Differential expression of the fractalkine chemokine receptor (CX3CR1) in human monocytes during differentiation

Elucidating the role of chemokines in inflammaging associated atherosclerotic cardiovascular diseases

Age-related inflammation or inflammaging is a critical deciding factor of physiological homeostasis during aging. Cardiovascular diseases (CVDs) are exquisitely associated with aging and inflammation and are one of the leading causes of high mortality in the elderly population. Inflammaging comprises dysregulation of crosstalk between the vascular and cardiac tissues that deteriorates the vasculature network leading to development of atherosclerosis and atherosclerotic-associated CVDs in elderly populations. Leukocyte differentiation, migration and recruitment holds a crucial position in both inflammaging and atherosclerotic CVDs through relaying the activity of an intricate network of inflammation-associated protein-protein interactions. Among these interactions, small immunoproteins such as chemokines play a major role in the progression of inflammaging and atherosclerosis. Chemokines are actively involved in lymphocyte migration and severe inflammatory response at the site of injury. They relay their functions via chemokine-G protein-coupled receptors-glycosaminoglycan signaling axis and is a principal part for the detection of age-related atherosclerosis and related CVDs. This review focuses on highlighting the detailed intricacies of the effects of chemokine-receptor interaction and chemokine oligomerization on lymphocyte recruitment and its evident role in clinical manifestations of atherosclerosis and related CVDs. Further, the role of chemokine mediated signaling for formulating next-generation therapeutics against atherosclerosis has also been discussed.

Activation of CD14+ Monocytes via the IFN-γ Signaling Pathway Is Associated with Immune-Related Adverse Events in Hepatocellular Carcinoma Patients Receiving PD-1 Inhibition Combination Therapy

(1) Background: Immune-related adverse events (irAEs) are a series of unique organ-specific inflammatory toxicities observed in patients with hepatocellular carcinoma (HCC) undergoing PD-1 inhibition combination therapy. The specific underlying mechanisms remain unclear. (2) Methods: We recruited 71 patients with HCC undergoing PD-1 inhibition combination therapy. These patients were then divided into two groups based on irAE occurrence: 34 had irAEs and 37 did not. Using Olink proteomics, we analyzed the aberrant inflammation-related proteins (IRPs) in these patient groups. For single-cell RNA sequencing (scRNA-seq) analysis, we collected peripheral blood mononuclear cells (PBMCs) from two representative patients at the pretreatment, irAE occurrence, and resolution stages. (3) Results: Our study revealed distinct plasma protein signatures in HCC patients experiencing irAEs after PD-1 inhibition combination therapy. We clarified the relationship between monocyte activation and irAEs, identified a strongly associated CD14-MC-CCL3 monocyte subset, and explored the role of the IFN-γ signaling pathway in monocyte activation during irAEs. (4) Conclusions: The activation of monocytes induced by the IFN-γ signaling pathway is an important mechanism underlying the occurrence of irAEs in HCC patients receiving PD-1 inhibition combination therapy.

Macrophagic HDAC3 inhibition ameliorates Dextran Sulfate Sodium induced inflammatory bowel disease through GBP5-NLRP3 pathway

Inflammatory bowel disease (IBD) is a chronic inflammatory intestinal disease, characterized by dysregulated immune response. HDAC3 is reported to be an epigenetic brake in inflammation, playing critical roles in macrophages. However, its role in IBD is unclear. In our study, we found HDAC3 was upregulated in CX3CR1-positive cells in the mucosa from IBD mice. Conditional knockout (cKO) of Hdac3 in CX3CR1 positive cells attenuated the disease severity of Dextran Sulfate Sodium (DSS)-induced colitis. In addition, inhibition of HDAC3 with RGFP966 could also alleviate the DSS-induced tissue injury and inflammation in IBD. The RNA sequencing results revealed that Hdac3 cKO restrained DSS-induced upregulation of genes in the pathways of cytokine-cytokine receptor interaction, complement and coagulation cascades, chemokine signaling, and extracellular matrix receptor interaction. We also identified that Guanylate-Binding Protein 5 (GBP5) was transcriptionally regulated by HDAC3 in monocytes by RNA sequencing. Inhibition of HDAC3 resulted in decreased transcriptional activity of interferon-gamma-induced expression of GBP5 in CX3CR1-positive cells, such as macrophages and microglia. Overexpression of HDAC3 upregulated the transcriptional activity of GBP5 reporter. Lastly, conditional knockout of Hdac3 in macrophages (Hdac3 mKO) attenuated the disease severity of DSS-induced colitis. In conclusion, inhibition of HDAC3 in macrophages could ameliorate the disease severity and inflammatory response in colitis by regulating GBP5-NLRP3 axis, identifying a new therapeutic avenue for the treatment of colitis.

Obesity-related Plasma CXCL10 Drives CX3CR1-dependent Monocytic Secretion of Macrophage Migration Inhibitory Factor

Obesity is characterized by excessive body fat accumulation and comorbidities such as diabetes mellitus, cardiovascular disease, and obstructive sleep apnea syndrome (OSAS). Both obesity and OSAS are associated with immune disturbance, alterations of systemic inflammatory mediators, and immune cell recruitment to metabolic tissues. Chemokine CXCL10 is an important regulator of proinflammatory immune responses and is significantly increased in patients with severe obesity. This research project aims to investigate the impact of CXCL10 on human monocytes in patients with obesity. We studied the distribution of the CD14/CD16 monocyte subsets as well as their CX3CR1 expression patterns in whole-blood measurements from 92 patients with obesity and/or OSAS with regard to plasma CXCL10 values and individual clinical parameters. Furthermore, cytokine secretion by THP-1 monocytes in response to CXCL10 was analyzed. Data revealed significantly elevated plasma CXCL10 in patients with obesity with an additive effect of OSAS. CXCL10 was found to drive monocytic secretion of macrophage migration inhibitory factor via receptor protein CX3CR1, which significantly correlated with the individual body mass index. Our data show, for the first time, to our knowledge, that CX3CR1 is involved in alternative CXCL10 signaling in human monocytes in obesity-related inflammation. Obesity is a multifactorial disease, and further investigations regarding the complex interplay between obesity-related inflammatory mediators and systemic immune balances will help to better understand and improve the individual situation of our patients.

Spinal Cord Stimulation Increases Chemoefficacy and Prevents Paclitaxel-Induced Pain via CX3CL1

INTRODUCTION

Despite increasing utilization of spinal cord stimulation (SCS), its effects on chemoefficacy, cancer progression, and chemotherapy-induced peripheral neuropathy (CIPN) pain remain unclear. Up to 30% of adults who are cancer survivors may suffer from CIPN, and there are currently no effective preventative treatments.

MATERIALS AND METHODS

Through a combination of bioluminescent imaging, behavioral, biochemical, and immunohistochemical approaches, we investigated the role of SCS and paclitaxel (PTX) on tumor growth and PTX-induced peripheral neuropathy (PIPN) pain development in T-cell-deficient male rats (Crl:NIH-Foxn1rnu) with xenograft human non-small cell lung cancer. We hypothesized that SCS can prevent CIPN pain and enhance chemoefficacy partially by modulating macrophages, fractalkine (CX3CL1), and inflammatory cytokines.

RESULTS

We show that preemptive SCS enhanced the antitumor efficacy of PTX and prevented PIPN pain. Without SCS, rats with and without tumors developed robust PIPN pain-related mechanical hypersensitivity, but only those with tumors developed cold hypersensitivity, suggesting T-cell dependence for different PIPN pain modalities. SCS increased soluble CX3CL1 and macrophages and decreased neuronal and nonneuronal insoluble CX3CL1 expression and inflammation in dorsal root ganglia.

CONCLUSION

Collectively, our findings suggest that preemptive SCS is a promising strategy to increase chemoefficacy and prevent PIPN pain via CX3CL1-macrophage modulation.

