Levo-tetrahydropalmatine retards the growth of ectopic endometrial implants and alleviates generalized hyperalgesia in experimentally induced endometriosis in rats

Epigenetic Dysregulation in Endometriosis: Implications for Pathophysiology and Therapeutics

Endometriosis is a prevalent gynecological condition associated with pelvic pain and infertility. Despite more than a century of research, the etiology of endometriosis still eludes scientific consensus. This lack of clarity has resulted in suboptimal prevention, diagnosis, and treatment options. Evidence of genetic contributors to endometriosis is interesting but limited; however, significant progress has been made in recent years in identifying an epigenetic role in the pathogenesis of endometriosis through clinical studies, in vitro cell culture experiments, and in vivo animal models. The predominant findings include endometriosis-related differential expression of DNA methyltransferases and demethylases, histone deacetylases, methyltransferases, and demethylases, and regulators of chromatin architecture. There is also an emerging role for miRNAs in controlling epigenetic regulators in the endometrium and endometriosis. Changes in these epigenetic regulators result in differential chromatin organization and DNA methylation, with consequences for gene expression independent of a genetic sequence. Epigenetically altered expression of genes related to steroid hormone production and signaling, immune regulation, and endometrial cell identity and function have all been identified and appear to play into the pathophysiological mechanisms of endometriosis and resulting infertility. This review summarizes and critically discusses early seminal findings, the ever-growing recent evidence of epigenetic contributions to the pathophysiology of endometriosis, and implications for proposed epigenetically targeted therapeutics.

The Present and the Future of Medical Therapies for Adenomyosis: A Narrative Review

Uterine Adenomyosis is a benign condition characterized by the presence of endometrium-like epithelial and stromal tissue in the myometrium. Several medical treatments have been proposed, but still, no guidelines directing the management of adenomyosis are available. While a hysterectomy is typically regarded as the definitive treatment for adenomyosis, the scarcity of high-quality data leaves patients desiring fertility with limited conservative options. Based on the available data, the levonorgestrel-IUD appears to offer the most favorable outcomes. Other treatments, including GnRH antagonists, dienogest, prolactin, and oxytocin modulators, show promise; however, further data are required to establish their efficacy definitively. Furthermore, there are many emerging therapies that have been developed that seem worthy of consideration in the near future. The aim of this narrative review was to explore the current medical treatments available for adenomyosis and to provide a glimpse of future therapies under assessment. For this scope, we performed a literature search on PubMed and Medline from incept to September 2022 using the keywords: "medical treatment", "non-steroidal anti-inflammatory", "progesterone intrauterine device", "dienogest", "combined oral contraceptives", "gonadotropin releasing hormone agonist", "gonadotropin releasing hormone antagonist", "danazol", "aromatase inhibitors", "ulipristal acetate", "anti-platelet therapy", "dopamine", "oxytocin antagonists", "STAT3", "KRAS", "MAPK", "micro-RNA", "mifepristone", "valproic acid", "levo-tetrahydropalamatine", and "andrographolide". The search was limited to articles in English, with subsequent screening of abstracts. Abstracts were screened to select relevant studies.

The Impact of Histone Modifications in Endometriosis Highlights New Therapeutic Opportunities

Endometriosis is a chronic disorder of the female reproductive system which afflicts a great number of women worldwide. Histone deacetylases (HDACs) prevent the relaxation of chromatin, thereby positively or negatively modulating gene transcription. The current review aims at studying the impact of histone modifications and their therapeutic targeting in endometriosis. In order to identify relevant studies, a literature review was conducted using the MEDLINE and LIVIVO databases. The current manuscript represents the most comprehensive, up-to-date review of the literature focusing on the particular role of HDACs and their inhibitors in the context of endometriosis. HDAC1, HDAC2, HDAC3, Sirtuin 1, and Sirtuin 3, are the five most studied HDAC enzymes which seem to, at least partly, influence the pathophysiology of endometriosis. Both well-established and novel HDACIs could possibly represent modern, efficacious anti-endometriotic drug agents. Altogether, histone modifications and their therapeutic targeting have been proven to have a strong impact on endometriosis.

The Unmet Needs for Studying Chronic Pelvic/Visceral Pain Using Animal Models

The different definitions of chronic pelvic/visceral pain used by international societies have changed over the years. These differences have a great impact on the way researchers study chronic pelvic/visceral pain. Recently, the role of systemic changes, including the role of the central nervous system, in the perpetuation and chronification of pelvic/visceral pain has gained weight. Consequently, researchers are using animal models that resemble those systemic changes rather than using models that are organ- or tissue-specific. In this review, we discuss the advantages and disadvantages of using bladder-centric and systemic models, enumerating some of the central nervous system changes and pain-related behaviors occurring in each model. We also present some drawbacks when using animal models and pain-related behavior tests and raise questions about possible, yet to be demonstrated, investigator-related bias. We also suggest new approaches to study chronic pelvic/visceral pain by refining existing animal models or using new ones.

A Comprehensive Review on the Chemical Properties, Plant Sources, Pharmacological Activities, Pharmacokinetic and Toxicological Characteristics of Tetrahydropalmatine

Tetrahydropalmatine (THP), a tetrahydroproberine isoquinoline alkaloid, is widely present in some botanical drugs, such as Stephania epigaea H.S. Lo (Menispermaceae; Radix stephaniae epigaeae), Corydalis yanhusuo (Y.H.Chou & Chun C.Hsu) W.T. Wang ex Z.Y. Su and C.Y. Wu (Papaveraceae; Corydalis rhizoma), and Phellodendron chinense C.K.Schneid (Berberidaceae; Phellodendri chinensis cortex). THP has attracted considerable attention because of its diverse pharmacological activities. In this review, the chemical properties, plant sources, pharmacological activities, pharmacokinetic and toxicological characteristics of THP were systematically summarized for the first time. The results indicated that THP mainly existed in Papaveraceae and Menispermaceae families. Its pharmacological activities include anti-addiction, anti-inflammatory, analgesic, neuroprotective, and antitumor effects. Pharmacokinetic studies showed that THP was inadequately absorbed in the intestine and had rapid clearance and low bioavailability in vivo, as well as self-microemulsifying drug delivery systems, which could increase the absorption level and absorption rate of THP and improve its bioavailability. In addition, THP may have potential cardiac and neurological toxicity, but toxicity studies of THP are limited, especially its long-duration and acute toxicity tests. In summary, THP, as a natural alkaloid, has application prospects and potential development value, which is promising to be a novel drug for the treatment of pain, inflammation, and other related diseases. Further research on its potential target, molecular mechanism, toxicity, and oral utilization should need to be strengthened in the future.

