Emerging Drug Targets for Endometriosis

The Known, the Unknown and the Future of the Pathophysiology of Endometriosis

Endometriosis is one of the most common causes of chronic pelvic pain and infertility, affecting 10% of women of reproductive age. A delay of up to 9 years is estimated between the onset of symptoms and the diagnosis of endometriosis. Endometriosis is currently defined as the presence of endometrial epithelial and stromal cells at ectopic sites; however, advances in research on endometriosis have some authors believing that endometriosis should be re-defined as "a fibrotic condition in which endometrial stroma and epithelium can be identified". There are several theories on the etiology of the disease, but the origin of endometriosis remains unclear. This review addresses the role of microRNAs (miRNAs), which are naturally occurring post-transcriptional regulatory molecules, in endometriotic lesion development, the inflammatory environment within the peritoneal cavity, including the role that cytokines play during the development of the disease, and how animal models have helped in our understanding of the pathology of this enigmatic disease.

Causal effects of endometriosis on SLE, RA and SS risk: evidence from meta-analysis and Mendelian randomization

BACKGROUND

Endometriosis is an underdiagnosed disorder that affects an estimated 6-10% of women of reproductive age. Endometriosis has been reported in epidemiological studies to be associated with autoimmune diseases. However, the relationship remains controversial.

METHODS

A meta-analysis of observational studies was undertaken to evaluate the risk of autoimmune diseases in patients with endometriosis. The relevant studies were retrieved via the databases Medline, Embase and Web of Science until July 20, 2023. Mendelian randomization (MR) was subsequently utilized to scrutinize the causal influence of genetic predisposition toward endometriosis on three autoimmune diseases.

RESULTS

The meta-analysis findings revealed a relationship between endometriosis and the onset of SLE (cohort studies: RR = 1.77, 95% confidence interval (CI): 1.47-2.13, I2 = 0%; Case-control and cross-sectional studies: OR = 5.23, 95% CI: 0.74-36.98, I2 = 98%), RA (cohort studies: RR = 2.18, 95% CI: 1.85-2.55, I2 = 92%; Case-control and cross-sectional studies: OR = 1.40, 95% CI: 1.19-1.64, I2 = 0%) and SS (cohort studies: RR = 1.49, 95% CI: 1.34-1.66, I2 = 0%). Similarly, in our MR study, the results of the inverse-variance-weighted (IVW) model suggested that genetic predisposition to endometriosis was causally associated with an increased risk for SLE (OR = 1.915, 95% CI: 1.204-3.045, p = 0.006) and RA (OR = 1.005, 95% CI: 1.001-1.009, p = 0.014).

CONCLUSIONS

Both our meta-analysis and MR study indicate that endometriosis increases the risk of autoimmune diseases. These findings not only broaden our understanding of the genetic mechanisms underlying the comorbidity of endometriosis and autoimmune diseases, but also offer a new strategy for autoimmune disease prevention.

Elucidating the role of Brain-Derived Neurotrophic Factor (BDNF) and its receptor Tyrosine Receptor Kinase B (TrkB) in the development and symptoms of endometriosis

Endometriosis (EMs) is a common disease among women of reproductive age, and as of now, the clinical understanding of the etiology of this disease remains unclear. The occurrence of EMs has a profound impact on the reproductive health of women, making early diagnosis and treatment of this disease a pressing challenge in clinical practice. Recent studies have found that Brain-Derived Neurotrophic Factor (BDNF), in combination with its high-affinity receptor Tyrosine Receptor Kinase B (TrkB), participates in the development of EMs and the appearance of clinically relevant symptoms by activating the Mitogen-Activated Protein Kinase (MAPK) pathway, the Phosphatidylinositol 3-Kinase/Protein Kinase B (PI3K/AKT) pathway, and the Phospholipase C-gamma (PLCγ) signaling pathway, or by interacting with other factors. In order to gain a deeper understanding of the pathogenesis related to EMs, this article reviews the roles of BDNF and TrkB in EMs, particularly in terms of aberrant apoptosis and autophagy, cell invasion, proliferation, angiogenesis, oxidative stress, and inflammatory reactions, as well as their relationship with the symptoms associated with EMs.

Fraxetin reduces endometriotic lesions through activation of ER stress, induction of mitochondria-mediated apoptosis, and generation of ROS

BACKGROUND

Fraxetin, a phytochemical obtained from Fraxinus rhynchophylla, is well known for its anti-inflammatory and anti-fibrotic properties. However, fraxetin regulates the progression of endometriosis, which is a benign reproductive disease that results in low quality of life and infertility.

HYPOTHESIS/PURPOSE

We hypothesized that fraxetin may have therapeutic effects on endometriosis and aimed to elucidate the underlying mechanisms of mitochondrial function and tiRNA regulation.

STUDY DESIGN

Endometriotic animal models and cells (End1/E6E7 and VK2/E6E7) were used to identify the mode of action of fraxetin.