Fractalkine Improves the Expression of Endometrium Receptivity-Related Genes and Proteins at Desferrioxamine-Induced Iron Deficiency in HEC-1A Cells

Fractalkine (CX3CL1/FKN) is a unique chemokine belonging to the CX3C chemokine subclass. FKN exists in two forms: a membrane-bound form expressed by both endometrium cells and trophoblasts thought to be implicated in maternal-fetal interaction and a soluble form expressed by endometrium cells. Endometrium receptivity is crucial in embryo implantation and a complex process regulated by large numbers of proteins, e.g., cytokines, progesterone receptor (PR), SOX-17, prostaglandin receptors (PTGER2), and tissue inhibitors of metalloproteinases (TIMPs). It has also been reported that iron is important in fertility and affects the iron status of the mother. Therefore, iron availability in the embryo contributes to fertilization and pregnancy. In this study, we focused on the effect of iron deficiency on the secreted cytokines (IL-6, IL-1β, leukocyte inhibitory factor, TGF-β), chemokines (IL-8, FKN), and other regulatory proteins (bone morphogenic protein 2, activin, follistatin, PR, SOX-17, prostaglandin E2 receptor, TIMP2), and the modifying effect of FKN on the expression of these proteins, which may improve endometrium receptivity. Endometrial iron deficiency was mediated by desferrioxamine (DFO) treatment of HEC-1A cells. FKN was added to the cells 24 h and 48 h after DFO with or without serum for modelling the possible iron dependence of the alterations. Our findings support the hypothesis that FKN ameliorates the effects of anemia on the receptivity-related genes and proteins in HEC-1A cells by increasing the secretion of the receptivity-related cytokines via the fractalkine receptor (CX3CR1). FKN may contribute to cell proliferation and differentiation by regulating activin, follistatin, and BMP2 expressions, and to implantation by altering the protein levels of PR, SOX-17, PTGER2, and TIMP2. FKN mitigates the negative effect of iron deficiency on the receptivity-related genes and proteins of HEC-1A endometrium cells, suggesting its important role in the regulation of endometrium receptivity.

Plasma Leptin Levels, Obstructive Sleep Apnea Syndrome, and Diabetes Are Associated with Obesity-Related Alterations of Peripheral Blood Monocyte Subsets

Obesity is a dramatically increasing disease, accompanied with comorbidities such as cardiovascular disease and obstructive sleep apnea syndrome (OSAS). Both obesity and OSAS per se are associated with systemic inflammation. However, the multifactorial impact of obesity, OSAS, and its concomitant diseases on the immunological characteristics of circulating monocytes has not yet been fully resolved. Monocyte subsets of 82 patients with obesity were analyzed in whole blood measurements in terms of the CD14/CD16 cell surface expression patterns and different monocytic adhesion molecules using flow cytometry. Plasma levels of adipokines adiponectin and leptin of all patients were evaluated and correlated with accompanying cellular and clinical values. Whole blood measurements revealed a significant overall redistribution of CD14/CD16 monocyte subsets in patients with obesity. Monocytic adhesion molecules CD11a, CD11b, and CX3CR1 were significantly elevated. The observed alterations significantly correlated with plasma leptin levels and diabetes status as crucial amplifying factors. The additive impact of obesity, diabetes, and OSAS on the immunological balance of peripheral blood monocytes requires a coordinated regimen in terms of therapeutic treatment, respiratory support, and weight loss to improve the systemic immunity in these patients.

Adaptive immune response in pathogenesis and treatment of head and neck squamous cell carcinoma: the influence of immunosuppression factors and gender

An obvious trend of the last decade in head and neck squamous cell carcinoma pathogenesis evaluation is awareness of the impact of immune response disorders on disease manifestation. The review presents an analysis of the differences in the type and degree of immunosuppression, as well as treatment response in head and neck squamous cell carcinoma patients in accordance with influencing carcinogenic factor, gender, age of the patient and concomitant diseases. An increase in CD8+ T-lymphocytes and a decrease of memory T-cells has been evaluated in smoking and alcohol abusing patients with head and neck squamous cell carcinoma, and a smaller number of CD8+ T-lymphocytes were detected in the tumor microenvironment compared to non-smoking and non-drinking patients. Studies have shown that the improved prognosis of patients with human papillomavirus (Hpv) – associated head and neck squamous cell carcinoma is largely due to the presence of antibodies against Hpv E6 and E7, E7-specific CD8+T lymphocytes in periphe ral blood and a high level of tumor-infiltrating T lymphocytes. The issue of gender differences in the type of immune response is widely discussed. It has been shown that the use of immune response checkpoint inhibitors is more effective in improving survival rates in men, and the use of these drugs in combination with chemotherapy is more effective in women. In addition, in elderly cancer patients, numerous age-associated T-lymphocyte’s function changes were revealed, including a decrease in the number of naive T-lymphocytes due to age-related involution of the thymus and an in crease in the relative number of memory cells and effector cells. Thus, it is clear that immunosuppression type, as well as treatment response, differ depending on the influencing factor, gender, age of the patient, as well as comorbidities.

Immunophenotyping of peripheral blood monocytes could help identify a baseline pro-inflammatory profile in women with recurrent reproductive failure

Recurrent pregnancy loss (RPL) and recurrent implantation failure (RIF) are two well-defined clinical entities, but the role of the monocytes in their pathophysiology needs to be clarified. This study aimed to evaluate the role of the three monocyte subsets (classical, intermediate, and non-classical) and relevant cytokines/chemokines in a cohort of RPL and RIF women to better characterize a baseline proinflammatory profile that could define inflammatory pathophysiology in these two different conditions. We evaluated 108 non-pregnant women: 53 RPL, 24 RIF, and 31 fertile healthy controls (HC). Multiparametric flow cytometry was used to quantify the frequency of surface chemokine receptors (CCR2, CCR5, and CX3CR1) on the monocyte subsets. Cytokines were assessed in plasma samples using a multiplex assay. The CX3CR1⁺ and CCR5⁺ intermediate monocytes were significantly higher in RPL and RIF compared to HC. A significant positive correlation was observed between CX3CR1⁺ intermediate monocytes and IL-17A (P = .03, r = 0.43). The Boruta algorithm followed by a multivariate logistic regression model was used to select the most relevant variables that could help define RPL and RIF: in RPL were CX3CR1 non-classical monocytes, TGF-β1, and CCR5 intermediate monocytes; in RIF: CCR5 intermediate monocytes and TGF-β3. The combination of these variables could predict RPL and RIF with 90 % and 82 %, respectively. Our study suggests that a combination of specific blood monocyte subsets and cytokines could aid in identifying RPL and RIF women with a pro-inflammatory profile. These findings could provide a more integrated understanding of these pathologies. Further investigation and validation in independent cohorts are warranted.

