The role of myeloid-derived suppressor cells (MDSC) in the inflammaging process

Granulocytic Myeloid-Derived Suppressor Cell Exosomal Prostaglandin E2 Ameliorates Collagen-Induced Arthritis by Enhancing IL-10+ B Cells

The results of recent studies have shown that granulocytic-myeloid derived suppressor cells (G-MDSCs) can secrete exosomes that transport various biologically active molecules with regulatory effects on immune cells. However, their roles in autoimmune diseases such as rheumatoid arthritis remain to be further elucidated. In the present study, we investigated the influence of exosomes from G-MDSCs on the humoral immune response in murine collagen-induced arthritis (CIA). G-MDSCs exosomes-treated mice showed lower arthritis index values and decreased inflammatory cell infiltration. Treatment with G-MDSCs exosomes promoted splenic B cells to secrete IL-10 both in vivo and in vitro. In addition, a decrease in the proportion of plasma cells and follicular helper T cells was observed in drainage lymph nodes from G-MDSCs exosomes-treated mice. Moreover, lower serum levels of IgG were detected in G-MDSCs exosomes-treated mice, indicating an alteration of the humoral environment. Mechanistic studies showed that exosomal prostaglandin E2 (PGE2) produced by G-MDSCs upregulated the phosphorylation levels of GSK-3β and CREB, which play a key role in the production of IL-10⁺ B cells. Taken together, our findings demonstrated that G-MDSC exosomal PGE2 attenuates CIA in mice by promoting the generation of IL-10⁺ Breg cells.

Update of Immunosenescence in Cerebral Small Vessel Disease

Aging of the central nervous system (CNS) is closely associated with chronic sterile low-grade inflammation in older organisms and related immune response. As an amplifier for neuro-inflammaging, immunosenescence remodels and deteriorates immune systems gradually with the passage of time, and finally contributes to severe outcomes like stroke, dementia and neurodegeneration in elderly adults. Cerebral small vessel disease (CSVD), one of the major causes of vascular dementia, has an intensive connection with the inflammatory response and immunosenescence plays a crucial role in the pathology of this disorder. In this review, we discuss the impact of immunosenescence on the development of CSVD and its underlying mechanism. Furthermore, the clinical practice significance of immunosenescence management and the diagnosis and treatment of CSVD will be also discussed.

Epigenetic crosstalk between hypoxia and tumor driven by HIF regulation

Hypoxia is the major influence factor in physiological and pathological courses which are mainly mediated by hypoxia-inducible factors (HIFs) in response to low oxygen tensions within solid tumors. Under normoxia, HIF signaling pathway is inhibited due to HIF-α subunits degradation. However, in hypoxic conditions, HIF-α is activated and stabilized, and HIF target genes are successively activated, resulting in a series of tumour-specific activities. The activation of HIFs, including HIF-1α, HIF-2α and HIF-3α, subsequently induce downstream target genes which leads to series of responses, the resulting abnormal processes or metabolites in turn affect HIFs stability. Given its functions in tumors progression, HIFs have been regarded as therapeutic targets for improved treatment efficacy. Epigenetics refers to alterations in gene expression that are stable between cell divisions, and sometimes between generations, but do not involve changes in the underlying DNA sequence of the organism. And with the development of research, epigenetic regulation has been found to play an important role in the development of tumors, which providing accumulating basic or clinical evidences for tumor treatments. Here, given how little has been reported about the overall association between hypoxic tumors and epigenetics, we made a more systematic review from epigenetic perspective in hope of helping others better understand hypoxia or HIF pathway, and providing more established and potential therapeutic strategies in tumors to facilitate epigenetic studies of tumors.

