Expression of C/EBPβ in myeloid progenitors during sepsis promotes immunosuppression

MDSCs in sepsis-induced immunosuppression and its potential therapeutic targets

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. In sepsis, a complicated immune response is initiated, which varies over time with sustained excessive inflammation and immunosuppression. Identifying a promising way to orchestrate sepsis-induced immunosuppression is a challenge. Myeloid-derived suppressor cells (MDSCs) comprise pathologically activated neutrophils and monocytes with potent immunosuppressive activity. They play an important part in inhibiting innate and adaptive immune responses, and have emerged as part of the immune response in sepsis. MDSCs numbers are persistently high in sepsis patients, and associated with nosocomial infections and other adverse clinical outcomes. However, their characteristics and functional mechanisms during sepsis have not been addressed fully. Our review sheds light on the features and suppressive mechanism of MDSCs. We also review the potential applications of MDSCs as biomarkers and targets for clinical treatment of sepsis.

Emerging functions of C/EBPβ in breast cancer

Breast tumorigenesis relies on complex interactions between tumor cells and their surrounding microenvironment, orchestrated by tightly regulated transcriptional networks. C/EBPβ is a key transcription factor that regulates the proliferation and differentiation of multiple cell types and modulates a variety of biological processes such as tissue homeostasis and the immune response. In addition, C/EBPβ has well-established roles in mammary gland development, is overexpressed in breast cancer, and has tumor-promoting functions. In this review, we discuss context-specific roles of C/EBPβ during breast tumorigenesis, isoform-specific gene regulation, and regulation of the tumor immune response. We present challenges in C/EBPβ biology and discuss the importance of C/EBPβ isoform-specific gene regulation in devising new therapeutic strategies.

C/EBPβ expression decreases in cervical cancer and leads to tumorigenesis

BACKGROUND

Cervical cancer is currently estimated to be the fourth most common cancer among women worldwide and the leading cause of cancer-related deaths in some of the world's poorest countries. C/EBPβ has tumor suppressor effects because it is necessary for oncogene-induced senescence. However, C/EBPβ also has an oncogenic role. The specific role of C/EBPβ in cervical cancer as a tumor suppressor or oncoprotein is unclear.

OBJECTIVE

To explore the role of the C/EBPβ protein in cervical tumorigenesis and progression.

METHODS

Quantitative RT-PCR was used to analyze C/EBPβ (15 cervical cancer tissue samples and 15 corresponding normal cervical tissue samples), miR-661, and MTA1 mRNA expression in clinical samples (10 cervical cancer tissue samples and 10 corresponding normal cervical tissue samples). Immunohistochemistry was used to analyze C/EBPβ (381 clinical samples), Ki67 (80 clinical samples) and PCNA ( 60 clinical samples) protein expression. MALDI-TOF MassARRAY was used to analyze C/EBPβ gene methylation (13 cervical cancer tissues and 13 corresponding normal cervical tissues). Cell proliferation was analyzed by CCK-8 in cervical cancer cell lines. Western blotting and immunohistochemistry were performed to detect C/EBPβ protein expression levels, and mRNA expression was analyzed by quantitative RT-PCR analysis. Flow cytometry was performed to measure cell cycle distribution and cell apoptosis. Colony formation, Transwell, cell invasion, and wound healing assays were performed to detect cell migration and invasion.

RESULTS

C/EBPβ protein expression was significantly reduced in cervical cancer tissues compared with cervicitis tissues (P < 0.01). Ki67 protein and PCNA protein expression levels were significantly higher in cervical cancer tissues compared with cervicitis tissues. The rate of C/EBPβ gene promoter methylation of CpG12, 13, 14 and CpG19 in cervical cancer tissues was significantly increased compared with normal cervical tissue (P < 0.05). In addition, C/EBPβ was overexpressed in cervical cancer cells and this overexpression inhibited cell proliferation, migration, invasion, arrested cells in S phase, and promoted apoptosis.

CONCLUSIONS

We have demonstrated that C/EBPβ decreased in cervical cancer tissues and overexpression of the C/EBPβ gene in cervical cancer cells could inhibit proliferation, invasion and migration.

