Local upregulation of transient receptor potential ankyrin 1 and transient receptor potential vanilloid 1 ion channels in rectosigmoid deep infiltrating endometriosis

A narrative review about the intricate crosstalk among endometrium, adipose tissue, and neurons in endometriosis. The multifaceted role of leptin

Endometriosis is a highly prevalent gynecological disease characterized by the presence of endometrium-like tissue outside the uterus, whose etiopathology is far from being elucidated. The most frequent complains of patients are pelvic pain and infertility. Increasing evidence supports the systemic impact of endometriosis suggesting that an intricate crosstalk among distinct organs underlies the development of the disease. In this setting, endometriosis patients present an increased risk for developing other diseases, such as cancer, cardiovascular pathologies, and autoimmune diseases, and manifest neurologic disturbances, including neuropathic hyperalgesia. Whilst the ovary-secreted estrogen dependency of ectopic endometrium growth is well established, we conjecture that adipose tissue-secreted molecules also intervene in endometriosis development and pain manifestation. In fact, women with endometriosis present a peculiar pattern of adipokine secretion that ensues the disease onset. Unexpectedly, the levels of adipose tissue-secreted molecules in those women present similarities with those found in patients with obesity, despite the recognized association of low body mass index with endometriosis. Taking this evidence into consideration, we hypothesize that endometriosis patients present a dysfunctional adipose tissue, which is associated with enhanced metabolism and unregulated browning that not only intervene in the control of body weight but also in peculiar pain processing pathways.

The TRPA1 cation channel is upregulated by cigarette smoke in mouse and human macrophages modulating lung inflammation

Cigarette smoke (CS) is a well-known source of several inflammatory, cytotoxic and genotoxic compounds that cause chronic lung diseases. The transient receptor potential ankyrin 1 (TRPA1), a smoking-responsive, non-selective cation channel, is expressed by both capsaicin-sensitive peptidergic sensory nerves and non-neuronal cells of the lung, but there are few and controversial data on its expression and function on macrophages. Here, we investigated TRPA1 mRNA and protein expression in mouse and human lung tissues and human 3D spheroids, with a particular focus on its expression and potential regulatory effects on pro- and anti-inflammatory macrophage functions in response to CS. TRPA1 was stably expressed in both human and mouse alveolar macrophages, being upregulated after CS exposure and its functional activity was demonstrated in mouse macrophage culture. Moreover, besides CS, the TRPA1 genotype itself affected the expression of M1- (Il-1β, Il-23) and M2-type (Il-10, Tgfβ) macrophage cytokines. Furthermore, CS extract increased TRPA1 mRNA in human lung spheroids showing more prominent expression in macrophage-containing 3D aggregates, while CS extract influenced an elevated TGFβ expression specifically in macrophage-containing spheroids. These results suggest the fine-tuning role of TRPA1 activation in CS-induced airway inflammation, particularly in macrophages, but further studies are needed to draw precise conclusions.

Endometriosis: cannabidiol therapy for symptom relief

Endometriosis is a common, chronic, incurable condition the hallmark of which is the presence of lesions (tissue resembling endometrium) in sites outside the womb, with symptoms including chronic debilitating pain and fatigue. However, current therapeutic options are limited. Recent advances in our understanding of the mechanisms that contribute to the development of lesions and pain experience in endometriosis as well as surveys of patients have increased interest in testing recently approved formulations containing cannabidiol (CBD) in this patient group. In this review, we summarise data from patient samples and animals models focussed on the pathophysiology of endometriosis, including pathways where CBD has activity. We consider the available formulations of CBD-containing products, their pharmacokinetics (PK), and their use in ongoing clinical trials in endometriosis and other pain conditions.

Nociceptor-to-macrophage communication through CGRP/RAMP1 signaling drives endometriosis-associated pain and lesion growth in mice

Endometriosis is a debilitating and painful gynecological inflammatory disease affecting up to 15% of women and transgender men. Current treatments are ineffective for a substantial proportion of patients, underscoring the need for additional therapies with long-term benefits. Nociceptors release neuropeptides, such as calcitonin gene-related peptide (CGRP), which are known to shape immunity through neuroimmune communication. Given the comorbidity between endometriosis and migraine and the integral role of immune cells and inflammation in endometriosis, we investigated the role of CGRP-mediated neuroimmune communication in endometriosis. Using samples from eight patients with endometriosis and a nonsurgical mouse model of the disease, we found that mouse and human endometriosis lesions contain both CGRP and its coreceptor, receptor activity modifying protein 1 (RAMP1). In mice, nociceptor ablation reduced pain, monocyte recruitment, and lesion size, suggesting that nociceptor activation and neuropeptide release contribute to endometriosis lesion growth and pain. Mechanistically, CGRP changed the phenotype of macrophages to a pro-endometriosis phenotype. CGRP-stimulated macrophages demonstrated impaired efferocytosis and supported increased endometrial cell growth in a RAMP1-dependent manner. Treatment of lesion-bearing mice with US Food and Drug Administration-approved drugs that block CGRP-RAMP1 signaling reduced mechanical hyperalgesia, spontaneous pain, and lesion size. Together, our data demonstrated the effectiveness and underlying cellular mechanisms of nonhormonal and nonopioid CGRP/RAMP1 blockade in a mouse model of endometriosis, suggesting that targeting this axis may lead to clinical benefit for patients with endometriosis.

