Macrophage-derived netrin-1 contributes to endometriosis-associated pain

Nerve-myeloid cell interactions in persistent human pain: a reappraisal using updated cell subset classifications

ABSTRACT

The past 20 years have seen a dramatic shift in our understanding of the role of the immune system in initiating and maintaining pain. Myeloid cells, including macrophages, dendritic cells, Langerhans cells, and mast cells, are increasingly implicated in bidirectional interactions with nerve fibres in rodent pain models. However, our understanding of the human setting is still poor. High-dimensional functional analyses have substantially changed myeloid cell classifications, with recently described subsets such as epidermal dendritic cells and DC3s unveiling new insight into how myeloid cells interact with nerve fibres. However, it is unclear whether this new understanding has informed the study of human chronic pain. In this article, we perform a scoping review investigating neuroimmune interactions between myeloid cells and peripheral nerve fibres in human chronic pain conditions. We found 37 papers from multiple pain states addressing this aim in skin, cornea, peripheral nerve, endometrium, and tumour, with macrophages, Langerhans cells, and mast cells the most investigated. The directionality of results between studies was inconsistent, although the clearest pattern was an increase in macrophage frequency across conditions, phases, and tissues. Myeloid cell definitions were often outdated and lacked correspondence with the stated cell types of interest; overreliance on morphology and traditional structural markers gave limited insight into the functional characteristics of investigated cells. We therefore critically reappraise the existing literature considering contemporary myeloid cell biology and advocate for the application of established and emerging high-dimensional proteomic and transcriptomic single-cell technologies to clarify the role of specific neuroimmune interactions in chronic pain.

Identification of miR-30c-5p microRNA in Serum as a Candidate Biomarker to Diagnose Endometriosis

The diagnosis of endometriosis by laparoscopy is delayed until advanced stages. In recent years, microRNAs have emerged as novel biomarkers for different diseases. These molecules are small non-coding RNA sequences involved in the regulation of gene expression and can be detected in peripheral blood. Our aim was to identify candidate serum microRNAs associated with endometriosis and their role as minimally invasive biomarkers. Serum samples were obtained from 159 women, of whom 77 were diagnosed with endometriosis by laparoscopy and 82 were healthy women. First, a preliminary study identified 29 differentially expressed microRNAs between the two study groups. Next, nine of the differentially expressed microRNAs in the preliminary analysis were evaluated in a new cohort of 67 women with endometriosis and 72 healthy women. Upon validation by quantitative real-time PCR technique, the circulating level of miR-30c-5p was significantly higher in the endometriosis group compared with the healthy women group. The area under the curve value of miR-30c-5p was 0.8437, demonstrating its diagnostic potential even when serum samples registered an acceptable limit of hemolysis. Dysregulation of this microRNA was associated with molecular pathways related to cancer and neuronal processes. We concluded that miR-30c-5p is a potential minimally invasive biomarker of endometriosis, with higher expression in the group of women with endometriosis diagnosed by laparoscopy.

Peritoneal immune microenvironment of endometriosis: Role and therapeutic perspectives

Endometriosis, an estrogen-dependent chronic inflammatory disease characterized by the growth of endometrium-like tissues outside the uterine cavity, affects 10% of reproductive-age women. Although the pathogenesis of endometriosis is uncertain, it is widely accepted that retrograde menstruation results in ectopic endometrial tissue implantation. Given that not all women with retrograde menstruation develop endometriosis, immune factors have been hypothesized to affect the pathogenesis of endometriosis. In this review, we demonstrate that the peritoneal immune microenvironment, including innate immunity and adaptive immunity, plays a central role in the pathogenesis of endometriosis. Current evidence supports the fact that immune cells, such as macrophages, natural killer (NK) cells, dendritic cells (DCs), neutrophils, T cells, and B cells, as well as cytokines and inflammatory mediators, contribute to the vascularization and fibrogenesis of endometriotic lesions, accelerating the implantation and development of ectopic endometrial lesions. Endocrine system dysfunction influences the immune microenvironment through overexpressed estrogen and progesterone resistance. In light of the limitations of hormonal therapy, we describe the prospects for potential diagnostic biomarkers and nonhormonal therapy based on the regulation of the immune microenvironment. Further studies are warranted to explore the available diagnostic biomarkers and immunological therapeutic strategies for endometriosis.