Effects of Stromal Cell Conditioned Medium and Antipurinergic Treatment on Macrophage Phenotype

The immunomodulatory capacity of the human mesenchymal stromal cell (MSC) secretome has been a critical driver for the development of cell-free MSC products, such as conditioned medium (CM), for regenerative medicine applications. This is particularly true as cell-free MSC products present several advantages over direct autologous or allogeneic MSC delivery with respect to safety, manufacturability, and defined potency. Recently, significant effort has been placed into creating novel MSC CM formulations with an immunomodulatory capacity tailored for specific regenerative contexts. For instance, the immunoregulatory nature of MSC CM has previously been tuned through a number of cytokine-priming strategies. Herein, we propose an alternate method to tailor the immunomodulatory "phenotype" of cytokine-primed MSC CM through coupling with the pharmacological agent, suramin. Suramin interferes with the signaling of purines including extracellular adenosine triphosphate (ATP), which plays a critical role in the activation of the innate immune system after injury. Toward this end, human THP-1-derived macrophages were activated to a proinflammatory phenotype and treated with (1) unprimed/native MSC CM, (2) interferon-γ/tumor necrosis factor α-primed MSC CM (primed CM), (3) suramin alone, or (4) primed MSC CM and suramin (primed CM/suramin). Markers of key macrophage functions-cytokine secretion, autophagy, oxidative stress modulation, and activation/migration-were assessed. Consistent with previous literature, primed CM elevated macrophage secretion of several proinflammatory and pleiotropic cytokines relative to native CM; whereas addition of suramin imparted consistent shifts in terms of TNFα (↓), interleukin-10 (↓), and hepatocyte growth factor (↑) irrespective of CM. In addition, both primed CM and suramin, individually and combined, increased reactive oxygen species production relative to native CM, and addition of suramin to primed CM shifted levels of CX3CL1, a factor involved in ATP-associated macrophage regulation. Varimax rotation assessment of the secreted cytokine profiles confirmed that primed CM/suramin resulted in a THP-1 phenotypic shift away from the lipopolysaccharide-activated proinflammatory state that was distinct from that of primed CM or native CM alone. This altered primed CM/suramin-associated phenotype may prove beneficial for healing in certain regenerative contexts. These results may inform future work coupling antipurinergic treatments with MSC-derived therapies in regenerative medicine applications.

Monocyte Recruitment for Vascular Tissue Regeneration

A strategy to recruit monocytes (MCs) from blood to regenerate vascular tissue from unseeded (cell-free) tissue engineered vascular grafts is presented. When immobilized on the surface of vascular grafts, the fusion protein, H2R5 can capture blood-derived MC under static or flow conditions in a shear stress dependent manner. The bound MC turns into macrophages (Mϕ) expressing both M1 and M2 phenotype specific genes. When H2R5 functionalized acellular-tissue engineered vessels (A-TEVs) are implanted into the mouse aorta, they remain patent and form a continuous endothelium expressing both endothelial cell (EC) and MC specific proteins. Underneath the EC layer, multiple cells layers are formed coexpressing both smooth muscle cell (SMC) and MC specific markers. Lineage tracing analysis using a novel CX3CR1-confetti mouse model demonstrates that fluorescently labeled MC populates the graft lumen by two and four weeks postimplantation, providing direct evidence in support of MC/Mϕ recruitment to the graft lumen. Given their abundance in the blood, circulating MCs may be a great source of cells that contribute directly to the endothelialization and vascular wall formation of acellular vascular grafts under the right chemical and biomechanical cues.

Placental dysfunction influences fetal monocyte subpopulation gene expression in preterm birth

The placenta is the primary organ for immune regulation, nutrient delivery, gas exchange, protection against environmental toxins, and physiologic perturbations during pregnancy. Placental inflammation and vascular dysfunction during pregnancy are associated with a growing list of prematurity-related complications. The goal of this study was to identify differences in gene expression profiles in fetal monocytes - cells that persist and differentiate postnatally - according to distinct placental histologic domains. Here, by using bulk RNA-Seq, we report that placental lesions are associated with gene expression changes in fetal monocyte subsets. Specifically, we found that fetal monocytes exposed to acute placental inflammation upregulate biological processes related to monocyte activation, monocyte chemotaxis, and platelet function, while monocytes exposed to maternal vascular malperfusion lesions downregulate these processes. Additionally, we show that intermediate monocytes might be a source of mitogens, such as HBEGF, NRG1, and VEGFA, implicated in different outcomes related to prematurity. This is the first study to our knowledge to show that placental lesions are associated with unique changes in fetal monocytes and monocyte subsets. As fetal monocytes persist and differentiate into various phagocytic cells following birth, our study may provide insight into morbidity related to prematurity and ultimately potential therapeutic targets.

Smoking-, Alcohol-, and Age-Related Alterations of Blood Monocyte Subsets and Circulating CD4/CD8 T Cells in Head and Neck Cancer

Head and neck squamous cell carcinoma (HNSCC) represents a heterogeneous malignant disease of the oral cavity, pharynx, and larynx. Although cigarette smoking, alcohol abuse, and aging are well-established associated factors for HNSCC, their respective influence on immunologic alterations of monocyte subsets or T-cell compositions in the peripheral blood has not yet been fully unveiled. Using flow cytometry, whole blood measurements of CD14/CD16 monocyte subsets and analyses of T-cell subsets in isolated PBMC fractions were carried out in 64 HNSCC patients in view of their tobacco and alcohol consumption, as well as their age, in comparison to healthy volunteers. Flow cytometric analysis revealed significantly increased expression of monocytic CD11b, as well as significantly decreased expression levels of CX3CR1 on classical and intermediate monocyte subsets in smoking-related and in alcohol-related HNSCC patients compared to healthy donors. Peripheral monocytes revealed an age-correlated significant decrease in PD-L1 within the entirety of the HNSCC cohort. Furthermore, we observed significantly decreased abundances of CD8+ effector memory T cells in active-smoking HNSCC patients and significantly increased percentages of CD8+ effector T cells in alcohol-abusing patients compared to the non-smoking/non-drinking patient cohort. Our data indicate an enhanced influence of smoking and alcohol abuse on the dynamics and characteristics of circulating monocyte subsets and CD4/CD8 T-cell subset proportions, as well as an age-related weakened immunosuppression in head and neck cancer patients.

Vasculogenic mimicry structures in melanoma support the recruitment of monocytes

The progression of cancer is facilitated by infiltrating leukocytes which can either actively kill cancer cells or promote their survival. Our current understanding of leukocyte recruitment into tumors is largely limited to the adhesion molecules and chemokines expressed by conventional blood vessels that are lined by endothelial cells (ECs). However, cancer cells themselves can form their own vascular structures (a process known as vasculogenic mimicry (VM)); but whether they actively participate in the recruitment of leukocytes remains to be elucidated. Herein, we demonstrate that VM-competent human melanoma cell lines express multiple adhesion molecules (e.g. CD44, intercellular adhesion molecule (ICAM)-1 and junction adhesion molecules (JAMs)) and chemokines (e.g. CXCL8 and CXCL12) relevant for leukocyte recruitment. Microfluidic-based adhesion assays revealed that similar to ECs, VM-competent melanoma cells facilitate the rolling and adhesion of leukocytes, particularly monocytes, under conditions of shear flow. Moreover, we identified ICAM-1 to be a key participant in this process. Transwell assays showed that, similar to ECs, VM-competent melanoma cells facilitate monocyte transmigration toward a chemotactic gradient. Gene expression profiling of human melanoma patient samples confirmed the expression of numerous leukocyte capture adhesion molecules and chemokines. Finally, immunostaining of patient tissue microarrays revealed that tumors with high VM content also contained higher numbers of leukocytes (including macrophages). Taken together, this study suggests an underappreciated role of VM vessels in solid tumors via their active participation in leukocyte recruitment and begins to identify key adhesion molecules and chemokines that underpin this process.

Immunopathology of RSV: An Updated Review

RSV is a leading cause of respiratory tract disease in infants and the elderly. RSV has limited therapeutic interventions and no FDA-approved vaccine. Gaps in our understanding of virus-host interactions and immunity contribute to the lack of biological countermeasures. This review updates the current understanding of RSV immunity and immunopathology with a focus on interferon responses, animal modeling, and correlates of protection.

