strip relaxation to the nitric oxide donor sodium nitroprusside (SNP) in control but not castrated rats. But SNP alone was more effective on castrated rats, comparable with sham treated with SNP plus zaprinast. T supplementation prevented or restored all above changes, including SNP and zaprinast in vitro responsiveness. In conclusion, our data show that T positively regulates PDE5 expression and functional activities in prostate, and T ablation not only suppresses prostate size but also reduces prostatic SM contractility, with several potential SM contraction/relaxation pathways implicated. Zaprinast findings strongly suggest a major role for PDE5/cGMP in this signaling cascade. PDE5 inhibition may represent a novel mechanism for treatment of BPH.

Novel drug targets for the pharmacotherapy of benign prostatic hyperplasia (BPH)

Benign prostatic hyperplasia (BPH) is the major cause of lower urinary tract symptoms in men aged 50 or older. Symptoms are not normally life threatening, but often drastically affect the quality of life. The number of men seeking treatment for BPH is expected to grow in the next few years as a result of the ageing male population. Estimates of annual pharmaceutical sales of BPH therapies range from $US 3 to 10 billion, yet this market is dominated by two drug classes. Current drugs are only effective in treating mild to moderate symptoms, yet despite this, no emerging contenders appear to be on the horizon. This is remarkable given the increasing number of patients with severe symptoms who are required to undergo invasive and unpleasant surgery. This review provides a brief background on prostate function and the pathophysiology of BPH, followed by a brief description of BPH epidemiology, the burden it places on society, and the current surgical and pharmaceutical therapies. The recent literature on emerging contenders to current therapies and novel drug targets is then reviewed, focusing on drug targets which are able to relax prostatic smooth muscle in a similar way to the α(1) -adrenoceptor antagonists, as this appears to be the most effective mechanism of action. Other mechanisms which may be of benefit are also discussed. It is concluded that recent basic research has revealed a number of novel drug targets such as muscarinic receptor or P2X-purinoceptor antagonists, which have the potential to produce more effective and safer drug treatments.

PPARγ: a molecular link between systemic metabolic disease and benign prostate hyperplasia

The emergent epidemic of metabolic syndrome and its complex list of sequelae mandate a more thorough understanding of benign prostatic hyperplasia and lower urinary tract symptoms (BPH/LUTS) in the context of systemic metabolic disease. Here we discuss the nature and origins of BPH, examine its role as a component of LUTS and review retrospective clinical studies that have drawn associations between BPH/LUTS and type II diabetes, inflammation and dyslipidemia. PPARγ signaling, which sits at the nexus of systemic metabolic disease and BPH/LUTS through its regulation of inflammation and insulin resistance, is proposed as a candidate for molecular manipulation in regard to BPH/LUTS. Finally, we introduce new cell and animal models that are being used to study the consequences of obesity, diabetes and inflammation on benign prostatic growth.

Cyclic GMP signaling in rat urinary bladder, prostate, and epididymis: tissue-specific changes with aging and in response to Leydig cell depletion

Aging of the male reproductive system leads to changes in endocrine signaling and is frequently associated with the emergence of prostate hyperplasia and bladder dysfunctions. Recent reports highlight prostate and bladder as promising targets for therapeutic interventions with inhibitors of the cyclic GMP (cGMP)-degrading phosphodiesterase 5 (PDE5). However, the cGMP signaling system in these organs is as yet poorly characterized, and the possibility of age-related alterations has not been addressed. This study investigates key proteins of cGMP pathways in bladder, prostate, and epididymis of young (3 months) and old (23-24 months) Wistar rats. Local differences in the abundance of PDE5, soluble guanylyl cyclase (sGC) and particulate guanylyl cyclases (GC-A, GC-B), endothelial nitric oxide synthase, and cGMP-dependent protein kinase I (PRKG1 (cGKI)) revealed pronounced tissue-specific peculiarities. Although cGMP-generating enzymes were not affected by age in all organs, we recognized age-related decreases of PDE5 expression in bladder and a selective diminishment of membrane-associated PRKG1 in epididymis. In disagreement with published data, all cGMP pathway proteins including PDE5 are poorly expressed in prostate. However, prostatic PRKG1 expression increases with aging. Androgen withdrawal during temporary Leydig cell elimination induced a massive (>12-fold) upregulation of PRKG1 in prostate but not in other (penis and epididymis) androgen-dependent organs. These findings identify PRKG1 as a key androgen-sensitive signaling protein in prostate of possible importance for growth regulation. The elucidated effects may have significance for age-associated pathologies in the male lower-urinary tract.

Mammalian Cyclic Nucleotide Phosphodiesterases: Molecular Mechanisms and Physiological Functions

The superfamily of cyclic nucleotide (cN) phosphodiesterases (PDEs) is comprised of 11 families of enzymes. PDEs break down cAMP and/or cGMP and are major determinants of cellular cN levels and, consequently, the actions of cN-signaling pathways. PDEs exhibit a range of catalytic efficiencies for breakdown of cAMP and/or cGMP and are regulated by myriad processes including phosphorylation, cN binding to allosteric GAF domains, changes in expression levels, interaction with regulatory or anchoring proteins, and reversible translocation among subcellular compartments. Selective PDE inhibitors are currently in clinical use for treatment of erectile dysfunction, pulmonary hypertension, intermittent claudication, and chronic pulmonary obstructive disease; many new inhibitors are being developed for treatment of these and other maladies. Recently reported x-ray crystallographic structures have defined features that provide for specificity for cAMP or cGMP in PDE catalytic sites or their GAF domains, as well as mechanisms involved in catalysis, oligomerization, autoinhibition, and interactions with inhibitors. In addition, major advances have been made in understanding the physiological impact and the biochemical basis for selective localization and/or recruitment of specific PDE isoenzymes to particular subcellular compartments. The many recent advances in understanding PDE structures, functions, and physiological actions are discussed in this review.