Niclosamide targets the dynamic progression of macrophages for the resolution of endometriosis in a mouse model

Due to the vital roles of macrophages in the pathogenesis of endometriosis, targeting macrophages could be a promising therapeutic direction. Here, we investigated the efficacy of niclosamide for the resolution of a perturbed microenvironment caused by dysregulated macrophages in a mouse model of endometriosis. Single-cell transcriptomic analysis revealed the heterogeneity of macrophages including three intermediate subtypes with sharing characteristics of traditional “small” or “large” peritoneal macrophages (SPMs and LPMs) in the peritoneal cavity. Endometriosis-like lesions (ELL) enhanced the differentiation of recruited macrophages, promoted the replenishment of resident LPMs, and increased the ablation of embryo-derived LPMs, which were stepwise suppressed by niclosamide. In addition, niclosamide restored intercellular communications between macrophages and B cells. Therefore, niclosamide rescued the perturbed microenvironment in endometriosis through its fine regulations on the dynamic progression of macrophages. Validation of similar macrophage pathogenesis in patients will further promote the clinical usage of niclosamide for endometriosis treatment.

Effect of PLGA Nanoparticle-Mediated Delivery of miRNA 503 on The Apoptosis of Ovarian Endometriosis Cells

OBJECTIVE

One of the challenges in gene therapy is the transfer of the gene to the target cell. MicroRNAs (miRNAs) regulate gene expression after transcription by binding directly to the messenger and play a vital role in cell behaviors and the pathogenesis of some diseases. This study was aimed at developing poly (lactic-co-glycolic acid) (PLGA)- based nanoparticles (NPs) for gene delivery to endometriotic cyst stromal cells (ECSCs).

MATERIALS AND METHODS

In this experimental study, endometriosis cells were isolated from women with severe endometriosis (DIE) and digested by the enzymatic method (40 μg/ml DNAase I and 300 μg/ml collagenase type 3). PLGA-based NPs were synthesized and characterized. The size of sole PLGA NPs and PLGA/miRNA were 60 ± 4 nm and 70 ± 5.1 nm respectively. Poly lactic-co-glycolic-based NPs were used as vector carriers for miRNA 503 transfection in endometriosis cells. The cells were divided into the five groups of control and four doses (25, 50, 75, and 100 μm) of miRNA 503/PLGA at 12, 24, 48, and 72 hours. Viability and apoptosis were evaluated by the MTT assay and Annexin Kits. Data were analyzed by one-way analysis of variance.

RESULTS

The results show that the size of PLGA/miRNA complex with dynamic light scattering (DLS) was 70 ± 5.1 nm and zeta potential values of the PLGA/PEI/miRNA complexes were 27.9 mV. Based on the MTT assay results, the optimal dose of miRNA 503/PLGA was 75 μm, at which the viability of ECSCs was 52.6% ± 1.2 (P≤0.001), and the optimal time was 48 hours. The apoptotic rates of ECSCs treated with PLGA/miRNA503 (34.75 ± 4.9%) were significantly higher than those of ECSCs treated with PLGA alone (3.35 ± 2.58%, P≤0.01).

CONCLUSION

Cell death increased with increasing the concentration of miRNA; thus, it can be suggested as a treatment for endometriosis.

Spinal TRPA1 Contributes to the Mechanical Hypersensitivity Effect Induced by Netrin-1

Netrin-1, a chemoattractant expressed by floor plate cells, and one of its receptors (deleted in colorectal cancer) has been associated with pronociceptive actions in a number of pain conditions. Here, we addressed the question of whether spinal TRPC4/C5 or TRPA1 are among the downstream receptors contributing to pronociceptive actions induced by netrin-1. The experiments were performed on rats using a chronic intrathecal catheter for administration of netrin-1 and antagonists of TRPC4/C5 or TRPA1. Pain sensitivity was assessed behaviorally by using mechanical and heat stimuli. Effect on the discharge rate of rostral ventromedial medullary (RVM) pain control neurons was studied in lightly anesthetized animals. Netrin-1, in a dose-related fashion, induced mechanical hypersensitivity that lasted up to three weeks. Netrin-1 had no effect on heat nociception. Mechanical hypersensitivity induced by netrin-1 was attenuated by TRPA1 antagonist Chembridge-5861528 and by the control analgesic compound pregabalin both during the early (first two days) and late (third week) phase of hypersensitivity. TRPC4/C5 antagonist ML-204 had a weak antihypersensitivity effect that was only in the early phase, whereas TRPC4/C5 antagonist HC-070 had no effect on hypersensitivity induced by netrin-1. The discharge rate in pronociceptive ON-like RVM neurons was increased by netrin-1 during the late but not acute phase, whereas netrin-1 had no effect on the discharge rate of antinociceptive RVM OFF-like neurons. The results suggest that spinal TRPA1 receptors and pronociceptive RVM ON-like neurons are involved in the maintenance of submodality-selective pronociceptive actions induced by netrin-1 in the spinal cord.