Toll-like Receptor 4 Inhibitor TAK-242 Improves Fulminant Hepatitis by Regulating Accumulation of Myeloid-Derived Suppressor Cell

Fulminant hepatitis (FH) is an acute clinical disease with a poor prognosis and high mortality rate. The purpose of this study was to determine the protective effect of the Toll-like receptor 4 (TLR4) inhibitor TAK-242 on lipopolysaccharide (LPS)/D-galactosamine (D-GalN)-induced explosive hepatitis and explore in vivo and in vitro mechanisms. Mice were pretreated with TAK-242 for 3 h prior to LPS (10 μg/kg)/D-GalN (250 mg/kg) administration. Compared to the LPS/D-GalN group, the TAK-242 pretreatment group showed significantly prolonged survival, reduced serum alanine aminotransferase and aspartate aminotransferase levels, relieved oxidative stress, and reduced inflammatory interleukin (IL)-6, IL-12, and tumor necrosis factor-α levels. In addition, TAK-242 increased the accumulation of myeloid-derived suppressor cells (MDSCs). Next, mice were treated with an anti-Gr-1 antibody to deplete MDSCs, and adoptive transfer experiments were performed. We found that TAK-242 protected against FH by regulating MDSCs. In the in vitro studies, TAK-242 regulated the accumulation of MDSCs and promoted the release of immunosuppressive inflammatory cytokines. In addition, TAK-242 inhibited protein expression of nuclear factor-κB and mitogen-activated protein kinases. In summary, TAK-242 had a hepatoprotective effect against LPS/D-GalN-induced explosive hepatitis in mice. Its protective effect may be involved in suppressing inflammation, reducing oxidative stress, and increasing the proportion of MDSCs.

Role of myeloid-derived suppressor cells in the promotion and immunotherapy of colitis-associated cancer

Colitis-associated cancer (CAC) is a specific type of colorectal cancer that develops from inflammatory bowel disease (IBD). Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that are essential for the pathological processes of inflammation and cancer. Accumulating evidence indicates that MDSCs play different but vital roles during IBD and CAC development and impede CAC immunotherapy. New insights into the regulatory network of MDSCs in the CAC pathogenesis are opening new avenues for developing strategies to enhance the effectiveness of CAC treatment. In this review, we explore the role of MDSCs in chronic inflammation, dysplasia and CAC and summarize the potential CAC therapeutic strategies based on MDSC blockade.

Immunesenescence: A Predisposing Risk Factor for the Development of COVID-19?

Bearing a strong resemblance to the phenotypic and functional remodeling of the immune system that occurs during aging (termed immunesenescence), the immune response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of Coronavirus disease 2019 (COVID-19), is characterized by an expansion of inflammatory monocytes, functional exhaustion of lymphocytes, dysregulated myeloid responses and the presence of highly activated senescent T cells. Alongside advanced age, male gender and pre-existing co-morbidities [e.g., obesity and type 2 diabetes (T2D)] are emerging as significant risk factors for COVID-19. Interestingly, immunesenescence is more profound in males when compared to females, whilst accelerated aging of the immune system, termed premature immunesenescence, has been described in obese subjects and T2D patients. Thus, as three distinct demographic groups with an increased susceptibility to COVID-19 share a common immune profile, could immunesenescence be a generic contributory factor in the development of severe COVID-19? Here, by focussing on three key aspects of an immune response, namely pathogen recognition, elimination and resolution, we address this question by discussing how immunesenescence may weaken or exacerbate the immune response to SARS-CoV-2. We also highlight how aspects of immunesenescence could render potential COVID-19 treatments less effective in older adults and draw attention to certain therapeutic options, which by reversing or circumventing certain features of immunesenescence may prove to be beneficial for the treatment of groups at high risk of severe COVID-19.

Connections between Metabolism and Epigenetic Modification in MDSCs

Myeloid-derived suppressor cells (MDSCs) are major immunosuppressive cells in the tumor microenvironment (TME). During the differentiation and development of MDSCs from myeloid progenitor cells, their functions are also affected by a series of regulatory factors in the TME, such as metabolic reprogramming, epigenetic modification, and cell signaling pathways. Additionally, there is a crosstalk between these regulatory factors. This review mainly introduces the metabolism (especially glucose metabolism) and significant epigenetic modification of MDSCs in the TME, and briefly introduces the connections between metabolism and epigenetic modification in MDSCs, in order to determine the further impact on the immunosuppressive effect of MDSCs, so as to serve as a more effective target for tumor therapy.