METHODS

An auto-implanted endometriosis animal model was established and the effects of fraxetin on lesion size reduction were analyzed. Cell-based assays including proliferation, cell cycle, migration, apoptosis, mitochondrial function, calcium efflux, and reactive oxygen species (ROS) were performed. Moreover, fraxetin signal transduction was demonstrated by western blotting and qPCR analyses.

RESULTS

Fraxetin inhibited proliferation and migration by inactivating the P38/JNK/ERK mitogen-activated protein kinase (MAPK) and AKT/S6 pathways. Fraxetin dissipates mitochondrial membrane potential, downregulates oxidative phosphorylation (OXPHOS), and disrupts redox and calcium homeostasis. Moreover, it triggered endoplasmic reticulum stress and intrinsic apoptosis. Furthermore, we elucidated the functional role of tiRNAHisGTG in endometriosis by transfection with its inhibitor. Finally, we established an endometriosis mouse model and verified endometriotic lesion regression and downregulation of adhesion molecules with inflammation.

CONCLUSION

This study suggests that fraxetin is a novel therapeutic agent that targets mitochondria and tiRNAs. This is the first study to demonstrate the mechanisms of tiRNAHisGTG with mitochondrial function and cell fates and can be applied as a non-hormonal method against the progression of endometriosis.

Digestive system deep infiltrating endometriosis: What do we know

Digestive system infiltrating endometriosis (DSIE) is an uncommon form of endometriosis in the digestive system. DSIE often occurs in the intestines (especially the sigmoid rectum), liver, gallbladder and pancreas. Clinically, DSIE presents with the same symptoms as endometriosis, including cyclic pain, bleeding and infertility, in addition to specific biliary/intestinal obstruction and gastrointestinal bleeding. Compared to general endometriosis, DSIE has unique biological behaviour and pathophysiological mechanisms. Most DSIEs are deep invasive endometrioses, characterized by metastasis to the lymph nodes and lymphatic vessels, angiogenesis, peripheral nerve recruitment, fibrosis and invasion of surrounding tissues. DSIE-related peripheral angiogenesis is divided into three patterns: angiogenesis, vasculogenesis and inosculation. These patterns are regulated by interactions between multiple hypoxia-hormone cytokines. The nerve growth factors regulate the extensive neurofibril recruitment in DSIE lesions, which accounts for severe symptoms of deep pain. They are also associated with fibrosis and the aggressiveness of DSIE. Cyclic changes in DSIE lesions, recurrent inflammation and oxidative stress promote repeated tissue injury and repair (ReTIAR) mechanisms in the lesions, accelerating fibril formation and cancer-related mutations. Similar to malignant tumours, DSIE can also exhibit aggressiveness derived from collective cell migration mediated by E-cadherin and N-cadherin. This often makes DSIE misdiagnosed as a malignant tumour of the digestive system in clinical practice. In addition to surgery, novel treatments are urgently required to effectively eradicate this lesion.

6-(7-Nitro-2,1,3-benzoxadiazol-4-ylthio) Hexanol Inhibits Proliferation and Induces Apoptosis of Endometriosis by Regulating Glutathione S-Transferase Mu Class 4

Endometriosis is a chronic disease associated with a disrupted oxidative balance and chronic inflammation. In this study, we investigated the role of glutathione S-transferase Mu class 4 (GSTM4) in endometriosis and determined whether 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio) hexanol (NBDHEX) regulates GSTM4 expression to affect cellular functions and oxidative stress. GSTM4 expression was detected by immunohistochemistry in endometrium from 15 endometriosis patients and 15 healthy controls. Western blotting was used to detect the expression of GSTM4, proliferating cell nuclear antigen (PCNA), matrix metalloproteinase-9 (MMP-9), Survivin, B-cell lymphoma-extra-large (Bcl-XL), Bax, kelch-like ECH-associated protein 1 (Keap1), and nuclear factor-erythroid 2-related factor 2 (Nrf2) in primary endometrial stromal cells with endometriosis (EESC) and normal endometrial stromal cells (NESC). The effects of NBDHEX on cell proliferation, migration, and invasion were evaluated using Cell Counting Kit-8 (CCK8) and Transwell assays. Apoptosis was detected by flow cytometry. The expression of GSTM4 was significantly increased in endometrium from endometriosis patients. Upon NBDHEX treatment, ESC exhibited reduced proliferation, migration and invasion abilities, and increased apoptosis. NBDHEX decreased the expression of endometriosis prognostic markers (PCNA and MMP-9) and anti-apoptotic proteins (Survivin and Bcl-xl), while it increased the expression of the apoptotic protein Bax. It had no effect on Keap1 expression, and it decreased the expression of Nrf2. The effect of siRNA-mediated knockdown of GSTM4 was similar to that of suppressing GSTM4 expression with NBDHEX treatment. These results indicate that GSTM4 is highly expressed in endometriosis and its expression is inhibited by NBDHEX. Decreased expression of GSTM4 inhibits cell growth, migration, and invasion, and negatively regulates Nrf2 to affect oxidative stress-induced apoptosis. Our results suggest that GSTM4 may play a role in ameliorating the progression of endometriosis. NBDHEX may have therapeutic potential in the treatment of endometriosis.