Tetramethylpyrazine Retards the Progression and Fibrogenesis of Endometriosis

The development of more efficacious, non-hormonal therapeutics for endometriosis is still an unmet medical need begging to be fulfilled. Growing evidence indicates that endometriotic lesions are wounds undergoing repeated tissue injury and repair, and, as such, platelets play an important role in lesional progression. Tetramethylpyrazine (TMP), a compound derived from a herb that has been used for thousands of years to combat “blood stasis” in traditional Chinese medicine, is a prescription drug in China for the treatment of cerebrovascular disorders. We tested the hypothesis that TMP can decelerate lesional progression through arresting epithelial-mesenchymal transition (EMT), fibroblast-to-myofibroblast transdifferentiation (FMT), and fibrogenesis. We found in our in vitro experiments that TMP treatment suppresses platelet-induced EMT, FMT, cellular contractility, and collagen production in a concentration-dependent manner. We also showed that in a mouse model of endometriosis, treatment with TMP significantly reduced lesion weight and the extent of lesional fibrosis and improved hyperalgesia, mostly likely through the reduction of lesional aggregation of platelets and the lesional expression of markers of EMT, FMT, and fibrogenesis. In light of our results and in view of its excellent safety profiles, TMP appears to be a promising drug candidate for treating endometriosis.

Effect of epigallocatechin-3-gallate on the status of DNA methylation of E-cadherin promoter region on endometriosis mouse

AIM

To evaluate whether epigallocatechin-3-gallate acts on endometriosis mouse, and changes the status of DNA methylation of E-cadherin promoter region.

METHODS

According to our previous research, the tracing nude mouse model of endometriosis was built up and randomly divided into three groups: control group (group A), epigallocatechin-3-gallate group (group B) and decitabine group (group C). Normal saline, epigallocatechin-3-gallate and decitabine were isometrically intraperitoneally injected into each group once in 2 days. In this period, the growth situations of lesions were monitored by living image system. After 16 days, the lesions were taken out and the distribution of E-cadherin and its methylated situation of promoter region were analyzed.

RESULTS

The region of interest of ectopic lesion increased from 4th to 16th day in group A (P < 0.01); in group B and C, the region of interest of ectopic lesion increased in the 0-8th day (P < 0.01), and decreased in the 8-16th day (P < 0.01). The positive expression rate of E-cadherin in group C was higher than group B, and group B was higher than group A (P < 0.01). The DNA methylation status of E-cadherin promoter region in group A was higher than group B, and group B was higher than group C (P < 0.01).

CONCLUSION

Epigallocatechin-3-gallate may inhibit the growth of endometrial lesion, affect the expression of E-cadherin on the cell membrane and reduce the status of DNA methylation of E-cadherin promoter region.

Sodium tanshinone IIA sulfonate restrains fibrogenesis through induction of senescence in mice with induced deep endometriosis

RESEARCH QUESTION

Does sodium tanshinone IIA sulfonate (STS) induce cellular senescence in endometriotic lesions and thus restrict lesional development and fibrogenesis in a recently established mouse model of deep endometriosis?

DESIGN

Prospective randomized animal experiment in which deep endometriosis was induced in female Balb/C mice, which were then randomly divided into three groups (low-dose STS, high-dose STS and inert vehicle control) and received treatment for 2 weeks. All mice were then sacrificed and their lesions excised and harvested. Lesion weight was quantified and all lesion samples were subjected to histochemical analysis of the extent of lesional fibrosis by Masson trichrome staining, and of cellular senescence by senescence-associated β-galactosidase (SA-β-gal), along with immunohistochemistry analyses of p53, CCN1, activate Salvador 1 (Sav1), hyaluronan synthase 2 (HAS2), survivin, granulocyte-macrophage colony-stimulating factor (GM-CSF) and CD163-positive M2 macrophages. Plasma P-selectin and hyaluronic acid levels were also quantified. Hotplate testing was also administered before the induction, then before and after treatment.

RESULTS

STS treatment resulted in significantly reduced lesion weight, stalled lesional fibrogenesis and improved hyperalgesia, seemingly through the induction of cellular senescence by activating p53, Sav1 and CCN1 while suppressing HAS2, survivin and GM-CSF, resulting in increased apoptosis and reduced lesional infiltration of alternatively activated macrophages. In addition, STS treatment significantly reduced the plasma concentration of P-selectin and hyaluronic acid, possibly leading to reduced lesional platelet aggregation.

CONCLUSIONS

STS appears to be a promising compound for treating endometriosis. The results suggest that senescence may restrict lesional progression and fibrogenesis, and targeting the senescence pathway may have desirable therapeutic potential.