TET2 promotes anti-tumor immunity by governing G-MDSCs and CD8+ T-cell numbers

The host immune response is a fundamental mechanism for attenuating cancer progression. Here we report a role for the DNA demethylase and tumor suppressor TET2 in host anti-tumor immunity. Deletion of Tet2 in mice elevates IL-6 levels upon tumor challenge. Elevated IL-6 stimulates immunosuppressive granulocytic myeloid-derived suppressor cells (G-MDSCs), which in turn reduce CD8⁺ T cells upon tumor challenge. Consequently, systematic knockout of Tet2 in mice leads to accelerated syngeneic tumor growth, which is constrained by anti-PD-1 blockade. Removal of G-MDSCs by the anti-mouse Ly6g antibodies restores CD8⁺ T-cell numbers in Tet2^-/- mice and reboots their anti-tumor activity. Importantly, anti-IL-6 antibody treatment blocks the expansion of G-MDSCs and inhibits syngeneic tumor growth. Collectively, these findings reveal a TET2-mediated IL-6/G-MDSCs/CD8⁺ T-cell immune response cascade that safeguards host adaptive anti-tumor immunity, offering a cell non-autonomous mechanism of TET2 for tumor suppression.

Recent advances in myeloid-derived suppressor cell biology

In recent years, studying the role of myeloid-derived suppressor cells (MDSCs) in many pathological inflammatory conditions has become a very active research area. Although the role of MDSCs in cancer is relatively well established, their role in non-cancerous pathological conditions remains in its infancy resulting in much confusion. Our objectives in this review are to address some recent advances in MDSC research in order to minimize such confusion and to provide an insight into their function in the context of other diseases. The following topics will be specifically focused upon: (1) definition and characterization of MDSCs; (2) whether all MDSC populations consist of immature cells; (3) technical issues in MDSC isolation, estimation and characterization; (4) the origin of MDSCs and their anatomical distribution in health and disease; (5) mediators of MDSC expansion and accumulation; (6) factors that determine the expansion of one MDSC population over the other; (7) the Yin and Yang roles of MDSCs. Moreover, the functions of MDSCs will be addressed throughout the text.

The emerging role of T follicular helper (TFH) cells in aging: Influence on the immune frailty

The world population is undergoing a rapid expansion of older adults. Aging is associated with numerous changes that affect all organs and systems, including every component of the immune system. Immunosenescence is a multifaceted process characterized by poor response to vaccine and higher incidence of bacterial and viral infections, cancer, cardiovascular and autoimmune diseases. Immunosenescence has been associated with chronic low-grade inflammation referred to as inflammaging, whose underlying mechanisms remain incompletely elucidated, including age-related changes affecting components of the innate and adaptive immune system. T follicular helper (T_FH) cells, present in lymphoid organs and in peripheral blood, are specialized in providing cognate help to B cells and are required for the production of immunoglobulins. Several subsets of T_FH cells have been identified in humans and mice and modifications in T_FH cell phenotype and function progressively occur with age. Dysfunctional T_FH cells play a role in cancer, autoimmune and cardiovascular diseases, all conditions particularly prevalent in elderly subjects. A specialized population of Treg cells, named T follicular regulatory (T_FR) cells, present in lymphoid organs and in peripheral blood, exerts opposing roles to T_FH cells in regulating immunity. Indeed, changes in T_FH/T_FR cell ratio constitute a relevant feature of aging. Herein we discuss the cellular and molecular changes in both T_FH cells and T_FR cells that occur in aging and recent findings suggesting that T_FH cells and/or their subsets could be involved in atherosclerosis, cancer, and autoimmunity.

Early Activation of Myeloid-Derived Suppressor Cells Participate in Sepsis-Induced Immune Suppression via PD-L1/PD-1 Axis

Background: Myeloid derived suppressor cells (MDSCs) have been reported to keep elevating during sepsis. The current study was performed to investigate the immunosuppressive effect of MDSCs and their subsets with the underlying mechanisms. Methods: The immunosuppressive status was manifested by the apoptosis of splenocytes, quantity of T cells and PD-1 expression. The dynamics of quantity and PD-L1 level of MDSCs and the subsets were determined over time. The subset of MDSCs with high PD-L1 level was co-cultured with T cells to observe the suppressive effect. Results: Abdominal abscess was observed after 7 days post-sepsis. Five biomarkers related to organ functions were all significantly higher in the CLP group. The survival rate was consistent with the middle grade severity of sepsis model. Apoptosis of splenocytes increased over time during sepsis; CD4 + T cell decreased from day 1 post-sepsis; CD8+ T cells significantly reduced at day 7. The PD-1 expression in spleen was upregulated from an early stage of sepsis, and negatively related with the quantity of T cells. MDSCs were low at day 1 post-sepsis, but increased to a high level later; the dynamics of PMN-MDSC was similar to MDSCs. PD-L1 on MDSCs was highest at day 1 post-sepsis; PMN-MDSC was the main subset expressing PD-L1. The PMN-MDSC with high PD-L1 expression level extracted on day 1 after surgery from CLP mice significantly inhibited the proliferation of T cells. Conclusions: Sepsis-induced immunosuppression is initiated from a very early stage, a high expression level of PD-L1 on MDSCs and the main subset, PMN-MDSC might play a critical role suppressive role on T cells through PD-L1/PD-1 axis.