Myeloid-derived suppressor cells: an emerging target for anticancer immunotherapy

The clinical responses observed following treatment with immune checkpoint inhibitors (ICIs) support immunotherapy as a potential anticancer treatment. However, a large proportion of patients cannot benefit from it due to resistance or relapse, which is most likely attributable to the multiple immunosuppressive cells in the tumor microenvironment (TME). Myeloid-derived suppressor cells (MDSCs), a heterogeneous array of pathologically activated immature cells, are a chief component of immunosuppressive networks. These cells potently suppress T-cell activity and thus contribute to the immune escape of malignant tumors. New findings indicate that targeting MDSCs might be an alternative and promising target for immunotherapy, reshaping the immunosuppressive microenvironment and enhancing the efficacy of cancer immunotherapy. In this review, we focus primarily on the classification and inhibitory function of MDSCs and the crosstalk between MDSCs and other myeloid cells. We also briefly summarize the latest approaches to therapies targeting MDSCs.

Myeloid-derived suppressor cells: an emerging target for anticancer immunotherapy

The clinical responses observed following treatment with immune checkpoint inhibitors (ICIs) support immunotherapy as a potential anticancer treatment. However, a large proportion of patients cannot benefit from it due to resistance or relapse, which is most likely attributable to the multiple immunosuppressive cells in the tumor microenvironment (TME). Myeloid-derived suppressor cells (MDSCs), a heterogeneous array of pathologically activated immature cells, are a chief component of immunosuppressive networks. These cells potently suppress T-cell activity and thus contribute to the immune escape of malignant tumors. New findings indicate that targeting MDSCs might be an alternative and promising target for immunotherapy, reshaping the immunosuppressive microenvironment and enhancing the efficacy of cancer immunotherapy. In this review, we focus primarily on the classification and inhibitory function of MDSCs and the crosstalk between MDSCs and other myeloid cells. We also briefly summarize the latest approaches to therapies targeting MDSCs.

ICU and Sepsis: Role of Myeloid and Lymphocyte Immune Cells

Sepsis is a severe immune system reaction to infection and a major cause of ICU-related fatalities. Because of the high mortality, high cost of treatment, and complex aetiology of sepsis, sepsis has a huge impact on healthcare. Some of the health complications in sepsis are abnormal cardiac functions, hypoperfusion, hypotension, tissue damage, multiple organ failure, and ultimately death. Individuals with weak immune systems and chronic medical conditions are highly vulnerable to sepsis. In sepsis, a patient shows the extreme immune response in the initial stage while prolonged immunosuppression in the later stages. Sepsis-driven immunosuppression ushers in death because sepsis cases develop secondary infections postrecovery. The later immunocompromised state in sepsis is attributed myeloid-derived suppressor cell upregulation and reduced immune activity displayed by lymphocytes (lymphocyte anergy). As a result, it is currently suggested that regulating the immune response is a better therapeutic approach than focusing on inflammation to improve the immune system's capacity to fight infections. Moreover, finding novel and accurate prognostic biomarkers that can help in rapid sepsis diagnoses and deciding better therapeutic strategies will significantly lower clinical case mortality rates.

The potential role of exosomal miRNAs and membrane proteins in acute HIV-infected people

Exosomes play an important role during human immunodeficiency virus (HIV) acute infection. Yet, information regarding its cargo and its association with HIV rapid progressors (RPs) and typical progressors (TPs) remain largely unknown. In this study, exosomal miRNAs sequencing and mass cytometry were used to identify differential exosomal miRNAs and membrane proteins that participate in the pathogenesis of TPs and RPs. We discovered that miR-144-5p, miR-1180-3p, miR-451a, miR-362-5p, and miR-625-5p are associated with the TPs and miR-362-5p with the RPs. Decreased autophagy, amino acid metabolism, immune response, and IL-6 are closely related to RPs. In addition, SP1 was selected as the most significant transcription factor (TF) associated with disease progression. CD49D, CD5, CCR5, CD40, CD14, and CD86 were selected as the differential exosomal membrane proteins between TPs and RPs. This study provides valuable information for clarifying the mechanism in people with acute HIV infection.