Role of the gut microbiota in the pathogenesis of endometriosis: a review

Endometriosis is classically defined as a chronic inflammatory heterogeneous disorder occurring in any part of the body, characterized by estrogen-driven periodic bleeding, proliferation, and fibrosis of ectopic endometrial glands and stroma outside the uterus. Endometriosis can take overwhelmingly serious damage to the structure and function of multi-organ, even impair whole-body systems, resulting in severe dysmenorrhea, chronic pelvic pain, infertility, fatigue and depression in 5-10% women of reproductive age. Precisely because of a huge deficiency of cognition about underlying etiology and complex pathogenesis of the debilitating disease, early diagnosis and treatment modalities with relatively minor side effects become bottlenecks in endometriosis. Thus, endometriosis warrants deeper exploration and expanded investigation in pathogenesis. The gut microbiota plays a significant role in chronic diseases in humans by acting as an important participant and regulator in the metabolism and immunity of the body. Increasingly, studies have shown that the gut microbiota is closely related to inflammation, estrogen metabolism, and immunity resulting in the development and progression of endometriosis. In this review, we discuss the diverse mechanisms of endometriosis closely related to the gut microbiota in order to provide new approaches for deeper exploration and expanded investigation for endometriosis on prevention, early diagnosis and treatment.

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.

Comprehensive insights into the multifaceted roles of the transient receptor potential vanilloid 1 channel in the digestive system

The transient receptor potential vanilloid (TRPV) channel, a family of calcium transporters comprising six distinct members (TRPV1-6), takes on a paramount role in maintaining intracellular Ca2+ homeostasis in mammalian cells. Notably, TRPV1, among its counterparts, has emerged as the subject of extensive scrutiny, owing to its pervasive presence in diverse cellular, tissue, and organ settings. This ubiquitous distribution underscores its fundamental involvement in the genesis of pain, making it a central focus in pain-related research. However, recent investigations have unveiled that TRPV1's functional significance transcends the realm of pain modulation, extending its influence to encompass a wide spectrum of physiological and pathological processes. The ambit of TRPV1's influence encompasses not only pain responses but also embraces the intricate domains of nervous system disorders, cancer metastasis, as well as afflictions pertaining to the skin and heart. Moreover, compelling evidence now demonstrates that TRPV1 also wields substantial sway in the domain of digestive diseases, further highlighting its versatility and far-reaching impact on human health. Therefore, this comprehensive review endeavors to delve into the multifaceted roles played by TRPV1 in the various organs constituting the digestive system.

Endometriosis-Related Chronic Pelvic Pain

Endometriosis, which is the presence of endometrial stroma and glands outside the uterus, is one of the most frequently diagnosed gynecologic diseases in reproductive women. Patients with endometriosis suffer from various pain symptoms such as dysmenorrhea, dyspareunia, and chronic pelvic pain. The pathophysiology for chronic pain in patients with endometriosis has not been fully understood. Altered inflammatory responses have been shown to contribute to pain symptoms. Increased secretion of cytokines, angiogenic factors, and nerve growth factors has been suggested to increase pain. Also, altered distribution of nerve fibers may also contribute to chronic pain. Aside from local contributing factors, sensitization of the nervous system is also important in understanding persistent pain in endometriosis. Peripheral sensitization as well as central sensitization have been identified in patients with endometriosis. These sensitizations of the nervous system can also explain increased incidence of comorbidities related to pain such as irritable bowel disease, bladder pain syndrome, and vulvodynia in patients with endometriosis. In conclusion, there are various possible mechanisms behind pain in patients with endometriosis, and understanding these mechanisms can help clinicians understand the nature of the pain symptoms and decide on treatments for endometriosis-related pain symptoms.

Mechanisms of peripheral sensitization in endometriosis patients with peritoneal lesions and acyclical pain

PURPOSE

Endometriosis (EM) is one of the most frequent differential diagnoses concerning chronic pelvic pain. Women under hormonal therapy (HT) often benefit from it but sometimes suffer a setback and develop acyclical pelvic pain. Due to the assumption that mechanisms of neurogenic inflammation are involved in the generation of chronic pelvic pain, we aimed to investigate the expression of sensory nerve markers in EM-associated nerve fibers of patients with/without HT.

METHODS

Laparoscopically excised peritoneal samples from 45 EM and 10 control women were immunohistochemically stained for: PGP9.5, Substance P (SP), NK1R, NGFp75, TRPV-1, and TrkA. Demographics and severity of pain were documented.

RESULTS

EM patients showed a higher nerve fiber density (PGP9.5 and SP) and increased expression of NGFp75, TRPV1, TrkA, and NK1R in blood vessels and immune cells compared with controls. Patients with HT have cycle-dependent pelvic pain but suffer from acyclical pelvic pain. Interestingly, reducing NK1R expression in blood vessels under HT was observed. A correlation between dyspareunia severity and nerve fibers density and between NGFRp75 expression in blood vessels and cycle-dependent pelvic pain severity was observed.

CONCLUSION

Patients under HT have no ovulation and no (menstrual) bleeding, which correlate with inflammation and cyclical pain. However, acyclical pain seems to be due to peripheral sensitization once it is present under treatment. Neurotransmitters, like SP and their receptors, are involved in mechanisms of neurogenic inflammation, which are relevant for pain initiation. These findings indicate that in both groups (EM with/without HT), neurogenic inflammation is present and responsible for acyclical pain.