Key Chemokine Pathways in Atherosclerosis and Their Therapeutic Potential

The search to improve therapies to prevent or treat cardiovascular diseases (CVDs) rages on, as CVDs remain a leading cause of death worldwide. Here, the main cause of CVDs, atherosclerosis, and its prevention, take center stage. Chemokines and their receptors have long been known to play an important role in the pathophysiological development of atherosclerosis. Their role extends from the initiation to the progression, and even the potential regression of atherosclerotic lesions. These important regulators in atherosclerosis are therefore an obvious target in the development of therapeutic strategies. A plethora of preclinical studies have assessed various possibilities for targeting chemokine signaling via various approaches, including competitive ligands and microRNAs, which have shown promising results in ameliorating atherosclerosis. Developments in the field also include detailed imaging with tracers that target specific chemokine receptors. Lastly, clinical trials revealed the potential of various therapies but still require further investigation before commencing clinical use. Although there is still a lot to be learned and investigated, it is clear that chemokines and their receptors present attractive yet extremely complex therapeutic targets. Therefore, this review will serve to provide a general overview of the connection between various chemokines and their receptors with atherosclerosis. The different developments, including mouse models and clinical trials that tackle this complex interplay will also be explored.

The Phagocytic Code Regulating Phagocytosis of Mammalian Cells

Mammalian phagocytes can phagocytose (i.e. eat) other mammalian cells in the body if they display certain signals, and this phagocytosis plays fundamental roles in development, cell turnover, tissue homeostasis and disease prevention. To phagocytose the correct cells, phagocytes must discriminate which cells to eat using a 'phagocytic code' - a set of over 50 known phagocytic signals determining whether a cell is eaten or not - comprising find-me signals, eat-me signals, don't-eat-me signals and opsonins. Most opsonins require binding to eat-me signals - for example, the opsonins galectin-3, calreticulin and C1q bind asialoglycan eat-me signals on target cells - to induce phagocytosis. Some proteins act as 'self-opsonins', while others are 'negative opsonins' or 'phagocyte suppressants', inhibiting phagocytosis. We review known phagocytic signals here, both established and novel, and how they integrate to regulate phagocytosis of several mammalian targets - including excess cells in development, senescent and aged cells, infected cells, cancer cells, dead or dying cells, cell debris and neuronal synapses. Understanding the phagocytic code, and how it goes wrong, may enable novel therapies for multiple pathologies with too much or too little phagocytosis, such as: infectious disease, cancer, neurodegeneration, psychiatric disease, cardiovascular disease, ageing and auto-immune disease.

Fractalkine enhances endometrial receptivity and activates iron transport towards trophoblast cells in an in vitro co-culture system of HEC-1A and JEG-3 cells

Endometrium receptivity and successful implantation require a complex network of regulatory factors whom production is strictly controlled especially at the implantation window. Many regulators like steroid hormones, prostaglandins, cytokines, extracellular matrix proteins and downstream cell signalling pathways are involved in the process of embryo-endometrium interaction. Our work reveals the effect of fractalkine (FKN), a unique chemokine on progesterone receptor, SOX-17 and NRF2 expressions in HEC-1A endometrial cell line. FKN activates fractalkine receptor signalling and the expression of SOX-17 through progesterone receptor in HEC-1A endometrial cells, and as a consequence it increases endometrial receptivity. Fractalkine also activates the NRF2-Keap-1 signal transduction pathway regulating the IL-6 and IL-1β cytokine productions, which increase endometrial receptivity, as well. The NRF2 transcription factor increases the expression of the iron exporter ferroportin in HEC-1A cells activating iron release towards JEG-3 trophoblast cells. The iron measurements show that iron content of endometrial cells decreases while heme concentration increases at FKN treatment. At the same time, the trophoblast cells show increased iron uptake and total iron content. Based on our results it seems that FKN enhances the establishment of endometrial receptivity and meanwhile it regulates the iron homeostasis of endometrium contributing to the iron availability of the trophoblast cells and the embryo.

Interleukin-6 mediates neutrophil mobilization from bone marrow in pulmonary hypertension

Myeloid cells, such as neutrophils, are produced in the bone marrow in high quantities and are important in the pathogenesis of vascular diseases such as pulmonary hypertension (PH). Although neutrophil recruitment into sites of inflammation has been well studied, the mechanisms of neutrophil egress from the bone marrow are not well understood. Using computational flow cytometry, we observed increased neutrophils in the lungs of patients and mice with PH. Moreover, we found elevated levels of IL-6 in the blood and lungs of patients and mice with PH. We observed that transgenic mice overexpressing Il-6 in the lungs displayed elevated neutrophil egress from the bone marrow and exaggerated neutrophil recruitment to the lungs, resulting in exacerbated pulmonary vascular remodeling, and dysfunctional hemodynamics. Mechanistically, we found that IL-6-induced neutrophil egress from the bone marrow was dependent on interferon regulatory factor 4 (IRF-4)-mediated CX₃CR1 expression in neutrophils. Consequently, Cx₃cr1 genetic deficiency in hematopoietic cells in Il-6-transgenic mice significantly reduced neutrophil egress from bone marrow and decreased neutrophil counts in the lungs, thus ameliorating pulmonary remodeling and hemodynamics. In summary, these findings define a novel mechanism of IL-6-induced neutrophil egress from the bone marrow and reveal a new therapeutic target to curtail neutrophil-mediated inflammation in pulmonary vascular disease.

Human NK cells prime inflammatory DC precursors to induce Tc17 differentiation

Adaptive immune responses are acknowledged to evolve from innate immunity. However, limited information exists regarding whether encounters between innate cells direct the generation of specialized T-cell subsets. We aim to understand how natural killer (NK) cells modulate cell-mediated immunity in humans. We found that human CD14+CD16- monocytes that differentiate into inflammatory dendritic cells (DCs) are shaped at the early stages of differentiation by cell-to-cell interactions with NK cells. Although a fraction of monocytes is eliminated by NK-cell-mediated cytotoxicity, the polarization of interferon-γ (IFN-γ) at the NKp30-stabilized synapses triggers a stable IFN-γ signature in surviving monocytes that persists after their differentiation into DCs. Notably, NK-cell-instructed DCs drive the priming of type 17 CD8+ T cells (Tc17) with the capacity to produce IFN-γ and interleukin-17A. Compared with healthy donors, this cellular network is impaired in patients with classical NK-cell deficiency driven by mutations in the GATA2 gene. Our findings reveal a previously unrecognized connection by which Tc17-mediated immunity might be regulated by NK-cell-mediated tuning of antigen-presenting cells.

Alterations of CCR2 and CX3CR1 on Three Monocyte Subsets During HIV-1/Treponema pallidum Coinfection

HIV-1/Treponema pallidum (T. pallidum) coinfection has become a global challenge, and three monocyte subsets express varying levels of the chemokine receptors CCR2 and CX3CR1. We recently evaluated the association between monocyte subsets and regulatory T cells in HIV-infected individuals with syphilis. Currently, the dynamic changes of CCR2 and CX3CR1 on monocyte subsets during HIV-1 and syphilis coinfection have not been fully investigated. In this study, cell surface staining was used to explore CCR2 and CX3CR1 expression on three monocyte subsets during HIV-1/T. pallidum coinfection. We found that CCR2 densities on the classical monocyte subsets decreased in acute HIV-1 infected (AHI) patients, chronic HIV-1-infected individuals without antiviral therapy (ART) (CHI+ ART–), chronic HIV-1-infected individuals receiving ART (CHI+ART+), rapid plasma reagin-positive (RPR+) individuals, CHI+ ART– plus RPR+ (CHI+RPR+ ART–) individuals, and CHI+ART+ plus RPR⁺ (CHI+RPR+ART+) individuals. CX3CR1 density increased on the three monocyte subsets during HIV-1 and/or T. pallidum infection. CX3CR1 density on the intermediate and non-classical monocyte subsets in CHI+ ART– individuals was lower than that in CHI+ART+ individuals, and CX3CR1 density on the three monocyte subsets in CHI+ART+ individuals was higher than that in CHI+RPR+ART+ individuals. Our data provide new insight into the roles of CCR2 and CX3CR1 on three monocyte subsets in HIV-1 and T. pallidum pathogenesis.