JEV Infection Induces M-MDSC Differentiation Into CD3+ Macrophages in the Brain

Japanese encephalitis virus (JEV) is one of the most important members of the flavivirus family. It is a typical zoonotic pathogen that has caused substantial social and economic losses worldwide. The relation between JEV-induced immunosuppression and inflammatory responses has not been thoroughly investigated. In this study, cells infiltrating the brain tissue of JEV-infected mice were mainly identified as monocytic myeloid-derived suppressor cells (M-MDSCs), which subsequently differentiated into CD3⁺ macrophages. Co-culture with T cells showed that both splenic M-MDSCs and brain infiltrated M-MDSCs isolated from JEV-infected mice inhibited T cell proliferation through ARG1 and iNOS. The splenectomy model revealed that JEV-induced M-MDSCs were mainly derived from bone marrow and migrated to the spleen and central nervous system (CNS). The results of the transcriptome analysis and IRF7-deficient mice indicated that the ZBP1-IRF7 signaling pathway stimulated by JEV RNA played a central role in the induction of M-MDSCs. M-MDSCs migrated into the CNS through the chemokine CCL2/N-CCL2 derived from astrocytes and brain infiltrated M-MDSCs differentiated into CD3⁺ macrophages through a mechanism mediated by M-CSF, IL-6 and IFN-γ in the brain microenvironment. These findings provide evidence for the mechanism that JEV regulates the differentiation of M-MDSCs and thereby exacerbates pathogenicity, which represents a potential therapeutic target for Japanese encephalitis (JE).

LPIN1 Is a Regulatory Factor Associated With Immune Response and Inflammation in Sepsis

Objectives

Sepsis is a clinical disease that is typically treated in the intensive care unit, and the complex pathophysiology under this disease has not been thoroughly understood. While ferroptosis is involved in inflammation and infection, its effect in sepsis is still unknown. The study aimed to identify ferroptosis-related genes in sepsis, providing translational potential therapeutic targets.

Methods

The dataset GSE65682 was used to download the sample source from the Gene Expression Omnibus (GEO) database. Consensus weighted gene co-expression network analysis (WGCNA) was performed to find suspected modules of sepsis. The differentially expressed genes (DEGs) most significantly associated with mortality were intersected with those altered by lipopolysaccharide (LPS) treatment and were further analyzed for the identification of main pathways of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The related pathway markers were further verified by qPCR.

Results

A total of 802 blood samples with sepsis were included for WGCNA, which identified 21 modules. Intersected with ferroptosis databases and LPS treatment groups, we identified two ferroptosis-related genes: PEBP1 and LPIN1. Only LPIN1 contributes to a poor outcome. Then, 205 DEGs were further identified according to the high or low LPIN1 expression. Among them, we constructed a gene regulatory network with several transcriptional factors using the NetworkAnalyst online tool and identified that these genes mostly correlate with inflammation and immune response. The immune infiltration analysis showed that lower expression of LPIN1 was related to macrophage infiltration and could be an independent predictor factor of the survival status in sepsis patients. Meanwhile, the multivariate Cox analysis showed that LPIN1 had a significant correlation with survival that was further verified by in vitro and in vivo experiments.

Conclusion

In conclusion, LPIN1 could become a reliable biomarker for patient survival in sepsis, which is associated with immune and inflammation status.

Immune Surveillance by Myeloid-Derived Suppressor Cells in Liver Diseases

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) are immunosuppressive in nature, originate in the bone marrow, and are mainly found in the blood, spleen, and liver. In fact, liver acts as an important organ for induction and accumulation of MDSCs, especially during infection, inflammation, and cancer. In humans and rodents, models of liver diseases revealed that MDSCs promote regeneration and drive the inflammatory processes, leading to hepatitis, fibrogenesis, and cirrhosis, ultimately resulting in hepatocellular carcinoma.

SUMMARY

This brief review is focused on the in-depth understanding of the key molecules involved in the expansion and regulation of MDSCs and their underlying immunosuppressive mechanisms in liver diseases.

KEY MESSAGE

Modulated MDSCs can be used for therapeutic purposes in inflammation, cancer, and sepsis.