More than tears: associations between exposure to chemical agents used by law enforcement and adverse reproductive health outcomes

Despite routine law enforcement use of chemical agents for crowd control, the reproductive health safety profiles of these products are unknown. Moreover, limited evidence has documented a link between such exposures and adverse reproductive health outcomes including abnormal uterine bleeding and potential pregnancy disruption. This cross-sectional study examined reproductive outcomes in adults with uteri exposed to chemical agents used by law enforcement, more commonly known as "tear gas". Participants were recruited through social media in the wake of police violence protests. Of the 1,276 participants included in analysis, 83% reported experiencing at least one of the outcomes of interest, included uterine cramping (69%), early menstrual bleeding (55%), breast tenderness (30%), and delayed menstrual bleeding (19%). Chemical agent exposure was significantly associated with higher odds of an adverse reproductive health outcome, those with 5 days or more of exposure have 2.6 times the odds (CI: 1.61, 4.22) of adverse outcomes and having a perception that one's menstruation may fluctuate according to psychosocial stressors was associated (OR = 1.94, CI: 1.36, 2.79) with a higher odds of an adverse reproductive health experience. These findings suggest a potential relationship between exposure to chemical agents and adverse reproductive health outcomes. Given the pervasive use of these chemical agents and their potential for reproductive health harm, further investigation into the safety of these products and their impacts on individual and community health is warranted urgently.

"ThermoTRP" Channel Expression in Cancers: Implications for Diagnosis and Prognosis (Practical Approach by a Pathologist)

Temperature-sensitive transient receptor potential (TRP) channels (so-called "thermoTRPs") are multifunctional signaling molecules with important roles in cell growth and differentiation. Several "thermoTRP" channels show altered expression in cancers, though it is unclear if this is a cause or consequence of the disease. Regardless of the underlying pathology, this altered expression may potentially be used for cancer diagnosis and prognostication. "ThermoTRP" expression may distinguish between benign and malignant lesions. For example, TRPV1 is expressed in benign gastric mucosa, but is absent in gastric adenocarcinoma. TRPV1 is also expressed both in normal urothelia and non-invasive papillary urothelial carcinoma, but no TRPV1 expression has been seen in invasive urothelial carcinoma. "ThermoTRP" expression can also be used to predict clinical outcomes. For instance, in prostate cancer, TRPM8 expression predicts aggressive behavior with early metastatic disease. Furthermore, TRPV1 expression can dissect a subset of pulmonary adenocarcinoma patients with bad prognosis and resistance to a number of commonly used chemotherapeutic agents. This review will explore the current state of this rapidly evolving field with special emphasis on immunostains that can already be added to the armoire of diagnostic pathologists.

Role of the endocannabinoid system in the pathophysiology of endometriosis and therapeutic implications

Endometriosis patients experience debilitating chronic pain, and the first-line treatment is ineffective at managing symptoms. Although surgical removal of the lesions provides temporary relief, more than 50% of the patients experience disease recurrence. Despite being a leading cause of hysterectomy, endometriosis lacks satisfactory treatments and a cure. Another challenge is the poor understanding of disease pathophysiology which adds to the delays in diagnosis and overall compromised quality of life. Endometriosis patients are in dire need of an effective therapeutic strategy that is both economical and effective in managing symptoms, while fertility is unaffected. Endocannabinoids and phytocannabinoids possess anti-inflammatory, anti-nociceptive, and anti-proliferative properties that may prove beneficial for endometriosis management, given that inflammation, vascularization, and pain are hallmark features of endometriosis. Endocannabinoids are a complex network of molecules that play a central role in physiological processes including homeostasis and tissue repair, but endocannabinoids have also been associated in the pathophysiology of several chronic inflammatory diseases including endometriosis and cancers. The lack of satisfactory treatment options combined with the recent legalization of recreational cannabinoids in some parts of the world has led to a rise in self-management strategies including the use of cannabinoids for endometriosis-related pain and other symptoms. In this review, we provide a comprehensive overview of endocannabinoids with a focus on their potential roles in the pathophysiology of endometriosis. We further provide evidence-driven perspectives on the current state of knowledge on endometriosis-associated pain, inflammation, and therapeutic avenues exploiting the endocannabinoid system for its management.

Unveil the pain of endometriosis: from the perspective of the nervous system

Endometriosis is a chronic inflammatory disease with pelvic pain and uncharacteristic accompanying symptoms. Endometriosis-associated pain often persists despite treatment of the disease, thus it brings a deleterious impact on their personal lives as well as imposing a substantial economic burden on them. At present, mechanisms underlie endometriosis-associated pain including inflammatory reaction, injury, aberrant blood vessels and the morphological and functional anomaly of the peripheral and central nervous systems. The nerve endings are influenced by the physical and chemical factors surrounding the lesion, via afferent nerve to the posterior root of the spinal nerve, then to the specific cerebral cortex involved in nociception. However, our understanding of the aetiology and mechanism of this complex pain process caused by endometriosis remains incomplete. Identifying the pathogenesis of endometriosis is crucial to disease management, offering proper treatment, and helping patients to seek novel targets for the maintenance and contributors of chronic pain. The main aim of this review is to focus on every possible mechanism of pain related to endometriosis in both peripheral and central nervous systems, and to present related mechanisms of action from the interaction between peripheral lesions and nerves to the changes in transmission of pain, resulting in hyperalgesia and the corresponding alterations in cerebral cortex and brain metabolism.