Myeloid-derived suppressor cells in obstetrical and gynecological diseases

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of myeloid-origin cells which have immunosuppressive activities in several conditions, such as cancer and inflammation. Recent research has also associated MDSCs with numerous obstetrical and gynecological diseases. During pregnancy, MDSCs accumulate to ensure maternal-fetal immune tolerance, whereas they are decreased in patients who suffer from early miscarriage or pre-eclampsia. While the etiology of endometriosis is still unknown, abnormal accumulation of MDSCs in the peripheral blood and peritoneal fluid, alongside an increased level of reactive oxygen species (ROS), has been observed in these patients, which is central to the cellular immune regulations by MDSCs. Additionally, the regulation of MDSCs observed in tumours is also applicable to gynecologic neoplasms, including ovarian cancer and cervical cancer. More recently, emerging evidence has shown that there are high levels of MDSCs in premature ovarian failure (POF) and in vitro fertilization (IVF), but the underlying mechanisms are unknown. In this review, the generation and mechanisms of MDSCs are summarized. In particular, the modulation of these cells in immune-related obstetrical and gynecological diseases is discussed, including potential treatment options targeting MDSCs.

Reduction of myeloid derived suppressor cells by inhibiting Notch pathway prevents the progression of endometriosis in mice model

Growing evidence suggested that immune dysregulation is one of the crucial drivers to the development of endometriosis (EMS). Myeloid derived suppressor cells (MDSCs) represent a heterogeneous subset of immature myeloid cells, and have been reported to promote the onset and progression of EMS. Notch signaling pathway played a major role in immunological reactions. Studies have found Notch signaling pathway could regulate MDSCs. However, how the biological effects of Notch signaling pathway on MDSCs may work in EMS is still unknown. In our study, we first built an endometriosis induced mice model. Then we treated mice with DAPT, a Notch signaling pathway inhibitor, or saline. We found that the DAPT could prevent the progression of EMS. The ADAM17, Notch1, Jagged1 and Hes1 were overexpressed in EMS mice, however, when mice were treated with DAPT, the overexpression was reduced. Meanwhile, we found a lower level of MDSCs in the DAPT treated EMS mice as compared to EMS mice without DAPT, accompanied by an increase of T helper (TH) 17 cells and a decrease of regulatory T cells (Tregs). We also investigated the reactive oxygen species (ROS) in peritoneal and endometriotic cells. Our results showed that ROS level decreased in both peritoneal and endometriotic cells in the study group treated with DAPT. Overall, our study indicates for the first time that blockage of Notch signaling could lessen MDSCs and ROS, and therefore preventing the development of endometriosis.

Energy metabolism manipulates the fate and function of tumour myeloid-derived suppressor cells

In recent years, a large number of studies have been carried out in the field of immune metabolism, highlighting the role of metabolic energy reprogramming in altering the function of immune cells. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells generated during a large array of pathological conditions, such as cancer, inflammation, and infection, and show remarkable ability to suppress T-cell responses. These cells can also change their metabolic pathways in response to various pathogen-derived or inflammatory signals. In this review, we focus on the roles of glucose, fatty acid (FA), and amino acid (AA) metabolism in the differentiation and function of MDSCs in the tumour microenvironment, highlighting their potential as targets to inhibit tumour growth and enhance tumour immune surveillance by the host. We further highlight the remaining gaps in knowledge concerning the mechanisms determining the plasticity of MDSCs in different environments and their specific responses in the tumour environment. Therefore, this review should motivate further research in the field of metabolomics to identify the metabolic pathways driving the enhancement of MDSCs in order to effectively target their ability to promote tumour development and progression.