Redox-responsive nanoassembly restrained myeloid-derived suppressor cells recruitment through autophagy-involved lactate dehydrogenase A silencing for enhanced cancer immunochemotherapy

Myeloid-derived suppressor cells (MDSCs) are the chief accomplices for assisting tumor's survival and suppressing anti-tumor immunity, which can be recruited by tumor-derived cytokines, such as granulocyte-colony stimulating factor (G-CSF) and granulocyte-macrophage colony stimulating factor (GM-CSF). The plentiful lactate dehydrogenase A (LDHA) in glycolysis is usually accompanied by abundant tumor-derived G-CSF and GM-CSF, further promoting MDSCs recruitment and immunosuppression. Herein, with the aim to achieve powerful anti-tumor immunity, an immunochemotherapy regimen basing on a redox-responsive nanoassembly (R-mPDV/PDV/DOX/siL) is developed, which integrates the combined strategy of restraining cytokines-mediated MDSCs recruitment through LDHA silencing and reinforcing tumor immunogenicity through anthracycline (DOX)-elicited immunogenic cell death (ICD) effects. This redox-responsive nanoassembly is self-assembled by three glutathione (GSH)-responsive polymers, which employ poly(δ-valerolactone) (PVL) as hydrophobic segment and 3, 3'-dithiodipropionic acid (DA) as linkage to connect hydrophilic segment. DOX is encapsulated in the core and LDHA siRNA (siL) is effectively compressed by cationic PAMAM. The cellular internalization and tumor-homing are strengthened by the specific recognition on integrin (α_vβ₃) by c(RGDfk) (RGD) ligand. After escaping from endosomes/lysosomes, R-mPDV/PDV/DOX/siL is disintegrated through GSH-elicited cleavage of DA, realizing burst release of drugs and high-efficient LDHA silencing. The reduced expression of LDHA suppresses the generation of G-CSF and GM-CSF cytokines, restrains MDSCs recruitment and reinforces anti-tumor immunity. Eventually, this therapeutic regimen of DOX and siL on R-mPDV/PDV/DOX/siL nanoassembly achieved powerful anti-tumor efficiency on 4 T1 orthotopic tumor, opening the new horizons for immunochemotherapy.

Myeloid-derived suppressor cells (MDSC): When good intentions go awry

MDSC are a heterogeneous population of immature myeloid cells that are released by biological stress such as tissue damage and inflammation. Conventionally, MDSC are known for their detrimental role in chronic inflammation and neoplastic conditions. However, their intrinsic functions in immunoregulation, wound healing, and angiogenesis are intended to protect from over-reactive immune responses, maintenance of immunotolerance, tissue repair, and homeostasis. Paradoxically, under certain conditions, MDSC can impair protective immune responses and exacerbate the disease. The transition from protective to harmful MDSC is most likely driven by environmental and epigenetic mechanisms induced by prolonged exposure to unresolved inflammatory triggers. Here, we review several examples of the dual impact of MDSC in conditions such as maternal-fetal tolerance, self-antigens immunotolerance, obesity-associated cancer, sepsis and trauma. Moreover, we also highlighted the evidence indicating that MDSC have a role in COVID-19 pathophysiology. Finally, we have summarized the evidence indicating epigenetic mechanisms associated with MDSC function.

Myeloid-Derived Suppressor Cell Differentiation in Cancer: Transcriptional Regulators and Enhanceosome-Mediated Mechanisms

Myeloid-derived Suppressor Cells (MDSCs) are a sub-population of leukocytes that are important for carcinogenesis and cancer immunotherapy. During carcinogenesis or severe infections, inflammatory mediators induce MDSCs via aberrant differentiation of myeloid precursors. Although several transcription factors, including C/EBPβ, STAT3, c-Rel, STAT5, and IRF8, have been reported to regulate MDSC differentiation, none of them are specifically expressed in MDSCs. How these lineage-non-specific transcription factors specify MDSC differentiation in a lineage-specific manner is unclear. The recent discovery of the c-Rel−C/EBPβ enhanceosome in MDSCs may help explain these context-dependent roles. In this review, we examine several transcriptional regulators of MDSC differentiation, and discuss the concept of non-modular regulation of MDSC signature gene expression by transcription factors such as c-Rel and C/EBPß.