Ectopic endometriosis in the pelvic cavity evokes bladder hypersensitivity via transient receptor potential ankyrin 1 hyperexpression in rats

INTRODUCTION AND HYPOTHESIS

In women with chronic pelvic pain (CPP), interstitial cystitis/bladder pain syndrome (IC/BPS) and endometriosis frequently coexist. The mechanism of these diseases coexisting is explained by cross-sensitization between endometriosis and IC/BPS. The overlapped symptoms may be related to cross-sensitization with transient receptor potential vanilloid 1 (TRPV1) and/or transient receptor potential ankyrin 1 (TRPA1) hyperexpression. This study was aimed at exploring whether bladder hypersensitivity is evoked in the surgically induced ectopic endometriosis rat and whether TRPV1 and/or TRPA1 play a vital role.

METHODS

A total of 63 Sprague-Dawley female rats were divided into two groups, 39 for physiological examination and 24 for molecular analysis. Surgical induction of ectopic endometriosis (ENDO, n=27), surgical sham treatment (n=18), and treatment for endometriosis by GnRH analog (ENDO-G) (n=18) were performed. Bladder function was investigated by cystometry (for TRPV1 in the sham [n=6] and ENDO [n=9] groups and for TRPA1 in the sham [n=6], ENDO [n=9], and ENDO+G [n=9] groups), and TRPV1 and TRPA1 mRNA expressions were measured using real-time qPCR in the bladder and dorsal root ganglia (DRGs).

RESULTS

On cystometry, the relative intercontraction interval (ICI) after/before resiniferatoxin (RTx; TRPV1 activator) infusion to the bladder showed no significant difference between the two groups, whereas relative ICI after/before allyl isothiocyanate (AITC; TRPA1 activator) infusion was significantly lower in the ENDO group than in the sham group. TRPA1 mRNA expression in the bladder and L5 DRG was considerably higher in the ENDO group than in the sham group on real-time qPCR. TRPA1 mRNA hyperexpression and bladder hypersensitivity after AITC infusion were reduced in the ENDO-G group.

CONCLUSIONS

Bladder cross-sensitization in ENDO rats occurs in association with hyperexpression of TRPA1 at both the DRG and the bladder mucosa. This can be understood by the "cross-sensitization of endometriosis to bladder" theory explaining overlapping symptoms among BPS/IC and ectopic endometriosis.

An Update on the Multifaceted Role of NF-kappaB in Endometriosis

Endometriosis remains a common but challenging gynecological disease among reproductive-aged women with an unclear pathogenesis and limited therapeutic options. Numerous pieces of evidence suggest that NF-κB signaling, a major regulator of inflammatory responses, is overactive in endometriotic lesions and contributes to the onset, progression, and recurrence of endometriosis. Several factors, such as estrogen, progesterone, oxidative stress, and noncoding RNAs, can regulate NF-κB signaling in endometriosis. In the present review, we discuss the mechanisms by which these factors regulate NF-κB during endometriosis progression and provide an update on the role of NF-κB in affecting endometriotic cells, peritoneal macrophages (PMs) as well as endometriosis-related symptoms, such as pain and infertility. Furthermore, the preclinical drugs for blocking NF-κB signaling in endometriosis are summarized, including plant-derived medicines, NF-κB inhibitors, other known drugs, and the potential anti-NF-κB drugs predicted through the Drug-Gene Interaction Database. The present review discusses most of the studies concerning the multifaceted role of NF-κB signaling in endometriosis and provides a summary of NF-κB-targeted treatment in detail.

Peptidergic neurons of the Edinger-Westphal nucleus express TRPA1 ion channel that is downregulated both upon chronic variable mild stress in male mice and in humans who died by suicide

BACKGROUND

Transient receptor potential ankyrin 1 (TRPA1), a cation channel, is expressed predominantly in primary sensory neurons, but its central distribution and role in mood control are not well understood. We investigated whether TRPA1 is expressed in the urocortin 1 (UCN1)-immunoreactive centrally projecting Edinger-Westphal nucleus (EWcp), and we hypothesized that chronic variable mild stress (CVMS) would reduce its expression in mice. We anticipated that TRPA1 mRNA would be present in the human EWcp, and that it would be downregulated in people who died by suicide.

METHODS

We exposed Trpa1 knockout and wild-type mice to CVMS or no-stress control conditions. We then performed behavioural tests for depression and anxiety, and we evaluated physical and endocrinological parameters of stress. We assessed EWcp Trpa1 and Ucn1 mRNA expression, as well as UCN1 peptide content, using RNA-scope in situ hybridization and immunofluorescence. We tested human EWcp samples for TRPA1 using reverse transcription polymerase chain reaction.

RESULTS

Trpa1 mRNA was colocalized with EWcp/UCN1 neurons. Non-stressed Trpa1 knockout mice expressed higher levels of Ucn1 mRNA, had less body weight gain and showed greater immobility in the forced swim test than wild-type mice. CVMS downregulated EWcp/Trpa1 expression and increased immobility in the forced swim test only in wild-type mice. We confirmed that TRPA1 mRNA expression was downregulated in the human EWcp in people who died by suicide.

LIMITATIONS

Developmental compensations and the global lack of TRPA1 may have influenced our findings. Because experimental data came from male brains only, we have no evidence for whether findings would be similar in female brains. Because a TRPA1-specific antibody is lacking, we have provided mRNA data only. Limited access to high-quality human tissues restricted sample size.

CONCLUSION

TRPA1 in EWcp/UCN1 neurons might contribute to the regulation of depression-like behaviour and stress adaptation response in mice. In humans, TRPA1 might contribute to mood control via EWcp/UCN1 neurons.

