Dienogest, a synthetic progestin, inhibits the proliferation of immortalized human endometrial epithelial cells with suppression of cyclin D1 gene expression

Dienogest attenuates STAT3 activation in ovarian endometriotic cysts

OBJECTIVE

Recent studies have suggested that endometriosis could be the result of excessive activation of signal transducer and activator of transcription 3 (STAT3), which is associated with the regulation of essential cellular mechanisms such as proliferation, invasion, and apoptosis. That finding implies that regulating STAT3 activation could play a key role in treating endometriosis. In the present study, we aimed to evaluate whether the anti-endometriotic effects of dienogest is mediated by the regulation of STAT3 activation.

STUDY DESIGN

STAT3 activation was evaluated in normal endometrial and ovarian endometriotic tissues obtained from patients with/without preoperative dienogest treatment. A subsequent in vitro analysis with endometriotic cyst stromal cells (ECSCs) was used to confirm the direct influence of dienogest in STAT3 activation.

RESULT

STAT3 activation is significantly higher in endometriotic tissues from non-treated patients than in normal endometrial tissues, and that difference is reversed by preoperative administration of dienogest. Similarly, the inhibitory effects of dienogest on STAT3 activation are demonstrated by in vitro results showing that dienogest treatment significantly inhibits IL-6-stimulated STAT3 activation in cultured ECSCs. That inhibition was accompanied by decreased expression of proliferative (PCNA), invasive (MMP-2), and anti-apoptotic (BCL-2) proteins. Furthermore, downregulating STAT3 activity with siRNA decreased PCNA, MMP-2, and BCL-2 expression in IL-6-treated ECSCs.

CONCLUSION

Dienogest inhibits STAT3 activation in ECSCs, which affects their proliferation, invasiveness, and apoptosis.

Medical Management of Ovarian Endometriomas: A Systematic Review and Meta-analysis

OBJECTIVE

To estimate the effect of medical management on the size of ovarian endometriomas.

DATA SOURCE

Online databases were searched from inception to October 2022, including Ovid MEDLINE, Ovid EMBASE, PubMed, EBM Reviews-Cochrane Central Register of Controlled Trials (CENTRAL), ClinicalTrials.gov , and Web of Science.

METHODS OF STUDY SELECTION

Following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, we included all English-language, full-text articles that reported on change in endometrioma size (either diameter or volume) after medical interventions. Studies evaluating surgical interventions or postoperative recurrence were excluded. All screening and data extraction were performed independently by two authors. Risk of bias assessment was performed with either the Cochrane Risk of Bias Tool for randomized controlled trials or a modified Newcastle-Ottawa Scale for observational studies.

TABULATION, INTEGRATION, AND RESULTS

After removal of duplicates, 9,332 studies were screened, with 33 full-text articles deemed eligible for inclusion. In the meta-analysis, dienogest showed significant reduction in cyst diameter (reduction 1.32 cm, 95% CI, 0.91-1.73, eight studies, n=418 cysts) and volume (mean difference of log-transformed volume 1.35, 95% CI, 0.87-1.83, seven studies, n=282 cysts). Similarly, significant reductions were seen with the oral contraceptive pill (OCP) (1.06 cm, 95% CI, 0.59-1.53, nine studies, n=455), gonadotropin-releasing hormone (GnRH) agonists (1.17 cm, 95% CI, 0.42-1.92, four studies, n=128 cysts), norethindrone acetate (0.6 cm, 95% CI, 0.27-0.94, two studies, n=88 cysts), and danazol (1.95 cm, 95% CI, 1.18-2.73, two studies, n=34 cysts). Norethindrone acetate with aromatase inhibitor was also effective in reducing endometrioma volume (mean difference of log-transformed volume 1.47, 95% CI, 0.16-2.78, two studies, n=34 cysts).

CONCLUSION

Medical management with dienogest, OCPs, GnRH agonists, norethindrone acetate, norethindrone acetate with aromatase inhibitor, or danazol can reduce the size of ovarian endometriomas.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, CRD 42022363319.

Possible Participation of Adenine Nucleotide Translocase ANT1 in the Cytotoxic Action of Progestins, Glucocorticoids, and Diclofenac on Tumor Cells

A comparative analysis of the cytostatic effects of progestins (gestobutanoyl, megestrol acetate, amol, dienogest, and medroxyprogesterone acetate), glucocorticoids (hydrocortisone, dexamethasone), and diclofenac on tumor cells was carried out in order to confirm their in silico predicted probabilities experimentally. The results showed the different sensitivity of HeLa, MCF-7, Hep-2, K-562, and Wi-38 cell lines to progestins, glucocorticoids, and diclofenac. The minimum IC50 was found for progestin gestobutanoyl (GB) as 18 µM for HeLa cells, and varied from 31 to 38 µM for MCF-7, Hep-2, and K-562. Glucocorticoids and diclofenac were much less cytotoxic in the HeLa, MCF-7, and Hep-2 cell lines than progestins, with IC50 values in the range of 150-3000 μM. Myelogenous leukemia K-562 cells were the least sensitive to the action of progestins and glucocorticoids but the most sensitive to diclofenac, which showed a pronounced cytotoxic effect with an IC50 of 31 μM. As we have shown earlier, progestins can uniquely modulate MPTP opening via the binding of adenine nucleotide translocase. On this basis, we evaluated the expression of adenylate nucleotide translocase ANT1 (SLC25 A4) as a possible participant in cytotoxic action in these cell lines after 48 h incubation with drugs. The results showed that progestins differently regulated ANT1 expression in different cell lines. Gestobutanoyl had the opposite effect on ANT1 expression in the HeLa, K562, and Wi-38 cells compared with the other progestins. It increased the ANT1 expression more than twofold in the HeLa and K562 cells but had no influence on the Wi-38 cells. Glucocorticoids and diclofenac increased ANT1 expression in the Wi-38 cells and decreased it in the K562, MCF-7, and Hep-2 cells. The modulation of ANT1 expression discovered in our study can be a new explanation of the cytotoxic and cytoprotective effects of hormones, which can vary depending on the cell type. ANT isoforms in normal and cancerous cells could be a new target for steroid hormone and anti-inflammatory drug action.