Identification of potential diagnostic biomarkers and therapeutic targets for endometriosis based on bioinformatics and machine learning analysis

PURPOSE

Endometriosis (EMs) is a major gynecological condition in women. Due to the absence of definitive symptoms, its early detection is very challenging; thus, it is crucial to find biomarkers to ease its diagnosis and therapy. Here, we aimed to identify potential diagnostic and therapeutic targets for EMs by constructing a regulatory network and using machine learning approaches.

METHODS

Three Gene Expression Omnibus (GEO) datasets were merged, and differentially expressed genes (DEGS) were identified after preprocessing steps. Using the DEGs, a transcription factor (TF)-mRNA-miRNA regulatory network was constructed, and hub genes were detected based on four different algorithms in CytoHubba. The hub genes were used to build a GaussianNB diagnostic model and also in docking analysis that were performed using Discovery Studio and AutoDock Vina software.

RESULTS

A total of 119 DEGs were identified between EMs and non-EMs samples. A regulatory network consisting of 52 mRNAs, 249 miRNAs, and 37 TFs was then constructed. The diagnostic model was introduced using the hub genes selected from the network (GATA6, HMOX1, HS3ST1, NFASC, and PTGIS) that its area under the curve (AUC) was 0.98 and 0.92 in the training and validation cohorts, respectively. Based on docking analysis, two chemical compounds, rofecoxib and retinoic acid, had potential therapeutic effects on EMs.

CONCLUSION

In conclusion, this study identified potential diagnostic and therapeutic targets for EMs which demand more experimental confirmations.

Endometriosis Treatment: Role of Natural Polyphenols as Anti-Inflammatory Agents

Endometriosis is an estrogen-dependent common chronic inflammatory disease defined by the presence of extrauterine endometrial tissue that promotes pelvic pain and fertility impairment. Its etiology is complex and multifactorial, and several not completely understood theories have been proposed to describe its pathogenesis. Indeed, this disease affects women's quality of life and their reproductive system. Conventional therapies for endometriosis treatment primarily focus on surgical resection, lowering systemic levels of estrogen, and treatment with non-steroidal anti-inflammatory drugs to counteract the inflammatory response. However, although these strategies have shown to be effective, they also show considerable side effects. Therefore, there is a growing interest in the use of herbal medicine for the treatment of endometriosis; however, to date, only very limited literature is present on this topic. Polyphenols display important anti-endometriotic properties; in particular, they are potent phytoestrogens that in parallel modulates estrogen activity and exerts anti-inflammatory activity. The aim of this review is to provide an overview on anti-inflammatory activity of polyphenols in the treatment of endometriosis.

A Lifelong Impact on Endometriosis: Pathophysiology and Pharmacological Treatment

Endometriosis is a chronic inflammatory disease associated with bothersome symptoms in premenopausal women and is complicated with long-term systemic impacts in the post-menopausal stage. It is generally defined by the presence of endometrial-like tissue outside the uterine cavity, which causes menstrual disorders, chronic pelvic pain, and infertility. Endometriotic lesions can also spread and grow in extra-pelvic sites; the chronic inflammatory status can cause systemic effects, including metabolic disorder, immune dysregulation, and cardiovascular diseases. The uncertain etiologies of endometriosis and their diverse presentations limit the treatment efficacy. High recurrence risk and intolerable side effects result in poor compliance. Current studies for endometriosis have paid attention to the advances in hormonal, neurological, and immunological approaches to the pathophysiology and their potential pharmacological intervention. Here we provide an overview of the lifelong impacts of endometriosis and summarize the updated consensus on therapeutic strategies.

Progesterone Resistance in Endometriosis: Current Evidence and Putative Mechanisms

Endometriosis is an estrogen-dependent disease characterized by the growth of endometrial-like tissue outside the uterus. Progestins are currently the most commonly used treatment for endometriosis because of their excellent therapeutic effects and limited side effects. However, progestins have been unsuccessful in some symptomatic patients. The inability of the endometrium to respond properly to progesterone is known as progesterone resistance. An increasing body of evidence suggests the loss of progesterone signaling and the existence of progesterone resistance in endometriosis. The mechanisms of progesterone resistance have received considerable scholarly attention in recent years. Abnormal PGR signaling, chronic inflammation, aberrant gene expression, epigenetic alterations, and environmental toxins are considered potential molecular causes of progesterone resistance in endometriosis. The general objective of this review was to summarize the evidence and mechanisms of progesterone resistance. A deeper understanding of how these mechanisms contribute to progesterone resistance may help develop a novel therapeutic regimen for women with endometriosis by reversing progesterone resistance.