The Potential Role for Impaired Mucosal Integrity in the Generation of Esophageal Pain Using Capsaicin in Humans: An Explorative Study

INTRODUCTION

Esophageal pain is mediated by sensory nerves, most importantly by the activation of the transient receptor potential vanilloid 1 (TRPV1) capsaicin receptor. TRPV1 is activated and sensitized by a broad range of pungent compounds, as well as inflammatory mediators and tissue irritants. Luminal stressors are suggested to impair the barrier function, which results in consequent activation of these sensory nerve terminals and pain. In this study, we investigated the effect of the perfusion of capsaicin, a TRPV1 agonist, on mucosal impedance and pain in asymptomatic volunteers.

METHODS

Thirteen asymptomatic volunteers completed a single-blind, saline-controlled, randomized crossover study. Capsaicin or saline was perfused for 30 minutes in the distal esophagus. Visual analog scale pain intensity scores and intraluminal impedance indicating mucosal integrity were determined. Distal and proximal biopsies were obtained 10 minutes later to measure TRPV1 messenger RNA and TRPV1 immunopositivity, as well as the intercellular space area.

RESULTS

Capsaicin perfusion resulted in significantly greater pain intensity (P = 0.047) and impaired recovery of the mucosal impedance compared with saline-treated controls (P = 0.027). Pain response was significantly associated with decreased mucosal impedance. Similar dynamics were seen in the proximal esophagus, but mucosal impedance recovered entirely to the preinfusion values there. There was a significant association between mucosal impedance and intercellular space width in the distal esophagus. TRPV1 transcription and expression were not significantly altered within this observation period.

DISCUSSION

Esophageal capsaicin perfusion results in pain, which is likely to be explained by impaired mucosal impedance and defective restoration capacity in the distal esophagus.

TRPA1 Role in Inflammatory Disorders: What Is Known So Far?

The transient receptor potential ankyrin 1 (TRPA1), a member of the TRP superfamily of channels, is primarily localized in a subpopulation of primary sensory neurons of the trigeminal, vagal, and dorsal root ganglia, where its activation mediates neurogenic inflammatory responses. TRPA1 expression in resident tissue cells, inflammatory, and immune cells, through the indirect modulation of a large series of intracellular pathways, orchestrates a range of cellular processes, such as cytokine production, cell differentiation, and cytotoxicity. Therefore, the TRPA1 pathway has been proposed as a protective mechanism to detect and respond to harmful agents in various pathological conditions, including several inflammatory diseases. Specific attention has been paid to TRPA1 contribution to the transition of inflammation and immune responses from an early defensive response to a chronic pathological condition. In this view, TRPA1 antagonists may be regarded as beneficial tools for the treatment of inflammatory conditions.

TRPA1 Expression and Pathophysiology in Immune Cells

The non-selective cation channel TRPA1 is best known as a broadly-tuned sensor expressed in nociceptive neurons, where it plays key functions in chemo-, thermo-, and mechano-sensing. However, in this review we illustrate how this channel is expressed also in cells of the immune system. TRPA1 has been detected, mainly with biochemical techniques, in eosinophils, mast cells, macrophages, dendritic cells, T cells, and B cells, but not in neutrophils. Functional measurements, in contrast, remain very scarce. No studies have been reported in basophils and NK cells. TRPA1 in immune cells has been linked to arthritis (neutrophils), anaphylaxis and atopic dermatitis (mast cells), atherosclerosis, renal injury, cardiac hypertrophy and inflammatory bowel disease (macrophages), and colitis (T cells). The contribution of TRPA1 to immunity is dual: as detector of cell stress, tissue injury, and exogenous noxious stimuli it leads to defensive responses, but in conditions of aberrant regulation it contributes to the exacerbation of inflammatory conditions. Future studies should aim at characterizing the functional properties of TRPA1 in immune cells, an essential step in understanding its roles in inflammation and its potential as therapeutic target.

Advances in TRP channel drug discovery: from target validation to clinical studies

Transient receptor potential (TRP) channels are multifunctional signalling molecules with many roles in sensory perception and cellular physiology. Therefore, it is not surprising that TRP channels have been implicated in numerous diseases, including hereditary disorders caused by defects in genes encoding TRP channels (TRP channelopathies). Most TRP channels are located at the cell surface, which makes them generally accessible drug targets. Early drug discovery efforts to target TRP channels focused on pain, but as our knowledge of TRP channels and their role in health and disease has grown, these efforts have expanded into new clinical indications, ranging from respiratory disorders through neurological and psychiatric diseases to diabetes and cancer. In this Review, we discuss recent findings in TRP channel structural biology that can affect both drug development and clinical indications. We also discuss the clinical promise of novel TRP channel modulators, aimed at both established and emerging targets. Last, we address the challenges that these compounds may face in clinical practice, including the need for carefully targeted approaches to minimize potential side-effects due to the multifunctional roles of TRP channels.