Dienogest May Reduce Estradiol- and Inflammatory Cytokine-Induced Cell Viability and Proliferation and Inhibit the Pathogenesis of Endometriosis: A Cell Culture- and Mouse Model-Based Study

Dienogest (DNG) is a therapeutic medication used in endometriosis treatment. Limited data are available regarding its mechanism of action on endometrial cells. Using in vivo and in vitro models, we investigated whether DNG treatment causes significant biological changes in human endometrial stromal cells (ESCs). The markers related to the pathogenesis of endometriosis in ESCs were evaluated using estradiol, tumor necrosis factor alpha (TNF-α), interleukin 1β (IL-1β), and IL-32, administered alone or in combination with DNG. Implanted endometrial tissues were compared between C57BL/6 mice that did or did not receive DNG treatment by using size measurements and immunohistochemistry. A significant decrease in cell viability, protein kinase B (AKT) phosphorylation, and the expression of p21-activated kinase 4 and vascular endothelial growth factor were observed in ESCs treated with estradiol plus DNG. Cell viability, AKT phosphorylation, and proliferating cell nuclear antigen (PCNA) expression also decreased significantly after TNF-α plus DNG treatment. Treatment with IL-1β or IL-32 plus DNG significantly decreased cell viability or PCNA expression, respectively. The size of the implanted endometrial tissue significantly decreased in mice treated with DNG, accompanied by decreased PCNA expression. Thus, DNG may reduce cell viability and proliferation induced by estradiol, TNF-α, IL-1β, and IL-32, and inhibit the endometriosis pathogenesis by decreasing PCNA expression.

A plant-based medicinal food inhibits the growth of human gastric carcinoma by reversing epithelial-mesenchymal transition via the canonical Wnt/β-catenin signaling pathway

Background

Natural products, especially those with high contents of phytochemicals, are promising alternative medicines owing to their antitumor properties and few side effects. In this study, the effects of a plant-based medicinal food (PBMF) composed of six medicinal and edible plants, namely, Coix seed, Lentinula edodes, Asparagus officinalis L., Houttuynia cordata, Dandelion, and Grifola frondosa, on gastric cancer and the underlying molecular mechanisms were investigated in vivo.

Methods

A subcutaneous xenograft model of gastric cancer was successfully established in nude mice inoculated with SGC-7901 cells. The tumor-bearing mice were separately underwent with particular diets supplemented with three doses of PBMF (43.22, 86.44, and 172.88 g/kg diet) for 30 days. Tumor volumes were recorded. Histopathological changes in and apoptosis of the xenografts were evaluated by hematoxylin and eosin staining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining, respectively. Serum levels of TNF-α, MMP-2, and MMP-9 were detected by enzyme-linked immunosorbent assay. The mRNA expression levels of β-catenin, GSK-3β, E-cadherin, N-cadherin, MMP-2/9, Snail, Bax, Bcl-2, Caspase-3/9, and Cyclin D1 were evaluated via real-time quantitative polymerase chain reaction. The protein expression levels of GSK-3β, E-cadherin, N-cadherin, and Ki-67 were determined by immunohistochemistry staining.

Results

PBMF treatment efficiently suppressed neoplastic growth, induced apoptosis, and aggravated necrosis in the xenografts of SGC-7901 cells. PBMF treatment significantly decreased the serum levels of MMP-2 and MMP-9 and significantly increased that of TNF-α. Furthermore, PBMF treatment notably upregulated the mRNA expression levels of GSK-3β, E-cadherin, Bax, Caspase-3, and Caspase-9 but substantially downregulated those of β-catenin, N-cadherin, MMP-2, MMP-9, Snail, and Cyclin D1 in tumor tissues. The Bax/Bcl-2 ratio was upregulated at the mRNA level. Moreover, PBMF treatment remarkably increased the protein expression levels of GSK-3β and E-cadherin but notably reduced those of Ki-67 and N-cadherin in tumor tissues.

Conclusions

The PBMF concocted herein exerts anti-gastric cancer activities via epithelial–mesenchymal transition reversal, apoptosis induction, and proliferation inhibition. The underlying molecular mechanisms likely rely on suppressing the Wnt/β-catenin signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03301-6.

Dienogest regulates apoptosis, proliferation, and invasiveness of endometriotic cyst stromal cells via endoplasmic reticulum stress induction

Dienogest, a specific progesterone receptor agonist, is used in the treatment of endometriosis. However, it is still unclear as to the mechanisms of therapeutic effects on endometriosis. Our recent study showed that endometriosis may be the result of aberrant endoplasmic reticulum (ER) stress induction due to progesterone resistance. This finding suggests that the regulation of ER stress induction may play a key role in treatment of endometriosis. Therefore, the anti-endometriotic effects of dienogest may be mediated by regulation of ER stress. To test this hypothesis, we elucidate whether dienogest affects endometriotic stromal cell apoptosis, proliferation and invasiveness by modulating ER stress-induced CCAAT/enhancer-binding protein homologous protein (CHOP) expression. Specifically, PRKR-like ER kinase (PERK)/eukaryotic initiation factor 2α (eIF2α)/activating transcription factor 4 (ATF4), inositol-requiring kinase 1 (IRE1)/TNF receptor-associated factor 2 (TRAF2)/apoptosis signal-regulating kinase 1 (ASK1)/c-Jun N-terminal kinase (JNK) signaling, and downstream CHOP were evaluated to determine the involved ER stress-mediated regulation mechanism of CHOP expression. Our results show that progesterone treatment did not have any significant effects on ER stress, apoptosis, proliferation, and invasion in estrogen-treated endometriotic cyst stromal cells (ECSCs). However, dienogest treatment upregulated the induction of ER stress. It also led to increased apoptosis, and decreased proliferation and invasiveness. These dienogest-induced changes in apoptosis, proliferation and invasiveness were reversed by the ER stress inhibitor salubrinal. Furthermore, dienogest-induced ER stress increased CHOP expression through activation of both PERK/elf2α/ATF4 and IRE1/TRAF2/ASK1/JNK signaling. This upregulation was blocked by transfection with PERK and IRE1 siRNA, which decreased apoptosis and increased the proliferation and invasiveness of dienogest-treated ECSCs. Taken together, our findings indicate that dienogest enhances ER stress induction in endometriotic stromal cells, which affects apoptosis, proliferation and invasiveness via CHOP upregulation.