Activation of immunosuppressive network in the aging process

Chronic low-grade inflammation has a key role in the aging process, a state called inflammaging. It is known that the chronic inflammatory condition generates counteracting immunosuppressive state in many diseases. Inflammaging is also associated with an immune deficiency; generally termed as immunosenescence, although it is not known whether it represents the senescence of immune cells or the active remodeling of immune system. Evidence has accumulated since the 1970's indicating that immunosenescence might be caused by an increased activity of immunosuppressive cells rather than cellular senescence. Immune cells display remarkable plasticity; many of these cells can express both proinflammatory and immunosuppressive phenotypes in a context-dependent manner. The immunosuppressive network involves the regulatory subtypes of T (Treg) and B (Breg) cells as well as regulatory phenotypes of macrophages (Mreg), dendritic (DCreg), natural killer (NKreg), and type II natural killer T (NKT) cells. The immunosuppressive network also includes monocytic (M-MDSC) and polymorphonuclear (PMN-MDSC) myeloid-derived suppressor cells which are immature myeloid cells induced by inflammatory mediators. This co-operative network is stimulated in chronic inflammatory conditions preventing excessive inflammatory responses but at the same time they exert harmful effects on the immune system and tissue homeostasis. Recent studies have revealed that the aging process is associated with the activation of immunosuppressive network, especially the functions of MDSCs, Tregs, and Mregs are increased. I will briefly review the properties of the regulatory phenotypes of immune cells and examine in detail the evidences for an activation of immunosuppressive network with aging.

Myeloid-derived suppressor cell function and epigenetic expression evolves over time after surgical sepsis

Background

Sepsis is an increasingly significant challenge throughout the world as one of the major causes of patient morbidity and mortality. Central to the host immunologic response to sepsis is the increase in circulating myeloid-derived suppressor cells (MDSCs), which have been demonstrated to be present and independently associated with poor long-term clinical outcomes. MDSCs are plastic cells and potentially modifiable, particularly through epigenetic interventions. The objective of this study was to determine how the suppressive phenotype of MDSCs evolves after sepsis in surgical ICU patients, as well as to identify epigenetic differences in MDSCs that may explain these changes.

Methods

Circulating MDSCs from 267 survivors of surgical sepsis were phenotyped at various intervals over 6 weeks, and highly enriched MDSCs from 23 of these samples were co-cultured with CD3/CD28-stimulated autologous T cells. microRNA expression from enriched MDSCs was also identified.

Results

We observed that MDSC numbers remain significantly elevated in hospitalized sepsis survivors for at least 6 weeks after their infection. However, only MDSCs obtained at and beyond 14 days post-sepsis significantly suppressed T lymphocyte proliferation and IL-2 production. These same MDSCs displayed unique epigenetic (miRNA) expression patterns compared to earlier time points.

Conclusions

We conclude that in sepsis survivors, immature myeloid cell numbers are increased but the immune suppressive function specific to MDSCs develops over time, and this is associated with a specific epigenome. These findings may explain the chronic and persistent immune suppression seen in these subjects.

Protective effect of dihydroartemisinin in inhibiting senescence of myeloid-derived suppressor cells from lupus mice via Nrf2/HO-1 pathway

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disease characterized by multi-organ injury. However, whether myeloid-derived suppressor cells (MDSCs) senescence exists and participates in SLE pathogenesis remains unclear. And whether dihydroartemisinin (DHA) attenuates the symptoms of SLE via relieving MDSCs senescence remains elusive. In the present study, we measured the senescence of MDSCs in SLE using SA-β-gal staining, senescence-associated secretory phenotype (SASP) and Western blot analysis of aging-related protein P21, P53 and P16. We identified that the MDSCs senescence promoted the SLE progress by adaptive transfer MDSCs assays. Meanwhile, we further showed DHA ameliorated the symptoms of pristane-induced lupus by histopathological detection, Western blot analysis, immunofluorescence, QPCR and flow cytometry analysis. DHA reversed MDSCs senescence by detecting SA-β-gal staining, senescence-associated secretory phenotype (SASP) and Western blot analysis of aging-related protein P21, P53 and P16. Furthermore, mechanistic analysis indicated that the inhibitory effect of DHA on MDSCs senescence was blocked by ML385, the specific antagonist of Nrf2, which revealed that the effect of DHA on MDSCs senescence was dependent on the induction of Nrf2/HO-1 pathway. Of note, we revealed that DHA inhibited MDSCs senescence to ameliorate the SLE development by adaptive transfer DHA-treated MDSCs assays. In conclusion, MDSCs senescence played a vital role in the pathogenesis of SLE, and DHA attenuated the symptoms of SLE via relieving MDSCs aging involved in the induction of Nrf2/HO-1 pathway.