Pain Bloc-R Alleviates Unresolved, Non-Pathological Aches and Discomfort in Healthy Adults—A Randomized, Double-Blind, Placebo-Controlled, Crossover Study

The lack of effective treatment for chronic discomfort without negative side effects highlights the need for alternative treatments. Pain Bloc-R is a natural health product composed of vitamins B₆, B₁₂, D, white willow bark extract, Angelica root extract, acetyl L-carnitine HCl, caffeine, L-theanine, Benfotiamine, and L-tetrahydropalmatine. The objective of this study was to compare the effects of Pain Bloc-R, acetaminophen, and placebo on unresolved aches and discomfort as assessed by the brief pain inventory (BPI) and modified Cornell musculoskeletal discomfort questionnaires. This randomized, double-blind, placebo-controlled, crossover study consisted of three 7-day periods with Pain Bloc-R, acetaminophen, or placebo, each separated by a 7-day washout. Twenty-seven healthy adults (ages 22–63 years) were randomized to receive the three interventions in different sequences. The BPI “pain at its worst” scores were significantly lower when participants took Pain Bloc-R than when they took acetaminophen (21.8% vs. 9.8% decrease, p = 0.026) after seven days of supplementation. Pain Bloc-R achieved a significant improvement in the “pain at its least” score, significantly decreased the interference of discomfort in walking, and significantly decreased musculoskeletal discomfort total scores (34%, p = 0.040) after seven days. In a post hoc subgroup analysis based on age and gender, male participants ≤45 years taking Pain Bloc-R reported significant reductions in pain severity and pain interference vs. acetaminophen. Pain Bloc-R performed as well as acetaminophen in managing unresolved non-pathological pain in otherwise healthy individuals.

The Link Between Stress and Endometriosis: from Animal Models to the Clinical Scenario

There is strong evidence from humans and animal models showing that abnormal functioning of the hypothalamic-pituitary-adrenal (HPA) axis and/or the inflammatory response system disrupts feedback regulation of both neuroendocrine and immune systems, contributing to disease. Stress is known to affect the physiology of pelvic organs and to disturb the HPA axis leading to chronic, painful, inflammatory disorders. A link between stress and disease has already been documented for many chronic conditions. Endometriosis is a complex chronic gynecological disease associated with severe pelvic pain and infertility that affects 10% of reproductive-aged women. Patients report the negative impact of endometriosis symptoms on quality of life, work/study productivity, and personal relationships, which in turn cause high levels of psychological and emotional distress. The relationship between stress and endometriosis is not clear. Still, we have recently demonstrated that stress increases the size and severity of the lesions as well as inflammatory parameters in an animal model. Furthermore, the "controllability" of stress influences the pathophysiology in this model, offering the possibility of using stress management techniques in patients. The crosstalk between stress-inflammation-pain through HPA axis activity indicates that stress relief should alleviate inflammation and, in turn, decrease painful responses. This opens up the opportunity of altering brain-body-brain pathways as potential new therapeutic option for endometriosis. The goal of this review is to gather the research evidence regarding the interaction between stress (psychological and physiological) and the development and progression of endometriosis on the exacerbation of its symptoms with the purpose of proposing new lines of emerging research and possible treatment modalities for this still incurable disease.

Central Sensitization-Related Changes in Brain Function Activity in a Rat Endometriosis-Associated Pain Model

Background

Pain sensitization processing in the central nervous system may be related to endometriosis-associated pain in patients. The purpose of this study was to understand the alterations in the abnormal pain response in central brain areas and explore the central sensitization mechanism of endometriosis-associated pain.

Methods

An endometriosis model was established in 40 Sprague-Dawley rats, and the rats underwent pain model assessment through behavioral tests. Twenty Sprague-Dawley rats underwent a sham operation as the control group. Thirteen pain rats and 8 control rats received Rs-fMRI examination to explore the brain functional activity areas, and the regional homogeneity (ReHo) method was used to analyze relevant functional signals among the whole brain. The states of neurons and expression of TRPV1 and NMDRA located in the abnormal ReHo signal brain regions were observed using Nissl staining, qRT-PCR and immunohistochemistry.

Results

The rats were divided into a pain group and a control group based on the different syndromes and behavioral assessments. We detected significant enhancement of ReHo signals in the anterior cingulate cortex, hippocampus, and thalamus and a reduction in the ReHo values in the basomedial amygdaloid nucleus (BM) and primary motor cortex (M1) in the pain rat group via Rs-fMRI examination. The number of Nissl bodies and apoptotic neurons was increased; moreover, the volume of neurons increased compensatorily in the cingulate cortex, thalamus and hippocampus in the pain group. TRPV1 and NMDRA were overexpressed in apoptotic neurons in the higher ReHo value brain regions in the endometriosis pain group.

Conclusion

These findings suggest that in rats with endometriosis-associated pain, ReHo signal enhancement was observed in the cingulate cortex, thalamus and hippocampus, which may be due to the increase in the number of apoptotic neurons or the compensatory increase in the volume of overactive neurons.

Endometriosis-Associated Pain - Do Preclinical Rodent Models Provide a Good Platform for Translation?

Pelvic pain is a common symptom of endometriosis. Our understanding of its etiology remains incomplete and medical management is limited by poor translation from preclinical models to clinical trials. In this review, we briefly consider the evidence, or lack thereof, that different subtypes of lesion, extra-uterine bleeding, and neuropathic pathways add to the complex and heterogeneous pain experience of women with the condition. We summarize the studies in rodent models of endometriosis that have used behavioral endpoints (evoked and non-evoked) to explore mechanisms of endometriosis-associated pain. Lesion innervation, activation of nerves by pronociceptive molecules released by immune cells, and a role for estrogen in modulating hyperalgesia are key endometriosis-associated pain mechanisms replicated in preclinical rodent models. The presence of ectopic (full thickness uterus or endometrial) tissue may be associated with changes in the spinal cord and brain, which appear to model changes reported in patients. While preclinical models using rats and mice have yielded insights that appear relevant to mechanisms responsible for the development of endometriosis-associated pain, they are limited in scope. Specifically, most studies are based on models that only resulted in the formation of superficial lesions and use induced (evoked) behavioral 'pain' tests. We suggest that translation for patient benefit will be improved by new approaches including models of ovarian and deep infiltrating disease and measurement of spontaneous pain behaviors. Future studies must also capitalize on new advances in the wider field of pain medicine to identify more effective treatments for endometriosis-associated pain.