Effects of progestin-only contraceptives on the endometrium

INTRODUCTION

The contraceptive activity of synthetic progestins is mediated through three basic mechanisms: (a) An anti-gonadotrophic action leading to the inhibition of ovulation; (b) Changes in cervical mucus characteristics that inhibit sperm penetration and (c) desynchronization of the endometrial picture necessary for implantation.

AREAS COVERED

Mechanisms involved in the progestin-induced endometrium desynchronization are individually reviewed for each of the routes of administration and, whenever possible, by individual members of the various families of synthetic progestin derivatives.

EXPERT OPINION

For contraceptive purposes, progestins are today administered through several routes: orally, as injections, subdermally and via the vagina or the uterine cavity. Given this variety of modalities, their effects may differ, depending on the route of administration, concentration reached at the level of the endometrium and the duration of use. These are characterized by inactivation of the endometrium. Progestin-only contraception provides a safe and effective control of fertility regulation, although, they are associated with the problem of endometrial break through bleeding that may lead to discontinuation. Unfortunately, in spite of a major research effort over two decades, there is not, as yet, an established long-term intervention available to manage bleeding irregularities, making mandatory a deeper understanding of the mechanisms involved is required.

A progestin isn't a progestin: dienogest for endometriosis as a blueprint for future research - Review as a contribution for discussion

The different etiopathogenetic mechanisms and the diversity of clinical features of endometriosis has not yet allowed to identify a causal pharmacological monotherapy satisfying the unresolved medical needs in this important female disease. Therefore, despite the search for new therapeutic principles for the indication, the strategy of gradual optimization of established therapeutic principles should not be disregarded.In the case of progestins, the fact that each compound has its own, specific profile may allow to study the therapeutic relevance of the various signal cascades influenced by their receptors.Using the example of the progestin dienogest, the different genomic and non-genomic mechanisms of action are discussed. It is pharmacodynamic profile is unique compared to other progestins.In light of the emerging multitude of pathomechanisms in endometriosis, a monotherapy may not be possible, and then the search for broad spectrum compounds or combination therapies with dual or multiple mode of action in a clinically relevant dose range might be considered. The progestogenic action may greatly benefit from, by way of example, additional anti-inflammatory and/or anti-fibrotic and/or pro-apoptotic activities. Such a strategy could lead to new drug classes.

Aromatase as a target for treating endometriosis

Endometriosis is a common gynecological disease that causes various clinical symptoms, such as chronic pelvic pain, dysmenorrhea and infertility, seriously affecting women's health and their quality of life. The symptoms and endometriotic lesions are relieved, in many cases, after menopause, when estrogen levels are lowered. Therefore, endometriosis is considered to be estrogen-dependent. Aromatase, the enzyme responsible for the last step of estrogen biosynthesis converting testosterone and androgen to estrogen, was previously reported to be more abundant in endometriotic tissues than in the normal endometrium, leading to an increased local estrogen concentration. Therefore, aromatase is considered a key therapeutic target for regulating local estrogen biosynthesis in endometriosis. A more complete understanding of the mechanisms that modulate aromatase and its activity is required to develop novel estrogen-targeted therapies for endometriosis. In this review article, we outline the current understanding of the pathological processes involved in estrogen production in endometriosis and propose novel strategies to treat this disorder.

Dienogest therapy during the early stages of recurrence of endometrioma might be an alternative therapeutic option to avoid repeat surgeries

AIM

We aimed to evaluate whether hormonal therapy immediately after postsurgical recurrence of ovarian endometrioma controls disease progression and can be an alternative therapeutic option to avoid multiple repeat surgeries.

METHODS

We enrolled 146 patients treated for endometrioma at the University Hospital of Kyoto Prefectural University of Medicine between 2009 and 2015. After laparoscopic cystectomy using the stripping technique, opening of cul-de-sac obliterations and complete resection of the deep infiltrating endometriosis lesions, the patients either received no treatment (n = 83), oral contraceptives (OC; n = 32) or dienogest (DNG; n = 27), depending on their medical history. Four patients were excluded because they changed their regimens during the follow-up period. All patients were followed up every 3 months. Patients who developed recurrence of endometrioma immediately received DNG, OC or gonadotropin-releasing hormone agonist.

RESULTS

Overall, 16 patients developed a recurrence of the endometrioma (12 in the nontreatment group, three in the OC group and one in the DNG group). The 11 patients with recurrence were treated with DNG immediately after the diagnosis of recurrent endometrioma. Among them, seven patients continued treatment with DNG (2 mg) for 24 months. After 24 months of treatment with DNG, complete resolution of recurrent endometrioma was achieved in four (57.1%) of seven patients. There was no improvement in the three patients who received OC and one patient who underwent secondary surgery.

CONCLUSION

DNG therapy early after recurrence of postsurgical endometrioma appears to be viable for reducing the risk of repeated surgery.

Short-term histopathological effects of dienogest therapy on ovarian endometriomas: in vivo, nonrandomized, controlled trial

Ovarian endometriosis is a common gynecological disorder. To date, progestins are recommended as the first-line medical treatment for symptomatic ovarian endometriosis. The aim of this study was to evaluate the main histopathological effects of short-term dienogest therapy in patients with ovarian endometriomas scheduled for surgery. A prospective, nonrandomized controlled trial, including 70 symptomatic women with single ovarian endometriotic cyst (diameter between 30-50 mm) was conducted. Women scheduled for surgery were divided into two groups, depending on the treatment established at enrollment: 36 women received progestin therapy with dienogest (P group) and 34 women received no therapy (C group). At histopathological examination necrosis, inflammation, decidualization, glandular atrophy and angiogenesis were blindly evaluated. At tissue level, decidualization was significantly more frequent in P group compared to C group (p = .001). A nonsignificant tendency (p = .29) towards a slight decreased inflammation in P group was found. No significant differences were observed between the two groups in terms of necrosis, glandular atrophy and angiogenesis. The study suggests that high decidualization rate and the tendency to reduced inflammatory reaction in the short-term administration of dienogest might contribute to its therapeutic efficacy.