Macrophage-Derived IL-1β Regulates Emergency Myelopoiesis via the NF-κB and C/ebpβ in Zebrafish

Myeloid phagocytes, neutrophils in particular, are easily consumed when they fight against a large number of invading microbes. Hence, they require efficient and constant replenishment from their progenitors via the well-orchestrated emergency myelopoiesis in the hematopoietic organs. The cellular and molecular details of the danger-sensing and warning processes to activate the emergency myelopoiesis are still under debate. In this study, we set up a systemic infection model in zebrafish (Danio rerio) larvae via circulative administration of LPS. We focused on the cross-talk of macrophages with myeloid progenitors in the caudal hematopoietic tissue. We revealed that macrophages first detected LPS and sent out the emergency message via il1β The myeloid progenitors, rather than hematopoietic stem and progenitor cells, responded and fulfilled the demand to adapt myeloid expansion through the synergistic cooperation of NF-κB and C/ebpβ. Our study unveiled a critical role of macrophages as the early "whistle blowers" to initiate emergency myelopoiesis.

Gene correlation network analysis to identify regulatory factors in sepsis

BACKGROUND AND OBJECTIVES

Sepsis is a leading cause of mortality and morbidity in the intensive care unit. Regulatory mechanisms underlying the disease progression and prognosis are largely unknown. The study aimed to identify master regulators of mortality-related modules, providing potential therapeutic target for further translational experiments.

METHODS

The dataset GSE65682 from the Gene Expression Omnibus (GEO) database was utilized for bioinformatic analysis. Consensus weighted gene co-expression netwoek analysis (WGCNA) was performed to identify modules of sepsis. The module most significantly associated with mortality were further analyzed for the identification of master regulators of transcription factors and miRNA.

RESULTS

A total number of 682 subjects with various causes of sepsis were included for consensus WGCNA analysis, which identified 27 modules. The network was well preserved among different causes of sepsis. Two modules designated as black and light yellow module were found to be associated with mortality outcome. Key regulators of the black and light yellow modules were the transcription factor CEBPB (normalized enrichment score = 5.53) and ETV6 (NES = 6), respectively. The top 5 miRNA regulated the most number of genes were hsa-miR-335-5p (n = 59), hsa-miR-26b-5p (n = 57), hsa-miR-16-5p (n = 44), hsa-miR-17-5p (n = 42), and hsa-miR-124-3p (n = 38). Clustering analysis in 2-dimension space derived from manifold learning identified two subclasses of sepsis, which showed significant association with survival in Cox proportional hazard model (p = 0.018).

CONCLUSIONS

The present study showed that the black and light-yellow modules were significantly associated with mortality outcome. Master regulators of the module included transcription factor CEBPB and ETV6. miRNA-target interactions identified significantly enriched miRNA.

20-Hydroxyecdysone receptor-activated Bombyx mori CCAAT/enhancer-binding protein gamma regulates the expression of BmCBP and subsequent histone H3 lysine 27 acetylation in Bo. mori

Cyclic adenosine monophosphate (cAMP) response element binding protein (CREB)-binding protein (CBP or CREBBP) plays important roles in regulating gene transcription and animal development. However, the process by which CBP is up-regulated to impact insect development is unknown. In this study, the regulatory mechanism of Bombyx mori CBP (BmCBP) expression induced by 20-hydroxyecdysone (20E) was investigated. In the Bo. mori cell line, DZNU-Bm-12, 20E enhanced BmCBP transcription and histone H3K27 acetylation. BmCBP RNA interference (RNAi) resulted in decreased histone H3K27 acetylation. Additionally, the luciferase activity analysis revealed that the transcription factor, Bo. mori CCAAT/enhancer-binding protein gamma (BmC/EBPg), activated BmCBP transcription, which was suppressed by BmC/EBPg RNAi and promoted by BmC/EBPg overexpression. Electrophoretic mobility shift assay and chromatin immunoprecipitation results demonstrated that BmC/EBPg could bind to the C/EBP cis-regulatory elements in two positions of the BmCBP promoter. Moreover, BmC/EBPg transcription was enhanced by the 20E receptor (BmEcR), which bound to the BmC/EBPg promoter. BmEcR RNAi significantly inhibited the transcriptional levels of BmC/EBPg and BmCBP in the presence of 20E. Furthermore, the BmEcR-BmC/EBPg pathway regulated the acetylation levels of histone H3K27. Altogether, these results indicate that BmEcR enhances the expression of BmC/EBPg, which binds to the BmCBP promoter, activates BmCBP expression and leads to histone H3K27 acetylation.