Evaluation of the brain functional activities in rats various location-endometriosis pain model

Background

Endometriosis (EM) is a common gynecological disease in women of reproductive age. These patients in approximately 80% suffer the various degree pain. This study will investigate synergistically the mechanism of the higher-position central sensitization and offer a pre-clinical experiment evidence for treatment of various location-EM patients with pain.

Methods

Twenty Sprague-Dawley rats were induced three types EM including abdominal EM (n=5), gastrocnemius EM (n=5) and ovary EM group (n=5) and one sham control group (n=5). All groups were measured the pain sensitization by hotplate test, then scanned by the functional magnetic resonance imaging (fMRI). The resting-state fMRI (rs-fMRI) date was analyzed using regional homogeneity (ReHo) approach to find out the abnormal functional activity brain regions. Nissl staining method observed the state of neurons in aberrant ReHo signal brain regions.

Results

Rats with EM pain sensitization were increased in abdominal EM and gastrocnemius EM than ovary EM group and sham control. The ReHo value is decreased in gastrocnemius EM in right thalamus and left olfactory tubercle compared with other three groups. The number of neurons was decreased; cavitation around nucleus, and pyknotic homogenous nuclei. Nissl bodies were stained deeply, and the shape was irregular in gastrocnemius EM by Nissl staining in right thalamus. In left olfactory tubercle, there was no significant difference in 4 groups.

Conclusions

The thalamus may be the potential key brain region for the central sensitization mechanism of various location-EM pain. The oxidative activation may be weakened in thalamus in gastrocnemius EM group with more severe pain. This finding could lend support for future research on the imageology and pathology of various location-EM pain.

Scutellarin Suppresses Platelet Aggregation and Stalls Lesional Progression in Mouse With Induced Endometriosis

Platelets play an important role in the development of endometriosis. Scutellarin is a flavonoid isolated from a medicinal herb traditionally used as a potent antiplatelet agent. In this study, we sought to evaluate its potential therapeutic effect, if any, in mice with induced endometriosis. Endometriosis was induced in 27 female Balb/c mice by intraperitoneal injection of uterine fragments. Two weeks after the induction, the 27 mice were randomly divided in equal sizes into 3 groups: untreated, which received only vehicle, and low-dose and high-dose groups, which received low- and high dose of scutellarin treatment. Hotplate test was administrated to all mice before endometriosis induction, and before and after the scutellarin treatment. Two weeks after the treatment, a blood sample was drawn before sacrifice and all lesions were harvested. The peripheral platelet activation rate and total lesion weight were assessed, and immunohistochemistry and histochemistry analyses were performed to evaluate the extent of proliferation, angiogenesis, fibroblast-to-myofibroblast transdifferentiation (FMT), and fibrosis in lesions. Compared with untreated mice, mice in both low-dose and high-dose groups had significantly reduced lesion weight and improved hyperalgesia. Scutellarin also reduced the peripheral-activated platelets rate and resulted in significantly reduced platelet aggregation, cellular proliferation, angiogenesis, the extent of FMT, and the extent of fibrosis in lesions. Thus, we conclude that scutellarin is efficacious in treating endometriosis in vivo by suppressing platelet aggregation, inhibiting proliferation, angiogenesis, and fibrogenesis, resulting in reduced lesion size and improved pain behavior. As such, scutellarin may be a potentially promising therapeutics for the treatment of endometriosis.

Age-Dependent Anti-migraine Effects of Valproic Acid and Topiramate in Rats

Background: Valproic acid (VPA) and topiramate (TPM), initially developed as antiepileptics, are approved for migraine prophylaxis in adults but not children. The differences in their antimigraine mechanism(s) by age remain unclear.

Methods: A migraine model induced by intra-cisternal (i.c.) capsaicin instillation in pediatric (4–5 weeks) and adult (8–9 weeks) rats was pretreated with VPA (30, 100 mg/kg) or TPM (10, 30, 100 mg/kg). Noxious meningeal stimulation by the irritant capsaicin triggered trigeminovascular system (TGVS) activation mimicking migraine condition, which were assessed peripherally by the depletion of calcitonin gene-related peptide (CGRP) in sensory nerve fibers of the dura mater, the increased CGRP immunoreactivity at trigeminal ganglia (TG) and centrally by the number of c-Fos-immunoreactive (c-Fos-ir) neurons in the trigeminocervical complex (TCC). Peripherally, CGRP released from dural sensory nerve terminals of TG triggered pain signal transmission in the primary afferent of trigeminal nerve, which in turn caused central sensitization of the TGVS due to TCC activation and hence contributed to migraine.

Results: In the VPA-treated group, the central responsiveness expressed by reducing the number of c-Fos-ir neurons, which had been increased by i.c. capsaicin, was significant in pediatric, but not adult, rats. Inversely, VPA was effective in peripheral inhibition of elevated CGRP immunoreactivity in the TG and CGRP depletion in the dura mater of adult, but not pediatric, rats. In TPM group, the central responsiveness was significant in both adult and pediatric groups. Peripherally, TPM significantly inhibited capsaicin-induced CGRP expression of TG in adult, but not pediatric, rats. Interestingly, the capsaicin-induced depletion of CGRP in dura was significantly rescued by TPM at high doses in adults, but at low dose in pediatric group.

Conclusion: These results suggest VPA exerted peripheral inhibition in adult, but central suppression in pediatric migraine-rats. In contrast, TPM involves both central and peripheral inhibition of migraine with an optimal therapeutic window in both ages. These findings may clarify the age-dependent anti-migraine mechanism of VPA and TPM, which may guide the development of new pediatric anti-migraine drugs in the future.