Progestins for the Treatment of Endometriosis: An Update

Endometriosis is a gynecological condition that affects approximately 10% of women of reproductive age, including 25–40% of infertile women. Dysmenorrhea, dyspareunia and chronic pelvic pain are the most common symptoms. Currently available medical therapies for endometriosis do not cure the disease, but are directed at symptom relief, typically utilizing the hormone responsiveness of endometriotic tissue to induce lesion atrophy. Unfortunately, pain relapse after treatment suspension is a common event. Treatment with pharmacological therapies for endometriosis should be conceived in terms of years, thus agents that must be withdrawn after a few months due to poor tolerability or severe metabolic side effects do not greatly benefit women with symptomatic endometriosis. The characteristics of progestins render this class an ideal pharmacological choice for administration over extended periods. The present paper will review the rationale for using progestins and their mechanism of action in endometriosis. Thereafter, the results obtained by various progestins in the treatment of endometriosis will be evaluated (danazol, gestrinone, norethisterone acetate, desogestrel, cyproterone acetate, megestrol acetate, medroxyprogesterone acetate, and levonorgestrel). A progestin called dienogest, recently introduced for the treatment of endometriosis, will be given special focus, describing its mechanism of action and clinical results.

Comparison of fertility-sparing treatments in patients with early endometrial cancer and atypical complex hyperplasia: A meta-analysis and systematic review

BACKGROUND

There are some fertility-sparing treatments in patients with early endometrial cancer (EEC) or atypical complex hyperplasia (ACH), and the objective is to compare them by evaluating the oncologic and reproductive outcomes.

METHODS

We searched the published literature using Medline, Cochrane, EMBASE, and Google Scholar databases up to January 3, 2017, with various combinations of keywords fertility-sparing treatments, progesterone, progestin, intrauterine devices, early endometrial cancer, and atypical complex hyperplasia. The primary endpoint is the complete response (CR) rate, and the secondary endpoints are the partial response (PR) rate, relapse rate (RR), pregnancy rate, and live birth rate.

RESULTS

Twenty-eight studies containing 1038 women with EEC or ACH were included for review and meta-analysis. The results demonstrated that women with EEC or ACH managed with progestin had a pooled CR rate of 71% (95% confidence interval [CI]: 63-77%). The pooled pregnancy outcomes showed that 34% of women taking progestin treatment for EEC or ACH became pregnant (95% CI: 30-38%); however, only 20% of them delivered live newborns. The pooled CR rate for women using intrauterine device (IUD) was 76% (95% CI: 67-83%), and pooled RR was 9% (95% CI: 5-17%). The pregnancy rate for women whom underwent IUD was 18% (95% CI: 7-37%), and 14% of them delivered live newborns. In patients using progestin plus IUD, the pooled CR rate was 87% (95% CI: 75-93%); among those patients, 40% became pregnant (95% CI: 20-63%), and 35% delivered live newborns. There is no publication bias for the CR rate.

CONCLUSION

For patients with EEC and ACH, treatments with progestin, with or without IUD, or IUD alone can reach good CR rate; however, the pregnancy outcomes might be worse in patients treated with IUD alone. Further randomized-controlled studies are warranted to find out a better solution.

Immunohistochemical Analysis of the Effect of Dienogest on Ovarian Endometriotic Cysts

Dienogest is a novel progestin with potent oral progestational activity that inhibits the clinical symptoms of endometriosis. We herein evaluated the effect of dienogest on ovarian endometriotic cysts via immunohistochemistry. Ovarian endometriotic cyst specimens were collected from 12 patients treated with dienogest and 20 patients not treated with hormones (controls). The expression of estrogen receptor (ER)-α, progesterone receptor A (PRA), and Ki-67 was studied by immunohistochemistry. As compared with the controls, the cell proliferation index was significantly reduced in both epithelial and stromal cells of the endometriotic cysts following the use of dienogest (P = 0.022 and P = 0.004, respectively). However, there was no significant difference between endometriotic cysts with and without the use of dienogest in the expressions of ER-α and PRA in the epithelial and stromal cells. Irrespective of the use of dienogest, the expression levels of ER-α and PRA in the epithelial cells were low (median: 32% and 8%, respectively). Conversely, the expression levels of ER-α and PRA in the stromal cells were well preserved (median: 68% and 92%, respectively). In the controls, there was no significant difference between endometriotic cysts in the expression levels of Ki-67, ER-α and PRA in epithelial and stromal cells during the proliferative and secretory phases. The finding of a reduction in the cell proliferation index by the use of dienogest with no change in the expressions of hormonal receptors may not support the direct progestational effect of dienogest on ovarian endometriotic cysts.

Does dienogest influence the inflammatory response of endometriotic cells? A systematic review

OBJECTIVE AND DESIGN

A systematic review of all literature was done to assess the ability of the progestin dienogest (DNG) to influence the inflammatory response of endometriotic cells.

MAIN OUTCOME MEASURES

In vitro and in vivo studies report an influence of DNG on the inflammatory response in eutopic or ectopic endometrial tissue (animal or human).

RESULTS

After strict inclusion criteria were satisfied, 15 studies were identified that reported a DNG influence on the inflammatory response in endometrial tissue. These studies identified a modulation of prostaglandin (PG) production and metabolism (PGE2, PGE2 synthase, cyclo-oxygenase-2 and microsomal PGE synthase-1), pro-inflammatory cytokine and chemokine production [interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor-α, monocyte chemoattractant protein-1 and stromal cell-derived factor-1], growth factor biosynthesis (vascular endothelial growth factor and nerve growth factor) and signaling kinases, responsible for the control of inflammation. Evidence supports a progesterone receptor-mediated inhibition of the inflammatory response in PR-expressing epithelial cells. It also indicated that DNG inhibited the inflammatory response in stromal cells, however, whether this was via a PR-mediated mechanism is not clear.

CONCLUSIONS

DNG has a significant effect on the inflammatory microenvironment of endometriotic lesions that may contribute to its clinical efficacy. A better understanding of the specific anti-inflammatory activity of DNG and whether this contributes to its clinical efficacy can help develop treatments that focus on the inhibition of inflammation while minimizing hormonal modulation.