Tissue Transglutaminase Appears in Monocytes and Macrophages but Not in Lymphocytes in White Matter Multiple Sclerosis Lesions

Leukocyte infiltration is an important pathological hallmark of multiple sclerosis (MS) and is therefore targeted by current MS therapies. The enzyme tissue transglutaminase (TG2) contributes to monocyte/macrophage migration and is present in MS lesions and could be a potential therapeutic target. We examined the cellular identity of TG2-expressing cells by immunohistochemistry in white matter lesions of 13 MS patients; 9 active and chronic active lesions from 4 patients were analyzed in detail. In these active MS lesions, TG2 is predominantly expressed in leukocytes (CD45⁺) but not in cells of the lymphocyte lineage, that is, T cells (CD3⁺) and B cells (CD20⁺). In general, cells of the monocyte/macrophage lineage (CD11b⁺ or CD68⁺) are TG2⁺ but no further distinction could be made regarding pro- or anti-inflammatory macrophage subtypes. In conclusion, TG2 is abundantly present in cells of the monocyte/macrophage lineage in active white matter MS lesions. We consider that TG2 can play a role in MS as it is associated with macrophage infiltration into the CNS. As such, TG2 potentially presents a novel target for therapeutic intervention that can support available MS therapies targeting lymphocyte infiltration.

Dissecting the phenotypic and functional heterogeneity of mouse inflammatory osteoclasts by the expression of Cx3cr1

Bone destruction relies on interactions between bone and immune cells. Bone-resorbing osteoclasts (OCLs) were recently identified as innate immune cells activating T cells toward tolerance or inflammation. Thus, pathological bone destruction not only relies on increased osteoclast differentiation, but also on the presence of inflammatory OCLs (i-OCLs), part of which express Cx3cr1. Here, we investigated the contribution of mouse Cx3cr1⁺ and Cx3cr1^neg i-OCLs to bone loss. We showed that Cx3cr1⁺ and Cx3cr1^neg i-OCLs differ considerably in transcriptional and functional aspects. Cx3cr1^neg i-OCLs have a high ability to resorb bone and activate inflammatory CD4⁺ T cells. Although Cx3cr1⁺ i-OCLs are associated with inflammation, they resorb less and have in vitro an immune-suppressive effect on Cx3cr1^neg i-OCLs, mediated by PD-L1. Our results provide new insights into i-OCL heterogeneity. They also reveal that different i-OCL subsets may interact to regulate inflammation. This contributes to a better understanding and prevention of inflammatory bone destruction.

Elevated soluble TNFα levels and upregulated TNFα mRNA expression in purified peripheral blood monocyte subsets associated with high-grade hepatocellular carcinoma

BACKGROUND

Chronic inflammation is involved in the initiation and progression of various cancers, including liver cancer. The current study focuses on the characterization of the peripheral immune response in hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) patients, before and after surgical procedure, in order to assess the effect of tumor resection in the immune system homeostasis and to determine possible prognostic factors associated with high-grade tumors. We developed a whole-blood assay to monitor immune alterations and functional competence of peripheral monocytes in a group of 10 healthy individuals (HG), in 20 HCC patients and 8 CCA patients, by multi-color flow cytometry, qRT-PCR, and ELISA techniques.

RESULTS

The qRT-PCR analysis showed an upregulation of TNFα expression by classical and intermediate monocytes purified from HCC patients presenting tumors in grade G3-G4 as compared to G1-G2 HCC patients. Moreover, ELISA assay confirmed elevated serum levels of TNFα in G3-G4 compared to G1-G2 HCC patients. A significant decrease of circulating non-classical monocytes was detected in both CCA and HCC patients before and after surgical procedure. In addition, a functional defect in circulating classical and intermediate monocytes was observed in both groups of cancer patients when compared to the HG, with partial recovery after the surgical intervention.

CONCLUSIONS

This integrated analysis permitted the identification of altered functional competence of monocyte subsets in CCA and HCC patients. In addition, our results point to a potential role of TNFα as a prognostic peripheral biomarker in HCC patients, indicating the presence of high-grade tumors that should be further validated.

Metastatic breast cancer cells induce altered microglial morphology and electrical excitability in vivo

BACKGROUND

An emerging problem in the treatment of breast cancer is the increasing incidence of metastases to the brain. Metastatic brain tumours are incurable and can cause epileptic seizures and cognitive impairment, so better understanding of this niche, and the cellular mechanisms, is urgently required. Microglia are the resident brain macrophage population, becoming "activated" by neuronal injury, eliciting an inflammatory response. Microglia promote proliferation, angiogenesis and invasion in brain tumours and metastases. However, the mechanisms underlying microglial involvement appear complex and better models are required to improve understanding of function.

METHODS

Here, we sought to address this need by developing a model to study metastatic breast cancer cell-microglial interactions using intravital imaging combined with ex vivo electrophysiology. We implanted an optical window on the parietal bone to facilitate observation of cellular behaviour in situ in the outer cortex of heterozygous Cx3cr1GFP/+ mice.

RESULTS

We detected GFP-expressing microglia in Cx3cr1GFP/+ mice up to 350 μm below the window without significant loss of resolution. When DsRed-expressing metastatic MDA-MB-231 breast cancer cells were implanted in Matrigel under the optical window, significant accumulation of activated microglia around invading tumour cells could be observed. This inflammatory response resulted in significant cortical disorganisation and aberrant spontaneously-occurring local field potential spike events around the metastatic site.

CONCLUSIONS

These data suggest that peritumoral microglial activation and accumulation may play a critical role in local tissue changes underpinning aberrant cortical activity, which offers a possible mechanism for the disrupted cognitive performance and seizures seen in patients with metastatic breast cancer.

Lactobacillus rescues postnatal neurobehavioral and microglial dysfunction in a model of maternal microbiome dysbiosis

Increasing reports of pregnancy events leading to maternal microbiome dysbiosis (MMD) show strong correlates with atypical neurodevelopmental outcomes. However, the mechanism(s) driving microbiome-mediated behavioral dysfunction in offspring remain understudied. Here, we demonstrate the presence of a novel gut commensal bacterium strain, Lactobacillus murinus HU-1, was sufficient to rescue behavioral deficits and brain region-specific microglial activationobserved in MMD-reared murine offspring. We furtheridentified a postnatal window of susceptibility that could prevent social impairments with timed maternal administration of the symbiotic bacterium. Moreover, MMD increased expression of microglial senescence genes, Trp53 and Il1β, and Cx3cr1 protein in the prefrontal cortex, which correlated with dysfunctional modeling of synapses and accompanied dysbiosis-induced microglial activation. MMD male offspring harboring Lactobacillus murinus HU-1 or lacking Cx3cr1 showed amelioration of these effects. The current study describes a new avenue of influence by which maternally transferred Lactobacillus drives proper development of social behavior in the offspring through microglia-specific regulation of Cx3cr1 signaling.

The Role of Macrophages in the Infarcted Myocardium: Orchestrators of ECM Remodeling

Myocardial infarction is the most common form of acute cardiac injury attributing to heart failure. While there have been significant advances in current therapies, mortality and morbidity remain high. Emphasis on inflammation and extracellular matrix remodeling as key pathological factors has brought to light new potential therapeutic targets including macrophages which are central players in the inflammatory response following myocardial infarction. Blood derived and tissue resident macrophages exhibit both a pro- and anti-inflammatory phenotype, essential for removing injured tissue and facilitating repair, respectively. Sustained activation of pro-inflammatory macrophages evokes extensive remodeling of cardiac tissue through secretion of matrix proteases and activation of myofibroblasts. As the heart continues to employ methods of remodeling and repair, a destructive cycle prevails ultimately leading to deterioration of cardiac function and heart failure. This review summarizes not only the traditionally accepted role of macrophages in the heart but also recent advances that have deepened our understanding and appreciation of this dynamic cell. We discuss the role of macrophages in normal and maladaptive matrix remodeling, as well as studies to date which have aimed to target the inflammatory response in combatting excessive matrix deposition and subsequent heart failure.