Chronic Treatment with Fluoxetine Induces Sex-Dependent Analgesic Effects and Modulates HDAC2 and mGlu2 Expression in Female Mice

Gender and sex differences in pain recognition and drug responses have been reported in clinical trials and experimental models of pain. Among antidepressants, contradictory results have been observed in patients treated with selective serotonin reuptake inhibitors (SSRIs). This study evaluated sex differences in response to the SSRI fluoxetine after chronic administration in the mouse formalin test. Adult male and female CD1 mice were intraperitoneally injected with fluoxetine (10 mg/kg) for 21 days and subjected to pain assessment. Fluoxetine treatment reduced the second phase of the formalin test only in female mice without producing behavioral changes in males. We also observed that fluoxetine was able to specifically increase the expression of metabotropic glutamate receptor type-2 (mGlu2) in females. Also a reduced expression of the epigenetic modifying enzyme, histone deacetylase 2 (HDAC2), in dorsal root ganglia (DRG) and dorsal horn (DH) together with an increase histone 3 acetylation (H3) level was observed in females but not in males. With this study we provide evidence that fluoxetine induces sex specific changes in HDAC2 and mGlu2 expression in the DH of the spinal cord and in DRGs and suggests a molecular explanation for the analgesic effects in female mice.

Impact of Psychological Stress on Pain Perception in an Animal Model of Endometriosis

PURPOSE

Pain in patients with endometriosis is considered a significant source of stress but does not always correlate with severity of the condition. We have demonstrated that stress can worsen endometriosis in an animal model. Here, we tested the impact of a psychological stress protocol on pain thresholds and pain receptors.

METHODS

Endometriosis was induced in female rats by suturing uterine horn tissue next to the intestinal mesentery. Sham rats had sutures only. Rats were exposed to water avoidance stress for 7 consecutive days or handled for 5 minutes (no stress). Fecal pellets and serum corticosterone (CORT) levels were measured as an index of anxiety. Pain perception was assessed using hot plate and Von Frey tests. Substance P, enkephalin, endomorphin-2, Mu opioid receptor (MOR), and neurokinin-1 receptor expression in the spinal cord were measured by immunohistochemistry.

RESULTS

Fecal pellets and CORT were significantly higher in the endo-stress (ES) group than endo-no stress (ENS; P < .01) and sham-no stress groups (SNS; P < .01). The ES rats had more colonic damage ( P < .001 vs SNS; P < .05 vs ENS), vesicle mast cell infiltration ( P < .01 vs ENS), and more severe vesicles than ENS. The ES developed significant hyperalgesia ( P < .05) but stress reversed the allodynic effect caused by endo ( P < .001). The MOR expression was significantly reduced in ENS versus SNS ( P < .05) and more enkephalin expression was found in endo groups.

CONCLUSION

Animals subjected to stress develop more severe symptoms but interestingly stress seems to have beneficial effects on abdominal allodynia, which could be a consequence of the stress-induced analgesia phenomenon.

Fos Protein as a Marker of Neuronal Activity: a Useful Tool in the Study of the Mechanism of Action of Natural Products with Analgesic Activity

Pain treatment is still ineffective in many conditions and remains one of the greatest challenges of modern medicine. Historically, due to the incredible variety of pharmacologically promising natural products (NPs) and the chemical complexity of their compounds, scientists have explored their use as a source of treatment for diseases or symptomatology. Fos protein and its precursor, the gene c-Fos, have been the subject of study in relation to the pathophysiology of pain as a possible tool to aid in its understanding. More recently, it has become a useful tool in the study of NPs with analgesic profile. Thus, this systematic review aimed to investigate the analgesic effect of NPs and derivatives through changes in Fos protein or c-Fos expression in nervous system central. The search terms "analgesics," "Fos," and "drug effects" were used in the databases PubMed, MEDLINE, Scopus, and Embase. Forty-six articles were identified. Twenty-five articles investigated Fos expression in the spinal cord, 1 in dorsal root ganglion, 11 in brain areas, and 9 investigated the association between the spinal cord and brain areas. Although Fos protein expression has been used as a tool in the studies of the mechanism of action of pain in relation to NPs with analgesic activity, the associations between brain areas and the spinal cord-and the possible pathways involved-have not yet been fully elucidated and deserve further study.

Relevant human tissue resources and laboratory models for use in endometriosis research

Endometriosis is characterized by the growth of endometrium‐like tissue outside the uterus, most commonly on the pelvic peritoneum and ovaries. Although it may be asymptomatic in some women, in others it can cause debilitating pain, infertility or other symptoms including fatigue. Current research is directed both at understanding the complex etiology and pathophysiology of the disorder and at the development of new nonsurgical approaches to therapy that lack the unwanted side effects of current medical management. Tools for endometriosis research fall into two broad categories; patient‐derived tissues, and fluids (and cells isolated from these sources) or models based on the use of cells or animals. In this review, we discuss the literature that has reported data from the use of these tools in endometriosis research and we highlight the strengths and weaknesses of each. Although many different models are reported in the literature, hypothesis‐driven research will only be facilitated with careful experimental design and selection of the most appropriate human tissue from patients with and without endometriosis and combinations of physiologically relevant in vitro and in vivo laboratory models.

Histone deacetylases inhibitors (HDACis) as novel therapeutic application in various clinical diseases

Accumulating evidence suggests that histone hypoacetylation which is partly mediated by histone deacetylase (HDAC), plays a causative role in the etiology of various clinical disorders such as cancer and central nervous diseases. HDAC inhibitors (HDACis) are natural or synthetic small molecules that can inhibit the activities of HDACs and restore or increase the level of histone acetylation, thus may represent the potential approach to treating a number of clinical disorders. This manuscript reviewed the progress of the most recent experimental application of HDACis as novel potential drugs or agents in a large number of clinical disorders including various brain disorders including neurodegenerative and neurodevelopmental cognitive disorders and psychiatric diseases like depression, anxiety, fear and schizophrenia, and cancer, endometriosis and cell reprogramming in somatic cell nuclear transfer in human and animal models of disease, and concluded that HDACis as potential novel therapeutic agents could be used alone or in adjunct to other pharmacological agents in various clinical diseases.