Dienogest reduces HSD17β1 expression and activity in endometriosis

Endometriosis is an estrogen-dependent disease. Abnormally biosynthesized estrogens in endometriotic tissues induce the growth of the lesion and worsen endometriosis-associated pelvic pain. Dienogest (DNG), a selective progesterone receptor agonist, is widely used to treat endometriosis and efficiently relieves the symptoms. However, its pharmacological action remains unknown. In this study, we elucidated the effect of DNG on enzymes involved in local estrogen metabolism in endometriosis. Surgically obtained specimens of 23 ovarian endometriomas (OE) and their homologous endometrium (EE), ten OE treated with DNG (OE w/D), and 19 normal endometria without endometriosis (NE) were analyzed. Spheroid cultures of stromal cells (SCs) were treated with DNG and progesterone. The expression of aromatase, 17β-hydroxysteroid dehydrogenase 1 (HSD17β1), HSD17β2, HSD17β7, HSD17β12, steroid sulfatase (STS), and estrogen sulfotransferase (EST) was evaluated by real-time quantitative PCR. The activity and protein level of HSD17β1 were measured with an enzyme assay using radiolabeled estrogens and immunohistochemistry respectively. OESCs showed increased expression of aromatase, HSD17β1, STS, and EST, along with decreased HSD17β2 expression, when compared with stromal cells from normal endometria without endometriosis (NESCs) (P<0.01) or stromal cells from homologous endometrium (EESCs) (P<0.01). In OESCs, DNG inhibited HSD17β1 expression and enzyme activity at 10(-7) M (P<0.01). Results of immunohistochemical analysis displayed reduced HSD17β1 staining intensity in OE w/D (P<0.05). In conclusion, DNG exerts comprehensive inhibition of abnormal estrogen production through inhibition of aromatase and HSD17β1, contributing to a therapeutic effect of DNG on endometriosis.

Progestins in the fertility-sparing treatment and retreatment of patients with primary and recurrent endometrial cancer

Endometrial cancer is the most common gynecologic cancer in developed countries. Approximately 3%-14% of endometrial cancers are diagnosed in young women under 40 who want to preserve their fertility. The incidence of endometrial cancer in this age group is increasing, for which fertility-sparing therapy is increasingly used because it is one of the most important quality of life issues in these women. Progestin therapy is the most common type of fertility-sparing therapy. In this review, the most up-to-date findings regarding fertility-sparing progestin therapy for young women with primary and recurrent endometrial cancer is addressed in terms of diagnosis, treatment, follow-up, and oncologic and reproductive outcomes. Fertility-sparing progestin therapy is highly effective in selected young women with primary and recurrent endometrial cancer. The selection of appropriate patients through comprehensive pretreatment evaluation is of paramount importance to achieve the best outcomes without compromising survival. Because of the high rate of recurrence after successful fertility-sparing therapy, close surveillance is mandatory, and prophylactic hysterectomy is the best option for patients who have completed family planning. Pregnancy outcomes are very promising with the aid of assisted reproductive technologies. Continuous daily oral medroxyprogesterone acetate and megestrol acetate are the preferred progestins for fertility-sparing therapy, but future studies should be performed to determine the optimal dose and treatment duration of these agents.

Pelvic pain and quality of life of women with endometriosis during quadriphasic estradiol valerate/dienogest oral contraceptive: a patient-preference prospective 24-week pilot study

OBJECTIVE

The progestin dienogest (DNG) given alone effectively reduces pelvic pain of women with endometriosis. It is not clear whether the same occurs when DNG is associated with estradiol (E2).

DESIGN

Patient preference prospective observational study.

SETTING

Outpatient centre of university hospital.

PATIENTS

40 patients with endometriosis and menstrual pain.

INTERVENTIONS

24-week treatment with a quadriphasic association of E2 valerate (E2V) and DNG or a nonsteroidal anti-inflammatory drug (NSAID) to be used only in case of pain (ketoprofene 200-mg tablets).

MAIN OUTCOME MEASURES

Menstrual pain and, when present, intermenstrual pain, and dyspareunia were investigated by means of a 10-cm visual analogue scale (VAS). Quality of life was investigated by the short form 36 (SF-36) of the health-related quality of life questionnaire.

RESULTS

Final study group consists of 34 patients, 19 in the E2V/DNG group and 15 in the NSAID group. After 24 weeks, no significant modification of menstrual pain, intermenstrual pain, dyspareunia, or SF-36 score was observed in the NSAID group. Treatment with E2V/DNG reduced the VAS score of menstrual pain by 61% (P < .0001). In the subgroups of women with intermenstrual pain or dyspareunia, E2V/DNG reduced these complaints by 65% (P = .013) and 52% (P = .016), respectively. The reduction in menstrual (P = .0001) and intermenstrual pain (p = 0.03) was significantly greater during E2V/DNG than NSAID. Quality of life improved during E2V/DNG (P = .0002), both in physical (P = .0003) and mental domains (P = .0065). Only a few minor adverse effects were described during E2V/DNG, and none caused withdrawal from treatment.

CONCLUSION

In patients with endometriosis and pelvic pain, the 24-week administration of the quadriphasic association of E2V/DNG decreases pelvic pain and improves quality of life.

Decorin induced by progesterone plays a crucial role in suppressing endometriosis

Dienogest, a synthetic progestin, has been shown to be effective against endometriosis, although it is still unclear as to how it affects the ectopic endometrial cells. Decorin has been shown to be a powerful endogenous tumor repressor acting in a paracrine fashion to limit tumor growth. Our objectives were to examine the direct effects of progesterone and dienogest on the in vitro proliferation of the human ectopic endometrial epithelial and stromal cell lines, and evaluate as to how decorin contributes to this effect. We also examined DCN mRNA expression in 50 endometriosis patients. The growth of both cell lines was inhibited in a dose-dependent manner by both decorin and dienogest. Using a chromatin immunoprecipitation assay, it was noted that progesterone and dienogest directly induced the binding of the decorin promoter in the EMOsis cc/TERT cells (immortalized human ovarian epithelial cells) and CRL-4003 cells (immortalized human endometrial stromal cells). Progesterone and dienogest also led to significant induced cell cycle arrest via decorin by promoting production of p21 in both cell lines in a dose-dependent manner. Decorin also suppressed the expression of MET in both cell lines. We confirmed that DCN mRNA expression in patients treated with dienogest was higher than that in the control group. In conclusion, decorin induced by dienogest appears to play a crucial role in suppressing endometriosis by exerting anti-proliferative effects and inducing cell cycle arrest via the production of p21 human ectopic endometrial cells and eutopic endometrial stromal cells.