mTOR and Aging: An Old Fashioned Dress

Aging is a physiologic/pathologic process characterized by a progressive impairment of cellular functions, supported by the alterations of several molecular pathways, leading to an increased cell susceptibility to injury. This deterioration is the primary risk factor for several major human pathologies. Numerous cellular processes, including genomic instability, telomere erosion, epigenetic alterations, loss of proteostasis, deregulated nutrient-sensing, mitochondrial dysfunction, stem cell exhaustion, and altered intercellular signal transduction represent common denominators of aging in different organisms. Mammalian target of rapamycin (mTOR) is an evolutionarily conserved nutrient sensing protein kinase that regulates growth and metabolism in all eukaryotic cells. Studies in flies, worms, yeast, and mice support the hypothesis that the mTOR signalling network plays a pivotal role in modulating aging. mTOR is emerging as the most robust mediator of the protective effects of various forms of dietary restriction, which has been shown to extend lifespan and slow the onset of age-related diseases across species. Herein we discuss the role of mTor signalling network in the development of classic age-related diseases, focused on cardiovascular system, immune response, and cancer.

AMPK activation inhibits the functions of myeloid-derived suppressor cells (MDSC): impact on cancer and aging

AMP-activated protein kinase (AMPK) has a crucial role not only in the regulation of tissue energy metabolism but it can also control immune responses through its cooperation with immune signaling pathways, thus affecting immunometabolism and the functions of immune cells. It is known that AMPK signaling inhibits the activity of the NF-κB system and thus suppresses pro-inflammatory responses. Interestingly, AMPK activation can inhibit several major immune signaling pathways, e.g., the JAK-STAT, NF-κB, C/EBPβ, CHOP, and HIF-1α pathways, which induce the expansion and activation of myeloid-derived suppressor cells (MDSC). MDSCs induce an immunosuppressive microenvironment in tumors and thus allow the escape of tumor cells from immune surveillance. Chronic inflammation has a key role in the expansion and activation of MDSCs in both tumors and inflammatory disorders. The numbers of MDSCs also significantly increase during the aging process concurrently with the immunosenescence associated with chronic low-grade inflammation. Increased fatty acid oxidation and lactate produced by aerobic glycolysis are important immunometabolic enhancers of MDSC functions. However, it seems that AMPK signaling regulates the functions of MDSCs in a context-dependent manner. Currently, the activators of AMPK signaling are promising drug candidates for cancer therapy and possibly for the extension of healthspan and lifespan. We will describe in detail the AMPK-mediated regulation of the signaling pathways controlling the expansion and activation of immunosuppressive MDSCs. We will propose that the beneficial effects mediated by AMPK activation, e.g., in cancers and the aging process, could be induced by the inhibition of MDSC functions.

CCR5/CCR5 ligand-induced myeloid-derived suppressor cells are related to the progression of endometriosis

RESEARCH QUESTION

Immunological disorders have been reported to promote the progression of endometriosis. Several recent studies have shown that myeloid-derived suppressor cells (MDSC) drive the progression of endometriosis. The aim of this case-control study was to test whether CCR5 and its ligands drive MDSC accumulation and play a role in the progression of endometriosis.

DESIGN

Thirty-six endometriosis patients and 20 controls were recruited. All subjects underwent laparoscopy. An ELISA kit was used to define CCR5 ligands in plasma and peritoneal fluid from endometriosis patients; flow cytometry was then used to characterize CCR5⁺MDSC in peripheral blood and peritoneal fluid.