Endometriosis-Derived Thromboxane A2 Induces Neurite Outgrowth

Hyperinnervation in endometriosis is now well documented, but so far only a few neurotrophins have been identified. Since endometriotic stromal cells secrete thromboxane A2 (TXA₂), we sought to determine whether TXA₂, derived from endometriotic stromal cells, induces neurite outgrowth. Using primary sensory neurons derived from rat dorsal root ganglia (DRG) and ectopic endometrial stromal cells (EESCs) derived from human ovarian endometrioma tissues, we treated the primary neurons with different concentrations of U-46619, a stable TXA₂ mimetic, and performed a neuronal growth assay. The primary neurons were also cocultured with a vehicle, nerve growth factor (NGF, serving as a positive control), the supernatant of EESC culture medium, or the supernatant of EESCs pretreated with ozagrel, a thromboxane synthase inhibitor, and a neuronal growth assay was performed. The total neurite length was evaluated through immunofluorescence microscopy. We found that U-46619 significantly increased the neurite outgrowth in DRG neurons in a concentration-dependent fashion ( P < .001). It also increased the number of neurite ends in a concentration-dependent fashion. Ozagrel treatment alone had no effect on the neurite growth ( P > .05), and the treatment with the supernatant of EESCs induced neurite outgrowth just as potently as that treated with NGF (positive control; P > .05). Remarkably, treatment with the EESC supernatant increased the neurite outgrowth by nearly 3-fold as compared with the control ( P < .01), but the pretreatment with ozagrel abolished the stimulatory effect of the EESC by 31.3% ( P < .05). These findings indicate that EESCs potently induce neurite outgrowth, and endometriosis-derived TXA₂ is responsible, at least in part, for this neurotrophic effect.

Nerve fibers and endometriotic lesions: partners in crime in inflicting pains in women with endometriosis

One of major objectives in treating endometriosis is to alleviate pain since dysmenorrhea and other types of pain top the list of complaints from women with endometriosis who seek medical attention. Indeed, endometriosis-associated pain (EAP) is the most debilitating of the disease that negatively impacts on the quality of life in affected women, contributing significantly to the burden of disease and adding to the substantial personal and societal costs. Unfortunately, the mechanisms underlying the EAP are still poorly understood. In the last two decades, one active research field in endometriosis is the investigation on the distribution and genesis of nerve fibers in eutopic and ectopic endometrium, and the attempt to use endometrial nerve fiber density for diagnostic purpose. Since EAP presumably starts with the terminal sensory nerves, in or around endometriotic lesions, that transduce noxious mediators to the central nervous system (CNS) which ultimately perceives pain, this field of research holds the promise to elucidate the molecular mechanisms underlying the EAP, thus opening new avenues for novel diagnostics and therapeutics. In this review, we shall first briefly provide some basic facts on nerve fibers, and then provide an overview of some major findings in this filed while also note some conflicting results and expose areas in need of further research. We point out that since recently accumulated evidence suggests that endometriotic lesions are wounds undergoing repeated tissue injury and repair, the relationship between endometriotic lesions and nerve fibers is not simply unidirectional, i.e. lesions promote hyperinnervations. Rather, it is bidirectional, i.e. endometriotic lesions and nerve fibers engage active cross-talks, resulting in the development of endometriosis and pain. That is, nerve fibers and endometriotic lesions are actually partners in crime in inflicting pains in women with endometriosis, aided and abetted possibly by other culprits, some yet to be identified. We provide a list of possible perpetrators likely to be involved in this crime. Finally, we discuss possible implications when viewing the relationship from this vista.

Tranylcypromine, a lysine-specific demethylase 1 (LSD1) inhibitor, suppresses lesion growth and improves generalized hyperalgesia in mouse with induced endometriosis

BACKGROUND

Growing evidence indicates that endometriosis is an epigenetic disease. Encouragingly, histone deacetylases (HDACs) and DNA methyltransferases have been shown to be promising targets by numerous in vitro studies. However, only a few studies have shown promising effects of HDAC inhibition in preclinical studies in endometriosis. While lysine-specific demethylase 1 (LSD1) is recently found to be aberrantly expressed in endometriosis, and that the treatment of endometriotic stromal cells with tranylcypromine (TC), an LSD1 inhibitor, significantly reduced cellular proliferation, cell cycle progression, and invasiveness, the in vivo effect of TC treatment is currently lacking. This study sought to evaluate the effect of TC in a mouse model of endometriosis.

METHODS

Forty-seven female C57BL/6 mice were used in this experimentation. All mice, except those randomly selected to form Sham surgery (M) and specificity control (S) groups, received an endometriosis-inducing surgery. Group S was set up mainly to ensure that the reduced generalized hyperalgesia in mice treated with TC is not due to any possible analgesic effect of TC, but rather resulting from the treatment effect specific to endometriosis. Two weeks after the surgery, mice that received surgery were further divided randomly into 3 groups: 1) untreated group (U); 2) low-dose TC group (L); 3) high-dose TC group (H). Group S received the same treatment as in group H. Two weeks after treatment, all mice were sacrificed and their ectopic endometrial tissues were harvested and analyzed by immunohistochemistry analysis. Hotplate test was administrated to all mice before the induction, treatment and sacrifice. Lesion size, hotplate latency, immunoreactivity against markers of proliferation, angiogenesis, H3K4 methylation, and of epithelial-mesenchymal transition (EMT).

RESULTS

TC treatment significantly and substantially reduced the lesion size and improved generalized hyperalgesia in a dose-dependent fashion in mice with induced endometriosis. In addition, TC treatment resulted in reduced immunoreactivity to biomarkers of proliferation, angiogenesis, and H3K4 methylation, leading to arrested EMT and lesion growth.