Morin Inhibits Ovarian Cancer Growth through the Inhibition of NF-κB Signaling Pathway

Background &Objective:

Ovarian cancer has the highest mortality in gynecological tumors without effective therapeutic drugs as a result of drug-resistance for long-term utilization. Morin has been reported to possess powerful anti-tumor effects in several cancers. The present study aims to investigate whether Morin could influence ovarian cancer growth and underlying mechanisms.

Methods:

Morin was administered to cultured cells in vitro and formed tumors in vivo. MTT and colony formation assays were performed to explore the effects of Morin on the proliferation and colony formation of OVCAR3 and SKOV3 ovarian cancer cells. Western blot, RT-qPCR, immunofluorescence as well as ELISA were used to detect protein and mRNA expression of target factors. Tumor formation was performed to investigate tumorigenesis ability of drug-treated cells.

Results:

The proliferation and colony size of OVCAR3 and SKOV3 were significantly decreased after Morin administration. The expression of NF-κB and inflammatory cytokine IL6/8 induced by TNF-α can be inhibited by Morin. Furthermore, Morin inhibited the volume of ovarian cancer tumors in nude mice.

Conclusion:

Morin effectively alleviates ovarian cancer growth, inhibits the inflammatory response, and reduces tumor size via modulation of the NF-κB pathway.

Insights Into Mechanisms of Tumor and Immune System Interaction: Association With Wound Healing

A large number of studies have presented a great deal of information about tumor and immune system interaction. Nevertheless, the problem of tumor evasion from the immune reaction is still difficult to resolve. Understanding the ways in which immunosuppressive tumor microenvironment develops and maintains its potential is of utmost importance to ensure the best use of the suppressed immune functions. The study presents a review covering the data on tumor-associated antigens, mechanisms of tumor evasion from the immune reactions, and search for common immunosuppressive processes of tumor growth and normal wound healing. The study discusses the important role of monocytes/macrophages in the regulation of immune system reactions. We suggest that the simultaneous actions of growth factors and pro-inflammatory cytokines may result in the suppression of the immune system. The study describes intracellular signaling molecules that take part in the regulation of the myeloid cell functions. If the hypothesis is proved correct, the indicated interaction of cytokines could be regarded as a prospective target for antitumor therapy.

Identifying crucial genes for prognosis in septic patients: Gene integration study based on PRISMA guidelines

BACKGROUND

Sepsis is a serious clinical condition with a poor prognosis, despite improvements in diagnosis and treatment.Therefore, novel biomarkers are necessary that can help with estimating prognosis and improving clinical outcomes of patients with sepsis.

METHODS

The gene expression profiles GSE54514 and GSE63042 were downloaded from the GEO database. DEGs were screened by t test after logarithmization of raw data; then, the common DEGs between the 2 gene expression profiles were identified by up-regulation and down-regulation intersection. The DEGs were analyzed using bioinformatics, and a protein-protein interaction (PPI) survival network was constructed using STRING. Survival curves were constructed to explore the relationship between core genes and the prognosis of sepsis patients based on GSE54514 data.

RESULTS

A total of 688 common DEGs were identified between survivors and non-survivors of sepsis, and 96 genes were involved in survival networks. The crucial genes Signal transducer and activator of transcription 5A (STAT5A), CCAAT/enhancer-binding protein beta (CEBPB), Myc proto-oncogene protein (MYC), and REL-associated protein (RELA) were identified and showed increased expression in sepsis survivors. These crucial genes had a positive correlation with patients' survival time according to the survival analysis.

CONCLUSIONS

Our findings indicate that the genes STAT5A, CEBPB, MYC, and RELA may be important in predicting the prognosis of sepsis patients.