RESULTS

Data showed that endometriosis patients displayed a significantly higher production of plasma CCL3 (P = 0.046) and peritoneal fluid CCL3/5 (P = 0.042/0.036) compared with those from the uterine leiomyoma group. Furthermore, the concentrations of peritoneal fluid CCL5 were elevated in late stage patients compared with those from the uterine leiomyoma group. Accumulation of blood CCR5⁺Mo-MDSC was detected in endometriosis patients compared with those from both the ovarian dermoid cysts and uterine leiomyoma groups. Endometriosis patients also showed an elevation of CCR5⁺MDSC and CCR5⁺Mo-MDSC in peritoneal fluid samples compared with uterine leiomyoma samples. It was also found that enrichment of CCR5⁺MDSC (r = 0.6807; P < 0.0001) and CCR5⁺Mo-MDSC (r = 0.6893; P < 0.0001) were correlated with enhanced production of CCL5 in peritoneal fluid from endometriosis patients.

CONCLUSIONS

This study showed that CCR5 and its ligands could drive the progression of endometriosis by enhancing the accumulation of MDSC. These findings might produce a promising treatment that targets CCR5⁺MDSC for endometriosis patients.

Immunosenescence: the potential role of myeloid-derived suppressor cells (MDSC) in age-related immune deficiency

The aging process is associated with chronic low-grade inflammation in both humans and rodents, commonly called inflammaging. At the same time, there is a gradual decline in the functional capacity of adaptive and innate immune systems, i.e., immunosenescence, a process not only linked to the aging process, but also encountered in several pathological conditions involving chronic inflammation. The hallmarks of immunosenescence include a decline in the numbers of naïve CD4+ and CD8+ T cells, an imbalance in the T cell subsets, and a decrease in T cell receptor (TCR) repertoire and signaling. Correspondingly, there is a decline in B cell lymphopoiesis and a reduction in antibody production. The age-related changes are not as profound in innate immunity as they are in adaptive immunity. However, there are distinct functional deficiencies in dendritic cells, natural killer cells, and monocytes/macrophages with aging. Interestingly, the immunosuppression induced by myeloid-derived suppressor cells (MDSC) in diverse inflammatory conditions also targets mainly the T and B cell compartments, i.e., inducing very similar alterations to those present in immunosenescence. Here, we will compare the immune profiles induced by immunosenescence and the MDSC-driven immunosuppression. Given that the appearance of MDSCs significantly increases with aging and MDSCs are the enhancers of other immunosuppressive cells, e.g., regulatory T cells (Tregs) and B cells (Bregs), it seems likely that MDSCs might remodel the immune system, thus preventing excessive inflammation with aging. We propose that MDSCs are potent inducers of immunosenescence.

Influence of Interleukin-8 and Neutrophil Extracellular Trap (NET) Formation in the Tumor Microenvironment: Is There a Pathogenic Role?

In this review, we will highlight several studies that revolve around interleukin-8 (IL-8) and show the multiple facets that could take in the tumor microenvironment. Chemokines that attract neutrophils (to a large extent, IL-8) can have a bimodal behavior inducing the migration of them in the first place and later favoring the formation of NETs in the place of emission focus of the chemokine. Also, this mechanism occurs when neutrophils migrate to tumor cells and where the extrusion of NETs in the tumor is observed. A possible participation of NETs in cancer progression was considered; however, until now, it is difficult to decide if NETosis plays a pro- or antitumor role, although it is necessary to emphasize that there is more experimentation focused on the protumorigenic aspect of the NETs. The formation of NETs has a relevant role in the inhibition of the immune response against the tumor generated by neutrophils and in turn favoring the processes involved in the development of tumor metastasis. It is striking that we do not have more complete information about the effects of circulating chemokines on neutrophils in cancer patients and hence the suitability of this review. No one has observed to date the impact that it could have on other cell populations to inhibit the arrival of neutrophils and the formation/elimination of NETs. However, the extent to which NETs affect the function of other cells of the immune system in the tumor context has not been directly demonstrated. It is necessary to identify possible combinations of immunotherapy that involve the modulation of neutrophil activity with other strategies (immunomodulatory antibodies or adoptive cell therapy). Therefore, knowing the mechanisms by which tumors take advantage of this ability of neutrophils to form NETs is very important in the search for antitumor therapies and thus be able to take advantage of the possible immunotherapeutic combinations that we currently have in clinical practice.