CONCLUSION

In light of our previously reported reduced cellular proliferation, cell cycle progression and invasiveness resulting from the LSD1 inhibition in in vitro studies, our data strongly suggest that LSD1 is a promising therapeutic target for endometriosis.

TRIAL REGISTRATION

Not applicable.

Impact of physical activity on pain perception in an animal model of endometriosis

BACKGROUND

Symptoms of endometriosis, such as pain and infertility, are considered significant sources of stress. In many chronic conditions, exercise can act as a stress buffer and influence pain perception. We tested the impact of swimming exercise on pain perception and pain receptors in an animal model of endometriosis.

METHODS

Endometriosis (Endo) was induced in female rats by suturing uterine horn tissue next to the intestinal mesentery. Sham rats received sutures only. Rats were exposed to swimming exercise for 7 consecutive days, while no-exercise rats were left in the home cage. Fecal pellets were counted after swimming as an index of anxiety, and serum corticosterone levels measured. Pain perception was assessed using the hot plate test for hyperalgesia and Von Frey test for allodynia. Mu-opioid receptor (MOR) and neurokinin-1 receptor expression in the spinal cord was measured by immunofluorescence.

RESULTS

Fecal pellet counts were higher in those animals that swam (p<0.05), but no significant difference in corticosterone was found. Although Endo-exercise rats had higher colonic damage (p<0.05) with more cellular infiltration, the lesions were smaller than in Endo-no exercise rats (p<0.05). Exercise did not ameliorate the hyperalgesia, whereas it improved allodynia in both groups. MOR expression was significantly higher in Endo-exercise vs. Endo-no exercise rats (p<0.01), similar to Sham-no exercise levels.

CONCLUSIONS

Our results point toward beneficial effects of swimming exercise during endometriosis progression. Physical interventions might be investigated further for their ability to reduce perceived stress and improve outcomes in endometriosis.

A red fluorescent nude mouse model of human endometriosis: advantages of a non-invasive imaging method

OBJECTIVES

To establish red fluorescent human endometriosis lesions in a nude mouse model and dynamically and non-invasively to compare intraperitoneal and subcutaneous injection models.

STUDY DESIGN

Primary cultures of endometrial stromal cells (ESCs) and epithelial cells (EECs) isolated from 24 patients with a normal uterine cavity were transfected with 2.5×10(8) (Group 1) and 1.25×10(8) (Group 2) plaque-forming units (PFU) of adenovirus encoding red fluorescent protein (Ad-RFP). Transfection efficiencies, fluorescence intensity and apoptosis rate of the two types of cells were compared in vitro. A mixture of 2.5×10(8) PFU Ad-RFP-infected approximately 400 EECs cell mass and 2×10(6) ESCs for 36h was injected individually into 24 female nude mice subcutaneously (Group A) or intraperitoneally (Group B). From Day 5 after injection, an in vivo imaging system (IVIS) was used to non-invasively observe and compare the lesions of the two groups every week until Day 33. Specifically, the fluorescent intensity, positive rates, persistence time and lesion weight in the implanted human endometriosis lesions were compared. A parametric Student's t-test and two-way analysis of variance were used for statistical analysis.

RESULTS

Compared with 1.25×10(8) PFU RFP, a titre of 2.5×10(8) PFU RFP ESCs and EECs incubated for 36h exhibited higher transfection efficiencies and higher fluorescence intensities in vitro. In vivo imaging of the fluorescent human endometriosis lesions originating from an RFP titre of 2.5×10(8) PFU showed that the intensity and lesion weight in Group A were significantly higher than in Group B. However, the two groups had the same RFP-positive rates and fluorescence persistence. The structure of each lesion was evaluated by immunohistochemistry to confirm its human endometrial origin.

CONCLUSIONS

The red fluorescent human endometriosis model established by subcutaneously injecting 2.5×10(8) PFU RFP-transfected stromal cells and epithelial cells into nude mice had a higher fluorescent positive rate from Day 5, higher intensity and weight but the same persistence as the intraperitoneal injection model.

Combination use of ferulic acid, ligustrazine and tetrahydropalmatine inhibits the growth of ectopic endometrial tissue: a multi-target therapy for endometriosis rats

ETHNOPHARMACOLOGICAL RELEVANCE

Ferulic acid (FA), ligustrazine (LZ) and tetrahydropalmatine (THP) are separately isolated from Chinese Angelica, Szechwan Lovage Rhizome and Rhizoma in the Jiawei-Foshou-San formula, a popular traditional Chinese medicine for irregular menses. It has been reported that the combination use of FA+LZ+THP has similar effect on endometriosis, but the underlying mechanisms are unclear. This study was to investigate the combination effects and mechanisms of FA+LZ+THP on endometriosis rats.

MATERIALS AND METHODS

Fifty endometriosis rats were intragastricly treated with FA+LZ+THP for 4 wk. The volume of ectopic endometrial tissue was measured to evaluate the effects. Then the changes in hypothalamic-pituitary-ovarian axis and ERE pathway were indicated by the levels of E2, GnRH, FSH and LH, and the expressions of ER, HSP90 and COX-2, respectively. In addition, peritoneal macrophages of each rat were cultured in vitro and treated with (FA+LZ+THP)-medicated serum for 24h. The proliferation and phagocytosis abilities, the levels of IL-1β and TNF-α, and the expression of IκBα were then measured for the changes of peritoneal macrophage activities.

RESULTS

Combination use of FA+LZ+THP diminished the volume of the ectopic endometrial tissues (P<0.05 or P<0.01). It also decreased the E2 level, suppressed the expression of GnRH, FSH and LH, and decreased the protein expression of ER, HSP90 and COX-2 (all P<0.05 or P<0.01). The phagocytosis ability of peritoneal macrophage was enhanced by (FA+LZ+THP)-medicated serum (P<0.05) with no change of proliferation (P>0.05). Moreover, IL-1β and TNF-α were downregulated (both P<0.05 or P<0.01) and IκBα was upregulated by the (FA+LZ+THP)-medicated serum (P<0.01).