Cell-autonomous FLT3L shedding via ADAM10 mediates conventional dendritic cell development in mouse spleen

Conventional dendritic cells (cDCs) derive from bone marrow (BM) precursors that undergo cascades of developmental programs to terminally differentiate in peripheral tissues. Pre-cDC1s and pre-cDC2s commit in the BM to each differentiate into CD8α⁺/CD103⁺ cDC1s and CD11b⁺ cDC2s, respectively. Although both cDCs rely on the cytokine FLT3L during development, mechanisms that ensure cDC accessibility to FLT3L have yet to be elucidated. Here, we generated mice that lacked a disintegrin and metalloproteinase (ADAM) 10 in DCs (Itgax-cre × Adam10-fl/fl; ADAM10^∆DC) and found that ADAM10 deletion markedly impacted splenic cDC2 development. Pre-cDC2s accumulated in the spleen with transcriptomic alterations that reflected their inability to differentiate and exhibited abrupt failure to survive as terminally differentiated cDC2s. Induced ADAM10 ablation also led to the reduction of terminally differentiated cDC2s, and restoration of Notch signaling, a major pathway downstream of ADAM10, only modestly rescued them. ADAM10^∆DC BM failed to generate cDC2s in BM chimeric mice with or without cotransferred ADAM10-sufficient BM, indicating that cDC2 development required cell-autonomous ADAM10. We determined cDC2s to be sources of soluble FLT3L, as supported by decreased serum FLT3L concentration and the retention of membrane-bound FLT3L on cDC2 surfaces in ADAM10^∆DC mice, and by demonstrating the release of soluble FLT3L by cDC2 in ex vivo culture supernatants. Through in vitro studies utilizing murine embryonic fibroblasts, we determined FLT3L to be a substrate for ADAM10. These data collectively reveal cDC2s as FLT3L sources and highlight a cell-autonomous mechanism that may enhance FLT3L accessibility for cDC2 development and survival.

Indispensable Role of CX3CR1+ Dendritic Cells in Regulation of Virus-Induced Neuroinflammation Through Rapid Development of Antiviral Immunity in Peripheral Lymphoid Tissues

A coordinated host immune response mediated via chemokine network plays a crucial role in boosting defense mechanisms against pathogenic infections. The speed of Ag presentation and delivery by CD11c⁺ dendritic cells (DCs) to cognate T cells in lymphoid tissues may decide the pathological severity of the infection. Here, we investigated the role of CX₃CR1 in the neuroinflammation induced by infection with Japanese encephalitis virus (JEV), a neurotrophic virus. Interestingly, CX₃CR1 deficiency strongly enhanced susceptibility to JEV only after peripheral inoculation via footpad. By contrast, both CX₃CR1^+/+ and CX₃CR1^-/- mice showed comparable susceptibility to JEV following inoculation via intranasal and intraperitoneal routes. CX₃CR1^-/- mice exhibited lethal neuroinflammation after JEV inoculation via footpad route, showing high mortality, morbidity, pro-inflammatory cytokine expression, and uncontrolled CNS-infiltration of peripheral leukocytes including Ly-6C^hi monocytes and Ly-6G^hi granulocytes. Furthermore, the absence of CX₃CR1⁺CD11c⁺ DCs appeared to enhance susceptibility of CX₃CR1^-/- mice to JE after peripheral JEV inoculation. CX₃CR1 ablation impaired the migration of CX₃CR1⁺CD11c⁺ DCs from JEV-inoculated sites to draining lymph nodes (dLNs), resulting in decreased NK cell activation and JEV-specific CD4⁺/CD8⁺ T-cell responses. However, CX₃CR1-competent mice showed rapid temporal expression of viral Ags in dLNs. Subsequently, JEV was rapidly cleared, with concomitant generation of antiviral NK cell activation and T-cell responses mediated by rapid migration of JEV Ag⁺CX₃CR1⁺CD11c⁺ DCs. Using biallelic functional CX₃CR1 expression system, the functional expression of CX₃CR1 on CD11c^hi DCs appeared to be essentially required for inducing rapid and effective responses of NK cell activation and Ag-specific CD4⁺ T cells in dLNs. Strikingly, adoptive transfer of CX₃CR1⁺CD11c⁺ DCs was found to completely restore the resistance of CX₃CR1^-/- recipients to JEV, as corroborated by the rapid delivery of JEV Ags in dLNs and attenuation of neuroinflammation in the CNS. Collectively, these results indicate that CX₃CR1⁺CD11c⁺ DCs play an important role in generating rapid and effective responses of antiviral NK cell activation and Ag-specific T cells after peripheral inoculation with the virus, thereby resulting in conferring resistance to viral infection by reducing the peripheral viral burden.

A novel myeloid cell in murine spleen defined through gene profiling

A novel myeloid antigen presenting cell can be generated through in vitro haematopoiesis in long‐term splenic stromal cocultures. The in vivo equivalent subset was recently identified as phenotypically and functionally distinct from the spleen subsets of macrophages, conventional (c) dendritic cells (DC), resident monocytes, inflammatory monocytes and eosinophils. This novel subset which is myeloid on the basis of cell surface phenotype, but dendritic‐like on the basis of cell surface marker expression and antigen presenting function, has been tentatively labelled “L‐DC.” Transcriptome analysis has now been employed to determine the lineage relationship of this cell type with known splenic cDC and monocyte subsets. Principal components analysis showed separation of “L‐DC” and monocytes from cDC subsets in the second principal component. Hierarchical clustering then indicated a close lineage relationship between this novel subset, resident monocytes and inflammatory monocytes. Resident monocytes were the most closely aligned, with no genes specifically expressed by the novel subset. This subset, however, showed upregulation of genes reflecting both dendritic and myeloid lineages, with strong upregulation of several genes, particularly CD300e. While resident monocytes were found to be dependent on Toll‐like receptor signalling for development and were reduced in number in Myd88‐/‐ and Trif‐/‐ mutant mice, both the novel subset and inflammatory monocytes were unaffected. Here, we describe a novel myeloid cell type closely aligned with resident monocytes in terms of lineage but distinct in terms of development and functional capacity.

Nonclassical Monocytes in Health and Disease

Monocytes are innate blood cells that maintain vascular homeostasis and are early responders to pathogens in acute infections. There are three well-characterized classes of monocytes: classical (CD14+CD16−in humans and Ly6Chiin mice), intermediate (CD14+CD16+in humans and Ly6C+Treml4+in mice), and nonclassical (CD14−CD16+in humans and Ly6Cloin mice). Classical monocytes are critical for the initial inflammatory response. Classical monocytes can differentiate into macrophages in tissue and can contribute to chronic disease. Nonclassical monocytes have been widely viewed as anti-inflammatory, as they maintain vascular homeostasis. They are a first line of defense in recognition and clearance of pathogens. However, their roles in chronic disease are less clear. They have been shown to be protective as well as positively associated with disease burden. This review focuses on the state of the monocyte biology field and the functions of monocytes, particularly nonclassical monocytes, in health and disease.