The CCAAT/Enhancer-Binding Protein Family: Its Roles in MDSC Expansion and Function

Immunosuppressive cells have been highlighted in research due to their roles in tumor progression and treatment failure. Myeloid-derived suppressor cells (MDSCs) are among the major immunosuppressive cell populations in the tumor microenvironment, and transcription factors (TFs) are likely involved in MDSC expansion and activation. As key regulatory TFs, members of the CCAAT/enhancer-binding protein (C/EBP) family possibly modulate many biological processes, including cell growth, differentiation, metabolism, and death. Current evidence suggests that C/EBPs maintain critical regulation of MDSCs and are involved in the differentiation and function of MDSCs within the tumor microenvironment. To better understand the MDSC-associated transcriptional network and identify new therapy targets, we herein review recent findings about the C/EBP family regarding their participation in the expansion and function of MDSCs.

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.

Role of the p38 MAPK/C/EBPβ Pathway in the Regulation of Phenotype and IL-10 and IL-12 Production by Tolerogenic Bone Marrow-Derived Dendritic Cells

Dendritic cells (DCs) play a major role in innate and adaptive immunity and self-immune tolerance. Immunogenic versus tolerogenic DC functions are dictated by their levels of costimulatory molecules and their cytokine expression profile. The transcription factor C/EBPβ regulates the expression of several inflammatory genes in many cell types including macrophages. However, little is known regarding the role of C/EBPβ in tolerogenic versus immunogenic DCs functions. We have previously reported that bone marrow-derived DCs generated with GM-CSF (GM/DCs) acquire the signature of semi-mature tolerogenic IL-10-producing DCs as opposed to immunogenic DCs generated with GM-CSF and IL-4 (IL-4/DCs). Here, we show that tolerogenic GM/DCs exhibit higher levels of phosphorylation and enhanced DNA binding activity of C/EBPβ and CREB than immunogenic IL-4/DCs. We also show that the p38 MAPK/CREB axis and GSK3 play an important role in regulating C/EBPβ phosphorylation and DNA binding activity. Inhibition of p38 MAPK in GM/DCs resulted in a drastic decrease of C/EBPβ and CREB DNA binding activities, a reduction of their IL-10 production and an increase of their IL-12p70 production, a characteristic of immunogenic IL-4/DCs. We also present evidence that GSK3 inhibition in GM/DCs reduced C/EBPβ DNA binding activity and increased expression of costimulatory molecules in GM/DCs and their production of IL-10. Analysis of GM/DCs of C/EBPβ^-/- mice showed that C/EBPβ was essential to maintain the semimature phenotype and the production of IL-10 as well as low CD4⁺ T cell proliferation. Our results highlight the importance of the p38MAPK-C/EBPβ pathway in regulating phenotype and function of tolerogenic GM/DCs.

Vascular Endothelial Cells Activate Peripheral Natural Killer T Cells and Participate in Regulation of Downstream Immune Cascades in Patients with Sepsis

Background

This study investigated the effect of supernatant of endothelial cells stimulated by peripheral blood serum from sepsis patients on phenotype and function of peripheral NKT cells.

Material/Methods

Twenty-one patients with sepsis and 21 healthy subjects were included. Peripheral blood (5 ml) was collected from all patients and healthy subjects. To isolate peripheral blood mononuclear cells (PBMCs), Ficoll lymphocyte separation solution was used. Flow cytometry was carried out to determine NKT cell ratio, activity, and cytokine secretion. Human umbilical vein endothelial cells were cultured with serum from sepsis patients for 48 h before changing to fresh medium, and supernatant was collected. The supernatant was used to co-culture PBMCs before analyzing NKT activity and cytokines.

Results

The ratios of CD3-CD56+NK cells and CD3+CD56+NKT cells were increased in peripheral blood from sepsis patients. Surface receptors p30, G2D, and p44 of CD3+CD56+NKT cells were elevated, while inhibitory receptors NKG2A and 158b were decreased. CD4+ NKT cells in peripheral blood from sepsis patients were enhanced. GranB, IFN-γ, IL-4, and IL-17 in NKT cells from sepsis patients were up-regulated. After co-culture with vascular endothelial cells treated with sepsis serum, expression of p30 and G2D in NKT cells was upregulated, and number of TCRVα24-positive cells was increased. In addition, ratio of CD4+NKT cells was increased, and intracellular expression of IL-4 and IFN-γ was elevated.