CONCLUSIONS

The combination use of FA, LZ and THP could inhibit the growth of ectopic endometrial tissue in endometriosis rats. It might be related to the down-regulation of hypothalamic-pituitary-ovarian axis, the amelioration in ERE pathway and the improvement of peritoneal macrophage activities.

Constitutive and tumor necrosis factor-α-induced activation of nuclear factor-κB in adenomyosis and its inhibition by andrographolide

OBJECTIVE

To investigate the action of nuclear factor (NF)-κB in adenomyosis and evaluate the potential therapeutic effect of andrographolide on tumor necrosis factor (TNF)-α-induced expression of NF-κB-mediated genes cyclooxygease-2 (COX-2), vascular endothelial growth factor (VEGF), and tissue factor (TF) in adenomyotic stromal cells.

DESIGN

Laboratory study using human tissues.

SETTING

Academic hospital.

PATIENT(S)

Twenty-nine patients (cases) with histologically confirmed adenomyosis and 14 (controls) without adenomyosis or endometriosis.

INTERVENTION(S)

Endometrial stromal cells derived from tissue samples harvested from both cases and controls were subjected to electrophoretic mobility shift assay, and gene and protein expression analyses.

MAIN OUTCOME MEASURE(S)

The NF-κB DNA-binding activity and protein levels of NF-κB subunits p50 and p65 and the messenger RNA (mRNA) and protein levels of NF-κB-mediated genes COX-2, VEGF, and TF in cases and controls, and their changes after stimulation with TNF-α and treatment with andrographolide.

RESULT(S)

The constitutive NF-κB DNA-binding activity and protein expression levels of p50 and p65, and mRNA and protein levels of COX-2, VEGF, and TF in cases were significantly higher than that of controls. The binding activity level correlated positively with dysmenorrhea severity in cases. The TNF-α stimulation further increased the binding activity, and the mRNA and protein levels of COX-2, VEGF, and TF, but treatment with andrographolide significantly reduced them.

CONCLUSION(S)

NF-κB may be a pivotal transcription factor involved in the development of adenomyosis. Targeting NF-κB with inhibitors, like andrographolide, may hold promises of treating adenomyosis.

Therapeutic potential of andrographolide for treating endometriosis

BACKGROUND

Mounting evidence shows that nuclear factor-κB (NF-κB) plays an important role in endometriosis. We therefore evaluated the therapeutic potential of andrographolide, an NF-κB inhibitor.

METHODS

Primary cell cultures were performed using ectopic endometrial tissue specimens and their homologous eutopic endometrial specimens from 16 women with endometriosis, as well as control samples from 4 women without endometriosis. Andrographolide was evaluated for an effect on cell proliferation and cell cycle, DNA-binding activity of NF-κB and expression of cyclooxygenase-2 (COX-2) and tissue factor (TF). In a rat model of endometriosis, andrographolide treatment was evaluated for an effect on lesion size, hotplate response latency and expression of phosphorylated p50 and p65, COX-2 and nerve growth factor (NGF) in ectopic endometrium.

RESULTS

Andrographolide dose dependently suppressed proliferation and cell cycle progression, attenuated DNA-binding activity of NF-κB in endometriotic stromal cells and inhibited COX-2 and TF expression. In the rat experiment, induced endometriosis resulted in reduced response latency. Andrographolide treatment significantly reduced lesion size in a dose-dependent manner and significantly increased response latency. Andrographolide treatment also significantly reduced immunoreactivity of COX-2, phosphorylated p50 and p65, and NGF in ectopic endometrium.

CONCLUSIONS

Treatment with andrographolide significantly suppresses the growth of ectopic endometrium in vitro and in vivo, and results in a significant improvement in generalized hyperalgesia in rats with induced endometriosis. Therefore, andrographolide may be cytoreductive and may relieve pain symptoms in women with endometriosis. With excellent safety and cost profiles, andrographolide could be a promising therapeutic agent for endometriosis.

Valproic acid and progestin inhibit lesion growth and reduce hyperalgesia in experimentally induced endometriosis in rats

Accumulating evidence suggests that endometriosis is an epigenetic disease. This study was designed to evaluate the effect of valproic acid (VPA) and progesterone (P4) in a rat model of endometriosis on serum tumor necrosis factor-α (TNF-α) levels, hot plate and tail-flick latencies, lesion size, and body weight. We used 77 adult female rats, and endometriosis was induced by autotransplanting pieces of uterus (ENDO) or fat (SHAM) to the pelvic cavity. The BLANK group received no surgery. After 2 weeks, the ENDO group was further divided, randomly, into 5 groups, receiving, respectively, treatment with low- and high-dose VPA, P4 alone, VPA + P4, and no treatment. The SHAM rats received no treatment. The BLANK rats were further divided into 2 groups, one received VPA treatment and the other, no treatment. After 4 weeks, all rats were sacrificed. Response latency in hot plate and tail-flick tests, body weight, and serum TNF-α levels were measured before the surgery, before and after the treatment, along with lesion size. We found that induced endometriosis reduced response latency. ENDO rats receiving VPA and/or P4 treatment had significantly reduced lesion size as compared with untreated ones, and had significantly improved response to noxious thermal stimuli. They also had significantly increased weight gain. Serum TNF-α levels increased following surgery but eventually decreased regardless of treatment or not. In conclusion, VPA is well tolerated. Treatment with VPA significantly reduces lesion growth and improves sensitivity to nocifensive stimuli. The improvement is specific to endometriosis-induced hyperalgesia. Thus, histone deacetylase inhibitors may be a promising therapeutics for treating endometriosis.