UNC5B Overexpression Alleviates Peripheral Neuropathic Pain by Stimulating Netrin-1-Dependent Autophagic Flux in Schwann Cells

Lesions or diseases of the somatosensory system can cause neuropathic pain (NP). Schwann cell (SC) autophagy plays an important role in NP. Uncoordinated gene 5 homolog B (UNC5B), the canonical dependent receptor of netrin-1, is known to be exclusively expressed in SCs and involved in NP; however, the underlying mechanisms were unclear. A rat model of sciatic nerve chronic constriction injury (CCI) was used to induce peripheral neuropathic pain. Adeno-associated virus (AAV) overexpressing UNC5B was applied to the injured nerve, and an autophagy inhibitor, 3-mechyladenine (3-MA), was intraperitoneally injected in some animals. Behavioral tests were performed to evaluate NP, the morphology of the injured nerves was analyzed, and autophagy-related proteins were detected. A rat SC line (RSC96) undergoing oxygen and glucose deprivation (OGD) was used to mimic an ischemic setting to examine the role of UNC5B in autophagy. Local UNC5B overexpression alleviated CCI-induced NP and rescued myelin degeneration. Meanwhile, UNC5B overexpression improved CCI-induced impairment of autophagic flux, while the autophagy inhibitor 3-MA reversed the analgesic effect of UNC5B. In cultured SCs, UNC5B helped recruit netrin-1 to the cell membrane. UNC5B overexpression promoted autophagic flux while inhibiting apoptosis, which was further augmented with exogenous netrin-1 and reversed by netrin-1 knockdown. The enhanced phosphorylation of AMP-activated protein kinase (AMPK) and Unc51-like autophagy activating kinase 1 (ULK1) by UNC5B overexpression was also correlated with netrin-1. Our results suggest that UNC5B facilitates autophagic flux in SCs via phosphorylation of AMPK and ULK1, dependent on its ligand netrin-1, protecting myelin and partly preventing injury-induced NP.

Inflammation-mediated macrophage polarization induces TRPV1/TRPA1 heteromers in endometriosis

Chronic pelvic pain (CPP) and infertility are the common characteristics of endometriosis. Macrophages and related inflammation play important roles in endometriosis pain. TRPV1 and TRPA1 form a heteromeric channel which is related to endometriosis pain. In the present study, the inflammation-mediated macrophage polarization along with TRPV1/TRPA1 heteromers in endometriosis was investigated in vivo and in vitro. Macrophage polarization and TRPV1/TRPA1 heteromers in endometriosis tissue of patients were assayed, and was further investigated in endometriosis mice by co-culturing macrophages derived from mice in different groups with human endometrium cells. Our results indicated that macrophage polarization, as CD86 and CD206 positive macrophages, were accompanied by TRPV1/TRPA1 heteromers in endometriosis tissues of patients with pain. Inflammatory factors in peritoneal lavage fluid and serum of mice were correlated with TRPV1/TRPA1 expression in endometriosis tissues of mice as well as macrophage polarization which tended to be consistent with TRPV1/TRPA1 heteromers in endometriosis tissue. Moreover, macrophage polarization in enterocoelia induced ectopic endometrial cells migration with the increase in TRPV1/TRPA1 heteromers. Our results suggest that endometriosis-induced celiac inflammation might mediate macrophage polarization along with the increase of TRPV1/TRPA1 heteromers, which may play a key role in endometriosis pain.

A nomogram for bladder pain syndrome/interstitial cystitis based on netrin-1

Purpose

This study aimed to combine plasma netrin-1 and clinical parameters to construct a diagnostic model for bladder pain syndrome/interstitial cystitis (BPS/IC).

Methods

We analyzed the independent diagnostic value of netrin-1 and the correlation with clinical symptom scores of BPS/IC. Clinical parameters were selected using LASSO regression, and a multivariate logistic regression model based on netrin-1 was established, and then a nomogram of BPS/IC prevalence was constructed. The nomogram was evaluated using calibration curves, the C-index, and decision curve analysis (DCA). Finally, the model was validated using an internal validation method.

Results

The area under the curve for the ability of netrin-1 to independently predict BPS/IC diagnosis was 0.858 (p < 0.001), with a sensitivity of 85% and specificity of 82%. The predicted nomogram included three variables: age, CD3 + /CD4 + T lymphocyte ratio, and netrin-1. The C-index of this nomogram was 0.882, and the predicted values were highly consistent with the actual results in the calibration curve. In addition, the internally validated C-index of 0.870 confirms the high reliability of the model. DCA results show that the net patient benefit of the netrin-1 combined with other clinical parameters was higher than that of the single netrin-1 model.

Conclusion

Netrin-1 can be used as a diagnostic marker for BPS/IC and is associated with pain. The nomogram constructed by combining netrin-1 and clinical parameters was able to predict BPS/IC with great accuracy. In addition, Netrin-1 may also serve as a novel therapeutic target for BPS/IC.