Nonsurgical mouse model of endometriosis-associated pain that responds to clinically active drugs

Endometriosis is an estrogen-dependent inflammatory disease that affects approximately 10% of women. Debilitating pelvic or abdominal pain is one of its major clinical features. Current animal models of endometriosis-associated pain require surgery either to implant tissue or to remove the ovaries. Moreover, existing models do not induce spontaneous pain, which is the primary symptom of patients with chronic pain, including endometriosis. A lack of models that accurately recapitulate the disease phenotype must contribute to the high failure rate of clinical trials for analgesic drugs directed at chronic pain, including those for endometriosis. We set out to establish a murine model of endometriosis-associated pain. Endometriosis was induced nonsurgically by injecting a dissociated uterine horn into a recipient mouse. The induced lesions exhibited histological features that resemble human lesions along with an increase in proinflammatory cytokines and recruitment of immune cells. We also observed the presence of calcitonin gene-related peptide-, TRPA1-, and TRPV1-expressing nerve fibers in the lesions. This model induced mechanical allodynia, spontaneous abdominal pain, and changes in thermal selection behavior that indicate discomfort. These behavioral changes were reduced by drugs used clinically for endometriosis, specifically letrozole (aromatase inhibitor) and danazol (androgen). Endometriosis also induced neuronal changes as evidenced by activation of the NF-κB signaling pathway in TRPA1- and TRPV1-expressing dorsal root ganglion neurons. In conclusion, we have established a model of endometriosis-associated pain that responds to clinically active drugs and can, therefore, be used to identify novel therapies.

Concentrations of the endocannabinoid N-arachidonoylethanolamine in the follicular fluid of women with endometriosis: the role of M1 polarised macrophages

Although N-arachidonoylethanolamine (AEA; also known as anandamide) is present in human follicular fluid (FF), its regulation remains unknown. Therefore, the aims of the present study were to: (1) investigate the relationships between FF AEA concentrations in women undergoing assisted reproductive technology and their age, body mass index, ART characteristics and fertility treatment outcomes; and (2) assess how different inflammatory patterns may trigger AEA production by human granulosa cells (hGCs). FF AEA concentrations were higher in women undergoing IVF than in those undergoing intracytoplasmic sperm injection group. FF AEA median concentrations were lower in women undergoing ART because of male factor infertility than in women with endometriosis (1.6 vs 2.5nM respectively), but not women with tubal, hormonal or unexplained infertility (1.6, 2.4 and 1.9nM respectively). To evaluate the effects of macrophages on AEA production by hGCs, hGCs were cocultured with monocyte-derived macrophages. The conditioned medium from M1 polarised macrophages increased AEA production by hGCs. This was accompanied by an increase in AEA-metabolising enzymes, particularly N-acyl phosphatidylethanolamine-specific phospholipase D. The results of the present study show that high FF AEA concentrations in patients with endometriosis may be associated with the recruitment of inflammatory chemokines within the ovary, which together may contribute to the decreased reproductive potential of women with endometriosis. Collectively, these findings add a new player to the hormone and cytokine networks that regulate fertility in women.

Aberrant reactive aldehyde detoxification by aldehyde dehydrogenase-2 influences endometriosis development and pain-associated behaviors

Endometriosis affects ∼176 million women worldwide, yet on average, women experience pain ∼10 years from symptom onset before being properly diagnosed. Standard treatments (drugs or surgery) often fail to provide long-term pain relief. Elevated levels of reactive aldehydes such as 4-hydroxynonenal (4-HNE) have been implicated in the peritoneal fluid of women with endometriosis and upon accumulation, reactive aldehydes can form protein-adducts and/or generate pain. A key enzyme in detoxifying reactive aldehydes to less reactive forms is the mitochondrial enzyme aldehyde dehydrogenase-2 (ALDH2). Here, we tested the hypothesis that aberrant reactive aldehyde detoxification by ALDH2 underlies endometriosis and its associated pain. We determined, in the eutopic and ectopic endometrium of women with severe (stage IV) peritoneal endometriosis, that ALDH2 enzyme activity was decreased, which was associated with decreased ALDH2 expression and increased 4-HNE adduct formation compared to the eutopic endometrium of controls in the proliferative phase. Using a rodent model of endometriosis and an ALDH2*2 knock-in mouse with decreased ALDH2 activity, we determined that increasing ALDH2 activity with the enzyme activator Alda-1 could prevent endometriosis lesion development as well as alleviate pain-associated behaviors in proestrus. Overall, our findings suggest that targeting the ALDH2 enzyme in endometriosis may lead to better treatment strategies and in the proliferative phase, that increased 4-HNE adduct formation within the endometrium may serve as a less invasive diagnostic biomarker to reduce years of suffering in women.

(Endo)Cannabinoids and Gynaecological Cancers

Gynaecological cancers can be primary neoplasms, originating either from the reproductive tract or the products of conception, or secondary neoplasms, representative of metastatic disease. For some of these cancers, the exact causes are unknown; however, it is recognised that the precise aetiopathogeneses for most are multifactorial and include exogenous (such as diet) and endogenous factors (such as genetic predisposition), which mutually interact in a complex manner. One factor that has been recognised to be involved in the pathogenesis and progression of gynaecological cancers is the endocannabinoid system (ECS). The ECS consists of endocannabinoids (bioactive lipids), their receptors, and metabolic enzymes responsible for their synthesis and degradation. In this review, the impact of plant-derived (Cannabis species) cannabinoids and endocannabinoids on gynaecological cancers will be discussed within the context of the complexity of the proteins that bind, transport, and metabolise these compounds in reproductive and other tissues. In particular, the potential of endocannabinoids, their receptors, and metabolic enzymes as biomarkers of specific cancers, such as those of the endometrium, will be addressed. Additionally, the therapeutic potential of targeting selected elements of the ECS as new action points for the development of innovative drugs will be presented.