Conclusions

The study demonstrates that the level of NKT cells in peripheral blood from sepsis patients is increased, and their activity is enhanced. In addition, vascular endothelial cells from sepsis patients can regulate the activity of NKT cells.

C/EBPβ Deletion Promotes Expansion of Poorly Functional Intestinal Regulatory T Cells

BACKGROUND AND AIMS

Inflammatory Bowel Diseases [IBDs] are chronic intestinal inflammatory conditions in part mediated by CD4+ T cells. Anti-inflammatory Foxp3+ regulatory T cells [Tregs] maintain immune homeostasis and protect against IBD development via multiple mechanisms, including cytokine secretion and cell-cell interaction. CCAAT enhancer binding protein-beta [C/EBPβ] is a stress-responsive transcription factor linked with IBD susceptibility. Whole-body C/EBPβ deficiency induces CD4+ T cell-predominant hyperproliferation, and we hypothesize that this may be due to impaired Treg function.

METHODS

We used the C/EBPβ-/- mice in the CD45RBHigh adoptive transfer model, to assess C/EBPβ-/- CD4+ T cells for their colitiogenic potential, and C/EBPβ-/- CD4+ Foxp3+ Tregs for their ability to inhibit colitis. We assessed Tregs from the C/EBPβ-/- mice for expression of Treg functional genes and proteins.

RESULTS

Naïve C/EBPβ-/- CD4+ T cells are more colitogenic in vivo. The exacerbated colitis does not appear to reflect impaired Treg development, however, as C/EBPβ-/- mice displayed more, rather than fewer intestinal CD4+Foxp3+ Tregs in vivo. Instead, this reflects impaired Treg function as seen by the reduced capacity to suppress T cell proliferation in vitro, along with decreased secretion of the anti-inflammatory cytokine IL-10. These findings were corroborated in vivo by additional adoptive co-transfer studies in which wildtype Tregs prevented colitis but C/EBPβ-/- Tregs did not.

CONCLUSION

C/EBPβ deficiency impairs Treg function and potentiates T cell-mediated colitis. A clearer understanding of the function of this transcription factor may provide a novel therapeutic strategy for IBD.

Microarray analysis of long non-coding RNA expression profiles in monocytic myeloid-derived suppressor cells in Echinococcus granulosus-infected mice

Background

Cystic echinococcosis is a worldwide chronic zoonotic disease caused by infection with the larval stage of Echinococcus granulosus. Previously, we found significant accumulation of myeloid-derived suppressor cells (MDSCs) in E. granulosus infection mouse models and that they play a key role in immunosuppressing T lymphocytes. Here, we compared the long non-coding RNA (lncRNA) and mRNA expression patterns between the splenic monocytic MDSCs (M-MDSCs) of E. granulosus protoscoleces-infected mice and normal mice using microarray analysis.

Methods

LncRNA functions were predicted using Gene Ontology enrichment and the Kyoto Encyclopedia of Genes and Genomes pathway analysis. Cis- and trans-regulation analyses revealed potential relationships between the lncRNAs and their target genes or related transcription factors.

Results

We found that 649 lncRNAs were differentially expressed (fold change ≥ 2, P < 0.05): 582 lncRNAs were upregulated and 67 lncRNAs were downregulated; respectively, 28 upregulated mRNAs and 1043 downregulated mRNAs were differentially expressed. The microarray data was validated by quantitative reverse transcription-PCR. The results indicated that mRNAs co-expressed with the lncRNAs are mainly involved in regulating the actin cytoskeleton, Salmonella infection, leishmaniasis, and the vascular endothelial growth factor (VEGF) signaling pathway. The lncRNA NONMMUT021591 was predicted to cis-regulate the retinoblastoma gene (Rb1), whose expression is associated with abnormal M-MDSCs differentiation. We found that 372 lncRNAs were predicted to interact with 60 transcription factors; among these, C/EBPβ (CCAAT/enhancer binding protein beta) was previously demonstrated to be a transcription factor of MDSCs.

Conclusions

Our study identified dysregulated lncRNAs in the M-MDSCs of E. granulosus infection mouse models; they might be involved in M-MDSC-derived immunosuppression in related diseases.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2905-6) contains supplementary material, which is available to authorized users.