Dienogest reduces proliferation, aromatase expression and angiogenesis, and increases apoptosis in human endometriosis

Dienogest is a novel progestin that is highly selective for progesterone receptors and inhibits endometriosis. However, it remains unknown how the administration of dienogest to patients with endometriosis impacts on their lesion tissues. The aim of this study was to evaluate the in vivo effect of dienogest on endometriosis tissue. We collected endometrioma tissues from patients treated with dienogest (N = 7) or not treated (N = 11, controls). Cell proliferation, aromatase expression and blood vessel density were evaluated by staining for Ki67, aromatase and the von Willebrand factor, respectively. Apoptosis was detected using the TUNEL assay. The proportion of Ki67 and aromatase positive epithelial cells was significantly lower in the dienogest group than in controls (p < 0.05, respectively). The number of TUNEL positive cells was significantly higher in the dienogest group (p < 0.05). The density of blood vessels in endometrioma was marginally lower in the dienogest group compared with controls (p = 0.20). Our study demonstrates that endometrioma taken from patients treated with dienogest show remarkable histological features such as reduction of proliferation, aromatase expression and angiogenesis, and increase of apoptosis. This study clarified the impact of dienogest on local histological events that explain its therapeutic effect on endometriosis.

The dynamics of nuclear receptors and nuclear receptor coregulators in the pathogenesis of endometriosis

BACKGROUND

Endometriosis is defined as the colonization and growth of endometrial tissue at anatomic sites outside the uterine cavity. Up to 15% of reproductive-aged women in the USA suffer from painful symptoms of endometriosis, such as infertility, pelvic pain, menstrual cycle abnormalities and increased risk of certain cancers. However, many of the current clinical treatments for endometriosis are not sufficiently effective and yield unacceptable side effects. There is clearly an urgent need to identify new molecular mechanisms that critically underpin the initiation and progression of endometriosis in order to develop more specific and effective therapeutics which lack the side effects of current therapies. The aim of this review is to discuss how nuclear receptors (NRs) and their coregulators promote the progression of endometriosis. Understanding the pathogenic molecular mechanisms for the genesis and maintenance of endometriosis as modulated by NRs and coregulators can reveal new therapeutic targets for alternative endometriosis treatments.

METHODS

This review was prepared using published gene expression microarray data sets obtained from patients with endometriosis and published literature on NRs and their coregulators that deal with endometriosis progression. Using the above observations, our current understanding of how NRs and NR coregulators are involved in the progression of endometriosis is summarized.

RESULTS

Aberrant levels of NRs and NR coregulators in ectopic endometriosis lesions are associated with the progression of endometriosis. As an example, endometriotic cell-specific alterations in gene expression are correlated with a differential methylation status of the genome compared with the normal endometrium. These differential epigenetic regulations can generate favorable cell-specific NR and coregulator milieus for endometriosis progression. Genetic alterations, such as single nucleotide polymorphisms and insertion/deletion polymorphisms of NR and coregulator genes, are frequently detected in ectopic lesions compared with the normal endometrium. These genetic variations impart new molecular properties to NRs and coregulators to increase their capacity to stimulate progression of endometriosis. Finally, post-translational modifications of NR coregulators, such as proteolytic processing, generate endometriosis-specific isoforms. Compared with the unmodified coregulators, these coregulator isoforms have unique functions that enhance the pathogenesis of endometriosis.

CONCLUSIONS

Epigenetic/genetic variations and posttranslational modifications of NRs and coregulators alter their original function so that they become potent 'drivers' of endometriosis progression.

Lipoxin A₄ prevents the progression of de novo and established endometriosis in a mouse model by attenuating prostaglandin E₂ production and estrogen signaling

Endometriosis, a leading cause of pelvic pain and infertility, is characterized by ectopic growth of endometrial-like tissue and affects approximately 176 million women worldwide. The pathophysiology involves inflammatory and angiogenic mediators as well as estrogen-mediated signaling and novel, improved therapeutics targeting these pathways are necessary. The aim of this study was to investigate mechanisms leading to the establishment and progression of endometriosis as well as the effect of local treatment with Lipoxin A₄ (LXA₄), an anti-inflammatory and pro-resolving lipid mediator that we have recently characterized as an estrogen receptor agonist. LXA₄ treatment significantly reduced endometriotic lesion size and downregulated the pro-inflammatory cytokines IL-1β and IL-6, as well as the angiogenic factor VEGF. LXA₄ also inhibited COX-2 expression in both endometriotic lesions and peritoneal fluid cells, resulting in attenuated peritoneal fluid Prostaglandin E₂ (PGE₂) levels_. Besides its anti-inflammatory effects, LXA₄ differentially regulated the expression and activity of the matrix remodeling enzyme matrix metalloproteinase (MMP)-9 as well as modulating transforming growth factor (TGF)-β isoform expression within endometriotic lesions and in peritoneal fluid cells. We also report for first time that LXA₄ attenuated aromatase expression, estrogen signaling and estrogen-regulated genes implicated in cellular proliferation in a mouse model of disease. These effects were observed both when LXA₄ was administered prior to disease induction and during established disease. Collectively, our findings highlight potential targets for the treatment of endometriosis and suggest a pleotropic effect of LXA₄ on disease progression, by attenuating pro-inflammatory and angiogenic mediators, matrix remodeling enzymes, estrogen metabolism and signaling, as well as downstream proliferative pathways.

Dienogest inhibits nerve growth factor expression induced by tumor necrosis factor-α or interleukin-1β

OBJECTIVE

Dienogest (DNG), a selective P receptor (PR) agonist, is used to treat endometriosis. To investigate whether DNG affects nerve growth factor (NGF) expression, we stimulated human endometrial epithelial cells (hEECs) with inflammatory cytokines.

DESIGN

Prospective basic research study using immortalized hEEC lines.

SETTING

Development Research, Mochida Pharmaceutical Co., Ltd., Japan.

PATIENT(S)

None.

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURE(S)

In immortalized hEECs, NGF production induced by tumor necrosis factor-α (TNF-α) or interleukin-1β (IL-1β) was evaluated in the presence or absence of the synthetic progestin DNG or endogenous P. The NGF messenger RNA (mRNA) and protein were measured using real-time reverse transcriptase-polymerase chain reaction (PCR) and ELISA, respectively. The NGF bioactivity in the culture medium was measured by assaying neurite outgrowth of PC-12 cells.

RESULT(S)

Tumor necrosis factor-α and IL-1β induced NGF mRNA and protein and increased NGF bioactivity in the culture medium. These activities were inhibited by DNG in a hEEC line that stably expresses PR. In contrast, in an hEEC line that constitutively expresses faint levels of PR, no inhibitory effect of DNG on NGF mRNA was detected. The NGF mRNA was also inhibited in hEEC lines that express only PR-A or only PR-B.