Pain in Endometriosis

Endometriosis is a chronic and debilitating condition affecting ∼10% of women. Endometriosis is characterized by infertility and chronic pelvic pain, yet treatment options remain limited. In many respects this is related to an underlying lack of knowledge of the etiology and mechanisms contributing to endometriosis-induced pain. Whilst many studies focus on retrograde menstruation, and the formation and development of lesions in the pathogenesis of endometriosis, the mechanisms underlying the associated pain remain poorly described. Here we review the recent clinical and experimental evidence of the mechanisms contributing to chronic pain in endometriosis. This includes the roles of inflammation, neurogenic inflammation, neuroangiogenesis, peripheral sensitization and central sensitization. As endometriosis patients are also known to have co-morbidities such as irritable bowel syndrome and overactive bladder syndrome, we highlight how common nerve pathways innervating the colon, bladder and female reproductive tract can contribute to co-morbidity via cross-organ sensitization.

The Inhibitory Effect of Extra Virgin Olive Oil and Its Active Compound Oleocanthal on Prostaglandin-Induced Uterine Hypercontraction and Pain-Ex Vivo and In Vivo Study

Primary dysmenorrhea is a common occurrence in adolescent women and is a type of chronic inflammation. Dysmenorrhea is due to an increase in oxidative stress, which increases cyclooxygenase-2 (COX-2) expression, increases the concentration of prostaglandin F2α (PGF2α), and increases the calcium concentration in uterine smooth muscle, causing excessive uterine contractions and pain. The polyphenolic compound oleocanthal (OC) in extra virgin olive oil (EVOO) has been shown to have an anti-inflammatory and antioxidant effect. This study aimed to investigate the inhibitory effect of extra virgin olive oil and its active ingredient oleocanthal (OC) on prostaglandin-induced uterine hyper-contraction, its antioxidant ability, and related mechanisms. We used force-displacement transducers to calculate uterine contraction in an ex vivo study. To analyze the analgesic effect, in an in vivo study, we used an acetic acid/oxytocin-induced mice writhing model and determined uterus contraction-related signaling protein expression. The active compound OC inhibited calcium/PGF2α-induced uterine hyper-contraction. In the acetic acid and oxytocin-induced mice writhing model, the intervention of the EVOO acetonitrile layer extraction inhibited pain by inhibiting oxidative stress and the phosphorylation of the protein kinase C (PKC)/extracellular signal-regulated kinases (ERK)/ myosin light chain (MLC) signaling pathway. These findings supported the idea that EVOO and its active ingredient, OC, can effectively decrease oxidative stress and PGF2α-induced uterine hyper-contraction, representing a further treatment for dysmenorrhea.

Upregulation of the TRPA1 Ion Channel in the Gastric Mucosa after Iodoacetamide-Induced Gastritis in Rats: A Potential New Therapeutic Target

Acute gastritis is often untreatable by acid secretion-inhibiting drugs. Understanding the protective mechanisms including the role of Transient Receptor Potential Ankyrin1 (TRPA1) and Vanilloid1 (TRPV1) channels localized on capsaicin-sensitive afferents and non-neuronal structures might identify novel therapeutic approaches. Therefore, we characterized a translational gastritis model using iodoacetamide (IAA) and investigated TRPA1/V1 expressions. Wistar rats and CD1, C57Bl/6J mice were exposed to IAA-containing (0.05, 0.1, 0.2, 0.3, 0.5%) drinking water for 7 or 14 days. Body weight and water consumption were recorded daily. Macroscopic lesions were scored, qualitative histopathologic investigation was performed, TRPA1/V1 immunopositivity and mRNA expressions were measured. IAA induced a concentration-dependent weight loss and reduced water intake in both species. Hyperemia, submucosal edema, inflammatory infiltration and hemorrhagic erosions developed after 7 days, while ulcers after 14 days in rats. Trpa1 mRNA/protein expressions were upregulated at both timepoints. Meanwhile, TRPV1 immunopositivity was upregulated in the gastric corpus after 0.05% IAA ingestion, but downregulated after 0.2%, whereas Trpv1 mRNA did not change. Interestingly, no macroscopic/microscopic changes were observed in mice. These are the first data for the concentration- and duration-dependent changes in the IAA-induced gastritis in rats accompanied by TRPA1 upregulation, therefore, its therapeutic potential in gastritis should further be investigated.

The Expression of Cold-Inducible RNA-Binding Protein mRNA in Sow Genital Tract Is Modulated by Natural Mating, But Not by Seminal Plasma

The RNA-binding proteins (RBPs), some of them induced by transient receptor potential (TRP) ion channels, are crucial regulators of RNA function that can contribute to reproductive pathogenesis, including inflammation and immune dysfunction. This study aimed to reveal the influence of spermatozoa, seminal plasma, or natural mating on mRNA expression of RBPs and TRP ion channels in different segments of the internal genital tract of oestrous, preovulatory sows. Particularly, we focused on mRNA expression changes of the cold-inducible proteins (CIPs) and related TRP channels. Pre-ovulatory sows were naturally mated (NM) or cervically infused with semen (Semen-AI) or sperm-free seminal plasma either from the entire ejaculate (SP-TOTAL) or the sperm-rich fraction (SP-AI). Samples (cervix to infundibulum) were collected by laparotomy under general anaesthesia for transcriptomic analysis (GeneChip^® Porcine Gene 1.0 ST Array) 24 h after treatments. The NM treatment induced most of the mRNA expression changes, compared to Semen-AI, SP-AI, and SP-TOTAL treatments including unique significative changes in CIRBP, RBM11, RBM15B, RBMS1, TRPC1, TRPC4, TRPC7, and TRPM8. The findings on the differential mRNA expression on RBPs and TRP ion channels, especially to CIPs and related TRP ion channels, suggest that spermatozoa and seminal plasma differentially modulated both protein families during the preovulatory phase, probably related to a still unknown early signalling mechanism in the sow reproductive tract.