Cytokines use different intracellular mechanisms to upregulate the membrane expression of CX3CR1 in human monocytes

Membrane expression of fractalkine (CX₃CL1)-receptor (CX₃CR1) is relevant in monocytes (Mo) because CX₃CR1-CX₃CL1 interactions might participate on both, homeostatic and pathologic conditions. We have previously demonstrated that CX₃CR1 levels are decreased during culture and when Mo are differentiated into dendritic cells, but enhanced when differentiated into macrophages. Regarding soluble factors, lipopolysaccharide (LPS) accelerated the loss of CX₃CR1, while interleukin (IL)-10 and Interferon-gamma (IFN-γ) prevented it. However, the comprehensive knowledge about the intracellular pathways that underlay the level of CX₃CR1 expression in Mo is still incomplete. In the current work, we studied the effect of anti-inflammatory cytokines (IL-4, IL-13, IL-10), alone or together with IFN- γ on CX₃CR1 expression. We found that only IL-10 and IFN-γ separately were able to prevent CX₃CR1 down-modulation during culture of human Mo. Besides, Mo incubated with IL-10 plus IFN-γ showed the highest CX₃CR1 expression by cell, suggesting cooperation between two different mechanism used by both cytokines. By studying intracellular mechanisms triggered by IL-10 and IFN-γ, we demonstrated that they specifically induced PI3K-dependent serine-phosphorylation of signal transducer and activator of transcription (STAT)3 or STAT1, respectively. Moreover, chemical inhibitors of STAT1 or STAT3 abrogated IFN-γ or IL-10 effects on CX₃CR1 expression. Strikingly, only IL-10 increased CX₃CR1 mRNA level, as consequence of augmenting mRNA stability. CX₃CR1 mRNA increase was PI3K-dependent, supporting the causal link between the action of IL-10 at the CX₃CR1 transcript and CX₃CR1 protein level on Mo. Thus, both cytokines up-regulate CX₃CR1 expression on human Mo by different intracellular mechanisms.

Candida albicans β-Glucan Differentiates Human Monocytes Into a Specific Subset of Macrophages

β-Glucan derived from cell walls of Candida albicans is a potent immune modulator. It has been shown to induce trained immunity in monocytes via epigenetic and metabolic reprogramming and to protect from lethal sepsis if applied prior to infection. Since β-glucan-trained monocytes have not been classified within the system of mononuclear phagocytes we analyzed these cells metabolically, phenotypically and functionally with a focus on monocyte-to-macrophage differentiation and compared them with naïve monocytes and other types of monocyte-derived cells such as classically (M1) or alternatively (M2) activated macrophages and monocyte-derived dendritic cells (moDCs). We show that β-glucan inhibits spontaneous apoptosis of monocytes independent from autocrine or paracrine M-CSF release and stimulates monocyte differentiation into macrophages. β-Glucan-differentiated macrophages exhibit increased cell size and granularity and enhanced metabolic activity when compared to naïve monocytes. Although β-glucan-primed cells expressed markers of alternative activation and secreted higher levels of IL-10 after lipopolysaccharide (LPS), their capability to release pro-inflammatory cytokines and to kill bacteria was unaffected. Our data demonstrate that β-glucan priming induces a population of immune competent long-lived monocyte-derived macrophages that may be involved in immunoregulatory processes.

Hemodialysis-related changes in phenotypical features of monocytes

Hemodialysis (HD) patients exhibit chronic inflammation and leukocyte activation. We investigated the surface-marker profile of monocytes by flow cytometry to assess the chronic effect of uremia and the acute effect of dialysis on their phenotypical and functional features in 16 healthy controls (CON) and 15 HD patients before and after a polysulfone-based dialysis session. Median fluorescence intensities were analyzed indicating expression of CD14, CD16, integrins (CD11b, CD18), chemokine receptors (CCR2, CX3CR1), scavenger receptors (CD36, CD163) and Toll-like receptor-2 (TLR2). Before and after dialysis, HD patients harbour 0.9-fold less CD14⁺⁺CD16^- (Mo1), 1.8-fold more CD14⁺⁺CD16⁺ (Mo2) and CD14⁺CD16⁺⁺ (Mo3) monocytes than CON. HD patients' Mo1 showed elevated expression of CD11b (1.7-fold), CD18 (1.2-fold) and CD36 (2.1-fold), whereas CD163 expression was reduced in Mo1 and Mo2 (0.6-fold) compared to CON. These markers remained unaffected by dialysis. CX3CR1 expression on Mo2 and Mo3 was lower in HD patients before (0.8-fold) and further diminished after dialysis (0.6-fold). Stimulation of monocytes resulted in diminished responses in HD patients compared to CON. In conclusion, a systematic analysis of the expression of particular surface markers on distinct monocyte subsets may help to distinguish between uremia and/or dialysis induced effects and to evaluate the functionality of monocytes and biocompatibility of HD.

Regional Distribution of CNS Antigens Differentially Determines T-Cell Mediated Neuroinflammation in a CX3CR1-Dependent Manner

T cells continuously sample CNS-derived antigens in the periphery, yet it is unknown how they sample and respond to CNS antigens derived from distinct brain areas. We expressed ovalbumin (OVA) neoepitopes in regionally distinct CNS areas (Cnp-OVA and Nes-OVA mice) to test peripheral antigen sampling by OVA-specific T cells under homeostatic and neuroinflammatory conditions. We show that antigen sampling in the periphery is independent of regional origin of CNS antigens in both male and female mice. However, experimental autoimmune encephalomyelitis (EAE) is differentially influenced in Cnp-OVA and Nes-OVA female mice. Although there is the same frequency of CD45^high CD11b+ CD11c+ CX3CL1+ myeloid cell-T-cell clusters in neoepitope-expressing areas, EAE is inhibited in Nes-OVA female mice and accelerated in CNP-OVA female mice. Accumulation of OVA-specific T cells and their immunomodulatory effects on EAE are CX3C chemokine receptor 1 (CX3CR1) dependent. These data show that despite similar levels of peripheral antigen sampling, CNS antigen-specific T cells differentially influence neuroinflammatory disease depending on the location of cognate antigens and the presence of CX3CL1/CX3CR1 signaling.SIGNIFICANCE STATEMENT Our data show that peripheral T cells similarly recognize neoepitopes independent of their origin within the CNS under homeostatic conditions. Contrastingly, during ongoing autoimmune neuroinflammation, neoepitope-specific T cells differentially influence clinical score and pathology based on the CNS regional location of the neoepitopes in a CX3CR1-dependent manner. Altogether, we propose a novel mechanism for how T cells respond to regionally distinct CNS derived antigens and contribute to CNS autoimmune pathology.

The homozygous CX3CR1-M280 mutation impairs human monocyte survival

Several reports have demonstrated that mouse Cx3cr1 signaling promotes monocyte/macrophage survival. In agreement, we previously found that, in a mouse model of systemic candidiasis, genetic deficiency of Cx3cr1 resulted in increased mortality and impaired tissue fungal clearance associated with decreased macrophage survival. We translated this finding by showing that the dysfunctional CX3CR1 variant CX3CR1-M280 was associated with increased risk and worse outcome of human systemic candidiasis. However, the impact of this mutation on human monocyte/macrophage survival is poorly understood. Herein, we hypothesized that CX3CR1-M280 impairs human monocyte survival. We identified WT (CX3CR1-WT/WT), CX3CR1-WT/M280 heterozygous, and CX3CR1-M280/M280 homozygous healthy donors of European descent, and we show that CX3CL1 rescues serum starvation-induced cell death in CX3CR1-WT/WT and CX3CR1-WT/M280 but not in CX3CR1-M280/M280 monocytes. CX3CL1-induced survival of CX3CR1-WT/WT monocytes is mediated via AKT and ERK activation, which are both impaired in CX3CR1-M280/M280 monocytes, associated with decreased blood monocyte counts in CX3CR1-M280/M280 donors at steady state. Instead, CX3CR1-M280/M280 does not affect monocyte CX3CR1 surface expression or innate immune effector functions. Together, we show that homozygocity of the M280 polymorphism in CX3CR1 is a potentially novel population-based genetic factor that influences human monocyte signaling.