CONCLUSION(S)

Nerve growth factor is one of the key mediators that generates the pain associated with endometriosis. Dienogest inhibits NGF expression through PR-A and PR-B in hEEC, which may contribute to the pharmacological mechanisms of how DNG relieves pain in endometriosis.

Progesterone enhances calcitriol antitumor activity by upregulating vitamin D receptor expression and promoting apoptosis in endometrial cancer cells

Human studies suggest that progesterone and calcitriol may prove beneficial in preventing or inhibiting oncogenesis, but the underlying mechanism is not fully understood. The current study investigates the effects of progesterone, calcitriol, and their combination on immortalized human endometrial epithelial cells and endometrial cancer cells and identifies their targets of action. Combination treatment with both agents enhanced vitamin D receptor expression and inhibited cell proliferation through caspase-3 activation and induction of G0-G1 cell-cycle arrest with associated downregulation of cyclins D1 and D3 and p27 induction. We used mass spectrometry-based proteomics to measure protein abundance differences between calcitriol-, progesterone-, or combination-exposed endometrial cells. A total of 117 proteins showed differential expression among these three treatments. Four proteins were then selected for validation studies: histone H1.4 (HIST1H1E), histidine triad nucleotide-binding protein 2 (HINT2), IFN-induced, double-stranded RNA-activated protein kinase (EIF2AK2), and Bcl-2-associated X protein (BAX). Abundance levels of selected candidates were low in endometrial cancer cell lines versus the immortalized endometrial epithelial cell line. All four proteins displayed elevated expression in cancer cells upon exposure to calcitriol, progesterone, or the combination. Further BAX analysis through gain- or loss-of-function experiments revealed that upregulation of BAX decreased cell proliferation by changing the BAX:BCL-2 ratio. Knockdown of BAX attenuated progesterone- and calcitriol-induced cell growth inhibition. Our results showed that progesterone and calcitriol upregulate the expression of BAX along with other apoptosis-related proteins, which induce inhibition of endometrial cancer cell growth by apoptosis and cell-cycle arrest.

The use of an oral contraceptive containing estradiol valerate and dienogest before office operative hysteroscopy: a feasibility study

To investigate the impact of a 3 months preoperative administration of an oral contraceptive, containing dienogest (DNG) and estradiol valerate (E₂V) on the outcome of office operative hysteroscopy (OOH). One-hundred and forty-two patients diagnosed at office hysteroscopy as having an asynchronous endometrium associated with either a broad-base sessile endometrial polyp (>1.5, <2.5 cm) or a uterine septum (>1/3 uterine cavity) or scheduled for tubal sterilization were enrolled into a prospective case-control study at University "Federico II" of Naples. 86/142 patients accepted the preoperative hormonal treatment (Group A), while 56/142 refused, thus becoming controls (Group B). Group A underwent OOH during the 10th-20th days of the third cycle of treatment. In Group B OOH was performed at enrolment, together with the diagnostic procedure. The study outcomes were: endometrial pattern, success rate, operating time, degree of surgical difficulty and pain score. An overall improvement of the endometrium was reported in 100% of cases in Group A. A statistically significant difference in success rate could not be demonstrated between two groups. Operative procedures were performed significantly quicker and easier in Group A than Group B (p < 0.001 and p < 0.05, respectively). The mean Visual Analog Scale (VAS) score was significantly lower in Group A (p < 0.001). A short pretreatment with combined oral contraceptive (COC) containing E₂V/DNG seems to have a favorable impact on endometrium which in turn may result in an improvement of the overall outcomes of OOH.

The role of prostaglandin E2 in endometriosis

Endometriosis is a leading cause of infertility in women of reproductive age. It involves the occurrence of endometrial tissue outside the uterine endometrium, mainly in the peritoneal cavity. Prostaglandin E(2) is up regulated in the peritoneal cavity in endometriosis and is produced by macrophages and ectopic endometrial cells. This prostaglandin is involved in the pathophysiology of the disease and elicits cell signals via four receptor types. Prostaglandin E(2) increases estrogen synthesis by up regulating steroidogenic acute regulatory protein (StAR) and aromatase. It inhibits apoptosis and up regulates fibroblast growth factor-9 (FGF-9) promoting cell proliferation. Prostaglandin E(2) affects leukocyte populations and promotes angiogenesis through its effect on estrogen and up regulation of vascular endothelial growth factor (VEGF). Dienogest is a synthetic progestin targeting expression of genes involved in prostaglandin synthesis.

Dienogest inhibits Toll-like receptor 4 expression induced by costimulation of lipopolysaccharide and high-mobility group box 1 in endometrial epithelial cells

OBJECTIVE

To investigate the effect of dienogest on the expression of Toll-like receptor (TLR) 4 in human endometrial epithelial cells.

DESIGN

Prospective basic research study.

SETTING

Pharmaceutical research center.

PATIENT(S)

None.

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURE(S)

TLR4 in the immortalized progesterone receptor-expressing human endometrial epithelial cell line, EM-PR, was activated with lipopolysaccharide and high-mobility group box 1 (LPS/HMGB1) in the presence or absence of the synthetic progestin dienogest or endogenous progesterone. The production of interleukin (IL)-8, IL-6, and monocyte chemoattractant protein (MCP)-1 and the mRNA expression of TLR4 were measured with the use of ELISA and real-time reverse-transcription polymerase chain reaction respectively and nuclear factor (NF)-κB reporter gene assays were performed. The role of TLR4 was assayed with the use of TLR4-siRNA-transfected cells.

RESULT(S)

Coadministration of LPS/HMGB1 induced the production of IL-8, IL-6, and MCP-1, TLR4 mRNA expression, and NF-κB activity in EM-PR cells, and dienogest inhibited all of these parameters. TLR4 knockdown using TLR4 siRNA reduced IL-8 production.

CONCLUSION(S)

Dienogest inhibits TLR4 mRNA expression and subsequent IL-8 production induced by TLR4 agonists via an inhibitory effect on NF-κB activation in human endometrial epithelial cells. This pharmacologic effect of dienogest may contribute to its therapeutic effect on abnormal inflammation of endometrium.