Steroids and TRP Channels: A Close Relationship

Transient receptor potential (TRP) channels are remarkable transmembrane protein complexes that are essential for the physiology of the tissues in which they are expressed. They function as non-selective cation channels allowing for the signal transduction of several chemical, physical and thermal stimuli and modifying cell function. These channels play pivotal roles in the nervous and reproductive systems, kidney, pancreas, lung, bone, intestine, among others. TRP channels are finely modulated by different mechanisms: regulation of their function and/or by control of their expression or cellular/subcellular localization. These mechanisms are subject to being affected by several endogenously-produced compounds, some of which are of a lipidic nature such as steroids. Fascinatingly, steroids and TRP channels closely interplay to modulate several physiological events. Certain TRP channels are affected by the typical genomic long-term effects of steroids but others are also targets for non-genomic actions of some steroids that act as direct ligands of these receptors, as will be reviewed here.

Ion Channels in The Pathogenesis of Endometriosis: A Cutting-Edge Point of View

BACKGROUND

Ion channels play a crucial role in many physiological processes. Several subtypes are expressed in the endometrium. Endometriosis is strictly correlated to estrogens and it is evident that expression and functionality of different ion channels are estrogen-dependent, fluctuating between the menstrual phases. However, their relationship with endometriosis is still unclear.

OBJECTIVE

To summarize the available literature data about the role of ion channels in the etiopathogenesis of endometriosis.

METHODS

A search on PubMed and Medline databases was performed from inception to November 2019.

RESULTS

Cystic fibrosis transmembrane conductance regulator (CFTR), transient receptor potentials (TRPs), aquaporins (AQPs), and chloride channel (ClC)-3 expression and activity were analyzed. CFTR expression changed during the menstrual phases and was enhanced in endometriosis samples; its overexpression promoted endometrial cell proliferation, migration, and invasion throughout nuclear factor kappa-light-chain-enhancer of activated B cells-urokinase plasminogen activator receptor (NFκB-uPAR) signaling pathway. No connection between TRPs and the pathogenesis of endometriosis was found. AQP5 activity was estrogen-increased and, through phosphatidylinositol-3-kinase and protein kinase B (PI3K/AKT), helped in vivo implantation of ectopic endometrium. In vitro, AQP9 participated in extracellular signal-regulated kinases/p38 mitogen-activated protein kinase (ERK/p38 MAPK) pathway and helped migration and invasion stimulating matrix metalloproteinase (MMP)2 and MMP9. ClC-3 was also overexpressed in ectopic endometrium and upregulated MMP9.

CONCLUSION

Available evidence suggests a pivotal role of CFTR, AQPs, and ClC-3 in endometriosis etiopathogenesis. However, data obtained are not sufficient to establish a direct role of ion channels in the etiology of the disease. Further studies are needed to clarify this relationship.

The role of the endocannabinoid system in aetiopathogenesis of endometriosis: A potential therapeutic target

Endometriosis affects a large proportion of women during their reproductive years and is associated with pain and infertility, also affecting psychological wellbeing and quality of life. The pathogenesis of the disease remains unclear, although it is believed to be multifactorial. The endocannabinoid system (ECS) consists of a number of ligands, receptors and enzymes, and has gained interests in endometriosis research. This review aims to summarise all available evidence reporting the roles of the ECS in endometriosis. A literature search of the PubMed, EMBASE, and Web of Science electronic medical databases was performed. Original and review articles published in peer-reviewed journals were included. No publication date or publication status restrictions were imposed. Significant differences in the concentrations and expressions of the components of the ECS were reported in the eutopic and ectopic endometrium, and the systemic circulation of women with endometriosis compared to controls. Endometriosis appears to be associated with downregulation of CB1 receptors and upregulation of TRPV1 receptors. The role of CB1 and progesterone in anti-inflammatory action and the role of TRPV1 in inflammation and pain are of particular interests. Furthermore, the ECS has been reported to be involved in processes relevant to endometriosis, including cell migration, cell proliferation, apoptosis, inflammation, and interacts with sex steroid hormones. The ECS may play a role in disease establishment, progression, and pain in endometriosis. However, reports are based on studies of limited size and there are inconsistencies among the definition of their control groups. There are also conflicting reports regarding precise involvement of the ECS in endometriosis. Future research with larger numbers, strict inclusion and exclusion criteria and detailed clinical information is imperative.

Villainous role of estrogen in macrophage-nerve interaction in endometriosis

Endometriosis is a complex and heterogeneous disorder with unknown etiology. Dysregulation of macrophages and innervation are important factors influencing the pathogenesis of endometriosis-associated pain. It is known to be an estrogen-dependent disease, estrogen can promote secretion of chemokines from peripheral nerves, enhancing the recruitment and polarization of macrophages in endometriotic tissue. Macrophages have a role in the expression of multiple nerve growth factors (NGF), which mediates the imbalance of neurogenesis in an estrogen-dependent manner. Under the influence of estrogen, co-existence of macrophages and nerves induces an innovative neuro-immune communication. Persistent stimulation by inflammatory cytokines from macrophages on nociceptors of peripheral nerves aggravates neuroinflammation through the release of inflammatory neurotransmitters. This neuro-immune interaction regulated by estrogen sensitizes peripheral nerves, leading to neuropathic pain in endometriosis. The aim of this review is to highlight the significance of estrogen in the interaction between macrophages and nerve fibers, and to suggest a potentially valuable therapeutic target for endometriosis-associated pain.