Enrichment of endogenous fractalkine and anti-inflammatory cells via aptamer-functionalized hydrogels

Early recruitment of non-classical monocytes and their macrophage derivatives is associated with augmented tissue repair and improved integration of biomaterial constructs. A promising therapeutic approach to recruit these subpopulations is by elevating local concentrations of chemoattractants such as fractalkine (FKN, CX3CL1). However, delivering recombinant or purified proteins is not ideal due to their short half-lives, suboptimal efficacy, immunogenic potential, batch variabilities, and cost. Here we report an approach to enrich endogenous FKN, obviating the need for delivery of exogenous proteins. In this study, modified FKN-binding-aptamers are integrated with poly(ethylene glycol) diacrylate to form aptamer-functionalized hydrogels ("aptagels") that localize, dramatically enrich and passively release FKN in vitro for at least one week. Implantation in a mouse model of excisional skin injury demonstrates that aptagels enrich endogenous FKN and stimulate significant local increases in Ly6C^loCX3CR1^hi non-classical monocytes and CD206⁺ M2-like macrophages. The results demonstrate that orchestrators of inflammation can be manipulated without delivery of foreign proteins or cells and FKN-aptamer functionalized biomaterials may be a promising approach to recruit anti-inflammatory subpopulations to sites of injury. Aptagels are readily synthesized, highly customizable and could combine different aptamers to treat complex diseases in which regulation or enrichment of multiple proteins may be therapeutic.

Gut Microbiota Species Can Provoke both Inflammatory and Tolerogenic Immune Responses in Human Dendritic Cells Mediated by Retinoic Acid Receptor Alpha Ligation

Dendritic cells are considered as the main coordinators of both mucosal and systemic immune responses, thus playing a determining role in shaping the outcome of effector cell responses. However, it is still uncovered how primary human monocyte-derived DC (moDC) populations drive the polarization of helper T (Th) cells in the presence of commensal bacteria harboring unique immunomodulatory properties. Furthermore, the individual members of the gut microbiota have the potential to modulate the outcome of immune responses and shape the immunogenicity of differentiating moDCs via the activation of retinoic acid receptor alpha (RARα). Here, we report that moDCs are able to mediate robust Th1 and Th17 responses upon stimulation by Escherichia coli Schaedler or Morganella morganii, while the probiotic Bacillus subtilis strain limits this effect. Moreover, physiological concentrations of all-trans retinoic acid (ATRA) are able to re-program the differentiation of moDCs resulting in altered gene expression profiles of the master transcription factors RARα and interferon regulatory factor 4, and concomitantly regulate the cell surface expression levels of CD1 proteins and also the mucosa-associated CD103 integrin to different directions. It was also demonstrated that the ATRA-conditioned moDCs exhibited enhanced pro-inflammatory cytokine secretion while reduced their co-stimulatory and antigen-presenting capacity thus reducing Th1 and presenting undetectable Th17 type responses against the tested microbiota strains. Importantly, these regulatory circuits could be prevented by the selective inhibition of RARα functionality. These results altogether demonstrate that selected commensal bacterial strains are able to drive strong effector immune responses by moDCs, while in the presence of ATRA, they support the development of both tolerogenic and inflammatory moDC in a RARα-dependent manner.

Microglial Dysregulation in OCD, Tourette Syndrome, and PANDAS

There is accumulating evidence that immune dysregulation contributes to the pathophysiology of obsessive-compulsive disorder (OCD), Tourette syndrome, and Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS). The mechanistic details of this pathophysiology, however, remain unclear. Here we focus on one particular component of the immune system: microglia, the brain's resident immune cells. The role of microglia in neurodegenerative diseases has been understood in terms of classic, inflammatory activation, which may be both a consequence and a cause of neuronal damage. In OCD and Tourette syndrome, which are not characterized by frank neural degeneration, the potential role of microglial dysregulation is much less clear. Here we review the evidence for a neuroinflammatory etiology and microglial dysregulation in OCD, Tourette syndrome, and PANDAS. We also explore new hypotheses as to the potential contributions of microglial abnormalities to pathophysiology, beyond neuroinflammation, including failures in neuroprotection, lack of support for neuronal survival, and abnormalities in synaptic pruning. Recent advances in neuroimaging and animal model work are creating new opportunities to elucidate these issues.

Cellular and molecular regulation of innate inflammatory responses

Innate sensing of pathogens by pattern-recognition receptors (PRRs) plays essential roles in the innate discrimination between self and non-self components, leading to the generation of innate immune defense and inflammatory responses. The initiation, activation and resolution of innate inflammatory response are mediated by a complex network of interactions among the numerous cellular and molecular components of immune and non-immune system. While a controlled and beneficial innate inflammatory response is critical for the elimination of pathogens and maintenance of tissue homeostasis, dysregulated or sustained inflammation leads to pathological conditions such as chronic infection, inflammatory autoimmune diseases. In this review, we discuss some of the recent advances in our understanding of the cellular and molecular mechanisms for the establishment and regulation of innate immunity and inflammatory responses.

Tissue-engineered human psoriatic skin supplemented with cytokines as an in vitro model to study plaque psoriasis

AIM

Psoriasis is a chronic inflammatory skin disease. To study its complex etiology, a psoriatic skin substitute model supplemented with a cytokine cocktail has been used.

MATERIALS & METHODS

Reconstructed psoriatic skin substitutes were supplemented with a cocktail of four cytokines: TNF-α, IL-1α, IL-6 and IL-17A, to monitor their impact on gene expression by DNA microarray.

RESULTS

Gene profiling analyses identified several deregulated genes reported as being also deregulated in psoriasis skin in vivo (S100A12, IL-8, DEFB4A and KYNU). The expression of those genes was dramatically increased compared with basal levels of controls (p < 0.005 to < 0.05).

CONCLUSION

Psoriatic substitutes supplemented with a cocktail of TNF-α, IL-1α, IL-6 and IL-17A showed similar transcriptome alterations to those found in psoriasis.

Effects of long-term exercise training on adipose tissue expression of fractalkine and MCP-1 in patients with type 2 diabetes and stable coronary artery disease: a substudy of a randomized controlled trial

PURPOSE

Adipose tissue inflammation plays a role in atherosclerosis and type 2 diabetes (T2DM). We aimed to investigate whether 12 months of exercise training in patients with both T2DM and coronary artery disease (CAD) reduced the genetic expression of the proinflammatory markers fractalkine (CX3CL1) and its receptor (CX3CR1) and monocyte chemoattractant protein-1 (MCP-1) in the subcutaneous adipose tissue. Expression of the genes in the circulating leukocytes and circulating levels of the markers were also investigated.

PATIENTS AND METHODS

A total of 137 patients with T2DM and CAD were included to study the effects of exercise on atherosclerosis progression and glucose control. Patients were randomized to exercise training (combined aerobic and strength training) or control. At inclusion and after 12 months, fasting blood samples and a subcutaneous adipose tissue sample were taken. RNA was extracted from the adipose tissue and circulating leukocytes, and the expression levels were examined by reverse transcription-polymerase chain reaction. Circulating fractalkine and MCP-1 were determined by enzyme-linked immunosorbent assay.

RESULTS

The analyses were performed in 114 patients who completed the study and adhered to the intervention principle. At baseline, gene expression of fractalkine and CX3CR1 in the adipose tissue was similar in the two groups. There were no change within either group and no between-group differences in changes from baseline. Circulating fractalkine increased after 12 months in the exercise group (P=0.044), significantly more compared to controls (P=0.042), however only in the patients with advanced vascular disease. Neither the expression levels of MCP-1 nor the circulating levels changed significantly in either group. At baseline, CX3CR1 expression in the adipose tissue was associated with body mass index (P<0.001).

CONCLUSION

No significant effects of long-term exercise training on adipose tissue expression of fractalkine, CX3CR1, or MCP-1 were found in our patients with combined CAD and T2DM. However, a slight increase in circulating fractalkine after the intervention was recorded. The association of CX3CR1 expression with body mass index might indicate increased immune activation in the adipose tissue.