Effects of dienogest on surgically induced endometriosis in rats after repeated oral administration

BACKGROUND

Dienogest demonstrates efficacy for lesion reduction and pain relief in clinical trials of endometriosis. The current study investigated an intraperitoneal animal model of endometriosis to further characterize the effects of dienogest.

METHODS

Endometrial-like lesions were induced in rats by autotransplantation of uterine tissue into the peritoneal cavity. Dienogest 0.3 or 1.0 mg/kg/day, danazol 100 mg/kg/day, or vehicle control were administered orally for 28 days. Changes in endometrial-like lesion size during treatment were assessed at laparotomy. Uterine horn weight was also measured as an index of the estrogenic effects of treatment.

RESULTS

Dienogest 0.3 mg/kg/day significantly reduced the total endometrial lesion area, with an effect equivalent to danazol 100 mg/kg/day. Unlike dienogest 1.0 mg/kg/day, dienogest 0.3 mg/kg/day had no effect on uterine horn weight, indicating an absence of estrogenic effects for this dose in rodents.

CONCLUSION

Dienogest 0.3 mg/kg/day for 28 days demonstrated potent inhibitory activity on the growth of endometrial tissue in this model, providing supportive evidence for the efficacy of dienogest in lesion reduction.

Maintenance therapy with dienogest following gonadotropin-releasing hormone agonist treatment for endometriosis-associated pelvic pain

OBJECTIVE

To examine whether long-term administration of dienogest following gonadotropin-releasing hormone agonist (GnRH-a) therapy would prolong the relief of pelvic pain while reducing the amount of irregular uterine bleeding.

STUDY DESIGN

This was a prospective, non-randomized clinical trial. Among the patients suffering from chronic pelvic pain associated with recurrent endometriosis, Group G (n=38) received GnRH-a for 4-6 months and then dienogest (1 mg/day) for 12 months. The dose of dienogest was increased to 1.5 or 2 mg/day when a patient had uncontrollable uterine bleeding {n=15 (39%)}. Group D (n=33) received only dienogest (2 mg/day) for 12 months. Pelvic pain was assessed using a visual analog scale (VAS). Uterine bleeding was semi-quantified using a pictorial blood loss assessment chart (PBAC).

RESULTS

In Group G, GnRH-a significantly reduced the VAS score for pelvic pain, and alleviation was maintained during the 12-month therapy with dienogest. There was no significant difference in pain reduction between Group G and Group D. The PBAC score during the first 6 months on dienogest was significantly smaller in Group G than in Group D.

CONCLUSION

Treatment with a GnRH-a followed by long-term dienogest therapy maintains the relief of endometriosis-associated pelvic pain achieved with GnRH-a therapy for at least 12 months. This regimen reduces the amount of irregular uterine bleeding that often occurs during the early phase of dienogest therapy.

Dienogest, a synthetic progestin, inhibits prostaglandin E2 production and aromatase expression by human endometrial epithelial cells in a spheroid culture system

Prostaglandin E(2) (PGE(2)) is a major mediator in the pathophysiology, and pathogenesis of gynecological diseases associated with abnormal endometrial disease with proliferation and inflammation, such as endometriosis. In this study, we investigated the effect of dienogest, a selective progesterone receptor agonist, on PGE(2) production and the expression of aromatase, an estrogen synthase, in human immortalized endometrial epithelial cells. Compared with monolayer culture, the cells showed enhanced PGE(2) production and expression of the PGE(2) synthases cyclooxygenase-2 (COX-2), and microsomal prostaglandin E(2) synthase-1 (mPGES-1) in a spheroid culture system. Dienogest inhibited PGE(2) production and this effect was reversed by RU486, a progesterone receptor antagonist. Dienogest inhibited the PGE(2) synthases mRNA and protein expression, and the nuclear factor-κB activation. Moreover, the suppressive effect of dienogest on PGE(2) production was sustained 24h after the drug was withdrawn. Dienogest but not COX inhibitors inhibited aromatase expression. These results suggest that progesterone receptor activation reduces the gene expressions of COX-2, mPGES-1, and aromatase. Our findings suggest that the pharmacological mechanism of dienogest includes the direct inhibition of PGE(2) synthase and aromatase expression and may contribute to the therapeutic effect on the progression of endometriosis.

Krüppel-like factor 4 mediates anti-proliferative effects of progesterone with G₀/G₁ arrest in human endometrial epithelial cells

Activation of the progesterone receptor (PR) inhibits cell proliferation in various reproductive tissues. However, the molecular mechanisms underlying the regulation of cell proliferation by PR remain poorly understood. It is well established that Krüppel-like factor 4 (KLF4), a family of zinc fingercontaining transcription factors, induces cell cycle arrest in epithelial cells. In this study, we investigated whether KLF4 served as a target of PR activation during cell proliferation using human endometrial epithelial cells. PR agonists, progesterone and dienogest, were found to produce a lasting increase in the expression of KLF4 mRNA, followed by a decrease in cyclin D1 mRNA, and inhibit cell proliferation with G₀/G₁ arrest. KLF4 knockdown using KLF4 small interferingRNA abrogated the inhibition of cell proliferation by PR agonists. In addition, forced expression of KLF4 inhibited cyclin D1 promoter transactivation. These results suggest that PR agonists induce KLF4 expression and then inhibit cyclin D1 expression, and consequently inhibit cell proliferation in human endometrial epithelial cells. In terms of human reproductive tissue, KLF4 may be a factor concerning cell cycle, directly responsive to PR activation.

Progestin effects in endometriosis treatment: new research on mechanisms

New research on mechanisms of progestin effects in endometriosis treatment has been performed with dienogest (DNG), which has recently been launched in this regard. It is effective in the same low dosage of 2 mg/day, similar to the use of contraception and hormone therapy, whereas other progestogens (with the exception of dydrogesterone) must be given in much higher dosages to treat typical symptoms of endometriosis. This short review summarizes experimental studies on DNG. They demonstrate strong antiproliferative effects in endometrial and endometriotic cells or experimental endometriosis, as well as anti-inflammatory and antiangiogenic actions. By direct action on the ovarian folliculogenesis DNG lead to only modest suppression of estradiol production in contrast to the high-dosed progestogens or to gonadotropin releasing hormone (GnRH) agonists. These effects add to the well-known tolerability because DNG is very neutral regarding cardiovascular, metabolic or central action which also makes it suitable for long-term therapy.